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Sample records for physiologic oxygen tension

  1. Macromolecular crowding meets oxygen tension in human mesenchymal stem cell culture - A step closer to physiologically relevant in vitro organogenesis

    NASA Astrophysics Data System (ADS)

    Cigognini, Daniela; Gaspar, Diana; Kumar, Pramod; Satyam, Abhigyan; Alagesan, Senthilkumar; Sanz-Nogués, Clara; Griffin, Matthew; O’Brien, Timothy; Pandit, Abhay; Zeugolis, Dimitrios I.

    2016-08-01

    Modular tissue engineering is based on the cells’ innate ability to create bottom-up supramolecular assemblies with efficiency and efficacy still unmatched by man-made devices. Although the regenerative potential of such tissue substitutes has been documented in preclinical and clinical setting, the prolonged culture time required to develop an implantable device is associated with phenotypic drift and/or cell senescence. Herein, we demonstrate that macromolecular crowding significantly enhances extracellular matrix deposition in human bone marrow mesenchymal stem cell culture at both 20% and 2% oxygen tension. Although hypoxia inducible factor - 1α was activated at 2% oxygen tension, increased extracellular matrix synthesis was not observed. The expression of surface markers and transcription factors was not affected as a function of oxygen tension and macromolecular crowding. The multilineage potential was also maintained, albeit adipogenic differentiation was significantly reduced in low oxygen tension cultures, chondrogenic differentiation was significantly increased in macromolecularly crowded cultures and osteogenic differentiation was not affected as a function of oxygen tension and macromolecular crowding. Collectively, these data pave the way for the development of bottom-up tissue equivalents based on physiologically relevant developmental processes.

  2. Macromolecular crowding meets oxygen tension in human mesenchymal stem cell culture - A step closer to physiologically relevant in vitro organogenesis

    PubMed Central

    Cigognini, Daniela; Gaspar, Diana; Kumar, Pramod; Satyam, Abhigyan; Alagesan, Senthilkumar; Sanz-Nogués, Clara; Griffin, Matthew; O’Brien, Timothy; Pandit, Abhay; Zeugolis, Dimitrios I.

    2016-01-01

    Modular tissue engineering is based on the cells’ innate ability to create bottom-up supramolecular assemblies with efficiency and efficacy still unmatched by man-made devices. Although the regenerative potential of such tissue substitutes has been documented in preclinical and clinical setting, the prolonged culture time required to develop an implantable device is associated with phenotypic drift and/or cell senescence. Herein, we demonstrate that macromolecular crowding significantly enhances extracellular matrix deposition in human bone marrow mesenchymal stem cell culture at both 20% and 2% oxygen tension. Although hypoxia inducible factor - 1α was activated at 2% oxygen tension, increased extracellular matrix synthesis was not observed. The expression of surface markers and transcription factors was not affected as a function of oxygen tension and macromolecular crowding. The multilineage potential was also maintained, albeit adipogenic differentiation was significantly reduced in low oxygen tension cultures, chondrogenic differentiation was significantly increased in macromolecularly crowded cultures and osteogenic differentiation was not affected as a function of oxygen tension and macromolecular crowding. Collectively, these data pave the way for the development of bottom-up tissue equivalents based on physiologically relevant developmental processes. PMID:27478033

  3. Macromolecular crowding meets oxygen tension in human mesenchymal stem cell culture - A step closer to physiologically relevant in vitro organogenesis.

    PubMed

    Cigognini, Daniela; Gaspar, Diana; Kumar, Pramod; Satyam, Abhigyan; Alagesan, Senthilkumar; Sanz-Nogués, Clara; Griffin, Matthew; O'Brien, Timothy; Pandit, Abhay; Zeugolis, Dimitrios I

    2016-01-01

    Modular tissue engineering is based on the cells' innate ability to create bottom-up supramolecular assemblies with efficiency and efficacy still unmatched by man-made devices. Although the regenerative potential of such tissue substitutes has been documented in preclinical and clinical setting, the prolonged culture time required to develop an implantable device is associated with phenotypic drift and/or cell senescence. Herein, we demonstrate that macromolecular crowding significantly enhances extracellular matrix deposition in human bone marrow mesenchymal stem cell culture at both 20% and 2% oxygen tension. Although hypoxia inducible factor - 1α was activated at 2% oxygen tension, increased extracellular matrix synthesis was not observed. The expression of surface markers and transcription factors was not affected as a function of oxygen tension and macromolecular crowding. The multilineage potential was also maintained, albeit adipogenic differentiation was significantly reduced in low oxygen tension cultures, chondrogenic differentiation was significantly increased in macromolecularly crowded cultures and osteogenic differentiation was not affected as a function of oxygen tension and macromolecular crowding. Collectively, these data pave the way for the development of bottom-up tissue equivalents based on physiologically relevant developmental processes. PMID:27478033

  4. Physiological oxygen tensions modulate expression of the mdr1b multidrug-resistance gene in primary rat hepatocyte cultures.

    PubMed Central

    Hirsch-Ernst, K I; Kietzmann, T; Ziemann, C; Jungermann, K; Kahl, G F

    2000-01-01

    P-Glycoprotein transporters encoded by mdr1 (multidrug resistance) genes mediate extrusion of an array of lipophilic xenobiotics from the cell. In rat liver, mdr transcripts have been shown to be expressed mainly in hepatocytes of the periportal region. Since gradients in oxygen tension (pO(2)) may contribute towards zonated gene expression, the influence of arterial and venous pO(2) on mRNA expression of the mdr1b isoform was examined in primary rat hepatocytes cultured for up to 3 days. Maximal mdr1b mRNA levels (100%) were observed under arterial pO(2) after 72 h, whereas less than half-maximal mRNA levels (40%) were attained under venous pO(2). Accordingly, expression of mdr protein and extrusion of the mdr1 substrate rhodamine 123 were maximal under arterial pO(2) and reduced under venous pO(2). Oxygen-dependent modulation of mdr1b mRNA expression was prevented by actinomycin D, indicating transcriptional regulation. Inhibition of haem synthesis by 25 microM CoCl(2) blocked mdr1b mRNA expression under both oxygen tensions, whereas 80 microM desferrioxamine abolished modulation by O(2). Haem (10 microM) increased mdr1b mRNA levels under arterial and venous pO(2). In hepatocytes treated with 50 microM H(2)O(2), mdr1b mRNA expression was elevated by about 1.6-fold at venous pO(2) and 1.5-fold at arterial pO(2). These results support the conclusion that haem proteins are crucial for modulation of mdr1b mRNA expression by O(2) in hepatocyte cultures and that reactive oxygen species may participate in O(2)-dependent signal transduction. Furthermore, the present study suggests that oxygen might be a critical modulator for zonated secretion of mdr1 substrates into the bile. PMID:10947958

  5. Oxygen tension level and human viral infections

    SciTech Connect

    Morinet, Frédéric; Casetti, Luana; François, Jean-Hugues; Capron, Claude; Pillet, Sylvie

    2013-09-15

    The role of oxygen tension level is a well-known phenomenon that has been studied in oncology and radiotherapy since about 60 years. Oxygen tension may inhibit or stimulate propagation of viruses in vitro as well as in vivo. In turn modulating oxygen metabolism may constitute a novel approach to treat viral infections as an adjuvant therapy. The major transcription factor which regulates oxygen tension level is hypoxia-inducible factor-1 alpha (HIF-1α). Down-regulating the expression of HIF-1α is a possible method in the treatment of chronic viral infection such as human immunodeficiency virus infection, chronic hepatitis B and C viral infections and Kaposi sarcoma in addition to classic chemotherapy. The aim of this review is to supply an updating concerning the influence of oxygen tension level in human viral infections and to evoke possible new therapeutic strategies regarding this environmental condition. - Highlights: • Oxygen tension level regulates viral replication in vitro and possibly in vivo. • Hypoxia-inducible factor 1 (HIF-1α) is the principal factor involved in Oxygen tension level. • HIF-1α upregulates gene expression for example of HIV, JC and Kaposi sarcoma viruses. • In addition to classical chemotherapy inhibition of HIF-1α may constitute a new track to treat human viral infections.

  6. Oxygen tension affects lubricin expression in chondrocytes.

    PubMed

    Hatta, Taku; Kishimoto, Koshi N; Okuno, Hiroshi; Itoi, Eiji

    2014-10-01

    We assessed the effects of oxygen tension on lubricin expression in bovine chondrocytes and cartilage explants and a role for hypoxia-inducible transcription factor (HIF)-1α in regulating lubricin expression was investigated using a murine chondroprogenitor cell line, ATDC5, and bovine chondrocytes isolated from superficial and middle/deep zones of femoral cartilage. ATDC5 cells and bovine chondrocytes were cultured in micromass under different oxygen tensions (21%, 5%, and 1%). ATDC5 cells and middle/deep zone chondrocytes that initially had low lubricin expression levels were also cultured with or without transforming growth factor (TGF)-β1. Quantitative reverse transcription (RT)-PCR was used to determine lubricin and chondrogenic marker gene mRNA levels and immunohistochemistry was used to assess lubricin protein expression. Explant cartilage plugs cultured under different oxygen tensions were also subjected to immunohistological analysis for lubricin. HIF-1α gene silencing was achieved by electroporatic transfer into ATDC5 cells. A low oxygen tension reduced lubricin gene expression levels in bovine superficial chondrocytes, TGF-β1-treated middle/deep zone chondrocytes, and TGF-β1-treated ATDC5 cells. Lubricin expression in explant cartilage was also suppressed under hypoxia. HIF-1α gene silencing in ATDC5 cells attenuated the lubricin expression response to the oxygen tension. These results corroborate with previous studies that the oxygen tension regulates lubricin gene expression and suggest that HIF-1α plays an important role in this regulation. The normal distribution of lubricin in articular cartilage may be due to the hypoxic oxygen environment of cartilage as it is an avascular tissue. An oxygen tension gradient may be a key factor for engineering cartilage tissue with a layered morphology. PMID:24712343

  7. Oxygen tension limits nitric oxide synthesis by activated macrophages.

    PubMed Central

    McCormick, C C; Li, W P; Calero, M

    2000-01-01

    Previous studies have established that constitutive calcium-dependent ('low-output') nitric oxide synthase (NOS) is regulated by oxygen tension. We have investigated the role of oxygen tension in the synthesis of NO by the 'high-output' calcium-independent NOS in activated macrophages. Hypoxia increased macrophage NOS gene expression in the presence of one additional activator, such as lipopolysaccharide or interferon-gamma, but not in the presence of both. Hypoxia markedly reduced the synthesis of NO by activated macrophages (as measured by accumulation of nitrite and citrulline), such that, at 1% oxygen tension, NO accumulation was reduced by 80-90%. The apparent K(m) for oxygen calculated from cells exposed to a range of oxygen tensions was found to be 10.8%, or 137 microM, O(2) This value is considerably higher than the oxygen tension in tissues, and is virtually identical to that reported recently for purified recombinant macrophage NOS. The decrease in NO synthesis did not appear to be due to diminished arginine or cofactor availability, since arginine transport and NO synthesis during recovery in normoxia were normal. Analysis of NO synthesis during hypoxia as a function of extracellular arginine indicated that an altered V(max), but not K(m)(Arg), accounted for the observed decrease in NO synthesis. We conclude that oxygen tension regulates the synthesis of NO in macrophages by a mechanism similar to that described previously for the calcium-dependent low-output NOS. Our data suggest that oxygen tension may be an important physiological regulator of macrophage NO synthesis in vivo. PMID:10970783

  8. Cerebral Microcirculation and Oxygen Tension in the Human Secondary Cortex

    PubMed Central

    Linninger, A. A.; Gould, I. G.; Marinnan, T.; Hsu, C.-Y.; Chojecki, M.; Alaraj, A.

    2013-01-01

    The three-dimensional spatial arrangement of the cortical microcirculatory system is critical for understanding oxygen exchange between blood vessels and brain cells. A three-dimensional computer model of a 3 × 3 × 3 mm3 subsection of the human secondary cortex was constructed to quantify oxygen advection in the microcirculation, tissue oxygen perfusion, and consumption in the human cortex. This computer model accounts for all arterial, capillary and venous blood vessels of the cerebral microvascular bed as well as brain tissue occupying the extravascular space. Microvessels were assembled with optimization algorithms emulating angiogenic growth; a realistic capillary bed was built with space filling procedures. The extravascular tissue was modeled as a porous medium supplied with oxygen by advection–diffusion to match normal metabolic oxygen demand. The resulting synthetic computer generated network matches prior measured morphometrics and fractal patterns of the cortical microvasculature. This morphologically accurate, physiologically consistent, multi-scale computer network of the cerebral microcirculation predicts the oxygen exchange of cortical blood vessels with the surrounding gray matter. Oxygen tension subject to blood pressure and flow conditions were computed and validated for the blood as well as brain tissue. Oxygen gradients along arterioles, capillaries and veins agreed with in vivo trends observed recently in imaging studies within experimental tolerances and uncertainty. PMID:23842693

  9. Deoxygenation Reduces Sickle Cell Blood Flow at Arterial Oxygen Tension.

    PubMed

    Lu, Xinran; Wood, David K; Higgins, John M

    2016-06-21

    The majority of morbidity and mortality in sickle cell disease is caused by vaso-occlusion: circulatory obstruction leading to tissue ischemia and infarction. The consequences of vaso-occlusion are seen clinically throughout the vascular tree, from the relatively high-oxygen and high-velocity cerebral arteries to the relatively low-oxygen and low-velocity postcapillary venules. Prevailing models of vaso-occlusion propose mechanisms that are relevant only to regions of low oxygen and low velocity, leaving a wide gap in our understanding of the most important pathologic process in sickle cell disease. Progress toward understanding vaso-occlusion is further challenged by the complexity of the multiple processes thought to be involved, including, but not limited to 1) deoxygenation-dependent hemoglobin polymerization leading to impaired rheology, 2) endothelial and leukocyte activation, and 3) altered cellular adhesion. Here, we chose to focus exclusively on deoxygenation-dependent rheologic processes in an effort to quantify their contribution independent of the other processes that are likely involved in vivo. We take advantage of an experimental system that, to our knowledge, uniquely enables the study of pressure-driven blood flow in physiologic-sized tubes at physiologic hematocrit under controlled oxygenation conditions, while excluding the effects of endothelium, leukocyte activation, adhesion, inflammation, and coagulation. We find that deoxygenation-dependent rheologic processes are sufficient to increase apparent viscosity significantly, slowing blood flow velocity at arterial oxygen tension even without additional contributions from inflammation, adhesion, and endothelial and leukocyte activation. We quantify the changes in apparent viscosity and define a set of functional regimes of sickle cell blood flow personalized for each patient that may be important in further dissecting mechanisms of in vivo vaso-occlusion as well as in assessing risk of patient

  10. Quantitating intracellular oxygen tension in vivo by phosphorescence lifetime measurement

    PubMed Central

    Hirakawa, Yosuke; Yoshihara, Toshitada; Kamiya, Mako; Mimura, Imari; Fujikura, Daichi; Masuda, Tsuyoshi; Kikuchi, Ryohei; Takahashi, Ippei; Urano, Yasuteru; Tobita, Seiji; Nangaku, Masaomi

    2015-01-01

    Hypoxia appears to have an important role in pathological conditions in many organs such as kidney; however, a method to quantify intracellular oxygen tension in vivo has not been well established. In this study, we established an optical method to quantify oxygen tension in mice kidneys using a cationic lipophilic phosphorescence probe, BTPDM1, which has an intracellular oxygen concentration-sensitive phosphorescence lifetime. Since this probe is distributed inside the tubular cells of the mice kidney, we succeeded in detecting acute renal hypoxic conditions and chronic kidney disease. This technique enabled us to estimate intracellular partial pressures of oxygen in vivo by extrapolating the calibration curve generated from cultured tubular cells. Since intracellular oxygen tension is directly related to cellular hypoxic reactions, such as the activation of hypoxia-inducible factors, our method will shed new light on hypoxia research in vivo. PMID:26644023

  11. Pulmonary surfactant surface tension influences alveolar capillary shape and oxygenation.

    PubMed

    Ikegami, Machiko; Weaver, Timothy E; Grant, Shawn N; Whitsett, Jeffrey A

    2009-10-01

    Alveolar capillaries are located in close proximity to the alveolar epithelium and beneath the surfactant film. We hypothesized that the shape of alveolar capillaries and accompanying oxygenation are influenced by surfactant surface tension in the alveolus. To prove our hypothesis, surfactant surface tension was regulated by conditional expression of surfactant protein (SP)-B in Sftpb(-/-) mice, thereby inhibiting surface tension-lowering properties of surfactant in vivo within 24 hours after depletion of Sftpb. Minimum surface tension of isolated surfactant was increased and oxygen saturation was significantly reduced after 2 days of SP-B deficiency in association with deformation of alveolar capillaries. Intravascularly injected 3.2-mum-diameter microbeads through jugular vein were retained within narrowed pulmonary capillaries after reduction of SP-B. Ultrastructure studies demonstrated that the capillary protrusion typical of the normal alveolar-capillary unit was reduced in size, consistent with altered pulmonary blood flow. Pulmonary hypertension and intrapulmonary shunting are commonly associated with surfactant deficiency and dysfunction in neonates and adults with respiratory distress syndromes. Increased surfactant surface tension caused by reduction in SP-B induced narrowing of alveolar capillaries and oxygen desaturation, demonstrating an important role of surface tension-lowering properties of surfactant in the regulation of pulmonary vascular perfusion. PMID:19202005

  12. Oxygen in demand: How oxygen has shaped vertebrate physiology.

    PubMed

    Dzal, Yvonne A; Jenkin, Sarah E M; Lague, Sabine L; Reichert, Michelle N; York, Julia M; Pamenter, Matthew E

    2015-08-01

    In response to varying environmental and physiological challenges, vertebrates have evolved complex and often overlapping systems. These systems detect changes in environmental oxygen availability and respond by increasing oxygen supply to the tissues and/or by decreasing oxygen demand at the cellular level. This suite of responses is termed the oxygen transport cascade and is comprised of several components. These components include 1) chemosensory detectors that sense changes in oxygen, carbon dioxide, and pH in the blood, and initiate changes in 2) ventilation and 3) cardiac work, thereby altering the rate of oxygen delivery to, and carbon dioxide clearance from, the tissues. In addition, changes in 4) cellular and systemic metabolism alters tissue-level metabolic demand. Thus the need for oxygen can be managed locally when increasing oxygen supply is not sufficient or possible. Together, these mechanisms provide a spectrum of responses that facilitate the maintenance of systemic oxygen homeostasis in the face of environmental hypoxia or physiological oxygen depletion (i.e. due to exercise or disease). Bill Milsom has dedicated his career to the study of these responses across phylogenies, repeatedly demonstrating the power of applying the comparative approach to physiological questions. The focus of this review is to discuss the anatomy, signalling pathways, and mechanics of each step of the oxygen transport cascade from the perspective of a Milsomite. That is, by taking into account the developmental, physiological, and evolutionary components of questions related to oxygen transport. We also highlight examples of some of the remarkable species that have captured Bill's attention through their unique adaptations in multiple components of the oxygen transport cascade, which allow them to achieve astounding physiological feats. Bill's research examining the oxygen transport cascade has provided important insight and leadership to the study of the diverse suite

  13. Measuring tissue oxygen tension: a review.

    PubMed

    Sheffield, P J

    1998-01-01

    Because of technological advances in tissue oximetry, clinicians and scientists have a better understanding of the role of oxygen in wound healing. In wound care and hyperbaric medicine applications, an oximeter is principally used with vascular assessment to help determine amputation level and to estimate healing potential. With the current emphasis on cost savings in the managed care setting, transcutaneous oximetry (PtcO2) has gained importance as a tool for predicting potential candidates for hyperbaric oxygen (HBO2) therapy. It is used to identify the presence of hypoxia in wounded tissue, to predict the responders to hyperoxia and in some instances to determine when HBO2 treatment is complete. This literature review describes the principal current methods for measuring tissue O2 and the values obtained in normal and wounded tissue under both normobaric and hyperbaric conditions. The review includes the Jefferson C. Davis Wound Care and Hyperbaric Medicine Center protocol for PtcO2 assessment of potential HBO2 candidates and suggestions for obtaining reproducible PtcO2 data. PMID:9789339

  14. Reversible uncoupling of oxidative phosphorylation at low oxygen tension.

    PubMed Central

    Kramer, R S; Pearlstein, R D

    1983-01-01

    The stoichiometry of oxidative phosphorylation at low oxygen tension (less than 3 torr; O2 less than 5 microM) has been measured in rat liver mitochondria. In a steady-state model in which respiration rate was experimentally controlled by either oxygen or substrate (succinate) limitation, flux-dependent variation in the phosphorylation efficiency (P/O ratio) of stimulated mitochondrial respiration was evaluated. P/O ratio remained constant over a wide range of respiration rates in mitochondria limited only by substrate availability. In contrast, oxygen-limited mitochondria demonstrated a continuous decline in P/O ratio as respiration was increasingly restricted. Significant differences in the two test conditions were demonstrated throughout the range of analysis. The effect of oxygen limitation on phosphorylation efficiency was shown to be completely reversed by restoring zero-order kinetics associated with high oxygen tension. These findings are discussed in regard to a proposed uncoupling of mitochondrial coupling site II at low oxygen tension arising as a consequence of energy-dissipating electron flux through the ubiquinone-cytochrome b-c1 region of the respiratory chain (complex III). PMID:6577456

  15. The effect of varying oxygen tensions on hydroxyproline synthesis in mouse calvaria in vitro.

    PubMed

    Gray, D H; Katz, J M; Speak, K S

    1980-01-01

    Six-day-old mouse calvaria were grown in vitro on a grid culture system in Medium 199 containing titriated proline. Gas atmospheres containing various oxygen concentrations up to 25% were introduced to influence the rate of collagen formation as determined by the synthesis of labelled hydroxyproline in the explants. There was an increase in synthesis in response to 15% oxygen with a possible further small increase in 25% oxygen. Measurement of the release of unlabelled hydroxyproline into the medium as an estimate of collagen breakdown indicates an increase in resorption with increasing oxygen concentrations up to 20%. In this model, therefore, there is increased collagen turnover with increasing oxygen tension in the physiologic range. Although the observations reflect collagen formation and do not necessarily measure bone formation, the results are consistent with data derived from other sources suggesting that bone formation is increased by improved oxygenation. PMID:7371261

  16. Assessments for oxygen therapy in COPD: are we under correcting arterial oxygen tensions?

    PubMed

    Dheda, K; Lim, K; Ollivere, B; Leftley, J; Lampe, F C; Salisbury, A; Dilworth, J P; Rajakulasingam, R K; Rajakulasingum, R K

    2004-12-01

    There is little data about the use of different oxygen sources during assessment for long-term oxygen therapy (LTOT) and how this impacts upon blood oxygen tensions and prescribed flow rates. Patients with chronic obstructive pulmonary disease (COPD), n=30, had assessments for LTOT using both an oxygen-concentrator and piped hospital oxygen (wall-oxygen) as supply sources. In addition, a random survey of 64 hospitals was conducted to determine what source of oxygen supply was used during assessments. Wall-oxygen was used by 89% of hospitals to perform assessments. During assessments, the median oxygen flow required to achieve an arterial oxygen tension (Pa,O2) >8 kPa was significantly greater for an oxygen-concentrator than for wall-oxygen, with a median difference (range) in flow of 1 (0-3) L. This difference was most likely in those with an forced expiratory volume <30% of predicted. At an oxygen flow of 1 L.min(-1), the mean P(a,O2) using an oxygen-concentrator was significantly lower than that of the wall-oxygen value, with a difference of 1.32+/-1.19 kPa (mean+/-SD). The common practice of using wall-oxygen to perform assessments significantly underestimates the required oxygen-concentrator flow rate. This may have implications for the long-term effect of domiciliary oxygen therapy. PMID:15572538

  17. Low oxygen tension favored expansion and hematopoietic reconstitution of CD34(+) CD38(-) cells expanded from human cord blood-derived CD34(+) Cells.

    PubMed

    Wang, Ziyan; Du, Zheng; Cai, Haibo; Ye, Zhaoyang; Fan, Jinli; Tan, Wen-Song

    2016-07-01

    Oxygen tension is an important factor that regulates hematopoietic stem cells (HSCs) in both in vivo hematopoietic microenvironment and ex vivo culture system. Although the effect of oxygen tension on ex vivo expansion of HSCs was extensively studied, there were no clear descriptions on physiological function and gene expression analysis of HSCs under different oxygen tensions. In this study, the effects of oxygen tension on ex vivo expansion characteristics of human umbilical cord blood (UCB)-derived CD34(+) cells are evaluated. Moreover, the physiological function of expanded CD34(+) cells was assessed by secondary expansion ability ex vivo and hematopoietic reconstitution ability in vivo. Also, genetic profiling was applied to analyze the expression of genes related to cell function. It was found that low oxygen tension favored expansion of CD34(+) CD38(-) cells. Additionally, CD34(+) cells expanded under low oxygen tension showed better secondary expansion ability and reconstitution ability than those under atmospheric oxygen concentration. Finally, the genetic profiling of CD34(+) CD38(-) cells cultured under low oxygen tension was more akin to freshly isolated cells. These results collectively demonstrate that low oxygen tension was able to better maintain both self-renewal and hematopoietic reconstitution potential and may lay an experimental basis for clinical transplantation of HSCs. PMID:26997358

  18. A New Approach for On-Demand Generation of Various Oxygen Tensions for In Vitro Hypoxia Models

    PubMed Central

    Li, Chunyan; Chaung, Wayne; Mozayan, Cameron; Chabra, Ranjeev; Wang, Ping; Narayan, Raj K.

    2016-01-01

    The development of in vitro disease models closely mimicking the functions of human disease has captured increasing attention in recent years. Oxygen tensions and gradients play essential roles in modulating biological systems in both physiologic and pathologic events. Thus, controlling oxygen tension is critical for mimicking physiologically relevant in vivo environments for cell, tissue and organ research. We present a new approach for on-demand generation of various oxygen tensions for in vitro hypoxia models. Proof-of-concept prototypes have been developed for conventional cell culture microplate by immobilizing a novel oxygen-consuming biomaterial on the 3D-printed insert. For the first time, rapid (~3.8 minutes to reach 0.5% O2 from 20.9% O2) and precisely controlled oxygen tensions/gradients (2.68 mmHg per 50 μm distance) were generated by exposing the biocompatible biomaterial to the different depth of cell culture media. In addition, changing the position of 3D-printed inserts with immobilized biomaterials relative to the cultured cells resulted in controllable and rapid changes in oxygen tensions (<130 seconds). Compared to the current technologies, our approach allows enhanced spatiotemporal resolution and accuracy of the oxygen tensions. Additionally, it does not interfere with the testing environment while maintaining ease of use. The elegance of oxygen tension manipulation introduced by our new approach will drastically improve control and lower the technological barrier of entry for hypoxia studies. Since the biomaterials can be immobilized in any devices, including microfluidic devices and 3D-printed tissues or organs, it will serve as the basis for a new generation of experimental models previously impossible or very difficult to implement. PMID:27219067

  19. Bladder urine oxygen tension for assessing renal medullary oxygenation in rabbits: experimental and modeling studies.

    PubMed

    Sgouralis, Ioannis; Kett, Michelle M; Ow, Connie P C; Abdelkader, Amany; Layton, Anita T; Gardiner, Bruce S; Smith, David W; Lankadeva, Yugeesh R; Evans, Roger G

    2016-09-01

    Oxygen tension (Po2) of urine in the bladder could be used to monitor risk of acute kidney injury if it varies with medullary Po2 Therefore, we examined this relationship and characterized oxygen diffusion across walls of the ureter and bladder in anesthetized rabbits. A computational model was then developed to predict medullary Po2 from bladder urine Po2 Both intravenous infusion of [Phe(2),Ile(3),Orn(8)]-vasopressin and infusion of N(G)-nitro-l-arginine reduced urinary Po2 and medullary Po2 (8-17%), yet had opposite effects on renal blood flow and urine flow. Changes in bladder urine Po2 during these stimuli correlated strongly with changes in medullary Po2 (within-rabbit r(2) = 0.87-0.90). Differences in the Po2 of saline infused into the ureter close to the kidney could be detected in the bladder, although this was diminished at lesser ureteric flow. Diffusion of oxygen across the wall of the bladder was very slow, so it was not considered in the computational model. The model predicts Po2 in the pelvic ureter (presumed to reflect medullary Po2) from known values of bladder urine Po2, urine flow, and arterial Po2 Simulations suggest that, across a physiological range of urine flow in anesthetized rabbits (0.1-0.5 ml/min for a single kidney), a change in bladder urine Po2 explains 10-50% of the change in pelvic urine/medullary Po2 Thus, it is possible to infer changes in medullary Po2 from changes in urinary Po2, so urinary Po2 may have utility as a real-time biomarker of risk of acute kidney injury. PMID:27385734

  20. Inner retinal metabolic rate of oxygen by oxygen tension and blood flow imaging in rat

    PubMed Central

    Wanek, Justin; Teng, Pang-yu; Albers, John; Blair, Norman P.; Shahidi, Mahnaz

    2011-01-01

    Abstract The metabolic function of inner retinal cells relies on the availability of nutrients and oxygen that are supplied by the retinal circulation. Assessment of retinal tissue vitality and function requires knowledge of both the rate of oxygen delivery and consumption. The purpose of the current study is to report a novel technique for assessment of the inner retinal metabolic rate of oxygen (MO2) by combined measurements of retinal blood flow and vascular oxygen tension (PO2) in rat. The application of this technology has the potential to broaden knowledge of retinal oxygen dynamics and advance understanding of disease pathophysiology. PMID:21991548

  1. Low Oxygen Tension Enhances Expression of Myogenic Genes When Human Myoblasts Are Activated from G0 Arrest

    PubMed Central

    Sellathurai, Jeeva; Nielsen, Joachim; Hejbøl, Eva Kildall; Jørgensen, Louise Helskov; Dhawan, Jyotsna; Nielsen, Michael Friberg Bruun; Schrøder, Henrik Daa

    2016-01-01

    Objectives Most cell culture studies have been performed at atmospheric oxygen tension of 21%, however the physiological oxygen tension is much lower and is a factor that may affect skeletal muscle myoblasts. In this study we have compared activation of G0 arrested myoblasts in 21% O2 and in 1% O2 in order to see how oxygen tension affects activation and proliferation of human myoblasts. Materials and Methods Human myoblasts were isolated from skeletal muscle tissue and G0 arrested in vitro followed by reactivation at 21% O2 and 1% O2. The effect was assesses by Real-time RT-PCR, immunocytochemistry and western blot. Results and Conclusions We found an increase in proliferation rate of myoblasts when activated at a low oxygen tension (1% O2) compared to 21% O2. In addition, the gene expression studies showed up regulation of the myogenesis related genes PAX3, PAX7, MYOD, MYOG (myogenin), MET, NCAM, DES (desmin), MEF2A, MEF2C and CDH15 (M-cadherin), however, the fraction of DES and MYOD positive cells was not increased by low oxygen tension, indicating that 1% O2 may not have a functional effect on the myogenic response. Furthermore, the expression of genes involved in the TGFβ, Notch and Wnt signaling pathways were also up regulated in low oxygen tension. The differences in gene expression were most pronounced at day one after activation from G0-arrest, thus the initial activation of myoblasts seemed most sensitive to changes in oxygen tension. Protein expression of HES1 and β-catenin indicated that notch signaling may be induced in 21% O2, while the canonical Wnt signaling may be induced in 1% O2 during activation and proliferation of myoblasts. PMID:27442119

  2. Oxygen Tension Regulates Human Mesenchymal Stem Cell Paracrine Functions

    PubMed Central

    Deschepper, Mickael; Moya, Adrien; Logeart-Avramoglou, Delphine; Boisson-Vidal, Catherine; Petite, Hervé

    2015-01-01

    Mesenchymal stem cells (MSCs) have captured the attention and research endeavors of the scientific world because of their differentiation potential. However, there is accumulating evidence suggesting that the beneficial effects of MSCs are predominantly due to the multitude of bioactive mediators secreted by these cells. Because the paracrine potential of MSCs is closely related to their microenvironment, the present study investigated and characterized select aspects of the human MSC (hMSC) secretome and assessed its in vitro and in vivo bioactivity as a function of oxygen tension, specifically near anoxia (0.1% O2) and hypoxia (5% O2), conditions that reflect the environment to which MSCs are exposed during MSC-based therapies in vivo. In contrast to supernatant conditioned media (CM) obtained from hMSCs cultured at either 5% or 21% of O2, CM from hMSCs cultured under near anoxia exhibited significantly (p < .05) enhanced chemotactic and proangiogenic properties and a significant (p < .05) decrease in the inflammatory mediator content. An analysis of the hMSC secretome revealed a specific profile under near anoxia: hMSCs increase their paracrine expression of the angiogenic mediators vascular endothelial growth factor (VEGF)-A, VEGF-C, interleukin-8, RANTES, and monocyte chemoattractant protein 1 but significantly decrease expression of several inflammatory/immunomodulatory mediators. These findings provide new evidence that elucidates aspects of great importance for the use of MSCs in regenerative medicine and could contribute to improving the efficacy of such therapies. Significance The present study investigated and characterized select aspects of the human mesenchymal stem cell (hMSC) secretome and assessed its in vitro and in vivo biological bioactivity as a function of oxygen tension, specifically near anoxia (0.1% O2) and hypoxia (5% O2), conditions that reflect the environment to which MSCs are exposed during MSC-based therapies in vivo. The present study

  3. Evolution and physiology of neural oxygen sensing.

    PubMed

    Costa, Kauê M; Accorsi-Mendonça, Daniela; Moraes, Davi J A; Machado, Benedito H

    2014-01-01

    Major evolutionary trends in animal physiology have been heavily influenced by atmospheric O2 levels. Amongst other important factors, the increase in atmospheric O2 which occurred in the Pre-Cambrian and the development of aerobic respiration beckoned the evolution of animal organ systems that were dedicated to the absorption and transportation of O2, e.g., the respiratory and cardiovascular systems of vertebrates. Global variations of O2 levels in post-Cambrian periods have also been correlated with evolutionary changes in animal physiology, especially cardiorespiratory function. Oxygen transportation systems are, in our view, ultimately controlled by the brain related mechanisms, which senses changes in O2 availability and regulates autonomic and respiratory responses that ensure the survival of the organism in the face of hypoxic challenges. In vertebrates, the major sensorial system for oxygen sensing and responding to hypoxia is the peripheral chemoreflex neuronal pathways, which includes the oxygen chemosensitive glomus cells and several brainstem regions involved in the autonomic regulation of the cardiovascular system and respiratory control. In this review we discuss the concept that regulating O2 homeostasis was one of the primordial roles of the nervous system. We also review the physiology of the peripheral chemoreflex, focusing on the integrative repercussions of chemoreflex activation and the evolutionary importance of this system, which is essential for the survival of complex organisms such as vertebrates. The contribution of hypoxia and peripheral chemoreflex for the development of diseases associated to the cardiovascular and respiratory systems is also discussed in an evolutionary context. PMID:25161625

  4. Evolution and physiology of neural oxygen sensing

    PubMed Central

    Costa, Kauê M.; Accorsi-Mendonça, Daniela; Moraes, Davi J. A.; Machado, Benedito H.

    2014-01-01

    Major evolutionary trends in animal physiology have been heavily influenced by atmospheric O2 levels. Amongst other important factors, the increase in atmospheric O2 which occurred in the Pre-Cambrian and the development of aerobic respiration beckoned the evolution of animal organ systems that were dedicated to the absorption and transportation of O2, e.g., the respiratory and cardiovascular systems of vertebrates. Global variations of O2 levels in post-Cambrian periods have also been correlated with evolutionary changes in animal physiology, especially cardiorespiratory function. Oxygen transportation systems are, in our view, ultimately controlled by the brain related mechanisms, which senses changes in O2 availability and regulates autonomic and respiratory responses that ensure the survival of the organism in the face of hypoxic challenges. In vertebrates, the major sensorial system for oxygen sensing and responding to hypoxia is the peripheral chemoreflex neuronal pathways, which includes the oxygen chemosensitive glomus cells and several brainstem regions involved in the autonomic regulation of the cardiovascular system and respiratory control. In this review we discuss the concept that regulating O2 homeostasis was one of the primordial roles of the nervous system. We also review the physiology of the peripheral chemoreflex, focusing on the integrative repercussions of chemoreflex activation and the evolutionary importance of this system, which is essential for the survival of complex organisms such as vertebrates. The contribution of hypoxia and peripheral chemoreflex for the development of diseases associated to the cardiovascular and respiratory systems is also discussed in an evolutionary context. PMID:25161625

  5. Oxygen Tension in the Aqueous Humor of Human Eyes under Different Oxygenation Conditions

    PubMed Central

    Sharifipour, Farideh; Idani, Esmaeil; Zamani, Mitra; Helmi, Toktam; Cheraghian, Bahman

    2013-01-01

    Purpose To measure oxygen tension in the aqueous humor of human eyes under different oxygenation conditions. Methods This prospective comparative interventional case series consisted of two parts. In the first part, 120 consecutive patients scheduled for cataract surgery were randomized into group I (control group) in which surgery was performed under local anesthesia inhaling 21% oxygen; group II in whom general anesthesia using 50% oxygen was employed; and group III receiving general anesthesia with 100% oxygen. After aspirating 0.2 ml aqueous humor under sterile conditions, the aqueous sample and a simultaneously drawn arterial blood sample were immediately analyzed using a blood gas analyzer. In part II the same procedures were performed in 10 patients after fitting a contact lens and patching the eye for 20 minutes (group IV) and in 10 patients after transcorneal delivery of oxygen at a flow rate of 5 L/min (group V). Results Mean aqueous PO2 in groups I, II and III was 112.3±6.2, 141.1±20.4, and 170.1±27 mmHg, respectively (P values <0.001) and mean arterial PO2 was 85.7±7.9, 184.6±46, and379.1±75.9 mmHg, respectively (P values <0.001). Aqueous PO2 was 77.2±9.2 mmHg in group IV and 152.3±10.9 mmHg in group V (P values <0.001). There was a significant correlation between aqueous and blood PO2 (r=0.537, P<0.001). The contribution of atmospheric oxygen to aqueous PO2 was 23.7%. Conclusion Aqueous oxygen tension is mostly dependent on the systemic circulation and in part on the atmosphere. Increasing inspiratory oxygen and transcorneal oxygen delivery both increase aqueous PO2 levels. PMID:23943686

  6. Effects of Environmental Oxygen Content and Dissolved Oxygen on the Surface Tension and Viscosity of Liquid Nickel

    NASA Astrophysics Data System (ADS)

    SanSoucie, M. P.; Rogers, J. R.; Kumar, V.; Rodriguez, J.; Xiao, X.; Matson, D. M.

    2016-07-01

    The NASA Marshall Space Flight Center's electrostatic levitation (ESL) laboratory has recently added an oxygen partial pressure controller. This system allows the oxygen partial pressure within the vacuum chamber to be measured and controlled in the range from approximately 10^{-28} {to} 10^{-9} bar, while in a vacuum atmosphere. The oxygen control system installed in the ESL laboratory's main chamber consists of an oxygen sensor, oxygen pump, and a control unit. The sensor is a potentiometric device that determines the difference in oxygen activity in two gas compartments (inside the chamber and the air outside of the chamber) separated by an electrolyte. The pump utilizes coulometric titration to either add or remove oxygen. The system is controlled by a desktop control unit, which can also be accessed via a computer. The controller performs temperature control for the sensor and pump, has a PID-based current loop and a control algorithm. Oxygen partial pressure has been shown to play a significant role in the surface tension of liquid metals. Oxide films or dissolved oxygen may lead to significant changes in surface tension. The effects on surface tension and viscosity by oxygen partial pressure in the surrounding environment and the melt dissolved oxygen content will be evaluated, and the results will be presented. The surface tension and viscosity will be measured at several different oxygen partial pressures while the sample is undercooled. Surface tension and viscosity will be measured using the oscillating droplet method.

  7. Oxygen tension measurement using an automatic blood gas analyser1

    PubMed Central

    Becket, J; Chakrabarti, M K; Gillies, I D S; Orchard, C; Hall, G M; Bourdillon, P J

    1981-01-01

    Two different methods of assessing the reliability of the oxygen electrode of one model of an automatic blood gas analyser (BGA) have been studied. In the first, a single automatic BGA was assessed by using outdated bank blood which was pumped around a small extracorporeal circuit into which known gas mixtures were passed. Oxygen tension was varied between 2 and 16 kPa. In the second, fresh heparinized blood was tonometered with calibrated gases and submitted to the automatic BGA used in the first part of the study and also to three other identical machines. Each of the machines was between 3 and 4 years old. Eighteen different units of blood were used in the first part of the study. The correlation coefficient between the automatic BGA and the Po2 in the extracorporeal circuit varied between 0.29 and 0.99. 31% of the total of 209 measurements made by the automatic BGA were more than 1.2 kPa from the reference value, 25% of them being between 1.2 and 4.0 kPa from the reference value. In the second part of the study, the correlation coefficient between this automatic BGA and the tonometered blood was 0.96. The correlation coefficients for the 3 other identical BGAs were 0.84, 0.97 and 0.88, indicating that the BGA used in the first part of the study was no worse than any of the others. It is suggested that although clinicians are likely to ignore readings of an automatic BGA that are more than 4.0 kPa from the true value and are likely to repeat the investigation, readings between 1.2 and 4.0 kPa from the true value may adversely affect patient management. PMID:7288796

  8. Oxygen tension measurement using an automatic blood gas analyser.

    PubMed

    Becket, J; Orchard, C; Chakrabarti, M K; Hall, G M; Gillies, I D; Bourdillon, P J

    1981-08-01

    Two different methods of assessing the reliability of the oxygen electrode of one model of an automatic blood gas analyser (BGA) have been studied. In the first, a single automatic BGA was assessed by using outdated bank blood which was pumped around a small extracorporeal circuit into which known gas mixtures were passed. Oxygen tension was varied between 2 and 16 kPa. In the second, fresh heparinized blood was tonometered with calibrated gases and submitted to the automatic BGA used in the first part of the study and also to three other identical machines. Each of the machines was between 3 and 4 years old.Eighteen different units of blood were used in the first part of the study. The correlation coefficient between the automatic BGA and the Po(2) in the extracorporeal circuit varied between 0.29 and 0.99. 31% of the total of 209 measurements made by the automatic BGA were more than 1.2 kPa from the reference value, 25% of them being between 1.2 and 4.0 kPa from the reference value. In the second part of the study, the correlation coefficient between this automatic BGA and the tonometered blood was 0.96. The correlation coefficients for the 3 other identical BGAs were 0.84, 0.97 and 0.88, indicating that the BGA used in the first part of the study was no worse than any of the others.It is suggested that although clinicians are likely to ignore readings of an automatic BGA that are more than 4.0 kPa from the true value and are likely to repeat the investigation, readings between 1.2 and 4.0 kPa from the true value may adversely affect patient management. PMID:7288796

  9. Extrapulmonary factors influencing the ratio of arterial oxygen tension to inspired oxygen concentration in burn patients.

    PubMed

    Martyn, J A; Aikawa, N; Wilson, R S; Szyfelbein, S K; Burke, J F

    1979-11-01

    The ratio of arterial oxygen tension to inspired oxygen concentration (PaO2/FIO2) as an index of respiratory function was evaluated in 22 patients with body surface area burns of 15--80%. These results indicate that this ratio is limited in its applicability because extrapulmonary factors, such as cardiac output, oxygen consumption, and arterial oxygen content, can affect this index by alterations in the amount of venous desaturation. Useful estimates of intrapulmonary right to left shunt (Qs/Qt) from PaO2/FIO2 were obtained only when arteriovenous oxygen content differences (avDO2) were between 3--5 ml/dl. There were avDO2 values above and below 3--5 ml/dl in at least 35% of the observations. Under these circumstances, PaO2/FIO2 did not correctly reflect changes in Qs/Qt. Blood gases from central venous catheters did not mirror changes in true mixed venous blood and, thus, can lead to erroneous estimations of Qs/Qt. Rational therapy of reduced arterial oxygen saturation requires measurement of both extra- and intrapulmonary factors contributing to arterial desaturation. Measurement of PaO2/FIO2 alone will not estimate these factors. PMID:487845

  10. Response of the protistan community of a rice field soil to different oxygen tensions.

    PubMed

    Takenouchi, Yuriko; Iwasaki, Kazufumi; Murase, Jun

    2016-07-01

    Heterotrophic protists in soil are grazers that control the biomass and community structure of bacteria, thereby enhancing nutrient recycling. Oxygen regulates the microeukaryotic community, but little is known about its response to microoxic conditions. Here we studied the impact of oxygen tension on culturable heterotrophic protists in a rice field soil. The number of protists, dominated by amoeba and flagellates, under oxygen tensions ranging from atmospheric level (21%) to below the Pasteur point (0.08%) were similar (10(4) cells g(-1) dry soil); no protists were detected under anoxic conditions. DGGE fingerprinting of microeukaryotes demonstrated a shift in the community structure depending on the oxygen tension during growth. Both common and specific amoeba and flagellates were identified at different oxygen tensions. Amoeba isolates (Acanthamoeba sp. and Hartmannella sp.) grew to the same extent under the oxygen tensions tested; the Acanthamoeba sp. isolate migrated more slowly under the lowest tension (0.08%). Our results demonstrated that amoeba and flagellates in soil adapt to a wide range of oxygen tensions with a shift in community structure. This suggests an ability to search for food in soil environments such as the oxic-anoxic interface of flooded soil or inside soil aggregates that are inaccessible to ciliates. PMID:27183973

  11. Gloxy: an oxygen-sensitive coal for accurate measurement of low oxygen tensions in biological systems.

    PubMed

    James, P E; Grinberg, O Y; Goda, F; Panz, T; O'Hara, J A; Swartz, H M

    1997-07-01

    This paper describes the characteristics of a new oxygen sensitive, paramagnetic material that has some significant advantages for measurements of tissue pO2 by in vivo EPR. This paramagnetic component of Welsh coal, termed "gloxy" was found to have valuable EPR features that allow accurate measurement of low oxygen tensions in vivo; these include large oxygen-dependent changes in linewidth, a high number of paramagnetic spin centers (resulting in high signal amplitude), and stability in tissue allowing repeated pO2 measurements to be made in vivo with high precision. Renal pO2 was measured deep in the medulla region of isolated perfused kidneys and found to be lower than that in the cortex (1.7 +/- 0.05 and 7.1 +/- 0.3 mm Hg, respectively). The quality of the EPR signal obtained from the renal outer medulla and also from tumors in mice was such that the pO2 measurements were obtained with a precision of +/-3% of the measured pO2 (Kidney: 1.7 +/- 0.05 mmHg; Tumor: 1.37 +/- 0.04 mmHg). In vitro tests on the viability of cells and in vivo studies using Gloxy demonstrate the stability and inertness of this oxygen-sensitive material. PMID:9211379

  12. Effects of Oxygen Partial Pressure on the Surface Tension of Liquid Nickel

    NASA Technical Reports Server (NTRS)

    SanSoucie, Michael P.; Rogers, Jan R.; Gowda, Vijaya Kumar Malahalli Shankare; Rodriguez, Justin; Matson, Douglas M.

    2015-01-01

    The NASA Marshall Space Flight Center's electrostatic levitation (ESL) laboratory has been recently upgraded with an oxygen partial pressure controller. This system allows the oxygen partial pressure within the vacuum chamber to be measured and controlled, theoretically in the range from 10-36 to 100 bar. The oxygen control system installed in the ESL laboratory's main chamber consists of an oxygen sensor, oxygen pump, and a control unit. The sensor is a potentiometric device that determines the difference in oxygen activity in two gas compartments (inside the chamber and the air outside of the chamber) separated by an electrolyte, which is yttria-stabilized zirconia. The pump utilizes coulometric titration to either add or remove oxygen. The system is controlled by a desktop control unit, which can also be accessed via a computer. The controller performs temperature control for the sensor and pump, PID-based current loop, and a control algorithm. Oxygen partial pressure has been shown to play a significant role in the surface tension of liquid metals. Oxide films or dissolved oxygen may lead to significant changes in surface tension. The effects of oxygen partial pressure on the surface tension of undercooled liquid nickel will be analyzed, and the results will be presented. The surface tension will be measured at several different oxygen partial pressures while the sample is undercooled. Surface tension will be measured using the oscillating drop method. While undercooled, each sample will be oscillated several times consecutively to investigate how the surface tension behaves with time while at a particular oxygen partial pressure.

  13. Near-simultaneous hemoglobin saturation and oxygen tension maps in mouse brain using an AOTF microscope.

    PubMed Central

    Shonat, R D; Wachman, E S; Niu, W; Koretsky, A P; Farkas, D L

    1997-01-01

    A newly developed microscope using acousto-optic tunable filters (AOTFs) was used to generate in vivo hemoglobin saturation (SO2) and oxygen tension (PO2) maps in the cerebral cortex of mice. SO2 maps were generated from the spectral analysis of reflected absorbance images collected at different wavelengths, and PO2 maps were generated from the phosphorescence lifetimes of an injected palladium-porphyrin compound using a frequency-domain measurement. As the inspiratory O2 was stepped from hypoxia (10% O2), through normoxia (21% O2), to hyperoxia (60% O2), measured SO2 and PO2 levels rose accordingly and predictably throughout. A plot of SO2 versus PO2 in different arterial and venous regions of the pial vessels conformed to the sigmoidal shape of the oxygen-hemoglobin dissociation curve, providing further validation of the two mapping procedures. The study demonstrates the versatility of the AOTF microscope for in vivo physiologic investigation, allowing for the generation of nearly simultaneous SO2 and PO2 maps in the cerebral cortex, and the frequency-domain detection of phosphorescence lifetimes. This class of study opens up exciting new possibilities for investigating the dynamics of hemoglobin and O2 binding during functional activation of neuronal tissues. Images FIGURE 1 FIGURE 3 FIGURE 4 FIGURE 6 PMID:9284290

  14. MRI of brain tissue oxygen tension under hyperbaric conditions.

    PubMed

    Muir, Eric R; Cardenas, Damon P; Duong, Timothy Q

    2016-06-01

    The brain depends on a continuous supply of oxygen to maintain its structural and functional integrity. This study measured T1 from MRI under normobaric air, normobaric oxygen, hyperbaric air, and hyperbaric oxygen (HBO) conditions as a marker of tissue pO2 since dissolved molecular oxygen acts as an endogenous contrast agent. Brain tissue T1 decreased corresponding to increased pO2 with increasing inhaled oxygen concentrations, and tissue oxygenation was estimated from the T1 changes between different inhaled oxygen levels. Tissue pO2 difference maps between different oxygen conditions showed heterogeneous pO2 changes in the brain. MRI-derived tissue pO2 was markedly lower than the arterial pO2 but was slightly higher than venous pO2. Additionally, for comparison with published extracellular tissue pO2 data obtained using oxygen electrodes and other invasive techniques, a model was used to estimate extracellular and intracellular pO2 from the MRI-derived mean tissue pO2. This required multiple assumptions, and so the effects of the assumptions and parameters used in modeling brain pO2 were evaluated. MRI-derived pO2 values were strongly dependent on assumptions about the extra- and intracellular compartments but were relatively less sensitive to variations in the relaxivity constant of oxygen and contribution from oxygen in the cerebral blood compartment. This approach may prove useful in evaluating tissue oxygenation in disease states such as stroke. PMID:27033683

  15. Method measuring oxygen tension and transport within subcutaneous devices

    PubMed Central

    Weidling, John; Sameni, Sara; Lakey, Jonathan R. T.; Botvinick, Elliot

    2014-01-01

    Abstract. Cellular therapies hold promise to replace the implantation of whole organs in the treatment of disease. For most cell types, in vivo viability depends on oxygen delivery to avoid the toxic effects of hypoxia. A promising approach is the in situ vascularization of implantable devices which can mediate hypoxia and improve both the lifetime and utility of implanted cells and tissues. Although mathematical models and bulk measurements of oxygenation in surrounding tissue have been used to estimate oxygenation within devices, such estimates are insufficient in determining if supplied oxygen is sufficient for the entire thickness of the implanted cells and tissues. We have developed a technique in which oxygen-sensitive microparticles (OSMs) are incorporated into the volume of subcutaneously implantable devices. Oxygen partial pressure within these devices can be measured directly in vivo by an optical probe placed on the skin surface. As validation, OSMs have been incorporated into alginate beads, commonly used as immunoisolation devices to encapsulate pancreatic islet cells. Alginate beads were implanted into the subcutaneous space of Sprague–Dawley rats. Oxygen transport through beads was characterized from dynamic OSM signals in response to changes in inhaled oxygen. Changes in oxygen dynamics over days demonstrate the utility of our technology. PMID:25162910

  16. Tissue oxygen tension in the cerebral cortex of the rabbit.

    PubMed

    Fennema, M; Wessel, J N; Faithful, N S; Erdmann, W

    1989-01-01

    Polarographic techniques were employed to measure oxygen partial pressure using 10 micron glass-protected gold microelectrodes. When inserting the electrode into the cortex, a PO2-profile is produced. The average PO2 was about 9 mm Hg. Nearly all measurements were below 25 mm Hg and measurements above 50 mm Hg were rare. When the FiO2 was increased from 0.3 to 1.0, tissue PO2 increased, then gradually decreased. This is probably due to vasoconstriction of pre-capillary sphincters. Acute hypoxia showed the opposite effect, but the autoregulation does not seem to be so effective. When CO2 was added to the inspiratory gas mixture the PO2 increased and showed little tendency to return to normal values. This increase in PO2 is due to the direct effect of CO2 and H+ on the blood vessels, causing vasodilation, and therefore an increase in blood flow and tissue oxygenation. PMID:2506739

  17. Three-dimensional mapping of oxygen tension in cortical arterioles before and after occlusion

    PubMed Central

    Kazmi, S. M. Shams; Salvaggio, Anthony J.; Estrada, Arnold D.; Hemati, Michael A.; Shaydyuk, Nazariy K.; Roussakis, Emannuel; Jones, Theresa A.; Vinogradov, Sergei A.; Dunn, Andrew K.

    2013-01-01

    Occlusions in single cortical microvessels lead to a reduction in oxygen supply, but this decrement has not been able to be quantified in three dimensions at the level of individual vessels using a single instrument. We demonstrate a combined optical system using two-photon phosphorescence lifetime and fluorescence microscopy (2PLM) to characterize the partial pressure of oxygen (pO2) in single descending cortical arterioles in the mouse brain before and after generating a targeted photothrombotic occlusion. Integrated real-time Laser Speckle Contrast Imaging (LSCI) provides wide-field perfusion maps that are used to monitor and guide the occlusion process while 2PLM maps changes in intravascular oxygen tension. We present the technique’s utility in highlighting the effects of vascular networking on the residual intravascular oxygen tensions measured after occlusion in three dimensions. PMID:23847732

  18. Three-dimensional mapping of oxygen tension in cortical arterioles before and after occlusion.

    PubMed

    Kazmi, S M Shams; Salvaggio, Anthony J; Estrada, Arnold D; Hemati, Michael A; Shaydyuk, Nazariy K; Roussakis, Emannuel; Jones, Theresa A; Vinogradov, Sergei A; Dunn, Andrew K

    2013-07-01

    Occlusions in single cortical microvessels lead to a reduction in oxygen supply, but this decrement has not been able to be quantified in three dimensions at the level of individual vessels using a single instrument. We demonstrate a combined optical system using two-photon phosphorescence lifetime and fluorescence microscopy (2PLM) to characterize the partial pressure of oxygen (pO2) in single descending cortical arterioles in the mouse brain before and after generating a targeted photothrombotic occlusion. Integrated real-time Laser Speckle Contrast Imaging (LSCI) provides wide-field perfusion maps that are used to monitor and guide the occlusion process while 2PLM maps changes in intravascular oxygen tension. We present the technique's utility in highlighting the effects of vascular networking on the residual intravascular oxygen tensions measured after occlusion in three dimensions. PMID:23847732

  19. Clinical, Biomechanical, and Physiological Translational Interpretations of Human Resting Myofascial Tone or Tension

    PubMed Central

    Masi, Alfonse T.; Nair, Kalyani; Evans, Tyler; Ghandour, Yousef

    2010-01-01

    Background Myofascial tissues generate integrated webs and networks of passive and active tensional forces that provide stabilizing support and that control movement in the body. Passive [central nervous system (CNS)–independent] resting myofascial tension is present in the body and provides a low-level stabilizing component to help maintain balanced postures. This property was recently called “human resting myofascial tone” (HRMT). The HRMT model evolved from electromyography (EMG) research in the 1950s that showed lumbar muscles usually to be EMG-silent in relaxed gravity-neutral upright postures. Methods Biomechanical, clinical, and physiological studies were reviewed to interpret the passive stiffness properties of HRMT that help to stabilize various relaxed functions such as quiet balanced standing. Biomechanical analyses and experimental studies of the lumbar multifidus were reviewed to interpret its passive stiffness properties. The lumbar multifidus was illustrated as the major core stabilizing muscle of the spine, serving an important passive biomechanical role in the body. Results Research into muscle physiology suggests that passive resting tension (CNS-independent) is generated in sarcomeres by the molecular elasticity of low-level cycling cross-bridges between the actomyosin filaments. In turn, tension is complexly transmitted to intimately enveloping fascial matrix fibrils and other molecular elements in connective tissue, which, collectively, constitute the myofascial unit. Postural myofascial tonus varies with age and sex. Also, individuals in the population are proposed to vary in a polymorphism of postural HRMT. A few people are expected to have outlier degrees of innate postural hypotonicity or hypertonicity. Such biomechanical variations likely predispose to greater risk of related musculoskeletal disorders, a situation that deserves greater attention in clinical practice and research. Axial myofascial hypertonicity was hypothesized to

  20. Determination of oxygen tension in the subcutaneous tissue of cosmonauts during the Salyut-6 mission

    NASA Technical Reports Server (NTRS)

    Baranski, S.; Bloszczynski, R.; Hermaszewski, M.; Kubiczkowa, J.; Piorko, A.; Saganiak, R.; Sarol, Z.; Skibniewsky, F.; Stendera, J.; Walichnowski, W.

    1982-01-01

    A polarographic technique was used to measure the oxygen tension in subcutaneous tissue of the forearm of a cosmonaut prior to, after, and on the fourth day of a space mission performed by Salut-6. A drop in the oxygen exchange rate in the peripheral tissues during weightlessness was observed. The mechanisms of this change are studied, taking into consideration the blood distribution in the organism and microcirculation disorders reflected by a decreased blood flow rate in arterial-venous junctions.

  1. Adverse effects of reduced oxygen tension on the proliferative capacity of rat kidney and insulin-secreting cell lines involve DNA damage and stress responses

    PubMed Central

    Chen, Jian-Hua; Jones, R. Huw; Tarry-Adkins, Jane; Smith, Noel H.; Ozanne, Susan E.

    2008-01-01

    Standard cell culture conditions do not reflect the physiological environment in terms of oxygen tension (20% vs 3%). The effects of lowering oxygen tension on cell proliferation in culture can be beneficial as well as detrimental depending on the cell line studied, but the molecular mechanism underlying such effects is not fully understood. We observed that the proliferative capacity of the rat cell lines NRK and INS-1 was inhibited when cultured under 3% oxygen as compared to 20% oxygen. Suppression of proliferation in NRK cells was accompanied by induction of DNA double strand breaks whereas in INS-1 cells it was accompanied by up-regulation of p53 and p27. Although Sirt1 was up-regulated in both cell lines by 3% oxygen the effects on antioxidant enzymes (MnSOD, CuZnSOD and catalase) were cell line specific. Marked up-regulation of heme oxygenase-1 (HO-1) was detected in both NRK and INS-1 cells when cultured in 3% oxygen. HO-1 expression can be readily induced by exposure to hydrogen peroxide in culture. These results suggest that reduced oxygen tension suppresses the proliferative capacity of these two cell lines through a stress response that is similar to an oxidative stress response but the molecular events that lead to the reduced cell proliferation are cell line specific. PMID:18692496

  2. Adverse effects of reduced oxygen tension on the proliferative capacity of rat kidney and insulin-secreting cell lines involve DNA damage and stress responses

    SciTech Connect

    Chen Jianhua Jones, R. Huw; Tarry-Adkins, Jane; Smith, Noel H.; Ozanne, Susan E.

    2008-10-01

    Standard cell culture conditions do not reflect the physiological environment in terms of oxygen tension (20% vs 3%). The effects of lowering oxygen tension on cell proliferation in culture can be beneficial as well as detrimental depending on the cell line studied, but the molecular mechanism underlying such effects is not fully understood. We observed that the proliferative capacity of the rat cell lines NRK and INS-1 was inhibited when cultured under 3% oxygen as compared to 20% oxygen. Suppression of proliferation in NRK cells was accompanied by induction of DNA double strand breaks whereas in INS-1 cells it was accompanied by up-regulation of p53 and p27. Although Sirt1 was up-regulated in both cell lines by 3% oxygen the effects on antioxidant enzymes (MnSOD, CuZnSOD and catalase) were cell line specific. Marked up-regulation of heme oxygenase-1 (HO-1) was detected in both NRK and INS-1 cells when cultured in 3% oxygen. HO-1 expression can be readily induced by exposure to hydrogen peroxide in culture. These results suggest that reduced oxygen tension suppresses the proliferative capacity of these two cell lines through a stress response that is similar to an oxidative stress response but the molecular events that lead to the reduced cell proliferation are cell line specific.

  3. The effect of oxygen tension on human articular chondrocyte matrix synthesis: Integration of experimental and computational approaches

    PubMed Central

    Li, S; Oreffo, ROC; Sengers, BG; Tare, RS

    2014-01-01

    Significant oxygen gradients occur within tissue engineered cartilaginous constructs. Although oxygen tension is an important limiting parameter in the development of new cartilage matrix, its precise role in matrix formation by chondrocytes remains controversial, primarily due to discrepancies in the experimental setup applied in different studies. In this study, the specific effects of oxygen tension on the synthesis of cartilaginous matrix by human articular chondrocytes were studied using a combined experimental-computational approach in a “scaffold-free” 3D pellet culture model. Key parameters including cellular oxygen uptake rate were determined experimentally and used in conjunction with a mathematical model to estimate oxygen tension profiles in 21-day cartilaginous pellets. A threshold oxygen tension (pO2 ≈ 8% atmospheric pressure) for human articular chondrocytes was estimated from these inferred oxygen profiles and histological analysis of pellet sections. Human articular chondrocytes that experienced oxygen tension below this threshold demonstrated enhanced proteoglycan deposition. Conversely, oxygen tension higher than the threshold favored collagen synthesis. This study has demonstrated a close relationship between oxygen tension and matrix synthesis by human articular chondrocytes in a “scaffold-free” 3D pellet culture model, providing valuable insight into the understanding and optimization of cartilage bioengineering approaches. Biotechnol. Bioeng. 2014;111: 1876–1885. PMID:24668194

  4. Methyl sterol and cyclopropane fatty acid composition of Methylococcus capsulatus grown at low oxygen tensions.

    PubMed Central

    Jahnke, L L; Nichols, P D

    1986-01-01

    Methylococcus capsulatus contained extensive intracytoplasmic membranes when grown in fed-batch cultures over a wide range of oxygen tensions (0.1 to 10.6%, vol/vol) and at a constant methane level. Although the biomass decreased as oxygen levels were lowered, consistently high amounts of phospholipid and methyl sterol were synthesized. The greatest amounts of sterol and phospholipid were found in cells grown between 0.5 and 1.1% oxygen (7.2 and 203 mumol/g [dry weight], respectively). While sterol was still synthesized in significant amounts in cells grown at 0.1% oxygen, the major sterol product was the dimethyl form. Analysis by capillary gas chromatography-mass spectrophotometry showed that the phospholipid esterified fatty acids were predominantly 16:0 and 16:1 and that the hexadecenoates consisted of cis delta 9, delta 10, and delta 11 isomers. At low oxygen tensions, the presence of large amounts (25%) of cyclopropane fatty acids (cy 17:0) with the methylene groups at the delta 9, delta 10, and delta 11 positions was detected. Although the delta 9 monoenoic isomer was predominant, growth at low oxygen levels enhanced the synthesis of the delta 10 isomers of 16:1 and cy 17:0. As the oxygen level was increased, the amount of cyclopropanes decreased, such that only a trace of cy 17:0 could be detected in cells grown at 10.6% oxygen. Although M. capsulatus grew at very low oxygen tensions, this growth was accompanied by changes in the membrane lipids. PMID:3087955

  5. Methyl sterol and cyclopropane fatty acid composition of Methylococcus capsulatus grown at low oxygen tensions

    NASA Technical Reports Server (NTRS)

    Jahnke, L. L.; Nichols, P. D.

    1986-01-01

    The sterol and fatty acid concentrations for M. capsulatus grown in fed-batch cultures over a wide range of oxygen tensions (0.1-10.6 percent) and at a constant methane level are evaluated. The analyses reveal that the biomass decreases as oxygen levels are lowered; the sterol concentration increases when the oxygen range is between 0.5-1.1 percent and decreases when the oxygen range is below 0.5 percent; and the amount of monounsaturated C16 decreases and the concentration of cyclopropane fatty acids increases after oxygen is reduced. It is noted that growth and membrane synthesis occur at low oxygen concentrations and that the synthesis of membrane lipids responds to growth conditions.

  6. Adaptation of chondrocytes to low oxygen tension: relationship between hypoxia and cellular metabolism.

    PubMed

    Rajpurohit, R; Koch, C J; Tao, Z; Teixeira, C M; Shapiro, I M

    1996-08-01

    In endochondral bone, the growth cartilage is the site of rapid growth. Since the vascular supply to the cartilage is limited, it is widely assumed that cells of the cartilage are hypoxic and that limitations in the oxygen supply regulate the energetic state of the maturing cells. In this report, we evaluate the effects of oxygen tension on chondrocyte energy metabolism, thiol status, and expression of transcription elements, HIF and AP-1. Imposition of an hypoxic environment on cultured chondrocytes caused a proportional increase in glucose utilization and elevated levels of lactate synthesis. Although we observed a statistical increase in the activities of phosphofructokinase, pyruvate kinase, lactate dehydrogenase, and creatine kinase after exposure to lowered oxygen concentrations, the effect was small. The cultured cells exhibited a decreased utilization of glutamine, possibly due to down regulation of mitochondrial function and inhibition of oxidative deamination. With respect to total energy generation, we noted that these cells are quite capable of maintaining the energy charge of the cell at low oxygen tensions. Indeed, no changes in the absolute quantity of adenine nucleotides or the energy charge ratio was observed. Hypoxia caused a decrease in the glutathione content of cultured chondrocytes and a concomitant rise in cell and medium cysteine levels. It is likely that the fall in cell glutathione level is due to decreased synthesis of the tripeptide under reduced oxygen stress and the limited supply of glutamate. The observed rise in cellular and medium cysteine levels probably reflects an increase in the rate of degradation of glutathione and a decrease in synthesis of the peptide. To explore how cells transduce these metabolic effects, gel retardation assays were used to study chondrocyte HIF and AP-1 binding activities. Chondrocyte nuclear preparations bound an HIF-oligonucleotide; however, at low oxygen tensions, no increase in HIF binding was

  7. Effects of oxygen tension and dextran-shelled/2H,3H-decafluoropentane-cored oxygen-loaded nanodroplets on secretion of gelatinases and their inhibitors in term human placenta.

    PubMed

    Prato, Mauro; Khadjavi, Amina; Magnetto, Chiara; Gulino, Giulia Rossana; Rolfo, Alessandro; Todros, Tullia; Cavalli, Roberta; Guiot, Caterina

    2016-01-01

    Matrix metalloproteinases (MMPs) and their endogenous inhibitors (TIMPs) need to be finely modulated in physiological processes. However, oxygen tension influences MMP/TIMP balances, potentially leading to pathology. Intriguingly, new 2H,3H-decafluoropentane-based oxygen-loaded nanodroplets (OLNDs) have proven effective in abrogating hypoxia-dependent dysregulation of MMP and TIMP secretion by single cell populations. This work explored the effects of different oxygen tensions and dextran-shelled OLNDs on MMP/TIMP production in an organized and multicellular tissue (term human placenta). Chorionic villous explants from normal third-trimester pregnancies were incubated with/without OLNDs in 3 or 20% O2. Explants cultured at higher oxygen tension released constitutive proMMP-2, proMMP-9, TIMP-1, and TIMP-2. Hypoxia significantly altered MMP-2/TIMP-2 and MMP-9/TIMP-1 ratios enhancing TIMP-2 and reducing proMMP-2, proMMP-9, and TIMP-1 levels. Intriguingly, OLNDs effectively counteracted the effects of low oxygen tension. Collectively, these data support OLND potential as innovative, nonconventional, and cost-effective tools to counteract hypoxia-dependent dysregulation of MMP/TIMP balances in human tissues. PMID:26523859

  8. Application of perfluorocarbon emulsions as fluorine-19 nuclear magnetic resonance molecular probes of cardiac tissues oxygen tension

    SciTech Connect

    Shukla, H.P.

    1994-01-01

    The basic and universal need for oxygen in mammalian tissue has long been recognized. The quantitation of oxygen tension (pO[sub 2]) in cardiac tissue is available by many techniques, but these are generally invasive or superficial. In addition, the role of cardiac pO[sub 2] along the oxygen gradient has yet to be defined. To date, no single method fits the ideal, i.e. non-invasive, sensitive, accurate, rapid, three-dimensional, and economical. The use of perfluorocarbon emulsions as tissue oximeters by [sup 19]F NMR relaxometry has the potential to fulfill many of these requirements. Development of a novel method requires the assessment of validity, reproducibility, and practicality. To this end, I have characterized the linear relationship between pO[sub 2] and the [sup 19]F spin-lattice relaxation rate (R1) for several perfluorocarbon (PFC) emulsions at high magnetic fields. The physical basis of underlying [sup 19]F relaxation mechanisms were modeled with respect to the structure and thermal behavior of perfluorocarbon molecules. Utility of these molecules in vivo was tested by spectroscopy and imaging of perfluorocarbons sequestered in the perfused rat heart. Under a wide range of steady-state oxygenation, the global cardiac tissue pO[sub 2] of perfused rat hearts responded in a manner consistent with physiological processes. The cardiac pO[sub 2] was measured by MRS either with high reproducibility ([plus minus]20 torr) or temporal resolution (1 sec). Independent validation of this method was provided in the total absence of oxygen consumption by the heart. Localized pO[sub 2] measurements in tissue were accomplished by [sup 19]F MRI of PFCs in arrested, perfused rat hearts, and found to change significantly with ischemia. It was concluded that the measurement of pO[sub 2] by NMR can provide important information about the physiological condition of the heart.

  9. Growth studies on Mycobacterium BCG: establishment of growth curves and measurement of the oxygen tension of the growth medium.

    PubMed

    Moore, D F; James, A M

    1982-01-01

    Mycobacterium BCG grew exponentially in shallow, static volumes of culture medium for approximately 10 days; the oxygen tension of the medium at all stages of growth was 100% saturation. Higher yields were obtained from Dubos than from glycerol-free medium. In static cultures, the oxygen tension of the culture and consequently the growth rate of BCG was dependent on the depth of the medium; active growth ceased at an oxygen tension of less than 40% saturation. BCG grew actively in a cell sediment, while cells growing in suspension made a negligible contribution to the yield. PMID:6757673

  10. Oxygen tension regulates the osteogenic, chondrogenic and endochondral phenotype of bone marrow derived mesenchymal stem cells

    SciTech Connect

    Sheehy, Eamon J.; Buckley, Conor T.; Kelly, Daniel J.

    2012-01-06

    Highlights: Black-Right-Pointing-Pointer Expansion in low oxygen enhances MSC proliferation and osteogenesis. Black-Right-Pointing-Pointer Differentiation in low oxygen enhances chondrogenesis and suppresses hypertrophy. Black-Right-Pointing-Pointer Oxygen can regulate the MSC phenotype for use in tissue engineering applications. -- Abstract: The local oxygen tension is a key regulator of the fate of mesenchymal stem cells (MSCs). The objective of this study was to investigate the effect of a low oxygen tension during expansion and differentiation on the proliferation kinetics as well as the subsequent osteogenic and chondrogenic potential of MSCs. We first hypothesised that expansion in a low oxygen tension (5% pO{sub 2}) would improve both the subsequent osteogenic and chondrogenic potential of MSCs compared to expansion in a normoxic environment (20% pO{sub 2}). Furthermore, we hypothesised that chondrogenic differentiation in a low oxygen environment would suppress hypertrophy of MSCs cultured in both pellets and hydrogels used in tissue engineering strategies. MSCs expanded at 5% pO{sub 2} proliferated faster forming larger colonies, resulting in higher cell yields. Expansion at 5% pO{sub 2} also enhanced subsequent osteogenesis of MSCs, whereas differentiation at 5% pO{sub 2} was found to be a more potent promoter of chondrogenesis than expansion at 5% pO{sub 2}. Greater collagen accumulation, and more intense staining for collagen types I and X, was observed in pellets maintained at 20% pO{sub 2} compared to 5% pO{sub 2}. Both pellets and hydrogels stained more intensely for type II collagen when undergoing chondrogenesis in a low oxygen environment. Differentiation at 5% pO{sub 2} also appeared to inhibit hypertrophy in both pellets and hydrogels, as demonstrated by reduced collagen type X and Alizarin Red staining and alkaline phosphatase activity. This study demonstrates that the local oxygen environment can be manipulated in vitro to either stabilise a

  11. Modeling Variable Phanerozoic Oxygen Effects on Physiology and Evolution.

    PubMed

    Graham, Jeffrey B; Jew, Corey J; Wegner, Nicholas C

    2016-01-01

    Geochemical approximation of Earth's atmospheric O2 level over geologic time prompts hypotheses linking hyper- and hypoxic atmospheres to transformative events in the evolutionary history of the biosphere. Such correlations, however, remain problematic due to the relative imprecision of the timing and scope of oxygen change and the looseness of its overlay on the chronology of key biotic events such as radiations, evolutionary innovation, and extinctions. There are nevertheless general attributions of atmospheric oxygen concentration to key evolutionary changes among groups having a primary dependence upon oxygen diffusion for respiration. These include the occurrence of Devonian hypoxia and the accentuation of air-breathing dependence leading to the origin of vertebrate terrestriality, the occurrence of Carboniferous-Permian hyperoxia and the major radiation of early tetrapods and the origins of insect flight and gigantism, and the Mid-Late Permian oxygen decline accompanying the Permian extinction. However, because of variability between and error within different atmospheric models, there is little basis for postulating correlations outside the Late Paleozoic. Other problems arising in the correlation of paleo-oxygen with significant biological events include tendencies to ignore the role of blood pigment affinity modulation in maintaining homeostasis, the slow rates of O2 change that would have allowed for adaptation, and significant respiratory and circulatory modifications that can and do occur without changes in atmospheric oxygen. The purpose of this paper is thus to refocus thinking about basic questions central to the biological and physiological implications of O2 change over geological time. PMID:27343111

  12. Impact of low oxygen tension on stemness, proliferation and differentiation potential of human adipose-derived stem cells

    SciTech Connect

    Choi, Jane Ru; Pingguan-Murphy, Belinda; Wan Abas, Wan Abu Bakar; Noor Azmi, Mat Adenan; Omar, Siti Zawiah; Chua, Kien Hui; Wan Safwani, Wan Kamarul Zaman

    2014-05-30

    Highlights: • Hypoxia maintains the stemness of adipose-derived stem cells (ASCs). • ASCs show an increased proliferation rate under low oxygen tension. • Oxygen level as low as 2% enhances the chondrogenic differentiation potential of ASCs. • HIF-1α may regulate the proliferation and differentiation activities of ASCs under hypoxia. - Abstract: Adipose-derived stem cells (ASCs) have been found adapted to a specific niche with low oxygen tension (hypoxia) in the body. As an important component of this niche, oxygen tension has been known to play a critical role in the maintenance of stem cell characteristics. However, the effect of O{sub 2} tension on their functional properties has not been well determined. In this study, we investigated the effects of O{sub 2} tension on ASCs stemness, differentiation and proliferation ability. Human ASCs were cultured under normoxia (21% O{sub 2}) and hypoxia (2% O{sub 2}). We found that hypoxia increased ASC stemness marker expression and proliferation rate without altering their morphology and surface markers. Low oxygen tension further enhances the chondrogenic differentiation ability, but reduces both adipogenic and osteogenic differentiation potential. These results might be correlated with the increased expression of HIF-1α under hypoxia. Taken together, we suggest that growing ASCs under 2% O{sub 2} tension may be important in expanding ASCs effectively while maintaining their functional properties for clinical therapy, particularly for the treatment of cartilage defects.

  13. Mitochondrial physiology and reactive oxygen species production are altered by hypoxia acclimation in killifish (Fundulus heteroclitus).

    PubMed

    Du, Sherry N N; Mahalingam, Sajeni; Borowiec, Brittney G; Scott, Graham R

    2016-04-15

    Many fish encounter hypoxia in their native environment, but the role of mitochondrial physiology in hypoxia acclimation and hypoxia tolerance is poorly understood. We investigated the effects of hypoxia acclimation on mitochondrial respiration, O2kinetics, emission of reactive oxygen species (ROS), and antioxidant capacity in the estuarine killifish ( ITALIC! Fundulus heteroclitus). Killifish were acclimated to normoxia, constant hypoxia (5 kPa O2) or intermittent diel cycles of nocturnal hypoxia (12 h:12 h normoxia:hypoxia) for 28-33 days and mitochondria were isolated from liver. Neither pattern of hypoxia acclimation affected the respiratory capacities for oxidative phosphorylation or electron transport, leak respiration, coupling control or phosphorylation efficiency. Hypoxia acclimation also had no effect on mitochondrial O2kinetics, but ITALIC! P50(the O2tension at which hypoxia inhibits respiration by 50%) was lower in the leak state than during maximal respiration, and killifish mitochondria endured anoxia-reoxygenation without any impact on mitochondrial respiration. However, both patterns of hypoxia acclimation reduced the rate of ROS emission from mitochondria when compared at a common O2tension. Hypoxia acclimation also increased the levels of protein carbonyls and the activities of superoxide dismutase and catalase in liver tissue (the latter only occurred in constant hypoxia). Our results suggest that hypoxia acclimation is associated with changes in mitochondrial physiology that decrease ROS production and may help improve hypoxia tolerance. PMID:26896545

  14. Enhanced proliferation and dopaminergic differentiation of ventral mesencephalic precursor cells by synergistic effect of FGF2 and reduced oxygen tension

    SciTech Connect

    Jensen, Pia; Gramsbergen, Jan-Bert; Zimmer, Jens; Widmer, Hans R.; Meyer, Morten

    2011-07-15

    Effective numerical expansion of dopaminergic precursors might overcome the limited availability of transplantable cells in replacement strategies for Parkinson's disease. Here we investigated the effect of fibroblast growth factor-2 (FGF2) and FGF8 on expansion and dopaminergic differentiation of rat embryonic ventral mesencephalic neuroblasts cultured at high (20%) and low (3%) oxygen tension. More cells incorporated bromodeoxyuridine in cultures expanded at low as compared to high oxygen tension, and after 6 days of differentiation there were significantly more neuronal cells in low than in high oxygen cultures. Low oxygen during FGF2-mediated expansion resulted also in a significant increase in tyrosine hydroxylase-immunoreactive (TH-ir) dopaminergic neurons as compared to high oxygen tension, but no corresponding effect was observed for dopamine release into the culture medium. However, switching FGF2-expanded cultures from low to high oxygen tension during the last two days of differentiation significantly enhanced dopamine release and intracellular dopamine levels as compared to all other treatment groups. In addition, the short-term exposure to high oxygen enhanced in situ assessed TH enzyme activity, which may explain the elevated dopamine levels. Our findings demonstrate that modulation of oxygen tension is a recognizable factor for in vitro expansion and dopaminergic differentiation of rat embryonic midbrain precursor cells.

  15. Hyaluronic acid hydrogel stiffness and oxygen tension affect cancer cell fate and endothelial sprouting

    PubMed Central

    Shen, Yu-I; Abaci, Hasan E.; Krupsi, Yoni; Weng, Lien-Chun; Burdick, Jason A.; Gerecht, Sharon

    2014-01-01

    Three-dimensional (3D) tissue culture models may recapitulate aspects of the tumorigenic microenvironment in vivo, enabling the study of cancer progression in vitro. Both hypoxia and matrix stiffness are known to regulate tumor growth. Using a modular culture system employing an acrylated hyaluronic acid (AHA) hydrogel, three hydrogel matrices with distinctive degrees of viscoelasticity — soft (78±16 Pa), medium (309± 57 Pa), and stiff (596± 73 Pa) — were generated using the same concentration of adhesion ligands. Oxygen levels within the hydrogel in atmospheric (21 %), hypoxic (5 %), and severely hypoxic (1 %) conditions were assessed with a mathematical model. HT1080 fibrosarcoma cells, encapsulated within the AHA hydrogels in high densities, generated nonuniform oxygen distributions, while lower cell densities resulted in more uniform oxygen distributions in the atmospheric and hypoxic environments. When we examined how varying viscoelasticity in atmospheric and hypoxic environments affects cell cycles and the expression of BNIP3 and BNIP3L (autophagy and apoptosis genes), and GLUT-1 (a glucose transport gene), we observed that HT1080 cells in 3D hydrogel adapted better to hypoxic conditions than those in a Petri dish, with no obvious correlation to matrix viscoelasticity, by recovering rapidly from possible autophagy/apoptotic events and alternating metabolism mechanisms. Further, we examined how HT1080 cells cultured in varying viscoelasticity and oxygen tension conditions affected endothelial sprouting and invasion. We observed that increased matrix stiffness reduced endothelial sprouting and invasion in atmospheric conditions; however, we observed increased endothelial sprouting and invasion under hypoxia at all levels of matrix stiffness with the upregulation of vascular endothelial growth factor (VEGF) and angiopoeitin-1 (ANG-1). Overall, HT1080 cells encapsulated in the AHA hydrogels under hypoxic stress recovered better from apoptosis and

  16. Designer Hydrogels for Precision Control of Oxygen Tension and Mechanical Properties

    PubMed Central

    Blatchley, Michael; Park, Kyung Min; Gerecht, Sharon

    2015-01-01

    Oxygen levels and mechanical properties provide vital cues to regulate myriad cellular functions and stem cell fate decisions. Here, we present a hybrid hydrogel system in which we can control independently oxygen levels and mechanical properties. We designed, synthesized and analyzed a hybrid hydrogel system comprised of two polymer backbones, gelatin and dextran. Both polymers were crosslinked via a laccase-mediated, oxygen consuming reaction. By specifically controlling the concentration of phenolic molecules available to react in our hydrogel, we could precisely control the time in which the hydrogel remained hypoxic (TH). We were able to achieve a range of TH from the order of minutes to greater than 10 hours. Additionally, by incorporating a secondary crosslinker, transglutaminase, mechanical properties could be adjusted in a user-defined fashion, with dynamic elastic modulus (G′) values ranging from <20 Pa to >1 kPa. Importantly, oxygen levels and substrate mechanical properties could be individually tuned and decoupled in our hybrid hydrogels, while retaining the potential to study possible synergistic effects between the two parameters. By precisely controlling oxygen tension and mechanical properties, we expect that research utilizing the new hybrid hydrogels will enhance our understanding of the complex 3D cellular processes mediated by each parameter individually and may also hold clinical interest as acellular therapies. PMID:26693017

  17. Bordetella bronchiseptica responses to physiological reactive nitrogen and oxygen stresses

    PubMed Central

    Omsland, Anders; Miranda, Katrina M.; Friedman, Richard L.; Boitano, Scott

    2008-01-01

    Bordetella bronchiseptica can establish prolonged airway infection consistent with a highly developed ability to evade mammalian host immune responses. Upon initial interaction with the host upper respiratory tract mucosa, B. bronchiseptica are subjected to antimicrobial reactive nitrogen species (RNS) and reactive oxygen species (ROS), effector molecules of the innate immune system. However, the responses of B. bronchiseptica to redox species at physiologically relevant concentrations (nM-µM) have not been investigated. Using predicted physiological concentrations of nitric oxide (NO), superoxide (O2.−) and hydrogen peroxide (H2O2) on low numbers of colony forming units (CFU) of B. bronchiseptica, all redox active species displayed dose-dependent antimicrobial activity. Susceptibility to individual redox active species was significantly increased upon introduction of a second species at sub-antimicrobial concentrations. An increased bacteriostatic activity of NO was observed relative to H2O2. The understanding of Bordetella responses to physiologically relevant levels of exogenous RNS and ROS will aid in defining the role of endogenous production of these molecules in host innate immunity against Bordetella and other respiratory pathogens. PMID:18462394

  18. Physiologically Low Oxygen Enhances Biomolecule Production and Stemness of Mesenchymal Stem Cell Spheroids.

    PubMed

    Shearier, Emily; Xing, Qi; Qian, Zichen; Zhao, Feng

    2016-04-01

    Multicellular human mesenchymal stem cell (hMSC) spheroids have been demonstrated to be valuable in a variety of applications, including cartilage regeneration, wound healing, and neoangiogenesis. Physiological relevant low oxygen culture can significantly improve in vitro hMSC expansion by preventing cell differentiation. We hypothesize that hypoxia-cultured hMSC spheroids can better maintain the regenerative properties of hMSCs. In this study, hMSC spheroids were fabricated using hanging drop method and cultured under 2% O2 and 20% O2 for up to 96 h. Spheroid diameter and viability were examined, as well as extracellular matrix (ECM) components and growth factor levels between the two oxygen tensions at different time points. Stemness was measured among the spheroid culture conditions and compared to two-dimensional cell cultures. Spheroid viability and structural integrity were studied using different needle gauges to ensure no damage would occur when implemented in vivo. Spheroid attachment and integration within a tissue substitute were also demonstrated. The results showed that a three-dimensional hMSC spheroid cultured at low oxygen conditions can enhance the production of ECM proteins and growth factors, while maintaining the spheroids' stemness and ability to be injected, attached, and potentially be integrated within a tissue. PMID:26830500

  19. Effect of body position and oxygen tension on foramen ovale recruitment.

    PubMed

    Moses, Kayla L; Beshish, Arij G; Heinowski, Nicole; Baker, Kim R; Pegelow, David F; Eldridge, Marlowe W; Bates, Melissa L

    2015-01-01

    While there is an increased prevalence of stroke at altitude in individuals who are considered to be low risk for thrombotic events, it is uncertain how venous thrombi reach the brain. The patent foramen ovale (PFO) is a recruitable intracardiac shunt between the right and left atrium. We aimed to determine whether body position and oxygen tension affect blood flow through the PFO in healthy adults. We hypothesized that hypoxia and body positions that promote right atrial filling would independently recruit the PFO. Subjects with a PFO (n = 11) performed 11 trials, combining four different fractions of inhaled oxygen (FiO₂) (1.0, 0.21, 0.15, and 0.10) and three positions (upright, supine, and 45° head down), with the exception of FiO₂ = 0.10, while 45° head down. After 5 min in each position, breathing the prescribed oxygen tension, saline bubbles were injected into an antecubital vein and a four-chamber echocardiogram was obtained to evaluate PFO recruitment. We observed a high incidence of PFO recruitment in all conditions, with increased recruitment in response to severe hypoxia and some contribution of body position at moderate levels of hypoxia. We suspect that increased pulmonary vascular pressure, secondary to hypoxia-induced pulmonary vasoconstriction, increased right atrial pressure enough to recruit the PFO. Additionally, we hypothesize that the minor increase in breathing resistance that was added by the mouthpiece, used during experimental trials, affected intrathoracic pressure and venous return sufficiently to recruit the PFO. PMID:25394826

  20. Metabolic consequences of agonistic behaviour: crab fights in declining oxygen tensions.

    PubMed

    Sneddon; Taylor; Huntingford

    1999-02-01

    The energetic consequences of fighting, which may depend on environmental conditions, can be an important factor shaping contest strategy and duration. Energy expenditure may be costly to fitness because it depletes reserves that could otherwise have been allocated to reproduction, and metabolites are produced that may constrain subsequent activities. We examined the variation in the metabolic consequences of fighting in relation to hypoxia. Contests were staged between pairs of size-matched male shore crabs Carcinus maenas L., under a range of water oxygen tensions (between 10 and 100% oxygen saturation) which crabs experience in their natural habitat. Fighting under normoxic and hypoxic conditions resulted in significantly elevated concentrations of haemolymph metabolites (L-lactate and glucose) compared with crabs at rest. However, these concentrations were much lower than in crabs that had been walking on a treadmill. Glycogen concentrations differed only under hypoxic conditions: glycogen stores were reduced in crabs after fighting and this reduction was similar to that after exercise on a treadmill. Contests were shorter when they were staged below a water P o2of 6.7 kPa ( approximately 30% normoxia). As water oxygen tensions were reduced, fighting crabs had greater concentrations of L-lactate and glucose in their blood and tissues whilst glycogen stores were reduced. Fights became shorter when crabs were exposed to severe hypoxia (P o2=2 kPa) for increasing lengths of time, and blood L-lactate concentrations increased. The results suggest that as fights progressed, crabs experienced an increasing metabolic debt, in the form of accumulation of L-lactate and a reduction in energy stores, which was amplified by hypoxic conditions. Copyright 1999 The Association for the Study of Animal Behaviour. PMID:10049475

  1. Nitric oxide inhibits succinate dehydrogenase-driven oxygen consumption in potato tuber mitochondria in an oxygen tension-independent manner.

    PubMed

    Simonin, Vagner; Galina, Antonio

    2013-01-01

    NO (nitric oxide) is described as an inhibitor of plant and mammalian respiratory chains owing to its high affinity for COX (cytochrome c oxidase), which hinders the reduction of oxygen to water. In the present study we show that in plant mitochondria NO may interfere with other respiratory complexes as well. We analysed oxygen consumption supported by complex I and/or complex II and/or external NADH dehydrogenase in Percoll-isolated potato tuber (Solanum tuberosum) mitochondria. When mitochondrial respiration was stimulated by succinate, adding the NO donors SNAP (S-nitroso-N-acetyl-DL-penicillamine) or DETA-NONOate caused a 70% reduction in oxygen consumption rate in state 3 (stimulated with 1 mM of ADP). This inhibition was followed by a significant increase in the Km value of SDH (succinate dehydrogenase) for succinate (Km of 0.77±0.19 to 34.3±5.9 mM, in the presence of NO). When mitochondrial respiration was stimulated by external NADH dehydrogenase or complex I, NO had no effect on respiration. NO itself and DETA-NONOate had similar effects to SNAP. No significant inhibition of respiration was observed in the absence of ADP. More importantly, SNAP inhibited PTM (potato tuber mitochondria) respiration independently of oxygen tensions, indicating a different kinetic mechanism from that observed in mammalian mitochondria. We also observed, in an FAD reduction assay, that SNAP blocked the intrinsic SDH electron flow in much the same way as TTFA (thenoyltrifluoroacetone), a non-competitive SDH inhibitor. We suggest that NO inhibits SDH in its ubiquinone site or its Fe-S centres. These data indicate that SDH has an alternative site of NO action in plant mitochondria. PMID:23039043

  2. Reactive Oxygen Species: Physiological and Physiopathological Effects on Synaptic Plasticity

    PubMed Central

    Beckhauser, Thiago Fernando; Francis-Oliveira, José; De Pasquale, Roberto

    2016-01-01

    In the mammalian central nervous system, reactive oxygen species (ROS) generation is counterbalanced by antioxidant defenses. When large amounts of ROS accumulate, antioxidant mechanisms become overwhelmed and oxidative cellular stress may occur. Therefore, ROS are typically characterized as toxic molecules, oxidizing membrane lipids, changing the conformation of proteins, damaging nucleic acids, and causing deficits in synaptic plasticity. High ROS concentrations are associated with a decline in cognitive functions, as observed in some neurodegenerative disorders and age-dependent decay of neuroplasticity. Nevertheless, controlled ROS production provides the optimal redox state for the activation of transductional pathways involved in synaptic changes. Since ROS may regulate neuronal activity and elicit negative effects at the same time, the distinction between beneficial and deleterious consequences is unclear. In this regard, this review assesses current research and describes the main sources of ROS in neurons, specifying their involvement in synaptic plasticity and distinguishing between physiological and pathological processes implicated. PMID:27625575

  3. Reactive Oxygen Species: Physiological and Physiopathological Effects on Synaptic Plasticity.

    PubMed

    Beckhauser, Thiago Fernando; Francis-Oliveira, José; De Pasquale, Roberto

    2016-01-01

    In the mammalian central nervous system, reactive oxygen species (ROS) generation is counterbalanced by antioxidant defenses. When large amounts of ROS accumulate, antioxidant mechanisms become overwhelmed and oxidative cellular stress may occur. Therefore, ROS are typically characterized as toxic molecules, oxidizing membrane lipids, changing the conformation of proteins, damaging nucleic acids, and causing deficits in synaptic plasticity. High ROS concentrations are associated with a decline in cognitive functions, as observed in some neurodegenerative disorders and age-dependent decay of neuroplasticity. Nevertheless, controlled ROS production provides the optimal redox state for the activation of transductional pathways involved in synaptic changes. Since ROS may regulate neuronal activity and elicit negative effects at the same time, the distinction between beneficial and deleterious consequences is unclear. In this regard, this review assesses current research and describes the main sources of ROS in neurons, specifying their involvement in synaptic plasticity and distinguishing between physiological and pathological processes implicated. PMID:27625575

  4. Influence of Low Oxygen Tensions and Sorption to Sediment Black Carbon on Biodegradation of Pyrene ▿

    PubMed Central

    Ortega-Calvo, José-Julio; Gschwend, Philip M.

    2010-01-01

    Sorption to sediment black carbon (BC) may limit the aerobic biodegradation of polycyclic aromatic hydrocarbons (PAHs) in resuspension events and intact sediment beds. We examined this hypothesis experimentally under conditions that were realistic in terms of oxygen concentrations and BC content. A new method, based on synchronous fluorescence observations of 14C-pyrene, was developed for continuously measuring the uptake of dissolved pyrene by Mycobacterium gilvum VM552, a representative degrader of PAHs. The effect of oxygen and pyrene concentrations on pyrene uptake followed Michaelis-Menten kinetics, resulting in a dissolved oxygen half-saturation constant (Kom) of 14.1 μM and a dissolved pyrene half-saturation constant (Kpm) of 6 nM. The fluorescence of 14C-pyrene in air-saturated suspensions of sediments and induced cells followed time courses that reflected simultaneous desorption and biodegradation of pyrene, ultimately causing a quasi-steady-state concentration of dissolved pyrene balancing desorptive inputs and biodegradation removals. The increasing concentrations of 14CO2 in these suspensions, as determined with liquid scintillation, evidenced the strong impact of sorption to BC-rich sediments on the biodegradation rate. Using the best-fit parameter values, we integrated oxygen and sorption effects and showed that oxygen tensions far below saturation levels in water are sufficient to enable significant decreases in the steady-state concentrations of aqueous-phase pyrene. These findings may be relevant for bioaccumulation scenarios that consider the effect of sediment resuspension events on exposure to water column and sediment pore water, as well as the direct uptake of PAHs from sediments. PMID:20472733

  5. Antioxidant functionality in hepatocytes using the enhanced collagen extracellular matrix under different oxygen tensions.

    PubMed

    Lee, Sang-Ho; Coger, Robin N; Clemens, Mark G

    2006-10-01

    Improvement of O(2) supply in bioartificial liver devices remains a critical issue in maintaining hepatocyte viability and functions. Therefore, the current study investigates whether enhanced oxygen (O(2)) transport through collagen extracellular matrix (ECM) can produce a more stable antioxidant defense in different O(2) tensions during prolonged incubation times. Total glutathione concentration of cultured hepatocytes in enhanced ECM was significantly higher than in normal ECM under the lowest O(2) tension phase (2.60mm of thickness from O(2) source), and was also significantly increased in 0.52 mm transport distance of hypoxia as compared to normoxic conditions. Catalase and glutathione reductase activities for hepatocytes within enhanced ECM were also significantly preserved relative to their values for the normal collagen ECM. Specifically, the enhanced ECM produced higher activities at a further transport distance (1.56 mm) from the O(2) source at the 24 h time-point, and remained higher up to the 96 h incubation time. In contrast, the glutathione peroxidase activities in both collagen ECM systems were similar. Hepatocyte viability in the enhanced ECM system was also consistently greater than that for normal ECM. These results suggest that the O(2) enhanced collagen ECM preserves the antioxidant defense system as compared to normal collagen ECM, ostensibly via increased micropathways for O(2) transport to the hepatocytes. PMID:17518651

  6. Optimizing the calculation of DM,CO and VC via the single breath single oxygen tension DLCO/NO method.

    PubMed

    Coffman, Kirsten E; Taylor, Bryan J; Carlson, Alex R; Wentz, Robert J; Johnson, Bruce D

    2016-01-15

    Alveolar-capillary membrane conductance (D(M,CO)) and pulmonary-capillary blood volume (V(C)) are calculated via lung diffusing capacity for carbon monoxide (DL(CO)) and nitric oxide (DL(NO)) using the single breath, single oxygen tension (single-FiO2) method. However, two calculation parameters, the reaction rate of carbon monoxide with blood (θ(CO)) and the D(M,NO)/D(M,CO) ratio (α-ratio), are controversial. This study systematically determined optimal θ(CO) and α-ratio values to be used in the single-FiO2 method that yielded the most similar D(M,CO) and V(C) values compared to the 'gold-standard' multiple-FiO2 method. Eleven healthy subjects performed single breath DL(CO)/DL(NO) maneuvers at rest and during exercise. D(M,CO) and V(C) were calculated via the single-FiO2 and multiple-FiO2 methods by implementing seven θ(CO) equations and a range of previously reported α-ratios. The RP θ(CO) equation (Reeves, R.B., Park, H.K., 1992. Respiration Physiology 88 1-21) and an α-ratio of 4.0-4.4 yielded DM,CO and VC values that were most similar between methods. The RP θ(CO) equation and an experimental α-ratio should be used in future studies. PMID:26521031

  7. Effect of increased oxygen tension on flicker-induced vasodilatation in the human retina

    PubMed Central

    Palkovits, Stefan; Told, Reinhard; Boltz, Agnes; Schmidl, Doreen; Popa Cherecheanu, Alina; Schmetterer, Leopold; Garhöfer, Gerhard

    2014-01-01

    In the retina, blood flow and neural activity are tightly coupled. Stimulation of the retina with flickering light is accompanied by an increase in blood flow. The current study seeks to investigate whether an increase in oxygen tension modulates flicker (FL)-induced vasodilatation in the human retina. A total of 52 healthy volunteers were included. Via a breathing mask, 100% oxygen (O2) was administered in one, a mixture of 8% carbon dioxide and 92% oxygen (C/O) in a second cohort. Retinal vessel diameters were measured with a Vessel Analyzer and FL responses were assessed before and during the breathing periods. At baseline, FL stimulation increased retinal vessel diameters by +3.7±2.3% in arteries and by +5.1±3.7% in veins. Breathing of C/O led to a decrease in arterial (−9.0±6.9%) and venous (−11.3±5.9%) vessel calibers. Flicker response was increased to 5.7±2.5% in arteries and to 8.6±4.1% in veins. Breathing of pure O2 induced a vasoconstriction of vessel diameters by −14.0±5.3% in arteries and −18.4±7.0% in veins and increased FL responses in arteries (+6.2±2.8%) and veins (+7.2±3.1%). Systemic hyperoxia increases FL-induced retinal vasodilatation in the retina. The mechanism by which oxygen modulates the hyperemic response to FL stimulation remains to be elucidated. PMID:25248833

  8. Contrasted Reactivity to Oxygen Tensions in Frankia sp. Strain CcI3 throughout Nitrogen Fixation and Assimilation

    PubMed Central

    Ghodhbane-Gtari, Faten; Hezbri, Karima; Ktari, Amir; Sbissi, Imed; Beauchemin, Nicholas; Gtari, Maher; Tisa, Louis S.

    2014-01-01

    Reconciling the irreconcilable is a primary struggle in aerobic nitrogen-fixing bacteria. Although nitrogenase is oxygen and reactive oxygen species-labile, oxygen tension is required to sustain respiration. In the nitrogen-fixing Frankia, various strategies have been developed through evolution to control the respiration and nitrogen-fixation balance. Here, we assessed the effect of different oxygen tensions on Frankia sp. strain CcI3 growth, vesicle production, and gene expression under different oxygen tensions. Both biomass and vesicle production were correlated with elevated oxygen levels under both nitrogen-replete and nitrogen-deficient conditions. The mRNA levels for the nitrogenase structural genes (nifHDK) were high under hypoxic and hyperoxic conditions compared to oxic conditions. The mRNA level for the hopanoid biosynthesis genes (sqhC and hpnC) was also elevated under hyperoxic conditions suggesting an increase in the vesicle envelope. Under nitrogen-deficient conditions, the hup2 mRNA levels increased with hyperoxic environment, while hup1 mRNA levels remained relatively constant. Taken together, these results indicate that Frankia protects nitrogenase by the use of multiple mechanisms including the vesicle-hopanoid barrier and increased respiratory protection. PMID:24987692

  9. Contrasted reactivity to oxygen tensions in Frankia sp. strain CcI3 throughout nitrogen fixation and assimilation.

    PubMed

    Ghodhbane-Gtari, Faten; Hezbri, Karima; Ktari, Amir; Sbissi, Imed; Beauchemin, Nicholas; Gtari, Maher; Tisa, Louis S

    2014-01-01

    Reconciling the irreconcilable is a primary struggle in aerobic nitrogen-fixing bacteria. Although nitrogenase is oxygen and reactive oxygen species-labile, oxygen tension is required to sustain respiration. In the nitrogen-fixing Frankia, various strategies have been developed through evolution to control the respiration and nitrogen-fixation balance. Here, we assessed the effect of different oxygen tensions on Frankia sp. strain CcI3 growth, vesicle production, and gene expression under different oxygen tensions. Both biomass and vesicle production were correlated with elevated oxygen levels under both nitrogen-replete and nitrogen-deficient conditions. The mRNA levels for the nitrogenase structural genes (nifHDK) were high under hypoxic and hyperoxic conditions compared to oxic conditions. The mRNA level for the hopanoid biosynthesis genes (sqhC and hpnC) was also elevated under hyperoxic conditions suggesting an increase in the vesicle envelope. Under nitrogen-deficient conditions, the hup2 mRNA levels increased with hyperoxic environment, while hup1 mRNA levels remained relatively constant. Taken together, these results indicate that Frankia protects nitrogenase by the use of multiple mechanisms including the vesicle-hopanoid barrier and increased respiratory protection. PMID:24987692

  10. BIOELECTRIC POTENTIALS IN HALICYSTIS : VII. THE EFFECTS OF LOW OXYGEN TENSION.

    PubMed

    Blinks, L R; Darsie, M L; Skow, R K

    1938-11-20

    The potential difference across the protoplasm of impaled cells of Halicystis is not affected by increase of oxygen tension in equilibrium with the sea water, nor with decrease down to about 1/10 its tension in the air (2 per cent O(2) in N(2)). When bubbling of 2 per cent O(2) is stopped, the P.D. drifts downward, to be restored on stirring the sea water, or rebubbling the gas. Bubbling 0.2 per cent O(2) causes the P.D. to drop to 20 mv. or less; 1.1 per cent O(2) to about 50 mv. Restoration of 2 per cent or higher O(2) causes recovery to 70 or 80 mv. often with a preliminary cusp which decreases the P.D. before it rises. Perfusion of aerated sea water through the vacuole is just as effective in restoring the P.D. as external aeration, indicating that the direction of the oxygen gradient is not significant. Low O(2) tension also inhibits the reversed, negative P.D. produced by adding NH(4)Cl to sea water, 0.2 per cent O(2) bringing this P.D. back to the same low positive values found without ammonia. Restoration of 2 per cent O(2) or air, restores this latent negativity. At slightly below the threshold for ammonia reversal, low O(2) may induce a temporary negativity when first bubbled, and a negative cusp may occur on aeration before positive P.D. is regained. This may be due to a decreased consumption of ammonia, or to intermediate pH changes. The locus of the P.D. alteration was tested by applying increased KCl concentrations to the cell exterior; the large cusps produced in aerated solutions become greatly decreased when the P.D. has fallen in 0.2 per cent O(2). This indicates that the originally high relative mobility or concentration of K(+) ion has approached that of Na(+) in the external protoplasmic surface under reduced O(2) tension. Results obtained with sulfate sea water indicate that Na(+) mobility approaches that of SO(4) (-) in 0.2 per cent O(2). P.D. measurements alone cannot tell whether this is due to an increase of the slower ion or a decrease of

  11. Herbivore tooth oxygen isotope compositions: Effects of diet and physiology

    NASA Astrophysics Data System (ADS)

    Kohn, Matthew J.; Schoeninger, Margaret J.; Valley, John W.

    1996-10-01

    The applicability of rapid and precise laser probe analysis of tooth enamel for δ18O has been verified, and the method has been applied to different modern herbivores in East Africa. Sampling and pretreatment procedures involve initial bleaching and grinding of enamel to <75 μm, and elimination of adsorbed water and organic compounds with BrF 5. Typical analytical reproducibilities for 0.5-2 mg samples are ±0.08‰ (± 1σ). Chemical and spectroscopic characterization of pretreated but unanalyzed samples show no alteration compared to fresh enamel. Solid reaction products are nearly pure CaF 2 with little evidence for residual O 2. Because laser probe fluorination extracts oxygen from all sites in the apatite structure (phosphate, structural carbonate, and hydroxyl), only unaltered tooth enamel (>95% apatite) can be analyzed reliably. Different East African herbivores exhibit previously unsuspected compositional differences. Average enamel δ18O values (V-SMOW) are approximately: 25‰ (goat), 27‰ (oryx), 28‰ (dikdik and zebra), 29‰ (topi), 30‰ (gerenuk), and 32‰ (gazelle). These compositions differ from generalized theoretical models, but are broadly consistent with expected isotope effects associated with differences in how much each animal (a) drinks, (b) eats C3 vs. C4 plants, and (c) pants vs. sweats. Consideration of diet, water turnover, and animal physiology will allow the most accurate interpretation of ancient teeth and targeting of environmentally-sensitive animals in paleoclimate studies.

  12. Influence of oxygen tension on myocardial performance. Evaluation by tissue Doppler imaging

    PubMed Central

    Frøbert, Ole; Moesgaard, Jacob; Toft, Egon; Poulsen, Steen Hvitfeldt; Søgaard, Peter

    2004-01-01

    Background Low O2 tension dilates coronary arteries and high O2 tension is a coronary vasoconstrictor but reports on O2-dependent effects on ventricular performance diverge. Yet oxygen supplementation remains first line treatment in cardiovascular disease. We hypothesized that hypoxia improves and hyperoxia worsens myocardial performance. Methods Seven male volunteers (mean age 38 ± 3 years) were examined with echocardiography at respiratory equilibrium during: 1) normoxia (≈21% O2, 79% N2), 2) while inhaling a hypoxic gas mixture (≈11% O2, 89% N2), and 3) while inhaling 100% O2. Tissue Doppler recordings were acquired in the apical 4-chamber, 2-chamber, and long-axis views. Strain rate and tissue tracking displacement analyses were carried out in each segment of the 16-segment left ventricular model and in the basal, middle and apical portions of the right ventricle. Results Heart rate increased with hypoxia (68 ± 4 bpm at normoxia vs. 79 ± 5 bpm, P < 0.001) and decreased with hyperoxia (59 ± 5 bpm, P < 0.001 vs. normoxia). Hypoxia increased strain rate in four left ventricular segments and global systolic contraction amplitude was increased (normoxia: 9.76 ± 0.41 vs hypoxia: 10.87 ± 0.42, P < 0.001). Tissue tracking displacement was reduced in the right ventricular segments and tricuspid regurgitation increased with hypoxia (7.5 ± 1.9 mmHg vs. 33.5 ± 1.8 mmHg, P < 0.001). The TEI index and E/E' did not change with hypoxia. Hyperoxia reduced strain rate in 10 left ventricular segments, global systolic contraction amplitude was decreased (8.83 ± 0.38, P < 0.001 vs. normoxia) while right ventricular function was unchanged. The spectral and tissue Doppler TEI indexes were significantly increased but E/E' did not change with hyperoxia. Conclusion Hypoxia improves and hyperoxia worsens systolic myocardial performance in healthy male volunteers. Tissue Doppler measures of diastolic function are unaffected by hypoxia/hyperoxia which support that the changes

  13. Home monitoring of transcutaneous oxygen tension in the early detection of hypoxaemia in infants and young children.

    PubMed Central

    Poets, C F; Samuels, M P; Noyes, J P; Jones, K A; Southall, D P

    1991-01-01

    Twenty three patients (age range 0.5-40 months) with recurrent cyanotic episodes underwent physiological recordings, including transcutaneous oxygen tension (TcPO2) from a monitor modified for use at home (Kontron 821S). Of 69 episodes in which the arterial oxygen saturation (SaO2, Nellcor N200) was less than or equal to 80% for greater than or equal to 20 seconds and/or central cyanosis was present, the TcPO2 monitor alarmed (less than or equal to 20 mmHg or 2.67 kPa) in every episode. The pulse oximeter identified hypoxaemia in 62 out of 69 episodes, failing in seven episodes due to signal loss from movement artefact. In only seven of 69 episodes was there an accompanying apnoeic pause (greater than or equal to 20 seconds), and heart rate fell to less than or equal to 80 beats/minute in only five of 28 episodes in which an electrocardiogram was recorded. In 32 episodes in which SaO2 fell to less than or equal to 60%, the TcPO2 monitor alarmed after a median time interval of 16 seconds (maximum time interval 30 seconds). The TcPO2 monitor was then used in an uncontrolled trial at home in 350 patients at increased risk of sudden death and/or hypoxaemia. Indications for monitoring included apparent life threatening events or cyanotic episodes (n = 163), prematurity and prematurity related disorders (n = 86), and sudden unexpected death in one or more siblings (n = 122). The TcPO2 monitor detected cyanotic episodes at home in 81 patients, 52 of whom received vigorous stimulation and/or mouth to mouth resuscitation. Twenty one of these 52 patients had further hypoxaemic episodes documented in hospital with pulse oximetry. In 30 patients, the TcPo2 monitor also identified the gradual development of hypoxaemia, as confirmed by pulse oximetry. Twenty of these needed additional inspired oxygen and six subsequently needed ventilatory support in hospital. This TcPo2 monitor is a reliable detector of both sudden and gradual onset hypoxaemia and is able to be used by parents

  14. A Novel Teflon-membrane Gas Tension Device for Denitrification-studies in Oxygen Minimum Zones

    NASA Astrophysics Data System (ADS)

    Reed, A. C.; McNeil, C. L.; D'Asaro, E. A.; Altabet, M. A.; Johnson, B.; Bourbonnais, A.

    2014-12-01

    Oxygen Minimum Zones (OMZs) are global hotspots for the biogeochemical transformation of biologically-available forms of nitrogen to unusable nitrogen-gas. We present a new Teflon-membrane based Gas Tension Device (GTD) for measuring the excess N2 signal generated by denitrification and anammox in OMZs, with a hydrostatic pressure-independent response and a depth range from 0 - 550 m, a significant advancement from previous GTD models. The GTD consists of a 4/1000" thick by 2" diameter Teflon-membrane with a water-side plenum connected to SeaBird 5T pump. Dissolved gases in the water equilibrate across the membrane with a low-dead-volume housing connected to a high-precision quart pressure sensor. Laboratory data characterizing the GTD will be presented. The e-folding (response) time ranges from 14 min at continuous (100%) pumping to 28 min at pulse (10%) pumping. We also demonstrate the pressure dependence of the partial pressures from Henry's Law in the laboratory for pure nitrogen, pure oxygen, and standard atmospheric ratios of gases. GTD's were field tested on two floats deployed in the Eastern Tropical North Pacific (ETNP) OMZ for 15 days that targeted a productive mesoscale surface eddy originating from the Mexican coast. We anticipated that high organic carbon export should stimulate denitrification within the OMZ below. The floats profiled between the surface and 400 m depth and concurrently measured T, S, PAR, O2 (SBE 43 and Optode), and nitrate (SUNA). The N2-profiles from the GTDs are validated against independently measured N2/Ar ratio data collected during the deployment.

  15. Effect of Oxygen Tension and Medium Components on Monomer Distribution of Alginate.

    PubMed

    Kıvılcımdan Moral, Çiğdem; Doğan, Özdemir; Sanin, Faika Dilek

    2015-06-01

    Alginate is a natural biopolymer composed of mannuronic and guluronic acid monomers. It is produced by algae and some species of Azotobacter and Pseudomonas. This study aims to investigate the effect of dissolved oxygen tension (DOT) and growth medium substrate and calcium concentrations on the monomeric composition of alginate produced by Azotobacter vinelandii ATCC® 9046 in a fermenter. Results showed that alginate production increased with increasing DOT from 1 to 5 %. The highest alginate production was obtained as 4.51 g/L under 20 g/L of sucrose and 50 mg/L of calcium at 5 % DOT. At these conditions, alginate was rich in mannuronic acid (up to 61 %) and it was particularly high at low calcium concentration. On the other hand, at extreme conditions such as high DOT level (10 % DOT) and low sucrose concentration (10 g/L), guluronic acid was dominant (ranging between 65 and 100 %). PMID:25877399

  16. Measuring oxygen tension modulation, induced by a new pre-radiotherapy therapeutic, in a mammary window chamber mouse model

    NASA Astrophysics Data System (ADS)

    Schafer, Rachel; Gmitro, Arthur F.

    2015-03-01

    Tumor regions under hypoxic or low oxygen conditions respond less effectively to many treatment strategies, including radiation therapy. A novel investigational therapeutic, NVX-108 (NuvOx Pharma), has been developed to increase delivery of oxygen through the use of a nano-emulsion of dodecofluoropentane. By raising pO2 levels prior to delivering radiation, treatment efficacy may be improved. To aid in evaluating the novel drug, oxygen tension was quantitatively measured, spatially and temporally, to record the effect of administrating NVX-108 in an orthotopic mammary window chamber mouse model of breast cancer. The oxygen tension was measured through the use of an oxygen-sensitive coating, comprised of phosphorescent platinum porphyrin dye embedded in a polystyrene matrix. The coating, applied to the surface of the coverslip of the window chamber through spin coating, is placed in contact with the mammary fat pad to record the oxygenation status of the surface tissue layer. Prior to implantation of the window chamber, a tumor is grown in the SCID mouse model by injection of MCF-7 cells into the mammary fat pad. Two-dimensional spatial distributions of the pO2 levels were obtained through conversion of measured maps of phosphorescent lifetime. The resulting information on the spatial and temporal variation of the induced oxygen modulation could provide valuable insight into the optimal timing between administration of NVX-108 and radiation treatment to provide the most effective treatment outcome.

  17. Herbivore tooth oxygen isotope compositions: Effects of diet and physiology

    SciTech Connect

    Kohn, M.J.; Valley, J.W.; Schoeninger, M.J.

    1996-10-01

    The applicability of rapid and precise laser probe analysis of tooth enamel for {delta}{sup 18}O has been verified, and the method has been applied to different modern herbivores in East Africa. Sampling and pretreatment procedures involve initial bleaching and grinding of enamel to <75 {mu}m, and elimination of adsorbed water and organic compounds with BrF{sub 5}. Typical analytical reproducibilities for 0.5-2 mg samples are {+-}0.08{per_thousand} ({+-} 1{sigma}). Chemical and spectroscopic characterization of pretreated but unanalyzed samples show no alteration compared to fresh enamel. Solid reaction products are nearly pure CaF{sub 2} with little evidence for residual O{sub 2}. Because laser probe fluorination extracts oxygen from all sites in the apatite structure (phosphate, structural carbonate, and hydroxyl), only unaltered tooth enamel ( >95% apatite) can be analyzed reliably. Different East African herbivores exhibit previously unsuspected compositional differences. Average enamel {delta}{sup 18}O values (V-SMOW) are approximately: 25{per_thousand} (goat). 27{per_thousand} (oryx), 28{per_thousand} (dikdik and zebra), 29{per_thousand} (topi), 30{per_thousand} (gerenuk), and 32{per_thousand} (gazelle). These compositions differ from generalized theoretical models, but are broadly consistent with expected isotope effects associated with differences in how much each animal (a) drinks, (b) eats C3 vs. C4 plants, and (c) pants vs. sweats. Consideration of diet, water turnover. and animal physiology will allow the most accurate interpretation of ancient teeth and targeting of environmentally-sensitive animals in paleoclimate studies. 66 refs., 2 figs., 2 tabs.

  18. Localized Increase of Tissue Oxygen Tension by Magnetic Targeted Drug Delivery

    PubMed Central

    Liong, Celine; Ortiz, Daniel; Ao-ieong, Eilleen; Navati, Mahantesh S.; Friedman, Joel M.; Cabrales, Pedro

    2014-01-01

    Hypoxia is the major hindrance to successful radiation therapy of tumors. Attempts to increase the oxygen (O2) tension (PO2) of tissue by delivering more O2 have been clinically disappointing, largely due to the way O2 is transported and released by the hemoglobin (Hb) within the red blood cells (RBCs). Systemic manipulation of O2 transport increases vascular resistance due to metabolic autoregulation of blood flow to prevent over oxygenation. This study investigates a new technology to increase O2 delivery to a target tissue by decreasing the Hb-O2 affinity of the blood circulating within the targeted tissue. As the Hb-O2 affinity decreases, the tissue PO2 to satisfy tissue O2 metabolic needs increases, without increasing O2 delivery or extraction. Paramagnetic nanoparticles (PMNPs) synthetized using gadolinium oxide, were coated with the cell permeable Hb allosteric effector, L35 (3,5-trichlorophenylureido-phenoxy-methylpropionic acid). L35 decreases Hb affinity for O2 and favors the release of O2. The L35-coaded PMNPs (L35-PMNPs) were intravenously infused (10 mg/kg) to hamster instrumented with the dorsal window chamber model. Magnetic field of 3 mT was applied to localize the effects of the L35-PMNPs to the window chamber. Systemic O2 transport characteristics and microvascular tissue oxygenation were measured after L35-PMNPs administration with and without magnetic field. The tissue PO2 untreated control animals was 25.2 mmHg. L35-PMNP without magnetic field decreased tissue PO2 to 23.4 mmHg, increased blood pressure and reduced blood flow, largely due to systemic modification of Hb-O2 affinity. L35-PMNP with magnetic field increased tissue PO2 to 27.9 mmHg, without systemic or microhemodynamics changes. These results indicate that localized modification of Hb-O2 affinity can increase PO2 of target tissue, without affecting systemic O2 delivery or triggering O2 autoregulation mechanisms. This technology can be used to treat local hypoxia and to increase O2 in

  19. Localized increase of tissue oxygen tension by magnetic targeted drug delivery

    NASA Astrophysics Data System (ADS)

    Liong, Celine; Ortiz, Daniel; Ao-ieong, Eilleen; Navati, Mahantesh S.; Friedman, Joel M.; Cabrales, Pedro

    2014-07-01

    Hypoxia is the major hindrance to successful radiation therapy of tumors. Attempts to increase the oxygen (O2) tension (PO2) of tissue by delivering more O2 have been clinically disappointing, largely due to the way O2 is transported and released by the hemoglobin (Hb) within the red blood cells (RBCs). Systemic manipulation of O2 transport increases vascular resistance due to metabolic autoregulation of blood flow to prevent over oxygenation. This study investigates a new technology to increase O2 delivery to a target tissue by decreasing the Hb-O2 affinity of the blood circulating within the targeted tissue. As the Hb-O2 affinity decreases, the tissue PO2 to satisfy tissue O2 metabolic needs increases without increasing O2 delivery or extraction. Paramagnetic nanoparticles (PMNPs), synthetized using gadolinium oxide, were coated with the cell permeable Hb allosteric effector L35 (3,5-trichlorophenylureido-phenoxy-methylpropionic acid). L35 decreases Hb affinity for O2 and favors the release of O2. The L35-coated PMNPs (L35-PMNPs) were intravenously infused (10 mg kg-1) to hamsters instrumented with the dorsal window chamber model. A magnetic field of 3 mT was applied to localize the effects of the L35-PMNPs to the window chamber. Systemic O2 transport characteristics and microvascular tissue oxygenation were measured after administration of L35-PMNPs with and without magnetic field. The tissue PO2 in untreated control animals was 25.2 mmHg. L35-PMNPs without magnetic field decreased tissue PO2 to 23.4 mmHg, increased blood pressure, and reduced blood flow, largely due to systemic modification of Hb-O2 affinity. L35-PMNPs with magnetic field increased tissue PO2 to 27.9 mmHg, without systemic or microhemodynamic changes. These results indicate that localized modification of Hb-O2 affinity can increase PO2 of target tissue without affecting systemic O2 delivery or triggering O2 autoregulation mechanisms. This technology can be used to treat local hypoxia and to

  20. Environmental changes in oxygen tension reveal ROS-dependent neurogenesis and regeneration in the adult newt brain.

    PubMed

    Hameed, L Shahul; Berg, Daniel A; Belnoue, Laure; Jensen, Lasse D; Cao, Yihai; Simon, András

    2015-01-01

    Organisms need to adapt to the ecological constraints in their habitat. How specific processes reflect such adaptations are difficult to model experimentally. We tested whether environmental shifts in oxygen tension lead to events in the adult newt brain that share features with processes occurring during neuronal regeneration under normoxia. By experimental simulation of varying oxygen concentrations, we show that hypoxia followed by re-oxygenation lead to neuronal death and hallmarks of an injury response, including activation of neural stem cells ultimately leading to neurogenesis. Neural stem cells accumulate reactive oxygen species (ROS) during re-oxygenation and inhibition of ROS biosynthesis counteracts their proliferation as well as neurogenesis. Importantly, regeneration of dopamine neurons under normoxia also depends on ROS-production. These data demonstrate a role for ROS-production in neurogenesis in newts and suggest that this role may have been recruited to the capacity to replace lost neurons in the brain of an adult vertebrate. PMID:26485032

  1. Microvascular and interstitial oxygen tension in the renal cortex and medulla studied in a 4-h rat model of LPS-induced endotoxemia.

    PubMed

    Dyson, Alex; Bezemer, Rick; Legrand, Matthieu; Balestra, Gianmarco; Singer, Mervyn; Ince, Can

    2011-07-01

    The pathophysiology of sepsis-induced acute kidney injury remains poorly understood. As changes in renal perfusion and oxygenation have been shown, we aimed to study the short-term effects of endotoxemia on microvascular and interstitial oxygenation in the cortex and medulla, in conjunction with global and renal hemodynamics. In a 4-h rat model of endotoxemia, we simultaneously assessed renal artery blood flow and microvascular and interstitial oxygen tensions in the renal cortex and medulla using ultrasonic flowmetry, dual wavelength phosphorimetry, and tissue oxygen tension monitoring, respectively. Whereas medullary microvascular and interstitial oxygen tensions decreased promptly in line with macrovascular blood flow, changes in cortical oxygenation were only seen later on. During the entire experimental protocol, the gradient between microvascular PO₂ and tissue oxygen tension remained unchanged in both cortex and outer medulla. At study end, urine output was significantly decreased despite a maintained oxygen consumption rate. In this 4-h rat model of endotoxemia, total renal oxygen consumption and the gradient between microvascular PO₂ and tissue oxygen tension remained unaltered, despite falls in renal perfusion and oxygen delivery and urine output. Taken in conjunction with the decrease in urine output, our results could represent either a functional renal impairment or an adaptive response. PMID:21368713

  2. Nitrite produced by Mycobacterium tuberculosis in human macrophages in physiologic oxygen impacts bacterial ATP consumption and gene expression

    PubMed Central

    Cunningham-Bussel, Amy; Zhang, Tuo; Nathan, Carl F.

    2013-01-01

    In high enough concentrations, such as produced by inducible nitric oxide synthase (iNOS), reactive nitrogen species (RNS) can kill Mycobacterium tuberculosis (Mtb). Lesional macrophages in macaques and humans with tuberculosis express iNOS, and mice need iNOS to avoid succumbing rapidly to tuberculosis. However, Mtb’s own ability to produce RNS is rarely considered, perhaps because nitrate reduction to nitrite is only prominent in axenic Mtb cultures at oxygen tensions ≤1%. Here we found that cultures of Mtb-infected human macrophages cultured at physiologic oxygen tensions produced copious nitrite. Surprisingly, the nitrite arose from the Mtb, not the macrophages. Mtb responded to nitrite by ceasing growth; elevating levels of ATP through reduced consumption; and altering the expression of 120 genes associated with adaptation to acid, hypoxia, nitric oxide, oxidative stress, and iron deprivation. The transcriptomic effect of endogenous nitrite was distinct from that of nitric oxide. Thus, whether or not Mtb is hypoxic, the host expresses iNOS, or hypoxia impairs the action of iNOS, Mtb in vivo is likely to encounter RNS by producing nitrite. Endogenous nitrite may slow Mtb’s growth and prepare it to resist host stresses while the pathogen waits for immunopathology to promote its transmission. PMID:24145454

  3. The role of reduced oxygen in the developmental physiology of growth and metamorphosis initiation in Drosophila

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rearing oxygen level is known to affect final body size in a variety of insects, but the physiological mechanisms by which oxygen affects size are incompletely understood. In Manduca and Drosophila, the larval size at which metamorphosis is initiated largely determines adult size, and metamorphosis ...

  4. Culture of bovine embryos in polyester mesh sections: the effect of pore size and oxygen tension on in vitro development.

    PubMed

    Somfai, T; Inaba, Y; Aikawa, Y; Ohtake, M; Kobayashi, S; Akai, T; Hattori, H; Konishi, K; Imai, K

    2010-12-01

    The purpose of this study was to assess the feasibility of polyester mesh culture for the in vitro production of bovine embryos, as polyester mesh is an alternative way for tracking individual embryos throughout culture using time-lapse cinematography (TLC). Bovine embryos were isolated during in vitro culture using sections of three different polyethylene terephthalate (PET) mesh products. In vitro matured and fertilized bovine oocytes were cultured in the 217 × 217, 230 × 230 or 238 × 238-μm openings of PET mesh sections or in simple micro-drops (control) for 7 days under either 20% or 5% O(2) tensions. No difference in embryo developmental rates was found between the culture groups in terms of cleavage, blastocyst formation and blastocyst expansion irrespective of O(2) tension. In contrast, under 20% O(2) tension, blastocysts that developed in PET mesh with 217 × 217-μm opening had significantly higher numbers of total and trophectoderm (TE) cells than control embryos; however, the numbers and proportions of inner cell mass (ICM) cells did not differ. Under 5% O(2) tension, no difference was found among the culture groups in the numbers of total, ICM and TE cells in embryos. All three PET mesh products investigated in this study were proven to be effective to prevent embryo movement. The results demonstrate that bovine embryos can be cultured in PET mesh sections without negative side-effects and suggest that embryo distance determined by the mesh affects embryo quality at atmospheric oxygen tension. Polyethylene terephthalate mesh with 217 × 217-μm openings was found to be the most suitable for further application in TLC. PMID:19845884

  5. The Metabolomic Profile of Spent Culture Media from Day-3 Human Embryos Cultured under Low Oxygen Tension

    PubMed Central

    de los Santos, Maria José; Gámiz, Pilar; de los Santos, José María; Romero, Josep Lluís; Prados, Nicolás; Alonso, Cristina; Remohí, José; Dominguez, Francisco

    2015-01-01

    Despite efforts made to improve the in vitro embryo culture conditions used during assisted reproduction procedures, human embryos must adapt to different in vitro oxygen concentrations and the new metabolic milieu provided by the diverse culture media used for such protocols. It has been shown that the embryo culture environment can affect not only cellular metabolism, but also gene expression in different species of mammalian embryos. Therefore we wanted to compare the metabolic footprint left by human cleavage-stage embryos under two types of oxygen atmospheric culture conditions (6% and 20% O2). The spent culture media from 39 transferred and implanted embryos from a total of 22 patients undergoing egg donation treatment was analyzed; 23 embryos came from 13 patients in the 6% oxygen concentration group, and 16 embryos from 9 patients were used in the 20% oxygen concentration group. The multivariate statistics we used in our analysis showed that human cleavage-stage embryos grown under both types of oxygen concentration left a similar metabolic fingerprint. We failed to observe any change in the net depletion or release of relevant analytes, such as glucose and especially fatty acids, by human cleavage-stage embryos under either type of culture condition. Therefore it seems that low oxygen tension during embryo culture does not alter the global metabolism of human cleavage-stage embryos. PMID:26562014

  6. An in vitro characterization of a silicone tonometer system for synchronous measurement of tissue oxygen- and carbon dioxide tension.

    PubMed

    Larsen, P N; Pedersen, I; Moesgaard, F

    1993-07-01

    A new tonometry system for continuous and synchronous measurement of tissue oxygen- and carbon dioxide tension is described and characterized in vitro. The tonometer system consists of an O2 and CO2 permeable silicone tube continuously flushed with isotonic saline by an injection pump. When the saline passes through the tonometer tube it equilibrates with O2 and CO2 outside the tube. The oxygen- and carbon dioxide tension of the flushing solution after passage of the tonometer tube are measured by a transcutaneous combined oxygen/carbon dioxide electrode (E5280 Radiometer A/S, Copenhagen, Denmark), connected to the tonometer tube via an airtight polycarbonate chamber. In order to characterize the tonometer system in vitro the tonometer tube was submerged in a test chamber containing isotonic saline, 33 degrees C to 41 degrees C, with varying partial pressures of O2 and CO2. For various lengths of the tonometer and flushing rates through the tonometer the partial pressures of oxygen and carbon dioxide in the flushing solution (pO2eq and pCO2eq), after passage through the tonometer were recorded and compared to the known partial pressures of oxygen and carbon dioxide in the test chamber solution (pO2 test and pCO2test). PO2eq and pCO2eq approached pO2test and pCO2test, when the length of the tonometer was increased, and the flushing rate through the tonometer was decreased. The relative differences (D) between pO2eq and pCO2eq at the one hand and pO2test and pCO2test at the other hand were calculated, and equilibration curves were constructed.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8378734

  7. Butler-Sugimoto monomolecular bilayer interface model: the effect of oxygen on the surface tension of a liquid metal and its wetting of a ceramic.

    PubMed

    Yen, Pei-Shan; Datta, Ravindra

    2014-07-15

    The influence of oxygen on liquid-gas surface tension of molten metals has been well-investigated experimentally and modeled theoretically via the Szyszkowski equation, derivable from the Butler molecular monolayer interface model. However, there is no corresponding model describing the experimentally observed profound effect of oxygen partial pressure on solid-liquid surface tension as well as on contact angle of molten metals on ceramic substrates. Here, we utilize the Butler-Sugimoto thermodynamic approach based on a monomolecular bilayer interface model to investigate the effect of oxygen partial pressure on liquid-gas as well as solid-liquid surface tension of molten Cu/Al2O3 and molten Ag/Al2O3 systems. It is shown that both liquid-gas and solid-liquid surface tension are a strong function of oxygen activity in the melt, which, in turn, depends on gas-phase oxygen partial pressure, in conformity with experiments. The change in solid-liquid surface tension and wetting is also greatly affected by the change in liquid-gas surface tension. This improved understanding is of practical significance in many applications. PMID:24863799

  8. Environmental changes in oxygen tension reveal ROS-dependent neurogenesis and regeneration in the adult newt brain

    PubMed Central

    Hameed, L Shahul; Berg, Daniel A; Belnoue, Laure; Jensen, Lasse D; Cao, Yihai; Simon, András

    2015-01-01

    Organisms need to adapt to the ecological constraints in their habitat. How specific processes reflect such adaptations are difficult to model experimentally. We tested whether environmental shifts in oxygen tension lead to events in the adult newt brain that share features with processes occurring during neuronal regeneration under normoxia. By experimental simulation of varying oxygen concentrations, we show that hypoxia followed by re-oxygenation lead to neuronal death and hallmarks of an injury response, including activation of neural stem cells ultimately leading to neurogenesis. Neural stem cells accumulate reactive oxygen species (ROS) during re-oxygenation and inhibition of ROS biosynthesis counteracts their proliferation as well as neurogenesis. Importantly, regeneration of dopamine neurons under normoxia also depends on ROS-production. These data demonstrate a role for ROS-production in neurogenesis in newts and suggest that this role may have been recruited to the capacity to replace lost neurons in the brain of an adult vertebrate. DOI: http://dx.doi.org/10.7554/eLife.08422.001 PMID:26485032

  9. A physiological model for extracorporeal oxygenation controller design.

    PubMed

    Walter, Marian; Weyer, Soren; Stollenwerk, Andre; Kopp, Rudger; Arens, Jutta; Leonhardt, Steffen

    2010-01-01

    Long term extracorporeal membrane oxygenation can be used in cases of severe lung failure to maintain sufficient gas exchange without the need to apply higher ventilation pressures which damage the lung additionally. The use of cardiopulmonary bypass devices is well established inside the operating room. The usage of such devices as long-term support in the intensive care unit is still experimental and limited to few cases. This is because neither machine architecture nor staff situation provides for the long term application scenario. In the joint research Project "smart ECLA" we target an advanced ECMO device featuring an automation system capable of maintaining gas concentrations automatically. One key requirement for systematic controller design is the availability of a process model, which will be presented in this article. PMID:21096765

  10. Microvascular oxygen tension and flow measurements in rodent cerebral cortex during baseline conditions and functional activation

    PubMed Central

    Yaseen, Mohammad A; Srinivasan, Vivek J; Sakadžić, Sava; Radhakrishnan, Harsha; Gorczynska, Iwona; Wu, Weicheng; Fujimoto, James G; Boas, David A

    2011-01-01

    Measuring cerebral oxygen delivery and metabolism microscopically is important for interpreting macroscopic functional magnetic resonance imaging (fMRI) data and identifying pathological changes associated with stroke, Alzheimer's disease, and brain injury. Here, we present simultaneous, microscopic measurements of cerebral blood flow (CBF) and oxygen partial pressure (pO2) in cortical microvessels of anesthetized rats under baseline conditions and during somatosensory stimulation. Using a custom-built imaging system, we measured CBF with Fourier-domain optical coherence tomography (OCT), and vascular pO2 with confocal phosphorescence lifetime microscopy. Cerebral blood flow and pO2 measurements displayed heterogeneity over distances irresolvable with fMRI and positron emission tomography. Baseline measurements indicate O2 extraction from pial arterioles and homogeneity of ascending venule pO2 despite large variation in microvessel flows. Oxygen extraction is linearly related to flow in ascending venules, suggesting that flow in ascending venules closely matches oxygen demand of the drained territory. Oxygen partial pressure and relative CBF transients during somatosensory stimulation further indicate arteriolar O2 extraction and suggest that arterioles contribute to the fMRI blood oxygen level dependent response. Understanding O2 supply on a microscopic level will yield better insight into brain function and the underlying mechanisms of various neuropathologies. PMID:21179069

  11. Diffusion capacity and CT measures of emphysema and airway wall thickness – relation to arterial oxygen tension in COPD patients

    PubMed Central

    Saure, Eirunn Waatevik; Bakke, Per Sigvald; Eagan, Tomas Mikal Lind; Aanerud, Marianne; Jensen, Robert Leroy; Grydeland, Thomas Blix; Johannessen, Ane; Nilsen, Roy Miodini; Thorsen, Einar; Hardie, Jon Andrew

    2016-01-01

    Background Decreased diffusing capacity of the lung for carbon monoxide (DLCO) is associated with emphysema. DLCO is also related to decreased arterial oxygen tension (PaO2), but there are limited data on associations between PaO2 and computed tomography (CT) derived measures of emphysema and airway wall thickness. Objective To examine whether CT measures of emphysema and airway wall thickness are associated with level of arterial oxygen tension beyond that provided by measurements of diffusion capacity and spirometry. Methods The study sample consisted of 271 smoking or ex-smoking COPD patients from the Bergen COPD Cohort Study examined in 2007–2008. Emphysema was assessed as percent of low-attenuation areas<−950 Hounsfield units (%LAA), and airway wall thickness as standardised measure at an internal perimeter of 10 mm (AWT-Pi10). Multiple linear regression models were fitted with PaO2 as the outcome variable, and %LAA, AWT-Pi10, DLCO and carbon monoxide transfer coefficient (KCO) as main explanatory variables. The models were adjusted for sex, age, smoking status, and haemoglobin concentration, as well as forced expiratory volume in one second (FEV1). Results Sixty two per cent of the subjects were men, mean (SD) age was 64 (7) years, mean (SD) FEV1 in percent predicted was 50 (15)%, and mean PaO2 (SD) was 9.3 (1.1) kPa. The adjusted regression coefficient (CI) for PaO2 was –0.32 (−0.04–(−0.019)) per 10% increase in %LAA (p<0.01). When diffusion capacity and FEV1 were added to the model, respectively, the association lost its statistical significance. No relationship between airway wall thickness and PaO2 was found. Conclusion CT assessment of airway wall thickness is not associated with arterial oxygen tension in COPD patients. Emphysema score measured by chest CT, is related to decreased PaO2, but cannot replace measurements of diffusion capacity in the clinical evaluation of hypoxaemia. PMID:27178139

  12. Community-level physiological profiling performed with an oxygen-sensitive fluorophore in a microtiter plate

    NASA Technical Reports Server (NTRS)

    Garland, Jay L.; Roberts, Michael S.; Levine, Lanfang H.; Mills, Aaron L.

    2003-01-01

    Community-level physiological profiling based upon fluorometric detection of oxygen consumption was performed on hydroponic rhizosphere and salt marsh litter samples by using substrate levels as low as 50 ppm with incubation times between 5 and 24 h. The rate and extent of response were increased in samples acclimated to specific substrates and were reduced by limiting nitrogen availability in the wells.

  13. Diabetes-Induced Decrease in Renal Oxygen Tension: Effects of an Altered Metabolism

    NASA Astrophysics Data System (ADS)

    Palm, Fredrik; Carlsson, Per-Ola; Fasching, Angelica; Hansell, Peter; Liss, Per

    During conditions with experimental diabetes mellitus, it is evident that several alterations in renal oxygen metabolism occur, including increased mitochondrial respiration and increased lactate accumulation in the renal tissue. Consequently, these alterations will contribute to decrease the interstitial pO2, preferentially in the renal medulla of animals with sustained long-term hyperglycemia.

  14. POLYCYCLIC AROMATIC HYDROCARBON BIODEGRADATION AS A FUNCTION OF OXYGEN TENSION IN CONTAMINATED SOIL

    EPA Science Inventory

    Laboratory tests were conducted to determine the effect of soil gas oxygen concentration on the degradation and mineralization of spiked 14C-pyrene and nonspiked 16 priority pollutant polycyclic aromatic hydrocarbons (PAH) present in the soil. The soil used for the evaluation was...

  15. [Changes in the oxygen tension level in different brain structures of rats in the waking-sleep cycle].

    PubMed

    Sarkisova, K Iu; Kolomeĭtseva, I A

    1990-01-01

    Changes of oxygen tension level (pO2) in the visual cortex, dorsal hippocampus, lateral hypothalamus and central grey substance were studied during wake-sleep cycle in rats. The dependence was established of pO2 level changes on the character of behavioural reactions and on the accompanying hippocampal EEG activity: during orienting-investigatory and active defensive behaviour and also during paradoxical sleep, accompanied by hippocampal theta rhythm, pO2 level increased; during passive-defensive behaviour "freezing" reaction accompanied by desynchronization of the hippocampal rhythmic, the level of pO2 decreased. The obtained data confirm Routtenberg hypothesis about two relatively independent systems of ascending activation with different types of hippocampal EEG activity and supplement it with a thesis that the activity of these systems is accompanied by different shifts of brain oxidative metabolism. PMID:2169159

  16. [The importance of transcutaneous oxygen tension monitoring in diabetic patient with complications].

    PubMed

    Baláž, David; Komorníková, Andrea; Sabaka, Peter; Gašpar, Ľudovít; Dukát, Andrej

    2015-02-01

    Monitoring of transcutaneous perfusion pressure of tissue oxygen (tcpO₂) is a simple, non-invasive method performed in diagnostic process of chronic diabetic complications. Primary, tcpO₂is used as an indicator of microcirculatory function. Properly placed and fixed Clark electrode is able to detect with high accuracy partial oxygen pressure on the skin surface by polarographic system of dissolved oxygen from capillary bed through tissues to upper layers of the skin. The microcirculation function is influenced by macrocirculation, thus, tcpO₂is a suitable parameter in diagnosis of peripheral arterial obliterative disease or other vascular pathologies. Combination of tcpO₂monitoring and skin perfusion pressure by laser Doppler technique gives us information not only about nutritive capillary flow, but also about vessels which precede capillary bed. The article discusses current guidelines for measurement of tcpO₂and evaluation of the results. Also reviews the results of recent studies which are interested in the use of tcpO₂in diabetic patients. PMID:25813252

  17. Development of sensors for monitoring oxygen and free radicals in plant physiology

    NASA Astrophysics Data System (ADS)

    Chaturvedi, Prachee

    Oxygen plays a critical role in the physiology of photosynthetic organisms, including bioenergetics, metabolism, development, and stress response. Oxygen levels affect photosynthesis, respiration, and alternative oxidase pathways. Likewise, the metabolic rate of spatially distinct plant cells (and therefore oxygen flux) is known to be affected by biotic stress (e.g., herbivory) and environmental stress (e.g., salt/nutrient stress). During aerobic metabolism, cells produce reactive oxygen species (ROS) as a by product. Plants also produce ROS during adaptation to stress (e.g., abscisic acid (ABA) mediated stress responses). If stress conditions are prolonged, ROS levels surpass the capacity of detoxifying mechanisms within the cell, resulting in oxidative damage. While stress response pathways such as ABA-mediated mechanisms have been well characterized (e.g., water stress, inhibited shoot growth, synthesis of storage proteins in seeds), the connection between ROS production, oxygen metabolism and stress response remains unknown. In part, this is because details of oxygen transport at the interface of cell(s) and the surrounding microenvironment remains nebulous. The overall goal of this research was to develop oxygen and Free radical sensors for studying stress signaling in plants. Recent developments in nanomaterials and data acquisition systems were integrated to develop real-time, non-invasive oxygen and Free radical sensors. The availability of these sensors for plant physiologists is an exciting opportunity to probe the functional realm of cells and tissues in ways that were not previously possible.

  18. Physiological characterization of xylose metabolism in Aspergillus niger under oxygen-limited conditions.

    PubMed

    Meijer, S; Panagiotou, G; Olsson, L; Nielsen, J

    2007-10-01

    The physiology of Aspergillus niger was studied under different aeration conditions. Five different aeration rates were investigated in batch cultivations of A. niger grown on xylose. Biomass, intra- and extra-cellular metabolites profiles were determined and ten different enzyme activities in the central carbon metabolism were assessed. The focus was on organic acid production with a special interest in succinate production. The fermentations revealed that oxygen limitation significantly changes the physiology of the micro-organism. Changes in extra cellular metabolite profiles were observed, that is, there was a drastic increase in polyol production (erythritol, xylitol, glycerol, arabitol, and mannitol) and to a lesser extent in the production of reduced acids (malate and succinate). The intracellular metabolite profiles indicated changes in fluxes, since several primary metabolites, like the intermediates of the TCA cycle accumulated during oxygen limitation (on average three fold increase). Also the enzyme activities showed changes between the exponential growth phase and the oxygen limitation phase. In general, the oxygen availability has a significant impact on the physiology of this fungus causing dramatic alterations in the central carbon metabolism that should be taken into account in the design of A. niger as a succinate cell factory. PMID:17335061

  19. Conjugatable water-soluble Pt(II) and Pd(II) porphyrin complexes: novel nano- and molecular probes for optical oxygen tension measurement in tissue engineering.

    PubMed

    Giuntini, F; Chauhan, V M; Aylott, J W; Rosser, G A; Athanasiadis, A; Beeby, A; MacRobert, A J; Brown, R A; Boyle, R W

    2014-07-01

    Measurement of oxygen tension in compressed collagen sheets was performed using matrix-embedded optical oxygen sensors based on platinum(II) and palladium(II) porphyrins supported on polyacrylamide nanoparticles. Bespoke, fully water-soluble, mono-functionalised Pt(II) and Pd(II) porphyrin complexes designed for conjugation under mild conditions were obtained using microwave-assisted metallation. The new sensors display a linear response (1/τ vs. O2) to varying oxygen tension over a biologically relevant range (7.0 × 10(-4) to 2.7 × 10(-1) mM) in aqueous solutions; a behaviour that is maintained following conjugation to polyacrylamide nanoparticles, and following embedding of the nanosensors in compressed collagen sheets, paving the way to innovative approaches for real-time resolution of oxygen gradients throughout 3D matrices useful for tissue regeneration. PMID:24818569

  20. Low oxygen tension induces Krüppel-Like Factor 6 expression in trophoblast cells.

    PubMed

    Racca, A C; Ridano, M E; Bandeira, C L; Bevilacqua, E; Avvad Portari, E; Genti-Raimondi, S; Graham, C H; Panzetta-Dutari, G M

    2016-09-01

    The transcription factor Krüppel-Like Factor 6 (KLF6) has important roles in cell differentiation, angiogenesis, apoptosis, and proliferation. Furthermore, there is evidence that KLF6 is required for proper placental development. While oxygen is a critical mediator of trophoblast differentiation and function, the involvement of oxygen in the regulation of KLF6 expression remains unexplored. In the present study we examined the expression of KLF6 in placental tissue from uncomplicated and preeclamptic pregnancies, the latter often characterized by an inadequately perfused placenta. We also determined the effect of hypoxia and the involvement of Hypoxia-Inducible Factor 1α (HIF-1α) on the expression of KLF6 in cultured trophoblast cells and placental tissues. Results revealed that villous, interstitial and endovascular extravillous cytotrophoblasts from placentas from normal and preeclamptic pregnancies express KLF6. In addition, KLF6 immunoreactivity was higher in the placental bed of preeclamptic pregnancies than in those of uncomplicated pregnancies. We demonstrated that hypoxia induced an early and transient increase in KLF6 protein levels in HTR8/SVneo extravillous cytotrophoblast cells and in placental explants. Reoxygenation returned KLF6 protein to basal levels. Moreover, hypoxia-induced up-regulation of KLF6 expression was dependent on HIF-1α as revealed by siRNA knockdown in HTR8/SVneo cells. These results indicate that KLF6 may mediate some of the effects of hypoxia in placental development. The regulation of KLF6 protein levels by oxygen has significant implications for understanding its putative role in diseases affected by tissue hypoxia. PMID:27577710

  1. Synoviocyte Derived-Extracellular Matrix Enhances Human Articular Chondrocyte Proliferation and Maintains Re-Differentiation Capacity at Both Low and Atmospheric Oxygen Tensions

    PubMed Central

    Kean, Thomas J.; Dennis, James E.

    2015-01-01

    Background Current tissue engineering methods are insufficient for total joint resurfacing, and chondrocytes undergo de-differentiation when expanded on tissue culture plastic. De-differentiated chondrocytes show poor re-differentiation in culture, giving reduced glycosaminoglycan (GAG) and collagen matrix accumulation. To address this, porcine synoviocyte-derived extracellular matrix and low (5%) oxygen tension were assessed for their ability to enhance human articular chondrocyte expansion and maintain re-differentiation potential. Methods Porcine synoviocyte matrices were devitalized using 3 non-detergent methods. These devitalized synoviocyte matrices were compared against tissue culture plastic for their ability to support human chondrocyte expansion. Expansion was further compared at both low (5%), and atmospheric (20%) oxygen tension on all surfaces. Expanded cells then underwent chondrogenic re-differentiation in aggregate culture at both low and atmospheric oxygen tension. Aggregates were assessed for their GAG and collagen content both biochemically and histologically. Results Human chondrocytes expanded twice as fast on devitalized synoviocyte matrix vs. tissue culture plastic, and cells retained their re-differentiation capacity for twice the number of population doublings. There was no significant difference in growth rate between low and atmospheric oxygen tension. There was significantly less collagen type I, collagen type II, aggrecan and more MMP13 expression in cells expanded on synoviocyte matrix vs. tissue culture plastic. There were also significant effects due to oxygen tension on gene expression, wherein there was greater collagen type I, collagen type II, SOX9 and less MMP13 expression on tissue culture plastic compared to synoviocyte matrix. There was a significant increase in GAG, but not collagen, accumulation in chondrocyte aggregates re-differentiated at low oxygen tension over that achieved in atmospheric oxygen conditions. Conclusions

  2. Exercise capacity in the Bidirectional Glenn Physiology: coupling cardiac index, ventricular function and oxygen extraction ratio

    PubMed Central

    Vallecilla, Carolina; Khiabani, Reza H.; Trusty, Phillip; Sandoval, Néstor; Fogel, Mark; Briceño, Juan Carlos; Yoganathan, Ajit P.

    2015-01-01

    In Bi-directional Glenn (BDG) physiology, the superior systemic circulation and pulmonary circulation are in series. Consequently, only blood from the superior vena cava is oxygenated in the lungs. Oxygenated blood then travels to the ventricle where it is mixed with blood returning from the lower body. Therefore, incremental changes in oxygen extraction ratio (OER) could compromise exercise tolerance. In this study, the effect of exercise on the hemodynamic and ventricular performance of BDG physiology was investigated using clinical patient data as inputs for a lumped parameter model coupled with oxygenation equations. Changes in cardiac index, Qp/Qs, systemic pressure, oxygen extraction ratio and ventricular/vascular coupling ratio were calculated for three different exercise levels. The patient cohort (n=29) was sub-grouped by age and pulmonary vascular resistance (PVR) at rest. It was observed that the changes in exercise tolerance are significant in both comparisons, but most significant when sub-grouped by PVR at rest. Results showed that patients over 2 years old with high PVR are above or close to the upper tolerable limit of OER (0.32) at baseline. Patients with high PVR at rest had very poor exercise tolerance while patients with low PVR at rest could tolerate low exercise conditions. In general, ventricular function of SV patients is too poor to increase CI and fulfill exercise requirements. The presented mathematical model provides a framework to estimate the hemodynamic performance of BDG patients at different exercise levels according to patient specific data. PMID:25913242

  3. Matrix forming characteristics of inner and outer human meniscus cells on 3D collagen scaffolds under normal and low oxygen tensions

    PubMed Central

    2013-01-01

    Background Limited intrinsic healing potential of the meniscus and a strong correlation between meniscal injury and osteoarthritis have prompted investigation of surgical repair options, including the implantation of functional bioengineered constructs. Cell-based constructs appear promising, however the generation of meniscal constructs is complicated by the presence of diverse cell populations within this heterogeneous tissue and gaps in the information concerning their response to manipulation of oxygen tension during cell culture. Methods Four human lateral menisci were harvested from patients undergoing total knee replacement. Inner and outer meniscal fibrochondrocytes (MFCs) were expanded to passage 3 in growth medium supplemented with basic fibroblast growth factor (FGF-2), then embedded in porous collagen type I scaffolds and chondrogenically stimulated with transforming growth factor β3 (TGF-β3) under 21% (normal or normoxic) or 3% (hypoxic) oxygen tension for 21 days. Following scaffold culture, constructs were analyzed biochemically for glycosaminoglycan production, histologically for deposition of extracellular matrix (ECM), as well as at the molecular level for expression of characteristic mRNA transcripts. Results Constructs cultured under normal oxygen tension expressed higher levels of collagen type II (p = 0.05), aggrecan (p < 0.05) and cartilage oligomeric matrix protein, (COMP) (p < 0.05) compared to hypoxic expanded and cultured constructs. Accumulation of ECM rich in collagen type II and sulfated proteoglycan was evident in normoxic cultured scaffolds compared to those under low oxygen tension. There was no significant difference in expression of these genes between scaffolds seeded with MFCs isolated from inner or outer regions of the tissue following 21 days chondrogenic stimulation (p > 0.05). Conclusions Cells isolated from inner and outer regions of the human meniscus demonstrated equivalent differentiation potential

  4. Reactive oxygen species: physiological roles in the regulation of vascular cells.

    PubMed

    Vara, D; Pula, G

    2014-01-01

    Reactive oxygen species (ROS) are now appreciated to play several important roles in a number of biological processes and regulate cell physiology and function. ROS are a heterogeneous chemical class that includes radicals, such as superoxide ion (O2(•-)), hydroxyl radical (OH(•)) and nitric oxide (NO(•)), and non-radicals, such as hydrogen peroxide (H2O2), singlet oxygen ((1)O2), hypochlorous acid (HOCl), and peroxynitrite (NO3 (-)). In the cardiovascular system, besides playing a critical role in the development and progression of vasculopathies and other important pathologies such as congestive heart failure, atherosclerosis and thrombosis, ROS also regulate physiological processes. Evidence from a wealth of cardiovascular research studies suggests that ROS act as second messengers and play an essential role in vascular homeostasis by influencing discrete signal transduction pathways in various systems and cell types. They are produced throughout the vascular system, regulate differentiation and contractility of vascular smooth muscle cells, control vascular endothelial cell proliferation and migration, mediate platelet activation and haemostasis, and significantly contribute to the immune response. Our understanding of ROS chemistry and cell biology has evolved to the point of realizing that different ROS have distinct and important roles in cardiovascular physiology. This review will outline sources, functions and molecular mechanisms of action of different ROS in the cardiovascular system and will describe their emerging role in healthy cardiovascular physiology and homeostasis. PMID:24894168

  5. Preflight studies on tolerance of pocket mice to oxygen and heat. I - Physiological studies

    NASA Technical Reports Server (NTRS)

    Leon, H. A.; Suri, K.; Mctigue, M.; Smith, J.; Cooper, W.; Miquel, J.; Ashley, W. W.; Behnke, A. R., Jr.; Saunders, J. F.

    1975-01-01

    Tests were carried out on pocket mice to ascertain their tolerance to elevated oxygen pressures alone and to a combination of hyperoxia and heat in excess of that expected during the flight of the mice on Apollo XVII. The mice withstood oxygen partial pressures up to 12 psi at normal room temperature (24 C, 75 F) over a period of 7 days. A few mice previously exposed to increased PO2 died in the course of exposure to an oxygen pressure of 10 psi or 12 psi (517 mm or 620 mm Hg) for 13 d in ambient heat of 32 C (90 F). Supplemental vitamin E and physiological saline loading given prior to exposure had no apparent protective effect. The overall conclusion was that the pocket mice which were to go on Apollo XVII could readily survive the ambient atmosphere to which they would be exposed.

  6. Sanguinate's effect on pial arterioles in healthy rats and cerebral oxygen tension after controlled cortical impact.

    PubMed

    Mullah, Saad H; Abutarboush, Rania; Moon-Massat, Paula F; Saha, Biswajit K; Haque, Ashraful; Walker, Peter B; Auker, Charles R; Arnaud, Francoise G; McCarron, Richard M; Scultetus, Anke H

    2016-09-01

    Sanguinate, a polyethylene glycol-conjugated carboxyhemoglobin, was investigated for cerebral vasoactivity in healthy male Sprague-Dawley rats (Study 1) and for its ability to increase brain tissue oxygen pressure (PbtO2) after controlled cortical impact (CCI) - traumatic brain injury (TBI) (Study 2). In both studies ketamine-acepromazine anesthetized rats were ventilated with 40% O2. In Study 1, a cranial window was used to measure the diameters of medium - (50-100μm) and small-sized (<50μm) pial arterioles before and after four serial infusions of Sanguinate (8mL/kg/h, cumulative 16mL/kg IV), volume-matched Hextend, or normal saline. In Study 2, PbtO2 was measured using a phosphorescence quenching method before TBI, 15min after TBI (T15) and then every 10min thereafter for 155min. At T15, rats received either 8mL/kg IV Sanguinate (40mL/kg/h) or no treatment (saline, 4mL/kg/h). Results showed: 1) in healthy rats, percentage changes in pial arteriole diameter were the same among the groups, 2) in TBI rats, PbtO2 decreased from 36.5±3.9mmHg to 19.8±3.0mmHg at T15 in both groups after TBI and did not recover in either group for the rest of the study, and 3) MAP increased 16±4mmHg and 36±5mmHg after Sanguinate in healthy and TBI rats, respectively, while MAP was unchanged in control groups. In conclusion, Sanguinate did not cause vasoconstriction in the cerebral pial arterioles of healthy rats but it also did not acutely increase PbtO2 when administered after TBI. Sanguinate was associated with an increase in MAP in both studies. PMID:27287870

  7. A Variability Study of Regional Alveolar Oxygen Tension Measurement in Humans Using Hyperpolarized 3He MRI

    PubMed Central

    Hamedani, Hooman; Kadlecek, Stephen J.; Ishii, Masaru; Emami, Kiarash; Kuzma, Nicholas N.; Xin, Yi; Rossman, Milton; Rizi, Rahim R.

    2013-01-01

    To presents the first systematic reproducibility measurement of alveolar partial pressure of oxygen (pAO2) in the human lung, regional variability is defined in terms of an intraclass correlation coefficient (ICC) between co-localized, same-subject measurements separated by one-week or couple of minutes (short-term). In addition, the repeatability of the average lung pAO2 is compared to that of the standard pulmonary function tests (PFT). PFT and pAO2 imaging were performed on eight subjects: 4 nonsmokers (1 man, 3 women; 56 ± 1.7 years), 4 smokers (1 woman, 3 men; 52 ± 7.5 years) in three visits during two weeks. Regional variability was assessed based on a mixed-effects model and an ICC. The coefficient of variation (CV) of mean and standard deviation of pAO2 in three days was also compared to CV of PFT results. Short-term regional reproducibility based on ICC was 0.71 and 0.63 for nonsmokers and smokers; respectively. The one-week variability was lower (ICC=0.59 and 0.47; respectively). The CV of whole-lung average pAO2 was significantly higher than that of FVC(forced vital capacity; P=0.02) but not from DLCO (diffusing capacity). The smoker group shows more variability in pAO2 measurements both between experiments and in each individual pAO2 maps. pAO2 had a similar repeatability to DLCO. PMID:23382040

  8. The acute effects of nicotine, tobacco smoke and carbon monoxide on myocardial oxygen tension in the anaesthetized cat

    PubMed Central

    Rink, Richard D.

    1978-01-01

    1 The acute effects of nicotine, tobacco smoke, and carbon monoxide on myocardial oxygen tension (MPo2) were estimated amperometrically in 33 anaesthetized open-chest cats with a glass-insulated 25 μm platinum cathode within a 22-gauge needle implanted in the left ventricular wall. 2 MPo2 was 1.6-60 mmHg (mean 23.5 mmHg) when arterial Po2 was >80 mmHg. Sequential intravenous infusions of nicotine (2-3 μg/kg every 45 s) or intracheal puffs (3-5 ml) of tobacco smoke commonly produced transitory increases (25-35 mmHg) of arterial pressure and 4-6 mmHg increments of MPo2. Intratracheal puffs (5 ml) of 5% carbon monoxide sufficient to increase carboxyhaemoglobin from 0.8 to 1.5% to 4-7% had no effect on arterial Po2 or blood pressure but typically decreased MPo2 by approximately 1-4 mmHg. Augmentation of MPo2 often succeeded carbon monoxide administration. 3 Arterial hypoxia (arterial Po2 < 60 mmHg) reduced mean MPo2 to 14.4 mmHg but anoxic levels were not observed. Pressor responses to nicotine and tobacco smoke were accompanied by small increases (usually 1-3 mmHg) of MPo2. Puffs of 5% carbon monoxide had less effect than during normoxia. Locations of low MPo2 (<10 mmHg) were unaffected as carboxyhaemoglobin was raised to 7-11% during hypoxaemia. 4 It is concluded that nicotine and tobacco smoke cause augmentation of myocardial oxygen supply, even during moderate hypoxaemia. By contrast, smoking dosages of carbon monoxide have the potential of producing a small reduction of MPo2 during normoxia, but the effect is negligible during moderate hypoxaemia. PMID:656704

  9. The Oxygen Dissociation Curve of Hemoglobin: Bridging the Gap between Biochemistry and Physiology

    NASA Astrophysics Data System (ADS)

    Gómez-Cambronero, Julian

    2001-06-01

    Cooperativity is a very difficult concept for biochemistry students in the health sciences. An analogy between breaking salt bonds and tearing apart a block of four stamps has been proposed for hemoglobin (Hb). However, since tearing is equated to binding of molecules, two intrinsically contradictory terms, students still have difficulty. I apply the pictorial analogy to the releasing of oxygen instead of the binding, thus bridging biochemistry (cooperativity) with physiology (oxygen dissociation). I embark on an imaginary journey from the lungs (saturation at 100 mmHg) to the oxygen-starved tissues. The stamps represent fully loaded Hb. By making two cuts the first "oxygen" is released. For the second, only one cut is needed. With one final cut, the last two stamps are separated. This means that less energy is needed to unload oxygen: just small drops in partial pressure do the trick in the right place (tissues) but not in the wrong one (lungs). In doing this, I use the three main models of learning: association, discovery and mentoring. Additionally, by guiding students to discover the truth by themselves, I can use hemoglobin as a wonderful excuse to apply the "Socratic method" in the classroom.

  10. Comparative In Vivo Effects of Hemoglobin-Based Oxygen Carriers (HBOC) with Varying Prooxidant and Physiological Reactivity

    PubMed Central

    Roman, Ioana; Sevastre, Bogdan; Hathazi, Denisa; Scurtu, Florina; Damian, Grigore; Silaghi-Dumitrescu, Radu

    2016-01-01

    A series of hemoglobin-based oxygen carrier candidates (HBOC), previously noted for their differences in prooxidative and physiological reactivity, were compared in terms of the negative effects displayed upon injection in Wistar rats. At the concentrations tested, antioxidant strategies based on albumin as well as based on rubrerythrin appear to offer observable physiological advantages. PMID:27097326

  11. Comparative In Vivo Effects of Hemoglobin-Based Oxygen Carriers (HBOC) with Varying Prooxidant and Physiological Reactivity.

    PubMed

    Toma, Vlad Al; Farcaș, Anca D; Roman, Ioana; Sevastre, Bogdan; Hathazi, Denisa; Scurtu, Florina; Damian, Grigore; Silaghi-Dumitrescu, Radu

    2016-01-01

    A series of hemoglobin-based oxygen carrier candidates (HBOC), previously noted for their differences in prooxidative and physiological reactivity, were compared in terms of the negative effects displayed upon injection in Wistar rats. At the concentrations tested, antioxidant strategies based on albumin as well as based on rubrerythrin appear to offer observable physiological advantages. PMID:27097326

  12. Preservation of high glycolytic phenotype by establishing new acute lymphoblastic leukemia cell lines at physiologic oxygen concentration

    SciTech Connect

    Sheard, Michael A.; Ghent, Matthew V.; Cabral, Daniel J.; Lee, Joanne C.; Khankaldyyan, Vazgen; Ji, Lingyun; Wu, Samuel Q.; Kang, Min H.; and others

    2015-05-15

    Cancer cells typically exhibit increased glycolysis and decreased mitochondrial oxidative phosphorylation, and they continue to exhibit some elevation in glycolysis even under aerobic conditions. However, it is unclear whether cancer cell lines employ a high level of glycolysis comparable to that of the original cancers from which they were derived, even if their culture conditions are changed to physiologically relevant oxygen concentrations. From three childhood acute lymphoblastic leukemia (ALL) patients we established three new pairs of cell lines in both atmospheric (20%) and physiologic (bone marrow level, 5%) oxygen concentrations. Cell lines established in 20% oxygen exhibited lower proliferation, survival, expression of glycolysis genes, glucose consumption, and lactate production. Interestingly, the effects of oxygen concentration used during cell line initiation were only partially reversible when established cell cultures were switched from one oxygen concentration to another for eight weeks. These observations indicate that ALL cell lines established at atmospheric oxygen concentration can exhibit relatively low levels of glycolysis and these levels are semi-permanent, suggesting that physiologic oxygen concentrations may be needed from the time of cell line initiation to preserve the high level of glycolysis commonly exhibited by leukemias in vivo. - Highlights: • Establishing new ALL cell lines in 5% oxygen resulted in higher glycolytic expression and function. • Establishing new ALL cell lines in 5% oxygen resulted in higher proliferation and lower cell death. • The divergent metabolic phenotypes selected in 5% and 20% oxygen are semi-permanent.

  13. Assessing the effects of a short-term green tea intervention in skin microvascular function and oxygen tension in older and younger adults.

    PubMed

    Wasilewski, Rebecca; Ubara, Emmanuel O; Klonizakis, Markos

    2016-09-01

    Green tea consumption has been associated with a reduction in cardiovascular disease risk factors. However, there is little evidence examining its potential differing effect between younger and older populations, whilst little is known on its effect on the circulatory system when oxygen demand is higher. Therefore the aim of this study was to evaluate the short-term effects of green tea consumption on microvascular functioning in both an older and younger population. Fifteen young [24 (4.0)] and fifteen older [61 (4.0)] participants, consumed two cups of green tea daily for 14days. We used Laser Doppler Flowmetry (LDF) to assess cutaneous microvascular function and Transcutaneous Oxygen monitoring (TcPO2) to assess skin oxygen tension. Systolic and diastolic blood pressure were also assessed on both visits. We observed significant improvements in axon-mediated microvascular vasodilation for the younger group [1.6 (0.59) vs 2.05 (0.72), p<0.05] and the older group [1.25 (0.58) vs 1.65 (0.5) p<0.05]. Improvements in skin oxygen tension were also noted for both groups in both noted TcPO2 measures (i.e. 1.25 (0.58) vs 1.65 (0.5) (p<0.05), for ΔTcPO2max for the older group, between visits) respectively. Improvements were also observed for systolic blood pressure in both the younger [120 (10) vs 112 (10), p<0.05] and older group [129 (12) v 124 (11), p<0.001]. In conclusion, we observed statistically-significant improvements in microvascular function and skin oxygen tension. Our results suggest that green tea may prove beneficial as a dietary element in lifestyle interventions aiming to lower cardiovascular disease risk, in both older and younger populations. PMID:27165772

  14. Physiological responses of the ghost shrimp Neotrypaea uncinata (Milne Edwards 1837) (Decapoda: Thalassinidea) to oxygen availability and recovery after severe environmental hypoxia.

    PubMed

    Leiva, Félix P; Urbina, Mauricio A; Cumillaf, Juan Pablo; Gebauer, Paulina; Paschke, Kurt

    2015-11-01

    Hypoxia is a common and widespread phenomenon in aquatic ecosystems, imposing a significant challenge for the animals that inhabit such waters. In different habitats, however, the characteristics of these hypoxic events may differ, therefore imposing different challenges. We investigated the tolerance of adult ghost shrimp Neotrypaea uncinata (an intertidal mudflat dweller) to different partial pressures of oxygen (pO2), severe hypoxia (2 kPa) and recovery from hypoxia after different exposure times, mimicking the natural tidal cycle (6 h and 12 h). We calculated critical oxygen tension and categorize the adult ghost shrimps as oxyregulators (R value=75.27%). All physiological measurements (metabolic rate, oxyhemocyanin, hemolymph protein and lactate concentrations) were affected by exposure to low partial pressures of oxygen, but most of them recovered (with exception of metabolic rate) control values (21 kPa) after 6h under normoxic conditions. Low metabolic rate, high release of hemolymphatic proteins and anaerobic metabolism are suggested as response mechanisms to overcome hypoxic events during low tide. PMID:26212148

  15. Box-modeling of bone and tooth phosphate oxygen isotope compositions as a function of environmental and physiological parameters.

    PubMed

    Langlois, C; Simon, L; Lécuyer, Ch

    2003-12-01

    A time-dependent box model is developed to calculate oxygen isotope compositions of bone phosphate as a function of environmental and physiological parameters. Input and output oxygen fluxes related to body water and bone reservoirs are scaled to the body mass. The oxygen fluxes are evaluated by stoichiometric scaling to the calcium accretion and resorption rates, assuming a pure hydroxylapatite composition for the bone and tooth mineral. The model shows how the diet composition, body mass, ambient relative humidity and temperature may control the oxygen isotope composition of bone phosphate. The model also computes how bones and teeth record short-term variations in relative humidity, air temperature and delta18O of drinking water, depending on body mass. The documented diversity of oxygen isotope fractionation equations for vertebrates is accounted for by our model when for each specimen the physiological and diet parameters are adjusted in the living range of environmental conditions. PMID:14711171

  16. Physiology

    ERIC Educational Resources Information Center

    Kay, Ian

    2008-01-01

    Underlying recent developments in health care and new treatments for disease are advances in basic medical sciences. This edition of "Webwatch" focuses on sites dealing with basic medical sciences, with particular attention given to physiology. There is a vast amount of information on the web related to physiology. The sites that are included here…

  17. Oxygen uptake in Pacific salmon Oncorhynchus spp.: when ecology and physiology meet.

    PubMed

    Eliason, E J; Farrell, A P

    2016-01-01

    Over the past several decades, a substantial amount of research has examined how cardiorespiratory physiology supports the diverse activities performed throughout the life cycle of Pacific salmon, genus Oncorhynchus. Pioneering experiments emphasized the importance of aerobic scope in setting the functional thermal tolerance for activity in fishes. Variation in routine metabolism can have important performance and fitness consequences as it is related to dominance, aggression, boldness, territoriality, growth rate, postprandial oxygen consumption, life history, season, time of day, availability of shelter and social interactions. Wild fishes must perform many activities simultaneously (e.g. swim, obtain prey, avoid predators, compete, digest and reproduce) and oxygen delivery is allocated among competing organ systems according to the capacity of the heart to deliver blood. For example, salmonids that are simultaneously swimming and digesting trade-off maximum swimming performance in order to support the oxygen demands of digestion. As adult Pacific salmonids cease feeding in the ocean prior to their home migration, endogenous energy reserves and cardiac capacity are primarily partitioned among the demands for swimming upriver, sexual maturation and spawning behaviours. Furthermore, the upriver spawning migration is under strong selection pressure, given that Pacific salmonids are semelparous (single opportunity to spawn). Consequently, these fishes optimize energy expenditures in a number of ways: strong homing, precise migration timing, choosing forward-assist current paths and exploiting the boundary layer to avoid the strong currents in the middle of the river, using energetically efficient swimming speeds, and recovering rapidly from anaerobic swimming. Upon arrival at the spawning ground, remaining energy can be strategically allocated to the various spawning behaviours. Strong fidelity to natal streams has resulted in reproductively isolated populations that

  18. Genomic and physiological analysis of oxygen sensitivity and hypoxia tolerance in PC12 cells.

    PubMed

    Seta, Karen; Kim, Hie-Won; Ferguson, Tsuneo; Kim, Richard; Pathrose, Peterson; Yuan, Yong; Lu, Gang; Spicer, Zachary; Millhorn, David E

    2002-10-01

    The mechanisms by which cells adapt and respond to changes in oxygen tension remain largely unknown. Our laboratory has used the PC12 cell line to study both biophysical and molecular responses to hypoxia. This chapter summarizes our findings. We found that membrane depolarization that occurred when PC12 cells were exposed to reduced O(2) was mediated by a specific potassium channel, the Kv1.2 channel. The membrane depolarization leads to increased Ca(2+) conductance through a voltage-sensitive channel, which in turn mediates the release of the neurotransmitters dopamine, adenosine, glutamate, and GABA. In addition, increased intracellular Ca(2+) and other signaling systems regulate hypoxia-induced gene expression, which contributes to the adaptive response to reduced O(2+). We identified several critical signaling pathways that regulate a complex gene expression profile in PC12 cells during hypoxia. These include the cAMP-protein kinase A, Ca(2+)-calmodulin, p42/44 mitogen-activated protein kinase (MAPK), stress-activated protein kinase (SAPK; p38 kinase), and the phosphatidylinositol 3-kinase-AKT as regulators of gene expression. Several of these pathways regulate hypoxia-specific transcription factors that are members of the hypoxia-inducible factor (HIF) family. Recently, we have successfully used subtractive cDNA libraries and microarray analysis to identify the genomic profile that mediates the cellular response to hypoxia. PMID:12438156

  19. Monitoring preantral follicle survival and growth in bovine ovarian biopsies by repeated use of neutral red and cultured in vitro under low and high oxygen tension.

    PubMed

    Jorssen, Ellen P A; Langbeen, An; Fransen, Erik; Martinez, Emilia L; Leroy, Jo L M R; Bols, Peter E J

    2014-08-01

    The development and optimization of preantral follicle culture methods are crucial in fertility preservation strategies. As preantral follicle dynamics are usually assessed by various invasive techniques, the need for alternative noninvasive evaluation tools exists. Recently, neutral red (NR) was put forward to visualize preantral follicles in situ within ovarian cortical fragments. However, intense light exposure of NR-stained tissues can lead to cell death because of increased reactive oxygen species production, which is also associated with elevated oxygen tension. Therefore, we hypothesize that after repeated NR staining, follicle viability and dynamics can be altered by changes in oxygen tension. In the present study, we aim (1) to determine whether NR can be used to repeatedly assess follicular growth, activation, and viability and (2) to assess the effect of a low (5% O2) or high (20% O2) oxygen tension on the viability, growth, and stage transition of preantral follicles cultured in vitro by means of repeated NR staining. Cortical slices (n = 132; six replicates) from bovine ovaries were incubated for 3 hours at 37 °C in a Leibovitz medium with 50 μg/mL NR. NR-stained follicles were evaluated in situ for follicle diameter and morphology. Next, cortical fragments were individually cultured in McCoy's 5A medium for 6 days at 37 °C, 5% CO2, and 5% or 20% O2. On Days 4 and 6, the fragments were restained by adding NR to the McCoy's medium and follicles were reassessed. In both low and high oxygen tension treatment groups, approximately 70% of the initial follicles survived a 6-day in vitro culture, but no significant difference in follicle survival on Day 4 or 6 could be observed compared with Day 0 (P > 0.05). A significant decrease in the number of primordial and increase in primary and secondary follicles was observed within 4 days of culture (P < 0.001). In addition, a significant increase of the mean follicle diameter in NR-stained follicles was

  20. Preservation of high glycolytic phenotype by establishing new acute lymphoblastic leukemia cell lines at physiologic oxygen concentration.

    PubMed

    Sheard, Michael A; Ghent, Matthew V; Cabral, Daniel J; Lee, Joanne C; Khankaldyyan, Vazgen; Ji, Lingyun; Wu, Samuel Q; Kang, Min H; Sposto, Richard; Asgharzadeh, Shahab; Reynolds, C Patrick

    2015-05-15

    Cancer cells typically exhibit increased glycolysis and decreased mitochondrial oxidative phosphorylation, and they continue to exhibit some elevation in glycolysis even under aerobic conditions. However, it is unclear whether cancer cell lines employ a high level of glycolysis comparable to that of the original cancers from which they were derived, even if their culture conditions are changed to physiologically relevant oxygen concentrations. From three childhood acute lymphoblastic leukemia (ALL) patients we established three new pairs of cell lines in both atmospheric (20%) and physiologic (bone marrow level, 5%) oxygen concentrations. Cell lines established in 20% oxygen exhibited lower proliferation, survival, expression of glycolysis genes, glucose consumption, and lactate production. Interestingly, the effects of oxygen concentration used during cell line initiation were only partially reversible when established cell cultures were switched from one oxygen concentration to another for eight weeks. These observations indicate that ALL cell lines established at atmospheric oxygen concentration can exhibit relatively low levels of glycolysis and these levels are semi-permanent, suggesting that physiologic oxygen concentrations may be needed from the time of cell line initiation to preserve the high level of glycolysis commonly exhibited by leukemias in vivo. PMID:25845499

  1. Nitroxyl (HNO) reacts with molecular oxygen and forms peroxynitrite at physiological pH. Biological Implications.

    PubMed

    Smulik, Renata; Dębski, Dawid; Zielonka, Jacek; Michałowski, Bartosz; Adamus, Jan; Marcinek, Andrzej; Kalyanaraman, Balaraman; Sikora, Adam

    2014-12-19

    Nitroxyl (HNO), the protonated one-electron reduction product of NO, remains an enigmatic reactive nitrogen species. Its chemical reactivity and biological activity are still not completely understood. HNO donors show biological effects different from NO donors. Although HNO reactivity with molecular oxygen is described in the literature, the product of this reaction has not yet been unambiguously identified. Here we report that the decomposition of HNO donors under aerobic conditions in aqueous solutions at physiological pH leads to the formation of peroxynitrite (ONOO(-)) as a major intermediate. We have specifically detected and quantified ONOO(-) with the aid of boronate probes, e.g. coumarin-7-boronic acid or 4-boronobenzyl derivative of fluorescein methyl ester. In addition to the major phenolic products, peroxynitrite-specific minor products of oxidation of boronate probes were detected under these conditions. Using the competition kinetics method and a set of HNO scavengers, the value of the second order rate constant of the HNO reaction with oxygen (k = 1.8 × 10(4) m(-1) s(-1)) was determined. The rate constant (k = 2 × 10(4) m(-1) s(-1)) was also determined using kinetic simulations. The kinetic parameters of the reactions of HNO with selected thiols, including cysteine, dithiothreitol, N-acetylcysteine, captopril, bovine and human serum albumins, and hydrogen sulfide, are reported. Biological and cardiovascular implications of nitroxyl reactions are discussed. PMID:25378389

  2. Nitroxyl (HNO) Reacts with Molecular Oxygen and Forms Peroxynitrite at Physiological pH

    PubMed Central

    Smulik, Renata; Dębski, Dawid; Zielonka, Jacek; Michałowski, Bartosz; Adamus, Jan; Marcinek, Andrzej; Kalyanaraman, Balaraman; Sikora, Adam

    2014-01-01

    Nitroxyl (HNO), the protonated one-electron reduction product of NO, remains an enigmatic reactive nitrogen species. Its chemical reactivity and biological activity are still not completely understood. HNO donors show biological effects different from NO donors. Although HNO reactivity with molecular oxygen is described in the literature, the product of this reaction has not yet been unambiguously identified. Here we report that the decomposition of HNO donors under aerobic conditions in aqueous solutions at physiological pH leads to the formation of peroxynitrite (ONOO−) as a major intermediate. We have specifically detected and quantified ONOO− with the aid of boronate probes, e.g. coumarin-7-boronic acid or 4-boronobenzyl derivative of fluorescein methyl ester. In addition to the major phenolic products, peroxynitrite-specific minor products of oxidation of boronate probes were detected under these conditions. Using the competition kinetics method and a set of HNO scavengers, the value of the second order rate constant of the HNO reaction with oxygen (k = 1.8 × 104 m−1 s−1) was determined. The rate constant (k = 2 × 104 m−1 s−1) was also determined using kinetic simulations. The kinetic parameters of the reactions of HNO with selected thiols, including cysteine, dithiothreitol, N-acetylcysteine, captopril, bovine and human serum albumins, and hydrogen sulfide, are reported. Biological and cardiovascular implications of nitroxyl reactions are discussed. PMID:25378389

  3. Oxygen and carbon isotope disequilibria in Galapagos corals: isotopic thermometry and calcification physiology

    SciTech Connect

    McConnaughey, T.A.

    1986-01-01

    Biological carbonate skeletons are built largely from carbon dioxide, which reacts to form carbonate ion within thin extracellular solutions. The light isotopes of carbon and oxygen react faster than the heavy isotopes, depleting the resulting carbonate ions in /sup 13/C and /sup 18/O. Calcium carbonate precipitation occurs sufficiently fast that the skeleton remains out of isotopic equilibrium with surrounding fluids. This explanation for isotopic disequilibrium in biological carbonates was partially simulated in vitro, producing results similar to those seen in non-photosynthetic corals. Photosynthetic corals have higher /sup 13/C//sup 12/C ratios due to the preferential removal of /sup 12/C (as organic carbon) from the reservoir of dissolved inorganic carbon. The oxygen isotopic variations in corals can be used to reconstruct past sea surface temperatures to an accuracy of about 0.5/sup 0/C. The carbon isotopic content of photosynthetic corals provides an indication of cloudiness. Using isotopic data from Galapagos corals, it was possible to construct proxy histories of the El Nino phenomenon. The physiology of skeletogenesis appears to be surprisingly similar in calcium carbonate, calcium phosphate, and silica precipitating systems.

  4. Hourly oxygen and total gas tension measurements at the Southern Ocean Time Series site reveal winter ventilation and spring net community production

    NASA Astrophysics Data System (ADS)

    Weeding, Ben; Trull, Thomas W.

    2014-01-01

    Using a moored instrument package at 35 m depth at the Southern Ocean Time Series (SOTS) site near 46°56'S 142°15'E from September 2010 to April 2011 (219 days), we obtained the first Southern Ocean Time Series of dissolved oxygen (from an optode sensor) and nitrogen (from a total gas tension sensor). Nitrogen was consistently supersaturated (100.8%-102.9%), while oxygen was highly subsaturated in early spring (as low as 93.5%) and reached supersaturation (maximum 104.9%) during only 37 days in early summer. The low oxygen levels in spring illustrate the importance of deep mixing in the Subantarctic Zone in ventilating the upper limb of the global overturning circulation. Using nitrogen as a proxy for physical processes, we isolated biological contributions to the oxygen time series to obtain net community production (NCP). Almost all NCP occurred in spring in the presence of deep mixed layers, with only small additional contributions in summer after water column stratification. The temperature and salinity time series also revealed distinct parcels of water. Rapid changes at their interfaces generated unrealistic NCP events in the standard calculation model, which were removed, while still retaining NCP contributions from each parcel. NCP totaled 2.2 ± 1.2 mol O2 m-2 over the deployment, within the range of previous estimates from low temporal resolution techniques. Examination of errors revealed particular sensitivity to entrainment, suggesting more rigorous understanding of this process is required, e.g., via profiling instruments.

  5. Quantifying the magnitude of the oxygen artefact inherent in culturing airway cells under atmospheric oxygen versus physiological levels.

    PubMed

    Kumar, Abhinav; Dailey, Lea Ann; Swedrowska, Magda; Siow, Richard; Mann, Giovanni E; Vizcay-Barrena, Gema; Arno, Matthew; Mudway, Ian S; Forbes, Ben

    2016-01-01

    To date, in vitro studies assessing the pulmonary toxicity of inhaled particles have provided poor correlation with in vivo results. We explored whether this discrepancy reflected cellular adaptations in pulmonary cells cultured under atmospheric oxygen concentrations (21%) compared with in vivo alveolar concentrations (100 mm Hg, ~ 13%) and whether this blunted cellular responses to nanoparticle challenge. At 21% oxygen, A549 cells had augmented intracellular glutathione concentrations, with evidence of increased tolerance to CuO nanoparticles, with reduced reactive oxygen species production, blunted transcriptional responses and delayed cell death, compared to cells cultured at 13% oxygen. These data support the contention that standard cell culture conditions pre-adapt cells to oxidative insults and emphasize the necessity of ensuring normoxic conditions in model systems to improve their predictive value. PMID:26823171

  6. Oxygen flux as an indicator of physiological stress in aquatic organisms: a real-time biomonitoring system of water quality

    NASA Astrophysics Data System (ADS)

    Sanchez, Brian C.; Yale, Gowri; Chatni, Rameez; Ochoa-Acuña, Hugo G.; Porterfield, D. Marshall; Mclamore, Eric S.; Sepúlveda, María S.

    2009-05-01

    The detection of harmful chemicals and biological agents in real time is a critical need for protecting water quality. We studied the real-time effects of five environmental contaminants with differing modes of action (atrazine, pentachlorophenol, cadmium chloride, malathion, and potassium cyanide) on respiratory oxygen consumption in 2-day post-fertilization fathead minnow (Pimephales promelas) eggs. Our objective was to assess the sensitivity of fathead minnow eggs using the self-referencing micro-optrode technique to detect instantaneous changes in oxygen consumption after brief exposures to low concentrations of contaminants. Oxygen consumption data indicated that the technique is indeed sensitive enough to reliably detect physiological alterations induced by all contaminants. After 2 h of exposure, we identified significant increases in oxygen consumption upon exposure to pentachlorophenol (100 and 1000 μg/L), cadmium chloride (0.0002 and 0.002 μg/L), and atrazine (150 μg/L). In contrast, we observed a significant decrease in oxygen flux after exposures to potassium cyanide (5.2, 22, and 44 μg/L) and atrazine (1500 μg/L). No effects were detected after exposures to malathion (200 and 340 μg/L). We have also tested the sensitivity of Daphnia magna embryos as another animal model for real-time environmental biomonitoring. Our results are so far encouraging and support further development of this technology as a physiologically coupled biomonitoring tool for the detection of environmental toxicants.

  7. NOTE: A haemodynamic model for the physiological interpretation of in vivo measurements of the concentration and oxygen saturation of haemoglobin

    NASA Astrophysics Data System (ADS)

    Fantini, Sergio

    2002-09-01

    We present a model that describes the effect of physiological parameters such as the speed of blood flow, local oxygen consumption, capillary recruitment, and vascular dilation/constriction on the concentration and oxygen saturation of haemoglobin in tissue. This model can be used to guide the physiological interpretation of haemodynamic and oximetric data collected in vivo with techniques such as optical imaging, near-infrared spectroscopy and functional magnetic resonance imaging. In addition to providing a formal description of well-established results (exercise-induced hyperemia, reperfusion hyperoxia, decrease in the concentration of deoxyhaemoglobin induced by brain activity, measurement of arterial saturation by pulse oximetry, etc.), this model suggests that the superposition of asynchronous contributions from the arterial, capillary and venous haemoglobin compartments may be at the origin of observed out-of-phase oscillations of the oxyhaemoglobin and deoxyhaemoglobin concentrations in tissue.

  8. Direct measurement of myocardial oxygen tension and high energy phosphate content under varying ventilatory conditions in rabbits.

    PubMed

    Vogt, Sebastian; Troitzsch, Dirk; Spath, Silvia; Portig, Irene; Moosdorf, Rainer

    2009-08-01

    Effective myocardial oxygen supply should not be compromised during cardiac surgery as it is essential to avoid circulatory and cardiac dysfunction. Local measurement of myocardial oxygen partial pressure (pO2) was therefore introduced into the operative monitoring of myocardial ischemia. The aim of the present study was to assess whether myocardial oxygen partial pressure correlates with the content of high energy phosphates (HEPs). Seven male rabbits were examined in parallel with measurement of myocardial pO2 by an implanted Clark electrode and 31phosphorus-NMR spectroscopy. The ventilatory management established hyperoxygenation followed by systemic hypoxia with hypercapnia for 20 min. Additionally, analysis of end-expiratory gas composition in combination with blood gas analysis was performed simultaneously, and hemodynamic parameter was recorded. Under hypoxic conditions the cardiovascular system was severely compromised, whereas the myocardial pO2 was only moderately impaired (pO2M 45.0+/-16.0 mm Hg). Immediately before cardiac arrest, low values of arterial and venous pO2 were found (17.6+/-6.0 and 12.9+/-6.1 mm Hg). In contrast to near normal myocardial pO2, HEP content in the myocardium was considerably reduced and inorganic phosphorus was increased. Artificial ventilation leading to systemic hypoxia and eventually circulatory arrest resulted in almost normal myocardial pO2 but severely compromised HEP content. This somewhat unexpected finding requires further clarification, but is in accordance with findings reported previously where regulatory mechanisms have been shown to play a role in the pathophysiology of severe hypoxic conditions such as those for cellular oxygen delivery and demand, P/O coupling and finally control of HEP production facilitating the interaction between respiratory chain and myoglobin oxygen transport. PMID:19807283

  9. Surface Tension

    NASA Technical Reports Server (NTRS)

    Theissen, David B.; Man, Kin F.

    1996-01-01

    The effect of surface tension is observed inmany everyday situations. For example, a slowly leaking faucet drips because the force surface tension allows the water to cling to it until a sufficient mass of water is accumulated to break free.

  10. Changes of blood flow, oxygen tension, action potential and vascular permeability induced by arterial ischemia or venous congestion on the spinal cord in canine model.

    PubMed

    Kobayashi, Shigeru; Yoshizawa, Hidezo; Shimada, Seiichiro; Guerrero, Alexander Rodríguez; Miyachi, Masaya

    2013-01-01

    It is generally considered that the genesis of myelopathy associated with the degenerative conditions of the spine may result from both mechanical compression and circulatory disturbance. Many references about spinal cord tissue ischemic damage can be found in the literature, but not detailed studies about spinal cord microvasculature damage related to congestion or blood permeability. This study investigates the effect of ischemia and congestion on the spinal cord using an in vivo model. The aorta was clamped as an ischemia model of the spinal cord and the inferior vena cava was clamped as a congestion model at the 6th costal level for 30 min using forceps transpleurally. Measurements of blood flow, partial oxygen pressure, and conduction velocity in the spinal cord were repeated over a period of 1 h after release of clamping. Finally, we examined the status of blood-spinal cord barrier under fluorescence and transmission electron microscope. Immediately after clamping of the inferior vena cava, the central venous pressure increased by about four times. Blood flow, oxygen tension and action potential were more severely affected by the aorta clamping; but this ischemic model did not show any changes of blood permeability in the spinal cord. The intramedullar edema was more easily produced by venous congestion than by arterial ischemia. In conclusions, venous congestion may be a preceding and essential factor of circulatory disturbance in the compressed spinal cord inducing myelopathy. PMID:22912247

  11. Gene Expression and Physiological Changes of Different Populations of the Long-Lived Bivalve Arctica islandica under Low Oxygen Conditions

    PubMed Central

    Philipp, Eva E. R.; Wessels, Wiebke; Gruber, Heike; Strahl, Julia; Wagner, Anika E.; Ernst, Insa M. A.; Rimbach, Gerald; Kraemer, Lars; Schreiber, Stefan; Abele, Doris; Rosenstiel, Philip

    2012-01-01

    The bivalve Arctica islandica is extremely long lived (>400 years) and can tolerate long periods of hypoxia and anoxia. European populations differ in maximum life spans (MLSP) from 40 years in the Baltic to >400 years around Iceland. Characteristic behavior of A. islandica involves phases of metabolic rate depression (MRD) during which the animals burry into the sediment for several days. During these phases the shell water oxygen concentrations reaches hypoxic to anoxic levels, which possibly support the long life span of some populations. We investigated gene regulation in A. islandica from a long-lived (MLSP 150 years) German Bight population and the short-lived Baltic Sea population, experimentally exposed to different oxygen levels. A new A. islandica transcriptome enabled the identification of genes important during hypoxia/anoxia events and, more generally, gene mining for putative stress response and (anti-) aging genes. Expression changes of a) antioxidant defense: Catalase, Glutathione peroxidase, manganese and copper-zinc Superoxide dismutase; b) oxygen sensing and general stress response: Hypoxia inducible factor alpha, Prolyl hydroxylase and Heat-shock protein 70; and c) anaerobic capacity: Malate dehydrogenase and Octopine dehydrogenase, related transcripts were investigated. Exposed to low oxygen, German Bight individuals suppressed transcription of all investigated genes, whereas Baltic Sea bivalves enhanced gene transcription under anoxic incubation (0 kPa) and, further, decreased these transcription levels again during 6 h of re-oxygenation. Hypoxic and anoxic exposure and subsequent re-oxygenation in Baltic Sea animals did not lead to increased protein oxidation or induction of apoptosis, emphasizing considerable hypoxia/re-oxygenation tolerance in this species. The data suggest that the energy saving effect of MRD may not be an attribute of Baltic Sea A. islandica chronically exposed to high environmental variability (oxygenation, temperature

  12. The influences of hyperbaric oxygen therapy with a lower pressure and oxygen concentration than previous methods on physiological mechanisms in dogs.

    PubMed

    Ishibashi, Maki; Hayashi, Akiyoshi; Akiyoshi, Hideo; Ohashi, Fumihito

    2015-03-01

    Recently, hyperbaric oxygen therapy with a lower pressure and oxygen concentration (L-HBOT) than previous methods has been used for dogs in Japan; however, the influences of L-HBOT on dogs have not been clarified. To verify the influences of L-HBOT on physiological mechanism in dogs, we investigated blood gas parameters, glutathione peroxidase (GPx) activity, heart rate variability, stress-related hormones and skin conductance (SC) in 4 clinically normal beagle dogs with catheters in their carotid arteries and jugular veins when they were quiet, after running, after receiving L-HBOT (30% oxygen concentration, 1.3 atmospheres absolute, 30 min) or after not receiving L-HBOT. The results showed there were no changes in blood gas parameters, heart rate variability and catecholamine levels after L-HBOT. GPx activity was significantly higher, and the SC and cortisol level were lower in dogs that received L-HBOT than those when they were quiet. These results suggested that L-HBOT may have a small influence on oxygenation dynamics, activate antioxidant enzymes such as GPx, restrain autonomic nervous activity and control the balance between oxidation and antioxidation inside the body. PMID:25482821

  13. The influences of hyperbaric oxygen therapy with a lower pressure and oxygen concentration than previous methods on physiological mechanisms in dogs

    PubMed Central

    ISHIBASHI, Maki; HAYASHI, Akiyoshi; AKIYOSHI, Hideo; OHASHI, Fumihito

    2014-01-01

    Recently, hyperbaric oxygen therapy with a lower pressure and oxygen concentration (L-HBOT) than previous methods has been used for dogs in Japan; however, the influences of L-HBOT on dogs have not been clarified. To verify the influences of L-HBOT on physiological mechanism in dogs, we investigated blood gas parameters, glutathione peroxidase (GPx) activity, heart rate variability, stress-related hormones and skin conductance (SC) in 4 clinically normal beagle dogs with catheters in their carotid arteries and jugular veins when they were quiet, after running, after receiving L-HBOT (30% oxygen concentration, 1.3 atmospheres absolute, 30 min) or after not receiving L-HBOT. The results showed there were no changes in blood gas parameters, heart rate variability and catecholamine levels after L-HBOT. GPx activity was significantly higher, and the SC and cortisol level were lower in dogs that received L-HBOT than those when they were quiet. These results suggested that L-HBOT may have a small influence on oxygenation dynamics, activate antioxidant enzymes such as GPx, restrain autonomic nervous activity and control the balance between oxidation and antioxidation inside the body. PMID:25482821

  14. The Tension Literature.

    ERIC Educational Resources Information Center

    Frederick, A. B.

    This is a bibliography of literature on the subject of tension. Books, films, and periodicals with a bearing on stress, relaxation, anxiety, and/or methods of controlling stress are listed from the fields of physiology, psychology, and philosophy. New methods such as transcendental meditation and biofeedback are analyzed briefly and criteria are…

  15. Transcutaneous oxygen tension measurements following peripheral transluminal angioplasty procedure has more specificity and sensitivity than ankle brachial index

    PubMed Central

    Pardo, M; Bernal, F L; Felices, J M; Achel, G D; Canteras, M

    2015-01-01

    Objective: To evaluate the superiority of transcutaneous oxygen pressure (TcPO2) before, during and after peripheral transluminal angioplasty (PTA) in comparison with ankle brachial index (ABI) in patients with diabetes. Methods: 40 consecutive patients with diabetes treated by PTA where included. This study shows results before, during and after PTA and their progression for 8 weeks. Results: The TcPO2 increased from 28.11 ± 8.1 to 48.03 ± 8.4 mmHg, 8 weeks after PTA (p < 0.001). The ABI increased from 0.48 ± 0.38 to 0.77 ± 0.39 after PTA (p < 0.001). After PTA, the stenosis of the vessel decreased from 58.33 ± 20.07% to 21.87 ± 13.57% (p < 0.001). TcPO2 was determined in all the patients, but ABI could not be determined in all patients. Furthermore, we determined patients with “false negatives” with an improvement in ABI and “false positives” in 12.5% of patients. Additionally, in this study, we monitored TcPO2 while performing PTA, revealing variations in each phase of the radiological procedure. Conclusion: The increase in TcPO2 measurements following PTA procedure has more specificity and sensitivity than does ABI. The use of TcPO2 may represent a more accurate alternative than traditional methods (ABI) used in assessing PTA results. The TcPO2 also allows the radiologist to assess changes in tissue oxygenation during PTA, allowing changes to the procedure and subsequent treatment. Advances in knowledge: This is the first time that a graph is shown with TcPO2 results during PTA performance in many patients. PMID:25431933

  16. Dynamic and selective HERV RNA expression in neuroblastoma cells subjected to variation in oxygen tension and demethylation.

    PubMed

    Hu, Lijuan; Uzhameckis, Dmitrijs; Hedborg, Fredrik; Blomberg, Jonas

    2016-01-01

    We studied HERV expression in cell lines after hypoxia, mitogenic stimulation, and demethylation, to better understand if hypoxia may play a role in ERV activation also within the nervous system, as represented by neuroblastoma cell lines. The level of RNA of four human ERV groups (HERVs) (HERVE, I/T, H, and W), and three housekeeping genes, of different cell lines including A549, COS-1, Namalwa, RD-L and Vero-E6, as well as human neuroblastoma cell lines SH-SY5Y, SK-N-DZ, and SK-N-AS were studied using reverse transcription and real-time quantitative PCR (QPCR). During the course of recovery from hypoxia a pronounced and selective activation of RNA expression of HERVW-like sequences, but not of HERVE, I/T, H, and three housekeeping genes, was found in the neuroblastoma cell lines, most pronounced in SK-N-DZ. In the SK-N-DZ cell line, we also tested the expression of HERVs after chemical treatments. HERVW-like sequences were selectively upregulated by 5-azacytidine, a demethylating agent. Some HERVW loci seem especially responsive to hypoxia and demethylation. HERV expression in neuroblastoma cells is selectively and profoundly influenced by some physiological and chemical stimuli. PMID:26818268

  17. Normoxia vs. Hyperoxia: Impact of Oxygen Tension Strategies on Outcomes for Patients Receiving Cardiopulmonary Bypass for Routine Cardiac Surgical Repair

    PubMed Central

    Brown, D. Mark; Holt, David W.; Edwards, Jeff T.; Burnett, Robert J.

    2006-01-01

    Abstract: Oxygen pressure field theory (OPFT) was originally described in the early 1900s by Danish physiologist, Dr. August Krogh. This revolutionary theory described microcirculation of blood gases at the capillary level using a theoretical cylindrical tissue model commonly referred to as the Krogh cylinder. In recent years, the principles and benefits of OPFT in long-term extracorporeal circulatory support (ECMO) have been realized. Cardiac clinicians have successfully mastered OPFT fundamentals and incorporated them into their clinical practice. These clinicians have experienced significantly improved survival rates as a result of OPFT strategies. The objective of this study was to determine if a hyperoxic strategy can lead to equally beneficial outcomes for short-term support as measured by total ventilator time and total length of stay in intensive care unit (ICU) in the cardiopulmonary bypass (CPB) patient at a private institution. Patients receiving traditional blood gas management while on CPB (group B, n = 17) were retrospectively compared with hyperoxic patients (group A, n = 19). Hyperoxic/OPFT management was defined as paO2 values of 300–350 mmHg and average VSAT > 75%. Traditional blood gas management was defined as paO2 values of 150–250 mmHg and average VSAT < 75%. No significant differences between treatment groups were found for patient weight, CPB/AXC times, BSA, pre/post Hgb, pre/post-platelet (PLT) counts, pre/post-creatinine levels, pre/post-BUN, UF volumes, or CPB urine output. Additionally, no significant statistical differences were found between treatment groups for total time in ICU (T-ICU) or total time on ventilator (TOV). Hyperoxic management strategies provided no conclusive evidence of outcome improvement for patients receiving CPB for routine cardiac surgical repair. Additional studies into the impact of hyperoxia in short-term extracorporeal circulatory support are needed. PMID:17089511

  18. The effects of graded changes in oxygen and carbon dioxide tension on coronary blood velocity independent of myocardial energy demand.

    PubMed

    Boulet, Lindsey M; Stembridge, Mike; Tymko, Michael M; Tremblay, Joshua C; Foster, Glen E

    2016-08-01

    In humans, coronary blood flow is tightly regulated by microvessels within the myocardium to match myocardial energy demand. However, evidence regarding inherent sensitivity of the microvessels to changes in arterial partial pressure of carbon dioxide and oxygen is conflicting because of the accompanied changes in myocardial energy requirements. This study aimed to investigate the changes in coronary blood velocity while manipulating partial pressures of end-tidal CO2 (Petco2) and O2 (Peto2). It was hypothesized that an increase in Petco2 (hypercapnia) or decrease in Peto2 (hypoxia) would result in a significant increase in mean blood velocity in the left anterior descending artery (LADVmean) due to an increase in both blood gases and energy demand associated with the concomitant cardiovascular response. Cardiac energy demand was assessed through noninvasive measurement of the total left ventricular mechanical energy. Healthy subjects (n = 13) underwent a euoxic CO2 test (Petco2 = -8, -4, 0, +4, and +8 mmHg from baseline) and an isocapnic hypoxia test (Peto2 = 64, 52, and 45 mmHg). LADVmean was assessed using transthoracic Doppler echocardiography. Hypercapnia evoked a 34.6 ± 8.5% (mean ± SE; P < 0.01) increase in mean LADVmean, whereas hypoxia increased LADVmean by 51.4 ± 8.8% (P < 0.05). Multiple stepwise regressions revealed that both mechanical energy and changes in arterial blood gases are important contributors to the observed changes in LADVmean (P < 0.01). In summary, regulation of the coronary vasculature in humans is mediated by metabolic changes within the heart and an inherent sensitivity to arterial blood gases. PMID:27233761

  19. Effects of reduced dissolved oxygen concentrations on physiology and fluorescence of hermatypic corals and benthic algae

    PubMed Central

    Smith, Jennifer E.; Thompson, Melissa

    2014-01-01

    While shifts from coral to seaweed dominance have become increasingly common on coral reefs and factors triggering these shifts successively identified, the primary mechanisms involved in coral-algae interactions remain unclear. Amongst various potential mechanisms, algal exudates can mediate increases in microbial activity, leading to localized hypoxic conditions which may cause coral mortality in the direct vicinity. Most of the processes likely causing such algal exudate induced coral mortality have been quantified (e.g., labile organic matter release, increased microbial metabolism, decreased dissolved oxygen availability), yet little is known about how reduced dissolved oxygen concentrations affect competitive dynamics between seaweeds and corals. The goals of this study were to investigate the effects of different levels of oxygen including hypoxic conditions on a common hermatypic coral Acropora yongei and the common green alga Bryopsis pennata. Specifically, we examined how photosynthetic oxygen production, dark and daylight adapted quantum yield, intensity and anatomical distribution of the coral innate fluorescence, and visual estimates of health varied with differing background oxygen conditions. Our results showed that the algae were significantly more tolerant to extremely low oxygen concentrations (2–4 mg L−1) than corals. Furthermore corals could tolerate reduced oxygen concentrations, but only until a given threshold determined by a combination of exposure time and concentration. Exceeding this threshold led to rapid loss of coral tissue and mortality. This study concludes that hypoxia may indeed play a significant role, or in some cases may even be the main cause, for coral tissue loss during coral-algae interaction processes. PMID:24482757

  20. High-Flow Nasal Cannula Oxygen Therapy in Adults: Physiological Benefits, Indication, Clinical Benefits, and Adverse Effects.

    PubMed

    Nishimura, Masaji

    2016-04-01

    High-flow nasal cannula (HFNC) oxygen therapy is carried out using an air/oxygen blender, active humidifier, single heated tube, and nasal cannula. Able to deliver adequately heated and humidified medical gas at flows up to 60 L/min, it is considered to have a number of physiological advantages compared with other standard oxygen therapies, including reduced anatomical dead space, PEEP, constant FIO2 , and good humidification. Although few large randomized clinical trials have been performed, HFNC has been gaining attention as an alternative respiratory support for critically ill patients. Published data are mostly available for neonates. For critically ill adults, however, evidence is uneven because the reports cover various subjects with diverse underlying conditions, such as hypoxemic respiratory failure, exacerbation of COPD, postextubation, preintubation oxygenation, sleep apnea, acute heart failure, and conditions entailing do-not-intubate orders. Even so, across the diversity, many published reports suggest that HFNC decreases breathing frequency and work of breathing and reduces the need for respiratory support escalation. Some important issues remain to be resolved, such as definitive indications for HFNC and criteria for timing the starting and stopping of HFNC and for escalating treatment. Despite these issues, HFNC has emerged as an innovative and effective modality for early treatment of adults with respiratory failure with diverse underlying diseases. PMID:27016353

  1. Effects of In Vitro Low Oxygen Tension Preconditioning of Adipose Stromal Cells on Their In Vivo Chondrogenic Potential: Application in Cartilage Tissue Repair

    PubMed Central

    Gauthier, Olivier; Lesoeur, Julie; Sourice, Sophie; Masson, Martial; Fellah, Borhane Hakim; Geffroy, Olivier; Lallemand, Elodie; Weiss, Pierre

    2013-01-01

    Purpose Multipotent stromal cell (MSC)-based regenerative strategy has shown promise for the repair of cartilage, an avascular tissue in which cells experience hypoxia. Hypoxia is known to promote the early chondrogenic differentiation of MSC. The aim of our study was therefore to determine whether low oxygen tension could be used to enhance the regenerative potential of MSC for cartilage repair. Methods MSC from rabbit or human adipose stromal cells (ASC) were preconditioned in vitro in control or chondrogenic (ITS and TGF-β) medium and in 21 or 5% O2. Chondrogenic commitment was monitored by measuring COL2A1 and ACAN expression (real-time PCR). Preconditioned rabbit and human ASC were then incorporated into an Si-HPMC hydrogel and injected (i) into rabbit articular cartilage defects for 18 weeks or (ii) subcutaneously into nude mice for five weeks. The newly formed tissue was qualitatively and quantitatively evaluated by cartilage-specific immunohistological staining and scoring. The phenotype of ASC cultured in a monolayer or within Si-HPMC in control or chondrogenic medium and in 21 or 5% O2 was finally evaluated using real-time PCR. Results/Conclusions 5% O2 increased the in vitro expression of chondrogenic markers in ASC cultured in induction medium. Cells implanted within Si-HPMC hydrogel and preconditioned in chondrogenic medium formed a cartilaginous tissue, regardless of the level of oxygen. In addition, the 3D in vitro culture of ASC within Si-HPMC hydrogel was found to reinforce the pro-chondrogenic effects of the induction medium and 5% O2. These data together indicate that although 5% O2 enhances the in vitro chondrogenic differentiation of ASC, it does not enhance their in vivo chondrogenesis. These results also highlight the in vivo chondrogenic potential of ASC and their potential value in cartilage repair. PMID:23638053

  2. Optimization of an oxygen-based approach for community-level physiological profiling of soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Current approaches for rapid assessment of carbon source utilization by whole soil communities (i.e., community-level physiological profiling or CLPP) provides a limited, biased view of microbial communities with little connection to in situ activities. We developed an alternative CLPP approach bas...

  3. Perioperative cerebral hemodynamics and oxygen metabolism in neonates with single-ventricle physiology

    PubMed Central

    Dehaes, Mathieu; Cheng, Henry H.; Buckley, Erin M.; Lin, Pei-Yi; Ferradal, Silvina; Williams, Kathryn; Vyas, Rutvi; Hagan, Katherine; Wigmore, Daniel; McDavitt, Erica; Soul, Janet S.; Franceschini, Maria Angela; Newburger, Jane W.; Ellen Grant, P.

    2015-01-01

    Congenital heart disease (CHD) patients are at risk for neurodevelopmental delay. The etiology of these delays is unclear, but abnormal prenatal cerebral maturation and postoperative hemodynamic instability likely play a role. A better understanding of these factors is needed to improve neurodevelopmental outcome. In this study, we used bedside frequency-domain near infrared spectroscopy (FDNIRS) and diffuse correlation spectroscopy (DCS) to assess cerebral hemodynamics and oxygen metabolism in neonates with single-ventricle (SV) CHD undergoing surgery and compared them to controls. Our goals were 1) to compare cerebral hemodynamics between unanesthetized SV and healthy neonates, and 2) to determine if FDNIRS-DCS could detect alterations in cerebral hemodynamics beyond cerebral hemoglobin oxygen saturation (SO2). Eleven SV neonates were recruited and compared to 13 controls. Preoperatively, SV patients showed decreased cerebral blood flow (CBFi), cerebral oxygen metabolism (CMRO2i) and SO2; and increased oxygen extraction fraction (OEF) compared to controls. Compared to preoperative values, unstable postoperative SV patients had decreased CMRO2i and CBFi, which returned to baseline when stable. However, SO2 showed no difference between unstable and stable states. Preoperative SV neonates are flow-limited and show signs of impaired cerebral development compared to controls. FDNIRS-DCS shows potential to improve assessment of cerebral development and postoperative hemodynamics compared to SO2 alone. PMID:26713191

  4. Influence of oxygen availability on physiology, verocytotoxin expression and adherence of Escherichia coli O157.

    PubMed

    James, B W; Keevil, C W

    1999-01-01

    A strain of Escherichia coli serotype O157 was grown in steady state chemostat culture under aerobic, oxygen-limited and anaerobic conditions. The growth and metabolic efficiency of oxygen-limited and anaerobic cultures was impaired, with biomass yield and the molar growth yield for glucose, Yglucose, reduced markedly in comparison with aerobic cultures. Steady state cells were typically short rods 2-3 microns long, and were encapsulated by a layer of extracellular material. The majority of cells were non-flagellated and fimbriae were not observed. Chemostat-grown cells were significantly more adhesive for HEp-2 monolayers than cells grown in aerobic batch culture. Furthermore, oxygen-limited and anaerobic cultures were significantly more adhesive for Hep-2 cells when compared with cells grown in aerobic chemostat culture, possibly reflecting increased pathogenicity associated with the induction of novel adhesins. Type 1 pili were not responsible for increased adherence. Verocytotoxins, VT1 and VT2, were expressed constitutively and were not influenced by oxygen availability. This study demonstrates that E. coli O157 is a versatile micro-organism, which responds to environmental conditions likely to be encountered during infection by inducing a phenotype which is more adhesive for human epithelial cells. PMID:10030015

  5. Recapitulating physiological and pathological shear stress and oxygen to model vasculature in health and disease

    NASA Astrophysics Data System (ADS)

    Abaci, Hasan Erbil; Shen, Yu-I.; Tan, Scott; Gerecht, Sharon

    2014-05-01

    Studying human vascular disease in conventional cell cultures and in animal models does not effectively mimic the complex vascular microenvironment and may not accurately predict vascular responses in humans. We utilized a microfluidic device to recapitulate both shear stress and O2 levels in health and disease, establishing a microfluidic vascular model (μVM). Maintaining human endothelial cells (ECs) in healthy-mimicking conditions resulted in conversion to a physiological phenotype namely cell elongation, reduced proliferation, lowered angiogenic gene expression and formation of actin cortical rim and continuous barrier. We next examined the responses of the healthy μVM to a vasotoxic cancer drug, 5-Fluorouracil (5-FU), in comparison with an in vivo mouse model. We found that 5-FU does not induce apoptosis rather vascular hyperpermeability, which can be alleviated by Resveratrol treatment. This effect was confirmed by in vivo findings identifying a vasoprotecting strategy by the adjunct therapy of 5-FU with Resveratrol. The μVM of ischemic disease demonstrated the transition of ECs from a quiescent to an activated state, with higher proliferation rate, upregulation of angiogenic genes, and impaired barrier integrity. The μVM offers opportunities to study and predict human ECs with physiologically relevant phenotypes in healthy, pathological and drug-treated environments.

  6. End-Tidal CO2 Tension Is Predictive of Effective Nocturnal Oxygen Therapy in Patients with Chronic Heart Failure and Central Sleep Apnea.

    PubMed

    Sugimura, Koichiro; Shinozaki, Tsuyoshi; Fukui, Shigefumi; Ogawa, Hiromasa; Shimokawa, Hiroaki

    2016-01-01

    Central sleep apnea (CSA) is characterized by recurring cycles of crescendo-decrescendo ventilation during sleep, and enhances sympathetic nerve activity. Thus CSA has a prognostic impact in patients with chronic heart failure (CHF). Although nocturnal oxygen (O2) therapy decreases frequency of CSA and improves functional exercise capacity, it is also known that some non-responders to the therapy exist. We thus aimed to identify predictors of responders to nocturnal O2 therapy in CHF patients with CSA. In 12 CHF patients with CSA hospitalized at our department, sleep study was performed at 2 consecutive nights. Patients nasally inhaled O2 at either the first or second night in a randomized manner. To predict the percentage reduction in apnea-hypopnea index (%ΔAHI) in response to the nocturnal O2 therapy, we performed multiple regression analysis with a stepwise method with variables including age, brain-natriuretic peptide, circulation time, baseline AHI, hypercapnic ventilatory response and end-tidal carbon dioxide tension (PETCO2). Nocturnal O2 therapy significantly decreased AHI (from 32 ± 13 /h to 12 ± 10 /h, P < 0.0001). Among the possible predictors, PETCO2 was the only variable that is predictive of % changes in AHI. Receiver operating characteristics analysis determined 4.25% as the optimal cutoff PETCO2 level to identify responder to nocturnal O2 therapy (> 50% reduction of AHI), with 88.9% of sensitivity and 66.7% of specificity. In conclusion, PETCO2 is useful to predict the efficacy of O2 therapy in CHF patients with CSA, providing important information to the current nocturnal O2 therapy. PMID:27169493

  7. Superiority of Transcutaneous Oxygen Tension Measurements in Predicting Limb Salvage After Below-the-Knee Angioplasty: A Prospective Trial in Diabetic Patients With Critical Limb Ischemia

    SciTech Connect

    Redlich, Ulf; Xiong, Yan Y.; Pech, Maciej; Tautenhahn, Joerg; Halloul, Zuhir; Lobmann, Ralf; Adolf, Daniela; Ricke, Jens; Dudeck, Oliver

    2011-04-15

    Purpose: To assess postprocedural angiograms, the ankle-brachial index (ABI), and transcutaneous oxygen tension (TcPO{sub 2}) to predict outcome after infrageniculate angioplasty (PTA) in diabetic patients with critical limb ischemia (CLI) scheduled for amputation. Materials and Methods: PTA was performed in 28 diabetic patients with CLI confined to infrapopliteal vessels. We recorded patency of crural vessels, including the vascular supply of the foot as well as the ABI and TcPO{sub 2} of the foot. Results: Technical success rate was 92.9% (n = 26), and limb-salvage rate at 12 months was 60.7% (n = 17). The number of patent straight vessels above and below the level of the malleoli increased significantly in patients avoiding amputation. Amputation was unnecessary in 88.2% (n = 15) patients when patency of at least one tibial artery was achieved. In 72.7% (n = 8) of patients, patency of the peroneal artery alone was not sufficient for limb salvage. ABI was of no predictive value for limb salvage. TcPO{sub 2} values increased significantly only in patients not requiring amputation (P = 0.015). In patients with only one tibial artery supplying the foot or only a patent peroneal artery in postprocedural angiograms, TcPO{sub 2} was capable of reliably predicting the outcome. Conclusion: Below-the-knee PTA as an isolated part of therapy was effective to prevent major amputation in more than a half of diabetic patients with CLI. TcPO{sub 2} was a valid predictor for limb salvage, even when angiographic outcome criteria failed.

  8. Differentiation of human adipocytes at physiological oxygen levels results in increased adiponectin secretion and isoproterenol-stimulated lipolysis

    PubMed Central

    Famulla, Susanne; Schlich, Raphaela; Sell, Henrike; Eckel, Jürgen

    2012-01-01

    Adipose tissue (AT) hypoxia occurs in obese humans and mice. Acute hypoxia in adipocytes causes dysregulation of adipokine secretion with an increase in inflammatory factors and diminished adiponectin release. O2 levels in humans range between 3 and 11% revealing that conventional in vitro culturing at ambient air and acute hypoxia treatment (1% O2) are performed under non-physiological conditions. In this study, we mimicked physiological conditions by differentiating human primary adipocytes under 10% or 5% O2 in comparison to 21% O2. Induction of differentiation markers was comparable between all three conditions. Adipokine release by adipocytes differentiated at lower oxygen levels was altered, with a marked upregulation of adiponectin, IL-6 and DPP4 secretion, and reduced leptin levels compared with adipocytes differentiated at 21% O2. Isoproterenol-induced lipolysis was significantly elevated in adipocytes differentiated at 10% and 5% compared with 21% O2. This effect was accompanied by increased protein expression of β-1 and -2 adrenergic receptor, HSL and perilipin. Conditioned medium (CM) of adipocytes differentiated at the three different conditions was generated for stimulation of human skeletal muscle cells (SkMC) or smooth muscle cells (SMC). CM-induced insulin resistance in SkMC was comparable for the different CMs. However, the SMC proliferative effect of CM from adipocytes differentiated at 10% O2 was significantly reduced compared with 21% O2. This study demonstrates that oxygen levels during adipogenesis are important factors altering adipocyte functionality such as adipokine release, in particular adiponectin secretion, as well as the hormone-induced lipolytic pathway. PMID:23700522

  9. Physiological and pathophysiological reactive oxygen species as probed by EPR spectroscopy: the underutilized research window on muscle ageing.

    PubMed

    A Abdel-Rahman, Engy; Mahmoud, Ali M; Khalifa, Abdulrahman M; Ali, Sameh S

    2016-08-15

    Reactive oxygen and nitrogen species (ROS and RNS) play crucial roles in triggering, mediating and regulating physiological and pathophysiological signal transduction pathways within the cell. Within the cell, ROS efflux is firmly controlled both spatially and temporally, making the study of ROS dynamics a challenging task. Different approaches have been developed for ROS assessment; however, many of these assays are not capable of direct identification or determination of subcellular localization of different ROS. Here we highlight electron paramagnetic resonance (EPR) spectroscopy as a powerful technique that is uniquely capable of addressing questions on ROS dynamics in different biological specimens and cellular compartments. Due to their critical importance in muscle functions and dysfunction, we discuss in some detail spin trapping of various ROS and focus on EPR detection of nitric oxide before highlighting how EPR can be utilized to probe biophysical characteristics of the environment surrounding a given stable radical. Despite the demonstrated ability of EPR spectroscopy to provide unique information on the identity, quantity, dynamics and environment of radical species, its applications in the field of muscle physiology, fatiguing and ageing are disproportionately infrequent. While reviewing the limited examples of successful EPR applications in muscle biology we conclude that the field would greatly benefit from more studies exploring ROS sources and kinetics by spin trapping, protein dynamics by site-directed spin labelling, and membrane dynamics and global redox changes by spin probing EPR approaches. PMID:26801204

  10. Metabolic physiology of the Humboldt squid, Dosidicus gigas: Implications for vertical migration in a pronounced oxygen minimum zone

    NASA Astrophysics Data System (ADS)

    Rosa, Rui; Seibel, Brad A.

    2010-07-01

    The Humboldt (or jumbo) squid, Dosidicus gigas, is an active predator endemic to the Eastern Pacific that undergoes diel vertical migrations into a pronounced oxygen minimum layer (OML). Here, we investigate the physiological mechanisms that facilitate these migrations and assess the associated costs and benefits. Exposure to hypoxic conditions equivalent to those found in the OML (∼10 μM O 2 at 10 °C) led to a significant reduction in the squid’s routine metabolic rate (RMR), from 8.9 to 1.6 μmol O 2 g -1 h -1 ( p < 0.05), and a concomitant increase in mantle muscle octopine levels (from 0.50 to 5.24 μmol g -1 tissue, p < 0.05). Enhanced glycolitic ATP production accounted for only 7.0% and 2.8% at 10 °C and 20 °C, respectively, of the energy deficit that resulted from the decline in aerobic respiration. The observed metabolic suppression presumably extends survival time in the OML by conserving the finite stores of fermentable substrate and avoiding the accumulation of the deleterious anaerobic end products in the tissues. RMR increased significantly with temperature ( p < 0.05), from 8.9 (at 10 °C) to 49.85 μmol O 2 g -1 h -1 (at 25 °C) which yielded a Q10 of 2.0 between 10 and 20 °C and 7.9 between 20 and 25 °C ( p < 0.05). These results suggest that 25 °C, although within the normal surface temperature range in the Gulf of California, is outside this species’ normal temperature range. By following the scattering layer into oxygen-enriched shallow water at night, D. gigas may repay any oxygen debt accumulated during the daytime. The dive to deeper water may minimize exposure to stressful surface temperatures when most prey have migrated to depth during the daytime. The physiological and ecological strategies demonstrated here may have facilitated the recent range expansion of this species into northern waters where expanding hypoxic zones prohibit competing top predators.

  11. Preventing and Treating Hypoxia: Using a Physiology Simulator to Demonstrate the Value of Pre-Oxygenation and the Futility of Hyperventilation

    PubMed Central

    Lerant, Anna A.; Hester, Robert L.; Coleman, Thomas G.; Phillips, William J.; Orledge, Jeffrey D.; Murray, W. Bosseau

    2015-01-01

    Introduction: Insufficient pre-oxygenation before emergency intubation, and hyperventilation after intubation are mistakes that are frequently observed in and outside the operating room, in clinical practice and in simulation exercises. Physiological parameters, as appearing on standard patient monitors, do not alert to the deleterious effects of low oxygen saturation on coronary perfusion, or that of low carbon dioxide concentrations on cerebral perfusion. We suggest the use of HumMod, a computer-based human physiology simulator, to demonstrate beneficial physiological responses to pre-oxygenation and the futility of excessive minute ventilation after intubation. Methods: We programmed HumMod, to A.) compare varying times (0-7 minutes) of pre-oxygenation on oxygen saturation (SpO2) during subsequent apnoea; B.) simulate hyperventilation after apnoea. We compared the effect of different minute ventilation rates on SpO2, acid-base status, cerebral perfusion and other haemodynamic parameters. Results: A.) With no pre-oxygenation, starting SpO2 dropped from 98% to 90% in 52 seconds with apnoea. At the other extreme, following full pre-oxygenation with 100% O2 for 3 minutes or more, the SpO2 remained 100% for 7.75 minutes during apnoea, and dropped to 90% after another 75 seconds. B.) Hyperventilation, did not result in more rapid normalization of SpO2, irrespective of the level of minute ventilation. However, hyperventilation did cause significant decreases in cerebral blood flow (CBF). Conclusions: HumMod accurately simulates the physiological responses compared to published human studies of pre-oxygenation and varying post intubation minute ventilations, and it can be used over wider ranges of parameters than available in human studies and therefore available in the literature. PMID:26283881

  12. Near-infrared spectroscopy assessed cerebral oxygenation during open abdominal aortic aneurysm repair: relation to end-tidal CO2 tension.

    PubMed

    Sørensen, H; Nielsen, H B; Secher, N H

    2016-08-01

    During open abdominal aortic aneurism (AAA) repair cerebral blood flow is challenged. Clamping of the aorta may lead to unintended hyperventilation as metabolism is reduced by perfusion of a smaller part of the body and reperfusion of the aorta releases vasodilatory substances including CO2. We intend to adjust ventilation according end-tidal CO2 tension (EtCO2) and here evaluated to what extent that strategy maintains frontal lobe oxygenation (ScO2) as determined by near infrared spectroscopy. For 44 patients [5 women, aged 70 (48-83) years] ScO2, mean arterial pressure (MAP), EtCO2, and ventilation were obtained retrospectively from the anesthetic charts. By clamping the aorta, ScO2 and EtCO2 were kept stable by reducing ventilation (median, -0.8 l min(-1); interquartile range, -1.1 to -0.4; P < 0.001). During reperfusion of the aorta a reduction in MAP by 8 mmHg (-15 to -1; P < 0.001) did not prevent an increase in ScO2 by 2 % (-1 to 4; P < 0.001) as EtCO2 increased 0.5 kPa (0.1-1.0; P < 0.001) despite an increase in ventilation by 1.8 l min(-1) (0.9-2.7; P < 0.001). Changes in ScO2 related to those in EtCO2 (r = 0.41; P = 0.0001) and cerebral deoxygenation (-15 %) was noted in three patients while cerebral hyperoxygenation (+15 %) manifests in one patient. Thus changes in ScO2 were kept within acceptable limits (±15 %) in 91 % of the patients. For the majority of the patients undergoing AAA repair ScO2 was kept within reasonable limits by reducing ventilation by approximately 1 l min(-1) upon clamping of the aorta and increasing ventilation by approximately 2 l min(-1) when the lower body is reperfused. PMID:26141676

  13. Surface Tension

    SciTech Connect

    2011-01-01

    Surface tension in the kitchen sink. At Berkeley Lab's Molecular Foundry, scientists study surface tension to understand how molecules "self-assemble." The coin trick in the video uses the re-arrangement of water molecules to seemingly create order out of disorder. The same principle can be used to create order in otherwise hard-to-handle nano materials. Scientists can then transfer these ordered materials onto surfaces by dipping them through the air-water interface, or (as we've recently shown) squeeze them so that they collapse into the water as two-molecule-thick nano sheets. http://newscenter.lbl.gov/feature-stories/2011/10/17/shaken-not-stirred/

  14. Functional Oxygen Sensitivity of Astrocytes

    PubMed Central

    Angelova, Plamena R.; Kasymov, Vitaliy; Christie, Isabel; Sheikhbahaei, Shahriar; Turovsky, Egor; Marina, Nephtali; Korsak, Alla; Zwicker, Jennifer; Teschemacher, Anja G.; Ackland, Gareth L.; Funk, Gregory D.; Kasparov, Sergey; Abramov, Andrey Y.

    2015-01-01

    In terrestrial mammals, the oxygen storage capacity of the CNS is limited, and neuronal function is rapidly impaired if oxygen supply is interrupted even for a short period of time. However, oxygen tension monitored by the peripheral (arterial) chemoreceptors is not sensitive to regional CNS differences in partial pressure of oxygen (PO2) that reflect variable levels of neuronal activity or local tissue hypoxia, pointing to the necessity of a functional brain oxygen sensor. This experimental animal (rats and mice) study shows that astrocytes, the most numerous brain glial cells, are sensitive to physiological changes in PO2. Astrocytes respond to decreases in PO2 a few millimeters of mercury below normal brain oxygenation with elevations in intracellular calcium ([Ca2+]i). The hypoxia sensor of astrocytes resides in the mitochondria in which oxygen is consumed. Physiological decrease in PO2 inhibits astroglial mitochondrial respiration, leading to mitochondrial depolarization, production of free radicals, lipid peroxidation, activation of phospholipase C, IP3 receptors, and release of Ca2+ from the intracellular stores. Hypoxia-induced [Ca2+]i increases in astrocytes trigger fusion of vesicular compartments containing ATP. Blockade of astrocytic signaling by overexpression of ATP-degrading enzymes or targeted astrocyte-specific expression of tetanus toxin light chain (to interfere with vesicular release mechanisms) within the brainstem respiratory rhythm-generating circuits reveals the fundamental physiological role of astroglial oxygen sensitivity; in low-oxygen conditions (environmental hypoxia), this mechanism increases breathing activity even in the absence of peripheral chemoreceptor oxygen sensing. These results demonstrate that astrocytes are functionally specialized CNS oxygen sensors tuned for rapid detection of physiological changes in brain oxygenation. SIGNIFICANCE STATEMENT Most, if not all, animal cells possess mechanisms that allow them to detect

  15. Functional Oxygen Sensitivity of Astrocytes.

    PubMed

    Angelova, Plamena R; Kasymov, Vitaliy; Christie, Isabel; Sheikhbahaei, Shahriar; Turovsky, Egor; Marina, Nephtali; Korsak, Alla; Zwicker, Jennifer; Teschemacher, Anja G; Ackland, Gareth L; Funk, Gregory D; Kasparov, Sergey; Abramov, Andrey Y; Gourine, Alexander V

    2015-07-22

    In terrestrial mammals, the oxygen storage capacity of the CNS is limited, and neuronal function is rapidly impaired if oxygen supply is interrupted even for a short period of time. However, oxygen tension monitored by the peripheral (arterial) chemoreceptors is not sensitive to regional CNS differences in partial pressure of oxygen (PO2 ) that reflect variable levels of neuronal activity or local tissue hypoxia, pointing to the necessity of a functional brain oxygen sensor. This experimental animal (rats and mice) study shows that astrocytes, the most numerous brain glial cells, are sensitive to physiological changes in PO2 . Astrocytes respond to decreases in PO2 a few millimeters of mercury below normal brain oxygenation with elevations in intracellular calcium ([Ca(2+)]i). The hypoxia sensor of astrocytes resides in the mitochondria in which oxygen is consumed. Physiological decrease in PO2 inhibits astroglial mitochondrial respiration, leading to mitochondrial depolarization, production of free radicals, lipid peroxidation, activation of phospholipase C, IP3 receptors, and release of Ca(2+) from the intracellular stores. Hypoxia-induced [Ca(2+)]i increases in astrocytes trigger fusion of vesicular compartments containing ATP. Blockade of astrocytic signaling by overexpression of ATP-degrading enzymes or targeted astrocyte-specific expression of tetanus toxin light chain (to interfere with vesicular release mechanisms) within the brainstem respiratory rhythm-generating circuits reveals the fundamental physiological role of astroglial oxygen sensitivity; in low-oxygen conditions (environmental hypoxia), this mechanism increases breathing activity even in the absence of peripheral chemoreceptor oxygen sensing. These results demonstrate that astrocytes are functionally specialized CNS oxygen sensors tuned for rapid detection of physiological changes in brain oxygenation. Significance statement: Most, if not all, animal cells possess mechanisms that allow them to

  16. Physiological energetics of the fourth instar of Chinese horseshoe crabs (Tachypleus tridentatus) in response to hypoxic stress and re-oxygenation.

    PubMed

    Shin, Paul K S; Chan, Cathy S K; Cheung, S G

    2014-08-30

    Hypoxia associated with eutrophication is a potential threat to the Chinese horseshoe crab Tachypleus tridentatus which inhabits intertidal sand flats in Asia. This study investigated the effect of dissolved oxygen level (DO) (6, 4 and 2 mg O2 l(-1)) on the physiological energetics in the juvenile T. tridentatus. They were exposed to various oxygen levels for three days and then transferred to normoxia for three days to examine the recovery from low oxygen stress. Feeding rate, respiration rate and scope for growth were reduced at lower DO levels while absorption efficiency and excretion rate were independent of DO levels. Although full recovery of the physiological responses and scope for growth from hypoxis stress was observed when normoxia resumed, their long term survival in suboptimal habitats with frequent occurrence of hypoxia deserves a close monitoring as hypoxia may be even more common in future in a warming world. PMID:24215995

  17. Physiological and clinical aspects of apnea diving.

    PubMed

    Muth, Claus-Martin; Ehrmann, Ulrich; Radermacher, Peter

    2005-09-01

    Apnea diving is a fascinating example of applied physiology. The record for apnea diving as an extreme sport is 171 meters, 8:58 minutes. The short time beneath the surface induces profound cardiovascular and respiratory effects. Variations of blood-gas tensions result from the interaction of metabolism and the rapid sequence of compression and decompression. Decompression sickness is possible. Apnea divers can reach depths beyond the theoretic physiologic limit by using the lung-packing maneuver. Apnea divers exhibit a fall in heart rate, which can be trained and is an oxygen-conserving effect, but increases the incidence of ventricular arrhythmia. PMID:16140133

  18. The Reactivity of Polymersome Encapsulated Hemoglobin with Physiologically Important Gaseous Ligands: Oxygen, Carbon Monoxide and Nitric Oxide.

    PubMed

    Rameez, Shahid; Banerjee, Uddyalok; Fontes, Jorge; Roth, Alexander; Palmer, Andre F

    2012-03-13

    Two distinct preparations of amphiphilic diblock copolymer vesicles (i.e. polymersomes), composed of (poly(ethylene oxide)-poly(butadiene)) (PEO-PBD), with molecular weights of 1.8 kDa and 10.4 kDa, offering different hydrophobic membrane thicknesses, were used to encapsulate the oxygen (O(2)) storage and transport protein hemoglobin (Hb) for possible application as a red blood cell (RBC) substitute. Key biophysical properties as well as the kinetics of polymersome encapsulated Hb (PEH) interaction with physiologically important gaseous ligands (O(2), carbon monoxide and nitric oxide) were measured as a function of the hydrophobic membrane thickness of the PEH particle. Taken together, the results of this work show that PEHs exhibit biophysical properties and retarded ligand binding/release kinetics (compared to cell-free Hb), which are similar to the behavior of RBCs. Therefore, PEHs have the potential to serve as safe and efficacious RBC substitutes for use in transfusion medicine. PMID:22865934

  19. Effect of dissolved oxygen on swimming ability and physiological response to swimming fatigue of whiteleg shrimp (Litopenaeus vannamei)

    NASA Astrophysics Data System (ADS)

    Duan, Yan; Zhang, Xiumei; Liu, Xuxu; Thakur, Dhanrajsingh N.

    2013-11-01

    The swimming endurance of whiteleg shrimp (Litopenaeus vannamei, 87.66 mm ± 0.25 mm, 7.73 g ± 0.06 g) was examined at various concentrations of dissolved oxygen (DO, 1.9, 3.8, 6.8 and 13.6 mg L-1) in a swimming channel against one of the five flow velocities (v 1, v 2, v 3, v 4 and v 5). Metabolite contents in the plasma, hepatopancreas and pleopods muscle of the shrimp were quantified before and after swimming fatigue. The results revealed that the swimming speed and DO concentration were significant factors that affected the swimming endurance of L. vannamei. The relationship between swimming endurance and swimming speed at various DO concentrations can be described by the power model (ν·t b = a). The relationship between DO concentration (mg L-1) and the swimming ability index (SAI), defined as SAI = Σ{0/9000} vdt(cm), can be described as SAI = 27.947 DO0.137 (R 2 = 0.9312). The level of DO concentration directly affected the physiology of shrimp, and exposure to low concentrations of DO led to the increases in lactate and energetic substrate content in the shrimp. In responding to the low DO concentration at 1.9 mg L-1 and the swimming stress, L. vannamei exhibited a mix of aerobic and anaerobic metabolism to satisfy the energetic demand, mainly characterized by the utilization of total protein and glycogen and the production of lactate and glucose. Fatigue from swimming led to severe loss of plasma triglyceride at v 1, v 2, and v 3 with 1.9 mg L-1 DO, and at v 1 with 3.8, 6.8 and 13.6 mg L-1 DO, whereas the plasma glucose content increased significantly at v 3, v 4 and v 5 with 3.8 and 6.8 mg L-1 DO, and at v 5 with 13.6 mg L-1 DO. The plasma total protein and hepatopancreas glycogen were highly depleted in shrimp by swimming fatigue at various DO concentrations, whereas the plasma lactate accumulated at high levels after swimming fatigue at different velocities. These results were of particular value to understanding the locomotory ability of whiteleg

  20. Tension Structure

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The fabric structure pictured is the Campus Center of La Verne College, La Verne, California. Unlike the facilities shown on the preceding pages, it is not air-supported. It is a "tension structure," its multi-coned fabric membrane supported by a network of cables attached to steel columns which function like circus tent poles. The spider-web in the accompanying photo is a computer graph of the tension pattern. The designers, Geiger-Berger Associates PC, of New York City, conducted lengthy computer analysis to determine the the best placement of columns and cables. The firm also served as structural engineering consultant on the Pontiac Silverdome and a number of other large fabric structures. Built by Birdair Structures, Inc., Buffalo, New York, the La Verne Campus Center was the first permanent facility in the United States enclosed by the space-spinoff fabric made of Owens-Corning Beta fiber glass coated with Du Pont Teflon TFE. The flexible design permits rearrangement of the interior to accommodate athletic events, student activities, theatrical productions and other recreational programs. Use of fabric covering reduced building cost 30 percent below conventional construction.

  1. Enhanced reactive oxygen species scavenging by overproduction of superoxide dismutase and catalase delays postharvest physiological deterioration of cassava storage roots.

    PubMed

    Xu, Jia; Duan, Xiaoguang; Yang, Jun; Beeching, John R; Zhang, Peng

    2013-03-01

    Postharvest physiological deterioration (PPD) of cassava (Manihot esculenta) storage roots is the result of a rapid oxidative burst, which leads to discoloration of the vascular tissues due to the oxidation of phenolic compounds. In this study, coexpression of the reactive oxygen species (ROS)-scavenging enzymes copper/zinc superoxide dismutase (MeCu/ZnSOD) and catalase (MeCAT1) in transgenic cassava was used to explore the intrinsic relationship between ROS scavenging and PPD occurrence. Transgenic cassava plants integrated with the expression cassette p54::MeCu/ZnSOD-35S::MeCAT1 were confirmed by Southern-blot analysis. The expression of MeCu/ZnSOD and MeCAT1 was verified by quantitative reverse transcription-polymerase chain reaction and enzymatic activity analysis both in the leaves and storage roots. Under exposure to the ROS-generating reagent methyl viologen or to hydrogen peroxide (H2O2), the transgenic plants showed higher enzymatic activities of SOD and CAT than the wild-type plants. Levels of malondialdehyde, chlorophyll degradation, lipid peroxidation, and H2O2 accumulation were dramatically reduced in the transgenic lines compared with the wild type. After harvest, the storage roots of transgenic cassava lines show a delay in their PPD response of at least 10 d, accompanied by less mitochondrial oxidation and H2O2 accumulation, compared with those of the wild type. We hypothesize that this is due to the combined ectopic expression of Cu/ZnSOD and CAT leading to an improved synergistic ROS-scavenging capacity of the roots. Our study not only sheds light on the mechanism of the PPD process but also develops an effective approach for delaying the occurrence of PPD in cassava. PMID:23344905

  2. The effects of cosmic Particle radiation on pocket mice aboard Apollo XVII: V. Preflight studies on tolerance of pocket mice to oxygen and heat. Part I. physiological studies.

    PubMed

    Leon, H A; Suri, K; McTigue, M; Smith, J; Cooper, W; Miquel, J; Ashley, W W; Behnke, A R; Saunders, J F

    1975-04-01

    Tests were carried out on pocket mice to ascertain their tolerance to elevated oxygen pressures alone and to a combination of hyperoxta and heat in excess of that expected during the flight of the mice on Apollo XVII. the mice withstood oxygen partial pressures up to 12 pst at normal room temperature (24 degrees C, 75 degrees F) over a period of 7 days. A few mice previously exposed to increased PO2 died in the course of exposure to an oxygen pressure of 10 pst or 12 psi (517 mm or 620 mm Hg) for 13 d in ambient heat of 32 degrees C (90 degrees F). Supplemental vitamin E and physiological saline loading given prior to exposure had no apparent protective effect. The overall conclusion was that the pocket mice which were to go on Apollo XVII could readily survive the ambient atmosphere to which they would be exposed. PMID:1156267

  3. Physiological roles of the light, oxygen, or voltage domains of phototropin 1 and phototropin 2 in Arabidopsis.

    PubMed

    Cho, Hae-Young; Tseng, Tong-Seung; Kaiserli, Eirini; Sullivan, Stuart; Christie, John M; Briggs, Winslow R

    2007-01-01

    Phototropins (phot1 and phot2) are plant blue-light receptors that mediate phototropism, chloroplast movement, stomatal opening, rapid inhibition of growth of etiolated seedlings, and leaf expansion in Arabidopsis (Arabidopsis thaliana). Their N-terminal region contains two light, oxygen, or voltage (LOV) domains, which bind flavin mononucleotide and form a covalent adduct between a conserved cysteine and the flavin mononucleotide chromophore upon photoexcitation. The C-terminal region contains a serine/threonine kinase domain that catalyzes blue-light-activated autophosphorylation. Here, we have transformed the phot1 phot2 (phot1-5 phot2-1) double mutant with PHOT expression constructs driven by the cauliflower mosaic virus 35S promoter. These constructs encode either wild-type phototropin or phototropin with one or both LOV-domain cysteines mutated to block their photochemistry. We selected multiple lines in each of the eight resulting categories of transformants for further physiological analyses. Specifically, we investigated whether LOV1 and LOV2 serve the same or different functions for phototropism and leaf expansion. Our results show that the LOV2 domain of phot1 plays a major role in phototropism and leaf expansion, as does the LOV2 domain of phot2. No complementation of phototropism or leaf expansion was observed for the LOV1 domain of phot1. However, phot2 LOV1 was unexpectedly found to complement phototropism to a considerable level. Similarly, transformants carrying a PHOT transgene with both LOV domains inactivated developed strong curvatures toward high fluence rate blue light. However, we found that the phot2-1 mutant is leaky and produces a small level of full-length phot2 protein. In vitro experiments indicate that cross phosphorylation can occur between functional phot2 and inactivated phot1 molecules. Such a mechanism may occur in vivo and therefore account for the functional activities observed in the PHOT transgenics with both lov domains

  4. Continuous measurement of oxygen tensions in the air-breathing organ of Pacific tarpon (Megalops cyprinoides) in relation to aquatic hypoxia and exercise.

    PubMed

    Seymour, Roger S; Farrell, Anthony P; Christian, Keith; Clark, Timothy D; Bennett, Michael B; Wells, Rufus M G; Baldwin, John

    2007-07-01

    The Pacific tarpon is an elopomorph teleost fish with an air-breathing organ (ABO) derived from a physostomous gas bladder. Oxygen partial pressure (PO(2)) in the ABO was measured on juveniles (238 g) with fiber-optic sensors during exposure to selected aquatic PO(2) and swimming speeds. At slow speed (0.65 BL s(-1)), progressive aquatic hypoxia triggered the first breath at a mean PO(2) of 8.3 kPa. Below this, opercular movements declined sharply and visibly ceased in most fish below 6 kPa. At aquatic PO(2) of 6.1 kPa and swimming slowly, mean air-breathing frequency was 0.73 min(-1), ABO PO(2) was 10.9 kPa, breath volume was 23.8 ml kg(-1), rate of oxygen uptake from the ABO was 1.19 ml kg(-1) min(-1), and oxygen uptake per breath was 2.32 ml kg(-1). At the fastest experimental speed (2.4 BL s(-1)) at 6.1 kPa, ABO oxygen uptake increased to about 1.90 ml kg(-1) min(-1), through a variable combination of breathing frequency and oxygen uptake per breath. In normoxic water, tarpon rarely breathed air and apparently closed down ABO perfusion, indicated by a drop in ABO oxygen uptake rate to about 1% of that in hypoxic water. This occurred at a wide range of ABO PO(2) (1.7-26.4 kPa), suggesting that oxygen level in the ABO was not regulated by intrinsic receptors. PMID:17387483

  5. Limiting factors to oxygen transport on Mount Everest 30 years after: a critique of Paolo Cerretelli's contribution to the study of altitude physiology.

    PubMed

    Ferretti, Guido

    2003-10-01

    In 1976, Paolo Cerretelli published an article entitled "Limiting factors to oxygen transport on Mount Everest" in the Journal of Applied Physiology. The paper demonstrated the role of cardiovascular oxygen transport in limiting maximal oxygen consumption (VO2max). In agreement with the predominant view of VO2max limitation at that time, however, its results were taken to mean that cardiovascular oxygen transport does not limit VO2max at altitude. So it was argued that the limiting factor could be in the periphery, and muscle blood flow was proposed as a possible candidate. Despite this suggestion, the conclusion generated a series of papers on muscle structural characteristics. These experiments demonstrated a loss of muscle oxidative capacity in chronic hypoxia, and thus provided an unambiguous refutation of the then widespread hypothesis that an increased muscle oxidative capacity is needed at altitude to compensate for the lack of oxygen. This analysis is followed by a short account of Cerretelli's more recent work, with a special attention to the subject of the so-called "lactate paradox". PMID:14530980

  6. Low-oxygen tensions found in Salmonella-infected gut tissue boost Salmonella replication in macrophages by impairing antimicrobial activity and augmenting Salmonella virulence.

    PubMed

    Jennewein, Jonas; Matuszak, Jasmin; Walter, Steffi; Felmy, Boas; Gendera, Kathrin; Schatz, Valentin; Nowottny, Monika; Liebsch, Gregor; Hensel, Michael; Hardt, Wolf-Dietrich; Gerlach, Roman G; Jantsch, Jonathan

    2015-12-01

    In Salmonella infection, the Salmonella pathogenicity island-2 (SPI-2)-encoded type three secretion system (T3SS2) is of key importance for systemic disease and survival in host cells. For instance, in the streptomycin-pretreated mouse model SPI-2-dependent Salmonella replication in lamina propria CD11c(-)CXCR1(-) monocytic phagocytes/macrophages (MΦ) is required for the development of colitis. In addition, containment of intracellular Salmonella in the gut critically depends on the antimicrobial effects of the phagocyte NADPH oxidase (PHOX), and possibly type 2 nitric oxide synthase (NOS2). For both antimicrobial enzyme complexes, oxygen is an essential substrate. However, the amount of available oxygen upon enteroinvasive Salmonella infection in the gut tissue and its impact on Salmonella-MΦ interactions was unknown. Therefore, we measured the gut tissue oxygen levels in a model of Salmonella enterocolitis using luminescence two-dimensional in vivo oxygen imaging. We found that gut tissue oxygen levels dropped from ∼78 Torr (∼11% O2) to values of ∼16 Torr (∼2% O2) during infection. Because in vivo virulence of Salmonella depends on the Salmonella survival in MΦ, Salmonella-MΦ interaction was analysed under such low oxygen values. These experiments revealed an increased intracellular replication and survival of wild-type and t3ss2 non-expressing Salmonella. These findings were paralleled by blunted nitric oxide and reactive oxygen species (ROS) production and reduced Salmonella ROS perception. In addition, hypoxia enhanced SPI-2 transcription and translocation of SPI-2-encoded virulence protein. Neither pharmacological blockade of PHOX and NOS2 nor impairment of T3SS2 virulence function alone mimicked the effect of hypoxia on Salmonella replication under normoxic conditions. However, if t3ss2 non-expressing Salmonella were used, hypoxia did not further enhance Salmonella recovery in a PHOX and NOS2-deficient situation. Hence, these data suggest that

  7. Growth and physiological responses of neotropical mangrove seedlings to root zone hypoxia.

    PubMed

    McKee, Karen L.

    1996-01-01

    Seedlings of Rhizophora mangle L., Avicennia germinans (L.) Stearn., and Laguncularia racemosa (L.) Gaertn. f. were cultured in aerated or N(2)-purged solution for 12 weeks to assess their relative responses to low oxygen tensions. All three species responded to low oxygen treatment by modifying physiological and morphological patterns to decrease carbon loss by root respiration. However, the extent to which seedling physiology and morphology were altered by low oxygen treatment differed among species. Maintenance of root oxygen concentrations, root respiration rates and root extension rates by R. mangle demonstrated an ability to avoid low oxygen stress with minimal changes in root morphology and physiology. In contrast, oxygen concentrations in A. germinans and L. racemosa roots declined from 16 to 5% or lower within 6 h of treatment. Root hypoxia led to significant decreases in respiration rates of intact root systems (31 and 53% below controls) and root extension rates (38 and 76% below controls) by A. germinans and L. racemosa, respectively, indicating a greater vulnerability of these species to low oxygen tensions in the root zone compared with R. mangle. I conclude that the relative performance of mangrove seedlings growing in anaerobic soils is influenced by interspecific differences in root aeration and concomitant effects on root morphology and physiology. PMID:14871780

  8. Physiologic effects of transfusing red blood cells with high or low affinity for oxygen to passively hyperventilated, anemic baboons: systemic and cerebral oxygen extraction.

    PubMed Central

    Valeri, C R; Rorth, M; Zaroulis, C G; Jakubowski, M S; Vescera, S V

    1975-01-01

    Anemic, passively hyperventilated baboons were given preserved red blood cells either with increased or with slightly reduced affinity for oxygen to restore the red cell volume. In the high affinity group there was a 50% increase in cerebral blood flow immediately after the transfusion, but there was no significant change in the low affinity group. The cardiac output decreased slightly in the low affinity group, and increased slightly but insignificantly in the high affinity group. Two hours after transfusion the cerebral blood flow had returned to normal in the high affinity group. In both groups there was a decrease in arterial blood pH and an increase in Po2 in blood from the pulmonary artery and the jugular vein after transfusion. A 40% restoration of the 2,3 DPG level occurred within 4 hours of the transfusion of red cells with high affinity for oxygen, and this rapid increase was associated with increases in blood pH and inorganic phosphorus levels. Preserved red cells with high affinity for oxygen and low 2, 3 DPG levels significantly increased the cerebral circulation during the 2-hour posttransfusion period. These findings lend support to the recommendation that preserved red cells with normal or elevated 2,3 DPG levels be administered to patients in hemorrhagic or septic shock, and to patients subjected to extracorporeal circulation during cardiac surgery in order to lessen the demand for increased blood flow and to ensure adequate tissue oxygenation during the postoperative period. PMID:1119857

  9. Micro-scale morphology and texture of biogenic iron oxide mats provide a physical record of microbial physiology and oxygen conditions

    NASA Astrophysics Data System (ADS)

    Krepski, S. T.; Hredzak-showalter, T.; Luther, G. W.; Chan, C. S.

    2011-12-01

    The ability of certain bacteria to deposit Fe oxide minerals has long been recognized. However, we are only beginning to gain greater insights into the physiology and mechanisms of microbial Fe(II) oxidation and biomineralization, due to a small but growing number of isolates and studies on Fe(II)-oxidizing bacteria (FeOB). We recently isolated a novel microaerophilic FeOB, Betaproteobacterium Gallionellales strain R-1 (Genbank accession number JN377592) from a freshwater Fe seep in Newark, Delaware, USA. Much like Gallionella ferruginea (93.6% 16S gene sequence similarity), this organism is a bean-shaped cell that forms mineralized extracellular Fe twisted stalks. Strain R-1 shows remarkable physiologic and morphological similarity to the marine Zetaproteobacterium FeOB Mariprofundus ferrooxydans, despite being distantly related. We use M. ferrooxydans and strain R-1 as model organisms to study microbial Fe biomineralization and link the formation of microbial Fe oxide mats to environmental conditions and FeOB physiology. To accomplish this, we construct flat glass microslide growth chambers, used in conjunction with solid-state voltammetric microelectrodes to measure the chemistry of FeOB microenvironments in situ while studying undisturbed microbial growth, motility, and mineral formation. The development of microbial Fe oxide bands (analogs of mats) begins when cells attach to a surface and deposit minerals. In low-oxygen zones of redox gradients, formed in part by microbial respiration, the bacteria converge into a narrow, mineralized growth band. Filaments orient directionally, as quantified with ArcGIS, towards increasing oxygen, and display uniquely biological characteristics such as branching and a narrow range of widths. Thus, the mineralized structures provide a physical record of FeOB physiology. Observations of putative filamentous Fe microfossils in thin section show that these characteristics can be preserved in the geologic record, even if some

  10. The effect of oxygen at physiological levels on the detection of free radical intermediates by electron paramagnetic resonance.

    PubMed

    Krishna, M C; Samuni, A

    1993-01-01

    It is well known that oxygen enhances the relaxation of free radical EPR probes through spin lattice and Heisenberg spin-spin interactions with consequent effect on the line height and width. The two relaxation processes have opposing effects on the signal heights and depend on the concentration of oxygen, the incident microwave power, and the presence of other paramagnetic species. During EPR studies of chemical, biochemical, and cellular processes involving free radicals, molecular oxygen has significant magnetic influence on the EPR signal intensity of the free radical species under investigation in addition to affecting the rates of production of the primary species and the stability of the spin adduct nitroxides. These effects are often overlooked and can cause artifacts and lead to erroneous interpretation. In the present study, the effects of oxygen and ferricyanide on the EPR signal height of stable and persistent spin adduct nitroxides at commonly employed microwave powers were examined. The results show that under commonly adopted EPR spectrometer instrumental conditions, artifactual changes in the EPR signal of spin adducts occur and the best way to avoid them is by keeping the oxygen level constant using a gas-permeable cell. PMID:8396553

  11. Oxygen Modulates Human Decidual Natural Killer Cell Surface Receptor Expression and Interactions with Trophoblasts1

    PubMed Central

    Wallace, Alison E.; Goulwara, Sonu S.; Whitley, Guy S.; Cartwright, Judith E.

    2014-01-01

    Decidual natural killer (dNK) cells have been shown to both promote and inhibit trophoblast behavior important for decidual remodeling in pregnancy and have a distinct phenotype compared to peripheral blood NK cells. We investigated whether different levels of oxygen tension, mimicking the physiological conditions of the decidua in early pregnancy, altered cell surface receptor expression and activity of dNK cells and their interactions with trophoblast. dNK cells were isolated from terminated first-trimester pregnancies and cultured in oxygen tensions of 3%, 10%, and 21% for 24 h. Cell surface receptor expression was examined by flow cytometry, and the effects of secreted factors in conditioned medium (CM) on the trophoblast cell line SGHPL-4 were assessed in vitro. SGHPL-4 cells treated with dNK cell CM incubated in oxygen tensions of 10% were significantly more invasive (P < 0.05) and formed endothelial-like networks to a greater extent (P < 0.05) than SGHPL-4 cells treated with dNK cell CM incubated in oxygen tensions of 3% or 21%. After 24 h, a lower percentage of dNK cells expressed CD56 at 21% oxygen (P < 0.05), and an increased percentage of dNK cells expressed NKG2D at 10% oxygen (P < 0.05) compared to other oxygen tensions, with large patient variation. This study demonstrates dNK cell phenotype and secreted factors are modulated by oxygen tension, which induces changes in trophoblast invasion and endovascular-like differentiation. Alterations in dNK cell surface receptor expression and secreted factors at different oxygen tensions may represent regulation of function within the decidua during the first trimester of pregnancy. PMID:25232021

  12. The influence of different space-related physiological variations on exercise capacity determined by oxygen uptake kinetics

    NASA Astrophysics Data System (ADS)

    Stegemann, J.

    Oxygen uptake kinetics, following defined variations of work load changes allow to estimate the contribution of aerob and anaerob energy supply which is the base for determining work capacity. Under the aspect of long duration missions with application of adequate dosed countermeasures, a reliable estimate of the astronaut's work capacity is important to adjust the necessary inflight training. Since the kinetics of oxygen uptake originate in the working muscle group itself, while measurements are performed at the mouth, various influences within the oxygen transport system might disturb the determinations. There are not only detraining effects but also well-known other influences, such as blood- and fluid shifts induced by weightlessness. They might have an impact on the circulatory system. Some of these factors have been simulated by immersion, blood donation, and changing of the body position.

  13. A physiological pattern of oxygenation using perfluorocarbon-based culture devices maximizes pancreatic islet viability and enhances β-cell function.

    PubMed

    Fraker, Chris A; Cechin, Sirlene; Álvarez-Cubela, Silvia; Echeverri, Felipe; Bernal, Andrés; Poo, Ramón; Ricordi, Camillo; Inverardi, Luca; Domínguez-Bendala, Juan

    2013-01-01

    Conventional culture vessels are not designed for physiological oxygen (O2) delivery. Both hyperoxia and hypoxia-commonly observed when culturing cells in regular plasticware-have been linked to reduced cellular function and death. Pancreatic islets, used for the clinical treatment of diabetes, are especially sensitive to sub- and supraphysiological O2 concentrations. A result of current culture standards is that a high percentage of islet preparations are never transplanted because of cell death and loss of function in the 24-48 h postisolation. Here, we describe a new culture system designed to provide quasiphysiological oxygenation to islets in culture. The use of dishes where islets rest atop a perfluorocarbon (PFC)-based membrane, coupled with a careful adjustment of environmental O2 concentration to target the islet physiological pO2 range, resulted in dramatic gains in viability and function. These observations underline the importance of approximating culture conditions as closely as possible to those of the native microenvironment, and fill a widely acknowledged gap in our ability to preserve islet functionality in vitro. As stem cell-derived insulin-producing cells are likely to suffer from the same limitations as those observed in real islets, our findings are especially timely in the context of current efforts to define renewable sources for transplantation. PMID:23068091

  14. Development to the blastocyst stage, the oxidative state, and the quality of early developmental stage of porcine embryos cultured in alteration of glucose concentrations in vitro under different oxygen tensions

    PubMed Central

    Karja, Ni Wayan Kurniani; Kikuchi, Kazuhiro; Fahrudin, Mokhamad; Ozawa, Manabu; Somfai, Tamás; Ohnuma, Katsuhiko; Noguchi, Junko; Kaneko, Hiroyuki; Nagai, Takashi

    2006-01-01

    Background Recent work has shown that glucose may induce cell injury through the action of free radicals generated by autooxidation or through hypoxanthine phosphoribosyltransferase inhibition. The effect of glucose during early in vitro culture (IVC) period of porcine embryos on their developmental competence, contents of reactive oxygen species (ROS) and glutathione (GSH), and the quality of the blastocysts yielded was examined. Methods In vitro matured and fertilized porcine oocytes were cultured for the first 2 days (Day 0 = day of fertilization) of IVC in NCSU-37 added with 1.5 to 20 mM glucose (Gluc-1.5 to -20 groups) or pyruvate and lactate (Pyr-Lac group). The embryos in all groups were cultured subsequently until Day 6 in NCSU-37 with 5.5 mM added glucose. The ROS and GSH level were measured at Day 1 and 2. DNA-fragmented nuclei and the total cell numbers in blastocyst were evaluated by TUNEL-staining at Day 6. Results Under 5% oxygen the blastocyst rates and total cell numbers in the blastocysts in all glucose groups were significantly lower than that in the Pyr-Lac group. Similar result in blastocyst rate was found under 20% oxygen (excluding the Gluc-10 group), but total cell numbers in the blastocysts was similar among the groups. At both oxygen tensions, the H2O2 levels of Day 1 embryos in all glucose groups were significantly higher than that in the Pyr-Lac group, while only the Gluc-1.5 group of Day 2 embryos showed a significantly higher H2O2 level than that in the Pyr-Lac group. The GSH contents of either Day 1 or Day 2 embryos developed under 5% oxygen were similar among the groups. Only the content of Day 2 embryos in 1.5 mM group was significantly lower than the embryos in the Pyr-Lac group under 20% oxygen. Total cell numbers in the blastocysts (except in the Gluc-20 group) were significantly lower in the embryos cultured under 20% oxygen than 5% oxygen. Only the Gluc-20 blastocysts developed under 5% oxygen showed significantly higher DNA

  15. Intra-Operative Tissue Oxygen Tension Is Increased by Local Insufflation of Humidified-Warm CO2 during Open Abdominal Surgery in a Rat Model

    PubMed Central

    Marshall, Jean K.; Lindner, Pernilla; Tait, Noel; Maddocks, Tracy; Riepsamen, Angelique; van der Linden, Jan

    2015-01-01

    Introduction Maintenance of high tissue oxygenation (PtO2) is recommended during surgery because PtO2 is highly predictive of surgical site infection and colonic anastomotic leakage. However, surgical site perfusion is often sub-optimal, creating an obstructive hurdle for traditional, systemically applied therapies to maintain or increase surgical site PtO2. This research tested the hypothesis that insufflation of humidified-warm CO2 into the abdominal cavity would increase sub-peritoneal PtO2 during open abdominal surgery. Materials and Methods 15 Wistar rats underwent laparotomy under general anesthesia. Three sets of randomized cross-over experiments were conducted in which the abdominal cavity was subjected to alternating exposure to 1) humidified-warm CO2 & ambient air; 2) humidified-warm CO2 & dry-cold CO2; and 3) dry-cold CO2 & ambient air. Sub-peritoneal PtO2 and tissue temperature were measured with a polarographic oxygen probe. Results Upon insufflation of humidified-warm CO2, PtO2 increased by 29.8 mmHg (SD 13.3; p<0.001), or 96.6% (SD 51.9), and tissue temperature by 3.0°C (SD 1.7 p<0.001), in comparison with exposure to ambient air. Smaller, but significant, increases in PtO2 were seen in experiments 2 and 3. Tissue temperature decreased upon exposure to dry-cold CO2 compared with ambient air (-1.4°C, SD 0.5, p = 0.001). Conclusions In a rat model, insufflation of humidified-warm CO2 into the abdominal cavity during open abdominal surgery causes an immediate and potentially clinically significant increase in PtO2. The effect is an additive result of the delivery of CO2 and avoidance of evaporative cooling via the delivery of the CO2 gas humidified at body temperature. PMID:25835954

  16. Alterations of oxygen uptake and the redox state of ubiquinone in rabbit sperm exposed to a variety of physiologic treatments.

    PubMed

    Killian, G J; Gelerinter, E; Chapman, D A

    1985-11-01

    The rate of TEMPONE reduction by electrons originating from ubiquinone in intact rabbit spermatozoa was observed for control, high ionic strength (HIS) medium-treated, and HIS-seminal plasma-treated (HIS-SP) samples. The presence of TEMPONE in the incubation medium had no effect on oxygen consumption, demonstrating the utility of TEMPONE as a nonperturbing probe of the ubiquinol redox state. The rate of TEMPONE reduction was significantly increased over control levels for sperm incubated in hypertonic medium and was correlated to a decrease in oxygen consumption and a relative increase in ATP in the total adenine nucleotide pool. This increase in TEMPONE reduction in HIS sperm was reversed by treatment of sperm with seminal plasma, but seminal plasma had no effect on oxygen consumption or relative amounts of ATP in the adenine nucleotide pool. These observations are consistent with state 3 respiration in control sperm and state 4 respiration in HIS- and HIS-SP-treated sperm. Arrhenius data were obtained for ejaculated and epididymal sperm subjected to a variety of treatments. Lines fitted to plots of Arrhenius data revealed that each treatment affected the activation energy and intercept relative to controls. Evidence is presented for a phase transition occurring at 13 degrees C based on changes in the rate of TEMPONE reduction by ubiquinol. It was noted that, above the phase transition, rate constants for the reaction were dependent upon both treatment and temperature, but below the transition the differential effects of treatment were no longer apparent. The present study has demonstrated that events taking place in the respiratory chain can be closely monitored by measuring oxygen uptake and TEMPONE reduction, and that these events are affected by alterations in the sperm environment. PMID:4084632

  17. Skin tension related to tension reduction sutures.

    PubMed

    Hwang, Kun; Kim, Han Joon; Kim, Kyung Yong; Han, Seung Ho; Hwang, Se Jin

    2015-01-01

    The aim of this study was to compare the skin tension of several fascial/subcutaneous tensile reduction sutures. Six upper limbs and 8 lower limbs of 4 fresh cadavers were used. At the deltoid area (10 cm below the palpable acromion) and lateral thigh (midpoint from the palpable greater trochanter to the lateral border of the patella), and within a 3 × 6-cm fusiform area of skin, subcutaneous tissue defects were created. At the midpoint of the defect, a no. 5 silk suture was passed through the dermis at a 5-mm margin of the defect, and the defect was approximated. The initial tension to approximate the margins was measured using a tensiometer.The tension needed to approximate skin without any tension reduction suture (S) was 6.5 ± 4.6 N (Newton). The tensions needed to approximate superficial fascia (SF) and deep fascia (DF) were 7.8 ± 3.4 N and 10.3 ± 5.1 N, respectively. The tension needed to approximate the skin after approximating the SF was 4.1 ± 3.4 N. The tension needed to approximate the skin after approximating the DF was 4.9 ± 4.0 N. The tension reduction effect of approximating the SF was 38.8 ± 16.4% (2.4 ± 1.5 N, P = 0.000 [ANOVA, Scheffé]). The tension reduction effect of approximating the DF was 25.2% ± 21.9% (1.5 ± 1.4 N, P = 0.001 [ANOVA, Scheffé]). The reason for this is thought to be that the SF is located closely to the skin unlike the DF. The results of this study might be a basis for tension reduction sutures. PMID:25569413

  18. Demonstration of Surface Tension.

    ERIC Educational Resources Information Center

    Rosenthal, Andrew J.

    2001-01-01

    Surface tension is a fundamental obstacle in the spontaneous formation of bubbles, droplets, and crystal nuclei in liquids. Describes a simple overhead projector demonstration that illustrates the power of surface tension that can prevent so many industrial processes. (ASK)

  19. Microfluidic Array with Integrated Oxygenation Control for Real-Time Live-Cell Imaging: Effect of Hypoxia on Physiology of Microencapsulated Pancreatic Islets

    PubMed Central

    Nourmohammadzadeh, Mohammad; Lo, Joe F.; Bochenek, Matt; Mendoza-Elias, Joshua E.; Wang, Qian; Li, Ze; Zeng, Liyi; Qi, Merigeng; Eddington, David T.; Oberholzer, José; Wang, Yong

    2014-01-01

    In this report, we present a novel microfluidic islet array based on a hydrodynamic trapping principle. The lab-on-a-chip studies with live-cell multiparametric imaging allow understanding of physiological and pathophysiological changes of microencapsulated islets under hypoxic conditions. Using this microfluidic array and imaging analysis techniques, we demonstrate that hypoxia impairs the function of microencapsulated islets at single islet level, showing a heterogeneous pattern reflected in intracellular calcium signaling, mitochondrial energetic, and redox activity. Our approach demonstrates an improvement over conventional hypoxia chambers that is able to rapidly equilibrate to true hypoxia levels through the integration of dynamic oxygenation. This work demonstrates the feasibility of array-based cellular analysis and opens up new modality to conduct informative analysis and cell-based screening for microencapsulated pancreatic islets. PMID:24083835

  20. Microfluidic Platform Generates Oxygen Landscapes for Localized Hypoxic Activation

    PubMed Central

    Rexius, Megan L.; Mauleon, Gerardo; Malik, Asrar B.; Rehman, Jalees; Eddington, David T.

    2014-01-01

    An open-well microfluidic platform generates an oxygen landscape using gas-perfused networks which diffuse across a membrane. The device enables real-time analysis of cellular and tissue responses to oxygen tension to define how cells adapt to heterogeneous oxygen conditions found in the physiological setting. We demonstrate that localized hypoxic activation of cells elicited specific metabolic and gene responses in human microvascular endothelial cells and bone marrow-derived mesenchymal stem cells. A robust demonstration of the compatibility of the device with standard laboratory techniques demonstrates the wide utility of the method. This platform is ideally suited to study real-time cell responses and cell-cell interactions within physiologically relevant oxygen landscapes. PMID:25315003

  1. TLP marine riser tensioner

    SciTech Connect

    Peppel, G.W.

    1988-03-08

    A riser tensioner for use in maintaining a tension on a marine riser from a tension leg platform, the tension leg platform moving relative to the marine riser and the marine riser having a center line is described comprising: (a) an elastomeric assembly, adjustably deformable in pad shear, for maintaining the riser in tension during vertical movement of the platform relative to the riser, the elastomeric assembly having upper and lower ends; (b) a gimbal assembly for pivotally connecting the upper end of the elastomeric assembly to the tension leg platform to accommodate misalignment between the riser and the tension leg platform; (c) a base ring to which the lower end of the elastomeric assembly is secured; and (d) a collar, securely mounted on the riser, for resting within the base ring to connect the lower end of the elastomeric assembly to the riser.

  2. Managing tension headaches at home

    MedlinePlus

    Tension-type headache - self-care; Muscle contraction headache - self-care; Headache - benign - self-care; Headache - tension- self-care; Chronic headaches - tension - self-care; Rebound headaches - tension - self- ...

  3. A quantitative method to monitor reactive oxygen species production by electron paramagnetic resonance in physiological and pathological conditions.

    PubMed

    Mrakic-Sposta, Simona; Gussoni, Maristella; Montorsi, Michela; Porcelli, Simone; Vezzoli, Alessandra

    2014-01-01

    The growing interest in the role of Reactive Oxygen Species (ROS) and in the assessment of oxidative stress in health and disease clashes with the lack of consensus on reliable quantitative noninvasive methods applicable. The study aimed at demonstrating that a recently developed Electron Paramagnetic Resonance microinvasive method provides direct evidence of the "instantaneous" presence of ROS returning absolute concentration levels that correlate with "a posteriori" assays of ROS-induced damage by means of biomarkers. The reliability of the choice to measure ROS production rate in human capillary blood rather than in plasma was tested (step I). A significant (P < 0.01) linear relationship between EPR data collected on capillary blood versus venous blood (R (2) = 0.95), plasma (R (2) = 0.82), and erythrocytes (R (2) = 0.73) was found. Then (step II) ROS production changes of various subjects' categories, young versus old and healthy versus pathological at rest condition, were found significantly different (range 0.0001-0.05 P level). The comparison of the results with antioxidant capacity and oxidative damage biomarkers concentrations showed that all changes indicating increased oxidative stress are directly related to ROS production increase. Therefore, the adopted method may be an automated technique for a lot of routine in clinical trials. PMID:25374651

  4. A Quantitative Method to Monitor Reactive Oxygen Species Production by Electron Paramagnetic Resonance in Physiological and Pathological Conditions

    PubMed Central

    Mrakic-Sposta, Simona; Gussoni, Maristella; Montorsi, Michela; Porcelli, Simone; Vezzoli, Alessandra

    2014-01-01

    The growing interest in the role of Reactive Oxygen Species (ROS) and in the assessment of oxidative stress in health and disease clashes with the lack of consensus on reliable quantitative noninvasive methods applicable. The study aimed at demonstrating that a recently developed Electron Paramagnetic Resonance microinvasive method provides direct evidence of the “instantaneous” presence of ROS returning absolute concentration levels that correlate with “a posteriori” assays of ROS-induced damage by means of biomarkers. The reliability of the choice to measure ROS production rate in human capillary blood rather than in plasma was tested (step I). A significant (P < 0.01) linear relationship between EPR data collected on capillary blood versus venous blood (R2 = 0.95), plasma (R2 = 0.82), and erythrocytes (R2 = 0.73) was found. Then (step II) ROS production changes of various subjects' categories, young versus old and healthy versus pathological at rest condition, were found significantly different (range 0.0001–0.05 P level). The comparison of the results with antioxidant capacity and oxidative damage biomarkers concentrations showed that all changes indicating increased oxidative stress are directly related to ROS production increase. Therefore, the adopted method may be an automated technique for a lot of routine in clinical trials. PMID:25374651

  5. Physiological significance of the slope of the regression equation between oxygen consumption and heart rate in exercise testing.

    PubMed

    Sunagawa, H; Honda, S; Mizoguchi, Y; Yoshii, K; Iwao, H

    1984-12-01

    The relationship between oxygen consumption (VO2) and heart rate (HR) was studied in 62 male children. Based on clinical evaluation and history, they were divided into three groups, i.e., athlete, ordinary and failed. There was a high linear correlation between HR and VO2 in each individual. The averaged values of the slope and standard deviations were 2.09 +/- 0.189 in the athlete group (n = 17), 2.60 +/- 0.140 in the ordinary group (n = 16) and 3.17 +/- 0.591 in the failed group (n = 29). The statistical differences were confirmed among the groups (p less than 0.005). The results suggested that the slope of the HR vs. VO2 relation was related to an inotropic state of cardiac function. We concluded that the slope was a more suitable and more direct evaluation of cardiac function during exercise. Moreover, the method was non-invasive and safe because it required no potentially hazardous maximum work load for the patients. PMID:6512949

  6. Dietary and physiological controls on the hydrogen and oxygen isotope ratios of hair from mid-20th century indigenous populations.

    PubMed

    Bowen, Gabriel J; Ehleringer, James R; Chesson, Lesley A; Thompson, Alexandra H; Podlesak, David W; Cerling, Thure E

    2009-08-01

    A semimechanistic model has recently been proposed to explain observed correlations between the H and O isotopic composition of hair from modern residents of the USA and the isotopic composition of drinking water, but the applicability of this model to hair from non-USA and preglobalization populations is unknown. Here we test the model against data from hair samples collected during the 1930s-1950s from populations of five continents. Although C and N isotopes confirm that the samples represent a much larger range of dietary "space" than the modern USA residents, the model is able to reproduce the observed delta(2)H and delta(18)O values given reasonable adjustments to 2 model parameters: the fraction of dietary intake derived from locally produced foods and the fraction of keratin H fixed during the in vivo synthesis of amino acids. The model is most sensitive to the local dietary intake, which appears to constitute between 60% and 80% of diet among the groups sampled. The isotopic data are consistent with a trophic-level effect on protein H isotopes, which we suggest primarily reflects mixing of (2)H-enriched water and (2)H-depleted food H in the body rather than fractionation during biosynthesis. Samples from Inuit groups suggest that humans with marine-dominated diets can be identified on the basis of coupled delta(2)H and delta(18)O values of hair. These results indicate a dual role for H and O isotopic measurements of keratin, including both biological (diet, physiology) and environmental (geographic movement, paleoclimate) reconstruction. PMID:19235792

  7. Estimating venous admixture using a physiological simulator.

    PubMed

    Hardman, J G; Bedforth, N M

    1999-03-01

    Estimation of venous admixture in patients with impaired gas exchange allows monitoring of disease progression, efficacy of interventions and assessment of the optimal inspired oxygen fraction. A pulmonary artery catheter allows accurate measurement, although the associated risks preclude its use solely for estimation of venous admixture. Non-invasive methods require assumed values for physiological variables. Many of the required data (e.g. haemoglobin concentration (Hb), base excess, inspired oxygen fraction, arterial oxygen (PaO2) and carbon dioxide (PaCO2) tensions, temperature) are available routinely in the intensive therapy unit. We have compared a typical iso-shunt-style estimation of venous admixture (assuming Hb, base excess, PaCO2 and temperature), and estimation using the Nottingham physiology simulator (NPS), with measured data. When the arteriovenous oxygen content difference (CaO2-CvO2) was assumed to be 50 ml litre-1, the 95% limits of agreement (LA95%) for venous admixture using the NPS were -3.9 +/- 8.5% and using an iso-shunt-style calculation, -6.4 +/- 10.6%. CaO2-CvO2 was 41.1 ml litre-1 in the patients studied, consistent with previous studies in the critically ill. When CaO2-CvO2 was assumed to be 40 ml litre-1, LA95% values were 0.5 +/- 8.2% and -2.1 +/- 10.1%, respectively. PMID:10434813

  8. Photoinduced tension of polymers

    SciTech Connect

    Maerov, S.B.; Avakian, P.; Matheson, R.R. Jr.

    1984-09-01

    Photoirradiation of polymer films at constant length induced a fast tension reduction (time scale; seconds) followed by slow tension buildup (time scale: minutes). Immediately after irradiation, fast tension buildup was followed by slow tension decay. Cycles were repeatable without significant hysteresis loss. The amplitude of both phenomena are intensity-dependent in the ultraviolet-visible spectral regions; both phenomena are thermal rather than photochemical effects. Light-absorbing chromophores in the polymer structure, or in additives such as dyes, lead to absorption of light and internal conversion into heat. The classical, rapid thermal expansion (or contraction) on heating (or cooling) leads to the fast relaxation (or buildup) of tension. The elastic, entropic response of the sample with its longer relaxation time leads to slow buildup (or decay) of tension. Fast and slow responses are observed sequentially with film of extensively crosslinked Riston photopolymer resist or with Kapton polyimide film, whereas, in experiments with latex rubber, the rubbery behavior dominates.

  9. Bolt-Tension Sensor

    NASA Technical Reports Server (NTRS)

    Goldie, James H.; Bushko, Dariusz A.; Gerver, Michael J.

    1995-01-01

    In technique for measuring tensile force of bolt, specially fabricated magnetostrictive washer used as force transducer. Compact, portable inductive electronic sensor placed against washer to measure tension force. New system provides accurate, economical, and convenient way to measure bolt tension in field. Measurements on test assembly shows that tension can be measured to accuracy of about plus or minus 1 percent of load capacity of typical bolt.

  10. Leadership Tensions and Dilemmas

    ERIC Educational Resources Information Center

    Edmunds, Bill; Mulford, Bill; Kendall, Diana; Kendall, Lawrie

    2008-01-01

    Results from the Tasmanian Successful School Principal Project (SSPP) survey concur with the four major leadership tensions and dilemmas identified in a background literature review. These tensions and dilemmas relate to internal/external control, ethic of care/responsibility, and an emphasis on professional/personal as well as…

  11. Physiology in Medicine: A physiologic approach to prevention and treatment of acute high-altitude illnesses.

    PubMed

    Luks, Andrew M

    2015-03-01

    With the growing interest in adventure travel and the increasing ease and affordability of air, rail, and road-based transportation, increasing numbers of individuals are traveling to high altitude. The decline in barometric pressure and ambient oxygen tensions in this environment trigger a series of physiologic responses across organ systems and over a varying time frame that help the individual acclimatize to the low oxygen conditions but occasionally lead to maladaptive responses and one or several forms of acute altitude illness. The goal of this Physiology in Medicine article is to provide information that providers can use when counseling patients who present to primary care or travel medicine clinics seeking advice about how to prevent these problems. After discussing the primary physiologic responses to acute hypoxia from the organ to the molecular level in normal individuals, the review describes the main forms of acute altitude illness--acute mountain sickness, high-altitude cerebral edema, and high-altitude pulmonary edema--and the basic approaches to their prevention and treatment of these problems, with an emphasis throughout on the physiologic basis for the development of these illnesses and their management. PMID:25539941

  12. Erythrocytes Are Oxygen-Sensing Regulators of the Cerebral Microcirculation.

    PubMed

    Wei, Helen Shinru; Kang, Hongyi; Rasheed, Izad-Yar Daniel; Zhou, Sitong; Lou, Nanhong; Gershteyn, Anna; McConnell, Evan Daniel; Wang, Yixuan; Richardson, Kristopher Emil; Palmer, Andre Francis; Xu, Chris; Wan, Jiandi; Nedergaard, Maiken

    2016-08-17

    Energy production in the brain depends almost exclusively on oxidative metabolism. Neurons have small energy reserves and require a continuous supply of oxygen (O2). It is therefore not surprising that one of the hallmarks of normal brain function is the tight coupling between cerebral blood flow and neuronal activity. Since capillaries are embedded in the O2-consuming neuropil, we have here examined whether activity-dependent dips in O2 tension drive capillary hyperemia. In vivo analyses showed that transient dips in tissue O2 tension elicit capillary hyperemia. Ex vivo experiments revealed that red blood cells (RBCs) themselves act as O2 sensors that autonomously regulate their own deformability and thereby flow velocity through capillaries in response to physiological decreases in O2 tension. This observation has broad implications for understanding how local changes in blood flow are coupled to synaptic transmission. PMID:27499087

  13. STEEL TRUSS TENSION RING SUPPORTING DOME ROOF. TENSION RING COVERED ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    STEEL TRUSS TENSION RING SUPPORTING DOME ROOF. TENSION RING COVERED BY ARCHITECTURAL FINISH. TENSION RING ROLLER SUPPORT AT COLUMN OBSCURED BY COLUMN COVERINGS. - Houston Astrodome, 8400 Kirby Drive, Houston, Harris County, TX

  14. Surface Tensions and Their Variations with Temperature and Impurities

    NASA Technical Reports Server (NTRS)

    Hardy, S. C.; Fine, J.

    1985-01-01

    The surface tensions in this work were determined using the sessile drop technique. This method is based on a comparison of the profile of a liquid drop with the profile calculated by solving the Young-Laplace equation. The comparison can be made in several ways; the traditional Bashforth-Adams procedure was used in conjunction with recently calculated drop shape tables which virtually eliminate interpolation errors. Although previous study has found little difference in measurements with pure and oxygen doped silicon, there is other evidence suggesting that oxygen in dilute concentrations severely depresses the surface tension of silicon. The surface tension of liquid silicon in purified argon atmospheres was measured. A temperature coefficient near -0.28 mJ/square meters K was found. The experiments show a high sensitivity of the surface tension to what is believed are low concentrations of oxygen. Thus one cannot rule out some effect of low levels of oxygen in the results. However, the highest surface tension values obtained in conditions which minimized the residual oxygen pressure are in good agreement with a previous measurement in pure hydrogen. Therefore, depression of the surface tension by oxygen is insignificant in these measurements.

  15. Managing tension headaches at home

    MedlinePlus

    Tension-type headache - self-care; Muscle contraction headache - self-care; Headache - benign - self-care; Headache - tension- self-care; Chronic headaches - tension - self-care; Rebound headaches - ...

  16. Echinococcal tension pneumothorax

    PubMed Central

    Bakir, Farhan; Al-Omeri, Muayyad M.

    1969-01-01

    Hydatid cyst is rarely mentioned among the causes of pneumothorax in text-books or monographs, especially those written in English. Five examples of tension pneumothorax secondary to ruptured hydatid cyst of the lung are reported: the mechanism of this tension effect and helpful diagnostic points are discussed. We think that surgical correction is the only satisfactory treatment of tension pneumothorax due to ruptured hydatid cyst: surgery is advocated in any suspected cyst as soon as it is discovered so as to avoid any such serious complication. Images PMID:5348321

  17. Managing the right tension.

    PubMed

    Dodd, Dominic; Favaro, Ken

    2006-12-01

    Of all the competing objectives every company faces, three pairs stand out: profitability versus growth, the short term versus the long term, and the whole organization versus the units. In each case, progress on one front usually comes at the expense of progress on the other. The authors researched the performance of more than 1000 companies worldwide over the past two decades and found that most struggle to succeed across the three tensions. From 1983 to 2003, for example, only 32% of these companies more often than not achieved positive profitability and revenue growth at the same time. The problem, the authors discovered, is not so much that managers don't recognize the tensions--those are all too familiar to anyone who has ever run a business. Rather, it is that managers frequently don't focus on the tension that matters most to their company. Even when they do identify the right tension, they usually make the mistake of prioritizing a "lead" objective within it-for example, profitability over growth. As a result, companies often end up moving first in this direction, then in that, and then back again, never quite resolving the tension. The companies that performed best adopted a very different approach. Instead of setting a lead objective, they looked at how best to strengthen what the two sides of each tension have in common: For profitability and growth,the common bond is customer benefit; for the short term and the long, it is sustainable earnings; and for the whole and its parts, it is particular organizational resources and capabilities. The authors describe how companies can select the right tension, what traps they may fall into when they focus on one side over the other, and how to escape these traps by managing to the bonds between objectives. PMID:17183794

  18. Mitochondrial oxidative phosphorylation: tissue oxygen sensor for regulation of coronary flow.

    PubMed

    Nuutinen, E M; Wilson, D F; Erecińska, M

    1984-01-01

    The observation that mitochondrial oxidative phosphorylation in vivo is dependent on oxygen tension throughout the physiological range (Wilson et al., 1979a , 1979b ) has made this metabolic pathway the most probable candidate for the tissue oxygen sensor in the regulation of local blood flow. We have utilized the oxygen dependent regulatory system for coronary blood flow to examine this possibility. Alterations in coronary flow were induced by: 1. Varied work load; 2. Infusion of Amytal (an inhibitor of mitochondrial respiration); 3. Infusion of DNP; 4. Hypoxia. Increased work load caused increased coronary flow with no decrease in effluent oxygen tension while Amytal infusion and hypoxia caused vasodilation with increased and decreased O2 tension respectively. This indicates that oxygen tension per se cannot be responsible for the observed vasodilation. Tissue energy metabolism was evaluated by measuring metabolite levels in hearts which were freeze-clamped in each state of perfusion. In all four methods of vasodilation, a decrease in cellular energy state ratio ([ATP]f/[ADP]f[Pi]) expressed as the calculated ratio of free adenine nucleotides, was observed for conditions which increased flow. Systematic variation of work load, Amytal or DNP concentration resulted in quantitatively the same correlation between tissue [ATP]f/[ADP]f[Pi] and coronary flow. It is concluded that mitochondrial oxidative phosphorylation is the oxygen sensor for the regulation of coronary blood flow by tissue oxygen tension. Infusion of adenosine, a known coronary vasodilator, induced vasodilation which was completely blocked by theophylline.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:6731096

  19. Normal-tension glaucoma (Low-tension glaucoma)

    PubMed Central

    Anderson, Douglas R

    2011-01-01

    Glaucoma is now considered an abnormal physiology in the optic nerve head that interacts with the level of intraocular pressure (IOP), with the degree and rate of damage depending on the IOP and presumably the degree of abnormal physiology. Diagnosis of normal-tension glaucoma (NTG), defined as glaucoma without a clearly abnormal IOP, depends on recognizing symptoms and signs associated with optic nerve vulnerability, in addition to absence of other explanations for disc abnormality and visual field loss. Among the findings are a halo or crescent of absence of retinal pigment epithelium around the disc, bilateral pre-chiasmal visual field defects, splinter hemorrhages at the disc margin, vascular dysregulation (low blood pressure, cold hands and feet, migraine headache with aura, and the like), or a family history of glaucoma. Possibly relevant, is a history of hemodynamic crisis, arterial obstructive disease, or sleep apnea. Neurological evaluation with imaging is needed only for atypical cases or ones that progress unexpectedly. Management follows the same principle of other chronic glaucomas, to lower the IOP by a substantial amount, enough to prevent disabling visual loss. However, many NTG cases are non-progressive. Therefore, it may often be wisein mild cases to determine whether the case is progressive and the rate of progression before deciding on how aggressivene to be with therapy. Efforts at neuroprotection and improvement in blood flow have not yet been shown effective. PMID:21150042

  20. Blood Vessel Tension Tester

    NASA Technical Reports Server (NTRS)

    1978-01-01

    In the photo, a medical researcher is using a specially designed laboratory apparatus for measuring blood vessel tension. It was designed by Langley Research Center as a service to researchers of Norfolk General Hospital and Eastern Virginia Medical School, Norfolk, Virginia. The investigators are studying how vascular smooth muscle-muscle in the walls of blood vessels-reacts to various stimulants, such as coffee, tea, alcohol or drugs. They sought help from Langley Research Center in devising a method of measuring the tension in blood vessel segments subjected to various stimuli. The task was complicated by the extremely small size of the specimens to be tested, blood vessel "loops" resembling small rubber bands, some only half a millimeter in diameter. Langley's Instrumentation Development Section responded with a miniaturized system whose key components are a "micropositioner" for stretching a length of blood vessel and a strain gage for measuring the smooth muscle tension developed. The micropositioner is a two-pronged holder. The loop of Mood vessel is hooked over the prongs and it is stretched by increasing the distance between the prongs in minute increments, fractions of a millimeter. At each increase, the tension developed is carefully measured. In some experiments, the holder and specimen are lowered into the test tubes shown, which contain a saline solution simulating body fluid; the effect of the compound on developed tension is then measured. The device has functioned well and the investigators say it has saved several months research time.

  1. Tension pneumothorax during flexible bronchoscopy in a nonintubated infant.

    PubMed

    Chan, Ian A; Gamble, Jonathan J

    2016-04-01

    We describe the case of a tension pneumothorax occurring during flexible bronchoscopy in a nonintubated infant. The pneumothorax likely occurred secondary to wall source oxygen insufflation via the bronchoscope without sufficient gas egress. The use of wall source oxygen via the bronchoscope working channel is inherently dangerous and should be avoided. PMID:26740408

  2. Cognitive Imagery and Physiological Feedback Relaxation Protocols Applied to Clinically Tense Young Adults: A Comparison of State, Trait, and Physiological Effects.

    ERIC Educational Resources Information Center

    Schandler, Steven L.; Dana, Edward R.

    1983-01-01

    Examined changes in tension behaviors and reductions in physiological tension associated with cognitive imagery and electromyographic biofeedback relaxation procedures in 45 college students. Results showed: imagery significantly reduced state anxiety. Self-rest was less effective; biofeedback greatly reduced physiological tension, but not state…

  3. Nonequilibrium surface tension

    NASA Astrophysics Data System (ADS)

    Lamorgese, A.; Mauri, R.

    2015-12-01

    A weakly nonlocal phase-field model is used to define surface tension in liquid binary mixtures in terms of the composition gradient in the interfacial region so that, at equilibrium, it depends linearly on the characteristic length that defines the interfacial width. In nonequilibrium conditions, surface tension changes with time: during mixing, it decreases as the inverse square root of time, while during phase separation, when nuclei coagulate, it increases exponentially to its equilibrium value. In addition, since temperature gradients modify the steepness of the concentration profile in the interfacial region, they induce gradients in the nonequilibrium surface tension, leading to the Marangoni thermocapillary migration of an isolated drop. Similarly, Marangoni stresses are induced in a composition gradient, leading to diffusiophoresis.

  4. Tension in active shapes.

    PubMed

    Papari, Giuseppe

    2014-01-01

    The concept of tension is introduced in the framework of active contours with prior shape information, and it is used to improve image segmentation. In particular, two properties of this new quantity are shown: 1) high values of the tension correspond to undesired equilibrium points of the cost function under minimization and 2) tension decreases if a curve is split into two or more parts. Based on these ideas, a tree is generated whose nodes are different local minima of the cost function. Deeper nodes in the tree are expected to correspond to lower values of the cost function. In this way, the search for the global optimum is reduced to visiting and pruning a binary tree. The proposed method has been applied to the problem of fish segmentation from low quality underwater images. Qualitative and quantitative comparison with existing algorithms based on the Euler–Lagrange diffusion equations shows the superiority of the proposed approach in avoiding undesired local minima. PMID:24235305

  5. Tension Pneumopericardium after Pericardiocentesis

    PubMed Central

    2016-01-01

    Pneumopericardium is defined as the presence of air inside the pericardial space. Usually, it is reported as a complication of blunt or penetrating chest trauma, but rare iatrogenic and spontaneous cases have been reported. Pneumopericardium is relatively stable if it does not generate a tension effect on the heart. However, it may progress to tension pneumopericardium, which requires immediate pericardial aspiration. We report a case of iatrogenic pneumopericardium occurred in a 70-year-old man who presented dyspnea at emergency department. The patient underwent pericardiocentesis for cardiac tamponade due to large pericardial effusion, and iatrogenic tension pneumopericardium occurred due to misuse of the drainage device. After evacuating the pericardial air through the previously implanted catheter, the patient became stable. We report this case to increase the awareness of this fatal condition and to help increase the use of precautions against the development of this condition during emergency procedures. PMID:26952636

  6. [Treatment of tension headache].

    PubMed

    Schoenen, J

    2000-01-01

    The scientific basis of tension- type headache suffers from the lack of precise pathophysiological knowledge and the heterogenecity of this disorder. Treatment of acute tension-type headache episodes is more effective with an NSAIDs (ibuprofen 400-800mg, naproxen 550-825mg, ketoprofen 50-75mg) than with aspirin or paracetamol. Caffein containing preparations of NSAIDs are slightly superior, but should not be taken frequently to avoid headache chronification. For chronic tension-type headache, relaxation therapies with EMG biofeedback and tricyclics have about the same efficacy rate of 40-50p.100. Physical therapy and acupuncture are in general less effective. There is thus clearly a need for better strategies, e.g. combination of available therapies and novel approaches. PMID:11139755

  7. Role of erythrocyte-released ATP in the regulation of microvascular oxygen supply in skeletal muscle.

    PubMed

    Ellsworth, M L; Ellis, C G; Sprague, R S

    2016-03-01

    In a 1914 book entitled The Respiratory Function of the Blood, Joseph Barcroft stated that 'the cell takes what it needs and leaves the rest'. He postulated that there must be both a 'call for oxygen' and a 'mechanism by which the call elicits a response...' In the past century, intensive investigation has provided significant insights into the haemodynamic and biophysical mechanisms involved in supplying oxygen to skeletal muscle. However, the identification of the mechanism by which tissue oxygen needs are sensed and the affector responsible for altering the upstream vasculature to enable the need to be appropriately met has been a challenge. In 1995, Ellsworth et al. proposed that the oxygen-carrying erythrocyte, by virtue of its capacity to release the vasoactive mediator ATP in response to a decrease in oxygen saturation, could serve both roles. Several in vitro and in situ studies have established that exposure of erythrocytes to reduced oxygen tension induces the release of ATP which does result in a conducted arteriolar vasodilation with a sufficiently rapid time course to make the mechanism physiologically relevant. The components of the signalling pathway for the controlled release of ATP from erythrocytes in response to exposure to low oxygen tension have been determined. In addition, the implications of defective ATP release on human pathological conditions have been explored. This review provides a perspective on oxygen supply and the role that such a mechanism plays in meeting the oxygen needs of skeletal muscle. PMID:26336065

  8. Sensing the Tension

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Spanning over 4 decades, NASA's bolt tension monitoring technology has benefited automakers, airplane builders, and other major manufacturers that rely on the devices to evaluate the performance of computerized torque wrenches and other assembly line mechanisms. In recent years, the advancement of ultrasonic sensors has drastically eased this process for users, ensuring that proper tension and torque are being applied to bolts and fasteners, with less time needed for data analysis. Langley Research Center s Nondestructive Evaluation Branch is one of the latest NASA programs to incorporate ultrasonic sensors within a bolt tension measurement instrument. As a multi-disciplined research group focused on spacecraft and aerospace transportation safety, one of the branch s many commitments includes transferring problem solutions to industry. In 1998, the branch carried out this obligation in a licensing agreement with Micro Control, Inc., of West Bloomfield, Michigan. Micro Control, an automotive inspection company, obtained the licenses to two Langley patents to provide an improved-but-inexpensive means of ultrasonic tension measurement.

  9. Surface tension of spherical drops from surface of tension

    NASA Astrophysics Data System (ADS)

    Homman, A.-A.; Bourasseau, E.; Stoltz, G.; Malfreyt, P.; Strafella, L.; Ghoufi, A.

    2014-01-01

    The determination of surface tension of curved interfaces is a topic that raised many controversies during the last century. Explicit liquid-vapor interface modelling (ELVI) was unable up to now to reproduce interfacial behaviors in drops due to ambiguities in the mechanical definition of the surface tension. In this work, we propose a thermodynamic approach based on the location of surface of tension and its use in the Laplace equation to extract the surface tension of spherical interfaces from ELVI modelling.

  10. Surface tension of spherical drops from surface of tension

    SciTech Connect

    Homman, A.-A.; Bourasseau, E.; Malfreyt, P.; Strafella, L.; Ghoufi, A.

    2014-01-21

    The determination of surface tension of curved interfaces is a topic that raised many controversies during the last century. Explicit liquid-vapor interface modelling (ELVI) was unable up to now to reproduce interfacial behaviors in drops due to ambiguities in the mechanical definition of the surface tension. In this work, we propose a thermodynamic approach based on the location of surface of tension and its use in the Laplace equation to extract the surface tension of spherical interfaces from ELVI modelling.

  11. Surface Tension and Capillary Rise

    ERIC Educational Resources Information Center

    Walton, Alan J.

    1972-01-01

    Discussion of the shortcomings of textbook explanations of surface tension, distinguishing between concepts of tension and capillary rise. The arguments require only a clear understanding of Newtonian mechanics, notably potential energy. (DF)

  12. Surface tension driven convection

    NASA Technical Reports Server (NTRS)

    Ostrach, S.

    1979-01-01

    In a normal gravitational environment, the free surface of a liquid in a container plays a passive role in the transport processes. However, at microgravity, the free surface can become the dominant factor. A simple but meaningful spaceflight experiment is proposed to investigate the nature and extent of flows induced by surface-tension gradients along the free surface. The influences of container geometry, wetability, contamination, and imposed heating modes will be investigated.

  13. FRET-based Molecular Tension Microscopy.

    PubMed

    Gayrard, Charlène; Borghi, Nicolas

    2016-02-01

    Cells generate and experience mechanical forces that may shape tissues and regulate signaling pathways in a variety of physiological or pathological situations. How forces propagate and transduce signals at the molecular level is poorly understood. The advent of FRET-based Molecular Tension Microscopy now allows to achieve mechanical force measurements at a molecular scale with molecular specificity in situ, and thereby better understand the mechanical architecture of cells and tissues, and mechanotransduction pathways. In this review, we will first expose the basic principles of FRET-based MTM and its various incarnations. We will describe different ways of measuring FRET, their advantages and drawbacks. Then, throughout the range of proteins of interest, cells and organisms to which it has been applied, we will review the tests developed to validate the approach, how molecular tension was related to cell functions, and conclude with possible developments and offshoots. PMID:26210398

  14. Simultaneous sampling of tissue oxygenation and oxygen consumption in skeletal muscle.

    PubMed

    Nugent, William H; Song, Bjorn K; Pittman, Roland N; Golub, Aleksander S

    2016-05-01

    Under physiologic conditions, microvascular oxygen delivery appears to be well matched to oxygen consumption in respiring tissues. We present a technique to measure interstitial oxygen tension (PISFO2) and oxygen consumption (VO2) under steady-state conditions, as well as during the transitions from rest to activity and back. Phosphorescence Quenching Microscopy (PQM) was employed with pneumatic compression cycling to achieve 1 to 10Hz sampling rates of interstitial PO2 and simultaneous recurrent sampling of VO2 (3/min) in the exteriorized rat spinotrapezius muscle. The compression pressure was optimized to 120-130mmHg without adverse effect on the tissue preparation. A cycle of 5s compression followed by 15s recovery yielded a resting VO2 of 0.98±0.03ml O2/100cm(3)min while preserving microvascular oxygen delivery. The measurement system was then used to assess VO2 dependence on PISFO2 at rest and further tested under conditions of isometric muscle contraction to demonstrate a robust ability to monitor the on-kinetics of tissue respiration and the compensatory changes in PISFO2 during contraction and recovery. The temporal and spatial resolution of this approach is well suited to studies seeking to characterize microvascular oxygen supply and demand in thin tissues. PMID:26683232

  15. Hyperbaric oxygen therapy in chronic vascular wound management.

    PubMed

    Wattel, F; Mathieu, D; Coget, J M; Billard, V

    1990-01-01

    Many nonhealing tissues are hypoxic, with oxygen tensions frequently ranging from 5 to 15 mmHg. In such an environment, the normal wound healing sequence is disrupted or halted and phagocytic killing activity depressed. So the adjunctive use of hyperbaric oxygen (HBO), based on physiologic data and clinical observations, can provide the substrate necessary to initiate and sustain the healing process. During a twelve-month period, 20 patients with a nonhealing wound were referred to the hyperbaric center: chronic arterial insufficiency ulcers in 9 cases, diabetic wounds (foot lesions) in 11 cases. Adjunctive HBO therapy, initiated twice a day, consisted of pure oxygen, 2.5 ATA, 90 min. The average length of sessions was 46 (15-108). Complete healing was observed in 15 of 20 cases. The wound management can be helped with the transcutaneous oxygen measurements under hyperbaric oxygen. The distal TCPO2 at 2.5 ATA pure oxygen is a reliable test to predict final outcome (healing or no change), when these values were not different in normal air and in normobaric oxygen: (table; see text) In hyperbaric oxygen therapy, when the distal TCPO2 value was inferior to 100 mmHg, all patients showed either no improvement or aggravation, and when the value was higher than 100 mmHg, wound healing was achieved with all patients. PMID:2306000

  16. Membrane tension and membrane fusion.

    PubMed

    Kozlov, Michael M; Chernomordik, Leonid V

    2015-08-01

    Diverse cell biological processes that involve shaping and remodeling of cell membranes are regulated by membrane lateral tension. Here we focus on the role of tension in driving membrane fusion. We discuss the physics of membrane tension, forces that can generate the tension in plasma membrane of a cell, and the hypothesis that tension powers expansion of membrane fusion pores in late stages of cell-to-cell and exocytotic fusion. We propose that fusion pore expansion can require unusually large membrane tensions or, alternatively, low line tensions of the pore resulting from accumulation in the pore rim of membrane-bending proteins. Increase of the inter-membrane distance facilitates the reaction. PMID:26282924

  17. Cable tensioned membrane solar collector module with variable tension control

    DOEpatents

    Murphy, Lawrence M.

    1985-01-01

    Disclosed is a solar collector comprising a membrane for concentrating sunlight, a plurality of elongated structural members for suspending the membrane member thereon, and a plurality of control members for adjustably tensioning the membrane member, as well as for controlling a focus produced by the membrane members. Each control member is disposed at a different corresponding one of the plurality of structural members. The collector also comprises an elongated flexible tensioning member, which serves to stretch the membrane member and to thereafter hold it in tension, and a plurality of sleeve members, which serve to provide the membrane member with a desired surface contour during tensioning of the membrane member. The tensioning member is coupled to the structural members such that the tensioning member is adjustably tensioned through the structural members. The tensioning member is also coupled to the membrane member through the sleeve members such that the sleeve members uniformly and symmetrically stretch the membrane member upon applying tension to the tensioning member with the control members.

  18. Cable tensioned membrane solar collector module with variable tension control

    DOEpatents

    Murphy, L.M.

    1984-01-09

    Disclosed is a solar collector comprising a membrane member for concentrating sunlight, a plurality of elongated structural members for suspending the membrane member thereon, and a plurality of control members for adjustably tensioning the membrane member, as well as for controlling a focus produced by the membrane members. Each control member is disposed at a different corresponding one of the plurality of structural members. The collector also comprises an elongated flexible tensioning member, which serves to stretch the membrane member and to thereafter hold it in tension, and a plurality of sleeve members which serve to provide the membrane member with a desired surface contour during tensioning of the membrane member. The tensioning member is coupled to the structural members such that the tensioning member is adjustably tensioned through the structural members. The tensioning member is also coupled to the membrane member through the sleeve members such that the sleeve members uniformly and symmetrically stretch the membrane member upon applying tension to the tensioning member with the control members.

  19. Rainbow surface tension analysis.

    PubMed

    Adler, Charles L; Smith, Valen A; Haddad, Natalie M

    2008-03-31

    In this paper we outline a new all-optical non-contact technique for measurement of the surface tension of a Newtonian fluid. It is based on the accurate measurement of the spacing of the supernumerary fringes produced by the diffraction pattern of a laser beam transmitted through or reflected by a thin vertically-draining film of the liquid. We discuss the basic theory and application of this technique, and several issues which must be addressed before it can be used commercially. PMID:18542611

  20. Tension leg platform system

    SciTech Connect

    Burns, R.B.

    1983-12-20

    A tension leg platform system for use in drilling wellbores into the floor of an offshore body of water. Includes in the system is a buoyancy control vessel having a plurality of pull down cables attached thereto which extend to the ocean floor. A plurality of spaced apart anchors disposed at the ocean floor are positioned to receive the lower ends of the respective pull down cables. A submergible hull slidably engages the respective hold down cables such that the hull can be controllably lowered to the ocean floor whereby a canopy carried on the hull will cover an uncontrollably flowing well to conduct the effluent to the water's surface.

  1. Evolution de la caracteristique courant-tension des varistances a base d'oxyde de zinc avec la pression partielle d'oxygene de l'atmosphere de frittage

    NASA Astrophysics Data System (ADS)

    Salmon, Roger; Bonnet, Jean-Pierre; Graciet, Michel; Onillon, Marc; Hagenmuller, Paul

    1980-05-01

    In order to decrease the resistivity of zinc oxide grains which is responsible for the intensity limitation observed at high current densities, the dependence of current-voltage characteristics of zinc oxide based varistors on oxygen partial pressure has been investigated. From these studies it appears that the conductivity increases with decreasing oxygen partial pressure, this phenomenon being more significant at low voltages than at higher ones. These results can be related to a slight increase of the donor density, while the superficial trap density decreases strongly, involving a collapse of the barrier height and of the non-linearity exponent.

  2. Tension bulla: a cause of reversible pulmonary hypertension.

    PubMed

    Waxman, Michael J; Waxman, Jacob D; Forman, John M

    2015-01-01

    A tension pneumothorax represents a medical emergency warranting urgent diagnosis and treatment. A rapidly expanding bulla may resemble the same clinical presentation but requires an entirely different treatment. A 53-year-old woman presented with increasing shortness of breath and her physical examination and chest x-ray were interpreted as showing a tension pneumothorax. A chest tube was placed which did not resolve the process. Placement of a second chest tube was likewise unsuccessful. A chest CT was then performed and was interpreted as showing an unresolved tension pneumothorax, despite seemingly adequate placement of the 2 chest tubes. Further review of the CT showed the border of a giant bulla and a tentative diagnosis was made of a rapidly expanding bulla with tension physiology. Echocardiogram revealed significant pulmonary hypertension. The bulla was surgically excised, the patient had marked improvement in her clinical symptoms and signs, and echocardiographic follow-up showed complete resolution of the pulmonary hypertension. PMID:25590488

  3. Hypoxia Inducible Factor Pathway and Physiological Adaptation: A Cell Survival Pathway?

    PubMed Central

    Kumar, Hemant; Choi, Dong-Kug

    2015-01-01

    Oxygen homeostasis reflects the constant body requirement to generate energy. Hypoxia (0.1–1% O2), physioxia or physoxia (∼1–13%), and normoxia (∼20%) are terms used to define oxygen concentration in the cellular environment. A decrease in oxygen (hypoxia) or excess oxygen (hyperoxia) could be deleterious for cellular adaptation and survival. Hypoxia can occur under both physiological (e.g., exercise, embryonic development, underwater diving, or high altitude) and pathological conditions (e.g., inflammation, solid tumor formation, lung disease, or myocardial infarction). Hypoxia plays a key role in the pathophysiology of heart disease, cancers, stroke, and other causes of mortality. Hypoxia inducible factor(s) (HIFs) are key oxygen sensors that mediate the ability of the cell to cope with decreased oxygen tension. These transcription factors regulate cellular adaptation to hypoxia and protect cells by responding acutely and inducing production of endogenous metabolites and proteins to promptly regulate metabolic pathways. Here, we review the role of the HIF pathway as a metabolic adaptation pathway and how this pathway plays a role in cell survival. We emphasize the roles of the HIF pathway in physiological adaptation, cell death, pH regulation, and adaptation during exercise. PMID:26491231

  4. Hypoxia Inducible Factor Pathway and Physiological Adaptation: A Cell Survival Pathway?

    PubMed

    Kumar, Hemant; Choi, Dong-Kug

    2015-01-01

    Oxygen homeostasis reflects the constant body requirement to generate energy. Hypoxia (0.1-1% O2), physioxia or physoxia (∼1-13%), and normoxia (∼20%) are terms used to define oxygen concentration in the cellular environment. A decrease in oxygen (hypoxia) or excess oxygen (hyperoxia) could be deleterious for cellular adaptation and survival. Hypoxia can occur under both physiological (e.g., exercise, embryonic development, underwater diving, or high altitude) and pathological conditions (e.g., inflammation, solid tumor formation, lung disease, or myocardial infarction). Hypoxia plays a key role in the pathophysiology of heart disease, cancers, stroke, and other causes of mortality. Hypoxia inducible factor(s) (HIFs) are key oxygen sensors that mediate the ability of the cell to cope with decreased oxygen tension. These transcription factors regulate cellular adaptation to hypoxia and protect cells by responding acutely and inducing production of endogenous metabolites and proteins to promptly regulate metabolic pathways. Here, we review the role of the HIF pathway as a metabolic adaptation pathway and how this pathway plays a role in cell survival. We emphasize the roles of the HIF pathway in physiological adaptation, cell death, pH regulation, and adaptation during exercise. PMID:26491231

  5. Coulomb string tension, asymptotic string tension, and the gluon chain

    SciTech Connect

    Greensite, Jeff; Szczepaniak, Adam P.

    2015-02-01

    We compute, via numerical simulations, the non-perturbative Coulomb potential and position-space ghost propagator in pure SU(3) gauge theory in Coulomb gauge. We find that that the Coulomb potential scales nicely in accordance with asymptotic freedom, that the Coulomb potential is linear in the infrared, and that the Coulomb string tension is about four times larger than the asymptotic string tension. We explain how it is possible that the asymptotic string tension can be lower than the Coulomb string tension by a factor of four.

  6. Tension in Highly Branched Polymers

    NASA Astrophysics Data System (ADS)

    Rubinstein, Michael

    2012-02-01

    We propose a systematic method of designing branched macromolecules capable of building up high tension in their covalent bonds, which can be controlled by changing solvent quality. This tension is achieved exclusively due to intramolecular interactions by focusing lower tensions from its numerous branches to a particular section of the designed molecule. The simplest molecular architecture, which allows this tension amplification, is a so-called pom-pom macromolecule consisting of a relatively short linear spacer and two z-arm stars at its ends. Tension developed in the stars due to crowding of their branches is amplified by a factor of z and focused to the spacer. There are other highly branched macromolecules, such as molecular brushes - comb polymers with high density of side branches, that have similar focusing and amplification properties. In addition molecular brushes transmit tension along their backbone. Adsorption or grafting of these branched molecules on a substrate results in further increase in tension as compared to molecules in solution. Molecular architectures similar to pom-pom and molecular brushes with a high tension amplification parts can be used in numerous sensor applications. Unique conformations of molecular brushes in a pre-wetting layer allow direct visualization by atomic force microscope. Detailed images of individual molecules spreading along the surface enable critical evaluation of theories of chain dynamics in polymer monolayer. Strong spreading of densely branched macromolecules on a planar substrate can lead to high tension in the molecular backbone sufficient to break covalent bonds.

  7. Nitinol Fatigue Investigation on Stent-Finish Specimens Using Tension-Tension Method

    NASA Astrophysics Data System (ADS)

    Lin, Z.; Pike, K.; Zipse, A.; Schlun, M.

    2011-07-01

    Nitinol fatigue strain limit versus both strain amplitude (range 0.25-1.25%) and mean strain (1.0, 2.0, and 4.0%) was investigated using a tension-tension method. In order to apply the fatigue testing results to a nitinol stent and evaluate stent fatigue performance, the dog-bone style specimens were processed from the same raw material common to implantable stent manufacturing, i.e., similar nitinol tubing, surface quality, and electropolished surface. To simulate a physiological environment, the tension-tension fatigue tests were conducted in water at 37 °C. This strain-controlled fatigue test was conducted with a run-out set at 106 cycles. The fatigue strain limit at 106 cycles as well as the mean strain effect and the effects of inclusions are discussed. Fatigue results appeared in a bi-modal pattern when the strain amplitude was at a level between too high, which made all specimens to fail, and too low, which allowed all specimens to survive.

  8. Flickering Analysis of Erythrocyte Mechanical Properties: Dependence on Oxygenation Level, Cell Shape, and Hydration Level

    PubMed Central

    Yoon, Young-Zoon; Hong, Ha; Brown, Aidan; Kim, Dong Chung; Kang, Dae Joon; Lew, Virgilio L.; Cicuta, Pietro

    2009-01-01

    Erythrocytes (red blood cells) play an essential role in the respiratory functions of vertebrates, carrying oxygen from lungs to tissues and CO2 from tissues to lungs. They are mechanically very soft, enabling circulation through small capillaries. The small thermally induced displacements of the membrane provide an important tool in the investigation of the mechanics of the cell membrane. However, despite numerous studies, uncertainties in the interpretation of the data, and in the values derived for the main parameters of cell mechanics, have rendered past conclusions from the fluctuation approach somewhat controversial. Here we revisit the experimental method and theoretical analysis of fluctuations, to adapt them to the case of cell contour fluctuations, which are readily observable experimentally. This enables direct measurements of membrane tension, of bending modulus, and of the viscosity of the cell cytoplasm. Of the various factors that influence the mechanical properties of the cell, we focus here on: 1), the level of oxygenation, as monitored by Raman spectrometry; 2), cell shape; and 3), the concentration of hemoglobin. The results show that, contrary to previous reports, there is no significant difference in cell tension and bending modulus between oxygenated and deoxygenated states, in line with the softness requirement for optimal circulatory flow in both states. On the other hand, tension and bending moduli of discocyte- and spherocyte-shaped cells differ markedly, in both the oxygenated and deoxygenated states. The tension in spherocytes is much higher, consistent with recent theoretical models that describe the transitions between red blood cell shapes as a function of membrane tension. Cell cytoplasmic viscosity is strongly influenced by the hydration state. The implications of these results to circulatory flow dynamics in physiological and pathological conditions are discussed. PMID:19751665

  9. Holding the Tension.

    PubMed

    Feudtner, Chris

    2016-05-01

    My colleagues and I had been asked by a member of a clinical team to help sort through the ethics of stopping a life-sustaining intervention for a very ill child. We had already talked with the parents, the physicians, and the folks from nursing, social work, and chaplaincy. Terms like "suffering," "cruel," "compassion," and "moral distress" had been uttered, as had terms like "inappropriate," "unethical," "neglectful," and "risk-management." The group had now stuffed all of these polarizing thoughts and feelings into this cramped room with only one door. And everyone was looking at me. What skill, competency, or inner capacity must one possess to hold and manage such tension? PMID:27150423

  10. Mass spectrometry for the measurement of intramyocardial gas tensions: methodology and application to the study of myocardial ischemia.

    PubMed

    Khuri, S F; O'Riordan, J; Flaherty, J T; Brawley, R K; Donahoo, J S; Gott, V L

    1975-01-01

    The methodology for use of the mass spectrometer for the measurement of intramyocardial gas tensions in the canine preparation is described. Baseling studies were carried out initially in 36 animals, and control levels for myocardial oxygen tension and myocardial carbon dioxide tension were 19 mm Hg (S.D. 6 mm Hg) and 43 mm Hg (S.D. 10 mm Hg), respectively. Myocardial oxygen tension was not altered significantly by varying the arterial oxygen tension between 65 and 300 mm Hg. However, myocardial carbon dioxide tension increased linearly with increased arterial carbon dioxide tension. In 15 dogs placed on total cardiopulmonary bypass, a perfusion pressure 40-60 mm lower than the control mean arterial pressure resulted in myocardial ischemia with a decrease in myocardial oxygen tension and an increase in myocardial carbon dioxide tension. A subsequent increase in perfusion pressure to control levels resulted in resolution of ischemia and return of myocardial oxygen and carbon dioxide tensions to their control level. In another series of open-chest dogs on cardiopulmonary bypass, a proximal constriction applied to the left coronary circumflex artery resulted in a marked decrease in myocardial oxygen tensions and a marked increase in myocardial carbon dioxide tensions in the region supplied by the constricted vessel. In yet another series of open-chest dogs, it was found that incremental decreases in coronary flow established by constriction of the circumflex artery resulted in an exponential increase in both myocardial carbon dioxide tensions and ST-segment elevation as determined by a 25-gauge multi-contact plunge electrode placed in the posterior left ventricular wall. It appears that mass spectrometry techniques for evaluating myocardial ischemia have several advantages over myocardial biopsy techniques for assay of ATP and lactate, and also over the technique of coronary sinus lactate determination. PMID:1209001

  11. Confronting Racial and Religious Tensions

    ERIC Educational Resources Information Center

    Wessler, Stephen

    2011-01-01

    When a community's demographics change quickly in terms of racial, religious, or ethnic makeup, Wessler notes, tension surfaces. Schools are the likeliest place for these kinds of tensions to openly come to a head. Schools can't always avoid conflicts among students who feel mutual prejudice and suspicion. But schools can address simmering…

  12. Fabrication of molecular tension probes.

    PubMed

    Kim, Sung Bae; Fujii, Rika

    2016-01-01

    A unique bioluminescent imaging probe is introduced for illuminating molecular tension appended by protein-protein interactions (PPIs) of interest. A full-length luciferase is sandwiched between two proteins of interest via minimal flexible linkers. The ligand-activated PPIs append intramolecular tension to the sandwiched luciferase, boosting or dropping the enzymatic activity in a quantitative manner. This method guides construction of a new lineage of bioassays for determining molecular tension appended by ligand-activated PPIs. The summary of the method is: •Molecular tension appended by protein-protein interactions (PPI) is visualized with a luciferase.•Estrogen activities are quantitatively illuminated with the molecular tension probes.•Full-length Renilla luciferase enhances the optical intensities after bending by PPI. PMID:27222821

  13. Fabrication of molecular tension probes

    PubMed Central

    Kim, Sung Bae; Fujii, Rika

    2016-01-01

    A unique bioluminescent imaging probe is introduced for illuminating molecular tension appended by protein–protein interactions (PPIs) of interest. A full-length luciferase is sandwiched between two proteins of interest via minimal flexible linkers. The ligand-activated PPIs append intramolecular tension to the sandwiched luciferase, boosting or dropping the enzymatic activity in a quantitative manner. This method guides construction of a new lineage of bioassays for determining molecular tension appended by ligand-activated PPIs. The summary of the method is: • Molecular tension appended by protein–protein interactions (PPI) is visualized with a luciferase. • Estrogen activities are quantitatively illuminated with the molecular tension probes. • Full-length Renilla luciferase enhances the optical intensities after bending by PPI. PMID:27222821

  14. The story of oxygen.

    PubMed

    Heffner, John E

    2013-01-01

    The history of oxygen from discovery to clinical application for patients with chronic lung disease represents a long and storied journey. Within a relatively short period, early investigators not only discovered oxygen but also recognized its importance to life and its role in respiration. The application of oxygen to chronic lung disease, however, took several centuries. In the modern era, physiologists pursued the chemical nature of oxygen and its physiologic interaction with cellular metabolism and gas transport. It took brazen clinicians, however, to pursue oxygen as a therapeutic resource for patients with chronic lung disease because of the concern in the 20th century of the risks of oxygen toxicity. Application of ambulatory oxygen devices allowed landmark investigations of the long-term effects of continuous oxygen that established its safety and efficacy. Although now well established for hypoxic patients, many questions remain regarding the benefits of oxygen for varying severity and types of chronic lung disease. PMID:23271817

  15. Cadmium-Induced Upregulation of Lipid Peroxidation and Reactive Oxygen Species Caused Physiological, Biochemical, and Ultrastructural Changes in Upland Cotton Seedlings

    PubMed Central

    Mei, Lei; Chen, Yue; Cheng, Xin; Zhu, S. J.

    2013-01-01

    Cadmium (Cd) toxicity was investigated in cotton cultivar (ZMS-49) using physiological, ultrastructural, and biochemical parameters. Biomass-based tolerance index decreased, and water contents increased at 500 μM Cd. Photosynthetic efficiency determined by chlorophyll fluorescence and photosynthetic pigments declined under Cd stress. Cd contents were more in roots than shoots. A significant decrease in nutrient levels was found in roots and stem. A significant decrease in nutrient levels was found in roots and stems. In response to Cd stress, more MDA and ROS contents were produced in leaves than in other parts of the seedlings. Total soluble proteins were reduced in all parts except in roots at 500 μM Cd. Oxidative metabolism was higher in leaves than aerial parts of the plant. There were insignificant alterations in roots and leaves ultrastructures such as a little increase in nucleoli, vacuoles, starch granules, and plastoglobuli in Cd-imposed stressful conditions. Scanning micrographs at 500 μM Cd showed a reduced number of stomata as well as near absence of closed stomata. Cd depositions were located in cell wall, vacuoles, and intracellular spaces using TEM-EDX technology. Upregulation of oxidative metabolism, less ultrastructural modification, and Cd deposition in dead parts of cells show that ZMS-49 has genetic potential to resist Cd stress, which need to be explored. PMID:24459668

  16. Tensional Homeostasis in Single Fibroblasts

    PubMed Central

    Webster, Kevin D.; Ng, Win Pin; Fletcher, Daniel A.

    2014-01-01

    Adherent cells generate forces through acto-myosin contraction to move, change shape, and sense the mechanical properties of their environment. They are thought to maintain defined levels of tension with their surroundings despite mechanical perturbations that could change tension, a concept known as tensional homeostasis. Misregulation of tensional homeostasis has been proposed to drive disorganization of tissues and promote progression of diseases such as cancer. However, whether tensional homeostasis operates at the single cell level is unclear. Here, we directly test the ability of single fibroblast cells to regulate tension when subjected to mechanical displacements in the absence of changes to spread area or substrate elasticity. We use a feedback-controlled atomic force microscope to measure and modulate forces and displacements of individual contracting cells as they spread on a fibronectin-patterned atomic-force microscope cantilever and coverslip. We find that the cells reach a steady-state contraction force and height that is insensitive to stiffness changes as they fill the micropatterned areas. Rather than maintaining a constant tension, the fibroblasts altered their contraction force in response to mechanical displacement in a strain-rate-dependent manner, leading to a new and stable steady-state force and height. This response is influenced by overexpression of the actin crosslinker α-actinin, and rheology measurements reveal that changes in cell elasticity are also strain- rate-dependent. Our finding of tensional buffering, rather than homeostasis, allows cells to transition between different tensional states depending on how they are displaced, permitting distinct responses to slow deformations during tissue growth and rapid deformations associated with injury. PMID:24988349

  17. BIOFEEDBACK TRAINING AND TENSION-TYPE HEADACHE.

    PubMed

    Šecić, Ana; Cvjeticanin, Timon; Kes, Vanja Bašić

    2016-03-01

    Biofeedback is a training method, which connects physiological and psychological processes in a person for the purposes of improving his/her physical, emotional, mental and spiritual health. In biofeedback treatment, an active role of the patient is stressed for him/her to be able to actively control the physiological and emotional processes. The aim of biofeedback is to improve the conscious control of the individual's involuntary physiological activity. Research has shown that biofeedback, either applied alone or in combination with other behavioral therapies (techniques), is an effective treatment for various medical and psychological disorders, from headache and hypertension to temporomandibular and attention deficit disorders. More than 90% of adults experience headache once a year, which makes headache one of the most common symptoms and diagnoses in medicine. Tension-type headaches occur in at least 40% of the population and their impact on the health insurance costs and diminished productivity is significant. Studies have shown that clinical biofeedback training is effective in treating headaches. Moreover, the authors stress the need for additional research and further development of methodology for this kind of research. PMID:27333731

  18. Tension-related activity in the orbitofrontal cortex and amygdala: an fMRI study with music.

    PubMed

    Lehne, Moritz; Rohrmeier, Martin; Koelsch, Stefan

    2014-10-01

    Tonal music is characterized by a continuous flow of tension and resolution. This flow of tension and resolution is closely related to processes of expectancy and prediction and is a key mediator of music-evoked emotions. However, the neural correlates of subjectively experienced tension and resolution have not yet been investigated. We acquired continuous ratings of musical tension for four piano pieces. In a subsequent functional magnetic resonance imaging experiment, we identified blood oxygen level-dependent signal increases related to musical tension in the left lateral orbitofrontal cortex (pars orbitalis of the inferior frontal gyrus). In addition, a region of interest analysis in bilateral amygdala showed activation in the right superficial amygdala during periods of increasing tension (compared with decreasing tension). This is the first neuroimaging study investigating the time-varying changes of the emotional experience of musical tension, revealing brain activity in key areas of affective processing. PMID:23974947

  19. Tension-related activity in the orbitofrontal cortex and amygdala: an fMRI study with music

    PubMed Central

    Lehne, Moritz; Rohrmeier, Martin

    2014-01-01

    Tonal music is characterized by a continuous flow of tension and resolution. This flow of tension and resolution is closely related to processes of expectancy and prediction and is a key mediator of music-evoked emotions. However, the neural correlates of subjectively experienced tension and resolution have not yet been investigated. We acquired continuous ratings of musical tension for four piano pieces. In a subsequent functional magnetic resonance imaging experiment, we identified blood oxygen level-dependent signal increases related to musical tension in the left lateral orbitofrontal cortex (pars orbitalis of the inferior frontal gyrus). In addition, a region of interest analysis in bilateral amygdala showed activation in the right superficial amygdala during periods of increasing tension (compared with decreasing tension). This is the first neuroimaging study investigating the time-varying changes of the emotional experience of musical tension, revealing brain activity in key areas of affective processing. PMID:23974947

  20. More About Measuring Interfacial Tension Between Liquids

    NASA Technical Reports Server (NTRS)

    Rashidnia, Nasser; Balasubramaniam, R.; Del Signore, David M.

    1995-01-01

    Report presents additional discussion of technique for measuring interfacial tension between two immiscible liquids. Technique described in "Measuring Interfacial Tension Between Immiscible Liquids" (LEW-15855).

  1. Physiological Waterfalls

    ERIC Educational Resources Information Center

    Leith, David E.

    1976-01-01

    Provides background information, defining areas within organ systems where physiological waterfalls exist. Describes pressure-flow relationships of elastic tubes (blood vessels, airways, renal tubules, various ducts). (CS)

  2. Application of Oxygen-Enriched Aeration in the Production of Bacitracin by Bacillus licheniformis

    PubMed Central

    Flickinger, M. C.; Perlman, D.

    1979-01-01

    The physiological effects of controlling the dissolved oxygen tension at 0.01, 0.02, and 0.05 atm by the use of oxygen-enriched aeration were investigated during growth and bacitracin production by Bacillus licheniformis ATCC 10716. Up to a 2.35-fold increase in the final antibiotic yield and a 4-fold increase in the rate of bacitracin synthesis were observed in response to O2-enriched aeration. The increase in antibiotic production was accompanied by increased respiratory activity and an increase in the specific productivity of the culture from 1.3 to 3.6 g of antibiotic per g of cell mass produced. Oxygen enrichment of the aeration decreased medium carbohydrate uptake and the maximum specific growth rate of B. licheniformis from 0.6 h−1 to as low as 0.15 h−1, depending upon the level of enrichment and the conditions of oxygen transfer rate (impeller speed). The response of this culture to O2 enrichment suggests that this method of controlling the dissolved oxygen tension for antibiotic-producing cultures may simulate conditions that would occur if the carbon source were fed slowly, as is often employed to optimize antibiotic production. Analysis of the biologically active bacitracins produced by B. licheniformis ATCC 10716 suggested that the ratio of biologically active peptides was not changed by O2 enrichment, nor were any new biologically active compounds formed. Images PMID:34361

  3. Metabolic Physiology in Pregnancy.

    PubMed

    Meo, Sultan Ayoub; Hassain, Asim

    2016-09-01

    The metabolic physiology during pregnancy is unique in the life of women. This change is a normal physiological adaptation to better accommodate the foetal growth and provides adequate blood, nutrition and oxygen. The metabolic changes prepare the mother\\'s body for pregnancy, childbirth and lactation. Early gestational period is considered as an anabolic phase, in which female body stores nutrients, enhance insulin sensitivity to encounter the maternal and feto-placental demands of late gestation and lactation. However, late gestational period is better named as a catabolic phase with reduced insulin sensitivity. The placenta plays a role as a sensor between mother and foetus physiology and acclimatizes the needs of the foetus to adequate growth and development. During pregnancy the female body changes its physiological and homeostatic mechanisms to meet the physiological needs of the foetus. However, if the maternal metabolic physiology during pregnancy is disturbed, it can cause hormonal imbalance, fat accumulation, decreased insulin sensitivity, increased insulin resistance and even gestational diabetes mellitus. PMID:27582161

  4. Do Optimal Prognostic Thresholds in Continuous Physiological Variables Really Exist? Analysis of Origin of Apparent Thresholds, with Systematic Review for Peak Oxygen Consumption, Ejection Fraction and BNP

    PubMed Central

    Leong, Tora; Rehman, Michaela B.; Pastormerlo, Luigi Emilio; Harrell, Frank E.; Coats, Andrew J. S.; Francis, Darrel P.

    2014-01-01

    Background Clinicians are sometimes advised to make decisions using thresholds in measured variables, derived from prognostic studies. Objectives We studied why there are conflicting apparently-optimal prognostic thresholds, for example in exercise peak oxygen uptake (pVO2), ejection fraction (EF), and Brain Natriuretic Peptide (BNP) in heart failure (HF). Data Sources and Eligibility Criteria Studies testing pVO2, EF or BNP prognostic thresholds in heart failure, published between 1990 and 2010, listed on Pubmed. Methods First, we examined studies testing pVO2, EF or BNP prognostic thresholds. Second, we created repeated simulations of 1500 patients to identify whether an apparently-optimal prognostic threshold indicates step change in risk. Results 33 studies (8946 patients) tested a pVO2 threshold. 18 found it prognostically significant: the actual reported threshold ranged widely (10–18 ml/kg/min) but was overwhelmingly controlled by the individual study population's mean pVO2 (r = 0.86, p<0.00001). In contrast, the 15 negative publications were testing thresholds 199% further from their means (p = 0.0001). Likewise, of 35 EF studies (10220 patients), the thresholds in the 22 positive reports were strongly determined by study means (r = 0.90, p<0.0001). Similarly, in the 19 positives of 20 BNP studies (9725 patients): r = 0.86 (p<0.0001). Second, survival simulations always discovered a “most significant” threshold, even when there was definitely no step change in mortality. With linear increase in risk, the apparently-optimal threshold was always near the sample mean (r = 0.99, p<0.001). Limitations This study cannot report the best threshold for any of these variables; instead it explains how common clinical research procedures routinely produce false thresholds. Key Findings First, shifting (and/or disappearance) of an apparently-optimal prognostic threshold is strongly determined by studies' average pVO2, EF or BNP. Second

  5. Monitoring oxygenation.

    PubMed

    Severinghaus, John W

    2011-06-01

    Cyanosis was used for a century after dentists began pulling teeth under 100% N(2)O in 1844 because brief (2 min) severe hypoxia is harmless. Deaths came with curare and potent anesthetic respiratory arrest. Leland Clark's invention of a polarographic blood oxygen tension electrode (1954) was introduced for transcutaneous PO2 monitoring to adjust PEEP and CPAP PO2 to prevent premature infant blindness from excess O2 (1972). Oximetry for warning military aviators was tried after WW II but not used for routine monitoring until Takuo Aoyagi (1973) discovered an equation to measure SaO2 by the ratio of ratios of red and IR light transmitted through tissue as it changed with arterial pulses. Pulse oximetry (1982) depended on simultaneous technology improvements of light emitting red and IR diodes, tiny cheap solid state sensors and micro-chip computers. Continuous monitoring of airway anesthetic concentration and oxygen also became very common after 1980. Death from anesthesia fell 10 fold between 1985 and 2000 as pulse oximetry became universally used, but no proof of a causative relationship to pulse oximetry exists. It is now assumed that all anesthesiologist became much more aware of the dangers of prolonged hypoxia, perhaps by using the pulse oximeters. PMID:21717228

  6. Rowing Physiology.

    ERIC Educational Resources Information Center

    Spinks, W. L.

    This review of the literature discusses and examines the methods used in physiological assessment of rowers, results of such assessments, and future directions emanating from research in the physiology of rowing. The first section discusses the energy demands of rowing, including the contribution of the energy system, anaerobic metabolism, and the…

  7. Adaptation to Oxygen

    PubMed Central

    Hassani, Bahia Khalfaoui; Steunou, Anne-Soisig; Liotenberg, Sylviane; Reiss-Husson, Françoise; Astier, Chantal; Ouchane, Soufian

    2010-01-01

    The appearance of oxygen in the Earth's atmosphere via oxygenic photosynthesis required strict anaerobes and obligate phototrophs to cope with the presence of this toxic molecule. Here we show that in the anoxygenic phototroph Rubrivivax gelatinosus, the terminal oxidases (cbb3, bd, and caa3) expand the range of ambient oxygen tensions under which the organism can initiate photosynthesis. Unlike the wild type, the cbb3−/bd− double mutant can start photosynthesis only in deoxygenated medium or when oxygen is removed, either by sparging cultures with nitrogen or by co-inoculation with strict aerobes bacteria. In oxygenated environments, this mutant survives nonphotosynthetically until the O2 tension is reduced. The cbb3 and bd oxidases are therefore required not only for respiration but also for reduction of the environmental O2 pressure prior to anaerobic photosynthesis. Suppressor mutations that restore respiration simultaneously restore photosynthesis in nondeoxygenated medium. Furthermore, induction of photosystem in the cbb3− mutant led to a highly unstable strain. These results demonstrate that photosynthetic metabolism in environments exposed to oxygen is critically dependent on the O2-detoxifying action of terminal oxidases. PMID:20335164

  8. Atomistic simulation of lipid and DiI dynamics in membrane bilayers under tension.

    PubMed

    Muddana, Hari S; Gullapalli, Ramachandra R; Manias, Evangelos; Butler, Peter J

    2011-01-28

    Membrane tension modulates cellular processes by initiating changes in the dynamics of its molecular constituents. To quantify the precise relationship between tension, structural properties of the membrane, and the dynamics of lipids and a lipophilic reporter dye, we performed atomistic molecular dynamics (MD) simulations of DiI-labeled dipalmitoylphosphatidylcholine (DPPC) lipid bilayers under physiological lateral tensions ranging from -2.6 mN m(-1) to 15.9 mN m(-1). Simulations showed that the bilayer thickness decreased linearly with tension consistent with volume-incompressibility, and this thinning was facilitated by a significant increase in acyl chain interdigitation at the bilayer midplane and spreading of the acyl chains. Tension caused a significant drop in the bilayer's peak electrostatic potential, which correlated with the strong reordering of water and lipid dipoles. For the low tension regime, the DPPC lateral diffusion coefficient increased with increasing tension in accordance with free-area theory. For larger tensions, free area theory broke down due to tension-induced changes in molecular shape and friction. Simulated DiI rotational and lateral diffusion coefficients were lower than those of DPPC but increased with tension in a manner similar to DPPC. Direct correlation of membrane order and viscosity near the DiI chromophore, which was just under the DPPC headgroup, indicated that measured DiI fluorescence lifetime, which is reported to decrease with decreasing lipid order, is likely to be a good reporter of tension-induced decreases in lipid headgroup viscosity. Together, these results offer new molecular-level insights into membrane tension-related mechanotransduction and into the utility of DiI in characterizing tension-induced changes in lipid packing. PMID:21152516

  9. The history of tissue tension.

    PubMed

    Peters, W S; Tomos, A D

    1996-06-01

    In recent years the phenomenon of tissue tension and its functional connection to elongation growth has regained much interest. In the present study we reconstruct older models of mechanical inhomogenities in growing plant organs, in order to establish an accurate historical background for the current discussion. We focus on the iatromechanic model developed in Stephen Hales' Vegetable Staticks, Wilhelm Hofmeister's mechanical model of negative geotropism, Julius Sachs' explanation of the development of tissue tension, and the differential-auxin-response-hypothesis by Kenneth Thimann and Charles Schneider. Each of these models is considered in the context of its respective historic and theoretical environment. In particular, the dependency of the biomechanical hypotheses on the cell theory and the hormone concept is discussed. We arrive at the conclusion that the historical development until the middle of our century is adequately described as a development towards more detailed explanations of how differential tensions are established during elongation growth in plant organs. Then we compare with the older models the structure of more recent criticism of hormonal theories of tropic curvature, and particularly the epidermal-growth-control hypothesis of Ulrich Kutschera. In contrast to the more elaborate of the older hypotheses, the recent models do not attempt an explanation of differential tensions, but instead focus on mechanical processes in organs, in which tissue tension already exists. Some conceptual implications of this discrepancy, which apparently were overlooked in the recent discussion, are briefly evaluated. PMID:11541099

  10. Anatomy & Physiology

    MedlinePlus

    ... Central Nervous System Peripheral Nervous System Review Quiz Endocrine System Characteristics of Hormones Endocrine Glands & Their Hormones Pituitary & ... Thyroid & Parathyroid Glands Adrenal Gland Pancreas Gonads Other Endocrine Glands ... Cardiovascular System Heart Structure of the Heart Physiology of the ...

  11. Singlet oxygen in photosensitization.

    PubMed

    Moan, Johan; Juzenas, Petras

    2006-01-01

    Oxygen is a ubiquitous element and a vitally important substance for life on the Earth, and especially for human life. Living organisms need oxygen for most, if not all, of their cellular functions. On the other hand, oxygen can produce metabolites that are toxic and potentially lethal to the same cells. Being reactive and chemically unstable reactive oxygen species (ROS) are the most important metabolites that initiate reduction and oxidation (redox) reactions under physiological conditions. Oxygen in its excited singlet state (1O2) is probably the most important intermediate in such reactions. Since the discovery of oxygen by Joseph Priestley in 1775 it has been recognized that oxygen can be both beneficial and harmful to life. PMID:16566709

  12. Surface tension in human pathophysiology and its application as a medical diagnostic tool

    PubMed Central

    Fathi-Azarbayjani, Anahita; Jouyban, Abolghasem

    2015-01-01

    Introduction: Pathological features of disease appear to be quite different. Despite this diversity, the common feature of various disorders underlies physicochemical and biochemical factors such as surface tension. Human biological fluids comprise various proteins and phospholipids which are capable of adsorption at fluid interfaces and play a vital role in the physiological function of human organs. Surface tension of body fluids correlates directly to the development of pathological states. Methods: In this review, the variety of human diseases mediated by the surface tension changes of biological phenomena and the failure of biological fluids to remain in their native state are discussed. Results: Dynamic surface tension measurements of human biological fluids depend on various parameters such as sex, age and changes during pregnancy or certain disease. It is expected that studies of surface tension behavior of human biological fluids will provide additional information and might become useful in medical practice. Theoretical background on surface tension measurement and surface tension values of reference fluids obtained from healthy and sick patients are depicted. Conclusion: It is well accepted that no single biomarker will be effective in clinical diagnosis. The surface tension measurement combined with routine lab tests may be a novel non-invasive method which can not only facilitate the discovery of diagnostic models for various diseases and its severity, but also be a useful tool for monitoring treatment efficacy. We therefore expect that studies of surface tension behavior of human biological fluids will provide additional useful information in medical practice. PMID:25901295

  13. Oxygen tensioactivity on liquid-metal drops.

    PubMed

    Ricci, E; Arato, E; Passerone, A; Costa, P

    2005-12-14

    The influence of oxygen on the surface tension of liquid metals is a topic of undoubted interest as the formation of oxide films, or even oxygen contamination of the metal interface, represents the main source of error in determining the surface tension. The evaluation of gas-atmosphere mass exchanges under stationary conditions allows the evaluation of an effective oxygen pressure at which the oxidation of metal becomes evident. This effective oxygen pressure can be considered as a property of the system and, according to experimental evidence, can be many orders of magnitude greater than the equilibrium pressure. The measurement of the surface tension is a good way of studying interface properties, their temporal change and their connections to transport and reaction rates. This paper represents a review of a work undertaken with the aim of understanding oxygen mass transport at the liquid metal surface in relation to the study of capillary phenomena at high temperature. PMID:16098947

  14. Physiological responses to Tai Chi in stable patients with COPD.

    PubMed

    Qiu, Zhi-Hui; Guo, Hong-Xi; Lu, Gan; Zhang, Ning; He, Bai-Ting; Zhou, Lian; Luo, Y M; Polkey, M I

    2016-01-15

    We compared the physiological work, judged by oxygen uptake, esophageal pressure swing and diaphragm electromyography, elicited by Tai Chi compared with that elicited by constant rate treadmill walking at 60% of maximal load in eleven patients with COPD (Mean FEV1 61% predicted, FEV1/FVC 47%). Dynamic hyperinflation was assessed by inspiratory capacity and twitch quadriceps tension (TwQ) elicited by supramaximal magnetic stimulation of the femoral nerve was also measured before and after both exercises. The EMGdi and esophageal pressure at the end of exercise were similar for both treadmill exercise and Tai Chi (0.109±0.047 mV vs 0.118±0.061 mV for EMGdi and 22.3±7.1 cmH2O vs 21.9±8.1 cmH2O for esophageal pressure). Moreover the mean values of oxygen uptake during Tai Chi and treadmill exercise did not differ significantly: 11.3 ml/kg/min (51.1% of maximal oxygen uptake derived from incremental exercise) and 13.4 ml/kg/min (52.5%) respectively, p>0.05. Respiratory rate during Tai Chi was significantly lower than that during treadmill exercise. Both Tai Chi and treadmill exercise elicited a fall in IC at end exercise, indicating dynamic hyperinflation, but this was statistically significant only after treadmill exercise. TwQ decreased significantly after Tai Chi but not after treadmill. We conclude that Tai Chi constitutes a physiologically similar stimulus to treadmill exercise and may therefore be an acceptable modality for pulmonary rehabilitation which may be culturally more acceptable in some parts of the world. PMID:26549554

  15. Researching with Children: Ethical Tensions

    ERIC Educational Resources Information Center

    Dockett, Sue; Einarsdottir, Johanna; Perry, Bob

    2009-01-01

    There is a need to reflect on both the processes and outcomes of the range of approaches aimed at promoting children's engagement in research, with the specific intent of listening to children's voices. This article considers some of the ethical tensions we have experienced when engaging children in research about their prior-to-school and school…

  16. Apparatus for determining surface tension

    NASA Technical Reports Server (NTRS)

    Razouk, R. E.

    1978-01-01

    System for studying capillary action uses pressure transducer and chart recorder instead of manometer. Apparatus enables measurements to be made under controlled atmospheres. It also may be remotely operated. These features are particularly useful when dealing with noxious liquids and for study of surface tension under high-pressure conditions that require use of all-metal apparatus.

  17. Snapping mechanical metamaterials under tension.

    PubMed

    Rafsanjani, Ahmad; Akbarzadeh, Abdolhamid; Pasini, Damiano

    2015-10-21

    A snapping mechanical metamaterial is designed, which exhibits a sequential snap-through behavior under tension. The tensile response of this mechanical metamaterial can be altered by tuning the architecture of the snapping segments to achieve a range of nonlinear mechanical responses, including monotonic, S-shaped, plateau, and non-monotonic snap-through behavior. PMID:26314680

  18. Everest Physiology Pre-2008.

    PubMed

    West, John B

    2016-01-01

    When Edmund Hillary and Tenzing Norgay reached the summit of Mt. Everest in 1953, it was the culmination of many attempts beginning in 1921. Alexander Kellas had actually predicted as early as 1920 that the mountain could be climbed, but the extreme altitude of 8848 m with the consequent oxygen deprivation had foiled previous attempts. One reason for the success of the 1953 expedition was the work done by the British physiologist Griffith Pugh in 1952 when he studied many of the physiological factors at high altitude including the oxygen requirements. Seven years later, Pugh and Hillary teamed up again for the Silver Hut Expedition in 1960-1961 that elucidated many of the problems of very high altitude. A group of physiologists spent several months at an altitude of 5800 m in a prefabricated hut and studied many aspects of exercise, pulmonary gas exchange, control of ventilation, and blood changes. Maximal exercise was measured as high as 7440 m and raised anew the question of whether Everest could ever be climbed without supplementary oxygen. The answer was shown to be yes in 1978 by Messner and Habeler, and 3 years later the American Medical Research Expedition to Everest clarified the physiological adaptations that allow humans to reach the highest point on earth. Five people reached the summit, the barometric pressure there was measured for the first time, and alveolar gas samples from the summit showed the critical importance of the extreme hyperventilation. However, the maximal oxygen consumption for the summit inspired PO2 of 43 mmHg was shown to be only about 1 l min(-1). In other words, the highest point on earth is very close to the limit of human tolerance to oxygen deprivation. As we celebrate the anniversary of Charles Darwin, it would be nice to have an evolutionary explanation for this, but in fact it is a cosmic coincidence. PMID:27343114

  19. Regulatory Physiology

    NASA Technical Reports Server (NTRS)

    Lane, Helen W.; Whitson, Peggy A.; Putcha, Lakshmi; Baker, Ellen; Smith, Scott M.; Stewart, Karen; Gretebeck, Randall; Nimmagudda, R. R.; Schoeller, Dale A.; Davis-Street, Janis

    1999-01-01

    As noted elsewhere in this report, a central goal of the Extended Duration Orbiter Medical Project (EDOMP) was to ensure that cardiovascular and muscle function were adequate to perform an emergency egress after 16 days of spaceflight. The goals of the Regulatory Physiology component of the EDOMP were to identify and subsequently ameliorate those biochemical and nutritional factors that deplete physiological reserves or increase risk for disease, and to facilitate the development of effective muscle, exercise, and cardiovascular countermeasures. The component investigations designed to meet these goals focused on biochemical and physiological aspects of nutrition and metabolism, the risk of renal (kidney) stone formation, gastrointestinal function, and sleep in space. Investigations involved both ground-based protocols to validate proposed methods and flight studies to test those methods. Two hardware tests were also completed.

  20. Physiological breeding.

    PubMed

    Reynolds, Matthew; Langridge, Peter

    2016-06-01

    Physiological breeding crosses parents with different complex but complementary traits to achieve cumulative gene action for yield, while selecting progeny using remote sensing, possibly in combination with genomic selection. Physiological approaches have already demonstrated significant genetic gains in Australia and several developing countries of the International Wheat Improvement Network. The techniques involved (see Graphical Abstract) also provide platforms for research and refinement of breeding methodologies. Recent examples of these include screening genetic resources for novel expression of Calvin cycle enzymes, identification of common genetic bases for heat and drought adaptation, and genetic dissection of trade-offs among yield components. Such information, combined with results from physiological crosses designed to test novel trait combinations, lead to more precise breeding strategies, and feed models of genotype-by-environment interaction to help build new plant types and experimental environments for future climates. PMID:27161822

  1. Physiology of vitreous surgery.

    PubMed

    Stefánsson, Einar

    2009-02-01

    Vitreous surgery has various physiological and clinical consequences, both beneficial and harmful. Vitrectomy reduces the risk of retinal neovascularization, while increasing the risk of iris neovascularization, reduces macular edema and stimulates cataract formation. These clinical consequences may be understood with the help of classical laws of physics and physiology. The laws of Fick, Stokes-Einstein and Hagen-Poiseuille state that molecular transport by diffusion or convection is inversely related to the viscosity of the medium. When the vitreous gel is replaced with less viscous saline, the transport of all molecules, including oxygen and cytokines, is facilitated. Oxygen transport to ischemic retinal areas is improved, as is clearance of VEGF and other cytokines from these areas, thus reducing edema and neovascularization. At the same time, oxygen is transported faster down a concentration gradient from the anterior to the posterior segment, while VEGF moves in the opposite direction, making the anterior segment less oxygenated and with more VEGF, stimulating iris neovascularization. Silicone oil is the exception that proves the rule: it is more viscous than vitreous humour, re-establishes the transport barrier to oxygen and VEGF, and reduces the risk for iris neovascularization in the vitrectomized-lentectomized eye. Modern vitreous surgery involves a variety of treatment options in addition to vitrectomy itself, such as photocoagulation, anti-VEGF drugs, intravitreal steroids and release of vitreoretinal traction. A full understanding of these treatment modalities allows sensible combination of treatment options. Retinal photocoagulation has repeatedly been shown to improve retinal oxygenation, as does vitrectomy. Oxygen naturally reduces VEGF production and improves retinal hemodynamics. The VEGF-lowering effect of photocoagulation and vitrectomy can be augmented with anti-VEGF drugs and the permeability effect of VEGF reduced with corticosteroids

  2. Spatial Variations in Vitreous Oxygen Consumption

    PubMed Central

    Murali, Karthik; Kang, Dongyang; Nazari, Hossein; Scianmarello, Nicholas; Cadenas, Enrique; Tai, Yu-Chong; Kashani, Amir; Humayun, Mark

    2016-01-01

    We investigated the spatial variation of vitreous oxygen consumption in enucleated porcine eyes. A custom made oxygen source was fabricated that could be localized to either the mid or posterior vitreous cavity and steady state vitreous oxygen tension was measured as a function of distance from the source using a commercially available probe. The reaction rate constant of ascorbate oxidation was estimated ex vivo by measuring the change in oxygen tension over time using vitreous harvested from porcine eyes. Vitreous ascorbate from mid and posterior vitreous was measured spectrophotometrically. When the oxygen source was placed in either the mid-vitreous (N = 6) or the posterior vitreous (N = 6), we measured a statistically significant decrease in vitreous oxygen tension as a function of distance from the oxygen source when compared to control experiments without an oxygen source; (p<0.005 for mid-vitreous and p<0.018 for posterior vitreous at all distances). The mid-vitreous oxygen tension change was significantly different from the posterior vitreous oxygen tension change at 2 and 3mm distances from the respective oxygen source (p<0.001). We also found a statistically significant lower concentration of ascorbate in the mid-vitreous as compared to posterior vitreous (p = 0.02). We determined the reaction rate constant, k = 1.61 M-1s-1 ± 0.708 M-1s-1 (SE), of the oxidation of ascorbate which was modeled following a second order rate equation. Our data demonstrates that vitreous oxygen consumption is higher in the posterior vitreous compared to the mid-vitreous. We also show spatial variations in vitreous ascorbate concentration. PMID:26930281

  3. Iron, oxygen, and the pulmonary circulation

    PubMed Central

    2015-01-01

    The human pulmonary vasculature vasoconstricts in response to a reduction in alveolar oxygen tension, a phenomenon termed hypoxic pulmonary vasoconstriction (HPV). This review describes the time course of this behavior, which occurs in distinct phases, and then explores the importance for HPV of the hypoxia-inducible factor (HIF) pathway. Next, the HIF-hydroxylase enzymes that act as molecular oxygen sensors within the HIF pathway are discussed. These enzymes are particularly sensitive to intracellular iron availability, which confers iron-sensing properties on the HIF pathway. Human studies of iron chelation and supplementation are then reviewed. These demonstrate that the iron sensitivity of the HIF pathway evident from in vitro experiments is relevant to human pulmonary vascular physiology. Next, the importance of iron status in high-altitude illness and chronic cardiopulmonary disease is explored, and the therapeutic potential of intravenous iron discussed. The review concludes by highlighting some further complexities that arise from interactions between the HIF pathway and other intracellular iron-sensing mechanisms. PMID:26066825

  4. Light Scattering by Surface Tension Waves.

    ERIC Educational Resources Information Center

    Weisbuch, G.; Garbay, F.

    1979-01-01

    This simple and inexpensive experiment is an illustration of the physical concepts of interaction between light and surface tension waves, and provides a new method of measuring surface tension. (Author/GA)

  5. The physiological basis of pulmonary gas exchange: implications for clinical interpretation of arterial blood gases.

    PubMed

    Wagner, Peter D

    2015-01-01

    The field of pulmonary gas exchange is mature, with the basic principles developed more than 60 years ago. Arterial blood gas measurements (tensions and concentrations of O₂ and CO₂) constitute a mainstay of clinical care to assess the degree of pulmonary gas exchange abnormality. However, the factors that dictate arterial blood gas values are often multifactorial and complex, with six different causes of hypoxaemia (inspiratory hypoxia, hypoventilation, ventilation/perfusion inequality, diffusion limitation, shunting and reduced mixed venous oxygenation) contributing variably to the arterial O₂ and CO₂ tension in any given patient. Blood gas values are then usually further affected by the body's abilities to compensate for gas exchange disturbances by three tactics (greater O₂ extraction, increasing ventilation and increasing cardiac output). This article explains the basic principles of gas exchange in health, mechanisms of altered gas exchange in disease, how the body compensates for abnormal gas exchange, and based on these principles, the tools available to interpret blood gas data and, quantitatively, to best understand the physiological state of each patient. This understanding is important because therapeutic intervention to improve abnormal gas exchange in any given patient needs to be based on the particular physiological mechanisms affecting gas exchange in that patient. PMID:25323225

  6. Oxygen requirement and tolerance of Campylobacter jejuni.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The human pathogen Campylobacter jejuni is considered a microaerophile, yet it has been shown to grow in vitro under atmospheres with elevated oxygen tensions. Hence, a better understanding of the oxygen requirement and tolerance of C. jejuni is required. Bacterial growth was measured under various ...

  7. Analysis of constant tension-induced rupture of lipid membranes using activation energy.

    PubMed

    Karal, Mohammad Abu Sayem; Levadnyy, Victor; Yamazaki, Masahito

    2016-05-11

    The stretching of biomembranes and lipid membranes plays important roles in various physiological and physicochemical phenomena. Here we analyzed the rate constant kp of constant tension-induced rupture of giant unilamellar vesicles (GUVs) as a function of tension σ using their activation energy Ua. To determine the values of kp, we applied constant tension to a GUV membrane using the micropipette aspiration method and observed the rupture of GUVs, and then analyzed these data statistically. First, we investigated the temperature dependence of kp for GUVs of charged lipid membranes composed of negatively charged dioleoylphosphatidylglycerol (DOPG) and electrically neutral dioleoylphosphatidylcholine (DOPC). By analyzing this result, the values of Ua of tension-induced rupture of DOPG/DOPC-GUVs were obtained. Ua decreased with an increase in σ, supporting the classical theory of tension-induced pore formation. The analysis of the relationship between Ua and σ using the theory on the electrostatic interaction effects on the tension-induced rupture of GUVs provided the equation of Ua including electrostatic interaction effects, which well fits the experimental data of the tension dependence of Ua. A constant which does not depend on tension, U0, was also found to contribute significantly to Ua. The Arrhenius equations for kp using the equation of Ua and the parameters determined by the above analysis fit well to the experimental data of the tension dependence of kp for DOPG/DOPC-GUVs as well as for DOPC-GUVs. On the basis of these results, we discussed the possible elementary processes underlying the tension-induced rupture of GUVs of lipid membranes. These results indicate that the Arrhenius equation using the experimentally determined Ua is useful in the analysis of tension-induced rupture of GUVs. PMID:27125194

  8. Fluoride glass: Crystallization, surface tension

    NASA Technical Reports Server (NTRS)

    Doremus, R. H.

    1988-01-01

    Fluoride glass was levitated acoustically in the ACES apparatus on STS-11, and the recovered sample had a different microstructure from samples cooled in a container. Further experiments on levitated samples of fluoride glass are proposed. These include nucleation, crystallization, melting observations, measurement of surface tension of molten glass, and observation of bubbles in the glass. Ground experiments are required on sample preparation, outgassing, and surface reactions. The results should help in the development and evaluation of containerless processing, especially of glass, in the development of a contaminent-free method of measuring surface tensions of melts, in extending knowledge of gas and bubble behavior in fluoride glasses, and in increasing insight into the processing and properties of fluoride glasses.

  9. Robust Tensioned Kevlar Suspension Design

    NASA Technical Reports Server (NTRS)

    Young, Joseph B.; Naylor, Bret J.; Holmes, Warren A.

    2012-01-01

    One common but challenging problem in cryogenic engineering is to produce a mount that has excellent thermal isolation but is also rigid. Such mounts can be achieved by suspending the load from a network of fibers or strings held in tension. Kevlar fibers are often used for this purpose owing to their high strength and low thermal conductivity. A suite of compact design elements has been developed to improve the reliability of suspension systems made of Kevlar.

  10. Surface Tension Confines Cryogenic Liquid

    NASA Technical Reports Server (NTRS)

    Castles, Stephen H.; Schein, Michael E.

    1989-01-01

    New type of Dewar provides passive, constant-temperature cryogenic cooling for scientific instruments under normal-to low-gravity conditions. Known as Surface-Tension-Contained Liquid Cryogen Cooler (STCLCC), keeps liquid cryogen in known location inside the Dewar by trapping liquid inside spongelike material. Unique sponge material fills most of volume of inner tank. Sponge is all-silica, open-cell material similar to that used for Space Shuttle thermal-protection tiles.

  11. Professional Identity Tensions of Beginning Teachers

    ERIC Educational Resources Information Center

    Pillen, Marieke; Beijaard, Douwe; den Brok, Perry

    2013-01-01

    This study reports on interviews with 24 beginning teachers about tensions they experienced regarding their professional identity. The interviewees reported a total of 59 tensions of tension that fell into three themes: (1) the change in role from student to teacher; (2) conflicts between desired and actual support given to students; and (3)…

  12. Oxygen Therapy

    MedlinePlus

    Oxygen therapy is a treatment that provides you with extra oxygen. Oxygen is a gas that your body needs to function. Normally, your lungs absorb oxygen from the air you breathe. But some conditions ...

  13. Conservation physiology

    PubMed Central

    Kronfeld-Schor, Noga

    2014-01-01

    Global change presents a huge and exciting challenge to the study of thermal physiology. The implication of thermoregulatory strategies and abilities for the survival of individuals and species, are of high importance for predicting species response to global change challenges and ways to mitigate them, and for conservation acts. A good example of such a study is the paper by Cooper and Withers in this issue.1

  14. Tensioning device for a stretched membrane collector

    DOEpatents

    Murphy, L.M.

    1984-01-01

    Disclosed is a solar concentrating collector comprising an elestic membrane member for concentrating sunlight, a frame for holding the membrane member in plane and in tension, and a tensioning means for varying the tension of the membrane member. The tensioning means is disposed at the frame and is adapted to releasably attach the membrane member thereto. The tensioning means is also adapted to uniformly and symmetrically subject the membrane member to stretching forces such that membrane stresses produced thereby are distributed uniformly over a thickness of the membrane member and reciprocal twisting moments are substantially prevented from acting about said frame.

  15. Tensioning device for a stretched membrane collector

    DOEpatents

    Murphy, Lawrence M.

    1984-01-01

    Disclosed is a solar concentrating collector comprising an elastic membrane member for concentrating sunlight, a frame for holding the membrane member in plane and in tension, and a tensioning means for varying the tension of the membrane member. The tensioning means is disposed at the frame and is adapted to releasably attach the membrane member thereto. The tensioning means is also adapted to uniformly and symmetrically subject the membrane member to stretching forces such that membrane stresses produced thereby are distributed uniformly over a thickness of the membrane member and reciprocal twisting moments are substantially prevented from acting about said frame.

  16. Small membranes under negative surface tension.

    PubMed

    Avital, Yotam Y; Farago, Oded

    2015-03-28

    We use computer simulations and a simple free energy model to study the response of a bilayer membrane to the application of a negative (compressive) mechanical tension. Such a tension destabilizes the long wavelength undulation modes of giant vesicles, but it can be sustained when small membranes and vesicles are considered. Our negative tension simulation results reveal two regimes-(i) a weak negative tension regime characterized by stretching-dominated elasticity and (ii) a strong negative tension regime featuring bending-dominated elastic behavior. This resembles the findings of the classic Evans and Rawicz micropipette aspiration experiment in giant unilamellar vesicles (GUVs) [E. Evans and W. Rawicz, Phys, Rev. Lett. 64, 2094 (1990)]. However, in GUVs the crossover between the two elasticity regimes occurs at a small positive surface tension, while in smaller membranes it takes place at a moderate negative tension. Another interesting observation concerning the response of a small membrane to negative surface tension is related to the relationship between the mechanical and fluctuation tensions, which are equal to each other for non-negative values. When the tension decreases to negative values, the fluctuation tension γ drops somewhat faster than the mechanical tension τ in the small negative tension regime, before it saturates (and becomes larger than τ) for large negative tensions. The bending modulus exhibits an "opposite" trend. It remains almost unchanged in the stretching-dominated elastic regime, and decreases in the bending-dominated regime. Both the amplitudes of the thermal height undulations and the projected area variations diverge at the onset of mechanical instability. PMID:25833604

  17. Small membranes under negative surface tension

    NASA Astrophysics Data System (ADS)

    Avital, Yotam Y.; Farago, Oded

    2015-03-01

    We use computer simulations and a simple free energy model to study the response of a bilayer membrane to the application of a negative (compressive) mechanical tension. Such a tension destabilizes the long wavelength undulation modes of giant vesicles, but it can be sustained when small membranes and vesicles are considered. Our negative tension simulation results reveal two regimes—(i) a weak negative tension regime characterized by stretching-dominated elasticity and (ii) a strong negative tension regime featuring bending-dominated elastic behavior. This resembles the findings of the classic Evans and Rawicz micropipette aspiration experiment in giant unilamellar vesicles (GUVs) [E. Evans and W. Rawicz, Phys, Rev. Lett. 64, 2094 (1990)]. However, in GUVs the crossover between the two elasticity regimes occurs at a small positive surface tension, while in smaller membranes it takes place at a moderate negative tension. Another interesting observation concerning the response of a small membrane to negative surface tension is related to the relationship between the mechanical and fluctuation tensions, which are equal to each other for non-negative values. When the tension decreases to negative values, the fluctuation tension γ drops somewhat faster than the mechanical tension τ in the small negative tension regime, before it saturates (and becomes larger than τ) for large negative tensions. The bending modulus exhibits an "opposite" trend. It remains almost unchanged in the stretching-dominated elastic regime, and decreases in the bending-dominated regime. Both the amplitudes of the thermal height undulations and the projected area variations diverge at the onset of mechanical instability.

  18. Effects of oxygen deprivation on incubated rat soleus muscle

    NASA Technical Reports Server (NTRS)

    Fagan, Julie M.; Tischler, Marc E.

    1989-01-01

    Isolated soleus muscle deprived of oxygen produces more lactate and alanine than oxygen-supplied muscle. Oxygenated muscle synthesized glutamine, while anoxic muscle used this amino acid. Oxygen deprivation decreased adenine nucleotides leading to the efflux of nucleosides. Protein synthesis and degradation responded differently to anoxia. Synthesis almost completely ceased, while proteolysis increased. Therefore, protein degradation in soleus muscle is enhanced when energy supplies and oxygen tension are low.

  19. Determination of membrane tension during balloon distension of intestine.

    PubMed

    Gregersen, H; Kassab, G S; Fung, Y C

    2004-09-01

    During the last decades, it has become increasingly common to make balloons distension in visceral organs in vivo. In particular this is true for studies of gastrointestinal motor function and biomechanics. Balloon distension is often used for assessment of small intestinal compliance and tension based on Laplace's law for cylindrical pressure pipes. This commonly used law is valid only when the balloon-distended intestine is cylindrical. Experimentally, it is seen that the diameter of the balloon-distended intestine is not a constant, but variable in the axial direction. Hence, it is necessary to improve Laplace's law for intestinal investigation. In this paper we develop the framework for determination of the tension distribution in circumferential and longitudinal direction during balloon distension. When the radii of curvature are measured from a photograph of the intestinal profile, then the membrane stress resultants can be computed everywhere in the intestine in contact with the balloon from the equations of equilibrium. The experimental data were obtained from small intestinal segments from five pigs and three guinea pigs. Papaverine was injected before the animals were sacrificed to relax the intestinal smooth muscle. The segments were immersed in a bath with calcium-free Krebs solution with dextran and EGTA. A balloon was distended in the lumen with pressures up to 15 cmH2O in the pigs and 10 cmH2O in the guinea pigs and radii were measured along the z-axis. The tension in circumferential direction had its maximum approximately 25% away from the middle of the balloon. The circumferential tension was 2-3 times higher than the longitudinal tension. In conclusion when we know the shape of the intestine, we can compute the circumferential and longitudinal components of tension. The large variation in tensions along the z axis must be considered when performing balloon distension studies in the gastrointestinal tract for studying physiological and

  20. Surface tension driven convection experiment

    NASA Technical Reports Server (NTRS)

    Ostrach, Simon; Kamotani, Yasuhiro

    1988-01-01

    Thermocapillary flow is driven by a thermally induced surface tension variation along a liquid free surface. In the Earth-gravity environment such flows are usually overshadowed by buoyancy driven flows, but at reduced gravity conditions their influence could be significant. A comprehensive theoretical and experimental research program was stated 12 years ago and is still being continued. Past work done at Case Western Reserve University as well as work done by others is reviewed. The justification for low-gravity experiments is presented.

  1. Axelrod's model with surface tension

    NASA Astrophysics Data System (ADS)

    Pace, Bruno; Prado, Carmen P. C.

    2014-06-01

    In this work we propose a subtle change in Axelrod's model for the dissemination of culture. The mechanism consists of excluding from the set of potentially interacting neighbors those that would never possibly exchange. Although the alteration proposed does not alter the state space topologically, it yields significant qualitative changes, specifically the emergence of surface tension, driving the system in some cases to metastable states. The transient behavior is considerably richer, and cultural regions become stable leading to the formation of different spatiotemporal patterns. A metastable "glassy" phase emerges between the globalized phase and the disordered, multicultural phase.

  2. Low Oxygen Modulates Multiple Signaling Pathways, Increasing Self-Renewal, While Decreasing Differentiation, Senescence, and Apoptosis in Stromal MIAMI Cells.

    PubMed

    Rios, Carmen; D'Ippolito, Gianluca; Curtis, Kevin M; Delcroix, Gaëtan J-R; Gomez, Lourdes A; El Hokayem, Jimmy; Rieger, Megan; Parrondo, Ricardo; de Las Pozas, Alicia; Perez-Stable, Carlos; Howard, Guy A; Schiller, Paul C

    2016-06-01

    Human bone marrow multipotent mesenchymal stromal cell (hMSC) number decreases with aging. Subpopulations of hMSCs can differentiate into cells found in bone, vasculature, cartilage, gut, and other tissues and participate in their repair. Maintaining throughout adult life such cell subpopulations should help prevent or delay the onset of age-related degenerative conditions. Low oxygen tension, the physiological environment in progenitor cell-rich regions of the bone marrow microarchitecture, stimulates the self-renewal of marrow-isolated adult multilineage inducible (MIAMI) cells and expression of Sox2, Nanog, Oct4a nuclear accumulation, Notch intracellular domain, notch target genes, neuronal transcriptional repressor element 1 (RE1)-silencing transcription factor (REST), and hypoxia-inducible factor-1 alpha (HIF-1α), and additionally, by decreasing the expression of (i) the proapoptotic proteins, apoptosis-inducing factor (AIF) and Bak, and (ii) senescence-associated p53 expression and β-galactosidase activity. Furthermore, low oxygen increases canonical Wnt pathway signaling coreceptor Lrp5 expression, and PI3K/Akt pathway activation. Lrp5 inhibition decreases self-renewal marker Sox2 mRNA, Oct4a nuclear accumulation, and cell numbers. Wortmannin-mediated PI3K/Akt pathway inhibition leads to increased osteoblastic differentiation at both low and high oxygen tension. We demonstrate that low oxygen stimulates a complex signaling network involving PI3K/Akt, Notch, and canonical Wnt pathways, which mediate the observed increase in nuclear Oct4a and REST, with simultaneous decrease in p53, AIF, and Bak. Collectively, these pathway activations contribute to increased self-renewal with concomitant decreased differentiation, cell cycle arrest, apoptosis, and/or senescence in MIAMI cells. Importantly, the PI3K/Akt pathway plays a central mechanistic role in the oxygen tension-regulated self-renewal versus osteoblastic differentiation of progenitor cells. PMID:27059084

  3. Decreased cardiac index as an indicator of tension pneumothorax in the ventilated patient.

    PubMed

    Beards, S C; Lipman, J

    1994-02-01

    We describe three critically ill patients receiving pressure-controlled ventilation who suffered acute hypotensive episodes associated with the development of tension pneumothoraces. In four documented episodes of tension pneumothorax a major decrease in cardiac index was the most consistently detected abnormality. The expected increases in central venous pressure and heart rate did not occur in three of the episodes in two of the patients, both of whom were receiving inotropic therapy. Any increases in airway pressure could not be assessed on pressure-controlled ventilation. The physiology of tension pneumothorax in the ventilated patient is described and the importance of decreased cardiac index as a haemodynamic indicator of tension pneumothorax is discussed. PMID:8129123

  4. Biofeedback for Developing Self-Control of Tension and Stress in One's Hierarchy of Psychological States.

    ERIC Educational Resources Information Center

    Cassel, Russell

    1985-01-01

    Describes six stage hierarchial patterns in the development of self-control through biofeedback. The stages include Skeletal and Striated Muscle Tension; Visceral Involvement-Anxiety Neuroses; Chronic Physiological Dysfunctioning; Decision Making Competency; Twilight Learning-Permissive Concentration; and Autogenic Feedback Training. (BL)

  5. Update on Normal Tension Glaucoma

    PubMed Central

    Mallick, Jyotiranjan; Devi, Lily; Malik, Pradeep K.; Mallick, Jogamaya

    2016-01-01

    Normal tension glaucoma (NTG) is labelled when typical glaucomatous disc changes, visual field defects and open anterior chamber angles are associated with intraocular pressure (IOP) constantly below 21 mmHg. Chronic low vascular perfusion, Raynaud's phenomenon, migraine, nocturnal systemic hypotension and over-treated systemic hypertension are the main causes of normal tension glaucoma. Goldmann applanation tonometry, gonioscopy, slit lamp biomicroscopy, optical coherence tomography and visual field analysis are the main tools of investigation for the diagnosis of NTG. Management follows the same principles of treatment for other chronic glaucomas: To reduce IOP by a substantial amount, sufficient to prevent disabling visual loss. Treatment is generally aimed to lower IOP by 30% from pre-existing levels to 12-14 mmHg. Betaxolol, brimonidine, prostaglandin analogues, trabeculectomy (in refractory cases), systemic calcium channel blockers (such as nifedipine) and 24-hour monitoring of blood pressure are considered in the management of NTG. The present review summarises risk factors, causes, pathogenesis, diagnosis and management of NTG. PMID:27413503

  6. [Tension headache--a review].

    PubMed

    Pfaffenrath, V; Wermuth, A; Pöllmann, W

    1988-12-01

    Tension headache (TH) is an ill-defined headache syndrome, characterized by bilateral, daily headaches with fronto-occipital localisation. TH is often accompanied by a migraine and an abuse of analgesics and/or ergotamine. In the etiology of TH vascular, muscular and psychogenic factors are assumed. Floating transitions to common migraine are discussed. The increased muscle tension is not specific for TH, but more probably a consequence of TH. In addition a decrease of the pain threshold with a deficiency of the antinociceptive system is supposed. The efficacy of tricyclic antidepressives in TH is based on potentiation of serotonergic and noradrenergic mechanisms and - besides their analgetic potencies - upon an increase of the pain threshold. TH prophylaxis is indicated if patients suffer from TH more than ten times per month. Medication are tricyclic antidepressives of the amitriptyline-type. Prophylaxis of TH can only be successful if a simultaneous abuse of analgesics and/or ergotamine is discontinued. In addition, EMG-biofeedback, as well as relaxation - and vasoconstriction training might be helpful in specific cases. PMID:3069680

  7. Physiological Acoustics

    NASA Astrophysics Data System (ADS)

    Young, Eric D.

    The analysis of physiological sound in the peripheral auditory system solves three important problems. First, sound energy impinging on the head must be captured and presented to the transduction apparatus in the ear as a suitable mechanical signal; second, this mechanical signal needs to be transduced into a neural representation that can be used by the brain; third, the resulting neural representation needs to be analyzed by central neurons to extract information useful to the animal. This chapter provides an overview of some aspects of the first two of these processes. The description is entirely focused on the mammalian auditory system, primarily on human hearing and on the hearing of a few commonly used laboratory animals (mainly rodents and carnivores). Useful summaries of non-mammalian hearing are available [1]. Because of the large size of the literature, review papers are referenced wherever possible.

  8. Initial tension loss in cerclage cables.

    PubMed

    Ménard, Jérémie; Émard, Maxime; Canet, Fanny; Brailovski, Vladimir; Petit, Yvan; Laflamme, George Y

    2013-10-01

    Cerclage cables, frequently used in the management of fractures and osteotomies, are associated with a high failure rate and significant loosening during surgery. This study compared the capacity to maintain tension of different types of orthopaedic cable systems. Multifilament Cobalt-Chrome (CoCr) cables with four different crimp/clamp devices (DePuy, Stryker, Zimmer and Smith&Nephew) and one non-metallic Nylon (Ny) cable from Kinamed were instrumented with a load cell to measure tension during insertion. Significant tension loss was observed with crimping for all cables (P<0.05). Removing the tensioner led to an additional unexpected tension loss (CoCr-DePuy: 18%, CoCr-Stryker: 29%, CoCr-Smith&Nephew: 33%, Ny: 46%, and CoCr-Zimmer: 52%). The simple CoCr (DePuy) cable system outperformed the more sophisticated locking devices due to its significantly better ability to prevent tension loss. PMID:23618753

  9. Measuring Interfacial Tension Between Immiscible Liquids

    NASA Technical Reports Server (NTRS)

    Rashidnia, Nasser; Balasubramaniam, R.; Delsignore, David M.

    1995-01-01

    Glass capillary tube technique measures interfacial tension between two immiscible liquids. Yields useful data over fairly wide range of interfacial tensions, both for pairs of liquids having equal densities and pairs of liquids having unequal densities. Data on interfacial tensions important in diverse industrial chemical applications, including enhanced extraction of oil; printing; processing foods; and manufacture of paper, emulsions, foams, aerosols, detergents, gel encapsulants, coating materials, fertilizers, pesticides, and cosmetics.

  10. Space Physiology within an Exercise Physiology Curriculum

    ERIC Educational Resources Information Center

    Carter, Jason R.; West, John B.

    2013-01-01

    Compare and contrast strategies remain common pedagogical practices within physiological education. With the support of an American Physiological Society Teaching Career Enhancement Award, we have developed a junior- or senior-level undergraduate curriculum for exercise physiology that compares and contrasts the physiological adaptations of…

  11. Myoglobin and Mitochondria: A relationship bound by Oxygen and Nitric Oxide

    PubMed Central

    Kamga, Christelle; Krishnamurthy, Suhas; Shiva, Sruti

    2012-01-01

    Since their initial discovery over a century ago, our knowledge of the functions of myoglobin and the mitochondrion has gradually evolved. The mitochondrion, once thought to be solely responsible for energy production, is now known to be an integral redox and apoptotic signal tranducer within the cell. Likewise, myoglobin, traditionally thought of only as an oxygen store, has emerged as a physiological catalyst that can modulate reactive oxygen species levels, facilitate oxygen diffusion and scavenge or generate nitric oxide (NO) depending on oxygen tensions within the cell. By virtue of its unique ability to regulate O2 and NO levels within the cell, myoglobin can modulate mitochondrial function in energy-demanding tissues such as the beating heart and exercising muscle. In this review, we present the conventional functions of myoglobin and mitochondria, and describe how these roles have been reassessed and advanced, particularly in the context of NO and nitrite signaling. We present the mechanisms by which mitochondria and myoglobin regulate one another within the cell through their interactions with NO and oxygen and discuss the implications of these interactions in terms of health and disease. PMID:22465476

  12. The effects of progressive anemia on jejunal mucosal and serosal tissue oxygenation in pigs.

    PubMed

    Haisjackl, M; Luz, G; Sparr, H; Germann, R; Salak, N; Friesenecker, B; Deusch, E; Meusburger, S; Hasibeder, W

    1997-03-01

    Anemia may promote intestinal hypoxia. We studied the effects of progressive isovolemic hemodilution on jejunal mucosal (Po2muc), and serosal tissue oxygen tension (Po2ser, Clark-type surface electrodes), mucosal microvascular hemoglobin oxygen saturation (Hbo2muc), and hematocrit (Hctmuc; tissue reflectance spectophotometry) in a jejunal segment. Twelve domestic pigs were anesthetized, paralyzed, and mechanically ventilated. Laparatomy was performed, arterial supply of a jejunal segment isolated, and constant pressure pump perfused. Seven animals were progressively hemodiluted to systemic hematocrits (Hctsys) of 20%, 15%, 10%, and 6%. Baseline for Po2muc, Po2ser and Hbo2muc was 23.5 +/- 2.1 mm Hg, 57.5 +/- 4 mm Hg, and 47.0% +/- 6.4% which were not different from the five controls. Despite a significant increase in jejunal blood flow, jejunal oxygen delivery decreased and oxygen extraction ratio increased significantly at Hctsys 10% and 6%. Po2ser decreased significantly below or at Hctsys of 15%, whereas Po2muc and Hbo2muc were maintained to Hctsys of 10%, but less than 10% Hbo2muc and mesenteric venous pH decreased significantly, implying that physiological limits of jejunal microvascular adaptation to severe anemia were reached. Decrease of Hctmuc was less pronounced than Hctsys. In conclusion, redistribution of jejunal blood flow and an increase in the ratio of mucosal to systemic hematocrit are the main mechanisms maintaining mucosal oxygen supply during progressive anemia. PMID:9052297

  13. The oxygen status algorithm: a computer program for calculating and displaying pH and blood gas data.

    PubMed

    Siggaard-Andersen, O; Siggaard-Andersen, M

    1990-01-01

    Input parameters for the program are the arterial pH, pCO2, and pO2 (measured by a blood gas analyzer), oxygen saturation, carboxy-, met-, and total hemoglobin (measured by a multi-wavelength spectrometer), supplemented by patient age, sex, temperature, inspired oxygen fraction, fraction of fetal hemoglobin, and ambient pressure. Output parameters are the inspired and alveolar oxygen partial pressures, pH,pCO2 and pO2 referring to the actual patient temperature, estimated shunt fraction, half-saturation tension, estimated 2,3-diphosphoglycerate concentration, oxygen content and oxygen capacity, extracellular base excess, and plasma bicarbonate concentration. Three parameters related to the blood oxygen availability are calculated: the oxygen extraction tension, concentration of extractable oxygen, and oxygen compensation factor. Calculations of the 'reverse' type may also be performed so that the effect of therapeutic measures on the oxygen status or the acid-base status can be predicted. The user may choose among several different units of measurement and two different conventions for symbols. The results are presented in a data display screen comprising all quantities together with age, sex, and temperature adjusted reference values. The program generates a 'laboratory diagnosis' of the oxygen status and the acid-base status and three graphs illustrating the oxygen status and the acid-base status of the patient: the oxygen graph, the acid-base chart and the blood gas map. A printed summary in one A4 page including a graphical display can be produced with an Epson or HP Laser compatible printer. The program is primarily intended for routine laboratories with a blood gas analyzer combined with a multi-wavelength spectrometer. Calculating the derived quantities may enhance the usefulness of the analyzers and improve patient care. The program may also be used as a teaching aid in acid-base and respiratory physiology. The program requires an IBM PC, XT, AT or similar

  14. [Tension pneumomediastinum and tension pneumothorax following tracheal perforation during cardiopulmonary resuscitation].

    PubMed

    Buschmann, C T; Tsokos, M; Kurz, S D; Kleber, C

    2015-07-01

    Tension pneumothorax can occur at any time during cardiopulmonary resuscitation (CPR) with external cardiac massage and invasive ventilation either from primary or iatrogenic rib fractures with concomitant pleural or parenchymal injury. Airway injury can also cause tension pneumothorax during CPR. This article presents the case of a 41-year-old woman who suffered cardiopulmonary arrest after undergoing elective mandibular surgery. During CPR the upper airway could not be secured by orotracheal intubation due to massive craniofacial soft tissue swelling. A surgical airway was established with obviously unrecognized iatrogenic tracheal perforation and subsequent development of tension pneumomediastinum and tension pneumothorax during ventilation. Neither the tension pneumomediastinum nor the tension pneumothorax were decompressed and accordingly resuscitation efforts remained unsuccessful. This case illustrates the need for a structured approach to resuscitate patients with ventilation problems regarding decompression of tension pneumomediastinum and/or tension pneumothorax during CPR. PMID:26036317

  15. Large deflection analysis of a tension-foil bearing

    NASA Technical Reports Server (NTRS)

    Elrod, David A.

    1996-01-01

    The rolling element bearings (REB's) which support many turbomachinery rotors offer high load capacity, low power requirements, and durability. Two disadvantages of REB's are as follows: rolling or sliding contact within the bearing has life-limiting consequences; and REB's provide essentially no damping. The REB's in the Space Shuttle Main Engine (SSME) turbopumps must sustain high static and dynamic loads, at high speeds, with a cryogenic fluid as lubricant and coolant. The pump end ball bearings limit the life of the SSME high pressure oxygen turbopump (HPOTP). Compliant foil bearing (CFB) manufacturers have proposed replacing turbopump REB's with CFB's. CFB's work well in aircraft air cycle machines, auxiliary power units, and refrigeration compressors. In a CFB, the rotor only contacts the foil support structure during start up and shut down. CFB damping is higher than REB damping. However, the load capacity of the CFB is low, compared to a REB. Furthermore, little stiffness and damping data exist for the CFB. A rotordynamic analysis for turbomachinery critical speeds and stability requires the input of bearing stiffness and damping coefficients. The two basic types of CFB are the tension-dominated bearing and the bending-dominated bearing. Many investigators have analyzed and measured characteristics of tension-dominated foil bearings, which are applied principally in magnetic tape recording. The bending-dominated CFB is used more in rotating machinery. Recently, a new tension-foil bearing configuration has been proposed for turbomachinery applications.

  16. Effect of cholesterol on the biophysical and physiological properties of a clinical pulmonary surfactant.

    PubMed

    Keating, Eleonora; Rahman, Luna; Francis, James; Petersen, Anne; Possmayer, Fred; Veldhuizen, Ruud; Petersen, Nils O

    2007-08-15

    Pulmonary surfactant is a complex mixture of lipids and proteins that forms a surface-active film at the air-water interface of alveoli capable of reducing surface tension to near 0 mN/m. The role of cholesterol, the major neutral lipid component of pulmonary surfactant, remains uncertain. We studied the physiological effect of cholesterol by monitoring blood oxygenation levels of surfactant-deficient rats treated or not treated with bovine lipid extract surfactant (BLES) containing zero or physiological amounts of cholesterol. Our results indicate no significant difference between BLES and BLES containing cholesterol immediately after treatment; however, during ventilation, BLES-treated animals maintained higher PaO2 values compared to BLES+cholesterol-treated animals. We used a captive bubble tensiometer to show that physiological amounts of cholesterol do not have a detrimental effect on the surface activity of BLES at 37 degrees C. The effect of cholesterol on topography and lateral organization of BLES Langmuir-Blodgett films was also investigated using atomic force microscopy. Our data indicate that cholesterol induces the formation of domains within liquid-ordered domains (Lo). We used time-of-flight-secondary ion mass spectrometry and principal component analysis to show that cholesterol is concentrated in the Lo phase, where it induces structural changes. PMID:17526587

  17. Age Differences in Types of Interpersonal Tensions

    ERIC Educational Resources Information Center

    Cichy, Kelly E.; Fingerman, Karen L.; Lefkowitz, Eva S.

    2007-01-01

    This study examined age differences in topics that generate interpersonal tensions as well as relationship level characteristics that may account for variability in the content of interpersonal tensions. Participants aged 13 to 99 years (N = 184) diagramed their close and problematic social networks, and then provided open-ended descriptions of…

  18. Tensions in Rhetorics of Presence and Performance

    ERIC Educational Resources Information Center

    Watanabe, Sundy Louise

    2012-01-01

    This dissertation draws on theories of survivance and rhetorical sovereignty to document and interrogate interactional tensions in rhetorics of presence and performance occurring between selected American Indian students and non-Native faculty, staff, and graduate research assistants within a research-extensive university context. Tensions arise,…

  19. Effect of Gravity on Surface Tension

    NASA Technical Reports Server (NTRS)

    Weislogel, M. M.; Azzam, M. O. J.; Mann, J. A.

    1998-01-01

    Spectroscopic measurements of liquid-vapor interfaces are made in +/- 1-g environments to note the effect of gravity on surface tension. A slight increase is detected at -1-g0, but is arguably within the uncertainty of the measurement technique. An increased dependence of surface tension on the orientation and magnitude of the gravitational vector is anticipated as the critical point is approached.

  20. Surface Tension Measurements of Chemically Modified Oleochemical

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Surface tension is an important physical property of a substance, which plays a part in a variety of physical phenomenon relevant to many industrial processes. For example, the efficiency of the atomization of a fuel has been shown to be effected dramatically by surface tension and viscosity. Beca...

  1. Pericellular oxygen concentration of cultured primary human trophoblasts

    PubMed Central

    Chen, Baosheng; Longtine, Mark S.; Nelson, D. Michael

    2012-01-01

    Introduction Oxygen is pivotal in placental development and function. In vitro culture of human trophoblasts provides a useful model to study this phenomenon, but a hotly debated issue is whether or not the oxygen tension of the culture conditions mimics in vivo conditions. We tested the hypothesis that ambient oxygen tensions in culture reflect the pericellular oxygen levels. Methods We used a microelectrode oxygen sensor to measure the concentration of dissolved oxygen in the culture medium equilibrated with 21%, 8% or <0.5% oxygen. Results The concentration of oxygen in medium without cells resembled that in the ambient atmosphere. The oxygen concentration present in medium bathing trophoblasts was remarkably dependent on the depth within the medium where sampling occurred, and the oxygen concentration within the overlying atmosphere was not reflected in medium immediately adjacent to the cells. Indeed, the pericellular oxygen concentration was in a range that most would consider severe hypoxia, at ≤ 0.6% oxygen or about 4.6 mm Hg, when the overlying atmosphere was 21% oxygen. Conclusions We conclude that culture conditions of 21% oxygen are unable to replicate the pO2 of 40–60 mm Hg commonly attributed to the maternal blood in the intervillous space in the second and third trimesters of pregnancy. We further surmise that oxygen atmospheres in culture conditions between 0.5% and 21% provide different oxygen fluxes in the immediate pericellular environment yet can still yield insights into the responses of human trophoblast to different oxygen conditions. PMID:23211472

  2. Arterial blood gas tensions and pH.

    PubMed Central

    Flenley, D C

    1980-01-01

    1 The definition of PO2 and its relationship to the oxygen saturation (SO2) by the oxygen dissociation curve (ODC) is described with details of the ligands of the ODC and the effects of haemoglobinopathies on P50 (the position of the ODC) and the slope of the ODC (Hill's 'n'). 2 The definition of PCO2 and description of CO2 transport by blood leads to consideration of the basis of acid base balance. 3 Acid base balance is expressed in terms of arterial blood (H+) (or pH) PCO2 relationship using a non-logarithmic diagram. 4 The measurement of arterial blood gas tensions is described with comments on arterial puncture and available modern automated blood gas electrodes and their calibration. 5 Non-invasive indirect measurements of blood gas tensions, by ear oximetry are described, with calibration figures on the Hewlett-Packard 47021A ear oximeter. End-tidal PO2 and PCO2 measurements by mass spectrometer or infra-red CO2 analyser, and of transcutaneous PO2 measurements by a heated polarographic electrode are described. 6 These measurements are necessary to study the effects of pharmacological agents on the chemical control of breathing, on pulmonary gas exchange, and on acid base balance in humans. The measurements are in everyday use in clinical practice, both to aid diagnosis of respiratory diseases, assess their severity, and to quantiate the effects of therapeutic agents. PMID:7356899

  3. Dialectical tensions in stroke survivor relationships.

    PubMed

    Brann, Maria; Himes, Kimberly Leezer; Dillow, Megan R; Weber, Keith

    2010-06-01

    Stroke is an unpredictable and life-altering medical occurrence that causes immediate change in survivors' relationships. This study unearthed dialectical tensions expressed by spouses of stroke survivors and examined how those dialectical tensions compare to those experienced by stroke survivors themselves. Sixteen spouses of stroke survivors participated in interviews, and four tensions ultimately emerged: self-orientation-partner-orientation, realism-idealism, uncertainty-acceptance, and emotional release-emotional reservation. Three dialectical tensions (i.e., uncertainty-acceptance, realism-idealism, self-orientation-partner-orientation) were similar to those communicated by stroke survivors. Recognizing dialectical tensions experienced and shared can open communication lines and ultimately improve the health of individuals and their relationships. PMID:20512714

  4. Subacute Tension Hemopneumothorax with Novel Electrocardiogram Findings

    PubMed Central

    Saks, Mark A.; Griswold-Theodorson, Sharon; Shinaishin, Furkan; Demangone, Dawn

    2010-01-01

    This case report describes a patient with a subacute right-sided tension hemopneumothorax following an occult stab. The patient’s electrocardiogram (ECG), performed as part of a standardized triage process, demonstrated significant abnormalities that misguided initial resuscitation, but resolved following evacuation of the tension hemopneumothorax. Tension pneumothorax is typically regarded as an immediately life-threatening condition that requires emergent management with needle or tube thoracostomy. However, we believe that subacute tension pneumothorax may be a rarely observed clinical phenomenon and may lead to unique ECG findings. We believe that the ECG changes we observed provided an early clue to the eventual diagnosis of a subacute tension pneumothorax and have not been previously described in this setting. . PMID:20411085

  5. Effect of nitric oxide on the transport and release of oxygen in fetal blood.

    PubMed

    Clementi, Maria Elisabetta; Orsini, Federica; Schininà, Maria Eugenia; Noia, Giuseppe; Giardina, Bruno

    2003-03-14

    It is well known that nitric oxide (NO), the most important vasodilator agent, plays an important role in lowering vascular resistance in the human umbilical-placental circulation and that its deficiency is related to the pathogenesis of pre-eclamptic disorder. Besides it has recently been demonstrated that human hemoglobin (HbA) is able to transport nitric oxide, as S-nitrosohemoglobin (SNO-Hb), from the arterial to the venous blood. In the present study we examine the functional properties of the adult and fetal nitrosated hemoglobins to see if the double transport of oxygen and NO may influence the fetal oxygenation and the relation between maternal and fetal blood. Our results show that S-nitrosation significantly increases the oxygen affinity of the adult Hb (HbA) with respect to native protein (no-nitrosated) while the functional properties of HbF are less influenced. The oxygen affinity modification, found for SNO-HbA, was ascribed to the nitrosation of cysteine beta 93: really, the same residue is also present in the gamma chains of fetal hemoglobin, while the increase of affinity is less evidenced; hence, it is probable that the 39 aminoacidic substitutions between beta and gamma chains allay the effects of S-nitrosation. As regards the physiological modulators (protons, chloride ions, 2,3-diphosphoglyceric acid, and temperature), they influence the oxygen affinity of the two hemoglobins S-nitrosated, in equal mode with respect to the native forms determining the same variation on the oxygen affinity. Hence, our results evidence the fact that the NO release by SNO-HbA "in vivo" would be limited to regions of extremely low oxygen tension (such as hypoxic regions), while in fetus, SNO-HbF would unload nitric oxide and oxygen at pressure values close to normal. PMID:12615064

  6. Physiological mechanisms for the modulation of pannexin 1 channel activity

    PubMed Central

    Sandilos, Joanna K; Bayliss, Douglas A

    2012-01-01

    It is widely recognized that ATP, along with other nucleotides, subserves important intercellular signalling processes. Among various nucleotide release mechanisms, the relatively recently identified pannexin 1 (Panx1) channel is gaining prominence by virtue of its ability to support nucleotide permeation and release in a variety of different tissues. Here, we review recent advances in our understanding of the factors that control Panx1 channel activity. By using electrophysiological and biochemical approaches, diverse mechanisms that dynamically regulate Panx1 channel function have been identified in various settings; these include, among others, activation by caspase-mediated channel cleavage in apoptotic immune cells, by G protein-coupled receptors in vascular smooth muscle, by low oxygen tension in erythrocytes and neurons, by high extracellular K+ in various cell types and by stretch/strain in airway epithelia. Delineating the distinct mechanisms of Panx1 modulation that prevail in different physiological contexts provides the possibility that these channels, and ATP release, could ultimately be targeted in a context-dependent manner. PMID:23070703

  7. Regulation of nitrite transport in red blood cells by hemoglobin oxygen fractional saturation.

    PubMed

    Vitturi, Dario A; Teng, Xinjun; Toledo, José C; Matalon, Sadis; Lancaster, Jack R; Patel, Rakesh P

    2009-05-01

    Allosteric regulation of nitrite reduction by deoxyhemoglobin has been proposed to mediate nitric oxide (NO) formation during hypoxia. Nitrite is predominantly an anion at physiological pH, raising questions about the mechanism by which it enters the red blood cell (RBC) and whether this is regulated and coupled to deoxyhemoglobin-mediated reduction. We tested the hypothesis that nitrite transport by RBCs is regulated by fractional saturation. Using human RBCs, nitrite consumption was faster at lower fractional saturations, consistent with faster reactions with deoxyheme. A membrane-based regulation was suggested by slower nitrite consumption with intact versus lysed RBCs. Interestingly, upon nitrite addition, intracellular nitrite concentrations attained a steady state that, despite increased rates of consumption, did not change with decreasing oxygen tensions, suggesting a deoxygenation-sensitive step that either increases nitrite import or decreases the rate of nitrite export. A role for anion exchanger (AE)-1 in the control of nitrite export was suggested by increased intracellular nitrite concentrations in RBCs treated with DIDS. Moreover, deoxygenation decreased steady-state levels of intracellular nitrite in AE-1-inhibited RBCs. Based on these data, we propose a model in which deoxyhemoglobin binding to AE-1 inhibits nitrite export under low oxygen tensions allowing for the coupling between deoxygenation and nitrite reduction to NO along the arterial-to-venous gradient. PMID:19286940

  8. An interlaminar tension strength specimen

    NASA Technical Reports Server (NTRS)

    Jackson, Wade C.; Martin, Roderick H.

    1992-01-01

    This paper describes a technique to determine interlaminar tension strength, sigma(sub 3c) of a fiber reinforced composite material using a curved beam. The specimen was a unidirectional curved beam, bent 90 degrees, with straight arms. Attached to each arm was a hinged loading mechanism which was held by the grips of a tensile testing machine. Geometry effects of the specimen, including the effects of loading arm length, inner radius, thickness, and width, were studied. The data sets fell into two categories: low strength corresponding to a macroscopic flaw related failure and high strength corresponding to a microscopic flaw related failure. From the data available, the loading arm length had no effect on sigma(sub 3c). The inner radius was not expected to have a significant effect on sigma(sub 3c), but this conclusion could not be confirmed because of differences in laminate quality for each curve geometry. The thicker specimens had the lowest value of sigma(sub 3c) because of poor laminate quality. Width was found to affect the value of sigma(sub 3c) only slightly. The wider specimens generally had a slightly lower strength since more material was under high stress, and hence, had a larger probability of containing a significant flaw.

  9. Dynamical Modeling of Surface Tension

    NASA Technical Reports Server (NTRS)

    Brackbill, Jeremiah U.; Kothe, Douglas B.

    1996-01-01

    In a recent review it is said that free-surface flows 'represent some of the difficult remaining challenges in computational fluid dynamics'. There has been progress with the development of new approaches to treating interfaces, such as the level-set method and the improvement of older methods such as the VOF method. A common theme of many of the new developments has been the regularization of discontinuities at the interface. One example of this approach is the continuum surface force (CSF) formulation for surface tension, which replaces the surface stress given by Laplace's equation by an equivalent volume force. Here, we describe how CSF formulation might be made more useful. Specifically, we consider a derivation of the CSF equations from a minimization of surface energy as outlined by Jacqmin (1996). This reformulation suggests that if one eliminates the computation of curvature in terms of a unit normal vector, parasitic currents may be eliminated. For this reformulation to work, it is necessary that transition region thickness be controlled. Various means for this, in addition to the one discussed by Jacqmin (1996), are discussed.

  10. Tear Oxygen Under Hydrogel and Silicone Hydrogel Contact Lenses in Humans

    PubMed Central

    Bonanno, Joseph A.; Clark, Christopher; Pruitt, John; Alvord, Larry

    2011-01-01

    Purpose To determine the tear oxygen tension under a variety of conventional and silicone hydrogel contact lenses in human subjects. Methods Three hydrogel and five silicone hydrogel lenses (Dk/t = 17 to 329) were coated on the back surface with an oxygen sensitive, bovine serum albumin-Pd meso-tetra (4-carboxyphenyl) porphine complex (BSA-porphine). Each lens type was placed on the right eye of 15 non-contact lens wearers to obtain a steady-state open eye tear oxygen tension using oxygen sensitive phosphorescence decay of BSA-porphine. A closed-eye oxygen tension estimate was obtained by measuring the change in tear oxygen tension after 5 min of eye closure. In separate experiments, a goggle was placed over the lens wearing eye and a gas mixture (PO2 = 51 torr) flowed over the lens to simulate anterior lens oxygen tension during eye closure. Results Mean open eye oxygen tension ranged from 58 to 133 torr. Closed eye estimates ranged from 11 to 42 torr. Oxygen tension under the goggle ranged from 8 to 48 torr and was higher than the closed eye estimate for six out of the eight lenses, suggesting that the average closed eye anterior lens surface oxygen tension is <51 torr. For Dk/t >30, the measured tear oxygen tension is significantly lower than that predicted from previous studies. Conclusions The phosphorescence decay methodology is capable of directly measuring the in vivo post lens PO2 of high Dk/t lenses without disturbing the contact lens or cornea. Our data indicate that increasing Dk/t up to and beyond 140 continues to yield increased flux into the central cornea. PMID:19609230

  11. Inhibition of histone deacetylase activity in reduced oxygen environment enhances the osteogenesis of mouse adipose-derived stromal cells.

    PubMed

    Xu, Yue; Hammerick, Kyle E; James, Aaron W; Carre, Antoine L; Leucht, Philipp; Giaccia, Amato J; Longaker, Michael T

    2009-12-01

    Recent studies suggest that oxygen tension has a great impact on the osteogenic differentiation capacity of mesenchymal cells derived from adipose tissue: reduced oxygen impedes osteogenesis. We have found that expansion of mouse adipose-derived stromal cells (mASCs) in reduced oxygen tension (10%) results in increased cell proliferation along with induction of histone deacetylase (HDAC) activity. In this study, we utilized two HDAC inhibitors (HDACi), sodium butyrate (NaB) and valproic acid (VPA), and studied their effects on mASCs expanded in various oxygen tensions (21%, 10%, and 1% O(2)). Significant growth inhibition was observed with NaB or VPA treatment in each oxygen tension. Osteogenesis was enhanced by treatment with NaB or VPA, particularly in reduced oxygen tensions (10% and 1% O(2)). Conversely, adipogenesis was decreased with treatments of NaB or VPA at all oxygen tensions. Finally, NaB- or VPA-treated, reduced oxygen tension-exposed (1% O(2)) ASCs were grafted into surgically created mouse tibial defects and resulted in significantly increased bone regeneration. In conclusion, HDACi significantly promote the osteogenic differentiation of mASCs exposed to reduced oxygen tension; HDACi may hold promise for future clinical applications of ASCs for skeletal regeneration. PMID:19505250

  12. Iron deficiency leads to inhibition of oxygen transfer and enhanced formation of virulence factors in cultures of Pseudomonas aeruginosa PAO1.

    PubMed

    Kim, Eun-Jin; Sabra, Wael; Zeng, An-Ping

    2003-09-01

    Pseudomonas aeruginosa PAO1 was recently found to exhibit two remarkable physiological responses to oxidative stress: (1) a strong reduction in the efficiency of oxygen transfer from the gas phase into the liquid phase, thus causing oxygen limitation in the culture and (2) formation of a clear polysaccharide capsule on the cell surface. In this work, it has been shown that the iron concentration in the culture plays a crucial role in evoking these phenomena. The physiological responses of two P. aeruginosa PAO1 isolates (NCCB 2452 and ATCC 15692) were examined in growth media with varied iron concentrations. In a computer-controlled bioreactor cultivation system for controlled dissolved oxygen tension (pO2), a strong correlation between the exhaustion of iron and the onset of oxygen limitation was observed. The oxygen transfer rate of the culture, characterized by the volumetric oxygen transfer coefficient, kLa, significantly decreased under iron-limited conditions. The formation of alginate and capsule was more strongly affected by iron concentration than by oxygen concentration. The reduction of the oxygen transfer rate and the subsequent oxygen limitation triggered by iron deficiency may represent a new and efficient way for P. aeruginosa PAO1 to adapt to growth conditions of iron limitation. Furthermore, the secretion of proteins into the culture medium was strongly enhanced by iron limitation. The formation of the virulence factor elastase and the iron chelators pyoverdine and pyochelin also significantly increased under iron-limited conditions. These results have implications for lung infection of cystic fibrosis patients by P. aeruginosa in view of the prevalence of iron limitation at the site of infection and the respiratory failure leading to death. PMID:12949186

  13. Low oxygen [correction of oxygene] tension may defence the bone tissue from unloading simulated osteopenia.

    PubMed

    Berezovskii, V A; Litovka, I G; Kostyuchenko, A S

    2004-07-01

    The main task of the present study is to investigate the influences of normobaric gas mixture with lowered PO2 (90-110 mm Hg) on the bones metabolism in rats after hind limb unloaded (HLU). We observed increased the glycosaminoglicans (GAG) concentration in blood serum rats with hind limb unloaded in atmospheric air (AA). An increased activity of acid phosphatase (AcP) and tartratresistant acid phosphatase (TRAcP) in blood serum of rats after HLU was observed. The activities of the alkaline phosphatase (AIP) in blood serum did not change. An increased osteocalcin (OST) and C-terminal Propeptide of type I Collagen (CICP) concentration in blood serum, but parathyroid hormone (PTH) decrease comparatively with the control. The above mentioned biochemistry markers in animals after 28 days unloading in normobaric gas mixture (NGM) were more stable and in spite of the same procedure in AA, all dates were near to the controls. PMID:16237821

  14. Brief: Field measurements of casing tension forces

    SciTech Connect

    Quigley, M.S.; Lewis, D.B.; Boswell, R.S.

    1995-02-01

    Tension forces acting on individual casing joints were accurately measured during installation of 10,158 ft of 9 5/8-in. {times} 47-lbm/ft casing and 11,960 ft of 11 7/8-in. {times} 71.8-lbm/ft casing. A unique casing load table (CLT) weighed the casing string after the addition of each casing joint. Strain gauges attached inside the pin ends of instrumented casing joints (ICJ`s) directly measured tension force on those joints. A high-speed computer data-acquisition system (DAS) automatically recorded data from all the sensors. Several casing joints were intentionally subjected to extreme deceleration to determine upper limits for dynamic tension forces. Data from these tests clearly show effects of wellbore friction and casing handling conditions. In every case, tension forces in the casing during maximum deceleration were considerably less than expected. In some cases, the highest tension forces occurred when the casing lifted out of the slips. Peak tension forces caused by setting the casing slips were typically no more than 5% greater than tension forces in the casing at rest. This dynamic amplification was far less than the 60% value used in the previous casing design method. Reducing the safety factor for installation loads has permitted use of lighter, less-expensive casing than dictated by older design criteria.

  15. Handheld magnetic sensor for measurement of tension

    NASA Astrophysics Data System (ADS)

    Singal, K.; Rajamani, R.

    2012-04-01

    This letter develops an analytical formulation for measurement of tension in a string using a handheld sensor. By gently pushing the sensor against the string, the tension in the string can be obtained. An experimental sensor prototype is constructed to verify the analytical formulation. The centimeter-sized prototype utilizes three moving pistons and magnetic field based measurements of their positions. Experimental data show that the sensor can accurately measure tension on a bench top rig. The developed sensor could be useful in a variety of orthopedic surgical procedures, including knee replacement, hip replacement, ligament repair, shoulder stabilization, and tendon repair.

  16. Free Volume in Membranes: Viscosity or Tension?

    PubMed Central

    Markin, V. S.; Sachs, F.

    2016-01-01

    Many papers have used fluorescent probe diffusion to infer membrane viscosity but the measurement is actually an assay of the free volume of the membrane. The free volume is also related to the membrane tension. Thus, changes in probe mobility refer equally well to changes in membrane tension. In complicated structures like cell membranes, it appears more intuitive to consider variations in free volume as referring to the effect of domains structures and interactions with the cytoskeleton than changes in viscosity since tension is a state variable and viscosity is not.

  17. Gastrothorax or tension pneumothorax: A diagnostic dilemma

    PubMed Central

    Singh, Sarvesh P; Sukesan, Subin; Kiran, Usha; Makhija, Neeti

    2011-01-01

    Gastrothorax, a rare complication following thoracoabdominal aortic aneurysm repair, is reported. The clinical features of a gastrothorax and tension pneumothorax are similar and thus, a gastrothorax can masquerade as a tension pneumothorax. The diagnosis is made by a high level of clinical suspicion, chest X-ray shows a distended stomach with air fluid levels and a computerised tomography is useful in assessing the diaphragm and establishing the positions of the various intra-abdominal organs. Also, the risk of an intercostal drainage tube placement and the role of nasogastric tube in avoiding the development of a tension gastrothorax is highlighted. PMID:21633581

  18. The surface tension of liquid gallium

    NASA Technical Reports Server (NTRS)

    Hardy, S. C.

    1985-01-01

    The surface tension of liquid gallium has been measured using the sessile drop technique in an Auger spectrometer. The experimental method is described. The surface tension in mJ/sq m is found to decrease linearly with increasing temperature and may be represented as 708-0.66(T-29.8), where T is the temperature in centigrade. This result is of interest because gallium has been suggested as a model fluid for Marangoni flow experiments. In addition, the surface tension is of technological significance in the processing of compound semiconductors involving gallium.

  19. Surface tension profiles in vertical soap films

    NASA Astrophysics Data System (ADS)

    Adami, N.; Caps, H.

    2015-01-01

    Surface tension profiles in vertical soap films are experimentally investigated. Measurements are performed by introducing deformable elastic objets in the films. The shape adopted by those objects once set in the film is related to the surface tension value at a given vertical position by numerically solving the adapted elasticity equations. We show that the observed dependency of the surface tension versus the vertical position is predicted by simple modeling that takes into account the mechanical equilibrium of the films coupled to previous thickness measurements.

  20. Surface tension in situ in flooded alveolus unaltered by albumin.

    PubMed

    Kharge, Angana Banerjee; Wu, You; Perlman, Carrie E

    2014-09-01

    In the acute respiratory distress syndrome, plasma proteins in alveolar edema liquid are thought to inactivate lung surfactant and raise surface tension, T. However, plasma protein-surfactant interaction has been assessed only in vitro, during unphysiologically large surface area compression (%ΔA). Here, we investigate whether plasma proteins raise T in situ in the isolated rat lung under physiologic conditions. We flood alveoli with liquid that omits/includes plasma proteins. We ventilate the lung between transpulmonary pressures of 5 and 15 cmH2O to apply a near-maximal physiologic %ΔA, comparable to that of severe mechanical ventilation, or between 1 and 30 cmH2O, to apply a supraphysiologic %ΔA. We pause ventilation for 20 min and determine T at the meniscus that is present at the flooded alveolar mouth. We determine alveolar air pressure at the trachea, alveolar liquid phase pressure by servo-nulling pressure measurement, and meniscus radius by confocal microscopy, and we calculate T according to the Laplace relation. Over 60 ventilation cycles, application of maximal physiologic %ΔA to alveoli flooded with 4.6% albumin solution does not alter T; supraphysiologic %ΔA raise T, transiently, by 51 ± 4%. In separate experiments, we find that addition of exogenous surfactant to the alveolar liquid can, with two cycles of maximal physiologic %ΔA, reduce T by 29 ± 11% despite the presence of albumin. We interpret that supraphysiologic %ΔA likely collapses the interfacial surfactant monolayer, allowing albumin to raise T. With maximal physiologic %ΔA, the monolayer likely remains intact such that albumin, blocked from the interface, cannot interfere with native or exogenous surfactant activity. PMID:24970853

  1. Oxygen Therapy

    MedlinePlus

    ... 85-95% pure oxygen. The concentrator runs on electricity or a battery. A concentrator for home usually ... systems deliver 100% oxygen, and do not require electricity. A small canister can be filled from the ...

  2. Oxygen analyzer

    DOEpatents

    Benner, William H.

    1986-01-01

    An oxygen analyzer which identifies and classifies microgram quantities of oxygen in ambient particulate matter and for quantitating organic oxygen in solvent extracts of ambient particulate matter. A sample is pyrolyzed in oxygen-free nitrogen gas (N.sub.2), and the resulting oxygen quantitatively converted to carbon monoxide (CO) by contact with hot granular carbon (C). Two analysis modes are made possible: (1) rapid determination of total pyrolyzable oxygen obtained by decomposing the sample at 1135.degree. C., or (2) temperature-programmed oxygen thermal analysis obtained by heating the sample from room temperature to 1135.degree. C. as a function of time. The analyzer basically comprises a pyrolysis tube containing a bed of granular carbon under N.sub.2, ovens used to heat the carbon and/or decompose the sample, and a non-dispersive infrared CO detector coupled to a mini-computer to quantitate oxygen in the decomposition products and control oven heating.

  3. Alveolar partial pressures of carbon dioxide and oxygen measured by a helium washout technique.

    PubMed Central

    Jordanoglou, J; Tatsis, G; Danos, J; Gougoulakis, S; Orfanidou, D; Gaga, M

    1990-01-01

    A non-invasive technique was developed for measuring alveolar carbon dioxide and oxygen tension during tidal breathing. This was achieved by solving the Bohr equations for mean alveolar carbon dioxide and oxygen tensions (PACO2, PAO2) from known values of the dead-space:tidal volume ratio measured by helium washout, and from the mixed expired partial pressure of carbon dioxide and oxygen. The derived values of wPACO2 and wPAO2 were compared with PaCO2 obtained from arterial gas analysis and PAO2 calculated from the ideal air equation. Four normal subjects and 58 patients were studied. Calculated and measured PCO2 values agreed closely with a difference in mean values (wPACO2 - PaCO2) of 0.01 kPa; the SD of the differences was 0.7 kPa. The difference in mean values between wPAO2 and PAO2 was 0.02 kPa; the SD of the differences was 0.93 kPa. The method is simple and not time consuming, and requires no special cooperation from the patients. It can be applied in the laboratory or at the bedside to any subject breathing tidally. Physiological deadspace:tidal volume ratio, PAO2 and PACO2, static lung volumes, respiratory exchange ratio, carbon dioxide production, oxygen uptake, tidal volume, and total ventilation can be measured with acceptable accuracy and reproducibility in one test. An arterial blood sample is needed initially to provide an independent measure of PaCO2 and for measurement of the alveolar-arterial PO2 difference. Subsequently, PaCO2 can be estimated from wPACO2 sufficiently well for clinical purposes and PaO2 or SaO2 can be monitored by non-invasive methods. Images PMID:2118690

  4. Tension in the LHC diffractive data?

    SciTech Connect

    Gotsman, Errol

    2015-04-10

    I discuss the LHC diffractive data, and compare it to predicted energy behaviour of various models. I suggest that the so called 'tension' between the experimental results, maybe due to the different Monte Carlo programs used.

  5. Managing bond tension in spreading macromolecules.

    NASA Astrophysics Data System (ADS)

    Sheyko, Sergey; Park, Insun; Nese, Alper; Matyjaszewski, Krzysztof; Shirvaniants, David; Rubinstein, Michael

    2009-03-01

    Mechanical activation of chemical bonds plays a vital role in biology, chemistry, and engineering. Unlike other activation stimuli, such as light and temperature, mechanical activation is site and direction specific. However, in a typical experiment, macroscopic stress is distributed over myriads of different molecules. This results in significant and ill-defined variation of both the magnitude and direction of forces at individual chemical bonds. Here, we show how to achieve a great degree of control over bond tension in flowing polymer films. The distinctive feature of this finding is that the mechanical tension is controlled on three different length scales. First, chemical bonds are activated within a narrowly defined area of a macroscopic film. Second, only certain molecules are activated within a mixture of molecules. Third, the tension can be focused to a specific bond within a flowing macromolecule. It is demonstrated that the focused tension breaks covalent bonds with a molecular-scale precision.

  6. The Equilibrium Spreading Tension of Pulmonary Surfactant.

    PubMed

    Dagan, Maayan P; Hall, Stephen B

    2015-12-01

    Monomolecular films at an air/water interface coexist at the equilibrium spreading tension (γ(e)) with the bulk phase from which they form. For individual phospholipids, γ(e) is single-valued, and separates conditions at which hydrated vesicles adsorb from tensions at which overcompressed monolayers collapse. With pulmonary surfactant, isotherms show that monolayers compressed on the surface of bubbles coexist with the three-dimensional collapsed phase over a range of surface tensions. γ(e) therefore represents a range rather than a single value of surface tension. Between the upper and lower ends of this range, rates of collapse for spread and adsorbed films decrease substantially. Changes during adsorption across this narrow region of coexistence between the two- and three-dimensional structures at least partially explain how alveolar films of pulmonary surfactant become resistant to collapse. PMID:26583569

  7. Mineralization of bone-related SaOS-2 cells under physiological hypoxic conditions.

    PubMed

    Müller, Werner E G; Schröder, Heinz C; Tolba, Emad; Diehl-Seifert, Bärbel; Wang, Xiaohong

    2016-01-01

    Inorganic polyphosphate (polyP) is a physiological energy-rich polymer with multiple phosphoric anhydride bonds. In cells such as bone-forming osteoblasts, glycolysis is the main pathway generating metabolic energy in the form of ATP. In the present study, we show that, under hypoxic culture conditions, the growth/viability of osteoblast-like SaOS-2 cells is not impaired. The addition of polyP to those cells, administered as amorphous calcium polyP nanoparticles (aCa-polyP-NP; approximate size 100 nm), significantly increased the proliferation of the cells. In the presence of polyP, the cells produce significant levels of lactate, the end product of anaerobic glycolysis. Under those conditions, an eight-fold increase in the steady-state level of the membrane-associated carbonic anhydrase IX is found, as well as a six-fold induction of the hypoxia-inducible factor 1. Consequently, biomineral formation onto the SaOS-2 cells decreases under low oxygen tension. If the polyP nanoparticles are added to the cells, the degree of mineralization is enhanced. These changes had been measured also in human mesenchymal stem cells. The assumption that the bicarbonate, generated by the carbonic anhydrase in the presence of polyP under low oxygen, is deposited as a constituent of the bioseeds formed during initial hydroxyapatite formation is corroborated by the identification of carbon besides of calcium, oxygen and phosphorus in the initial biomineral deposit onto the cells using the sensitive technology of high-resolution energy dispersive spectrometry mapping. Based on these data, we conclude that polyP is required for the supply of metabolic energy during bone mineral formation under physiological, hypoxic conditions, acting as a 'metabolic fuel' for the cells to grow. PMID:26453899

  8. Oxygen analyzer

    DOEpatents

    Benner, W.H.

    1984-05-08

    An oxygen analyzer which identifies and classifies microgram quantities of oxygen in ambient particulate matter and for quantitating organic oxygen in solvent extracts of ambient particulate matter. A sample is pyrolyzed in oxygen-free nitrogen gas (N/sub 2/), and the resulting oxygen quantitatively converted to carbon monoxide (CO) by contact with hot granular carbon (C). Two analysis modes are made possible: (1) rapid determination of total pyrolyzable obtained by decomposing the sample at 1135/sup 0/C, or (2) temperature-programmed oxygen thermal analysis obtained by heating the sample from room temperature to 1135/sup 0/C as a function of time. The analyzer basically comprises a pyrolysis tube containing a bed of granular carbon under N/sub 2/, ovens used to heat the carbon and/or decompose the sample, and a non-dispersive infrared CO detector coupled to a mini-computer to quantitate oxygen in the decomposition products and control oven heating.

  9. A pumpless microfluidic device driven by surface tension for pancreatic islet analysis.

    PubMed

    Xing, Yuan; Nourmohammadzadeh, Mohammad; Elias, Joshua E Mendoza; Chan, Manwai; Chen, Zequn; McGarrigle, James J; Oberholzer, José; Wang, Yong

    2016-10-01

    We present a novel pumpless microfluidic array driven by surface tension for studying the physiology of pancreatic islets of Langerhans. Efficient fluid flow in the array is achieved by surface tension-generated pressure as a result of inlet and outlet size differences. Flow properties are characterized in numerical simulation and further confirmed by experimental measurements. Using this device, we perform a set of biological assays, which include real-time fluorescent imaging and insulin secretion kinetics for both mouse and human islets. Our results demonstrate that this system not only drastically simplifies previously published experimental protocols for islet study by eliminating the need for external pumps/tubing and reducing the volume of solution consumption, but it also achieves a higher analytical spatiotemporal resolution due to efficient flow exchanges and the extremely small volume of solutions required. Overall, the microfluidic platform presented can be used as a potential powerful tool for understanding islet physiology, antidiabetic drug development, and islet transplantation. PMID:27534648

  10. Hyperbaric oxygenation in fluid microembolism.

    PubMed

    James, Philip B

    2007-03-01

    Because clinicians require objectively demonstrable neurological deficits to confirm a diagnosis, the recognition of embolic events in the nervous system is generally restricted to the effects of ischemic necrosis produced by arterial occlusion. However, magnetic resonance imaging (MRI) has shown that lesser degrees of damage associated with small emboli are common, especially in the mid brain, and are usually clinically silent. They are frequently associated with atheromatous embolism in the elderly, but microembolic debris, such as fat, is common in the systemic venous return of healthy people and generally trapped in the microcirculation of the lung being removed by phagocytosis. However, pulmonary filtration may fail and microemboli may also pass through an atrial septal defect in so-called 'paradoxical' embolism. Studies of bubbles formed on decompression in diving have demonstrated the importance of pulmonary filtration in the protection of the nervous system and that filtration is size dependant, as small bubbles may escape entrapment. Fluid and even small solid emboli, arresting in or passing through the cerebral circulation, do not cause infarction, but disturb the blood-brain barrier inducing what has been termed the 'perivenous syndrome'. The nutrition of areas of the white matter of both the cerebral medulla and the spinal cord depends on long draining veins which have been shown to have surrounding capillary free zones. Because of the high oxygen extraction in the microcirculation of the gray matter of the central nervous system, the venous blood has low oxygen content. When this is reduced further by embolic events, tissue oxygenation may fall to critically low levels, leading to blood-brain barrier dysfunction, inflammation, demyelination and eventually, axonal damage. These are the hallmarks of the early lesions of multiple sclerosis where MR spectroscopy has also shown the presence of lactic acid. Significant elevation of the venous oxygen tension

  11. Cellular mechanotransduction relies on tension-induced and chaperone-assisted autophagy.

    PubMed

    Ulbricht, Anna; Eppler, Felix J; Tapia, Victor E; van der Ven, Peter F M; Hampe, Nico; Hersch, Nils; Vakeel, Padmanabhan; Stadel, Daniela; Haas, Albert; Saftig, Paul; Behrends, Christian; Fürst, Dieter O; Volkmer, Rudolf; Hoffmann, Bernd; Kolanus, Waldemar; Höhfeld, Jörg

    2013-03-01

    Mechanical tension is an ever-present physiological stimulus essential for the development and homeostasis of locomotory, cardiovascular, respiratory, and urogenital systems. Tension sensing contributes to stem cell differentiation, immune cell recruitment, and tumorigenesis. Yet, how mechanical signals are transduced inside cells remains poorly understood. Here, we identify chaperone-assisted selective autophagy (CASA) as a tension-induced autophagy pathway essential for mechanotransduction in muscle and immune cells. The CASA complex, comprised of the molecular chaperones Hsc70 and HspB8 and the cochaperone BAG3, senses the mechanical unfolding of the actin-crosslinking protein filamin. Together with the chaperone-associated ubiquitin ligase CHIP, the complex initiates the ubiquitin-dependent autophagic sorting of damaged filamin to lysosomes for degradation. Autophagosome formation during CASA depends on an interaction of BAG3 with synaptopodin-2 (SYNPO2). This interaction is mediated by the BAG3 WW domain and facilitates cooperation with an autophagosome membrane fusion complex. BAG3 also utilizes its WW domain to engage in YAP/TAZ signaling. Via this pathway, BAG3 stimulates filamin transcription to maintain actin anchoring and crosslinking under mechanical tension. By integrating tension sensing, autophagosome formation, and transcription regulation during mechanotransduction, the CASA machinery ensures tissue homeostasis and regulates fundamental cellular processes such as adhesion, migration, and proliferation. PMID:23434281

  12. Membrane Tension Inhibits Deformation by Coat Proteins in Clathrin-Mediated Endocytosis

    NASA Astrophysics Data System (ADS)

    Hassinger, Julian; Drubin, David; Oster, George; Rangamani, Padmini

    2016-02-01

    In clathrin-mediated endocytosis (CME), clathrin and various adaptor proteins coat a patch of the plasma membrane, which is reshaped to form a budded vesicle. Experimental studies have demonstrated that elevated membrane tension can inhibit bud formation by a clathrin coat. In this study, we investigate the impact of membrane tension on the mechanics of membrane budding by simulating clathrin coats that either grow in area or progressively induce greater curvature. At low membrane tension, progressively increasing the area of a curvature-generating coat causes the membrane to smoothly evolve from a flat to budded morphology, whereas the membrane remains essentially flat at high membrane tensions. Interestingly, at physiologically relevant, intermediate membrane tensions, the shape evolution of the membrane undergoes a snapthrough instability in which increasing coat area causes the membrane to "snap" from an open, U-shaped bud to a closed, $\\Omega$-shaped bud. This instability is accompanied by a large energy barrier, which could cause a developing endocytic pit to stall if the binding energy of additional coat is insufficient to overcome this barrier. Similar results were found for a coat of constant area in which the spontaneous curvature progressively increases. Additionally, a pulling force on the bud, simulating a force from actin polymerization, is sufficient to drive a transition from an open to closed bud, overcoming the energy barrier opposing this transition.

  13. Inhibition of Histone Deacetylase Activity in Reduced Oxygen Environment Enhances the Osteogenesis of Mouse Adipose-Derived Stromal Cells

    PubMed Central

    Xu, Yue; Hammerick, Kyle E.; James, Aaron W.; Carre, Antoine L.; Leucht, Philipp; Giaccia, Amato J.

    2009-01-01

    Recent studies suggest that oxygen tension has a great impact on the osteogenic differentiation capacity of mesenchymal cells derived from adipose tissue: reduced oxygen impedes osteogenesis. We have found that expansion of mouse adipose-derived stromal cells (mASCs) in reduced oxygen tension (10%) results in increased cell proliferation along with induction of histone deacetylase (HDAC) activity. In this study, we utilized two HDAC inhibitors (HDACi), sodium butyrate (NaB) and valproic acid (VPA), and studied their effects on mASCs expanded in various oxygen tensions (21%, 10%, and 1% O2). Significant growth inhibition was observed with NaB or VPA treatment in each oxygen tension. Osteogenesis was enhanced by treatment with NaB or VPA, particularly in reduced oxygen tensions (10% and 1% O2). Conversely, adipogenesis was decreased with treatments of NaB or VPA at all oxygen tensions. Finally, NaB- or VPA-treated, reduced oxygen tension–exposed (1% O2) ASCs were grafted into surgically created mouse tibial defects and resulted in significantly increased bone regeneration. In conclusion, HDACi significantly promote the osteogenic differentiation of mASCs exposed to reduced oxygen tension; HDACi may hold promise for future clinical applications of ASCs for skeletal regeneration. PMID:19505250

  14. Endurance exercise performance: the physiology of champions

    PubMed Central

    Joyner, Michael J; Coyle, Edward F

    2008-01-01

    Efforts to understand human physiology through the study of champion athletes and record performances have been ongoing for about a century. For endurance sports three main factors – maximal oxygen consumption , the so-called ‘lactate threshold’ and efficiency (i.e. the oxygen cost to generate a give running speed or cycling power output) – appear to play key roles in endurance performance. and lactate threshold interact to determine the ‘performance ‘ which is the oxygen consumption that can be sustained for a given period of time. Efficiency interacts with the performance to establish the speed or power that can be generated at this oxygen consumption. This review focuses on what is currently known about how these factors interact, their utility as predictors of elite performance, and areas where there is relatively less information to guide current thinking. In this context, definitive ideas about the physiological determinants of running and cycling efficiency is relatively lacking in comparison with and the lactate threshold, and there is surprisingly limited and clear information about the genetic factors that might pre-dispose for elite performance. It should also be cautioned that complex motivational and sociological factors also play important roles in who does or does not become a champion and these factors go far beyond simple physiological explanations. Therefore, the performance of elite athletes is likely to defy the types of easy explanations sought by scientific reductionism and remain an important puzzle for those interested in physiological integration well into the future. PMID:17901124

  15. Hydraulic stud tensioning aids pump performance

    SciTech Connect

    Marchand, G.J.

    1986-03-31

    This article considers the use of hydraulic stud tensioners on mud pump fluid ends. It contains tensioner testing and application. A typical problem involving a fluid end stud is presented to illustrate the use of hydraulic tensioning. Hydraulic stud tensioners give optimum preload reliability over traditional torque tensioning methods. Accurately controlling preload increases stud fatigue life and minimizes maintenance. At one time it was acceptable just to get fluid end connections tight by means of slogging wrenches, impact wrenches, or two of your biggest men on a 10-ft cheater pipe. If the connection did not leak during hydrotest, it was accepted and put into operation. Users of mud pumps are faced with fluid ends that may ''breathe'' excessively due to improper stud preload. Today's equipment is smaller in size and larger in horsepower than ever before, using large retaining studs requiring torques of 3,000 ft-lb and up. In present compact designs, many bolted connections have become virtually inaccessible using traditional tightening procedures. No longer will large wrenches, cheater pipes, and sledge hammers clear surrounding equipment.

  16. From viscosity and surface tension to marangoni flow in melts

    NASA Astrophysics Data System (ADS)

    Sun, Shouyi; Zhang, Ling; Jahanshahi, Sharif

    2003-10-01

    This article covers some of our recent work on slag viscosity, the surface tension of liquid Cu-O alloys, and the relative role of Marangoni and bulk flow on refractory wear in iron-silicate slags. A viscosity model developed for slags containing SiO2, Al2O3, Fe2O3, CaO, MgO, MnO, FeO, PbO, NiO, Cu2O, ZnO, CoO, and TiO2 is capable of representing the effects of temperature, silica, and network-modifier cations within a wide range of temperatures and compositions. It forms a useful part of a computational package for multiphase-equilibrium (MPE) calculations and for predicting slag viscosities. The models are well applicable to a range of industrial slags (blast furnace, new iron making, base-metal and Platinum Group Metals (PGM) smelting, and coal-ash slags). The package has also some capability of predicting the viscosity of slags containing suspended solids. The surface tension of liquid copper-oxygen alloys has also been analyzed. The adsorption behavior of oxygen in liquid copper is well represented by the combined Langmuir-Gibbs isotherm. According to the rate data for silica-rod dissolution in liquid iron-silicate slags at 1573 K, the preferential attack at the slag line diminishes as the linear velocity of flow at the surface of the rotating silica rod reaches 9 to 16 cm/s. A tentative analysis gives the critical condition, that relates the critical Reynolds (Re) and Marangoni (Ma) number by the equation Re*2=0.13 Ma*.

  17. Tension Distribution in a Tendon-Driven Robotic Finger

    NASA Technical Reports Server (NTRS)

    Abdallah, Muhammad E. (Inventor); Platt, Robert (Inventor); Wampler, II, Charles W. (Inventor)

    2013-01-01

    A method is provided for distributing tension among tendons of a tendon-driven finger in a robotic system, wherein the finger characterized by n degrees of freedom and n+1 tendons. The method includes determining a maximum functional tension and a minimum functional tension of each tendon of the finger, and then using a controller to distribute tension among the tendons, such that each tendon is assigned a tension value less than the maximum functional tension and greater than or equal to the minimum functional tension. The method satisfies the minimum functional tension while minimizing the internal tension in the robotic system, and satisfies the maximum functional tension without introducing a coupled disturbance to the joint torques. A robotic system includes a robot having at least one tendon-driven finger characterized by n degrees of freedom and n+1 tendons, and a controller having an algorithm for controlling the tendons as set forth above.

  18. Exposure of the hydrophobic components of porcine lung surfactant to oxidant stress alters surface tension properties.

    PubMed Central

    Gilliard, N; Heldt, G P; Loredo, J; Gasser, H; Redl, H; Merritt, T A; Spragg, R G

    1994-01-01

    We have tested the hypothesis that oxidation of lung surfactant results in loss of surface tension lowering function. Porcine lung surfactant was exposed to conditions known to cause lipid peroxidation (0.2 mM FeCl2 + 0.1 mM H2O2 or 5 microM CuCl2). Lipid peroxidation was verified by detection of conjugated dienes, thiobarbituric acid reactive substances, fluorescent products, hydroxy alkenals, and loss of unsaturated fatty acids. Exposed samples had significantly diminished surface tension lowering ability in vitro as measured in a bubble surfactometer. Samples exposed to FeCl2 + H2O2 had significantly diminished surface tension lowering ability in vivo as indicated by their reduced ability to improve lung compliance of surfactant-deficient fetal rabbits. Oxidation of phospholipid mixtures with surface tension lowering activity and containing unsaturated acyl groups resulted in partial loss of activity as determined in vitro. These results suggest that the effect of oxidants on lung surfactant function is due, in part, to effects on the phospholipid components and that acute pulmonary inflammation accompanied by oxygen radical production may result in surfactant lipid peroxidation and loss of surface tension lowering function. PMID:8200999

  19. Space physiology within an exercise physiology curriculum.

    PubMed

    Carter, Jason R; West, John B

    2013-09-01

    Compare and contrast strategies remain common pedagogical practices within physiological education. With the support of an American Physiological Society Teaching Career Enhancement Award, we have developed a junior- or senior-level undergraduate curriculum for exercise physiology that compares and contrasts the physiological adaptations of chronic terrestrial exercise (TEx) and microgravity (μG). We used a series of peer-reviewed publications to demonstrate that many of the physiological adaptations to TEx and μG are opposite. For example, TEx typically improves cardiovascular function and orthostatic tolerance, whereas μG can lead to declines in both. TEx leads to muscle hypertrophy, and μG elicits muscle atrophy. TEx increases bone mineral density and red blood cell mass, whereas μG decreases bone mineral density and red blood cell mass. Importantly, exercise during spaceflight remains a crucial countermeasure to limit some of these adverse physiological adaptations to μG. This curriculum develops critical thinking skills by dissecting peer-reviewed articles and discussing the strengths and weaknesses associated with simulated and actual μG studies. Moreover, the curriculum includes studies on both animals and humans, providing a strong translational component to the curriculum. In summary, we have developed a novel space physiology curriculum delivered during the final weeks of an exercise physiology course in which students gain critical new knowledge that reinforces key concepts presented throughout the semester. PMID:24022767

  20. Attainable superheating of the oxygen-nitrogen-helium solutions

    NASA Astrophysics Data System (ADS)

    Kaverin, A. M.; Andbaeva, V. N.; Baidakov, V. G.

    2015-01-01

    Method of measuring the lifetime of the superheated liquid was used to determine temperatures of the limit superheating of the solution of oxygen-nitrogen-helium. The method of calculating the properties of this solution (temperature of limit superheating, saturated vapor pressure, and density) based on the data on the properties of solutions of oxygen-helium and nitrogen-helium was proposed. The surface tension of the solution of oxygen-nitrogen-helium was determined in a special experiment.

  1. Evolution of Air Breathing: Oxygen Homeostasis and the Transitions from Water to Land and Sky

    PubMed Central

    Hsia, Connie C. W.; Schmitz, Anke; Lambertz, Markus; Perry, Steven F.; Maina, John N.

    2014-01-01

    Life originated in anoxia, but many organisms came to depend upon oxygen for survival, independently evolving diverse respiratory systems for acquiring oxygen from the environment. Ambient oxygen tension (PO2) fluctuated through the ages in correlation with biodiversity and body size, enabling organisms to migrate from water to land and air and sometimes in the opposite direction. Habitat expansion compels the use of different gas exchangers, for example, skin, gills, tracheae, lungs, and their intermediate stages, that may coexist within the same species; coexistence may be temporally disjunct (e.g., larval gills vs. adult lungs) or simultaneous (e.g., skin, gills, and lungs in some salamanders). Disparate systems exhibit similar directions of adaptation: toward larger diffusion interfaces, thinner barriers, finer dynamic regulation, and reduced cost of breathing. Efficient respiratory gas exchange, coupled to downstream convective and diffusive resistances, comprise the “oxygen cascade”—step-down of PO2 that balances supply against toxicity. Here, we review the origin of oxygen homeostasis, a primal selection factor for all respiratory systems, which in turn function as gatekeepers of the cascade. Within an organism's lifespan, the respiratory apparatus adapts in various ways to upregulate oxygen uptake in hypoxia and restrict uptake in hyperoxia. In an evolutionary context, certain species also become adapted to environmental conditions or habitual organismic demands. We, therefore, survey the comparative anatomy and physiology of respiratory systems from invertebrates to vertebrates, water to air breathers, and terrestrial to aerial inhabitants. Through the evolutionary directions and variety of gas exchangers, their shared features and individual compromises may be appreciated. PMID:23720333

  2. Team tension as a vital sign.

    PubMed

    Nason, F

    1981-03-01

    Current efforts to provide comprehensive health care have accentuated the need for new models that integrate the biological, psychological, and social fields. One approach to meeting this need has been the development of health care teams. However, the multidisciplinary perspectives of such teams often result in tension and discord. While this tension may be partly attributable to institutional or professional biases or lack of adequate decision-making techniques, it may also be an essential diagnostic tool for exploring and integrating the paradoxes of the patient's homeostatic system. This approach captures and bridges some of the inadequacies of our prevailing knowledge base. The team's tension can be experienced as an essential empathic connectedness to the patient's life situation. Resolution of the team's internalized conflict becomes a paradigm for the patient's reintegration of his or her own paradoxical or contradictory needs. PMID:7215794

  3. Surface tension maximum of liquid 3He

    NASA Astrophysics Data System (ADS)

    Matsumoto, Koichi; Hasegawa, Syuichi; Suzuki, Masaru; Okuda, Yuichi

    2000-07-01

    The surface tension of liquid 3He was measured using the capillary-rise method. Suzuki et al. have reported that its temperature dependence was almost quenched below 120 mK. Here we have examined it with higher precision and found that it has a small maximum around 100 mK. The amount of the maximum is about 3×10 -4 as a fraction of the surface tension at 0 K. The density of liquid 3He increases with temperature by about 5×10 -4 in Δ ρ/ ρ between 0 and 100 mK. This density change could be one of the reasons of the surface tension maximum around 100 mK.

  4. Tension Stiffened and Tendon Actuated Manipulator

    NASA Technical Reports Server (NTRS)

    Doggett, William R. (Inventor); Dorsey, John T. (Inventor); Ganoe, George G. (Inventor); King, Bruce D. (Inventor); Jones, Thomas C. (Inventor); Mercer, Charles D. (Inventor); Corbin, Cole K. (Inventor)

    2015-01-01

    A tension stiffened and tendon actuated manipulator is provided performing robotic-like movements when acquiring a payload. The manipulator design can be adapted for use in-space, lunar or other planetary installations as it is readily configurable for acquiring and precisely manipulating a payload in both a zero-g environment and in an environment with a gravity field. The manipulator includes a plurality of link arms, a hinge connecting adjacent link arms together to allow the adjacent link arms to rotate relative to each other and a cable actuation and tensioning system provided between adjacent link arms. The cable actuation and tensioning system includes a spreader arm and a plurality of driven and non-driven elements attached to the link arms and the spreader arm. At least one cable is routed around the driven and non-driven elements for actuating the hinge.

  5. Carbon speciation and surface tension of fog

    USGS Publications Warehouse

    Capel, P.D.; Gunde, R.; Zurcher, F.; Giger, W.

    1990-01-01

    The speciation of carbon (dissolved/particulate, organic/inorganic) and surface tension of a number of radiation fogs from the urban area of Zurich, Switzerland, were measured. The carbon species were dominated by "dissolved" organic carbon (DOC; i.e., the fraction that passes through a filter), which was typically present at levels of 40-200 mg/L. Less than 10% of the DOC was identified as specific individual organic compounds. Particulate organic carbon (POC) accounted for 26-41% of the mass of the particles, but usually less than 10% of the total organic carbon mass. Inorganic carbon species were relatively minor. The surface tensions of all the measured samples were less than pure water and were correlated with their DOC concentrations. The combination of high DOC and POC and low surface tension suggests a mechanism for the concentration of hydrophobic organic contaminants in the fog droplet, which have been observed by numerous investigators. ?? 1990 American Chemical Society.

  6. Focal adhesions, stress fibers and mechanical tension

    PubMed Central

    Burridge, Keith; Guilluy, Christophe

    2016-01-01

    Stress fibers and focal adhesions are complex protein arrays that produce, transmit and sense mechanical tension. Evidence accumulated over many years led to the conclusion that mechanical tension generated within stress fibers contributes to the assembly of both stress fibers themselves and their associated focal adhesions. However, several lines of evidence have recently been presented against this model. Here we discuss the evidence for and against the role of mechanical tension in driving the assembly of these structures. We also consider how their assembly is influenced by the rigidity of the substratum to which cells are adhering. Finally, we discuss the recently identified connections between stress fibers and the nucleus, and the roles that these may play, both in cell migration and regulating nuclear function. PMID:26519907

  7. Appreciating Oxygen

    ERIC Educational Resources Information Center

    Weiss, Hilton M.

    2008-01-01

    Photosynthetic flora and microfauna utilize light from the sun to convert carbon dioxide and water into carbohydrates and oxygen. While these carbohydrates and their derivative hydrocarbons are generally considered to be fuels, it is the thermodynamically energetic oxygen molecule that traps, stores, and provides almost all of the energy that…

  8. Oxygen safety

    MedlinePlus

    ... Watch out for splattering grease. It can catch fire. Keep children with oxygen away from the stove top and oven. Cooking ... under the bed. Keep liquids that may catch fire away from your oxygen. This includes cleaning products that contain oil, grease, ...

  9. The Aponeurotic Tension Model of Craniofacial Growth in Man

    PubMed Central

    Standerwick, Richard G; Roberts, W. Eugene

    2009-01-01

    Craniofacial growth is a scientific crossroad for the fundamental mechanisms of musculoskeletal physiology. Better understanding of growth and development will provide new insights into repair, regeneration and adaptation to applied loads. Traditional craniofacial growth concepts are insufficient to explain the dynamics of airway/vocal tract development, cranial rotation, basicranial flexion and the role of the cranial base in expression of facial proportions. A testable hypothesis is needed to explore the physiological pressure propelling midface growth and the role of neural factors in expression of musculoskeletal adaptation after the cessation of anterior cranial base growth. A novel model for craniofacial growth is proposed for: 1. brain growth and craniofacial adaptation up to the age of 20; 2. explaining growth force vectors; 3. defining the role of muscle plasticity as a conduit for craniofacial growth forces; and 4. describing the effect of cranial rotation in the expression of facial form. Growth of the viscerocranium is believed to be influenced by the superficial musculoaponeurotic systems (SMAS) of the head through residual tension in the occipitofrontalis muscle as a result of cephalad brain growth and cranial rotation. The coordinated effects of the regional SMAS develop a craniofacial musculoaponeurotic system (CFMAS), which is believed to affect maxillary and mandibular development. PMID:19572022

  10. A continuum method for modeling surface tension

    NASA Technical Reports Server (NTRS)

    Brackbill, J. U.; Kothe, D. B.; Zemach, C.

    1992-01-01

    In the novel method presented for modeling the effects of surface tension on fluid motion, the interfaces between fluids with different, color-represented properties are finite-thickness transition regions across which the color varies continuously. A force density proportional to the surface curvature of constant color is defined at each point in the transition region; this force-density is normalized in such a way that the conventional description of surface tension on an interface is recovered when the ratio of local transition-reion thickness to local curvature radius approaches zero. The properties of the method are illustrated by computational results for 2D flows.

  11. Tension chylothorax complicating acute malignant airway obstruction.

    PubMed

    Piastra, Marco; Pietrini, Domenico; Ruggiero, Antonio; Rizzo, Daniela; Marzano, Laura; Attinà, Giorgio; De Luca, Daniele; De Rosa, Gabriella; Conti, Giorgio

    2011-05-01

    Acute upper airway obstruction represents one of the most challenging emergencies in pediatric practice. In particular, a tension chylothorax complicating a malignant airway obstruction is a rare and life-threatening complication. We report a rapidly progressing tension chylothorax associated with a cervical mass in a 10-month-old male infant. To our knowledge, the extension of a cervical mass to the supraclavear region resulting in a compressive chylothorax represents an exceptional event in pediatrics. Early recognition and prompt treatment resulted to be essential to relieve the compression and to avoid end-stage hemodynamic and respiratory function derangement. PMID:21546802

  12. Physiological responses to environmental factors related to space flight

    NASA Technical Reports Server (NTRS)

    Pace, N.; Grunbaum, B. W.; Kodama, A. M.; Mains, R. C.; Rahlmann, D. F.

    1975-01-01

    Physiological procedures and instrumentation developed for the measurement of hemodynamic and metabolic parameters during prolonged periods of weightlessness are described along with the physiological response of monkeys to weightlessness. Specific areas examined include: cardiovascular studies; thyroid function; blood oxygen transport; growth and reproduction; excreta analysis for metabolic balance studies; and electrophoretic separation of creatine phosphokinase isoenzymes in human blood.

  13. Physiological Information Database (PID)

    EPA Science Inventory

    EPA has developed a physiological information database (created using Microsoft ACCESS) intended to be used in PBPK modeling. The database contains physiological parameter values for humans from early childhood through senescence as well as similar data for laboratory animal spec...

  14. The anatomy of microbial cell state transitions in response to oxygen

    PubMed Central

    Schmid, Amy K.; Reiss, David J.; Kaur, Amardeep; Pan, Min; King, Nichole; Van, Phu T.; Hohmann, Laura; Martin, Daniel B.; Baliga, Nitin S.

    2007-01-01

    Adjustment of physiology in response to changes in oxygen availability is critical for the survival of all organisms. However, the chronology of events and the regulatory processes that determine how and when changes in environmental oxygen tension result in an appropriate cellular response is not well understood at a systems level. Therefore, transcriptome, proteome, ATP, and growth changes were analyzed in a halophilic archaeon to generate a temporal model that describes the cellular events that drive the transition between the organism’s two opposing cell states of anoxic quiescence and aerobic growth. According to this model, upon oxygen influx, an initial burst of protein synthesis precedes ATP and transcription induction, rapidly driving the cell out of anoxic quiescence, culminating in the resumption of growth. This model also suggests that quiescent cells appear to remain actively poised for energy production from a variety of different sources. Dynamic temporal analysis of relationships between transcription and translation of key genes suggests several important mechanisms for cellular sustenance under anoxia as well as specific instances of post-transcriptional regulation. PMID:17785531

  15. Correlative NAD(P)H-FLIM and oxygen sensing-PLIM for metabolic mapping.

    PubMed

    Kalinina, Sviatlana; Breymayer, Jasmin; Schäfer, Patrick; Calzia, Enrico; Shcheslavskiy, Vladislav; Becker, Wolfgang; Rück, Angelika

    2016-08-01

    Cellular responses to oxygen tension have been studied extensively. Oxygen tension can be determined by considering the phosphorescence lifetime of a phosphorescence sensor. The simultaneous usage of FLIM of coenzymes as NAD(P)H and FAD(+) and PLIM of oxygen sensors could provide information about correlation of metabolic pathways and oxygen tension. We investigated correlative NAD(P)H-FLIM and oxygen sensing-PLIM for simultaneously analyzing cell metabolism and oxygen tension. Cell metabolism and pO2 were observed under different hypoxic conditions in squamous carcinoma cell cultures and in complex ex vivo systems. Increased hypoxia induced an increase of the phosphorescence lifetime of Ru(BPY)3 and in most cases a decrease in the lifetime of NAD(P)H which is in agreement to the expected decrease of the protein-bound NAD(P)H during hypoxia. Oxygen was modulated directly in the mitochondrial membrane. Blocking of complex III and accumulation of oxygen could be observed by both the decrease of the phosphorescence lifetime of Ru(BPY)3 and a reduction of the lifetime of NAD(P)H which was a clear indication of acute changes in the redox state of the cells. For the first time simultaneous FLIM/PLIM has been shown to be able to visualize intracellular oxygen tension together with a change from oxidative to glycolytic phenotype. PMID:26990032

  16. Oxygen therapy and intraocular oxygenation.

    PubMed Central

    Jampol, L M

    1987-01-01

    When delivered to the corneal surface of rabbits or monkeys, 100% oxygen can significantly increase the pO2 in the aqueous humor. Under hyperbaric conditions (two atmospheres), an observed rise in the aqueous pO2 in rabbits breathing room air can be increased further by exposing the rabbit cornea to 100% oxygen. The high oxygen levels under hyperbaric conditions are mediated by intravascular and transcorneal delivery of oxygen. The increase in the pO2 levels in the aqueous can prevent sickling of intracameral human erythrocytes containing sickle hemoglobin. Thus, oxygen therapy transcorneally or systemically could potentially be used to treat a sickle cell hyphema. The exposure of rabbit eyes to 100% oxygen at the corneal surface is followed by autoregulation (constriction) of the iris vasculature. We could demonstrate no constriction in the eyes of two normal human volunteers or of four patients with chronic stable rubeosis iridis. Preretinal vitreous pO2 levels can be significantly raised by exposing monkeys to hyperbaric 100% oxygen. This procedure may be of value in treating acute, reversible ischemic inner retinal diseases. Transcorneal or vascular delivery of oxygen to the eye under normobaric or hyperbaric conditions may be effective in treating ischemic diseases of the anterior segment, such as anterior segment necrosis or rubeosis iridis, or ischemic inner retinal diseases. Images FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 B FIGURE 5 C FIGURE 5 A FIGURE 6 PMID:3447339

  17. Physiological polyamines: simple primordial stress molecules

    PubMed Central

    Rhee, H J; Kim, Eui-Jin; Lee, J K

    2007-01-01

    Abstract Physiological polyamines are ubiquitous polycations with pleiotropic biochemical activities, including regulation of gene expression, cell proliferation and modulation of cell signalling. Reports that the polyamines with cytoprotective activities were induced by diverse stresses raised the hypothesis that physiological polyamines may play a role in inducing stress response. In a wide range of organisms, physiological polyamines were not only induced by diverse stresses, such as reactive oxygen species (ROS), heat, ultraviolet (UV) and psychiatric stress but were able to confer beneficial effects for survival. Recent biochemical and genetic evidences show that polyamines can function as an ROS scavenger, acid tolerance factor and chemical chaperone, and positive regulators for expression of stress response genes which may explain their protective functions against diverse stresses. Taken together, these data suggest that physiological polyamines can function as primordial stress molecules in bacteria, plants and mammals, and may play an essential role in regulation of pathogen-host interactions. PMID:17760833

  18. Oxygen and Early Animal Evolution

    NASA Astrophysics Data System (ADS)

    Xiao, S.

    2012-12-01

    It is often hypothesized that the rise of animals was triggered by an increase in O2 levels in the atmosphere and oceans. However, this hypothesis is remarkably difficult to test, because the timing of animal divergences is poorly resolved, the physiology of early animals is often unknown, estimates of past pO2 levels come with large error bars, and causal relationships between oxygenation and animal evolution are difficult to establish. Nonetheless, existing phylogenetic, paleontological, and geochemical data indicate that the evolution of macroscopic animals and motile macrometazoans with energetically expensive lifestyles may be temporally coupled with ocean oxygenation events in the Ediacaran Period. Thus, it is plausible that ocean oxygenation may have been a limiting factor in the early evolution of macroscopic, complex, and metabolically aggressive animals (particularly bilaterian animals). However, ocean oxygenation and animal evolution were likely engaged in two-way interactions: Ediacaran oxygenation may have initially lifted a physiological barrier for the evolution of animal size, motility, and active lifestyles, but subsequent animal diversification in the Paleozoic may have also changed oceanic redox structures. Viewed in a broader context, the early evolutionary history of animals was contingent upon a series of events, including genetic preparation (developmental genetics), environmental facilitation (oceanic oxygenation), and ecological escalation (Cambrian explosion), but the rise of animals to ecological importance also had important geobiological impacts on oceanic redox structures, sedimentary fabrics, and global geochemical cycles.

  19. Tensions between Evaluations and Communication Practices

    ERIC Educational Resources Information Center

    Laudel, Grit; Glaser, Jochen

    2006-01-01

    When publications are used in the evaluation of research performance, tensions between the simplifying, standardizing approaches of evaluations and the communication practices of scientific communities are likely to arise. An analysis of data gathered in an evaluation at the Australian National University demonstrates that many academic…

  20. Multiple Intelligences: Its Tensions and Possibilities

    ERIC Educational Resources Information Center

    Eisner, Elliot W.

    2004-01-01

    This article explores the tensions between Howard Gardner's theory of multiple intelligences and current educational policies emphasizing standardized and predictable outcomes. The article situates Gardner's theory within the historical interests among psychometricians in identifying those core processes that constitute human intelligence.…

  1. Robust atomistic calculation of dislocation line tension

    NASA Astrophysics Data System (ADS)

    Szajewski, B. A.; Pavia, F.; Curtin, W. A.

    2015-12-01

    The line tension Γ of a dislocation is an important and fundamental property ubiquitous to continuum scale models of metal plasticity. However, the precise value of Γ in a given material has proven difficult to assess, with literature values encompassing a wide range. Here results from a multiscale simulation and robust analysis of the dislocation line tension, for dislocation bow-out between pinning points, are presented for two widely-used interatomic potentials for Al. A central part of the analysis involves an effective Peierls stress applicable to curved dislocation structures that markedly differs from that of perfectly straight dislocations but is required to describe the bow-out both in loading and unloading. The line tensions for the two interatomic potentials are similar and provide robust numerical values for Al. Most importantly, the atomic results show notable differences with singular anisotropic elastic dislocation theory in that (i) the coefficient of the \\text{ln}(L) scaling with dislocation length L differs and (ii) the ratio of screw to edge line tension is smaller than predicted by anisotropic elasticity. These differences are attributed to local dislocation core interactions that remain beyond the scope of elasticity theory. The many differing literature values for Γ are attributed to various approximations and inaccuracies in previous approaches. The results here indicate that continuum line dislocation models, based on elasticity theory and various core-cut-off assumptions, may be fundamentally unable to reproduce full atomistic results, thus hampering the detailed predictive ability of such continuum models.

  2. Five tensions between science and democracy

    SciTech Connect

    Guston, D.J.

    1995-12-31

    The historical aspects of dialogue between the scientific establishments and the congress are used to illustrate and define the continuing tensions between these parties since 1880. Five areas are addressed as how best to cope and deal with the issues which in all probability will not go away. 1 ref.

  3. Tension in Chemistry and Its Contents

    PubMed Central

    Hoffmann, Roald

    2015-01-01

    This article makes a case for a positive role of tension in the creative process in chemistry. I begin with an argument that there is an inherent tension in what makes molecules interesting—their positioning along various polar axes. One of these, the age-old differentiation between useful (to society and for personal profit) commercialization and pure understanding of molecules and their reactions is characteristic. The question of whether there are any bad molecules then leads me to ethical concerns in chemistry, and a particular working out of these in interactions of chemists in the Middle East. An analysis is made of the special tensions involved in publishing, especially in citation ethics; chemists publish a lot, so this is situation ethics worked out on a daily basis. I then find in the literature of psychology good evidence for the positive value of moderate stress in stimulating creativity. It is obvious that too much tension leads to distress, and there are some institutional aspects of chemistry that do not come out well here. But all in all, the dynamic middle is alive, and it leads to good new science. PMID:26155730

  4. Tension Builds over AFT Reform Agenda

    ERIC Educational Resources Information Center

    Sawchuk, Stephen

    2012-01-01

    Can a teachers' union successfully be both a hardball-playing defender of its rights and a collaborative force for the common good? It is both a question of philosophy and, increasingly, one of policy direction for the American Federation of Teachers (AFT), whose biennial convention in Detroit showed delegates grappling with the tension between…

  5. Reorganising the Teaching-Research Tension

    ERIC Educational Resources Information Center

    de Jonghe, Anne-Marie

    2005-01-01

    In this paper we examine the tensions resulting from the transformation processes going on in research and teaching, typical at traditional universities that have been actively developing their research mission. We will also look at universities that only recently decided to focus on research and wonder if they will be able to better manage or…

  6. Measuring the surface tension of soap bubbles

    NASA Technical Reports Server (NTRS)

    Sorensen, Carl D.

    1992-01-01

    The objectives are for students to gain an understanding of surface tension, to see that pressure inside a small bubble is larger than that inside a large bubble. These concepts can be used to explain the behavior of liquid foams as well as precipitate coarsening and grain growth. Equipment, supplies, and procedures are explained.

  7. Educational Leadership: Key Challenges and Ethical Tensions

    ERIC Educational Resources Information Center

    Duignan, Patrick

    2007-01-01

    "Educational Leadership" is a major research book on contemporary leadership challenges for educational leaders. In this groundbreaking new work, educational leaders in schools, including teachers, are provided with ways of analysing and resolving common but complex leadership challenges. Ethical tensions inherent in these challenges are…

  8. Optimal tissue tension for secure laparoscopic knots.

    PubMed

    Raut, Vikram N; Takaori, Kyoichi; Uemoto, Shinji

    2011-02-01

    Security and strength of a knot are main concerns of the surgeon since last 4000 years. The advancement of endoscopic and minimally invasive surgery in last few decades had a significant influence on a knot tying. The most difficult methods of a knot tying are performed during endoscopic procedures, in which the surgeon execute instrumentation from outside the body without palpation of organs and three-dimensional vision. In addition, laparoscopic instruments due to friction in transmission mechanism have very poor force feedback. This results into difficulty in applying the appropriate grasping force to the tissue, resulting in slippage or damage to the tissue. Our hypothesis highlights the need of tissue approximation at the 'optimum tissue tension' sufficient to resist the slippage of suture/clip without strangulation. The purpose of suture is to maintain an approximation of the tissue until healing progresses to the point where artificial support is no longer necessary for the wound to resist normal stress. When the approximation is too tight, tension in tissue leads to diminished blood supply resulting into the necrosis. Various tissues need different blood supply and different tissue pressure for optimum healings. Proposed hypothesis helps to improve the feedback of current knot pushers or clip applicators used in laparoscopic surgery using optimum tissue tension. Tissue approximation at an optimal tissue tension translates into the secure laparoscopic knot/clip application resulting in prevention of wound dehiscence, anastomosis leak, and secondary haemorrhages. PMID:21071154

  9. Potentiometer, constant tension and lubrication device

    NASA Technical Reports Server (NTRS)

    Smith, H. J.

    1972-01-01

    Wiper assembly is described for feedback potentiometers which provides self cleaning, self lubrication, and tension within controlled limits. Each end of the assembly contains loose fitting leather pad thoroughly soaked in wiper lubricating fluid. Cleaning and lubrication of potentiometer resulting from use of lubrication soaked leather accomplishes noise free operation.

  10. "Jena Six": Case Study in Racial Tensions

    ERIC Educational Resources Information Center

    Maxwell, Lesli A.

    2007-01-01

    This article reports the racial tensions in Jena, Louisiana. On Aug. 31, 2006, school leaders in Jena, Louisiana, arrived to find two nooses hanging from an oak tree on the campus of Jena High School. The events since that incident--including the beating of a white student and resulting criminal charges against six black schoolmates that have…

  11. Improved Yield Estimation by Trellis Tension Monitoring

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Most yield estimation practices for commercial vineyards rely on hand-sampling fruit on one or a small number of dates during the growing season. Limitations associated with the static yield estimates may be overcome with Trellis Tension Monitors (TTMs), systems that measure dynamically changes in t...

  12. Line tension of multicomponent bilayer membranes

    NASA Astrophysics Data System (ADS)

    Dehghan, Ashkan; Pastor, Kyle A.; Shi, An-Chang

    2015-02-01

    The line tension or edge energy of bilayer membranes self-assembled from binary amphiphilic molecules is studied using self-consistent-field theory (SCFT). Specifically, solutions of the SCFT equations corresponding to an infinite membrane with a circular pore, or an open membrane, are obtained for a coarse-grained model in which the amphiphilic species and hydrophilic solvents are represented by A B and E D diblock copolymers and C homopolymers, respectively. The edge energy of the membrane is extracted from the free energy of the open membranes. Results for membranes composed of mixtures of symmetric and cone- or inverse cone-shaped amphiphilic molecules with neutral and/or repulsive interactions are obtained and analyzed. It is observed that an increase in the concentration of the cone-shaped species leads to a decrease of the line tension. In contrast, adding inverse cone-shaped copolymers results in an increase of the line tension. Furthermore, the density profile of the copolymers reveals that the line tension is regulated by the distribution of the amphiphiles at the bilayer edge.

  13. Surface tension of evaporating nanofluid droplets

    SciTech Connect

    Chen, Ruey-Hung; Phuoc, Tran X.; Martello, Donald

    2011-05-01

    Measurements of nanofluid surface tension were made using the pendant droplet method. Three different types of nanoparticles were used - laponite, silver and Fe2O3 - with de-ionized water (DW) as the base fluid. The reported results focus on the following categories; (1) because some nanoparticles require surfactants to form stable colloids, the individual effects of the surfactant and the particles were investigated; (2) due to evaporation of the pendant droplet, the particle concentration increases, affecting the apparent surface tension; (3) because of the evaporation process, a hysteresis was found where the evaporating droplet can only achieve lower values of surface tension than that of nanofluids at the same prepared concentrations: and (4) the Stefan equation relating the apparent surface tension and heat of evaporation was found to be inapplicable for nanofluids investigated. Comparisons with findings for sessile droplets are also discussed, pointing to additional effects of nanoparticles other than the non-equilibrium evaporation process.

  14. Children as Public Actors: Navigating the Tensions

    ERIC Educational Resources Information Center

    Shier, Harry

    2010-01-01

    Drawing on comparative research with children's participation practitioners in Nicaragua and the United Kingdom, this study explores the thinking that guides their practice. Earlier models are considered inadequate to describe complex, multidimensional participation processes. Whilst several differences are observed, the key issues or tensions are…

  15. Internationalization and Global Tension: Lessons From History

    ERIC Educational Resources Information Center

    Altbach, Philip G.; de Wit, Hans

    2015-01-01

    Increasing political and military tension in several parts of the world will inevitably affect international higher education. Nationalist, religious, and ideological conflicts challenge the original ideas of international cooperation and exchange in higher education as promoters of peace and mutual understanding and of global engagement. Since…

  16. Tensions and Dilemmas in Leading Australia's Schools

    ERIC Educational Resources Information Center

    Gurr, David; Drysdale, Lawrie

    2012-01-01

    In this article we address several tensions and dilemmas that are impacting on Australian principals and other school leaders. The first section explores areas associated with improving teaching and learning and includes discussion of education trends, the construction of new learning environments and the implication of these for more…

  17. Oxygen-Loaded Nanodroplets Effectively Abrogate Hypoxia Dysregulating Effects on Secretion of MMP-9 and TIMP-1 by Human Monocytes

    PubMed Central

    Gulino, Giulia Rossana; Magnetto, Chiara; Khadjavi, Amina; Panariti, Alice; Rivolta, Ilaria; Soster, Marco; Argenziano, Monica; Cavalli, Roberta; Giribaldi, Giuliana; Guiot, Caterina; Prato, Mauro

    2015-01-01

    Monocytes play a key role in the inflammatory stage of the healing process. To allow monocyte migration to injured tissues, the balances between secreted matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) must be finely modulated. However, a reduction of blood supply and local oxygen tension can modify the phenotype of immune cells. Intriguingly, hypoxia might be targeted by new effective oxygenating devices such as 2H,3H-decafluoropentane- (DFP-) based oxygen-loaded nanodroplets (OLNs). Here, hypoxia effects on gelatinase/TIMP release from human peripheral monocytes were investigated, and the therapeutic potential of dextran-shelled OLNs was evaluated. Normoxic monocytes constitutively released ~500 ng/mL MMP-9, ~1.3 ng/mL TIMP-1, and ~0.6 ng/mL TIMP-2 proteins. MMP-2 was not detected. After 24 hours, hypoxia significantly altered MMP-9/TIMP-1 balance by reducing MMP-9 and increasing TIMP-1, without affecting TIMP-2 secretion. Interestingly OLNs, not displaying toxicity to human monocytes after cell internalization, effectively counteracted hypoxia, restoring a normoxia-like MMP-9/TIMP-1 ratio. The action of OLNs was specifically dependent on time-sustained oxygen diffusion up to 24 h from their DFP-based core. Therefore, OLNs appear as innovative, nonconventional, cost-effective, and nontoxic therapeutic tools, to be potentially employed to restore the physiological invasive phenotype of immune cells in hypoxia-associated inflammation. PMID:25878404

  18. Physiological and pathological cardiac hypertrophy.

    PubMed

    Shimizu, Ippei; Minamino, Tohru

    2016-08-01

    The heart must continuously pump blood to supply the body with oxygen and nutrients. To maintain the high energy consumption required by this role, the heart is equipped with multiple complex biological systems that allow adaptation to changes of systemic demand. The processes of growth (hypertrophy), angiogenesis, and metabolic plasticity are critically involved in maintenance of cardiac homeostasis. Cardiac hypertrophy is classified as physiological when it is associated with normal cardiac function or as pathological when associated with cardiac dysfunction. Physiological hypertrophy of the heart occurs in response to normal growth of children or during pregnancy, as well as in athletes. In contrast, pathological hypertrophy is induced by factors such as prolonged and abnormal hemodynamic stress, due to hypertension, myocardial infarction etc. Pathological hypertrophy is associated with fibrosis, capillary rarefaction, increased production of pro-inflammatory cytokines, and cellular dysfunction (impairment of signaling, suppression of autophagy, and abnormal cardiomyocyte/non-cardiomyocyte interactions), as well as undesirable epigenetic changes, with these complex responses leading to maladaptive cardiac remodeling and heart failure. This review describes the key molecules and cellular responses involved in physiological/pathological cardiac hypertrophy. PMID:27262674

  19. Physiologic time: A hypothesis

    NASA Astrophysics Data System (ADS)

    West, Damien; West, Bruce J.

    2013-06-01

    The scaling of respiratory metabolism with body size in animals is considered by many to be a fundamental law of nature. One apparent consequence of this law is the scaling of physiologic time with body size, implying that physiologic time is separate and distinct from clock time. Physiologic time is manifest in allometry relations for lifespans, cardiac cycles, blood volume circulation, respiratory cycle, along with a number of other physiologic phenomena. Herein we present a theory of physiologic time that explains the allometry relation between time and total body mass averages as entailed by the hypothesis that the fluctuations in the total body mass are described by a scaling probability density.

  20. The Role of Oxygen during Fracture Healing

    PubMed Central

    Lu, Chuanyong; Saless, Neema; Wang, Xiaodong; Sinha, Arjun; Decker, Sebastian; Kazakia, Galateia; Hou, Huagang; Williams, Benjamin; Swartz, Harold M.; Hunt, Thomas K.; Miclau, Theodore; Marcucio, Ralph S.

    2016-01-01

    Oxygen affects the activity of multiple skeletogenic cells and is involved in many processes that are important for fracture healing. However, the role of oxygen in fracture healing has not been fully studied. Here we systematically examine the effects of oxygen tension on fracture healing and test the ability of hyperoxia to rescue healing defects in a mouse model of ischemic fracture healing. Mice with tibia fracture were housed in custom-built gas chambers and groups breathed a constant atmosphere of 13% oxygen (hypoxia), 21% oxygen (normoxia), or 50% oxygen (hyperoxia). The influx of inflammatory cells to the fracture site, stem cell differentiation, tissue vascularization, and fracture healing were analyzed. In addition, the efficacy of hyperoxia (50% breathing oxygen) as a treatment regimen for fracture nonunion was tested. Hypoxic animals had decreased tissue vascularity, decreased bone formation, and delayed callus remodeling. Hyperoxia increased tissue vascularization, altered fracture healing in un-complicated fractures, and improved bone repair in ischemia-induced delayed fracture union. However, neither hypoxia nor hyperoxia significantly altered chondrogenesis or osteogenesis during early stages of fracture healing, and infiltration of macrophages and neutrophils was not affected by environmental oxygen after bone injury. In conclusion, our results indicate that environmental oxygen levels affect tissue vascularization and fracture healing, and that providing oxygen to patients with fractures accompanied by ischemia may be beneficial. PMID:23063782

  1. Passive tension in cardiac muscle: contribution of collagen, titin, microtubules, and intermediate filaments.

    PubMed Central

    Granzier, H L; Irving, T C

    1995-01-01

    The passive tension-sarcomere length relation of rat cardiac muscle was investigated by studying passive (or not activated) single myocytes and trabeculae. The contribution of collagen, titin, microtubules, and intermediate filaments to tension and stiffness was investigated by measuring (1) the effects of KCl/KI extraction on both trabeculae and single myocytes, (2) the effect of trypsin digestion on single myocytes, and (3) the effect of colchicine on single myocytes. It was found that over the working range of sarcomeres in the heart (lengths approximately 1.9-2.2 microns), collagen and titin are the most important contributors to passive tension with titin dominating at the shorter end of the working range and collagen at longer lengths. Microtubules made a modest contribution to passive tension in some cells, but on average their contribution was not significant. Finally, intermediate filaments contributed about 10% to passive tension of trabeculae at sarcomere lengths from approximately 1.9 to 2.1 microns, and their contribution dropped to only a few percent at longer lengths. At physiological sarcomere lengths of the heart, cardiac titin developed much higher tensions (> 20-fold) than did skeletal muscle titin at comparable lengths. This might be related to the finding that cardiac titin has a molecular mass of 2.5 MDa, 0.3-0.5 MDa smaller than titin of mammalian skeletal muscle, which is predicted to result in a much shorter extensible titin segment in the I-band of cardiac muscle. Passive stress plotted versus the strain of the extensible titin segment showed that the stress-strain relationships are similar in cardiac and skeletal muscle. The difference in passive stress between cardiac and skeletal muscle at the sarcomere level predominantly resulted from much higher strains of the I-segment of cardiac titin at a given sarcomere length. By expressing a smaller titin isoform, without changing the properties of the molecule itself, cardiac muscle is able to

  2. Fully Enzymatic Membraneless Glucose|Oxygen Fuel Cell That Provides 0.275 mA cm(-2) in 5 mM Glucose, Operates in Human Physiological Solutions, and Powers Transmission of Sensing Data.

    PubMed

    Ó Conghaile, Peter; Falk, Magnus; MacAodha, Domhnall; Yakovleva, Maria E; Gonaus, Christoph; Peterbauer, Clemens K; Gorton, Lo; Shleev, Sergey; Leech, Dónal

    2016-02-16

    Coimmobilization of pyranose dehydrogenase as an enzyme catalyst, osmium redox polymers [Os(4,4'-dimethoxy-2,2'-bipyridine)2(poly(vinylimidazole))10Cl](+) or [Os(4,4'-dimethyl-2,2'-bipyridine)2(poly(vinylimidazole))10Cl](+) as mediators, and carbon nanotube conductive scaffolds in films on graphite electrodes provides enzyme electrodes for glucose oxidation. The recombinant enzyme and a deglycosylated form, both expressed in Pichia pastoris, are investigated and compared as biocatalysts for glucose oxidation using flow injection amperometry and voltammetry. In the presence of 5 mM glucose in phosphate-buffered saline (PBS) (50 mM phosphate buffer solution, pH 7.4, with 150 mM NaCl), higher glucose oxidation current densities, 0.41 mA cm(-2), are obtained from enzyme electrodes containing the deglycosylated form of the enzyme. The optimized glucose-oxidizing anode, prepared using deglycosylated enzyme coimmobilized with [Os(4,4'-dimethyl-2,2'-bipyridine)2(poly(vinylimidazole))10Cl](+) and carbon nanotubes, was coupled with an oxygen-reducing bilirubin oxidase on gold nanoparticle dispersed on gold electrode as a biocathode to provide a membraneless fully enzymatic fuel cell. A maximum power density of 275 μW cm(-2) is obtained in 5 mM glucose in PBS, the highest to date under these conditions, providing sufficient power to enable wireless transmission of a signal to a data logger. When tested in whole human blood and unstimulated human saliva maximum power densities of 73 and 6 μW cm(-2) are obtained for the same fuel cell configuration, respectively. PMID:26750758

  3. Can respiratory physiology predict thermal niches?

    PubMed

    Verberk, Wilco C E P; Bartolini, Fabrizio; Marshall, David J; Pörtner, Hans-O; Terblanche, John S; White, Craig R; Giomi, Folco

    2016-02-01

    Predicting species responses to global warming is the holy grail of climate change science. As temperature directly affects physiological rates, it is clear that a mechanistic understanding of species vulnerability should be grounded in organismal physiology. Here, we review what respiratory physiology can offer the field of thermal ecology, showcasing different perspectives on how respiratory physiology can help explain thermal niches. In water, maintaining adequate oxygen delivery to fuel the higher metabolic rates under warming conditions can become the weakest link, setting thermal tolerance limits. This has repercussions for growth and scaling of metabolic rate. On land, water loss is more likely to become problematic as long as O2 delivery and pH balance can be maintained, potentially constraining species in their normal activity. Therefore, high temperatures need not be lethal, but can still affect the energy intake of an animal, with concomitant consequences for long-term fitness. While respiratory challenges and adaptive responses are diverse, there are clear recurring elements such as oxygen uptake, CO2 excretion, and water homeostasis. We show that respiratory physiology has much to offer the field of thermal ecology and call for an integrative, multivariate view incorporating respiratory challenges, thermal responses, and energetic consequences. Fruitful areas for future research are highlighted. PMID:26333058

  4. Rheology and interfacial tension of biopolymers

    NASA Astrophysics Data System (ADS)

    Kandadai, Madhuvanthi A.

    The rheology and interfacial tension of biomaterials are important factors governing their potential use in biomedical applications. This dissertation presents a study of the rheology and interfacial tension of three very different biomaterials: (1) A hydrophobically modified Hyaluronic acid (HA) with polypeptide side chains, (2) Actin fibers and (3) a highly hydrophobic fluoroalkane, Perfluoropentane, and the effect of various surfactants and their mixtures on lowering its interfacial tension in an aqueous interface. In Chapter 1, we present a description of the properties and applications of these materials and a detailed literature review relevant to our studies to better understand the motivation of our work. In Chapter 2 we describe the techniques used for our studies. In Chapter 3, we present our studies on the hydrophobically modified HA with polyleucine side chains and compare them to unmodified HA of same or similar backbone molecular weights. We found a significantly enhanced viscosity for the modified HA compared to unmodified HA at the same concentration. We also found a viscoelastic behavior that was dependent on the concentration of the solution and grafting ratio of the hydrophobic side chains. The associative thickening properties of modified HA investigated with various rheological experiments and simulation results are presented in this chapter. In Chapter 4, we present our studies on the properties of actin fibers. We used a novel microrheometer VROC(TM) (Viscometer-rheometer-on-a-chip) for studying actin fibers at very high shear rates. We show that at very high shear rats, the actin filaments show irreversible network breakdown. We also studied the surface tension of actin filaments and monomer solutions at the interface with air and report induction times of these materials. In Chapter 5, we study the interfacial tension of a highly hydrophobic fluoroalkane, Perfluoropentane, in the presence of different surfactants and their mixtures. The

  5. Case-Based Learning of Blood Oxygen Transport

    ERIC Educational Resources Information Center

    Cliff, William H.

    2006-01-01

    A case study about carbon monoxide poisoning was used help students gain a greater understanding of the physiology of oxygen transport by the blood. A review of student answers to the case questions showed that students can use the oxygen-hemoglobin dissociation curve to make meaningful determinations of oxygen uptake and delivery. However, the…

  6. 59. SIDE VIEW OF TENSION CARRIAGE: Side view towards the ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    59. SIDE VIEW OF TENSION CARRIAGE: Side view towards the south of the California Street cable's tension carriage. - San Francisco Cable Railway, Washington & Mason Streets, San Francisco, San Francisco County, CA

  7. The Extended Oxygen Window Concept for Programming Saturation Decompressions Using Air and Nitrox

    PubMed Central

    Kot, Jacek; Sicko, Zdzislaw

    2015-01-01

    Saturation decompression is a physiological process of transition from one steady state, full saturation with inert gas at pressure, to another one: standard conditions at surface. It is defined by the borderline condition for time spent at a particular depth (pressure) and inert gas in the breathing mixture (nitrogen, helium). It is a delicate and long lasting process during which single milliliters of inert gas are eliminated every minute, and any disturbance can lead to the creation of gas bubbles leading to decompression sickness (DCS). Most operational procedures rely on experimentally found parameters describing a continuous slow decompression rate. In Poland, the system for programming of continuous decompression after saturation with compressed air and nitrox has been developed as based on the concept of the Extended Oxygen Window (EOW). EOW mainly depends on the physiology of the metabolic oxygen window—also called inherent unsaturation or partial pressure vacancy—but also on metabolism of carbon dioxide, the existence of water vapor, as well as tissue tension. Initially, ambient pressure can be reduced at a higher rate allowing the elimination of inert gas from faster compartments using the EOW concept, and maximum outflow of nitrogen. Then, keeping a driving force for long decompression not exceeding the EOW allows optimal elimination of nitrogen from the limiting compartment with half-time of 360 min. The model has been theoretically verified through its application for estimation of risk of decompression sickness in published systems of air and nitrox saturation decompressions, where DCS cases were observed. Clear dose-reaction relation exists, and this confirms that any supersaturation over the EOW creates a risk for DCS. Using the concept of the EOW, 76 man-decompressions were conducted after air and nitrox saturations in depth range between 18 and 45 meters with no single case of DCS. In summary, the EOW concept describes physiology of

  8. The Extended Oxygen Window Concept for Programming Saturation Decompressions Using Air and Nitrox.

    PubMed

    Kot, Jacek; Sicko, Zdzislaw; Doboszynski, Tadeusz

    2015-01-01

    Saturation decompression is a physiological process of transition from one steady state, full saturation with inert gas at pressure, to another one: standard conditions at surface. It is defined by the borderline condition for time spent at a particular depth (pressure) and inert gas in the breathing mixture (nitrogen, helium). It is a delicate and long lasting process during which single milliliters of inert gas are eliminated every minute, and any disturbance can lead to the creation of gas bubbles leading to decompression sickness (DCS). Most operational procedures rely on experimentally found parameters describing a continuous slow decompression rate. In Poland, the system for programming of continuous decompression after saturation with compressed air and nitrox has been developed as based on the concept of the Extended Oxygen Window (EOW). EOW mainly depends on the physiology of the metabolic oxygen window--also called inherent unsaturation or partial pressure vacancy--but also on metabolism of carbon dioxide, the existence of water vapor, as well as tissue tension. Initially, ambient pressure can be reduced at a higher rate allowing the elimination of inert gas from faster compartments using the EOW concept, and maximum outflow of nitrogen. Then, keeping a driving force for long decompression not exceeding the EOW allows optimal elimination of nitrogen from the limiting compartment with half-time of 360 min. The model has been theoretically verified through its application for estimation of risk of decompression sickness in published systems of air and nitrox saturation decompressions, where DCS cases were observed. Clear dose-reaction relation exists, and this confirms that any supersaturation over the EOW creates a risk for DCS. Using the concept of the EOW, 76 man-decompressions were conducted after air and nitrox saturations in depth range between 18 and 45 meters with no single case of DCS. In summary, the EOW concept describes physiology of

  9. Girdin/GIV is upregulated by cyclic tension, propagates mechanical signal transduction, and is required for the cellular proliferation and migration of MG-63 cells

    SciTech Connect

    Hu, Jiang-Tian; Li, Yan; Yu, Bing; Gao, Guo-Jie; Zhou, Ting; Li, Song

    2015-08-21

    To explore how Girdin/GIV is regulated by cyclic tension and propagates downstream signals to affect cell proliferation and migration. Human osteoblast-like MG-63 cells were exposed to cyclic tension force at 4000 μstrain and 0.5 Hz for 6 h, produced by a four-point bending system. Cyclic tension force upregulated Girdin and Akt expression and phosphorylation in cultured MG-63 cells. Girdin and Akt each promoted the phosphorylation of the other under stimulated tension. In vitro MTT and transwell assays showed that Girdin and Akt are required for cell proliferation and migration during cellular quiescence. Moreover, STAT3 was determined to be essential for Girdin expression under stimulated tension force in the physiological condition, as well as for osteoblast proliferation and migration during quiescence. These findings suggest that the STAT3/Girdin/Akt pathway activates in osteoblasts in response to mechanical stimulation and may play a significant role in triggering osteoblast proliferation and migration during orthodontic treatment. - Highlights: • Tension force upregulates Girdin and Akt expression and phosphorylation. • Girdin and Akt promotes the phosphorylation of each other under tension stimulation. • Girdin and Akt are required for MG-63 cell proliferation and migration. • STAT3 is essential for Girdin expression after application of the tension forces.

  10. The stimulus interval-tension relation in enzymatically isolated single myocytes of the frog heart.

    PubMed Central

    Cecchi, G; Colomo, F; Poggesi, C; Tesi, C

    1992-01-01

    1. Apparatus for recording the small tensions developed by electrically stimulated single intact myocytes of frog heart is described. A laser-light optoelectronic transducer was used. The compliance of the force probes was 10-20 nm/nN, with a frequency response of 600-900 Hz in Ringer solution. The myocyte shortening during an ordinary twitch contraction was no greater than 1% of the slack length. The overall sensitivity of the transducer system was 5-10 mV/nN, with a total noise of 0.5-1 nN peak to peak. The experiments were performed at 20-23 degrees C on either atrial or ventricular myocytes at 2.15-2.2 microns sarcomere length, in 1 mM-Ca2+ Ringer solution. 2. Isoprenaline (5 microM), increases in external Ca2+ concentration ([Ca2+]o), and shortening of stimulus interval potentiated the myocyte twitch tension. The dependence of twitch characteristics on these inotropic interventions for all the atrial and ventricular myocytes tested was comparable to that of multicellular preparations under similar experimental conditions. This implies that the enzymatic isolation procedure had not altered the physiological properties of the myocytes. 3. The stimulus interval-tension relation for premature twitches of atrial and ventricular myocytes showed (i) a very steep rising phase in the region of intervals just longer than 0.52 and 0.66 s (the duration of the mechanical refractoriness in atrial or ventricular cells), (ii) a peak, at intervals of 0.7-0.8 s, where the twitch tension was strongly potentiated compared to that of the controls, and (iii) as the stimulus interval was further increased, a progressive return to the control level. The stimulus interval-tension relation for steady-state conditions exhibited similar characteristics. 4. The degree of tension potentiation by isoprenaline was greater in the controls than in the earliest test twitches. The result was that the stimulus interval-tension relations for isoprenaline-treated myocytes showed a gentler rise and

  11. Separation anxiety: Stress, tension and cytokinesis

    SciTech Connect

    Mohan, Krithika; Iglesias, Pablo A.; Robinson, Douglas N.

    2012-07-15

    Cytokinesis, the physical separation of a mother cell into two daughter cells, progresses through a series of well-defined changes in morphology. These changes involve distinct biochemical and mechanical processes. Here, we review the mechanical features of cells during cytokinesis, discussing both the material properties as well as sources of stresses, both active and passive, which lead to the observed changes in morphology. We also describe a mechanosensory feedback control system that regulates protein localization and shape progression during cytokinesis. -- Highlights: Black-Right-Pointing-Pointer Cytokinesis progresses through three distinct mechanical phases. Black-Right-Pointing-Pointer Cortical tension initially resists deformation of mother cell. Black-Right-Pointing-Pointer Late in cytokinesis, cortical tension provides stress, enabling furrow ingression. Black-Right-Pointing-Pointer A mechanosensory feedback control system regulates cytokinesis.

  12. DNA loops generate intracentromere tension in mitosis

    PubMed Central

    Lawrimore, Josh; Vasquez, Paula A.; Falvo, Michael R.; Taylor, Russell M.; Vicci, Leandra; Yeh, Elaine; Forest, M. Gregory

    2015-01-01

    The centromere is the DNA locus that dictates kinetochore formation and is visibly apparent as heterochromatin that bridges sister kinetochores in metaphase. Sister centromeres are compacted and held together by cohesin, condensin, and topoisomerase-mediated entanglements until all sister chromosomes bi-orient along the spindle apparatus. The establishment of tension between sister chromatids is essential for quenching a checkpoint kinase signal generated from kinetochores lacking microtubule attachment or tension. How the centromere chromatin spring is organized and functions as a tensiometer is largely unexplored. We have discovered that centromere chromatin loops generate an extensional/poleward force sufficient to release nucleosomes proximal to the spindle axis. This study describes how the physical consequences of DNA looping directly underlie the biological mechanism for sister centromere separation and the spring-like properties of the centromere in mitosis. PMID:26283798

  13. Surface tension and deformation in soft adhesion

    NASA Astrophysics Data System (ADS)

    Jensen, Katharine

    Modern contact mechanics was originally developed to account for the competition between adhesion and elasticity for relatively stiff deformable materials like rubber, but much softer sticky materials are ubiquitous in biology, engineering, and everyday consumer products. In such soft materials, the solid surface tension can also play an important role in resisting shape change, and significantly modify the physics of contact with soft matter. We report indentation and pull-off experiments that bring small, rigid spheres into adhesive contact with compliant silicone gel substrates, varying both the surface functionalization of the spheres and the bulk elastic properties of the gels. We map the resulting deformation profiles using optical microscopy and image analysis. We examine the substrate geometry in light of capillary and elastic theories in order to explore the interplay of surface tension and bulk elasticity in governing soft adhesion.

  14. Surface Tension and Fingering of Miscible Interfaces

    NASA Technical Reports Server (NTRS)

    Abib, Mohammed; Liu, Jian-Bang; Ronney, Paul D.

    1999-01-01

    Experiments on miscible, buoyantly unstable reaction-diffusion fronts and non-reacting displacement fronts in Hele-Shaw cells show a fingering-type instability whose wavelengths (lambda*) are consistent with an interfacial tension (sigma) at the front caused by the change in chemical composition, even though the solutions are miscible in all proportions. In conjunction with the Saffman-Taylor model, the relation sigma = K/tau, where tau is the interface thickness and K approximately equal 4 +/- 2 x 10(exp -6) dyne, enables prediction of our measured values of lambda* as well as results from prior experiments on miscible interfaces. These results indicate that even for miscible fluids, surface tension is generally a more significant factor than diffusion in interfacial stability and flow characteristics.

  15. Chewing over physiology integration.

    PubMed

    Abdulkader, Fernando; Azevedo-Martins, Anna Karenina; Miranda, Manoel de Arcisio; Brunaldi, Kellen

    2005-03-01

    An important challenge for both students and teachers of physiology is to integrate the different areas in which physiological knowledge is didactically divided. In developing countries, such an issue is even more demanding, because budget restrictions often affect the physiology program with laboratory classes being the first on the list when it comes to cuts in expenses. With the aim of addressing this kind of problem, the graduate students of our department organized a physiology summer course offered to undergraduate students. The objective was to present the different physiological systems in an integrated fashion. The strategy pursued was to plan laboratory classes whose experimental results were the basis for the relevant theoretical discussions. The subject we developed to illustrate physiology integration was the study of factors influencing salivary secretion. PMID:15718383

  16. Surface tension confined liquid cryogen cooler

    NASA Technical Reports Server (NTRS)

    Castles, Stephen H. (Inventor); Schein, Michael E. (Inventor)

    1989-01-01

    A cryogenic cooler is provided for use in craft such as launch, orbital, and space vehicles subject to substantial vibration, changes in orientation, and weightlessness. The cooler contains a small pore, large free volume, low density material to restrain a cryogen through surface tension effects during launch and zero-g operations and maintains instrumentation within the temperature range of 10 to 140 K. The cooler operation is completely passive, with no inherent vibration or power requirements.

  17. Surface Tension Demonstration Aboard the ISS

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Astronaut Donald R. Pettit, Expedition Six NASA ISS science officer, photographed this view of a surface tension demonstration using water that is held in place by a metal loop. The experiment took place in the Destiny laboratory on the International Space Station (ISS). The Expedition Six crew was delivered to the station via the Space Shuttle Orbiter Endeavor STS-113 mission which was launched on November 23, 2002.

  18. Tensions of Teaching Media Literacy in Teacher Education

    ERIC Educational Resources Information Center

    Ngomba-Westbrook, Nalova Elaine

    2013-01-01

    This study investigates the tensions a teacher educator faces in facilitating a media literacy teacher education course at the university level. Teaching tensions are conceptualized as a three-tier framework. At the first level, tensions may arise in the selection and application of pedagogies associated with critical and new/21st century…

  19. Nuclear myosin I regulates cell membrane tension.

    PubMed

    Venit, Tomáš; Kalendová, Alžběta; Petr, Martin; Dzijak, Rastislav; Pastorek, Lukáš; Rohožková, Jana; Malohlava, Jakub; Hozák, Pavel

    2016-01-01

    Plasma membrane tension is an important feature that determines the cell shape and influences processes such as cell motility, spreading, endocytosis and exocytosis. Unconventional class 1 myosins are potent regulators of plasma membrane tension because they physically link the plasma membrane with adjacent cytoskeleton. We identified nuclear myosin 1 (NM1) - a putative nuclear isoform of myosin 1c (Myo1c) - as a new player in the field. Although having specific nuclear functions, NM1 localizes predominantly to the plasma membrane. Deletion of NM1 causes more than a 50% increase in the elasticity of the plasma membrane around the actin cytoskeleton as measured by atomic force microscopy. This higher elasticity of NM1 knock-out cells leads to 25% higher resistance to short-term hypotonic environment and rapid cell swelling. In contrast, overexpression of NM1 in wild type cells leads to an additional 30% reduction of their survival. We have shown that NM1 has a direct functional role in the cytoplasm as a dynamic linker between the cell membrane and the underlying cytoskeleton, regulating the degree of effective plasma membrane tension. PMID:27480647

  20. A newly developed Kolsky tension bar.

    SciTech Connect

    Lu, Wei-Yang; Song, Bo; Antoun, Bonnie R.; Connelly, Kevin; Korellis, John S.

    2010-03-01

    Investigation of damage and failure of materials under impact loading relies on reliable dynamic tensile experiments. A precise Kolsky tension bar is highly desirable. Based on the template of the Kolsky compression bar that we recently developed and presented at 2009 SEM conference, a new Kolsky tension bar apparatus was completed at Sandia National Laboratories, California. It is secured to the same optical table. Linear bearings with interior Frelon coating were employed to support the whole tension bar system including the bars and gun barrel. The same laser based alignment system was used to efficiently facilitate highly precise alignment of the bar system. However, the gun part was completely re-designed. One end of the gun barrel, as a part of loading device, was directly jointed to the bar system. A solid cylindrical striker is launched inside the gun barrel and then impacts on a flange attached to the other end of the gun barrel to facilitate a sudden tensile loading on the whole system. This design improves the quality of impact to easily produce a perfect stress wave and is convenient to utilize pulse shaping technique. A calibration and dynamic characterization of an aluminum specimen are presented.

  1. Nuclear myosin I regulates cell membrane tension

    PubMed Central

    Venit, Tomáš; Kalendová, Alžběta; Petr, Martin; Dzijak, Rastislav; Pastorek, Lukáš; Rohožková, Jana; Malohlava, Jakub; Hozák, Pavel

    2016-01-01

    Plasma membrane tension is an important feature that determines the cell shape and influences processes such as cell motility, spreading, endocytosis and exocytosis. Unconventional class 1 myosins are potent regulators of plasma membrane tension because they physically link the plasma membrane with adjacent cytoskeleton. We identified nuclear myosin 1 (NM1) - a putative nuclear isoform of myosin 1c (Myo1c) - as a new player in the field. Although having specific nuclear functions, NM1 localizes predominantly to the plasma membrane. Deletion of NM1 causes more than a 50% increase in the elasticity of the plasma membrane around the actin cytoskeleton as measured by atomic force microscopy. This higher elasticity of NM1 knock-out cells leads to 25% higher resistance to short-term hypotonic environment and rapid cell swelling. In contrast, overexpression of NM1 in wild type cells leads to an additional 30% reduction of their survival. We have shown that NM1 has a direct functional role in the cytoplasm as a dynamic linker between the cell membrane and the underlying cytoskeleton, regulating the degree of effective plasma membrane tension. PMID:27480647

  2. A tension stress loading unit designed for characterizing indentation response of single crystal silicon under tension stress

    NASA Astrophysics Data System (ADS)

    Huang, Hu; Zhao, Hongwei; Shi, Chengli; Hu, Xiaoli; Cui, Tao; Tian, Ye

    2013-09-01

    In this paper, a tension stress loading unit is designed to provide tension stress for brittle materials by combining the piezo actuator and the flexible hinge. The structure of the tension stress loading unit is analyzed and discussed via the theoretical method and finite element simulations. Effects of holding time, the installed specimen and hysteresis of the piezo actuator on output performances of the tension stress loading unit are studied in detail. An experiment system is established by combing the indentation testing unit and the developed tension stress loading unit to characterize indentation response of single crystal silicon under tension stress. Experiment results indicate that tension stress leads to increasing of indentation displacement for the same inden-tation load of single crystal silicon. This paper provides a new tool for studying indentation response of brittle materials under tension stress.

  3. Thermodynamic approach to oxygen delivery in vivo by natural and artificial oxygen carriers.

    PubMed

    Bucci, Enrico

    2009-06-01

    Oxygen is a toxic gas, still indispensable to aerobic life. This paper explores how normal physiology uses the physico-chemical and thermodynamic characteristics of oxygen for transforming a toxic gas into a non toxic indispensable metabolite. Plasma oxygen concentration is in the range of 10(-5) M, insufficient to sustain metabolism. Oxygen carriers, present in blood, release oxygen into plasma, thereby replacing consumed oxygen and buffering PO(2) near their P(50). They are the natural cell-bound carriers, like hemoglobin inside red cells, myoglobin inside myocytes, and artificial cell-free hemoglobin-based oxygen carriers (HBOC) dissolved in plasma. Metabolic oxygen replacement can be defined as cell-bound and cell-free delivery. Cell-bound delivery is retarded by the slow diffusion of oxygen in plasma and interstitial fluids. The 40% hematocrit of normal blood compensates for the delay, coping with the fast oxygen consumption by mitochondria. Facilitated oxygen diffusion by HBOCs corrects for the slow diffusion, making cell-free delivery relatively independent from P(50). At all oxygen affinities, HBOCs produce hyperoxygenations that are compensated by vasoconstrictions. There is a strict direct correlation between the rate of oxygen replacement and hemoglobin content of blood. The free energy loss of the gradient adds a relevant regulation of tissues oxygenation. Oxygen is retained intravascularly by the limited permeability to gases of vessel walls. PMID:19349106

  4. Radiosensitization of mouse skin by oxygen and depletion of glutathione

    SciTech Connect

    Stevens, G.; Joiner, M.; Joiner, B.

    1995-09-30

    To determine the oxygen enhancement ratio (OER) and shape of the oxygen sensitization curve of mouse foot skin, the extent to which glutathione (GSH) depletion radiosensitized skin, and the dependence of such sensitization on the ambient oxygen tension. Carbogen caused the greatest radiosensitization of skin, with a reproducible enhancement of 2.2 relative to the anoxic response. The OER of 2.2 is lower than other reports for mouse skin. This may indicate that the extremes of oxygenation were not produced, although there was no direct evidence for this. Depletion of GSH caused minimal radiosensitization when skin was irradiated under anoxic or well-oxygenated conditions. Radiosensitization by GSH depletion was maximal at intermediate oxygen tensions of 10-21% O{sub 2} in the ambient gas. Increasing the extent of GSH depletion led to increasing radiosensitization, with sensitization enhancement ratios of 1.2 and 1.1, respectively, for extensive and intermediated levels of GSH depletion. In mice exposed to 100% O{sub 2}, a significant component of skin radiosensitivity was due to diffusion of oxygen directly through the skin. Pentobarbitone anesthesia radiosensitized skin in mice exposed to 100% O{sub 2} by a factor of 1.2, but did not further sensitize skin in mice exposed to carbogen. Glutathione levels and the local oxygen tension at the time of irradiation were important determinants of mouse foot skin radiosensitivity. The extent to which GSH levels altered the radiosensitivity of skin was critically dependent on the local oxygen tension. These results have significant implications for potential clinical applications of GSH depletion. 53 refs., 7 figs., 2 tabs.

  5. Fatigue behavior of carbon fiber reinforced epoxy composites -[{+-}45]{sub 4s} laminate under tension-tension and tension - compression fatigue loading test

    SciTech Connect

    Ma, C.C.M.; Tai, N.H.; Wu, G.Y.; Lin, S.H.

    1996-12-31

    Fatigue behaviors of carbon fiber reinforced epoxy laminated composite have been investigated. The [{+-}45]4S laminates of T300/976 Carbon/Epoxy were utilized. The static tensile strength and tension-tension tension-compression fatigue loading tests at various levels of stress amplitude were measured. The median rank method was applied to predict the statistical probability of experimental data of fatigue life. The S-N curves for various survival probabilities were established using the pooled Weibull distribution function. The theoretical prediction methods could be applied to illustrate the fatigue behavior of thermoset matrix polymer composites. Furthermore, the fatigue behaviors under tension - tension and tension-compression fatigue loading test were investigated. Both the stiffness degradation and the surface temperature change during fatigue test are discussed.

  6. Hyperbaric Oxygen Therapy – Can It Be the New Era in Dentistry?

    PubMed Central

    Devaraj, Divya; Srisakthi, D.

    2014-01-01

    Hyperbaric oxygen therapy is a rapidly developing treatment modality in various fields of dentistry. It is the administration of 100% oxygen to the patient for a specified time period, to increase the oxygen tension in the tissues and also its dissolution in the blood. This review aims to briefly discuss the history, mode of action, indications, contraindications, complications and the applications of hyperbaric oxygen therapy in dentistry. PMID:24701552

  7. Pumpless Transport of Low Surface Tension Liquids in Surface Tension Confined (STC) Tracks

    NASA Astrophysics Data System (ADS)

    Megaridis, Constantine; Schutzius, Thomas; Elsharkawy, Mohamed; Tiwari, Manish

    2012-11-01

    Surfaces with patterned wettability have potential applications in microfluidics, fog capture, pool boiling, etc. With recent fabrication advancements, surfaces with adjacent superhydrophobic and superhydrophilic regions are feasible at a reasonable cost; with properly designed patterns, one can produce microfluidic paths (a.k.a. surface tension confined or STC tracks) where a liquid is confined and transported by surface tension alone. The surface tension of water is relatively high (72 mN/m), as compared with oils (~25 mN/m) and organic solvents (~20 mN/m). This makes the design of STC channels for oils and organic solvents far more difficult. In this study, open STC tracks for pumpless transport of low-surface tension liquids (acetone, ethanol, and hexadecane) on microfluidic chips are fabricated using a large-area, wet-processing technique. Wettable, wax-based, submillimeter-wide tracks are applied by a fountain-pen procedure on superoleophobic, fluoroacrylic carbon nanofiber (CNF) composite coatings. The fabricated anisotropic wetting patterns confine the low-surface tension liquids onto the flow tracks, driving them with meniscus velocities exceeding 3 cm/s. Scaling arguments and Washburn's equation provide estimates of the liquid velocities measured in these tracks, which also act as rails for directional sliding control of mm-sized water droplets. The present facile patterned wettability approach can be extended to deposit micrometer-wide tracks.

  8. Oxygen-Concentrating Cell

    NASA Technical Reports Server (NTRS)

    Buehler, K.

    1986-01-01

    High-purity oxygen produced from breathing air or from propellantgrade oxygen in oxygen-concentrating cell. Operating economics of concentrator attractive: Energy consumption about 4 Wh per liter of oxygen, slightly lower than conventional electrochemical oxygen extractors.

  9. Using oxygen at home

    MedlinePlus

    ... DO NOT use oil-based products, such as petroleum jelly (Vaseline). Ask your oxygen equipment provider about ... oxygen; Hypoxia - home oxygen; Hospice - home oxygen References American Thoracic Society. Why do I need oxygen therapy? ...

  10. [The physiology of gas exchange in divers].

    PubMed

    Rieder, H U

    1989-04-01

    After a short reminder of Boyle's law and the physiology of oxygen and nitrogen, a mathematical model will be discussed (without formulas). Its limitations are shown in relation to the calculation of partial gas pressures in different human organs. Such models are already used in closed circuit anesthesia delivery systems and valuable insights can be obtained by this way, which enable us to calculate better nitrogen decompression tables. PMID:2727653

  11. Microbial physiology vol. 29

    SciTech Connect

    Rose, A.H. ); Tempest, D.W. )

    1988-01-01

    This book contains the following chapters: Hydrogen metabolism in Rhizobium: energetics, regulation, enzymology and genetics; The physiology and biochemistry of pili; Carboxysomes and ribulose bisphosphate carboxylase/oxygenase; Archaebacteria: the comparative enzymology of their central metabolic pathways; and Physiology of lipoteichoic acids in bacteria.

  12. Phun Week: Understanding Physiology

    ERIC Educational Resources Information Center

    Limson, Mel; Matyas, Marsha Lakes

    2009-01-01

    Topics such as sports, exercise, health, and nutrition can make the science of physiology relevant and engaging for students. In addition, many lessons on these topics, such as those on the cardiovascular, respiratory, and digestive systems, align with national and state life science education standards. Physiology Understanding Week (PhUn…

  13. Reproduction, Physiology and Biochemistry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This chapter focuses on the reproduction, physiology, and biochemistry of the root-knot nematodes. The extensive amount of information on the reproduction and cytogenetics of species of Meloidogyne contrasts with the limited information on physiology, biochemistry, and biochemical pathways. In commo...

  14. Toward a general psychological model of tension and suspense

    PubMed Central

    Lehne, Moritz; Koelsch, Stefan

    2015-01-01

    Tension and suspense are powerful emotional experiences that occur in a wide variety of contexts (e.g., in music, film, literature, and everyday life). The omnipresence of tension and suspense suggests that they build on very basic cognitive and affective mechanisms. However, the psychological underpinnings of tension experiences remain largely unexplained, and tension and suspense are rarely discussed from a general, domain-independent perspective. In this paper, we argue that tension experiences in different contexts (e.g., musical tension or suspense in a movie) build on the same underlying psychological processes. We discuss key components of tension experiences and propose a domain-independent model of tension and suspense. According to this model, tension experiences originate from states of conflict, instability, dissonance, or uncertainty that trigger predictive processes directed at future events of emotional significance. We also discuss possible neural mechanisms underlying tension and suspense. The model provides a theoretical framework that can inform future empirical research on tension phenomena. PMID:25717309

  15. Toward a general psychological model of tension and suspense.

    PubMed

    Lehne, Moritz; Koelsch, Stefan

    2015-01-01

    Tension and suspense are powerful emotional experiences that occur in a wide variety of contexts (e.g., in music, film, literature, and everyday life). The omnipresence of tension and suspense suggests that they build on very basic cognitive and affective mechanisms. However, the psychological underpinnings of tension experiences remain largely unexplained, and tension and suspense are rarely discussed from a general, domain-independent perspective. In this paper, we argue that tension experiences in different contexts (e.g., musical tension or suspense in a movie) build on the same underlying psychological processes. We discuss key components of tension experiences and propose a domain-independent model of tension and suspense. According to this model, tension experiences originate from states of conflict, instability, dissonance, or uncertainty that trigger predictive processes directed at future events of emotional significance. We also discuss possible neural mechanisms underlying tension and suspense. The model provides a theoretical framework that can inform future empirical research on tension phenomena. PMID:25717309

  16. The effect of inhaled bronchoconstrictors on transcutaneous gas tensions in normal adult subjects.

    PubMed

    Gray, B; Barnes, N

    1987-01-01

    The administration of histamine and leukotriene D4 (LTD4) by nebulised aerosol in logarithmically increasing doses to normal subjects resulted in significant bronchoconstriction. Transcutaneous oxygen tension (tcPO2) was monitored during and after the bronchial challenge tests. Following histamine challenge there was significant hypoxaemia in all subjects (mean fall in tcPO2, 20 mmHg). However, following LTD4 administration, there was a small and insignificant fall in tcPO2. Transcutaneous carbon dioxide tension (tcPCO2) was also monitored throughout bronchial challenge, but showed no significant change. We suggest that the hypoxaemia following histamine challenge was due to increased ventilation/perfusion (V/Q) mismatching in the lung induced by histamine deposition. PMID:3673787

  17. Surface tension measurement from the indentation of clamped thin films.

    PubMed

    Xu, Xuejuan; Jagota, Anand; Paretkar, Dadhichi; Hui, Chung-Yuen

    2016-06-21

    We developed an indentation technique to measure the surface tension of relatively stiff solids. In the proposed method, a suspended thin solid film is indented by a rigid sphere and its deflection is measured by optical interferometry. The film deflection is jointly resisted by surface tension, elasticity and residual stress. Using a version of nonlinear von Karman plate theory that includes surface tension, we are able to separate the contribution of elasticity to the total tension in the film. Surface tension is determined by extrapolating the sum of surface tension and residual stress to zero film thickness. We measured the surface tension of polydimethylsiloxane (PDMS) using this technique and obtained a value of 19.5 ± 3.6 mN m(-1), consistent with the surface energy of PDMS reported in the literature. PMID:27189735

  18. Investigations on the Incompletely Developed Plane Diagonal-Tension Field

    NASA Technical Reports Server (NTRS)

    Kuhn, Paul

    1940-01-01

    This report presents the results of an investigation on the incompletely developed diagonal-tension field. Actual diagonal-tension beams work in an intermediate stage between pure shear and pure diagonal tension; the theory developed by wagner for diagonal tension is not directly applicable. The first part of the paper reviews the most essential items of the theory of pure diagonal tension as well as previous attempts to formulate a theory of incomplete diagonal tension. The second part of the paper describes strain measurement made by the N. A. C. A. to obtain the necessary coefficients for the proposed theory. The third part of the paper discusses the stress analysis of diagonal-tension beams by means of the proposed theory.

  19. Wide and high resolution tension measurement using FRET in embryo

    PubMed Central

    Yamashita, Satoshi; Tsuboi, Takashi; Ishinabe, Nanako; Kitaguchi, Tetsuya; Michiue, Tatsuo

    2016-01-01

    During embryonic development, physical force plays an important role in morphogenesis and differentiation. Stretch sensitive fluorescence resonance energy transfer (FRET) has the potential to provide non-invasive tension measurements inside living tissue. In this study, we introduced a FRET-based actinin tension sensor into Xenopus laevis embryos and demonstrated that this sensor captures variation of tension across differentiating ectoderm. The actinin tension sensor, containing mCherry and EGFP connected by spider silk protein, was validated in human embryonic kidney (HEK) cells and embryos. It co-localized with actin filaments and changed FRET efficiencies in response to actin filament destruction, myosin deactivation, and osmotic perturbation. Time-lapse FRET analysis showed that the prospective neural ectoderm bears higher tension than the epidermal ectoderm during gastrulation and neurulation, and cells morphogenetic behavior correlated with the tension difference. These data confirmed that the sensor enables us to measure tension across tissues concurrently and with high resolution. PMID:27335157

  20. Review of literature surface tension data for molten silicon

    NASA Technical Reports Server (NTRS)

    Hardy, S.

    1981-01-01

    Measurements of the surface tension of molten silicon are reported. For marangoni flow, the important parameter is the variation of surface tension with temperature, not the absolute value of the surface tension. It is not possible to calculate temperature coefficients using surface tension measurements from different experiments because the systematic errors are usually larger than the changes in surface tension because of temperature variations. The lack of good surface tension data for liquid silicon is probably due to its extreme chemical reactivity. A material which resists attack by molten silicon is not found. It is suggested that all of the sessile drip surface tension measurements are probably for silicon which is contaminated by the substrate materials.

  1. Wide and high resolution tension measurement using FRET in embryo.

    PubMed

    Yamashita, Satoshi; Tsuboi, Takashi; Ishinabe, Nanako; Kitaguchi, Tetsuya; Michiue, Tatsuo

    2016-01-01

    During embryonic development, physical force plays an important role in morphogenesis and differentiation. Stretch sensitive fluorescence resonance energy transfer (FRET) has the potential to provide non-invasive tension measurements inside living tissue. In this study, we introduced a FRET-based actinin tension sensor into Xenopus laevis embryos and demonstrated that this sensor captures variation of tension across differentiating ectoderm. The actinin tension sensor, containing mCherry and EGFP connected by spider silk protein, was validated in human embryonic kidney (HEK) cells and embryos. It co-localized with actin filaments and changed FRET efficiencies in response to actin filament destruction, myosin deactivation, and osmotic perturbation. Time-lapse FRET analysis showed that the prospective neural ectoderm bears higher tension than the epidermal ectoderm during gastrulation and neurulation, and cells morphogenetic behavior correlated with the tension difference. These data confirmed that the sensor enables us to measure tension across tissues concurrently and with high resolution. PMID:27335157

  2. Tension-compression-tension tertiary twins in coarse-grained polycrystalline pure magnesium at room temperature

    DOE PAGESBeta

    Yu, Qin; Jiang, Yanyao; Wang, Jian

    2015-04-07

    Using electron backscatter diffraction, the microstructural features of tension–compression–tension (T–C–T) tertiary twins are studied in coarse-grained pure polycrystalline magnesium subjected to monotonic compression along the extrusion direction in ambient air. T–C–T tertiary twins are developed due to the formation of a compression–tension double twin inside a primary tension twin. All the observed T–C–T twin variants are of TiCjTj type. TiCi+1Ti+1 (or TiCi–1Ti–1) variants are observed more frequently than TiCi+2Ti+2 (or TiCi–2Ti–2) variants. Moreover, the number of tertiary twin lamellae increases with the applied compressive strain.

  3. Structural design significance of tension-tension fatigue data on composites

    NASA Technical Reports Server (NTRS)

    Grimes, G. C.

    1977-01-01

    Constant cycle tension-tension fatigue and related static tension data have been generated on six single composite material/orientation combinations and twenty-one hybrid composite material/orientation combinations. Anomalies are related to the temperature rise and stopped interval creep, whereas endurance limit stresses (runouts) are associated with static proportional limit values, when they occur, and internal damage. The significance of these room temperature-dry data on the design allowables and weight of aerodynamic structueres is discussed. Such structures are helicopter rotor blades and wing and horizontal stabilizer lower surfaces. Typical criteria for turning these data into preliminary allowables are shown, as are examples of such allowables developed from the data. These values are then compared to those that might be used if the structures were made of metal.

  4. Upregulation of cardioprotective SUR2A by sub-hypoxic drop in oxygen.

    PubMed

    Mohammed Abdul, Khaja Shameem; Jovanović, Sofija; Sukhodub, Andriy; Du, Qingyou; Jovanović, Aleksandar

    2014-11-01

    The effects of hypoxia on gene expression have been vigorously studied, but possible effects of small changes in oxygen tension have never been addressed. SUR2A is an atypical ABC protein serving as a regulatory subunit of sarcolemmal ATP-sensitive K(+) (KATP) channels. Up-regulation of SUR2A is associated with cardioprotection and improved physical endurance. Here, we have found that a 24h-long exposure to slightly decreased ambient fractional concentration of oxygen (20% oxygen), which is an equivalent to oxygen tension at 350m above sea level, significantly increased levels of SUR2A in the heart despite that this drop of oxygen did not affect levels of O2, CO2 and hematocrit in the blood or myocardial levels of ATP, lactate and NAD/NADH/NAD(+). Hearts from mice exposed to 20% oxygen were significantly more resistant to ischaemia-reperfusion when compared to control ones. Decrease in fractional oxygen concentration of just 0.9% was associated with phosphorylation of ERK1/2, but not Akt, which was essential for up-regulation of SUR2A. These findings indicate that a small drop in oxygen tension up-regulates SUR2A in the heart by activating ERK signaling pathway. This is the first report to suggest that a minimal change in oxygen tension could have a profound signaling effect. PMID:25064694

  5. Physiology in conservation translocations

    PubMed Central

    Tarszisz, Esther; Dickman, Christopher R.; Munn, Adam J.

    2014-01-01

    Conservation translocations aim to restore species to their indigenous ranges, protect populations from threats and/or reinstate ecosystem functions. They are particularly important for the conservation and management of rare and threatened species. Despite tremendous efforts and advancement in recent years, animal conservation translocations generally have variable success, and the reasons for this are often uncertain. We suggest that when little is known about the physiology and wellbeing of individuals either before or after release, it will be difficult to determine their likelihood of survival, and this could limit advancements in the science of translocations for conservation. In this regard, we argue that physiology offers novel approaches that could substantially improve translocations and associated practices. As a discipline, it is apparent that physiology may be undervalued, perhaps because of the invasive nature of some physiological measurement techniques (e.g. sampling body fluids, surgical implantation). We examined 232 publications that dealt with translocations of terrestrial vertebrates and aquatic mammals and, defining ‘success’ as high or low, determined how many of these studies explicitly incorporated physiological aspects into their protocols and monitoring. From this review, it is apparent that physiological evaluation before and after animal releases could progress and improve translocation/reintroduction successes. We propose a suite of physiological measures, in addition to animal health indices, for assisting conservation translocations over the short term and also for longer term post-release monitoring. Perhaps most importantly, we argue that the incorporation of physiological assessments of animals at all stages of translocation can have important welfare implications by helping to reduce the total number of animals used. Physiological indicators can also help to refine conservation translocation methods. These approaches fall

  6. Neuronal responses to physiological stress.

    PubMed

    Kagias, Konstantinos; Nehammer, Camilla; Pocock, Roger

    2012-01-01

    Physiological stress can be defined as any external or internal condition that challenges the homeostasis of a cell or an organism. It can be divided into three different aspects: environmental stress, intrinsic developmental stress, and aging. Throughout life all living organisms are challenged by changes in the environment. Fluctuations in oxygen levels, temperature, and redox state for example, trigger molecular events that enable an organism to adapt, survive, and reproduce. In addition to external stressors, organisms experience stress associated with morphogenesis and changes in inner chemistry during normal development. For example, conditions such as intrinsic hypoxia and oxidative stress, due to an increase in tissue mass, have to be confronted by developing embryos in order to complete their development. Finally, organisms face the challenge of stochastic accumulation of molecular damage during aging that results in decline and eventual death. Studies have shown that the nervous system plays a pivotal role in responding to stress. Neurons not only receive and process information from the environment but also actively respond to various stresses to promote survival. These responses include changes in the expression of molecules such as transcription factors and microRNAs that regulate stress resistance and adaptation. Moreover, both intrinsic and extrinsic stresses have a tremendous impact on neuronal development and maintenance with implications in many diseases. Here, we review the responses of neurons to various physiological stressors at the molecular and cellular level. PMID:23112806

  7. Neuronal Responses to Physiological Stress

    PubMed Central

    Kagias, Konstantinos; Nehammer, Camilla; Pocock, Roger

    2012-01-01

    Physiological stress can be defined as any external or internal condition that challenges the homeostasis of a cell or an organism. It can be divided into three different aspects: environmental stress, intrinsic developmental stress, and aging. Throughout life all living organisms are challenged by changes in the environment. Fluctuations in oxygen levels, temperature, and redox state for example, trigger molecular events that enable an organism to adapt, survive, and reproduce. In addition to external stressors, organisms experience stress associated with morphogenesis and changes in inner chemistry during normal development. For example, conditions such as intrinsic hypoxia and oxidative stress, due to an increase in tissue mass, have to be confronted by developing embryos in order to complete their development. Finally, organisms face the challenge of stochastic accumulation of molecular damage during aging that results in decline and eventual death. Studies have shown that the nervous system plays a pivotal role in responding to stress. Neurons not only receive and process information from the environment but also actively respond to various stresses to promote survival. These responses include changes in the expression of molecules such as transcription factors and microRNAs that regulate stress resistance and adaptation. Moreover, both intrinsic and extrinsic stresses have a tremendous impact on neuronal development and maintenance with implications in many diseases. Here, we review the responses of neurons to various physiological stressors at the molecular and cellular level. PMID:23112806

  8. Fatigue Damage in Notched Composite Laminates Under Tension-Tension Cyclic Loads

    NASA Technical Reports Server (NTRS)

    Stinchcomb, W. W.; Henneke, E. G.; Reifsnider, K. L.; Kress, G. R.

    1985-01-01

    The results are given of an investigation to determine the damage states which develop in graphite epoxy laminates with center holes due to tension-tension cyclic loads, to determine the influence of stacking sequence on the initiation and interaction of damage modes and the process of damage development, and to establish the relationships between the damage states and the strength, stiffness, and life of the laminates. Two quasi-isotropic laminates were selected to give different distributions of interlaminar stresses around the hole. The laminates were tested under cyclic loads (R=0.1, 10 Hz) at maximum stresses ranging between 60 and 95 percent of the notched tensile strength.

  9. Physiological ecology meets climate change

    PubMed Central

    Bozinovic, Francisco; Pörtner, Hans-Otto

    2015-01-01

    In this article, we pointed out that understanding the physiology of differential climate change effects on organisms is one of the many urgent challenges faced in ecology and evolutionary biology. We explore how physiological ecology can contribute to a holistic view of climate change impacts on organisms and ecosystems and their evolutionary responses. We suggest that theoretical and experimental efforts not only need to improve our understanding of thermal limits to organisms, but also to consider multiple stressors both on land and in the oceans. As an example, we discuss recent efforts to understand the effects of various global change drivers on aquatic ectotherms in the field that led to the development of the concept of oxygen and capacity limited thermal tolerance (OCLTT) as a framework integrating various drivers and linking organisational levels from ecosystem to organism, tissue, cell, and molecules. We suggest seven core objectives of a comprehensive research program comprising the interplay among physiological, ecological, and evolutionary approaches for both aquatic and terrestrial organisms. While studies of individual aspects are already underway in many laboratories worldwide, integration of these findings into conceptual frameworks is needed not only within one organism group such as animals but also across organism domains such as Archaea, Bacteria, and Eukarya. Indeed, development of unifying concepts is relevant for interpreting existing and future findings in a coherent way and for projecting the future ecological and evolutionary effects of climate change on functional biodiversity. We also suggest that OCLTT may in the end and from an evolutionary point of view, be able to explain the limited thermal tolerance of metazoans when compared to other organisms. PMID:25798220

  10. Physiological ecology meets climate change.

    PubMed

    Bozinovic, Francisco; Pörtner, Hans-Otto

    2015-03-01

    In this article, we pointed out that understanding the physiology of differential climate change effects on organisms is one of the many urgent challenges faced in ecology and evolutionary biology. We explore how physiological ecology can contribute to a holistic view of climate change impacts on organisms and ecosystems and their evolutionary responses. We suggest that theoretical and experimental efforts not only need to improve our understanding of thermal limits to organisms, but also to consider multiple stressors both on land and in the oceans. As an example, we discuss recent efforts to understand the effects of various global change drivers on aquatic ectotherms in the field that led to the development of the concept of oxygen and capacity limited thermal tolerance (OCLTT) as a framework integrating various drivers and linking organisational levels from ecosystem to organism, tissue, cell, and molecules. We suggest seven core objectives of a comprehensive research program comprising the interplay among physiological, ecological, and evolutionary approaches for both aquatic and terrestrial organisms. While studies of individual aspects are already underway in many laboratories worldwide, integration of these findings into conceptual frameworks is needed not only within one organism group such as animals but also across organism domains such as Archaea, Bacteria, and Eukarya. Indeed, development of unifying concepts is relevant for interpreting existing and future findings in a coherent way and for projecting the future ecological and evolutionary effects of climate change on functional biodiversity. We also suggest that OCLTT may in the end and from an evolutionary point of view, be able to explain the limited thermal tolerance of metazoans when compared to other organisms. PMID:25798220

  11. Retinal oxygenation via the choroidal circulation.

    PubMed Central

    Landers, M B

    1978-01-01

    The possibility of supplying normal amounts of oxygen to the inner layers of the retina by diffusion from the choroid in the presence of retinal arterial obstruction was studied in cats and rhesus monkeys. While the animals were under general anesthesia, an oxygen electrode was placed in the vitreous cavity immediately adjacent to the retina, and a retinal artery blocker probe was used to occlude various segments of the retina blood supply. The inspired oxygen concentration was alternated between 20% and 100%. The choroidal circulation was intermittently occluded by elevating the intraocular pressure. In all animals it was possible to return the oxygen tension of the innermost retina to normal concentrations or above while the retinal arterial circulation alone was occluded, by having the animal breathe 100% oxygen at one atmosphere pressure. This could not be done when the intraocular pressure was elevated to 85 mm Hg, occluding the choroidal as well as the retinal circulation. The electroretinogram and the visually evoked response were recorded in cats while the retinal circulation was occluded and the inspired oxygen concentration changed from 20% to 100% at one atmosphere pressure. The electroretinogram and the visually evoked response were extinguished by occluding the retinal circulation while the animal was breathing 20% oxygen, and these responses were returned to normal by changing to a 100% inspired oxygen concentration. Images FIGURE 6 PMID:112752

  12. The string tension of SU(3) representations

    NASA Astrophysics Data System (ADS)

    Deldar, Sedigheh

    In this thesis, I study the theory of confinement by measuring the potentials and in particular the string tension, between static sources in a background of gluons in pure gauge SU(3). The potentials between static sources in a variety of representations (fundamental, 8, 6, 15-antisymmetric, 10, 27 and 15- symmetric) have been computed by measuring Wilson loops. Wilson loops for higher representations have been measured in terms of Wilson loops of the fundamental representation. The string tensions have been computed from fitting the potentials to a Coloumbic plus a linear term. The simulations have been done primarily on anisotropic lattices, using a O(a2) tadpole improved action. A range of lattice spacings (0.43 fm, 0.25 fm and 0.11 fm) and volumes (83 × 24, 103 × 24, 163 × 24 and 183 × 24) has been used to extrapolate to the continuum and to control finite volume effects. In addition, a simulation at a single lattice spacing has been performed on an isotropic (84) lattice. The potentials between static sources in various representations in SU(3) have also been calculated based on the fat-center-vortices model. At intermediate distances, the results from both the numerical and model calculations are in qualitative agreement with ``Casimir scaling,'' which says that the string tension is proportional to the quadratic operator of the representation. For large distances (as large as 2.4 fm) no color screening or change of the potential slope has been observed from the lattice calculations of this work. However, from the fat-center- vortices model, screening and change of the potential slope is seen for zero triality and non-zero triality representations, respectively.

  13. Surface Tension Driven Convection Experiment Completed

    NASA Technical Reports Server (NTRS)

    Jacobson, Thomas P.; Sedlak, Deborah A.

    1997-01-01

    The Surface Tension Driven Convection Experiment (STDCE) was designed to study basic fluid mechanics and heat transfer on thermocapillary flows generated by temperature variations along the free surfaces of liquids in microgravity. STDCE first flew on the USML-1 mission in July 1992 and was rebuilt for the USML-2 mission that was launched in October 1995. This was a collaborative project with principal investigators from Case Western Reserve University (CWRU), Professors Simon Ostrach and Yasuhiro Kamotani, along with a team from the NASA Lewis Research Center composed of civil servants and contractors from Aerospace Design & Fabrication, Inc. (ADF), Analex, and NYMA, Inc.

  14. Tensions in private health insurance regulation.

    PubMed

    Willcox, Sharon

    2003-02-01

    This article provides an analysis of the regulatory framework of Australian private health insurance linked to four major implicit regulatory objectives: promoting access to health insurance for consumers; promoting financial solvency and industry viability of registered health benefits organisations; promoting competition between registered health benefits organisations; and promoting accountability to consumers. Through an analysis of regulatory changes, case law and policy documents on the performance of the health insurance industry, it is argued that existing health insurance regulation exhibits inevitable tensions due to shifting and often conflicting government objectives about the role of private health insurance. PMID:12650003

  15. Lump Solitons in Surface Tension Dominated Flows

    NASA Astrophysics Data System (ADS)

    Milewski, Paul; Berger, Kurt

    1999-11-01

    The Kadomtsev-Petviashvilli I equation (KPI) which models small-amplitude, weakly three-dimensional surface-tension dominated long waves is integrable and allows for algebraically decaying lump solitary waves. It is not known (theoretically or numerically) whether the full free-surface Euler equations support such solutions. We consider an intermediate model, the generalised Benney-Luke equation (gBL) which is isotropic (not weakly three-dimensional) and contains KPI as a limit. We show numerically that: 1. gBL supports lump solitary waves; 2. These waves collide elastically and are stable; 3. They are generated by resonant flow over an obstacle.

  16. Small-Bolt Torque-Tension Tester

    NASA Technical Reports Server (NTRS)

    Posey, Alan J.

    2009-01-01

    The device described here measures the torque-tension relationship for fasteners as small as #0. The small-bolt tester consists of a plate of high-strength steel into which three miniature load cells are recessed. The depth of the recess is sized so that the three load cells can be shimmed, the optimum height depending upon the test hardware. The three miniature load cells are arranged in an equilateral triangular configuration with the test bolt aligned with the centroid of the three. This is a kinematic arrangement.

  17. An integrated physiology model to study regional lung damage effects and the physiologic response

    PubMed Central

    2014-01-01

    Background This work expands upon a previously developed exercise dynamic physiology model (DPM) with the addition of an anatomic pulmonary system in order to quantify the impact of lung damage on oxygen transport and physical performance decrement. Methods A pulmonary model is derived with an anatomic structure based on morphometric measurements, accounting for heterogeneous ventilation and perfusion observed experimentally. The model is incorporated into an existing exercise physiology model; the combined system is validated using human exercise data. Pulmonary damage from blast, blunt trauma, and chemical injury is quantified in the model based on lung fluid infiltration (edema) which reduces oxygen delivery to the blood. The pulmonary damage component is derived and calibrated based on published animal experiments; scaling laws are used to predict the human response to lung injury in terms of physical performance decrement. Results The augmented dynamic physiology model (DPM) accurately predicted the human response to hypoxia, altitude, and exercise observed experimentally. The pulmonary damage parameters (shunt and diffusing capacity reduction) were fit to experimental animal data obtained in blast, blunt trauma, and chemical damage studies which link lung damage to lung weight change; the model is able to predict the reduced oxygen delivery in damage conditions. The model accurately estimates physical performance reduction with pulmonary damage. Conclusions We have developed a physiologically-based mathematical model to predict performance decrement endpoints in the presence of thoracic damage; simulations can be extended to estimate human performance and escape in extreme situations. PMID:25044032

  18. Insulin Inhibits Low Oxygen-Induced ATP Release from Human Erythrocytes: Implication for Vascular Control

    PubMed Central

    Hanson, Madelyn S.; Ellsworth, Mary L.; Achilleus, David; Stephenson, Alan H.; Bowles, Elizabeth A.; Sridharan, Meera; Adderley, Shaquria; Sprague, Randy S.

    2010-01-01

    Objective ATP released from human erythrocytes in response to reduced oxygen tension (pO2) participates in the matching of oxygen (O2) supply with need in skeletal muscle by stimulating increases in blood flow to areas with increased O2 demand. Here we investigated the hypothesis that hyperinsulinemia inhibits ATP release from erythrocytes and impairs their ability to stimulate dilation of isolated arterioles exposed to decreased extra-luminal pO2. Methods Erythrocyte ATP release was stimulated pharmacologically (mastoparan 7) and physiologically (reduced pO2) in the absence or presence of insulin. We also examined the ability of isolated skeletal muscle arterioles perfused with buffer containing erythrocytes treated with insulin or its vehicle (saline) to dilate in response to decreased extra-luminal pO2. Results Insulin significantly attenuated mastoparan 7– and reduced pO2–induced ATP release. In vessels perfused with untreated erythrocytes, low extra-luminal pO2 resulted in an increase in vessel diameter. In contrast, when erythrocytes were treated with insulin, no vasodilation occurred. Conclusions These studies demonstrate that insulin inhibits ATP release from erythrocytes in response to reduced pO2 and impairs their ability to stimulate dilation of skeletal muscle arterioles. These results suggest that hyperinsulinemia could hinder the matching of O2 supply with need in skeletal muscle. PMID:19412833

  19. The physiology of global change: linking patterns to mechanisms.

    PubMed

    Somero, George N

    2012-01-01

    Global change includes alterations in ocean temperature, oxygen availability, salinity, and pH, abiotic variables with strong and interacting influences on the physiology of all taxa. Physiological stresses resulting from changes in these four variables may cause broad biogeographic shifts as well as localized changes in distribution in mosaic habitats. To elucidate these causal linkages, I address the following questions: What types of physiological limitations can alter species' distributions and, in cases of extreme stress, cause extinctions? Which species are most threatened by these physiological challenges--and why? How do contents of genomes establish capacities to respond to global change, notably in the case of species that have evolved in highly stable habitats? How fully can phenotypic acclimatization offset abiotic stress? Can physiological measurements, including new molecular ("-omic") approaches, provide indices of the degree of sublethal stress an organism experiences? And can physiological evolution keep pace with global change? PMID:22457968

  20. Clinical hyperbaric oxygen therapy, wound perfusion, and transcutaneous oximetry.

    PubMed

    Niinikoski, Juha H A

    2004-03-01

    Hyperbaric oxygen therapy (HBOT) is an important adjunct in the management of problem wounds which exist in chronic oxygen deficiency and in which the local oxygen tension is below optimal for healing. In the treatment of hypoxic and ischemic wounds, the most important effects of hyperbaric oxygenation are the stimulation of fibroblast proliferation and differentiation, increased collagen formation and cross-linking, augmented neovascularization, and the stimulation of leukocyte microbial killing. Ischemic soft tissues also benefit from hyperoxygenation through improved preservation of energy metabolism and reduction of edema. Hyperbaric oxygen is administered in either a multiplace or a monoplace hyperbaric chamber. Normally, pressures of 2 to 2.5 ATA are used for a period of 90 minutes once or twice daily. For an objective assessment of wound perfusion and oxygenation, transcutaneous oximetry provides a simple, reliable, noninvasive, diagnostic technique. It can be used for assessment of tissue perfusion in the vicinity of the problem wound. Transcutaneous oximetry may be used in the assessment of wound healing potential, selection of amputation level, and patient selection for HBOT. In diabetic patients with chronic foot ulcers peri-wound transcutaneous oxygen tensions (TcP(O2)) over 400 mmHg in 2.5 ATA hyperbaric oxygen or over 50 mmHg in normobaric pure oxygen predict healing success with adjuncted HBOT with high accuracy. PMID:14961187

  1. Interpreting expressive performance through listener judgments of musical tension.

    PubMed

    Farbood, Morwaread M; Upham, Finn

    2013-01-01

    This study examines listener judgments of musical tension for a recording of a Schubert song and its harmonic reduction. Continuous tension ratings collected in an experiment and quantitative descriptions of the piece's musical features, include dynamics, pitch height, harmony, onset frequency, and tempo, were analyzed from two different angles. In the first part of the analysis, the different processing timescales for disparate features contributing to tension were explored through the optimization of a predictive tension model. The results revealed the optimal time windows for harmony were considerably longer (~22 s) than for any other feature (~1-4 s). In the second part of the analysis, tension ratings for the individual verses of the song and its harmonic reduction were examined and compared. The results showed that although the average tension ratings between verses were very similar, differences in how and when participants reported tension changes highlighted performance decisions made in the interpretation of the score, ambiguity in tension implications of the music, and the potential importance of contrast between verses and phrases. Analysis of the tension ratings for the harmonic reduction also provided a new perspective for better understanding how complex musical features inform listener tension judgments. PMID:24416024

  2. Interpreting expressive performance through listener judgments of musical tension

    PubMed Central

    Farbood, Morwaread M.; Upham, Finn

    2013-01-01

    This study examines listener judgments of musical tension for a recording of a Schubert song and its harmonic reduction. Continuous tension ratings collected in an experiment and quantitative descriptions of the piece's musical features, include dynamics, pitch height, harmony, onset frequency, and tempo, were analyzed from two different angles. In the first part of the analysis, the different processing timescales for disparate features contributing to tension were explored through the optimization of a predictive tension model. The results revealed the optimal time windows for harmony were considerably longer (~22 s) than for any other feature (~1–4 s). In the second part of the analysis, tension ratings for the individual verses of the song and its harmonic reduction were examined and compared. The results showed that although the average tension ratings between verses were very similar, differences in how and when participants reported tension changes highlighted performance decisions made in the interpretation of the score, ambiguity in tension implications of the music, and the potential importance of contrast between verses and phrases. Analysis of the tension ratings for the harmonic reduction also provided a new perspective for better understanding how complex musical features inform listener tension judgments. PMID:24416024

  3. Theoretical Analysis of Membrane Tension in Moving Cells

    PubMed Central

    Schweitzer, Yonatan; Lieber, Arnon D.; Keren, Kinneret; Kozlov, Michael M.

    2014-01-01

    Lateral tension in cell plasma membranes plays an essential role in regulation of a number of membrane-related intracellular processes and cell motion. Understanding the physical factors generating the lateral tension and quantitative determination of the tension distribution along the cell membrane is an emerging topic of cell biophysics. Although experimental data are accumulating on membrane tension values in several cell types, the tension distribution along the membranes of moving cells remains largely unexplored. Here we suggest and analyze a theoretical model predicting the tension distribution along the membrane of a cell crawling on a flat substrate. We consider the tension to be generated by the force of actin network polymerization against the membrane at the cell leading edge. The three major factors determining the tension distribution are the membrane interaction with anchors connecting the actin network to the lipid bilayer, the membrane interaction with cell adhesions, and the force developing at the rear boundary due to the detachment of the remaining cell adhesion from the substrate in the course of cell crawling. Our model recovers the experimentally measured values of the tension in fish keratocytes and their dependence on the number of adhesions. The model predicts, quantitatively, the tension distribution between the leading and rear membrane edges as a function of the area fractions of the anchors and the adhesions. PMID:24411240

  4. Vibration of thin, tensioned, helically wrapped plates

    NASA Astrophysics Data System (ADS)

    Lopez, Ernesto; Müftü, Sinan

    2011-02-01

    Free vibration analysis of a thin tensioned plate, wrapped around a cylindrical guide in a helical manner is presented. The system is a model of a thin, flexible web wrapped around a turn-bar. The equation of motion of the wrapped plate is derived by using the energy method and with the Kirchhoff-Love assumptions. The weak form of the equation of motion was obtained by the finite element method and the eigenvalue problem was solved numerically. The effects of parameters such as plate tension, guide radius, longitudinal and helical wrap angles, plate width, and the lengths of the non-wrapped segments were investigated. Eigenmodes with same mode numbers were observed in symmetric and anti-symmetric fashion about the center of the plate, for symmetrically wrapped plates. It was shown that the plate/shell boundary of the wrapped plate effectively acts like a support. For non-helically wrapped plates the free edges cause a frequency clustering of the lateral modes about the dominant longitudinal mode. The frequency clustering diminishes when helical wrap is introduced.

  5. Constantly energized no-load tension packer

    SciTech Connect

    Preston, D.C.; Reiter, K.C.

    1981-12-29

    A retrievable, constantly energized, no-load packer is securable within a well and removable by application of tension. Upper and lower slip means are expandable into gripping engagement with the casing. A control body extends to the upper and lower slips and is encircled by packing means. A release housing extends from the lower expansion means with latch means being provided for securing the control body with the release housing, the latch means being shiftable to disengage the control body from the release housing for retrieval of the apparatus. Lock sleeve means are connected to the release housing for securing the latch means and one of the control body and release housing and are shearably releasable therefrom for disengagement of the control body and the release housing, the application of tension through the control string being carried by the control body without being transmitted through the lock sleeve means to set the apparatus. A tubular member securable to the running string is telescopically manipulatable within the body of the apparatus to provide a conventional slick joint upon selective release from the body of the apparatus. Effective pressure area means are provided for transmitting to the packer means a compressive force resulting from a differential pressure from above or below across the packing means when the slip means are in expanded position and the packing means are sealed relative to the casing whereby the packing means are constantly energized and maintained in sealed relation with the casing.

  6. Thermally Insulating, Kinematic Tensioned-Fiber Suspension

    NASA Technical Reports Server (NTRS)

    Voellmer, George M.

    2004-01-01

    A salt pill and some parts of a thermally insulating, kinematic suspension system that holds the salt pill rigidly in an adiabatic-demagnetization refrigerator (ADR) is presented. "Salt pill" in this context denotes a unit comprising a cylindrical container, a matrix of gold wires in the container, and a cylinder of ferric ammonium alum (a paramagnetic salt) that has been deposited on the wires. The structural members used in this system for both thermal insulation and positioning are aromatic polyamide fibers (Kevlar(R) or equivalent) under tension. This suspension system is designed to satisfy several special requirements to ensure the proper operation of the ADR. These requirements are to (1) maintain the salt pill at a specified position within the cylindrical bore of an electromagnet; (2) prevent vibrations, which would cause dissipation of heat in the salt pill; and (3) minimize the conduction of heat from the electromagnet bore and other neighboring objects to the salt pill; all while (4) protecting the salt pill (which is fragile) against all tensile and bending loads other than those attributable to its own weight. In addition, the system is required to consist of two subsystems -- one for the top end and one for the bottom end of the salt pill -- that can be assembled and tensioned separately from each other and from the salt pill, then later attached to the salt pill.

  7. Maximal Oxygen Intake and Maximal Work Performance of Active College Women.

    ERIC Educational Resources Information Center

    Higgs, Susanne L.

    Maximal oxygen intake and associated physiological variables were measured during strenuous exercise on women subjects (N=20 physical education majors). Following assessment of maximal oxygen intake, all subjects underwent a performance test at the work level which had elicited their maximal oxygen intake. Mean maximal oxygen intake was 41.32…

  8. Reproduction, physiology and biochemistry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This chapter summarizes fundamental knowledge and recent discoveries about the reproduction, physiology and biochemistry of plant-parasitic nematodes. Various types of reproduction are reviewed, including sexual reproduction and mitotic and meiotic parthenogenesis. Although much is known about the p...

  9. The Physiologically Difficult Airway.

    PubMed

    Mosier, Jarrod M; Joshi, Raj; Hypes, Cameron; Pacheco, Garrett; Valenzuela, Terence; Sakles, John C

    2015-12-01

    Airway management in critically ill patients involves the identification and management of the potentially difficult airway in order to avoid untoward complications. This focus on difficult airway management has traditionally referred to identifying anatomic characteristics of the patient that make either visualizing the glottic opening or placement of the tracheal tube through the vocal cords difficult. This paper will describe the physiologically difficult airway, in which physiologic derangements of the patient increase the risk of cardiovascular collapse from airway management. The four physiologically difficult airways described include hypoxemia, hypotension, severe metabolic acidosis, and right ventricular failure. The emergency physician should account for these physiologic derangements with airway management in critically ill patients regardless of the predicted anatomic difficulty of the intubation. PMID:26759664

  10. Endogenous Pyrogen Physiology.

    ERIC Educational Resources Information Center

    Beisel, William R.

    1980-01-01

    Discusses the physiology of endogenous pyrogen (EP), the fever-producing factor of cellular origin. Included are: its hormone-like role, its molecular nature, bioassay procedures, cellular production and mechanisms of EP action. (SA)

  11. The Physiologically Difficult Airway

    PubMed Central

    Mosier, Jarrod M.; Joshi, Raj; Hypes, Cameron; Pacheco, Garrett; Valenzuela, Terence; Sakles, John C.

    2015-01-01

    Airway management in critically ill patients involves the identification and management of the potentially difficult airway in order to avoid untoward complications. This focus on difficult airway management has traditionally referred to identifying anatomic characteristics of the patient that make either visualizing the glottic opening or placement of the tracheal tube through the vocal cords difficult. This paper will describe the physiologically difficult airway, in which physiologic derangements of the patient increase the risk of cardiovascular collapse from airway management. The four physiologically difficult airways described include hypoxemia, hypotension, severe metabolic acidosis, and right ventricular failure. The emergency physician should account for these physiologic derangements with airway management in critically ill patients regardless of the predicted anatomic difficulty of the intubation. PMID:26759664

  12. Barometric calibration of a luminescent oxygen probe.

    PubMed

    Golub, Aleksander S; Pittman, Roland N

    2016-04-01

    The invention of the phosphorescence quenching method for the measurement of oxygen concentration in blood and tissue revolutionized physiological studies of oxygen transport in living organisms. Since the pioneering publication by Vanderkooi and Wilson in 1987, many researchers have contributed to the measurement of oxygen in the microcirculation, to oxygen imaging in tissues and microvessels, and to the development of new extracellular and intracellular phosphorescent probes. However, there is a problem of congruency in data from different laboratories, because of interlaboratory variability of the calibration coefficients in the Stern-Volmer equation. Published calibrations for a common oxygen probe, Pd-porphyrin + bovine serum albumin (BSA), vary because of differences in the techniques used. These methods are used for the formation of oxygen standards: chemical titration, calibrated gas mixtures, and an oxygen electrode. Each method in turn also needs calibration. We have designed a barometric method for the calibration of oxygen probes by using a regulated vacuum to set multiple PO2 standards. The method is fast and accurate and can be applied to biological fluids obtained during or after an experiment. Calibration over the full physiological PO2 range (1-120 mmHg) takes ∼15 min and requires 1-2 mg of probe. PMID:26846556

  13. Macrophages Under Low Oxygen Culture Conditions Respond to Ion Parametric Resonance Magnetic Fields

    EPA Science Inventory

    Macrophages, when entering inflamed tissue, encounter low oxygen tension due to the impairment of blood supply and/or the massive infiltration of cells that consume oxygen. Previously, we showed that such macrophages release more bacteriotoxic hydrogen peroxide (H202) when expose...

  14. Macrophages Under Low Oxygen Culture ConditionsRespond to Ion Parametric Resonance Magnetic Fields

    EPA Science Inventory

    Macrophages, when entering inflamed tissue, encounter low oxygen tension due to the impairment of blood supply and/or the massive infiltration of cells that consume oxygen. Previously, we showed that such macrophages release more bacteriotoxic hydrogen peroxide (H202) when expose...

  15. A product of its environment: the epaulette shark (Hemiscyllium ocellatum) exhibits physiological tolerance to elevated environmental CO2

    PubMed Central

    Heinrich, Dennis D. U.; Rummer, Jodie L.; Morash, Andrea J.; Watson, Sue-Ann; Simpfendorfer, Colin A.; Heupel, Michelle R.; Munday, Philip L.

    2014-01-01

    Ocean acidification, resulting from increasing anthropogenic CO2 emissions, is predicted to affect the physiological performance of many marine species. Recent studies have shown substantial reductions in aerobic performance in some teleost fish species, but no change or even enhanced performance in others. Notably lacking, however, are studies on the effects of near-future CO2 conditions on larger meso and apex predators, such as elasmobranchs. The epaulette shark (Hemiscyllium ocellatum) lives on shallow coral reef flats and in lagoons, where it may frequently encounter short-term periods of environmental hypoxia and elevated CO2, especially during nocturnal low tides. Indeed, H. ocellatum is remarkably tolerant to short periods (hours) of hypoxia, and possibly hypercapnia, but nothing is known about its response to prolonged exposure. We exposed H. ocellatum individuals to control (390 µatm) or one of two near-future CO2 treatments (600 or 880 µatm) for a minimum of 60 days and then measured key aspects of their respiratory physiology, namely the resting oxygen consumption rate, which is used to estimate resting metabolic rate, and critical oxygen tension, a proxy for hypoxia sensitivity. Neither of these respiratory attributes was affected by the long-term exposure to elevated CO2. Furthermore, there was no change in citrate synthase activity, a cellular indicator of aerobic energy production. Plasma bicarbonate concentrations were significantly elevated in sharks exposed to 600 and 880 µatm CO2 treatments, indicating that acidosis was probably prevented by regulatory changes in acid–base relevant ions. Epaulette sharks may therefore possess adaptations that confer tolerance to CO2 levels projected to occur in the ocean by the end of this century. It remains uncertain whether other elasmobranchs, especially pelagic species that do not experience such diurnal fluctuations in their environment, will be equally tolerant. PMID:27293668

  16. Surface Tension of Super-Cooled Fe-O Liquid Alloys

    NASA Astrophysics Data System (ADS)

    Kim, Han Gyeol; Choe, Joongkil; Inoue, Takashi; Ozawa, Shumpei; Lee, Joonho

    2016-08-01

    The surface tension of liquid Fe-O alloys was measured at temperatures ranging from 1621 K to 2006 K (1348 °C to 1733 °C) under a He-Ar atmosphere by using the oscillating drop method with an electromagnetic levitation facility. The experimental results were compared with the calculated ones based on the ideal adsorption model and the two-step adsorption model. Since the calculation results based on the two-step adsorption model showed better agreements with the experimental data, it was concluded that there is interactions between the adsorbed oxygen on the surface of liquid iron.

  17. Surface Tension of Super-Cooled Fe-O Liquid Alloys

    NASA Astrophysics Data System (ADS)

    Kim, Han Gyeol; Choe, Joongkil; Inoue, Takashi; Ozawa, Shumpei; Lee, Joonho

    2016-06-01

    The surface tension of liquid Fe-O alloys was measured at temperatures ranging from 1621 K to 2006 K (1348 °C to 1733 °C) under a He-Ar atmosphere by using the oscillating drop method with an electromagnetic levitation facility. The experimental results were compared with the calculated ones based on the ideal adsorption model and the two-step adsorption model. Since the calculation results based on the two-step adsorption model showed better agreements with the experimental data, it was concluded that there is interactions between the adsorbed oxygen on the surface of liquid iron.

  18. Effect of initial tension on mechanics of adhered graphene blisters

    NASA Astrophysics Data System (ADS)

    Liao, Pinzhen; Xu, Pei

    2015-09-01

    The effect of initial tension on mechanics of adhered graphene blisters is investigated by extending Hencky's solution to cases with an initial tension. The system parameters including maximum blister deflection, pressure difference across the membrane, and critical delamination pressure under various initial tensions are modeled and calculated. The dependences of critical pressure on the radius and depth of etched microcavity are also demonstrated and compared with the previous work which does not consider the initial tension. The results show that the added adhesion energy between monolayer graphene membrane and SiO2 substrate can reach 0.0954 J/m2 with a reported maximum initial tension of 2.4 N/m taken into account, which accounts for 21.2 % of the measured average value 0.45 J/m2. Thus, the initial tension should be considered in further adhesion energy measurements of graphene/substrate interfaces.

  19. Surface tension of low-temperature aqueous solutions

    SciTech Connect

    Horibe, A.; Fukusako, S.; Yamada, M.

    1996-03-01

    Measurements of the surface tension have been carried out to determine the effects of both temperature and concentration on the surface tension of aqueous solutions of sodium chloride, propylene glycol, and ethylene glycol. A differential capillary-rise method was employed for the measurements. The results show that the surface tension of the ethylene glycol solution and the propylene glycol solution increases as the concentration of the solution decreases, while for the sodium chloride solution the surface tension increases monotonically as the concentration increases. The surface tension of the liquids was found to be an almost-linear function of temperature from 20{degrees}C to just above the freezing temperature. Equations for the surface tension of the three binary aqueous solutions as a function of temperature and concentration are presented.

  20. Surface Tension Mediated Under-Water Adhesion of Rigid Spheres on Soft, Charged Surfaces

    NASA Astrophysics Data System (ADS)

    Sinha, Shayandev; Das, Siddhartha

    2015-11-01

    Understanding the phenomenon of surface-tension-mediated under-water adhesion is necessary for studying a plethora of physiological and technical phenomena, such as the uptake of bacteria or nanoparticle by cells, attachment of virus on bacterial surfaces, biofouling on large ocean vessels and marine devices, etc. This adhesion phenomenon becomes highly non-trivial in case the soft surface where the adhesion occurs is also charged. Here we propose a theory for analyzing such an under-water adhesion of a rigid sphere on a soft, charged surface, represented by a grafted polyelectrolyte layer (PEL). We develop a model based on the minimization of free energy that, in addition to considering the elastic and the surface-tension-mediated adhesion energies, also accounts for the PEL electric double layer (EDL) induced electrostatic energies. We show that in the presence of surface charges, adhesion gets enhanced. This can be explained by the fact that the increase in the elastic energy is better balanced by the lowering of the EDL energy associated with the adhesion process. The entire behaviour is further dictated by the surface tension components that govern the adhesion energy.

  1. Oxygen Generating Biomaterials Preserve Skeletal Muscle Homeostasis under Hypoxic and Ischemic Conditions

    PubMed Central

    Ward, Catherine L.; Corona, Benjamin T.; Yoo, James J.; Harrison, Benjamin S.; Christ, George J.

    2013-01-01

    Provision of supplemental oxygen to maintain soft tissue viability acutely following trauma in which vascularization has been compromised would be beneficial for limb and tissue salvage. For this application, an oxygen generating biomaterial that may be injected directly into the soft tissue could provide an unprecedented treatment in the acute trauma setting. The purpose of the current investigation was to determine if sodium percarbonate (SPO), an oxygen generating biomaterial, is capable of maintaining resting skeletal muscle homeostasis under otherwise hypoxic conditions. In the current studies, a biologically and physiologically compatible range of SPO (1–2 mg/mL) was shown to: 1) improve the maintenance of contractility and attenuate the accumulation of HIF1α, depletion of intramuscular glycogen, and oxidative stress (lipid peroxidation) that occurred following ∼30 minutes of hypoxia in primarily resting (duty cycle = 0.2 s train/120 s contraction interval <0.002) rat extensor digitorum longus (EDL) muscles in vitro (95% N2–5% CO2, 37°C); 2) attenuate elevations of rat EDL muscle resting tension that occurred during contractile fatigue testing (3 bouts of 25 100 Hz tetanic contractions; duty cycle = 0.2 s/2 s = 0.1) under oxygenated conditions in vitro (95% O2–5% CO2, 37°C); and 3) improve the maintenance of contractility (in vivo) and prevent glycogen depletion in rat tibialis anterior (TA) muscle in a hindlimb ischemia model (i.e., ligation of the iliac artery). Additionally, injection of a commercially available lipid oxygen-carrying compound or the components (sodium bicarbonate and hydrogen peroxide) of 1 mg/mL SPO did not improve EDL muscle contractility under hypoxic conditions in vitro. Collectively, these findings demonstrate that a biological and physiological concentration of SPO (1–2 mg/mL) injected directly into rat skeletal muscle (EDL or TA muscles) can partially preserve resting skeletal muscle homeostasis under

  2. A Comparison of Exercise and Meditation in Reducing Physiological Response to Stress.

    ERIC Educational Resources Information Center

    Sime, Wesley E.

    The purpose of this investigation was to compare the effects of brief treadmill exercise and meditation with a placebo-control treatment for reduction in several physiological and psychological measures of stress, anxiety, and tension before and after a written final examination in 48 high-test anxiety subjects. The subjects, 24 men and 24 women,…

  3. [Physiological-hygienic aspects of the work of tractor drivers engaged in open-soil vegetable planting].

    PubMed

    Bochkareva, A I; Akhundova, L Kh; Kafizova, F K

    1990-01-01

    The labour conditions of tractor drivers engaged in open soil vegetable planting in subtropical zones were characterized by the unfavourable influence of weather, noise and vibration, dust and exhaust contamination, and by static tension. The physiological studies performed revealed considerable tensions of the CVS, CNS, thermoregulatory and muscle systems in the drivers. The specificity of the identified changes confirmed marked decrease in the functional resources of the organism, which should be taken into account when providing medical services to the drivers. PMID:2096090

  4. Critical oxygen levels and metabolic suppression in oceanic oxygen minimum zones.

    PubMed

    Seibel, Brad A

    2011-01-15

    The survival of oceanic organisms in oxygen minimum zones (OMZs) depends on their total oxygen demand and the capacities for oxygen extraction and transport, anaerobic ATP production and metabolic suppression. Anaerobic metabolism and metabolic suppression are required for daytime forays into the most extreme OMZs. Critical oxygen partial pressures are, within a range, evolved to match the minimum oxygen level to which a species is exposed. This fact demands that low oxygen habitats be defined by the biological response to low oxygen rather than by some arbitrary oxygen concentration. A broad comparative analysis of oxygen tolerance facilitates the identification of two oxygen thresholds that may prove useful for policy makers as OMZs expand due to climate change. Between these thresholds, specific physiological adaptations to low oxygen are required of virtually all species. The lower threshold represents a limit to evolved oxygen extraction capacity. Climate change that pushes oxygen concentrations below the lower threshold (~0.8 kPa) will certainly result in a transition from an ecosystem dominated by a diverse midwater fauna to one dominated by diel migrant biota that must return to surface waters at night. Animal physiology and, in particular, the response of animals to expanding hypoxia, is a critical, but understudied, component of biogeochemical cycles and oceanic ecology. Here, I discuss the definition of hypoxia and critical oxygen levels, review adaptations of animals to OMZs and discuss the capacity for, and prevalence of, metabolic suppression as a response to temporary residence in OMZs and the possible consequences of climate change on OMZ ecology. PMID:21177952

  5. Air breathing in the Arctic: influence of temperature, hypoxia, activity and restricted air access on respiratory physiology of the Alaska blackfish Dallia pectoralis

    PubMed Central

    Lefevre, Sjannie; Damsgaard, Christian; Pascale, Desirae R.; Nilsson, Göran E.; Stecyk, Jonathan A. W.

    2014-01-01

    The Alaska blackfish (Dallia pectoralis) is an air-breathing fish native to Alaska and the Bering Sea islands, where it inhabits lakes that are ice-covered in the winter, but enters warm and hypoxic waters in the summer to forage and reproduce. To understand the respiratory physiology of this species under these conditions and the selective pressures that maintain the ability to breathe air, we acclimated fish to 5°C and 15°C and used respirometry to measure: standard oxygen uptake () in normoxia (19.8 kPa PO2) and hypoxia (2.5 kPa), with and without access to air; partitioning of standard in normoxia and hypoxia; maximum and partitioning after exercise; and critical oxygen tension (Pcrit). Additionally, the effects of temperature acclimation on haematocrit, haemoglobin oxygen affinity and gill morphology were assessed. Standard was higher, but air breathing was not increased, at 15°C or after exercise at both temperatures. Fish acclimated to 5°C or 15°C increased air breathing to compensate and fully maintain standard in hypoxia. Fish were able to maintain through aquatic respiration when air was denied in normoxia, but when air was denied in hypoxia, standard was reduced by ∼30–50%. Pcrit was relatively high (5 kPa) and there were no differences in Pcrit, gill morphology, haematocrit or haemoglobin oxygen affinity at the two temperatures. Therefore, Alaska blackfish depends on air breathing in hypoxia and additional mechanisms must thus be utilised to survive hypoxic submergence during the winter, such as hypoxia-induced enhancement in the capacities for carrying and binding blood oxygen, behavioural avoidance of hypoxia and suppression of metabolic rate. PMID:25394628

  6. Tensioning of a belt around a drum using membrane element

    NASA Technical Reports Server (NTRS)

    Chen, C. H. S.

    1980-01-01

    An application of the membrane element to the problem of the tensioning of a conveyer belt which wraps around a drum is presented. Two cases were investigated: (1) belt tension increase due to drum edge wear; and (2) material trapped between the drum and the belt. In both cases it was found that the increase in belt tension was due to the additional stretching of the belt resulting from the drum radius change rather than from the transverse deflection of the belt.

  7. Automatic Tension Adjuster For Flexible-Shaft Grinder

    NASA Technical Reports Server (NTRS)

    Burley, Richard K.; Hoult, William S.

    1990-01-01

    Flexible shaft of grinding tool automatically maintained in tension by air pressure. Probelike tool bent to reach hard-to-reach areas for grinding and polishing. Unless shaft held in tension, however, it rubs against its sheath, overheating and wearing out quickly. By taking up slack in flexible cable, tension adjuster reduces friction and enables tool to operate more efficiently, in addition to lengthening operating life.

  8. Cosmological evolution of cosmic strings with time-dependent tension

    SciTech Connect

    Yamaguchi, Masahide

    2005-08-15

    We discuss the cosmological evolution of cosmic strings with time-dependent tension. We show that, in the case that the tension changes as a power of time, the cosmic string network obeys the scaling solution: the characteristic scale of the string network grows with the time. But due to the time dependence of the tension, the ratio of the energy density of infinite strings to that of the background universe is not necessarily constant.

  9. Tension fatigue analysis and life prediction for composite laminates

    NASA Technical Reports Server (NTRS)

    O'Brien, T. K.; Rigamonti, M.; Zanotti, C.

    1989-01-01

    A methodology is presented for the tension fatigue analysis and life prediction of composite laminates subjected to tension fatigue loading. The methodology incorporates both the generic fracture mechanics characterization of delamination and the assessment of the infuence of damage on laminate fatigue life. Tension fatigue tests were conducted on quasi-isotropic and orthotropic glass epoxy, graphite epoxy, and glass/graphite epoxy hybrid laminates, demonstrating good agreement between measured and predicted lives.

  10. The free boundary Euler equations with large surface tension

    NASA Astrophysics Data System (ADS)

    Disconzi, Marcelo M.; Ebin, David G.

    2016-07-01

    We study the free boundary Euler equations with surface tension in three spatial dimensions, showing that the equations are well-posed if the coefficient of surface tension is positive. Then we prove that under natural assumptions, the solutions of the free boundary motion converge to solutions of the Euler equations in a domain with fixed boundary when the coefficient of surface tension tends to infinity.

  11. Space Station Freedom Solar Array tension mechanism development

    NASA Technical Reports Server (NTRS)

    Allmon, Curtis; Haugen, Bert

    1994-01-01

    A tension mechanism is used to apply a tension force to the Space Station Freedom Solar Array Blanket. This tension is necessary to meet the deployed frequency requirement of the array as well as maintain the flatness of the flexible substrate solar cell blanket. The mechanism underwent a series of design iterations before arriving at the final design. This paper discusses the design and testing of the mechanism.

  12. Extracorporeal Membrane Oxygenation Circuitry

    PubMed Central

    Horton, Stephen B.; McMullan, D. Michael; Bartlett, Robert H

    2013-01-01

    The extracorporeal membrane oxygenation (ECMO) circuit is made of a number of components that have been customized to provide adequate tissue oxygen delivery in patients with severe cardiac and/or respiratory failure for a prolonged period of time (days to weeks). A standard ECMO circuit consists of a mechanical blood pump, gas exchange device, and a heat exchanger all connected together with circuit tubing. ECMO circuits can vary from simple to complex and may include a variety of blood flow and pressure monitors, continuous oxyhemoglobin saturation monitors, circuit access sites and a bridge connecting the venous access and arterial infusion limbs of the circuit. Significant technical advancements have been made in the equipment available for short and long term ECMO applications. Contemporary ECMO circuits have greater biocompatibility and allow for more prolonged cardiopulmonary support time, while minimizing the procedure-related complications of bleeding, thrombosis and other physiologic derangements that were so common with the early application of ECMO. Modern era ECMO circuitry and components are simpler, safer, more compact and can be used across a wide variety of patient sizes from neonates to adults. PMID:23735989

  13. Dynamic film and interfacial tensions in emulsion and foam systems

    SciTech Connect

    Kim, Y.H.; Koczo, K.; Wasan, D.T.

    1997-03-01

    In concentrated fluid dispersions the liquid films are under dynamic conditions during film rupture or drainage. Aqueous foam films stabilized with sodium decylsulfonate and aqueous emulsion films stabilized with the nonionic Brij 58 surfactant were formed at the tip of a capillary and the film tension was measured under static and dynamic conditions. In the stress relaxation experiments the response of the film tension to a sudden film area expansion was studied. These experiments also allowed the direct measurement of the Gibbs film elasticity. In the dynamic film tension experiments, the film area was continuously increased by a constant rate and the dynamic film tension was monitored. The measured film tensions were compared with the interfacial tensions of the respective single air/water and oil/water interfaces, which were measured using the same radius of curvature, relative expansion, and expansion rate as in the film studies. It was found that under dynamic conditions the film tension is higher than twice the single interfacial tension (IFT) and a mechanism was suggested to explain the difference. When the film, initially at equilibrium, is expanded and the interfacial area increases, a substantial surfactant depletion occurs inside the film. As a result, the surfactant can be supplied only from the adjoining meniscus (Plateau border) by surface diffusion, and the film tension is controlled by the diffusion and adsorption of surfactant in the meniscus. The results have important implications for the stability and rheology of foams and emulsions with high dispersed phase ratios (polyhedral structure).

  14. A growing-drop technique for measuring dynamic interfacial tension

    SciTech Connect

    MacLeod, C.A.; Radke, C.J.

    1993-10-01

    A novel, growing-drop technique is described for measuring dynamic interfacial tension due to sorption of surface-active solutes. The proposed method relates the instantaneous pressure and size of expanding liquid drops to interfacial tension and is useful for measuring both liquid/gas and liquid/liquid tensions over a wide range of time scales, currently from 10 ms to several hours. Growing-drop measurements on surfactant-free water/air and water/octanol interfaces yield constant tensions equal to their known literature values. For surfactant-laden, liquid drops, the growing-drop technique captures the actual transient tension evolution of a single interface, rather than interval times as with the classic maximum-drop-pressure and drop.-volume tension measurements. Dynamic tensions measured for 0.25 mM aqueous 1-decanol solution/air and 0.02 kg/m{sup 3} aqueous Triton X-100 solution/dodecane interfaces show nonmonotonic behavior, indicating slow surfactant transport relative to the imposed rates of interfacial dilatation. The dynamic tension of a purified and fresh 6 mM aqueous sodium dodecyl sulfate (SDS) solution/air interface shows only a monotonic decrease, indicating rapid surfactant transport relative to the imposed rates of dilatation. ConverselY, an aged SDS solution, naturally containing trace dodecanol impurities, exhibits dynamic tensions which reflect a superposition of the rapidly equilibrating SDS and the slowly adsorbing dodecanol.

  15. Investigation of Dynamic Oxygen Adsorption in Molten Solder Jetting Technology

    NASA Technical Reports Server (NTRS)

    Megaridis, Constantine M.; Bellizia, Giulio; McNallan, Michael; Wallace, David B.

    2003-01-01

    Surface tension forces play a critical role in fluid dynamic phenomena that are important in materials processing. The surface tension of liquid metals has been shown to be very susceptible to small amounts of adsorbed oxygen. Consequently, the kinetics of oxygen adsorption can influence the capillary breakup of liquid-metal jets targeted for use in electronics assembly applications, where low-melting-point metals (such as tin-containing solders) are utilized as an attachment material for mounting of electronic components to substrates. By interpreting values of surface tension measured at various surface ages, adsorption and diffusion rates of oxygen on the surface of the melt can be estimated. This research program investigates the adsorption kinetics of oxygen on the surface of an atomizing molten-metal jet. A novel oscillating capillary jet method has been developed for the measurement of dynamic surface tension of liquids, and in particular, metal melts which are susceptible to rapid surface degradation caused by oxygen adsorption. The experimental technique captures the evolution of jet swells and necks continuously along the jet propagation axis and is used in conjunction with an existing linear, axisymmetric, constant-property model to determine the variation of the instability growth rate, and, in turn, surface tension of the liquid as a function of surface age measured from the exit orifice. The conditions investigated so far focus on a time window of 2-4ms from the jet orifice. The surface properties of the eutectic 63%Sn-37%Pb solder alloy have been investigated in terms of their variation due to O2 adsorption from a N2 atmosphere containing controlled amounts of oxygen (from 8 ppm to 1000 ppm). The method performed well for situations where the oxygen adsorption was low in that time window. The value of surface tension for the 63Sn-37Pb solder in pure nitrogen was found to be 0.49 N/m, in good agreement with previously published work. A characteristic

  16. Neuropeptide physiology in helminths.

    PubMed

    Mousley, Angela; Novozhilova, Ekaterina; Kimber, Michael J; Day, Tim A

    2010-01-01

    Parasitic worms come from two distinct, distant phyla, Nematoda (roundworms) and Platyhelminthes (flatworms). The nervous systems of worms from both phyla are replete with neuropeptides and there is ample physiological evidence that these neuropeptides control vital aspects of worm biology. In each phyla, the physiological evidence for critical roles for helminth neuropeptides is derived from both parasitic and free-living members. In the nematodes, the intestinal parasite Ascaris suum and the free-living Caenorhabditis elegans have yielded most of the data; in the platyhelminths, the most physiological data has come from the blood fluke Schistosoma mansoni. FMRFamide-like peptides (FLPs) have many varied effects (excitation, relaxation, or a combination) on somatic musculature, reproductive musculature, the pharynx and motor neurons in nematodes. Insulin-like peptides (INSs) play an essential role in nematode dauer formation and other developmental processes. There is also some evidence for a role in somatic muscle control for the somewhat heterogeneous grouping ofpeptides known as neuropeptide-like proteins (NLPs). In platyhelminths, as in nematodes, FLPs have a central role in somatic muscle function. Reports of FLP physiological action in platyhelminths are limited to a potent excitation of the somatic musculature. Platyhelminths are also abundantly endowed with neuropeptide Fs (NPFs), which appear absent from nematodes. There is not yet any data linking platyhelminth NPF to any particular physiological outcome, but this neuropeptide does potently and specifically inhibit cAMP accumulation in schistosomes. In nematodes and platyhelminths, there is an abundance of physiological evidence demonstrating that neuropeptides play critical roles in the biology of both free-living and parasitic helminths. While it is certainly true that there remains a great deal to learn about the biology of neuropeptides in both phyla, physiological evidence presently available points

  17. On the Surface Tension of Nanobubbles

    NASA Astrophysics Data System (ADS)

    Bau, Haim; Grogan, Joseph; Norton, Michael; Ross, Frances

    2013-11-01

    Using our custom-made liquid cell, the nanoaquarium, we imaged with a transmission electron microscope the formation, growth, and detachment of single nanobubbles, nucleating in a supersaturated aqueous solution. The supersaturation results from electron-induced radiolysis of water. The bubbles are first observed when their radii are about 20 nm and detach when their radii are about 200 nm. Based on our experimental data, we determined the bubbles' growth rates as functions of time, and found the growth rates to be highly reproducible and nearly independent of time (and bubbles' radii). Comparison of the theoretical predictions for bubble growth rate with our experimental observations suggests that the surface tension of the bubble-liquid interface must depend on the bubble's radius. The work was supported, in part, by NSF grants 1066573 and 1129722.

  18. Concrete hulls for tension-leg platforms

    SciTech Connect

    De Oliveira, J.G. ); Fjeld, S. )

    1990-06-01

    This paper describes the main features of a concrete-hull tension-leg-platform (TLP) concept developed for the Heidrun field in the Haltenbanken area of the Norwegian sector of the North Sea. The hydrodynamic response and the methods adopted to optimize the hull dimensions, as well as the mooring system and hull mechanical outfitting, are discussed first. Then construction methods are briefly described. Inspection, maintenance, and repair are also addressed. Finally, the advantages of the concrete-hull TLP concept are summarized, including the concrete hull's adaptability to a large range of design requirements, low cost, and short construction time. This paper shows that the concrete-hull TLP is a very cost-efficient solution for the development of deepwater fields.

  19. Modeling polymer gel that strengthen under tension

    NASA Astrophysics Data System (ADS)

    Biswas, Santidan; Yashin, Victor V.; Balazs, Anna C.

    We develop a constitutive model of a responsive polymer gel, which can reversibly form additional crosslinks when under tension. We assume that the polymer chains incorporate the folded domains encompassing the reactive functional groups (cryptic sites). Under extension of the network, the domains unfold and expose the cryptic sites, which can then form labile bonds with the linker chains grafted to the network. Once the deformation is removed, the linkers detach from the cryptic sites, and unfolded domains go back to the folded configuration thus hiding the cryptic sites. The gel behavior under applied force is described by the equations of elasticity of the polymer network coupled to the kinetic equations for the folding and binding transitions. The developed model could be used for designing new polymer gel-based materials that exhibit self-strengthening in response to a mechanical action.

  20. Tension pneumothorax due to perforated colon.

    PubMed

    Abdullah, Muhammad; Stonelake, Paul

    2016-01-01

    A very rare case of traumatic diaphragmatic hernia is reported in a 65-year-old woman who presented 46 years after her initial thoracoabdominal injury with tension faecopneumothorax caused by a perforated colon in the chest cavity. She presented in a critical condition with severe respiratory distress, sepsis and acute kidney injury. She had a long-standing history of bronchial asthma with respiratory complications and had experienced progressive shortness of breath for the past year. A recent CT scan had excluded the presence of a diaphragmatic hernia but showed a significantly raised left hemidiaphragm. On admission, chest X-rays showed a significantly raised left hemidiaphragm and mediastinal shift, but the possibility of a diaphragmatic hernia with strangulated bowel in the chest was not suspected until the patient was reviewed by the surgical and intensive care unit consultants the next morning and a repeat CT performed. She had a successful outcome after her emergency operation. PMID:27247208

  1. Tension-induced mechanical properties of stanene

    NASA Astrophysics Data System (ADS)

    Tao, Lele; Yang, Chuanghua; Wu, Liyuan; Han, Lihong; Song, Yuxin; Wang, Shumin; Lu, Pengfei

    2016-05-01

    In this paper, elastic properties of stanene under equiaxial or uniaxial tensions along armchair and zigzag directions are investigated by first-principles calculations. The stress-strain relation is calculated and the relaxation of the internal atom positions is analyzed. The high-order elastic constants are calculated by fitting the polynomial expressions. The Young’s modulus and Poisson ratio of the stanene is calculated to be 24.14 N/m and 0.39 N/m, respectively. The stanene exhibits lower Young’s modulus than those of the proceeding group IV elements, which is attributed to the smaller sp2-sp3 bond energy in stanene than those of silicene and germanene. Calculated values of ultimate stresses and strains, second-order elastic constants (SOCEs) and the in-plane Young’s modulus are all positive. It proves that stanene is mechanically stable.

  2. A mistaken case of tension pneumothorax

    PubMed Central

    Newman, Michael Joseph

    2014-01-01

    The patient was an otherwise usually fit and well 25-year-old man who presented to A&E department in extremis. The initial working diagnosis was a tension pneumothorax, and he was subsequently treated with needle thoracocentesis causing a release of air. A chest radiograph was taken, after which a chest drain was inserted. Bilious fluid was drained from the chest drain. The patient was taken for an emergency CT, which demonstrated a Bochdalek diaphragmatic hernia, with the spleen and bowel found to be causing a near total left lung collapse. He was taken to the theatre to return the bowel to the correct anatomical position, in addition to undergoing a sleeve gastrectomy, and diaphragmatic defect repair. The patient has had a complex and protracted recovery in the intensive therapy unit (ITU) with complications including wound dehiscence, gastrectomy leak requiring additional surgical repair, fluid overload and bilateral pleural empyema. PMID:24835806

  3. Surface tension effects on submerged electrosprays

    PubMed Central

    Marín, Álvaro G.; Loscertales, Ignacio G.; Barrero, Antonio

    2012-01-01

    Electrosprays are a powerful technique to generate charged micro/nanodroplets. In the last century, the technique has been extensively studied, developed, and recognized with a shared Nobel price in Chemistry in 2002 for its wide spread application in mass spectrometry. However, nowadays techniques based on microfluidic devices are competing to be the next generation in atomization techniques. Therefore, an interesting development would be to integrate the electrospray technique into a microfluidic liquid-liquid device. Several works in the literature have attempted to build a microfluidic electrospray with disputable results. The main problem for its integration is the lack of knowledge of the working parameters of the liquid-liquid electrospray. The “submerged electrosprays” share similar properties as their counterparts in air. However, in the microfluidic generation of micro/nanodroplets, the liquid-liquid interfaces are normally stabilized with surface active agents, which might have critical effects on the electrospray behavior. In this work, we review the main properties of the submerged electrosprays in liquid baths with no surfactant, and we methodically study the behavior of the system for increasing surfactant concentrations. The different regimes found are then analyzed and compared with both classical and more recent experimental, theoretical and numerical studies. A very rich phenomenology is found when the surface tension is allowed to vary in the system. More concretely, the lower states of electrification achieved with the reduced surface tension regimes might be of interest in biological or biomedical applications in which excessive electrification can be hazardous for the encapsulated entities. PMID:24155865

  4. Auger tension leg platform cathodic protection system

    SciTech Connect

    Goolsby, A.D.; Smith, J.D.

    1995-11-01

    In 1986, Shell began investigating corrosion control systems for a generic 3,000 ft. water depth Tension Leg Platform (TLP) type structure to be located in the north-central Gulf of Mexico. In 1987, the 2,850 ft. deep Garden Banks block 426 ``Auger`` location was chosen for the first TLP, and the detailed design process began in earnest. During late 1993 and early 1994, the Auger hull was mated with the other components at its permanent site, and first oil and gas production began April 15, 1994. This paper describes the corrosion control design for the exterior submerged and buried steel surfaces of the 2,850 ft. (869 m) water depth Auger Tension Leg Platform structure. Each major type of component (hull, subsea marine wellhead/guidebase, tendon foundation template, tendon, and production riser) has its own combination of coating system and cathodic protection system designed for a thirty five year lifetime. Cathodic protection (CP) is achieved using a variety of sacrificial anode alloys and geometries (e.g. bracelet, flush-mount, and standoff anodes). Anode and cathode CP design parameters for each component depend upon water depth, and were developed using field test data, laboratory studies, field measurements on existing structures, and available literature information. CP design was performed using design spreadsheets constructed for each component, which optimized anode geometries. Extensive quality assurance efforts were part of the anode procurement process, to ensure performance for the intended life of the corrosion-control systems. Results of early in-service CP surveys of the tendons and guidebases are presented, showing the successful achievement of cathodic protection against seawater corrosion. Corrosion control of one additional system, the eight point lateral mooring system, is not addressed here.

  5. Mitochondrial stress controls the radiosensitivity of the oxygen effect: Implications for radiotherapy

    PubMed Central

    Richardson, Richard B.; Harper, Mary-Ellen

    2016-01-01

    It has been more than 60 years since the discovery of the oxygen effect that empirically demonstrates the direct association between cell radiosensitivity and oxygen tension, important parameters in radiotherapy. Yet the mechanisms underlying this principal tenet of radiobiology are poorly understood. Better understanding of the oxygen effect may explain difficulty in eliminating hypoxic tumor cells, a major cause of regrowth after therapy. Our analysis utilizes the Howard-Flanders and Alper formula, which describes the relationship of radiosensitivity with oxygen tension. Here, we assign and qualitatively assess the relative contributions of two important mechanisms. The first mechanism involves the emission of reactive oxygen species from the mitochondrial electron transport chain, which increases with oxygen tension. The second mechanism is related to an energy and repair deficit, which increases with hypoxia. Following a radiation exposure, the uncoupling of the oxidative phosphorylation system (proton leak) in mitochondria lowers the emission of reactive oxygen species which has implications for fractionated radiotherapy, particularly of hypoxic tumors. Our analysis shows that, in oxygenated tumor and normal cells, mitochondria, rather than the nucleus, are the primary loci of radiotherapy effects, especially for low linear energy transfer radiation. Therefore, the oxygen effect can be explained by radiation-induced effects in mitochondria that generate reactive oxygen species, which in turn indirectly target nuclear DNA. PMID:26894978

  6. Assessing physiological complexity.

    PubMed

    Burggren, W W; Monticino, M G

    2005-09-01

    Physiologists both admire and fear complexity, but we have made relatively few attempts to understand it. Inherently complex systems are more difficult to study and less predictable. However, a deeper understanding of physiological systems can be achieved by modifying experimental design and analysis to account for complexity. We begin this essay with a tour of some mathematical views of complexity. After briefly exploring chaotic systems, information theory and emergent behavior, we reluctantly conclude that, while a mathematical view of complexity provides useful perspectives and some narrowly focused tools, there are too few generally practical take-home messages for physiologists studying complex systems. Consequently, we attempt to provide guidelines as to how complex systems might be best approached by physiologists. After describing complexity based on the sum of a physiological system's structures and processes, we highlight increasingly refined approaches based on the pattern of interactions between structures and processes. We then provide a series of examples illustrating how appreciating physiological complexity can improve physiological research, including choosing experimental models, guiding data collection, improving data interpretations and constructing more rigorous system models. Finally, we conclude with an invitation for physiologists, applied mathematicians and physicists to collaborate on describing, studying and learning from studies of physiological complexity. PMID:16109885

  7. Development of Warp Yarn Tension During Shedding: A Theoretical Approach

    NASA Astrophysics Data System (ADS)

    Ghosh, Subrata; Chary, Prabhakara; Roy, Sukumar

    2015-10-01

    Theoretical investigation on the process of development of warp yarn tension during weaving for tappet shedding is carried out, based on the dynamic nature of shed geometry. The path of warp yarn on a weaving machine is divided into four different zones. The tension developed in each zone is estimated for every minute rotation of the bottom shaft. A model has been developed based on the dynamic nature of shed geometry and the possible yarn flow from one zone to another. A computer program, based on the model of shedding process, is developed for predicting the warp yarn tension variation during shedding. The output of the model and the experimental values of yarn tension developed in zone-D i.e. between the back rest and the back lease rod are compared, which shows a good agreement between them. The warp yarn tension values predicted by the model in zone-D are 10-13 % lesser than the experimentally measured values. By analyzing the theoretical data of the peak value of developed yarn tension at four zones i.e. zone-A, zone-B, zone-C and zone-D, it is observed that the peak yarn tension value of A, B, C-zones are much higher than the peak tension near the back rest i.e. at zone-D. It is about twice or more than the yarn tension near the back rest. The study also reveals that the developed yarn tension peak values are different for the extreme positions of a heald. The impact of coefficient of friction on peak value of yarn tension is nominal.

  8. Membrane tension regulates clathrin-coated pit dynamics

    NASA Astrophysics Data System (ADS)

    Liu, Allen

    2014-03-01

    Intracellular organization depends on close communication between the extracellular environment and a network of cytoskeleton filaments. The interactions between cytoskeletal filaments and the plasma membrane lead to changes in membrane tension that in turns help regulate biological processes. Endocytosis is thought to be stimulated by low membrane tension and the removal of membrane increases membrane tension. While it is appreciated that the opposing effects of exocytosis and endocytosis have on keeping plasma membrane tension to a set point, it is not clear how membrane tension affects the dynamics of clathrin-coated pits (CCPs), the individual functional units of clathrin-mediated endocytosis. Furthermore, although it was recently shown that actin dynamics counteracts membrane tension during CCP formation, it is not clear what roles plasma membrane tension plays during CCP initiation. Based on the notion that plasma membrane tension is increased when the membrane area increases during cell spreading, we designed micro-patterned surfaces of different sizes to control the cell spreading sizes. Total internal reflection fluorescence microscopy of living cells and high content image analysis were used to quantify the dynamics of CCPs. We found that there is an increased proportion of CCPs with short (<20s) lifetime for cells on larger patterns. Interestingly, cells on larger patterns have higher CCP initiation density, an effect unexpected based on the conventional view of decreasing endocytosis with increasing membrane tension. Furthermore, by analyzing the intensity profiles of CCPs that were longer-lived, we found CCP intensity decreases with increasing cell size, indicating that the CCPs are smaller with increasing membrane tension. Finally, disruption of actin dynamics significantly increased the number of short-lived CCPs, but also decreased CCP initiation rate. Together, our study reveals new mechanistic insights into how plasma membrane tension regulates

  9. Human physiology in space

    NASA Technical Reports Server (NTRS)

    Vernikos, J.

    1996-01-01

    The universality of gravity (1 g) in our daily lives makes it difficult to appreciate its importance in morphology and physiology. Bone and muscle support systems were created, cellular pumps developed, neurons organised and receptors and transducers of gravitational force to biologically relevant signals evolved under 1g gravity. Spaceflight provides the only microgravity environment where systematic experimentation can expand our basic understanding of gravitational physiology and perhaps provide new insights into normal physiology and disease processes. These include the surprising extent of our body's dependence on perceptual information, and understanding the effect and importance of forces generated within the body's weightbearing structures such as muscle and bones. Beyond this exciting prospect is the importance of this work towards opening the solar system for human exploration. Although both appear promising, we are only just beginning to taste what lies ahead.

  10. Hydrodynamics, Fungal Physiology, and Morphology.

    PubMed

    Serrano-Carreón, L; Galindo, E; Rocha-Valadéz, J A; Holguín-Salas, A; Corkidi, G

    2015-01-01

    Filamentous cultures, such as fungi and actinomycetes, contribute substantially to the pharmaceutical industry and to enzyme production, with an annual market of about 6 billion dollars. In mechanically stirred reactors, most frequently used in fermentation industry, microbial growth and metabolite productivity depend on complex interactions between hydrodynamics, oxygen transfer, and mycelial morphology. The dissipation of energy through mechanically stirring devices, either flasks or tanks, impacts both microbial growth through shearing forces on the cells and the transfer of mass and energy, improving the contact between phases (i.e., air bubbles and microorganisms) but also causing damage to the cells at high energy dissipation rates. Mechanical-induced signaling in the cells triggers the molecular responses to shear stress; however, the complete mechanism is not known. Volumetric power input and, more importantly, the energy dissipation/circulation function are the main parameters determining mycelial size, a phenomenon that can be explained by the interaction of mycelial aggregates and Kolmogorov eddies. The use of microparticles in fungal cultures is also a strategy to increase process productivity and reproducibility by controlling fungal morphology. In order to rigorously study the effects of hydrodynamics on the physiology of fungal microorganisms, it is necessary to rule out the possible associated effects of dissolved oxygen, something which has been reported scarcely. At the other hand, the processes of phase dispersion (including the suspended solid that is the filamentous biomass) are crucial in order to get an integral knowledge about biological and physicochemical interactions within the bioreactor. Digital image analysis is a powerful tool for getting relevant information in order to establish the mechanisms of mass transfer as well as to evaluate the viability of the mycelia. This review focuses on (a) the main characteristics of the two most

  11. Single-ventricle physiology.

    PubMed

    Schwartz, Steven M; Dent, Catherine L; Musa, Ndidi L; Nelson, David P

    2003-07-01

    The patient with single-ventricle physiology presents a significant challenge to the intensive care team at all stages of management. An integrated approach that applies a working knowledge of cardiac anatomy, cardiopulmonary physiology, and the basic principles of intensive care is essential to guide management for each individual patient. This management requires cooperative and constructive involvement of surgeons, cardiologists, and intensivists, as well as a nursing and respiratory care team experienced in the management of single-ventricle patients. The outcome of each stage of palliation for single-ventricle lesions should continue to improve as new ideas are developed and as older ideas are subjected to rigorous scientific analyses. PMID:12848312

  12. Specifications Physiological Monitoring System

    NASA Technical Reports Server (NTRS)

    1985-01-01

    The operation of a physiological monitoring system (PMS) is described. Specifications were established for performance, design, interface, and test requirements. The PMS is a compact, microprocessor-based system, which can be worn in a pack on the body or may be mounted on a Spacelab rack or other appropriate structure. It consists of two modules, the Data Control Unit (DCU) and the Remote Control/Display Unit (RCDU). Its purpose is to collect and distribute data from physiological experiments in the Spacelab and in the Orbiter.

  13. Tension-compression-tension tertiary twins in coarse-grained polycrystalline pure magnesium at room temperature

    SciTech Connect

    Yu, Qin; Jiang, Yanyao; Wang, Jian

    2015-04-07

    Using electron backscatter diffraction, the microstructural features of tension–compression–tension (T–C–T) tertiary twins are studied in coarse-grained pure polycrystalline magnesium subjected to monotonic compression along the extrusion direction in ambient air. T–C–T tertiary twins are developed due to the formation of a compression–tension double twin inside a primary tension twin. All the observed T–C–T twin variants are of TiCjTj type. TiCi+1Ti+1 (or TiCi–1Ti–1) variants are observed more frequently than TiCi+2Ti+2 (or TiCi–2Ti–2) variants. Moreover, the number of tertiary twin lamellae increases with the applied compressive strain.

  14. John Scott Haldane: The father of oxygen therapy

    PubMed Central

    Sekhar, KC; Rao, SSC Chakra

    2014-01-01

    John Scott Haldane was a versatile genius who solved several problems of great practical significance. His ability to look beyond the laboratory and investigate theory added crucial findings in the field of respiratory physiology. His work on high altitude physiology, diving physiology, oxygen therapy, and carbon monoxide poisoning led to a sea change in clinical medicine and improved safety and reduced mortality and morbidity in many high risk situations. PMID:25024490

  15. John Scott Haldane: The father of oxygen therapy.

    PubMed

    Sekhar, Kc; Rao, Ssc Chakra

    2014-05-01

    John Scott Haldane was a versatile genius who solved several problems of great practical significance. His ability to look beyond the laboratory and investigate theory added crucial findings in the field of respiratory physiology. His work on high altitude physiology, diving physiology, oxygen therapy, and carbon monoxide poisoning led to a sea change in clinical medicine and improved safety and reduced mortality and morbidity in many high risk situations. PMID:25024490

  16. Surface tension and long range corrections of cylindrical interfaces

    SciTech Connect

    Bourasseau, E.; Ghoufi, A.

    2015-12-21

    The calculation of the surface tension of curved interfaces has been deeply investigated from molecular simulation during this last past decade. Recently, the thermodynamic Test-Area (TA) approach has been extended to the calculation of surface tension of curved interfaces. In the case of the cylindrical vapour-liquid interfaces of water and Lennard-Jones fluids, it was shown that the surface tension was independent of the curvature of the interface. In addition, the surface tension of the cylindrical interface is higher than that of the planar interface. Molecular simulations of cylindrical interfaces have been so far performed (i) by using a shifted potential, (ii) by means of large cutoff without periodic boundary conditions, or (iii) by ignoring the long range corrections to the surface tension due to the difficulty to estimate them. Indeed, unlike the planar interfaces there are no available operational expressions to consider the tail corrections to the surface tension of cylindrical interfaces. We propose here to develop the long range corrections of the surface tension for cylindrical interfaces by using the non-exponential TA (TA2) method. We also extend the formulation of the Mecke-Winkelmann corrections initially developed for planar surfaces to cylindrical interfaces. We complete this study by the calculation of the surface tension of cylindrical surfaces of liquid tin and copper using the embedded atom model potentials.

  17. Pendant-Drop Surface-Tension Measurement On Molten Metal

    NASA Technical Reports Server (NTRS)

    Man, Kin Fung; Thiessen, David

    1996-01-01

    Method of measuring surface tension of molten metal based on pendant-drop method implemented in quasi-containerless manner and augmented with digital processing of image data. Electrons bombard lower end of sample rod in vacuum, generating hanging drop of molten metal. Surface tension of drop computed from its shape. Technique minimizes effects of contamination.

  18. 57. VIEW DOWN TENSION RUNS FROM CATWALK OVER WINDERS: View ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    57. VIEW DOWN TENSION RUNS FROM CATWALK OVER WINDERS: View towards northwest looking down the tension runs for the cables. Photograph taken from atop the catwalk over the winding machinery. The California Street cable is on the left and the Hyde Street cable on the right. - San Francisco Cable Railway, Washington & Mason Streets, San Francisco, San Francisco County, CA

  19. Critical Conversations: Tensions and Opportunities of the Dialogical Classroom

    ERIC Educational Resources Information Center

    Fecho, Bob; Collier, Nicole D.; Friese, Elizabeth E. G.; Wilson, Amy Alexandra

    2010-01-01

    English teachers and educators of English teachers should work within rather than against the tensions present in their classrooms. For us, nothing could be more key. Until university teacher educators construct and enact classrooms that embrace the dialogical tensions and possibilities within those settings, new and veteran teachers in the…

  20. 32. DETAIL OF MAIN DRIVE WHEELS AND BELT TENSIONING DEVICE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    32. DETAIL OF MAIN DRIVE WHEELS AND BELT TENSIONING DEVICE OF MAIN POWER TRAIN, LOOKING SOUTHEAST, LOOKING FORM BEHIND THE CLASSIFIER. THESE WHEELS DROVE THE BULL WHEELS ON THE STAMP BATTERIES ABOVE. THE TENSIONING DEVICE AT CENTER RIGHT CONTROLLED THE SPEED OF THE STAMPS. - Skidoo Mine, Park Route 38 (Skidoo Road), Death Valley Junction, Inyo County, CA