Expression of drought-tolerant N2 fixation in heterogeneous inbred families derived from PI 471938 and Hutcheson soybean

USDA-ARS?s Scientific Manuscript database

Nitrogen fixation of soybean is particularly vulnerable to drought, since, in most genotypes, N2 fixation activity decreases very early in the soil drying cycle. Although a few soybean genotypes, including ‘PI 471938’, have been identified that express N2 fixation tolerance of drought, it is unknown...

Toward FRP-Based Brain-Machine Interfaces—Single-Trial Classification of Fixation-Related Potentials

PubMed Central

Finke, Andrea; Essig, Kai; Marchioro, Giuseppe; Ritter, Helge

2016-01-01

The co-registration of eye tracking and electroencephalography provides a holistic measure of ongoing cognitive processes. Recently, fixation-related potentials have been introduced to quantify the neural activity in such bi-modal recordings. Fixation-related potentials are time-locked to fixation onsets, just like event-related potentials are locked to stimulus onsets. Compared to existing electroencephalography-based brain-machine interfaces that depend on visual stimuli, fixation-related potentials have the advantages that they can be used in free, unconstrained viewing conditions and can also be classified on a single-trial level. Thus, fixation-related potentials have the potential to allow for conceptually different brain-machine interfaces that directly interpret cortical activity related to the visual processing of specific objects. However, existing research has investigated fixation-related potentials only with very restricted and highly unnatural stimuli in simple search tasks while participant’s body movements were restricted. We present a study where we relieved many of these restrictions while retaining some control by using a gaze-contingent visual search task. In our study, participants had to find a target object out of 12 complex and everyday objects presented on a screen while the electrical activity of the brain and eye movements were recorded simultaneously. Our results show that our proposed method for the classification of fixation-related potentials can clearly discriminate between fixations on relevant, non-relevant and background areas. Furthermore, we show that our classification approach generalizes not only to different test sets from the same participant, but also across participants. These results promise to open novel avenues for exploiting fixation-related potentials in electroencephalography-based brain-machine interfaces and thus providing a novel means for intuitive human-machine interaction. PMID:26812487

Diversity and activity of nitrogen fixing archaea and bacteria associated with micro-environments of wetland rice

NASA Astrophysics Data System (ADS)

Schmidt, Hannes; Woebken, Dagmar

2017-04-01

Wetland rice is one of the world's most important crop plants. The cultivation on waterlogged paddy soils is strongly limited by nitrogen (N), which is typically supplied by industrial fertilizers that are not only costly but also exhibit hazardous effects on the environment. It has been reported that "Biological Nitrogen Fixation" through N2-fixing bacteria and archaea (diazotrophs) can alleviate the N-shortage in rice cultivation, thus carrying out an important ecosystem function. However, our understanding of the diversity and in situ N2 fixation activity of diazotrophs in flooded rice fields is still rudimentary. Moreover, knowledge on the impact of biochemical gradients established by root activity (i.e. exudation, radial oxygen loss) on the functioning of N-fixing microorganisms in paddy soil ecosystems is limited. We aimed at studying underlying processes on biologically relevant scales. Greenhouse studies were performed to identify key factors that control rice-diazotroph association and related N2 fixation activities. Paddy soils of different geographical origin were cultivated with two commercially used genotypes of wetland rice. Samples were separated into bulk soil, rhizosphere soil, rhizoplane, and roots at flowering stage of rice plant development. These samples were subjected to functional assays and various molecular biological techniques in order to analyze the associated diazotroph communities. Based on Illumina amplicon sequencing of nifH genes and transcripts, we show that the diversity and potential activity of diazotroph communities varies according to micro-environments. We will comparatively discuss the influence of (a) the soil microbial "seed bank" and (b) plant genotype in shaping the respective microbiomes and selecting for potentially active diazotrophs. Actual N2 fixation activities of soil-genotype combinations and micro-environments will be shown on the basis of incubation assays using 15N2-containing atmospheres. Areas of potential N-transfer between diazotrophs and rice roots will be presented via the detection and visualization of spatial colonization patterns of selected diazotrophic groups on rice rhizoplanes. Our approach will help to increase the understanding of the contribution of Biological Nitrogen Fixation to rice cultivation in paddy soil ecosystems.

Visual encoding and fixation target selection in free viewing: presaccadic brain potentials

PubMed Central

Nikolaev, Andrey R.; Jurica, Peter; Nakatani, Chie; Plomp, Gijs; van Leeuwen, Cees

2013-01-01

In scrutinizing a scene, the eyes alternate between fixations and saccades. During a fixation, two component processes can be distinguished: visual encoding and selection of the next fixation target. We aimed to distinguish the neural correlates of these processes in the electrical brain activity prior to a saccade onset. Participants viewed color photographs of natural scenes, in preparation for a change detection task. Then, for each participant and each scene we computed an image heat map, with temperature representing the duration and density of fixations. The temperature difference between the start and end points of saccades was taken as a measure of the expected task-relevance of the information concentrated in specific regions of a scene. Visual encoding was evaluated according to whether subsequent change was correctly detected. Saccades with larger temperature difference were more likely to be followed by correct detection than ones with smaller temperature differences. The amplitude of presaccadic activity over anterior brain areas was larger for correct detection than for detection failure. This difference was observed for short “scrutinizing” but not for long “explorative” saccades, suggesting that presaccadic activity reflects top-down saccade guidance. Thus, successful encoding requires local scanning of scene regions which are expected to be task-relevant. Next, we evaluated fixation target selection. Saccades “moving up” in temperature were preceded by presaccadic activity of higher amplitude than those “moving down”. This finding suggests that presaccadic activity reflects attention deployed to the following fixation location. Our findings illustrate how presaccadic activity can elucidate concurrent brain processes related to the immediate goal of planning the next saccade and the larger-scale goal of constructing a robust representation of the visual scene. PMID:23818877

Hot topics and controversies in arthroplasty: cementless femoral fixation in elderly patients.

PubMed

Dutton, Andrew; Rubash, Harry E

2008-01-01

Cementless femoral fixation has been established as the gold standard for hip arthroplasty in young patients because of its exceptional longevity. Because older Americans are living longer and staying active, cementless femoral fixation for hip arthroplasty should be considered in all patients who have good bone quality. Numerous studies have shown excellent results using cementless fixation for hip arthroplasty in elderly patients. Histologic analysis, radiographic review, and dual-energy x-ray absorptiometry have shown solid osseointegration for biologic fixation and minimal bone loss. Cementless fixation provides superb functional outcomes with results comparable to those achieved using cemented fixation for hip arthroplasty. Additional advantages of cementless femoral fixation include shorter surgical times and substantial savings in health care costs.

Biomechanical effect of interspinous process distraction height after lumbar fixation surgery: An in vitro model.

PubMed

Fu, Lin; Ma, Jianxiong; Lu, Bin; Jia, Haobo; Zhao, Jie; Kuang, Mingjie; Feng, Rui; Xu, Liyan; Bai, Haohao; Sun, Lei; Wang, Ying; Ma, Xinlong

2017-07-01

Pedicle screw fixation may induce abnormal activity at adjacent segment and accelerate the degeneration of lumbar vertebrae. Dynamic stabilizers could provide an intermediate solution between conservative treatment and fusion surgery. Lumbar vertebral segment cephalad to instrumented fixation was the most common localization of adjacent segment degeneration. The aim of this study is to explore the use of interspinous process devices in the lumbar vertebral segment cephalad to fixation segment in changing the mechanical distribution and limiting abnormal activity of the spine. Eight specimens were tested in the following groups: intact group, instability group (bilateral facetectomy at L3-L4), fixation group (bilateral facetectomy and pedicle screw fixation at L3-L4), and hybrid fixation group (fixation at L3-L4 and simulating interspinous device implantation of 6, 8, 10, 12, 14, 16, and 18 mm at L2-L3). Range of motion, motion of vertebral body, and strain distribution change were recorded. The range of motion in extension with 16- and 18-mm hybrid constructs was significantly lower than intact, instability, and fixation groups. In flexion and lateral bending, the strain values of L4 inferior articular process with 18-mm hybrid construct have a significant difference compared with other groups. In axial rotation, under the condition of a contralateral state, the strain values of L2 superior articular process with 18-mm hybrid construct have a significant difference compared with intact and fixation groups. The strain value of the L4 inferior articular process had negative correlation with height distraction in three dimensions, except extension. A negative correlation between the strain value of the L2 superior articular process and distraction height was found in contralateral bending and contralateral axial rotation. Interspinous process devices above the fixation segment can change the mechanical distribution of the spine and limit activity in some of the segments of the spine, which may delay the degeneration of the adjacent segment.

Image Guidance to Aid Pedicle Screw Fixation of a Lumbar Fracture-Dislocation Injury in a Toddler.

PubMed

Houten, John K; Nahkla, Jonathan; Ghandi, Shashank

2017-09-01

Pedicle screw fixation of the lumbar spine in children age <2 years is particularly challenging, as successful cannulation of the small pedicle dimensions requires a high level of precision and there are no implants specifically designed for the infant spine. Image-guided navigation is commonly used in adult spinal surgery and may be particularly helpful for the placement of spinal screws in areas where the bony anatomy is small and/or anatomically complex, as in the upper cervical area. A 19-month-old female presented with a fracture-dislocation injury of L1-2. Intraoperative imaging using the O-arm multidimensional imaging system was networked to a workstation, and neuronavigation was used to place pedicle instrumentation with 3.5-mm-diameter polyaxial screws designed for posterior cervical fixation. At a 48-month follow-up, the patient was neurologically intact, demonstrated normal physical development, and was engaging in normal physical activity for her age. Radiographs obtained approximately 4 years postsurgery showed no evidence of loss for fixation. Image-guided placement of pedicle screws may be a useful aid in achieving accurate and safe fixation in the small dimensions of the infant spine. Copyright © 2017 Elsevier Inc. All rights reserved.

Long-term results of various therapy concepts in severe pilon fractures.

PubMed

Koulouvaris, Panagiotis; Stafylas, Kosmas; Mitsionis, Gregory; Vekris, Marios; Mavrodontidis, Alexandros; Xenakis, Theodore

2007-07-01

Intra-articular fractures of the tibia plafond are among the most challenging of orthopaedic problems. This is a retrospective case-control study of surgically treated pilon fractures which was undertaken to compare the internal fixation with the two external fixation methods. This is a case-control study of 55 patients with 55 pilon fractures. There were 36 type C and 19 type B. Of these fractures, 24 were open and 31 closed. Three surgical protocols were used. In 20 patients, Group A, a half pin external fixator with ankle spanning was performed. The mean age of patients was 42.0 years (22.0-74.0), SD 14.1 and the mean follow-up was 77.7 months (38.0-132.0), SD 25.4. In 22 patients, Group B, a single ankle sparring ring hybrid external fixator under a small arthrotomy was performed. The mean age of patients was 48.4 years (28.0-76.0), SD 12.4 and mean follow-up was 67.9 months (36.0-132.0), SD 27.8. In 13 patients, Group C, a two-staged internal fixation was performed. The mean age was 45.6 years (30.0-66.0), SD 9.7 and the mean follow-up was 78.6 months (55.0-132.0), SD 25.4. We addressed the dissimilarity of the type of fracture in each group performing supplementary stratified analyses within each fracture type group. Group A had union in 6.9 months, group B in 5.6 months and group C in 5.1 months; P = 0.009. Six patients (Group A), two (Group B), and one (Group C) had limitation of ankle motion; P = 0.47. One patient from group C developed infection and the plate was removed. Four patients (Group A), one (Group B), and one (Group C) have developed posttraumatic arthritis (loss of joint space and pain); P = 0.25. Seven patients from Group A have reduced their activities; P = 0.004. In stratified statistical analysis by type of fracture, the associations noted for both fracture groups combined were also noted separately within each fracture group. In this long term follow-up study, the two-staged internal fixation and the hybrid fixation with small arthrotomy were equally efficacious in achieving bone union. Patients in external fixation with the ankle spanning had a significantly higher rate of delayed union. Also more patients in this group have reduced their activities.

Use of Resorbable Fixation System in Pediatric Facial Fractures.

PubMed

Wong, Frankie K; Adams, Saleigh; Hudson, Donald A; Ozaki, Wayne

2017-05-01

Resorbable fixation system (RFS) is an alternative to titanium in open reduction and internal fixation of pediatric facial fractures. This study retrospectively reviewed all medical records in a major metropolitan pediatric hospital in Cape Town, South Africa from September 2010 through May 2014. Inclusion criteria were children under the age of 13 with facial fractures who have undergone open reduction and internal fixation using RFS. Intraoperative and postoperative complications were reviewed. A total of 21 patients were included in this study. Twelve were males and 9 were females. Good dental occlusion was achieved in all patients and there were no complications intraoperatively. Three patients developed postoperative implanted-related complications: all 3 patients developed malocclusions and 1 developed an additional sterile abscess over the right zygomatic bone. For the latter, incision and drainage was performed and the problem resolved without additional operations. Resorbable fixation system is an alternative to titanium products in the setting of pediatric facial fractures without complications involving delayed union or malunion. The combination of intermaxillary fixation and RFS is not needed postoperatively for adequate fixation of mandible fractures. Resorbable fixation system is able to provide adequate internal fixation when both low-stress and high-stress craniofacial fractures occur simultaneously.

Patellar fixation protected with a load-sharing cable: a mechanical and clinical study.

PubMed

Perry, C R; McCarthy, J A; Kain, C C; Pearson, R L

1988-01-01

The stability of patellar fracture fixation protected with a load-sharing cable was studied in cadavers. A transverse patellar osteotomy was produced and stabilized with standard patellar fixation with or without a figure-of-eight cable that extends from the proximal pole of the patella to the tibial tubercle. Standard fixation techniques (interfragmentary cancellous screws or modified tension-band wiring) alone failed after significantly fewer cycles of flexion and extension than did the same fixation when supplemented with a load-sharing cable. In the clinical evaluation of the load-sharing cable, 14 consecutive patients with displaced patellar fractures were treated. No immobilization was used and the patients were started on passive and active range of motion and weight-bearing ambulation in the early postoperative period. Thirteen fractures healed uneventfully. The increased stability of patellar fracture fixation protected with a load-sharing cable offers three advantages: (a) adjunctive casting is unnecessary, (b) comminuted fractures can be "pieced" together anatomically with less concern for loss of fixation, and (c) early postoperative passive and active range of motion can be achieved.

N2-fixation dynamics during ecosystem recovery in longleaf pine savannas

NASA Astrophysics Data System (ADS)

Tierney, J. A.

2016-12-01

Biological nitrogen fixation (BNF) can alleviate nitrogen (N) deficiencies that inhibit ecosystem recovery. BNF may be particularly important in ecosystems recovering from land-use change and perturbations from fire, as these disturbances can exacerbate N limitation. Here, we investigated how BNF dynamics change throughout ecosystem development in restored longleaf pine savannas, and how BNF responds to fire. We conducted this study in 59 1-ha plots of longleaf pine distributed across gradients of stand age and fire frequency at two sites in the southeastern US. We determined BNF contributions by three functional groups of N2-fixers (herbaceous legumes, biological soil crusts, and asymbiotic N2-fixing bacteria) by quantifying their abundances, assessing nitrogenase activity, and scaling these estimates up to the plot-level. To determine aboveground N demands, we measured tree growth using diameter increments and allometric equations paired with tissue-specific N concentrations. We fit linear models to evaluate the effects of stand age and time since fire on BNF and N demands throughout stand development, and performed separate analyses on mature stands to determine how fire return interval affects BNF. We observed distinct temporal patterns of N2-fixation across stand development among the three groups of N2 fixers. N2-fixation by legumes and asymbiotic bacteria remained low until stands reached maturity, while N2-fixation by biological soil crusts (BSCs) was high in juvenile stands and decreased with stand age. These patterns suggest a compensatory shift in the importance of these functional groups throughout stand development such that contributions from BSCs are critical for meeting N demands when disturbances may hinder the establishment of legumes and asymbiotic bacteria. N2-fixation by BSCs and asymbiotic bacteria throughout stand development was not affected by time since fire, but legume abundance increased the year following fire, suggesting a recovery mechanism provided by this group. Our findings suggest that BSCs are the most important source of new N in the early phases of ecosystem restoration. In contrast, legumes appear to be critical in mature longleaf pine stands that burn frequently, and particularly for supplying new N in the year following a fire event.

Aphotic N2 fixation along an oligotrophic to ultraoligotrophic transect in the western tropical South Pacific Ocean

NASA Astrophysics Data System (ADS)

Benavides, Mar; Shoemaker, Katyanne M.; Moisander, Pia H.; Niggemann, Jutta; Dittmar, Thorsten; Duhamel, Solange; Grosso, Olivier; Pujo-Pay, Mireille; Hélias-Nunige, Sandra; Fumenia, Alain; Bonnet, Sophie

2018-05-01

The western tropical South Pacific (WTSP) Ocean has been recognized as a global hot spot of dinitrogen (N2) fixation. Here, as in other marine environments across the oceans, N2 fixation studies have focused on the sunlit layer. However, studies have confirmed the importance of aphotic N2 fixation activity, although until now only one had been performed in the WTSP. In order to increase our knowledge of aphotic N2 fixation in the WTSP, we measured N2 fixation rates and identified diazotrophic phylotypes in the mesopelagic layer along a transect spanning from New Caledonia to French Polynesia. Because non-cyanobacterial diazotrophs presumably need external dissolved organic matter (DOM) sources for their nutrition, we also identified DOM compounds using Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) with the aim of searching for relationships between the composition of DOM and non-cyanobacterial N2 fixation in the aphotic ocean. N2 fixation rates were low (average 0.63 ± 0.07 nmol N L-1 d-1) but consistently detected across all depths and stations, representing ˜ 6-88 % of photic N2 fixation. N2 fixation rates were not significantly correlated with DOM compounds. The analysis of nifH gene amplicons revealed a wide diversity of non-cyanobacterial diazotrophs, mostly matching clusters 1 and 3. Interestingly, a distinct phylotype from the major nifH subcluster 1G dominated at 650 dbar, coinciding with the oxygenated Subantarctic Mode Water (SAMW). This consistent pattern suggests that the distribution of aphotic diazotroph communities is to some extent controlled by water mass structure. While the data available are still too scarce to elucidate the distribution and controls of mesopelagic non-cyanobacterial diazotrophs in the WTSP, their prevalence in the mesopelagic layer and the consistent detection of active N2 fixation activity at all depths sampled during our study suggest that aphotic N2 fixation may contribute significantly to fixed nitrogen inputs in this area and/or areas downstream of water mass circulation.

Effects of long-term elevated CO2, warming, and prolonged drought on Pleurozium-associated diazotrophic activity and abundance

NASA Astrophysics Data System (ADS)

Dyrnum, Kristine; Priemé, Anders; Michelsen, Anders

2014-05-01

Nitrogen (N2) fixation is the primary natural influx of N to terrestrial ecosystems, and changes in N2 fixation may have consequences for primary productivity and thus ecosystem function. We studied the activity and abundance of diazotrophs associated with the feather moss Pleurozium schreberi in a temperate heathland, after seven years of global change manipulations, including elevated atmospheric CO2 (510 ppm), increased temperature (0.5-1.5 ° C), and prolonged pre-summer droughts (4-6 weeks /year). Acetylene reduction assay was carried out monthly to monitor N2 fixation rates throughout one year, while nif H copy abundance, serving as a diazotroph abundance estimate, was measured by quantitative polymerase chain reaction (q-PCR). Prolonged summer droughts significantly increased both N2 fixation and nif H copy abundance, contrasting previous studies that demonstrate a direct negative correlation between N2 fixation and water availability. A shift in the relative abundance of N2-fixing bacteria from the green, upper parts of the moss stem to the lower, brown parts was observed. This shift could make diazotrophs less sensitive to desiccation, enabling N2 fixation to be upheld for longer during drought and thus causing higher abundance. Increased temperature likewise had a positive effect on the diazotroph abundance, although this did not translate into increased activity. Possibly, warming protects diazotrophs during extreme cold events, while actual N2 fixation is limited by water, disregarding a rise in potential N2 fixation caused by higher abundance. Increased CO2 caused no significant diazotroph response. Our study showed that long-term increase in temperature and recurrent drought events cause higher diazotroph abundance in Pleurozium schreberi and thus enhance the potential N2 fixations rate. Furthermore, our results indicate that diazotrophs may alter colonization patterns and thereby actively remain in the moss fraction less likely affected by desiccation. In consequence, Pleurozium-associated N2 fixation may become an even more important contributor of N for terrestrial ecosystems in a predicted future climate.

Treatment of Unicameral Bone Cysts of the Proximal Femur With Internal Fixation Lessens the Risk of Additional Surgery.

PubMed

Wilke, Benjamin; Houdek, Matthew; Rao, Rameshwar R; Caird, Michelle S; Larson, A Noelle; Milbrandt, Todd

2017-09-01

Little data exist to guide the treatment of unicameral bone cysts in the proximal femur. Methods of treatment include corticosteroid injections, curettage and bone grafting, and internal fixation. The authors completed a multi-institutional, retrospective review to evaluate their experience with proximal femoral unicameral bone cysts. They posed the following questions: (1) Does internal fixation reduce the risk of further procedures for the treatment of a unicameral bone cyst? (2) Is radiographic healing faster with internal fixation? Following institutional review board approval, the authors conducted a retrospective review of 36 patients treated for a unicameral bone cyst of the proximal femur at their institutions between 1974 and 2014. Medical records and radiographs were reviewed to identify patient demographics and treatment outcomes. Tumor locations included femoral neck (n=13), intertrochanteric (n=16), and subtrochanteric (n=7). Initial treatment included steroid injection (n=2), curettage and bone grafting (n=9), and internal fixation with curettage and bone grafting (n=25). Mean time was 9 months to radiographic healing and 15 months to return to full activity. The number of patients requiring additional surgeries was increased among those who did not undergo internal fixation. There was no difference in time to radiographic healing. However, time to return to normal activities was reduced if patients had received internal fixation. A significant reduction in additional procedures was observed when patients had been treated with internal fixation. Although this did not influence time to radiographic healing, patients did return to normal activities sooner. Internal fixation should be considered in the treatment of proximal femoral unicameral bone cysts. [Orthopedics. 2017; 40(5):e862-e867.]. Copyright 2017, SLACK Incorporated.

Impact of Pacemaker Lead Characteristics on Pacemaker Related Infection and Heart Perforation: A Nationwide Population-Based Cohort Study.

PubMed

Lin, Yu-Sheng; Chen, Tien-Hsing; Hung, Sheng-Ping; Chen, Dong Yi; Mao, Chun-Tai; Tsai, Ming-Lung; Chang, Shih-Tai; Wang, Chun-Chieh; Wen, Ming-Shien; Chen, Mien-Cheng

2015-01-01

Several risk factors for pacemaker (PM) related complications have been reported. However, no study has investigated the impact of lead characteristics on pacemaker-related complications. Patients who received a new pacemaker implant from January 1997 to December 2011 were selected from the Taiwan National Health Insurance Database. This population was grouped according to the pacemaker lead characteristics in terms of fixation and insulation. The impact of the characteristics of leads on early heart perforation was analyzed by multivariable logistic regression analysis, while the impact of the lead characteristics on early and late infection and late heart perforation over a three-year period were analyzed using Cox regression. This study included 36,104 patients with a mean age of 73.4±12.5 years. In terms of both early and late heart perforations, there were no significant differences between groups across the different types of fixation and insulations. In the multivariable Cox regression analysis, the pacemaker-related infection rate was significantly lower in the active fixation only group compared to either the both fixation (OR, 0.23; 95% CI, 0.07-0.80; P = 0.020) or the passive fixation group (OR, 0.26; 95% CI, 0.08-0.83; P = 0.023). There was no difference in heart perforation between active and passive fixation leads. Active fixation leads were associated with reduced risk of pacemaker-related infection.

Pacemaker Implantation Associated Myocardial Micro-Damage: A Randomised Comparison between Active and Passive Fixation Leads.

PubMed

Blažek, Patrick; Ferri-Certić, Jerko; Vražić, Hrvoje; Lennerz, Carsten; Grebmer, Christian; Kaitani, Kazuaki; Karch, Martin; Starčević, Boris; Semmler, Verena; Kolb, Christof

2018-03-20

Fixation of the pacemaker leads during pacemaker implantation leads to an increase of cardiac Troponin T (cTnT) that can be interpreted as a sign of minimal myocardial damage. This trial evaluates whether the mechanism type of lead fixation influences the magnitude of cTnT release. Patients having a de-novo cardiac pacemaker implantation or a lead revision were centrally randomized to receive either a ventricular lead with an active (screw) or passive (tine) fixation mechanism. High-sensitive Troponin T (hsTnT) was determined on the day of the procedure beforehand and on the following day. 326 Patients (median age (IQR) 75.0 (69.0-80.0) years, 64% male) from six international centers were randomized to receive ventricular leads with an active (n = 166) or passive (n = 160) fixation mechanism. Median (IQR) hsTnT levels increased by 0.009 (0.004-0.021) ng/ml in the group receiving screw-in ventricular leads and by 0.008 (0.003-0.030) ng/ml in the group receiving tined ventricular leads (n.s.). In conclusion pacemaker implantations are followed by a release of hsTnT. The choice between active or passive fixation ventricular leads does not have a significant influence on the extent of myocardial injury and the magnitude of hsTnT release.

Biomechanical principles and mechanobiologic aspects of flexible and locked plating.

PubMed

Claes, Lutz

2011-02-01

The goal of minimally invasive surgery in extramedullary internal fixation has led to the development of flexible plates, bridging plates, and locked internal fixators. The change from conventional compression plates to these new implants, however, resulted in different biomechanics of fixation and different mechanobiologic processes for fracture healing. The aim of a flexible fixation is the stimulation of fracture healing by callus formation. Fracture healing follows mechanobiologic rules based mainly on interfragmentary strain, which is dependent on the stability of the fixation construct and the type of fracture. Knowledge of the mechanobiologic processes and the factors influencing the stability of fracture fixation are necessary for the surgeon to choose the correct technique for fracture fixation. Problems in the selection of the correct technique and limitations with the available implants as well as possible future developments are discussed.

[Development and current situation of reconstruction methods following total sacrectomy].

PubMed

Huang, Siyi; Ji, Tao; Guo, Wei

2018-05-01

To review the development of the reconstruction methods following total sacrectomy, and to provide reference for finding a better reconstruction method following total sacrectomy. The case reports and biomechanical and finite element studies of reconstruction following total sacrectomy at home and abroad were searched. Development and current situation were summarized. After developing for nearly 30 years, great progress has been made in the reconstruction concept and fixation techniques. The fixation methods can be summarized as the following three strategies: spinopelvic fixation (SPF), posterior pelvic ring fixation (PPRF), and anterior spinal column fixation (ASCF). SPF has undergone technical progress from intrapelvic rod and hook constructs to pedicle and iliac screw-rod systems. PPRF and ASCF could improve the stability of the reconstruction system. Reconstruction following total sacrectomy remains a challenge. Reconstruction combining SPF, PPRF, and ASCF is the developmental direction to achieve mechanical stability. How to gain biological fixation to improve the long-term stability is an urgent problem to be solved.

Biotube

NASA Technical Reports Server (NTRS)

Richards, Stephanie E. (Compiler); Levine, Howard G.; Romero, Vergel

2016-01-01

Biotube was developed for plant gravitropic research investigating the potential for magnetic fields to orient plant roots as they grow in microgravity. Prior to flight, experimental seeds are placed into seed cassettes, that are capable of containing up to 10 seeds, and inserted between two magnets located within one of three Magnetic Field Chamber (MFC). Biotube is stored within an International Space Station (ISS) stowage locker and provides three levels of containment for chemical fixatives. Features include monitoring of temperature, fixative/ preservative delivery to specimens, and real-time video imaging downlink. Biotube's primary subsystems are: (1) The Water Delivery System that automatically activates and controls the delivery of water (to initiate seed germination). (2) The Fixative Storage and Delivery System that stores and delivers chemical fixative or RNA later to each seed cassette. (3) The Digital Imaging System consisting of 4 charge-coupled device (CCD) cameras, a video multiplexer, a lighting multiplexer, and 16 infrared light-emitting diodes (LEDs) that provide illumination while the photos are being captured. (4) The Command and Data Management System that provides overall control of the integrated subsystems, graphical user interface, system status and error message display, image display, and other functions.

Kinetics of nif Gene Expression in a Nitrogen-Fixing Bacterium

PubMed Central

Poza-Carrión, César; Jiménez-Vicente, Emilio; Navarro-Rodríguez, Mónica; Echavarri-Erasun, Carlos

2014-01-01

Nitrogen fixation is a tightly regulated trait. Switching from N2 fixation-repressing conditions to the N2-fixing state is carefully controlled in diazotrophic bacteria mainly because of the high energy demand that it imposes. By using quantitative real-time PCR and quantitative immunoblotting, we show here how nitrogen fixation (nif) gene expression develops in Azotobacter vinelandii upon derepression. Transient expression of the transcriptional activator-encoding gene, nifA, was followed by subsequent, longer-duration waves of expression of the nitrogenase biosynthetic and structural genes. Importantly, expression timing, expression levels, and NifA dependence varied greatly among the nif operons. Moreover, the exact concentrations of Nif proteins and their changes over time were determined for the first time. Nif protein concentrations were exquisitely balanced, with FeMo cofactor biosynthetic proteins accumulating at levels 50- to 100-fold lower than those of the structural proteins. Mutants lacking nitrogenase structural genes or impaired in FeMo cofactor biosynthesis showed overenhanced responses to derepression that were proportional to the degree of nitrogenase activity impairment, consistent with the existence of at least two negative-feedback regulatory mechanisms. The first such mechanism responded to the levels of fixed nitrogen, whereas the second mechanism appeared to respond to the levels of the mature NifDK component. Altogether, these findings provide a framework to engineer N2 fixation in nondiazotrophs. PMID:24244007

Kinetics of Nif gene expression in a nitrogen-fixing bacterium.

PubMed

Poza-Carrión, César; Jiménez-Vicente, Emilio; Navarro-Rodríguez, Mónica; Echavarri-Erasun, Carlos; Rubio, Luis M

2014-02-01

Nitrogen fixation is a tightly regulated trait. Switching from N2 fixation-repressing conditions to the N2-fixing state is carefully controlled in diazotrophic bacteria mainly because of the high energy demand that it imposes. By using quantitative real-time PCR and quantitative immunoblotting, we show here how nitrogen fixation (nif) gene expression develops in Azotobacter vinelandii upon derepression. Transient expression of the transcriptional activator-encoding gene, nifA, was followed by subsequent, longer-duration waves of expression of the nitrogenase biosynthetic and structural genes. Importantly, expression timing, expression levels, and NifA dependence varied greatly among the nif operons. Moreover, the exact concentrations of Nif proteins and their changes over time were determined for the first time. Nif protein concentrations were exquisitely balanced, with FeMo cofactor biosynthetic proteins accumulating at levels 50- to 100-fold lower than those of the structural proteins. Mutants lacking nitrogenase structural genes or impaired in FeMo cofactor biosynthesis showed overenhanced responses to derepression that were proportional to the degree of nitrogenase activity impairment, consistent with the existence of at least two negative-feedback regulatory mechanisms. The first such mechanism responded to the levels of fixed nitrogen, whereas the second mechanism appeared to respond to the levels of the mature NifDK component. Altogether, these findings provide a framework to engineer N2 fixation in nondiazotrophs.

Are watershed and lacustrine controls on planktonic N2 fixation hierarchically structured?

PubMed

Scott, J Thad; Doyle, Robert D; Prochnow, Shane J; White, Joseph D

2008-04-01

N2 fixation can be an important source of N to limnetic ecosystems and can influence the structure of phytoplankton communities. However, watershed-scale conditions that favor N2 fixation in lakes and reservoirs have not been well studied. We measured N2 fixation and lacustrine variables monthly over a 19-month period in Waco Reservoir, Texas, USA, and linked these data with nutrient-loading estimates from a physically based watershed model. Readily available topographic, soil, land cover, effluent discharge, and climate data were used in the Soil and Water Assessment Tool (SWAT) to derive watershed nutrient-loading estimates. Categorical and regression tree (CART) analysis revealed that lacustrine and watershed correlates of N2 fixation were hierarchically structured. Lacustrine conditions showed greater predictive capability temporally. For instance, low NO3(-) concentration (<25 microg N/L) and high water temperatures (>27 degrees C) in the reservoir were correlated with the initiation of N2 fixation seasonally. When lacustrine conditions were favorable for N2 fixation, watershed conditions appeared to influence spatial patterns of N2 fixation within the reservoir. For example, spatially explicit patterns of N2 fixation were correlated with the ratio of N:P in nutrient loadings and the N loading rate, which were driven by anthropogenic activity in the watershed and periods of low stream flow, respectively. Although N2 fixation contributed <5% of the annual N load to the reservoir, 37% of the N load was derived from atmospheric N2 fixation during summertime when stream flow in the watershed was low. This study provides evidence that watershed anthropogenic activity can exert control on planktonic N2 fixation, but that temporality is controlled by lacustrine conditions. Furthermore, this study also supports suggestions that reduced inflows may increase the propensity of N2-fixing cyanobacterial blooms in receiving waters of anthropogenically modified landscapes.

Methanotrophy Induces Nitrogen Fixation in Boreal Mosses

NASA Astrophysics Data System (ADS)

Tiirola, M. A.

2014-12-01

Many methanotrophic bacterial groups fix nitrogen in laboratory conditions. Furthermore, nitrogen (N) is a limiting nutrient in many environments where methane concentrations are highest. Despite these facts, methane-induced N fixation has previously been overlooked, possibly due to methodological problems. To study the possible link between methanotrophy and diazotrophy in terrestrial and aquatic habitats, we measured the co-occurrence of these two processes in boreal forest, peatland and stream mosses using a stable isotope labeling approach (15 N2 and 13 CH4 double labeling) and sequencing of the nifH gene marker. N fixation associated with forest mosses was dependent on the annual N deposition, whereas methane stimulate N fixation neither in high (>3 kg N ha -1 yr -1) nor low deposition areas, which was in accordance with the nifH gene sequencing showing that forest mosses (Pleurozium schreberi and Hylocomium splendens ) carried mainly cyanobacterial N fixers. On the other extreme, in stream mosses (Fontinalis sp.) methane was actively oxidized throughout the year, whereas N fixation showed seasonal fluctuation. The co-occurrence of the two processes in single cell level was proven by co-localizing both N and methane-carbon fixation with the secondary ion mass spectrometry (SIMS) approach. Methanotrophy and diazotrophy was also studied in peatlands of different primary successional stages in the land-uplift coast of Bothnian Bay, in the Siikajoki chronosequence, where N accumulation rates in peat profiles indicate significant N fixation. Based on experimental evidence it was counted that methane-induced N fixation explained over one-third of the new N input in the younger peatland successional stages, where the highest N fixation rates and highest methane oxidation activities co-occurred in the water-submerged Sphagnum moss vegetation. The linkage between methanotrophic carbon cycling and N fixation may therefore constitute an important mechanism in the rapid accumulation of N during the primary succession of peatlands. It is still an open issue whether methanotrophy induces N fixation directly or by enhancing phototrophic or heterotrophic N fixation.

Stimulation of nitrogen fixation in soddy-podzolic soils with fungi

NASA Astrophysics Data System (ADS)

Kurakov, A. V.; Prokhorov, I. S.; Kostina, N. V.; Makhova, E. G.; Sadykova, V. S.

2006-09-01

Stimulation of nitrogen fixation in soddy-podzolic soils is related to the hydrolytic activity of fungi decomposing plant polymers. It was found that the rate of nitrogen fixation upon the simultaneous inoculation of the strains of nitrogen-fixing bacteria Bacillus cereus var. mycoides and the cellulolytic fungus Trichoderma asperellum into a sterile soil enriched with cellulose or Jerusalem artichoke residues is two to four times higher than upon the inoculation of the strains of Bacillus cereus var. mycoides L1 only. The increase in the nitrogen fixation depended on the resistance of the substrates added into the soil to fungal hydrolysis. The biomass of the fungi decomposing plant polymers increased by two-four times. The nitrogen-fixing activity of the soil decreased when the growth of the fungi was inhibited with cycloheximide, which attested to a close correlation between the intensity of the nitrogen fixation and the decomposition of the plant polymers by fungi. The introduction of an antifungal antibiotic, together with starch or with plant residues, significantly (by 60-90%) decreased the rate of nitrogen fixation in the soll.

Cell fixation and preservation for droplet-based single-cell transcriptomics.

PubMed

Alles, Jonathan; Karaiskos, Nikos; Praktiknjo, Samantha D; Grosswendt, Stefanie; Wahle, Philipp; Ruffault, Pierre-Louis; Ayoub, Salah; Schreyer, Luisa; Boltengagen, Anastasiya; Birchmeier, Carmen; Zinzen, Robert; Kocks, Christine; Rajewsky, Nikolaus

2017-05-19

Recent developments in droplet-based microfluidics allow the transcriptional profiling of thousands of individual cells in a quantitative, highly parallel and cost-effective way. A critical, often limiting step is the preparation of cells in an unperturbed state, not altered by stress or ageing. Other challenges are rare cells that need to be collected over several days or samples prepared at different times or locations. Here, we used chemical fixation to address these problems. Methanol fixation allowed us to stabilise and preserve dissociated cells for weeks without compromising single-cell RNA sequencing data. By using mixtures of fixed, cultured human and mouse cells, we first showed that individual transcriptomes could be confidently assigned to one of the two species. Single-cell gene expression from live and fixed samples correlated well with bulk mRNA-seq data. We then applied methanol fixation to transcriptionally profile primary cells from dissociated, complex tissues. Low RNA content cells from Drosophila embryos, as well as mouse hindbrain and cerebellum cells prepared by fluorescence-activated cell sorting, were successfully analysed after fixation, storage and single-cell droplet RNA-seq. We were able to identify diverse cell populations, including neuronal subtypes. As an additional resource, we provide 'dropbead', an R package for exploratory data analysis, visualization and filtering of Drop-seq data. We expect that the availability of a simple cell fixation method will open up many new opportunities in diverse biological contexts to analyse transcriptional dynamics at single-cell resolution.

Adjustable stiffness, external fixator for the rat femur osteotomy and segmental bone defect models.

PubMed

Glatt, Vaida; Matthys, Romano

2014-10-09

The mechanical environment around the healing of broken bone is very important as it determines the way the fracture will heal. Over the past decade there has been great clinical interest in improving bone healing by altering the mechanical environment through the fixation stability around the lesion. One constraint of preclinical animal research in this area is the lack of experimental control over the local mechanical environment within a large segmental defect as well as osteotomies as they heal. In this paper we report on the design and use of an external fixator to study the healing of large segmental bone defects or osteotomies. This device not only allows for controlled axial stiffness on the bone lesion as it heals, but it also enables the change of stiffness during the healing process in vivo. The conducted experiments have shown that the fixators were able to maintain a 5 mm femoral defect gap in rats in vivo during unrestricted cage activity for at least 8 weeks. Likewise, we observed no distortion or infections, including pin infections during the entire healing period. These results demonstrate that our newly developed external fixator was able to achieve reproducible and standardized stabilization, and the alteration of the mechanical environment of in vivo rat large bone defects and various size osteotomies. This confirms that the external fixation device is well suited for preclinical research investigations using a rat model in the field of bone regeneration and repair.

Regional alterations in long bone /sup 85/Sr clearance produced by internal fixation devices. Part II. Histomorphometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simmons, D.J.; Daum, W.J.; Calhoun, J.H.

1988-01-01

The effects of each of the surgical stages involved in compression plating on the development of cortical thinning and porosity were assessed in the intact midshaft, stress-shielded femoral segments of adult mongrel dogs 6 months postoperatively. The data were evaluated in terms of a postsurgical tetracycline-based measure of remodeling and terminal /sup 85/Sr clearance (SrC) values for the plated segments of bone. Drilling had no effect on any parameter. Screw application was associated with minimal cortical thinning (p less than 0.05), while plate fixation clearly promoted thinning (p less than 0.01) and porosity (p less than 0.05). The percentage ofmore » labeled osteons, a measure of remodeling activity, increased only after plate fixation (p less than 0.05), and the labeling patterns suggested that most osteons had formed during the first 4 postsurgical months. That none of these changes were correlated with the 6-month SrC values suggests that the development of plate-induced osteopenia involves disparate histomorphometric time constants, rather than lack of any association.« less

Two MicroRNAs Linked to Nodule Infection and Nitrogen-Fixing Ability in the Legume Lotus japonicus1[W

PubMed Central

De Luis, Ana; Markmann, Katharina; Cognat, Valérie; Holt, Dennis B.; Charpentier, Myriam; Parniske, Martin; Stougaard, Jens; Voinnet, Olivier

2012-01-01

Legumes overcome nitrogen shortage by developing root nodules in which symbiotic bacteria fix atmospheric nitrogen in exchange for host-derived carbohydrates and mineral nutrients. Nodule development involves the distinct processes of nodule organogenesis, bacterial infection, and the onset of nitrogen fixation. These entail profound, dynamic gene expression changes, notably contributed to by microRNAs (miRNAs). Here, we used deep-sequencing, candidate-based expression studies and a selection of Lotus japonicus mutants uncoupling different symbiosis stages to identify miRNAs involved in symbiotic nitrogen fixation. Induction of a noncanonical miR171 isoform, which targets the key nodulation transcription factor Nodulation Signaling Pathway2, correlates with bacterial infection in nodules. A second candidate, miR397, is systemically induced in the presence of active, nitrogen-fixing nodules but not in that of noninfected or inactive nodule organs. It is involved in nitrogen fixation-related copper homeostasis and targets a member of the laccase copper protein family. These findings thus identify two miRNAs specifically responding to symbiotic infection and nodule function in legumes. PMID:23071252

Lexical Activation during Sentence Comprehension in Adolescents with History of Specific Language Impairment

PubMed Central

Borovsky, Arielle; Burns, Erin; Elman, Jeffrey L.; Evans, Julia L.

2015-01-01

One remarkable characteristic of speech comprehension in typically developing (TD) children and adults is the speed with which the listener can integrate information across multiple lexical items to anticipate upcoming referents. Although children with Specific Language Impairment (SLI) show lexical deficits (Sheng & McGregor, 2010) and slower speed of processing (Leonard et al., 2007), relatively little is known about how these deficits manifest in real-time sentence comprehension. In this study, we examine lexical activation in the comprehension of simple transitive sentences in adolescents with a history of SLI and age-matched, TD peers. Participants listened to sentences that consisted of the form, Article-Agent-Action-Article-Theme, (e.g., The pirate chases the ship) while viewing pictures of four objects that varied in their relationship to the Agent and Action of the sentence (e.g., Target, Agent-Related, Action-Related, and Unrelated). Adolescents with SLI were as fast as their TD peers to fixate on the sentence’s final item (the Target) but differed in their post-action onset visual fixations to the Action-Related item. Additional exploratory analyses of the spatial distribution of their visual fixations revealed that the SLI group had a qualitatively different pattern of fixations to object images than did the control group. The findings indicate that adolescents with SLI integrate lexical information across words to anticipate likely or expected meanings with the same relative fluency and speed as do their TD peers. However, the failure of the SLI group to show increased fixations to Action-Related items after the onset of the action suggests lexical integration deficits that result in failure to consider alternate sentence interpretations. PMID:24099807

N sub 2 -fixation by freshly isolated Nostoc from coralloid roots of the cycad Macrozamia riedlei (Fisch. ex Gaud. ) Gardn

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lindblad, P.; Atkins, C.A.; Pate, J.S.

1991-03-01

Nitrogenase (EC 1.7.99.2) activity (acetylene reduction) and nitrogen fixation ({sup 15}N{sub 2} fixation) were measured in cyanobacteria freshly isolated from the coralloid roots of Macrozamia riedlei (Fisch. ex Gaud.) Gardn. The data indicate that cyanobacteria within cycad coralloid roots are differentiated specifically for symbiotic functioning in a microaerobic environment. Specializations include a high heterocyst frequency, enhanced permeability to O{sub 2}, and a direct dependence on the cycad for substrates to support nitrogenase activity.

Biomechanical consequences of callus development in Hoffmann, Wagner, Orthofix and Ilizarov external fixators.

PubMed

Juan, J A; Prat, J; Vera, P; Hoyos, J V; Sánchez-Lacuesta, J; Peris, J L; Dejoz, R; Alepuz, R

1992-09-01

A theoretical analysis by a finite elements model (FEM) of some external fixators (Hoffmann, Wagner, Orthofix and Ilizarov) was carried out. This study considered a logarithmic progress of callus elastic characteristics. A standard configuration of each fixator was defined where design and application characteristics were modified. A comparison among standard configurations and influence of every variation was made with regard to displacement and load transmission at the fracture site. An experimental evaluation of standard configurations was performed with a testing machine. After experimental validation of the theoretical model was achieved, an application of physiological loads which act on a fractured limb during normal gait was analysed. A minimal contribution from an external fixator to the total rigidity of the bone-callus-fixator system was assessed when a callus showing minimum elastic characteristics had just been established. Insufficient rigidity from the fixation devices to assure an adequate immobilization during the early stages of fracture healing was verified. However, regardless of the external fixator, callus development was the overriding element for the rigidity of the fixator-bone system.

Kinetics of transfemoral amputees with osseointegrated fixation performing common activities of daily living.

PubMed

Lee, Winson C C; Frossard, Laurent A; Hagberg, Kerstin; Haggstrom, Eva; Brånemark, Rickard; Evans, John H; Pearcy, Mark J

2007-07-01

Direct anchorage of a lower-limb prosthesis to the bone through an implanted fixation (osseointegration) has been suggested as an excellent alternative for amputees experiencing complications from use of a conventional socket-type prosthesis. However, an attempt needs to be made to optimize the mechanical design of the fixation and refine the rehabilitation program. Understanding the load applied on the fixation is a crucial step towards this goal. The load applied on the osseointegrated fixation of nine transfemoral amputees was measured using a load transducer, when the amputees performed activities which included straight-line level walking, ascending and descending stairs and a ramp as well as walking around a circle. Force and moment patterns along each gait cycle, magnitudes and time of occurrence of the local extrema of the load, as well as impulses were analysed. Managing a ramp and stairs, and walking around a circle did not produce a significant increase (P>0.05) in load compared to straight-line level walking. The patterns of the moment about the medio-lateral axis were different among the six activities which may reflect the different strategies used in controlling the prosthetic knee joint. This study increases the understanding of biomechanics of bone-anchored osseointegrated prostheses. The loading data provided will be useful in designing the osseointegrated fixation to increase the fatigue life and to refine the rehabilitation protocol.

History of internal fixation (part 1): early developments with wires and plates before World War II.

PubMed

Hernigou, Philippe; Pariat, Jacques

2017-06-01

Though the date at which an orthopaedic implant was first used cannot be ascertained with any certainty, the fixation of bone fracture using an iron wire was reported for the first time in a French manuscript in 1775. The first techniques of operative fracture treatment were developed at the end of the 18th and in the beginning of the 19th centuries. The use of cerclage wires to fix fractures was the most frequent fixation at this time. The French Berenger-Feraud (1832-1900) had written the first book on internal fixation. However internal fixation of fractures could not become a practical method before Lister had ensured the safety of open reduction and internal fixation in the treatment of fractures. Lister is not only the father of asepsis; he also used metal wires to fix even closed fractures. The first internal fixation by means of a plate and screws was described by Carl Hansmann in 1858 in Hamburg. Nevertheless, Arbuthnot Lane (1892) and Albin Lambotte (1905) are considered to be the founders of this method, which was further developed by Sherman in the first part of the 20th century.

Biological N2 fixation mainly controlled by Sphagnum tissue N:P ratio in ombrotrophic bogs

NASA Astrophysics Data System (ADS)

Zivkovic, Tatjana; Moore, Tim R.

2017-04-01

Most of the 18 Pg nitrogen (N) accumulated in northern nutrient-poor and Sphagnum-dominated peatlands (bogs and fens) can be attributed to N2-fixation by diazotrophs either associated with the live Sphagnum or non-symbiotically in the deeper peat such as through methane consumption close to the water table. Where atmospheric N deposition is low (< 0.2 g m-2 y-1), ombrotrophic bogs rely on N2-fixation as the primary source of N that sustains primary production. Due to high energetic requirements, N2-fixation depends on the available phosphorus (P). Anthropogenic impacts in the last 200 years increased atmospheric N deposition, resulting in a switch from N to P limitation in Sphagnum, suggested by the increase in tissue N:P to >16. It is unclear how Sphagnum-hosted diazotrophic activity may be affected by N deposition and thus changes in N:P ratio. First, we investigated the effects of long-term addition of different sources of nitrogen (0, 1.6, 3.2 and 6.4 g N m-2 y-1as NH4Cl and NaNO3), and phosphorus (5 g P m-2 y-1as KH2PO4) on Sphagnum nutrient status (N, P and N:P ratio), net primary productivity (NPP) and Sphagnum-associated N2fixation at Mer Bleue, a temperate ombrotrophic bog. We show that N concentration in Sphagnum tissue increased with larger rates of N addition, with a stronger effect on Sphagnum from NH4 than NO3. The addition of P created a 3.5 fold increase in Sphagnum P content compared to controls. Sphagnum NPP decreased linearly with the rise in N:P ratio, while linear growth declined exponentially with increase in Sphagnum N content. Rates of N2-fixation determined in the laboratory significantly decreased in response to even the smallest addition of both N species. In contrast, the addition of P increased N2 fixation by up to 100 times compared to N treatments and up to 5-30 times compared to controls. The change in N2-fixation was best modeled by the N:P ratio, across all experimental treatments. Secondly, to test the role of N:P ratio on N2-fixation across a range of bogs, eight study sites along the latitudinal gradient from temperate, boreal to subarctic zone in eastern Canada were selected. From each bog, two predominant microptopographies, hummocks and hollows, were tested for both N2-fixation activity in the laboratory and Sphagnum tissue concentrations of N, P and N:P ratio. We found that 65% of the variance in the increase of N2-fixation activity was explained by the decrease in N:P ratio in hollows (n = 73) but only about 20% in hummocks (n = 78). Changes in neither N or P concentration alone explained the increase in N2-fixation better than N:P ratio. We interpret that the difference between hollows and hummocks results from the availability of moisture that further limits N2-fixation. When moisture is not a limiting factor, i.e. in hollows, N:P ratio will be the best predictor of N2-fixation in bogs. Both studies suggest that the relative P availability to Sphagnum-associated diazotrophs, measured as a tissue N:P ratio, best describes N2-fixation activity in bogs, especially ones exposed to larger N deposition.

Nitrogen fixation in a non-heterocystous cyanobacterial mat from a mountain river

NASA Astrophysics Data System (ADS)

Berrendero, Esther; Valiente, Eduardo Fernández; Perona, Elvira; Gómez, Claudia L.; Loza, Virginia; Muñoz-Martín, M. Ángeles; Mateo, Pilar

2016-08-01

In situ nitrogen fixation was investigated in a cyanobacterial mat growing on the bed of rocks of the Muga River, Spain. The filamentous non-heterocystous cyanobacterium Schizothrix dominated the mat, showing nitrogenase activity in the light at similar rates to those found in nearby heterocystous Rivularia colonies. N2 fixation in the light was significantly increased by an inhibitor of PSII and oxygen evolution, DCMU (3-[3,4-dichlorophenyl]-1,1-dimethylurea), and anaerobic conditions. However, no nitrogenase activity was found in the dark. Addition of fructose as a respiratory substrate induced nitrogenase activity in samples incubated under aerobic conditions in the dark but not in anaerobic conditions. Microelectrode oxygen profiles showed internal microaerobic microzones where nitrogen fixation might concentrate. Analyses of the 16S rRNA gene revealed only the presence of sequences belonging to filamentous non-heterocystous cyanobacteria. nifH gene diversity showed that the major phylotypes also belonged to this group. One of the three strains isolated from the Schizothrix mat was capable of fixing N2 and growing in the absence of combined N. This was consistent with the nifH gene analysis. These results suggest a relevant contribution of non-heterocystous cyanobacteria to nitrogen fixation in these mats.

Development of second generation gold-supported palladium material with low-leaching and recyclable characteristics in aromatic amination.

PubMed

Al-Amin, Mohammad; Arai, Satoshi; Hoshiya, Naoyoki; Honma, Tetsuo; Tamenori, Yusuke; Sato, Takatoshi; Yokoyama, Mami; Ishii, Akira; Takeuchi, Masashi; Maruko, Tomohiro; Shuto, Satoshi; Arisawa, Mitsuhiro

2013-08-02

An improved process for the preparation of sulfur-modified gold-supported palladium material [SAPd, second generation] is presented. The developed preparation method is safer and generates less heat (aqueous Na2S2O8 and H2SO4) for sulfur fixation on a gold surface, and it is superior to the previous method of preparing SAPd (first generation), which requires the use of the more heat-generating and dangerous piranha solution (concentrated H2SO4 and 35% H2O2) in the sulfur fixation step. This safer and improved preparation method is particularly important for the mass production of SAPd (second generation) for which the catalytic activity was examined in ligand-free Buchwald-Hartwig cross-coupling reactions. The catalytic activities were the same between the first and second generation SAPds in aromatic aminations, but the lower palladium leaching properties and safer preparative method of second generation SAPd are a significant improvement over the first generation SAPd.

Nitrogen fixation rates associated with the invasive macroalgae Sargassum horneri around Catalina Island, CA

NASA Astrophysics Data System (ADS)

DeLiberto, A.

2016-02-01

Nitrogen fixation is an important process which allows organisms access to biologically unavailable dinitrogen gas. Bacteria, known as diazotrophs use the enzyme nitrogenase to convert N2 to NH3. These bacteria, including certain species of heterotrophic bacteria and cyanobacteria, can be symbiotically associated with marine macroalgae, facilitating nutrient cycling in oligotrophic regions. As many species within the genera Sargassum are associated with nitrogen fixation, this study hypothesized that nitrogenase activity would be associated with the benthic invasive Sargassum horneri on Catalina Island. In the past decade, Sargassum horneri, an invasive from Japan, has spread throughout the waters around Catalina Island. Using the acetylene reduction procedure using flame ionization detection, initial nitrogenase activity of S. horneri sampled from Indian Rock was observed. Nitrogen fixation rates increased with decomposition, particularly in dark/anaerobic treatments, suggesting the presence of heterotrophic bacteria. In addition, acetate additions greatly increase nitrogen fixation rates, once again indicating heterotrophic nitrogen fixing bacteria.

Photosynthetic activity during olive (Olea europaea) leaf development correlates with plastid biogenesis and Rubisco levels.

PubMed

Maayan, Inbar; Shaya, Felix; Ratner, Kira; Mani, Yair; Lavee, Shimon; Avidan, Benjamin; Shahak, Yosepha; Ostersetzer-Biran, Oren

2008-11-01

Olive leaves are known to mature slowly, reaching their maximum photosynthetic activity only after full leaf expansion. Poor assimilation rates, typical to young olive leaves, were previously associated with low stomata conductance. Yet, very little is known about chloroplast biogenesis throughout olive leaf development. Here, the photosynthetic activity and plastids development throughout leaf maturation is characterized by biochemical and ultrastructural analyses. Although demonstrated only low photosynthetic activity, the plastids found in young leaves accumulated both photosynthetic pigments and proteins required for photophosphorylation and carbon fixation. However, Rubisco (ribulose-1,5-bisphosphate carboxylase-oxygenase), which catalyzes the first major step of carbon fixation and one of the most abundant proteins in plants, could not be detected in the young leaves and only slowly accumulated throughout development. In fact, Rubisco levels seemed tightly correlated with the observed photosynthetic activities. Unlike Rubisco, numerous proteins accumulated in the young olive leaves. These included the early light induced proteins, which may be required to reduce the risk of photodamage, because of light absorption by photosynthetic pigments. Also, high levels of ribosomal L11 subunit, transcription factor elF-5A, Histones H2B and H4 were observed in the apical leaves, and in particular a plastidic-like aldolase, which accounted for approximately 30% of the total proteins. These proteins may upregulate in their levels to accommodate the high demand for metabolic energy in the young developing plant tissue, further demonstrating the complex sink-to-source relationship between young and photosynthetically active mature leaves.

Molecular Ecological and Stable Isotopic Studies of Nitrogen Fixation in Modern Microbial Mats

NASA Technical Reports Server (NTRS)

Bebout, B. M.; Crumbliss, L. L.; DesMarais, D. J.; Hogan, M. E.; Omoregie, E.; Turk, K. A.; Zehr, J. P.

2003-01-01

Nitrogen is usually the element limiting biological productivity in the marine environment. Microbial mats, laminated microbial communities analogous to some of the oldest forms of life on Earth, are often the sites of high rates of N fixation (the energetically expensive conversion of atmospheric dinitrogen into a biologically useful form). The N fixing enzyme nitrogenase is generally considered to be of ancient origin, and is widely distributed throughout the Bacterial and Archaeal domains of life, indicating an important role for this process over evolutionary time. The stable isotopic signature of N fixation is purportedly recognizable in organic matter (ancient kerogens as well as present-day microbial mats) as a delta (15)N(sub organic) near zero. We studied two microbial mats exhibiting different rates of N fixation in order to better understand the impact of N fixation on the delta (15)N (sub organic) of the mats, as well as what organisms are important in this process. Mats dominated by the cyanobacterium Microcoleus chthonoplastes grow in permanently submerged hypersaline salterns, and exhibit low rates of N fixation, whereas mats dominated by the cyanobacterium Lyngbya spp grow in an intertidal area, and exhibit rates of N fixation an order of magnitude higher. To examine successional stages in mat growth, both developing and established mats at each location were sampled. PCR and RT-PCR based approaches were used to identify, respectively, the organisms containing nifH (one of the genes that encode nitrogenase) as well as those expressing nifH in these mats. Both mats exhibited a distinct diel cycle of N fixation, with highest rates occurring at night. The delta (15)N(sub organic) of the subtidal Microcoleus mats is near zero whereas the delta (15)N(sub organic) is slightly more positive (+ 2-3%), in the intertidal Lyngbya mats, an interesting difference in view of the fact that overall rates of activity in the intertidal mats are much higher that those in the submerged hypersaline mats. Developing mats in both the subtidal and intertidal locations had delta (15)N(sub organic) values very near those of the established mats. Further work is necessary in order to determine the importance of other transformations of nitrogen on the delta (15)N(sub organic) signature of the mats.

Eying the future: Eye movement in past and future thinking.

PubMed

El Haj, Mohamad; Lenoble, Quentin

2017-06-07

We investigated eye movement during past and future thinking. Participants were invited to retrieve past events and to imagine future events while their scan path was recorded by an eye-tracker. Past thinking triggered more fixation (p < .05), and saccade counts (p < .05) than future thinking. Past and future thinking triggered a similar duration of fixations and saccades, as well as a similar amplitude of saccades. Interestingly, participants rated past thinking as more vivid than future thinking (p < .01). Therefore, the vividness of past thinking seems to be accompanied by an increased number of fixations and saccades. Fixations and saccades in past thinking can be interpreted as an attempt by the visual system to find (through saccades) and activate (through fixations) stored memory representations. The same interpretation can be applied to future thinking as this ability requires activation of past experiences. However, future thinking triggers fewer fixations and saccades than past thinking: this may be due to its decreased demand on visual imagery, but could also be related to a potentially deleterious effect of eye movements on spatial imagery required for future thinking. Copyright © 2017 Elsevier Ltd. All rights reserved.

Symbiosis revisited: phosphorus and acid buffering stimulate N2 fixation but not Sphagnum growth

NASA Astrophysics Data System (ADS)

van den Elzen, Eva; Kox, Martine A. R.; Harpenslager, Sarah F.; Hensgens, Geert; Fritz, Christian; Jetten, Mike S. M.; Ettwig, Katharina F.; Lamers, Leon P. M.

2017-03-01

In pristine Sphagnum-dominated peatlands, (di)nitrogen (N2) fixing (diazotrophic) microbial communities associated with Sphagnum mosses contribute substantially to the total nitrogen input, increasing carbon sequestration. The rates of symbiotic nitrogen fixation reported for Sphagnum peatlands, are, however, highly variable, and experimental work on regulating factors that can mechanistically explain this variation is largely lacking. For two common fen species (Sphagnum palustre and S. squarrosum) from a high nitrogen deposition area (25 kg N ha-1 yr-1), we found that diazotrophic activity (as measured by 15 - 15N2 labeling) was still present at a rate of 40 nmol N gDW-1 h-1. This was surprising, given that nitrogen fixation is a costly process. We tested the effects of phosphorus availability and buffering capacity by bicarbonate-rich water, mimicking a field situation in fens with stronger groundwater or surface water influence, as potential regulators of nitrogen fixation rates and Sphagnum performance. We expected that the addition of phosphorus, being a limiting nutrient, would stimulate both diazotrophic activity and Sphagnum growth. We indeed found that nitrogen fixation rates were doubled. Plant performance, in contrast, did not increase. Raised bicarbonate levels also enhanced nitrogen fixation, but had a strong negative impact on Sphagnum performance. These results explain the higher nitrogen fixation rates reported for minerotrophic and more nutrient-rich peatlands. In addition, nitrogen fixation was found to strongly depend on light, with rates 10 times higher in light conditions suggesting high reliance on phototrophic organisms for carbon. The contrasting effects of phosphorus and bicarbonate on Sphagnum spp. and their diazotrophic communities reveal strong differences in the optimal niche for both partners with respect to conditions and resources. This suggests a trade-off for the symbiosis of nitrogen fixing microorganisms with their Sphagnum hosts, in which a sheltered environment apparently outweighs the less favorable environmental conditions. We conclude that microbial activity is still nitrogen limited under eutrophic conditions because dissolved nitrogen is being monopolized by Sphagnum. Moreover, the fact that diazotrophic activity can significantly be upregulated by increased phosphorus addition and acid buffering, while Sphagnum spp. do not benefit, reveals remarkable differences in optimal conditions for both symbiotic partners and calls into question the regulation of nitrogen fixation by Sphagnum under these eutrophic conditions. The high nitrogen fixation rates result in high additional nitrogen loading of 6 kg ha-1 yr-1 on top of the high nitrogen deposition in these ecosystems.

Fixation of displaced subcapital femoral fractures. Compression screw fixation versus double divergent pins.

PubMed

Christie, J; Howie, C R; Armour, P C

1988-03-01

One hundred and twenty-seven consecutive patients with displaced subcapital fractures of the femoral neck (Garden Grade III or IV) all under 80 years of age and independently mobile, were randomly allocated to fixation with either double divergent pins or a single sliding screw-plate device. The incidence of non-union and infection in the sliding screw-plate group was significantly higher, and we believe that when internal fixation is considered appropriate multiple pinning should be used. Mobility after treatment was disappointing in about half of the patients, and we feel that internal fixation can only be justified in patients who are physiologically well preserved and who maintain a high level of activity.

Nitrogen Fixation in Thermophilic Chemosynthetic Microbial Communities Depending on Hydrogen, Sulfate, and Carbon Dioxide

PubMed Central

Nishihara, Arisa; Haruta, Shin; McGlynn, Shawn E.; Thiel, Vera; Matsuura, Katsumi

2018-01-01

The activity of nitrogen fixation measured by acetylene reduction was examined in chemosynthetic microbial mats at 72–75°C in slightly-alkaline sulfidic hot springs in Nakabusa, Japan. Nitrogenase activity markedly varied from sampling to sampling. Nitrogenase activity did not correlate with methane production, but was detected in samples showing methane production levels less than the maximum amount, indicating a possible redox dependency of nitrogenase activity. Nitrogenase activity was not affected by 2-bromo-ethane sulfonate, an inhibitor of methanogenesis. However, it was inhibited by the addition of molybdate, an inhibitor of sulfate reduction and sulfur disproportionation, suggesting the involvement of sulfate-reducing or sulfur-disproportionating organisms. Nitrogenase activity was affected by different O2 concentrations in the gas phase, again supporting the hypothesis of a redox potential dependency, and was decreased by the dispersion of mats with a homogenizer. The loss of activity that occurred from dispersion was partially recovered by the addition of H2, sulfate, and carbon dioxide. These results suggested that the observed activity of nitrogen fixation was related to chemoautotrophic sulfate reducers, and fixation may be active in a limited range of ambient redox potential. Since thermophilic chemosynthetic communities may resemble ancient microbial communities before the appearance of photosynthesis, the present results may be useful when considering the ancient nitrogen cycle on earth. PMID:29367473

Active Segmentation.

PubMed

Mishra, Ajay; Aloimonos, Yiannis

2009-01-01

The human visual system observes and understands a scene/image by making a series of fixations. Every fixation point lies inside a particular region of arbitrary shape and size in the scene which can either be an object or just a part of it. We define as a basic segmentation problem the task of segmenting that region containing the fixation point. Segmenting the region containing the fixation is equivalent to finding the enclosing contour- a connected set of boundary edge fragments in the edge map of the scene - around the fixation. This enclosing contour should be a depth boundary.We present here a novel algorithm that finds this bounding contour and achieves the segmentation of one object, given the fixation. The proposed segmentation framework combines monocular cues (color/intensity/texture) with stereo and/or motion, in a cue independent manner. The semantic robots of the immediate future will be able to use this algorithm to automatically find objects in any environment. The capability of automatically segmenting objects in their visual field can bring the visual processing to the next level. Our approach is different from current approaches. While existing work attempts to segment the whole scene at once into many areas, we segment only one image region, specifically the one containing the fixation point. Experiments with real imagery collected by our active robot and from the known databases 1 demonstrate the promise of the approach.

Fixation procedure for transmission electron microscopy of Chara rhizoids under microgravity in a Spacelab (IML-2).

PubMed

Braun, M; Buchen, B; Sievers, A

1996-06-27

A special fixation device and fixation procedure have been developed to investigate for the first time the ultrastructure of gravity-sensing, unicellular Chara rhizoids grown for 30 h under microgravity (MG) conditions during the IML-2 mission. The fixation unit allowed culture, fixation and storage of Chara rhizoids in the same chamber without transferring the samples. The procedure was easy and safe to perform and required a minimum of crew time. Rhizoids fixated with glutaraldehyde in space and further processed for electron microscopy on ground showed that the fixation was of high quality and corresponded to the fixation quality of rhizoids in the ground controls. Thus, the equipment accomplished the manifold problems related to the physical effects of MG. The polarity of the rhizoids was maintained in MG. Well-preserved organelles and microtubules showed no obvious difference in ultrastructure or distribution after 30-h growth in MG compared to ground controls. The statoliths were more randomly distributed, however, only up to 50 microns basal to the tip. Thus, changing the gravity conditions does to disturb the cellular organisation of the rhizoids enabling the tip-growing cells to follow their genetic program in development and growth also under MG.

The Role of Minimally Invasive Plate Osteosynthesis in Rib Fixation: A Review

PubMed Central

Bemelman, Michael; van Baal, Mark; Yuan, Jian Zhang; Leenen, Luke

2016-01-01

More than a century ago, the first scientific report was published about fracture fixation with plates. During the 1950’s, open reduction and plate fixation for fractures were standardized by the founders of Arbeitsgemeinschaft für osteosynthesefragen/Association for the Study of Internal Fixation. Since the introduction of plate fixation for fractures, several plates and screws have been developed, all with their own characteristics. To accomplice more fracture stability, it was thought the bigger the plate, the better. The counter side was a compromised blood supply of the bone, often resulting in bone necrosis and ultimately delayed or non-union. With the search and development of new materials and techniques for fracture fixation, less invasive procedures have become increasingly popular. This resulted in the minimally invasive plate osteosynthesis (MIPO) technique for fracture fixation. With the MIPO technique, procedures could be performed with smaller incisions and thus with less soft tissue damage and a better preserved blood supply. The last 5 years rib fixation has become increasingly popular, rising evidence has become available suggesting that surgical rib fixation improves outcome of patients with a flail chest or isolated rib fractures. Many surgical approaches for rib fixation have been described in the old literature, however, most of these techniques are obscure nowadays. Currently mostly large incisions with considerable surgical insult are used to stabilize rib fractures. We think that MIPO deserves a place in the surgical treatment of rib fractures. We present the aspects of diagnosis, preoperative planning and operative techniques in regard to MIPO rib fixation. PMID:26889439

The Acetylene-Ethylene Assay for N2 Fixation: Laboratory and Field Evaluation 1

PubMed Central

Hardy, R. W. F.; Holsten, R. D.; Jackson, E. K.; Burns, R. C.

1968-01-01

The methodology, characteristics and application of the sensitive C2H2-C2H4 assay for N2 fixation by nitrogenase preparations and bacterial cultures in the laboratory and by legumes and free-living bacteria in situ is presented in this comprehensive report. This assay is based on the N2ase-catalyzed reduction of C2H2 to C2H4, gas chromatographic isolation of C2H2 and C2H4, and quantitative measurement with a H2-flame analyzer. As little as 1 μμmole C2H4 can be detected, providing a sensitivity 103-fold greater than is possible with 15N analysis. A simple, rapid and effective procedure utilizing syringe-type assay chambers is described for the analysis of C2H2-reducing activity in the field. Applications to field samples included an evaluation of N2 fixation by commercially grown soybeans based on over 2000 analyses made during the course of the growing season. Assay values reflected the degree of nodulation of soybean plants and indicated a calculated seasonal N2 fixation rate of 30 to 33 kg N2 fixed per acre, in good agreement with literature estimates based on Kjeldahl analyses. The assay was successfully applied to measurements of N2 fixation by other symbionts and by free living soil microorganisms, and was also used to assess the effects of light and temperature on the N2 fixing activity of soybeans. The validity of measuring N2 fixation in terms of C2H2 reduction was established through extensive comparisons of these activities using defined systems, including purified N2ase preparations and pure cultures of N2-fixing bacteria. With this assay it now becomes possible and practicable to conduct comprehensive surveys of N2 fixation, to make detailed comparisons among different N2-fixing symbionts, and to rapidly evaluate the effects of cultural practices and environmental factors on N2 fixation. The knowledge obtained through extensive application of this assay should provide the basis for efforts leading to the maximum agricultural exploitation of the N2 fixation reaction. PMID:16656902

Biomechanical stability of a supra-acetabular pedicle screw internal fixation device (INFIX) vs external fixation and plates for vertically unstable pelvic fractures.

PubMed

Vigdorchik, Jonathan M; Esquivel, Amanda O; Jin, Xin; Yang, King H; Onwudiwe, Ndidi A; Vaidya, Rahul

2012-09-27

We have recently developed a subcutaneous anterior pelvic fixation technique (INFIX). This internal fixator permits patients to sit, roll over in bed and lie on their sides without the cumbersome external appliances or their complications. The purpose of this study was to evaluate the biomechanical stability of this novel supraacetabular pedicle screw internal fixation construct (INFIX) and compare it to standard internal fixation and external fixation techniques in a single stance pelvic fracture model. Nine synthetic pelves with a simulated anterior posterior compression type III injury were placed into three groups (External Fixator, INFIX and Internal Fixation). Displacement, total axial stiffness, and the stiffness at the pubic symphysis and SI joint were calculated. Displacement and stiffness were compared by ANOVA with a Bonferroni adjustment for multiple comparisons The mean displacement at the pubic symphysis was 20, 9 and 0.8 mm for external fixation, INFIX and internal fixation, respectively. Plate fixation was significantly stiffer than the INFIX and external Fixator (P = 0.01) at the symphysis pubis. The INFIX device was significantly stiffer than external fixation (P = 0.017) at the symphysis pubis. There was no significant difference in SI joint displacement between any of the groups. Anterior plate fixation is stiffer than both the INFIX and external fixation in single stance pelvic fracture model. The INFIX was stiffer than external fixation for both overall axial stiffness, and stiffness at the pubic symphysis. Combined with the presumed benefit of minimizing the complications associated with external fixation, the INFIX may be a more preferable option for temporary anterior pelvic fixation in situations where external fixation may have otherwise been used.

Solar Water Splitting and Nitrogen Fixation with Layered Bismuth Oxyhalides.

PubMed

Li, Jie; Li, Hao; Zhan, Guangming; Zhang, Lizhi

2017-01-17

Hydrogen and ammonia are the chemical molecules that are vital to Earth's energy, environmental, and biological processes. Hydrogen with renewable, carbon-free, and high combustion-enthalpy hallmarks lays the foundation of next-generation energy source, while ammonia furnishes the building blocks of fertilizers and proteins to sustain the lives of plants and organisms. Such merits fascinate worldwide scientists in developing viable strategies to produce hydrogen and ammonia. Currently, at the forefronts of hydrogen and ammonia syntheses are solar water splitting and nitrogen fixation, because they go beyond the high temperature and pressure requirements of methane stream reforming and Haber-Bosch reaction, respectively, as the commercialized hydrogen and ammonia production routes, and inherit the natural photosynthesis virtues that are green and sustainable and operate at room temperature and atmospheric pressure. The key to propelling such photochemical reactions lies in searching photocatalysts that enable water splitting into hydrogen and nitrogen fixation to make ammonia efficiently. Although the past 40 years have witnessed significant breakthroughs using the most widely studied TiO 2 , SrTiO 3 , (Ga 1-x Zn x )(N 1-x O x ), CdS, and g-C 3 N 4 for solar chemical synthesis, two crucial yet still unsolved issues challenge their further progress toward robust solar water splitting and nitrogen fixation, including the inefficient steering of electron transportation from the bulk to the surface and the difficulty of activating the N≡N triple bond of N 2 . This Account details our endeavors that leverage layered bismuth oxyhalides as photocatalysts for efficient solar water splitting and nitrogen fixation, with a focus on addressing the above two problems. We first demonstrate that the layered structures of bismuth oxyhalides can stimulate an internal electric field (IEF) that is capable of efficiently separating electrons and holes after their formation and of precisely channeling their migration from the bulk to the surface along the different directions, thus enabling more electrons to reach the surface for water splitting and nitrogen fixation. Simultaneously, their oxygen termination feature and the strain differences between interlayers and intralayers render the easy generation of surface oxygen vacancies (OVs) that afford Lewis-base and unsaturated-unsaturated sites for nitrogen activation. With these rationales as the guideline, we can obtain striking visible-light hydrogen- and ammonia-evolving rates without using any noble-metal cocatalysts. Then we show how to utilize IEF and OV based strategies to improve the solar water splitting and nitrogen fixation performances of bismuth oxyhalide photocatalysts. Finally, we highlight the challenges remaining in using bismuth oxyhalides for solar hydrogen and ammonia syntheses, and the prospect of further development of this research field. We believe that our mechanistic insights could serve as a blueprint for the design of more efficient solar water splitting and nitrogen fixation systems, and layered bismuth oxyhalides might open up new photocatalyst paradigm for such two solar chemical syntheses.

The small unicellular diazotrophic symbiont, UCYN-A, is a key player in the marine nitrogen cycle.

PubMed

Martínez-Pérez, Clara; Mohr, Wiebke; Löscher, Carolin R; Dekaezemacker, Julien; Littmann, Sten; Yilmaz, Pelin; Lehnen, Nadine; Fuchs, Bernhard M; Lavik, Gaute; Schmitz, Ruth A; LaRoche, Julie; Kuypers, Marcel M M

2016-09-12

Microbial dinitrogen (N 2 ) fixation, the nitrogenase enzyme-catalysed reduction of N 2 gas into biologically available ammonia, is the main source of new nitrogen (N) in the ocean. For more than 50 years, oceanic N 2 fixation has mainly been attributed to the activity of the colonial cyanobacterium Trichodesmium 1,2 . Other smaller N 2 -fixing microorganisms (diazotrophs)-in particular the unicellular cyanobacteria group A (UCYN-A)-are, however, abundant enough to potentially contribute significantly to N 2 fixation in the surface waters of the oceans 3-6 . Despite their abundance, the contribution of UCYN-A to oceanic N 2 fixation has so far not been directly quantified. Here, we show that in one of the main areas of oceanic N 2 fixation, the tropical North Atlantic 7 , the symbiotic cyanobacterium UCYN-A contributed to N 2 fixation similarly to Trichodesmium. Two types of UCYN-A, UCYN-A1 and -A2, were observed to live in symbioses with specific eukaryotic algae. Single-cell analyses showed that both algae-UCYN-A symbioses actively fixed N 2 , contributing ∼20% to N 2 fixation in the tropical North Atlantic, revealing their significance in this region. These symbioses had growth rates five to ten times higher than Trichodesmium, implying a rapid transfer of UCYN-A-fixed N into the food web that might significantly raise their actual contribution to N 2 fixation. Our analysis of global 16S rRNA gene databases showed that UCYN-A occurs in surface waters from the Arctic to the Antarctic Circle and thus probably contributes to N 2 fixation in a much larger oceanic area than previously thought. Based on their high rates of N 2 fixation and cosmopolitan distribution, we hypothesize that UCYN-A plays a major, but currently overlooked role in the oceanic N cycle.

Sporicidal activity of chemical and physical tissue fixation methods.

PubMed Central

Vardaxis, N J; Hoogeveen, M M; Boon, M E; Hair, C G

1997-01-01

AIMS: The effects of alcohol based fixation and microwave stimulated alcohol fixation were investigated on spores of Bacillus stearothermophilus and Bacillus subtilis (var. niger). METHODS: Spores were exposed to 10% formalin, or different concentrations of various alcohol containing fixatives (Kryofix/Spuitfix). Adequate controls were also set up in conjunction with the test solutions. The spores were immersed with and without adjunctive microwave stimulation in the various solutions tested. Possible surviving spores were recovered in revival broth and after incubation, and Gram staining viable counts were performed. RESULTS: Alcohol based fixatives did not have a sporicidal effect on B stearothermophilus or B subtilis (var. niger) spores, and microwave stimulated alcohol fixation at 450 W and up to 75 degrees C did not have a sporicidal effect. CONCLUSIONS: When alcohol based fixatives are used for fixation, precautions should be taken with the material thus treated, as it may contain viable spores or other pathogens, which are destroyed after 24 hours of formalin treatment. Of the physicochemical methods tested involving microwaving, none was successful in eliminating viable spores from the test material. PMID:9215128

Nitrogen fixation activity in biological soil crusts dominated by cyanobacteria in the Subpolar Urals (European North-East Russia).

PubMed

Patova, Elena; Sivkov, Michail; Patova, Anna

2016-09-01

The nitrogen fixation by biological soil crusts with a dominance of cyanobacteria was studied using the acetylene reduction assay in the territory of the Subpolar Urals (65°11' N, 60°18' E), Russia. The field measurements of nitrogen fixation activity were conducted in situ for two different types of soil crusts dominated by Stigonema (V1 type) and Nostoc with Scytonema (V2 type). The nitrogen fixation process had similar dynamics in both crusts but nitrogen fixation rates were different. The crusts of the V2 type showed a significantly higher acetylene reduction activity, with ethylene production rate of 1.76 ± 0.49 g C2H4 m(-2) h(-1) at 15°C, compared with V1-type soil crusts, with a rate of 0.53 ± 0.21 mg C2H4 m(-2) h(-1) at 15°C. The daily value of acetylene reduction activity in V2-type soil crusts was 32.7 ± 6.2 mg C2H4 m(-2) d(-1) and in V1-type crusts, 12.3 ± 1.8 mg C2H4 m(-2) d(-1) After recalculation for N, the daily values of nitrogen fixation were in the range 3.3-22.3 mg N m(-2) d(-1), which is a few times higher than the values of N input from the precipitation to the soil in the studied regions. The dependence of nitrogen-fixation activity on temperature and light intensity of biological soil crusts was investigated. On the basis of temperature models obtained from the dependence, the nitrogen balance was calculated for the growing season (approximately 120 days). The crusts dominated by Stigonema species were fixing 0.3 g N m(-2) (ethylene production rate, 1.10 g C2H4 m(-2)) and crusts dominated by Nostoc and Scytonema were fixing 1.3 g N m(-2) (4.10 g C2H4 m(-2)). © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

FIXATION OF FISH TISSUES. IN: THE LABORATORY FISH.

EPA Science Inventory

This chapter deals with the fixation of fish tissues and whole fish. Traditionally, fixation has been applied to animal tissues mainly for histological or pathological studies. Development of new molecular and immunologic tools now allows tissue and cellular localization of nucle...

3D perfusion bioreactor-activated porous granules on implant fixation and early bone formation in sheep.

PubMed

Ding, Ming; Henriksen, Susan S; Martinetti, Roberta; Overgaard, Søren

2017-11-01

Early fixation of total joint arthroplasties is crucial for ensuring implant survival. An alternative bone graft material in revision surgery is needed to replace the current gold standard, allograft, seeing that the latter is associated with several disadvantages. The incubation of such a construct in a perfusion bioreactor has been shown to produce viable bone graft materials. This study aimed at producing larger amounts of viable bone graft material (hydroxyapatite 70% and β-tricalcium-phosphate 30%) in a novel perfusion bioreactor. The abilities of the bioreactor-activated graft material to induce early implant fixation were tested in a bilateral implant defect model in sheep, with allograft as the control group. Defects were bilaterally created in the distal femurs of the animals, and titanium implants were inserted. The concentric gaps around the implants were randomly filled with either allograft, granules, granules with bone marrow aspirate or bioreactor-activated graft material. Following an observation time of 6 weeks, early implant fixation and bone formation were assessed by micro-CT scanning, mechanical testing, and histomorphometry. Bone formations were seen in all groups, while no significant differences between groups were found regarding early implant fixation. The microarchitecture of the bone formed by the synthetic graft materials resembled that of allograft. Histomorphometry revealed that allograft induced significantly more bone and less fibrous tissue (p < 0.05). In conclusion, bone formation was observed in all groups, while the bioreactor-activated graft material did not reveal additional effects on early implant fixation comparable to allograft in this model. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2465-2476, 2017. © 2016 Wiley Periodicals, Inc.

Fixation of carbon dioxide into dimethyl carbonate over titanium-based zeolitic thiophene-benzimidazolate framework

EPA Science Inventory

A titanium-based zeolitic thiophene-benzimidazolate framework has been designed for the direct synthesis of dimethyl carbonate (DMC) from methanol and carbon dioxide. The developed catalyst activates carbon dioxide and delivers over 16% yield of DMC without the use of any dehydra...

Long-term non-invasive and continuous measurements of legume nodule activity.

PubMed

Cabeza, Ricardo A; Liese, Rebecca; Fischinger, Stephanie A; Sulieman, Saad; Avenhaus, Ulrike; Lingner, Annika; Hein, Hans; Koester, Beke; Baumgarten, Vanessa; Dittert, Klaus; Schulze, Joachim

2015-02-01

Symbiotic nitrogen fixation is a process of considerable economic, ecological and scientific interest. The central enzyme nitrogenase reduces H(+) alongside N2 , and the evolving H2 allows a continuous and non-invasive in vivo measurement of nitrogenase activity. The objective of this study was to show that an elaborated set-up providing such measurements for periods as long as several weeks will produce specific insight into the nodule activity's dependence on environmental conditions and genotype features. A system was developed that allows the air-proof separation of a root/nodule and a shoot compartment. H2 evolution in the root/nodule compartment can be monitored continuously. Nutrient solution composition, temperature, CO2 concentration and humidity around the shoots can concomitantly be maintained and manipulated. Medicago truncatula plants showed vigorous growth in the system when relying on nitrogen fixation. The set-up was able to provide specific insights into nitrogen fixation. For example, nodule activity depended on the temperature in their surroundings, but not on temperature or light around shoots. Increased temperature around the nodules was able to induce higher nodule activity in darkness versus light around shoots for a period of as long as 8 h. Conditions that affected the N demand of the shoots (ammonium application, Mg or P depletion, super numeric nodules) induced consistent and complex daily rhythms in nodule activity. It was shown that long-term continuous measurements of nodule activity could be useful for revealing special features in mutants and could be of importance when synchronizing nodule harvests for complex analysis of their metabolic status. © 2014 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.

Nitrogen Fixation By Sulfate-Reducing Bacteria in Coastal and Deep-Sea Sediments

NASA Astrophysics Data System (ADS)

Bertics, V. J.; Löscher, C.; Salonen, I.; Schmitz-Streit, R.; Lavik, G.; Kuypers, M. M.; Treude, T.

2011-12-01

Sulfate-reducing bacteria (SRB) can greatly impact benthic nitrogen (N) cycling, by for instance inhibiting coupled denitrification-nitrification through the production of sulfide or by increasing the availability of fixed N in the sediment via dinitrogen (N2)-fixation. Here, we explored several coastal and deep-sea benthic habitats within the Atlantic Ocean and Baltic Sea, for the occurrence of N2-fixation mediated by SRB. A combination of different methods including microbial rate measurements of N2-fixation and sulfate reduction, geochemical analyses (porewater nutrient profiles, mass spectrometry), and molecular analyses (CARD-FISH, HISH-SIMS, "nested" PCR, and QPCR) were applied to quantify and identify the responsible processes and organisms, respectively. Furthermore, we looked deeper into the question of whether the observed nitrogenase activity was associated with the final incorporation of N into microbial biomass or whether the enzyme activity served another purpose. At the AGU Fall Meeting, we will present and compare data from numerous stations with different water depths, temperatures, and latitudes, as well as differences in key geochemical parameters, such as organic carbon content and oxygen availability. Current metabolic and molecular data indicate that N2-fixation is occurring in many of these benthic environments and that a large part of this activity may linked to SRB.

Calibration and standardization of microwave ovens for fixation of brain and peripheral nerve tissue.

PubMed

Login, G R; Leonard, J B; Dvorak, A M

1998-06-01

Rapid and reproducible fixation of brain and peripheral nerve tissue for light and electron microscopy studies can be done in a microwave oven. In this review we report a standardized nomenclature for diverse fixation techniques that use microwave heating: (1) microwave stabilization, (2) fast and ultrafast primary microwave-chemical fixation, (3) microwave irradiation followed by chemical fixation, (4) primary chemical fixation followed by microwave irradiation, and (5) microwave fixation used in various combinations with freeze fixation. All of these methods are well suited to fix brain tissue for light microscopy. Fast primary microwave-chemical fixation is best for immunoelectron microscopy studies. We also review how the physical characteristics of the microwave frequency and the dimensions of microwave oven cavities can compromise microwave fixation results. A microwave oven can be calibrated for fixation when the following parameters are standardized: irradiation time; water load volume, initial temperature, and placement within the oven; fixative composition, volume, and initial temperature; and specimen container shape and placement within the oven. Using two recently developed calibration tools, the neon bulb array and the agar-saline-Giemsa tissue phantom, we report a simple calibration protocol that identifies regions within a microwave oven for uniform microwave fixation. Copyright 1998 Academic Press.

Symbiotic Nitrogen Fixation and the Challenges to Its Extension to Nonlegumes

PubMed Central

Mus, Florence; Crook, Matthew B.; Garcia, Kevin; Garcia Costas, Amaya; Geddes, Barney A.; Kouri, Evangelia D.; Paramasivan, Ponraj; Ryu, Min-Hyung; Oldroyd, Giles E. D.; Poole, Philip S.; Udvardi, Michael K.; Voigt, Christopher A.

2016-01-01

Access to fixed or available forms of nitrogen limits the productivity of crop plants and thus food production. Nitrogenous fertilizer production currently represents a significant expense for the efficient growth of various crops in the developed world. There are significant potential gains to be had from reducing dependence on nitrogenous fertilizers in agriculture in the developed world and in developing countries, and there is significant interest in research on biological nitrogen fixation and prospects for increasing its importance in an agricultural setting. Biological nitrogen fixation is the conversion of atmospheric N2 to NH3, a form that can be used by plants. However, the process is restricted to bacteria and archaea and does not occur in eukaryotes. Symbiotic nitrogen fixation is part of a mutualistic relationship in which plants provide a niche and fixed carbon to bacteria in exchange for fixed nitrogen. This process is restricted mainly to legumes in agricultural systems, and there is considerable interest in exploring whether similar symbioses can be developed in nonlegumes, which produce the bulk of human food. We are at a juncture at which the fundamental understanding of biological nitrogen fixation has matured to a level that we can think about engineering symbiotic relationships using synthetic biology approaches. This minireview highlights the fundamental advances in our understanding of biological nitrogen fixation in the context of a blueprint for expanding symbiotic nitrogen fixation to a greater diversity of crop plants through synthetic biology. PMID:27084023

Inactivation of Lactobacillus rhamnosus GG by fixation modifies its probiotic properties.

PubMed

Markowicz, C; Kubiak, P; Grajek, W; Schmidt, M T

2016-01-01

Probiotics are microorganisms that have beneficial effects on the host and are safe for oral intake in a suitable dose. However, there are situations in which the administration of living microorganisms poses a risk for immunocompromised host. The objective of this study was to evaluate the influence of several fixation methods on selected biological properties of Lactobacillus rhamnosus GG that are relevant to its probiotic action. Fixation of the bacterial cells with ethanol, 2-propanol, glutaraldehyde, paraformaldehyde, and heat treatment resulted in a significant decrease of alkaline phosphatase, peroxidase, and β-galactosidase activities. Most of the fixation procedures reduced bacterial cell hydrophobicity and increased adhesion capacity. The fixation procedures resulted in a different perception of the bacterial cells by enterocytes, which was shown as changes in gene expression in enterocytes. The results show that some procedures of inactivation allow a fraction of the enzymatic activity to be maintained. The adhesion properties of the bacterial cells were enhanced, but the response of enterocytes to fixed cells was different than to live bacteria. Inactivation allows maintenance and modification of some of the properties of the bacterial cells.

External fixation of "intertrochanteric" fractures.

PubMed

Gani, Naseem Ul; Kangoo, Khursheed Ahmed; Bashir, Arshad; Muzaffer, Rahil; Bhat, Mohammad Farooq; Farooq, Munir; Badoo, Abdul Rashid; Dar, Imtiyaz Hussian; Wani, Mudassir Maqbool

2009-10-10

In developing countries, due to limited availability of modern anesthesia and overcrowding of the hospitals with patients who need surgery, high-risk patients with "intertrochanteric" fractures remain unsuita ble for open reduction and internal fixation.The aim of this study was to analyze the results of external fixation of "intertrochanteric" fractures in high-risk geriatric patients in a developing country.The results of 62 ambulatory high-risk geriatric patients with a mean age of 70 years (range 58-90 years) with "intertrochanteric" fractures, in whom external fixation was performed, are reported.Eight patients died during follow-up due to medical causes unrelated to the surgical procedure. So only 54 patients were available for final assessment. Procedure is simple, performed under local anesthesia, requires less time for surgery and is associated with less blood loss. Good fixation and early ambulation was achieved in most of the patients. Average time to union was 14 weeks. Thirty-one patients developed superficial pin tract infection and 28 patients had average shortening of 15 mm due to impaction and varus angulation. Functional outcome was assessed using Judet's point system. Good to excellent results were achieved in 44 patients.This study demonstrated that external fixation of "intertrochantric" fractures performed under local anesthesia offers significant advantage in ambulatory high-risk geriatric patients especially in a developing country.

An in-vitro biomechanical study of different fixation techniques for the extended trochanteric osteotomy in revision THA.

PubMed

Zhu, Zhonglin; Ding, Hui; Shao, Hongyi; Zhou, Yixin; Wang, Guangzhi

2013-04-09

The wire fixation and the cable grip fixation have been developed for the extended trochanteric osteotomy (ETO) in the revision of total hip arthroplasty (THA). Many studies reported the postoperative performance of the patients, but with little quantitative biomechanical comparison of the two fixation systems. An in-vitro testing approach was designed to record the loosening between the femoral bed and the greater trochanter after fixations. Ten cadaveric femurs were chosen in this study. Each femur underwent the THA, revision by ETO and fixations. The tension to the greater trochanter was from 0 to 500N in vertical and lateral direction, respectively. The translation and rotation of the greater trochanter with respect to the bony bed were captured by an optical tracking system. In the vertical tension tests, the overall translation of the greater trochanter was observed 0.4 mm in the cable fixations and 7.0 mm in the wire fixations. In the lateral tension tests, the overall motion of the greater trochanter was 2.0 mm and 1.2° in the cable fixations, while it was 6.2 mm and 5.3° in the wire fixations. The result was significantly different between the two fixation systems. The stability of the proximal femur after ETO using different fixations in the revision THA was investigated. The cable grip fixation was significantly more stable than the wire fixation.

GAFFE: a gaze-attentive fixation finding engine.

PubMed

Rajashekar, U; van der Linde, I; Bovik, A C; Cormack, L K

2008-04-01

The ability to automatically detect visually interesting regions in images has many practical applications, especially in the design of active machine vision and automatic visual surveillance systems. Analysis of the statistics of image features at observers' gaze can provide insights into the mechanisms of fixation selection in humans. Using a foveated analysis framework, we studied the statistics of four low-level local image features: luminance, contrast, and bandpass outputs of both luminance and contrast, and discovered that image patches around human fixations had, on average, higher values of each of these features than image patches selected at random. Contrast-bandpass showed the greatest difference between human and random fixations, followed by luminance-bandpass, RMS contrast, and luminance. Using these measurements, we present a new algorithm that selects image regions as likely candidates for fixation. These regions are shown to correlate well with fixations recorded from human observers.

Cold stability of microtubules in wood-forming tissues of conifers during seasons of active and dormant cambium.

PubMed

Begum, Shahanara; Shibagaki, Masaki; Furusawa, Osamu; Nakaba, Satoshi; Yamagishi, Yusuke; Yoshimoto, Joto; Jin, Hyun-O; Sano, Yuzou; Funada, Ryo

2012-01-01

The cold stability of microtubules during seasons of active and dormant cambium was analyzed in the conifers Abies firma, Abies sachalinensis and Larix leptolepis by immunofluorescence microscopy. Samples were fixed at room temperature and at a low temperature of 2-3°C to examine the effects of low temperature on the stability of microtubules. Microtubules were visible in cambium, xylem cells and phloem cells after fixation at room temperature during seasons of active and dormant cambium. By contrast, fixation at low temperature depolymerized microtubules in cambial cells, differentiating tracheids, differentiating xylem ray parenchyma and phloem ray parenchyma cells during the active season. However, similar fixation did not depolymerize microtubules during cambial dormancy in winter. Our results indicate that the stability of microtubules in cambial cells and cambial derivatives at low temperature differs between seasons of active and dormant cambium. Moreover, the change in the stability of microtubules that we observed at low temperature might be closely related to seasonal changes in the cold tolerance of conifers. In addition, low-temperature fixation depolymerized microtubules in cambial cells and differentiating cells that had thin primary cell walls, while such low-temperature fixation did not depolymerize microtubules in differentiating secondary xylem ray parenchyma cells and tracheids that had thick secondary cell walls. The stability of microtubules at low temperature appears to depend on the structure of the cell wall, namely, primary or secondary. Therefore, we propose that the secondary cell wall might be responsible for the cold stability of microtubules in differentiating secondary xylem cells of conifers.

Biochemical Approaches to Improved Nitrogen Fixation

USDA-ARS?s Scientific Manuscript database

Improving symbiotic nitrogen fixation by legumes has emerged again as an important topic on the world scene due to the energy crisis and lack of access to nitrogen fertilizer in developing countries. We have taken a biochemical genomics approach to improving symbiotic nitrogen fixation in legumes. L...

Microbial Response to UV Exposure and Nitrogen Limitation in Desert Soil Crusts

NASA Astrophysics Data System (ADS)

Fulton, J. M.; Van Mooy, B. A.

2016-12-01

Microbiotic soil crusts have diverse biomarker distributions and C and N stable isotopic compositions that covary with soil type. Sparse plant cover and the relative lack of soil disturbance in arid/semi-arid landscapes allows populations of soil cyanobacteria to develop along with fungi and heterotrophic bacteria. Microbial communities in this extreme environment depend in part on the production of scytonemin, a UV protective pigment, by cyanobacteria near the top of the crust. N limitation of microbial growth also affects soil crust population dynamics, increasing the requirement of N2fixation by diazotrophic cyanobacteria. We collected 56 soil crust samples from 27 locations throughout the Great Salt Lake Desert, including four transects spanning high-elevation, erosion-dominated soils to lower elevation soils dominated by silt-accumulation. Erosion-dominated soil surfaces included rounded gravel and cobbles; in the interstices there were poorly-developed microbiotic crusts on sandy loam with low δ15N values near 0‰ that point toward microbial growth dependent on cyanobacterial N2 fixation. Nutrients regenerated by heterotrophic bacteria may have been eroded from the system, providing a positive feedback for N2 fixation. High scytonemin:chlorophyll a ratios suggest that cyanobacteria required enhanced protection from UV damage in these crusts. A similar increase in scytonemin:chlorophyll a ratio during soil crust rehydration experiments also points toward the importance of UV protection. Glycolipid:phospholipid ratios were lowest where N2 fixation was favored, however, suggesting that the cyanobacterial population was relatively small, possibly because of the metabolic cost of N2fixation. Microbiotic crusts on silt loam soils, on the other hand, had higher δ15N values between 3.5 and 7.8‰, consistent with heterotrophic growth and nutrient recycling. Lower scytonemin:chlorophyll a ratios suggest that relatively high photosynthetic activity was supported in these well-developed crusts. Vertical migration may have reduced the scytonemin requirement of cyanobacteria. Higher glycolipid:phospholipid ratios suggest that cyanobacteria and algae had greater relative abundance than heterotrophic bacteria in well-developed compared with erosion-dominated crusts.

Nitrogen fixation in boreal peatlands: the effects of increased N deposition on N2-fixation

NASA Astrophysics Data System (ADS)

Popma, J. M.; Wieder, R.; Lamers, L.; Vile, M. A.

2013-12-01

Boreal peatlands are of great importance to global carbon and nitrogen cycling. While covering only 3-4 % of the terrestrial surface, they account for 25-30 % of the world's soil C and 9-15 % of the world's soil N. In Western Canada atmospheric dry deposition rates are extremely low: approximately 1 kg N ha-1 yr-1. Though these systems have been functioning as net sinks over the past 11,000 years, natural and anthropogenic disturbances might compromise the historical balance of C and N. Biological N2-fixation has recently been shown to represent a very significant input of N into these systems, contributing to 62% of total N in Western Canada. Interactions between N deposition and biological N2-fixation are as yet, unknown, but the impact of elevated deposition of N-compounds from increased industrial expansion of oil sands mining to peatlands, is concerning. Given that nitrogenase, the enzyme responsible for catalyzing N2-fixation, is energetically costly when active, enhanced inputs of atmospheric N deposition could be a major determinant for enzyme activity and rates of biological N input to these bogs. Understanding interactions between N deposition and N2 fixation in boreal peatlands can aid in predicting the consequences of increased N deposition and setting critical loads. We conducted a field-fertilization experiment in a poor fen in Alberta, Canada, to determine the effects of enhanced N deposition on a dominant fen species Sphagnum angustifolium. The experiment consisted of seven N treatments: Control, 0, 5, 10, 15, 20 and 25 kg N ha-1 y1, n=3. N2-fixation was measured during summer 2012 and 2013 using the acetylene reduction assay (ARA). ARA rates were converted to rates of N2-fixation by calibrating ARA with paired 15N2-incubations. In both 2012 and 2013, with increasing N deposition from 0 kg N ha-1 yr-1 to 25 kg N ha-1 yr-1, rates of N2 fixation decreased, with highest rates in the 0 kg N ha-1 yr-1 treatment mosses (54.2 × 1.40; 48.58 × 7.12 kg N ha-1 yr-1, mean × std err for 2012 and 2013, respectively) followed by progressively lower rates with a low of 5.02 × 0.87 in 2012 and 8.94 × 3.09 in 2013 (mean × std err). As biological N2-fixation is an energetically costly process, up-regulating enzyme activity when N availability is low and down-regulating activity when N deposition is enhanced makes thermodynamic and evolutionary sense. N2-fixation shows to be one of the most early-warning indicators to the early response of boreal peatlands to increased N deposition, and can aid in setting critical loads to protect these historically pristine ecosystems.

A Subconscious Interaction between Fixation and Anticipatory Pursuit

PubMed Central

Bal, Japjot; Heinen, Stephen J.

2017-01-01

Ocular smooth pursuit and fixation are typically viewed as separate systems, yet there is evidence that the brainstem fixation system inhibits pursuit. Here we present behavioral evidence that the fixation system modulates pursuit behavior outside of conscious awareness. Human observers (male and female) either pursued a small spot that translated across a screen, or fixated it as it remained stationary. As shown previously, pursuit trials potentiated the oculomotor system, producing anticipatory eye velocity on the next trial before the target moved that mimicked the stimulus-driven velocity. Randomly interleaving fixation trials reduced anticipatory pursuit, suggesting that a potentiated fixation system interacted with pursuit to suppress eye velocity in upcoming pursuit trials. The reduction was not due to passive decay of the potentiated pursuit signal because interleaving “blank” trials in which no target appeared did not reduce anticipatory pursuit. Interspersed short fixation trials reduced anticipation on long pursuit trials, suggesting that fixation potentiation was stronger than pursuit potentiation. Furthermore, adding more pursuit trials to a block did not restore anticipatory pursuit, suggesting that fixation potentiation was not overridden by certainty of an imminent pursuit trial but rather was immune to conscious intervention. To directly test whether cognition can override fixation suppression, we alternated pursuit and fixation trials to perfectly specify trial identity. Still, anticipatory pursuit did not rise above that observed with an equal number of random fixation trials. The results suggest that potentiated fixation circuitry interacts with pursuit circuitry at a subconscious level to inhibit pursuit. SIGNIFICANCE STATEMENT When an object moves, we view it with smooth pursuit eye movements. When an object is stationary, we view it with fixational eye movements. Pursuit and fixation are historically regarded as controlled by different neural circuitry, and alternating between invoking them is thought to be guided by a conscious decision. However, our results show that pursuit is actively suppressed by prior fixation of a stationary object. This suppression is involuntary, and cannot be avoided even if observers are certain that the object will move. The results suggest that the neural fixation circuitry is potentiated by engaging stationary objects, and interacts with pursuit outside of conscious awareness. PMID:29061701

A Subconscious Interaction between Fixation and Anticipatory Pursuit.

PubMed

Watamaniuk, Scott N J; Bal, Japjot; Heinen, Stephen J

2017-11-22

Ocular smooth pursuit and fixation are typically viewed as separate systems, yet there is evidence that the brainstem fixation system inhibits pursuit. Here we present behavioral evidence that the fixation system modulates pursuit behavior outside of conscious awareness. Human observers (male and female) either pursued a small spot that translated across a screen, or fixated it as it remained stationary. As shown previously, pursuit trials potentiated the oculomotor system, producing anticipatory eye velocity on the next trial before the target moved that mimicked the stimulus-driven velocity. Randomly interleaving fixation trials reduced anticipatory pursuit, suggesting that a potentiated fixation system interacted with pursuit to suppress eye velocity in upcoming pursuit trials. The reduction was not due to passive decay of the potentiated pursuit signal because interleaving "blank" trials in which no target appeared did not reduce anticipatory pursuit. Interspersed short fixation trials reduced anticipation on long pursuit trials, suggesting that fixation potentiation was stronger than pursuit potentiation. Furthermore, adding more pursuit trials to a block did not restore anticipatory pursuit, suggesting that fixation potentiation was not overridden by certainty of an imminent pursuit trial but rather was immune to conscious intervention. To directly test whether cognition can override fixation suppression, we alternated pursuit and fixation trials to perfectly specify trial identity. Still, anticipatory pursuit did not rise above that observed with an equal number of random fixation trials. The results suggest that potentiated fixation circuitry interacts with pursuit circuitry at a subconscious level to inhibit pursuit. SIGNIFICANCE STATEMENT When an object moves, we view it with smooth pursuit eye movements. When an object is stationary, we view it with fixational eye movements. Pursuit and fixation are historically regarded as controlled by different neural circuitry, and alternating between invoking them is thought to be guided by a conscious decision. However, our results show that pursuit is actively suppressed by prior fixation of a stationary object. This suppression is involuntary, and cannot be avoided even if observers are certain that the object will move. The results suggest that the neural fixation circuitry is potentiated by engaging stationary objects, and interacts with pursuit outside of conscious awareness. Copyright © 2017 the authors 0270-6474/17/3711424-07$15.00/0.

Eye movement-invariant representations in the human visual system.

PubMed

Nishimoto, Shinji; Huth, Alexander G; Bilenko, Natalia Y; Gallant, Jack L

2017-01-01

During natural vision, humans make frequent eye movements but perceive a stable visual world. It is therefore likely that the human visual system contains representations of the visual world that are invariant to eye movements. Here we present an experiment designed to identify visual areas that might contain eye-movement-invariant representations. We used functional MRI to record brain activity from four human subjects who watched natural movies. In one condition subjects were required to fixate steadily, and in the other they were allowed to freely make voluntary eye movements. The movies used in each condition were identical. We reasoned that the brain activity recorded in a visual area that is invariant to eye movement should be similar under fixation and free viewing conditions. In contrast, activity in a visual area that is sensitive to eye movement should differ between fixation and free viewing. We therefore measured the similarity of brain activity across repeated presentations of the same movie within the fixation condition, and separately between the fixation and free viewing conditions. The ratio of these measures was used to determine which brain areas are most likely to contain eye movement-invariant representations. We found that voxels located in early visual areas are strongly affected by eye movements, while voxels in ventral temporal areas are only weakly affected by eye movements. These results suggest that the ventral temporal visual areas contain a stable representation of the visual world that is invariant to eye movements made during natural vision.

When and how to operate the posterior malleolus fragment in trimalleolar fractures: a systematic literature review.

PubMed

Verhage, Samuel Marinus; Hoogendoorn, Jochem Maarten; Krijnen, Pieta; Schipper, Inger Birgitta

2018-05-12

Whether or not and how to fixate the posterior malleolus fracture seems to depend on the fracture fragment size and its amount of dislocation, but clear guidelines for daily practice are lacking. In this review, we summarize the literature on preferred treatment of the posterior fragment in trimalleolar fractures. A systematic review of publications between January 1995 and April 30 2017 on this topic in the PubMed, Embase, and Cochrane databases was performed according to the PRISMA statement. Seventeen (2 prospective and 15 retrospective) of the 180 identified studies were included. Six studies report on indications for fixation of posterior malleolus fracture fragments. Eleven studies compare different fixation approaches and techniques for the posterior fragment. Meta-analysis was not possible due to varying fixation criteria and outcomes. There was no clear association between posterior fragment size and functional outcome or development of osteoarthritis. The non-anatomical reduction of the fragment was of more influence on outcome. Radiological and functional outcome was better after open reduction and internal fixation via the posterolateral approach than after percutaneous anterior-to-posterior screw fixation. The posterior fragment size is not a clear indication for its fixation. A step-off, however, seems an important indicator for developing posttraumatic osteoarthritis and worse functional outcome. Posterior fragments involving the intra-articular surface need to be reduced and fixated to prevent postoperative persisting step-off. Furthermore, fixation of the posterior malleolus via an open posterolateral approach seems superior to percutaneous anterior-to-posterior fixation. However, these results need to be confirmed in a prospective comparative trial. Therapeutic level II.

The comparative risk of developing postoperative complications in patients with distal radius fractures following different treatment modalities

PubMed Central

Qiu, Wen-Jun; Li, Yi-Fan; Ji, Yun-Han; Xu, Wei; Zhu, Xiao-Dong; Tang, Xian-Zhong; Zhao, Huan-Li; Wang, Gui-Bin; Jia, Yue-Qing; Zhu, Shi-Cai; Zhang, Feng-Fang; Liu, Hong-Mei

2015-01-01

In this study, we performed a network meta-analysis to compare the outcomes of seven most common surgical procedures to fix DRF, including bridging external fixation, non-bridging external fixation, K-wire fixation, plaster fixation, dorsal plating, volar plating, and dorsal and volar plating. Published studies were retrieved through PubMed, Embase and Cochrane Library databases. The database search terms used were the following keywords and MeSH terms: DRF, bridging external fixation, non-bridging external fixation, K-wire fixation, plaster fixation, dorsal plating, volar plating, and dorsal and volar plating. The network meta-analysis was performed to rank the probabilities of postoperative complication risks for the seven surgical modalities in DRF patients. This network meta-analysis included data obtained from a total of 19 RCTs. Our results revealed that compared to DRF patients treated with bridging external fixation, marked differences in pin-track infection (PTI) rate were found in patients treated with plaster fixation, volar plating, and dorsal and volar plating. Cluster analysis showed that plaster fixation is associated with the lowest probability of postoperative complication in DRF patients. Plaster fixation is associated with the lowest risk for postoperative complications in DRF patients, when compared to six other common DRF surgical methods examined. PMID:26549312

Facet-dependent solar ammonia synthesis of BiOCl nanosheets via a proton-assisted electron transfer pathway

NASA Astrophysics Data System (ADS)

Li, Hao; Shang, Jian; Shi, Jingu; Zhao, Kun; Zhang, Lizhi

2016-01-01

Under the pressure of a fossil fuels shortage and global climate change, solar ammonia synthesis and the need to develop N2 fixation under mild conditions is becoming more urgent need; however, their intrinsic mechanisms still remain unclear. Herein, we demonstrate that the kinetic inertia of N2 can be overcome using oxygen vacancies (OVs) of BiOCl as the catalytic centers to create lower energy molecular steps, which are amendable for the solar light driven N-N triple bond cleavage via a proton-assisted electron transfer pathway. Moreover, the distinct structures of OVs on different BiOCl facets strongly determine the N2 fixation pathways by influencing both the adsorption structure and the activation level of N2. The fixation of terminal end-on bound N2 on the OVs of BiOCl {001} facets follows an asymmetric distal mode by selectively generating NH3, while the reduction of side-on bridging N2 on the OVs of BiOCl {010} facets is more energetically favorable in a symmetric alternating mode to produce N2H4 as the main intermediate.Under the pressure of a fossil fuels shortage and global climate change, solar ammonia synthesis and the need to develop N2 fixation under mild conditions is becoming more urgent need; however, their intrinsic mechanisms still remain unclear. Herein, we demonstrate that the kinetic inertia of N2 can be overcome using oxygen vacancies (OVs) of BiOCl as the catalytic centers to create lower energy molecular steps, which are amendable for the solar light driven N-N triple bond cleavage via a proton-assisted electron transfer pathway. Moreover, the distinct structures of OVs on different BiOCl facets strongly determine the N2 fixation pathways by influencing both the adsorption structure and the activation level of N2. The fixation of terminal end-on bound N2 on the OVs of BiOCl {001} facets follows an asymmetric distal mode by selectively generating NH3, while the reduction of side-on bridging N2 on the OVs of BiOCl {010} facets is more energetically favorable in a symmetric alternating mode to produce N2H4 as the main intermediate. Electronic supplementary information (ESI) available: Other experimental details, additional SEM and TEM images, X-ray diffraction patterns (XRD), UV-Vis diffuse reflectance spectra (DRS), and additional data. See DOI: 10.1039/c5nr07380d

An antibacterial and absorbable silk-based fixation material with impressive mechanical properties and biocompatibility

NASA Astrophysics Data System (ADS)

Shi, Chenglong; Pu, Xiaobing; Zheng, Guan; Feng, Xinglong; Yang, Xuan; Zhang, Baoliang; Zhang, Yu; Yin, Qingshui; Xia, Hong

2016-11-01

Implant-associated infections and non-absorbing materials are two important reasons for a second surgical procedure to remove internal fixation devices after an orthopedic internal fixation surgery. The objective of this study was to produce an antibacterial and absorbable fixation screw by adding gentamicin to silk-based materials. The antibacterial activity was assessed against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in vitro by plate cultivation and scanning electron microscopy (SEM). We also investigated the properties, such as the mechanical features, swelling properties, biocompatibility and degradation, of gentamicin-loaded silk-based screws (GSS) in vitro. The GSS showed significant bactericidal effects against S. aureus and E. coli. The antibacterial activity remained high even after 4 weeks of immersion in protease solution. In addition, the GSS maintained the remarkable mechanical properties and excellent biocompatibility of pure silk-based screws (PSS). Interestingly, after gentamicin incorporation, the degradation rate and water-absorbing capacity increased and decreased, respectively. These GSS provide both impressive material properties and antibacterial activity and have great potential for use in orthopedic implants to reduce the incidence of second surgeries.

Treatment of Early Post-Op Wound Infection after Internal Fixation

DTIC Science & Technology

2017-10-01

the fracture stable while the bone heals. Approximately 10%-40% of severe fractures fixed with internal fixation develop a deep wound infection during...effect of treatment of post-op wound infection in bones after fracture fixation or joint fusion and either: (Group 1) operative debridement and PO

Overcoming Organizational Fixation: Creating and Sustaining an Innovation Culture

ERIC Educational Resources Information Center

Stempfle, Joachim

2011-01-01

Fixation on established paradigms and practices can severely limit the capability of organizations to change, thereby jeopardizing the ability of organizations to keep up with changes in their environment and new technological developments. Overcoming organizational fixation is therefore a requirement for any organization that strives to achieve…

Fixation of carbon dioxide into dimethyl carbonate over ...

EPA Pesticide Factsheets

A titanium-based zeolitic thiophene-benzimidazolate framework has been designed for the direct synthesis of dimethyl carbonate (DMC) from methanol and carbon dioxide. The developed catalyst activates carbon dioxide and delivers over 16% yield of DMC without the use of any dehydrating agent or requirement for azeotropic distillation. Prepared for submission to Nature Scientific reports.

Anaerobic Nitrogen Fixers on Mars

NASA Astrophysics Data System (ADS)

Lewis, B. G.

2000-07-01

The conversion of atmospheric nitrogen gas to the protein of living systems is an amazing process of nature. The first step in the process is biological nitrogen fixation, the transformation of N2 to NH3. The phenomenon is crucial for feeding the billions of our species on Earth. On Mars, the same process may allow us to discover how life can adapt to a hostile environment, and render it habitable. Hostile environments also exist on Earth. For example, nothing grows in coal refuse piles due to the oxidation of pyrite and marcasite to sulfuric acid. Yet, when the acidity is neutralized, alfalfa and soybean plants develop root nodules typical of symbiotic nitrogen fixation with Rhizobium species possibly living in the pyritic material. When split open, these nodules exhibited the pinkish color of leghemoglobin, a protein in the nodule protecting the active nitrogen-fixing enzyme nitrogenase against the toxic effects of oxygen. Although we have not yet obtained direct evidence of nitrogenase activity in these nodules (reduction of acetylene to ethylene, for example), these findings suggested the possibility that nitrogen fixation was taking place in this hostile, non-soil material. This immediately raises the possibility that freeliving anaerobic bacteria which fix atmospheric nitrogen on Earth, could do the same on Mars.

Effect of salinity on diazotrophic activity and microbial composition of phototrophic communities from Bitter-1 soda lake (Kulunda Steppe, Russia).

PubMed

Namsaraev, Zorigto; Samylina, Olga; Sukhacheva, Marina; Borisenko, Gennadii; Sorokin, Dimitry Y; Tourova, Tatiana

2018-04-16

Bitter-1 is a shallow hypersaline soda lake in Kulunda Steppe (Altai region, Russia). During a study period between 2005 and 2016, the salinity in the littoral area of the lake fluctuated within the range from 85 to 400 g/L (in July of each year). Light-dependent nitrogen fixation occurred in this lake up to the salt-saturating conditions. The rates increased with a decrease in salinity, both under environmental conditions and in laboratory simulations. The salinities below 100 g/L were favorable for light-dependent nitrogen fixation, while the process was dramatically inhibited above 200 g/L salts. The analysis of nifH genes in environmental samples and in enrichment cultures of diazotrophic phototrophs suggested that anaerobic fermenting and sulfate-reducing bacteria could participate in the dark nitrogen fixation process up to soda-saturating conditions. However, we cannot exclude the possibility that haloalkaliphilic nonheterocystous cyanobacteria (Euhalothece sp. and Geitlerinema sp.) and anoxygenic purple sulfur bacteria (Ectothiorhodospira sp.) might also play a role in the process at light conditions. The heterocystous cyanobacterium Nodularia sp. develops at low salinity (below 80 g/L) that is not characteristic for Bitter-1 Lake and thus does not make a significant contribution to the nitrogen fixation in this lake.

Nitrogen fixation in transposon mutants from Bradyrhizobium japonicum USDA 110 impaired in nitrate reductase.

PubMed

Camacho, María; Burgos, Araceli; Chamber-Pérez, Manuel A

2003-04-01

Tn5 transposon mutagenesis was carried out in Bradyrhizobium japonicum strain USDA 110 to produce defective mutants. From over one thousand clones expressing low levels of nitrate reductase activity as free-living bacteria, approximately five percent had significantly different ratios of nodulation, N2 fixation or nitrate reductase activity compared to the wild strain when determined in bacteroids from soybean nodules. Tn5 insertions were checked previously and mutants were arranged into four different groups. Only one of these groups, designated AN, was less effective at N2 fixation than the wild strain, suggesting a mutation in a domain shared by nitrogenase and NR. The remaining groups of insertions successfully nodulated and were as effective at N2 fixation as the wild strain, but showed diminished ability to reduce nitrate both in nodules and in the isolated bacteroids when assayed in vitro with NADH or methyl viologen as electron donors. PCR amplification demonstrated that Tn5 insertions took place in different genes on each mutant group and the type of mutant (CC) expressing almost no nitrate reductase activity under all treatments seemed to possess transposable elements in two genes. Induction of nitrate reductase activity by nitrate was observed only in those clones expressing a low constitutive activity (AN and AE). Nitrate reductase activity in bacteroids along nodule growth decreased in all groups including the ineffective AN group, whose nodulation was highly inhibited by nitrate at 5 mmol/L N. Host-cultivar interaction seemed to influence the regulation of nitrate reductase activity in bacteroids. Total or partial repression of nitrate reductase activity in bacteroids unaffected by N2 fixation (CC, AJ and AE groups) improved nodule resistance to nitrate and N yields of shoots over those of the wild strain. These observations may suggest that some of the energy supplied to bacteroids was wasted by its constitutive NRA.

Active visual search in non-stationary scenes: coping with temporal variability and uncertainty

NASA Astrophysics Data System (ADS)

Ušćumlić, Marija; Blankertz, Benjamin

2016-02-01

Objective. State-of-the-art experiments for studying neural processes underlying visual cognition often constrain sensory inputs (e.g., static images) and our behavior (e.g., fixed eye-gaze, long eye fixations), isolating or simplifying the interaction of neural processes. Motivated by the non-stationarity of our natural visual environment, we investigated the electroencephalography (EEG) correlates of visual recognition while participants overtly performed visual search in non-stationary scenes. We hypothesized that visual effects (such as those typically used in human-computer interfaces) may increase temporal uncertainty (with reference to fixation onset) of cognition-related EEG activity in an active search task and therefore require novel techniques for single-trial detection. Approach. We addressed fixation-related EEG activity in an active search task with respect to stimulus-appearance styles and dynamics. Alongside popping-up stimuli, our experimental study embraces two composite appearance styles based on fading-in, enlarging, and motion effects. Additionally, we explored whether the knowledge obtained in the pop-up experimental setting can be exploited to boost the EEG-based intention-decoding performance when facing transitional changes of visual content. Main results. The results confirmed our initial hypothesis that the dynamic of visual content can increase temporal uncertainty of the cognition-related EEG activity in active search with respect to fixation onset. This temporal uncertainty challenges the pivotal aim to keep the decoding performance constant irrespective of visual effects. Importantly, the proposed approach for EEG decoding based on knowledge transfer between the different experimental settings gave a promising performance. Significance. Our study demonstrates that the non-stationarity of visual scenes is an important factor in the evolution of cognitive processes, as well as in the dynamic of ocular behavior (i.e., dwell time and fixation duration) in an active search task. In addition, our method to improve single-trial detection performance in this adverse scenario is an important step in making brain-computer interfacing technology available for human-computer interaction applications.

Novel Use of Active Leptospermum Honey for Ringed Fixator Pin Site Care in Diabetic Charcot Deformity Patients.

PubMed

Lazarides, Alexander L; Hamid, Kamran S; Kerzner, Michael S

2018-04-01

Open reduction with external fixation (OREF) utilizing fine wire ringed fixators for correction of Charcot deformity has gained popularity over the past decade. Pin site infections are a well-documented complication of external fixation as well as a driver of escalating health care costs. We aimed to demonstrate the safety and efficacy of a novel method of pin site care utilizing active Leptospermum honey-impregnated dressings (MediHoney) in diabetic patients undergoing deformity correction with OREF. Twenty-one diabetic patients with Charcot deformities of the lower extremity were prospectively enrolled and followed for pin site complications following OREF for deformity correction. Active Leptospermum honey dressings were applied at metal-cutaneous interfaces at the end of the OREF procedure and replaced weekly for a total of 8 weeks. Patients were monitored for pin site infections from the time of surgery until external fixator removal. Sixteen consecutive patients receiving standard OREF for Charcot deformities were evaluated retrospectively to serve as a control group. Of the 21 enrolled patients, 19 underwent OREF and followed up throughout the study period. Treated patients had a mean age of 58.5 years and mean body mass index measuring 33.3 kg/m 2 as documented prior to surgery. The 15 patients with hemoglobin A1c labs drawn in the 3 months preceding surgery averaged 7.5. Fixators were removed at an average of 12.1 weeks after adequate bony healing. Of the 244 pin sites in 19 patients, 3 pin sites (1.2% of pins) in 2 patients (10.5% of patients) showed evidence of superficial infection. All infections resolved with oral antibiotics. Infection rates were significantly reduced when compared to the standard care control group. Pilot data in a prospectively collected case series demonstrate safety and efficacy of active Leptospermum honey-impregnated dressings when used for fine wire ringed fixator pin site care in diabetic Charcot deformity patients. Further investigation in the form of a prospective randomized controlled study is warranted to demonstrate the potential value of this novel intervention. Level IV.

Capture of fixation by rotational flow; a deterministic hypothesis regarding scaling and stochasticity in fixational eye movements

PubMed Central

Wilkinson, Nicholas M.; Metta, Giorgio

2014-01-01

Visual scan paths exhibit complex, stochastic dynamics. Even during visual fixation, the eye is in constant motion. Fixational drift and tremor are thought to reflect fluctuations in the persistent neural activity of neural integrators in the oculomotor brainstem, which integrate sequences of transient saccadic velocity signals into a short term memory of eye position. Despite intensive research and much progress, the precise mechanisms by which oculomotor posture is maintained remain elusive. Drift exhibits a stochastic statistical profile which has been modeled using random walk formalisms. Tremor is widely dismissed as noise. Here we focus on the dynamical profile of fixational tremor, and argue that tremor may be a signal which usefully reflects the workings of oculomotor postural control. We identify signatures reminiscent of a certain flavor of transient neurodynamics; toric traveling waves which rotate around a central phase singularity. Spiral waves play an organizational role in dynamical systems at many scales throughout nature, though their potential functional role in brain activity remains a matter of educated speculation. Spiral waves have a repertoire of functionally interesting dynamical properties, including persistence, which suggest that they could in theory contribute to persistent neural activity in the oculomotor postural control system. Whilst speculative, the singularity hypothesis of oculomotor postural control implies testable predictions, and could provide the beginnings of an integrated dynamical framework for eye movements across scales. PMID:24616670

External fixation of “intertrochanteric” fractures

PubMed Central

Gani, Naseem ul; Kangoo, Khursheed Ahmed; Bashir, Arshad; Muzaffer, Rahil; Bhat, Mohammad Farooq; Farooq, Munir; Badoo, Abdul Rashid; Dar, Imtiyaz Hussian; Wani, Mudassir Maqbool

2009-01-01

In developing countries, due to limited availability of modern anesthesia and overcrowding of the hospitals with patients who need surgery, high-risk patients with “intertrochanteric” fractures remain unsuita ble for open reduction and internal fixation. The aim of this study was to analyze the results of external fixation of “intertrochanteric” fractures in high-risk geriatric patients in a developing country. The results of 62 ambulatory high-risk geriatric patients with a mean age of 70 years (range 58–90 years) with “intertrochanteric” fractures, in whom external fixation was performed, are reported. Eight patients died during follow-up due to medical causes unrelated to the surgical procedure. So only 54 patients were available for final assessment. Procedure is simple, performed under local anesthesia, requires less time for surgery and is associated with less blood loss. Good fixation and early ambulation was achieved in most of the patients. Average time to union was 14 weeks. Thirty-one patients developed superficial pin tract infection and 28 patients had average shortening of 15 mm due to impaction and varus angulation. Functional outcome was assessed using Judet's point system. Good to excellent results were achieved in 44 patients. This study demonstrated that external fixation of “intertrochantric” fractures performed under local anesthesia offers significant advantage in ambulatory high-risk geriatric patients especially in a developing country. PMID:21808680

Photographic fixative poisoning

MedlinePlus

Photographic developer poisoning; Hydroquinone poisoning; Quinone poisoning; Sulfite poisoning ... Poisonous ingredients include: Hydroquinones Quinones Sodium ... fixative can also break down (decompose) to form sulfur dioxide ...

Application of 3D printed customized external fixator in fracture reduction.

PubMed

Qiao, Feng; Li, Dichen; Jin, Zhongmin; Gao, Yongchang; Zhou, Tao; He, Jinlong; Cheng, Li

2015-01-01

Long bone fracture is common in traumatic osteopathic patients. Good reduction is beneficial for bone healing, preventing the complications such as delayed union, nonunion, malunion, but is hard to achieve. Repeated attempts during the surgery would increase the operation time, cause new damage to the fracture site and excessive exposure to radiation. Robotic and navigation techniques can help improve the reduction accuracy, however, the high cost and complexity of operation have limited their clinical application. We combined 3D printing with computer-assisted reduction technique to develop a customised external fixator with the function of fracture reduction. The original CT data obtained by scanning the fracture was imported to computer for reconstructing and reducing the 3D image of the fracture, based on which the external fixator (named as Q-Fixator) was designed and then fabricated by 3D printing techniques. The fracture reduction and fixation was achieved by connecting the pins inserted in the bones with the customised Q-Fixator. Experiments were conducted on three fracture models to demonstrate the reduction results. Good reduction results were obtained on all three fractured bone models, with an average rotation of 1.21°(± 0.24), angulation of 1.84°(± 0.28), and lateral displacement of 2.22 mm(± 0.62). A novel customised external fixator for long bone fracture reduction was readily developed using 3D printing technique. The customised external fixator had the advantages of easy manipulation, accurate reduction, minimally invasion and experience-independence. Future application of the customised external fixator can be extended to include the fixation function with stress adjustment and potentially optimise the fracture healing process. Copyright © 2015 Elsevier Ltd. All rights reserved.

Carbon and nitrogen fixation differ between successional stages of biological soil crusts in the Colorado Plateau and Chihuahuan Desert

USGS Publications Warehouse

Housman, D.C.; Powers, H.H.; Collins, A.D.; Belnap, J.

2006-01-01

Biological soil crusts (cyanobacteria, mosses and lichens collectively) perform essential ecosystem services, including carbon (C) and nitrogen (N) fixation. Climate and land-use change are converting later successional soil crusts to early successional soil crusts with lower C and N fixation rates. To quantify the effect of such conversions on C and N dynamics in desert ecosystems we seasonally measured diurnal fixation rates in different biological soil crusts. We classified plots on the Colorado Plateau (Canyonlands) and Chihuahuan Desert (Jornada) as early (Microcoleus) or later successional (Nostoc/Scytonema or Placidium/Collema) and measured photosynthesis (Pn), nitrogenase activity (NA), and chlorophyll fluorescence (Fv/Fm) on metabolically active (moist) soil crusts. Later successional crusts typically had greater Pn, averaging 1.2-1.3-fold higher daily C fixation in Canyonlands and 2.4-2.8-fold higher in the Jornada. Later successional crusts also had greater NA, averaging 1.3-7.5-fold higher daily N fixation in Canyonlands and 1.3-25.0-fold higher in the Jornada. Mean daily Fv/Fm was also greater in later successional Canyonlands crusts during winter, and Jornada crusts during all seasons except summer. Together these findings indicate conversion of soil crusts back to early successional stages results in large reductions of C and N inputs into these ecosystems.

Comparing different preparation methods to study human fibrin fibers and platelets using TEM.

PubMed

Buys, Antoinette V; Pretorius, Etheresia

2012-06-01

For the study of cellular ultrastructure, the sample needs to be stabilized by fixation, with the ultimate aim to preserve the native tissue organization and to protect the tissue against later stages of preparation. Chemical and freezing fixation are most used, and chemical fixation employs agents that permeate tissues and cells by diffusion and covalently bind with their major biochemical constituents to fix them. Most widely used chemical fixatives are aldehydes, e.g., formaldehyde and glutaraldehyde, which are noncoagulating, crosslinking agents. Cryofixation methods for ultrastructural studies are also popular, and high-pressure freezing immobilizes all cell constituents and arrests biological activity by removing the thermal energy from the system. In the current research, we used platelet-rich plasma (PRP) to study expansive fibrin fibers and platelet ultrastructure to compare the two fixation techniques. We also used thrombin and calcium chloride as a clotting agent to determine the technique most suitable for the formation of extensive fibrin networks. Chemically fixated fibrin fibers were more compact and condensed and also showed a banding pattern on longitudinal sections. High-pressure frozen samples were more dispersed while platelets fixated showed better preserved cellular membranes and organelle structure. PRP coagulated by addition of CaCl(2) showed blood platelets that are noticeably more activated compared with PRP; however, with thrombin, a sharp ultrastructure was seen. We conclude that PRP mixed with thrombin, and freeze substituted, is the most suitable method for the study of extensive fibrin fibers as well as platelets. Copyright © 2011 Wiley Periodicals, Inc.

Perception of Object-Context Relations: Eye-Movement Analyses in Infants and Adults

PubMed Central

Bornstein, Marc H.; Mash, Clay; Arterberry, Martha E.

2011-01-01

Twenty-eight 4-month-olds’ and 22 20-year-olds’ attention to object-context relations was investigated using a common eye-movement paradigm. Infants and adults scanned both objects and contexts. Infants showed equivalent preferences for animals and vehicles and for congruent and incongruent object-context relations overall, more fixations of objects in congruent object-context relations, more fixations of contexts in incongruent object-context relations, more fixations of objects than contexts in vehicle scenes, and more fixation shifts in incongruent than congruent vehicle scenes. Adults showed more fixations of congruent than incongruent scenes, vehicles than animals, and objects than contexts, equal fixations of animals and their contexts but more fixations of vehicles than their contexts, and more shifts of fixation when inspecting animals in context than vehicles in context. These findings for location, number, and order of eye movements indicate that object-context relations play a dynamic role in the development and allocation of attention. PMID:21244146

Nitrogenase-mimic iron-containing chalcogels for photochemical reduction of dinitrogen to ammonia.

PubMed

Liu, Jian; Kelley, Matthew S; Wu, Weiqiang; Banerjee, Abhishek; Douvalis, Alexios P; Wu, Jinsong; Zhang, Yongbo; Schatz, George C; Kanatzidis, Mercouri G

2016-05-17

A nitrogenase-inspired biomimetic chalcogel system comprising double-cubane [Mo2Fe6S8(SPh)3] and single-cubane (Fe4S4) biomimetic clusters demonstrates photocatalytic N2 fixation and conversion to NH3 in ambient temperature and pressure conditions. Replacing the Fe4S4 clusters in this system with other inert ions such as Sb(3+), Sn(4+), Zn(2+) also gave chalcogels that were photocatalytically active. Finally, molybdenum-free chalcogels containing only Fe4S4 clusters are also capable of accomplishing the N2 fixation reaction with even higher efficiency than their Mo2Fe6S8(SPh)3-containing counterparts. Our results suggest that redox-active iron-sulfide-containing materials can activate the N2 molecule upon visible light excitation, which can be reduced all of the way to NH3 using protons and sacrificial electrons in aqueous solution. Evidently, whereas the Mo2Fe6S8(SPh)3 is capable of N2 fixation, Mo itself is not necessary to carry out this process. The initial binding of N2 with chalcogels under illumination was observed with in situ diffuse-reflectance Fourier transform infrared spectroscopy (DRIFTS). (15)N2 isotope experiments confirm that the generated NH3 derives from N2 Density functional theory (DFT) electronic structure calculations suggest that the N2 binding is thermodynamically favorable only with the highly reduced active clusters. The results reported herein contribute to ongoing efforts of mimicking nitrogenase in fixing nitrogen and point to a promising path in developing catalysts for the reduction of N2 under ambient conditions.

Visual Perception by Drivers of the Advertisements Located at Selected Major Routes

NASA Astrophysics Data System (ADS)

Bichajło, Lesław

2017-10-01

This article characterizes the research based on the analysis of the eye fixation points on the advertisements. The research has been realized in real road and traffic conditions. The group of 12 drivers was equipped with the glasses occulometric measurement system mounted on the driver’s head. The participants were driving their private cars. The analysis was concentrated on the fixations on the advertisement tables located along the selected national roads in Rzeszów area (Poland). For better recognition if the advertisements have distracted the drivers the number of fixations on the advertisements has been compared with the fixations on the road signs. The active drivers have observed many visual attractors like advertisements, road signs and cars being ahead and on another lane. Passive drivers have low number of fixations on road signs and advertisements. Their fixations typically have been localized on survey and they probably used the peripheral vision in order to recognition of road sign shapes. The results show, that: the percentage of fixations on the advertisement and road signs is different for each participants; the highest percentage of fixated advertisements was on the section with small number of advertisements, but in the city area, when a group of advertisements was on the road, the participants selected some of them, yet no participant fixated all advertisements localized in a small distance between them; the single advertisement visible from the long distance strongly attracts the visual perception; the percentage of the fixated advertisements was higher than road signs.

Methane-Stimulated Benthic Marine Nitrogen Fixation at Deep-Sea Methane Seeps

NASA Astrophysics Data System (ADS)

Dekas, A. E.; Orphan, V.

2011-12-01

Biological nitrogen fixation (the conversion of N2 to NH3) is a critical process in the oceans, counteracting the production of N2 gas by dissimilatory bacterial metabolisms and providing a source of bioavailable nitrogen to many nitrogen-limited ecosystems. Although current measurements of N2 production and consumption in the oceans indicate that the nitrogen cycle is not balanced, recent findings on the limits of nitrogen fixation suggest that the perceived imbalance is an artifact of an incomplete assessment of marine diazotrophy. One currently poorly studied and potentially underappreciated habitat for diazotrophic organisms is the sediments of the deep-sea. In the present study we investigate the distribution and magnitude of benthic marine diazotrophy at several active deep-sea methane seeps (Mound 12, Costa Rica; Eel River Basin, CA, USA; Hydrate Ridge, OR, USA; and Monterey Canyon, CA, USA). Using 15N2 and 15NH4 sediment incubation experiments followed by single-cell (FISH-NanoSIMS) and bulk isotopic analysis (EA-IRMS), we observed total protein synthesis (15N uptake from 15NH4) and nitrogen fixation (15N update from 15N2). The highest rates of nitrogen fixation observed in the methane seep sediment incubation experiments were over an order of magnitude greater than those previously published from non-seep deep-sea sediments (Hartwig and Stanley, Deep-Sea Research, 1978, 25:411-417). However, methane seep diazotrophy appears to be highly spatially variable, with sediments exhibiting no nitrogen fixation originating only centimeters away from sediments actively incorporating 15N from 15N2. The greatest spatial variability in diazotrophy was observed with depth in the sediment, and corresponded to steep gradients in sulfate and methane. The maximum rates of nitrogen fixation were observed within the methane-sulfate transition zone, where organisms mediating the anaerobic oxidation of methane are typically in high abundance. Additionally, incubation experiments without added methane were observed to have little to no nitrogen fixation activity. In previous work, we demonstrated the capability of uncultured methanotrophic archaea (ANME-2) to fix nitrogen when associated with sulfate reducing bacterial symbionts. These new results suggest that these microbes may be the dominant nitrogen-fixing organisms in methane seep sediment. Intriguingly, characterization of the diversity of nifH genes from our sediment incubations as well as published nifH sequences reported from other seep habitats suggest the potential for other diazotrophic microorganisms in addition to the ANME-2 archaea. To further explore this possibility, FISH-NanoSIMS analyses were conducted on two dominant free-living sulfate-reducing lineages from seep incubations demonstrating nitrogen fixation activity. Preliminary results from this analysis suggest that single cells belonging to the Desulfobulbaceae may also be involved in nitrogen fixation in methane seeps. Despite this demonstrated potential, the extent of methane-independent diazotrophy by non-ANME diazotrophs appears to be low within the methane seep environment. Further studies are necessary to assess the greater diversity and activity of diazotrophs in other deep-sea sedimentary habitats.

Seasonal patterns of climate controls over nitrogen fixation by Alnus viridis subsp

Treesearch

Jennifer S. Mitchell; Roger W. Ruess

2009-01-01

Patterns of and controls over N2 fixation by green alder were studied in post-fire, mid-succession, and white spruce upland forests in interior Alaska, focusing on the hypothesis that ecosystem-level nitrogen (N) inputs decrease with successional development. N2-fixation rates tracked plant phenology during the 1997 (...

Basin-wide N2 fixation in the deep waters of the Mediterranean Sea

NASA Astrophysics Data System (ADS)

Benavides, Mar; Bonnet, Sophie; Hernández, Nauzet; Martínez-Pérez, Alba María.; Nieto-Cid, Mar; Álvarez-Salgado, Xosé Antón; Baños, Isabel; Montero, María. F.; Mazuecos, Ignacio P.; Gasol, Josep M.; Osterholz, Helena; Dittmar, Thorsten; Berman-Frank, Ilana; Arístegui, Javier

2016-06-01

Recent findings indicate that N2 fixation is significant in aphotic waters, presumably due to heterotrophic diazotrophs depending on organic matter for their nutrition. However, the relationship between organic matter and heterotrophic N2 fixation remains unknown. Here we explore N2 fixation in the deep chlorophyll maximum and underneath deep waters across the whole Mediterranean Sea and relate it to organic matter composition, characterized by optical and molecular methods. Our N2 fixation rates were in the range of those previously reported for the euphotic zone of the Mediterranean Sea (up to 0.43 nmol N L-1 d-1) and were significantly correlated to the presence of relatively labile organic matter with fluorescence and molecular formula properties representative for peptides and unsaturated aliphatics and associated with the presence of more oxygenated ventilated water masses. Finally, and despite that the aphotic N2 fixation contributes largely to total water column diazotrophic activity (>50%), its contribution to overall nitrogen inputs to the basin is negligible (<0.5%).

Discriminating between intentional and unintentional gaze fixation using multimodal-based fuzzy logic algorithm for gaze tracking system with NIR camera sensor

NASA Astrophysics Data System (ADS)

Naqvi, Rizwan Ali; Park, Kang Ryoung

2016-06-01

Gaze tracking systems are widely used in human-computer interfaces, interfaces for the disabled, game interfaces, and for controlling home appliances. Most studies on gaze detection have focused on enhancing its accuracy, whereas few have considered the discrimination of intentional gaze fixation (looking at a target to activate or select it) from unintentional fixation while using gaze detection systems. Previous research methods based on the use of a keyboard or mouse button, eye blinking, and the dwell time of gaze position have various limitations. Therefore, we propose a method for discriminating between intentional and unintentional gaze fixation using a multimodal fuzzy logic algorithm applied to a gaze tracking system with a near-infrared camera sensor. Experimental results show that the proposed method outperforms the conventional method for determining gaze fixation.

Orienting movements in area 9 identified by long-train ICMS.

PubMed

Lanzilotto, M; Perciavalle, V; Lucchetti, C

2015-03-01

The effect of intracortical microstimulation has been studied in several cortical areas from motor to sensory areas. The frontal pole has received particular attention, and several microstimulation studies have been conducted in the frontal eye field, supplementary eye field, and the premotor ear-eye field, but no microstimulation studies concerning area 9 are currently available in the literature. In the present study, to fill up this gap, electrical microstimulation was applied to area 9 in two macaque monkeys using long-train pulses of 500-700-800 and 1,000 ms, during two different experimental conditions: a spontaneous condition, while the animals were not actively fixating on a visual target, and during a visual fixation task. In these experiments, we identified backward ear movements, goal-directed eye movements, and the development of head forces. Kinematic parameters for ear and eye movements overlapped in the spontaneous condition, but they were different during the visual fixation task. In this condition, ear and eye kinematics have an opposite behavior: movement amplitude, duration, and maximal and mean velocities increase during a visual fixation task for the ear, while they decrease for the eye. Therefore, a top-down visual attention engagement could modify the kinematic parameters for these two effectors. Stimulation with the longest train durations, i.e., 800/1,000 ms, evokes not only the highest eye amplitude, but also a significant development of head forces. In this research article, we propose a new vision of the frontal oculomotor fields, speculating a role for area 9 in the control of goal-directed orienting behaviors and gaze shift control.

Revisiting N2 fixation in Guerrero Negro intertidal microbial mats with a functional single-cell approach

PubMed Central

Woebken, Dagmar; Burow, Luke C; Behnam, Faris; Mayali, Xavier; Schintlmeister, Arno; Fleming, Erich D; Prufert-Bebout, Leslie; Singer, Steven W; Cortés, Alejandro López; Hoehler, Tori M; Pett-Ridge, Jennifer; Spormann, Alfred M; Wagner, Michael; Weber, Peter K; Bebout, Brad M

2015-01-01

Photosynthetic microbial mats are complex, stratified ecosystems in which high rates of primary production create a demand for nitrogen, met partially by N2 fixation. Dinitrogenase reductase (nifH) genes and transcripts from Cyanobacteria and heterotrophic bacteria (for example, Deltaproteobacteria) were detected in these mats, yet their contribution to N2 fixation is poorly understood. We used a combined approach of manipulation experiments with inhibitors, nifH sequencing and single-cell isotope analysis to investigate the active diazotrophic community in intertidal microbial mats at Laguna Ojo de Liebre near Guerrero Negro, Mexico. Acetylene reduction assays with specific metabolic inhibitors suggested that both sulfate reducers and members of the Cyanobacteria contributed to N2 fixation, whereas 15N2 tracer experiments at the bulk level only supported a contribution of Cyanobacteria. Cyanobacterial and nifH Cluster III (including deltaproteobacterial sulfate reducers) sequences dominated the nifH gene pool, whereas the nifH transcript pool was dominated by sequences related to Lyngbya spp. Single-cell isotope analysis of 15N2-incubated mat samples via high-resolution secondary ion mass spectrometry (NanoSIMS) revealed that Cyanobacteria were enriched in 15N, with the highest enrichment being detected in Lyngbya spp. filaments (on average 4.4 at% 15N), whereas the Deltaproteobacteria (identified by CARD-FISH) were not significantly enriched. We investigated the potential dilution effect from CARD-FISH on the isotopic composition and concluded that the dilution bias was not substantial enough to influence our conclusions. Our combined data provide evidence that members of the Cyanobacteria, especially Lyngbya spp., actively contributed to N2 fixation in the intertidal mats, whereas support for significant N2 fixation activity of the targeted deltaproteobacterial sulfate reducers could not be found. PMID:25303712

Revisiting N 2 fixation in Guerrero Negro intertidal microbial mats with a functional single-cell approach

DOE PAGES

Woebken, Dagmar; Burow, Luke C.; Behnam, Faris; ...

2014-10-10

Photosynthetic microbial mats are complex, stratified ecosystems in which high rates of primary production create a demand for nitrogen, met partially by N 2 fixation. Dinitrogenase reductase ( nifH) genes and transcripts from Cyanobacteria and heterotrophic bacteria (for example, Deltaproteobacteria) were detected in these mats, yet their contribution to N 2 fixation is poorly understood. We used a combined approach of manipulation experiments with inhibitors, nifH sequencing and single-cell isotope analysis to investigate the active diazotrophic community in intertidal microbial mats at Laguna Ojo de Liebre near Guerrero Negro, Mexico. Acetylene reduction assays with specific metabolic inhibitors suggested that bothmore » sulfate reducers and members of the Cyanobacteria contributed to N 2 fixation, whereas 15N 2 tracer experiments at the bulk level only supported a contribution of Cyanobacteria. Cyanobacterial and nifH Cluster III (including deltaproteobacterial sulfate reducers) sequences dominated the nifH gene pool, whereas the nifH transcript pool was dominated by sequences related to Lyngbya spp. Single-cell isotope analysis of 15N 2-incubated mat samples via high-resolution secondary ion mass spectrometry (NanoSIMS) revealed that Cyanobacteria were enriched in 15N, with the highest enrichment being detected in Lyngbya spp. filaments (on average 4.4 at% 15N), whereas the Deltaproteobacteria (identified by CARD-FISH) were not significantly enriched. We investigated the potential dilution effect from CARD-FISH on the isotopic composition and concluded that the dilution bias was not substantial enough to influence our conclusions. As a result, our combined data provide evidence that members of the Cyanobacteria, especially Lyngbya spp., actively contributed to N 2 fixation in the intertidal mats, whereas support for significant N 2 fixation activity of the targeted deltaproteobacterial sulfate reducers could not be found.« less

Comparison of Nitrogen Fixation Activity in Tall and Short Spartina alterniflora Salt Marsh Soils 1

PubMed Central

Hanson, Roger B.

1977-01-01

A comparison of the N2 fixers in the tall Spartina alterniflora and short S. alterniflora marsh soils was investigated. Zero-order kinetics and first-order kinetics of acetylene reduction were used to describe the activity of the N2 fixers in marsh soil slurries. It was found that the Vmax values were approximately 10 times greater for the N2 fixers in the tall Spartina than in the short Spartina marsh when raffinose was used as the energy source. In addition, the (Ks + Sn) values were approximately 4 to 15 times lower for the N2 fixers in the tall Spartina than in short Spartina marsh. First-order kinetics of nitrogen fixation for several substrates indicate that the N2 fixers in the tall Spartina marsh were two to seven times more active than those in the short Spartina marsh. Ammonium chloride (25 μg/ml) did not inhibit nitrogen fixation in the tall Spartina marsh, but there was a 50% inhibition in nitrogen fixation in the short Spartina marsh. On the other hand, sodium nitrate inhibited nitrogen fixation almost 100% at 25 μg/ml in both soil environments. Amino nitrogen (25 to 100 μg/ml) had little or no effect on nitrogen fixation. The results indicate that the N2 fixers in the tall Spartina marsh were physiologically more responsive to nutrient addition than those in the short Spartina marsh. This difference in the two populations may be related to the difference in daily tidal influence in the respective areas and thus provide another explanation for the enhanced S. alterniflora production in the creek bank soil system. PMID:16345213

Comparison of effects of seven treatment methods for distal radius fracture on minimizing complex regional pain syndrome

PubMed Central

Sun, Tao

2016-01-01

Introduction Using network meta-analysis, we evaluated the adverse effects of the seven most common treatment methods, i.e., bridging external fixation, non-bridging external fixation, K-wire fixation, plaster fixation, dorsal plating, volar plating, and dorsal and volar plating, by their associated risk of developing complex regional pain syndrome (CRPS) in distal radius fracture (DRF) patients. Material and methods Following an exhaustive search of scientific literature databases for high quality studies, randomized controlled trials (RCTs) related to our study topic were screened and selected based on stringent predefined inclusion and exclusion criteria. Data extracted from the selected studies were used for statistical analyses using Stata 12.0 software. Results A total of 17 RCTs, including 1658 DRF patients, were enrolled in this network meta-analysis. Among the 1658 DRF patients, 452 received bridging external fixation, 525 received non-bridging external fixation, 154 received K-wire fixation, 84 received plaster fixation, 132 received dorsal plating, 123 received volar plating, and 188 received dorsal and volar plating. When compared to bridging external fixation patients, there was no marked difference in the CRPS risk in DRF patients receiving different treatments (all p > 0.05). However, the surface under the cumulative ranking curves (SUCRA) for plaster fixation (77.0%) and non-bridging external fixation (71.3%) were significantly higher compared with the other five methods. Conclusions Our findings suggest that compared with bridging external fixation, K-wire fixation, dorsal plating, volar plating, dorsal and volar plating, plaster fixation and non-bridging external fixation might be the better treatment methods to reduce the risk of CRPS in DRF patients. PMID:28144268

Radiologic Changes by Early Motion in Neck Fractures of the Fifth Metacarpal Treated with Antegrade Intramedullary Fixation.

PubMed

Heo, Youn Moo; Kim, Sang Bum; Yi, Jin Woong; Kim, Tae Gyun; Lim, Byoung Gu

2016-02-01

As intramedullary (IM) fixation is one of the fixation methods used in neck fractures of the fifth metacarpal, an early motion of injured finger can be allowed. The purpose of this study is to evaluate whether immediate active motion affects the stability of antegrade IM fixation in surgical treatment of neck fractures of the fifth metacarpal bone and to assess related factors. Thirty one patients treated by closed reduction and antegrade IM fixation were consecutively enrolled. All patients started active motion of the little finger since 7 postoperative days and only daily activities including writing, typing or washing were allowed until the union of fracture. All fractures were healed within four to eight weeks. The changes of angulation, fifth metacarpal length and tip to head distance of K-wire were compared between immediate postoperative radiographs and radiographs at eight weeks. In addition, the effects by age, gender, initial angulation and comminution of the metacarpal neck were assessed. The average change of angulation was 0.12°, 5th metacarpal length was 1.49mm and tip to head distance of K-wire was 1.31mm. There was no significant difference in the change of angulation (p = 0.137). But, there were significant differences in the change of 5th metacarpal length and tip to head distance of K-wire ([Formula: see text]). The change of angulation was related to a comminution of the metacarpal neck and that of 5th metacarpal length was related to age and sex. The change of 5th metacarpal length and tip to head distance of K-wire can occur by an early mobilization in the antegrade IM fixation for neck fractures of the fifth metacarpal. However, we thought that an early active motion after surgery is important to increase the patients' satisfaction, even though careful selection of candidates is necessary.

Implantation of active fixation leads in coronary veins for left ventricular stimulation: report of five cases.

PubMed

Hansky, Bert; Vogt, Juergen; Gueldner, Holger; Schulte-Eistrup, Sebastian; Lamp, Barbara; Heintze, Johannes; Horstkotte, Dieter; Koerfer, Reiner

2007-01-01

Securing transvenous left ventricular (LV) pacing leads without an active fixation mechanism in proximal coronary vein (CV) segments is usually challenging and frequently impossible. We investigated how active fixation leads can be safely implanted in this location, how to avoid perforating the free wall of the CV, and how to recognize and respond to perforations. In five patients with no alternative to LV pacing from proximal CV segments, 4 Fr SelectSecure (Medtronic, Minneapolis, MN, USA) leads, which have a fixed helix, were implanted through a modified 6 Fr guide catheter with a pre-shaped tip (Launcher, Medtronic). Active fixation leads were successfully implanted in proximal CVs in five patients. There were no complications. Acute and chronic pacing thresholds were comparable to those of conventional CV leads. The pre-shaped guide catheter tip remains in close proximity to the myocardial aspect of the CV, directing the lead helix toward a safe implantation site. If only proximal CV pacing sites are available, 4 Fr SelectSecure leads can be safely implanted through a modified Launcher guide catheter, avoiding more invasive implantation techniques. Other than venous stenting or implantation of leads with retractable tines, SelectSecure leads are expected to remain extractable.

Nitrogen Fixation (Acetylene Reduction) by Epiphytes of Freshwater Macrophytes

PubMed Central

Finke, Linda R.; Seeley, H. W.

1978-01-01

The involvement of epiphytic microorganisms in nitrogen fixation was investigated in a shallow freshwater pond near Ithaca, N.Y. The acetylene reduction technique was used to follow diel and seasonal cycles of nitrogen fixation by epiphytes of Myriophyllum spicatum. Acetylene-reducing activity was maximal between noon and 6 p.m., but substantial levels of activity relative to daytime rates continued through the night. Experiments with the seasonal course of activity showed a gradual decline during the autumn months and no activity in January or February. Activity commenced in May, with an abrupt increase to levels between 0.45 and 0.95 nmol of ethylene formed per mg (dry weight) of plant per h. Through most of the summer months, mean rates of acetylene reduction remained between 0.15 and 0.60 nmol/mg (dry weight) per h. It was calculated from diel and seasonal cycles that, in the pond areas studied, epiphytes were capable of adding from 7.5 to 12.5 μg of N per mg of plant per year to the pond. This amount is significant relative to the total amount of nitrogen incorporated into the plant. Blue-green algae (cyanobacteria), particularly Gloeotrichia, appeared to bear prime responsibility for nitrogen fixation, but photosynthetic bacteria of the genus Rhodopseudomonas were isolated from M. spicatum and shown to support high rates of acetylene reduction. PMID:16345301

The Active Side of Stereopsis: Fixation Strategy and Adaptation to Natural Environments.

PubMed

Gibaldi, Agostino; Canessa, Andrea; Sabatini, Silvio P

2017-03-20

Depth perception in near viewing strongly relies on the interpretation of binocular retinal disparity to obtain stereopsis. Statistical regularities of retinal disparities have been claimed to greatly impact on the neural mechanisms that underlie binocular vision, both to facilitate perceptual decisions and to reduce computational load. In this paper, we designed a novel and unconventional approach in order to assess the role of fixation strategy in conditioning the statistics of retinal disparity. We integrated accurate realistic three-dimensional models of natural scenes with binocular eye movement recording, to obtain accurate ground-truth statistics of retinal disparity experienced by a subject in near viewing. Our results evidence how the organization of human binocular visual system is finely adapted to the disparity statistics characterizing actual fixations, thus revealing a novel role of the active fixation strategy over the binocular visual functionality. This suggests an ecological explanation for the intrinsic preference of stereopsis for a close central object surrounded by a far background, as an early binocular aspect of the figure-ground segregation process.

The time course of saccadic decision making: dynamic field theory.

PubMed

Wilimzig, Claudia; Schneider, Stefan; Schöner, Gregor

2006-10-01

Making a saccadic eye movement involves two decisions, the decision to initiate the saccade and the selection of the visual target of the saccade. Here we provide a theoretical account for the time-courses of these two processes, whose instabilities are the basis of decision making. We show how the cross-over from spatial averaging for fast saccades to selection for slow saccades arises from the balance between excitatory and inhibitory processes. Initiating a saccade involves overcoming fixation, as can be observed in the countermanding paradigm, which we model accounting both for the temporal evolution of the suppression probability and its dependence on fixation activity. The interaction between the two forms of decision making is demonstrated by predicting how the cross-over from averaging to selection depends on the fixation stimulus in gap-step-overlap paradigms. We discuss how the activation dynamics of our model may be mapped onto neuronal structures including the motor map and the fixation cells in superior colliculus.

A "footprint" of plant carbon fixation cycle functions during the development of a heterotrophic fungus.

PubMed

Lyu, Xueliang; Shen, Cuicui; Xie, Jiatao; Fu, Yanping; Jiang, Daohong; Hu, Zijin; Tang, Lihua; Tang, Liguang; Ding, Feng; Li, Kunfei; Wu, Song; Hu, Yanping; Luo, Lilian; Li, Yuanhao; Wang, Qihua; Li, Guoqing; Cheng, Jiasen

2015-08-11

Carbon fixation pathway of plants (CFPP) in photosynthesis converts solar energy to biomass, bio-products and biofuel. Intriguingly, a large number of heterotrophic fungi also possess enzymes functionally associated with CFPP, raising the questions about their roles in fungal development and in evolution. Here, we report on the presence of 17 CFPP associated enzymes (ten in Calvin-Benson-Basham reductive pentose phosphate pathway and seven in C4-dicarboxylic acid cycle) in the genome of Sclerotinia sclerotiorum, a heterotrophic phytopathogenic fungus, and only two unique enzymes: ribulose-1, 5-bisphosphate carboxylase-oxygenase (Rubisco) and phosphoribulokinase (PRK) were absent. This data suggested an incomplete CFPP-like pathway (CLP) in fungi. Functional profile analysis demonstrated that the activity of the incomplete CLP was dramatically regulated during different developmental stages of S. sclerotiorum. Subsequent experiments confirmed that many of them were essential to the virulence and/or sclerotial formation. Most of the CLP associated genes are conserved in fungi. Phylogenetic analysis showed that many of them have undergone gene duplication, gene acquisition or loss and functional diversification in evolutionary history. These findings showed an evolutionary links in the carbon fixation processes of autotrophs and heterotrophs and implicated the functions of related genes were in course of continuous change in different organisms in evolution.

Modeling and minimizing interference from corneal birefringence in retinal birefringence scanning for foveal fixation detection

PubMed Central

Irsch, Kristina; Gramatikov, Boris; Wu, Yi-Kai; Guyton, David

2011-01-01

Utilizing the measured corneal birefringence from a data set of 150 eyes of 75 human subjects, an algorithm and related computer program, based on Müller-Stokes matrix calculus, were developed in MATLAB for assessing the influence of corneal birefringence on retinal birefringence scanning (RBS) and for converging upon an optical/mechanical design using wave plates (“wave-plate-enhanced RBS”) that allows foveal fixation detection essentially independently of corneal birefringence. The RBS computer model, and in particular the optimization algorithm, were verified with experimental human data using an available monocular RBS-based eye fixation monitor. Fixation detection using wave-plate-enhanced RBS is adaptable to less cooperative subjects, including young children at risk for developing amblyopia. PMID:21750772

Nodule and Leaf Nitrate Reductases and Nitrogen Fixation in Medicago sativa L. under Water Stress

PubMed Central

Aparicio-Tejo, P.; Sánchez-Díaz, Manuel

1982-01-01

The effect of water stress on patterns of nitrate reductase activity in the leaves and nodules and on nitrogen fixation were investigated in Medicago sativa L. plants watered 1 week before drought with or without NO3−. Nitrogen fixation was decreased by water stress and also inhibited strongly by the presence of NO3−. During drought, leaf nitrate reductase activity (NRA) decreased significantly particularly in plants watered with NO3−, while with rewatering, leaf NRA recovery was quite important especially in the NO3−-watered plants. As water stress progressed, the nodular NRA increased both in plants watered with NO3− and in those without NO3− contrary to the behavior of the leaves. Beyond −15.105 pascal, nodular NRA began to decrease in plants watered with NO3−. This phenomenon was not observed in nodules of plants given water only. Upon rewatering, it was observed that in plants watered with NO3− the nodular NRA increased again, while in plants watered but not given NO3−, such activity began to decrease. Nitrogen fixation increased only in plants without NO3−. PMID:16662233

Evidence of cartilage repair by joint distraction in a canine model of osteoarthritis.

PubMed

Wiegant, Karen; Intema, Femke; van Roermund, Peter M; Barten-van Rijbroek, Angelique D; Doornebal, Arie; Hazewinkel, Herman A W; Lafeber, Floris P J G; Mastbergen, Simon C

2015-02-01

Knee osteoarthritis (OA) is a degenerative joint disorder characterized by cartilage, bone, and synovial tissue changes that lead to pain and functional impairment. Joint distraction is a treatment that provides long-term improvement in pain and function accompanied by cartilage repair, as evaluated indirectly by imaging studies and measurement of biochemical markers. The purpose of this study was to evaluate cartilage tissue repair directly by histologic and biochemical assessments after joint distraction treatment. In 27 dogs, OA was induced in the right knee joint (groove model; surgical damage to the femoral cartilage). After 10 weeks of OA development, the animals were randomized to 1 of 3 groups. Two groups were fitted with an external fixator, which they wore for a subsequent 10 weeks (one group with and one without joint distraction), and the third group had no external fixation (OA control group). Pain/function was studied by force plate analysis. Cartilage integrity and chondrocyte activity of the surgically untouched tibial plateaus were analyzed 25 weeks after removal of the fixator. Changes in force plate analysis values between the different treatment groups were not conclusive. Features of OA were present in the OA control group, in contrast to the generally less severe damage after joint distraction. Those treated with joint distraction had lower macroscopic and histologic damage scores, higher proteoglycan content, better retention of newly formed proteoglycans, and less collagen damage. In the fixator group without distraction, similarly diminished joint damage was found, although it was less pronounced. Joint distraction as a treatment of experimentally induced OA results in cartilage repair activity, which corroborates the structural observations of cartilage repair indicated by surrogate markers in humans. Copyright © 2015 by the American College of Rheumatology.

A mechanistic, globally-applicable model of plant nitrogen uptake, retranslocation and fixation

NASA Astrophysics Data System (ADS)

Fisher, J. B.; Tan, S.; Malhi, Y.; Fisher, R. A.; Sitch, S.; Huntingford, C.

2008-12-01

Nitrogen is one of the nutrients that can most limit plant growth, and nitrogen availability may be a controlling factor on biosphere responses to climate change. We developed a plant nitrogen assimilation model based on a) advective transport through the transpiration stream, b) retranslocation whereby carbon is expended to resorb nitrogen from leaves, c) active uptake whereby carbon is expended to acquire soil nitrogen, and d) biological nitrogen fixation whereby carbon is expended for symbiotic nitrogen fixers. The model relies on 9 inputs: 1) net primary productivity (NPP), 2) plant C:N ratio, 3) available soil nitrogen, 4) root biomass, 5) transpiration rate, 6) saturated soil depth,7) leaf nitrogen before senescence, 8) soil temperature, and 9) ability to fix nitrogen. A carbon cost of retranslocation is estimated based on leaf nitrogen and compared to an active uptake carbon cost based on root biomass and available soil nitrogen; for nitrogen fixers both costs are compared to a carbon cost of fixation dependent on soil temperature. The NPP is then allocated to optimize growth while maintaining the C:N ratio. The model outputs are total plant nitrogen uptake, remaining NPP available for growth, carbon respired to the soil and updated available soil nitrogen content. We test and validate the model (called FUN: Fixation and Uptake of Nitrogen) against data from the UK, Germany and Peru, and run the model under simplified scenarios of primary succession and climate change. FUN is suitable for incorporation into a land surface scheme of a General Circulation Model and will be coupled with a soil model and dynamic global vegetation model as part of a land surface model (JULES).

Rates of Dinitrogen Fixation and the Abundance of Diazotrophs in North American Coastal Waters Between Cape Hatteras and Georges Bank

NASA Technical Reports Server (NTRS)

Mulholland, M.R.; Bernhardt, P. W.; Blanco-Garcia, J. L.; Mannino, A.; Hyde, K.; Mondragon, E.; Turk, K.; Moisander, P. H.; Zehr, J. P.

2012-01-01

We coupled dinitrogen (N2) fixation rate estimates with molecular biological methods to determine the activity and abundance of diazotrophs in coastal waters along the temperate North American Mid-Atlantic continental shelf during multiple seasons and cruises. Volumetric rates of N2 fixation were as high as 49.8 nmol N L(sup -1) d(sup -1) and areal rates as high as 837.9 micromol N m(sup -2) d(sup -1) in our study area. Our results suggest that N2 fixation occurs at high rates in coastal shelf waters that were previously thought to be unimportant sites of N2 fixation and so were excluded from calculations of pelagic marine N2 fixation. Unicellular N2-fixing group A cyanobacteria were the most abundant diazotrophs in the Atlantic coastal waters and their abundance was comparable to, or higher than, that measured in oceanic regimes where they were discovered. High rates of N2 fixation and the high abundance of diazotrophs along the North American Mid-Atlantic continental shelf highlight the need to revise marine N budgets to include coastal N2 fixation. Integrating areal rates of N2 fixation over the continental shelf area between Cape Hatteras and Nova Scotia, the estimated N2 fixation in this temperate shelf system is about 0.02 Tmol N yr(sup -1), the amount previously calculated for the entire North Atlantic continental shelf. Additional studies should provide spatially, temporally, and seasonally resolved rate estimates from coastal systems to better constrain N inputs via N2 fixation from the neritic zone.

A dataset of stereoscopic images and ground-truth disparity mimicking human fixations in peripersonal space

PubMed Central

Canessa, Andrea; Gibaldi, Agostino; Chessa, Manuela; Fato, Marco; Solari, Fabio; Sabatini, Silvio P.

2017-01-01

Binocular stereopsis is the ability of a visual system, belonging to a live being or a machine, to interpret the different visual information deriving from two eyes/cameras for depth perception. From this perspective, the ground-truth information about three-dimensional visual space, which is hardly available, is an ideal tool both for evaluating human performance and for benchmarking machine vision algorithms. In the present work, we implemented a rendering methodology in which the camera pose mimics realistic eye pose for a fixating observer, thus including convergent eye geometry and cyclotorsion. The virtual environment we developed relies on highly accurate 3D virtual models, and its full controllability allows us to obtain the stereoscopic pairs together with the ground-truth depth and camera pose information. We thus created a stereoscopic dataset: GENUA PESTO—GENoa hUman Active fixation database: PEripersonal space STereoscopic images and grOund truth disparity. The dataset aims to provide a unified framework useful for a number of problems relevant to human and computer vision, from scene exploration and eye movement studies to 3D scene reconstruction. PMID:28350382

Interrupted: The roles of distributed effort and incubation in preventing fixation and generating problem solutions.

PubMed

Sio, Ut Na; Kotovsky, Kenneth; Cagan, Jonathan

2017-05-01

Fixation on inappropriate concepts is a key barrier to problem solving. Previous research has shown that continuous work is likely to cause repeated retrieval of those concepts, resulting in increased fixation. Accordingly, distributing effort across problems through multiple, brief, and interlaced sessions (distributed effort) should prevent such fixation and in turn enhance problem solving. This study examined whether distributed effort can provide an advantage for problem solving, particularly for problems that can induce fixation (Experiment 1), and whether and how incubation can be combined with distributed effort to further enhance performance (Experiment 2). Remote Associates Test (RAT) problems were used as the problem-solving tasks. Half of them (i.e., misleading RAT) were more likely to mislead individuals to fixate on incorrect associates than the other half. Experiments revealed a superiority of distributed over massed effort on misleading RAT performance and a differing time course of incubation for the massed and distributed groups. We conclude that distributed effort facilitates problem solving, most likely via overcoming fixation. Cognitive mechanisms other than the commonly posited forgetting of inappropriate ideas may occur during incubation to facilitate problem solving. The experiments in this article offer support for the occurrence of spreading activation during incubation.

Activity of neurons in area 6 of the cat during fixation and eye movements.

PubMed

Weyand, T G; Gafka, A C

1998-01-01

We studied the visuomotor properties of 645 neurons in area 6 of five cats trained in oculomotor tasks. The area we recorded from corresponds well with territories believed to contain the feline homologue of the frontal eye fields observed in primates. Despite an expectation that cells with pre-saccadic activity would be common, only a small fraction (approximately 5%) of the cells displayed activity that could be linked to subsequent saccadic eye movements. These pre-motor cells appeared to be distributed over a broad region of cortex mixed in with other cell types. As in primates, saccade-related activity tended to occur only during "purposeful" saccades. At least 30% (208/645) of the neurons were visual, with many of these cells possessing huge receptive fields that appeared to include the entire contralateral visual field. Visual responsiveness was generally attenuated by fixation during the oculomotor tasks. Although attentional mechanisms may play a role in this attenuation, this cortical area also exhibits powerful lateral interactions in which spatially displaced visual stimuli suppress each other. Most cells, visually responsive or not, were affected by fixation. Nearly equal proportions of cells showed increases or decreases in activity during fixation. For many of the cells affected by fixation, the source of this modulation appears to reflect cognitive, rather than sensory or motor processes. This included cells that showed anticipatory activity, and cells that responded to the reward only when it was presented in the context of the task. Based on the paucity of pre-saccadic neurons, it would be difficult to conclude that this region of cortex in the cat is homologous to the frontal eye fields of the monkey. However, when considered in the context of differences in the oculomotor habits of these two animals, we believe the homology fits. In addition to pre-motor neurons, the properties of several other cell types found in this area could contribute to the control of gaze.

Resolution of Conflicting Signals at the Single-Cell Level in the Regulation of Cyanobacterial Photosynthesis and Nitrogen Fixation.

PubMed

Mohr, Wiebke; Vagner, Tomas; Kuypers, Marcel M M; Ackermann, Martin; Laroche, Julie

2013-01-01

Unicellular, diazotrophic cyanobacteria temporally separate dinitrogen (N2) fixation and photosynthesis to prevent inactivation of the nitrogenase by oxygen. This temporal segregation is regulated by a circadian clock with oscillating activities of N2 fixation in the dark and photosynthesis in the light. On the population level, this separation is not always complete, since the two processes can overlap during transitions from dark to light. How do single cells avoid inactivation of nitrogenase during these periods? One possibility is that phenotypic heterogeneity in populations leads to segregation of the two processes. Here, we measured N2 fixation and photosynthesis of individual cells using nanometer-scale secondary ion mass spectrometry (nanoSIMS) to assess both processes in a culture of the unicellular, diazotrophic cyanobacterium Crocosphaera watsonii during a dark-light and a continuous light phase. We compared single-cell rates with bulk rates and gene expression profiles. During the regular dark and light phases, C. watsonii exhibited the temporal segregation of N2 fixation and photosynthesis commonly observed. However, N2 fixation and photosynthesis were concurrently measurable at the population level during the subjective dark phase in which cells were kept in the light rather than returned to the expected dark phase. At the single-cell level, though, cells discriminated against either one of the two processes. Cells that showed high levels of photosynthesis had low nitrogen fixing activities, and vice versa. These results suggest that, under ambiguous environmental signals, single cells discriminate against either photosynthesis or nitrogen fixation, and thereby might reduce costs associated with running incompatible processes in the same cell.

Resolution of Conflicting Signals at the Single-Cell Level in the Regulation of Cyanobacterial Photosynthesis and Nitrogen Fixation

PubMed Central

Mohr, Wiebke; Vagner, Tomas; Kuypers, Marcel M. M.; Ackermann, Martin; LaRoche, Julie

2013-01-01

Unicellular, diazotrophic cyanobacteria temporally separate dinitrogen (N2) fixation and photosynthesis to prevent inactivation of the nitrogenase by oxygen. This temporal segregation is regulated by a circadian clock with oscillating activities of N2 fixation in the dark and photosynthesis in the light. On the population level, this separation is not always complete, since the two processes can overlap during transitions from dark to light. How do single cells avoid inactivation of nitrogenase during these periods? One possibility is that phenotypic heterogeneity in populations leads to segregation of the two processes. Here, we measured N2 fixation and photosynthesis of individual cells using nanometer-scale secondary ion mass spectrometry (nanoSIMS) to assess both processes in a culture of the unicellular, diazotrophic cyanobacterium Crocosphaera watsonii during a dark-light and a continuous light phase. We compared single-cell rates with bulk rates and gene expression profiles. During the regular dark and light phases, C. watsonii exhibited the temporal segregation of N2 fixation and photosynthesis commonly observed. However, N2 fixation and photosynthesis were concurrently measurable at the population level during the subjective dark phase in which cells were kept in the light rather than returned to the expected dark phase. At the single-cell level, though, cells discriminated against either one of the two processes. Cells that showed high levels of photosynthesis had low nitrogen fixing activities, and vice versa. These results suggest that, under ambiguous environmental signals, single cells discriminate against either photosynthesis or nitrogen fixation, and thereby might reduce costs associated with running incompatible processes in the same cell. PMID:23805199

Reproducibility of EEG-fMRI results in a patient with fixation-off sensitivity.

PubMed

Formaggio, Emanuela; Storti, Silvia Francesca; Galazzo, Ilaria Boscolo; Bongiovanni, Luigi Giuseppe; Cerini, Roberto; Fiaschi, Antonio; Manganotti, Paolo

2014-07-01

Blood oxygenation level-dependent (BOLD) activation associated with interictal epileptiform discharges in a patient with fixation-off sensitivity (FOS) was studied using a combined electroencephalography-functional magnetic resonance imaging (EEG-fMRI) technique. An automatic approach for combined EEG-fMRI analysis and a subject-specific hemodynamic response function was used to improve general linear model analysis of the fMRI data. The EEG showed the typical features of FOS, with continuous epileptiform discharges during elimination of central vision by eye opening and closing and fixation; modification of this pattern was clearly visible and recognizable. During all 3 recording sessions EEG-fMRI activations indicated a BOLD signal decrease related to epileptiform activity in the parietal areas. This study can further our understanding of this EEG phenomenon and can provide some insight into the reliability of the EEG-fMRI technique in localizing the irritative zone.

Dynamic Fixation of Humeral Shaft Fractures Using Active Locking Plates: A Prospective Observational Study.

PubMed

Madey, Steven M; Tsai, Stanley; Fitzpatrick, Daniel C; Earley, Kathleen; Lutsch, Michael; Bottlang, Michael

2017-01-01

Rigid locked plating constructs can suppress fracture healing by inhibiting interfragmentary motion required to stimulate natural bone healing by callus formation. Dynamic fixation with active locking plates reduces construct stiffness, enables controlled interfragmentary motion, and has been shown to induce faster and stronger bone healing in vivo compared to rigid locking plates. This prospective observational study represents the first clinical use of active locking plates. It documents our early clinical experience with active plates for stabilization of humeral shaft fractures to assess their durability and understand potential complications. Eleven consecutive patients with humeral shaft fractures (AO/OTA types 12 A-C) were prospectively enrolled at a level I and a level II trauma center. Fractures were stabilized by using active locking plates without supplemental bone graft or bone morphogenic proteins. The screw holes of active locking plates are elastically suspended in elastomer envelopes inside the plate, enabling up to 1.5 mm of controlled interfragmentary motion. Progression of fracture healing and integrity of implant fixation was assessed radiographically at 3, 6, 12, and 24 weeks post surgery. Patient-reported functional outcome measures were obtained at 6, 12, and 24 weeks post surgery. The primary endpoint of this study was plate durability in absence of plate bending or breakage, or failure of the elastically suspended locking hole mechanism. Secondary endpoints included fracture healing, complications requiring revision surgery, and functional outcome scores. The eleven patients had six simple AO/ OTA type 12A fractures, three wedge type 12B fractures, and two comminuted type 12C fracture, including one open fracture. All active locking plates endured the 6-month loading period without any signs of fatigue or failure. Ten of eleven fractures healed at 10.9 ± 5.2 weeks, as evident by bridging callus and pain-free function. One fracture required revision surgery 37 weeks post surgery due to late fixation failure at the screwbone interface in the presence of a atrophic delayed union. The average Disability of the Arm, Shoulder and Hand (DASH) score improved from 31 ± 22 at week 6 to 13 ± 15 by week 24, approaching that of the normal, healthy population (DASH = 10.1). By week 12, the difference between Constant shoulder scores, expressed as the difference between the affected and contralateral arm (8 ± 8), was considered excellent. By week 24, the SF-12 physical health score (44 ± 9) and mental health score (48 ± 11) approached the mean value of 50 that represents the norm for the general U.S. population. Absence of failure of the plate and locking holes suggests that dynamic fixation of humeral shaft fractures with active plates provides safe and effective fixation. Moreover, early callus bridging and excellent functional outcome scores suggest that dynamic fixation with active locking plates may promote increased fracture healing over standard locked plating.

Kennedy Space Center Fixation Tube (KFT)

NASA Technical Reports Server (NTRS)

Richards, Stephanie E.; Levine, Howard G.; Romero, Vergel

2016-01-01

Experiments performed on the International Space Station (ISS) frequently require the experimental organisms to be preserved until they can be returned to earth for analysis in the appropriate laboratory facility. The Kennedy Fixation Tube (KFT) was developed to allow astronauts to apply fixative, chemical compounds that are often toxic, to biological samples without the use of a glovebox while maintaining three levels of containment (Fig. 1). KFTs have been used over 200 times on-orbit with no leaks of chemical fixative. The KFT is composed of the following elements: a polycarbonate main tube where the fixative is loaded preflight, the sample tube where the plant or other biological specimens is placed during operations, the expansion plug, actuator, and base plug that provides fixative containment (Fig. 2). The main tube is pre-filled with 25 mL of fixative solution prior to flight. When actuated, the specimen contained within the sample tube is immersed with approximately 22 mL (+/- 2 mL) of the fixative solution. The KFT has been demonstrated to maintain its containment at ambient temperatures, 4degC refrigeration and -100 C freezing conditions.

Antimicrobial efficacy of external fixator pins coated with a lipid stabilized hydroxyapatite/chlorhexidine complex to prevent pin tract infection in a goat model.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dejong, E. Schuyler; Deberardino, T. M.; Brooks, D. E.

Background: Pin tract infection is a common complication of external fixation. An antiinfective external fixator pin might help to reduce the incidence of pin tract infection and improve pin fixation. Methods: Stainless steel and titanium external fixator pins, with and without a lipid stabilized hydroxyapatite/chlorhexidine coating, were evaluated in a goat model. Two pins contaminated with an identifiable Staphylococcus aureus strain were inserted into each tibia of 12 goats. The pin sites were examined daily. On day 14, the animals were killed, and the pin tips cultured. Insertion and extraction torques were measured. Results: Infection developed in 100% of uncoatedmore » pins, whereas coated pins demonstrated 4.2% infected, 12.5% colonized, and the remainder, 83.3%, had no growth (p < 0.01). Pin coating decreased the percent loss of fixation torque over uncoated pins (p = 0.04). Conclusion: These results demonstrate that the lipid stabilized hydroxyapatite/chlorhexidine coating was successful in decreasing infection and improving fixation of external fixator pins.« less

Effect of mineral phosphates on growth and nitrogen fixation of diazotrophic cyanobacteria Anabaena variabilis and Westiellopsis prolifica.

PubMed

Yandigeri, Mahesh S; Yadav, Arvind K; Meena, Kamlesh Kumar; Pabbi, Sunil

2010-03-01

The nitrogen fixing cyanobacterial strains namely Anabaena variabilis (Nostocales, Nostocaceae) and Westiellopsis prolifica (Nostocales, Hapalosiphonaceae) were evaluated for their nitrogen fixation and growth potential in response to different concentrations (10, 20 and 30 mg P) of the alternate insoluble P-sources Mussorie Rock Phosphate and Tricalcium Phosphate. Distinct and significant intergeneric differences were observed with respect to nitrogen fixation measured as Acetylene Reduction Activity (ARA) and growth potential as soluble proteins, total carbohydrate content, dry weight and total chlorophyll content in response to different concentrations of Mussorie Rock Phosphate and Tricalcium Phosphate. Both the strains showed higher soluble protein content at 20 mg P (Mussorie Rock Phosphate) that increased with time of incubation in A. variabilis. Both cyanobacteria recorded maximum Acetylene Reduction Activity at 20 mg P (Tricalcium Phosphate) followed by activity in presence of soluble phosphate (K2HPO4). The mean activity at all concentrations of insoluble phosphate (Mussorie Rock Phosphate and Tricalcium Phosphate) was more than in the presence of soluble phosphate.

CYTOCHEMISTRY OF PHOSPHATASES OF THE SARCOPLASMIC RETICULUM

PubMed Central

Tice, Lois W.; Engel, A. G.

1966-01-01

The distribution of the Mg-dependent ATPase associated with a microsomal fraction of rabbit psoas muscle was studied histochemically and its localization in relation to the vesicles of the fraction and to the structure of intact fixed muscle was determined. Although enzyme activity was retained after fixation in hydroxyadipaldehyde and in glyoxal, it was lost after fixation in glutaraldehyde or after 4 hr fixation in formaldehyde. Activity was optimally demonstrated when incubations were conducted at 17°C, in media containing 125 mM Trismaleate buffer, pH 7.5, 5 mM ATP, 4 mM MgCl2, and 1 mM Pb(NO3)2. After such incubations, activity was present throughout the sarcoplasmic reticulum, but was absent from the T system. Activation by Na or K could not be demonstrated histochemically. However, the other biochemical properties of the enzyme in the isolated vesicles and in intact muscle were similar with respect to Mg dependence, substrate specificity, inhibition by Ca, N-ethyl maleimide, p-hydroxymercuribenzoate, and lack of inhibition by ouabain. PMID:4226392

Nitrogen fixation dynamics of two diazotrophic communities in Mono Lake, California

USGS Publications Warehouse

Oremland, R.S.

1990-01-01

Two types of diazotrophic microbial communities were found in the littoral zone of alkaline hypersaline Mono Lake, California. One consisted of anaerobic bacteria inhabiting the flocculent surface layers of sediments. Nitrogen fixation (acetylene reduction) by flocculent surface layers occurred under anaerobic conditions, was not stimulated by light or by additions of organic substrates, and was inhibited by O2, nitrate, and ammonia. The second community consisted of a ball-shaped association of a filamentous chlorophyte (Ctenocladus circinnatus) with diazotrophic, nonheterocystous cyanobacteria, as well as anaerobic bacteria (Ctenocladus balls). Nitrogen fixation by Ctenocladus balls was usually, but not always, stimulated by light. Rates of anaerobic dark fixation equaled those in the light under air. Fixation in the light was stimulated by 3-(3,4-dichlorophenyl)-1,1-dimethylurea and by propanil [N-(3,4-dichlorophenyl)propanamide]. 3-(3,4-Dichlorophenyl)-1,1-dimethyl urea-elicited nitrogenase activity was inhibited by ammonia (96%) and nitrate (65%). Fixation was greatest when Ctenocladus balls were incubated anaerobically in the light with sulfide. Dark anaerobic fixation was not stimulated by organic substrates in short-term (4-h) incubations, but was in long-term (67-h) ones. Areal estimates of benthic N2 fixation were measured seasonally, using chambers. Highest rates (~29.3 ??mol of C2H4 m-2 h-1) occurred under normal diel regimens of light and dark. These estimates indicate that benthic N2 fixation has the potential to be a significant nitrogen source in Mono Lake.

PHYSIOLOGY OF NITROGEN FIXATION BY BACILLUS POLYMYXA

PubMed Central

Grau, F. H.; Wilson, P. W.

1962-01-01

Grau, F. H. (University of Wisconsin, Madison) and P. W. Wilson. Physiology of nitrogen fixation by Bacillus polymyxa. J. Bacteriol. 83:490–496. 1962.—Of 17 strains of Bacillus polymyxa tested for fixation of molecular nitrogen, 15 fixed considerable quantities (30 to 150 μg N/ml). Two strains of the closely related B. macerans did not use N2, but possibly other members of this species may do so. Confirmation of fixation was obtained by showing incorporation of N15 into cell material. Both iron and molybdenum are specifically required for fixation; without the addition of these metals to the nitrogen-free medium, the growth rate and the total nitrogen fixed were reduced about 30 to 50%. No requirement for added molybdenum could be shown when ammonia was the nitrogen source, and the absence of iron caused only a slight decrease in growth. Washed-cell suspensions of B. polymyxa containing an active hydrogenase readily incorporated N15 into cell materials when provided with mannitol, glucose, or pyruvate but not when formate was the substrate. Hydrogen is a specific inhibitor of fixation, reducing both the rate and final amount of nitrogen fixed; it did not reduce growth on ammonia. Fixation was strictly anaerobic, 1% oxygen in the gas phase being sufficient to stop fixation. Arsenate is a powerful inhibitor of fixation of N2 by washed-cell suspensions of B. polymyxa, indicating that high-energy phosphate may be significant for this process. PMID:13901244

Electrical Microstimulation of the Superior Colliculus in Strabismic Monkeys.

PubMed

Fleuriet, Jérome; Walton, Mark M G; Ono, Seiji; Mustari, Michael J

2016-06-01

Visually guided saccades are disconjugate in human and nonhuman strabismic primates. The superior colliculus (SC) is a region of the brain topographically organized in visual and motor maps where the saccade goal is spatially coded. The present study was designed to investigate if a site of stimulation on the topographic motor map was evoking similar or different saccade vectors for each eye. We used microelectrical stimulation (MS) of the SC in two strabismic (one esotrope and one exotrope) and two control macaques under binocular and monocular viewing conditions. We compared the saccade amplitudes and directions for each SC site and each condition independently of the fixating eye and then between each fixating eye. A comparison with disconjugacies of visually guided saccades was also performed. We observed different saccade vectors for the two eyes in strabismic monkeys, but conjugate saccades in normal monkeys. Evoked saccade vectors for the left eye when that eye was fixating the target were different from those of the right eye when it was fixating. The disconjugacies evoked by the MS were not identical but similar to those observed for visually guided saccades especially for the dominant eye. Our results suggest that, in strabismus, the saccade generator does not interpret activation of a single location of the SC as the same desired displacement for each eye. This finding is important for advancing understanding of the development of neural circuits in strabismus. French Abstract.

Individual Differences in Infant Oculomotor Behavior During the Viewing of Complex Naturalistic Scenes.

PubMed

Wass, Sam V; Smith, Tim J

2014-07-01

Little research hitherto has examined how individual differences in attention, as assessed using standard experimental paradigms, relate to individual differences in how attention is spontaneously allocated in more naturalistic contexts. Here, we analyzed the time intervals between refoveating eye movements (fixation durations) while typically developing 11-month-old infants viewed a 90-min battery ranging from complex dynamic to noncomplex static materials. The same infants also completed experimental assessments of cognitive control, psychomotor reaction times (RT), processing speed (indexed via peak look during habituation), and arousal (indexed via tonic pupil size). High test-retest reliability was found for fixation duration, across testing sessions and across types of viewing material. Increased cognitive control and increased arousal were associated with reduced variability in fixation duration. For fixations to dynamic stimuli, in which a large proportion of saccades may be exogenously cued, we found that psychomotor RT measures were most predictive of mean fixation duration; for fixations to static stimuli, in contrast, in which there is less exogenous attentional capture, we found that psychomotor RT did not predict performance, but that measures of cognitive control and arousal did. The implications of these findings for understanding the development of attentional control in naturalistic settings are discussed.

Medicago truncatula copper transporter 1 (MtCOPT1) delivers copper for symbiotic nitrogen fixation.

PubMed

Senovilla, Marta; Castro-Rodríguez, Rosario; Abreu, Isidro; Escudero, Viviana; Kryvoruchko, Igor; Udvardi, Michael K; Imperial, Juan; González-Guerrero, Manuel

2018-04-01

Copper is an essential nutrient for symbiotic nitrogen fixation. This element is delivered by the host plant to the nodule, where membrane copper (Cu) transporter would introduce it into the cell to synthesize cupro-proteins. COPT family members in the model legume Medicago truncatula were identified and their expression determined. Yeast complementation assays, confocal microscopy and phenotypical characterization of a Tnt1 insertional mutant line were carried out in the nodule-specific M. truncatula COPT family member. Medicago truncatula genome encodes eight COPT transporters. MtCOPT1 (Medtr4g019870) is the only nodule-specific COPT gene. It is located in the plasma membrane of the differentiation, interzone and early fixation zones. Loss of MtCOPT1 function results in a Cu-mitigated reduction of biomass production when the plant obtains its nitrogen exclusively from symbiotic nitrogen fixation. Mutation of MtCOPT1 results in diminished nitrogenase activity in nodules, likely an indirect effect from the loss of a Cu-dependent function, such as cytochrome oxidase activity in copt1-1 bacteroids. These data are consistent with a model in which MtCOPT1 transports Cu from the apoplast into nodule cells to provide Cu for essential metabolic processes associated with symbiotic nitrogen fixation. © 2018 The Authors. New Phytologist © 2018 New Phytologist Trust.

Finite Element Simulation and Additive Manufacturing of Stiffness-Matched NiTi Fixation Hardware for Mandibular Reconstruction Surgery

PubMed Central

Jahadakbar, Ahmadreza; Shayesteh Moghaddam, Narges; Amerinatanzi, Amirhesam; Dean, David; Karaca, Haluk E.; Elahinia, Mohammad

2016-01-01

Process parameters and post-processing heat treatment techniques have been developed to produce both shape memory and superelastic NiTi using Additive Manufacturing. By introducing engineered porosity, the stiffness of NiTi can be tuned to the level closely matching cortical bone. Using additively manufactured porous superelastic NiTi, we have proposed the use of patient-specific, stiffness-matched fixation hardware, for mandible skeletal reconstructive surgery. Currently, Ti-6Al-4V is the most commonly used material for skeletal fixation devices. Although this material offers more than sufficient strength for immobilization during the bone healing process, the high stiffness of Ti-6Al-4V implants can cause stress shielding. In this paper, we present a study of mandibular reconstruction that uses a dry cadaver mandible to validate our geometric and biomechanical design and fabrication (i.e., 3D printing) of NiTi skeletal fixation hardware. Based on the reference-dried mandible, we have developed a Finite Element model to evaluate the performance of the proposed fixation. Our results show a closer-to-normal stress distribution and an enhanced contact pressure at the bone graft interface than would be in the case with Ti-6Al-4V off-the-shelf fixation hardware. The porous fixation plates used in this study were fabricated by selective laser melting. PMID:28952598

Finite Element Simulation and Additive Manufacturing of Stiffness-Matched NiTi Fixation Hardware for Mandibular Reconstruction Surgery.

PubMed

Jahadakbar, Ahmadreza; Shayesteh Moghaddam, Narges; Amerinatanzi, Amirhesam; Dean, David; Karaca, Haluk E; Elahinia, Mohammad

2016-12-19

Process parameters and post-processing heat treatment techniques have been developed to produce both shape memory and superelastic NiTi using Additive Manufacturing. By introducing engineered porosity, the stiffness of NiTi can be tuned to the level closely matching cortical bone. Using additively manufactured porous superelastic NiTi, we have proposed the use of patient-specific, stiffness-matched fixation hardware, for mandible skeletal reconstructive surgery. Currently, Ti-6Al-4V is the most commonly used material for skeletal fixation devices. Although this material offers more than sufficient strength for immobilization during the bone healing process, the high stiffness of Ti-6Al-4V implants can cause stress shielding. In this paper, we present a study of mandibular reconstruction that uses a dry cadaver mandible to validate our geometric and biomechanical design and fabrication (i.e., 3D printing) of NiTi skeletal fixation hardware. Based on the reference-dried mandible, we have developed a Finite Element model to evaluate the performance of the proposed fixation. Our results show a closer-to-normal stress distribution and an enhanced contact pressure at the bone graft interface than would be in the case with Ti-6Al-4V off-the-shelf fixation hardware. The porous fixation plates used in this study were fabricated by selective laser melting.

Vasoactive intestinal peptide and electrical activity influence neuronal survival

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brenneman, D.E.; Eiden, L.E.

1986-02-01

Blockage of electrical activity in dissociated spinal cord cultures results in a significant loss of neurons during a critical period in development. Decreases in neuronal cell numbers and SVI-labeled tetanus toxin fixation produced by electrical blockage with tetrodotoxin (TTX) were prevented by addition of vasoactive intestinal peptide (VIP) to the nutrient medium. The most effective concentration of VIP was 0.1 nM. At higher concentrations, the survival-enhancing effect of VIP on TTX-treated cultures was attenuated. Addition of the peptide alone had no significant effect on neuronal cell counts or tetanus toxin fixation. With the same experimental conditions, two closely related peptides,more » PHI-27 (peptide, histidyl-isoleucine amide) and secretin, were found not to increase the number of neurons in TTX-treated cultures. Interference with VIP action by VIP antiserum resulted in neuronal losses that were not significantly different from those observed after TTX treatment. These data indicate that under conditions of electrical blockade a neurotrophic action of VIP on neuronal survival can be demonstrated.« less

An improved methodology for investigating the parameters influencing migration resistance of abdominal aortic stent-grafts.

PubMed

Corbett, Timothy J; Callanan, Anthony; O'Donnell, Michael R; McGloughlin, Tim M

2010-02-01

To develop an improved methodology for investigating the parameters influencing stent-graft migration, with particular focus on the limitations of existing methods. A physiological silicone rubber abdominal aortic aneurysm (AAA) model for fixation studies was manufactured based on an idealized AAA geometry: the model had a 24-mm neck, a 50-mm aneurysm, 12-mm-diameter legs, a 60 degrees bifurcation angle, and 2-mm-thick walls. The models were authenticated in neck fixation experiments. The displacement force required to migrate stent-grafts in physiological pulsatile flow was tested dynamically in water at 37 degrees C. A commercially available longitudinally rigid stent-graft (AneuRx) and a homemade device with little longitudinal rigidity were studied in a number of different configurations to investigate the effect of neck fixation length and systolic pressure on displacement force. The AneuRx (6.95+/-0.49 to 8.52+/-0.5 N) performed significantly better than the homemade device (2.57+/-0.11 to 4.62+/-0.25 N) in pulsatile flow. The opposite was true in the neck fixation tests because the longitudinal stiffness of the AneuRx was not accounted for. Increasing pressure or decreasing fixation length compromised the fixation of the homemade device. This relationship was not as clear for the AneuRx because decreasing proximal fixation resulted in an increase in iliac fixation, which could assist fixation in this device. Assessing the migration resistance of stent-grafts based solely on proximal fixation discriminates against devices that are longitudinally stiff. Current in vivo models may give inaccurate displacement forces due to the high degree of oversizing in these studies. A novel in vitro approach, accounting for longitudinal rigidity and realistic graft oversizing, was developed to determine the resistance of aortic stent-grafts to migration in the period immediately after device implantation.

The Pattern of Visual Fixation Eccentricity and Instability in Optic Neuropathy and Its Spatial Relationship to Retinal Ganglion Cell Layer Thickness.

PubMed

Mallery, Robert M; Poolman, Pieter; Thurtell, Matthew J; Wang, Jui-Kai; Garvin, Mona K; Ledolter, Johannes; Kardon, Randy H

2016-07-01

The purpose of this study was to assess whether clinically useful measures of fixation instability and eccentricity can be derived from retinal tracking data obtained during optical coherence tomography (OCT) in patients with optic neuropathy (ON) and to develop a method for relating fixation to the retinal ganglion cell complex (GCC) thickness. Twenty-nine patients with ON underwent macular volume OCT with 30 seconds of confocal scanning laser ophthalmoscope (cSLO)-based eye tracking during fixation. Kernel density estimation quantified fixation instability and fixation eccentricity from the distribution of fixation points on the retina. Preferred ganglion cell layer loci (PGCL) and their relationship to the GCC thickness map were derived, accounting for radial displacement of retinal ganglion cell soma from their corresponding cones. Fixation instability was increased in ON eyes (0.21 deg2) compared with normal eyes (0.06982 deg2; P < 0.001), and fixation eccentricity was increased in ON eyes (0.48°) compared with normal eyes (0.24°; P = 0.03). Fixation instability and eccentricity each correlated moderately with logMAR acuity and were highly predictive of central visual field loss. Twenty-six of 35 ON eyes had PGCL skewed toward local maxima of the GCC thickness map. Patients with bilateral dense central scotomas had PGCL in homonymous retinal locations with respect to the fovea. Fixation instability and eccentricity measures obtained during cSLO-OCT assess the function of perifoveal retinal elements and predict central visual field loss in patients with ON. A model relating fixation to the GCC thickness map offers a method to assess the structure-function relationship between fixation and areas of preserved GCC in patients with ON.

The Pattern of Visual Fixation Eccentricity and Instability in Optic Neuropathy and Its Spatial Relationship to Retinal Ganglion Cell Layer Thickness

PubMed Central

M. Mallery, Robert; Poolman, Pieter; J. Thurtell, Matthew; Wang, Jui-Kai; K. Garvin, Mona; Ledolter, Johannes; Kardon, Randy H.

2016-01-01

Purpose The purpose of this study was to assess whether clinically useful measures of fixation instability and eccentricity can be derived from retinal tracking data obtained during optical coherence tomography (OCT) in patients with optic neuropathy (ON) and to develop a method for relating fixation to the retinal ganglion cell complex (GCC) thickness. Methods Twenty-nine patients with ON underwent macular volume OCT with 30 seconds of confocal scanning laser ophthalmoscope (cSLO)-based eye tracking during fixation. Kernel density estimation quantified fixation instability and fixation eccentricity from the distribution of fixation points on the retina. Preferred ganglion cell layer loci (PGCL) and their relationship to the GCC thickness map were derived, accounting for radial displacement of retinal ganglion cell soma from their corresponding cones. Results Fixation instability was increased in ON eyes (0.21 deg2) compared with normal eyes (0.06982 deg2; P < 0.001), and fixation eccentricity was increased in ON eyes (0.48°) compared with normal eyes (0.24°; P = 0.03). Fixation instability and eccentricity each correlated moderately with logMAR acuity and were highly predictive of central visual field loss. Twenty-six of 35 ON eyes had PGCL skewed toward local maxima of the GCC thickness map. Patients with bilateral dense central scotomas had PGCL in homonymous retinal locations with respect to the fovea. Conclusions Fixation instability and eccentricity measures obtained during cSLO-OCT assess the function of perifoveal retinal elements and predict central visual field loss in patients with ON. A model relating fixation to the GCC thickness map offers a method to assess the structure–function relationship between fixation and areas of preserved GCC in patients with ON. PMID:27409502

A model based on temporal dynamics of fixations for distinguishing expert radiologists' scanpaths

NASA Astrophysics Data System (ADS)

Gandomkar, Ziba; Tay, Kevin; Brennan, Patrick C.; Mello-Thoms, Claudia

2017-03-01

This study investigated a model which distinguishes expert radiologists from less experienced radiologists based on features describing spatio-temporal dynamics of their eye movement during interpretation of digital mammograms. Eye movements of four expert and four less experienced radiologists were recorded during interpretation of 120 two-view digital mammograms of which 59 had biopsy proven cancers. For each scanpath, a two-dimensional recurrence plot, which represents the radiologist's refixation pattern, was generated. From each plot, six features indicating the spatio-temporal dynamics of fixations were extracted. The first feature measured the percentage of recurrent fixations; the second indicated the percentage of recurrent fixations which was fixated later in several consecutive fixations; the third measured the percentage of recurrent fixations that form a repeated sequence of fixations and the fourth assessed whether the recurrent fixations were occurring sequentially close together. The number of switches between the two mammographic views was also measured, as was the average number of consecutive fixations in each view before switching. These six features along with total time on case and average fixation duration were fed into a support vector machine whose performance was evaluated using 10-fold cross validation. The model achieved a sensitivity of 86.3% and a specificity of 85.2% for distinguishing experts' scanpaths. The obtained result suggests that spatio-temporal dynamics of eye movements can characterize expertise level and has potential applications for monitoring the development of expertise among radiologists as a result of different training regimes and continuing education schemes.

Biomechanical Evaluation of Standard Versus Extended Proximal Fixation Olecranon Plates for Fixation of Olecranon Fractures.

PubMed

Boden, Allison L; Daly, Charles A; Dalwadi, Poonam P; Boden, Stephanie A; Hutton, William C; Muppavarapu, Raghuveer C; Gottschalk, Michael B

2018-01-01

Small olecranon fractures present a significant challenge for fixation, which has resulted in development of plates with proximal extension. Olecranon-specific plates with proximal extensions are widely thought to offer superior fixation of small proximal fragments but have distinct disadvantages: larger dissection, increased hardware prominence, and the increased possibility of impingement. Previous biomechanical studies of olecranon fracture fixation have compared methods of fracture fixation, but to date there have been no studies defining olecranon plate fixation strength for standard versus extended olecranon plates. The purpose of this study is to evaluate the biomechanical utility of the extended plate for treatment of olecranon fractures. Sixteen matched pairs of fresh-frozen human cadaveric elbows were used. Of the 16, 8 matched pairs received a transverse osteotomy including 25% and 8 including 50% of the articular surface on the proximal fragment. One elbow from each pair was randomly assigned to a standard-length plate, and the other elbow in the pair received the extended-length plate, for fixation of the fracture. The ulnae were cyclically loaded and subsequently loaded to failure, with ultimate load, number of cycles, and gap formation recorded. There was no statistically significant difference between the standard and extended fixation plates in simple transverse fractures at either 25% or 50% from the proximal most portion of the articular surface of the olecranon. Standard fixation plates are sufficient for the fixation of small transverse fractures, but caution should be utilized particularly with comminution and nontransverse fracture patterns.

Nitrogenase-mimic iron-containing chalcogels for photochemical reduction of dinitrogen to ammonia

DOE PAGES

Liu, Jian; Kelley, Matthew S.; Wu, Weiqiang; ...

2016-05-02

A nitrogenase-inspired biomimetic chalcogel system comprising double-cubane [Mo 2Fe 6S 8(SPh) 3] and single-cubane (Fe 4S 4) biomimetic clusters demonstrates photocatalytic N 2 fixation and conversion to NH 3 in ambient temperature and pressure conditions. Replacing the Fe 4S 4 clusters in this system with other inert ions such as Sb 3+, Sn 4+, Zn 2+ also gave chalcogels that were photocatalytically active. Finally, molybdenum-free chalcogels containing only Fe 4S 4 clusters are also capable of accomplishing the N2 fixation reaction with even higher efficiency than their Mo 2Fe 6S 8(SPh) 3-containing counterparts. In this study, our results suggest thatmore » redox-active iron-sulfide–containing materials can activate the N 2 molecule upon visible light excitation, which can be reduced all of the way to NH 3 using protons and sacrificial electrons in aqueous solution. Evidently, whereas the Mo 2Fe 6S 8(SPh) 3 is capable of N 2 fixation, Mo itself is not necessary to carry out this process. The initial binding of N 2 with chalcogels under illumination was observed with in situ diffuse-reflectance Fourier transform infrared spectroscopy (DRIFTS). 15N 2 isotope experiments confirm that the generated NH 3 derives from N 2. Density functional theory (DFT) electronic structure calculations suggest that the N 2 binding is thermodynamically favorable only with the highly reduced active clusters. Finally, the results reported herein contribute to ongoing efforts of mimicking nitrogenase in fixing nitrogen and point to a promising path in developing catalysts for the reduction of N 2 under ambient conditions.« less

Development of an activity-directed selection system enabled significant improvement of the carboxylation efficiency of Rubisco.

PubMed

Cai, Zhen; Liu, Guoxia; Zhang, Junli; Li, Yin

2014-07-01

Photosynthetic CO(2) fixation is the ultimate source of organic carbon on earth and thus is essential for crop production and carbon sequestration. Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyzes the first step of photosynthetic CO(2) fixation. However, the extreme low carboxylation efficiency of Rubisco makes it the most attractive target for improving photosynthetic efficiency. Extensive studies have focused on re-engineering a more efficient enzyme, but the effort has been impeded by the limited understanding of its structure-function relationships and the lack of an efficient selection system towards its activity. To address the unsuccessful molecular engineering of Rubisco, we developed an Escherichia coli-based activity-directed selection system which links the growth of host cell solely to the Rubisco activity therein. A Synechococcus sp. PCC7002 Rubisco mutant with E49V and D82G substitutions in the small subunit was selected from a total of 15,000 mutants by one round of evolution. This mutant showed an 85% increase in specific carboxylation activity and a 45% improvement in catalytic efficiency towards CO(2). The small-subunit E49V mutation was speculated to influence holoenzyme catalysis through interaction with the large-subunit Q225. This interaction is conserved among various Rubisco from higher plants and Chlamydomonas reinhardtii. Knowledge of these might provide clues for engineering Rubisco from higher plants, with the potential of increasing the crop yield.

Coliform Bacteria and Nitrogen Fixation in Pulp and Paper Mill Effluent Treatment Systems

PubMed Central

Gauthier, Francis; Neufeld, Josh D.; Driscoll, Brian T.; Archibald, Frederick S.

2000-01-01

The majority of pulp and paper mills now biotreat their combined effluents using activated sludge. On the assumption that their wood-based effluents have negligible fixed N, and that activated-sludge microorganisms will not fix significant N, these mills routinely spend large amounts adding ammonia or urea to their aeration tanks (bioreactors) to permit normal biomass growth. N2 fixation in seven Eastern Canadian pulp and paper mill effluent treatment systems was analyzed using acetylene reduction assays, quantitative nitrogenase (nifH) gene probing, and bacterial isolations. In situ N2 fixation was undetectable in all seven bioreactors but was present in six associated primary clarifiers. One primary clarifier was studied in greater detail. Approximately 50% of all culturable cells in the clarifier contained nifH, of which >90% were Klebsiella strains. All primary-clarifier coliform bacteria growing on MacConkey agar were identified as klebsiellas, and all those probed contained nifH. In contrast, analysis of 48 random coliform isolates from other mill water system locations showed that only 24 (50%) possessed the nifH gene, and only 13 (27%) showed inducible N2-fixing activity. Thus, all the pulp and paper mill primary clarifiers tested appeared to be sites of active N2 fixation (0.87 to 4.90 mg of N liter−1 day−1) and a microbial community strongly biased toward this activity. This may also explain why coliform bacteria, especially klebsiellas, are indigenous in pulp and paper mill water systems. PMID:11097883

The Activity of Nodules of the Supernodulating Mutant Mtsunn Is not Limited by Photosynthesis under Optimal Growth Conditions

PubMed Central

Cabeza, Ricardo A.; Lingner, Annika; Liese, Rebecca; Sulieman, Saad; Senbayram, Mehmet; Tränkner, Merle; Dittert, Klaus; Schulze, Joachim

2014-01-01

Legumes match the nodule number to the N demand of the plant. When a mutation in the regulatory mechanism deprives the plant of that ability, an excessive number of nodules are formed. These mutants show low productivity in the fields, mainly due to the high carbon burden caused through the necessity to supply numerous nodules. The objective of this study was to clarify whether through optimal conditions for growth and CO2 assimilation a higher nodule activity of a supernodulating mutant of Medicago truncatula (M. truncatula) can be induced. Several experimental approaches reveal that under the conditions of our experiments, the nitrogen fixation of the supernodulating mutant, designated as sunn (super numeric nodules), was not limited by photosynthesis. Higher specific nitrogen fixation activity could not be induced through short- or long-term increases in CO2 assimilation around shoots. Furthermore, a whole plant P depletion induced a decline in nitrogen fixation, however this decline did not occur significantly earlier in sunn plants, nor was it more intense compared to the wild-type. However, a distinctly different pattern of nitrogen fixation during the day/night cycles of the experiment indicates that the control of N2 fixing activity of the large number of nodules is an additional problem for the productivity of supernodulating mutants. PMID:24727372

Propidium iodide staining: a new application in fluorescence microscopy for analysis of cytoarchitecture in adult and developing rodent brain.

PubMed

Hezel, Marcus; Ebrahimi, Fahim; Koch, Marco; Dehghani, Faramarz

2012-10-01

Immunohistochemical visualization of antigens in specimen has evolved to an indispensable technique in biomedical research for investigations of cell morphology and pathology both in bright field and fluorescence microscopy. While there are couple of staining methods that reveal entire cytoarchitecture in bright field microscopy such as Nissl or hemalaun-eosin, there are still limitations in visualizations of cytoarchitecture in fluorescence microscopy. The present study reports a simple staining method that provides the required illustration of cell allocations and cellular composition in fluorescence microscopy in adult and in developing rodent central nervous system using the fluorophore propidium iodide (PI, 5μg/mL). PI is a well-accepted marker for degenerating cells when applied prior to fixation (pre-fixation PI staining). Here, PI was added to the sections after the fixation (post-fixation PI staining). This revised labeling procedure led to similar cytoarchitectural staining patterns in fluorescence microscopy as observed with hemalaun in bright field microscopy. This finding was proven in organotypic hippocampal slice cultures (OHSC) and brain sections obtained from different postnatal developmental stages. Excitotoxically lesioned OHSC subjected to pre-fixation PI staining merely showed brightly labeled condensed nuclei of degenerating neurons. In contrast, post-fixation PI staining additionally revealed extensive labeling of neuronal cell bodies and glial cells within the OHSC, thus allowing visualization of stratification of neuronal layers and cell morphology. Furthermore, post-fixation PI staining was combined with NeuN, calbindin, calretinin, glial fibrillary acidic protein or Griffonia simplicifolia isolectin B4 (IB(4)) in post natal (p1 and p9) and adult rats. In early post-natal brain sections almost all mentioned cellular markers led to an incomplete staining of the native cell organization and resulted in an inaccurate estimation of cell morphology when compared to adult brains. In contrast, post-fixation PI staining allowed investigation of the whole cytoarchitecture independent of the developmental stage. Taken together, post-fixation PI staining provides a detailed insight in the morphology of both developing and adult brain tissues in fluorescence microscopy. Copyright © 2012 Elsevier Ltd. All rights reserved.

Effect of air pollution on nitrogen fixation in lichens

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kallio, S.; Varheenmaa, T.

1974-01-01

Clear decrease (80-90%) of acetylene reduction in Stereocaulon paschale and Nephroma arcticum was observed in the polluted city area of Turku (SW Finland) within a period of three-four weeks, while nitrogenase activity remained unchanged in the specimens outside the city area. Carbon dioxide fixation in these lichens lowered 20-50%.

Fixation-Dependent Memory for Natural Scenes: An Experimental Test of Scanpath Theory

ERIC Educational Resources Information Center

Foulsham, Tom; Kingstone, Alan

2013-01-01

Many modern theories propose that perceptual information is represented by the sensorimotor activity elicited by the original stimulus. Scanpath theory (Noton & Stark, 1971) predicts that reinstating a sequence of eye fixations will help an observer recognize a previously seen image. However, the only studies to investigate this are…

Femoral press-fit fixation in ACL reconstruction using bone-patellar tendon-bone autograft: results at 15 years follow-up.

PubMed

Widuchowski, Wojciech; Widuchowska, Malgorzata; Koczy, Bogdan; Dragan, Szymon; Czamara, Andrzej; Tomaszewski, Wieslaw; Widuchowski, Jerzy

2012-06-27

If anterior cruciate ligament (ACL) reconstruction is to be performed, decision regarding graft choice and its fixation remains one of the most controversial. Multiple techniques for ACL reconstruction are available. To avoid disadvantages related to fixation devices, a hardware-free, press-fit ACL reconstruction technique was developed. The aim of this study was to evaluate clinical outcome and osteoarthritis progression in long term after ACL reconstruction with central third patellar-tendon autograft fixed to femur by press-fit technique. Fifty two patients met inclusion/excusion criteria for this study. The patients were assessed preoperatively and at 15 years after surgery with International Knee Documentation Committee Knee Ligament Evaluation Form, Lysholm knee score, Tegner activity scale and radiographs. Good overall clinical outcomes and self-reported assessments were documented, and remained good at 15 years. The mean Lysholm and Tegner scores improved from 59.7 ± 18.5 and 4.2 ± 1.0 preoperatively to 86.4 ± 5.6 (p = 0.004) and 6.9 ± 1.4 (p = 0.005) respectively at follow-up. The IKDC subjective score improved from 60.1 ± 9.2 to 80.2 ± 8.1 (p = 0.003). According to IKDC objective score, 75% of patients had normal or nearly normal knee joints at follow-up. Grade 0 or 1 results were seen in 85% of patients on laxity testing. Degenerative changes were found in 67% of patients. There was no correlation between arthritic changes and stability of knee and subjective evaluation (p > 0.05). ACL reconstruction with patellar tendon autograft fixed to femur with press-fit technique allows to achieve good self-reported assessments and clinical ligament evaluation up to 15 years. Advantages of the bone-patellar-tendon-bone (BPTB) press-fit fixation include unlimited bone-to-bone healing, cost effectiveness, avoidance of disadvantages associated with hardware, and ease for revision surgery. BPTB femoral press-fit fixation technique can be safely applied in clinical practice and enables patients to return to preinjury activities including high-risk sports.

Effects of artificial tracheal fixation on tracheal epithelial regeneration and prevention of tracheal stenosis.

PubMed

Nakaegawa, Yuta; Nakamura, Ryosuke; Tada, Yasuhiro; Suzuki, Ryo; Takezawa, Toshiaki; Nakamura, Tatsuo; Omori, Koichi

2017-06-01

Tight fixation of the artificial trachea is important for epithelialization and tracheal stenosis. The authors have developed an artificial trachea and have used it for tracheal reconstruction. Although various studies on tracheal reconstruction have been conducted, no studies have examined the effect of artificial tracheal fixation on tracheal stenosis and regeneration. Therefore, the purpose of the present study was to evaluate the effect of artificial tracheal fixation. Preliminary animal experiment. Artificial tracheae were implanted into rabbits with partial tracheal defects. Tracheal stenosis and regeneration of the tracheal epithelium on the artificial tracheae were evaluated by endoscopic examination, scanning electron microscopic analysis, and histological examination. The artificial tracheae fixed to the tracheal defects were classified into three groups (0-point, 4-point, and 8-point) by the number of fixation points. At 14 and 28 days post-implantation, the luminal surface of the implantation area was mostly covered with epithelium in all fixation groups. However, a small amount of granulation tissue was observed in the 0-point fixation group at 14 days post-implantation. Moreover, tracheal stenosis did not occur in the 8-point fixation group, but stenosis was detected in the other groups.

Low temperature delays timing and enhances the cost of nitrogen fixation in the unicellular cyanobacterium Cyanothece

PubMed Central

Brauer, Verena S; Stomp, Maayke; Rosso, Camillo; van Beusekom, Sebastiaan AM; Emmerich, Barbara; Stal, Lucas J; Huisman, Jef

2013-01-01

Marine nitrogen-fixing cyanobacteria are largely confined to the tropical and subtropical ocean. It has been argued that their global biogeographical distribution reflects the physiologically feasible temperature range at which they can perform nitrogen fixation. In this study we refine this line of argumentation for the globally important group of unicellular diazotrophic cyanobacteria, and pose the following two hypotheses: (i) nitrogen fixation is limited by nitrogenase activity at low temperature and by oxygen diffusion at high temperature, which is manifested by a shift from strong to weak temperature dependence of nitrogenase activity, and (ii) high respiration rates are required to maintain very low levels of oxygen for nitrogenase, which results in enhanced respiratory cost per molecule of fixed nitrogen at low temperature. We tested these hypotheses in laboratory experiments with the unicellular cyanobacterium Cyanothece sp. BG043511. In line with the first hypothesis, the specific growth rate increased strongly with temperature from 18 to 30 °C, but leveled off at higher temperature under nitrogen-fixing conditions. As predicted by the second hypothesis, the respiratory cost of nitrogen fixation and also the cellular C:N ratio rose sharply at temperatures below 21 °C. In addition, we found that low temperature caused a strong delay in the onset of the nocturnal nitrogenase activity, which shortened the remaining nighttime available for nitrogen fixation. Together, these results point at a lower temperature limit for unicellular nitrogen-fixing cyanobacteria, which offers an explanation for their (sub)tropical distribution and suggests expansion of their biogeographical range by global warming. PMID:23823493

Fixation-related FMRI analysis in the domain of reading research: using self-paced eye movements as markers for hemodynamic brain responses during visual letter string processing.

PubMed

Richlan, Fabio; Gagl, Benjamin; Hawelka, Stefan; Braun, Mario; Schurz, Matthias; Kronbichler, Martin; Hutzler, Florian

2014-10-01

The present study investigated the feasibility of using self-paced eye movements during reading (measured by an eye tracker) as markers for calculating hemodynamic brain responses measured by functional magnetic resonance imaging (fMRI). Specifically, we were interested in whether the fixation-related fMRI analysis approach was sensitive enough to detect activation differences between reading material (words and pseudowords) and nonreading material (line and unfamiliar Hebrew strings). Reliable reading-related activation was identified in left hemisphere superior temporal, middle temporal, and occipito-temporal regions including the visual word form area (VWFA). The results of the present study are encouraging insofar as fixation-related analysis could be used in future fMRI studies to clarify some of the inconsistent findings in the literature regarding the VWFA. Our study is the first step in investigating specific visual word recognition processes during self-paced natural sentence reading via simultaneous eye tracking and fMRI, thus aiming at an ecologically valid measurement of reading processes. We provided the proof of concept and methodological framework for the analysis of fixation-related fMRI activation in the domain of reading research. © The Author 2013. Published by Oxford University Press.

Carbon fixation in sediments of Sino-Pacific seas-differential contributions of bacterial and archaeal domains

NASA Astrophysics Data System (ADS)

Das, Anindita; Cao, Wenrui; Zhang, Hongjie; Saren, Gaowa; Jiang, Mingyu; Yu, Xinke

2017-11-01

Oceanic stretches experiencing perpetual darkness and extreme limitation of utilizable organic matter often rely on chemosynthetic carbon (C)-fixation. However, C-fixation is not limited to carbon-deplete environments alone but might also occur in varying degrees in carbon-replete locales depending on the nature and concentration of utilizable carbon, electron donors and acceptors. Quantification of microbial C-fixation and relative contribution of domains bacteria and archaea are therefore crucial. The present experiment estimates the differential rates of C-fixation by archaea and bacteria along with the effects of different electron donors. Four Sino-Pacific marine sediments from Bashi strait (Western Pacific Warm Pool), East China Sea, South China Sea and Okinawa Trough were examined. Total microbial C-uptake was estimated by doping of aqueous NaH14CO3. Total bacterial C-uptake was measured by blocking archaeal metabolism using inhibitor GC7. Archaeal contribution was estimated by subtracting total bacterial from total microbial C-uptake. Effect of electron donor addition was analyzed by spiking with ammonium, sulfide, and reduced metals. Results suggested that C-fixation in marine sediments was not the function of archaea alone, which was in contrast to results from several recent publications. C-fixing bacteria are also equally active. Often in spite of great effort of one domain to fix carbon, the system does not become net C-fixing due to equal and opposite C-releasing activity of the other domain. Thus a C-releasing bacterial or archaeal community can become C-fixing with the change of nature and concentration of electron donors.

Internal Versus External Fixation of Charcot Midfoot Deformity Realignment.

PubMed

Lee, Daniel J; Schaffer, Joseph; Chen, Tien; Oh, Irvin

2016-07-01

Internal and external fixation techniques have been described for realignment and arthrodesis of Charcot midfoot deformity. There currently is no consensus on the optimal method of surgical reconstruction. This systematic review compared the clinical results of surgical realignment with internal and external fixation, specifically in regard to return to functional ambulation, ulcer occurrence, nonunion, extremity amputation, unplanned further surgery, deep infection, wound healing problems, peri- or intraoperative fractures, and total cases with any complication. A search of multiple databases for all relevant articles published from January 1, 1990, to March 22, 2014, was performed. A logistic regression model evaluated each of the outcomes and its association with the type of fixation method. The odds of returning to functional ambulation were 25% higher for internal fixation (odds ratio [OR], 1.259). Internal fixation had a 42% reduced rate of ulcer occurrence (OR, 0.578). External fixation was 8 times more likely to develop radiographic nonunion than internal fixation (OR, 8.2). Internal fixation resulted in a 1.5-fold increase in extremity amputation (OR, 1.488), a 2-fold increase in deep infection (OR, 2.068), a 3.4-fold increase in wound healing complications (OR, 3.405), and a 1.5-fold increase in the total number of cases experiencing any complication (OR, 1.525). This was associated with a 20% increase in the need for unplanned further surgery with internal fixation (OR, 1.221). Although internal fixation may decrease the risk of nonunion and increase return to functional ambulation, it had a higher rate of overall complications than external fixation for realignment and arthrodesis of Charcot midfoot deformity. [Orthopedics. 2016; 39(4):e595-e601.]. Copyright 2016, SLACK Incorporated.

Protocol for HER2 FISH Using a Non-cross-linking, Formalin-free Tissue Fixative to Combine Advantages of Cryo-preservation and Formalin Fixation

PubMed Central

Loibner, Martina; Oberauner-Wappis, Lisa; Viertler, Christian; Groelz, Daniel; Zatloukal, Kurt

2017-01-01

Morphologic assessment of formalin-fixed, paraffin-embedded (FFPE) tissue samples has been the gold standard for cancer diagnostics for decades due to its excellent preservation of morphology. Personalized medicine increasingly provides individually adapted and targeted therapies for characterized individual diseases enabled by combined morphological and molecular analytical technologies and diagnostics. Performance of morphologic and molecular assays from the same FFPE specimen is challenging because of the negative impact of formalin due to chemical modification and cross-linking of nucleic acids and proteins. A non-cross-linking, formalin-free tissue fixative has been recently developed to fulfil both requirements, i.e., to preserve morphology like FFPE and biomolecules like cryo-preservation. Since FISH is often required in combination with histopathology and molecular diagnostics, we tested the applicability of FISH protocols on tissues treated with this new fixative. We found that formalin post-fixation of histological sections of non-cross-linking, formalin-free and paraffin-embedded (NCFPE) breast cancer tissue generated equivalent results to those with FFPE tissue in human epidermal growth factor receptor 2 (HER2) FISH analysis. This protocol describes how a FISH assay originally developed and validated for FFPE tissue can be used for NCFPE tissues by a simple post-fixation step of histological sections. PMID:29364207

Biomechanical investigation of different surgical strategies for the treatment of rib fractures using a three-dimensional human respiratory model.

PubMed

Shih, Kao-Shang; Truong, Thanh An; Hsu, Ching-Chi; Hou, Sheng-Mou

2017-11-02

Rib fracture is a common injury and can result in pain during respiration. Conservative treatment of rib fracture is applied via mechanical ventilation. However, ventilator-associated complications frequently occur. Surgical fixation is another approach to treat rib fractures. Unfortunately, this surgical treatment is still not completely defined. Past studies have evaluated the biomechanics of the rib cage during respiration using a finite element method, but only intact conditions were modelled. Thus, the purpose of this study was to develop a realistic numerical model of the human rib cage and to analyse the biomechanical performance of intact, injured and treated rib cages. Three-dimensional finite element models of the human rib cage were developed. Respiratory movement of the human rib cage was simulated to evaluate the strengths and limitations of different scenarios. The results show that a realistic human respiratory movement can be simulated and the predicted results were closely related to previous study (correlation coefficient>0.92). Fixation of two fractured ribs significantly decreased the fixation index (191%) compared to the injured model. This fixation may provide adequate fixation stability as well as reveal lower bone stress and implant stress compared with the fixation of three or more fractured ribs.

Individual Differences in Infant Oculomotor Behavior During the Viewing of Complex Naturalistic Scenes

PubMed Central

Wass, Sam V; Smith, Tim J

2014-01-01

Little research hitherto has examined how individual differences in attention, as assessed using standard experimental paradigms, relate to individual differences in how attention is spontaneously allocated in more naturalistic contexts. Here, we analyzed the time intervals between refoveating eye movements (fixation durations) while typically developing 11-month-old infants viewed a 90-min battery ranging from complex dynamic to noncomplex static materials. The same infants also completed experimental assessments of cognitive control, psychomotor reaction times (RT), processing speed (indexed via peak look during habituation), and arousal (indexed via tonic pupil size). High test–retest reliability was found for fixation duration, across testing sessions and across types of viewing material. Increased cognitive control and increased arousal were associated with reduced variability in fixation duration. For fixations to dynamic stimuli, in which a large proportion of saccades may be exogenously cued, we found that psychomotor RT measures were most predictive of mean fixation duration; for fixations to static stimuli, in contrast, in which there is less exogenous attentional capture, we found that psychomotor RT did not predict performance, but that measures of cognitive control and arousal did. The implications of these findings for understanding the development of attentional control in naturalistic settings are discussed. PMID:25635173

The effect of extracapsular injuries on growth and development of the mandible condyle: an experimental study in growing dogs.

PubMed

Liu, Siying; Tian, Lei; Ding, Mingchao; Liu, Yanpu; Li, Guiyu; Chen, Jinwu; Ding, Yin

2016-11-01

To investigate the effects of condylar extracapsular injuries on the development of the mandibular condyle and try to find a way to treat condylar hyperplasia by electively using such injuries to restrict the overdeveloped mandibular condyle. Sixty 6-month-old beagle puppies were divided randomly into five groups: blank control; unilateral fracture to the condylar neck; unilateral fracture to the condylar neck treated with rigid internal fixation; unilateral periosteum injury; unilateral decortication of the condylar neck. Computed tomography, 99 m Tc single-photon emission computed tomography, and tetracycline-calcein double-labeling were performed after surgery. The puppies were sacrificed 12 and 24 weeks after surgery. Morphologic analyses and examination of growth activity were done. Unilateral fracture of the condylar neck without fixation caused local morphologic changes during the early postoperative period, but compensatory growth of the condyle altered such changes after healing. The other types of injury failed to inhibit the growth of the condyle and the mandible, whereas functional deviation of the chin was found after unilateral fracture of the condylar neck with or without fixation. The four types of extracapsular injury described here failed to inhibit the growth of the mandibular condyle and could not be selected as alternatives to treat condylar hyperplasia. Copyright © 2016 Elsevier Inc. All rights reserved.

The relationship between nitrogen fixation and the production of HD from D2 by cell-free extracts of soya-bean nodule bacteroids

PubMed Central

Turner, G. L.; Bergersen, F. J.

1969-01-01

1. Cell-free extracts prepared from soya-bean nodule bacteroids produced HD from D2 in the presence of dithionite, an ATP-generating system and nitrogen. 2. Crude extracts of bacteroids or of Azotobacter vinelandii showed some background D2 exchange when any one of these was omitted. 3. Partial purification of bacteroid extracts diminished this background activity and gave increased D2 exchange and nitrogen fixation. 4. Although increasing pN2 stimulated both reactions, the apparent Km (N2) for nitrogen fixation was much higher than the apparent Km (N2) for D2 exchange when partially purified bacteroid extracts were used. 5. Carbon monoxide was a competitive inhibitor of nitrogen fixation by partially purified bacteroid extracts, but D2 exchange was inhibited in a non-competitive fashion. 6. These results are discussed in relation to the possible existence of enzyme-bound intermediates of nitrogen fixation. PMID:5353527

Significance of Phosphoenolpyruvate Carboxylase during Ammonium Assimilation

PubMed Central

Guy, Robert D.; Vanlerberghe, Greg C.; Turpin, David H.

1989-01-01

The effect of N-assimilation on the partitioning of carbon fixation between phosphoenolpyruvate carboxylase (PEPcase) and ribulose bisphosphate carboxylase/oxygenase (Rubisco) was determined by measuring stable carbon isotope discrimination during photosynthesis by an N-limited green alga, Selenastrum minutum (Naeg.) Collins. This was facilitated by a two process model accounting for simultaneous CO2 fixation and respiratory CO2 release. Discrimination by control cells was consistent with the majority of carbon being fixed by Rubisco. During nitrogen assimilation however, discrimination was greatly reduced indicating an enhanced flux through PEPcase which accounted for upward of 70% of total carbon fixation. This shift toward anaplerotic metabolism supports a large increase in tricarboxylic acid cycle activity primarily between oxaloacetate and α-ketoglutarate thereby facilitating the provision of carbon skeletons for amino acid synthesis. This provides an example of a unique set of conditions under which anaplerotic carbon fixation by PEPcase exceeds photosynthetic carbon fixation by Rubisco in a C3 organism. Images Figure 6 PMID:16666678

Significance of Phosphoenolpyruvate Carboxylase during Ammonium Assimilation: Carbon Isotope Discrimination in Photosynthesis and Respiration by the N-Limited Green Alga Selenastrum minutum.

PubMed

Guy, R D; Vanlerberghe, G C; Turpin, D H

1989-04-01

The effect of N-assimilation on the partitioning of carbon fixation between phosphoenolpyruvate carboxylase (PEPcase) and ribulose bisphosphate carboxylase/oxygenase (Rubisco) was determined by measuring stable carbon isotope discrimination during photosynthesis by an N-limited green alga, Selenastrum minutum (Naeg.) Collins. This was facilitated by a two process model accounting for simultaneous CO(2) fixation and respiratory CO(2) release. Discrimination by control cells was consistent with the majority of carbon being fixed by Rubisco. During nitrogen assimilation however, discrimination was greatly reduced indicating an enhanced flux through PEPcase which accounted for upward of 70% of total carbon fixation. This shift toward anaplerotic metabolism supports a large increase in tricarboxylic acid cycle activity primarily between oxaloacetate and alpha-ketoglutarate thereby facilitating the provision of carbon skeletons for amino acid synthesis. This provides an example of a unique set of conditions under which anaplerotic carbon fixation by PEPcase exceeds photosynthetic carbon fixation by Rubisco in a C(3) organism.

Use of an Active-Fixation Coronary Sinus Lead to Implant a Biventricular Pacemaker via the Femoral Vein

PubMed Central

Shandling, Adrian; Donohue, Daniel; Tobias, Serge; Wu, Iris; Brar, Ramandeep

2010-01-01

Cardiac resynchronization therapy, which involves the placement of a pacing lead in the right atrium and in each ventricle, is effective in treating heart failure that is caused by left bundle branch block and cardiomyopathy. The left ventricular lead is usually placed into a lateral branch of the coronary sinus via the subclavian route. When the subclavian route is unavailable, insertion of a standard, passive-fixation coronary sinus lead via the femoral approach is feasible; however, the likelihood of subsequent dislodgment is high. Herein, we describe the placement of a novel, self-retaining, active-fixation coronary sinus lead—the Attain StarFix® Model 4195 OTW Lead—in an elderly heart-failure patient, via the femoral approach. We believe that this is the 1st report of this procedure. PMID:20200636

[Domestic external fixator application in the treatment of limb deformities: 7 289 cases application report].

PubMed

Qin, S H; Guo, B F; Zheng, X J; Jiao, S F; Xia, H T; Peng, A M; Pan, Q; Zang, J C; Wang, Z J

2017-09-01

Objective: To discuss the clinical application and effects of domestic external fixator in the treatment of patients with malformations of limbs. Methods: A total of 7 289 patients with malformation of limbs who had been operated in Qin Sihe orthopedic surgery team from January 1989 to June 2016 were retrospective analyzed. The patients were treated with domestic external fixator, including 4 033 males and 3 256 females, aging from 2 to 82 years with a mean age of 23.4 years. There were 2 732 patients using Ilizarov external fixator, 4 713 patients using hybrid external fixator, 57 patients using monobrachial external fixator, 232 patients using Ilizarov external fixator and hybrid external fixator. The Ilizarov, hybrid and monobrachial external fixator were used in 67, 65 and 0 patients on the upper limbs and in 2 665, 4 616 and 57 patients on the lower limbs. There were 3 028 patients operated on the left limbs, 3 260 patients operated on the right limbs and 1 001 patients operated on the bilateral limbs. The top three types of diseases were sequelae of poliomyelitis, cerebral palsy and post-traumatic stress disorder peromely. Deformity types inclued talipes equinovarus, knee flexion deformity, cavus foot and so on. Results: All the patients were followed up for a period of 2.5 months to 22.4 years, with an average follow-up time of 5.4 years. All of the external fixators were used for single once, and there was no substitute for external fixator quality problem. All the patients were completed surgery goal until removing external fixation except 1 patient gave up treatment and 1 removed the fixator because of metal allergy. The common complications included wire or pin infection and joint movement limitation and so on. Conclusions: The domestic external fixator developed and produced based on the characteristics of Chinese limb deformity disability. The domestic external fixator can be used to treat kinds of limb deformities with the advantages of practical, economical, adjustable, universal and portable. The domestic external fixator could meet the clinical demand for fixation of the osteotomy end of the limbs, the correction of the deformity, the repair of the defects and the limb lengthening.

Temporary and definitive external fixation of war injuries: use of a French dedicated fixator.

PubMed

Mathieu, Laurent; Ouattara, Naklan; Poichotte, Antoine; Saint-Macari, Erwan; Barbier, Olivier; Rongiéras, Fréderic; Rigal, Sylvain

2014-08-01

External fixation is the recommended stabilization method for both open and closed fractures of long bones in forward surgical hospitals. Specific combat surgical tactics are best performed using dedicated external fixators. The Percy Fx (Biomet) fixator was developed for this reason by the French Army Medical Service, and has been used in various theatres of operations for more than ten years. The tactics of Percy Fx (Biomet) fixator use were analysed in two different situations: for the treatment of French soldiers wounded on several battlefields and then evacuated to France and for the management of local nationals in forward medical treatment facilities in Afghanistan and Chad. Overall 48 externals fixators were implanted on 37 French casualties; 28 frames were temporary and converted to definitive rigid frames or internal fixation after medical evacuation. The 77 Afghan patients totalled 85 external fixators, including 13 temporary frames applied in Forward Surgical Teams (FSTs) prior to their arrival at the Kabul combat support hospital. All of the 47 Chadian patients were treated in a FST with primary definitive frames because of delayed surgical management and absence of higher level of care in Chad. Temporary frames were mostly used for French soldiers to facilitate strategic air medical evacuation following trauma damage control orthopaedic principles. Definitive rigid frames permitted achieving treatment of all types of war extremity injuries, even in poor conditions.

The serotonin transporter gene polymorphism and the effect of baseline on amygdala response to emotional faces.

PubMed

von dem Hagen, Elisabeth A H; Passamonti, Luca; Nutland, Sarah; Sambrook, Jennifer; Calder, Andrew J

2011-03-01

Previous research has found that a common polymorphism in the serotonin transporter gene (5-HTTLPR) is an important mediator of individual differences in brain responses associated with emotional behaviour. In particular, relative to individuals homozygous for the l-allele, carriers of the s-allele display heightened amygdala activation to emotional compared to non-emotional stimuli. However, there is some debate as to whether this difference is driven by increased activation to emotional stimuli, resting baseline differences between the groups, or decreased activation to neutral stimuli. We performed functional imaging during an implicit facial expression processing task in which participants viewed angry, sad and neutral faces. In addition to neutral faces, we included two further baseline conditions, houses and fixation. We found increased amygdala activation in s-allele carriers relative to l-homozygotes in response to angry faces compared to neutral faces, houses and fixation. When comparing neutral faces to houses or fixation, we found no significant difference in amygdala response between the two groups. In addition, there was no significant difference between the groups in response to fixation when compared with a houses baseline. Overall, these results suggest that the increased amygdala response observed in s-allele carriers to emotional faces is primarily driven by an increased response to emotional faces rather than a decreased response to neutral faces or an increased resting baseline. The results are discussed in relation to the tonic and phasic hypotheses of 5-HTTLPR-mediated modulation of amygdala activity. Copyright © 2010 Elsevier Ltd. All rights reserved.

Vector disparity sensor with vergence control for active vision systems.

PubMed

Barranco, Francisco; Diaz, Javier; Gibaldi, Agostino; Sabatini, Silvio P; Ros, Eduardo

2012-01-01

This paper presents an architecture for computing vector disparity for active vision systems as used on robotics applications. The control of the vergence angle of a binocular system allows us to efficiently explore dynamic environments, but requires a generalization of the disparity computation with respect to a static camera setup, where the disparity is strictly 1-D after the image rectification. The interaction between vision and motor control allows us to develop an active sensor that achieves high accuracy of the disparity computation around the fixation point, and fast reaction time for the vergence control. In this contribution, we address the development of a real-time architecture for vector disparity computation using an FPGA device. We implement the disparity unit and the control module for vergence, version, and tilt to determine the fixation point. In addition, two on-chip different alternatives for the vector disparity engines are discussed based on the luminance (gradient-based) and phase information of the binocular images. The multiscale versions of these engines are able to estimate the vector disparity up to 32 fps on VGA resolution images with very good accuracy as shown using benchmark sequences with known ground-truth. The performances in terms of frame-rate, resource utilization, and accuracy of the presented approaches are discussed. On the basis of these results, our study indicates that the gradient-based approach leads to the best trade-off choice for the integration with the active vision system.

Vector Disparity Sensor with Vergence Control for Active Vision Systems

PubMed Central

Barranco, Francisco; Diaz, Javier; Gibaldi, Agostino; Sabatini, Silvio P.; Ros, Eduardo

2012-01-01

This paper presents an architecture for computing vector disparity for active vision systems as used on robotics applications. The control of the vergence angle of a binocular system allows us to efficiently explore dynamic environments, but requires a generalization of the disparity computation with respect to a static camera setup, where the disparity is strictly 1-D after the image rectification. The interaction between vision and motor control allows us to develop an active sensor that achieves high accuracy of the disparity computation around the fixation point, and fast reaction time for the vergence control. In this contribution, we address the development of a real-time architecture for vector disparity computation using an FPGA device. We implement the disparity unit and the control module for vergence, version, and tilt to determine the fixation point. In addition, two on-chip different alternatives for the vector disparity engines are discussed based on the luminance (gradient-based) and phase information of the binocular images. The multiscale versions of these engines are able to estimate the vector disparity up to 32 fps on VGA resolution images with very good accuracy as shown using benchmark sequences with known ground-truth. The performances in terms of frame-rate, resource utilization, and accuracy of the presented approaches are discussed. On the basis of these results, our study indicates that the gradient-based approach leads to the best trade-off choice for the integration with the active vision system. PMID:22438737

Photoactive TiO2 antibacterial coating on surgical external fixation pins for clinical application

PubMed Central

Villatte, Guillaume; Massard, Christophe; Descamps, Stéphane; Sibaud, Yves; Forestier, Christiane; Awitor, Komla-Oscar

2015-01-01

External fixation is a method of osteosynthesis currently used in traumatology and orthopedic surgery. Pin tract infection is a common problem in clinical practice. Infection occurs after bacterial colonization of the pin due to its contact with skin and the local environment. One way to prevent such local contamination is to create a specific coating that could be applied in the medical field. In this work, we developed a surface coating for external fixator pins based on the photocatalytic properties of titanium dioxide, producing a bactericidal effect with sufficient mechanical strength to be compatible with surgical use. The morphology and structure of the sol-gel coating layers were characterized using, respectively, scanning electron microscopy and X-ray diffraction. The resistance properties of the coating were investigated by mechanical testing. Photodegradation of acid orange 7 in aqueous solution was used as a probe to assess the photocatalytic activity of the titanium dioxide layers under ultraviolet irradiation. The bactericidal effect induced by the process was evaluated against two strains, ie, Staphylococcus aureus and multiresistant Staphylococcus epidermidis. The coated pins showed good mechanical strength and an efficient antibacterial effect after 1 hour of ultraviolet irradiation. PMID:26005347

Evaluation of the effectiveness of an intravenous line and fluid bottle fixation design.

PubMed

Chiou, Piao-Yi; Chien, Chih-Yin; Shiu, Ting-Ru; Lin, Pei-Jiun; Lin, Wan-Yu; Jiang, Yi-Rung

2015-01-01

It's important to improve the stability of intravenous (IV) lines and bottles during patient activity and nursing care. We developed an intravenous line and fluid bottle fixation design (ILFBFD) which includes a bottle retaining clip and line fixation kit. We randomly assigned 60 participants each to the experimental and control groups. Participants were asked to push an IV stand without and with ILFBFD 11 meters on uneven pavement and a sloping floor. The distance the IV bottle moved was recorded. Self-administered questionnaires were used to collect the opinions of the participants. Use of ILFBFD, resulted in less movement in the anteroposterior and left/right directions (differences of 46.98 cm2, t= 12.80, p < 0.000 and 39.24 cm2, t= 8.01, p< 0.000, respectively) compared with not using ILFBFD. The average scores for bottle movement when participants walked on a flat floor, uneven pavement and sloping floor, IV line tangling and dropping, and organization of Liv lines were significantly better in those using than not using ILFBFD. The results can be used in clinical practice to reduce knotting of IV lines, and to enhance the safety and quality of patient care.

Prokaryotic Responses to Ammonium and Organic Carbon Reveal Alternative CO2 Fixation Pathways and Importance of Alkaline Phosphatase in the Mesopelagic North Atlantic

PubMed Central

Baltar, Federico; Lundin, Daniel; Palovaara, Joakim; Lekunberri, Itziar; Reinthaler, Thomas; Herndl, Gerhard J.; Pinhassi, Jarone

2016-01-01

To decipher the response of mesopelagic prokaryotic communities to input of nutrients, we tracked changes in prokaryotic abundance, extracellular enzymatic activities, heterotrophic production, dark dissolved inorganic carbon (DIC) fixation, community composition (16S rRNA sequencing) and community gene expression (metatranscriptomics) in 3 microcosm experiments with water from the mesopelagic North Atlantic. Responses in 3 different treatments amended with thiosulfate, ammonium or organic matter (i.e., pyruvate plus acetate) were compared to unamended controls. The strongest stimulation was found in the organic matter enrichments, where all measured rates increased >10-fold. Strikingly, in the organic matter treatment, the dark DIC fixation rates—assumed to be related to autotrophic metabolisms—were equally stimulated as all the other heterotrophic-related parameters. This increase in DIC fixation rates was paralleled by an up-regulation of genes involved in DIC assimilation via anaplerotic pathways. Alkaline phosphatase was the metabolic rate most strongly stimulated and its activity seemed to be related to cross-activation by nonpartner histidine kinases, and/or the activation of genes involved in the regulation of elemental balance during catabolic processes. These findings suggest that episodic events such as strong sedimentation of organic matter into the mesopelagic might trigger rapid increases of originally rare members of the prokaryotic community, enhancing heterotrophic and autotrophic carbon uptake rates, ultimately affecting carbon cycling. Our experiments highlight a number of fairly unstudied microbial processes of potential importance in mesopelagic waters that require future attention. PMID:27818655

Unicompartmental knee prostheses: in vitro wear assessment of the menisci tibial insert after two different fixation methods

NASA Astrophysics Data System (ADS)

Affatato, S.; Spinelli, M.; Zavalloni, M.; Carmignato, S.; Lopomo, N.; Marcacci, M.; Viceconti, M.

2008-10-01

Knee osteoarthritis is a complex clinical scenario where many biological and mechanical factors influence the severity of articular degenerative changes. Minimally invasive knee prosthetic surgery, with only a compartment replacement (unicompartmental knee replacement), might be a good compromise between osteotomy and total knee prosthesis. The focus of this study was to develop and validate a protocol to assess the fixation method of the femoral components in mechanical simulation, for pre-clinical validation; the wear behaviour of two different fixation frames was quantified and compared. In particular, two different wear tests were conducted using the same knee simulator, the same load profiles and the same kinematics; two different fixation methods were applied to the femoral sleds (synthetic femur and metal block). Surface characterization on both articulating bearings was performed by a roughness measuring machine and coordinate measuring machine. The wear produced by the tibial inserts using the synthetic femur was considerably higher than the wear registered by the metal-block holder. Roughness measurements on femoral sleds showed a limited number of scratches with high Rt values for the metal-block set-up; the damaged surface broadened in the case of femoral condyles and tibial inserts mounted on composite bone, but lower Rt and linear penetration values were measured. The two holding frames showed different wear activities as a consequence of dissimilar dynamic performance. Further observations should be made in vivo to prove the actual importance of synthetic bone simulations and specific material behaviour.

Electrical Microstimulation of the Superior Colliculus in Strabismic Monkeys

PubMed Central

Fleuriet, Jérome; Walton, Mark M. G.; Ono, Seiji; Mustari, Michael J.

2016-01-01

Purpose Visually guided saccades are disconjugate in human and nonhuman strabismic primates. The superior colliculus (SC) is a region of the brain topographically organized in visual and motor maps where the saccade goal is spatially coded. The present study was designed to investigate if a site of stimulation on the topographic motor map was evoking similar or different saccade vectors for each eye. Methods We used microelectrical stimulation (MS) of the SC in two strabismic (one esotrope and one exotrope) and two control macaques under binocular and monocular viewing conditions. We compared the saccade amplitudes and directions for each SC site and each condition independently of the fixating eye and then between each fixating eye. A comparison with disconjugacies of visually guided saccades was also performed. Results We observed different saccade vectors for the two eyes in strabismic monkeys, but conjugate saccades in normal monkeys. Evoked saccade vectors for the left eye when that eye was fixating the target were different from those of the right eye when it was fixating. The disconjugacies evoked by the MS were not identical but similar to those observed for visually guided saccades especially for the dominant eye. Conclusions Our results suggest that, in strabismus, the saccade generator does not interpret activation of a single location of the SC as the same desired displacement for each eye. This finding is important for advancing understanding of the development of neural circuits in strabismus. French Abstract PMID:27309621

Traffic Lights in Trichodesmium. Regulation of Photosynthesis for Nitrogen Fixation Studied by Chlorophyll Fluorescence Kinetic Microscopy1

PubMed Central

Küpper, Hendrik; Ferimazova, Naila; Šetlík, Ivan; Berman-Frank, Ilana

2004-01-01

We investigated interactions between photosynthesis and nitrogen fixation in the non-heterocystous marine cyanobacterium Trichodesmium IMS101 at the single-cell level by two-dimensional (imaging) microscopic measurements of chlorophyll fluorescence kinetics. Nitrogen fixation was closely associated with the appearance of cells with high basic fluorescence yield (F0), termed bright cells. In cultures aerated with normal air, both nitrogen fixation and bright cells appeared in the middle of the light phase. In cultures aerated with 5% oxygen, both processes occurred at a low level throughout most of the day. Under 50% oxygen, nitrogen fixation commenced at the beginning of the light phase but declined soon afterwards. Rapid reversible switches between fluorescence levels were observed, which indicated that the elevated F0 of the bright cells originates from reversible uncoupling of the photosystem II (PSII) antenna from the PSII reaction center. Two physiologically distinct types of bright cells were observed. Type I had about double F0 compared to the normal F0 in the dark phase and a PSII activity, measured as variable fluorescence (Fv = Fm − F0), similar to normal non-diazotrophic cells. Correlation of type I cells with nitrogen fixation, oxygen concentration, and light suggests that this physiological state is connected to an up-regulation of the Mehler reaction, resulting in oxygen consumption despite functional PSII. Type II cells had more than three times the normal F0 and hardly any PSII activity measurable by variable fluorescence. They did not occur under low-oxygen concentrations, but appeared under high-oxygen levels outside the diazotrophic period, suggesting that this state represents a reaction to oxidative stress not necessarily connected to nitrogen fixation. In addition to the two high-fluorescence states, cells were observed to reversibly enter a low-fluorescence state. This occurred mainly after a cell went through its bright phase and may represent a fluorescence-quenching recovery phase. PMID:15299119

Isolating Discriminant Neural Activity in the Presence of Eye Movements and Concurrent Task Demands

PubMed Central

Touryan, Jon; Lawhern, Vernon J.; Connolly, Patrick M.; Bigdely-Shamlo, Nima; Ries, Anthony J.

2017-01-01

A growing number of studies use the combination of eye-tracking and electroencephalographic (EEG) measures to explore the neural processes that underlie visual perception. In these studies, fixation-related potentials (FRPs) are commonly used to quantify early and late stages of visual processing that follow the onset of each fixation. However, FRPs reflect a mixture of bottom-up (sensory-driven) and top-down (goal-directed) processes, in addition to eye movement artifacts and unrelated neural activity. At present there is little consensus on how to separate this evoked response into its constituent elements. In this study we sought to isolate the neural sources of target detection in the presence of eye movements and over a range of concurrent task demands. Here, participants were asked to identify visual targets (Ts) amongst a grid of distractor stimuli (Ls), while simultaneously performing an auditory N-back task. To identify the discriminant activity, we used independent components analysis (ICA) for the separation of EEG into neural and non-neural sources. We then further separated the neural sources, using a modified measure-projection approach, into six regions of interest (ROIs): occipital, fusiform, temporal, parietal, cingulate, and frontal cortices. Using activity from these ROIs, we identified target from non-target fixations in all participants at a level similar to other state-of-the-art classification techniques. Importantly, we isolated the time course and spectral features of this discriminant activity in each ROI. In addition, we were able to quantify the effect of cognitive load on both fixation-locked potential and classification performance across regions. Together, our results show the utility of a measure-projection approach for separating task-relevant neural activity into meaningful ROIs within more complex contexts that include eye movements. PMID:28736519

Short-term N2 fixation kinetics in a moss-associated cyanobacteria.

PubMed

Jean, Marie-Eve; Cassar, Nicolas; Setzer, Cameron; Bellenger, Jean-Philippe

2012-08-21

N(2) fixation by moss-associated cyanobacteria plays an important role in the nitrogen cycling of terrestrial ecosystems. Recent studies have mainly focused on boreal ecosystems; little is known about such association in other ecosystems. Moss-associated cyanobacteria are subject to rapid changes (hourly or less) in environmental conditions that may affect N(2) fixation kinetics. Using a recently developed method (Acetylene Reduction Assays by Cavity ring-down laser Absorption Spectroscopy, ARACAS) with higher sensitivity and sampling frequency than the conventional method, we characterize short-term kinetics of N(2) fixation by cyanobacteria on moss carpets from warm and cold temperate forests. We report the identification of a heretofore unknown multispecies true-moss-cyanobacteria diazotrophic association. We demonstrate that short-term change in abiotic variables greatly influences N(2) fixation. We also show that difference in relative proportion of two epiphytic diazotrophs is consistent with divergent influences of temperature on their N(2) fixation kinetics. Further research is needed to determine whether this difference is consistent with a latitudinal trend.

Fixation Probability in a Haploid-Diploid Population

PubMed Central

Bessho, Kazuhiro; Otto, Sarah P.

2017-01-01

Classical population genetic theory generally assumes either a fully haploid or fully diploid life cycle. However, many organisms exhibit more complex life cycles, with both free-living haploid and diploid stages. Here we ask what the probability of fixation is for selected alleles in organisms with haploid-diploid life cycles. We develop a genetic model that considers the population dynamics using both the Moran model and Wright–Fisher model. Applying a branching process approximation, we obtain an accurate fixation probability assuming that the population is large and the net effect of the mutation is beneficial. We also find the diffusion approximation for the fixation probability, which is accurate even in small populations and for deleterious alleles, as long as selection is weak. These fixation probabilities from branching process and diffusion approximations are similar when selection is weak for beneficial mutations that are not fully recessive. In many cases, particularly when one phase predominates, the fixation probability differs substantially for haploid-diploid organisms compared to either fully haploid or diploid species. PMID:27866168

Biomechanical Comparison Study of Three Fixation Methods for Proximal Chevron Osteotomy of the First Metatarsal in Hallux Valgus.

PubMed

Kim, Jin Su; Cho, Hun Ki; Young, Ki Won; Kim, Ji Soo; Lee, Kyung Tai

2017-12-01

Fixation of proximal chevron metatarsal osteotomy has been accomplished using K-wires traditionally and with a locking plate recently. However, both methods have many disadvantages. Hence, we developed an intramedullary fixation technique using headless cannulated screws and conducted a biomechanical study to evaluate the superiority of the technique to K-wire and locking plate fixations. Proximal chevron metatarsal osteotomy was performed on 30 synthetic metatarsal models using three fixation techniques. Specimens in group I were fixated with K-wires (1.6 mm × 2) and in group II with headless cannulated screws (3.0 mm × 2) distally through the intramedullary canal. Specimens in group III were fixated with a locking X-shaped plate (1.3-mm thick) and screws (2.5 mm × 4). Eight metatarsal specimens were selected from each group for walking fatigue test. Bending stiffness and dorsal angulation were measured by 1,000 repetitions of a cantilever bending protocol in a plantar to dorsal direction. The remaining two samples from each group were subjected to 5 mm per minute axial loading to assess the maximal loading tolerance. All samples in group I failed walking fatigue test while group II and group III tolerated the walking fatigue test. Group II showed greater resistance to bending force and smaller dorsal angulation than group III ( p = 0.001). On the axial loading test, group I and group II demonstrated superior maximum tolerance to group III (54.8 N vs. 47.2 N vs. 28.3 N). Authors have demonstrated proximal chevron metatarsal osteotomy with intramedullary screw fixation provides superior biomechanical stability to locking plate and K-wire fixations. The new technique using intramedullary screw fixation can offer robust fixation and may lead to better outcomes in surgical treatment of hallux valgus.

Fixation parameter test-retest repeatability of the worse eye in central field loss.

PubMed

Samet, Saba; Tarita-Nistor, Luminita; González, Esther G; Mandelcorn, Mark S; Mandelcorn, Efrem D; Steinbach, Martin J

2018-06-01

Patients with bilateral central field loss develop peripheral retinal loci (PRLs) in the functional eccentric retina. PRL characteristics and visual performance in the better-seeing eye (BE) of these patients have previously been reported. In this study, we determined the test-retest repeatability of fixation parameters, including fixation stability, PRL eccentricity, and PRL span in the worse-seeing eye (WE). Retrospective consecutive case series. Thirty-six patients with bilateral central field loss referred from the Toronto Western Hospital Retina Clinic, who had completed 2 consecutive fixation examinations on the same day. Fixation stability was recorded using the Nidek MP-1 microperimeter (Nidek Technologies Srl., Padova, Italy). For each fixation recording, the following parameters were retrieved: (i) 68.2% bivariate contour ellipse area (BCEA), (ii) PRL span (major and minor axes of the BCEA), (iii) PRL meridian (polar angle), and (iv) PRL eccentricity. Test-retest repeatability for each parameter was assessed using Bland-Altman plots to determine 95% limits of agreement. The mean difference between the fixation trial pairs and the 95% limits of agreement for fixation stability, PRL major axis, PRL minor axis, PRL meridian, and PRL eccentricity were 0.06 ± 0.47 log deg 2 , 0.05° ± 1.42°, 0.07° ± 0.63°, -0.44° ± 66.0°, and -0.23° ±1.56°, respectively. The fixation parameters in the WE showed robust repeatability, comparable to that of the BE as determined from previous studies. The WE's fixation repeatability should be considered in the interpretation of fixation outcome measures subsequent to treatment interventions. Crown Copyright © 2018. Published by Elsevier Inc. All rights reserved.

Variable Nitrogen Fixation in Wild Populus

PubMed Central

Doty, Sharon L.; Sher, Andrew W.; Fleck, Neil D.; Khorasani, Mahsa; Bumgarner, Roger E.; Khan, Zareen; Ko, Andrew W. K.; Kim, Soo-Hyung; DeLuca, Thomas H.

2016-01-01

The microbiome of plants is diverse, and like that of animals, is important for overall health and nutrient acquisition. In legumes and actinorhizal plants, a portion of essential nitrogen (N) is obtained through symbiosis with nodule-inhabiting, N2-fixing microorganisms. However, a variety of non-nodulating plant species can also thrive in natural, low-N settings. Some of these species may rely on endophytes, microorganisms that live within plants, to fix N2 gas into usable forms. Here we report the first direct evidence of N2 fixation in the early successional wild tree, Populus trichocarpa, a non-leguminous tree, from its native riparian habitat. In order to measure N2 fixation, surface-sterilized cuttings of wild poplar were assayed using both 15N2 incorporation and the commonly used acetylene reduction assay. The 15N label was incorporated at high levels in a subset of cuttings, suggesting a high level of N-fixation. Similarly, acetylene was reduced to ethylene in some samples. The microbiota of the cuttings was highly variable, both in numbers of cultured bacteria and in genetic diversity. Our results indicated that associative N2-fixation occurred within wild poplar and that a non-uniformity in the distribution of endophytic bacteria may explain the variability in N-fixation activity. These results point to the need for molecular studies to decipher the required microbial consortia and conditions for effective endophytic N2-fixation in trees. PMID:27196608

Fractures of the proximal fifth metatarsal: percutaneous bicortical fixation.

PubMed

Mahajan, Vivek; Chung, Hyun Wook; Suh, Jin Soo

2011-06-01

Displaced intraarticular zone I and displaced zone II fractures of the proximal fifth metatarsal bone are frequently complicated by delayed nonunion due to a vascular watershed. Many complications have been reported with the commonly used intramedullary screw fixation for these fractures. The optimal surgical procedure for these fractures has not been determined. All these observations led us to evaluate the effectiveness of percutaneous bicortical screw fixation for treating these fractures. Twenty-three fractures were operatively treated by bicortical screw fixation. All the fractures were evaluated both clinically and radiologically for the healing. All the patients were followed at 2 or 3 week intervals till fracture union. The patients were followed for an average of 22.5 months. Twenty-three fractures healed uneventfully following bicortical fixation, with a mean healing time of 6.3 weeks (range, 4 to 10 weeks). The average American Orthopaedic Foot & Ankle Society (AOFAS) score was 94 (range, 90 to 99). All the patients reported no pain at rest or during athletic activity. We removed the implant in all cases at a mean of 23.2 weeks (range, 18 to 32 weeks). There was no refracture in any of our cases. The current study shows the effectiveness of bicortical screw fixation for displaced intraarticular zone I fractures and displaced zone II fractures. We recommend it as one of the useful techniques for fixation of displaced zone I and II fractures.

Simon-type effects: chronometric evidence for keypress schemata in typewriting.

PubMed

Logan, Gordon D

2003-08-01

In 4 experiments, chronometric evidence for keypress schemata in typing was sought by presenting stimuli to be typed in positions that were displaced from a central fixation point. Reaction times were shorter when stimulus positions corresponded to keyboard locations of the letters to be typed, suggesting that position was an important part of the internal representation of the response. Experiment 1 presented single letters left and right of fixation. Experiment 2 presented single letters above and below fixation. Experiment 3 presented words left and right of fixation and found evidence of parallel activation of keypress schemata. Experiment 4 found no effect of the eccentricity of the keyboard locations and responding fingers, suggesting that response-location codes are categorical, not metric. The results are consistent with D. E. Rumelhart and D. A. Norman's (1982) theory of typewriting.

Chemosynthetic symbionts of marine invertebrate animals are capable of nitrogen fixation.

PubMed

Petersen, Jillian M; Kemper, Anna; Gruber-Vodicka, Harald; Cardini, Ulisse; van der Geest, Matthijs; Kleiner, Manuel; Bulgheresi, Silvia; Mußmann, Marc; Herbold, Craig; Seah, Brandon K B; Antony, Chakkiath Paul; Liu, Dan; Belitz, Alexandra; Weber, Miriam

2016-10-24

Chemosynthetic symbioses are partnerships between invertebrate animals and chemosynthetic bacteria. The latter are the primary producers, providing most of the organic carbon needed for the animal host's nutrition. We sequenced genomes of the chemosynthetic symbionts from the lucinid bivalve Loripes lucinalis and the stilbonematid nematode Laxus oneistus. The symbionts of both host species encoded nitrogen fixation genes. This is remarkable as no marine chemosynthetic symbiont was previously known to be capable of nitrogen fixation. We detected nitrogenase expression by the symbionts of lucinid clams at the transcriptomic and proteomic level. Mean stable nitrogen isotope values of Loripes lucinalis were within the range expected for fixed atmospheric nitrogen, further suggesting active nitrogen fixation by the symbionts. The ability to fix nitrogen may be widespread among chemosynthetic symbioses in oligotrophic habitats, where nitrogen availability often limits primary productivity.

NanoSIMS Analyses of Mo Indicate Nitrogenase Activity and Help Solve a N and C Fixation Puzzle in a Marine Cyanobacterium

NASA Astrophysics Data System (ADS)

Pett-Ridge, J.; Weber, P. K.; Finzi, J.; Hutcheon, I. D.; Capone, D. G.

2006-12-01

Diazotrophic cyanobacteria are capable of both CO2 and N2 fixation, yet must separate these two functions because the nitrogenase enzymes used in N2 fixation are strongly inhibited by O2 produced during photosynthesis. Some lineages, such as Anabaena, use specialized cells (heterocysts) to maintain functional segregation. However the mechanism of this segregation is poorly understood in Trichodesmium, a critical component of marine primary production in the tropical and subtropical North Atlantic. While some Trichodesmium studies suggest a temporal segregation of the nitrogen and carbon fixing processes, others indicate nitrogen fixation is spatially isolated in differentiated cells called diazocytes. In order to isolate the intracellular location of N fixation in both species, we used a combination of TEM, SEM and NanoSIMS analysis to map the distribution of C, N and Mo (a critical nitrogenase co-factor) isotopes in intact cells. NanoSIMS is a powerful surface analysis tool which combines nanometer-scale imaging resolution with the high sensitivity of mass spectrometry. Using cells grown in a 13CO^2 and 15N2 enriched atmosphere, our analyses indicate that in Anabaena, heterocysts are consistently enriched in Mo, and Mo accumulation suggests active N fixation (as opposed to N storage). In the non- heterocystous Trichodesmium, Mo is concentrated in sub-regions of individual cells, and is not associated with regions of N storage (cyanophycin granules). We suggest that NanoSIMS mapping of metal enzyme co- factors is a unique method of identifying physiological and morphological characteristics within individual bacterial cells. This combination of NanoSIMS analysis and high resolution microscopy allows isotopic analysis to be linked to morphological features and holds great promise for fine-scale studies of bacteria metabolism.

Fixation systems of greater trochanteric osteotomies: biomechanical and clinical outcomes.

PubMed

Jarit, Gregg J; Sathappan, Sathappan S; Panchal, Anand; Strauss, Eric; Di Cesare, Paul E

2007-10-01

The development of cerclage systems for fixation of greater trochanteric osteotomies has progressed from monofilament wires to multifilament cables to cable grip and cable plate systems. Cerclage wires and cables have various clinical indications, including fixation for fractures and for trochanteric osteotomy in hip arthroplasty. To achieve stable fixation and eventual union of the trochanteric osteotomy, the implant must counteract the destabilizing forces associated with pull of the peritrochanteric musculature. The material properties of cables and cable grip systems are superior to those of monofilament wires; however, potential complications with the use of cables include debris generation and third-body polyethylene wear. Nevertheless, the cable grip system provides the strongest fixation and results in lower rates of nonunion and trochanteric migration. Cable plate constructs show promise but require further clinical studies to validate their efficacy and safety.

Raman-activated cell sorting and metagenomic sequencing revealing carbon-fixing bacteria in the ocean.

PubMed

Jing, Xiaoyan; Gou, Honglei; Gong, Yanhai; Su, Xiaolu; Xu, La; Ji, Yuetong; Song, Yizhi; Thompson, Ian P; Xu, Jian; Huang, Wei E

2018-05-04

It is of great significance to understand CO 2 fixation in the oceans. Using single cell Raman spectra (SCRS) as biochemical profiles, Raman activated cell ejection (RACE) was able to link phenotypes and genotypes of cells. Here we show that mini-metagenomic sequences from RACE can be used as a reference to reconstruct nearly complete genomes of key functional bacteria by binning shotgun metagenomic sequencing data. By applying this approach to 13 C-bicarbonate spiked seawater from euphotic zone of the Yellow Sea of China, the dominant bacteria Synechococcus spp. and Pelagibacter spp. were revealed, and both of them contain carotenoid and were able to incorporate 13 C into the cells at the same time. Genetic analysis of the reconstructed genomes suggests that both Synechococcus spp. and Pelagibacter spp. contained all genes necessary for carotenoid synthesis, light energy harvesting and CO 2 fixation. Interestingly, the reconstructed genome indicates that Pelagibacter spp. harbored intact sets of genes for β-carotene (precursor of retional), proteorhodopsin synthesis and anaplerotic CO 2 fixation. This novel approach shines light on the role of marine "microbial dark matter" in global carbon cycling, by linking yet-to-be-cultured Synechococcus spp. and Pelagibacter spp. to carbon fixation and flow activities in situ. This article is protected by copyright. All rights reserved. © 2018 Society for Applied Microbiology and John Wiley & Sons Ltd.

Transcriptional Profiling of Nitrogen Fixation in Azotobacter vinelandii▿†

PubMed Central

Hamilton, Trinity L.; Ludwig, Marcus; Dixon, Ray; Boyd, Eric S.; Dos Santos, Patricia C.; Setubal, João C.; Bryant, Donald A.; Dean, Dennis R.; Peters, John W.

2011-01-01

Most biological nitrogen (N2) fixation results from the activity of a molybdenum-dependent nitrogenase, a complex iron-sulfur enzyme found associated with a diversity of bacteria and some methanogenic archaea. Azotobacter vinelandii, an obligate aerobe, fixes nitrogen via the oxygen-sensitive Mo nitrogenase but is also able to fix nitrogen through the activities of genetically distinct alternative forms of nitrogenase designated the Vnf and Anf systems when Mo is limiting. The Vnf system appears to replace Mo with V, and the Anf system is thought to contain Fe as the only transition metal within the respective active site metallocofactors. Prior genetic analyses suggest that a number of nif-encoded components are involved in the Vnf and Anf systems. Genome-wide transcription profiling of A. vinelandiicultured under nitrogen-fixing conditions under various metal amendments (e.g., Mo or V) revealed the discrete complement of genes associated with each nitrogenase system and the extent of cross talk between the systems. In addition, changes in transcript levels of genes not directly involved in N2fixation provided insight into the integration of central metabolic processes and the oxygen-sensitive process of N2fixation in this obligate aerobe. The results underscored significant differences between Mo-dependent and Mo-independent diazotrophic growth that highlight the significant advantages of diazotrophic growth in the presence of Mo. PMID:21724999

Atlantoaxial rotatory fixation as a rare complication from head positioning in otologic surgery: Report of two cases in young children.

PubMed

Sakaida, Hiroshi; Akeda, Koji; Sudo, Akihiro; Takeuchi, Kazuhiko

2017-01-01

Atlantoaxial rotatory fixation is a condition in which the first and second vertebrae of the cervical spine become interlocked in a rotated position. This condition can result in serious consequences and thus have a significant impact on patients, especially when diagnosis and treatment are delayed. Some cases of atlantoaxial rotatory fixation have been described in association with otologic surgery or plastic surgery involving the ear. We present the cases of two pediatric patients who developed atlantoaxial rotatory fixation following otologic surgery and we review the relevant literature. One patient was a 7-year-old boy who underwent tympanoplasty for cholesteatoma. The other patient was a 5-year-old girl with profound sensorineural hearing loss who underwent cochlear implantation. Both patients developed atlantoaxial rotatory fixation on the day after surgery, and they were treated conservatively. Our literature search using relevant terms identified 12 similar published cases. Thus, a total of 14 patients, including our 2 patients, were evaluated. Most of the patients were children and typically they complained of painful torticollis and exhibited a characteristic posture called the "cock-robin" position on the day after surgery. Mostly, the direction of torticollis was opposite to the side of surgery. Most of the patients received conservative treatment alone, but three underwent surgical treatment. The correlation between the direction of torticollis and the side of surgery suggests that rotation of the head during surgery has an impact on development of postoperative atlantoaxial rotatory fixation. Thus, children undergoing otologic surgery are thought to be at a risk of postoperative atlantoaxial rotatory fixation. Although rare, the surgical team needs to be aware of this adverse event and pay close attention to this possibility throughout the perioperative period. Perioperative management should include informed consent, preoperative assessment of the range of head and neck motion, proper intraoperative positioning and monitoring of the position, and postoperative follow-up. Postoperative atlantoaxial rotatory fixation is not completely preventable, but good perioperative management can minimize the damage resulting from this condition.

Proposed Use of the Computer as a Tool to Aid Analysis of Properties of Materials in Fixators of Spine

PubMed Central

Santos, Antonio; Moreira, Fernando

2014-01-01

With objective of analyzing the mechanical behavior of the internal fixators of spine and of the bony structure, the pieces and the group were made (it structures bony x internal fixator) with the aid a software of solid modeling. The materials used in the rehearsals had been the titanium, now in the market and a castor oil polyurethane destined to the development of you implant bony. PMID:24825938

Crystal Engineering of an nbo Topology Metal-Organic Framework for Chemical Fixation of CO₂ under Ambient Conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Wen-Yang; Chen, Yao; Niu, Youhong

Crystal engineering of the nbo metal–organic framework (MOF) platform MOF-505 with a custom-designed azamacrocycle ligand (1,4,7,10-tetrazazcyclododecane-N,N',N'',N'''-tetra-p-methylbenzoic acid) leads to a high density of well-oriented Lewis active sites within the cuboctahedral cage in MMCF-2, [Cu₂(Cu-tactmb)(H₂O)₃(NO₃)₂]. This MOF demonstrates high catalytic activity for the chemical fixation of CO₂ into cyclic carbonates at room temperature under 1 atm pressure.

Do you see what I see? Mobile eye-tracker contextual analysis and inter-rater reliability.

PubMed

Stuart, S; Hunt, D; Nell, J; Godfrey, A; Hausdorff, J M; Rochester, L; Alcock, L

2018-02-01

Mobile eye-trackers are currently used during real-world tasks (e.g. gait) to monitor visual and cognitive processes, particularly in ageing and Parkinson's disease (PD). However, contextual analysis involving fixation locations during such tasks is rarely performed due to its complexity. This study adapted a validated algorithm and developed a classification method to semi-automate contextual analysis of mobile eye-tracking data. We further assessed inter-rater reliability of the proposed classification method. A mobile eye-tracker recorded eye-movements during walking in five healthy older adult controls (HC) and five people with PD. Fixations were identified using a previously validated algorithm, which was adapted to provide still images of fixation locations (n = 116). The fixation location was manually identified by two raters (DH, JN), who classified the locations. Cohen's kappa correlation coefficients determined the inter-rater reliability. The algorithm successfully provided still images for each fixation, allowing manual contextual analysis to be performed. The inter-rater reliability for classifying the fixation location was high for both PD (kappa = 0.80, 95% agreement) and HC groups (kappa = 0.80, 91% agreement), which indicated a reliable classification method. This study developed a reliable semi-automated contextual analysis method for gait studies in HC and PD. Future studies could adapt this methodology for various gait-related eye-tracking studies.

External versus internal fixation for bicondylar tibial plateau fractures: systematic review and meta-analysis.

PubMed

Metcalfe, David; Hickson, Craig J; McKee, Lesley; Griffin, Xavier L

2015-12-01

It is uncertain whether external fixation or open reduction internal fixation (ORIF) is optimal for patients with bicondylar tibial plateau fractures. A systematic review using Ovid MEDLINE, Embase Classic, Embase, AMED, the Cochrane Library, Open Grey, Orthopaedic Proceedings, WHO International Clinical Trials Registry Platform, Current Controlled Trials, US National Institute for Health Trials Registry, and the Cochrane Central Register of Controlled Trials. The search was conducted on 3rd October 2014 and no language limits were applied. Inclusion criteria were all clinical study designs comparing external fixation with open reduction internal fixation of bicondylar tibial plateau fractures. Studies of only one treatment modality were excluded, as were those that included unicondylar tibial plateau fractures. Treatment effects from studies reporting dichotomous outcomes were summarised using odds ratios. Continuous outcomes were converted to standardized mean differences to assess the treatment effect, and inverse variance methods used to combine data. A fixed effect model was used for meta-analyses. Patients undergoing external fixation were more likely to have returned to preinjury activities by six and twelve months (P = 0.030) but not at 24 months follow-up. However, external fixation was complicated by a greater number of infections (OR 2.59, 95 % CI 1.25-5.36, P = 0.01). There were no statistically significant differences in the rates of deep infection, venous thromboembolism, compartment syndrome, or need for re-operation between the two groups. Although external fixation and ORIF are associated with different complication profiles, both are acceptable strategies for managing bicondylar tibial plateau fractures.

Early sensitivity for eyes within faces: a new neuronal account of holistic and featural processing

PubMed Central

Nemrodov, Dan; Anderson, Thomas; Preston, Frank F.; Itier, Roxane J.

2017-01-01

Eyes are central to face processing however their role in early face encoding as reflected by the N170 ERP component is unclear. Using eye tracking to enforce fixation on specific facial features, we found that the N170 was larger for fixation on the eyes compared to fixation on the forehead, nasion, nose or mouth, which all yielded similar amplitudes. This eye sensitivity was seen in both upright and inverted faces and was lost in eyeless faces, demonstrating it was due to the presence of eyes at fovea. Upright eyeless faces elicited largest N170 at nose fixation. Importantly, the N170 face inversion effect (FIE) was strongly attenuated in eyeless faces when fixation was on the eyes but was less attenuated for nose fixation and was normal when fixation was on the mouth. These results suggest the impact of eye removal on the N170 FIE is a function of the angular distance between the fixated feature and the eye location. We propose the Lateral Inhibition, Face Template and Eye Detector based (LIFTED) model which accounts for all the present N170 results including the FIE and its interaction with eye removal. Although eyes elicit the largest N170 response, reflecting the activity of an eye detector, the processing of upright faces is holistic and entails an inhibitory mechanism from neurons coding parafoveal information onto neurons coding foveal information. The LIFTED model provides a neuronal account of holistic and featural processing involved in upright and inverted faces and offers precise predictions for further testing. PMID:24768932

Nitrogen Fixation by Anaerobes is Stimulated by Low Oxygen and Insensitive to Combined Nitrogen in Coastal Sediments

NASA Astrophysics Data System (ADS)

Jenkins, B. D.; Spinette, R.; Jones, A.; Puggioni, G.; Ehrlich, A.; Brown, S. M.

2016-02-01

Coastal sediments are typically zones of nitrogen removal via coupled nitrification-denitrification pathways. Increasingly, there are reports of nitrogen fixation in anthropogenically impacted sediments containing ample combined nitrogen. In previous work in the estuarine sediments of Narragansett Bay, we found that anaerobes related to Desulfovibrio spp. and in the Desulfuromonadales express genes for nitrogen fixation (nifH). We also determined that nitrogen fixation rates and gene expression are elevated during periods of seasonal hypoxia. Statistical modeling shows that a combination of elevated phytoplankton biomass as with a duration of hypoxia for a week or longer lead to conditions that promote nitrogen fixation as measured by acetylene reduction. Interestingly, diazotrophs closely related to those identified in Narragansett Bay are present and active in other low oxygen systems, suggesting that expansion of hypoxic events may lead to unanticipated consequences for the benthic nitrogen cycle in many ecosystems. To determine controls on diazotrophy on the organismal level, we isolated and sequenced the genomes of two Narragansett Bay members of the Desulfovibrio. We found that these organisms are insensitive to nitrate and urea, as they are missing the genes to assimilate these nitrogen sources. However, their nitrogen fixation is suppressed by increasing concentrations of ammonium, indicating that they may be sensitive to this nitrogen source in the environment. The paradox of detectable nitrogen fixation in the background of measurable ammonium in estuarine systems is a newly emergent theme and suggests that there are complex microbial interactions and/or structure to the nutrient regimes allowing for fixation.

Importance of N2-Fixation on the Productivity at the North-Western Azores Current/Front System, and the Abundance of Diazotrophic Unicellular Cyanobacteria.

PubMed

Riou, Virginie; Fonseca-Batista, Debany; Roukaerts, Arnout; Biegala, Isabelle C; Prakya, Shree Ram; Magalhães Loureiro, Clara; Santos, Mariana; Muniz-Piniella, Angel E; Schmiing, Mara; Elskens, Marc; Brion, Natacha; Martins, M Ana; Dehairs, Frank

2016-01-01

To understand the impact of the northwestern Azores Current Front (NW-AzC/AzF) system on HCO3--and N2-fixation activities and unicellular diazotrophic cyanobacteria (UCYN) distribution, we combined geochemical and biological approaches from the oligotrophic surface to upper mesopelagic waters. N2-fixation was observed to sustain 45-85% of the HCO3--fixation in the picoplanktonic fraction performing 47% of the total C-fixation at the deep chlorophyll maximum north and south of the AzF. N2-fixation rates as high as 10.9 μmol N m-3 d-1 and surface nitrate δ15N as low as 2.7‰ were found in the warm (18-24°C), most saline (36.5-37.0) and least productive waters south of the AzF, where UCYN were the least abundant. However, picoplanktonic UCYN abundances up to 55 cells mL-1 were found at 45-200m depths in the coolest nutrient-rich waters north of the AzF. In this area, N2-fixation rates up to 4.5 μmol N m-3 d-1 were detected, associated with depth-integrated H13CO3--fixation rates at least 50% higher than observed south of the AzF. The numerous eddies generated at the NW-AzC/AzF seem to enhance exchanges of plankton between water masses, as well as vertical and horizontal diapycnal diffusion of nutrients, whose increase probably enhances the growth of diazotrophs and the productivity of C-fixers.

Do object refixations during scene viewing indicate rehearsal in visual working memory?

PubMed

Zelinsky, Gregory J; Loschky, Lester C; Dickinson, Christopher A

2011-05-01

Do refixations serve a rehearsal function in visual working memory (VWM)? We analyzed refixations from observers freely viewing multiobject scenes. An eyetracker was used to limit the viewing of a scene to a specified number of objects fixated after the target (intervening objects), followed by a four-alternative forced choice recognition test. Results showed that the probability of target refixation increased with the number of fixated intervening objects, and these refixations produced a 16% accuracy benefit over the first five intervening-object conditions. Additionally, refixations most frequently occurred after fixations on only one to two other objects, regardless of the intervening-object condition. These behaviors could not be explained by random or minimally constrained computational models; a VWM component was required to completely describe these data. We explain these findings in terms of a monitor-refixate rehearsal system: The activations of object representations in VWM are monitored, with refixations occurring when these activations decrease suddenly.

A novel anchoring system for use in a nonfusion scoliosis correction device.

PubMed

Wessels, Martijn; Homminga, Jasper J; Hekman, Edsko E G; Verkerke, Gijsbertus J

2014-11-01

Insertion of a pedicle screw in the mid- and high thoracic regions has a serious risk of facet joint damage. Because flexible implant systems require intact facet joints, we developed an enhanced fixation that is less destructive to spinal structures. The XSFIX is a posterior fixation system that uses cables that are attached to the transverse processes of a vertebra. To determine whether a fixation to the transverse process using the XSFIX is strong enough to withstand the loads applied by the XSLATOR (a novel, highly flexible nonfusion implant system) and thus, whether it is a suitable alternative for pedicle screw fixation. The strength of a novel fixation system using transverse process cables was determined and compared with the strength of a similar fixation using polyaxial pedicle screws on different vertebral levels. Each of the 58 vertebrae, isolated from four adult human cadavers, was instrumented with either a pedicle screw anchor (PSA) system or a prototype of the XSFIX. The PSA consisted of two polyaxial pedicle screws and a 5 mm diameter rod. The XSFIX prototype consisted of two bodies that were fixed to the transverse processes, interconnected with a similar rod. Each fixation system was subjected to a lateral or an axial torque. The PSA demonstrated fixation strength in lateral loading and torsion higher than required for use in the XSLATOR. The XSFIX demonstrated high enough fixation strength (in both lateral loading and torsion), only in the high and midthoracic regions (T10-T12). This experiment showed that the fixation strength of XSFIX is sufficient for use with the XSLATOR only in mid- and high thoracic regions. For the low thoracic and lumbar region, the PSA is a more rigid fixation. Because the performance of the new fixation system appears to be favorable in the high and midthoracic regions, a clinical study is the next challenge. Copyright © 2014 Elsevier Inc. All rights reserved.

Application of stable‐isotope labelling techniques for the detection of active diazotrophs

PubMed Central

Angel, Roey; Panhölzl, Christopher; Gabriel, Raphael; Herbold, Craig; Wanek, Wolfgang; Richter, Andreas; Eichorst, Stephanie A.

2017-01-01

Summary Investigating active participants in the fixation of dinitrogen gas is vital as N is often a limiting factor for primary production. Biological nitrogen fixation is performed by a diverse guild of bacteria and archaea (diazotrophs), which can be free‐living or symbionts. Free‐living diazotrophs are widely distributed in the environment, yet our knowledge about their identity and ecophysiology is still limited. A major challenge in investigating this guild is inferring activity from genetic data as this process is highly regulated. To address this challenge, we evaluated and improved several 15N‐based methods for detecting N2 fixation activity (with a focus on soil samples) and studying active diazotrophs. We compared the acetylene reduction assay and the 15N2 tracer method and demonstrated that the latter is more sensitive in samples with low activity. Additionally, tracing 15N into microbial RNA provides much higher sensitivity compared to bulk soil analysis. Active soil diazotrophs were identified with a 15N‐RNA‐SIP approach optimized for environmental samples and benchmarked to 15N‐DNA‐SIP. Lastly, we investigated the feasibility of using SIP‐Raman microspectroscopy for detecting 15N‐labelled cells. Taken together, these tools allow identifying and investigating active free‐living diazotrophs in a highly sensitive manner in diverse environments, from bulk to the single‐cell level. PMID:29027346

Improving carbon fixation pathways

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ducat, DC; Silver, PA

2012-08-01

A recent resurgence in basic and applied research on photosynthesis has been driven in part by recognition that fulfilling future food and energy requirements will necessitate improvements in crop carbon-fixation efficiencies. Photosynthesis in traditional terrestrial crops is being reexamined in light of molecular strategies employed by photosynthetic microbes to enhance the activity of the Calvin cycle. Synthetic biology is well-situated to provide original approaches for compartmentalizing and enhancing photosynthetic reactions in a species independent manner. Furthermore, the elucidation of alternative carbon-fixation routes distinct from the Calvin cycle raises possibilities that novel pathways and organisms can be utilized to fix atmosphericmore » carbon dioxide into useful materials.« less

Potential Benefits of Rib Fracture Fixation in Patients with Flail Chest and Multiple Non-flail Rib Fractures.

PubMed

Qiu, Meiguang; Shi, Zhanjun; Xiao, Jun; Zhang, Xuming; Ling, Shishui; Ling, Hao

2016-12-01

The purpose of this study is to evaluate the potential benefits of rib fracture fixation in patients with flail chest and multiple non-flail rib fractures versus conventional treatment modalities. A retrospective reviewed study compared 86 cases which received surgical treatment between June 2009 and May 2013 to 76 cases which received conservative treatment between January 2006 and May 2009. The patients were divided into the flail chest ( n  = 38) and multiple non-flail rib fracture groups ( n  = 124). In the flail chest group, the mechanical ventilation time, ICU monitoring time, tracheostomies, thoracic deformity, and impaired pulmonary function and return to full-time employment were compared. In the multiple non-flail rib fracture group, fracture healing, visual analog scale (VAS) pain score, inpatient length of stay, atelectatic, pulmonary complications, and normal activity-returning time were compared. Patients in the flail chest operative fixation group had significantly shorter ICU stay, decreased ventilator requirements, fewer tracheostomies, less thoracic deformity and impaired pulmonary function, and more returned to full-time employment. Patients in the multiple non-flail rib fracture operative fixation had shorter hospital stay, less pain, earlier return to normal activity, more fracture healing, less atelectasis, and fewer pulmonary infections. This study demonstrates the potential benefits of surgical stabilization of flail chest and multiple non-flail rib fractures with plate fixation. When compared with conventional conservative management, operatively managed patients demonstrated improved clinical outcomes.

Treatment of inherently unstable open or infected fractures by open wound management and external skeletal fixation.

PubMed

Ness, M G

2006-02-01

To assess the use of external skeletal fixation with open wound management for the treatment of inherently unstable open or infected fractures in dogs. A retrospective review of 10 cases. Fracture stabilisation and wound management required only a single anaesthetic, and despite the challenging nature of these injuries, the final outcome was acceptable or good in every case. However, minor complications associated with the fixator pins were quite common, and two dogs developed complications which required additional surgery. Open management of wounds, even when bone was exposed, proved to be an effective technique, and external skeletal fixators were usually effective at maintaining stability throughout an inevitably extended fracture healing period.

Further Studies on the Lyo and Desmo Components of Several Hydrolytic Enzymes and Their Histochemical Significance

PubMed Central

Hannibal, Mark J.; Nachlas, Marvin M.

1959-01-01

This report describes additional studies of the lyo and desmo components of esterase, alkaline phosphatase, acid phosphatase, leucine aminopeptidase, and β-glucuronidase. The techniques used have already been reported (7). Enzyme diffusion occurs to different degrees in different fixatives, and varies somewhat with each enzyme. Loss of enzymatic activity during fixation occurs as a result of both inactivation due to the chemical reaction of the fixative with the enzymic protein, and diffusion of the lyo component into the fixative. The amount of diffusion into formalin can be reduced by the addition of salts, sucrose, or methocel. The pH of the aqueous medium significantly influences the removal of the lyo fraction from the tissue section. A striking similarity can be noted in the proportions of each fraction of enzyme present in the kidney of the rat, dog, and man. The procedure of fixation and paraffin embedding of tissue blocks does not wholly prevent the diffusion of the lyo component from the tissue sections when they are subsequently immersed in the aqueous incubation medium. PMID:13654449

"Cold" Fixation: Reconciliation of Nitrogen Fixation Rates and Diazotroph Assemblages in the Arctic Ocean

NASA Astrophysics Data System (ADS)

Fong, A. A.; Waite, A.; Rost, B.; Richter, K. U.

2016-02-01

Measurements of biological nitrogen fixation are typically conducted in oligotrophic subtropical and tropical marine environments where concentrations of fixed inorganic nitrogen are low. To date, only a handful of nitrogen fixation studies have been conducted in high latitude marine environments, but further investigation is needed to resolve the distribution of cold ocean diazotrophic assemblages. Nitrogen fixation rates and nifH gene distributions were measured at seven stations from 5°E to 20°E, north of 81°N in the Arctic Ocean at the onset of summer 2015. Discrete water samples in ice-covered regions were collected from the sea surface to 200 m for 15N2-tracer additions and targeted nifH gene and transcript analyses. Previous work suggests that heterotrophic bacteria dominate diazotrophic communities in the Arctic Ocean. Therefore, additional nifH gene surveys of sinking particles were conducted to test for enrichment on organic matter-rich microenvironments. Together, these measurements aim to reconcile diazotrophic activity with microbial community composition, further elucidating how nitrogen fixers could impact current concepts in polar carbon and nutrient cycling.

Active ocular vergence improves postural control in elderly as close viewing distance with or without a single cognitive task.

PubMed

Matheron, Eric; Yang, Qing; Delpit-Baraut, Vincent; Dailly, Olivier; Kapoula, Zoï

2016-01-01

Performance of the vestibular, visual, and somatosensory systems decreases with age, reducing the capacity of postural control, and increasing the risk of falling. The purpose of this study is to measure the effects of vision, active vergence eye movements, viewing distance/vergence angle and a simple cognitive task on postural control during an upright stance, in completely autonomous elderly individuals. Participated in the study, 23 elderly subjects (73.4 ± 6.8 years) who were enrolled in a center dedicated to the prevention of falling. Their body oscillations were measured with the DynaPort(®) device, with three accelerometers, placed at the lumbosacral level, near the center of mass. The conditions were the following: eyes open fixating on LED at 20 cm or 150 cm (vergence angle 17.0° and 2.3° respectively) with or without additional cognitive tasks (counting down from one hundred), performing active vergence by alternating the fixation between the far and the near LED (convergence and divergence), eyes closed after having fixated the far LED. The results showed that the postural stability significantly decreased when fixating on the LED at a far distance (weak convergence angle) with or without cognitive tasks; active convergence-divergence between the LEDs improved the postural stability while eye closure decreased it. The privilege of proximity (with increased convergence at near), previously established with foot posturography, is shown here to be valid for accelerometry with the center of mass in elderly. Another major result is the beneficial contribution of active vergence eye movements to better postural stability. The results bring new perspectives for the role of eye movement training to preserve postural control and autonomy in elderly. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Comparison of cemented and uncemented fixation in total knee arthroplasty.

PubMed

Brown, Thomas E; Harper, Benjamin L; Bjorgul, Kristian

2013-05-01

As a result of reading this article, physicians should be able to :1. Understand the rationale behind using uncemented fixation in total knee arthroplasty.2.Discuss the current literature comparing cemented and uncemented total knee arthroplasty3. Describe the value of radiostereographic analysis in assessing implant stability.4. Appreciate the limitations in the available literature advocating 1 mode of fixation in total knee arthroplasty. Total knee arthroplasty performed worldwide uses either cemented, cementless, or hybrid (cementless femur with a cemented tibia) fixation of the components. No recent literature review concerning the outcomes of cemented vs noncemented components has been performed. Noncemented components offer the potential advantage of a biologic interface between the bone and implants, which could demonstrate the greatest advantage in long-term durable fixation in the follow-up of young patients undergoing arthroplasty. Several advances have been made in the backing of the tibial components that have not been available long enough to yield long-term comparative follow-up studies. Short-term radiostereographic analysis studies have yielded differing results. Although long-term, high-quality studies are still needed, material advances in biologic fixation surfaces, such as trabecular metal and hydroxyapatite, may offer promising results for young and active patients undergoing total knee arthroplasty when compared with traditional cemented options. Copyright 2013, SLACK Incorporated.

Inactivation of Influenza A virus, Adenovirus, and Cytomegalovirus with PAXgene tissue fixative and formalin.

PubMed

Kap, Marcel; Arron, Georgina I; Loibner, M; Hausleitner, Anja; Siaulyte, Gintare; Zatloukal, Kurt; Murk, Jean-Luc; Riegman, Peter

2013-08-01

Formalin fixation is known to inactivate most viruses in a vaccine production context, but nothing is published about virus activity in tissues treated with alternative, non-crosslinking fixatives. We used a model assay based on cell culture to test formalin and PAXgene Tissue fixative for their virus-inactivating abilities. MDCK, A549, and MRC-5 cells were infected with Influenza A virus, Adenovirus, and Cytomegalovirus, respectively. When 75% of the cells showed a cytopathic effect (CPE), the cells were harvested and incubated for 15 min, or 1, 3, 6, or 24 hours, with PBS (positive control), 4% formalin, or PAXgene Tissue Fix. The cells were disrupted and the released virus was used to infect fresh MDCK, A549, and MRC-5 cells cultured on cover slips in 24-well plates. The viral cultures were monitored for CPE and by immunocytochemistry (ICC) to record viral replication and infectivity. Inactivation of Adenovirus by formalin occurred after 3 h, while Influenza A virus as well as Cytomegalovirus were inactivated by formalin after 15 min. All three virus strains were inactivated by PAXgene Tissue fixative after 15 min. We conclude that PAXgene Tissue fixative is at least as effective as formalin in inactivating infectivity of Influenza A virus, Adenovirus, and Cytomegalovirus.

Iliac screw for reconstructing posterior pelvic ring in Tile type C1 pelvic fractures.

PubMed

Li, Yonggang; Sang, Xiguang; Wang, Zhiyong; Cheng, Lin; Liu, Hao; Qin, Tao; Di, Kai

2018-06-18

It is often difficult to achieve stable fixation in Tile type C1 pelvic fractures and there is no standard fixation technique for these types of injuries. Iliac screw fixation can be used for treating Type C1 pelvic fractures. A retrospective review was performed on 47 patients who underwent iliac screw fixation in posterior column of ilium (PCI) for Tile type C1 pelvic fractures from July 2007 to December 2014. All patients were treated with fracture reduction, sacral nerve root decompression (if needed), internal fixation by iliac screw and connecting rod. The data on surgical time, intraoperative bleeding volume, postoperative neurologic functions and postoperative complications were analyzed. Patients were follow-up for at least 12months. The mean surgical time was 148minutes, and the mean intraoperative bleeding volume was 763ml. Patients were encouraged in-bed activities immediately after surgery. The postoperative Majeed functional score was 48-100 points (mean 80.2), corresponding to an excellent and good recovery of 91.5%. Postoperative X-radiographs and CT scans indicated satisfactory fracture reduction. Iliac screw fixation combined with sacral nerve canal decompression could effectively restore pelvic alignment and improve neurological functions for complex pelvic trauma. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Biomechanical comparison of locking plate and crossing metallic and absorbable screws fixations for intra-articular calcaneal fractures.

PubMed

Ni, Ming; Wong, Duo Wai-Chi; Mei, Jiong; Niu, Wenxin; Zhang, Ming

2016-09-01

The locking plate and percutaneous crossing metallic screws and crossing absorbable screws have been used clinically to treat intra-articular calcaneal fractures, but little is known about the biomechanical differences between them. This study compared the biomechanical stability of calcaneal fractures fixed using a locking plate and crossing screws. Three-dimensional finite-element models of intact and fractured calcanei were developed based on the CT images of a cadaveric sample. Surgeries were simulated on models of Sanders type III calcaneal fractures to produce accurate postoperative models fixed by the three implants. A vertical force was applied to the superior surface of the subtalar joint to simulate the stance phase of a walking gait. This model was validated by an in vitro experiment using the same calcaneal sample. The intact calcaneus showed greater stiffness than the fixation models. Of the three fixations, the locking plate produced the greatest stiffness and the highest von Mises stress peak. The micromotion of the fracture fixated with the locking plate was similar to that of the fracture fixated with the metallic screws but smaller than that fixated with the absorbable screws. Fixation with both plate and crossing screws can be used to treat intra-articular calcaneal fractures. In general, fixation with crossing metallic screws is preferable because it provides sufficient stability with less stress shielding.

Regulation of nif gene expression and the energetics of N2 fixation over the diel cycle in a hot spring microbial mat.

PubMed

Steunou, Anne-Soisig; Jensen, Sheila I; Brecht, Eric; Becraft, Eric D; Bateson, Mary M; Kilian, Oliver; Bhaya, Devaki; Ward, David M; Peters, John W; Grossman, Arthur R; Kühl, Michael

2008-04-01

Nitrogen fixation, a prokaryotic, O2-inhibited process that reduces N2 gas to biomass, is of paramount importance in biogeochemical cycling of nitrogen. We analyzed the levels of nif transcripts of Synechococcus ecotypes, NifH subunit and nitrogenase activity over the diel cycle in the microbial mat of an alkaline hot spring in Yellowstone National Park. The results showed a rise in nif transcripts in the evening, with a subsequent decline over the course of the night. In contrast, immunological data demonstrated that the level of the NifH polypeptide remained stable during the night, and only declined when the mat became oxic in the morning. Nitrogenase activity was low throughout the night; however, it exhibited two peaks, a small one in the evening and a large one in the early morning, when light began to stimulate cyanobacterial photosynthetic activity, but O2 consumption by respiration still exceeded the rate of O2 evolution. Once the irradiance increased to the point at which the mat became oxic, the nitrogenase activity was strongly inhibited. Transcripts for proteins associated with energy-producing metabolisms in the cell also followed diel patterns, with fermentation-related transcripts accumulating at night, photosynthesis- and respiration-related transcripts accumulating during the day and late afternoon, respectively. These results are discussed with respect to the energetics and regulation of N2 fixation in hot spring mats and factors that can markedly influence the extent of N2 fixation over the diel cycle.

Molecular Determinants of a Symbiotic Chronic Infection

PubMed Central

Gibson, Katherine E.; Kobayashi, Hajime

2009-01-01

Rhizobial bacteria colonize legume roots for the purpose of biological nitrogen fixation. A complex series of events, coordinated by host and bacterial signal molecules, underlie the development of this symbiotic interaction. Rhizobia elicit de novo formation of a novel root organ within which they establish a chronic intracellular infection. Legumes permit rhizobia to invade these root tissues while exerting control over the infection process. Once rhizobia gain intracellular access to their host, legumes also strongly influence the process of bacterial differentiation that is required for nitrogen fixation. Even so, symbiotic rhizobia play an active role in promoting their goal of host invasion and chronic persistence by producing a variety of signal molecules that elicit changes in host gene expression. In particular, rhizobia appear to advocate for their access to the host by producing a variety of signal molecules capable of suppressing a general pathogen defense response. PMID:18983260

Prevention of Thumb Web Space Contracture With Multiplanar External Fixation.

PubMed

Harper, Carl M; Iorio, Matthew L

2016-09-01

Thumb web space contracture following hand trauma can be disabling with numerous reconstructive procedures existing to correct the resultant deformity. Following marked soft tissue injury to the hand we utilized the Stryker Hoffmann II Micro External Fixator System to link the first and second metacarpals by a multiplanar system using 1.6 or 2.0 mm self-drilling half-pins and 3 mm carbon fiber connecting rods. This facilitated placement of the thumb in maximal palmar abduction as well as allowed adjustment of thumb position throughout the postoperative period. This technique was performed on 5 patients. Two patients were treated with a first web space external fixator for table saw injuries to the radial aspect of the hand. An additional 2 patients were treated with a first web space external fixator following metacarpophalangeal joint capsular release in the setting of thermal burns. A fifth patient underwent second ray amputation, trapeziectomy and trapezoidectomy for squamous cell carcinoma with subsequent stabilization with the external fixator. The external fixator was left in place until soft tissues were healed (average 5.5 wk). The patients were allowed to mobilize their hand in as much as the external fixator allowed, and no device-associated complications were noted. Thumb web space was preserved with passive and supple thumb circumduction and web space abduction/adduction in all patients at an average follow-up of 5 months. The average Quick Dash Score was 35±5 and the average Modern Activity Subjective Survey of 2007 was 30±8.

[Treatment of sternoclavicular joint dislocation with sternoclavicular hook plate fixation].

PubMed

Liu, Pan; Yuan, Jia-bin; Liu, Zhong-qian; Lu, Bing; Wang, Yue

2015-08-01

To evaluate the technique and therapeutic effect of sternoclavicular hook plate fixation in treating sternoclavicular joint (SCJ) dislocation. From January 2010 to March 2014,6 patients with SCJ dislocation were treated with sternoclavicular hook plate fixation in our hospital. Among the 6 patients, 5 patients were male and 1 patient was female, and the average age was 34 years, ranging from 26 to 48 years. The course of the disease ranged from 3 to 20 days. All the SCJ dislocations were caused by external injury and accompanied with the symptoms of swelling pain and obvious shoulder joint activity restricted in affected side. All SCJ dislocations were anterior dislocation by the diagnosis of X-ray and CT scan. The postoperative curative effect was evaluated according to Rockwood score. All the patients' operative incision were healed well and in good appearance. X-ray showed that the dislocated SCJ was well reduced and the plate was on right position. All the 6 patients were followed up for 4 to 18 months, with an average of 12 months. The results were evaluated according to Rockwood score, 4 got excellent results, 1 good and 1 fair. No fixation loosening, redislocation or side injury such as vessel, nerve or pleura injury were found. With sternoclavicular hook plate fixation, SCJ dislocation could be reduced while keeping its amphiarthrodial function and the completeness of the cartilage surface. Sternoclavicular hook plate fixation has advantages of safety and stabilization in fixation, and patients can begin function exercises earlier.

The computer-aided parallel external fixator for complex lower limb deformity correction.

PubMed

Wei, Mengting; Chen, Jianwen; Guo, Yue; Sun, Hao

2017-12-01

Since parameters of the parallel external fixator are difficult to measure and calculate in real applications, this study developed computer software that can help the doctor measure parameters using digital technology and generate an electronic prescription for deformity correction. According to Paley's deformity measurement method, we provided digital measurement techniques. In addition, we proposed an deformity correction algorithm to calculate the elongations of the six struts and developed a electronic prescription software. At the same time, a three-dimensional simulation of the parallel external fixator and deformed fragment was made using virtual reality modeling language technology. From 2013 to 2015, fifteen patients with complex lower limb deformity were treated with parallel external fixators and the self-developed computer software. All of the cases had unilateral limb deformity. The deformities were caused by old osteomyelitis in nine cases and traumatic sequelae in six cases. A doctor measured the related angulation, displacement and rotation on postoperative radiographs using the digital measurement techniques. Measurement data were input into the electronic prescription software to calculate the daily adjustment elongations of the struts. Daily strut adjustments were conducted according to the data calculated. The frame was removed when expected results were achieved. Patients lived independently during the adjustment. The mean follow-up was 15 months (range 10-22 months). The duration of frame fixation from the time of application to the time of removal averaged 8.4 months (range 2.5-13.1 months). All patients were satisfied with the corrected limb alignment. No cases of wound infections or complications occurred. Using the computer-aided parallel external fixator for the correction of lower limb deformities can achieve satisfactory outcomes. The correction process can be simplified and is precise and digitized, which will greatly improve the treatment in a clinical application.

Fixation Probability in a Haploid-Diploid Population.

PubMed

Bessho, Kazuhiro; Otto, Sarah P

2017-01-01

Classical population genetic theory generally assumes either a fully haploid or fully diploid life cycle. However, many organisms exhibit more complex life cycles, with both free-living haploid and diploid stages. Here we ask what the probability of fixation is for selected alleles in organisms with haploid-diploid life cycles. We develop a genetic model that considers the population dynamics using both the Moran model and Wright-Fisher model. Applying a branching process approximation, we obtain an accurate fixation probability assuming that the population is large and the net effect of the mutation is beneficial. We also find the diffusion approximation for the fixation probability, which is accurate even in small populations and for deleterious alleles, as long as selection is weak. These fixation probabilities from branching process and diffusion approximations are similar when selection is weak for beneficial mutations that are not fully recessive. In many cases, particularly when one phase predominates, the fixation probability differs substantially for haploid-diploid organisms compared to either fully haploid or diploid species. Copyright © 2017 by the Genetics Society of America.

Measuring vigilance decrement using computer vision assisted eye tracking in dynamic naturalistic environments.

PubMed

Bodala, Indu P; Abbasi, Nida I; Yu Sun; Bezerianos, Anastasios; Al-Nashash, Hasan; Thakor, Nitish V

2017-07-01

Eye tracking offers a practical solution for monitoring cognitive performance in real world tasks. However, eye tracking in dynamic environments is difficult due to high spatial and temporal variation of stimuli, needing further and thorough investigation. In this paper, we study the possibility of developing a novel computer vision assisted eye tracking analysis by using fixations. Eye movement data is obtained from a long duration naturalistic driving experiment. Source invariant feature transform (SIFT) algorithm was implemented using VLFeat toolbox to identify multiple areas of interest (AOIs). A new measure called `fixation score' was defined to understand the dynamics of fixation position between the target AOI and the non target AOIs. Fixation score is maximum when the subjects focus on the target AOI and diminishes when they gaze at the non-target AOIs. Statistically significant negative correlation was found between fixation score and reaction time data (r =-0.2253 and p<;0.05). This implies that with vigilance decrement, the fixation score decreases due to visual attention shifting away from the target objects resulting in an increase in the reaction time.

Arthroplasty for Unreconstructable Acute Fractures and Failed Fracture Fixation About the Hip and Knee in the Active Elderly: A New Paradigm.

PubMed

Kyle, Richard F; Duwelius, Paul J; Haidukewych, George J; Schmidt, Andrew H

2017-02-15

The techniques, materials, and designs for total joint arthroplasty underwent major improvements in the past 30 years. During this time, trauma surgeons classified the severity of fractures as well as identified certain articular fractures that do not have good outcomes and have a high rate of failure after internal fixation. Advanced improvements in arthroplasty have increased its reliability and longevity. Total joint arthroplasty is becoming a standard of care for some acute articular fractures, particularly displaced femoral neck fractures in the active elderly. Total joint arthroplasty also has become the standard of care after failed internal fixation in patients who have very complicated fractures about the knee, hip, and shoulder. As the population ages, fractures worldwide continue to rapidly increase. Elderly patients have a high risk for fractures that result from falls because of their poor bone quality. The current active elderly population participates in higher risk activities than previous elderly populations, which places them at risk for more injuries. This has become both a worldwide healthcare problem and an economic problem. Surgeons need to manage fractures in the active elderly with the latest advancements in technology and patient selection to ensure rapid recovery and the reduction of complications.

Necrotizing fasciitis after internal fixation of fracture of femoral trochanteric☆☆☆

PubMed Central

Santos, Leandro Emílio Nascimento; Pires, Robinson Esteves Santos; Figueiredo, Leonardo Brandão; Soares, Eduardo Augusto Marques

2014-01-01

Necrotizing fasciitis is a rare and potentially lethal soft tissue infection. We report a case of trochanteric femur fracture in a patient who underwent fracture fixation and developed necrotizing fasciitis. A literature review on the topic will be addressed. PMID:26229777

Diurnal variation in the coupling of photosynthetic electron transport and carbon fixation in iron-limited phytoplankton in the NE subarctic Pacific

NASA Astrophysics Data System (ADS)

Schuback, N.; Flecken, M.; Maldonado, M. T.; Tortell, P. D.

2015-10-01

Active chlorophyll a fluorescence approaches, including fast repetition rate fluorometry (FRRF), have the potential to provide estimates of phytoplankton primary productivity at unprecedented spatial and temporal resolution. FRRF-derived productivity rates are based on estimates of charge separation at PSII (ETRRCII), which must be converted into ecologically relevant units of carbon fixation. Understanding sources of variability in the coupling of ETRRCII and carbon fixation provides physiological insight into phytoplankton photosynthesis, and is critical for the application of FRRF as a primary productivity measurement tool. In the present study, we simultaneously measured phytoplankton carbon fixation and ETRRCII in the iron-limited NE subarctic Pacific, over the course of a diurnal cycle. We show that rates of ETRRCII are closely tied to the diurnal cycle in light availability, whereas rates of carbon fixation appear to be influenced by endogenous changes in metabolic energy allocation under iron-limited conditions. Unsynchronized diurnal oscillations of the two rates led to 3.5 fold changes in the conversion factor coupling ETRRCII and carbon fixation (Φe:C / nPSII). Consequently, diurnal variability in phytoplankton carbon fixation cannot be adequately captured with FRRF approaches if a constant conversion factor is applied. Utilizing several auxiliary photophysiological measurements, we observed that a high conversion factor is associated with conditions of excess light, and correlates with the expression of non-photochemical quenching (NPQ) in the pigment antenna, as derived from FRRF measurements. The observed correlation between NPQ and the conversion factor Φe:C / nPSII has the potential to improve estimates of phytoplankton carbon fixation rates from FRRF measurements alone.

Diurnal variation in the coupling of photosynthetic electron transport and carbon fixation in iron-limited phytoplankton in the NE subarctic Pacific

NASA Astrophysics Data System (ADS)

Schuback, Nina; Flecken, Mirkko; Maldonado, Maria T.; Tortell, Philippe D.

2016-02-01

Active chlorophyll a fluorescence approaches, including fast repetition rate fluorometry (FRRF), have the potential to provide estimates of phytoplankton primary productivity at an unprecedented spatial and temporal resolution. FRRF-derived productivity rates are based on estimates of charge separation in reaction center II (ETRRCII), which must be converted into ecologically relevant units of carbon fixation. Understanding sources of variability in the coupling of ETRRCII and carbon fixation provides physiological insight into phytoplankton photosynthesis and is critical for the application of FRRF as a primary productivity measurement tool. In the present study, we simultaneously measured phytoplankton carbon fixation and ETRRCII in the iron-limited NE subarctic Pacific over the course of a diurnal cycle. We show that rates of ETRRCII are closely tied to the diurnal cycle in light availability, whereas rates of carbon fixation appear to be influenced by endogenous changes in metabolic energy allocation under iron-limited conditions. Unsynchronized diurnal oscillations of the two rates led to 3.5-fold changes in the conversion factor between ETRRCII and carbon fixation (Kc / nPSII). Consequently, diurnal variability in phytoplankton carbon fixation cannot be adequately captured with FRRF approaches if a constant conversion factor is applied. Utilizing several auxiliary photophysiological measurements, we observed that a high conversion factor is associated with conditions of excess light and correlates with the increased expression of non-photochemical quenching (NPQ) in the pigment antenna, as derived from FRRF measurements. The observed correlation between NPQ and Kc / nPSII requires further validation but has the potential to improve estimates of phytoplankton carbon fixation rates from FRRF measurements alone.

Biomechanical analyses of mesh fixation in TAPP and TEP hernia repair.

PubMed

Schwab, R; Schumacher, O; Junge, K; Binnebösel, M; Klinge, U; Becker, H P; Schumpelick, V

2008-03-01

Reliable laparoscopic fixation of meshes prior to their fibrous incorporation is intended to minimize recurrences following transabdominal preperitoneal hernia repair (TAPP) and totally extraperitoneal repair (TEP) repair of inguinal hernias. However, suture-, tack- and staple-based fixation systems are associated with postoperative chronic inguinal pain. Initial fixation with fibrin sealant offers an atraumatic alternative, but there is little data demonstrating directly whether fibrin-based mesh adhesion provides adequate biomechanical stability for repair of inguinal hernia by TAPP and TEP. Using a newly developed, standardized simulation model for abdominal wall hernias, sublay repairs were performed with six different types of commercially available hernia mesh. The biomechanical stability achieved, and the protection afforded by the mesh-hernia overlap, were compared for three different techniques: nonfixation, point-by-point suture fixation, and fibrin sealant fixation. Mesh dislocation from the repaired hernia defect was consistently seen with nonfixation. This was reliably prevented with all six mesh types when fixed using either sutures or fibrin sealant. The highest stress resistance across the whole abdominal wall was found following superficial fixation with fibrin sealant across the mesh types. There was a highly statistically significant improvement in fixation stability with fibrin sealant versus fixation using eight single sutures (p = 0.008), as assessed by the range of achievable peak pressure stress up to 200 mmHg. To ensure long-term freedom from recurrence, intraoperative mesh-hernia overlap must be retained. This can be achieved with fibrin sealant up to the incorporation of the mesh - without trauma and with biomechanical stability.

Mechanical evaluation of the SLM fabricated, stiffness-matched, mandibular bone fixation plates

NASA Astrophysics Data System (ADS)

Jahadakbar, Ahmadreza; Shayesteh Moghaddam, Narges; Amerinatanzi, Amirhesam; Dean, David; Elahinia, Mohammad

2018-03-01

The standard of the care for the treatment of mandibular segmental defects is the use of Ti-6Al-4V bone fixation plates and screws to immobilize the grafted bone and the host mandible. While Ti-6Al-4V bone fixation plates provide strong immobilization during the healing period, they may disturb the stress distribution in the repaired mandible. The highly stiff Ti-6Al-4V fixation carries a great portion of the load which was previously borne by the mandible, and stress shielding may occur on the surrounding cortical bone. Based on the bone remodeling theory, stress shielding causes bone resorption in the effected region and may eventually lead to the failure of the surgical reconstruction. To address this issue, we have developed a new generation of the patient-specific, porous NiTi bone fixation plates which benefit from stiffness-matching of the adjacent bone. Using the CT scan data of the patient's defective mandible, the geometry for the required bone fixation plates is designed and the stiffness of the surrounding regions is measured. By introducing specific level and type of porosity to the bone fixation plate, its stiffness can be tuned. Finite Element simulations has verified the reduced level of stress shielding on the reconstructed mandible, in case of using the proposed bone fixation plates. Selective Lase Sintering has been used for fabrication of the porous NiTi bone fixation plates with six different levels of stiffness. Finite element simulations, and mechanical tests have been done to verify the performance of the fabricated parts resulting from our design and fabrication method.

Increased wound complication with intramedullary screw fixation of clavicle fractures: Is it thermal necrosis?

PubMed

Domos, Peter; Tytherleigh-Strong, Graham; Van Rensburg, Lee

2017-01-01

Adult mid-shaft clavicle fractures are common injuries. For displaced fractures, open reduction with plate or intramedullary (IM) fixation is the widely used techniques. All methods have their own potential drawbacks, especially related to local soft tissue complications. There is little information about outcome and management of local wound complications after clavicle fracture fixations. Ninety-seven patients underwent open reduction and internal fixation, 17 were treated with IM screw fixation and 80 with plate fixation. Wound complication occurred in eight patients (8.2%) and rates differed significantly between IM and plate fixations (29.4% vs. 3.8%). Patients were assessed on average 58.3 months with visual analogue pain scores (VASs), Oxford Shoulder Score (OSS), and QuickDash (QD) score. Five patients had wound breakdown and three patients had wound erythema. In seven patients with stable fixation, it was possible to "dress and suppress" with average 3 weeks of oral antibiotics. One patient had unstable fixation and required longer antibiotic treatment with early screw removal. One patient developed a chronic discharging wound, requiring debridement and later plate removal. At final follow-up, all wounds remained healed, bony union was achieved in all. The average scores were: VAS 1, OSS 46, and QD 4.5. Good function with dry healed wound and united clavicle can be achieved. Further studies are required to investigate the difference in soft tissue complication rates, which may be due to the IM technique of retrograde drilling with a guide wire and due to aseptic thermal bone necrosis, rather than true infection.

Diazotrophy in the Deep: An analysis of the distribution, magnitude, geochemical controls, and biological mediators of deep-sea benthic nitrogen fixation

NASA Astrophysics Data System (ADS)

Dekas, Anne Elizabeth

Biological nitrogen fixation (the conversion of N2 to NH3) is a critical process in the oceans, counteracting the production of N2 gas by dissimilatory bacterial metabolisms and providing a source of bioavailable nitrogen to many nitrogen-limited ecosystems. One currently poorly studied and potentially underappreciated habitat for diazotrophic organisms is the sediments of the deep-sea. Although nitrogen fixation was once thought to be negligible in non-photosynthetically driven benthic ecosystems, the present study demonstrates the occurrence and expression of a diversity of nifH genes (those necessary for nitrogen fixation), as well as a widespread ability to fix nitrogen at high rates in these locations. The following research explores the distribution, magnitude, geochemical controls, and biological mediators of nitrogen fixation at several deep-sea sediment habitats, including active methane seeps (Mound 12, Costa Rica; Eel River Basin, CA, USA; Hydrate Ridge, OR, USA; and Monterey Canyon, CA, USA), whale-fall sites (Monterey Canyon, CA), and background deep-sea sediment (off-site Mound 12 Costa Rica, off-site Hydrate Ridge, OR, USA; and Monterey Canyon, CA, USA). The first of the five chapters describes the FISH-NanoSIMS method, which we optimized for the analysis of closely associated microbial symbionts in marine sediments. The second describes an investigation of methane seep sediment from the Eel River Basin, where we recovered nifH sequences from extracted DNA, and used FISH-NanoSIMS to identify methanotrophic archaea (ANME-2) as diazotrophs, when associated with functional sulfate-reducing bacterial symbionts. The third and fourth chapters focus on the distribution and diversity of active diazotrophs (respectively) in methane seep sediment from Mound 12, Costa Rica, using a combination of 15N-labeling experiments, FISH-NanoSIMS, and RNA and DNA analysis. The fifth chapter expands the scope of the investigation by targeting diverse samples from methane seep, whale-fall, and background sediment collected along the Eastern Pacific Margin, and comparing the rates of nitrogen fixation observed to geochemical measurements collected in parallel. Together, these analyses represent the most extensive investigation of deep-sea nitrogen fixation to date, and work towards understanding the contribution of benthic nitrogen fixation to global marine nitrogen cycling.

Biomechanical Comparison Study of Three Fixation Methods for Proximal Chevron Osteotomy of the First Metatarsal in Hallux Valgus

PubMed Central

Kim, Jin Su; Young, Ki Won; Kim, Ji Soo; Lee, Kyung Tai

2017-01-01

Background Fixation of proximal chevron metatarsal osteotomy has been accomplished using K-wires traditionally and with a locking plate recently. However, both methods have many disadvantages. Hence, we developed an intramedullary fixation technique using headless cannulated screws and conducted a biomechanical study to evaluate the superiority of the technique to K-wire and locking plate fixations. Methods Proximal chevron metatarsal osteotomy was performed on 30 synthetic metatarsal models using three fixation techniques. Specimens in group I were fixated with K-wires (1.6 mm × 2) and in group II with headless cannulated screws (3.0 mm × 2) distally through the intramedullary canal. Specimens in group III were fixated with a locking X-shaped plate (1.3-mm thick) and screws (2.5 mm × 4). Eight metatarsal specimens were selected from each group for walking fatigue test. Bending stiffness and dorsal angulation were measured by 1,000 repetitions of a cantilever bending protocol in a plantar to dorsal direction. The remaining two samples from each group were subjected to 5 mm per minute axial loading to assess the maximal loading tolerance. Results All samples in group I failed walking fatigue test while group II and group III tolerated the walking fatigue test. Group II showed greater resistance to bending force and smaller dorsal angulation than group III (p = 0.001). On the axial loading test, group I and group II demonstrated superior maximum tolerance to group III (54.8 N vs. 47.2 N vs. 28.3 N). Conclusions Authors have demonstrated proximal chevron metatarsal osteotomy with intramedullary screw fixation provides superior biomechanical stability to locking plate and K-wire fixations. The new technique using intramedullary screw fixation can offer robust fixation and may lead to better outcomes in surgical treatment of hallux valgus. PMID:29201305

Is there difference in chronic pain after Suture and Stapler fixation method of mesh in Ventral Hernia? Is stapler fixation method quicker? A randomized controlled trial.

PubMed

Shaukat, Noureen; Jaleel, Farhat; Jawaid, Masood; Zulfiqar, Imrana

2018-01-01

Chronic pain occurs in 20-30% of patients after hernia surgery. As a consequence of this chronic pain, almost one third of patients have limitations in daily activities. Frequency and severity of this pain varies with different techniques of hernia repair. The objective of this study was to compare polypropylene suture and skin staples for securing mesh in uncomplicated ventral hernioplasty in terms of acute and chronic postoperative pain and to compare the time taken for mesh fixation between polypropylene sutures and skin stapler in ventral hernioplasty. This study was conducted in Surgery Department of Dow University Hospital, Dow University of Health Sciences, Ojha Campus and included 53 patients from Jan 2015 to Dec 2016, after taking informed consent. All patients were operated under general anesthesia by the same surgical team. Patients were randomized into two groups; in one group mesh fixed with 2/0 polypropylene suture while in other group mesh stapler was used. Time taken to apply mesh was noted in minutes from laying the mesh over anterior rectus sheath to completion of fixation by either method. The severity of post-operative pain was measured with VAS (1-10) after one week, one month and after one year after surgery. Data was analysed using SPSS version 17. Patient characteristics and operative outcome were similar in the two groups and statistically non-significant in both. Early postoperative pain was more after suture fixation but it was not statistically significant. Mean ± SD pain score was after one week 3.47±2.7 after sutures while 2.91±1.88 after stapler. After four weeks, 0.40±0.49 after suture while 0.35±0.48 after stapler fixation. In both study groups 30-34% of the patients felt some pain in follow-up after one year. Severity of pain was 0.60±0.62 after suture while 1.65±1.94 after stapler fixation which is statistically significant as well (p<0.007). Mean operative time was 15.33±6.33 minutes for suture fixation while 1.56±0.41 minutes for fixation by staples, p-value < 0.001. The method of fixation does not appear to cause significant difference in early post-operative pain but chronic pain is more after stapler fixation of mesh. However, operative time was reduced significantly in staple fixation group as compared to suture fixation group.

Pectoralis Major Repair With Unicortical Button Fixation And Suture Tape.

PubMed

Sanchez, Anthony; Ferrari, Marcio B; Frangiamore, Salvatore J; Sanchez, George; Kruckeberg, Bradley M; Provencher, Matthew T

2017-06-01

Although injuries of the pectoralis major muscle are generally uncommon, ruptures of the pectoralis major are occasionally seen in younger, more active patients who participate in weightlifting activities. These injuries usually occur during maximal contraction of the muscle, while in extension and external rotation. In the case of a rupture, operative treatment is advocated especially in young, active patients regardless of the chronicity of the injury. Various surgical techniques for reattachment of the avulsed tendon have been described, but bone tunnel and suture anchor repair techniques are most widely used. In this Technical Note, we present our preferred technique for acute pectoralis major rupture repair involving use of cortical buttons for tendon stump-to-bone fixation.

Performance of the Research Animal Holding Facility (RAHF) and General Purpose Work Station (GPWS) and other hardware in the microgravity environment

NASA Technical Reports Server (NTRS)

Hogan, Robert P.; Dalton, Bonnie P.

1991-01-01

This paper discusses the performance of the Research Animal Holding Facility (RAHF) and General Purpose Work Station (GPWS) plus other associated hardware during the recent flight of Spacelab Life Sciences 1 (SLS-1). The RAHF was developed to provide proper housing (food, water, temperature control, lighting and waste management) for up to 24 rodents during flights on the Spacelab. The GPWS was designed to contain particulates and toxic chemicals generated during plant and animal handling and dissection/fixation activities during space flights. A history of the hardware development involves as well as the redesign activities prior to the actual flight are discussed.

Keep your eyes on the ball: smooth pursuit eye movements enhance prediction of visual motion.

PubMed

Spering, Miriam; Schütz, Alexander C; Braun, Doris I; Gegenfurtner, Karl R

2011-04-01

Success of motor behavior often depends on the ability to predict the path of moving objects. Here we asked whether tracking a visual object with smooth pursuit eye movements helps to predict its motion direction. We developed a paradigm, "eye soccer," in which observers had to either track or fixate a visual target (ball) and judge whether it would have hit or missed a stationary vertical line segment (goal). Ball and goal were presented briefly for 100-500 ms and disappeared from the screen together before the perceptual judgment was prompted. In pursuit conditions, the ball moved towards the goal; in fixation conditions, the goal moved towards the stationary ball, resulting in similar retinal stimulation during pursuit and fixation. We also tested the condition in which the goal was fixated and the ball moved. Motion direction prediction was significantly better in pursuit than in fixation trials, regardless of whether ball or goal served as fixation target. In both fixation and pursuit trials, prediction performance was better when eye movements were accurate. Performance also increased with shorter ball-goal distance and longer presentation duration. A longer trajectory did not affect performance. During pursuit, an efference copy signal might provide additional motion information, leading to the advantage in motion prediction.

[Tensile strength of bone fixation of hydroxyapatite coated Schanz screws of the Heidelberg External Fixation System (HEFS)--comparative torque measurements in clinical use and in cadaver tibia].

PubMed

Placzek, R; Deuretzbacher, G; Meiss, A L

2002-12-01

It is claimed in the literature that hydroxyapatite(HA)-coated screws of external fixators have superior fixation strength in bone, which is postulated to lead to a substantial decrease in loosening and infection rates. We report on a study of the maximum torque values developed while inserting and removing 30 HA-coated Schanz screws of 8 Heidelberg external fixation systems applied to the tibia to correct leg length differences and axial deformities. The infection rate was determined in accordance with defined criteria, and was found to be about 20% for the HA-coated screws. Screws without infection showed an extraction torque above insertion torque, screws with infection an extraction torque below. A significant correlation (p = 0.05) was seen between infection and decrease in fixation strength (quotient: loosening torque/tightening torque). To exclude the impact of such biological processes as osteointegration and bone remodelling, the clinical results were compared with the torques measured for coated and uncoated Schanz screws in a human cadaveric tibia. A significantly higher fixation strength in bone was found for HA-coated screws in comparison with uncoated screws (p = 0.002). These data warrant a clinical study directly comparing HA-coated and uncoated Schanz screws.

How successful are mutants in multiplayer games with fluctuating environments? Sojourn times, fixation and optimal switching

PubMed Central

Galla, Tobias

2018-01-01

Using a stochastic model, we investigate the probability of fixation, and the average time taken to achieve fixation, of a mutant in a population of wild-types. We do this in a context where the environment in which the competition takes place is subject to stochastic change. Our model takes into account interactions which can involve multiple participants. That is, the participants take part in multiplayer games. We find that under certain circumstances, there are environmental switching dynamics which minimize the time that it takes for the mutants to fixate. To analyse the dynamics more closely, we develop a method by which to calculate the sojourn times for general birth–death processes in fluctuating environments. PMID:29657810

How successful are mutants in multiplayer games with fluctuating environments? Sojourn times, fixation and optimal switching

NASA Astrophysics Data System (ADS)

Baron, Joseph W.; Galla, Tobias

2018-03-01

Using a stochastic model, we investigate the probability of fixation, and the average time taken to achieve fixation, of a mutant in a population of wild-types. We do this in a context where the environment in which the competition takes place is subject to stochastic change. Our model takes into account interactions which can involve multiple participants. That is, the participants take part in multiplayer games. We find that under certain circumstances, there are environmental switching dynamics which minimize the time that it takes for the mutants to fixate. To analyse the dynamics more closely, we develop a method by which to calculate the sojourn times for general birth-death processes in fluctuating environments.

Benthic N2 fixation in coral reefs and the potential effects of human-induced environmental change

PubMed Central

Cardini, Ulisse; Bednarz, Vanessa N; Foster, Rachel A; Wild, Christian

2014-01-01

Tropical coral reefs are among the most productive and diverse ecosystems, despite being surrounded by ocean waters where nutrients are in short supply. Benthic dinitrogen (N2) fixation is a significant internal source of “new” nitrogen (N) in reef ecosystems, but related information appears to be sparse. Here, we review the current state (and gaps) of knowledge on N2 fixation associated with coral reef organisms and their ecosystems. By summarizing the existing literature, we show that benthic N2 fixation is an omnipresent process in tropical reef environments. Highest N2 fixation rates are detected in reef-associated cyanobacterial mats and sea grass meadows, clearly showing the significance of these functional groups, if present, to the input of new N in reef ecosystems. Nonetheless, key benthic organisms such as hard corals also importantly contribute to benthic N2 fixation in the reef. Given the usually high coral coverage of healthy reef systems, these results indicate that benthic symbiotic associations may be more important than previously thought. In fact, mutualisms between carbon (C) and N2 fixers have likely evolved that may enable reef communities to mitigate N limitation. We then explore the potential effects of the increasing human interferences on the process of benthic reef N2 fixation via changes in diazotrophic populations, enzymatic activities, or availability of benthic substrates favorable to these microorganisms. Current knowledge indicates positive effects of ocean acidification, warming, and deoxygenation and negative effects of increased ultraviolet radiation on the amount of N fixed in coral reefs. Eutrophication may either boost or suppress N2 fixation, depending on the nutrient becoming limiting. As N2 fixation appears to play a fundamental role in nutrient-limited reef ecosystems, these assumptions need to be expanded and confirmed by future research efforts addressing the knowledge gaps identified in this review. PMID:24967086

[Clinical application of percutaneous iliosacral screws combined with pubic ramus screws in Tile B pelvic fracture].

PubMed

Xu, Qi-Fei; Lin, Kui-Ran; Zhao, Dai-Jie; Zhang, Song-Qin; Feng, Sheng-Kai; Li, Chen

2017-03-25

To investigate the application and effect of minimally invasive percutaneous anterior pelvic pubic ramus screw fixation in Tile B fractures. A retrospective review was conducted on 56 patients with posterior pelvic ring injury combined with fractures of anterior pubic and ischiadic ramus treated between May 2010 and August 2015, including 31 males and 25 females with an average age of 36.8 years old ranging from 35 to 65 years old. Based on the Tile classification, there were 13 cases of Tile B1 type, 28 cases of Tile B2 type and 15 cases of Tile B3 type. Among them, 26 patients were treated with sacroiliac screws combined with external fixation (external fixator group) and the other 30 patients underwent sacroiliac screw fixation combined with anterior screw fixation (pubic ramus screw group). Postoperative complications, postoperative ambulation time, fracture healing, blood loss, Majeed pelvic function score and visual analogue scale(VAS) were compared between two groups. Fifty-four patients were followed up from 3 to 24 months with a mean of 12 months. There were no significant difference in the peri-operative bleeding and operation time between two groups( P >0.05). The postoperative activity time and fracture healing time of pubic ramus screw group were shorter than those of the external fixator group, the differences were statistically significant( P <0.05). The Majeed score, VAS score of pubic ramus screw group were higher than those of the external fixator group, the differences were statistically significant( P <0.05). The incidence of postoperative complications of pubic ramus screw was lower than that of the external fixator group, the difference was statistically significant ( P <0.05). Percutaneous iliosacral screws fixation combined with the pubic ramus screw is an effective and safty treatment method to the Tile B pelvic fracture. It has advantages of early ambulation, relief of the pain and few complications.

The Biological Deep Sea Hydrothermal Vent as a Model to Study Carbon Dioxide Capturing Enzymes

PubMed Central

Minic, Zoran; Thongbam, Premila D.

2011-01-01

Deep sea hydrothermal vents are located along the mid-ocean ridge system, near volcanically active areas, where tectonic plates are moving away from each other. Sea water penetrates the fissures of the volcanic bed and is heated by magma. This heated sea water rises to the surface dissolving large amounts of minerals which provide a source of energy and nutrients to chemoautotrophic organisms. Although this environment is characterized by extreme conditions (high temperature, high pressure, chemical toxicity, acidic pH and absence of photosynthesis) a diversity of microorganisms and many animal species are specially adapted to this hostile environment. These organisms have developed a very efficient metabolism for the assimilation of inorganic CO2 from the external environment. In order to develop technology for the capture of carbon dioxide to reduce greenhouse gases in the atmosphere, enzymes involved in CO2 fixation and assimilation might be very useful. This review describes some current research concerning CO2 fixation and assimilation in the deep sea environment and possible biotechnological application of enzymes for carbon dioxide capture. PMID:21673885

Binding of isolated plant lectin by rhizobia during episodes of reduced gravity obtained by parabolic flight

NASA Technical Reports Server (NTRS)

Henry, R. L.; Green, P. D.; Wong, P. P.; Guikema, J. A.; Spooner, B. S. (Principal Investigator)

1990-01-01

Development of a legume root nodule is a complex process culminating in a plant/bacterial symbiosis possessing the capacity for biological dinitrogen fixation. Formation of root nodules is initiated by the binding and stabilization of rhizobia to plant root hairs, mediated in part by a receptor/ligand recognition system composed of lectins on the plant root surface and lectin-binding sites on the rhizobial cell surface. The dinitrogen fixation activity of these root nodules may be an important feature of enclosed, space-based life support systems, and may provide an ecological method to recycle nitrogen for amino acid production. However, the effects on nodule development of varied gravitational fields, or of root nutrient delivery hardware, remain unknown. We have investigated the effects of microgravity on root nodule formation, with preliminary experiments focused upon the receptor/ligand component. Microgravity, obtained during parabolic flight aboard NASA 930, has no apparent effect on the binding of purified lectin to rhizobia, a result that will facilitate forthcoming experiments using intact root tissues.

The biological deep sea hydrothermal vent as a model to study carbon dioxide capturing enzymes.

PubMed

Minic, Zoran; Thongbam, Premila D

2011-01-01

Deep sea hydrothermal vents are located along the mid-ocean ridge system, near volcanically active areas, where tectonic plates are moving away from each other. Sea water penetrates the fissures of the volcanic bed and is heated by magma. This heated sea water rises to the surface dissolving large amounts of minerals which provide a source of energy and nutrients to chemoautotrophic organisms. Although this environment is characterized by extreme conditions (high temperature, high pressure, chemical toxicity, acidic pH and absence of photosynthesis) a diversity of microorganisms and many animal species are specially adapted to this hostile environment. These organisms have developed a very efficient metabolism for the assimilation of inorganic CO₂ from the external environment. In order to develop technology for the capture of carbon dioxide to reduce greenhouse gases in the atmosphere, enzymes involved in CO₂ fixation and assimilation might be very useful. This review describes some current research concerning CO₂ fixation and assimilation in the deep sea environment and possible biotechnological application of enzymes for carbon dioxide capture.

Seasonal patterns of periphyton nitrogen fixation in calcareous wetlands

NASA Astrophysics Data System (ADS)

Liao, X.; Inglett, P.

2011-12-01

Periphyton mats are an ecologically important component of the Everglades ecosystem and plays various vital ecological functions. However, nitrogen fixation of periphyton, has received little attention throughout much of the Everglades system. The objective of this study was to characterize the seasonal pattern of periphyton N2 fixation in the Hole-in-the-Donut (HID) of Florida Everglades, where farmed marl prairie wetlands have been restored through complete soil removal (CSR) to reduce nutrient levels. Two restored areas (i.e., cleared in 2000 and 2003) and a reference (natural and unfarmed) marl prairie wetland sites were selected in the HID. Seven times of sampling were performed across the wet and dry season during the 2010 and 2011. The annual fixed nitrogen was approximately 0.4gN m-2 yr-1 in the restored sites which was higher in the reference site (~0.2gN m-2 yr-1). All the three sites showed similar seasonal patterns of N2 fixation that is higher values were observed in the wet season; but the peak value was one month later in reference sits (i.e., September) comparing to the restored areas (i.e., July). The peak of periphyton AR rates in the 2000- and 2003-restored areas appeared in July (i.e., wet season) within the range of 20-79 nmols g-1dw h-1 and 31-53nmols g-1dw h-1, respectively. In contrast, the peak of reference site was observed in September with the range of 2-5 nmols g-1dw h-1. Stable N isotopic ratios (i.e., δ15N) also varied with time but didn't show consistent seasonal pattern as nitrogen fixation. N2 fixation positively correlated with periphyton total phosphorus (TP) and negatively correlated with total nitrogen and phosphorus molar ratios (TN:TP), indicating that N2 fixation would be a indicator of nutrient limitation. In general, δ15N was negatively correlated with nitrogenase activity but the correlation became weakened in the wet season, especially in the flooded July and September, which would be explained by other environmental factors and higher denitrification activities in that time.

Spontaneous eye movements in goldfish: oculomotor integrator performance, plasticity, and dependence on visual feedback.

PubMed

Mensh, B D; Aksay, E; Lee, D D; Seung, H S; Tank, D W

2004-03-01

To quantify performance of the goldfish oculomotor neural integrator and determine its dependence on visual feedback, we measured the relationship between eye drift-velocity and position during spontaneous gaze fixations in the light and in the dark. In the light, drift-velocities were typically less than 1 deg/s, similar to those observed in humans. During brief periods in darkness, drift-velocities were only slightly larger, but showed greater variance. One hour in darkness degraded fixation-holding performance. These findings suggest that while visual feedback is not essential for online fixation stability, it may be used to tune the mechanism of persistent neural activity in the oculomotor integrator.

Figure-ground processing during fixational saccades in V1: indication for higher-order stability.

PubMed

Gilad, Ariel; Pesoa, Yair; Ayzenshtat, Inbal; Slovin, Hamutal

2014-02-26

In a typical visual scene we continuously perceive a "figure" that is segregated from the surrounding "background" despite ongoing microsaccades and small saccades that are performed when attempting fixation (fixational saccades [FSs]). Previously reported neuronal correlates of figure-ground (FG) segregation in the primary visual cortex (V1) showed enhanced activity in the "figure" along with suppressed activity in the noisy "background." However, it is unknown how this FG modulation in V1 is affected by FSs. To investigate this question, we trained two monkeys to detect a contour embedded in a noisy background while simultaneously imaging V1 using voltage-sensitive dyes. During stimulus presentation, the monkeys typically performed 1-3 FSs, which displaced the contour over the retina. Using eye position and a 2D analytical model to map the stimulus onto V1, we were able to compute FG modulation before and after each FS. On the spatial cortical scale, we found that, after each FS, FG modulation follows the stimulus retinal displacement and "hops" within the V1 retinotopic map, suggesting visual instability. On the temporal scale, FG modulation is initiated in the new retinotopic position before it disappeared from the old retinotopic position. Moreover, the FG modulation developed faster after an FS, compared with after stimulus onset, which may contribute to visual stability of FG segregation, along the timeline of stimulus presentation. Therefore, despite spatial discontinuity of FG modulation in V1, the higher-order stability of FG modulation along time may enable our stable and continuous perception.

Screening and Selection of Maize to Enhance Associative Bacterial Nitrogen Fixation 1

PubMed Central

Ela, Stephen W.; Anderson, Mary Ann; Brill, Winston J.

1982-01-01

The ability of maize (corn, Zea mays L.) to support bacterial nitrogen fixation in or on maize roots has been increased, through screening and selection. Isotopic N fixed from 15N2 was found on the roots. The nitrogen-fixing association was found in germplasm from tropical maize, but this activity can be transferred to maize currently used in midwestern United States agriculture. PMID:16662718

Biomechanical study of different fixation techniques for the treatment of sacroiliac joint injuries using finite element analyses and biomechanical tests.

PubMed

Lee, Chian-Her; Hsu, Ching-Chi; Huang, Po-Yuang

2017-08-01

The pelvis is one of the most stressed areas of the human musculoskeletal system due to the transfer of truncal loads to the lower extremities. Sacroiliac joint injury may lead to abnormal joint mechanics and an unstable pelvis. Various fixation techniques have been evaluated and discussed. However, it may be difficult to investigate each technique due to variations in bone quality, bone anatomy, fracture pattern, and fixation location. Additionally, the finite element method is one useful technology that avoids these variations. Unfortunately, most previous studies neglected the effects of the lumbar spine and femurs when they investigated the biomechanics of pelvises. Thus, the aim of this study was to investigate the biomechanical performance of intact, injured, and treated pelvises using numerical and experimental approaches. Three-dimensional finite element models of the spine-pelvis-femur complex with and without muscles and ligaments were developed. The intact pelvis, the pelvis with sacroiliac joint injury, and three types of pelvic fixation techniques were analyzed. Concurrently, biomechanical tests were conducted to validate the numerical outcomes using artificial pelvises. Posterior iliosacral screw fixation showed relatively better fixation stability and lower risks of implant failure and pelvic breakage than sacral bar fixation and a locking compression plate fixation. The present study can help surgeons and engineers understand the biomechanics of intact, injured, and treated pelvises. Both the simulation technique and the experimental setup can be applied to investigate different pelvic injuries. Copyright © 2017 Elsevier Ltd. All rights reserved.

[Technology of cementless hip endoprosthetics].

PubMed

Ungethüm, M; Blömer, W

1987-06-01

The success achieved with non-cemented hip arthroplasty depends mainly on the stability of the fixation, the quality of the stabilizing bone being just as important as favourable biomechanical conditions. The results of the intensive research and development with respect to the particular features of a non-cemented hip endoprosthesis can be divided into the following basic categories: Biomechanical aspects with special reference to bone related to the design of the prosthesis; material characteristics, such as fatigue strength, tribology, corrosion resistance, and biocompatibility; and development of new materials and coatings to permit direct bonding of implant and bone. With regard to the stem of hip prostheses, the different design parameters of various types are examined to determine their typical design characteristics, such as bearing surface of the collar, geometry of cross section, anatomically adapted shaping, and surface of the implant forming the contact with the bone. The latter can be divided into macroprofiles and macro- and micro-porous coated surfaces. On the other hand, the methods of cementless fixation of acetabular cups can be primarily divided into conical and spherical screw fixation and pegged fixation with additional macroprofiles of porous surfaces. In a separate study of the biomechanical aspects of screwed sockets, the special importance of socket shape and thread geometry are presented with reference to primary stability and long-term fixation of prostheses.

Resorbable bone fixation alloys, forming, and post-fabrication treatments.

PubMed

Ibrahim, Hamdy; Esfahani, Sajedeh Nasr; Poorganji, Behrang; Dean, David; Elahinia, Mohammad

2017-01-01

Metallic alloys have been introduced as biodegradable metals for various biomedical applications over the last decade owing to their gradual corrosion in the body, biocompatibility and superior strength compared to biodegradable polymers. Mg alloys possess advantageous properties that make them the most extensively studied biodegradable metallic material for orthopedic applications such as their low density, modulus of elasticity, close to that of the bone, and resorbability. Early resorption (i.e., <3months) and relatively inadequate strength are the main challenges that hinder the use of Mg alloys for bone fixation applications. The development of resorbable Mg-based bone fixation hardware with superior mechanical and corrosion performance requires a thorough understanding of the physical and mechanical properties of Mg alloys. This paper discusses the characteristics of successful Mg-based skeletal fixation hardware and the possible ways to improve its properties using different methods such as mechanical and heat treatment processes. We also review the most recent work pertaining to Mg alloys and surface coatings. To this end, this paper covers (i) the properties and development of Mg alloys and coatings with an emphasis on the Mg-Zn-Ca-based alloys; (ii) Mg alloys fabrication techniques; and (iii) strategies towards achieving Mg-based, resorbable, skeletal fixation devices. Copyright © 2016 Elsevier B.V. All rights reserved.

Suture Button Fixation Versus Syndesmotic Screws in Supination-External Rotation Type 4 Injuries: A Cost-Effectiveness Analysis.

PubMed

Neary, Kaitlin C; Mormino, Matthew A; Wang, Hongmei

2017-01-01

In stress-positive, unstable supination-external rotation type 4 (SER IV) ankle fractures, implant selection for syndesmotic fixation is a debated topic. Among the available syndesmotic fixation methods, the metallic screw and the suture button have been routinely compared in the literature. In addition to strength of fixation and ability to anatomically restore the syndesmosis, costs associated with implant use have recently been called into question. This study aimed to examine the cost-effectiveness of the suture button and determine whether suture button fixation is more cost-effective than two 3.5-mm syndesmotic screws not removed on a routine postoperative basis. Economic and decision analysis; Level of evidence, 2. Studies with the highest evidence levels in the available literature were used to estimate the hardware removal and failure rates for syndesmotic screws and suture button fixation. Costs were determined by examining the average costs for patients who underwent surgery for unstable SER IV ankle fractures at a single level-1 trauma institution. A decision analysis model that allowed comparison of the 2 fixation methods was developed. Using a 20% screw hardware removal rate and a 4% suture button hardware removal rate, the total cost for 2 syndesmotic screws was US$20,836 and the total effectiveness was 5.846. This yielded a total cost of $3564 per quality-adjusted life-year (QALY) over an 8-year time period. The total cost for suture button fixation was $19,354 and the total effectiveness was 5.904, resulting in a total cost of $3294 per QALY over the same time period. A sensitivity analysis was then conducted to assess suture button fixation costs as well as screw and suture button hardware removal rates. Other possible treatment scenarios were also examined, including 1 screw and 2 suture buttons for operative fixation of the syndesmosis. To become more cost-effective, the screw hardware removal rate would have to be reduced to less than 10%. Furthermore, fixation with a single suture button continued to be the dominant treatment strategy compared with 2 suture buttons, 1 screw, and 2 screws for syndesmotic fixation. This cost-effectiveness analysis suggests that for unstable SER IV ankle fractures, suture button fixation is more cost-effective than syndesmotic screws not removed on a routine basis. Suture button fixation was a dominant treatment strategy, because patients spent on average $1482 less and had a higher quality of life by 0.058 QALYs compared with patients who received fixation with 2 syndesmotic screws. Assuming that functional outcomes and failure rates were equivalent, screw fixation only became more cost-effective when the screw hardware removal rate was reduced to less than 10% or when the suture button cost exceeded $2000. In addition, fixation with a single suture button device proved more cost-effective than fixation with either 1 or 2 syndesmotic screws.

Neural network models for spatial data mining, map production, and cortical direction selectivity

NASA Astrophysics Data System (ADS)

Parsons, Olga

A family of ARTMAP neural networks for incremental supervised learning has been developed over the last decade. The Sensor Exploitation Group of MIT Lincoln Laboratory (LL) has incorporated an early version of this network as the recognition engine of a hierarchical system for fusion and data mining of multiple registered geospatial images. The LL system has been successfully fielded, but it is limited to target vs. non-target identifications and does not produce whole maps. This dissertation expands the capabilities of the LL system so that it learns to identify arbitrarily many target classes at once and can thus produce a whole map. This new spatial data mining system is designed particularly to cope with the highly skewed class distributions of typical mapping problems. Specification of a consistent procedure and a benchmark testbed has permitted the evaluation of candidate recognition networks as well as pre- and post-processing and feature extraction options. The resulting default ARTMAP network and mapping methodology set a standard for a variety of related mapping problems and application domains. The second part of the dissertation investigates the development of cortical direction selectivity. The possible role of visual experience and oculomotor behavior in the maturation of cells in the primary visual cortex is studied. The responses of neurons in the thalamus and cortex of the cat are modeled when natural scenes are scanned by several types of eye movements. Inspired by the Hebbian-like synaptic plasticity, which is based upon correlations between cell activations, the second-order statistical structure of thalamo-cortical activity is examined. In the simulations, patterns of neural activity that lead to a correct refinement of cell responses are observed during visual fixation, when small ocular movements occur, but are not observed in the presence of large saccades. Simulations also replicate experiments in which kittens are reared under stroboscopic illumination. The abnormal fixational eye movements of these cats may account for the puzzling finding of a specific loss of cortical direction selectivity but preservation of orientation selectivity. This work indicates that the oculomotor behavior of visual fixation may play an important role in the refinement of cell response selectivity.

Distal radius fractures and the volar lunate facet fragment: Kirschner wire fixation in addition to volar-locked plating.

PubMed

Moore, Amy M; Dennison, David G

2014-06-01

The volar lunate facet fragment of a distal radius fracture may not be stabilized with volar-locked plating alone due to the small size and distal location of the fragment. Identification and stabilization of this small fragment is critical as unstable fixation may result in radiocarpal and radioulnar joint subluxation. The addition of spring wire fixation with volar plating can provide stable internal fixation of this critical fracture fragment. A retrospective review (2006-2011) identified nine patients with distal radius fractures with an associated volar lunate facet fragment that were treated with volar-locked plating and spring wire fixation of the volar lunate facet fragment. Radiographic indices, range of motion, grip strength, and postoperative Patient-related wrist evaluation (PRWE) scores were obtained to assess pain and function. All distal radius fractures healed, and the volar lunate facet fragment reduction was maintained. The mean follow-up was 54 weeks. Mean active range of motion was 46° wrist flexion, 51° wrist extension, 80° pronation, and 68° supination. The mean grip strength was 21 Kg, achieving 66 % of the uninjured limb. The average PRWE score was 17. No patient required removal of hardware or had evidence of tendon irritation. The addition of spring wire fixation to volar-locked plating provided stable fixation of the volar lunate facet fragment of distal radius fractures without complication. This technique addresses a limitation of volar-locked plating to control the small volar lunate facet fragment in distal radius fractures otherwise amenable to volar plating. A retrospective case series, Level IV.

Evaluation and comparison of clinical results of femoral fixation devices in arthroscopic anterior cruciate ligament reconstruction.

PubMed

Aydin, Deniz; Ozcan, Mert

2016-03-01

Several femoral fixation devices are available for hamstring tendon autograft in anterior cruciate ligament (ACL) reconstruction, but the best technique is debatable. We hypothesised that different suspensory femoral fixation techniques have no superiority over each other. The aim of this study was to evaluate and compare the clinical results of different suspensory femoral fixation devices in arthroscopic ACL reconstruction. This was a Level III, retrospective, comparative study. A total of 100 consecutive patients who underwent arthroscopic ACL reconstruction in a single institution with a mean follow-up time of 40 months (12-67 months) were divided into three groups according to femoral fixation devices as 'Endobutton' (n=34), 'Transfix' (n=35) and 'Aperfix' (n=31). The length of painful period after surgery, time to return to work and sporting activities, final range of motion, anterior drawer and Lachman tests, knee instability symptoms, International Knee Documentation Committee (IKDC) subjective knee evaluation score, Short Form 36 (SF-36) score, Lysholm knee score and Tegner point of the patients were evaluated and compared between groups. There were no significant differences between the groups. All techniques led to significant recovery in knee instability tests and symptoms. In this study, the clinical results of different suspensory femoral fixation techniques were found to be similar. We believe that different femoral fixation techniques have no effect on clinical results provided that the technique is correctly applied. The surgeon must choose a technique appropriate to his or her experience. Copyright © 2015 Elsevier B.V. All rights reserved.

Plate fixation versus intramedullary nailing of completely displaced midshaft fractures of the clavicle: a prospective randomised controlled trial.

PubMed

Fuglesang, H F S; Flugsrud, G B; Randsborg, P H; Oord, P; Benth, J Š; Utvåg, S E

2017-08-01

This is a prospective randomised controlled trial comparing the functional outcomes of plate fixation and elastic stable intramedullary nailing (ESIN) of completely displaced mid-shaft fractures of the clavicle in the active adult population. We prospectively recruited 123 patients and randomised them to either plate fixation or ESIN. Patients completed the Quick Disabilities of the Arm, Shoulder and Hand (DASH) score at one to six weeks post-operatively. They were followed up at six weeks, three and six months and one year with radiographs, and their clinical outcome was assessed using both the DASH and the Constant Score. Plate fixation provided a faster functional recovery during the first six months compared with ESIN, but there was no difference after one year. The duration of surgery was shorter for ESIN (mean 53.4 minutes, 22 to 120) than for plate fixation (mean 69.7 minutes, 35 to 106, p < 0.001). The recovery after ESIN was slower with increasing fracture comminution and with open reduction (p < 0.05). Both methods return the patients to their pre-injury functional levels, but plate fixation has a faster recovery period in comminuted fractures than ESIN. ESIN has a shorter operative time and lower infection and implant rates of failure when using 2.5 mm nails or wider, suggesting that this is the preferred method in mid-shaft fractures with no comminution, whereas plate fixation is the superior method in comminuted fractures. Cite this article: Bone Joint J 2017;99-B:1095-1101. ©2017 The British Editorial Society of Bone & Joint Surgery.

Ocean acidification alters the photosynthetic responses of a coccolithophorid to fluctuating ultraviolet and visible radiation.

PubMed

Jin, Peng; Gao, Kunshan; Villafañe, Virginia E; Campbell, Douglas A; Helbling, E Walter

2013-08-01

Mixing of seawater subjects phytoplankton to fluctuations in photosynthetically active radiation (400-700 nm) and ultraviolet radiation (UVR; 280-400 nm). These irradiance fluctuations are now superimposed upon ocean acidification and thinning of the upper mixing layer through stratification, which alters mixing regimes. Therefore, we examined the photosynthetic carbon fixation and photochemical performance of a coccolithophore, Gephyrocapsa oceanica, grown under high, future (1,000 μatm) and low, current (390 μatm) CO₂ levels, under regimes of fluctuating irradiances with or without UVR. Under both CO₂ levels, fluctuating irradiances, as compared with constant irradiance, led to lower nonphotochemical quenching and less UVR-induced inhibition of carbon fixation and photosystem II electron transport. The cells grown under high CO₂ showed a lower photosynthetic carbon fixation rate but lower nonphotochemical quenching and less ultraviolet B (280-315 nm)-induced inhibition. Ultraviolet A (315-400 nm) led to less enhancement of the photosynthetic carbon fixation in the high-CO₂-grown cells under fluctuating irradiance. Our data suggest that ocean acidification and fast mixing or fluctuation of solar radiation will act synergistically to lower carbon fixation by G. oceanica, although ocean acidification may decrease ultraviolet B-related photochemical inhibition.

[Biodegradable fixation systems in pediatric craniofacial surgery: 10-year experience with 324 patients].

PubMed

Yasonov, S A; Lopatin, A V; Bel'chenko, V A; Vasil'ev, I G

Over the past 15 years, resorbable materials have been successfully used for osteosynthesis, but their high cost prevents widespread application. However, the use of resorbable systems could be a method of choice, especially in treatment of children in the active growth period. Obviously, biodegradable materials not only are highly competitive with known metal constructs in terms of fixation rigidity, biocompatibility, and a low risk of infection but also have an undeniable advantage, such as gradual resorption allowing quick return of damaged bones to the physiological conditions of functioning. A special feature of bioresorbable systems is that they can be assembled using ultrasonic welding, which greatly facilitates the fixation process and also provides necessary rigidity, even in cases of joining very thin bones when reliable fixation with screws is impossible. Over the past 10 years, we have used biodegradable systems in 324 patients. In 244 of them, we used traditional (plate/screw) systems; in 80 cases, an ultrasonic welding system was chosen for osteosynthesis. In the present work, we discuss, based on clinical evidence, the advantages and disadvantages of both fixation systems for reconstructive craniofacial surgery in children.

An ethanol-based fixation method for anatomical and micro-morphological characterization of leaves of various tree species.

PubMed

Chieco, C; Rotondi, A; Morrone, L; Rapparini, F; Baraldi, R

2013-02-01

The use of formalin constitutes serious health hazards for laboratory workers. We investigated the suitability and performance of the ethanol-based fixative, FineFIX, as a substitute for formalin for anatomical and cellular structure investigations of leaves by light microscopy and for leaf surface and ultrastructural analysis by scanning electron microscopy (SEM). We compared the anatomical features of leaf materials prepared using conventional formalin fixation with the FineFIX. Leaves were collected from ornamental tree species commonly used in urban areas. FineFIX was also compared with glutaraldehyde fixation and air drying normally used for scanning electron microscopy to develop a new method for evaluating leaf morphology and microstructure in three ornamental tree species. The cytological features of the samples processed for histological analysis were well preserved by both fixatives as demonstrated by the absence of nuclear swelling or shrinkage, cell wall detachment or tissue flaking, and good presentation of cytoplasmic vacuolization. In addition, good preservation of surface details and the absence of shrinkage artefacts confirmed the efficacy of FineFIX fixation for SEM analysis. Cuticular wax was preserved only in air dried samples. Samples treated with chemical substances during the fixation and dehydration phases showed various alterations of the wax structures. In some air dried samples a loss of turgidity of the cells was observed that caused general wrinkling of the epidermal surfaces. Commercial FineFIX is an adequate substitute for formalin in histology and it can be applied successfully also for SEM investigation, while reducing the health risks of glutaraldehyde or other toxic fixatives. To investigate the potential for plants to absorb and capture particulates in air, which requires preservation of the natural morphology of trichomes and epicuticular waxes, a combination of FineFIX fixation and air drying is recommended.

Paying attention to saccadic intrusions.

PubMed

Gowen, E; Abadi, R V; Poliakoff, E

2005-12-01

Fixation to a target in primary gaze is invariably interrupted by physiological conjugate saccadic intrusions (SI). These small idiosyncratic eye movements (usually <1 degrees in amplitude) take the form of an initial horizontal fast eye movement away from the desired eye position, followed after a variable duration by a return saccade or drift. As the aetiology of SI is still unclear, it was the aim of this study to investigate whether SI are related to exogenous or endogenous attentional processes. This was achieved by varying (a) the "bottom-up" target viewing conditions (target presence, servo control of the target, target background, target size) and (b) the 'top-down' attentional state (instruction change--'look' or 'hold eyes steady' and passive fixation versus active--'respond to change' fixation) in 13 subjects (the number of participants in each task varied between 7 and 11). We also manipulated the orientation of pure exogenous attention through a cue-target task, during which subjects were required to respond to a target, preceded by a non-informative cue by either pressing a button or making a saccade towards the target. SI amplitude, duration, frequency and direction were measured. SI amplitude was found to be significantly higher when the target was absent and SI frequency significantly lower during open loop conditions. Target size and background influenced SI behaviour in an idiosyncratic manner, although there was a trend for subjects to exhibit lower SI frequencies and amplitudes when a patterned background was present and larger SI amplitudes with larger target sizes. SI frequency decreased during the "hold eyes steady" passive command as well as during active fixation but SI direction was not influenced by the exogenous cue-target task. These results suggest that SI are related to endogenous rather than exogenous attention mechanisms. Our experiments lead us to propose that SI represent shifts in endogenous attention that reflect a baseline attention state present during laboratory fixation tasks and may prove to be a useful tool to explore higher cortical control of fixation.

Efficient Nitrogen Fixation via a Redox-Flexible Single-Iron Site with Reverse-Dative Iron → Boron σ Bonding.

PubMed

Lu, Jun-Bo; Ma, Xue-Lu; Wang, Jia-Qi; Liu, Jin-Cheng; Xiao, Hai; Li, Jun

2018-05-10

Model systems of the FeMo cofactor of nitrogenase have been explored extensively in catalysis to gain insights into their ability for nitrogen fixation that is of vital importance to the human society. Here we investigate the trigonal pyramidal borane-ligand Fe complex by first-principles calculations, and find that the variation of oxidation state of Fe along the reaction path correlates with that of the reverse-dative Fe → B bonding. The redox-flexibility of the reverse-dative Fe → B bonding helps to provide an electron reservoir that buffers and stabilizes the evolution of Fe oxidation state, which is essential for forming the key intermediates of N 2 activation. Our work provides insights for understanding and optimizing homogeneous and surface single-atom catalysts with reverse-dative donating ligands for efficient dinitrogen fixation. The extension of this kind of molecular catalytic active center to heterogeneous catalysts with surface single-clusters is also discussed.

Carbohydrate Partitioning and the Capacity of Apparent Nitrogen Fixation of Soybean Plants Grown Outdoors

PubMed Central

Millhollon, Eddie P.; Williams, Larry E.

1986-01-01

Patterns of leaf carbohydrate partitioning and nodule activity in soybean plants grown under natural conditions and the irradiance level required to produce sufficient carbohydrate to obtain maximum rates of apparent N2-fixation (acetylene reduction) were measured. Soybean plants, grown outdoors, maintained constant levels of leaf soluble sugars while leaf starch pools varied diurnally. When root temperature was kept at 25°C and shoot temperature was allowed to vary with ambient temperature, the plants maintained constant rates of apparent N2-fixation and root+nodule respiration. Results from a second experiment, in which the entire plant was kept at 25°C, were similar to those of the first experiment. Shoot carbon exchange rate of plants from the second experiment was light saturated at photosynthetic photon flux densities between 400 and 600 micromoles per square meter per second. When plants were subjected to an extended 40-hour dark period to deplete carbohydrate reserves, apparent N2-fixation was unaffected during the first 10 hours of darkness, decreased rapidly between 10 and 16 hours, and plateaued at one-third the initial level thereafter. After the extended dark period, plants were exposed to photosynthetic photon flux density from 200 to 1000 micromoles per square meter per second for 10 hours. Photosynthetic photon flux densities of 200 micromoles per square meter per second and greater resulted in maximum leaf soluble sugar content and nodule activity. Leaf starch content increased with irradiance levels up to 600 micromoles per square meter per second with no further increase at higher irradiance levels. Results presented here indicate that maximum nodule activity occurs at irradiance levels that do not saturate the plant's photosynthetic apparatus. This response would allow for maximum N2-fixation to occur in a nodulated legume during periods of inclement weather. PMID:16664789

Objective visual assessment of antiangiogenic treatment for wet age-related macular degeneration.

PubMed

Baseler, Heidi A; Gouws, André; Crossland, Michael D; Leung, Carmen; Tufail, Adnan; Rubin, Gary S; Morland, Antony B

2011-10-01

To assess cortical responses in patients undergoing antiangiogenic treatment for wet age-related macular degeneration (AMD) using functional magnetic resonance imaging (fMRI) as an objective, fixation-independent measure of topographic visual function. A patient with bilateral neovascular AMD was scanned using fMRI before and at regular intervals while undergoing treatment with intravitreal antiangiogenic injections (ranibizumab). Blood oxygenation level-dependent signals were measured in the brain while the patient viewed a stimulus consisting of a full-field flickering (6 Hz) white light alternating with a uniform gray background (18 s on and 18 s off). Topographic distribution and magnitude of activation in visual cortex were compared longitudinally throughout the treatment period (<1 year) and with control patients not currently undergoing treatment. Clinical behavioral tests were also administered, including visual acuity, microperimetry, and reading skills. The area of visual cortex activated increased significantly after the first treatment to include more posterior cortex that normally receives inputs from lesioned parts of the retina. Subsequent treatments yielded no significant further increase in activation area. Behavioral measures all generally showed an improvement with treatment but did not always parallel one another. The untreated control patient showed a consistent lack of significant response in the cortex representing retinal lesions. Retinal treatments may not only improve vision but also result in a concomitant improvement in fixation stability. Current clinical behavioral measures (e.g., acuity and perimetry) are largely dependent on fixation stability and therefore cannot separate improvements of visual function from fixation improvements. fMRI, which provides an objective and sensitive measure of visual function independent of fixation, reveals a significant increase in visual cortical responses in patients with wet AMD after treatment with antiangiogenic injections. Despite recent evidence that visual cortex degenerates subsequent to retinal lesions, our results indicate that it can remain responsive as its inputs are restored.

Synthetic biology for CO2 fixation.

PubMed

Gong, Fuyu; Cai, Zhen; Li, Yin

2016-11-01

Recycling of carbon dioxide (CO 2 ) into fuels and chemicals is a potential approach to reduce CO 2 emission and fossil-fuel consumption. Autotrophic microbes can utilize energy from light, hydrogen, or sulfur to assimilate atmospheric CO 2 into organic compounds at ambient temperature and pressure. This provides a feasible way for biological production of fuels and chemicals from CO 2 under normal conditions. Recently great progress has been made in this research area, and dozens of CO 2 -derived fuels and chemicals have been reported to be synthesized by autotrophic microbes. This is accompanied by investigations into natural CO 2 -fixation pathways and the rapid development of new technologies in synthetic biology. This review first summarizes the six natural CO 2 -fixation pathways reported to date, followed by an overview of recent progress in the design and engineering of CO 2 -fixation pathways as well as energy supply patterns using the concept and tools of synthetic biology. Finally, we will discuss future prospects in biological fixation of CO 2 .

Posterior cervical fixation for fracture and degenerative disc disease.

PubMed

An, H S; Coppes, M A

1997-02-01

There are numerous newer techniques that have been developed for the internal fixation of the cervical spine in recent years. Wiring techniques are still appropriate for posterior stabilization of the cervical spine. The halo vest is still widely used for the conservative management of cervical fractures and for postoperative external immobilization. The authors stress that the surgical indications for more modern rigid implants should be adhered to strictly. These implants also should be selected by weighing their advantages versus potential risks. In the upper cervical spine, the surgeon may choose traditional wiring methods and newer C1-C2 screw fixation, occipitocervical plate fixation. For the lower cervical spine, triple wiring technique or lateral mass plating may be used. The surgeon must choose an appropriate device based on the mechanism of injury, pathoanatomy of the lesion, and familiarity with the device, keeping in mind that the goals of internal fixation are stabilization, reduction and maintenance of alignment, early rehabilitation and perhaps enhancement of fusion rates, and avoidance of use of an external halo vest.

The Redox Balance in Erythrocytes, Plasma, and Periosteum of Patients with Titanium Fixation of the Jaw

PubMed Central

Borys, Jan; Maciejczyk, Mateusz; Krȩtowski, Adam J.; Antonowicz, Bozena; Ratajczak-Wrona, Wioletta; Jabłońska, Ewa; Załęski, Piotr; Waszkiel, Danuta; Ładny, Jerzy R.; Żukowski, Piotr; Zalewska, Anna

2017-01-01

Titanium miniplates and screws are commonly used for fixation of jaw fractured or osteotomies. Despite the opinion of their biocompatibility, in clinical practice symptoms of chronic inflammation around the fixation develop in some patients, even many years after the application of miniplates and screws. The cause of these complications is still an unanswered question. Taking into account that oxidative stress is one of the toxic action of titanium, we have evaluated the antioxidant barrier as well as oxidative stress in the erythrocytes, plasma and periosteum covering the titanium fixation of the jaw. The study group was composed of 32 patients aged 20–30 with inserted miniplates and screws. The antioxidant defense: catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase-1 (SOD1), uric acid (UA), total antioxidant capacity (TAC), as well as oxidative damage products: advanced oxidation protein products (AOPP), advanced glycation end products (AGE), dityrosine, kynurenine, N-formylkynurenine, tryptophan, malondialdehyde (MDA), 4-hydroxynonenal (4-HNE), total oxidant status (TOS), and oxidative status index (OSI) were evaluated. SOD1 activity (↓37%), and tryptophan levels (↓34%) showed a significant decrease while AOPP (↑25%), TOS (↑80%) and OSI (↑101%) were significantly elevated in maxillary periosteum of patients who underwent bimaxillary osteotomies as compared to the control group. SOD-1 (↓55%), TAC (↓58.6%), AGE (↓60%) and N-formylkynurenine (↓34%) was statistically reduced while AOPP (↑38%), MDA (↑29%), 4-HNE (↑114%), TOS (↑99%), and OSI (↑381%) were significantly higher in the mandibular periosteum covering miniplates/screw compared with the control tissues. There were no correlations between antioxidants and oxidative stress markers in the periosteum of all patients and the blood. As exposure to the Ti6Al4V titanium alloy leads to disturbances of redox balance in the periosteum surrounding titanium implants of the maxilla and the mandible so antioxidant supplementation should be recommended to the patients undergoing treatment of dentofacial deformities with the use of titanium implants. The results we obtained may also indicate a need to improve the quality of titanium jaw fixations through increase of TiO2 passivation layer thickness or to develop new, the most highly biodegradable materials for their production. PMID:28638348

[Arthroscopic reconstruction of anterior cruciate ligament with press-fit technique].

PubMed

Halder, A M

2010-08-01

Problems related to the use of interference screws for fixation of bone-patellar tendon-bone grafts for anterior cruciate ligament (ACL) replacement have led to increasing interest in press-fit techniques. Most of the described techniques use press-fit fixation on either the femoral or tibial side. Therefore an arthroscopic technique was developed which achieves bone-patellar tendon-bone graft fixation by press-fit on both sides without the need for supplemental fixation material. The first consecutive 40 patients were examined clinically with a KT-1000 arthrometer and radiologically after a mean of 28.7 months (range 20-40 months) postoperatively. The mean difference in side-to-side laxity was 1.3 mm (SD 2.2 mm) and the results according to the International Knee Documentation Committee (IKDC) score were as follows: 7 A, 28 B, 5 C, 0 D. The presented press-fit technique avoids all complications related to the use of interference screws. It achieves primary stable fixation of the bone-patellar tendon-bone graft thereby allowing early functional rehabilitation. However, fixation strength depends on bone quality and the arthroscopic procedure is demanding. The results showed reliable stabilization of the operated knees.

Arthroscopic anterior cruciate ligament reconstruction using the double press- fit technique: an alternative to interference screw fixation.

PubMed

Halder, Andreas M; Ludwig, Silke; Neumann, Wolfram

2002-01-01

Patellar tendon autograft fixation in arthroscopic anterior cruciate ligament reconstruction is commonly accomplished using interference screws. However, improper insertion of the screws may reduce primary stability, injure the posterior femoral cortex, or displace hardware into the joint. Even if placed properly, metallic screws interfere with postoperative magnetic resonance imaging. In case of revision surgery, removing screws may be difficult and leaves bone defects. Retrospective study. An arthroscopic technique was developed that achieves patellar tendon autograft fixation by press-fit without any supplemental internal fixation. Forty patients were examined clinically and by KT-1000 arthrometer 28.7 months (range, 22 to 40 months) postoperatively. The mean difference in side-to-side laxity was 1.3 mm (SD 2.2) and the results according to the IKDC score were as follows: 7 A, 28 B, 5 C, and 0 D. The double press-fit technique we present avoids all complications related to the use of interference screws and creates an ideal environment for osseous integration of the bone-patellar tendon-bone autograft. Concurrently, it achieves a stable fixation of the autograft and allows early functional rehabilitation. However, fixation strength depends on bone quality and the arthroscopic procedure is demanding.

The structure and functioning of Dynastab DK - K fixator (knee joint) and its usefullness in clinical use.

PubMed

Deszczyński, J; Karpiński, J; Deszczyńska, H

1999-12-30

The autor describes following stages of research on external fixator Dynastab DK - K (knee joint) with in - built artificial joint enabling physiological range of movement of the knee and the use of the device in functional treatment of articular fractures of the knee. The final clinical prototype of the device was developed according to the results of the experiments with anatomical preparations of knee joints in which the trajectory of the physiological movement of the knee was stated. These observations were used to construct mechanical joint with the range of movement adequate to this of the healthy knee. The positive and negative aspects in DK - K fixator are also described. The fixator was appled in 6 difficult cases of articular fractures of knee with good results.

Bladder incarceration following anterior pelvic infix of a traumatic pubic symphysis diastasis treated with immediate open reduction and internal fixation.

PubMed

Jain, Mantu; Nanda, Saurav Narayan; Mohapatra, Soumya Shrikanta; Samal, Barada Prasanna

2017-08-01

Stabilization after a pelvic fracture can be accomplished using multiple techniques. The anterior external fixator has been traditionally used in variety of unstable pelvis either singly or in combination of posterior screws. These devices are cumbersome and restrict side turning and sitting particularly in obese patients. An alternative, anterior subcutaneous pelvic internal fixation technique (ASPIF) was developed which is well tolerated by patients for mobility and comfort and biomechanically more stable construct Complications of this construct included irritation of the lateral femoral cutaneous nerve, femoral nerve palsy &heterotypic ossification with reduced rates of infections and aseptic loosening as compared to external fixator. Bladder incarceration following treatment has never been reported and we encountered such a problem during management which we want to highlight.

EEG Negativity in Fixations Used for Gaze-Based Control: Toward Converting Intentions into Actions with an Eye-Brain-Computer Interface

PubMed Central

Shishkin, Sergei L.; Nuzhdin, Yuri O.; Svirin, Evgeny P.; Trofimov, Alexander G.; Fedorova, Anastasia A.; Kozyrskiy, Bogdan L.; Velichkovsky, Boris M.

2016-01-01

We usually look at an object when we are going to manipulate it. Thus, eye tracking can be used to communicate intended actions. An effective human-machine interface, however, should be able to differentiate intentional and spontaneous eye movements. We report an electroencephalogram (EEG) marker that differentiates gaze fixations used for control from spontaneous fixations involved in visual exploration. Eight healthy participants played a game with their eye movements only. Their gaze-synchronized EEG data (fixation-related potentials, FRPs) were collected during game's control-on and control-off conditions. A slow negative wave with a maximum in the parietooccipital region was present in each participant's averaged FRPs in the control-on conditions and was absent or had much lower amplitude in the control-off condition. This wave was similar but not identical to stimulus-preceding negativity, a slow negative wave that can be observed during feedback expectation. Classification of intentional vs. spontaneous fixations was based on amplitude features from 13 EEG channels using 300 ms length segments free from electrooculogram contamination (200–500 ms relative to the fixation onset). For the first fixations in the fixation triplets required to make moves in the game, classified against control-off data, a committee of greedy classifiers provided 0.90 ± 0.07 specificity and 0.38 ± 0.14 sensitivity. Similar (slightly lower) results were obtained for the shrinkage Linear Discriminate Analysis (LDA) classifier. The second and third fixations in the triplets were classified at lower rate. We expect that, with improved feature sets and classifiers, a hybrid dwell-based Eye-Brain-Computer Interface (EBCI) can be built using the FRP difference between the intended and spontaneous fixations. If this direction of BCI development will be successful, such a multimodal interface may improve the fluency of interaction and can possibly become the basis for a new input device for paralyzed and healthy users, the EBCI “Wish Mouse.” PMID:27917105

Conversion of external fixation to open reduction and internal fixation for complex distal radius fractures.

PubMed

Natoli, R M; Baer, M R; Bednar, M S

2016-05-01

Distal radius fractures are common injuries treated in a multitude of ways. One treatment paradigm not extensively studied is initial treatment by external fixation (EF) followed by conversion to open reduction internal fixation (ORIF). Such a paradigm may be beneficial in damage control situations, when there is extensive soft tissue injury, or when appropriate personnel/hospital resources are not available for immediate internal fixation. There is no increased risk of infection when converting EF to ORIF in the treatment of complex distal radius fractures when conversion occurs early or if EF pin sites are overlapped by the definitive fixation. Using an IRB approved protocol, medical records over nine years were queried to identify patients with distal radius fractures that had undergone initial EF and were later converted to ORIF. Charts were reviewed for demographic data, injury characteristics, operative details, time to conversion from EF to ORIF, assessment of whether the EF pin sites overlapped the definitive fixation, presence of infection after ORIF, complications, and occupational therapy measurements of range of motion and strength. In total, 16 patients were identified, only one of which developed an infection following conversion to ORIF. Fisher's exact testing showed that infection did not depend on open fracture, time to conversion of one week or less, presence of EF pin sites overlapping definitive fixation, fracture classification, high energy mechanism of injury, or concomitant injury to the DRUJ. Planned staged conversion from EF to ORIF for complex distal radius fractures does not appear to result in an increased rate of infection if conversion occurs early or if the EF pin sites are overlapped by definitive fixation. This treatment paradigm may be reasonable for treating complex distal radius fractures in damage control situations, when there is extensive soft tissue injury, or when appropriate personnel/hospital resources are not available for immediate internal fixation. IV, retrospective case series. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

The Cost-Effectiveness of Surgical Fixation of Distal Radial Fractures: A Computer Model-Based Evaluation of Three Operative Modalities.

PubMed

Rajan, Prashant V; Qudsi, Rameez A; Dyer, George S M; Losina, Elena

2018-02-07

There is no consensus on the optimal fixation method for patients who require a surgical procedure for distal radial fractures. We used cost-effectiveness analyses to determine which of 3 modalities offers the best value: closed reduction and percutaneous pinning, open reduction and internal fixation, or external fixation. We developed a Markov model that projected short-term and long-term health benefits and costs in patients undergoing a surgical procedure for a distal radial fracture. Simulations began at the patient age of 50 years and were run over the patient's lifetime. The analysis was conducted from health-care payer and societal perspectives. We estimated transition probabilities and quality-of-life values from the literature and determined costs from Medicare reimbursement schedules in 2016 U.S. dollars. Suboptimal postoperative outcomes were determined by rates of reduction loss (4% for closed reduction and percutaneous pinning, 1% for open reduction and internal fixation, and 11% for external fixation) and rates of orthopaedic complications. Procedural costs were $7,638 for closed reduction and percutaneous pinning, $10,170 for open reduction and internal fixation, and $9,886 for external fixation. Outputs were total costs and quality-adjusted life-years (QALYs), discounted at 3% per year. We considered willingness-to-pay thresholds of $50,000 and $100,000. We conducted deterministic and probabilistic sensitivity analyses to evaluate the impact of data uncertainty. From the health-care payer perspective, closed reduction and percutaneous pinning dominated (i.e., produced greater QALYs at lower costs than) open reduction and internal fixation and dominated external fixation. From the societal perspective, the incremental cost-effectiveness ratio for closed reduction and percutaneous pinning compared with open reduction and internal fixation was $21,058 per QALY and external fixation was dominated. In probabilistic sensitivity analysis, open reduction and internal fixation was cost-effective roughly 50% of the time compared with roughly 45% for closed reduction and percutaneous pinning. When considering data uncertainty, there is only a 5% to 10% difference in the frequency of probability combinations that find open reduction and internal fixation to be more cost-effective. The current degree of uncertainty in the data produces difficulty in distinguishing either strategy as being more cost-effective overall and thus it may be left to surgeon and patient shared decision-making. Economic Level III. See Instructions for Authors for a complete description of levels of evidence.

Perception and motor activity: reality is always virtual

NASA Astrophysics Data System (ADS)

Bridgeman, Bruce

1999-05-01

We differentiate a cognitive branch of the visual system from a sensorimotor branch with the Roelofs, effect, a perception that a target's position is biased in the direction opposite the offset of a surrounding frame. Previous research left the possibility that accurate motor responses to a perceptually mislocated target might be mediated by oculomotor fixation of the target. Subjects performed judging and jabbing tasks to probe cognitive and motor system representations respectively while engaging in a saccadic task that prevented fixation of the target. Three experiments with an oculomotor distractor task evaluated judging and jabbing responses to the target. Three experiments did not show a Roelofs effect in spite of the prevention of fixation on the target. Motor response did not show a Roelofs effect in spite of the prevention of fixation on the target. Further, a decision about which of two targets to jab does not result in cognitive-system information affect motor response. The Roelofs effect was presented, however, in judging trials that also involved the saccadic task.

Irreversibly increased nitrogen fixation in Trichodesmium experimentally adapted to elevated carbon dioxide

PubMed Central

Hutchins, David A.; Walworth, Nathan G.; Webb, Eric A.; Saito, Mak A.; Moran, Dawn; McIlvin, Matthew R.; Gale, Jasmine; Fu, Fei-Xue

2015-01-01

Nitrogen fixation rates of the globally distributed, biogeochemically important marine cyanobacterium Trichodesmium increase under high carbon dioxide (CO2) levels in short-term studies due to physiological plasticity. However, its long-term adaptive responses to ongoing anthropogenic CO2 increases are unknown. Here we show that experimental evolution under extended selection at projected future elevated CO2 levels results in irreversible, large increases in nitrogen fixation and growth rates, even after being moved back to lower present day CO2 levels for hundreds of generations. This represents an unprecedented microbial evolutionary response, as reproductive fitness increases acquired in the selection environment are maintained after returning to the ancestral environment. Constitutive rate increases are accompanied by irreversible shifts in diel nitrogen fixation patterns, and increased activity of a potentially regulatory DNA methyltransferase enzyme. High CO2-selected cell lines also exhibit increased phosphorus-limited growth rates, suggesting a potential advantage for this keystone organism in a more nutrient-limited, acidified future ocean. PMID:26327191

Irreversibly increased nitrogen fixation in Trichodesmium experimentally adapted to elevated carbon dioxide

NASA Astrophysics Data System (ADS)

Hutchins, David A.; Walworth, Nathan G.; Webb, Eric A.; Saito, Mak A.; Moran, Dawn; McIlvin, Matthew R.; Gale, Jasmine; Fu, Fei-Xue

2015-09-01

Nitrogen fixation rates of the globally distributed, biogeochemically important marine cyanobacterium Trichodesmium increase under high carbon dioxide (CO2) levels in short-term studies due to physiological plasticity. However, its long-term adaptive responses to ongoing anthropogenic CO2 increases are unknown. Here we show that experimental evolution under extended selection at projected future elevated CO2 levels results in irreversible, large increases in nitrogen fixation and growth rates, even after being moved back to lower present day CO2 levels for hundreds of generations. This represents an unprecedented microbial evolutionary response, as reproductive fitness increases acquired in the selection environment are maintained after returning to the ancestral environment. Constitutive rate increases are accompanied by irreversible shifts in diel nitrogen fixation patterns, and increased activity of a potentially regulatory DNA methyltransferase enzyme. High CO2-selected cell lines also exhibit increased phosphorus-limited growth rates, suggesting a potential advantage for this keystone organism in a more nutrient-limited, acidified future ocean.

Development of a Three-Dimensional (3D) Printed Biodegradable Cage to Convert Morselized Corticocancellous Bone Chips into a Structured Cortical Bone Graft.

PubMed

Chou, Ying-Chao; Lee, Demei; Chang, Tzu-Min; Hsu, Yung-Heng; Yu, Yi-Hsun; Liu, Shih-Jung; Ueng, Steve Wen-Neng

2016-04-20

This study aimed to develop a new biodegradable polymeric cage to convert corticocancellous bone chips into a structured strut graft for treating segmental bone defects. A total of 24 adult New Zealand white rabbits underwent a left femoral segmental bone defect creation. Twelve rabbits in group A underwent three-dimensional (3D) printed cage insertion, corticocancellous chips implantation, and Kirschner-wire (K-wire) fixation, while the other 12 rabbits in group B received bone chips implantation and K-wire fixation only. All rabbits received a one-week activity assessment and the initial image study at postoperative 1 week. The final image study was repeated at postoperative 12 or 24 weeks before the rabbit scarification procedure on schedule. After the animals were sacrificed, both femurs of all the rabbits were prepared for leg length ratios and 3-point bending tests. The rabbits in group A showed an increase of activities during the first week postoperatively and decreased anterior cortical disruptions in the postoperative image assessments. Additionally, higher leg length ratios and 3-point bending strengths demonstrated improved final bony ingrowths within the bone defects for rabbits in group A. In conclusion, through this bone graft converting technique, orthopedic surgeons can treat segmental bone defects by using bone chips but with imitate characters of structured cortical bone graft.

Development of a Three-Dimensional (3D) Printed Biodegradable Cage to Convert Morselized Corticocancellous Bone Chips into a Structured Cortical Bone Graft

PubMed Central

Chou, Ying-Chao; Lee, Demei; Chang, Tzu-Min; Hsu, Yung-Heng; Yu, Yi-Hsun; Liu, Shih-Jung; Ueng, Steve Wen-Neng

2016-01-01

This study aimed to develop a new biodegradable polymeric cage to convert corticocancellous bone chips into a structured strut graft for treating segmental bone defects. A total of 24 adult New Zealand white rabbits underwent a left femoral segmental bone defect creation. Twelve rabbits in group A underwent three-dimensional (3D) printed cage insertion, corticocancellous chips implantation, and Kirschner-wire (K-wire) fixation, while the other 12 rabbits in group B received bone chips implantation and K-wire fixation only. All rabbits received a one-week activity assessment and the initial image study at postoperative 1 week. The final image study was repeated at postoperative 12 or 24 weeks before the rabbit scarification procedure on schedule. After the animals were sacrificed, both femurs of all the rabbits were prepared for leg length ratios and 3-point bending tests. The rabbits in group A showed an increase of activities during the first week postoperatively and decreased anterior cortical disruptions in the postoperative image assessments. Additionally, higher leg length ratios and 3-point bending strengths demonstrated improved final bony ingrowths within the bone defects for rabbits in group A. In conclusion, through this bone graft converting technique, orthopedic surgeons can treat segmental bone defects by using bone chips but with imitate characters of structured cortical bone graft. PMID:27104525

Photosynthetic carbon fixation characteristics of fruiting structures of Brassica campestris L

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singal, H.R.; Sheoran, I.S.; Singh, R.

1987-04-01

Activities of key enzymes of the Calvin cycle and C/sub 4/ metabolism, rates of CO/sub 2/ fixation, and the initial products of photosynthetic /sup 14/CO/sub 2/ fixation were determined in the podwall, seed coat (fruiting structures), and the subtending leaf (leaf below a receme) of Brassica campestris L. cv Toria. Compared to activities of ribulose-1,5-bisphosphate carboxylase and other Calvin cycle enzymes, e.g. NADP-glyceraldehyde-3-phosphate-dehydrogenase and ribulose-5-phosphate kinase, the activities of phosphoenol pyruvate carboxylase and other enzymes of C/sub 4/ metabolism, viz. NADP-malate dehydrogenase, NADP-malic enzyme, glutamate pyruvate transaminase, and glutamate oxaloacetate transaminase, were generally much higher in seed than in podwallmore » and leaf. Podwall and leaf were comparable to each other. Pulse-chase experiments showed that in seed the major product of /sup 14/CO/sub 2/ assimilation was malate (in short time), whereas in podwall and leaf, the label initially appeared in 3-PGA. With time, the label moved to sucrose. In contrast to legumes, Brassica pods were able to fix net CO/sub 2/ during light. However, respiratory losses were very high during the dark period.« less

THE INTERFERENCE OF INACTIVE SERUM AND EGG-WHITE IN THE PHENOMENON OF COMPLEMENT FIXATIONS.

PubMed

Noguchi, H; Bronfenbrenner, J

1911-01-05

The fixing property of a specific precipitate and of syphilitic serum in the presence of certain antigenic lipoids, can be removed by adding certain non-complementary proteins of blood serum or hen's egg. This disappearance of the complementary activity in the syphilis reaction, as well as in the true Bordet-Gengou reaction, is a phenomenon which incidentally accompanies the fixation of certain serum constituents, some of which possess a complementary activity. The presence or absence of the complementary property in these protein components does not influence fixation. Whether the disappearance of the complementary activity during the phenomenon of so-called fixation is due to a mechanical precipitation of the molecules through absorption or whether it is due to a physico-chemical alteration of the active molecules, is unknown. It is more probable that a chemical interaction takes place in the case of the syphilis reaction. Certain sera, for example, those derived from man and goat, show a low fixability. It is interesting to note that the fixability is gradually diminished when these sera and egg-white are heated to a temperature above 56 degrees C., and totally disappears at 85 degrees C. The coagulation of proteins with absolute alcohol or by boiling, destroys their interfering property. The fact that the fixation is not selectively directed towards complement, has a very important meaning for exact serology. The one-sided accuracy as to the complementary unity is no longer sufficient for quantitative work. Both the complementary and the volumetric unity of a serum serving as the source of complement should be taken into consideration. Besides, the fixability of the sera of various species of animals must also be considered. From these facts a formula may be derived for deciding the degree of suitableness of a serum. see PDF for Equation X is the degree of suitableness; K, the species constant for the fixability; P, the complementary activity; and V, the volume of serum. It will be seen that the suitableness is proportional to the fixability constant and the complementary unity, and inversely proportional to the volume of serum employed. As to what species yields the largest value for X, we refer the reader to our studies published elsewhere.

Shorter spontaneous fixation durations in infants with later emerging autism.

PubMed

Wass, Sam V; Jones, Emily J H; Gliga, Teodora; Smith, Tim J; Charman, Tony; Johnson, Mark H

2015-02-06

Little is known about how spontaneous attentional deployment differs on a millisecond-level scale in the early development of autism spectrum disorders (ASD). We measured fine-grained eye movement patterns in 6-to 9-month-old infants at high or low familial risk (HR/LR) of ASD while they viewed static images. We observed shorter fixation durations (i.e. the time interval between saccades) in HR than LR infants. Preliminary analyses indicate that these results were replicated in a second cohort of infants. Fixation durations were shortest in those infants who went on to receive an ASD diagnosis at 36 months. While these findings demonstrate early-developing atypicality in fine-grained measures of attentional deployment early in the etiology of ASD, the specificity of these effects to ASD remains to be determined.

The Narrative Labyrinth of Violent Dying

ERIC Educational Resources Information Center

Rynearson, E. K.

2005-01-01

This essay outlines the dynamics of retelling the violent death of a loved one and the narrative "dilemma" of vulnerable family members fixated on retelling. To counter this fixation, the author presents a mythic retelling of violent death (the Myth of Theseus) as narrative basis for developing a restorative retelling. The essay begins by…

The Path of Carbon in Photosynthesis X. Carbon Dioxide Assimilation in Plants

DOE R&D Accomplishments Database

Calvin, M.; Bassham, J. A.; Benson, A. A.; Lynch, V.; Ouellet, C.; Schou, L.; Stepka, W.; Tolbert, N. E.

1950-04-01

The conclusions which have been drawn from the results of C{sup 14}O{sub 2} fixation experiments with a variety of plants are developed in this paper. The evidence for thermochemical reduction of carbon dioxide fixation intermediates is presented and the results are interpreted from such a viewpoint.

An Efficient and Reproducible Protocol for Distraction Osteogenesis in a Rat Model Leading to a Functional Regenerated Femur.

PubMed

Pithioux, Martine; Roseren, Flavy; Jalain, Christian; Launay, Franck; Charpiot, Philippe; Chabrand, Patrick; Roffino, Sandrine; Lamy, Edouard

2017-10-23

This protocol describes the use of a newly developed external fixator for distraction osteogenesis in a rat femoral model. Distraction osteogenesis (DO) is a surgical technique leading to bone regeneration after an osteotomy. The osteotomized extremities are moved away from each other by gradual distraction to reach the desired elongation. This procedure is widely used in humans for lower and upper limb lengthening, treatment after a bone nonunion, or the regeneration of a bone defect following surgery for bone tumor excision, as well as in maxillofacial reconstruction. Only a few studies clearly demonstrate the efficiency of their protocol in obtaining a functional regenerated bone, i.e., bone that will support physiological weight-bearing without fracture after removal of the external fixator. Moreover, protocols for DO vary and reproducibility is limited by lack of information, making comparison between studies difficult. The aim of this study was to develop a reproducible protocol comprising an appropriate external fixator design for rat limb lengthening, with a detailed surgical technique that permits physiological weight-bearing by the animal after removal of the external fixator.

Minimal internal fixation augmented by small wire transfixion frames for high-energy tibial plateau fractures.

PubMed

Katsenis, Dimitris; Athanasiou, Vasilis; Vasilis, Athanasiou; Megas, Panayiotis; Panayiotis, Megas; Tyllianakis, Minos; Minos, Tillianakis; Lambiris, Elias

2005-04-01

To evaluate the outcome of bicondylar tibial plateau fractures treated with minimal internal fixation augmented by small wire external fixation frames and to assess the necessity of bridging the knee joint by extending the external fixation to the distal femur. This is a retrospective study of 48 tibial plateau fractures. There were 40 (83.5%) Schatzker type VI fractures, 8 Schatzker type V fractures, and 18 (37.5%) fractures were open. A complex injury according to the Tscherne-Lobenhoffer classification was recorded in 30 (62.5%) patients. All fractures were treated with combined minimally invasive internal and external fixation. Closed reduction was achieved in 32 (66.6%) of the fractures. Extension of the external fixation to the distal femur was done in 30 (62.5%) fractures. Results were assessed according to the criteria of Honkonen-Jarvinen. Follow-up ranged from 28 to 60 months with an average of 38 months. All fractures but 1 united at an average of 13.5 weeks (range 11-18 weeks). One patient developed an infected nonunion of the diaphyseal segment of his fracture. Thirty-nine (81%) patients achieved an excellent or good radiologic result. An excellent or good final clinical result was recorded in 36 patients (76%). Bridging the knee joint did not affect significantly the result (P < 0.418). No significant correlation was found between the type of fracture and the final score (P < 0.458). Hybrid internal and external fixation combined with tibiofemoral extension of the fixation is an attractive treatment option for complex tibial plateau fractures.

Microsaccade production during saccade cancelation in a stop-signal task

PubMed Central

Godlove, David C.; Schall, Jeffrey D.

2014-01-01

We obtained behavioral data to evaluate two alternative hypotheses about the neural mechanisms of gaze control. The “fixation” hypothesis states that neurons in rostral superior colliculus (SC) enforce fixation of gaze. The “microsaccade” hypothesis states that neurons in rostral SC encode microsaccades rather than fixation per se. Previously reported neuronal activity in monkey SC during the saccade stop-signal task leads to specific, dissociable behavioral predictions of these two hypotheses. When subjects are required to cancel partially-prepared saccades, imbalanced activity spreads across rostral and caudal SC with a reliable temporal profile. The microsaccade hypothesis predicts that this imbalance will lead to elevated microsaccade production biased toward the target location, while the fixation hypothesis predicts reduced microsaccade production. We tested these predictions by analyzing the microsaccades produced by 4 monkeys while they voluntarily canceled partially prepared eye movements in response to explicit stop signals. Consistent with the fixation hypothesis and contradicting the microsaccade hypothesis, we found that each subject produced significantly fewer microsaccades when normal saccades were successfully canceled. The few microsaccades escaping this inhibition tended to be directed toward the target location. We additionally investigated interactions between initiating microsaccades and inhibiting normal saccades. Reaction times were longer when microsaccades immediately preceded target presentation. However, pre-target microsaccade production did not affect stop-signal reaction time or alter the probability of canceling saccades following stop signals. These findings demonstrate that imbalanced activity within SC does not necessarily produce microsaccades and add to evidence that saccade preparation and cancelation are separate processes. PMID:25448116

Tricalcium phosphate solubilization and nitrogen fixation by newly isolated Aneurinibacillus aneurinilyticus CKMV1 from rhizosphere of Valeriana jatamansi and its growth promotional effect.

PubMed

Chauhan, Anjali; Guleria, Shiwani; Balgir, Praveen P; Walia, Abhishek; Mahajan, Rishi; Mehta, Preeti; Shirkot, Chand Karan

Aneurinibacillus aneurinilyticus strain CKMV1 was isolated from rhizosphere of Valeriana jatamansi and possessed multiple plant growth promoting traits like production of phosphate solubilization (260mg/L), nitrogen fixation (202.91nmolethylenemL -1 h -1 ), indole-3-acetic acid (IAA) (8.1μg/mL), siderophores (61.60%), HCN (hydrogen cyanide) production and antifungal activity. We investigated the ability of isolate CKMV1 to solubilize insoluble P via mechanism of organic acid production. High-performance liquid chromatography (HPLC) study showed that isolate CKMV1 produced mainly gluconic (1.34%) and oxalic acids. However, genetic evidences for nitrogen fixation and phosphate solubilization by organic acid production have been reported first time for A. aneurinilyticus strain CKMV1. A unique combination of glucose dehydrogenase (gdh) gene and pyrroloquinoline quinone synthase (pqq) gene, a cofactor of gdh involved in phosphate solubilization has been elucidated. Nitrogenase (nif H) gene for nitrogen fixation was reported from A. aneurinilyticus. It was notable that isolate CKMV1 exhibited highest antifungal against Sclerotium rolfsii (93.58%) followed by Fusarium oxysporum (64.3%), Dematophora necatrix (52.71%), Rhizoctonia solani (91.58%), Alternaria sp. (71.08%) and Phytophthora sp. (71.37%). Remarkable increase was observed in seed germination (27.07%), shoot length (42.33%), root length (52.6%), shoot dry weight (62.01%) and root dry weight (45.7%) along with NPK (0.74, 0.36, 1.82%) content of tomato under net house condition. Isolate CKMV1 possessed traits related to plant growth promotion, therefore, could be a potential candidate for the development of biofertiliser or biocontrol agent and this is the first study to include the Aneurinibacillus as PGPR. Copyright © 2016 Sociedade Brasileira de Microbiologia. Published by Elsevier Editora Ltda. All rights reserved.

Volcano fixes nitrogen into plant-available forms

USGS Publications Warehouse

Huebert, B.; Vitousek, P.; Sutton, J.; Elias, T.; Heath, J.; Coeppicus, S.; Howell, S.; Blomquist, B.

1999-01-01

Hawaiian montane ecosystems developing on recent tephra deposits contain more fixed nitrogen than conventional sources can explain. Heath and Huebert (1999) demonstrated that cloud water interception is the mechanism by which this extra nitrogen is deposited, but could not identify its source. We show here that atmospheric dinitrogen is fixed at the surface of active lava flows, producing concentrations of NO which are higher than those found in most urban rush hour air pollution. Over a period of hours this NO is blown away from the island and oxidized to nitrate. Interruptions in the trade wind flow can return this nitrate to the island to be deposited in cloud water. Thus, fixation on active lava flows is able to provide nitrogen to developing ecosystems on flows emplaced earlier.

Chemical characterization and complement fixation of pectins from Cola cordifolia leaves.

PubMed

Austarheim, Ingvild; Christensen, Bjørn E; Aas, Hoai Thi Nguyen; Thöle, Christian; Diallo, Drissa; Paulsen, Berit S

2014-02-15

Defatted leaves from the medicinal tree Cola cordifolia were extracted with 50% EtOH, 50 °C and 100 °C water. The polysaccharide rich extracts were fractionated and the structure of the polysaccharides elucidated. Linkage analysis of the polysaccharides indicates a rhamnogalacturonan type I backbone where both Rha and parts of GalA are substituted in position 3, indicating a highly branched polymer with short side chains. The purified fractions were tested for complement fixation, macrophage stimulating activity and anti-adhesion activity towards Helicobacter pylori. Here we report on complex and polydisperse types of pectins (Mw: 3-1300 kDa) as well as the presence of low Mw (<3 kDa) acidic oligosaccharides. The fractions showed a moderate complement fixing activity and no macrophage activating effects after LPS removal. Anti-adhesion activity towards H. pylori was not found. Copyright © 2013 Elsevier Ltd. All rights reserved.

Joint Distraction Treatments of Intra-Articular Fracture-Induced Posttraumatic Osteoarthritis in a Large Animal Model

DTIC Science & Technology

2017-10-01

that was developed this Year for use in the upcoming Aim 2 studies. 15. SUBJECT TERMS External Fixator, Fracture Fixation Delay, Yucatan Minipig 16... Yucatan minipig model of PTOA after IAF that was developed during our previous work (W81XWH-10-1-0864) to investigate the use of joint distraction to...proactive treatment for PTOA. 2. KEYWORDS Post-traumatic Osteoarthritis Intra-articular Fracture Yucatan Miniature Pig Impact Ankle Cartilage

Aspects of the physiological ecology of dinitrogen fixation in terrestrial Nostoc sp

DOE Office of Scientific and Technical Information (OSTI.GOV)

DuBois, J.D.

1983-01-01

Biological dinitrogen fixation was measured in the Elizabeth's Prairie section of the Lynx Prairie Preserve, Adams County, Ohio using the acetylene-reduction technique. Cyanobacteria (principally Nostoc sp.) contributed almost all of the biologically fixed N at the site until late June, at which time heterotrophic diazotrophs became the dominant dinitrogen fixers. These changes in activity were attributable to fluctuations in Nostoc sp. colony cover, temperature, and soil water potential. Extrapolation of the data, showed Nostoc sp. and heterotrophic diazotrophs contributing 4.60 +/- 1.17 Kg N/ha/yr and 3.19 +/- 1.18 Kg N/ha/yr, respectively. The rate of total dinitrogen fixation for the site,more » 8.20 +/- 2.55 Kg N/ha/yr, is among the highest reported for temperate grassland ecosystems. Laboratory experiments were conducted to characterize 1) the in vivo freeze recovery physiology of nitrogenase activity and 2) polyphosphate bodies and acid phosphatase activity during dark (energy stress) periods. Photosynthetic conditions were necessary for maximum recovery of nitrogenase activity. Though damage may occur to nitrogenase, some of the enzyme is capable of surviving a freeze-thaw period in vivo. However, complete recovery of nitrogenase activity may entail de novo synthesis of nitrogenase. The rate of acid phosphatase activity was measured using p-nitrophenyl phosphate as an exogenous substrate. Cells incubated in the light for 72 h showed acid phosphatase activity localized around the perimeter of the polyphosphate bodies. When cells were incubated in the dark, acid phosphatase activity occurred throughout the polyphosphate body matrix.« less

Feasibility and fidelity of practising surgical fixation on a virtual ulna bone

PubMed Central

LeBlanc, Justin; Hutchison, Carol; Hu, Yaoping; Donnon, Tyrone

2013-01-01

Background Surgical simulators provide a safe environment to learn and practise psychomotor skills. A goal for these simulators is to achieve high levels of fidelity. The purpose of this study was to develop a reliable surgical simulator fidelity questionnaire and to assess whether a newly developed virtual haptic simulator for fixation of an ulna has comparable levels of fidelity as Sawbones. Methods Simulator fidelity questionnaires were developed. We performed a stratified randomized study with surgical trainees. They performed fixation of the ulna using a virtual simulator and Sawbones. They completed the fidelity questionnaires after each procedure. Results Twenty-two trainees participated in the study. The reliability of the fidelity questionnaire for each separate domain (environment, equipment, psychological) was Cronbach α greater than 0.70, except for virtual environment. The Sawbones had significantly higher levels of fidelity than the virtual simulator (p < 0.001) with a large effect size difference (Cohen d < 1.3). Conclusion The newly developed fidelity questionnaire is a reliable tool that can potentially be used to determine the fidelity of other surgical simulators. Increasing the fidelity of this virtual simulator is required before its use as a training tool for surgical fixation. The virtual simulator brings with it the added benefits of repeated, independent safe use with immediate, objective feedback and the potential to alter the complexity of the skill. PMID:23883510

Impact of sacropelvic fixation on the development of postoperative sacroiliac joint pain following multilevel stabilization for degenerative spine disease.

PubMed

Finger, T; Bayerl, S; Bertog, M; Czabanka, M; Woitzik, J; Vajkoczy, P

2016-11-01

We hypothesised, that the inclusion of the ilium for multilevel lumbosacral fusions reduces the incidence of postoperative sacroiliac joint (SIJ) pain. The primary objective of this study was to compare the frequency of postoperative SIJ pain in patients undergoing multilevel stabilization with and without sacropelvic fixation for multilevel degenerative spine disease. In addition, we aimed at identifying factors that may predict the worsening or new onset of postoperative SIJ pain. A total of 63 patients with multisegmental fusion surgery with a minimum follow up of 12 months were evaluated. 34 patients received sacral fixation (SF group) and 29 patients received an additional sacropelvic fixation device (SPF group). Primary outcome parameters were changes in SIJ pain between the groups and the influence of pelvic parameters, the patient́s age, the patient́s body mass index (BMI) and the length of the stabilization on the SIJ pain. Between the two surgical groups there were no differences concerning age (p=0.3), BMI (p=0.56), length of follow up (p=0.96), length of the construct (p=0.56). In total 31.7% of the patients had a worsening/new onset of SIJ pain after surgery. An additional fixation of the SIJ with iliac screws or iliosacral plate did not have an influence on the SIJ pain (p=0.67). Likewise, pelvic parameters were not predictive for the outcome of the SIJ pain. Only an increased preoperative BMI correlated with a higher chance of a new onset of SIJ pain (p=0.037). In our retrospective study there was no influence of a sacropelvic fixation techniques on the SIJ pain in patients with multilevel degenerative spine disease after multilevel stabilization surgeries. The patients' BMI is the only preoperative factor that correlated with a higher incidence to develop postoperative SIJ pain, independently of the implantation of a sacropelvic fixation device. Copyright © 2016 Elsevier B.V. All rights reserved.

Bryophyte-Cyanobacteria Associations during Primary Succession in Recently Deglaciated Areas of Tierra del Fuego (Chile)

PubMed Central

Arróniz-Crespo, María; Pérez-Ortega, Sergio; De los Ríos, Asunción; Green, T. G. Allan; Ochoa-Hueso, Raúl; Casermeiro, Miguel Ángel; de la Cruz, María Teresa; Pintado, Ana; Palacios, David; Rozzi, Ricardo; Tysklind, Niklas; Sancho, Leopoldo G.

2014-01-01

Bryophyte establishment represents a positive feedback process that enhances soil development in newly exposed terrain. Further, biological nitrogen (N) fixation by cyanobacteria in association with mosses can be an important supply of N to terrestrial ecosystems, however the role of these associations during post-glacial primary succession is not yet fully understood. Here, we analyzed chronosequences in front of two receding glaciers with contrasting climatic conditions (wetter vs drier) at Cordillera Darwin (Tierra del Fuego) and found that most mosses had the capacity to support an epiphytic flora of cyanobacteria and exhibited high rates of N2 fixation. Pioneer moss-cyanobacteria associations showed the highest N2 fixation rates (4.60 and 4.96 µg N g−1 bryo. d−1) very early after glacier retreat (4 and 7 years) which may help accelerate soil development under wetter conditions. In drier climate, N2 fixation on bryophyte-cyanobacteria associations was also high (0.94 and 1.42 µg N g−1 bryo. d−1) but peaked at intermediate-aged sites (26 and 66 years). N2 fixation capacity on bryophytes was primarily driven by epiphytic cyanobacteria abundance rather than community composition. Most liverworts showed low colonization and N2 fixation rates, and mosses did not exhibit consistent differences across life forms and habitat (saxicolous vs terricolous). We also found a clear relationship between cyanobacteria genera and the stages of ecological succession, but no relationship was found with host species identity. Glacier forelands in Tierra del Fuego show fast rates of soil transformation which imply large quantities of N inputs. Our results highlight the potential contribution of bryophyte-cyanobacteria associations to N accumulation during post-glacial primary succession and further describe the factors that drive N2-fixation rates in post-glacial areas with very low N deposition. PMID:24819926

Bryophyte-cyanobacteria associations during primary succession in recently Deglaciated areas of Tierra del Fuego (Chile).

PubMed

Arróniz-Crespo, María; Pérez-Ortega, Sergio; De Los Ríos, Asunción; Green, T G Allan; Ochoa-Hueso, Raúl; Casermeiro, Miguel Ángel; de la Cruz, María Teresa; Pintado, Ana; Palacios, David; Rozzi, Ricardo; Tysklind, Niklas; Sancho, Leopoldo G

2014-01-01

Bryophyte establishment represents a positive feedback process that enhances soil development in newly exposed terrain. Further, biological nitrogen (N) fixation by cyanobacteria in association with mosses can be an important supply of N to terrestrial ecosystems, however the role of these associations during post-glacial primary succession is not yet fully understood. Here, we analyzed chronosequences in front of two receding glaciers with contrasting climatic conditions (wetter vs drier) at Cordillera Darwin (Tierra del Fuego) and found that most mosses had the capacity to support an epiphytic flora of cyanobacteria and exhibited high rates of N2 fixation. Pioneer moss-cyanobacteria associations showed the highest N2 fixation rates (4.60 and 4.96 µg N g-1 bryo. d-1) very early after glacier retreat (4 and 7 years) which may help accelerate soil development under wetter conditions. In drier climate, N2 fixation on bryophyte-cyanobacteria associations was also high (0.94 and 1.42 µg N g-1 bryo. d-1) but peaked at intermediate-aged sites (26 and 66 years). N2 fixation capacity on bryophytes was primarily driven by epiphytic cyanobacteria abundance rather than community composition. Most liverworts showed low colonization and N2 fixation rates, and mosses did not exhibit consistent differences across life forms and habitat (saxicolous vs terricolous). We also found a clear relationship between cyanobacteria genera and the stages of ecological succession, but no relationship was found with host species identity. Glacier forelands in Tierra del Fuego show fast rates of soil transformation which imply large quantities of N inputs. Our results highlight the potential contribution of bryophyte-cyanobacteria associations to N accumulation during post-glacial primary succession and further describe the factors that drive N2-fixation rates in post-glacial areas with very low N deposition.

Clavicle hook plate fixation for distal-third clavicle fracture (Neer type II): comparison of clinical and radiologic outcomes between Neer types IIA and IIB.

PubMed

Lee, Wonyong; Choi, Chong-Hyuk; Choi, Yun-Rak; Lim, Kyung-Han; Chun, Yong-Min

2017-07-01

The purpose of this study was to investigate clinical and radiologic outcomes of clavicle hook plate fixation for distal-third clavicle fracture (Neer type II) and to compare the clinical and radiologic outcomes and complications between Neer type IIA and type IIB. We retrospectively reviewed 35 patients who underwent open reduction and internal fixation with AO hook locking compression plate (LCP) for distal clavicle fracture, including 13 patients with Neer type IIA and 22 patients with type IIB. Visual analog scale pain score, shoulder scores (subjective shoulder value, University of California-Los Angeles shoulder score, American Shoulder and Elbow Surgeons score), and active range of motion were evaluated to determine clinical outcome. Coracoclavicular distance was measured, and that of the injured side at last follow-up was compared with that of the uninjured side to evaluate radiologic outcomes. AO hook LCP fixation for distal-third clavicle fracture (Neer type II) produced satisfactory radiologic outcomes, including high union rates (100%) and coracoclavicular distance maintenance, as well as satisfactory clinical outcomes, including visual analog scale score for pain, shoulder scores (subjective shoulder value, University of California-Los Angeles shoulder score, American Shoulder and Elbow Surgeons score), and active range of motion. There were no significant differences between Neer type IIA and type IIB. With regard to complications, 22.9% of patients experienced shoulder stiffness and 17.1% had subacromial erosion; however, there were no significant differences between the 2 groups. The AO hook LCP is a suitable choice for Neer type IIA and type IIB distal-third clavicle fracture fixation. Copyright © 2016 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

Visually cued motor synchronization: modulation of fMRI activation patterns by baseline condition.

PubMed

Cerasa, Antonio; Hagberg, Gisela E; Bianciardi, Marta; Sabatini, Umberto

2005-01-03

A well-known issue in functional neuroimaging studies, regarding motor synchronization, is to design suitable control tasks able to discriminate between the brain structures involved in primary time-keeper functions and those related to other processes such as attentional effort. The aim of this work was to investigate how the predictability of stimulus onsets in the baseline condition modulates the activity in brain structures related to processes involved in time-keeper functions during the performance of a visually cued motor synchronization task (VM). The rational behind this choice derives from the notion that using different stimulus predictability can vary the subject's attention and the consequently neural activity. For this purpose, baseline levels of BOLD activity were obtained from 12 subjects during a conventional-baseline condition: maintained fixation of the visual rhythmic stimuli presented in the VM task, and a random-baseline condition: maintained fixation of visual stimuli occurring randomly. fMRI analysis demonstrated that while brain areas with a documented role in basic time processing are detected independent of the baseline condition (right cerebellum, bilateral putamen, left thalamus, left superior temporal gyrus, left sensorimotor cortex, left dorsal premotor cortex and supplementary motor area), the ventral premotor cortex, caudate nucleus, insula and inferior frontal gyrus exhibited a baseline-dependent activation. We conclude that maintained fixation of unpredictable visual stimuli can be employed in order to reduce or eliminate neural activity related to attentional components present in the synchronization task.

Hybrid Fixation for Ankle Fusion in Diabetic Charcot Arthropathy.

PubMed

El-Mowafi, Hani; Abulsaad, Mazen; Kandil, Yasser; El-Hawary, Ahmed; Ali, Samer

2018-01-01

Ankle fusion is difficult to achieve in the diabetic Charcot ankle Brodsky type 3a because of the poor quality of the bone and the inability to achieve a stable biomechanical construct. The aim of this study was to report the outcome of ankle fusion using a combination of an intramedullary nail and a circular external fixator in patients with diabetic Charcot arthropathy. We prospectively studied 24 patients with diabetic Charcot arthropathy of the ankle who were treated by fusion of the tibiotalar joint using a combined retrograde intramedullary nail and Ilizarov external fixator. Their mean age was 50.7 ± 6.9 (range, 43-62) years. The mean follow-up after surgery was 36.4 ± 5.8 (range, 24-98) months. Twenty-two patients (92%) achieved clinical and radiographic solid bony fusion. No patients in this series needed amputation. All the patients were pain free, and the mean American Orthopaedic Foot & Ankle Society Score (AOFAS) improved significantly from 34.6 ± 6.8 to 66.4 ± 4.5 at the last follow-up. Two patients developed an ulcer over the heel due to a prominent nail. The ulcer healed after nail removal. Eight patients developed pin tract infection. We report a successful outcomes of ankle fusions using combined intramedullary nail locked only proximally and ring external fixator (hybrid fixation) in patients with diabetic Charcot arthropathy. Level IV, case series.

Surface fixation of dried blood by glutaraldehyde and peracetic acid.

PubMed

Kampf, G; Bloss, R; Martiny, H

2004-06-01

The difficulties of successful prion inactivation by chemical agents has led to changes in recommendations regarding the reprocessing of instruments including flexible endoscopes. One of the changes is the preference for peracetic acid instead of glutaraldehyde in order to avoid fixation of organic material, but the surface fixation by various active agents has not been fully investigated. We used a standardized amount of dried blood soil on metal carriers (on average 22 mg). One part of the carriers was exposed to different disinfectants (four based on peracetic acid, three based on glutaraldehyde, two based on quaternary ammonium compounds (QAC), one based on QAC and amines, one based on phenols and one cleaning agent) and air dried. The difference compared with the non-exposed soiled carrier was taken as the measure of blood removal by exposure to the disinfectants. In addition the other part of the carriers was exposed to a cleaning agent and air dried. The cleaning agent itself was capable of removing more than 99% of the dried blood and served as a control for non-fixation. The rate of fixation of dried blood was calculated as the ratio of the weight of residual soil on 'soiled, disinfected and cleaned' carriers and on 'soiled and disinfected' carriers. All experiments were repeated eight times. Blood removal varied between 90.3% +/- 1.5% (phenol-based disinfectant) and < 10% (glutaraldehyde-based preparations). Fixation of the remainder was between 76.9 +/- 8.4% and 102.5 +/- 1.1% with glutaraldehyde and between 19.2% +/- 3.3% and 78.1% +/- 2.4% with peracetic acid. No other preparations showed a potential for blood fixation (< 1.3%). Our findings underline the potential for blood fixation, not only by glutaraldehyde, but also by peracetic acid, and support the evidence that effective cleaning should precede the chemical disinfection. Copyright 2004 The Hospital Infection Society

Comparison of inhibition of N2 fixation and ureide accumulation under water deficit in four common bean genotypes of contrasting drought tolerance

PubMed Central

Coleto, I.; Pineda, M.; Rodiño, A. P.; De Ron, A. M.; Alamillo, J. M.

2014-01-01

Background and Aims Drought is the principal constraint on world production of legume crops. There is considerable variability among genotypes in sensitivity of nitrogen fixation to drought, which has been related to accumulation of ureides in soybean. The aim of this study was to search for genotypic differences in drought sensitivity and ureide accumulation in common bean (Phaseolus vulgaris) germplasm that may be useful in the improvement of tolerance to water deficit in common bean. Methods Changes in response to water deficit of nitrogen fixation rates, ureide content and the expression and activity of key enzymes for ureide metabolism were measured in four P. vulgaris genotypes differing in drought tolerance. Key Results A variable degree of drought-induced nitrogen fixation inhibition was found among the bean genotypes. In addition to inhibition of nitrogen fixation, there was accumulation of ureides in stems and leaves of sensitive and tolerant genotypes, although this was higher in the leaves of the most sensitive ones. In contrast, there was no accumulation of ureides in the nodules or roots of stressed plants. In addition, the level of ureides in the most sensitive genotype increased after inhibition of nitrogen fixation, suggesting that ureides originate in vegetative tissues as a response to water stress, probably mediated by the induction of allantoinase. Conclusions Variability of drought-induced inhibition of nitrogen fixation among the P. vulgaris genotypes was accompanied by subsequent accumulation of ureides in stems and leaves, but not in nodules. The results indicate that shoot ureide accumulation after prolonged exposure to drought could not be the cause of inhibition of nitrogen fixation, as has been suggested in soybean. Instead, ureides seem to be produced as part of a general response to stress, and therefore higher accumulation might correspond to higher sensitivity to the stressful conditions. PMID:24638821

Comparison of inhibition of N2 fixation and ureide accumulation under water deficit in four common bean genotypes of contrasting drought tolerance.

PubMed

Coleto, I; Pineda, M; Rodiño, A P; De Ron, A M; Alamillo, J M

2014-05-01

Drought is the principal constraint on world production of legume crops. There is considerable variability among genotypes in sensitivity of nitrogen fixation to drought, which has been related to accumulation of ureides in soybean. The aim of this study was to search for genotypic differences in drought sensitivity and ureide accumulation in common bean (Phaseolus vulgaris) germplasm that may be useful in the improvement of tolerance to water deficit in common bean. Changes in response to water deficit of nitrogen fixation rates, ureide content and the expression and activity of key enzymes for ureide metabolism were measured in four P. vulgaris genotypes differing in drought tolerance. A variable degree of drought-induced nitrogen fixation inhibition was found among the bean genotypes. In addition to inhibition of nitrogen fixation, there was accumulation of ureides in stems and leaves of sensitive and tolerant genotypes, although this was higher in the leaves of the most sensitive ones. In contrast, there was no accumulation of ureides in the nodules or roots of stressed plants. In addition, the level of ureides in the most sensitive genotype increased after inhibition of nitrogen fixation, suggesting that ureides originate in vegetative tissues as a response to water stress, probably mediated by the induction of allantoinase. Variability of drought-induced inhibition of nitrogen fixation among the P. vulgaris genotypes was accompanied by subsequent accumulation of ureides in stems and leaves, but not in nodules. The results indicate that shoot ureide accumulation after prolonged exposure to drought could not be the cause of inhibition of nitrogen fixation, as has been suggested in soybean. Instead, ureides seem to be produced as part of a general response to stress, and therefore higher accumulation might correspond to higher sensitivity to the stressful conditions.

Can we improve fixation and outcomes? Use of bone substitutes.

PubMed

Moroni, Antonio; Larsson, Sune; Hoang Kim, Amy; Gelsomini, Letizia; Giannoudis, Peter V

2009-07-01

Hip fractures secondary to osteoporosis are common in the elderly. Stabilizing these fractures until union is achieved is a challenge due to poor bone stock and insufficient purchase of the implant to the bone. The reported high rate of complications has prompted extensive research in the development of fixation techniques. Furthermore, manipulation of both the local fracture environment in terms of application of growth factors, scaffolds, and mesenchymal cells and the systemic administration of agents promoting bone formation and bone strength has been considered as a treatment option with promising results. There are only a few evidence-based studies reporting on fixation augmentation techniques. This article reports on the efficacy of bone graft substitutes for the fixation of hip fractures, in particular calcium phosphates, which have been used as granules, cements, and implant coatings.

The eye-tracking of social stimuli in patients with Rett syndrome and autism spectrum disorders: a pilot study.

PubMed

Schwartzman, José Salomão; Velloso, Renata de Lima; D'Antino, Maria Eloísa Famá; Santos, Silvana

2015-05-01

To compare visual fixation at social stimuli in Rett syndrome (RT) and autism spectrum disorders (ASD) patients. Visual fixation at social stimuli was analyzed in 14 RS female patients (age range 4-30 years), 11 ASD male patients (age range 4-20 years), and 17 children with typical development (TD). Patients were exposed to three different pictures (two of human faces and one with social and non-social stimuli) presented for 8 seconds each on the screen of a computer attached to an eye-tracker equipment. Percentage of visual fixation at social stimuli was significantly higher in the RS group compared to ASD and even to TD groups. Visual fixation at social stimuli seems to be one more endophenotype making RS to be very different from ASD.

Isotopic Biomarkers of Nitrogenase Metalloenzymes: Forging Links Between the Cycles of Nitrogen and Trace Metals

NASA Astrophysics Data System (ADS)

Zhang, X.; McRose, D. L.; Darnajoux, R.; Bellenger, J. P.; Kraepiel, A. M. L.

2015-12-01

Biological N2 fixation, catalyzed by the metalloenzyme nitrogenase, is a critical process that makes life possible on Earth. Environmental N2 fixation has been automatically attributed to canonical Mo-based nitrogenases despite over two decades of knowledge that two other metalloenzyme forms of nitrogenase exist: those containing catalytic V or Fe-only. A key area of missing information is the contribution of the "alternative" V and Fe-only nitrogenases, as the interpretation of field data to construct budgets and assess N availability depends on the type of nitrogenase metalloenzyme used to fix N2. Additionally, substantial changes in metal speciation over geological time may have favored the use of different metalloenzymes, with implications for evolution of the biosphere. Despite the potential importance of alternative nitrogenases in modern and ancient N cycling, few methods can determine their contributions to environmental N2 fixation. Here, we present new isotopic methods to distinguish between the activities of Mo, V, and Fe-only nitrogenases. We show evidence for alternative N2 fixation in diverse environments (cyanolichens, microbial mats, sediments, leaf litter), thereby linking a key process in the nitrogen cycle to specific metalloenzyme forms of nitrogenase. The results invite a reexamination of the conditions under which the different nitrogenase metalloenzymes are active and may lead to new insights into the coupling of the cycles of nitrogen and trace metals.

Effect of chronic oil pollution on salt-marsh nitrogen fixation (acetylene redution). [Spartina alterniflora

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomson, A.D.; Webb, K.L.

1984-03-01

Annual acetylene reduction rates associated with intertidal communities in a chronically oil polluted Virgina salt marsh were compared to rates measured in an undisturbed marsh. Chronic oil treatment resulted in visible damage to the higher plants of the Spartina alterniflora zones; however, vegetation-associated acetylene reduction was not different from the untreated control. Sediment rates generally were affected little by oil application, except during the summer when rates in the median tidal elevation zones were considerably higher than those of the control. Acetylene reduction occurred in all transects, each of which extended from upper mudflat to the Spartina patens zone. Intertidalmore » sediment acetylene reduction was patchy, both spatially and seasonally. Estimated rates were greatest near the surface; free-living bacterial N/sub 2/ fixation activity averaged 2.23 mg N per m/sup 2/ per d (range = undetectable to 365 mg N per m/sup 2/ per d) in the untreated and 3.17 mg N per m/sup 2/ per d (range = undetectable to 564 mg N per m/sup 2/ per d) in the oil-treated marsh during the year. Vegetation-associated N/sub 2/ fixation activity yielded highest overall mean rates (156 mg N per M/sub 2/ per d). The seasonal pattern of sediment and vegetation-associated fixation may be controlled by temperature and availability of oxidizable substrates. 39 references, 2 figures, 5 tables.« less

Identification of an algal carbon fixation-enhancing factor extracted from Paramecium bursaria.

PubMed

Kato, Yutaka; Imamura, Nobutaka

2011-01-01

The green ciliate Paramecium bursaria contains several hundred symbiotic Chlorella species. We previously reported that symbiotic algal carbon fixation is enhanced by P. bursaria extracts and that the enhancing factor is a heat-stable, low-molecular-weight, water-soluble compound. To identify the factor, further experiments were carried out. The enhancing activity remained even when organic compounds in the extract were completely combusted at 700 degrees C, suggesting that the factor is an inorganic substance. Measurement of the major cations, K+, Ca2+, and Mg2+, by an electrode and titration of the extract resulted in concentrations of 0.90 mM, 0.55 mM, and 0.21 mM, respectively. To evaluate the effect of these cations, a mixture of the cations at the measured concentrations was prepared, and symbiotic algal carbon fixation was measured in the solution. The results demonstrated that the fixation was enhanced to the same extent as with the P. bursaria extract, and thus this mixture of K+, Ca2+, and Mg2+ was concluded to be the carbon fixation-enhancing factor. There was no effect of the cation mixture on free-living C. vulgaris. Comparison of the cation concentrations of nonsymbiotic and symbiotic Paramecium extracts revealed that the concentrations of K+ and Mg2+ in nonsymbiotic Paramecium extracts were too low to enhance symbiotic algal carbon fixation, suggesting that symbiotic P. bursaria provide suitable cation conditions for photosynthesis to its symbiotic Chlorella.

Lateralization of posterior alpha EEG reflects the distribution of spatial attention during saccadic reading.

PubMed

Kornrumpf, Benthe; Dimigen, Olaf; Sommer, Werner

2017-06-01

Visuospatial attention is an important mechanism in reading that governs the uptake of information from foveal and parafoveal regions of the visual field. However, the spatiotemporal dynamics of how attention is allocated during eye fixations are not completely understood. The current study explored the use of EEG alpha-band oscillations to investigate the spatial distribution of attention during reading. We reanalyzed two data sets, focusing on the lateralization of alpha activity at posterior scalp sites. In each experiment, participants read short lists of German nouns in two paradigms: either by freely moving their eyes (saccadic reading) or by fixating the screen center while the text moved passively from right to left at the same average speed (RSVP paradigm). In both paradigms, upcoming words were either visible or masked, and foveal processing load was manipulated by varying the words' lexical frequencies. Posterior alpha lateralization revealed a sustained rightward bias of attention during saccadic reading, but not in the RSVP paradigm. Interestingly, alpha lateralization was not influenced by word frequency (foveal load) or preview during the preceding fixation. Hence, alpha did not reflect transient attention shifts within a given fixation. However, in both experiments, we found that in the saccadic reading condition a stronger alpha lateralization shortly before a saccade predicted shorter fixations on the subsequently fixated word. These results indicate that alpha lateralization can serve as a measure of attention deployment and its link to oculomotor behavior in reading. © 2017 Society for Psychophysiological Research.

Finite element analysis of locking plate and two types of intramedullary nails for treating mid-shaft clavicle fractures.

PubMed

Ni, Ming; Niu, Wenxin; Wong, Duo Wai-Chi; Zeng, Wei; Mei, Jiong; Zhang, Ming

2016-08-01

Both plate and intramedullary nail fixations, including straight and anatomic nails, have been clinically adopted for the treatment of displaced mid-shaft clavicle fractures. However, the biomechanical performances of these fixations and implants have not been well evaluated. This study aims to compare the construct stability, stress distribution and fracture micro-motion of three fixations based on finite element (FE) method. The FE model of clavicle was reconstructed from CT images of a male volunteer. A mid-shaft fracture gap was created in the intact clavicle. Three fixation styles were simulated including locking plate (LP), anatomic intramedullary nail (CRx), and straight intramedullary nail (RCP). Two loading scenarios (axial compression and inferior bending) were applied at the distal end of the clavicle to simulate arm abduction, while the sternal end was fixed. Under both conditions, the LP was the stiffest, followed by the CRx, and the RCP was the weakest. LP also displayed a more evenly stress distribution for both implant and bone. RCP had a higher stress compared with CRx in both conditions. Moreover, all implants sustained higher stress level under the loading condition of bending than compression. The plate fixation significantly stabilizes the fracture gap, reduces the implant stress, and serves as the recommended fixation for the mid-shaft clavicle fracture. The CRx is an alternative device to treat clavicle shaft fracture, but the shoulder excessive activities should be avoided after operation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Influence of fixation point of latissimus dorsi tendon transfer for irreparable rotator cuff tear on glenohumeral external rotation: A cadaver study.

PubMed

Bargoin, K; Boissard, M; Kany, J; Grimberg, J

2016-12-01

Latissimus dorsi tendon transfer is a surgical option for treating irreparable posterosuperior rotator cuff tears, notably when attempting to reconstruct active external rotation. We hypothesized that the positioning of the transfer's point of fixation would differ depending on the desired elbow-to-body external rotation or external rotation with the elbow abducted. Seven shoulders from four whole frozen cadavers were used. We created two systems to install the subject in a semi-seated position to allow external rotation elbow to body and the arm abducted 90°. Traction sutures were positioned on the latissimus dorsi muscle and a massive tear of the rotator cuff was created. We tested six different transfer positions. Muscle contraction of the latissimus dorsi was stimulated using 10-N and 20-N suspended weights. The point of fixation of the latissimus dorsi on the humeral head had an influence on the elbow-to-body external rotation and with 90° abduction (P<0.001). The fixation point for a maximum external rotation with the elbow to the body was the anterolateral position (P<0.016). The fixation point for a maximum external rotation at 90° abduction was the position centered on the infraspinatus footprint (P<0.078). The optimal point of fixation differs depending on whether external rotation is restored at 0° or 90° abduction. Fundamental study, anatomic study. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Distribution and Magnitude of Dinitrogen Fixation in the Eastern Tropical North Pacific Oxygen Deficient Zone.

NASA Astrophysics Data System (ADS)

Selden, C.; Mulholland, M. R.; Widner, B.; Bernhardt, P. W.; Macías Tapia, A.; Jayakumar, A.

2016-12-01

The Eastern Tropical North Pacific Ocean (ETNP) hosts one of the world's three major open ocean oxygen deficient zones (ODZs). Hotspots for fixed nitrogen (N) loss processes, ODZs have classically been discounted as areas of significant dinitrogen (N2) fixation, the microbe-mediated reduction of N2 to ammonium (NH4+), which has historically been ascribed primarily to euphotic, nutrient-deplete tropical waters. Challenging this paradigm, active expression of nifH (the dinitrogen reductase structural gene) has recently been documented in the ETNP, Eastern Tropical South Pacific, and Arabian Sea ODZs, implying a closer coupling of fixed nitrogen input and loss processes than previously thought. Here, we report rates of N­2 fixation measured in the ETNP ODZ along vertical gradients of oxygen, light, and dissolved N concentrations. Detailed vertical profiles of N2 fixation rates and dissolved N concentrations made within the ODZ were compared with similar profiles from oxic waters outside the ODZ. In addition, different organic carbon sources were investigated as potential rate-limiting factors for N2 fixation in sub-euphotic waters. By establishing the magnitude and distribution of N­2 fixation in the ETNP ODZ, this study contributes to current understanding of N cycling in anoxic and aphotic waters, and serves to elucidate nuances in the global N budget, enabling more accurate biogeochemical modeling. Understanding these processes in present day ODZs is crucial for predicting how ongoing anthropogenic intensification of coastal ODZs will alter biogeochemical cycles in the future.

Acid-resistant calcium silicate-based composite implants with high-strength as load-bearing bone graft substitutes and fracture fixation devices.

PubMed

Wei, Chung-Kai; Ding, Shinn-Jyh

2016-09-01

To achieve the excellent mechanical properties of biodegradable materials used for cortical bone graft substitutes and fracture fixation devices remains a challenge. To this end, the biomimetic calcium silicate/gelatin/chitosan oligosaccharide composite implants were developed, with an aim of achieving high strength, controlled degradation, and superior osteogenic activity. The work focused on the effect of gelatin on mechanical properties of the composites under four different kinds of mechanical stresses including compression, tensile, bending, and impact. The evaluation of in vitro degradability and fatigue at two simulated body fluid (SBF) of pH 7.4 and 5.0 was also performed, in which the pH 5.0 condition simulated clinical conditions caused by bacterial induced local metabolic acidosis or tissue inflammation. In addition, human mesenchymal stem cells (hMSCs) were sued to examine osteogenic activity. Experimental results showed that the appropriate amount of gelatin positively contributed to failure enhancement in compressive and impact modes. The 10wt% gelatin-containing composite exhibits the maximum value of the compressive strength (166.1MPa), which is within the reported compressive strength for cortical bone. The stability of the bone implants was apparently affected by the in vitro fatigue, but not by the initial pH environments (7.4 or 5.0). The gelatin not only greatly enhanced the degradation of the composite when soaked in the dynamic SBF solution, but effectively promoted attachment, proliferation, differentiation, and formation of mineralization of hMSCs. The 10wt%-gelatin composite with high initial strength may be a potential implant candidate for cortical bone repair and fracture fixation applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

Complex proximal humeral fractures: a prospective study of 22 cases treated using the "Bilboquet" device.

PubMed

Doursounian, L; Kilinc, A; Cherrier, B; Nourissat, G

2011-02-01

Despite recent improvements in surgical devices, complex proximal humerus fractures internal fixation still encounters frequent mechanical failures. The aim of this study was to confirm that the Bilboquet device (a design mimicking the cup-and-ball game) helps solving mechanical difficulties associated with these fractures internal fixation and to present a simplified version of the original surgical procedure. This non-randomised prospective study included 22 fractures in 22 patients, mean age: 70 years. According to the Neer classification there were three-part fractures in seven cases and four-part fractures in 15 cases. Fractures were all reduced and treated by internal fixation in a simplified surgical procedure using the Bilboquet device. Mean postoperative follow-up was 34 months. The mean Constant score was 66 and the weighted Constant score was 86. Mean active forward elevation was 108° and mean active external rotation was 28°. No per- or postoperative complications occurred. Initial reduction of the tuberosity was incomplete in four cases. Union was obtained in all fractures. There was no secondary tilting of the head, and no migration or pseudarthrosis of the tuberosities. Five patients developed postoperative avascular necrosis of the humeral head. The Bilboquet staple component provides a supporting platform for the entire humeral head area. This peripheral stabilization associated with tension band wiring explains the lack of secondary displacement in these cases. Although the Bilboquet device provides a solution to the mechanical problems of complex fractures of the proximal humerus, it does not solve the problem of secondary avascular necrosis of the humeral head, which occurred in 23% of the patients in this series and in 33% of patients in the four-part fractures subgroup. IV (non-randomised prospective study). Copyright © 2010 Elsevier Masson SAS. All rights reserved.

Factors affecting the use of increment cores to assess fixation

Treesearch

Stan T. Lebow

2001-01-01

As part of an effort to ensure that treated wood products have minimal environmental and handling concerns, an American Wood Preservers Association task force is considering the development of a test to assess the degree of fixation of Waterborne wood preservatives. The proposed test involves removal and leaching of increment cores. This paper describes a laboratory...

Cervical osteotomy in ankylosing spondylitis: evaluation of new developments.

PubMed

Langeloo, Danielle D; Journee, Henricus L; Pavlov, Paul W; de Kleuver, Marinus

2006-04-01

Cervical osteotomy can be performed on patients with cervical kyphosis due to ankylosing spondylitis. This study reviews the role of two new developments in cervical osteotomy surgery: internal fixation and transcranial electrical stimulated motor evoked potential monitoring (TES-MEP). From 1999 to 2004, 16 patients underwent a C7-osteotomy with internal fixation. In 11 patients, cervical osteotomy was performed in a sitting position with halo-cast immobilization (group S), five patients underwent surgery in prone position with Mayfield clamp fixation (group P). In group P, longer fusion towards T4-T6 could be obtained that created a more stable fixation. Therefore, post-operative immobilization protocol of group P was simplified from halo-cast to cervical orthosis. Consolidation was obtained in all patients without loss of correction. Post-operative chin-brow to vertical angle measured 5 degrees (range 0-15). TES-MEP was successfully performed during all surgical procedures. In total, nine neurological events were registered. Additional surgical intervention resulted in recovery of amplitudes in six of nine events. In two patients spontaneous recovery took place. One patient showed no recovery of amplitudes despite surgical intervention and a partial C6 spinal cord lesion occurred. We conclude that C7 osteotomy with internal fixation has been shown to be a reliable and stable technique. When surgery is performed the in prone position, distal fixation can be optimally obtained allowing post-operative treatment by cervical orthosis instead of a halo-cast. TES-MEP monitoring has been shown to be a reliable neuromonitoring technique with high clinical relevancy during cervical osteotomy because it allows timely intervention before occurrence of permanent cord damage in a large proportion of the patients.

A Medicago truncatula Tobacco Retrotransposon Insertion Mutant Collection with Defects in Nodule Development and Symbiotic Nitrogen Fixation1[W][OA

PubMed Central

Pislariu, Catalina I.; D. Murray, Jeremy; Wen, JiangQi; Cosson, Viviane; Muni, RajaSekhara Reddy Duvvuru; Wang, Mingyi; A. Benedito, Vagner; Andriankaja, Andry; Cheng, Xiaofei; Jerez, Ivone Torres; Mondy, Samuel; Zhang, Shulan; Taylor, Mark E.; Tadege, Million; Ratet, Pascal; Mysore, Kirankumar S.; Chen, Rujin; Udvardi, Michael K.

2012-01-01

A Tnt1-insertion mutant population of Medicago truncatula ecotype R108 was screened for defects in nodulation and symbiotic nitrogen fixation. Primary screening of 9,300 mutant lines yielded 317 lines with putative defects in nodule development and/or nitrogen fixation. Of these, 230 lines were rescreened, and 156 lines were confirmed with defective symbiotic nitrogen fixation. Mutants were sorted into six distinct phenotypic categories: 72 nonnodulating mutants (Nod−), 51 mutants with totally ineffective nodules (Nod+ Fix−), 17 mutants with partially ineffective nodules (Nod+ Fix+/−), 27 mutants defective in nodule emergence, elongation, and nitrogen fixation (Nod+/− Fix−), one mutant with delayed and reduced nodulation but effective in nitrogen fixation (dNod+/− Fix+), and 11 supernodulating mutants (Nod++Fix+/−). A total of 2,801 flanking sequence tags were generated from the 156 symbiotic mutant lines. Analysis of flanking sequence tags revealed 14 insertion alleles of the following known symbiotic genes: NODULE INCEPTION (NIN), DOESN’T MAKE INFECTIONS3 (DMI3/CCaMK), ERF REQUIRED FOR NODULATION, and SUPERNUMERARY NODULES (SUNN). In parallel, a polymerase chain reaction-based strategy was used to identify Tnt1 insertions in known symbiotic genes, which revealed 25 additional insertion alleles in the following genes: DMI1, DMI2, DMI3, NIN, NODULATION SIGNALING PATHWAY1 (NSP1), NSP2, SUNN, and SICKLE. Thirty-nine Nod− lines were also screened for arbuscular mycorrhizal symbiosis phenotypes, and 30 mutants exhibited defects in arbuscular mycorrhizal symbiosis. Morphological and developmental features of several new symbiotic mutants are reported. The collection of mutants described here is a source of novel alleles of known symbiotic genes and a resource for cloning novel symbiotic genes via Tnt1 tagging. PMID:22679222

A Medicago truncatula tobacco retrotransposon insertion mutant collection with defects in nodule development and symbiotic nitrogen fixation.

PubMed

Pislariu, Catalina I; Murray, Jeremy D; Wen, JiangQi; Cosson, Viviane; Muni, RajaSekhara Reddy Duvvuru; Wang, Mingyi; Benedito, Vagner A; Andriankaja, Andry; Cheng, Xiaofei; Jerez, Ivone Torres; Mondy, Samuel; Zhang, Shulan; Taylor, Mark E; Tadege, Million; Ratet, Pascal; Mysore, Kirankumar S; Chen, Rujin; Udvardi, Michael K

2012-08-01

A Tnt1-insertion mutant population of Medicago truncatula ecotype R108 was screened for defects in nodulation and symbiotic nitrogen fixation. Primary screening of 9,300 mutant lines yielded 317 lines with putative defects in nodule development and/or nitrogen fixation. Of these, 230 lines were rescreened, and 156 lines were confirmed with defective symbiotic nitrogen fixation. Mutants were sorted into six distinct phenotypic categories: 72 nonnodulating mutants (Nod-), 51 mutants with totally ineffective nodules (Nod+ Fix-), 17 mutants with partially ineffective nodules (Nod+ Fix+/-), 27 mutants defective in nodule emergence, elongation, and nitrogen fixation (Nod+/- Fix-), one mutant with delayed and reduced nodulation but effective in nitrogen fixation (dNod+/- Fix+), and 11 supernodulating mutants (Nod++Fix+/-). A total of 2,801 flanking sequence tags were generated from the 156 symbiotic mutant lines. Analysis of flanking sequence tags revealed 14 insertion alleles of the following known symbiotic genes: NODULE INCEPTION (NIN), DOESN'T MAKE INFECTIONS3 (DMI3/CCaMK), ERF REQUIRED FOR NODULATION, and SUPERNUMERARY NODULES (SUNN). In parallel, a polymerase chain reaction-based strategy was used to identify Tnt1 insertions in known symbiotic genes, which revealed 25 additional insertion alleles in the following genes: DMI1, DMI2, DMI3, NIN, NODULATION SIGNALING PATHWAY1 (NSP1), NSP2, SUNN, and SICKLE. Thirty-nine Nod- lines were also screened for arbuscular mycorrhizal symbiosis phenotypes, and 30 mutants exhibited defects in arbuscular mycorrhizal symbiosis. Morphological and developmental features of several new symbiotic mutants are reported. The collection of mutants described here is a source of novel alleles of known symbiotic genes and a resource for cloning novel symbiotic genes via Tnt1 tagging.

The impact of simulated chronic nitrogen deposition on the biomass and N₂-fixation activity of two boreal feather moss-cyanobacteria associations.

PubMed

Gundale, Michael J; Bach, Lisbet H; Nordin, Annika

2013-01-01

Bryophytes achieve substantial biomass and play several key functional roles in boreal forests that can influence how carbon (C) and nitrogen (N) cycling respond to atmospheric deposition of reactive nitrogen (Nr). They associate with cyanobacteria that fix atmospheric N₂, and downregulation of this process may offset anthropogenic Nr inputs to boreal systems. Bryophytes also promote soil C accumulation by thermally insulating soils, and changes in their biomass influence soil C dynamics. Using a unique large-scale (0.1 ha forested plots), long-term experiment (16 years) in northern Sweden where we simulated anthropogenic Nr deposition, we measured the biomass and N₂-fixation response of two bryophyte species, the feather mosses Hylocomium splendens and Pleurozium schreberi. Our data show that the biomass declined for both species; however, N₂-fixation rates per unit mass and per unit area declined only for H. splendens. The low and high treatments resulted in a 29% and 54% reduction in total feather moss biomass, and a 58% and 97% reduction in total N₂-fixation rate per unit area, respectively. These results help to quantify the sensitivity of feather moss biomass and N₂ fixation to chronic Nr deposition, which is relevant for modelling ecosystem C and N balances in boreal ecosystems.

Kirschner-wire fixation for postburn flexion contracture deformity and consequences on articular surface.

PubMed

Sungur, Nezih; Ulusoy, Mustafa Gürhan; Boyacgil, Süreyya; Ortaparmak, Hülya; Akyüz, Mihriban; Ortak, Turgut; Koçer, Uğur; Sensöz, Omer

2006-02-01

Kirschner-wire (K-wire) fixation for 3-6 weeks is an approved method for stabilization of the fingers after the release of flexion contracture deformity. On the other hand, articular surface damage in small joints due to pin fixation is still a topic of debate. Reports claiming permanent joint destruction due to this procedure exist in the literature. To clarify this doubt, a prospective study was carried out in 72 patients with flexion contracture of the hand fingers. After the surgical release of the deformity, immobilization of the interphalangeal (IP) and metacarpophalangeal (MCP) joints was carried out with K-wire fixation for 3 weeks. Clinical evaluation of the patients was accomplished with total active motion (TAM), grip, and pinch force measurements, whereas magnetic resonance (MR) and radionuclide imaging were used as radiodiagnostic tools. Mean follow-up period of the patients was 32 months. Satisfactory results were obtained in terms of functional and esthetic aspects. Evaluation of the data derived from the clinical and radiologic measurements revealed no permanent articular surface damage. K-wire fixation was documented to be an invaluable therapeutic approach not only to prevent recurrence of the contracture deformity but also to stabilize the skin graft effectively. This technique was concluded to provide effective immobilization without permanent articular damage.

Ocean Acidification Alters the Photosynthetic Responses of a Coccolithophorid to Fluctuating Ultraviolet and Visible Radiation1[OPEN

PubMed Central

Jin, Peng; Gao, Kunshan; Villafañe, Virginia E.; Campbell, Douglas A.; Helbling, E. Walter

2013-01-01

Mixing of seawater subjects phytoplankton to fluctuations in photosynthetically active radiation (400–700 nm) and ultraviolet radiation (UVR; 280–400 nm). These irradiance fluctuations are now superimposed upon ocean acidification and thinning of the upper mixing layer through stratification, which alters mixing regimes. Therefore, we examined the photosynthetic carbon fixation and photochemical performance of a coccolithophore, Gephyrocapsa oceanica, grown under high, future (1,000 μatm) and low, current (390 μatm) CO2 levels, under regimes of fluctuating irradiances with or without UVR. Under both CO2 levels, fluctuating irradiances, as compared with constant irradiance, led to lower nonphotochemical quenching and less UVR-induced inhibition of carbon fixation and photosystem II electron transport. The cells grown under high CO2 showed a lower photosynthetic carbon fixation rate but lower nonphotochemical quenching and less ultraviolet B (280–315 nm)-induced inhibition. Ultraviolet A (315–400 nm) led to less enhancement of the photosynthetic carbon fixation in the high-CO2-grown cells under fluctuating irradiance. Our data suggest that ocean acidification and fast mixing or fluctuation of solar radiation will act synergistically to lower carbon fixation by G. oceanica, although ocean acidification may decrease ultraviolet B-related photochemical inhibition. PMID:23749851

Interaction of root nodule size and oxygen pressure on the rate of nitrogen fixation by cowpea and peanut

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sen, D.; Weaver, R.W.

1987-04-01

Size and anatomical features of nodules influence the rate of O/sub 2/ diffusion into nodules. Availability of oxygen can be a limiting factor in nitrogen fixation. Larger nodules have thicker cortices and low surface to volume ratio leading to lower rates of gaseous diffusion. Increased oxygen pressure in the environment alters the rate of nitrogen fixation but the rate of change may depend on the nodule size. This was investigated by measuring /sup 15/N/sub 2/ incorporation into nodules. Root nodules from 38 day old cowpea and peanut plants were collected and sorted into size groups having diameters of >3 mm,more » 2-3 mm, and just below 2 mm. Samples of each size group were enclosed in tubes and exposed to various combination of oxygen (8-28%) and /sup 15/N/sub 2/. With higher O/sub 2/ pressure all nodules showed increased N/sub 2/ fixation but the largest nodules showed the maximum increase. Specific activity of larger nodules was higher for N/sub 2/ fixation. For the sizes of nodules examined the largest nodules did not reflect any of the disadvantages of the large size but the benefits of higher rates of O/sub 2/ entry was evident.« less

Arthrodesis of the knee following failed arthroplasty.

PubMed

Van Rensch, P J H; Van de Pol, G J; Goosen, J H M; Wymenga, A B; De Man, F H R

2014-08-01

Primary stability in arthrodesis of the knee can be achieved by external fixation, intramedullary nailing or plate fixation. Each method has different features and results. We present a practical algorithm for arthrodesis of the knee following a failed (infected) arthroplasty, based on our own results and a literature review. Between 2004 and 2010, patients were included with an indication for arthrodesis after failed (revision) arthroplasty of the knee. Patients were analyzed with respect to indication, fusion method and bone contact. End-point was solid fusion. Twenty-six arthrodeses were performed. Eighteen patients were treated because of an infected arthroplasty. In total, ten external fixators, ten intramedullary nails and six plate fixations were applied; solid fusion was achieved in 3/10, 8/10 and 3/6, respectively. There is no definite answer as to which method is superior in performing an arthrodesis of the knee. Intramedullary nailing achieved the best fusion rates, but was used most in cases without--or cured--infection. Our data and the contemporary literature suggest that external fixation can be abandoned as standard fusion method, but can be of use following persisting infection. The Ilizarov circular external fixator, however, seems to render high fusion rates. Good patient selection and appropriate individual treatment are the key to a successful arthrodesis. Based upon these findings, a practical algorithm was developed.

Functional Single-Cell Approach to Probing Nitrogen-Fixing Bacteria in Soil Communities by Resonance Raman Spectroscopy with 15N2 Labeling.

PubMed

Cui, Li; Yang, Kai; Li, Hong-Zhe; Zhang, Han; Su, Jian-Qiang; Paraskevaidi, Maria; Martin, Francis L; Ren, Bin; Zhu, Yong-Guan

2018-04-17

Nitrogen (N) fixation is the conversion of inert nitrogen gas (N 2 ) to bioavailable N essential for all forms of life. N 2 -fixing microorganisms (diazotrophs), which play a key role in global N cycling, remain largely obscure because a large majority are uncultured. Direct probing of active diazotrophs in the environment is still a major challenge. Herein, a novel culture-independent single-cell approach combining resonance Raman (RR) spectroscopy with 15 N 2 stable isotope probing (SIP) was developed to discern N 2 -fixing bacteria in a complex soil community. Strong RR signals of cytochrome c (Cyt c, frequently present in diverse N 2 -fixing bacteria), along with a marked 15 N 2 -induced Cyt c band shift, generated a highly distinguishable biomarker for N 2 fixation. 15 N 2 -induced shift was consistent well with 15 N abundance in cell determined by isotope ratio mass spectroscopy. By applying this biomarker and Raman imaging, N 2 -fixing bacteria in both artificial and complex soil communities were discerned and imaged at the single-cell level. The linear band shift of Cyt c versus 15 N 2 percentage allowed quantification of N 2 fixation extent of diverse soil bacteria. This single-cell approach will advance the exploration of hitherto uncultured diazotrophs in diverse ecosystems.

Anatomical Evidence that the Superior Colliculus Controls Saccades through Central Mesencephalic Reticular Formation Gating of Omnipause Neuron Activity

PubMed Central

Wang, Niping; Perkins, Eddie; Zhou, Lan; Warren, Susan

2013-01-01

Omnipause neurons (OPNs) within the nucleus raphe interpositus (RIP) help gate the transition between fixation and saccadic eye movements by monosynaptically suppressing activity in premotor burst neurons during fixation, and releasing them during saccades. Premotor neuron activity is initiated by excitatory input from the superior colliculus (SC), but how the tectum's saccade-related activity turns off OPNs is not known. Since the central mesencephalic reticular formation (cMRF) is a major SC target, we explored whether this nucleus has the appropriate connections to support tectal gating of OPN activity. In dual-tracer experiments undertaken in macaque monkeys (Macaca fascicularis), cMRF neurons labeled retrogradely from injections into RIP had numerous anterogradely labeled terminals closely associated with them following SC injections. This suggested the presence of an SC–cMRF–RIP pathway. Furthermore, anterograde tracers injected into the cMRF of other macaques labeled axonal terminals in RIP, confirming this cMRF projection. To determine whether the cMRF projections gate OPN activity, postembedding electron microscopic immunochemistry was performed on anterogradely labeled cMRF terminals with antibody to GABA or glycine. Of the terminals analyzed, 51.4% were GABA positive, 35.5% were GABA negative, and most contacted glycinergic cells. In summary, a trans-cMRF pathway connecting the SC to the RIP is present. This pathway contains inhibitory elements that could help gate omnipause activity and allow other tectal drives to induce the bursts of firing in premotor neurons that are necessary for saccades. The non-GABAergic cMRF terminals may derive from fixation units in the cMRF. PMID:24107960

Anatomical evidence that the superior colliculus controls saccades through central mesencephalic reticular formation gating of omnipause neuron activity.

PubMed

Wang, Niping; Perkins, Eddie; Zhou, Lan; Warren, Susan; May, Paul J

2013-10-09

Omnipause neurons (OPNs) within the nucleus raphe interpositus (RIP) help gate the transition between fixation and saccadic eye movements by monosynaptically suppressing activity in premotor burst neurons during fixation, and releasing them during saccades. Premotor neuron activity is initiated by excitatory input from the superior colliculus (SC), but how the tectum's saccade-related activity turns off OPNs is not known. Since the central mesencephalic reticular formation (cMRF) is a major SC target, we explored whether this nucleus has the appropriate connections to support tectal gating of OPN activity. In dual-tracer experiments undertaken in macaque monkeys (Macaca fascicularis), cMRF neurons labeled retrogradely from injections into RIP had numerous anterogradely labeled terminals closely associated with them following SC injections. This suggested the presence of an SC-cMRF-RIP pathway. Furthermore, anterograde tracers injected into the cMRF of other macaques labeled axonal terminals in RIP, confirming this cMRF projection. To determine whether the cMRF projections gate OPN activity, postembedding electron microscopic immunochemistry was performed on anterogradely labeled cMRF terminals with antibody to GABA or glycine. Of the terminals analyzed, 51.4% were GABA positive, 35.5% were GABA negative, and most contacted glycinergic cells. In summary, a trans-cMRF pathway connecting the SC to the RIP is present. This pathway contains inhibitory elements that could help gate omnipause activity and allow other tectal drives to induce the bursts of firing in premotor neurons that are necessary for saccades. The non-GABAergic cMRF terminals may derive from fixation units in the cMRF.

Shorter spontaneous fixation durations in infants with later emerging autism

PubMed Central

Wass, Sam V.; Jones, Emily J. H.; Gliga, Teodora; Smith, Tim J.; Charman, Tony; Johnson, Mark H.; Baron-Cohen, Simon; Bedford, Rachael; Bolton, Patrick; Chandler, Susie; Davies, Kim; Fernandes, Janice; Garwood, Holly; Hudry, Kristelle; Maris, Helen; Pasco, Greg; Pickles, Andrew; Ribiero, Helena; Tucker, Leslie; Volein, Agnes

2015-01-01

Little is known about how spontaneous attentional deployment differs on a millisecond-level scale in the early development of autism spectrum disorders (ASD). We measured fine-grained eye movement patterns in 6-to 9-month-old infants at high or low familial risk (HR/LR) of ASD while they viewed static images. We observed shorter fixation durations (i.e. the time interval between saccades) in HR than LR infants. Preliminary analyses indicate that these results were replicated in a second cohort of infants. Fixation durations were shortest in those infants who went on to receive an ASD diagnosis at 36 months. While these findings demonstrate early-developing atypicality in fine-grained measures of attentional deployment early in the etiology of ASD, the specificity of these effects to ASD remains to be determined. PMID:25655672

Surgical plate fixation of multiple rib fractures: a case report.

PubMed

Mitev, Konstantin; Neziri, Dashurie; Stoicovski, Emil; Mitrev, Zan

2018-05-29

The healthcare system in developing countries is limited; particularly, medical specialties such as emergency and trauma medicine are underdeveloped. Consequently, trauma injuries sustained in traffic accidents result in chronic morbidity more often than similar cases in developed countries. Multiple rib fractures induce significant patient morbidity. Current international guidelines recommend a multidisciplinary, surgery-based treatment approach to achieve optimal clinical benefit. We admitted a 41-year-old Albanian man to our emergency department following a pedestrian-vehicle accident 5 days earlier. He presented with severe upper thoracic pain, chest deformity, dyspnea, tachycardia, subcutaneous emphysema, and hematoma. Chest radiography pointed to hypoventilated lung fields and a minor pleural effusion. Computed tomographic scans indicated displaced fractures of right lateral ribs 5 -11, hyperdensity regions from bone fragments, and pulmonary contusion. The treatment consisted of surgical fixation of ribs 7-10 using titanium reconstruction plates and cortical locking screws. The patient's clinical condition rapidly improved postoperatively. Follow-up at 6 weeks confirmed a full return to preoperative daily activities and a high quality of life. In this case report, we present a novel and promising development in the field of trauma medicine in the Republic of Macedonia. Trauma injuries can be treated via advanced multidisciplinary medical care according to international standards, allowing optimal health recovery.

Comparing fixation used for calcaneal displacement osteotomies: a look at removal rates and cost.

PubMed

Lucas, Douglas E; Simpson, G Alex; Philbin, Terrence M

2015-02-01

The calcaneal displacement osteotomy is a procedure frequently used by foot and ankle surgeons for hindfoot angular deformity. Traditional techniques use compression screw fixation that can result in prominent hardware. While the results of the procedure are generally good, a common concern is the development of plantar heel pain related to prominent hardware. The primary purpose of this study is to retrospectively compare clinical outcomes of 2 fixation methods for the osteotomy. Secondarily a cost analysis will compare implant costs to hardware removal costs. Records were reviewed for patients who had undergone a calcaneal displacement osteotomy fixated with either lag screw or a locked lateral compression plate (LLCP). Neuropathy, previous ipsilateral calcaneus surgery, heel pad trauma, or incomplete radiographic follow-up were exclusionary. Thirty-two patients (19.4%) required hardware removal from the screw fixation group compared to 1 (1.6%) of the LLCP group, which is significant (P < .05). Time to radiographic healing was not significantly different (P = .87). The screw fixation group required more follow-up visits over a longer period of time (P < .05). Implant cost was remarkably different with screw fixation costing on average $247.12, compared to the LLCP costing $1175.59. Although the LLCP cost was significantly higher, cost savings were identified when the cost of removal and removal rates were included. This study demonstrates that this device provides adequate stabilization for healing in equivalent time to screw fixation. The LLCP required decreased rates of hardware removal with fewer postoperative visits over a shorter period of time. Significant savings were demonstrated in the LLCP group despite the higher implant cost. Therapeutic, Level III, Retrospective Comparative Study. © 2014 The Author(s).

Local strategies to prevent and treat osteoporosis.

PubMed

Torstrick, F Brennan; Guldberg, Robert E

2014-03-01

Despite advances in systemic osteoporosis therapeutic outcomes, management of fragility fractures and implant fixation in osteoporotic bone remain difficult clinical challenges. Low initial bone density and a prolonged healing response can lead to fracture nonunion and aseptic implant loosening. Local treatment strategies could be used to prevent fracture, accelerate healing, and increase implant fixation by locally stimulating anabolic pathways or inhibiting catabolic pathways. Local strategies under investigation include direct drug release from injectable materials or implant surface coatings. Common locally delivered drugs include bisphosphonates, parathyroid hormone, and bone morphogenetic proteins, yet additional compounds targeting novel pathways in bone biology are also being actively explored. Mechanical stimulation via low intensity pulsed ultrasound, alone or in combination with drug therapy, may also prove effective to promote local bone healing and implant fixation within osteoporotic bone.

Tendon healing in a bone tunnel. Part II: Histologic analysis after biodegradable interference fit fixation in a model of anterior cruciate ligament reconstruction in sheep.

PubMed

Weiler, Andreas; Hoffmann, Reinhard F G; Bail, Hermann J; Rehm, Oliver; Südkamp, Norbert P

2002-02-01

Tendon-to-bone healing of soft-tissue grafts has been described to progress by the development of a fibrous interzone that undergoes a maturation process leading to the development of an indirect type of ligament insertion. Previous studies used extra-articular models or fixation far away from the joint line; thus, no data are available investigating tendon-to-bone healing of a soft-tissue graft fixed anatomically. Therefore, we studied the tendon-to-bone healing of the anatomic soft-tissue graft interference fit fixation in a model of anterior cruciate ligament (ACL) reconstruction in sheep. Animal study. Thirty-five mature sheep underwent ACL reconstruction with an autologous Achilles tendon split graft. Grafts were directly fixed with biodegradable poly-(D,L-lactide) interference screws. Animals were euthanized after 6, 9, 12, 24, and 52 weeks and histologic evaluations were performed. Undecalcified specimens were evaluated under normal and polarized light. Additionally, animals received a polychrome sequential labeling (tetracycline, xylenol orange, and calcein green) to determine bone growth per time under fluorescent light. Intratunnel histologic findings at 6 weeks showed a tendon-bone junction with only a partial fibrous interzone between the graft tissue and the surrounding bone. A mature intratunnel tendon-bone junction with a zone of fibrocartilage was found at 9 to 12 weeks. At the tunnel entrance site a wide regular ligamentous insertion site was seen in all specimens after 24 weeks. This insertion showed regular patterns such as the direct type of insertion of a normal ligament with a dense basophilic transition zone consisting of mineralized cartilage. A fibrous interzone between the graft tissue and the bone tunnel was only partially developed, which is in contrast to all previous studies in which nonanatomic fixation was used. Thus, it is reasonable to assume that the tendon-to-bone healing in the present study may progress partially by direct-contact healing without the development of a fibrous interzone. To our knowledge, this is the first report describing the development of a direct type of ligament insertion after ACL replacement with a soft-tissue graft. This is in contrast to previous studies reporting the development of an indirect type of insertion when using nonanatomic fixation far away from the joint line. Thus, histologic data strongly indicate that anatomic interference fit fixation is beneficial for tendon-to-bone incorporation by leading to the development of a direct type of ligament insertion.

Shedding light on the paradox of high alkaline phosphatase utilization at high end-product concentrations

NASA Astrophysics Data System (ADS)

Baltar, F.; Lundin, D.; Palovaara, J.; Reinthaler, T.; Herndl, G. J.; Pinhassi, J.

2016-02-01

Alkaline phosphatase (APase) activity is supposed to be regulated by the concentration of its endproduct, decreasing with increasing inorganic phosphate (Pi) concentrations. Since Pi is readily available in the deep ocean, APase activity would be expected to be low. However, high APase activities at high Pi concentrations have been found in the deep Indian and Atlantic Ocean. To understand how APase activities are regulated and what mechanisms are responsible for its regulation we performed microcosm experiments with mesopelagic North Atlantic waters. Treatments consisted of enrichment with either ammonium or organic carbon, and were compared to unamended controls. We assessed changes in prokaryotic abundance, APase, leucine aminopeptidase, heterotrophic production, dark CO2 fixation and community gene expression (metatranscriptomics) between treatments and control. In the organic matter enrichments, APase increased along with all measured rates, whereas only dark CO2 fixation and APase were enhanced in the ammonium enrichment. In the organic matter enrichment, genes for heterotrophic metabolism were strongly upregulated, whereas genes for ammonia oxidation and CO2 fixation were upregulated in the ammonium treatment. In both treatments, the Pho regulon -a global regulatory mechanism involved in bacterial Pi management- was also upregulated, including genes encoding alkaline phosphatases. The activation of the Pho regulon seemed to be related to cross-activation by nonpartner histidine kinases, and/or the activation of genes involved in the regulation of elemental balance during catabolic processes. Increased C or N bioavailability thus appear to elicit a Pi deficiency inside cells and activate the Pho regulon. These results indicate possible ways (e.g. pulses of C or N or changes in elemental ratios) in which APase can be activated irrespectively of the environmental Pi concentration.

Virtual faces expressing emotions: an initial concomitant and construct validity study.

PubMed

Joyal, Christian C; Jacob, Laurence; Cigna, Marie-Hélène; Guay, Jean-Pierre; Renaud, Patrice

2014-01-01

Facial expressions of emotions represent classic stimuli for the study of social cognition. Developing virtual dynamic facial expressions of emotions, however, would open-up possibilities, both for fundamental and clinical research. For instance, virtual faces allow real-time Human-Computer retroactions between physiological measures and the virtual agent. The goal of this study was to initially assess concomitants and construct validity of a newly developed set of virtual faces expressing six fundamental emotions (happiness, surprise, anger, sadness, fear, and disgust). Recognition rates, facial electromyography (zygomatic major and corrugator supercilii muscles), and regional gaze fixation latencies (eyes and mouth regions) were compared in 41 adult volunteers (20 ♂, 21 ♀) during the presentation of video clips depicting real vs. virtual adults expressing emotions. Emotions expressed by each set of stimuli were similarly recognized, both by men and women. Accordingly, both sets of stimuli elicited similar activation of facial muscles and similar ocular fixation times in eye regions from man and woman participants. Further validation studies can be performed with these virtual faces among clinical populations known to present social cognition difficulties. Brain-Computer Interface studies with feedback-feedforward interactions based on facial emotion expressions can also be conducted with these stimuli.

CARBON-14 FIXATION IN POLLEN OF YELLOW LUPINE (LUPINUS LUTEUS LINN.)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schwien, W.G.; Frazier, J.C.; Moser, H.C.

1962-10-31

Carbon-14 fixation studies were made on germinated pollen of yellow lupine to ascertain whether the chlorophyll reported to be in these grains was functional photosynthetically. Light and dark exposures to atmospheres containing 20 and 500 mu c of carbon-14 labeled carbon dioxide were made for 1.5 and 45 minutes, respectively. The exposed pollen was extracted in 80% ethanol, the resulting extract reduced in volume, and chromatographed two dimensionally. When the chromatograms were cut inio numbered small squares and their activity counted in an automatic sample counting system, a marked similarity was observed in the pattern of radioactivity from all exposures.more » Eluting and co- chromatographing this activity from the squares, with known standards, demonstrated labeling to be specific to certain intermediates of the Krebs cycle and their derived amine acids. The labeling in these intermediates and the absence of labeling in photosynthetic metabolites is strong evidence that only respiratory fixation of carbon-14 occurs in the germinated pollen of this variety of yellow lupine under the conditions of the experiment. (auth)« less

The significance of microsaccades for vision and oculomotor control.

PubMed

Collewijn, Han; Kowler, Eileen

2008-12-18

Over the past decade several research groups have taken a renewed interest in the special role of a type of small eye movement, called 'microsaccades', in various visual processes, such as the activation of neurons in the central nervous system, or the prevention of image fading. As the study of microsaccades and their relation to visual processes goes back at least half a century, it seems appropriate to review the more recent reports in light of the history of research on maintained oculomotor fixation, in general, and on microsaccades in particular. Our review shows that there is no compelling evidence to support the view that microsaccades (or, fixation saccades more generally) serve a necessary role in improving oculomotor control or in keeping the visual world visible. The role of the retinal transients produced by small saccades during fixation needs to be evaluated in the context of both the brisk image motions present during active visual tasks performed by freely moving people, as well as the role of selective attention in modulating the strength of signals throughout the visual field.

Inhibitory control in mind and brain 2.0: Blocked-input models of saccadic countermanding

PubMed Central

Logan, Gordon D.; Yamaguchi, Motonori; Schall, Jeffrey D.; Palmeri, Thomas J.

2015-01-01

The interactive race model of saccadic countermanding assumes that response inhibition results from an interaction between a go unit, identified with gaze-shifting neurons, and a stop unit, identified with gaze-holding neurons, in which activation of the stop unit inhibits the growth of activation in the go unit to prevent it from reaching threshold. The interactive race model accounts for behavioral data and predicts physiological data in monkeys performing the stop-signal task. We propose an alternative model that assumes that response inhibition results from blocking the input to the go unit. We show that the blocked-input model accounts for behavioral data as accurately as the original interactive race model and predicts aspects of the physiological data more accurately. We extend the models to address the steady-state fixation period before the go stimulus is presented and find that the blocked-input model fits better than the interactive race model. We consider a model in which fixation activity is boosted when a stop signal occurs and find that it fits as well as the blocked input model but predicts very high steady-state fixation activity after the response is inhibited. We discuss the alternative linking propositions that connect computational models to neural mechanisms, the lessons to be learned from model mimicry, and generalization from countermanding saccades to countermanding other kinds of responses. PMID:25706403

Glue versus suture for mesh fixation in inguinal hernia repair.

PubMed

Chandrasekar, Shruthi; Jeyakumar, S; Ganapathy, Tharun

2018-03-22

Inguinal hernia is one of the most common surgical problem presenting to the surgical OPD. Surgery is the mainstay of treatment for inguinal hernia today. Surgery for inguinal hernia has undergone a great evolution over a period of several centuries. Lichenstein's tension free hernioplasty is the one of the first surgeries taught to a surgical resident. The main aim of surgeries in this era is to give the best possible results with the least possible pain, scar and time. This has given rise to so many modifications to the classical Lichenstein's procedure and also to laparoscopic hernioplasty. Pain after inguinal hernia surgery is found to be debilitating and altering the quality of life in several patients, which has been attributed to the traumatic fixation of the mesh with sutures. This has paved way to the development of various atraumatic methods of fixation, tissue glue is one such development. Hence this study, to compare traumatic and atraumatic methods of mesh fixation in inguinal hernia repair. The aim of this study was to compare suture fixation versus tissue glue fixation of the mesh in inguinal hernia repair. Primary objective was to compare the immediate and chronic post-operative pain. Secondary objective was to compare the time taken for the procedure by the two methods in use and also to compare the presence of any complications. and methodology: This study was done in the General Surgery department of XXX hospital, medical college and research centre, kattangulathur after Ethics committee clearance. It is a single blinded study. The study was done on 51 patients consenting for the study and meeting the inclusion criterias from the period of March 2016 to August 2017 out of which 26 were selected for glue mesh fixation and 25 for suture mesh fixation according to simple randomization. The suture group patients underwent classical Lichenstein's tension free hernioplasty and the glue group underwent Lichenstein's hernioplasty with glue where dots of glue were used to fix the mesh instead of sutures. The tissue glue used in this study was N Butyl- 2 - Cyanoacrylate. All patients in the study underwent surgery only by one group of surgeons to maintain homogeneity and were observed in the hospital for 72 h. A note of the pain on VAS scale was made at 12, 24, 48, 72 h, 1 week, 1 month, 3 months and 6 months. Operative time and any complications were also recorded. Results developed using SPSS software show that there is a significant difference in the time taken by both the methods, with glue taking a significantly lower time than sutures. Significance is also seen in the difference in the immediate and chronic post-operative pain between both the groups. However the complication rates in both the groups were found to be the same. It can thus be concluded from this study that tissue glue mesh fixation is superior to suture mesh fixation in open inguinal repair in terms of operative time, immediate and chronic post-operative time. Copyright © 2018. Published by Elsevier Ltd.

An alternative means of retaining ocular structure and improving immunoreactivity for light microscopy studies

PubMed Central

Sun, Ning; Shibata, Brad; Hess, John F.

2015-01-01

Purpose Several properties of ocular tissue make fixation for light microscopy problematic. Because the eye is spherical, immersion fixation necessarily results in a temporal gradient of fixation, with surfaces fixing more rapidly and thoroughly than interior structures. The problem is compounded by the fact that the layers of the eye wall are compositionally quite different, resulting in different degrees of fixation-induced shrinkage and distortion. Collectively, these result in non-uniform preservation, as well as buckling and/or retinal detachment. This gradient problem is most acute for the lens, where the density of proteins can delay fixation of the central lens for days, and where the fixation gradient parallels the age gradient of lens cells, which complicates data interpretation. Our goal was to identify a simple method for minimizing some of the problems arising from immersion fixation, which avoided covalent modification of antigens, retained high quality structure, and maintained tissue in a state that is amenable to common cytochemical techniques. Methods A simple and inexpensive derivative of the freeze-substitution approach was developed and compared to fixation by immersion in formalin. Preservation of structure, immunoreactivity, GFP and tdTomato fluorescence, lectin reactivity, outer segment auto fluorescence, Click-iT chemistry, compatibility with in situ hybdrdization, and the ability to rehydrate eyes after fixation by freeze substitution for subsequent cryo sectioning were assessed. Results An inexpensive and simple variant of the freeze substitution approach provides excellent structural preservation for light microscopy, and essentially eliminates ocular buckling, retinal detachment, and outer segment auto-fluorescence, without covalent modification of tissue antigens. The approach shows a notable improvement in preservation of immunoreactivity. TdTomato intrinsic fluorescence is also preserved, as is compatibility with in situ hybridization, lectin labeling, and the Click-iT chemistry approach to labeling the thymidine analog EdU. On the negative side, this approach dramatically reduced intrinsic GFP fluorescence. Conclusions A simple, cost-effective derivative of the freeze substitution process is described that is of particular value in the study of rodent or other small eyes, where fixation gradients, globe buckling, retinal detachment, differential shrinkage, autofluorescence, and tissue immunoreactivity have been problematic. PMID:25991907

[FAB immunoglobulin fragments. I. The comparative characteristics of the serological and virus-neutralizing properties of a gamma globulin against tick-borne encephalitis and of the FAB fragments isolated from it].

PubMed

Barban, P S; Minaeva, V M; Pantiukhina, A N; Startseva, M G

1976-06-01

A comparative study was made of the serological properties and virus-neutralizing activity of antiencephalitis gamma-globulin and Fab-fragments isolated from it by gel-filtration. Horse immunoglobulins against the autumno-summer tick-borne encephalitis virus could be disintegrated with the aid of papaine to monovalent Fab-fragments which (according to the complement fixation reaction, the test of suppression of the complement fixation, and the HAIT) retained the serological activity whose level was compared with that of the serological activity of gamma-globulin. Fab-fragments possessed a marked virus-neutralizing activity. The mean value of a logarithm of the neutralization index was 2.65 +/- 0.2 for Fab-fragments and 3.74 +/- 0.38 for gamma-globulin (P less than 0.01).

History of internal fixation with plates (part 2): new developments after World War II; compressing plates and locked plates.

PubMed

Hernigou, Philippe; Pariat, Jacques

2017-07-01

The first techniques of operative fracture with plates were developed in the 19th century. In fact, at the beginning these methods consisted of an open reduction of the fracture usually followed by a very unstable fixation. As a consequence, the fracture had to be opened with a real risk of (sometimes lethal) infection, and due to unstable fixation, protection with a cast was often necessary. During the period between World Wars I and II, plates for fracture fixation developed with great variety. It became increasingly recognised that, because a fracture of a long bone normally heals with minimal resorption at the bone ends, this may result in slight shortening and collapse, so a very rigid plate might prevent such collapse. However, as a consequence, delayed healing was observed unless the patient was lucky enough to have the plate break. One way of dealing with this was to use a slotted plate in which the screws could move axially, but the really important advance was recognition of the role of compression. After the first description of compression by Danis with a "coapteur", Bagby and Müller with the AO improved the technique of compression. The classic dynamic compression plates from the 1970s were the key to a very rigid fixation, leading to primary bone healing. Nevertheless, the use of strong plates resulted in delayed union and the osteoporosis, cancellous bone, comminution, and/or pathological bone resulted in some failures due to insufficient stability. Finally, new devices represented by locking plates increased the stability, contributing to the principles of a more biological osteosynthesis while giving enough stability to allow immediate full weight bearing in some patients.

RNA-seq transcriptome profiling reveals that Medicago truncatula nodules acclimate N2 fixation before emerging P deficiency reaches the nodules

PubMed Central

Cabeza, Ricardo A.; Liese, Rebecca; Lingner, Annika; von Stieglitz, Ilsabe; Neumann, Janice; Salinas-Riester, Gabriela; Pommerenke, Claudia; Dittert, Klaus; Schulze, Joachim

2014-01-01

Legume nodules are plant tissues with an exceptionally high concentration of phosphorus (P), which, when there is scarcity of P, is preferentially maintained there rather than being allocated to other plant organs. The hypothesis of this study was that nodules are affected before the P concentration in the organ declines during whole-plant P depletion. Nitrogen (N2) fixation and P concentration in various organs were monitored during a whole-plant P-depletion process in Medicago truncatula. Nodule gene expression was profiled through RNA-seq at day 5 of P depletion. Until that point in time P concentration in leaves reached a lower threshold but was maintained in nodules. N2-fixation activity per plant diverged from that of fully nourished plants beginning at day 5 of the P-depletion process, primarily because fewer nodules were being formed, while the activity of the existing nodules was maintained for as long as two weeks into P depletion. RNA-seq revealed nodule acclimation on a molecular level with a total of 1140 differentially expressed genes. Numerous genes for P remobilization from organic structures were increasingly expressed. Various genes involved in nodule malate formation were upregulated, while genes involved in fermentation were downregulated. The fact that nodule formation was strongly repressed with the onset of P deficiency is reflected in the differential expression of various genes involved in nodulation. It is concluded that plants follow a strategy to maintain N2 fixation and viable leaf tissue as long as possible during whole-plant P depletion to maintain their ability to react to emerging new P sources (e.g. through active P acquisition by roots). PMID:25151618

Low-level and high-level modulations of fixational saccades and high frequency oscillatory brain activity in a visual object classification task

PubMed Central

Kosilo, Maciej; Wuerger, Sophie M.; Craddock, Matt; Jennings, Ben J.; Hunt, Amelia R.; Martinovic, Jasna

2013-01-01

Until recently induced gamma-band activity (GBA) was considered a neural marker of cortical object representation. However, induced GBA in the electroencephalogram (EEG) is susceptible to artifacts caused by miniature fixational saccades. Recent studies have demonstrated that fixational saccades also reflect high-level representational processes. Do high-level as opposed to low-level factors influence fixational saccades? What is the effect of these factors on artifact-free GBA? To investigate this, we conducted separate eye tracking and EEG experiments using identical designs. Participants classified line drawings as objects or non-objects. To introduce low-level differences, contours were defined along different directions in cardinal color space: S-cone-isolating, intermediate isoluminant, or a full-color stimulus, the latter containing an additional achromatic component. Prior to the classification task, object discrimination thresholds were measured and stimuli were scaled to matching suprathreshold levels for each participant. In both experiments, behavioral performance was best for full-color stimuli and worst for S-cone isolating stimuli. Saccade rates 200–700 ms after stimulus onset were modulated independently by low and high-level factors, being higher for full-color stimuli than for S-cone isolating stimuli and higher for objects. Low-amplitude evoked GBA and total GBA were observed in very few conditions, showing that paradigms with isoluminant stimuli may not be ideal for eliciting such responses. We conclude that cortical loops involved in the processing of objects are preferentially excited by stimuli that contain achromatic information. Their activation can lead to relatively early exploratory eye movements even for foveally-presented stimuli. PMID:24391611

Attentional load and sensory competition in human vision: modulation of fMRI responses by load at fixation during task-irrelevant stimulation in the peripheral visual field.

PubMed

Schwartz, Sophie; Vuilleumier, Patrik; Hutton, Chloe; Maravita, Angelo; Dolan, Raymond J; Driver, Jon

2005-06-01

Perceptual suppression of distractors may depend on both endogenous and exogenous factors, such as attentional load of the current task and sensory competition among simultaneous stimuli, respectively. We used functional magnetic resonance imaging (fMRI) to compare these two types of attentional effects and examine how they may interact in the human brain. We varied the attentional load of a visual monitoring task performed on a rapid stream at central fixation without altering the central stimuli themselves, while measuring the impact on fMRI responses to task-irrelevant peripheral checkerboards presented either unilaterally or bilaterally. Activations in visual cortex for irrelevant peripheral stimulation decreased with increasing attentional load at fixation. This relative decrease was present even in V1, but became larger for successive visual areas through to V4. Decreases in activation for contralateral peripheral checkerboards due to higher central load were more pronounced within retinotopic cortex corresponding to 'inner' peripheral locations relatively near the central targets than for more eccentric 'outer' locations, demonstrating a predominant suppression of nearby surround rather than strict 'tunnel vision' during higher task load at central fixation. Contralateral activations for peripheral stimulation in one hemifield were reduced by competition with concurrent stimulation in the other hemifield only in inferior parietal cortex, not in retinotopic areas of occipital visual cortex. In addition, central attentional load interacted with competition due to bilateral versus unilateral peripheral stimuli specifically in posterior parietal and fusiform regions. These results reveal that task-dependent attentional load, and interhemifield stimulus-competition, can produce distinct influences on the neural responses to peripheral visual stimuli within the human visual system. These distinct mechanisms in selective visual processing may be integrated within posterior parietal areas, rather than earlier occipital cortex.

Behavioral model of visual perception and recognition

NASA Astrophysics Data System (ADS)

Rybak, Ilya A.; Golovan, Alexander V.; Gusakova, Valentina I.

1993-09-01

In the processes of visual perception and recognition human eyes actively select essential information by way of successive fixations at the most informative points of the image. A behavioral program defining a scanpath of the image is formed at the stage of learning (object memorizing) and consists of sequential motor actions, which are shifts of attention from one to another point of fixation, and sensory signals expected to arrive in response to each shift of attention. In the modern view of the problem, invariant object recognition is provided by the following: (1) separated processing of `what' (object features) and `where' (spatial features) information at high levels of the visual system; (2) mechanisms of visual attention using `where' information; (3) representation of `what' information in an object-based frame of reference (OFR). However, most recent models of vision based on OFR have demonstrated the ability of invariant recognition of only simple objects like letters or binary objects without background, i.e. objects to which a frame of reference is easily attached. In contrast, we use not OFR, but a feature-based frame of reference (FFR), connected with the basic feature (edge) at the fixation point. This has provided for our model, the ability for invariant representation of complex objects in gray-level images, but demands realization of behavioral aspects of vision described above. The developed model contains a neural network subsystem of low-level vision which extracts a set of primary features (edges) in each fixation, and high- level subsystem consisting of `what' (Sensory Memory) and `where' (Motor Memory) modules. The resolution of primary features extraction decreases with distances from the point of fixation. FFR provides both the invariant representation of object features in Sensor Memory and shifts of attention in Motor Memory. Object recognition consists in successive recall (from Motor Memory) and execution of shifts of attention and successive verification of the expected sets of features (stored in Sensory Memory). The model shows the ability of recognition of complex objects (such as faces) in gray-level images invariant with respect to shift, rotation, and scale.

Disease-mediated declines in N-fixation inputs by Alnus tenuifolia to early-successional floodplains in interior and south-central Alaska

Treesearch

R.W. Ruess; J.M. McFarland; L.M. Trummer; J.K. Rohrs-Richey

2009-01-01

Atmospheric nitrogen (N) fixation by Alnus tenuifolia can account for up to 70 percent of the N accumulated during vegetation development along river flood plains in interior Alaska. We assessed disease incidence and related mortality of a recent outbreak or fungal stem cankers on A. tenuifolia across three regions in Alaska...

Studies of Antigens for Complement Fixation and Gel Diffusion Tests in the Diagnosis of Infections Caused by Brucella ovis and Other Brucella

PubMed Central

Myers, Donald M.; Jones, Lois M.; Varela-Diaz, Victor M.

1972-01-01

Sonically treated and saline-extracted antigens of Brucella ovis, B. canis, B. abortus, and B. melitensis were compared in gel diffusion, complement fixation, and serum absorption tests. All the sonically extracted antigens showed cross-reactions with sera from animals infected or immunized with these species, whereas the saline-extracted antigens were specific for the surface of the rough or smooth colonial phase of the species or strain. The saline-extracted antigens of B. ovis and B. melitensis were both eluted as a single peak in the void volume by Sephadex G-200 column chromatography, in gel diffusion had staining characteristics of lipoproteins, but in immunoelectrophoresis showed distinct mobility patterns. Serological activity for both gel diffusion and complement fixation tests was demonstrated in the immunoglobulin G-containing fraction of sera taken from sheep 12 to 412 days after infection with B. ovis. The gel diffusion test with saline extract of B. ovis is as sensitive as the complement fixation test for the diagnosis of ram epididymitis and is more practical. Images PMID:4624210

Lower complication rate and faster return to sports in patients with acute syndesmotic rupture treated with a new knotless suture button device.

PubMed

Colcuc, Christian; Blank, Marc; Stein, Thomas; Raimann, Florian; Weber-Spickschen, Sanjay; Fischer, Sebastian; Hoffmann, Reinhard

2017-12-09

Suture button devices for tibiofibular syndesmosis injuries provide semirigid dynamic stabilization, but complications including knot irritation have been reported. No randomized trials of the new knotless suture button devices have been performed. We hypothesized that knotless suture button devices eliminate knot irritation and facilitate quicker return to sports. This study was performed to compare the clinical outcomes, complication rates, and time to return to sports between a new knotless suture button device and syndesmotic screw fixation. This study included 54 patients treated for ankle syndesmotic injury from 2012 to 2014 with a knotless suture button device or syndesmotic screw fixation. Clinical outcomes were measured using the American Orthopaedics Foot and Ankle Society score, Foot and Ankle Disability Index, Olerud and Molander score, and visual analog scale for pain and function. Secondary outcome measures were the complication rate and time required to return to sports. Patients underwent clinical and radiological evaluations preoperatively and three times during the 1-year postoperative follow-up. 54 of 62 eligible patients were analyzed, median age 37 (18-60) and underwent the 1-year follow-up. The screw fixation and knotless suture button groups comprised 26 and 28 patients, respectively. The complication rate was significantly lower (p = 0.03) and time to return to sports was significantly shorter in the knotless suture button than screw fixation group (average, 14 versus 19 weeks, respectively; p = 0.006). No significant differences were identified in clinical outcomes or visual analog scale scores for pain and function between the groups. Age, injury mechanism, and body mass index did not significantly affect the time required to return to sports activities. The type of fixation was the only independent variable that reached statistical significance (p = 0.006). Syndesmotic screw fixation and the new knotless suture button device both resulted in good clinical results. Lower complication rate and the earlier time to return to sports make the new knotless suture button device recommendable especially for highly active patients. Randomized controlled trial, Level I.

A novel injectable calcium phosphate-based nanocomposite for the augmentation of cannulated pedicle-screw fixation

PubMed Central

Sun, Haolin; Liu, Chun; Liu, Huiling; Bai, Yanjie; Zhang, Zheng; Li, Xuwen; Li, Chunde; Yang, Huilin; Yang, Lei

2017-01-01

Polymethyl methacrylate (PMMA)-augmented cannulated pedicle-screw fixation has been routinely performed for the surgical treatment of lumbar degenerative diseases. Despite its satisfactory clinical outcomes and prevalence, problems and complications associated with high-strength, stiff, and nondegradable PMMA have largely hindered the long-term efficacy and safety of pedicle-screw fixation in osteoporotic patients. To meet the unmet need for better bone cement for cannulated pedicle-screw fixation, a new injectable and biodegradable nanocomposite that was the first of its kind was designed and developed in the present study. The calcium phosphate-based nanocomposite (CPN) exhibited better anti-pullout ability and similar fluidity and dispersing ability compared to clinically used PMMA, and outperformed conventional calcium phosphate cement (CPC) in all types of mechanical properties, injectability, and biodegradability. In term of axial pullout strength, the CPN-augmented cannulated screw reached the highest force of ~120 N, which was higher than that of PMMA (~100 N) and CPC (~95 N). The compressive strength of the CPN (50 MPa) was three times that of CPC, and the injectability of the CPN reached 95%. In vivo tests on rat femur revealed explicit biodegradation of the CPN and subsequent bone ingrowth after 8 weeks. The promising results for the CPN clearly suggest its potential for replacing PMMA in the application of cannulated pedicle-screw fixation and its worth of further study and development for clinical uses. PMID:28490878

Engineering Pseudomonas protegens Pf-5 for nitrogen fixation and its application to improve plant growth under nitrogen-deficient conditions.

PubMed

Setten, Lorena; Soto, Gabriela; Mozzicafreddo, Matteo; Fox, Ana Romina; Lisi, Christian; Cuccioloni, Massimiliano; Angeletti, Mauro; Pagano, Elba; Díaz-Paleo, Antonio; Ayub, Nicolás Daniel

2013-01-01

Nitrogen is the second most critical factor for crop production after water. In this study, the beneficial rhizobacterium Pseudomonas protegens Pf-5 was genetically modified to fix nitrogen using the genes encoding the nitrogenase of Pseudomonas stutzeri A1501 via the X940 cosmid. Pf-5 X940 was able to grow in L medium without nitrogen, displayed high nitrogenase activity and released significant quantities of ammonium to the medium. Pf-5 X940 also showed constitutive expression and enzymatic activity of nitrogenase in ammonium medium or in nitrogen-free medium, suggesting a constitutive nitrogen fixation. Similar to Pseudomonas protegens Pf-5, Pseudomonas putida, Pseudomonas veronii and Pseudomonas taetrolens but not Pseudomonas balearica and Pseudomonas stutzeri transformed with cosmid X940 showed constitutive nitrogenase activity and high ammonium production, suggesting that this phenotype depends on the genome context and that this technology to obtain nitrogen-fixing bacteria is not restricted to Pf-5. Interestingly, inoculation of Arabidopsis, alfalfa, tall fescue and maize with Pf-5 X940 increased the ammonium concentration in soil and plant productivity under nitrogen-deficient conditions. In conclusion, these results open the way to the production of effective recombinant inoculants for nitrogen fixation on a wide range of crops.

Engineering Pseudomonas protegens Pf-5 for Nitrogen Fixation and its Application to Improve Plant Growth under Nitrogen-Deficient Conditions

PubMed Central

Setten, Lorena; Soto, Gabriela; Mozzicafreddo, Matteo; Fox, Ana Romina; Lisi, Christian; Cuccioloni, Massimiliano; Angeletti, Mauro; Pagano, Elba; Díaz-Paleo, Antonio; Ayub, Nicolás Daniel

2013-01-01

Nitrogen is the second most critical factor for crop production after water. In this study, the beneficial rhizobacterium Pseudomonas protegens Pf-5 was genetically modified to fix nitrogen using the genes encoding the nitrogenase of Pseudomonas stutzeri A1501 via the X940 cosmid. Pf-5 X940 was able to grow in L medium without nitrogen, displayed high nitrogenase activity and released significant quantities of ammonium to the medium. Pf-5 X940 also showed constitutive expression and enzymatic activity of nitrogenase in ammonium medium or in nitrogen-free medium, suggesting a constitutive nitrogen fixation. Similar to Pseudomonas protegens Pf-5, Pseudomonas putida, Pseudomonas veronii and Pseudomonas taetrolens but not Pseudomonas balearica and Pseudomonas stutzeri transformed with cosmid X940 showed constitutive nitrogenase activity and high ammonium production, suggesting that this phenotype depends on the genome context and that this technology to obtain nitrogen-fixing bacteria is not restricted to Pf-5. Interestingly, inoculation of Arabidopsis, alfalfa, tall fescue and maize with Pf-5 X940 increased the ammonium concentration in soil and plant productivity under nitrogen-deficient conditions. In conclusion, these results open the way to the production of effective recombinant inoculants for nitrogen fixation on a wide range of crops. PMID:23675499

Coordinated regulation of growth, activity and transcription in natural populations of the unicellular nitrogen-fixing cyanobacterium Crocosphaera.

PubMed

Wilson, Samuel T; Aylward, Frank O; Ribalet, Francois; Barone, Benedetto; Casey, John R; Connell, Paige E; Eppley, John M; Ferrón, Sara; Fitzsimmons, Jessica N; Hayes, Christopher T; Romano, Anna E; Turk-Kubo, Kendra A; Vislova, Alice; Armbrust, E Virginia; Caron, David A; Church, Matthew J; Zehr, Jonathan P; Karl, David M; DeLong, Edward F

2017-07-31

The temporal dynamics of phytoplankton growth and activity have large impacts on fluxes of matter and energy, yet obtaining in situ metabolic measurements of sufficient resolution for even dominant microorganisms remains a considerable challenge. We performed Lagrangian diel sampling with synoptic measurements of population abundances, dinitrogen (N 2 ) fixation, mortality, productivity, export and transcription in a bloom of Crocosphaera over eight days in the North Pacific Subtropical Gyre (NPSG). Quantitative transcriptomic analyses revealed clear diel oscillations in transcript abundances for 34% of Crocosphaera genes identified, reflecting a systematic progression of gene expression in diverse metabolic pathways. Significant time-lagged correspondence was evident between nifH transcript abundance and maximal N 2 fixation, as well as sepF transcript abundance and cell division, demonstrating the utility of transcriptomics to predict the occurrence and timing of physiological and biogeochemical processes in natural populations. Indirect estimates of carbon fixation by Crocosphaera were equivalent to 11% of net community production, suggesting that under bloom conditions this diazotroph has a considerable impact on the wider carbon cycle. Our cross-scale synthesis of molecular, population and community-wide data underscores the tightly coordinated in situ metabolism of the keystone N 2 -fixing cyanobacterium Crocosphaera, as well as the broader ecosystem-wide implications of its activities.

Distractor Evoked Deviations of Saccade Trajectory Are Modulated by Fixation Activity in the Superior Colliculus: Computational and Behavioral Evidence

PubMed Central

Wang, Zhiguo; Theeuwes, Jan

2014-01-01

Previous studies have shown that saccades may deviate towards or away from task irrelevant visual distractors. This observation has been attributed to active suppression (inhibition) of the distractor location unfolding over time: early in time inhibition at the distractor location is incomplete causing deviation towards the distractor, while later in time when inhibition is complete the eyes deviate away from the distractor. In a recent computational study, Wang, Kruijne and Theeuwes proposed an alternative theory that the lateral interactions in the superior colliculus (SC), which are characterized by short-distance excitation and long-distance inhibition, are sufficient for generating both deviations towards and away from distractors. In the present study, we performed a meta-analysis of the literature, ran model simulations and conducted two behavioral experiments to further explore this unconventional theory. Confirming predictions generated by the model simulations, the behavioral experiments show that a) saccades deviate towards close distractors and away from remote distractors, and b) the amount of deviation depends on the strength of fixation activity in the SC, which can be manipulated by turning off the fixation stimulus before or after target onset (Experiment 1), or by varying the eccentricity of the target and distractor (Experiment 2). PMID:25551552

Spinopelvic Fixation of Sacroiliac Joint Fractures and Fracture-Dislocations: A Clinical 8 Years Follow-Up Study.

PubMed

Sobhan, Mohammad R; Abrisham, Seyed Mohammad J; Vakili, Mahmood; Shirdel, Saeed

2016-10-01

Pelvic ring injuries and sacroiliac dislocations have significant impacts on patient's quality of life. Several techniques have been described for posterior pelvic fixation. The current study has been designed to evaluate the spinopelvic method of fixation for sacroiliac fractures and fracture-dislocations. Between January 2006 and December 2014, 14 patients with sacroiliac joint fractures, dislocation and fracture-dislocation were treated by Spinopelvic fixation at Shahid Sadoughi Training Hospital, Yazd, Iran. Patients were seen in follow up, on average, out to 32 months after surgery. Computed tomographic (CT) scans of patients with sacral fractures were reviewed to determine the presence of injuries. A functional assessment of the patients was performed using Majeed's score. Patient demographics, reduction quality, loss of fixation, outcomes and complications, return to activity, and screw hardware characteristics are described. The injury was unilateral in 11 (78.5%) patients and bilateral in 3 (21.5%). Associated injuries were present in all patients, including fractures, dislocation and abdominal injuries. Lower limb length discrepancy was less than 10 mm in all patients except two. Displacement, as a measure of quality of reduction was less than 5 mm in 13 patients. The mean Majeed score was 78/100. Wound infection and hardware failure were observed in 3 (21.4%) and 1 (7.1%) cases, respectively. In this study most patients (85%) return to work postoperatively. According to the findings, spinopelvic fixation is a safe and effective technique for treatment of sacroiliac injuries. This method can obtain early partial to full weight bearing and possibly reduce the complications.

Metacarpal Neck Fractures: A Review of Surgical Indications and Techniques

PubMed Central

Padegimas, Eric M.; Warrender, William J.; Jones, Christopher M.; Ilyas, Asif M.

2016-01-01

Context Hand injuries are a common emergency department presentation. Metacarpal fractures account for 40% of all hand fractures and can be seen in the setting of low or high energy trauma. The most common injury pattern is a metacarpal neck fracture. In this study, the authors aim to review the surgical indications for metacarpal neck fractures, the fixation options available along with the risk and benefits of each. Evidence Acquisition Literature review of the different treatment modalities for metacarpal neck fractures. Review focuses on surgical indications and the risks and benefits of different operative techniques. Results The indications for surgery are based on the amount of dorsal angulation of the distal fragment. The ulnar digits can tolerate greater angulation as the radial digits more easily lose grip strength. The most widely utilized fixation techniques are pinning with k-wires, dorsal plating, or intramedullary fixation. There is currently no consensus on an optimal fixation technique as surgical management has been found to have a complication rate up to 36%. Plate and screw fixation demonstrated especially high complication rates. Conclusions Metacarpal neck fractures are a common injury in young and active patients that results in substantial missed time from work. While the surgical indications are well-described, there is no consensus on the optimal treatment modality because of high complication rates. Dorsal plating has higher complication rates than closed reduction and percutaneous pinning, but is necessary in comminuted fractures. The lack of an ideal fixation construct suggests that further study of the commonly utilized techniques as well as novel techniques is necessary. PMID:27800460

Design and analysis of synthetic carbon fixation pathways

PubMed Central

Bar-Even, Arren; Noor, Elad; Lewis, Nathan E.; Milo, Ron

2010-01-01

Carbon fixation is the process by which CO2 is incorporated into organic compounds. In modern agriculture in which water, light, and nutrients can be abundant, carbon fixation could become a significant growth-limiting factor. Hence, increasing the fixation rate is of major importance in the road toward sustainability in food and energy production. There have been recent attempts to improve the rate and specificity of Rubisco, the carboxylating enzyme operating in the Calvin–Benson cycle; however, they have achieved only limited success. Nature employs several alternative carbon fixation pathways, which prompted us to ask whether more efficient novel synthetic cycles could be devised. Using the entire repertoire of approximately 5,000 metabolic enzymes known to occur in nature, we computationally identified alternative carbon fixation pathways that combine existing metabolic building blocks from various organisms. We compared the natural and synthetic pathways based on physicochemical criteria that include kinetics, energetics, and topology. Our study suggests that some of the proposed synthetic pathways could have significant quantitative advantages over their natural counterparts, such as the overall kinetic rate. One such cycle, which is predicted to be two to three times faster than the Calvin–Benson cycle, employs the most effective carboxylating enzyme, phosphoenolpyruvate carboxylase, using the core of the naturally evolved C4 cycle. Although implementing such alternative cycles presents daunting challenges related to expression levels, activity, stability, localization, and regulation, we believe our findings suggest exciting avenues of exploration in the grand challenge of enhancing food and renewable fuel production via metabolic engineering and synthetic biology. PMID:20410460

Ubiquitous Gammaproteobacteria dominate dark carbon fixation in coastal sediments.

PubMed

Dyksma, Stefan; Bischof, Kerstin; Fuchs, Bernhard M; Hoffmann, Katy; Meier, Dimitri; Meyerdierks, Anke; Pjevac, Petra; Probandt, David; Richter, Michael; Stepanauskas, Ramunas; Mußmann, Marc

2016-08-01

Marine sediments are the largest carbon sink on earth. Nearly half of dark carbon fixation in the oceans occurs in coastal sediments, but the microorganisms responsible are largely unknown. By integrating the 16S rRNA approach, single-cell genomics, metagenomics and transcriptomics with (14)C-carbon assimilation experiments, we show that uncultured Gammaproteobacteria account for 70-86% of dark carbon fixation in coastal sediments. First, we surveyed the bacterial 16S rRNA gene diversity of 13 tidal and sublittoral sediments across Europe and Australia to identify ubiquitous core groups of Gammaproteobacteria mainly affiliating with sulfur-oxidizing bacteria. These also accounted for a substantial fraction of the microbial community in anoxic, 490-cm-deep subsurface sediments. We then quantified dark carbon fixation by scintillography of specific microbial populations extracted and flow-sorted from sediments that were short-term incubated with (14)C-bicarbonate. We identified three distinct gammaproteobacterial clades covering diversity ranges on family to order level (the Acidiferrobacter, JTB255 and SSr clades) that made up >50% of dark carbon fixation in a tidal sediment. Consistent with these activity measurements, environmental transcripts of sulfur oxidation and carbon fixation genes mainly affiliated with those of sulfur-oxidizing Gammaproteobacteria. The co-localization of key genes of sulfur and hydrogen oxidation pathways and their expression in genomes of uncultured Gammaproteobacteria illustrates an unknown metabolic plasticity for sulfur oxidizers in marine sediments. Given their global distribution and high abundance, we propose that a stable assemblage of metabolically flexible Gammaproteobacteria drives important parts of marine carbon and sulfur cycles.

Epiphytic Cyanobacteria on Chara vulgaris Are the Main Contributors to N2 Fixation in Rice Fields

PubMed Central

Ariosa, Yoanna; Quesada, Antonio; Aburto, Juan; Carrasco, David; Carreres, Ramón; Leganés, Francisco; Fernández Valiente, Eduardo

2004-01-01

The distribution of nitrogenase activity in the rice-soil system and the possible contribution of epiphytic cyanobacteria on rice plants and other macrophytes to this activity were studied in two locations in the rice fields of Valencia, Spain, in two consecutive crop seasons. The largest proportion of photodependent N2 fixation was associated with the macrophyte Chara vulgaris in both years and at both locations. The nitrogen fixation rate associated with Chara always represented more than 45% of the global nitrogenase activity measured in the rice field. The estimated average N2 fixation rate associated with Chara was 27.53 kg of N ha−1 crop−1. The mean estimated N2 fixation rates for the other parts of the system for all sampling periods were as follows: soil, 4.07 kg of N ha−1 crop−1; submerged parts of rice plants, 3.93 kg of N ha−1 crop−1; and roots, 0.28 kg of N ha−1 crop−1. Micrographic studies revealed the presence of epiphytic cyanobacteria on the surface of Chara. Three-dimensional reconstructions by confocal scanning laser microscopy revealed no cyanobacterial cells inside the Chara structures. Quantification of epiphytic cyanobacteria by image analysis revealed that cyanobacteria were more abundant in nodes than in internodes (on average, cyanobacteria covered 8.4% ± 4.4% and 6.2% ± 5.0% of the surface area in the nodes and internodes, respectively). Epiphytic cyanobacteria were also quantified by using a fluorometer. This made it possible to discriminate which algal groups were the source of chlorophyll a. Chlorophyll a measurements confirmed that cyanobacteria were more abundant in nodes than in internodes (on average, the chlorophyll a concentrations were 17.2 ± 28.0 and 4.0 ± 3.8 μg mg [dry weight] of Chara−1 in the nodes and internodes, respectively). These results indicate that this macrophyte, which is usually considered a weed in the context of rice cultivation, may help maintain soil N fertility in the rice field ecosystem. PMID:15345425

Ilizarov bone transport versus fibular graft for reconstruction of tibial bone defects in children.

PubMed

Abdelkhalek, Mostafa; El-Alfy, Barakat; Ali, Ayman M

2016-11-01

The aim of this study was to compare the results of treatment of segmental tibial defects in the pediatric age group using an Ilizarov external fixator versus a nonvascularized fibular bone graft. This study included 24 patients (age range from 5.5 to 15 years) with tibial bone defects: 13 patients were treated with bone transport (BT) and 11 patients were treated with a nonvascularized fibular graft (FG). The outcome parameters were bone results (union, deformity, infection, leg-length discrepancy) and functional results: external fixation index and external fixation time. In group A (BT), one patient developed refracture at the regenerate site, whereas, in group B (FG), after removal of the external fixator, one of the FGs developed a stress fracture. The external fixator time in group A was 10.7 months (range 8-14.5) versus 7.8 months (range 4-11.5 months) in group B (FG). In group A (BT), one patient had a limb-length discrepancy (LLD), whereas, in group B (FG), three patients had LLD. The functional and bone results of the Ilizarov BT technique were excellent in 23.1 and 30.8%, good in 38.5 and 46.2, fair in 30.8 and 15.4, and poor in 7.6 and 7.6%, respectively. The poor functional result was related to the poor bone result because of prolonged external fixator time resulting in significant pain, limited ankle motion, whereas the functional and bone results of fibular grafting were excellent in 9.1 and 18.2%, good in 63.6 and 45.5%, fair in 18.2 and 27.2%, and poor in 9.1 and 9.1%, respectively. Segmental tibial defects can be effectively treated with both methods. The FG method provides satisfactory results, with early removal of the external fixator. However, it had a limitation in patients with severe infection and those with LLD. Also, it requires a long duration of limb bracing until adequate hypertrophy of the graft. The Ilizarov method has the advantages of early weight bearing, treatment of postinfection bone defect in a one-stage surgery, and the possibility to treat the associated LLD. However, it has a long external fixation time.

Recent Developments in Ground-Borne Noise and Vibration Control

NASA Astrophysics Data System (ADS)

Nelson, J. T.

1996-05-01

Vibration control provisions available to the transit designer include (among others) precision straightened rail, ballast mats, floating slabs and very soft direct fixation fasteners, in addition to rail grinding, wheel truing, and continuous welded rail. Recently, the Los Angeles Metro has developed specifications for a soft resilient direct fixation fastener to fit the same base dimensions as the standard direct fixation fastener. In San Francisco, low resonance frequency (8 Hz) floating slabs have been constructed to mitigate predicted ground vibration impacts at nearby residential structures. In Atlanta, low resonance frequency loading slabs have been constructed to maintain a low vibration environment in a medical building planned to be built over the subway structure. In Portland and Pasadena, ballast mats have been recommended to control light rail transit ground vibration impacts on housing located at typically 35 feet from the alignment. Each of these provisions are briefly described in view of recent applications at U.S. transit systems.

Intramedullary nailing in opening wedge high tibial osteotomy-in vitro test for validation of a method of fixation.

PubMed

Burchard, Rene; Katerla, Denise; Hammer, Marina; Pahlkötter, Anke; Soost, Christian; Dietrich, Gerhard; Ohrndorf, Arne; Richter, Wolfgang; Lengsfeld, Markus; Christ, Hans-Jürgen; Graw, Jan Adriaan; Fritzen, Claus-Peter

2018-02-01

Opening wedge high tibial osteotomy (HTO) as a treatment in unicompartimental osteoarthritis of the knee can significantly relieve pain and prevent or at least delay an early joint replacement. The fixation of the osteotomy has undergone development and refinements during the last years. The angle-stable plate fixator is currently one of the most commonly used plates in HTOs. The angular stable fixation between screws and the plate offers a high primary stability to retain the correction with early weight-bearing protocols. This surgical technique is performed as a standard of care and generally well tolerated by the patients. Nevertheless, some studies observed that many patients complained about discomfort related to the implant. Therefore, the stability of two different intramedullary nails, a short implant used in humeral fractures and a long device used in tibial fractures for stabilization in valgus HTOs, was investigated as an alternative fixation technique. The plate fixator was defined as reference standard. Nine synthetic tibia models were standardly osteotomized and stabilized by one of the fixation devices. Axial compression was realized using a special testing machine and two protocols were performed: a multi-step fatigue test and a load-to-failure test. Overall motion, medial, and lateral displacements were documented. Fractures always occurred at the lateral cortex. Axial cyclic loading up to 800 N was tolerated by all implants without failure. The tibia nail provided highest fatigue strength under the load-to-failure conditions. The results suggest that intramedullary nailing might be used as an alternative concept in HTO.

New concept of 3D printed bone clip (polylactic acid/hydroxyapatite/silk composite) for internal fixation of bone fractures.

PubMed

Yeon, Yeung Kyu; Park, Hae Sang; Lee, Jung Min; Lee, Ji Seung; Lee, Young Jin; Sultan, Md Tipu; Seo, Ye Bin; Lee, Ok Joo; Kim, Soon Hee; Park, Chan Hum

Open reduction with internal fixation is commonly used for the treatment of bone fractures. However, postoperative infection associated with internal fixation devices (intramedullary nails, plates, and screws) remains a significant complication, and it is technically difficult to fix multiple fragmented bony fractures using internal fixation devices. In addition, drilling in the bone to install devices can lead to secondary fracture, bone necrosis associated with postoperative infection. In this study, we developed bone clip type internal fixation device using three- dimensional (3D) printing technology. Standard 3D model of the bone clip was generated based on computed tomography (CT) scan of the femur in the rat. Polylacticacid (PLA), hydroxyapatite (HA), and silk were used for bone clip material. The purpose of this study was to characterize 3D printed PLA, PLA/HA, and PLA/HA/Silk composite bone clip and evaluate the feasibility of these bone clips as an internal fixation device. Based on the results, PLA/HA/Silk composite bone clip showed similar mechanical property, and superior biocompatibility compared to other types of the bone clip. PLA/HA/Silk composite bone clip demonstrated excellent alignment of the bony segments across the femur fracture site with well-positioned bone clip in an animal study. Our 3D printed bone clips have several advantages: (1) relatively noninvasive (drilling in the bone is not necessary), (2) patient-specific design (3) mechanically stable device, and (4) it provides high biocompatibility. Therefore, we suggest that our 3D printed PLA/HA/Silk composite bone clip is a possible internal fixation device.

Outcome of 28 open pilon fractures with injury severity-based fixation.

PubMed

Danoff, Jonathan R; Saifi, Comron; Goodspeed, David C; Reid, J Spence

2015-04-01

Open pilon fracture management and treatment poses a significant challenge to orthopedic surgeons. The purpose of this study was to determine patient outcomes for open pilon fractures based on wound complication and infection rates, as well as subjective outcome instruments. This was a retrospective consecutive case series of 28 fractures with Orthopaedic Trauma Association (OTA)-type 43-B and 43-C open pilon fractures. Mean length of follow-up was 36 months and minimum of 1 year. Ten fractures were Gustilo and Anderson grade IIIB, and the remaining fractures were grades I-IIIA. Patients were initially treated with spanning external fixation and staged wound debridement followed by osteosynthesis of the articular surface. Metaphyseal fixation was by either plate fixation or Ilizarov frame. The primary outcome was the incidence of deep tissue infection requiring surgery. Secondary outcomes included the incidence of other complications (nonunion, malunion, amputation) and functional outcomes (Short Musculoskeletal Functional Assessment Questionnaire and AAOS Foot and Ankle Questionnaire). Four patients developed deep tissue infections, three in the internal fixation group and one in the Ilizarov group, and all were treated successfully with staged debridement. There were two delayed unions required bone grafting, and infection-free union was ultimately achieved in all fractures. Two patients underwent arthrodesis secondary to post-traumatic arthritis, while no patients experienced malunions or amputations. The use of staged wound debridement in conjunction with either plate fixation or Ilizarov frame achieves low rates of wound infection and stable fixation after anatomic joint reconstruction for OTA-type 43-B and 43-C open pilon fractures.

Diversity and Activity of Diazotrophs in Great Barrier Reef Surface Waters.

PubMed

Messer, Lauren F; Brown, Mark V; Furnas, Miles J; Carney, Richard L; McKinnon, A D; Seymour, Justin R

2017-01-01

Discrepancies between bioavailable nitrogen (N) concentrations and phytoplankton growth rates in the oligotrophic waters of the Great Barrier Reef (GBR) suggest that undetermined N sources must play a significant role in supporting primary productivity. One such source could be biological dinitrogen (N 2 ) fixation through the activity of "diazotrophic" bacterioplankton. Here, we investigated N 2 fixation and diazotroph community composition over 10° S of latitude within GBR surface waters. Qualitative N 2 fixation rates were found to be variable across the GBR but were relatively high in coastal, inner and outer GBR waters, reaching 68 nmol L -1 d -1 . Diazotroph assemblages, identified by amplicon sequencing of the nifH gene, were dominated by the cyanobacterium Trichodesmium erythraeum , γ-proteobacteria from the Gamma A clade, and δ-proteobacterial phylotypes related to sulfate-reducing genera. However, diazotroph communities exhibited significant spatial heterogeneity, correlated with shifts in dissolved inorganic nutrient concentrations. Specifically, heterotrophic diazotrophs generally increased in relative abundance with increasing concentrations of phosphate and N, while Trichodesmium was proportionally more abundant when concentrations of these nutrients were low. This study provides the first in-depth characterization of diazotroph community composition and N 2 fixation dynamics within the oligotrophic, N-limited surface waters of the GBR. Our observations highlight the need to re-evaluate N cycling dynamics within oligotrophic coral reef systems, to include diverse N 2 fixing assemblages as a potentially significant source of dissolved N within the water column.

Identification of anti-Lea by platelet complement fixation.

PubMed

Ando, B; Ibayashi, H

1986-01-01

Two anti-Lea sera which were able to detect Lea antigen on platelets were identified in a screening for anti-platelet antibodies by means of a platelet complement fixation test. These two antisera hemolyzed erythrocytes without enzyme treatment. The anti-Lea activity could be completely absorbed by red cells, platelets and lymphocytes of Le(a+b-) donors but not by cells from Le(a-b+) or Le(a-b-) donors. The antibody activity against red cells was eliminated by treatment of the antisera with dithiothreitol, thereby suggesting that the activity resided in the IgM class of immunoglobulins. As the anti-Lea was more reactive at 37 degrees C than at room temperature against both red cells and platelets, we suggest that transfusion of platelets of Lea-negative donors should be considered for patients with this type of anti-Lea.

Biomechanical Evaluation of All-Polyethylene Pegged Bony Ingrowth Glenoid Fixation Techniques on Implant Micromotion.

PubMed

Wiater, Brett P; Moravek, James E; Kurdziel, Michael D; Baker, Kevin C; Wiater, J Michael

2016-01-01

Newer glenoid components that allow for hybrid cement fixation via traditional cementation of peripheral pegs and bony ingrowth into an interference-fit central peg introduce the possibility of long-term biological fixation. However, little biomechanical work has been done on the initial stability of these components and the various fixation options. We conducted a study in which all-polyethylene glenoid components with a centrally fluted peg were implanted in polyurethane blocks with interference-fit, hybrid cement, and fully cemented fixation (5 per fixation group). Biomechanical evaluation of glenoid loosening, according to ASTM Standard F-2028-12, subjected the glenoids to 50,000 cycles of rim loading, and glenoid component motion was recorded with 2 differential variable reluctance transducers fixed to each glenoid prosthesis. Fully cemented fixation exhibited significantly less mean distraction in comparison with interference-fit fixation (P < .001) and hybrid cement fixation (P < .001). Hybrid cement fixation exhibited significantly less distraction (P < .001), more compression (P < .001), and no significant difference in glenoid translation (P = .793) in comparison with interference-fit fixation. Fully cemented fixation exhibited the most resistance to glenoid motion in comparison with hybrid cement fixation and interference-fit fixation. However, hybrid cement fixation and interference-fit fixation exhibited equivocal motion. Given these results, cementation of peripheral pegs may confer no additional initial stability over that provided by uncemented interference-fit fixation.

Nonconscious memory for motion activates MT+.

PubMed

Thakral, Preston P; Slotnick, Scott D

2014-11-12

Extrastriate region MT+ is widely thought to reflect conscious motion processing. The primary aim of the present functional MRI study was to assess whether MT+ is activated during nonconscious memory for motion. During the encoding phase, moving and stationary abstract shapes were presented to the left or right of fixation. During the retrieval phase, the same shapes were presented at fixation and participants classified each shape as 'moving-left', 'moving-right', 'stationary-left', or 'stationary-right'. The contrast of moving>stationary shapes at encoding was used to identify the location of MT+. Event-related activity was then extracted from MT+ within each hemisphere. MT+ activity was significantly greater for moving-misses than for stationary-misses, which indicates that nonconscious memory for motion activates MT+. Furthermore, nonconscious memory activity (moving-misses) had an earlier temporal onset than conscious memory activity (moving-hits). The present results are the first, to our knowledge, to demonstrate that MT+ is associated with nonconscious motion processing. Therefore, activity in this region or in other visual-sensory regions should not be assumed to reflect conscious processing.

Pedicle screw-rod fixation: a feasible treatment for dogs with severe degenerative lumbosacral stenosis.

PubMed

Tellegen, Anna R; Willems, Nicole; Tryfonidou, Marianna A; Meij, Björn P

2015-12-07

Degenerative lumbosacral stenosis is a common problem in large breed dogs. For severe degenerative lumbosacral stenosis, conservative treatment is often not effective and surgical intervention remains as the last treatment option. The objective of this retrospective study was to assess the middle to long term outcome of treatment of severe degenerative lumbosacral stenosis with pedicle screw-rod fixation with or without evidence of radiological discospondylitis. Twelve client-owned dogs with severe degenerative lumbosacral stenosis underwent pedicle screw-rod fixation of the lumbosacral junction. During long term follow-up, dogs were monitored by clinical evaluation, diagnostic imaging, force plate analysis, and by using questionnaires to owners. Clinical evaluation, force plate data, and responses to questionnaires completed by the owners showed resolution (n = 8) or improvement (n = 4) of clinical signs after pedicle screw-rod fixation in 12 dogs. There were no implant failures, however, no interbody vertebral bone fusion of the lumbosacral junction was observed in the follow-up period. Four dogs developed mild recurrent low back pain that could easily be controlled by pain medication and an altered exercise regime. Pedicle screw-rod fixation offers a surgical treatment option for large breed dogs with severe degenerative lumbosacral stenosis with or without evidence of radiological discospondylitis in which no other treatment is available. Pedicle screw-rod fixation alone does not result in interbody vertebral bone fusion between L7 and S1.

Effect of insecticides and phenolics on nitrogen fixation by Nostoc linckia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Megharaj, M.; Venkateswarlu, K.; Rao, A.S.

1988-08-01

The nitrogen-fixing blue-green algae (cyanobacteria) significantly influence the nitrogen economy of temperate and tropical soils. Although the genera Nostoc and Tolypothrix have been particularly implicated in the fixation of significantly large amounts of atmospheric nitrogen, these diazotrophs received little attention in relation to insecticide treatment and the available few reports do not indicate a permanent deleterious effect of insecticides on their nitrogenase activity. As it has been well established that the effect of insecticides on nitrogen fixation by cyanobacteria is independent of that on growth, an attempt was, therefore, made to determine the influence of four insecticides (monocrotophos, quinalphos, cypermethrinmore » and fenvalerate) and four phenolics (p-nitrophenol (PNP), m-nitrophenol (MNP), 2,4-dinitrophenol (DNP) and catechol) on nitrogen-fixing capacity of N.linckia, isolated from a black soil.« less

Calcium phosphate cement augmentation in the treatment of depressed tibial plateau fractures with open reduction and internal fixation.

PubMed

Oztürkmen, Yusuf; Caniklioğlu, Mustafa; Karamehmetoğlu, Mahmut; Sükür, Erhan

2010-01-01

We aimed to evaluate the clinical and radiological outcomes of open reduction and internal fixation augmented with calcium phosphate cement (CPC) in the treatment of depressed tibial plateau fractures. Twenty-eight knees of 28 patients [19 males and 9 females; mean age, 41.2 years (range 22-72 years)] who had open reduction and internal fixation combined with CPC augmentation were included in this study. Seventeen fractures were Schatzker type II, 5 were type III, 3 were type IV, 2 were type V, and 1 was type VI. CPC was used to fill the subchondral bone defects in all knees. Fixation of the fragments was done with screws in 3 knees (10%). Standard proximal tibial plates or buttress plates were used in 25 knees (90%) with an additional split fragment extending distally to achieve internal fixation. Full weight-bearing was allowed in 6.4 weeks (range 6-12 weeks) after surgery. Resorption of CPC granules was defined as the decrease in the size and density of grafting material on radiographs. Rasmussen's radiological and clinical scores were determined postoperatively. Functionality was assessed with Lysholm knee scoring system. Activity was graded with Tegner's activity scale. Union was achieved in all patients with a mean follow-up of 22.2 months (range 6-36 months). There were no intraoperative complications. At the latest follow-up radiographs, resorption of the graft was observed in 25 knees (89%). Rasmussen's radiologic score was excellent in 17 patients (61%), good in 9 patients (32%), and fair in 2 patients (7%). Rasmussen's clinical score was excellent in 9 patients (32%), good in 18 patients (64%), and fair in 1 patient (4%). According to the Lysholm knee score, functional results were excellent in 16 patients (57%), good in 8 patients (29%), and fair in 4 patients (14%). Twenty-two patients (78%) achieved the preoperative activity level after surgery, and there was no significant difference between the mean preoperative and postoperative Tegner scores (4.11±0.68 and 4.04±0.64, respectively, p=0.161). CPC is a safe biomaterial with many advantages in augmenting the open reduction and internal fixation of depressed tibial plateau fractures, including elimination of morbidity associated with bone graft harvesting, the unlimited supply of bone substitute, the optimum filling of irregular bone defects, and shortening of the postoperative full weight-bearing time.

The impact of simulated chronic nitrogen deposition on the biomass and N2-fixation activity of two boreal feather moss–cyanobacteria associations

PubMed Central

Gundale, Michael J.; Bach, Lisbet H.; Nordin, Annika

2013-01-01

Bryophytes achieve substantial biomass and play several key functional roles in boreal forests that can influence how carbon (C) and nitrogen (N) cycling respond to atmospheric deposition of reactive nitrogen (Nr). They associate with cyanobacteria that fix atmospheric N2, and downregulation of this process may offset anthropogenic Nr inputs to boreal systems. Bryophytes also promote soil C accumulation by thermally insulating soils, and changes in their biomass influence soil C dynamics. Using a unique large-scale (0.1 ha forested plots), long-term experiment (16 years) in northern Sweden where we simulated anthropogenic Nr deposition, we measured the biomass and N2-fixation response of two bryophyte species, the feather mosses Hylocomium splendens and Pleurozium schreberi. Our data show that the biomass declined for both species; however, N2-fixation rates per unit mass and per unit area declined only for H. splendens. The low and high treatments resulted in a 29% and 54% reduction in total feather moss biomass, and a 58% and 97% reduction in total N2-fixation rate per unit area, respectively. These results help to quantify the sensitivity of feather moss biomass and N2 fixation to chronic Nr deposition, which is relevant for modelling ecosystem C and N balances in boreal ecosystems. PMID:24196519

Evaluation of the tepary bean (Phaseolus acutifolius) diversity panel for response to the NL 3 strain of Bean Common Mosaic Necrosis Virus (BCMNV) and for biological nitrogen fixation with Bradyrhizobium strains

USDA-ARS?s Scientific Manuscript database

Aphid-transmitted Bean Common Mosaic Necrosis Virus (BCMNV) and Bean Common Mosaic Virus (BCMV) are potyviruses that are seed transmitted in tepary bean. Developing resistance to these viruses will be critical for expanding production in areas where they are endemic. Biological nitrogen fixation (BN...

CARBON DIOXIDE FIXATION.

DOE Office of Scientific and Technical Information (OSTI.GOV)

FUJITA,E.

2000-01-12

Solar carbon dioxide fixation offers the possibility of a renewable source of chemicals and fuels in the future. Its realization rests on future advances in the efficiency of solar energy collection and development of suitable catalysts for CO{sub 2} conversion. Recent achievements in the efficiency of solar energy conversion and in catalysis suggest that this approach holds a great deal of promise for contributing to future needs for fuels and chemicals.

Plating of patella fractures: techniques and outcomes.

PubMed

Taylor, Benjamin C; Mehta, Sanjay; Castaneda, Joaquin; French, Bruce G; Blanchard, Chris

2014-09-01

Operative treatment of displaced patella fractures with tension band fixation remains the gold standard, but is associated with a significant rate of complications and symptomatic implants. Despite the evolution of tension band fixation to include cannulated screws, surprisingly little other development has been made to improve overall patient outcomes. In this article, we present the techniques and outcomes of patella plating for displaced patella fractures and patella nonunions.

Nitrification and CO2 fixation in hot springs in the presence and absence of a nitrification inhibitor

NASA Astrophysics Data System (ADS)

Hungate, B. A.; Dijkstra, P.; Brown, J.; Mau, R. L.; Thomas, S.; Dodsworth, J. A.; Hedlund, B. P.; Boyd, E. S.; de la Torre, J. R.; Jewell, T.

2012-12-01

Ammonium oxidation occurs in terrestrial and aquatic ecosystems, and from temperatures approaching freezing to close to 80 °C. This reaction is catalyzed by ammonium oxidase associated with both Bacteria and Archaea, although those associated with Archaea appear dominant at temperatures above ~ 60°C. For bacteria, this process is coupled to active CO2 uptake, although whether Archaea use this reaction in situ to drive C fixation has yet to be definitively established. For some hot spring communities, the Thaumarcheota (specifically close relatives of Nitrosocaldus yellowstonii) represent a substantial proportion of the microbial community. We conducted gross nitrification and CO2 fixation measurements to determine 1- the upper in situ temperature limit for nitrification and 2- the contribution of ammonium oxidizers to the community C fixation by inhibiting nitrification using allylthiourea (ATU). We used 15NO3- pool dilution to determine nitrification in sediment slurries and incubated sediment with 14C-labeled bicarbonate to measure C fixation. Sediment samples were collected from the Great Boiling Spring near Gerlach, Nevada. The water temperature ranged between 83 and 50°C depending on the location in the main pool. We collected samples at 82, 72, 59, and 51 °C. The sediment was homogenized, 15NO3- was added. The nitrification inhibitor ATU was added before adding the 15N label. One sample was immediately stored cold, while another was incubated overnight at the collection temperature. In parallel experiments, 14C bicarbonate was added to the headspace and likewise incubated in situ for several hours in the presence and absence of ATU. We observed significant nitrification at temperatures from 51-72 °C, but not at 82 °C. This nitrification was blocked by ATU. We also observed significant CO2 fixation at 51 and 59 °C, but not at higher temperature. CO2 fixation was not blocked by the nitrification inhibitor. We conclude that 1- ammonium oxidizers are responsible for at most a small proportion of the community CO2 fixation, and 2- at the highest temperature assessed, nitrification is negligible even though the organism capable of ammonium oxidization is still present.

Deciphering the factors associated with the colonization of rice plants by cyanobacteria.

PubMed

Bidyarani, Ngangom; Prasanna, Radha; Chawla, Gautam; Babu, Santosh; Singh, Rajendra

2015-04-01

Cyanobacteria-rice plant interactions were analyzed using a hydroponics experiment. The activity of plant defense and pathogenesis-related enzymes, scanning electron microscopy, growth, nitrogen fixation (measured as ARA), and DNA fingerprinting assays proved useful in illustrating the nature of associations of cyanobacteria with rice plants. Microscopic analyses revealed the presence of short filaments and coiled masses of filaments of cyanobacteria near the epidermis and cortex of roots and shoot tissues. Among the six cyanobacterial strains employed, Calothrix sp. (RPC1), Anabaena laxa (RPAN8), and Anabaena azollae (C16) were the best performing strains, in terms of colonization in roots and stem. These strains also enhanced nitrogen fixation and stimulated the activity of plant defense/cell wall-degrading enzymes. A significantly high correlation was also recorded between the elicited plant enzymes, growth, and ARA. DNA fingerprinting using highly iterated palindromic sequences (HIP-TG) further helped in proving the establishment of inoculated organisms in the roots/shoots of rice plants. This study illustrated that the colonization of cyanobacteria in the plant tissues is facilitated by increased elicitation of plant enzymes, leading to improved plant growth, nutrient mobilization, and enhanced plant fitness. Such strains can be promising candidates for developing "cyanobacteria colonized-nitrogen-fixing rice plants" in the future. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Transcriptome analysis of two recombinant inbred lines of common bean contrasting for symbiotic nitrogen fixation

PubMed Central

Kamfwa, Kelvin; Zhao, Dongyan; Kelly, James D.

2017-01-01

Common bean (Phaseolus vulgaris L.) fixes atmospheric nitrogen (N2) through symbiotic nitrogen fixation (SNF) at levels lower than other grain legume crops. An understanding of the genes and molecular mechanisms underlying SNF will enable more effective strategies for the genetic improvement of SNF traits in common bean. In this study, transcriptome profiling was used to identify genes and molecular mechanisms underlying SNF differences between two common bean recombinant inbred lines that differed in their N-fixing abilities. Differential gene expression and functional enrichment analyses were performed on leaves, nodules and roots of the two lines when grown under N-fixing and non-fixing conditions. Receptor kinases, transmembrane transporters, and transcription factors were among the differentially expressed genes identified under N-fixing conditions, but not under non-fixing conditions. Genes up-regulated in the stronger nitrogen fixer, SA36, included those involved in molecular functions such as purine nucleoside binding, oxidoreductase and transmembrane receptor activities in nodules, and transport activity in roots. Transcription factors identified in this study are candidates for future work aimed at understanding the functional role of these genes in SNF. Information generated in this study will support the development of gene-based markers to accelerate genetic improvement of SNF in common bean. PMID:28192540

Improved fixation quality provided by a Bessel beacon in an adaptive optics system.

PubMed

Lambert, Andrew J; Daly, Elizabeth M; Dainty, Christopher J

2013-07-01

We investigate whether a structured probe beam that creates the beacon for use in a retinal imaging adaptive optics system can provide useful side effects. In particular we investigate whether a Bessel beam that is seen by the subject as a set of concentric rings has a dampening effect on fixation variations of the subject under observation. This calming effect would allow longer periods of observation, particularly for patients with abnormal fixation. An experimental adaptive optics system developed for retinal imaging is used to monitor the fluctuations in aberrations for artificial and human subjects. The probe beam is alternated between a traditional beacon and one provided by a Bessel beam created by SLM. Time-frequency analysis is used to indicate the differences in power and time variation during fixation depending on whether the Bessel beam or the traditional beacon is employed. Comparison is made with the response for an artificial eye to discount systemic variations. Significant evidence is accrued to indicate the reduced fluctuations in fixation when the Bessel beam is employed to create the beacon. © 2013 The Authors Ophthalmic & Physiological Optics © 2013 The College of Optometrists.

Fractures of the growing mandible.

PubMed

Kushner, George M; Tiwana, Paul S

2009-03-01

Oral and maxillofacial surgeons must constantly weigh the risks of surgical intervention for pediatric mandible fractures against the wonderful healing capacity of children. The majority of pediatric mandibular fractures can be managed with closed techniques using short periods of maxillomandibular fixation or training elastics alone. Generally, the use of plate- and screw-type internal fixation is reserved for difficult fractures. This article details general and special considerations for this surgery including: craniofacial growth & development, surgical anatomy, epidemiology evaluation, various fractures, the role rigid internal fixation and the Risdon cable in pediatric maxillofacial trauma. It concludes with suggestions concerning long-term follow-up care in light of the mobility, insurance obstacles, and family dynamics facing the patient population.

Malunited fracture of the body and condyle of the mandible : A Case Report.

PubMed

Yeluri, Ramakrishna; Baliga, Sudhindra; Munshi, Autar Krishen

2010-07-01

Mandibular fractures are the most common facial fractures seen in hospitalized children and their incidence increases with age. Treatment options include soft diet, intermaxillary fixation with eyelet wires, arch bars, circummandibular wiring, or stents. Alternative options include open reduction and internal fixation through either an intraoral or extraoral approach. Many factors complicate the management of pediatric mixed-dentition mandibular fractures: tooth eruption, short roots, developing tooth buds and growth issues. One major factor is the inherent instability of the occlusion in the mixed deciduous-permanent tooth phase. This case report documents a child in mixed dentition period with a complication arising due to direct fixation of the fractured mandible.

Image-Guided Internal Fixation of an Oblique Sagittal Split Fracture of C1 Lateral Mass with Motion Preservation: A Technical Report.

PubMed

Malcolm, James G; Tan, Lee A; Johnson, Andrew K

2017-07-20

A sagittal split fracture of the C1 lateral mass is an unstable subtype of C1 fractures and has a high propensity for developing late deformities and pain with nonoperative management. A primary internal fixation of this type of fracture has been recently described with good clinical outcomes and preservation of motion. We present a modified technique of primary internal fixation using an obliquely inserted C1 lag screw with imaging guidance. We successfully treated a 55-year-old woman with a unilateral C1 oblique sagittal split fracture who failed nonoperative management. Technical nuances are discussed with a review of pertinent literature.

A Brief History of Limb Lengthening.

PubMed

Birch, John G

2017-09-01

In the last 35 years, orthopaedic surgeons have witnessed 3 major advances in the technique of limb lengthening: "distraction osteogenesis" facilitated by Gavriil Ilizarov method and infinitely-adaptable circular fixator with fine-wire bone fragment fixation; the introduction of the "6-strut" computer program-assisted circular fixators to effect complex deformity correction simultaneously; and the development of motorized intramedullary lengthening nails. However, the principles and associated complications of these techniques are on the basis of observations by Codivilla, Putti, and Abbott from as much as 110 years ago. This review notes the contribution of these pioneers in limb lengthening, and the contribution of Thor Heyerdahl principles of tolerance and diversity to the dissemination of Ilizarov principles to the Western world.

Climatic and Grazing Controls on Biological Soil Crust Nitrogen Fixation in Semi-arid Ecosystems

NASA Astrophysics Data System (ADS)

Schwabedissen, S. G.; Reed, S.; Lohse, K. A.; Magnuson, T. S.

2014-12-01

Nitrogen, next to water, is believed to be the main limiting resource in arid and semi-arid ecosystems. Biological soil crusts (biocrusts) -a surface community of mosses, lichens and cyanobacteria-have been found to be the main influx of "new" nitrogen (N) into many dryland ecosystems. Controls on biocrust N fixation rates include climate (temperature and moisture), phosphorus availability, and disturbance factors such as trampling, yet a systematic examination of climatic and disturbance controls on biocrusts communities is lacking. Biocrust samples were collected along an elevation gradient in the Reynolds Creek Experimental Watershed near Murphy, Idaho. Four sites were selected from a sagebrush steppe ecosystem with precipitation ranging from ≤250mm/yr to ≥1100mm/yr. Each site included 5 grazed plots and one historic exclosure plot that has been free from grazing for more than 40 years. Five samples each were collected from under plants and from interplant spaces from the grazed plots and exclosures and analyzed for potential N fixation using an acetylene reduction assay. We hypothesized that N fixation rates would be the highest in the exclosures of the two middle sites along the elevation gradient, due to the lack of disturbance and optimal temperature and moisture, respectively. As predicted, results showed higher rates of potential N fixation in exclosures than non-exclosures at a mid-elevation 8.4 ± 3.1 kg N/ha/yr in the exclosures compared to 1.8 ± 1.5 kg N/ha/yr indicating that grazing may reduce N fixation activity. Interestingly, rates were 2-5 times lower under plant canopies compared to interplant spaces at all but the highest elevation site. Findings from our study suggest that biocrust N fixation may be a dominant input of N into theses dryland systems and, in line with our hypotheses, that climate, location within the landscape, and disturbance may interact to regulate the rates of this fundamental ecosystem process.

Biomechanical characteristics of fixation methods for floating pubic symphysis.

PubMed

Song, Wenhao; Zhou, Dongsheng; He, Yu

2017-03-07

Floating pubic symphysis (FPS) is a relatively rare injury caused by high-energy mechanisms. There are several fixation methods used to treat FPS, including external fixation, subcutaneous fixation, internal fixation, and percutaneous cannulated screw fixation. To choose the appropriate fixation, it is necessary to study the biomechanical performance of these different methods. The goal of this study was to compare the biomechanical characteristics of six methods by finite element analysis. A three-dimensional finite element model of FPS was simulated. Six methods were used in the FPS model, including external fixation (Ext), subcutaneous rod fixation (Sub-rod), subcutaneous plate fixation (Sub-plate), superior pectineal plate fixation (Int-sup), infrapectineal plate fixation (Int-ifa), and cannulated screw fixation (Int-scr). Compressive and rotational loads were then applied in all models. Biomechanical characteristics that were recorded and analyzed included construct stiffness, micromotion of the fracture gaps, von Mises stress, and stress distribution. The construct stiffness of the anterior pelvic ring was decreased dramatically when FPS occurred. Compressive stiffness was restored by the three internal fixation and Sub-rod methods. Unfortunately, rotational stiffness was not restored satisfactorily by the six methods. For micromotion of the fracture gaps, the displacement was reduced significantly by the Int-sup and Int-ifa methods under compression. The internal fixation methods and Sub-plate method performed well under rotation. The maximum von Mises stress of the implants was not large. For the plate-screw system, the maximum von Mises stress occurred over the region of the fracture and plate-screw joints. The maximum von Mises stress appeared on the rod-screw and screw-bone interfaces for the rod-screw system. The present study showed the biomechanical advantages of internal fixation methods for FPS from a finite element view. Superior stabilization of the anterior pelvic ring and fracture gaps was obtained by internal fixation. Subcutaneous fixation had satisfactory outcomes as well. Sub-rod fixation offered good anti-compression, while the Sub-plate fixation provided favorable anti-rotational capacity.

Two- to 4-Year Followup of a Short Stem THA Construct: Excellent Fixation, Thigh Pain a Concern.

PubMed

Amendola, Richard L; Goetz, Devon D; Liu, Steve S; Callaghan, John J

2017-02-01

Short stem cementless femoral components were developed to aid insertion through smaller incisions, preserve metaphyseal bone, and potentially decrease or limit the incidence of thigh pain. Despite some clinical success, the senior author (DDG) believed a higher percentage of his patients who had received a cementless short stem design were experiencing thigh pain, which, coupled with concerns about bone ingrowth fixation, motivated the review of this case series. (1) What is the proportion of patients treated with a short stem cementless THA femoral component that develop thigh pain and what are the hip scores of this population? (2) What are the radiographic results, specifically with respect to bone ingrowth fixation and stress shielding, of this design? (3) Are there particular patient or procedural factors that are associated with thigh pain with this short stem design? Two hundred sixty-one primary THAs were performed in 238 patients by one surgeon between November 2010 and August 2012. During this time period, all patients undergoing primary THA by this surgeon received the same cementless short titanium taper stem. Seven patients (eight hips) died and five patients (five hips) were lost to followup, leaving 226 patients (248 hips) with a mean followup of 3 years (range, 2-5 years). Patients rated their thigh pain during activity or rest at final followup on a 10-point visual analog scale. Harris hip scores (HHS) were obtained at every clinic appointment. Thigh pain was evaluated at the final followup or by contacting the patient by phone. Radiographs were evaluated for bone-implant fixation, bone remodeling, and osteolysis. An attempt was made to correlate thigh pain with patient demographics, implant specifications, or radiographic findings. Seventy-six percent of hips (180 of 238) had no thigh pain, 16% of hips (37 of 238) had mild thigh pain, and 9% (21 of 238) had moderate or severe thigh pain. Preoperatively, mean HHS was 47 (SD, 16) and at last followup, mean HHS was 88 (SD, 13). There were two femoral revisions, one for severe thigh pain and the other for infection. All but two components demonstrated bone ingrowth fixation (99%). Femoral stress shielding was mild in 64% of hips (135 of 212), moderate in 0.5% (one of 212), and severe in no hips. There is an inverse linear relationship between age and severity of thigh pain (r = -0.196; p < 0.0024). Although reliable fixation was achieved and good HHS were attained, the frequency and severity of thigh pain with this short cementless stem were concerning. The surgeon has subsequently abandoned this short stem design and returned to a conventional length stem. Future study direction might investigate the biomechanical grounds for the thigh pain associated with this stem design. Level IV, therapeutic study.

Scaphoid Waist Internal Fixation for Fractures Trial (SWIFFT) protocol: a pragmatic multi-centre randomised controlled trial of cast treatment versus surgical fixation for the treatment of bi-cortical, minimally displaced fractures of the scaphoid waist in adults.

PubMed

Dias, Joseph; Brealey, Stephen; Choudhary, Surabhi; Cook, Liz; Costa, Matthew; Fairhurst, Caroline; Hewitt, Catherine; Hodgson, Stephen; Jefferson, Laura; Jeyapalan, Kanagaratnam; Keding, Ada; Leighton, Paul; Rangan, Amar; Richardson, Gerry; Rothery, Claire; Taub, Nicholas; Thompson, John; Torgerson, David

2016-06-04

A scaphoid fracture is the most common type of carpal fracture affecting young active people. The optimal management of this fracture is uncertain. When treated with a cast, 88 to 90 % of these fractures unite; however, for the remaining 10-12 % the non-union almost invariably leads to arthritis. The alternative is surgery to fix the scaphoid with a screw at the outset. We will conduct a randomised controlled trial (RCT) of 438 adult patients with a "clear" and "bicortical" scaphoid waist fracture on plain radiographs to evaluate the clinical effectiveness and cost-effectiveness of plaster cast treatment (with fixation of those that fail to unite) versus early surgical fixation. The plaster cast treatment will be immobilisation in a below elbow cast for 6 to 10 weeks followed by mobilisation. If non-union is confirmed on plain radiographs and/or Computerised Tomogram at 6 to 12 weeks, then urgent surgical fixation will be performed. This is being compared with immediate surgical fixation with surgeons using their preferred technique and implant. These treatments will be undertaken in trauma units across the United Kingdom. The primary outcome and end-point will be the Patient Rated Wrist Evaluation (a patient self-reported assessment of wrist pain and function) at 52 weeks and also measured at 6, 12, 26 weeks and 5 years. Secondary outcomes include an assessment of radiological union of the fracture; quality of life; recovery of wrist range and strength; and complications. We will also qualitatively investigate patient experiences of their treatment. Scaphoid fractures are an important public health problem as they predominantly affect young active individuals in the more productive working years of their lives. Non-union, if untreated, can lead to arthritis which can disable patients at a very young age. There is a rapidly increasing trend for immediate surgical fixation of these fractures but there is insufficient evidence from existing RCTs to support this. The SWIFFT Trial is a rigorously designed and adequately powered study which aims to contribute to the evidence-base to inform clinical decisions for the treatment of this common fracture in adults. The trial is registered with the International Standard Randomised Controlled Trial Register ( ISRCTN67901257 ). Date registration assigned was 13/02/2013.

The effect of hubs and shortcuts on fixation time in evolutionary graphs

NASA Astrophysics Data System (ADS)

Askari, Marziyeh; Moradi Miraghaei, Zeinab; Aghababaei Samani, Keivan

2017-07-01

How can a new species (like a gene, an idea, or a strategy) take over the whole of a population? This process, which is called fixation, is considerably affected by the structure of the population. There are two key quantities to quantify the fixation process, namely fixation probability and fixation time. Fixation probability has been vastly studied in recent years, but fixation time has not been completely explored, yet. This is because the discovery of a relationship between fixation time and network structure is quite challenging. In this paper we investigate this relationship for a number of well-known complex networks. We show that the existence of a few high-degree nodes (hubs) in the network results in a longer fixation time, while the existence of a few short-cuts decreases the fixation time. Furthermore we investigate the effect of network parameters, such as connection probability, on fixation time. We show that by increasing the density of edges, fixation time decreases for all types of studied networks. Finally, we survey the effect of rewiring probability in a Watts-Strogatz network on fixation time.

Comparison of Tibiofemoral Contact Mechanics After Various Transtibial and All-Inside Fixation Techniques for Medial Meniscus Posterior Root Radial Tears in a Porcine Model.

PubMed

Chung, Kyu Sung; Choi, Choong Hyeok; Bae, Tae Soo; Ha, Jeong Ku; Jun, Dal Jae; Wang, Joon Ho; Kim, Jin Goo

2018-04-01

To compare tibiofemoral contact mechanics after fixation for medial meniscus posterior root radial tears (MMPRTs). Seven fresh knees from mature pigs were used. Each knee was tested under 5 conditions: normal knee, MMPRT, pullout fixation with simple sutures, fixation with modified Mason-Allen sutures, and all-inside fixation using Fastfix 360. The peak contact pressure and contact surface area were evaluated using a capacitive sensor positioned between the meniscus and tibial plateau, under a 1,000-N compression force, at different flexion angles (0°, 30°, 60°, and 90°). The peak contact pressure was significantly higher in MMPRTs than in normal knees (P = .018). Although the peak contact pressure decreased significantly after fixation at all flexion angles (P = .031), it never recovered to the values noted in the normal meniscus. No difference was observed among fixation groups (P = .054). The contact surface area was significantly lower in MMPRTs than in the normal meniscus (P = .018) and increased significantly after fixation at all flexion angles (P = .018) but did not recover to within normal limits. For all flexion angles except 60°, the contact surface area was significantly higher for fixation with Mason-Allen sutures than for fixation with simple sutures or all-inside fixation (P = .027). At 90° of flexion, the contact surface area was significantly better for fixation with simple sutures than for all-inside fixation (P = .031). The peak contact pressure and contact surface area improved significantly after fixation, regardless of the fixation method, but did not recover to the levels noted in the normal meniscus after any type of fixation. Among the fixation methods evaluated in this time 0 study, fixation using modified Mason-Allen sutures provided a superior contact surface area compared with that noted after fixation using simple sutures or all-inside fixation, except at 60° of flexion. However, this study had insufficient power to accurately detect the differences between the outcomes of various fixation methods. Our results in a porcine model suggest that fixation can restore tibiofemoral contact mechanics in MMPRT and that fixation with a locking mechanism leads to superior biomechanical properties. Copyright © 2017 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

Induction of Photosynthetic Carbon Fixation in Anoxia Relies on Hydrogenase Activity and Proton-Gradient Regulation-Like1-Mediated Cyclic Electron Flow in Chlamydomonas reinhardtii.

PubMed

Godaux, Damien; Bailleul, Benjamin; Berne, Nicolas; Cardol, Pierre

2015-06-01

The model green microalga Chlamydomonas reinhardtii is frequently subject to periods of dark and anoxia in its natural environment. Here, by resorting to mutants defective in the maturation of the chloroplastic oxygen-sensitive hydrogenases or in Proton-Gradient Regulation-Like1 (PGRL1)-dependent cyclic electron flow around photosystem I (PSI-CEF), we demonstrate the sequential contribution of these alternative electron flows (AEFs) in the reactivation of photosynthetic carbon fixation during a shift from dark anoxia to light. At light onset, hydrogenase activity sustains a linear electron flow from photosystem II, which is followed by a transient PSI-CEF in the wild type. By promoting ATP synthesis without net generation of photosynthetic reductants, the two AEF are critical for restoration of the capacity for carbon dioxide fixation in the light. Our data also suggest that the decrease in hydrogen evolution with time of illumination might be due to competition for reduced ferredoxins between ferredoxin-NADP(+) oxidoreductase and hydrogenases, rather than due to the sensitivity of hydrogenase activity to oxygen. Finally, the absence of the two alternative pathways in a double mutant pgrl1 hydrogenase maturation factor G-2 is detrimental for photosynthesis and growth and cannot be compensated by any other AEF or anoxic metabolic responses. This highlights the role of hydrogenase activity and PSI-CEF in the ecological success of microalgae in low-oxygen environments. © 2015 American Society of Plant Biologists. All Rights Reserved.

Diurnal variation in the functioning of cowpea nodules.

PubMed

Rainbird, R M; Atkins, C A; Pate, J S

1983-06-01

Nitrogenase (EC 1.7.99.2) activity of nodules of cowpea (Vigna unguiculata [L.] Walp), maintained under conditions of a 12-hour day at 30 degrees C and 800 to 1,000 microeinsteins per square meter per second (photosynthetically active radiation) and a 12-hour night at 20 degrees C, showed a marked diurnal variation with the total electron flux through the enzyme at night being 60% of that in the photoperiod. This diurnal pattern was, however, due to changes in hydrogen evolution. The rate of nitrogen fixation, measured by short-term (15)N(2) assimilation or estimated from the difference in hydrogen evolution in air or Ar:O(2) (80:20; v/v), showed no diurnal variation. Carbon dioxide released from nodules showed a diurnal variation synchronized with that of nitrogenase functioning and, as a consequence, the apparent ;respiratory cost' of nitrogen fixation in the photoperiod was almost double that at night (9.74 +/- 0.38 versus 5.70 +/- 0.90 moles CO(2) evolved per mole N(2) fixed). Separate carbon and nitrogen balances constructed for nodules during the photoperiod and dark period showed that, at night, nodule functioning required up to 40% less carbohydrate to achieve the same level of nitrogen fixation as during the photoperiod (2.4 versus 1.4 moles hexose per mole N(2) fixed).Stored reserves of nonstructural carbohydrate of the nodule only partly satisfied the requirement for carbon at night, and fixation was dependent on continued import of translocated assimilates at all times. Measurements of the soluble nitrogen pools of the nodule together with (15)N studies indicated that, both during the day and night, nitrogenous products of fixation were effectively translocated to all organs of the host plant despite low rates of transpiration at night. Reduced fluxes of water through the plant at night were apparently counteracted by increased concentration of nitrogen, especially as ureides, in the xylem stream.

A Minimal Nitrogen Fixation Gene Cluster from Paenibacillus sp. WLY78 Enables Expression of Active Nitrogenase in Escherichia coli

PubMed Central

Zhao, Dehua; Liu, Xiaomeng; Zhang, Bo; Xie, Jianbo; Hong, Yuanyuan; Li, Pengfei; Chen, Sanfeng; Dixon, Ray; Li, Jilun

2013-01-01

Most biological nitrogen fixation is catalyzed by molybdenum-dependent nitrogenase, an enzyme complex comprising two component proteins that contains three different metalloclusters. Diazotrophs contain a common core of nitrogen fixation nif genes that encode the structural subunits of the enzyme and components required to synthesize the metalloclusters. However, the complement of nif genes required to enable diazotrophic growth varies significantly amongst nitrogen fixing bacteria and archaea. In this study, we identified a minimal nif gene cluster consisting of nine nif genes in the genome of Paenibacillus sp. WLY78, a gram-positive, facultative anaerobe isolated from the rhizosphere of bamboo. We demonstrate that the nif genes in this organism are organized as an operon comprising nifB, nifH, nifD, nifK, nifE, nifN, nifX, hesA and nifV and that the nif cluster is under the control of a σ70 (σA)-dependent promoter located upstream of nifB. To investigate genetic requirements for diazotrophy, we transferred the Paenibacillus nif cluster to Escherichia coli. The minimal nif gene cluster enables synthesis of catalytically active nitrogenase in this host, when expressed either from the native nifB promoter or from the T7 promoter. Deletion analysis indicates that in addition to the core nif genes, hesA plays an important role in nitrogen fixation and is responsive to the availability of molybdenum. Whereas nif transcription in Paenibacillus is regulated in response to nitrogen availability and by the external oxygen concentration, transcription from the nifB promoter is constitutive in E. coli, indicating that negative regulation of nif transcription is bypassed in the heterologous host. This study demonstrates the potential for engineering nitrogen fixation in a non-nitrogen fixing organism with a minimum set of nine nif genes. PMID:24146630

Distraction for proximal interphalangeal joint contractures: long-term results.

PubMed

Houshian, Shirzad; Jing, Shan Shan; Kazemian, Gholam Hussein; Emami-Moghaddam-Tehrani, Mohammad

2013-10-01

To report the medium- to long-term outcomes of joint distraction using a unilateral external fixator in the treatment of chronic post-traumatic proximal interphalangaeal (PIP) joint contractures. Between September 2001 and October 2011, 94 consecutive patients (98 PIP joints) with a mean age of 43 years (range, 17-69 y) were treated with external fixation for chronic flexion deformity of the PIP joint from trauma. The average time from injury to surgery was 48 months (range, 6-84 mo), and the duration of joint distraction was 10 days (range, 7-22 d). Patients were followed for a mean period of 54 months (range, 12-72 mo). The average gain in joint flexion was 25° and in joint extension was 40°. The mean improvement in the active range of movement was 67° (range. 30°-90°). There was no loss of motion on the latest follow-up. Patients younger than 40 years fared slightly better than those older than 40 years. Two patients developed swelling, pain, and erythema during treatment, which resolved upon temporarily stopping the distraction process. There were 12 cases of superficial pin-site infections, which were managed conservatively without serious complications or adverse outcome. External fixation is a simple and effective treatment modality for chronic traumatic PIP joint contractures with good predictable medium- to long-term results. Careful patient selection and monitoring are required. Copyright © 2013 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

Comparative Study of Intramedullary Hammertoe Fixation.

PubMed

Obrador, Caterina; Losa-Iglesias, Marta; Becerro-de-Bengoa-Vallejo, Ricardo; Kabbash, Christina A

2018-04-01

Temporary Kirschner wire fixation (K-wire) is a widely used, low-cost fixation method for the correction of hammertoe deformity. Reported complications associated with K-wires prompted the development of new implants over the past decade. However, there is a lack of literature on comparative studies analyzing functional outcomes using validated questionnaires. The purpose of this study was to analyze functional outcomes in patients who had undergone proximal interphalangeal joint fusion using 2 types of intramedullary implant, the Smart Toe and the TenFuse, and to compare them with the outcomes in patients treated with standard K-wire fixation. A retrospective review of operative hammertoe correction by a single surgeon was performed in 96 patients followed for more than 12 months. Functional outcome was assessed using the Foot Function Index (FFI), the Short Form 36 (SF-36), and the 10-point visual analog scale (VAS) validated questionnaires. Complications and fusion rates were also evaluated. Several patients in the study underwent corrections in different toes; thus, a total of 186 toes were included in the study. From these, 65 toes (34.9%) were treated with K-wire fixation, 94 (50.5%) with Smart Toe titanium implant, and 27 (14.5%) with TenFuse allograft implant. No statistically significant differences in functional outcome and incidence of complications were observed among the 3 fixation groups, although the 2 intramedullary implants were associated with greater fusion rates and patient satisfaction. Breakage of the Smart Toe implant was significantly higher than that of the other fixations, with 10.6% of implants breaking within the first year postoperatively. SF-36 and VAS scores decreased 12 months after surgery for the 3 types of fixation, with no statistically significant differences observed. The use of Smart Toe and TenFuse implants provided operative outcomes comparable to those obtained using a K-wire fixation and slightly better patient satisfaction. Our results suggest that utilization of these implants for hammertoe correction was a reasonable choice that provided good alignment, pain reduction, and improved function at final follow-up. However, they are more expensive than K-wires. For this reason, in-depth cost-benefit studies would be required to justify their use as a standard treatment. Level III, comparative series.

Effects of three different preservation methods on the mechanical properties of human and bovine cortical bone.

PubMed

Unger, Stefan; Stefan, Unger; Blauth, Michael; Michael, Blauth; Schmoelz, Werner; Werner, Schmoelz

2010-12-01

In the development of new strategies for fracture fixation, new methods have to be tested biomechanically under in vitro conditions before clinical trials can be performed. The gold standard for laboratory evaluations is fresh-frozen specimen. As the availability of fresh-frozen specimens is limited and since their use bears infectious risks, specimens treated with various chemical embalming fluids are also used. These preservation methods may alter the mechanical properties of the specimens used. Therefore, the aims of the present study were to determine the effects of three different preservation methods (formalin fixation (FO), Thiel-fixation (TH), and alcohol-glycerine fixation (AG)) on the elastic and postyield mechanical properties of cortical bone and to compare these properties to those of fresh-frozen (FF) specimens. Cylindrical cortical specimens (diameter 3mm, length 60 mm) were obtained from human femurs (n=48) and bovine tibiae (n=40). Before specimen immersion in different fixation fluids, bone mineral density (BMD) as well as the initial Young's modulus was determined. The Young's modulus was determined in a nondestructive bending test, and measurements were repeated after 6 months of immersion in fixative solution. Subsequent to the nondestructive test, a destructive 3-point bending test was conducted to assess the postyield and fracture properties. The BMD as well as the initial Young's modulus showed no significant differences between the four test groups. After 6 months in fixative solution, the Young's modulus was significantly lowered in human Thiel specimens and only showed minor changes in formalin- and alcohol-glycerine-treated specimens. The plastic energy absorption of human and bovine specimens was altered significantly. Formalin as well as alcohol-glycerine fixation yielded a significant decrease in plastic energy absorption, whereas Thiel fixation significantly increased the plastic energy absorption. Because of the significantly altered plastic mechanical properties of cortical bone, the use fresh-frozen bone specimens is recommended in biomechanical studies investigating failure loads of orthopaedic implants. The use of embalmed specimens should be restricted to pilot tests. Copyright © 2010 Elsevier Inc. All rights reserved.

Eighth international congress on nitrogen fixation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1990-01-01

This volume contains the proceedings of the Eighth International Congress on Nitrogen Fixation held May 20--26, 1990 in Knoxville, Tennessee. The volume contains abstracts of individual presentations. Sessions were entitled Recent Advances in the Chemistry of Nitrogen Fixation, Plant-microbe Interactions, Limiting Factors of Nitrogen Fixation, Nitrogen Fixation and the Environment, Bacterial Systems, Nitrogen Fixation in Agriculture and Industry, Plant Function, and Nitrogen Fixation and Evolution.

Eighth international congress on nitrogen fixation. Final program

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1990-12-31

This volume contains the proceedings of the Eighth International Congress on Nitrogen Fixation held May 20--26, 1990 in Knoxville, Tennessee. The volume contains abstracts of individual presentations. Sessions were entitled Recent Advances in the Chemistry of Nitrogen Fixation, Plant-microbe Interactions, Limiting Factors of Nitrogen Fixation, Nitrogen Fixation and the Environment, Bacterial Systems, Nitrogen Fixation in Agriculture and Industry, Plant Function, and Nitrogen Fixation and Evolution.

Developmental changes in face visual scanning in autism spectrum disorder as assessed by data-based analysis

PubMed Central

Amestoy, Anouck; Guillaud, Etienne; Bouvard, Manuel P.; Cazalets, Jean-René

2015-01-01

Individuals with autism spectrum disorder (ASD) present reduced visual attention to faces. However, contradictory conclusions have been drawn about the strategies involved in visual face scanning due to the various methodologies implemented in the study of facial screening. Here, we used a data-driven approach to compare children and adults with ASD subjected to the same free viewing task and to address developmental aspects of face scanning, including its temporal patterning, in healthy children, and adults. Four groups (54 subjects) were included in the study: typical adults, typically developing children, and adults and children with ASD. Eye tracking was performed on subjects viewing unfamiliar faces. Fixations were analyzed using a data-driven approach that employed spatial statistics to provide an objective, unbiased definition of the areas of interest. Typical adults expressed a spatial and temporal strategy for visual scanning that differed from the three other groups, involving a sequential fixation of the right eye (RE), left eye (LE), and mouth. Typically developing children, adults and children with autism exhibited similar fixation patterns and they always started by looking at the RE. Children (typical or with ASD) subsequently looked at the LE or the mouth. Based on the present results, the patterns of fixation for static faces that mature from childhood to adulthood in typical subjects are not found in adults with ASD. The atypical patterns found after developmental progression and experience in ASD groups appear to remain blocked in an immature state that cannot be differentiated from typical developmental child patterns of fixation. PMID:26236264

The operative outcomes of displaced medial-end clavicle fractures.

PubMed

Sidhu, Verinder S; Hermans, Deborah; Duckworth, David G

2015-11-01

Nonoperative treatment of displaced medial clavicle fractures often leads to poor functional outcomes and painful nonunions. This study investigates the functional outcomes of patients undergoing operative fixation of these fractures. We investigated 27 patients undergoing operative fixation of a medial clavicle fracture; 24 had an acute, displaced fracture and 3 had fixation for nonunions. Preoperative radiographs or computed tomography scans were obtained, and data collected included age, sex, mechanism of injury, and fixation method. Follow-up included physical examination and radiographs for assessment of union; Disabilities of the Arm, Shoulder, and Hand scores at 12 months; and the recording of complications. The median age was 37 years (interquartile range, 17-47 years). There were 26 male patients and one female patient included, with 7 physeal injuries and 20 adult injuries. The most common mechanism of fracture was vehicular accident (n = 15). Three patients had operations for nonunions and 2 for a periprosthetic fracture medial to an existing plate. The fracture was fixed with plate and screws in 19 cases and with transosseous sutures in 8 cases. The median Disabilities of the Arm, Shoulder, and Hand score at 12 months was 0.4 (interquartile range, 0-5.0), with a union rate of 100% at 12 months. All patients had full shoulder range of motion at final follow-up and were able to return to preinjury occupational activities. There were no significant complications. Operative fixation of displaced medial clavicle fractures results in anatomic reconstruction and excellent functional outcomes, even in the setting of fixation performed for symptomatic nonunion. Early intervention can minimize the risk of painful nonunion. Crown Copyright © 2015. Published by Elsevier Inc. All rights reserved.

Review of techniques for monitoring the healing fracture of bones for implementation in an internally fixated pelvis.

PubMed

Wong, Lydia Chwang Yuh; Chiu, Wing Kong; Russ, Matthias; Liew, Susan

2012-03-01

Sacral fractures from high-impact trauma often cause instability in the pelvic ring structure. Treatment is by internal fixation which clamps the fractured edges together to promote healing. Healing could take up to 12 weeks whereby patients are bedridden to avoid hindrances to the fracture from movement or weight bearing activities. Immobility can lead to muscle degradation and longer periods of rehabilitation. The ability to determine the time at which the fracture is stable enough to allow partial weight-bearing is important to reduce hospitalisation time. This review looks into different techniques used for monitoring the fracture healing of bones which could lead to possible methods for in situ and non-invasive assessment of healing fracture in a fixated pelvis. Traditional techniques being used include radiology and CT scans but were found to be unreliable at times and very subjective in addition to being non in situ. Strain gauges have proven to be very effective for accurate assessment of fracture healing as well as stability for long bones with external fixators but may not be suitable for an internally fixated pelvis. Ultrasound provides in situ monitoring of stiffness recovery but only assesses local fracture sites close to the skin surface and has only been tested on long bones. Vibration analysis can detect non-uniform healing due to its assessment of the overall structure but may suffer from low signal-to-noise ratio due to damping. Impedance techniques have been used to assess properties of non-long bones but recent studies have only been conducted on non-biological materials and more research needs to be done before it can be applicable for monitoring healing in the fixated pelvis. Copyright © 2011 IPEM. Published by Elsevier Ltd. All rights reserved.

Neural mechanisms of attention become more specialised during infancy: Insights from combined eye tracking and EEG.

PubMed

Kulke, Louisa; Atkinson, Janette; Braddick, Oliver

2017-03-01

The Fixation Shift Paradigm (FSP) measures infants' ability to shift gaze from a central fixation stimulus to a peripheral target (e.g. Hood & Atkinson, 1993: Infant Behavior and Development, 16(4), 405-422). Cortical maturation has been suggested as crucial for the developing ability to shift attention. This study investigated the development of neural mechanisms by combining EEG with simultaneous eye tracking during FSP testing, in typically developing infants aged between 1 and 8 months. The most prominent neural response was a frontal positivity which occurred only in the hemisphere contralateral to the target in the youngest infants but became more ipsilateral with age. This changing lateralisation was associated with improving ability to shift attention (decreasing saccade latencies and fewer 'sticky fixations'-failures to disengage attention from the central target). These findings suggest that the lateralisation of neural responses develops during infancy, possibly due to developing intracortical connections, allowing infants to shift attention more efficiently. Successful use of combined simultaneous remote eye tracking and EEG to measure infant attention shifts. Neural responses involved in attention shifts change in the first year of life. The lateralisation of EEG responses changes with age in the first year of life. Frontal cortex is involved in attention shifts from around 2 months of age. © 2016 Wiley Periodicals, Inc.

In‐loop flow [11C]CO2 fixation and radiosynthesis of N,N′‐[11C]dibenzylurea

PubMed Central

Downey, Joseph; Bongarzone, Salvatore; Hader, Stefan

2017-01-01

Cyclotron‐produced carbon‐11 is a highly valuable radionuclide for the production of positron emission tomography (PET) radiotracers. It is typically produced as relatively unreactive carbon‐11 carbon dioxide ([11C]CO2), which is most commonly converted into a more reactive precursor for synthesis of PET radiotracers. The development of [11C]CO2 fixation methods has more recently enabled the direct radiolabelling of a diverse array of structures directly from [11C]CO2, and the advantages afforded by the use of a loop‐based system used in 11C‐methylation and 11C‐carboxylation reactions inspired us to apply the [11C]CO2 fixation “in‐loop.” In this work, we developed and investigated a new ethylene tetrafluoroethylene (ETFE) loop‐based [11C]CO2 fixation method, enabling the fast and efficient, direct‐from‐cyclotron, in‐loop trapping of [11C]CO2 using mixed DBU/amine solutions. An optimised protocol was integrated into a proof‐of‐concept in‐loop flow radiosynthesis of N,N′‐[11C]dibenzylurea. This reaction exhibited an average 78% trapping efficiency and a crude radiochemical purity of 83% (determined by radio‐HPLC), giving an overall nonisolated radiochemical yield of 72% (decay‐corrected) within just 3 minutes from end of bombardment. This proof‐of‐concept reaction has demonstrated that efficient [11C]CO2 fixation can be achieved in a low‐volume (150 μL) ETFE loop and that this can be easily integrated into a rapid in‐loop flow radiosynthesis of carbon‐11–labelled products. This new in‐loop methodology will allow fast radiolabelling reactions to be performed using cheap/disposable ETFE tubing setup (ideal for good manufacturing practice production) thereby contributing to the widespread usage of [11C]CO2 trapping/fixation reactions for the production of PET radiotracers. PMID:28977686

In-loop flow [11 C]CO2 fixation and radiosynthesis of N,N'-[11 C]dibenzylurea.

PubMed

Downey, Joseph; Bongarzone, Salvatore; Hader, Stefan; Gee, Antony D

2018-03-01

Cyclotron-produced carbon-11 is a highly valuable radionuclide for the production of positron emission tomography (PET) radiotracers. It is typically produced as relatively unreactive carbon-11 carbon dioxide ([ 11 C]CO 2 ), which is most commonly converted into a more reactive precursor for synthesis of PET radiotracers. The development of [ 11 C]CO 2 fixation methods has more recently enabled the direct radiolabelling of a diverse array of structures directly from [ 11 C]CO 2 , and the advantages afforded by the use of a loop-based system used in 11 C-methylation and 11 C-carboxylation reactions inspired us to apply the [ 11 C]CO 2 fixation "in-loop." In this work, we developed and investigated a new ethylene tetrafluoroethylene (ETFE) loop-based [ 11 C]CO 2 fixation method, enabling the fast and efficient, direct-from-cyclotron, in-loop trapping of [ 11 C]CO 2 using mixed DBU/amine solutions. An optimised protocol was integrated into a proof-of-concept in-loop flow radiosynthesis of N,N'-[ 11 C]dibenzylurea. This reaction exhibited an average 78% trapping efficiency and a crude radiochemical purity of 83% (determined by radio-HPLC), giving an overall nonisolated radiochemical yield of 72% (decay-corrected) within just 3 minutes from end of bombardment. This proof-of-concept reaction has demonstrated that efficient [ 11 C]CO 2 fixation can be achieved in a low-volume (150 μL) ETFE loop and that this can be easily integrated into a rapid in-loop flow radiosynthesis of carbon-11-labelled products. This new in-loop methodology will allow fast radiolabelling reactions to be performed using cheap/disposable ETFE tubing setup (ideal for good manufacturing practice production) thereby contributing to the widespread usage of [ 11 C]CO 2 trapping/fixation reactions for the production of PET radiotracers. © 2017 The Authors. Journal of Labelled Compounds and Radiopharmaceuticals Published by John Wiley & Sons, Ltd.

Less-invasive stabilization of rib fractures by intramedullary fixation: a biomechanical evaluation.

PubMed

Bottlang, Michael; Helzel, Inga; Long, William; Fitzpatrick, Daniel; Madey, Steven

2010-05-01

This study evaluated intramedullary fixation of rib fractures with Kirschner wires and novel ribs splints. We hypothesized that rib splints can provide equivalent fixation strength while avoiding complications associated with Kirschner wires, namely wire migration and cutout. The durability, strength, and failure modes of rib fracture fixation with Kirschner wires and rib splints were evaluated in 22 paired human ribs. First, intact ribs were loaded to failure to determine their strength. After fracture fixation with Kirschner wires and rib splints, fixation constructs were dynamically loaded to 360,000 cycles at five times the respiratory load to determine their durability. Finally, constructs were loaded to failure to determine residual strength and failure modes. All constructs sustained dynamic loading without failure. Dynamic loading caused three times more subsidence in Kirschner wire constructs (1.2 mm +/- 1.4 mm) than in rib splint constructs (0.4 mm +/- 0.2 mm, p = 0.09). After dynamic loading, rib splint constructs remained 48% stronger than Kirschner wire constructs (p = 0.001). Five of 11 Kirschner wire constructs failed catastrophically by cutting through the medial cortex, leading to complete loss of stability and wire migration through the lateral cortex. The remaining six constructs failed by wire bending. Rib splint constructs failed by development of fracture lines along the superior and interior cortices. No splint construct failed catastrophically, and all splint constructs retained functional reduction and fixation. Because of their superior strength and absence of catastrophic failure mode, rib splints can serve as an attractive alternative to Kirschner wires for intramedullary stabilization of rib fractures, especially in the case of posterior rib fractures where access for plating is limited.

The fixation effect of a silk fibroin-bacterial cellulose composite plate in segmental defects of the zygomatic arch: an experimental study.

PubMed

Lee, Jung Min; Kim, Ji Heui; Lee, Ok Joo; Park, Chan Hum

2013-06-01

Bioresorbable fixation systems have been popular for the treatment of facial fractures. However, their mechanical properties are uncertain and complications have been reported. To overcome these problems, we developed a bioresorbable fixation plate using a composite of silk fibroin and bacterial cellulose (SF-BC) with biodegradability and increased biocompatibility. To investigate the regenerative effect of the bioresorbable SF-BC fixation plate on zygomatic arch defects in rats. In vivo animal study. The SF-BC composite plate had a tensile strength similar to that of a polylactic acid plate and a tight, pore-free microstructure. Bilateral segmental bone defects (2 mm in length) were created in the zygomatic arches of adult rats. One side was fixed with the SF-BC composite plate, and the other side was left without fixation. Academic research laboratory. Fifteen adult Sprague-Dawley rats. Fixation of the zygomatic arch defect with the SF-BC composite plate. Micro-computed tomography and histological evaluation of bone samples. Gross inspection revealed no specific complication. At 1, 2, 4, and 8 postoperative weeks, the zygomatic arches were explored by micro-computed tomography and histological examination. Control sides did not heal completely and showed bony degeneration and necrosis during the 8-week follow-up. However, we observed new bone formation in sides treated with the SF-BC composite plate, and bony defects were completely healed within 8 weeks. The SF-BC composite plate is a potential candidate for a new bioresorbable fixation system. Our composite material could considerably shorten bone regeneration time. Additional study of the control of biodegradability and mechanical properties of SF-BC composite plates and a comparative study with the resorbable plates currently in use should be undertaken.

Clinical results of resection arthrodesis by triangular external fixation for posttraumatic arthrosis of the ankle joint in 89 cases.

PubMed

Kiene, J; Schulz, Arndt P; Hillbricht, S; Jürgens, Ch; Paech, A

2009-01-28

The methods for ankle arthrodesis differ significantly, probably a sign that no method is clearly superior to others. In the last ten years there is a clear favour toward internal fixation. We retrospectively evaluate the technique and evaluate the clinical long term results of external fixation in a triangular frame. From 1994 to 2001 a consecutive series of 95 patients with end stage arthritis of the ankle joint were treated. Retrospectively the case notes were evaluated regarding trauma history, medical complaints, further injuries and illnesses, walking and pain status and occupational issues and the clinical examination before arthrodesis. Mean age at the index procedure was 45.4 years (18-82), 67 patients were male (70.5%). Via a bilateral approach the malleoli and the joint surfaces were resected. An AO fixator was applied with two Steinmann-nails inserted with approximately 8 cm distance in the distal tibia, one in the neck of the talus and one in the dorsal calcaneus. The fixator was removed after approximately 12 weeks. Follow up examination at mean 4.4 years included a standardised questionnaire and a clinical examination including the criteria of the AOFAS-Score and radiographs. Due to different complications, 8 (8.9%) further surgical procedures were necessary including 1 below knee amputation. In 4 patients a non-union of the ankle arthrodesis developed (4.5%). The mean AOFAS score improved from 20.8 to 69.3 points. Non-union rates and clinical results of arthrodesis by triangular external fixation of the ankle joint do not differ to internal fixation methods. The complication rate and the reduced patient comfort reserve this method mainly for infected arthritis and complicated soft tissue situations.

Clinical results of resection arthrodesis by triangular external fixation for posttraumatic arthrosis of the ankle joint in 89 cases

PubMed Central

2009-01-01

The methods for ankle arthrodesis differ significantly, probably a sign that no method is clearly superior to others. In the last ten years there is a clear favour toward internal fixation. We retrospectively evaluate the technique and evaluate the clinical long term results of external fixation in a triangular frame. Patients and Methods From 1994 to 2001 a consecutive series of 95 patients with end stage arthritis of the ankle joint were treated. Retrospectively the case notes were evaluated regarding trauma history, medical complaints, further injuries and illnesses, walking and pain status and occupational issues and the clinical examination before arthrodesis. Mean age at the index procedure was 45.4 years (18-82), 67 patients were male (70.5%). Via a bilateral approach the malleoli and the joint surfaces were resected. An AO fixator was applied with two Steinmann-nails inserted with approximately 8 cm distance in the distal tibia, one in the neck of the talus and one in the dorsal calcaneus. The fixator was removed after approximately 12 weeks. Follow up examination at mean 4.4 years included a standardised questionnaire and a clinical examination including the criteria of the AOFAS-Score and radiographs. Results: Due to different complications, 8 (8.9%) further surgical procedures were necessary including 1 below knee amputation. In 4 patients a non-union of the ankle arthrodesis developed (4.5%). The mean AOFAS score improved from 20.8 to 69.3 points. Conclusion Non-union rates and clinical results of arthrodesis by triangular external fixation of the ankle joint do not differ to internal fixation methods. The complication rate and the reduced patient comfort reserve this method mainly for infected arthritis and complicated soft tissue situations. PMID:19258207

Bronchoscopic Implantation of a Novel Wireless Electromagnetic Transponder in the Canine Lung: A Feasibility Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mayse, Martin L.; Parikh, Parag J.; Lechleiter, Kristen M.

2008-09-01

Purpose: The success of targeted radiation therapy for lung cancer treatment is limited by tumor motion during breathing. A real-time, objective, nonionizing, electromagnetic localization system using implanted electromagnetic transponders has been developed (Beacon electromagnetic transponder, Calypso Medical Technologies, Inc., Seattle, WA). We evaluated the feasibility and fixation of electromagnetic transponders bronchoscopically implanted in small airways of canine lungs and compared to results using gold markers. Methods and Materials: After approval of the Animal Studies Committee, five mongrel dogs were anesthetized, intubated, and ventilated. Three transponders were inserted into the tip of a plastic catheter, passed through the working channel ofmore » a flexible bronchoscope, and implanted into small airways of a single lobe using fluoroscopic guidance. This procedure was repeated for three spherical gold markers in the opposite lung. One, 7, 14, 28, and 60 days postimplantation imaging was used to assess implant fixation. Results: Successful bronchoscopic implantation was possible for 15 of 15 transponders and 12 of 15 gold markers; 3 markers were deposited in the pleural space. Fixation at 1 day was 15 of 15 for transponders and 12 of 12 for gold markers. Fixation at 60 days was 6 of 15 for transponders and 7 of 12 for gold markers, p value = 0.45. Conclusions: Bronchoscopic implantation of both transponders and gold markers into the canine lung is feasible, but fixation rates are low. If fixation rates can be improved, implantable electromagnetic transponders may allow improved radiation therapy for lung cancer by providing real-time continuous target tracking. Developmental work is under way to improve the fixation rates and to reduce sensitivity to implantation technique.« less

Hydrocephalus Caused by Fat Embolism: A Rare Complication of Atlanto-Axial Fixation for Odontoid Fractures.

PubMed

Wang, Chun-Hao; Chang, Peng-Yuan; Wu, Jau-Ching; Tu, Tsung-Hsi; Wu, Ching-Lan; Huang, Wen-Cheng; Cheng, Henrich

2016-06-01

Odontoid fracture is not uncommon and surgical treatment that uses posterior screw/rod fixation is an acceptable option. This is the first report of delayed hydrocephalus due to subarachnoid fat migration as a complication of posterior atlanto-axial (AA) fixation. A 27-year-old man underwent posterior C1 lateral mass and C2 pedicle screw fixation for a recent Anderson-D'Alonzo type 2 odontoid fracture. Autologous bone graft was wired for onlay fusion. The surgery was smooth, except that there was an incidental durotomy intraoperatively. The patient had significant relief of his neck pain, although computed tomography (CT) demonstrated a medial breach of the left C1 screw postoperation; however, he gradually developed headache and dizziness after discharge. Five weeks after operation, magnetic resonance imaging demonstrated a large pseudo-meningocele at the surgical site, which was managed conservatively. Nine weeks after the AA fixation, the patient was sent to the emergency department for altered consciousness. A brain CT demonstrated hydrocephalus and multiple fat emboli in the subarachnoid and intraventricular space. A ventriculoperitoneal shunt was inserted to manage the hydrocephalus and pseudo-meningocele. The patient recovered well and was followed up to 13 months after operation. To date, this was the first report of delayed hydrocephalus caused by fat embolism after AA fixation surgery. Incidental durotomy in posterior AA fixation may predispose the patient to a serious complication of fat-cerebrospinal fluid embolism and subsequent hydrocephalus. There should be a heightened awareness for such a complication. Both CT and magnetic resonance imaging are useful for the diagnosis of subarachnoid fat droplets. Copyright © 2016 Elsevier Inc. All rights reserved.

Double calcaneal osteotomy with percutaneous Steinmann pin fixation as part of treatment for flexible flatfoot deformity: a review of consecutive cases highlighting our experience with pin fixation.

PubMed

Boffeli, Troy J; Abben, Kyle W

2015-01-01

Surgical correction of flexible flatfoot deformity and posterior tibial tendon dysfunction has been extensively reported in published studies. When appropriate, calcaneal osteotomies for flatfoot correction have been a favorite of foot and ankle surgeons because of the corrective power achieved without the need to fuse any rearfoot joints. The medial displacement calcaneal osteotomy and Evans calcaneal osteotomy, together termed the double calcaneal osteotomy, have been reported several times by various investigators with a wide variety of fixation options. We undertook an institutional review board-approved retrospective review of 9 consecutive patients (11 feet), who had undergone double calcaneal osteotomy with 2 percutaneous Steinmann pin fixation for the correction of flexible flatfoot deformity, with or without posterior tibial tendon dysfunction. All patients had radiographic evidence of bone healing of the posterior calcaneal osteotomy and incorporation of the Evans osteotomy bone graft at 6 weeks and demonstrated clinical healing at 6 weeks. All patients had 2 percutaneous Steinmann pins placed through both osteotomies, and these were removed an average of 6 weeks postoperatively. No patient developed pin site complications. The only complication noted was sural neuritis, which was likely incision related. No patients had delayed union or nonunion, and we did not identify any graft shifting postoperatively. The present retrospective series highlights our experience with 2 percutaneous Steinmann pin fixation, demonstrating equal or better results than many previous published fixation methods for double calcaneal osteotomy. It is cost-effective and minimizes the potential risk of iatrogenic Achilles pathologic features associated with screw fixation. Copyright © 2015 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

Anterior cervical pedicle screw and plate fixation using fluoroscope-assisted pedicle axis view imaging: a preliminary report of a new cervical reconstruction technique

PubMed Central

Kato, Fumihiko; Ito, Keigo; Nakashima, Hiroaki; Machino, Masaaki

2009-01-01

Anterior procedures in the cervical spine are feasible in cases having anterior aetiologies such as anterior neural compression and/or severe kyphosis. Halo vests or anterior plates are used concurrently for cases with long segmental fixation. Halo vests are bothersome and anterior plate fixation is not adequately durable. We developed a new anterior pedicle screw (APS) and plate fixation procedure that can be used with fluoroscope-assisted pedicle axis view imaging. Six patients (3 men and 3 women; mean age, 54 years) with anterior multisegmental aetiology were included in this study. Their original diagnoses comprised cervical myelopathy and/or radiculopathy (n = 4), posterior longitudinal ligament ossification (n = 1) and post-traumatic kyphosis (n = 1). All patients underwent anterior decompression and strut grafting with APS and plate fixation. Mean operative time was 192 min and average blood loss was 73 ml. Patients were permitted to ambulate the next day with a cervical collar. Local sagittal alignment was characterised by 3.5° of kyphosis preoperatively, which improved to 6.8° of lordosis postoperatively and 5.2° of lordosis at final follow-up. Postoperative improvement and early bony union were observed in all cases. There was no serious complication except for two cases of dysphagia. Postoperative imaging demonstrated screw exposure in one screw, but no pedicle perforation. APS and plate fixation is useful in selected cases of multisegmental anterior reconstruction of cervical spine. However, the adequate familiarity and experience with both cervical pedicle screw fixation and the imaging technique used for visualising the pedicle during surgery are crucial for this procedure. PMID:19343377

A tricalcium phosphate/polyether ether ketone anchor bionic fixation device for anterior cruciate ligament reconstruction: Safety and efficacy in a beagle model.

PubMed

Mao, Genwen; Qin, Zili; Li, Zheng; Li, Xiang; Qiu, Yusheng; Bian, Weiguo

2018-05-02

The goal of this study was to develop a bionic fixation device based on the use of a tricalcium phosphate/polyether ether ketone anchor and harvesting of the ulnar carpal flexor muscle tendon for application as a ligament graft in a beagle anterior cruciate ligament (ACL) reconstruction model, with the goal of accelerating the ligament graft-to-bone tunnel healing and providing a robust stability through exploration of this new kind of autologous ligament graft. The safety and efficacy of this fixation device were explored 3 and 6 months after surgery in a beagle ACL reconstruction model using biomechanical tests and comprehensive histological observation. The data were compared using a two-tailed Student's t test and a paired t test. A p value <0.05 was defined as statistically significant. All the models were successfully established. This fixation device possessed the excellent mechanical properties for ACL reconstruction. A comprehensive histological observation revealed that a cartilage layer was visible in the transition zone between the tendon and bone interface at both 3 and 6 months postoperation. The trabecular of the new bone was observed six months after surgery and was found to be similar to a direct connection. This fixation technique provided not only a robust primary mechanical fixation but also a bionic fixation for long-term knee joint stability by accelerating the healing of the tendon to the bone tunnel, showing a high potential for use in clinical practice. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2018. © 2018 Wiley Periodicals, Inc.

Comparison of clinical outcomes of iris fixation and scleral fixation as treatment for intraocular lens dislocation.

PubMed

Kim, Kyeong Hwan; Kim, Wan Soo

2015-09-01

To compare the efficacy and safety of iris fixation with scleral fixation in surgical repositioning of dislocated intraocular lenses (IOLs). Retrospective, consecutive, comparative interventional case series. setting: Referral hospital. Seventy-eight consecutive patients who underwent surgical repositioning of dislocated intraocular lenses using suturing to the sclera or iris. Forty-four eyes of 44 patients underwent scleral fixation and 35 eyes of 34 patients underwent iris fixation of dislocated intraocular lenses. Visual acuity, refractive stability, operation time, and perioperative complications, including recurrence of IOL dislocation. Corrected distance visual acuity (CDVA) improved significantly 1 month postoperatively in both groups (P < .01 each), and remained stable for 12 months. One week postoperatively, however, CDVA improved significantly in the scleral fixation (P = .040) but not in the iris fixation (P = .058) group. The amount of refractive error significantly diminished 1 day after surgery (P = .028 in the scleral fixation and P = .046 in the iris fixation group). For the astigmatic components, Jackson crossed cylinders equivalent to conventional cylinders of positive power at axes of 0 degrees (J0) and 45 degrees (J45), J45 differed significantly in the scleral fixation and iris fixation groups (P = .009), whereas J0 was similar (P > .05). Operation time was significantly shorter (P = .0007), while immediate postoperative inflammation was significantly more severe (P = .001), in the iris fixation than in the scleral fixation group. Recurrence rates were similar (P > .05), but the mean time to recurrence was significantly shorter in the iris fixation than in the scleral fixation group (P = .031). Iris fixation and scleral fixation techniques had similar efficacy in the repositioning of dislocated intraocular lenses. Although operation time was shorter for iris fixation, it had several disadvantages, including induced astigmatism, immediate postoperative inflammation, earlier recurrence, and less stable refraction. Copyright © 2015 Elsevier Inc. All rights reserved.

Combined circular external fixation and open reduction internal fixation with pro-syndesmotic screws for repair of a diabetic ankle fracture

PubMed Central

Facaros, Zacharia; Ramanujam, Crystal L.; Stapleton, John J.

2010-01-01

The surgical management of ankle fractures among the diabetic population is associated with higher complication rates compared to the general population. Efforts toward development of better methods in prevention and treatment are continuously evolving for these injuries. The presence of peripheral neuropathy and the possible development of Charcot neuroarthropathy in this high risk patient population have stimulated much surgical interest to create more stable osseous constructs when open reduction of an ankle fracture/dislocation is required. The utilization of multiple syndesmotic screws (pro-syndesmotic screws) to further stabilize the ankle mortise has been reported by many foot and ankle surgeons. In addition, transarticular Steinmann pins have been described as an adjunct to traditional open reduction with internal fixation (ORIF) of the ankle to better stabilize the talus, thus minimizing risk of further displacement, malunion, and Charcot neuroarthropathy. The authors present a unique technique of ORIF with pro-syndesmotic screws and the application of a multi-plane circular external fixator for management of a neglected diabetic ankle fracture that prevented further deformity while allowing a weight-bearing status. This techniqu may be utilized for the management of complex diabetic ankle fractures that are prone to future complications and possible limb loss. PMID:22396812

Risk of population extinction from fixation of deleterious and reverse mutations.

PubMed

Lande, R

1998-01-01

A model is developed for alternate fixations of mildly deleterious and wild-type alleles arising by forward and reverse mutation in a finite population. For almost all parameter values, this gives an equilibrium load that agrees closely with the general expression derived from diffusion theory. Nearly neutral mutations with selection coefficient a few times larger than 1/(2N(e)) do the most damage by increasing the equilibrium load. The model of alternate fixations facilitates dynamical analysis of the expected load and the mean time to extinction in a population that has been suddenly reduced from a very large size to a small size. Reverse mutation can substantially improve population viability, increasing the mean time to extinction by an order of magnitude or more, but because many mutations are irreversible the effects may not be large. Populations with initially high mean fitness and small effective size, N(e) below a few hundred individuals, may be at serious risk of extinction from fixation of deleterious mutations within 10(3) to 10(4) generations.

Mechanical evaluation of aluminum alloy ring fixator.

PubMed

Tosborvorn, Somboon; Cheechareon, Sukrom; Ruttanuchun, Kittiput; Sirivedin, Suparerk; Rhienumporn, Chaitawat

2006-11-01

To test the homemade ring fixator as a tool for correction of bony deformity. The authors developed an aluminum alloy ring fixator and tested it to find out the accuracy of manufacturing and strength of the ring systems under axial load with the Roundness Testing Machine and Lloyd Universal Testing Machine. The mean diameter of the twenty five-drill holes was 6.5843872 +/- 0.0521594 mm (mean +/- SD). Distance between particular drill holes, which reflected the precision of drilling, had a high accuracy with standard deviation from 0.1138 to 0.1870 mm. The roundness of the rings was 0.2421376 +/- 0.12437977 mm (mean +/- SD). The system structure had minimal permanent deformity at breaking point, mean yield strength of the system was 4786.9 +/- 14.353 N (mean +/- SD). This was caused by the failure of the wire. Mean stiffness of the system was 127 N./mm. The aluminum alloy ring fixator was strong enough and well tolerated for clinical usage

Determination of ankle external fixation stiffness by expedited interactive finite element analysis.

PubMed

Nielsen, Jonathan K; Saltzman, Charles L; Brown, Thomas D

2005-11-01

Interactive finite element analysis holds the potential to quickly and accurately determine the mechanical stiffness of alternative external fixator frame configurations. Using as an example Ilizarov distraction of the ankle, a finite element model and graphical user interface were developed that provided rapid, construct-specific information on fixation rigidity. After input of specific construct variables, the finite element software determined the resulting tibial displacement for a given configuration in typically 15s. The formulation was employed to investigate constructs used to treat end-stage arthritis, both in a parametric series and for five specific clinical distraction cases. Parametric testing of 15 individual variables revealed that tibial half-pins were much more effective than transfixion wires in limiting axial tibial displacement. Factors most strongly contributing to stiffening the construct included placing the tibia closer to the fixator rings, and mounting the pins to the rings at the nearest circumferential location to the bone. Benchtop mechanical validation results differed inappreciably from the finite element computations.

Intra-articular fractures of the distal tibia

PubMed Central

Sitnik, Alexandre; Beletsky, Aleksander; Schelkun, Steven

2017-01-01

Results of the treatment of intra-articular fractures of the distal tibia have improved significantly during the last two decades. Recognition of the role of soft tissues has led to the development of a staged treatment strategy. At the first stage, joint-bridging external fixation and fibular fixation are performed. This leads to partial reduction of the distal tibial fracture and allows time for the healing of soft tissues and detailed surgical planning. Definitive open reduction and internal fixation of the tibial fracture is performed at a second stage, when the condition of the soft tissues is safe. The preferred surgical approach(es) is chosen based on the fracture morphology as determined from standard radiographic views and computed tomography. Meticulous atraumatic soft-tissue handling and the use of modern fixation techniques for the metaphyseal component such as minimally invasive plate osteosynthesis further facilitate healing. Cite this article: EFORT Open Rev 2017;2:352-361. DOI: 10.1302/2058-5241.2.150047 PMID:28932487

[Three-dimensional Finite Element Analysis to T-shaped Fracture of Pelvis in Sitting Position].

PubMed

Fan, Yanping; Lei, Jianyin; Liu, Haibo; Li, Zhiqiang; Cai, Xianhua; Chen, Weiyi

2015-10-01

We developed a three-dimensional finite element model of the pelvis. According to Letournel methods, we established a pelvis model of T-shaped fracture with its three different fixation systems, i. e. double column reconstruction plates, anterior column plate combined with posterior column screws and anterior column plate combined with quadrilateral area screws. It was found that the pelvic model was effective and could be used to simulate the mechanical behavior of the pelvis. Three fixation systems had great therapeutic effect on the T-shaped fracture. All fixation systems could increase the stiffness of the model, decrease the stress concentration level and decrease the displacement difference along the fracture line. The quadrilateral area screws, which were drilled into cortical bone, could generate beneficial effect on the T-type fracture. Therefore, the third fixation system mentioned above (i. e. the anterior column plate combined with quadrilateral area screws) has the best biomechanical stability to the T-type fracture.

Results of operative treatment of avulsion fractures of the iliac crest apophysis in adolescents.

PubMed

Li, Xigong; Xu, Sanzhong; Lin, Xiangjin; Wang, Quan; Pan, Jun

2014-04-01

Avulsion fracture of the iliac crest apophysis is a rare condition that commonly occurs in adolescent athletes. Conservative treatment for this injury can produce excellent functional outcomes. However, the rehabilitation process requires a rather long immobilisation period. This study aimed to evaluate the use of cannulated screws for fixation of avulsion fractures of iliac crest apophysis. Ten patients with avulsion fractures of iliac crest apophysis were treated by open reduction and internal fixation using cannulated screws. The mean age of patients was 14.6 years (range, 13-15 years). The mean intraoperative blood loss was 14.9 ml (range, 10-25 ml). The mean operative time was 40.3 min (range, 33-52 min). The mean follow-up period was 11.2 months (range, 6-20 months). At the 4-week follow-up, all patients returned to previously normal activity without pain and had no evidence of lower extremity muscle weakness. At the final follow-up, all patients resumed their athletic activity without any complications. Open reduction and internal fixation for the treatment of avulsion fracture of iliac crest apophysis can be recommended for patients requiring rapid rehabilitation. Copyright © 2013 Elsevier Ltd. All rights reserved.

[Clinical applications of sternoclavicular hook plate for the treatment of sternoclavicular joint dislocation].

PubMed

Chen, Fang-Hu; Zhao, Xiao-Ping; Zheng, Wen-Biao; Zeng, Han-Bing; Ran, Bo; Huang, Hui; Wang, Hai-Bao

2013-05-01

To observe the clinical therapeutic effects of sternoclavicular hook plate for the treatment of sternoclavicular joint dislocation. From June 2010 to June 2012, 7 patients with sternoclavicular joint dislocation were treated with sternoclavicular hook plate fixation. Among the 7 patients, 5 patients were male and 2 patients were female, and the average age was 42.3 years, ranging from 38 to 54 years. The course of the disease ranged from 1 to 4 weeks. All the patients had trauma history. The clinical manifestations included: obvious swelling and pain of sternoclavicular joint, restricted shoulder joint activity. The sternoclavicular joint dislocation was proved by preoperative X-ray and CT. The postoperative curative effect was evaluated according to Rockwood scoring method. According to Rockwood scoring method, the excellent results obtained in 6 cases, good in 1. There were no complications such as internal fixation loosening or broken, second dislocation, pain in the sternoclavicular joint, and deformity. The function of shoulder joint was good, and the limb activity was free and no pain appeared. The sternoclavicular hook plate for the treatment of sternoclavicular joint dislocation has follow advantages: simple procedure, stable fixation, definite therapeutic effects.

Ischemic time impacts biological integrity of phospho-proteins in PI3K/Akt, Erk/MAPK, and p38 MAPK signaling networks.

PubMed

Holzer, Timothy R; Fulford, Angie D; Arkins, Austin M; Grondin, Janet M; Mundy, Christopher W; Nasir, Aejaz; Schade, Andrew E

2011-06-01

Post-translational modifications of proteins, such as phosphorylation, are labile events dynamically regulated by opposing kinase and phosphatase activities. Preanalytical factors, such as ischemic time before fixation, affect these activities and can have a significant impact on the ability to elucidate signaling pathways in tissue. Immunohistochemical analysis of phosphorylated proteins involved in PI3K/Akt, Erk/MAPK, and p38 MAPK signaling networks was performed in human cell line xenografts from lung, brain, ovary, and prostate tumors. In order to replicate real-world practices, the tissues were subjected to ischemic times of 0 (baseline), 1, 4, and 24 hours before fixation in formalin. Two key concepts emerge from this analysis: (1) the stability of different phospho-epitopes within a given tumor type is variable (e.g. phospho-PRAS40 is more labile than phospho-S6 ribosomal protein) and (2) the stability of a given phospho-epitope (e.g. phospho-MAPKAPK2) varies significantly across different tumor types. These results highlight the importance of proper tissue acquisition and rapid fixation to preserve the biological integrity of signal transduction pathways that may guide therapeutic decision making.

Reverse Anterior Cruciate Ligament Reconstruction Fixation: A Biomechanical Comparison Study of Tibial Cross-Pin and Femoral Interference Screw Fixation.

PubMed

Lawley, Richard J; Klein, Samuel E; Chudik, Steven C

2017-03-01

To evaluate the biomechanical performance of tibial cross-pin (TCP) fixation relative to femoral cross-pin (FCP), femoral interference screw (FIS), and tibial interference screw (TIS) fixation. We randomized 40 porcine specimens (20 tibias and 20 femurs) to TIS fixation (group 1, n = 10), FIS fixation (group 2, n = 10), TCP fixation (group 3, n = 10), or FCP fixation (group 4, n = 10) and performed biomechanical testing to compare ultimate load, stiffness, yield load, cyclic displacement, and load at 5-mm displacement. We performed cross-pin fixation of the looped end and interference screw fixation of the free ends of 9-mm-diameter bovine extensor digitorum communis tendon grafts. Graft fixation constructs were cyclically loaded and then loaded to failure in line with the tunnels. Regarding yield load, FIS was superior to TIS (704 ± 125 N vs 504 ± 118 N, P = .002), TCP was superior to TIS (1,449 ± 265 N vs 504 ± 118 N, P < .001), and TCP was superior to FCP (1,449 ± 265 N vs 792 ± 397 N, P < .001). Cyclic displacement for FCP was superior to TCP. Cyclic displacement for TIS versus FIS showed no statistically significant difference (2.5 ± 1.0 mm vs 2.2 ± 0.6 mm, P = .298). Interference screw fixation consistently failed by graft slippage, whereas TCP fixation failed by tibial bone failure. FCP fixation failed by either femoral bone failure or failure elsewhere in the testing apparatus. Regarding yield load, TCP fixation performed biomechanically superior to the clinically proven FCP at time zero. Because TIS fixation shows the lowest yield strength, it represents the weak link, and combined TCP-FIS fixation theoretically would be biomechanically superior relative to combined FCP-TIS fixation with regard to yield load. Cyclic displacement showed a small difference in favor of FCP over TCP fixation and no difference between TIS and FIS. Time-zero biomechanics of TCP fixation paired with FIS fixation show that this method of fixation can be considered a potential alternative to current practice and may pose clinical benefits in different clinical scenarios of anterior cruciate ligament reconstruction. Copyright © 2016 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

Children with autism spectrum disorder (ASD) attend typically to faces and objects presented within their picture communication systems.

PubMed

Gillespie-Smith, K; Riby, D M; Hancock, P J B; Doherty-Sneddon, G

2014-05-01

Children with autism spectrum disorder (ASD) may require interventions for communication difficulties. One type of intervention is picture communication symbols which are proposed to improve comprehension of linguistic input for children with ASD. However, atypical attention to faces and objects is widely reported across the autism spectrum for several types of stimuli. In this study we used eye-tracking methodology to explore fixation duration and time taken to fixate on the object and face areas within picture communication symbols. Twenty-one children with ASD were compared with typically developing matched groups. Children with ASD were shown to have similar fixation patterns on face and object areas compared with typically developing matched groups. It is proposed that children with ASD attend to the images in a manner that does not differentiate them from typically developing individuals. Therefore children with and without autism have the same opportunity to encode the available information. We discuss what this may imply for interventions using picture symbols. © 2013 The Authors. Journal of Intellectual Disability Research © 2013 John Wiley & Sons Ltd, MENCAP & IASSIDD.

Chromatin structure and methylation of rat rRNA genes studied by formaldehyde fixation and psoralen cross-linking.

PubMed Central

Stancheva, I; Lucchini, R; Koller, T; Sogo, J M

1997-01-01

By using formaldehyde cross-linking of histones to DNA and gel retardation assays we show that formaldehyde fixation, similar to previously established psoralen photocross-linking, discriminates between nucleosome- packed (inactive) and nucleosome-free (active) fractions of ribosomal RNA genes. By both cross-linking techniques we were able to purify fragments from agarose gels, corresponding to coding, enhancer and promoter sequences of rRNA genes, which were further investigated with respect to DNA methylation. This approach allows us to analyse independently and in detail methylation patterns of active and inactive rRNA gene copies by the combination of Hpa II and Msp I restriction enzymes. We found CpG methylation mainly present in enhancer and promoter regions of inactive rRNA gene copies. The methylation of one single Hpa II site, located in the promoter region, showed particularly strong correlation with the transcriptional activity. PMID:9108154

Temporal variation of applied inter fragmentary displacement at a bone fracture in harmony with maturation of the fracture callus.

PubMed

Gardner, T N; Evans, M; Simpson, H

1998-09-01

The amplitude of inter fragmentary displacement in long bone fractures greatly influences the pattern and speed of healing. Unfortunately, the amplitude of natural cyclical displacement arising from patient activity is random because of the inherent flexibility of fixation devices under natural loading. Although fixators may be designed to control the amplitude of this displacement, the amplitudes most beneficial to healing have not been determined. Furthermore, the appropriate amplitude must vary during healing as the reparative tissue (callus) progresses histologically and stiffens during maturation. In this study on an experimental fracture, the amplitude of applied cyclical displacement is varied during healing to correspond with the inverse of the callus stiffness versus time curve. In vivo mechanical stiffness tests on the callus indicate that the end point of the fixation period is achieved more rapidly than with a constant level of applied displacement.

Treatment of stress fracture of the olecranon in throwing athletes with internal fixation through a small incision

PubMed Central

2012-01-01

The present study is a report of retrospective case series of stress fracture of the olecranon. Six patients presented posterior elbow pain in throwing in baseball and softball, but fracture was not diagnosed in radiographs. We detected stress fracture of the olecranon using computed tomographic (CT) scan and treated the patient with internal fixation with a headless cannulated double threaded screw through a small skin incision. All patients returned to competitive level without elbow complaints after the operation. When throwing athletes present with unusual posterior elbow pain and no significant findings on radiographs, a CT scan examination should be performed. We recommend surgical treatment of internal fixation with a screw through a small skin incision, as a good option for stress fracture of the olecranon in order to allow early return to sports activity in competitive athletes. PMID:23241173

Comparison of Risk of Carpal Tunnel Syndrome in Patients with Distal Radius Fractures After 7 Treatments

PubMed Central

Zhao, Huan-Li; Wang, Gui-Bin; Jia, Yue-Qing; Zhu, Shi-Cai; Zhang, Feng-Fang; Liu, Hong-Mei

2015-01-01

Background To compare risk of carpal tunnel syndrome (CTS) in distal radius fracture (DRF) patients after 7 treatments using bridging external fixation (BrEF), non-bridging external fixation (non-BrEF), plaster fixation, K-wire fixation, dorsal plating fixation, volar plating fixation, and dorsal and volar plating by performing a network meta-analysis. Material/Methods An exhaustive search of electronic databases identified randomized controlled trails (RCTs) closely related to our study topic. The published articles were screened, based on predefined inclusion and exclusion criteria, to select high-quality studies for the present network meta-analysis. Data extracted from the selected studies were analyzed using STATA version 12.0 software. Results The literature search and selection process identified 12 eligible RCTs that contained a total of 1370 DRF patients (394 patients with BrEF, 377 patients with non-BrEF, 89 patients with K-wire fixation, 192 patients with plaster fixation, 42 patients with dorsal plating fixation, 152 patients with volar plating fixation, and 124 patients with dorsal and volar plating fixation). Our network meta-analysis results demonstrated no significant differences in CTS risk among the 7 treatments (P>0.05). The value of surface under the cumulative ranking curve (SUCRA), however, suggested that dorsal plating fixation is the optimal treatment, with the lowest risk of CTS in DRF patients (dorsal plating fixation: 89.2%; dorsal and volar plating: 57.8%; plaster fixation: 50.9%; non-BrEF: 50.6%; volar plating fixation: 39.6%; BrEF: 38.4%; K-wire fixation: 23.6%). Conclusions Our network meta-analysis provides evidence that dorsal plating fixation significantly decreases the risk of CTS and could be the method of choice in DRF patients. PMID:26391617

Pain and convalescence following laparoscopic ventral hernia repair.

PubMed

Eriksen, Jens Ravn

2011-12-01

Severe pain is usual after laparoscopic ventral hernia repair (LVHR). Mesh fixation with titanium tacks may play a key role in the development of acute and chronic pain and alternative fixation methods should therefore be investigated. This PhD thesis was based on three studies and aimed too: 1) assess the intensity and impact of postoperative pain by detailed patient-reported description of pain and convalescence after LVHR (Study I), 2) evaluate the feasibility of fibrin sealant (FS) for mesh fixation in an experimental pig model (Study II), and 3) investigate FS vs. tacks for mesh fixation in LVHR in a randomised, double-blinded, clinical controlled study with acute postoperative pain as the primary outcome (Study III). In Study I - a prospective descriptive study - 35 patients were prospectively included and underwent LVHR. Scores of pain, quality of life, convalescence, fatigue, and general well-being were obtained from each patient. Follow-up was six months. Average pain from postoperative day (POD) 0-2 and POD 0-6 measured on a 0-100 mm visual analogue scale (VAS) was 61 and 48, respectively. Pain scores reached preoperative values at POD 30. The incidence of severe chronic pain was 7%. No parameter predicted postoperative pain significantly. Significant correlations were found between pain, and general well-being (rS= -0.8, p < 0.001), satisfaction (rS= -0.67, p < quality of life score (rS= -0.63, p < 0.001) six months postoperatively. Patients resumed normal daily activity at POD 14. In Study II - a randomised experimental study in pigs - nine pigs were operated laparoscopically with insertion of two different meshes fixed with either FS or tacks. All pigs were euthanized on POD 30. The primary outcome parameter was strength of ingrowth between the mesh and the anterior abdominal wall. A mechanical peel test was performed for each tissue sample. The secondary outcome parameters were grade and strength of adhesions to the mesh, shrinkage and displacement/folding of the mesh and histological parameters. All nine pigs survived without complications until sacrifice. No meshes were displaced from their initial position at autopsy, but in two cases mesh folding was observed. No significant difference in strength of ingrowth was found between different fixation methods or mesh types. Furthermore, no significant difference was found in grade or strength of adhesions or any histological parameters. In Study III - a randomised, controlled, double-blinded, multicenter trial - 40 patients with umbilical hernia defects between 1.5-5 cm, were randomly assigned to receive FS or titanium tacks for mesh fixation in LVHR. Patients, care givers and those assessing the outcomes were blinded to group assignment. The primary outcome was average pain from POD 0-2 (VAS score). Secondary outcome parameters were fatigue, general well-being and time to resume normal daily activity. Follow-up was one month for all. Patients in the FS group reported significantly less pain at POD 0-2 (median VAS 38 (range 6-98) vs. 60 (18-96), p = 0.01). Absolute VAS score difference between groups was 20 mm (95% CI 4-35 mm) at activity, and 19 mm (95% CI 3-34 mm) at rest. Patients in the FS group reported significantly less discomfort from POD 0-2 and POD 0-10, compared with the tack group. No significant difference was found in fatigue score between groups. No significant difference in hospital stay, hernia diameter, or morphine consumption in the post anesthesia care unit was found between groups. Patients in the FS group resumed normal daily activity at POD 7 (1-66) versus POD 18 (1-95) in the tack group (p = 0.03). No recurrences were observed. No adverse events or side effects were observed. No significant differences in predefined complications were found between groups. In conclusion, pain is a significant clinical problem after LVHR with impact on general well-being, quality of life and patient satisfaction. This issue must have first priority in future ventral hernia repair research. It is now documented, that the simple application of fibrin glue instead of titanium tacks for mesh fixation in LVHR of defects < 5 cm significantly reduced acute pain, discomfort and the period of convalescence. Long-term follow-up will show the value of FS fixation in terms of chronic pain and recurrence. As FS potentially may solve many of the outcome problems associated with LVHR, future studies should include larger hernia defects including large incisional hernias, as the operative technique may be different.

Knee arthrodesis with circular external fixation.

PubMed

Garberina, M J; Fitch, R D; Hoffmann, E D; Hardaker, W T; Vail, T P; Scully, S P

2001-01-01

Knee arthrodesis can enable limb salvage in patients with disability secondary to trauma, infected total knee arthroplasty, pyarthrosis, and other complications. Historically, intramedullary nailing has resulted in the highest overall knee fusion rates. However, intramedullary nailing is relatively contraindicated in the presence of active infection. Nineteen patients who underwent knee arthrodesis with circular external fixation were studied retrospectively. Postoperative radiographs were evaluated for evidence of bony fusion, which was defined as trabecular bridging between the femur and tibia. Patients were interviewed and graded using the functional assessment portion of the Knee Society clinical rating system. Fusion was successful in 13 of 19 (68%) patients. Overall, patients spent an average of 4 months 8 days wearing the circular external fixator. Average time to radiographic and clinical evidence of arthrodesis (defined as lack of motion across the fusion site) was 4 months 18 days. No patient with successful fusion considered himself or herself housebound. All but one of these patients require some form of assistive device for ambulation. Complications occurred in 16 of 19 (84%) patients overall. Superficial pin tract infection (55%) and nonunion (32%) were the most common. Circular external fixation is an effective method for obtaining knee arthrodesis in patients who are not good candidates for intramedullary nailing.

Technical tip: tightrope fixation of neer type II distal clavicle fracture supported by a case series.

PubMed

Haque, Syed; Khan, Anwar; Sharma, A; Sundararajan, Sabapathy

2014-03-27

We present a case series of 3 patients who underwent a novel technique of tight rope fixation for Neer type II distal clavicle fracture. 2-3 cm incision was made lateral to the fracture site moving inferomedially. Part of the distal end of clavicle was exposed close to fracture site and further dissection was carried out to reveal the coracoid process. Tight rope fixation of the distal ends of clavicle and coracoid was performed to achieve satisfactory fracture reduction on x-ray. 4 weeks of sling with gentle pendulum movement were followed by active shoulder movement exercises. Radiographic union was reached at 6 weeks' time, while the patients achieved proper shoulder functionality 3 months following the operation. Neer type II distal clavicle fractures are characterized by disruption of the coracoclavicular ligament with wide proximal fragment displacement. Overall, type II distal clavicle fractures have a 20-30% nonunion rate if treated non-surgically. Various techniques have been described for the treatment of these fractures, including hook plate and nailing. Tight rope fixation provides proper apposition of the fracture fragments for union by maintaining a reduced coracoclavicular interval.

Products of dark CO sub 2 fixation in pea root nodules support bacteroid metabolism. [Pisum sativum L

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rosendahl, L.; Pedersen, W.B.; Vance, C.P.

1990-05-01

Products of the nodule cytosol in vivo dark ({sup 14}C)CO{sub 2} fixation were detected in the plant cytosol as well as in the bacteroids of pea (Pisum sativum L. cv Bodil) nodules. The distribution of the metabolites of the dark CO{sub 2} fixation products was compared in effective (fix{sup +}) nodules infected by a wild-type Rhizobium leguminosarum (MNF 300), and ineffective (fix{sup {minus}}) nodules of the R. leguminosarum mutant MNF 3080. The latter has a defect in the dicarboxylic acid transport system of the bacterial membrane. The {sup 14}C incorporation from ({sup 14}C)CO{sub 2} was about threefold greater in themore » wild-type nodules than in the mutant nodules. Similarly, in wild-type nodules the in vitro phosphoenolpyruvate carboxylase activity was substantially greater than that of the mutant. Almost 90% of the {sup 14}C label in the cytosol was found in organic acids in both symbioses. The results indicate a central role for nodule cytosol dark CO{sub 2} fixation in the supply of the bacteroids with dicarboxylic acids.« less

Fixation to features and neural processing of facial expressions in a gender discrimination task

PubMed Central

Neath, Karly N.; Itier, Roxane J.

2017-01-01

Early face encoding, as reflected by the N170 ERP component, is sensitive to fixation to the eyes. Whether this sensitivity varies with facial expressions of emotion and can also be seen on other ERP components such as P1 and EPN, was investigated. Using eye-tracking to manipulate fixation on facial features, we found the N170 to be the only eye-sensitive component and this was true for fearful, happy and neutral faces. A different effect of fixation to features was seen for the earlier P1 that likely reflected general sensitivity to face position. An early effect of emotion (~120 ms) for happy faces was seen at occipital sites and was sustained until ~350 ms post-stimulus. For fearful faces, an early effect was seen around 80 ms followed by a later effect appearing at ~150 ms until ~300 ms at lateral posterior sites. Results suggests that in this emotion-irrelevant gender discrimination task, processing of fearful and happy expressions occurred early and largely independently of the eye-sensitivity indexed by the N170. Processing of the two emotions involved different underlying brain networks active at different times. PMID:26277653

Single-screw Fixation of Adolescent Salter-II Proximal Humeral Fractures: Biomechanical Analysis of the "One Pass Door Lock" Technique.

PubMed

Miller, Mark Carl; Redman, Christopher N; Mistovich, R Justin; Muriuki, Muturi; Sangimino, Mark J

2017-09-01

Pin fixation of Salter-II proximal humeral fractures in adolescents approaching skeletal maturity has potential complications that can be avoided with single-screw fixation. However, the strength of screw fixation relative to parallel and diverging pin fixation is unknown. To compare the biomechanical fixation strength between these fixation modalities, we used synthetic composite humeri, and then compared these results in composite bone with cadaveric humeri specimens. Parallel pinning, divergent pinning, and single-screw fixation repairs were performed on synthetic composite humeri with simulated fractures. Six specimens of each type were tested in axial loading and other 6 were tested in torsion. Five pair of cadaveric humeri were tested with diverging pins and single screws for comparison. Single-screw fixation was statistically stronger than pin fixation in axial and torsional loading in both composite and actual bone. There was no statistical difference between composite and cadaveric bone specimens. Single-screw fixation can offer greater stability to adolescent Salter-II fractures than traditional pinning. Single-screw fixation should be considered as a viable alternative to percutaneous pin fixation in transitional patients with little expected remaining growth.

Total fixation of cricoarytenoid joint of a patient with rheumatoid arthritis and Hashimoto thyroiditis.

PubMed

Stojanović, Stevan P; Zivić, Ljubica; Stojanović, Jasmina; Belić, Branislav

2010-01-01

The incidence of cricoarytenoid joint fixation in case of rheumatoid arthritis is 17 to 33%. In later stages of rheumatoid arthritis, a gradual fixation of cricoarytenoid joint develops and both halves of the larynx become less movable which calls for endotracheal intubation; while total fixation of this joint demands surgical tracheotomy. Hashimoto thyroiditis can display symptoms which are difficult to distinguish from the ones present in total fixation of cricoarytenoid joint caused by rheumatoid arthritis. A 60-year-old woman in terminal stage of rheumatoid arthritis and Hashimoto thyroiditis, diagnosed after clinical and other examinations. She was treated for strident breathing with surgical tracheotomy. The microscopic examination of the larynx with the use of laryngoscopic pincers suggested the immovability of the right and very limited movability of the left arytenoid cartilage. A computerized endovideostroboscopy showed only passive vertical vibrating movements of the right vocal cord and irregular vibrations of the left vocal cord. Total fixation of the cricoarytenoid joint can be caused by many pathological processes, but so far references have shown no case of rheumatoid arthritis and Hashimoto thyroiditis. In differential diagnostics, one of many examinations is the microscopic examination of the larynx, but it is very important to determine the movability of the arytenoid cartilage with the use of appropriate instruments in total endotracheal anaesthesia while the patient is fully relaxed. Movements in cricoarytenoid joints in patients with Hashimoto thyroiditis and the same conditions are preserved.

Fibrin glue versus autologous blood for conjunctival autograft fixation in pterygium surgery.

PubMed

Boucher, Sophie; Conlon, Ronan; Teja, Salina; Teichman, Joshua C; Yeung, Season; Ziai, Setareh; Baig, Kashif

2015-08-01

To compare the outcomes between autologous blood- and fibrin glue-fixated conjunctival autografts in pterygium excision surgery. Retrospective case series. Forty eyes of 40 patients who had a primary nasal pterygium excision. A retrospective comparative case series of 40 eyes (40 patients) that had a primary nasal pterygium excision. All eyes had a conjunctival autograft from the superior bulbar conjunctiva to cover the scleral bed. Twenty eyes (20 patients) had fixation of the autograft using autologous blood (AB), and 20 eyes (20 patients) had fixation using fibrin glue (FG). One year of follow-up data included conjunctival graft stability (graft loss, graft retraction), pterygium recurrence, visual acuity, and postoperative complications. Descriptive and inferential statistics were performed. Intraoperatively, no complications occurred in either group. Graft loss occurred in 6 patients in the AB group, compared with none in the FG group. Graft retraction occurred in 3 patients in the AB group and 2 patients in the FG group. At 1 year postoperatively, pterygium recurrence occurred in 4 patients in the AB group and 1 patient in the FG group. One patient in the AB group developed a small pyogenic granuloma that resolved by 6 months with conservative management. Visual acuity remained stable in both groups. Conjunctival autograft fixation with autologous blood resulted in less stable conjunctival autografts and a higher recurrence rate compared with fixation with fibrin glue. Copyright © 2015 Canadian Ophthalmological Society. Published by Elsevier Inc. All rights reserved.

Successful correction of tibial bone deformity through multiple surgical procedures, liquid nitrogen-pretreated bone tumor autograft, three-dimensional external fixation, and internal fixation in a patient with primary osteosarcoma: a case report.

PubMed

Takeuchi, Akihiko; Yamamoto, Norio; Shirai, Toshiharu; Nishida, Hideji; Hayashi, Katsuhiro; Watanabe, Koji; Miwa, Shinji; Tsuchiya, Hiroyuki

2015-12-07

In a previous report, we described a method of reconstruction using tumor-bearing autograft treated by liquid nitrogen for malignant bone tumor. Here we present the first case of bone deformity correction following a tumor-bearing frozen autograft via three-dimensional computerized reconstruction after multiple surgeries. A 16-year-old female student presented with pain in the left lower leg and was diagnosed with a low-grade central tibial osteosarcoma. Surgical bone reconstruction was performed using a tumor-bearing frozen autograft. Bone union was achieved at 7 months after the first surgical procedure. However, local tumor recurrence and lung metastases occurred 2 years later, at which time a second surgical procedure was performed. Five years later, the patient developed a 19° varus deformity and underwent a third surgical procedure, during which an osteotomy was performed using the Taylor Spatial Frame three-dimensional external fixation technique. A fourth corrective surgical procedure was performed in which internal fixation was achieved with a locking plate. Two years later, and 10 years after the initial diagnosis of tibial osteosarcoma, the bone deformity was completely corrected, and the patient's limb function was good. We present the first report in which a bone deformity due to a primary osteosarcoma was corrected using a tumor-bearing frozen autograft, followed by multiple corrective surgical procedures that included osteotomy, three-dimensional external fixation, and internal fixation.

Pathogen Inactivating Properties and Increased Sensitivity in Molecular Diagnostics by PAXgene, a Novel Non-Crosslinking Tissue Fixative.

PubMed

Loibner, Martina; Buzina, Walter; Viertler, Christian; Groelz, Daniel; Hausleitner, Anja; Siaulyte, Gintare; Kufferath, Iris; Kölli, Bettina; Zatloukal, Kurt

2016-01-01

Requirements on tissue fixatives are getting more demanding as molecular analysis becomes increasingly relevant for routine diagnostics. Buffered formaldehyde in pathology laboratories for tissue fixation is known to cause chemical modifications of biomolecules which affect molecular testing. A novel non-crosslinking tissue preservation technology, PAXgene Tissue (PAXgene), was developed to preserve the integrity of nucleic acids in a comparable way to cryopreservation and also to preserve morphological features comparable to those of formalin fixed samples. Because of the excellent preservation of biomolecules by PAXgene we investigated its pathogen inactivation ability and biosafety in comparison to formalin by in-vitro testing of bacteria, human relevant fungi and human cytomegalovirus (CMV). Guidelines for testing disinfectants served as reference for inactivation assays. Furthermore, we tested the properties of PAXgene for detection of pathogens by PCR based assays. All microorganisms tested were similarly inactivated by PAXgene and formalin except Clostridium sporogenes, which remained viable in seven out of ten assays after PAXgene treatment and in three out of ten assays after formalin fixation. The findings suggest that similar biosafety measures can be applied for PAXgene and formalin fixed samples. Detection of pathogens in PCR-based diagnostics using two CMV assays resulted in a reduction of four to ten quantification cycles of PAXgene treated samples which is a remarkable increase of sensitivity. PAXgene fixation might be superior to formalin fixation when molecular diagnostics and highly sensitive detection of pathogens is required in parallel to morphology assessment.

Fixation and mounting of porcine aortic valves for use in mock circuits.

PubMed

Schlöglhofer, Thomas; Aigner, Philipp; Stoiber, Martin; Schima, Heinrich

2013-10-01

Investigations of the circulatory system in vitro use mock circuits that require valves to mimic the cardiac situation. Whereas mechanical valves increase water hammer effects due to inherent stiffness and do not allow the use of pressure lines or catheters, bioprosthetic valves are expensive and of limited durability in test fluids. Therefore, we developed a cheap, fast, alternative method to mount valves obtained from the slaughterhouse in mock circuits. Porcine aortic roots were obtained from the abattoir and used either in native condition or after fixation. Fixation was performed at a constant retrograde pressure to ensure closed valve position. Fixation time was 4 h in a 0.5%-glutaraldehyde phosphate buffer. The fixed valves were molded into a modular mock circulation connector using a fast curing silicone. Valve functionality was evaluated in a pulsatile setting (cardiac output = 4.7 l/min, heart rate = 80 beats/min) and compared before and after fixation. Leaflet motion was recorded with a high-speed camera and valve insufficiency was quantified by leakage flow under steady pressure application (80 mmHg). Under physiological conditions the aortic valves showed almost equal leaflet motion in native and fixed conditions. However, the leaflets of the native valves showed lower stiffness and more fluttering during systole than the fixed specimens. Under retrograde pressure, fresh and fixed valves showed small leakage flows of <30 ml/min. The new mounting and fixation procedure is a fast method to fabricate low cost biologic valves for the use in mock circuits.

Azolla filiculoides Nitrogenase Activity Decrease Induced by Inoculation with Chlamydomonas sp. †

PubMed Central

Habte, Mitiku

1986-01-01

Experiments were conducted to determine the influence of Chlamydomonas sp. on nitrogen fixation (C2H2 → C2H4) in Azolla filiculoides and on the nitrogen fixation and growth of free-living Anabaena azollae 2B organisms. Inoculation of azolla medium with Chlamydomonas sp. was associated with decreased nitrogenase activity in A. filiculoides and with increases in the density of a fungal population identified as Acremonium sp. Subsequent inoculation of azolla medium with this fungus was also accompanied by a significant decrease in nitrogenase activity of A. filiculoides. However, the extent of depression of nitrogenase activity was significantly higher when azolla medium was inoculated with Chlamydomonas sp. than when it was inoculated with Acremonium sp. Inoculation of nitrogen-free Stanier medium with either Acremonium sp. or Chlamydomonas sp. did not adversely affect the growth or nitrogenase activity of free-living A. azollae. Decreased nitrogenase activity in A. filiculoides is apparently related to the adverse influence of the green alga and the fungus on the macrosymbiont. The mechanisms that might be involved are discussed. PMID:16347211

Amygdala activation in response to facial expressions in pediatric obsessive-compulsive disorder

PubMed Central

Britton, Jennifer C.; Stewart, S. Evelyn; Killgore, William D.S.; Rosso, Isabelle M.; Price, Lauren M.; Gold, Andrea L.; Pine, Daniel S.; Wilhelm, Sabine; Jenike, Michael A.; Rauch, Scott L.

2010-01-01

Background Exaggerated amygdala activation to threatening faces has been detected in adults and children with anxiety disorders, compared to healthy comparison subjects. However, the profile of amygdala activation in response to facial expressions in obsessive-compulsive disorder (OCD) may be a distinguishing feature; a prior study found that compared with healthy adults, adults with OCD exhibited less amygdala activation to emotional and neutral faces, relative to fixation (Cannistraro et al., 2004). Methods In the current event-related functional magnetic resonance imaging (fMRI) study, a pediatric OCD sample (N=12) and a healthy comparison sample (HC, N=17) performed a gender discrimination task while viewing emotional faces (happy, fear, disgust) and neutral faces. Results Compared to the HC group, the OCD group showed less amygdala/hippocampus activation in all emotion and neutral conditions relative to fixation. Conclusions Like previous reports in adult OCD, pediatric OCD may have a distinct neural profile from other anxiety disorders, with respect to amygdala activation in response to emotional stimuli that are not disorder-specific. PMID:20602430

Using Synthetic Biology to Distinguish and Overcome Regulatory and Functional Barriers Related to Nitrogen Fixation

PubMed Central

Wang, Xia; Yang, Jian-Guo; Chen, Li; Wang, Ji-Long; Cheng, Qi; Dixon, Ray; Wang, Yi-Ping

2013-01-01

Biological nitrogen fixation is a complex process requiring multiple genes working in concert. To date, the Klebsiella pneumoniae nif gene cluster, divided into seven operons, is one of the most studied systems. Its nitrogen fixation capacity is subject to complex cascade regulation and physiological limitations. In this report, the entire K. pneumoniae nif gene cluster was reassembled as operon-based BioBrick parts in Escherichia coli. It provided ∼100% activity of native K. pneumoniae system. Based on the expression levels of these BioBrick parts, a T7 RNA polymerase–LacI expression system was used to replace the σ54-dependent promoters located upstream of nif operons. Expression patterns of nif operons were critical for the maximum activity of the recombinant system. By mimicking these expression levels with variable-strength T7-dependent promoters, ∼42% of the nitrogenase activity of the σ54-dependent nif system was achieved in E. coli. When the newly constructed T7-dependent nif system was challenged with different genetic and physiological conditions, it bypassed the original complex regulatory circuits, with minor physiological limitations. Therefore, we have successfully replaced the nif regulatory elements with a simple expression system that may provide the first step for further research of introducing nif genes into eukaryotic organelles, which has considerable potentials in agro-biotechnology. PMID:23935879

Open reduction and internal fixation compared to closed reduction and external fixation in distal radial fractures

PubMed Central

Kopylov, Philippe; Geijer, Mats; Tägil, Magnus

2009-01-01

Background and purpose In unstable distal radial fractures that are impossible to reduce or to maintain in reduced position, the treatment of choice is operation. The type of operation and the choice of implant, however, is a matter of discussion. Our aim was to investigate whether open reduction and internal fixation would produce a better result than traditional external fixation. Methods 50 patients with an unstable or comminute distal radius fracture were randomized to either closed reduction and bridging external fixation, or open reduction and internal fixation using the TriMed system. The primary outcome parameter was grip strength, but the patients were followed for 1 year with objective clinical assessment, subjective outcome using DASH, and radiographic examination. Results At 1 year postoperatively, grip strength was 90% (SD 16) of the uninjured side in the internal fixation group and 78% (17) in the external fixation group. Pronation/supination was 150° (15) in the internal fixation group and 136° (20) in the external fixation group at 1 year. There were no differences in DASH scores or in radiographic parameters. 5 patients in the external fixation group were reoperated due to malunion, as compared to 1 in the internal fixation group. 7 other cases were classified as radiographic malunion: 5 in the external fixation group and 2 in the internal fixation group. Interpretation Internal fixation gave better grip strength and a better range of motion at 1 year, and tended to have less malunions than external fixation. No difference could be found regarding subjective outcome. PMID:19857180

[Comparison of external fixation with or without limited internal fixation for open knee fractures].

PubMed

Li, K N; Lan, H; He, Z Y; Wang, X J; Yuan, J; Zhao, P; Mu, J S

2018-03-01

Objective: To explore the characteristics and methods of different fixation methods and prevention of open knee joint fracture. Methods: The data of 86 cases of open knee joint fracture admitted from January 2002 to December 2015 in Department of Orthopaedics, Affiliated Hospital of Chengdu University were analyzed retrospectively.There were 65 males and 21 females aged of 38.6 years. There were 38 cases treated with trans articular external fixation alone, 48 cases were in the trans articular external fixation plus auxiliary limited internal fixation group. All the patients were treated according to the same three stages except for different fixation methods. Observation of external fixation and fracture fixation, fracture healing, wound healing and treatment, treatment and related factors of infection control and knee function recovery. χ(2) test was used to analyze data. Results: Eleven patients had primary wound healing, accounting for 12.8%. Seventy-five patients had two wounds healed, accounting for 87.2%. Only 38 cases of trans articular external fixator group had 31 cases of articular surface reduction, accounting for 81.6%; Five cases of trans articular external fixator assisted limited internal fixation group had 5 cases of poor reduction, accounting for 10.4%; There was significant difference between the two groups (χ(2)=44.132, P <0.05). Take a single cross joint external fixation group, a total of 23 cases of patients with infection, accounted for 60.5% of external fixation group; trans articular external fixation assisted limited internal fixation group there were 30 cases of patients with infection, accounting for the assistance of external fixator and limited internal fixation group 62.5%; There was significant difference between the two groups(χ(2)=0.035, P >0.05). Five cases of fracture nonunion cases of serious infection, patients voluntarily underwent amputation. The Lysholm Knee Scale: In the external fixation group, 23 cases were less than 50 points, accounting for 60.5%, 15 cases were more than 50 points, accounting for 39.5%, external fixation and limited internal fixation group 20 cases were less than 50 points, accounting for 41.7%, 28 cases were more than 50 points, accounting for 58.3%; There was significant difference between the two groups(χ(2)=1.279, P >0.05). Conclusions: Prevention and control of infection is a central link in the treatment of open fracture of the knee. Trans articular external fixator plus limited internal fixation is an important measure to treat open fracture of the knee-joint.

Transcriptomic Analysis and Microscopic Observations in the Cyanobacterium UCYN-A during Diel Cycles

NASA Astrophysics Data System (ADS)

Muñoz-Marin, M. D. C.; Farnelid, H.; Zehr, J. P.

2016-02-01

Candidatus Atelocyanobacterium thalassa (UCYN-A) is a nitrogen-fixing marine cyanobacterium recently recognized for its widespread distribution and significant contributions to oceanic nitrogen (N2)-fixation. UCYN-A is a group of related cyanobacteria that are symbiotic with a single-celled eukaryotic phytoplankter, the haptophyte Braarudosphaera bigelowii. UCYN-A fixes N2 and expresses nitrogenase during the day. Since the nitrogenase is inactivated by oxygen evolved through photosynthesis, most cyanobacteria use temporal or spatial separation of photosynthesis and N2 fixation. Genomic studies revealed that UCYN-A lacks the entire PSII apparatus (photosystem II). The lack of oxygenic photosynthesis at least partially explains why they can fix nitrogen during the day, although the host is a photoautotroph. However, UCYN-A has retained photosystem I (PSI), and PSI activity may be important in the energetics of N2 fixation in the symbiosis. Because UCYN-A lacks photosystem II, which normally supplies electrons to photosystem I from water, UCYN-A needs alternative electron donors if it uses photosystem I to make the reductant NADPH. In order to determine if UCYN-A expresses photosynthetic genes and which other proteins may be involved with energy metabolism, we developed a whole genome array to examine gene transcription over the diel cycle in two strains. Our results show that there is a temporal separation of the expression of photosynthesis genes from the expression of nitrogenase genes. Moreover, the transcription profile of NADH dehydrogenases and hydrogenases suggest they may be involved as alternative electron donors for the N2 fixation. In addition, we used a double-CARD-FISH (Catalyzed Reporter Deposition-Fluorescence in situ Hybridization) assay to study cell division of the host and symbiont during diel cycles in relation to UCYN-A gene expression carried out during the transcriptomic analysis. These results help us move toward a deeper understanding of the metabolism of this unusual cyanobacterium and the differences in environmental adaptations between these two strains.

Gap formation following primary repair of the anterior cruciate ligament: A biomechanical evaluation.

PubMed

van der List, Jelle P; DiFelice, Gregory S

2017-03-01

Historically, inconsistent and unpredictable results of open primary anterior cruciate ligament (ACL) repair were reported. Recently, however, good results of arthroscopic primary ACL repair of proximal tears have been reported. Purpose of this study was to assess the direct postoperative gap formation and maximum failure load following simulated knee motion after primary ACL repair. Six matched-paired human cadaveric knees (mean age: 52years, range: 48 to 56years) were used. After primary proximal ACL repair with either suture button fixation or suture anchor fixation, knees were cycled five, 50 and 100 times with a simulated active quadriceps force. Gap formation between the femoral wall and ligament was measured using a digital caliper and maximum failure load was tested. Gap formation after five, 50 and 100cycles of the knee were 0.30mm (±0.23), 0.75mm (±0.55) and 0.97mm (±0.70), respectively, with no significant differences between both fixation techniques. The overall maximum failure load was 243N (±143) with no difference between both techniques. Most common failure mode was slipping of suture from the fixation. Following proximal ACL repair, gap formation of approximately one millimeter was measured after repetitious knee cycling with mean maximum failure load of 243N. These findings are likely to be sufficient for careful early active range of motion (ROM) when extrapolating from other available studies. Future studies with second-look arthroscopy are necessary to assess the gap formation and healing in patients treated with primary repair. Copyright © 2016 Elsevier B.V. All rights reserved.

Analysis of usage and associated cost of external fixators at an urban level 1 trauma centre.

PubMed

Chaus, George W; Dukes, Chase; Hak, David J; Mauffrey, Cyril; Mark Hammerberg, E

2014-10-01

To determine the usage, indication, duration, and cost associated with external fixation usage. Additionally, to show the significant cost associated with external fixator use and reinvigorate discussions on external fixator reuse. A retrospective review of a prospectively gathered trauma database was undertaken to identify all patients treated with external fixation frames for pelvic and lower extremity injuries between September 2007 and July 2010. We noted the indications for frame use, and we determined the average duration of external fixation for each indication. The cost of each frame was calculated from implant records. 341 lower extremity and pelvic fractures were treated with external fixation frames during the study period. Of these, 92% were used as temporary external fixation. The average duration of temporary external fixation was 10.5 days. The cost of external fixation frame components was $670,805 per year. The average cost per external fixation frame was $5900. The majority of external fixators are intended as temporary frames, in place for a limited period of time prior to definitive fixation of skeletal injuries. As such, most frames are not intended to withstand physiologic loads, nor are they expected provide a precise maintenance of reduction. Given the considerable expense associated with external fixation frame components, the practice of purchasing external fixation frame components as disposable "single-use" items appears to be somewhat wasteful. Level II. Copyright © 2014 Elsevier Ltd. All rights reserved.

cDNA-AFLP analysis of differential gene expression related to cell chemotactic and encystment of Azospirillum brasilense.

PubMed

Li, Huamin; Cui, Yanhua; Wu, Lixian; Tu, Ran; Chen, Sanfeng

2011-12-20

Our previous study indicated org35 was involved in chemotaxis and interacted with nitrogen fixation transcriptional activator NifA via PAS domain. In order to reveal the role of org35 in nitrogen regulation, the downstream target genes of org35 were identified. We here report differentially expressed genes in org35 mutants comparing with wild type Sp7 by means of cDNA-AFLP. Four up-regulated transcript-derived fragments (TDFs) homologues of chemotaxis transduction proteins were found, including CheW, methyl-accepting chemotaxis protein and response regulator CheY-like receiver. Three distinct TDFs (AB46, AB58 and AB63) were similar to PHB de-polymerase C-terminus, cell shape-determining protein and flagellin domain protein. And 11 TDFs showed similarities with signal transduction proteins, including homologous protein of the nitrogen regulation protein NtrY and nitrate/nitrite response regulator protein NarL. These data suggested that the Azospirillum brasilense org35 was a multi-effecter and involved in chemotaxis, cyst development and regulation of nitrogen fixation. Copyright © 2010 Elsevier GmbH. All rights reserved.

Active sensing in the categorization of visual patterns

PubMed Central

Yang, Scott Cheng-Hsin; Lengyel, Máté; Wolpert, Daniel M

2016-01-01

Interpreting visual scenes typically requires us to accumulate information from multiple locations in a scene. Using a novel gaze-contingent paradigm in a visual categorization task, we show that participants' scan paths follow an active sensing strategy that incorporates information already acquired about the scene and knowledge of the statistical structure of patterns. Intriguingly, categorization performance was markedly improved when locations were revealed to participants by an optimal Bayesian active sensor algorithm. By using a combination of a Bayesian ideal observer and the active sensor algorithm, we estimate that a major portion of this apparent suboptimality of fixation locations arises from prior biases, perceptual noise and inaccuracies in eye movements, and the central process of selecting fixation locations is around 70% efficient in our task. Our results suggest that participants select eye movements with the goal of maximizing information about abstract categories that require the integration of information from multiple locations. DOI: http://dx.doi.org/10.7554/eLife.12215.001 PMID:26880546

Image-Guided Internal Fixation of an Oblique Sagittal Split Fracture of C1 Lateral Mass with Motion Preservation: A Technical Report

PubMed Central

Malcolm, James G; Johnson, Andrew K

2017-01-01

A sagittal split fracture of the C1 lateral mass is an unstable subtype of C1 fractures and has a high propensity for developing late deformities and pain with nonoperative management. A primary internal fixation of this type of fracture has been recently described with good clinical outcomes and preservation of motion. We present a modified technique of primary internal fixation using an obliquely inserted C1 lag screw with imaging guidance. We successfully treated a 55-year-old woman with a unilateral C1 oblique sagittal split fracture who failed nonoperative management. Technical nuances are discussed with a review of pertinent literature. PMID:28948116

Visual processing during natural reading

PubMed Central

Weiss, Béla; Knakker, Balázs; Vidnyánszky, Zoltán

2016-01-01

Reading is a unique human ability that plays a pivotal role in the development and functioning of our modern society. However, its neural basis remains poorly understood since previous research was focused on reading words with fixed gaze. Here we developed a methodological framework for single-trial analysis of fixation onset-related EEG activity (FOREA) that enabled us to investigate visual information processing during natural reading. To reveal the effect of reading skills on orthographic processing during natural reading, we measured how altering the configural properties of the written text by modifying inter-letter spacing affects FOREA. We found that orthographic processing is reflected in FOREA in three consecutive time windows (120–175 ms, 230–265 ms, 345–380 ms after fixation onset) and the magnitude of FOREA effects in the two later time intervals showed a close association with the participants’ reading speed: FOREA effects were larger in fast than in slow readers. Furthermore, these expertise-driven configural effects were clearly dissociable from the FOREA signatures of visual perceptual processes engaged to handle the increased crowding (155–220 ms) as a result of decreasing letter spacing. Our findings revealed that with increased reading skills orthographic processing becomes more sensitive to the configural properties of the written text. PMID:27231193

All Internal Segmental Bone Transport and Optional Lengthening With a Newly Developed Universal Cylinder-Kombi-Tube Module for Motorized Nails-Description of a Surgical Technique.

PubMed

Krettek, Christian; El Naga, Ashraf

2017-10-01

Segmental transport is an effective method of treatment for segmental defects, but the need for external fixation during the transport phase is a disadvantage. To avoid external fixation, we have developed a Cylinder-Kombi-Tube Segmental Transport (CKTST) module for combination with a commercially available motorized lengthening nail. This CKTST module allows for an all-internal segmental bone transport and also allows for optional lengthening if needed. The concept and surgical technique of CKTST are described and illustrated with a clinical case.

Fixation distance and fixation duration to vertical road signs.

PubMed

Costa, Marco; Simone, Andrea; Vignali, Valeria; Lantieri, Claudio; Palena, Nicola

2018-05-01

The distance of first-fixation to vertical road signs was assessed in 22 participants while driving a route of 8.34 km. Fixations to road signs were recorded by a mobile eye-movement-tracking device synchronized to GPS and kinematic data. The route included 75 road signs. First-fixation distance and fixation duration distributions were positively skewed. Median distance of first-fixation was 51 m. Median fixation duration was 137 ms with a modal value of 66 ms. First-fixation distance was linearly related to speed and fixation duration. Road signs were gazed at a much closer distance than their visibility distance. In a second study a staircase procedure was used to test the presentation-time threshold that lead to a 75% accuracy in road sign identification. The threshold was 35 ms, showing that short fixations to a road signs could lead to a correct identification. Copyright © 2018 Elsevier Ltd. All rights reserved.

Dual Target Search is Neither Purely Simultaneous nor Purely Successive.

PubMed

Cave, Kyle R; Menneer, Tamaryn; Nomani, Mohammad S; Stroud, Michael J; Donnelly, Nick

2017-08-31

Previous research shows that visual search for two different targets is less efficient than search for a single target. Stroud, Menneer, Cave and Donnelly (2012) concluded that two target colours are represented separately based on modeling the fixation patterns. Although those analyses provide evidence for two separate target representations, they do not show whether participants search simultaneously for both targets, or first search for one target and then the other. Some studies suggest that multiple target representations are simultaneously active, while others indicate that search can be voluntarily simultaneous, or switching, or a mixture of both. Stroud et al.'s participants were not explicitly instructed to use any particular strategy. These data were revisited to determine which strategy was employed. Each fixated item was categorised according to whether its colour was more similar to one target or the other. Once an item similar to one target is fixated, the next fixated item is more likely to be similar to that target than the other, showing that at a given moment during search, one target is generally favoured. However, the search for one target is not completed before search for the other begins. Instead, there are often short runs of one or two fixations to distractors similar to one target, with each run followed by a switch to the other target. Thus, the results suggest that one target is more highly weighted than the other at any given time, but not to the extent that search is purely successive.

Tendon transfer fixation: comparing a tendon to tendon technique vs. bioabsorbable interference-fit screw fixation.

PubMed

Sabonghy, Eric Peter; Wood, Robert Michael; Ambrose, Catherine Glauber; McGarvey, William Christopher; Clanton, Thomas Oscar

2003-03-01

Tendon transfer techniques in the foot and ankle are used for tendon ruptures, deformities, and instabilities. This fresh cadaver study compares the tendon fixation strength in 10 paired specimens by performing a tendon to tendon fixation technique or using 7 x 20-25 mm bioabsorbable interference-fit screw tendon fixation technique. Load at failure of the tendon to tendon fixation method averaged 279N (Standard Deviation 81N) and the bioabsorbable screw 148N (Standard Deviation 72N) [p = 0.0008]. Bioabsorbable interference-fit screws in these specimens show decreased fixation strength relative to the traditional fixation technique. However, the mean bioabsorbable screw fixation strength of 148N provides physiologic strength at the tendon-bone interface.

A Novel Fixation System for Acetabular Quadrilateral Plate Fracture: A Comparative Biomechanical Study

PubMed Central

Zha, Guo-Chun; Sun, Jun-Ying; Dong, Sheng-Jie; Zhang, Wen; Luo, Zong-Ping

2015-01-01

This study aims to assess the biomechanical properties of a novel fixation system (named AFRIF) and to compare it with other five different fixation techniques for quadrilateral plate fractures. This in vitro biomechanical experiment has shown that the multidirectional titanium fixation (MTF) and pelvic brim long screws fixation (PBSF) provided the strongest fixation for quadrilateral plate fracture; the better biomechanical performance of the AFRIF compared with the T-shaped plate fixation (TPF), L-shaped plate fixation (LPF), and H-shaped plate fixation (HPF); AFRIF gives reasonable stability of treatment for quadrilateral plate fracture and may offer a better solution for comminuted quadrilateral plate fractures or free floating medial wall fracture and be reliable in preventing protrusion of femoral head. PMID:25802849

Plate Versus Intramedullary Nail Fixation of Anterior Tibial Stress Fractures: A Biomechanical Study.

PubMed

Markolf, Keith L; Cheung, Edward; Joshi, Nirav B; Boguszewski, Daniel V; Petrigliano, Frank A; McAllister, David R

2016-06-01

Anterior midtibial stress fractures are an important clinical problem for patients engaged in high-intensity military activities or athletic training activities. When nonoperative treatment has failed, intramedullary (IM) nail and plate fixation are 2 surgical options used to arrest the progression of a fatigue fracture and allow bone healing. A plate will be more effective than an IM nail in preventing the opening of a simulated anterior midtibial stress fracture from tibial bending. Controlled laboratory study. Fresh-frozen human tibias were loaded by applying a pure bending moment in the sagittal plane. Thin transverse saw cuts, 50% and 75% of the depth of the anterior tibial cortex, were created at the midtibia to simulate a fatigue fracture. An extensometer spanning the defect was used to measure the fracture opening displacement (FOD) before and after the application of IM nail and plate fixation constructs. IM nails were tested without locking screws, with a proximal screw only, and with proximal and distal screws. Plates were tested with unlocked bicortical screws (standard compression plate) and locked bicortical screws; both plate constructs were tested with the plate edge placed 1 mm from the anterior tibial crest (anterior location) and 5 mm posterior to the crest. For the 75% saw cut depth, the mean FOD values for all IM nail constructs were 13% to 17% less than those for the saw cut alone; the use of locking screws had no significant effect on the FOD. The mean FOD values for all plate constructs were significantly less than those for all IM nail constructs. The mean FOD values for all plates were 28% to 46% less than those for the saw cut alone. Anterior plate placement significantly decreased mean FOD values for both compression and locked plate constructs, but the mean percentage reductions for locked and unlocked plates were not significantly different from each other for either plate placement. The percentage FOD reductions for all plate constructs and the unlocked IM nail were significantly less with a 50% saw cut depth. Plate fixation was superior to IM nail fixation in limiting the opening of a simulated midtibial stress fracture, and anterior-posterior placement of the plate was an important variable for this construct. Results from these tests can help guide the selection of fixation hardware for patients requiring surgical treatment for a midtibial stress fracture. © 2016 The Author(s).

Fixation of carbon dioxide by a hydrogen-oxidizing bacterium for value-added products.

PubMed

Yu, Jian

2018-06-09

With rapid technology progress and cost reduction, clean hydrogen from water electrolysis driven by renewable powers becomes a potential feedstock for CO 2 fixation by hydrogen-oxidizing bacteria. Cupriavidus necator (formally Ralstonia eutropha), a representative member of the lithoautotrophic prokaryotes, is a promising producer of polyhydroxyalkanoates and single cell proteins. This paper reviews the fundamental properties of the hydrogen-oxidizing bacterium, the metabolic activities under limitation of individual gases and nutrients, and the value-added products from CO 2 , including the products with large potential markets. Gas fermentation and bioreactor safety are discussed for achieving high cell density and high productivity of desired products under chemolithotrophic conditions. The review also updates the recent research activities in metabolic engineering of C. necator to produce novel metabolites from CO 2 .

Pacing from the right ventricular septum: is there a danger to the coronary arteries?

PubMed

Teh, Andrew W; Medi, Caroline; Rosso, Raphael; Lee, Geoffrey; Gurvitch, Ronen; Mond, Harry G

2009-07-01

Pacing from right ventricular (RV) septal sites has been suggested as an alternative to RV apical pacing in an attempt to avoid long-term adverse consequences on left ventricular function. Concern has been raised as to the relationship of the left anterior descending coronary artery (LAD) to pacing leads in these positions. We retrospectively analyzed three cases in which patients with RV active-fixation leads in situ also had coronary angiography. Multiple fluoroscopic views were used to determine the relationship of the lead tip at various pacing sites to the coronary arteries. A lead placed on the anterior wall was in close proximity to the LAD, whereas septal and free wall positioning was not. Placement of RV active-fixation leads on the septum avoids potential coronary artery compromise.

Design and control of active vision based mechanisms for intelligent robots

NASA Technical Reports Server (NTRS)

Wu, Liwei; Marefat, Michael M.

1994-01-01

In this paper, we propose a design of an active vision system for intelligent robot application purposes. The system has the degrees of freedom of pan, tilt, vergence, camera height adjustment, and baseline adjustment with a hierarchical control system structure. Based on this vision system, we discuss two problems involved in the binocular gaze stabilization process: fixation point selection and vergence disparity extraction. A hierarchical approach to determining point of fixation from potential gaze targets using evaluation function representing human visual behavior to outside stimuli is suggested. We also characterize different visual tasks in two cameras for vergence control purposes, and a phase-based method based on binarized images to extract vergence disparity for vergence control is presented. A control algorithm for vergence control is discussed.

Carbon sequestration in soybean crop soils: the role of hydrogen-coupled CO2 fixation

NASA Astrophysics Data System (ADS)

Graham, A.; Layzell, D. B.; Scott, N. A.; Cen, Y.; Kyser, T. K.

2011-12-01

Conversion of native vegetation to agricultural land in order to support the world's growing population is a key factor contributing to global climate change. However, the extent to which agricultural activities contribute to greenhouse gas emissions compared to carbon storage is difficult to ascertain, especially for legume crops, such as soybeans. Soybean establishment often leads to an increase in N2O emissions because N-fixation leads to increased soil available N during decomposition of the low C:N legume biomass. However, soybean establishment may also reduce net greenhouse gas emissions by increasing soil fertility, plant growth, and soil carbon storage. The mechanism behind increased carbon storage, however, remains unclear. One explanation points to hydrogen coupled CO2 fixation; the process by which nitrogen fixation releases H2 into the soil system, thereby promoting chemoautotrophic carbon fixation by soil microbes. We used 13CO2 as a tracer to track the amount and fate of carbon fixed by hydrogen coupled CO2 fixation during one-year field and laboratory incubations. The objectives of the research are to 1) quantify rates of 13CO2 fixation in soil collected from a field used for long-term soybean production 2) examine the impact of H2 gas concentration on rates of 13CO2 fixation, and 3) measure changes in δ13C signature over time in 3 soil fractions: microbial biomass, light fraction, and acid stable fraction. If this newly-fixed carbon is incorporated into the acid-stable soil C fraction, it has a good chance of contributing to long-term soil C sequestration under soybean production. Soil was collected in the field both adjacent to root nodules (nodule soil) and >3cm away (root soil) and labelled with 13CO2 (1% v/v) in the presence and absence of H2 gas. After a two week labelling period, δ13C signatures already revealed differences in the four treatments of bulk soil: -17.1 for root, -17.6 for nodule, -14.2 for root + H2, and -6.1 for nodule + H2. Labelled soil was then placed in nylon mesh bags and buried in the field at a depth of 15cm in a soybean field at the Central Experiment Farm in Ottawa, Ontario. Samples will be removed at intervals of 1,2,3,6,9,12, and 15 months, and the δ13C of three soil fractions will be examined to reveal changes in carbon storage over time. Our results will provide insights into the fate of carbon fixed during hydrogen coupled CO2 fixation, and demonstrate whether this CO2 fixation can contribute to the long-term greenhouse gas balance of soybean production systems.

A new adjustable parallel drill guide for internal fixation of femoral neck fracture: a developmental and experimental study.

PubMed

Yuenyongviwat, Varah; Tuntarattanapong, Pakjai; Tangtrakulwanich, Boonsin

2016-01-11

Internal fixation is one treatment for femoral neck fracture. Some devices and techniques reported improved accuracy and decreased fluoroscopic time. However, these are not widely used nowadays due to the lack of available special instruments and techniques. To improve the surgical procedure, the authors designed a new adjustable drill guide and tested the efficacy of the device. The authors developed a new adjustable drill guide for cannulated screw guide wire insertion for multiple screw fixation. Eight orthopaedic surgeons performed the experimental study to evaluate the efficacy of this device. Each surgeon performed guide wire insertion for multiple screw fixation in six synthetic femurs: three times with the new device and three times with the conventional technique. The fluoroscopic time, operative time and surgeon satisfaction were evaluated. In the operations with the new adjustable drill guide, the fluoroscopic and operative times were significantly lower than the operations with the conventional technique (p < 0.05). The mean score for the level of satisfaction of this device was also statistically significantly better (p = 0.02) than the conventional technique. The fluoroscopic and operative times with the new adjustable drill guide were reduced for multiple screw fixation of femoral neck fracture and the satisfaction of the surgeons was good.

Vibration Testing Procedures for Bone Stiffness Assessment in Fractures Treated with External Fixation.

PubMed

Mattei, Lorenza; Longo, Antonia; Di Puccio, Francesca; Ciulli, Enrico; Marchetti, Stefano

2017-04-01

A bone healing assessment is crucial for the successful treatment of fractures, particularly in terms of the timing of support devices. However, in clinical practice, this assessment is only made qualitatively through bone manipulation and X-rays, and hence cannot be repeated as often as might be required. The present study reconsiders the quantitative method of frequency response analysis for healing assessments, and specifically for fractures treated with an external fixator. The novelty consists in the fact that bone excitation and response are achieved through fixator pins, thus overcoming the problem of transmission through soft-tissues and their damping effect. The main objective was to develop and validate a test procedure in order to characterize the treated bone. More than 80 tests were performed on a tibia phantom alone, a phantom with pins, and a phantom with a complete fixator. Different excitation techniques and input-output combinations were compared. The results demonstrated the effectiveness of a procedure based on impact tests using a micro-hammer. Pins and fixator were demonstrated to influence the frequency response of the phantom by increasing the number of resonant frequencies. This procedure will be applied in future studies to monitor healing both in in vitro and in vivo conditions.

Imaging the Drosophila retina: zwitterionic buffers PIPES and HEPES induce morphological artifacts in tissue fixation.

PubMed

Nie, Jing; Mahato, Simpla; Zelhof, Andrew C

2015-02-03

Tissue fixation is crucial for preserving the morphology of biological structures and cytological details to prevent postmortem degradation and autolysis. Improper fixation conditions could lead to artifacts and thus incorrect conclusions in immunofluorescence or histology experiments. To resolve reported structural anomalies with respect to Drosophila photoreceptor cell organization we developed and utilized a combination of live imaging and fixed samples to investigate the exact biogenesis and to identify the underlying source for the reported discrepancies in structure. We found that piperazine-N,N'-bis(ethanesulfonic acid) (PIPES) and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES), two zwitterionic buffers commonly used in tissue fixation, can cause severe lumen and cell morphological defects in Drosophila pupal and adult retina; the inter-rhabdomeral lumen becomes dilated and the photoreceptor cells are significantly reduced in size. Correspondingly, the localization pattern of Eyes shut (EYS), a luminal protein, is severely altered. In contrast, tissues fixed in the phosphate buffered saline (PBS) buffer results in lumen and cell morphologies that are consistent with live imaging. We suggest that PIPES and HEPES buffers should be utilized with caution for fixation when examining the interplay between cells and their extracellular environment, especially in Drosophila pupal and adult retina research.

Abnormality in face scanning by children with autism spectrum disorder is limited to the eye region: Evidence from multi-method analyses of eye tracking data

PubMed Central

Yi, Li; Fan, Yuebo; Quinn, Paul C.; Feng, Cong; Huang, Dan; Li, Jiao; Mao, Guoquan; Lee, Kang

2012-01-01

There has been considerable controversy regarding whether children with autism spectrum disorder (ASD) and typically developing children (TD) show different eye movement patterns when processing faces. We investigated ASD and age- and IQ-matched TD children's scanning of faces using a novel multi-method approach. We found that ASD children spent less time looking at the whole face generally. After controlling for this difference, ASD children's fixations of the other face parts, except for the eye region, and their scanning paths between face parts were comparable either to the age-matched or IQ-matched TD groups. In contrast, in the eye region, ASD children's scanning differed significantly from that of both TD groups: (a) ASD children fixated significantly less on the right eye (from the observer's view); (b) ASD children's fixations were more biased towards the left eye region; and (c) ASD children fixated below the left eye, whereas TD children fixated on the pupil region of the eye. Thus, ASD children do not have a general abnormality in face scanning. Rather, their abnormality is limited to the eye region, likely due to their strong tendency to avoid eye contact. PMID:23929830

Limb lengthening over plate

PubMed Central

Kulkarni, Ruta; Singh, Nishant; Kulkarni, Govind S; Kulkarni, Milind; Kulkarni, Sunil; Kulkarni, Vidisha

2012-01-01

Background: The limb lengthening over plate eliminates the associated risk of infection with limb lengthening over intramedullary nail. We present our experience of limb lengthening in 15 patients with a plate fixed on the proximal segment, followed by corticotomy and application of external fixator. Materials and Methods: 15 patients (7 females, 8 males) were included in this consecutive series. The average age was 18.1 years (range 8–35 years). Fifteen tibiae and one femur were lengthened in 15 patients. Lengthening was achieved at 1 mm/day followed by distal segment fixation with three or four screws on reaching the target length. Results: The preoperative target length was successfully achieved in all patients at a mean of 4.1 cm (range 1.8–6.5 cm). The mean duration of external fixation was 75.3 days (range 33–116 days) with the mean external fixation index at 19.2 days/cm (range 10.0–38.3 days/cm). One patient suffered deep infection up to the plate, three patients had mild procurvatum deformities, and one patient developed mild tendo achilles contracture. Conclusion: Lengthening over a plate allows early removal of external fixator and eliminates the risk of creating deep intramedullary infection as with lengthening over nail. Lengthening over plate is also applicable to children with open physis. PMID:22719123

Sensitive period in stereopsis: random dot stereopsis after long-standing strabismus.

PubMed

Hatch, S W; Laudon, R

1993-12-01

Bifoveal fixation is a requirement for random dot stereopsis. It is believed that random dot stereopsis is not possible after treatment of long-standing strabismus because binocular cortical cells are permanently damaged when strabismus is present during the sensitive period. Although the sensitive period for amblyopia has been clearly documented, the sensitive period for stereopsis is uncertain. We present a case we have followed from age 22 months to 10 years. This patient had intermittent esotropia until approximately age 3 years 4 months; he then had constant esotropia from about age 3 years 4 months to age 9 years 7 months. After orthoptic treatment at age 9 years, the patient returned to intermittent esotropia. He subsequently developed bifoveal fixation as measured by 30 sec arc of contour stereopsis and 250 to 500 sec arc of random dot stereopsis. This patient demonstrates that bifoveal fixation can be obtained after long-standing strabismus. We suggest that the sensitive period for stereopsis development, for this patient, was from birth to age 3 years.

Application of alternative fixatives to formalin in diagnostic pathology

PubMed Central

Gatta, L. Benerini; Cadei, M.; Balzarini, P.; Castriciano, S.; Paroni, R.; Verzeletti, A.; Cortellini, V.; De Ferrari, F.; Grigolato, P.

2012-01-01

Fixation is a critical step in the preparation of tissues for histopathology. The aim of this study was to investigate the effects of different fixatives vs formalin on proteins and DNA, and to evaluate alternative fixation for morphological diagnosis and nucleic acid preservation for molecular methods. Forty tissues were fixed for 24 h with six different fixatives: the gold standard fixative formalin, the historical fixatives Bouin and Hollande, and the alternative fixatives Greenfix, UPM and CyMol. Tissues were stained (Haematoxylin-Eosin, Periodic Acid Schiff, Trichromic, Alcian-blue, High Iron Diamine stainings), and their antigenicity was determined by immunohistochemistry (performed with PAN-CK, CD31, Ki-67, S100, CD68, AML antibodies). DNA extraction, KRAS sequencing, FISH for CEP-17, and flow cytometry analysis of nuclear DNA content were applied. For cell morphology the alternative fixatives (Greenfix, UPM, CyMol) were equivalent to formalin. As expected, Hollande proved to be the best fixative for morphology. The morphology obtained with Bouin was comparable to the one with formalin. Hollande was the best fixative for histochemistry. Bouin proved to be equivalent to formalin. The alternative fixatives were equivalent to formalin, although with greater variability in haematoxylin-eosin staining. It proved the possibility to obtain immunohistochemical staining largely equivalent to that following formalin-fixation with the following fixatives: Greenfix, Hollande, UPM and CyMol. The tissues fixed in Bouin did not provide results comparable to those obtained with formalin. The DNA extracted from samples fixed with alternative fixatives was found to be suitable for molecular analysis. PMID:22688293

[Tibial press-fit fixation of flexor tendons for reconstruction of the anterior cruciate ligament].

PubMed

Ettinger, M; Liodakis, E; Haasper, C; Hurschler, C; Breitmeier, D; Krettek, C; Jagodzinski, M

2012-09-01

Press-fit fixation of hamstring tendon autografts for anterior cruciate ligament reconstruction is an interesting technique because no hardware is necessary. This study compares the biomechanical properties of press-fit fixations to an interference screw fixation. Twenty-eight human cadaveric knees were used for hamstring tendon explantation. An additional bone block was harvested from the tibia. We used 28 porcine femora for graft fixation. Constructs were cyclically stretched and then loaded until failure. Maximum load to failure, stiffness and elongation during failure testing and cyclic loading were investigated. The maximum load to failure was 970±83 N for the press-fit tape fixation (T), 572±151 N for the bone bridge fixation (TS), 544±109 N for the interference screw fixation (I), 402±77 N for the press-fit suture fixation (S) and 290±74 N for the bone block fixation technique (F). The T fixation had a significantly better maximum load to failure compared to all other techniques (p<0.001). This study demonstrates that a tibial press-fit technique which uses an additional bone block has better maximum load to failure results compared to a simple interference screw fixation.

Vertical eye position-dependence of the human vestibuloocular reflex during passive and active yaw head rotations.

PubMed

Thurtell, M J; Black, R A; Halmagyi, G M; Curthoys, I S; Aw, S T

1999-05-01

Vertical eye position-dependence of the human vestibuloocular reflex during passive and active yaw head rotations. The effect of vertical eye-in-head position on the compensatory eye rotation response to passive and active high acceleration yaw head rotations was examined in eight normal human subjects. The stimuli consisted of brief, low amplitude (15-25 degrees ), high acceleration (4,000-6,000 degrees /s2) yaw head rotations with respect to the trunk (peak velocity was 150-350 degrees /s). Eye and head rotations were recorded in three-dimensional space using the magnetic search coil technique. The input-output kinematics of the three-dimensional vestibuloocular reflex (VOR) were assessed by finding the difference between the inverted eye velocity vector and the head velocity vector (both referenced to a head-fixed coordinate system) as a time series. During passive head impulses, the head and eye velocity axes aligned well with each other for the first 47 ms after the onset of the stimulus, regardless of vertical eye-in-head position. After the initial 47-ms period, the degree of alignment of the eye and head velocity axes was modulated by vertical eye-in-head position. When fixation was on a target 20 degrees up, the eye and head velocity axes remained well aligned with each other. However, when fixation was on targets at 0 and 20 degrees down, the eye velocity axis tilted forward relative to the head velocity axis. During active head impulses, the axis tilt became apparent within 5 ms of the onset of the stimulus. When fixation was on a target at 0 degrees, the velocity axes remained well aligned with each other. When fixation was on a target 20 degrees up, the eye velocity axis tilted backward, when fixation was on a target 20 degrees down, the eye velocity axis tilted forward. The findings show that the VOR compensates very well for head motion in the early part of the response to unpredictable high acceleration stimuli-the eye position- dependence of the VOR does not become apparent until 47 ms after the onset of the stimulus. In contrast, the response to active high acceleration stimuli shows eye position-dependence from within 5 ms of the onset of the stimulus. A model using a VOR-Listing's law compromise strategy did not accurately predict the patterns observed in the data, raising questions about how the eye position-dependence of the VOR is generated. We suggest, in view of recent findings, that the phenomenon could arise due to the effects of fibromuscular pulleys on the functional pulling directions of the rectus muscles.

Plasticity of crassulacean acid metabolism at subtropical latitudes: a pineapple case study.

PubMed

Rainha, Nuno; Medeiros, Violante P; Câmara, Mariana; Faustino, Hélder; Leite, João P; Barreto, Maria do Carmo; Cruz, Cristina; Pacheco, Carlos A; Ponte, Duarte; Bernardes da Silva, Anabela

2016-01-01

Plants with the crassulacean acid metabolism (CAM) express high-metabolic plasticity, to adjust to environmental stresses. This article hypothesizes that irradiance and nocturnal temperatures are the major limitations for CAM at higher latitudes such as the Azores (37°45'N). Circadian CAM expression in Ananas comosus L. Merr. (pineapple) was assessed by the diurnal pattern of leaf carbon fixation into l-malate at the solstices and equinoxes, and confirmed by determining maximal phosphoenolpyruvate carboxylase (PEPC) activity in plant material. Metabolic adjustments to environmental conditions were confirmed by gas exchange measurements, and integrated with environmental data to determine CAM's limiting factors: light and temperature. CAM plasticity was observed at the equinoxes, under similar photoperiods, but different environmental conditions. In spring, CAM expression was similar between vegetative and flowering plants, while in autumn, flowering (before anthesis) and fructifying (with fully developed fruit before ripening) plants accumulated more l-malate. Below 100 µmol m(-2) s(-1) , CAM phase I was extended, reducing CAM phase III during the day. Carbon fixation inhibition may occur by two major pathways: nocturnal temperature (<15°C) inhibiting PEPC activity and l-malate accumulation; and low irradiance influencing the interplay between CAM phase I and III, affecting carboxylation and decarboxylation. Both have important consequences for plant development in autumn and winter. Observations were confirmed by flowering time prediction using environmental data, emphasizing that CAM expression had a strong seasonal regulation due to a complex network response to light and temperature, allowing pineapple to survive in environments not suitable for high productivity. © 2015 Scandinavian Plant Physiology Society.

Comparative analysis of international standards for the fatigue testing of posterior spinal fixation systems.

PubMed

Villa, Tomaso; La Barbera, Luigi; Galbusera, Fabio

2014-04-01

Preclinical evaluation of the long-term reliability of devices for lumbar fixation is a mandatory activity before they are put into market. The experimental setups are described in two different standards edited by the International Organization for Standardization (ISO) and the American Society for Testing Materials (ASTM), but the evaluation of the suitability of such tests to simulate the actual loading with in vivo situations has never been performed. To calculate through finite element (FE) simulations the stress in the rods of the fixator when subjected to ASTM and ISO standards. To compare the calculated stresses arising in the same fixator once it has been virtually mounted in a physiological environment and loaded with physiological forces and moments. FE simulations and validation experimental tests. FE models of the ISO and ASTM setups were created to conduct simulations of the tests prescribed by standards and calculate stresses in the rods. Validation of the simulations were performed through experimental tests; the same fixator was virtually mounted in an L2-L4 FE model of the lumbar spine and stresses in the rods were calculated when the spine was subjected to physiological forces and moments. The comparison between FE simulations and experimental tests showed good agreement between results obtained using the two methodologies, thus confirming the suitability of the FE method to evaluate stresses in the device in different loading situations. The usage of a physiological load with ASTM standard is impossible due to the extreme severity of the ASTM configuration; in this circumstance, the presence of an anterior support is suggested. Also, ISO prescriptions, although the choice of the setup correctly simulates the mechanical contribution of the discs, seem to overstress the device as compared with a physiological loading condition. Some daily activities, other than walking, can induce a further state of stress in the device that should be taken into account in setting up new experimental procedures. ISO standard loading prescriptions seems to be more severe than the expected physiological ones. The ASTM standard should be completed by including some anterior supporting device and declaring the value of the load to be imposed. Moreover, a further enhancement of standards would be simulating other movements representative of daily activities different from walking. Copyright © 2014 Elsevier Inc. All rights reserved.

Porcine Intestinal Mast Cells. Evaluation of Different Fixatives for Histochemical Staining Techniques Considering Tissue Shrinkage

PubMed Central

Rieger, J.; Twardziok, S.; Huenigen, H.; Hirschberg, R.M.; Plendl, J.

2013-01-01

Staining of mast cells (MCs), including porcine ones, is critically dependent upon the fixation and staining technique. In the pig, mucosal and submucosal MCs do not stain or stain only faintly after formalin fixation. Some fixation methods are particularly recommended for MC staining, for example the fixation with Carnoy or lead salts. Zinc salt fixation (ZSF) has been reported to work excellently for the preservation of fixation-sensitive antigens. The aim of this study was to establish a reliable histological method for counting of MCs in the porcine intestinum. For this purpose, different tissue fixation and staining methods that also allow potential subsequent immunohistochemical investigations were evaluated in the porcine mucosa, as well as submucosa of small and large intestine. Tissues were fixed in Carnoy, lead acetate, lead nitrate, Zamboni and ZSF and stained subsequently with either polychromatic methylene blue, alcian blue or toluidine blue. For the first time our study reveals that ZSF, a heavy metal fixative, preserves metachromatic staining of porcine MCs. Zamboni fixation was not suitable for histochemical visualization of MCs in the pig intestine. All other tested fixatives were suitable. Alcian blue and toluidine blue co-stained intestinal goblet cells which made a prima facie identification of MCs difficult. The polychromatic methylene blue proved to be the optimal staining. In order to compare MC counting results of the different fixation methods, tissue shrinkage was taken into account. As even the same fixation caused shrinkagedifferences between tissue from small and large intestine, different factors for each single fixation and intestinal localization had to be calculated. Tissue shrinkage varied between 19% and 57%, the highest tissue shrinkage was found after fixation with ZSF in the large intestine, the lowest one in the small intestine after lead acetate fixation. Our study emphasizes that MC counting results from data using different fixation techniques can only be compared if the respective studyimmanent shrinkage factor has been determined and quantification results are adjusted accordingly. PMID:24085270

[Effectiveness comparison of flexible fixation and rigid fixation in treatment of ankle pronation-external rotation fractures with distal tibiofibular syndesmosis].

PubMed

Li, Yuewei; Zhang, Minghui; Li, Xiaorong; Chen, Xiaoyong; Deng, Jianlong

2017-07-01

To compare the effectiveness of flexible fixation and rigid fixation in the treatment of ankle pronation-external rotation fractures with distal tibiofibular syndesmosis. A retrospective analysis was made on the clinical data of 50 patients with ankle pronation-external rotation fractures and distal tibiofibular syndesmosis treated between January 2013 and December 2015. Suture-button fixation was used in 23 patients (flexible fixation group) and cortical screw fixation in 27 patients (rigid fixation group). There was no significant difference in age, gender, weight, side, fracture type, and time from trauma to surgery between 2 groups ( P >0.05). The operation time, medial clear space (MCS), tibiofibular clear space (TFCS), tibiofibular overlap (TFO), American Orthopaedic Foot and Ankle Society (AOFAS) score, and Foot and Ankle Disability Index (FADI) score were compared between 2 groups. The operation time was (83.0±9.1) minutes in the flexible fixation group and was (79.6±13.1) minutes in the rigid fixation group, showing no significant difference ( t =1.052, P =0.265). All patients achieved healing of incision by first intention. The patients were followed up 12-20 months (mean, 14 months). The X-ray films showed good healing of fracture in 2 groups. There was no screw fracture, delayed union or nounion. The fracture healing time was (12.1±2.5) months in the flexible fixation group and was (11.3±3.2) months in the rigid fixation group, showing no significant difference between 2 groups ( t =1.024, P =0.192). Reduction loss occurred after removal of screw in 2 cases of the rigid fixation group. At last follow-up, there was no significant difference in MCS, TFCS, TFO, AOFAS score and FADI score between 2 groups ( P >0.05). Suture-button fixation has similar effectiveness to screw fixation in ankle function and imaging findings, and flexible fixation has lower risk of reduction loss of distal tibiofibular syndesmosis than rigid fixation.

Comparison of Monolateral External Fixation and Internal Fixation for Skeletal Stabilisation in the Management of Small Tibial Bone Defects following Successful Treatment of Chronic Osteomyelitis.

PubMed

Wang, Yicun; Jiang, Hui; Deng, Zhantao; Jin, Jiewen; Meng, Jia; Wang, Jun; Zhao, Jianning; Sun, Guojing; Qian, Hongbo

2017-01-01

To compare the salvage rate and complication between internal fixation and external fixation in patients with small bone defects caused by chronic infectious osteomyelitis debridement. 125 patients with chronic infectious osteomyelitis of tibia fracture who underwent multiple irrigation, debridement procedure, and local/systemic antibiotics were enrolled. Bone defects, which were less than 4 cm, were treated with bone grafting using either internal fixation or monolateral external fixation. 12-month follow-up was conducted with an interval of 3 months to evaluate union of bone defect. Patients who underwent monolateral external fixation had higher body mass index and fasting blood glucose, longer time since injury, and larger bone defect compared with internal fixation. No significant difference was observed in incidence of complications (23.5% versus 19.3%), surgery time (156 ± 23 minutes versus 162 ± 21 minutes), and time to union (11.1 ± 3.0 months versus 10.9 ± 3.1 months) between external fixation and internal fixation. Internal fixation had no significant influence on the occurrence of postoperation complications after multivariate adjustment when compared with external fixation. Furthermore, patients who underwent internal fixation experienced higher level of daily living scales and lower level of anxiety. It was relatively safe to use internal fixation for stabilization in osteomyelitis patients whose bone defects were less than 4 cm and infection was well controlled.

Comparison of Monolateral External Fixation and Internal Fixation for Skeletal Stabilisation in the Management of Small Tibial Bone Defects following Successful Treatment of Chronic Osteomyelitis

PubMed Central

Wang, Yicun; Jiang, Hui; Deng, Zhantao; Meng, Jia; Wang, Jun

2017-01-01

Background To compare the salvage rate and complication between internal fixation and external fixation in patients with small bone defects caused by chronic infectious osteomyelitis debridement. Methods 125 patients with chronic infectious osteomyelitis of tibia fracture who underwent multiple irrigation, debridement procedure, and local/systemic antibiotics were enrolled. Bone defects, which were less than 4 cm, were treated with bone grafting using either internal fixation or monolateral external fixation. 12-month follow-up was conducted with an interval of 3 months to evaluate union of bone defect. Results Patients who underwent monolateral external fixation had higher body mass index and fasting blood glucose, longer time since injury, and larger bone defect compared with internal fixation. No significant difference was observed in incidence of complications (23.5% versus 19.3%), surgery time (156 ± 23 minutes versus 162 ± 21 minutes), and time to union (11.1 ± 3.0 months versus 10.9 ± 3.1 months) between external fixation and internal fixation. Internal fixation had no significant influence on the occurrence of postoperation complications after multivariate adjustment when compared with external fixation. Furthermore, patients who underwent internal fixation experienced higher level of daily living scales and lower level of anxiety. Conclusions It was relatively safe to use internal fixation for stabilization in osteomyelitis patients whose bone defects were less than 4 cm and infection was well controlled. PMID:29333448

Return to sports after plate fixation of humeral head fractures 65 cases with minimum 24-month follow-up.

PubMed

Ahrens, Philipp; Martetschläger, Frank; Siebenlist, Sebastian; Attenberger, Johann; Crönlein, Moritz; Biberthaler, Peter; Stöckle, Ulrich; Sandmann, Gunther H

2017-04-26

Humeral head fractures requiring surgical intervention are severe injuries, which might affect the return to sports and daily activities. We hypothesize that athletic patients will be constrained regarding their sporting activities after surgically treated humeral head fractures. Despite a long rehabilitation program physical activities will change and an avoidance of overhead activities will be noticed. Case series with 65 Patients, with a minimum follow-up of 24 months participated in this study. All patients were treated using a locking plate fixation. Their sporting activity was investigated at the time of the injury and re-investigated after an average of 3.83 years. The questionnaire setup included the evaluation of shoulder function, sporting activities, intensity, sport level and frequency evaluation. Level of evidence IV. At the time of injury 61 Patients (94%) were engaged in recreational sporting activities. The number of sporting activities declined from 26 to 23 at the follow-up examination. There was also a decline in sports frequency and duration of sports activities. The majority of patients remains active in their recreational sporting activity at a comparable duration and frequency both pre- and postoperatively. Nevertheless, shoulder centered sport activities including golf, water skiing and martial arts declined or were given up.

Could persistency of current of injury forecast successful active-fixation pacing lead implantation?

PubMed

Shali, Shalaimaiti; Su, Yangang; Qin, Shengmei; Ge, Junbo

2018-05-01

Presence of adequate current of injury (COI) was recognized as a sign of favorable pacemaker lead outcome. Little is known regarding the value of its dynamic behavior. We sought to test whether persistency of COI could predict active-fixation pacing lead performance. COI was monitored up to 10min after right ventricular (RV) pacing electrode fixation. COI persistency was defined as the percentage of COI magnitude relative to its initial measurement. An unacceptable pacing threshold (≥1.0V in acute evaluation or ≥2.0V over 2-year follow-up) with or without lead dislodgement was considered as lead failure. Lead implantation was attempted for 217 times in 174 patients (age 66.3±7.8years, 78 female). Acute lead failures occurred 43 times. Independent predictors of acute lead failure were RV enlargement (odds ratio [OR] 1.23, 95% confidential interval [CI] 1.11-2.04, P=0.033), absence of COI (OR 3.13, 95%CI 2.08-9.09, P=0.027), and COI persistency at 5min (OR 0.32, 95%CI 0.20-0.69, P=0.001) and 10min (OR 0.41, 95%CI 0.13-0.77, P=0.001). The optimal cutoffs were COI 5min persistency ≥50% (sensitivity 81.4%; specificity 81.9%) and COI 10min persistency ≥20% (sensitivity 86%; specificity 88.6%). There were 12 lead failures during 24.0±6.4months of follow-up. Patients with COI 5min persistency ≥50% had higher event-free survival compared to those with COI 5min persistency <50% (hazard ratio 3.54, 95% CI 1.04-12.06, P=0.043). COI persistency appears to be a valuable indicator for both acute and long-term outcome of active-fixation pacemaker leads. A precipitous decline in COI may require more attention to make sure of the lead performance. Copyright © 2018 Elsevier Ireland Ltd. All rights reserved.

The Micro-RNA172c-APETALA2-1 Node as a Key Regulator of the Common Bean-Rhizobium etli Nitrogen Fixation Symbiosis1[OPEN

PubMed Central

Nova-Franco, Bárbara; Íñiguez, Luis P.; Valdés-López, Oswaldo; Leija, Alfonso; Fuentes, Sara I.; Ramírez, Mario; Paul, Sujay

2015-01-01

Micro-RNAs are recognized as important posttranscriptional regulators in plants. The relevance of micro-RNAs as regulators of the legume-rhizobia nitrogen-fixing symbiosis is emerging. The objective of this work was to functionally characterize the role of micro-RNA172 (miR172) and its conserved target APETALA2 (AP2) transcription factor in the common bean (Phaseolus vulgaris)-Rhizobium etli symbiosis. Our expression analysis revealed that mature miR172c increased upon rhizobial infection and continued increasing during nodule development, reaching its maximum in mature nodules and decaying in senescent nodules. The expression of AP2-1 target showed a negative correlation with miR172c expression. A drastic decrease in miR172c and high AP2-1 mRNA levels were observed in ineffective nodules. Phenotypic analysis of composite bean plants with transgenic roots overexpressing miR172c or a mutated AP2-1 insensitive to miR172c cleavage demonstrated the pivotal regulatory role of the miR172 node in the common bean-rhizobia symbiosis. Increased miR172 resulted in improved root growth, increased rhizobial infection, increased expression of early nodulation and autoregulation of nodulation genes, and improved nodulation and nitrogen fixation. In addition, these plants showed decreased sensitivity to nitrate inhibition of nodulation. Through transcriptome analysis, we identified 114 common bean genes that coexpressed with AP2-1 and proposed these as being targets for transcriptional activation by AP2-1. Several of these genes are related to nodule senescence, and we propose that they have to be silenced, through miR172c-induced AP2-1 cleavage, in active mature nodules. Our work sets the basis for exploring the miR172-mediated improvement of symbiotic nitrogen fixation in common bean, the most important grain legume for human consumption. PMID:25739700

The micro-RNA72c-APETALA2-1 node as a key regulator of the common bean-Rhizobium etli nitrogen fixation symbiosis.

PubMed

Nova-Franco, Bárbara; Íñiguez, Luis P; Valdés-López, Oswaldo; Alvarado-Affantranger, Xochitl; Leija, Alfonso; Fuentes, Sara I; Ramírez, Mario; Paul, Sujay; Reyes, José L; Girard, Lourdes; Hernández, Georgina

2015-05-01

Micro-RNAs are recognized as important posttranscriptional regulators in plants. The relevance of micro-RNAs as regulators of the legume-rhizobia nitrogen-fixing symbiosis is emerging. The objective of this work was to functionally characterize the role of micro-RNA172 (miR172) and its conserved target APETALA2 (AP2) transcription factor in the common bean (Phaseolus vulgaris)-Rhizobium etli symbiosis. Our expression analysis revealed that mature miR172c increased upon rhizobial infection and continued increasing during nodule development, reaching its maximum in mature nodules and decaying in senescent nodules. The expression of AP2-1 target showed a negative correlation with miR172c expression. A drastic decrease in miR172c and high AP2-1 mRNA levels were observed in ineffective nodules. Phenotypic analysis of composite bean plants with transgenic roots overexpressing miR172c or a mutated AP2-1 insensitive to miR172c cleavage demonstrated the pivotal regulatory role of the miR172 node in the common bean-rhizobia symbiosis. Increased miR172 resulted in improved root growth, increased rhizobial infection, increased expression of early nodulation and autoregulation of nodulation genes, and improved nodulation and nitrogen fixation. In addition, these plants showed decreased sensitivity to nitrate inhibition of nodulation. Through transcriptome analysis, we identified 114 common bean genes that coexpressed with AP2-1 and proposed these as being targets for transcriptional activation by AP2-1. Several of these genes are related to nodule senescence, and we propose that they have to be silenced, through miR172c-induced AP2-1 cleavage, in active mature nodules. Our work sets the basis for exploring the miR172-mediated improvement of symbiotic nitrogen fixation in common bean, the most important grain legume for human consumption. © 2015 American Society of Plant Biologists. All Rights Reserved.

Bone suture anchor fixation in the lower extremity: a review of insertion principles and a comparative biomechanical evaluation.

PubMed

Scranton, Pierce E; Lawhon, S Michael; McDermott, John E

2005-07-01

Suture anchors have been developed for the fixation of ligaments, capsules, or tendons to bone. These devices have led to improved fixation, smaller incisions, earlier limb mobility, and improved outcomes. They were originally developed for use in shoulder reconstructions but are now used in almost all extremities. In the lower leg they are used in the tibia, the talus, the calcaneus, tarsal bones, and phalanges. Nevertheless, techniques for insertion and mechanisms of failure are not well described. Five suture anchors were studied to determine the pullout strength in four distal cadaver femurs and four proximal cadaver tibias from 55- and 62-year-old males. Eight hundred ninety Newton line was used, testing the anchors to failure with an Instron testing device (Instron, Norwood, MA). The anchor devices were inserted randomly and tested blindly (12 tests per anchor device, 60 tests in all). Two anchors in each group tested failed at low loads. Both types of plastic anchors had failures at the eyelet. Average pullout strength varied from 85.4 to 185.6 N. Insertion techniques are specific for each device, and they must be followed for optimal fixation. In this study, in all five groups of anchors tested two of the 12 anchors in each group failed with minimal force. On the basis of this finding we recommend that, if suture anchor fixation is necessary, at least two anchors should be used. Since there appears to be a percentage of failure in all devices, the second anchor can serve as a backup. It is imperative that surgeons be familiar with the insertion techniques of each device before use.

Effect of Microgravity on Early Events of Biological Nitrogen Fixation in Medicago Truncatula: Initial Results from the SyNRGE Experiment

NASA Technical Reports Server (NTRS)

Stutte, Gary W.; Roberts, Michael S.

2011-01-01

SyNRGE (Symbiotic Nodulation in a Reduced Gravity Environment) was a sortie mission on STS-135 in the Biological Research in Canisters (BRIC) hardware to study the effect of microgravity on a plant-microbe symbiosis resulting in biological nitrogen fixation. Medicago truncatula, a model species of the legume family, was inoculated with its bacterial symbiont, Sinorhizobium meliloti, to observe early events associated with infection and nodulation in Petri Dish Fixation Units (PDFUs). Two sets of experiments were conducted in orbit and in 24-hour delayed ground controls. Experiment one was designed to determine if S. meliloti infect M. truncatula and initiate physiological changes associated with nodule formation. Roots of five-day-old M. truncatula cultivar Jemalong A17 (Enodll::gus) were inoculated 24 hr before launch with either S. meliloti strain 1021 or strain ABS7 and integrated into BRIC-PDFU hardware placed in a 4 C Cold Bag for launch on Atlantis. Inoculated plants and uninoculated controls were maintained in the dark at ambient temperature in the middeck of STS-135 for 11 days before fixation in RNAlater(tM) by crew activation of the PDFU. Experiment two was designed to determine if microgravity altered the process of bacterial infection and host plant nodule formation. Seeds of two M. truncatula cultivar Jemalong A17 lines, the Enodll::gus used in experiment 1, and SUNN, a super-nodulating mutant of A17, were germinated on orbit for 11 days in the middeck cabin and returned to Earth alive inside of BRIC-PDFU's at 4 C. S. meliloti strains 1021 and ABS7 were cultivated separately in broth culture on orbit and also returned to Earth alive. After landing, flight- and groundgrown plants and bacteria were transferred from BRIC-PDFU's into Nunc(tm) 4-well plates for reciprocity crosses. Rates of plant growth and nodule development on Buffered Nodulation Medium (lacking nitrogen) were measured for 14 days. Preliminary analysis' of Experiment 1 confirms that legumes and bacteria cultivated in space 'initiate the symbiotic interaction leading to nitrogen fixation and that bacteria retain the ability to form nodules on M. truncatula roots. Initial assessment of experiment 2 shows 100% seed germination and excellent bacterial growth in microgravity.

Response of enzymes involved in the processes of antioxidation towards benthiocarb and methylparathion in cyanobacteria Nostoc muscorum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhunia, A.K.; Roy, D.; Basu, N.K.

1991-08-01

Recently, it has been observed in the authors' laboratory that growth, nitrogen fixation, protein content of cyanobacteria Nostoc muscorum were reduced by methylparathion and benthiocarb treatment. Though many works on toxicity of pesticides on cyanobacteria, specially on growth, photosynthesis and nitrogen fixation are available, the effects of pesticides on antioxidant enzyme levels is still unclear. In this communication, studies have been presented on the effects of organophosphate insecticide methyl-parathione and carbamate herbicide benthiocarb, on glutathione content, glutathione reductase (GR) and superoxide dismutase (SOD) activities of filamentous, nitrogen-fixing cyanobacteria Nostoc muscorum.

Comparison of screw fixation with elastic fixation methods in the treatment of syndesmosis injuries in ankle fractures.

PubMed

Seyhan, Mustafa; Donmez, Ferdi; Mahirogullari, Mahir; Cakmak, Selami; Mutlu, Serhat; Guler, Olcay

2015-07-01

17 patients with ankle syndesmosic injury were treated with a 4.5mm single cortical screw fixation (passage of screw 4 cortices) and 15 patients were treated with single-level elastic fixation material. All patients were evaluated according to the AOFAS ankle and posterior foot scale at the third, sixth and twelfth months after the fixation. The ankle range of movement was recorded together with the healthy side. The Student's t test was used for statistical comparisons. No statistical significant difference was observed between the AOFAS scores (p>0.05). The range of dorsiflexion and plantar flexion motion of the elastic fixation group at the 6th and 12th months were significantly better compared to the screw fixation group (p<0.01). Elastic fixation is as functional as screw fixation in the treatment of ankle syndesmosis injuries. The unnecessary need of a second surgical intervention for removal of the fixation material is another advantageous aspect of this method of fixation. Copyright © 2015. Published by Elsevier Ltd.

Nitrogen and Phosphorus Addition Affects Biological N2 Fixation and Sphagnum Moss in an Ombrotrophic Bog

NASA Astrophysics Data System (ADS)

Zivkovic, T.; Ardichvili, A.; Moore, T. R.

2016-12-01

Most of the 18 Pg nitrogen (N) accumulated in northern nutrient-poor and Sphagnum-dominated peatlands (bogs and fens) can be attributed to N2 fixation by diazotrophs either associated with the live Sphagnum or non-symbiotically in the deeper peat. Where atmospheric N deposition is low (< 0.2 g m-2 y-1), ombrotrophic bogs rely on N2 fixation as the primary source of N that sustains primary production. The industrial revolution and anthropogenic impacts in the last 200 years have resulted in larger atmospheric N deposition as ammonium (NH4) and nitrate (NO3). One effect of increased N deposition in Sphagnum is a switch from N to phosphorus (P) limitation suggested by the increase in tissue N:P>16. It is unclear how Sphagnum hosted diazotrophic activity may be affected by N deposition and thus changes in N:P ratio. We investigated the effects of long-term addition of different sources of nitrogen (0, 1.6, 3.2 and 6.4 g N m-2 y-1 as NH4Cl and NaNO3), and phosphorus (5 g P m-2 y-1 as KH2PO4) on Sphagnum nutrient status (N, P and N:P), net primary productivity (NPP) and Sphagnum-associated N2 fixation at Mer Bleue, a temperate ombrotrophic bog. Our study shows that N concentration in Sphagnum tissue increased with larger rates of N addition, with a stronger effect on Sphagnum from NH4 than NO3. The addition of P created a 3.5 fold increase in Sphagnum P content compared to controls. Sphagnum NPP decreased linearly with the rise in N:P ratio, while linear growth declined exponentially with increase in Sphagnum N content. N2 fixation significantly decreased in response to even the smallest addition of both N species. In contrast, the addition of P increased N2 fixation by up to 100 times compared to N treatments and up to 5-30 times compared to controls. The change in N2 fixation was best modeled by the N:P ratio, across all experimental treatments. Although elevated N deposition substantially decreases N2 fixation, the N:P ratio in Sphagnum may be a good predictor, likely owing to a strong P-limitation.

Regional assessments of the Nation's water quality—Improved understanding of stream nutrient sources through enhanced modeling capabilities

USGS Publications Warehouse

Preston, Stephen D.; Alexander, Richard B.; Woodside, Michael D.

2011-01-01

The U.S. Geological Survey (USGS) recently completed assessments of stream nutrients in six major regions extending over much of the conterminous United States. SPARROW (SPAtially Referenced Regressions On Watershed attributes) models were developed for each region to explain spatial patterns in monitored stream nutrient loads in relation to human activities and natural resources and processes. The model information, reported by stream reach and catchment, provides contrasting views of the spatial patterns of nutrient source contributions, including those from urban (wastewater effluent and diffuse runoff from developed land), agricultural (farm fertilizers and animal manure), and specific background sources (atmospheric nitrogen deposition, soil phosphorus, forest nitrogen fixation, and channel erosion).

Risk Stratification for Avascular Necrosis of the Femoral Head After Internal Fixation of Femoral Neck Fractures by Post-Operative Bone SPECT/CT.

PubMed

Han, Sangwon; Oh, Minyoung; Yoon, Seokho; Kim, Jinsoo; Kim, Ji-Wan; Chang, Jae-Suk; Ryu, Jin-Sook

2017-03-01

Avascular necrosis (AVN) of the femoral head is a major complication after internal fixation of a femoral neck fracture and determines the functional prognosis. We investigated postoperative bone single-photon emission computed tomography/computed tomography (SPECT/CT) for assessing the risk of femoral head AVN. We retrospectively reviewed 53 consecutive patients who underwent bone SPECT/CT within 2 weeks of internal fixation of a femoral neck fracture and follow-up serial hip radiographs over at least 12 months. Nine patients developed femoral head AVN. In 15 patients who showed normal uptake on immediate postoperative SPECT/CT, no AVN occurred, whereas 9 of 38 patients who showed cold defects of the femoral head later developed AVN. The negative predictive value of immediate postoperative SPECT/CT for AVN was 100 %, whereas the positive predictive value was 24 %. Among 38 patients with cold defects, 1 developed AVN 3 months postoperatively. A follow-up bone SPECT/CT was performed in the other 37 patients at 2-10 months postoperatively. The follow-up bone SPECT/CT revealed completely normalized femoral head uptake in 27, partially normalized uptake in 8, and persistent cold defects in 2 patients. AVN developed in 3.7 % (1/27), 62.5 % (5/8), and 100 % (2/2) of each group, respectively. According to the time point of imaging, radiotracer uptake patterns of the femoral head on postoperative bone SPECT/CT indicate the risk of AVN after internal fixation of femoral neck fractures differently. Postoperative bone SPECT/CT may help orthopedic surgeons determine the appropriate follow-up of these patients.

Transgenic Perturbation of the Decarboxylation Phase of Crassulacean Acid Metabolism Alters Physiology and Metabolism But Has Only a Small Effect on Growth

DOE PAGES

Dever, Louisa V.; Boxall, Susanna F.; Knerova, Jana; ...

2014-11-05

Here, mitochondrial NAD-malic enzyme (ME) and/or cytosolic/plastidic NADP-ME combined with the cytosolic/plastidic pyruvate orthophosphate dikinase (PPDK) catalyze two key steps during light-period malate decarboxylation that underpin secondary CO 2 fixation in some Crassulacean acid metabolism (CAM) species. We report the generation and phenotypic characterization of transgenic RNA interference lines of the obligate CAM species Kalanchoë fedtschenkoi with reduced activities of NAD-ME or PPDK. Transgenic line rNAD-ME1 had 8%, and rPPDK1 had 5% of the wild-type level of activity, and showed dramatic changes in the light/dark cycle of CAM CO 2 fixation. In well-watered conditions, these lines fixed all of theirmore » CO 2 in the light; they thus performed C 3 photosynthesis. The alternative malate decarboxylase, NADP-ME, did not appear to compensate for the reduction in NAD-ME, suggesting that NAD-ME was the key decarboxylase for CAM. The activity of other CAM enzymes was reduced as a consequence of knocking out either NAD-ME or PPDK activity, particularly phosphoenolpyruvate carboxylase (PPC) and PPDK in rNAD-ME1. Furthermore, the circadian clock-controlled phosphorylation of PPC in the dark was reduced in both lines, especially in rNAD-ME1. This had the consequence that circadian rhythms of PPC phosphorylation, PPC kinase transcript levels and activity, and the classic circadian rhythm of CAM CO 2 fixation were lost, or dampened toward arrhythmia, under constant light and temperature conditions. Surprisingly, oscillations in the transcript abundance of core circadian clock genes also became arrhythmic in the rNAD-ME1 line, suggesting that perturbing CAM in K. fedtschenkoi feeds back to perturb the central circadian clock.« less

Transgenic Perturbation of the Decarboxylation Phase of Crassulacean Acid Metabolism Alters Physiology and Metabolism But Has Only a Small Effect on Growth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dever, Louisa V.; Boxall, Susanna F.; Knerova, Jana

Here, mitochondrial NAD-malic enzyme (ME) and/or cytosolic/plastidic NADP-ME combined with the cytosolic/plastidic pyruvate orthophosphate dikinase (PPDK) catalyze two key steps during light-period malate decarboxylation that underpin secondary CO 2 fixation in some Crassulacean acid metabolism (CAM) species. We report the generation and phenotypic characterization of transgenic RNA interference lines of the obligate CAM species Kalanchoë fedtschenkoi with reduced activities of NAD-ME or PPDK. Transgenic line rNAD-ME1 had 8%, and rPPDK1 had 5% of the wild-type level of activity, and showed dramatic changes in the light/dark cycle of CAM CO 2 fixation. In well-watered conditions, these lines fixed all of theirmore » CO 2 in the light; they thus performed C 3 photosynthesis. The alternative malate decarboxylase, NADP-ME, did not appear to compensate for the reduction in NAD-ME, suggesting that NAD-ME was the key decarboxylase for CAM. The activity of other CAM enzymes was reduced as a consequence of knocking out either NAD-ME or PPDK activity, particularly phosphoenolpyruvate carboxylase (PPC) and PPDK in rNAD-ME1. Furthermore, the circadian clock-controlled phosphorylation of PPC in the dark was reduced in both lines, especially in rNAD-ME1. This had the consequence that circadian rhythms of PPC phosphorylation, PPC kinase transcript levels and activity, and the classic circadian rhythm of CAM CO 2 fixation were lost, or dampened toward arrhythmia, under constant light and temperature conditions. Surprisingly, oscillations in the transcript abundance of core circadian clock genes also became arrhythmic in the rNAD-ME1 line, suggesting that perturbing CAM in K. fedtschenkoi feeds back to perturb the central circadian clock.« less

Stress and stability of plate-screw fixation and screw fixation in the treatment of Schatzker type IV medial tibial plateau fracture: a comparative finite element study.

PubMed

Huang, Xiaowei; Zhi, Zhongzheng; Yu, Baoqing; Chen, Fancheng

2015-11-25

The purpose of this study is to compare the stress and stability of plate-screw fixation and screw fixation in the treatment of Schatzker type IV medial tibial plateau fracture. A three-dimensional (3D) finite element model of the medial tibial plateau fracture (Schatzker type IV fracture) was created. An axial force of 2500 N with a distribution of 60% to the medial compartment was applied to simulate the axial compressive load on an adult knee during single-limb stance. The equivalent von Mises stress, displacement of the model relative to the distal tibia, and displacement of the implants were used as the output measures. The mean stress value of the plate-screw fixation system was 18.78 MPa, which was significantly (P < 0.001) smaller than that of the screw fixation system. The maximal value of displacement (sum) in the plate-screw fixation system was 2.46 mm, which was lower than that in the screw fixation system (3.91 mm). The peak stress value of the triangular fragment in the plate-screw fixation system model was 42.04 MPa, which was higher than that in the screw fixation model (24.18 MPa). But the mean stress of the triangular fractured fragment in the screw fixation model was significantly higher in terms of equivalent von Mises stress (EVMS), x-axis, and z-axis (P < 0.001). This study demonstrated that the load transmission mechanism between plate-screw fixation system and screw fixation system was different and the stability provided by the plate-screw fixation system was superior to the screw fixation system.

A spatially nonselective baseline signal in parietal cortex reflects the probability of a monkey’s success on the current trial

PubMed Central

Zhang, Mingsha; Wang, Xiaolan; Goldberg, Michael E.

2014-01-01

We recorded the activity of neurons in the lateral intraparietal area of two monkeys while they performed two similar visual search tasks, one difficult, one easy. Each task began with a period of fixation followed by an array consisting of a single capital T and a number of lowercase t’s. The monkey had to find the capital T and report its orientation, upright or inverted, with a hand movement. In the easy task the monkey could explore the array with saccades. In the difficult task the monkey had to continue fixating and find the capital T in the visual periphery. The baseline activity measured during the fixation period, at a time in which the monkey could not know if the impending task would be difficult or easy or where the target would appear, predicted the monkey’s probability of success or failure on the task. The baseline activity correlated inversely with the monkey's recent history of success and directly with the intensity of the response to the search array on the current trial. The baseline activity was unrelated to the monkey’s spatial locus of attention as determined by the location of the cue in a cued visual reaction time task. We suggest that rather than merely reflecting the noise in the system, the baseline signal reflects the cortical manifestation of modulatory state, motivational, or arousal pathways, which determine the efficiency of cortical sensorimotor processing and the quality of the monkey’s performance. PMID:24889623

Recent advances in fixation of the craniomaxillofacial skeleton.

PubMed

Meslemani, Danny; Kellman, Robert M

2012-08-01

Fixation of the craniomaxillofacial skeleton is an evolving aspect for facial plastic, oral and maxillofacial, and plastic surgery. This review looks at the recent advances that aid in reduction and fixation of the craniomaxillofacial skeleton. More surgeons are using resorbable plates for craniomaxillofacial fixation. A single miniplate on the inferior border of the mandible may be sufficient to reduce and fixate an angle fracture. Percutaneous K-wires may assist in plating angle fractures. Intraoperative computed tomography (CT) may prove to be useful for assessing reduction and fixation. Resorbable plates are becoming increasingly popular in orthognathic surgery and facial trauma surgery. There are newer operative techniques for fixating the angle of the mandible. Also, the utilization of the intraoperative CT provides immediate feedback for accurate reduction and fixation. Prebent surgical plates save operative time, decrease errors, and provide more accurate fixation.

Cortical bone trajectory screw fixation versus traditional pedicle screw fixation for 2-level posterior lumbar interbody fusion: comparison of surgical outcomes for 2-level degenerative lumbar spondylolisthesis.

PubMed

Sakaura, Hironobu; Miwa, Toshitada; Yamashita, Tomoya; Kuroda, Yusuke; Ohwada, Tetsuo

2018-01-01

OBJECTIVE The cortical bone trajectory (CBT) screw technique is a new nontraditional pedicle screw (PS) insertion method. However, the biomechanical behavior of multilevel CBT screw/rod fixation remains unclear, and surgical outcomes in patients after 2-level posterior lumbar interbody fusion (PLIF) using CBT screw fixation have not been reported. Thus, the purposes of this study were to examine the clinical and radiological outcomes after 2-level PLIF using CBT screw fixation for 2-level degenerative lumbar spondylolisthesis (DS) and to compare these outcomes with those after 2-level PLIF using traditional PS fixation. METHODS The study included 22 consecutively treated patients who underwent 2-level PLIF with CBT screw fixation for 2-level DS (CBT group, mean follow-up 39 months) and a historical control group of 20 consecutively treated patients who underwent 2-level PLIF using traditional PS fixation for 2-level DS (PS group, mean follow-up 35 months). Clinical symptoms were evaluated using the Japanese Orthopaedic Association (JOA) scoring system. Bony union was assessed by dynamic plain radiographs and CT images. Surgery-related complications, including symptomatic adjacent-segment disease (ASD), were examined. RESULTS The mean operative duration and intraoperative blood loss were 192 minutes and 495 ml in the CBT group and 218 minutes and 612 ml in the PS group, respectively (p < 0.05 and p > 0.05, respectively). The mean JOA score improved significantly from 12.3 points before surgery to 21.1 points (mean recovery rate 54.4%) at the latest follow-up in the CBT group and from 12.8 points before surgery to 20.4 points (mean recovery rate 51.8%) at the latest follow-up in the PS group (p > 0.05). Solid bony union was achieved at 90.9% of segments in the CBT group and 95.0% of segments in the PS group (p > 0.05). Symptomatic ASD developed in 2 patients in the CBT group (9.1%) and 4 patients in the PS group (20.0%, p > 0.05). CONCLUSIONS Two-level PLIF with CBT screw fixation for 2-level DS could be less invasive and result in improvement of clinical symptoms equal to those of 2-level PLIF using traditional PS fixation. The incidence of symptomatic ASD and the rate of bony union were lower in the CBT group than in the PS group, although these differences were not significant.

Biomechanical Comparison of External Fixation and Compression Screws for Transverse Tarsal Joint Arthrodesis.

PubMed

Latt, L Daniel; Glisson, Richard R; Adams, Samuel B; Schuh, Reinhard; Narron, John A; Easley, Mark E

2015-10-01

Transverse tarsal joint arthrodesis is commonly performed in the operative treatment of hindfoot arthritis and acquired flatfoot deformity. While fixation is typically achieved using screws, failure to obtain and maintain joint compression sometimes occurs, potentially leading to nonunion. External fixation is an alternate method of achieving arthrodesis site compression and has the advantage of allowing postoperative compression adjustment when necessary. However, its performance relative to standard screw fixation has not been quantified in this application. We hypothesized that external fixation could provide transverse tarsal joint compression exceeding that possible with screw fixation. Transverse tarsal joint fixation was performed sequentially, first with a circular external fixator and then with compression screws, on 9 fresh-frozen cadaveric legs. The external fixator was attached in abutting rings fixed to the tibia and the hindfoot and a third anterior ring parallel to the hindfoot ring using transverse wires and half-pins in the tibial diaphysis, calcaneus, and metatarsals. Screw fixation comprised two 4.3 mm headless compression screws traversing the talonavicular joint and 1 across the calcaneocuboid joint. Compressive forces generated during incremental fixator foot ring displacement to 20 mm and incremental screw tightening were measured using a custom-fabricated instrumented miniature external fixator spanning the transverse tarsal joint. The maximum compressive force generated by the external fixator averaged 186% of that produced by the screws (range, 104%-391%). Fixator compression surpassed that obtainable with screws at 12 mm of ring displacement and decreased when the tibial ring was detached. No correlation was found between bone density and the compressive force achievable by either fusion method. The compression across the transverse tarsal joint that can be obtained with a circular external fixator including a tibial ring exceeds that which can be obtained with 3 headless compression screws. Screw and external fixator performance did not correlate with bone mineral density. This study supports the use of external fixation as an alternative method of generating compression to help stimulate fusion across the transverse tarsal joints. The findings provide biomechanical evidence to support the use of external fixation as a viable option in transverse tarsal joint fusion cases in which screw fixation has failed or is anticipated to be inadequate due to suboptimal bone quality. © The Author(s) 2015.

RNA-Seq analysis of nodule development at five different developmental stages of soybean (Glycine max) inoculated with Bradyrhizobium japonicum strain 113-2

PubMed Central

Yuan, Song L.; Li, Rong; Chen, Hai F.; Zhang, Chan J.; Chen, Li M.; Hao, Qing N.; Chen, Shui L.; Shan, Zhi H.; Yang, Zhong L.; Zhang, Xiao J.; Qiu, De Z.; Zhou, Xin A.

2017-01-01

Nodule development directly affects nitrogen fixation efficiency during soybean growth. Although abundant genome-based information related to nodule development has been released and some studies have reported the molecular mechanisms that regulate nodule development, information on the way nodule genes operate in nodule development at different developmental stages of soybean is limited. In this report, notably different nodulation phenotypes in soybean roots inoculated with Bradyrhizobium japonicum strain 113-2 at five developmental stages (branching stage, flowering stage, fruiting stage, pod stage and harvest stage) were shown, and the expression of nodule genes at these five stages was assessed quantitatively using RNA-Seq. Ten comparisons were made between these developmental periods, and their differentially expressed genes were analysed. Some important genes were identified, primarily encoding symbiotic nitrogen fixation-related proteins, cysteine proteases, cystatins and cysteine-rich proteins, as well as proteins involving plant-pathogen interactions. There were no significant shifts in the distribution of most GO functional annotation terms and KEGG pathway enrichment terms between these five development stages. A cystatin Glyma18g12240 was firstly identified from our RNA-seq, and was likely to promote nodulation and delay nodule senescence. This study provides molecular material for further investigations into the mechanisms of nitrogen fixation at different soybean developmental stages. PMID:28169364

Hybrid external fixation in high-energy elbow fractures: a modular system with a promising future.

PubMed

Lerner, A; Stahl, S; Stein, H

2000-12-01

Severe, high-energy, periarticular elbow injuries producing a "floating joint" are a major surgical challenge. Their reconstruction and rehabilitation are not well documented. Therefore, the following reports our experience with treating such injuries caused by war wounds. Seven adults with compound open peri- and intra-articular elbow fractures were treated in hybrid ring tubular fixation frames. After debridement, bone stabilization, and neurovascular reconstructions, early controlled daily movements were started in the affected joint. These seven patients had together seven humeral, five radial, and six ulnar fractures. All fractures united at a median time of 180 days. No deep infection developed. The functional end results assessed by the Khalfayan functional score were excellent in two, good in one, and fair in four of these severely mangled upper extremities. None was amputated. The Mangled Extremity Severity Score has been shown to be unable to provide a reliable assessment for severe high-energy limb injuries surgically managed with the modular hybrid thin wire tubular external fixation system. This hybrid system is a very useful addition to the surgical armamentarium of orthopedic trauma surgeons. It both allows complex surgical reconstructions and reduces the incidence of deep infections in these heavily contaminated injuries. The hybrid circular (thin wire) external fixation system is very modular and may provide secure skeletal stabilization even in cases of severely comminuted juxta-articular fractures on both sides of the elbow joint (floating elbow) with severe damage to soft tissues. This fixation system allows individual fixation of forearm bone fractures, thus allowing the preservation of pronation-supination movements.

Early experience with a novel nonmetallic cable in reconstructive hip surgery.

PubMed

Ting, Nicholas T; Wera, Glenn D; Levine, Brett R; Della Valle, Craig J

2010-09-01

Metallic wires and cables are commonly used in primary and revision THA for fixation of periprosthetic fractures and osteotomies of the greater trochanter. These systems provide secure fixation and high healing rates but fraying, third-body generation, accelerated wear of the bearing surface, and injury to the surgical team remain concerning. We determined the rate of cable failure, union, and complications associated with a novel, nonmetallic cerclage cable in periprosthetic fracture and osteotomy fixation during THA. We retrospectively reviewed 29 patients who had primary and revision THAs using nonmetallic cables. Indications for use included fixation of an extended trochanteric osteotomy, intraoperative fracture of the proximal femur, strut allograft fixation, and a Vancouver B1 periprosthetic fracture of the femur. All patients were evaluated clinically and radiographically immediately postoperatively, at 3 weeks, 6 weeks, 3 months, and then annually thereafter. The minimum followup was 13 months (mean, 21 months; range, 13-30 months). Two of the 29 patients (7%) developed a nonunion; all remaining osteotomies, fractures and allografts had healed at the time of most recent evaluation. Four patients (14%) dislocated postoperatively; two were treated successfully with closed reduction, while the other two required reoperation. We identified no evidence of breakage or other complications directly attributable to the cables. The nonmetallic periprosthetic cables used in this series provided adequate fixation to allow for both osteotomy and fracture healing. We did not observe any complications directly related to the cables. Level of Evidence Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Time Savings and Surgery Task Load Reduction in Open Intraperitoneal Onlay Mesh Fixation Procedure.

PubMed

Roy, Sanjoy; Hammond, Jeffrey; Panish, Jessica; Shnoda, Pullen; Savidge, Sandy; Wilson, Mark

2015-01-01

This study assessed the reduction in surgeon stress associated with savings in procedure time for mechanical fixation of an intraperitoneal onlay mesh (IPOM) compared to a traditional suture fixation in open ventral hernia repair. Nine general surgeons performed 36 open IPOM fixation procedures in porcine model. Each surgeon conducted two mechanical (using ETHICON SECURESTRAP ™ Open) and two suture fixation procedures. Fixation time was measured using a stopwatch, and related surgeon stress was assessed using the validated SURG-TLX questionnaire. T-tests were used to compare between-group differences, and a two-sided 95% confidence interval for the difference in stress levels was established using nonparametric methodology. The mechanical fixation group demonstrated an 89.1% mean reduction in fixation time, as compared to the suture group (p < 0.00001). Surgeon stress scores measured using SURG-TLX were 55.5% lower in the mechanical compared to the suture fixation group (p < 0.001). Scores in five of the six sources of stress were significantly lower for mechanical fixation. Mechanical fixation with ETHICON SECURESTRAP ™ Open demonstrated a significant reduction in fixation time and surgeon stress, which may translate into improved operating efficiency, improved performance, improved surgeon quality of life, and reduced overall costs of the procedure.

Time Savings and Surgery Task Load Reduction in Open Intraperitoneal Onlay Mesh Fixation Procedure

PubMed Central

Roy, Sanjoy; Hammond, Jeffrey; Panish, Jessica; Shnoda, Pullen; Savidge, Sandy; Wilson, Mark

2015-01-01

Background. This study assessed the reduction in surgeon stress associated with savings in procedure time for mechanical fixation of an intraperitoneal onlay mesh (IPOM) compared to a traditional suture fixation in open ventral hernia repair. Study Design. Nine general surgeons performed 36 open IPOM fixation procedures in porcine model. Each surgeon conducted two mechanical (using ETHICON SECURESTRAPTM Open) and two suture fixation procedures. Fixation time was measured using a stopwatch, and related surgeon stress was assessed using the validated SURG-TLX questionnaire. T-tests were used to compare between-group differences, and a two-sided 95% confidence interval for the difference in stress levels was established using nonparametric methodology. Results. The mechanical fixation group demonstrated an 89.1% mean reduction in fixation time, as compared to the suture group (p < 0.00001). Surgeon stress scores measured using SURG-TLX were 55.5% lower in the mechanical compared to the suture fixation group (p < 0.001). Scores in five of the six sources of stress were significantly lower for mechanical fixation. Conclusions. Mechanical fixation with ETHICON SECURESTRAPTM Open demonstrated a significant reduction in fixation time and surgeon stress, which may translate into improved operating efficiency, improved performance, improved surgeon quality of life, and reduced overall costs of the procedure. PMID:26240834