Photosynthesis-related characteristics of the midrib and the interveinal lamina in leaves of the C3-CAM intermediate plant Mesembryanthemum crystallinum.

PubMed

Kuźniak, Elżbieta; Kornas, Andrzej; Kaźmierczak, Andrzej; Rozpądek, Piotr; Nosek, Michał; Kocurek, Maciej; Zellnig, Günther; Müller, Maria; Miszalski, Zbigniew

2016-06-01

Leaf veins are usually encircled by specialized bundle sheath cells. In C4 plants, they play an important role in CO2 assimilation, and the photosynthetic activity is compartmentalized between the mesophyll and the bundle sheath. In C3 and CAM (Crassulacean acid metabolism) plants, the photosynthetic activity is generally attributed to the leaf mesophyll cells, and the vascular parenchymal cells are rarely considered for their role in photosynthesis. Recent studies demonstrate that enzymes required for C4 photosynthesis are also active in the veins of C3 plants, and their vascular system contains photosynthetically competent parenchyma cells. However, our understanding of photosynthesis in veins of C3 and CAM plants still remains insufficient. Here spatial analysis of photosynthesis-related properties were applied to the midrib and the interveinal lamina cells in leaves of Mesembryanthemum crystallinum, a C3-CAM intermediate plant. The midrib anatomy as well as chloroplast structure and chlorophyll fluorescence, diurnal gas exchange profiles, the immunoblot patterns of PEPC (phosphoenolpyruvate carboxylase) and RubisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase), H2O2 localization and antioxidant enzyme activities were compared in the midrib and in the interveinal mesophyll cells in leaves of C3 and CAM plants. Leaf midribs were structurally competent to perform photosynthesis in C3 and CAM plants. The midrib chloroplasts resembled those in the bundle sheath cells of C4 plants and were characterized by limited photosynthetic activity. The metabolic roles of midrib chloroplasts differ in C3 and CAM plants. It is suggested that in leaves of C3 plants the midrib chloroplasts could be involved in the supply of CO2 for carboxylation, and in CAM plants they could provide malate to different metabolic processes and mediate H2O2 signalling. © The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Leaf hydraulic conductance varies with vein anatomy across Arabidopsis thaliana wild-type and leaf vein mutants.

PubMed

Caringella, Marissa A; Bongers, Franca J; Sack, Lawren

2015-12-01

Leaf venation is diverse across plant species and has practical applications from paleobotany to modern agriculture. However, the impact of vein traits on plant performance has not yet been tested in a model system such as Arabidopsis thaliana. Previous studies analysed cotyledons of A. thaliana vein mutants and identified visible differences in their vein systems from the wild type (WT). We measured leaf hydraulic conductance (Kleaf ), vein traits, and xylem and mesophyll anatomy for A. thaliana WT (Col-0) and four vein mutants (dot3-111 and dot3-134, and cvp1-3 and cvp2-1). Mutant true leaves did not possess the qualitative venation anomalies previously shown in the cotyledons, but varied quantitatively in vein traits and leaf anatomy across genotypes. The WT had significantly higher mean Kleaf . Across all genotypes, there was a strong correlation of Kleaf with traits related to hydraulic conductance across the bundle sheath, as influenced by the number and radial diameter of bundle sheath cells and vein length per area. These findings support the hypothesis that vein traits influence Kleaf , indicating the usefulness of this mutant system for testing theory that was primarily established comparatively across species, and supports a strong role for the bundle sheath in influencing Kleaf . © 2015 John Wiley & Sons Ltd.

Evidence for a Role for NAD(P)H Dehydrogenase in Concentration of CO2 in the Bundle Sheath Cell of Zea mays.

PubMed

Peterson, Richard B; Schultes, Neil P; McHale, Neil A; Zelitch, Israel

2016-05-01

Prior studies with Nicotiana and Arabidopsis described failed assembly of the chloroplastic NDH [NAD(P)H dehydrogenase] supercomplex by serial mutation of several subunit genes. We examined the properties of Zea mays leaves containing Mu and Ds insertions into nuclear gene exons encoding the critical o- and n-subunits of NDH, respectively. In vivo reduction of plastoquinone in the dark was sharply diminished in maize homozygous mutant compared to normal leaves but not to the extreme degree observed for the corresponding lesions in Arabidopsis. The net carbon assimilation rate (A) at high irradiance and saturating CO2 levels was reduced by one-half due to NDH mutation in maize although no genotypic effect was evident at very low CO2 levels. Simultaneous assessment of chlorophyll fluorescence and A in maize at low (2% by volume) and high (21%) O2 levels indicated the presence of a small, yet detectable, O2-dependent component of total linear photosynthetic electron transport in 21% O2 This O2-dependent component decreased with increasing CO2 level indicative of photorespiration. Photorespiration was generally elevated in maize mutant compared to normal leaves. Quantification of the proportion of total electron transport supporting photorespiration enabled estimation of the bundle sheath cell CO2 concentration (Cb) using a simple kinetic model of ribulose bisphosphate carboxylase/oxygenase function. The A versus Cb relationships overlapped for normal and mutant lines consistent with occurrence of strictly CO2-limited photosynthesis in the mutant bundle sheath cell. The results are discussed in terms of a previously reported CO2 concentration model [Laisk A, Edwards GE (2000) Photosynth Res 66: 199-224]. © 2016 American Society of Plant Biologists. All Rights Reserved.

Elements Required for an Efficient NADP-Malic Enzyme Type C4 Photosynthesis1[C][W][OPEN

PubMed Central

Wang, Yu; Long, Stephen P.; Zhu, Xin-Guang

2014-01-01

C4 photosynthesis has higher light, nitrogen, and water use efficiencies than C3 photosynthesis. Although the basic anatomical, cellular, and biochemical features of C4 photosynthesis are well understood, the quantitative significance of each element of C4 photosynthesis to the high photosynthetic efficiency are not well defined. Here, we addressed this question by developing and using a systems model of C4 photosynthesis, which includes not only the Calvin-Benson cycle, starch synthesis, sucrose synthesis, C4 shuttle, and CO2 leakage, but also photorespiration and metabolite transport between the bundle sheath cells and mesophyll cells. The model effectively simulated the CO2 uptake rates, and the changes of metabolite concentrations under varied CO2 and light levels. Analyses show that triose phosphate transport and CO2 leakage can help maintain a high photosynthetic rate by balancing ATP and NADPH amounts in bundle sheath cells and mesophyll cells. Finally, we used the model to define the optimal enzyme properties and a blueprint for C4 engineering. As such, this model provides a theoretical framework for guiding C4 engineering and studying C4 photosynthesis in general. PMID:24521879

Collagen structure of tendon relates to function.

PubMed

Franchi, Marco; Trirè, Alessandra; Quaranta, Marilisa; Orsini, Ester; Ottani, Victoria

2007-03-30

A tendon is a tough band of fibrous connective tissue that connects muscle to bone, designed to transmit forces and withstand tension during muscle contraction. Tendon may be surrounded by different structures: 1) fibrous sheaths or retinaculae; 2) reflection pulleys; 3) synovial sheaths; 4) peritendon sheaths; 5) tendon bursae. Tendons contain a) few cells, mostly represented by tenoblasts along with endothelial cells and some chondrocytes; b) proteoglycans (PGs), mainly decorin and hyaluronan, and c) collagen, mostly type I. Tendon is a good example of a high ordered extracellular matrix in which collagen molecules assemble into filamentous collagen fibrils (formed by microfibrils) which aggregate to form collagen fibers, the main structural components. It represents a multihierarchical structure as it contains collagen molecules arranged in fibrils then grouped in fibril bundles, fascicles and fiber bundles that are almost parallel to the long axis of the tendon, named as primary, secondary and tertiary bundles. Collagen fibrils in tendons show prevalently large diameter, a D-period of about 67 nm and appear built of collagen molecules lying at a slight angle (< 5 degrees). Under polarized light microscopy the collagen fiber bundles appear crimped with alternative dark and light transverse bands. In recent studies tendon crimps observed via SEM and TEM show that the single collagen fibrils suddenly changing their direction contain knots. These knots of collagen fibrils inside each tendon crimp have been termed "fibrillar crimps", and even if they show different aspects they all may fulfil the same functional role. As integral component of musculoskeletal system, the tendon acts to transmit muscle forces to the skeletal system. There is no complete understanding of the mechanisms in transmitting/absorbing tensional forces within the tendon; however it seems likely that a flattening of tendon crimps may occur at a first stage of tendon stretching. Increasing stretching, other transmission mechanisms such as an interfibrillar coupling via PGs linkages and a molecular gliding within the fibrils structure may be involved.

Characterizing regulatory and functional differentiation between maize mesophyll and bundle sheath cells by transcriptomic analysis.

PubMed

Chang, Yao-Ming; Liu, Wen-Yu; Shih, Arthur Chun-Chieh; Shen, Meng-Ni; Lu, Chen-Hua; Lu, Mei-Yeh Jade; Yang, Hui-Wen; Wang, Tzi-Yuan; Chen, Sean C-C; Chen, Stella Maris; Li, Wen-Hsiung; Ku, Maurice S B

2012-09-01

To study the regulatory and functional differentiation between the mesophyll (M) and bundle sheath (BS) cells of maize (Zea mays), we isolated large quantities of highly homogeneous M and BS cells from newly matured second leaves for transcriptome profiling by RNA sequencing. A total of 52,421 annotated genes with at least one read were found in the two transcriptomes. Defining a gene with more than one read per kilobase per million mapped reads as expressed, we identified 18,482 expressed genes; 14,972 were expressed in M cells, including 53 M-enriched transcription factor (TF) genes, whereas 17,269 were expressed in BS cells, including 214 BS-enriched TF genes. Interestingly, many TF gene families show a conspicuous BS preference in expression. Pathway analyses reveal differentiation between the two cell types in various functional categories, with the M cells playing more important roles in light reaction, protein synthesis and folding, tetrapyrrole synthesis, and RNA binding, while the BS cells specialize in transport, signaling, protein degradation and posttranslational modification, major carbon, hydrogen, and oxygen metabolism, cell division and organization, and development. Genes coding for several transporters involved in the shuttle of C(4) metabolites and BS cell wall development have been identified, to our knowledge, for the first time. This comprehensive data set will be useful for studying M/BS differentiation in regulation and function.

The Evolutionary Basis of Naturally Diverse Rice Leaves Anatomy

PubMed Central

Chatterjee, Jolly; Dionora, Jacqueline; Elmido-Mabilangan, Abigail; Wanchana, Samart; Thakur, Vivek; Bandyopadhyay, Anindya; Brar, Darshan S.; Quick, William Paul

2016-01-01

Rice contains genetically and ecologically diverse wild and cultivated species that show a wide variation in plant and leaf architecture. A systematic characterization of leaf anatomy is essential in understanding the dynamics behind such diversity. Therefore, leaf anatomies of 24 Oryza species spanning 11 genetically diverse rice genomes were studied in both lateral and longitudinal directions and possible evolutionary trends were examined. A significant inter-species variation in mesophyll cells, bundle sheath cells, and vein structure was observed, suggesting precise genetic control over these major rice leaf anatomical traits. Cellular dimensions, measured along three growth axes, were further combined proportionately to construct three-dimensional (3D) leaf anatomy models to compare the relative size and orientation of the major cell types present in a fully expanded leaf. A reconstruction of the ancestral leaf state revealed that the following are the major characteristics of recently evolved rice species: fewer veins, larger and laterally elongated mesophyll cells, with an increase in total mesophyll area and in bundle sheath cell number. A huge diversity in leaf anatomy within wild and domesticated rice species has been portrayed in this study, on an evolutionary context, predicting a two-pronged evolutionary pathway leading to the ‘sativa leaf type’ that we see today in domesticated species. PMID:27792743

The Evolutionary Basis of Naturally Diverse Rice Leaves Anatomy.

PubMed

Chatterjee, Jolly; Dionora, Jacqueline; Elmido-Mabilangan, Abigail; Wanchana, Samart; Thakur, Vivek; Bandyopadhyay, Anindya; Brar, Darshan S; Quick, William Paul

2016-01-01

Rice contains genetically and ecologically diverse wild and cultivated species that show a wide variation in plant and leaf architecture. A systematic characterization of leaf anatomy is essential in understanding the dynamics behind such diversity. Therefore, leaf anatomies of 24 Oryza species spanning 11 genetically diverse rice genomes were studied in both lateral and longitudinal directions and possible evolutionary trends were examined. A significant inter-species variation in mesophyll cells, bundle sheath cells, and vein structure was observed, suggesting precise genetic control over these major rice leaf anatomical traits. Cellular dimensions, measured along three growth axes, were further combined proportionately to construct three-dimensional (3D) leaf anatomy models to compare the relative size and orientation of the major cell types present in a fully expanded leaf. A reconstruction of the ancestral leaf state revealed that the following are the major characteristics of recently evolved rice species: fewer veins, larger and laterally elongated mesophyll cells, with an increase in total mesophyll area and in bundle sheath cell number. A huge diversity in leaf anatomy within wild and domesticated rice species has been portrayed in this study, on an evolutionary context, predicting a two-pronged evolutionary pathway leading to the 'sativa leaf type' that we see today in domesticated species.

Genome-scale modeling of the evolutionary path to C4 photosynthesis

NASA Astrophysics Data System (ADS)

Myers, Christopher R.; Bogart, Eli

In C4 photosynthesis, plants maintain a high carbon dioxide level in specialized bundle sheath cells surrounding leaf veins and restrict CO2 assimilation to those cells, favoring CO2 over O2 in competition for Rubisco active sites. In C3 plants, which do not possess such a carbon concentrating mechanism, CO2 fixation is reduced due to this competition. Despite the complexity of the C4 system, it has evolved convergently from more than 60 independent origins in diverse families of plants around the world over the last 30 million years. We study the evolution of the C4 system in a genome-scale model of plant metabolism that describes interacting mesophyll and bundle sheath cells and enforces key nonlinear kinetic relationships. Adapting the zero-temperature string method for simulating transition paths in physics and chemistry, we find the highest-fitness paths connecting C3 and C4 positions in the model's high-dimensional parameter space, and show that they reproduce known aspects of the C3-C4 transition while making additional predictions about metabolic changes along the path. We explore the relationship between evolutionary history and C4 biochemical subtype, and the effects of atmospheric carbon dioxide levels.

Differential positioning of C(4) mesophyll and bundle sheath chloroplasts: recovery of chloroplast positioning requires the actomyosin system.

PubMed

Kobayashi, Hiroaki; Yamada, Masahiro; Taniguchi, Mitsutaka; Kawasaki, Michio; Sugiyama, Tatsuo; Miyake, Hiroshi

2009-01-01

In C(4) plants, bundle sheath (BS) chloroplasts are arranged in the centripetal position or in the centrifugal position, although mesophyll (M) chloroplasts are evenly distributed along cell membranes. To examine the molecular mechanism for the intracellular disposition of these chloroplasts, we observed the distribution of actin filaments in BS and M cells of the C(4) plants finger millet (Eleusine coracana) and maize (Zea mays) using immunofluorescence. Fine actin filaments encircled chloroplasts in both cell types, and an actin network was observed adjacent to plasma membranes. The intracellular disposition of both chloroplasts in finger millet was disrupted by centrifugal force but recovered within 2 h in the dark. Actin filaments remained associated with chloroplasts during recovery. We also examined the effects of inhibitors on the rearrangement of chloroplasts. Inhibitors of actin polymerization, myosin-based activities and cytosolic protein synthesis blocked migration of chloroplasts. In contrast, a microtubule-depolymerizing drug had no effect. These results show that C(4) plants possess a mechanism for keeping chloroplasts in the home position which is dependent on the actomyosin system and cytosolic protein synthesis but not tubulin or light.

Anatomical and neurohistological observations on the heart of the rose ringed parakeet, Psittacula krameri.

PubMed

Qayyum, M A; Shaad, F U

1976-01-01

Anatomy, histology and innervation of the heart of the rose ringed parakeet, Psittacula krameri have been studied in the present investigation. The sinuatrial node is found to be well-developed. It is located towards the right side of the cephalic end of the interatrial septum and composed of a few nucleated cells and a large fibrous mass. The atrioventricular node is poorly defined, present at the caudal end of the interatrial septum. The node is somewhat triangular in shape and is composed of elongated and multinucleated specialized fibres. The node is not covered by any connective tissue sheath. The poor development of the atrio ventricular node and the absence of any sheath around it may be correlated with the fast rate of the heart beat. The atrioventricular bundle is observed at the cephalic end of the interventricular septum. A branch from the right limb of the atrioventricular bundle is noted to pass directly into the right atrioventricular valve. The heart is richly innervated. Ganglion cells along with nerve fibres have been observed at the sulcus terminalis and the atrioventricular junction. A direct nervous connection could be observed between the sinuatrial and atrioventricular nodes. It is argued that the impulse which originates in the sinuatrial node would reach the atrioventricular node through the unspecialized muscle fibres and nerve fibres of the interatrial septum. Nerve cells could not be traced in the substance of the sinuatrial node, atrioventricular node and atrioventricular bundle.

Structure and immunocytochemical localization of photosynthetic enzymes in the lamina joint and sheath pulvinus of the C4 grass Arundinella hirta.

PubMed

Wakayama, Masataka; Ohnishi, Jun-ichi; Ueno, Osamu

2013-03-01

The C(4) grass Arundinella hirta exhibits a unique C(4) anatomy, with isolated Kranz cells (distinctive cells) and C(4)-type expression of photosynthetic enzymes in the leaf sheath and stem as well as in the leaf blade. The border zones between these organs are pale green. Those between the leaf blade and sheath and between the sheath and stem are called the lamina joint and sheath pulvinus, respectively, and are involved in gravity sensing. We investigated the structure and localization of C(3) and C(4) photosynthetic enzymes in these tissues. In both zones the epidermis lacked stomata. The inner tissue was composed of parenchyma cells and vascular bundles. The parenchyma cells were densely packed with small intercellular spaces and contained granal chloroplasts with large starch grains. No C(4)-type cellular differentiation was recognized. Western blot analysis showed that the lamina joint and pulvinus accumulated substantial amounts of phosphoenolpyruvate carboxylase (PEPC), pyruvate,Pi dikinase (PPDK), and ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco). Immunogold electron microscopy revealed PEPC in the cytosol and both PPDK and rubisco in the chloroplasts of parenchyma cells, suggesting the occurrence of C(3) and C(4) enzymes within a single type of chlorenchyma cell. These data indicate that the lamina joint and pulvinus have unique expression patterns of C(3) and C(4) enzymes, unlike those in C(4)-type anatomy.

A novel RNA binding protein affects rbcL gene expression and is specific to bundle sheath chloroplasts in C4 plants

PubMed Central

2013-01-01

Background Plants that utilize the highly efficient C4 pathway of photosynthesis typically possess kranz-type leaf anatomy that consists of two morphologically and functionally distinct photosynthetic cell types, the bundle sheath (BS) and mesophyll (M) cells. These two cell types differentially express many genes that are required for C4 capability and function. In mature C4 leaves, the plastidic rbcL gene, encoding the large subunit of the primary CO2 fixation enzyme Rubisco, is expressed specifically within BS cells. Numerous studies have demonstrated that BS-specific rbcL gene expression is regulated predominantly at post-transcriptional levels, through the control of translation and mRNA stability. The identification of regulatory factors associated with C4 patterns of rbcL gene expression has been an elusive goal for many years. Results RLSB, encoded by the nuclear RLSB gene, is an S1-domain RNA binding protein purified from C4 chloroplasts based on its specific binding to plastid-encoded rbcL mRNA in vitro. Co-localized with LSU to chloroplasts, RLSB is highly conserved across many plant species. Most significantly, RLSB localizes specifically to leaf bundle sheath (BS) cells in C4 plants. Comparative analysis using maize (C4) and Arabidopsis (C3) reveals its tight association with rbcL gene expression in both plants. Reduced RLSB expression (through insertion mutation or RNA silencing, respectively) led to reductions in rbcL mRNA accumulation and LSU production. Additional developmental effects, such as virescent/yellow leaves, were likely associated with decreased photosynthetic function and disruption of associated signaling networks. Conclusions Reductions in RLSB expression, due to insertion mutation or gene silencing, are strictly correlated with reductions in rbcL gene expression in both maize and Arabidopsis. In both plants, accumulation of rbcL mRNA as well as synthesis of LSU protein were affected. These findings suggest that specific accumulation and binding of the RLSB binding protein to rbcL mRNA within BS chloroplasts may be one determinant leading to the characteristic cell type-specific localization of Rubisco in C4 plants. Evolutionary modification of RLSB expression, from a C3 “default” state to BS cell-specificity, could represent one mechanism by which rbcL expression has become restricted to only one cell type in C4 plants. PMID:24053212

Interactions of C4 subtype metabolic activities and transport in maize are revealed through the characterization of DCT2 mutants

USDA-ARS?s Scientific Manuscript database

C4 photosynthesis is an elaborate set of metabolic pathways that utilize specialized anatomical and biochemical adaptations to concentrate CO2 around RuBisCO. The activities of the C4 pathways are coordinated between two specialized leaf cell types, mesophyll (M) and bundle sheath (BS), and rely hea...

On the contributions of photorespiration and compartmentation to the contrasting intramolecular 2H profiles of C3 and C4 plant sugars

Treesearch

Youping Zhou; Benli Zhang; Hilary Stuart-Williams; Kliti Grice; Charles H. Hocart; Arthur Gessler; Zachary E. Kayler; Graham D. Farquhar

2018-01-01

Compartmentation of C4 photosynthetic biochemistry into bundle sheath (BS) and mesophyll (M) cells, and photorespiration in C3 plants is predicted to have hydrogen isotopic consequences for metabolites at both molecular and site-specific levels. Molecular-level evidence was recently reported (Zhou et al., 2016), but...

Thermal Aspects of Using Alternative Nuclear Fuels in Supercritical Water-Cooled Reactors

NASA Astrophysics Data System (ADS)

Grande, Lisa Christine

A SuperCritical Water-cooled Nuclear Reactor (SCWR) is a Generation IV concept currently being developed worldwide. Unique to this reactor type is the use of light-water coolant above its critical point. The current research presents a thermal-hydraulic analysis of a single fuel channel within a Pressure Tube (PT)-type SCWR with a single-reheat cycle. Since this reactor is in its early design phase many fuel-channel components are being investigated in various combinations. Analysis inputs are: steam cycle, Axial Heat Flux Profile (AHFP), fuel-bundle geometry, and thermophysical properties of reactor coolant, fuel sheath and fuel. Uniform and non-uniform AHFPs for average channel power were applied to a variety of alternative fuels (mixed oxide, thorium dioxide, uranium dicarbide, uranium nitride and uranium carbide) enclosed in an Inconel-600 43-element bundle. The results depict bulk-fluid, outer-sheath and fuel-centreline temperature profiles together with the Heat Transfer Coefficient (HTC) profiles along the heated length of fuel channel. The objective is to identify the best options in terms of fuel, sheath material and AHFPS in which the outer-sheath and fuel-centreline temperatures will be below the accepted temperature limits of 850°C and 1850°C respectively. The 43-element Inconel-600 fuel bundle is suitable for SCWR use as the sheath-temperature design limit of 850°C was maintained for all analyzed cases at average channel power. Thoria, UC2, UN and UC fuels for all AHFPs are acceptable since the maximum fuel-centreline temperature does not exceed the industry accepted limit of 1850°C. Conversely, the fuel-centreline temperature limit was exceeded for MOX at all AHFPs, and UO2 for both cosine and downstream-skewed cosine AHFPs. Therefore, fuel-bundle modifications are required for UO2 and MOX to be feasible nuclear fuels for SCWRs.

Structure and enzyme expression in photosynthetic organs of the atypical C4 grass Arundinella hirta.

PubMed

Wakayama, Masataka; Ohnishi, Jun-ichi; Ueno, Osamu

2006-05-01

In its leaf blade, Arundinella hirta has unusual Kranz cells that lie distant from the veins (distinctive cells; DCs), in addition to the usual Kranz units composed of concentric layers of mesophyll cells (MCs) and bundle sheath cells (BSCs; usual Kranz cells) surrounding the veins. We examined whether chlorophyllous organs other than leaf blades--namely, the leaf sheath, stem, scale leaf, and constituents of the spike--also have this unique anatomy and the C4 pattern of expression of photosynthetic enzymes. All the organs developed DCs to varying degrees, as well as BSCs. The stem, rachilla, and pedicel had C4-type anatomy with frequent occurrence of DCs, as in the leaf blade. The leaf sheath, glume, and scale leaf had a modified C4 anatomy with MCs more than two cells distant from the Kranz cells; DCs were relatively rare. An immunocytochemical study of C3 and C4 enzymes revealed that all the organs exhibited essentially the same C4 pattern of expression as in the leaf blade. In the scale leaf, however, intense expression of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) occurred in the MCs as well as in the BSCs and DCs. In the leaf sheath, the distant MCs also expressed Rubisco. In Arundinella hirta, it seems that the ratio of MC to Kranz cell volumes, and the distance from the Kranz cells, but not from the veins, affects the cellular expression of photosynthetic enzymes. We suggest that the main role of DCs is to keep a constant quantitative balance between the MCs and Kranz cells, which is a prerequisite for effective C4 pathway operation.

Ultrastructure of the extracellular matrix of bovine dura mater, optic nerve sheath and sclera.

PubMed

Raspanti, M; Marchini, M; Della Pasqua, V; Strocchi, R; Ruggeri, A

1992-10-01

The sclera, the outermost sheath of the optic nerve and the dura mater have been investigated histologically and ultrastructurally. Although these tissues appear very similar under the light microscope, being dense connective tissues mainly composed of collagen bundles and a limited amount of cells and elastic fibres, they exhibit subtle differences on electron microscopy. In the dura and sclera collagen appears in the form of large, nonuniform fibrils, similar to those commonly found in tendons, while in the optic nerve sheath the fibrils appear smaller and uniform, similar to those commonly observed in reticular tissues, vessel walls and skin. Freeze-fracture also reveals these fibrils to have different subfibrillar architectures, straight or helical, which correspond to 2 distinct forms of collagen fibril previously described (Raspanti et al. 1989). The other extracellular matrix components also vary with the particular collagen fibril structure. Despite their common embryological derivation, the dura mater, optic nerve sheath and sclera exhibit diversification of their extracellular matrix consistent with the mechanical loads to which these tissues are subjected. Our observations indicate that the outermost sheath of the optic nerve resembles the epineurium of peripheral nerves rather than the dura to which it is commonly likened.

Starch Accumulation in the Bundle Sheaths of C3 Plants: A Possible Pre-Condition for C4 Photosynthesis.

PubMed

Miyake, Hiroshi

2016-05-01

C4 plants have evolved >60 times from their C3 ancestors. C4 photosynthesis requires a set of closely co-ordinated anatomical and biochemical characteristics. However, it is now recognized that the evolution of C4 plants requires fewer changes than had ever been considered, because of the genetic, biochemical and anatomical pre-conditions of C3 ancestors that were recruited into C4 photosynthesis. Therefore, the pre-conditions in C3 plants are now being actively investigated to clarify the evolutionary trajectory from C3 to C4 plants and to engineer C4 traits efficiently into C3 crops. In the present mini review, the anatomical characteristics of C3 and C4 plants are briefly reviewed and the importance of the bundle sheath for the evolution of C4 photosynthesis is described. For example, while the bundle sheath of C3 rice plants accumulates large amounts of starch in the developing leaf blade and at the lamina joint of the mature leaf, the starch sheath function is also observed during leaf development in starch accumulator grasses regardless of photosynthetic type. The starch sheath function of C3 plants is therefore also implicated as a possible pre-condition for the evolution of C4 photosynthesis. The phylogenetic relationships between the types of storage carbohydrates and of photosynthesis need to be clarified in the future. © The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Chilling-induced physiological, anatomical and biochemical responses in the leaves of Miscanthus × giganteus and maize (Zea mays L.).

PubMed

Bilska-Kos, Anna; Panek, Piotr; Szulc-Głaz, Anna; Ochodzki, Piotr; Cisło, Aneta; Zebrowski, Jacek

2018-06-08

Miscanthus × giganteus and Zea mays, closely-related C 4 grasses, originated from warm climates react differently to low temperature. To investigate the response to cold (12-14 °C) in these species, the photosynthetic and anatomical parameters as well as biochemical properties of the cell wall were studied. The research was performed using M. giganteus (MG) and two Z. mays lines differentiated for chilling-sensitivity: chilling-tolerant (Zm-T) and chilling-sensitive (Zm-S). The chilled plants of Zm-S line demonstrated strong inhibition of net CO 2 assimilation and a clear decrease in F' v /F' m , F v /F m and ɸ PSII, while in MG and Zm-T plants these parameters were almost unchanged. The anatomical studies revealed that MG plants had thinner leaves, epidermis and mesophyll cell layer as well as thicker cell walls in the comparison to both maize lines. Cold led to an increase in leaf thickness and mesophyll cell layer thickness in the Zm-T maize line, while the opposite response was observed in Zm-S. In turn, in chilled plants of MG and Zm-T lines, some anatomical parameters associated with bundle sheath cells were higher. In addition, Zm-S line showed the strong increase in the cell wall thickness at cold for mesophyll and bundle sheath cells. Chilling-treatment induced the changes in the cell wall biochemistry of tested species, mainly in the content of glucuronoarabinoxylan, uronic acid, β-glucan and phenolic compounds. This work presents a new approach in searching of mechanism(s) of tolerance/sensitivity to low temperature in two thermophilic plants: Miscanthus and maize. Copyright © 2018 Elsevier GmbH. All rights reserved.

Sensitivity Analysis of Fuel Centerline Temperatures in SuperCritical Water-cooled Reactors (SCWRs)

NASA Astrophysics Data System (ADS)

Abdalla, Ayman

SuperCritical Water-cooled Reactors (SCWRs) are one of the six nuclear-reactor concepts currently being developed under the Generation-IV International Forum (GIF). A main advantage of SCW Nuclear Power Plants (NPPs) is that they offer higher thermal efficiencies compared to those of current conventional NPPs. Unlike today's conventional NPPs, which have thermal efficiencies between 30 - 35%, SCW NPPs will have thermal efficiencies within a range of 45 - 50%, owing to high operating temperatures and pressures (i.e., coolant temperatures as high as 625°C at 25 MPa pressure). The use of current fuel bundles with UO2 fuel at the high operating parameters of SCWRs may cause high fuel centerline temperatures, which could lead to fuel failure and fission gas release. Studies have shown that when the Variant-20 (43-element) fuel bundle was examined at SCW conditions, the fuel centerline temperature industry limit of 1850°C for UO2 and the sheath temperature design limit of 850°C might be exceeded. Therefore, new fuel-bundle designs, which comply with the design requirements, are required for future use in SCWRs. The main objective of this study to conduct a sensitivity analysis in order to identify the main factors that leads to fuel centerline temperature reduction. Therefore, a 54-element fuel bundle with smaller diameter of fuel elements compared to that of the 43-element bundle was designed and various nuclear fuels are examined for future use in a generic Pressure Tube (PT) SCWR. The 54-element bundle consists of 53 heated fuel elements with an outer diameter of 9.5 mm and one central unheated element of 20-mm outer diameter which contains burnable poison. The 54-element fuel bundle has an outer diameter of 103.45 mm, which is the same as the outer diameter of the 43-element fuel bundle. After developing the 54-element fuel bundle, one-dimensional heat-transfer analysis was conducted using MATLAB and NIST REFPROP programs. As a result, the Heat Transfer Coefficient (HTC), bulk-fluid, sheath and fuel centerline temperature profiles were generated along the heated length of 5.772 m for a generic fuel channel. The fuel centerline and sheath temperature profiles have been determined at four Axial Heat Flux Profiles (AHFPs) using an average thermal power per channel of 8.5 MWth. The four examined AHFPs are the uniform, cosine, upstream-skewed and downstream-skewed profiles. Additionally, this study focuses on investigating a possibility of using low, enhanced and high thermal-conductivity fuels. The low thermal-conductivity fuels, which have been examined in this study, are uranium dioxide (UO 2), Mixed Oxide (MOX) and Thoria (ThO2) fuels. The examined enhanced thermal-conductivity fuels are uranium dioxide - silicon carbide (UO2 - SiC) and uranium dioxide - beryllium oxide (UO2 - BeO). Lastly, uranium carbide (UC), uranium dicarbide (UC2) and uranium nitride (UN) are the selected high thermal-conductivity fuels, which have been proposed for use in SCWRs. A comparison has been made between the low, enhanced and high thermal-conductivity fuels in order to identify the fuel centerline temperature behaviour when different nuclear fuels are used. Also, in the process of conducting the sensitivity analysis, the HTC was calculated using the Mokry et al. correlation, which is the most accurate supercritical water heat-transfer correlation so far. The sheath and the fuel centerline temperature profiles were determined for two cases. In Case 1, the HTC was calculated based on the Mokry et al. correlation, while in Case 2, the HTC values calculated for Case 1 were multiplied by a factor of 2. This factor was used in order to identify the amount of decrease in temperatures if the heat transfer is enhanced with appendages. Results of this analysis indicate that the use of the newly developed 54-element fuel bundle along with the proposed fuels is promising when compared with the Variant-20 (43-element) fuel bundle. Overall, the fuel centerline and sheath temperatures were below the industry and design limits when most of the proposed fuels were examined in the 54-element fuel bundle, however, the fuel centerline temperature limit was exceeded while MOX fuel was examined. Keywords: SCWRs, Fuel Centerline Temperature, Sheath Temperature, High Thermal Conductivity Fuels, Low Thermal Conductivity Fuels, HTC.

Functional Redundancy and Divergence within the Arabidopsis RETICULATA-RELATED Gene Family1[W][OA

PubMed Central

Pérez-Pérez, José Manuel; Esteve-Bruna, David; González-Bayón, Rebeca; Kangasjärvi, Saijaliisa; Caldana, Camila; Hannah, Matthew A.; Willmitzer, Lothar; Ponce, María Rosa; Micol, José Luis

2013-01-01

A number of Arabidopsis (Arabidopsis thaliana) mutants exhibit leaf reticulation, having green veins that stand out against paler interveinal tissues, fewer cells in the interveinal mesophyll, and normal perivascular bundle sheath cells. Here, to examine the basis of leaf reticulation, we analyzed the Arabidopsis RETICULATA-RELATED (RER) gene family, several members of which cause leaf reticulation when mutated. Although transcripts of RE, RER1, and RER3 were mainly detected in the bundle sheath cells of expanded leaves, functional RER3:GREEN FLUORESCENT PROTEIN was visualized in the chloroplast membranes of all photosynthetic cells. Leaf reticulation in the re and rer3 loss-of-function mutants occurred, along with accumulation of reactive oxygen species, in a photoperiod-dependent manner. A comparison of re and rer3 leaf messenger RNA expression profiles showed more than 200 genes were similarly misexpressed in both mutants. In addition, metabolic profiles of mature leaves revealed that several biosynthetic pathways downstream of pyruvate are altered in re and rer3. Double mutant analysis showed that only re rer1 and rer5 rer6 exhibited synergistic phenotypes, indicating functional redundancy. The redundancy between RE and its closest paralog, RER1, was confirmed by overexpressing RER1 in re mutants, which partially suppressed leaf reticulation. Our results show that RER family members can be divided into four functional modules with divergent functions. Moreover, these results provide insights into the origin of the reticulated phenotype, suggesting that the RER proteins functionally interconnect photoperiodic growth, amino acid homeostasis, and reactive oxygen species metabolism during Arabidopsis leaf growth. PMID:23596191

Functional Analysis of Corn Husk Photosynthesis[W][OA

PubMed Central

Pengelly, Jasper J.L.; Kwasny, Scott; Bala, Soumi; Evans, John R.; Voznesenskaya, Elena V.; Koteyeva, Nuria K.; Edwards, Gerald E.; Furbank, Robert T.; von Caemmerer, Susanne

2011-01-01

The husk surrounding the ear of corn/maize (Zea mays) has widely spaced veins with a number of interveinal mesophyll (M) cells and has been described as operating a partial C3 photosynthetic pathway, in contrast to its leaves, which use the C4 photosynthetic pathway. Here, we characterized photosynthesis in maize husk and leaf by measuring combined gas exchange and carbon isotope discrimination, the oxygen dependence of the CO2 compensation point, and photosynthetic enzyme activity and localization together with anatomy. The CO2 assimilation rate in the husk was less than that in the leaves and did not saturate at high CO2, indicating CO2 diffusion limitations. However, maximal photosynthetic rates were similar between the leaf and husk when expressed on a chlorophyll basis. The CO2 compensation points of the husk were high compared with the leaf but did not vary with oxygen concentration. This and the low carbon isotope discrimination measured concurrently with gas exchange in the husk and leaf suggested C4-like photosynthesis in the husk. However, both Rubisco activity and the ratio of phosphoenolpyruvate carboxylase to Rubisco activity were reduced in the husk. Immunolocalization studies showed that phosphoenolpyruvate carboxylase is specifically localized in the layer of M cells surrounding the bundle sheath cells, while Rubisco and glycine decarboxylase were enriched in bundle sheath cells but also present in M cells. We conclude that maize husk operates C4 photosynthesis dispersed around the widely spaced veins (analogous to leaves) in a diffusion-limited manner due to low M surface area exposed to intercellular air space, with the functional role of Rubisco and glycine decarboxylase in distant M yet to be explained. PMID:21511990

Elastic fibres are broadly distributed in tendon and highly localized around tenocytes

PubMed Central

Grant, Tyler M; Thompson, Mark S; Urban, Jill; Yu, Jing

2013-01-01

Elastic fibres have the unique ability to withstand large deformations and are found in numerous tissues, but their organization and structure have not been well defined in tendon. The objective of this study was to characterize the organization of elastic fibres in tendon to understand their function. Immunohistochemistry was used to visualize elastic fibres in bovine flexor tendon with fibrillin-1, fibrillin-2 and elastin antibodies. Elastic fibres were broadly distributed throughout tendon, and highly localized longitudinally around groups of cells and transversely between collagen fascicles. The close interaction of elastic fibres and cells suggests that elastic fibres are part of the pericellular matrix and therefore affect the mechanical environment of tenocytes. Fibres present between fascicles are likely part of the endotenon sheath, which enhances sliding between adjacent collagen bundles. These results demonstrate that elastic fibres are highly localized in tendon and may play an important role in cellular function and contribute to the tissue mechanics of the endotenon sheath. PMID:23587025

Ultrastructure of the extracellular matrix of bovine dura mater, optic nerve sheath and sclera.

PubMed Central

Raspanti, M; Marchini, M; Della Pasqua, V; Strocchi, R; Ruggeri, A

1992-01-01

The sclera, the outermost sheath of the optic nerve and the dura mater have been investigated histologically and ultrastructurally. Although these tissues appear very similar under the light microscope, being dense connective tissues mainly composed of collagen bundles and a limited amount of cells and elastic fibres, they exhibit subtle differences on electron microscopy. In the dura and sclera collagen appears in the form of large, nonuniform fibrils, similar to those commonly found in tendons, while in the optic nerve sheath the fibrils appear smaller and uniform, similar to those commonly observed in reticular tissues, vessel walls and skin. Freeze-fracture also reveals these fibrils to have different subfibrillar architectures, straight or helical, which correspond to 2 distinct forms of collagen fibril previously described (Raspanti et al. 1989). The other extracellular matrix components also vary with the particular collagen fibril structure. Despite their common embryological derivation, the dura mater, optic nerve sheath and sclera exhibit diversification of their extracellular matrix consistent with the mechanical loads to which these tissues are subjected. Our observations indicate that the outermost sheath of the optic nerve resembles the epineurium of peripheral nerves rather than the dura to which it is commonly likened. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 PMID:1295858

Photosynthetic Trichomes Contain a Specific Rubisco with a Modified pH-Dependent Activity.

PubMed

Laterre, Raphaëlle; Pottier, Mathieu; Remacle, Claire; Boutry, Marc

2017-04-01

Ribulose-1,5-biphosphate carboxylase/oxygenase (Rubisco) is the most abundant enzyme in plants and is responsible for CO 2 fixation during photosynthesis. This enzyme is assembled from eight large subunits (RbcL) encoded by a single chloroplast gene and eight small subunits (RbcS) encoded by a nuclear gene family. Rubisco is primarily found in the chloroplasts of mesophyll (C3 plants), bundle-sheath (C4 plants), and guard cells. In certain species, photosynthesis also takes place in the secretory cells of glandular trichomes, which are epidermal outgrowths (hairs) involved in the secretion of specialized metabolites. However, photosynthesis and, in particular, Rubisco have not been characterized in trichomes. Here, we show that tobacco ( Nicotiana tabacum ) trichomes contain a specific Rubisco small subunit, NtRbcS-T, which belongs to an uncharacterized phylogenetic cluster (T). This cluster contains RbcS from at least 33 species, including monocots, many of which are known to possess glandular trichomes. Cluster T is distinct from the cluster M, which includes the abundant, functionally characterized RbcS isoforms expressed in mesophyll or bundle-sheath cells. Expression of NtRbcS-T in Chlamydomonas reinhardtii and purification of the full Rubisco complex showed that this isoform conferred higher V max and K m values as well as higher acidic pH-dependent activity than NtRbcS-M, an isoform expressed in the mesophyll. This observation was confirmed with trichome extracts. These data show that an ancient divergence allowed for the emergence of a so-far-uncharacterized RbcS cluster. We propose that secretory trichomes have a particular Rubisco uniquely adapted to secretory cells where CO 2 is released by the active specialized metabolism. © 2017 American Society of Plant Biologists. All Rights Reserved.

Cytology of the minor-vein phloem in 320 species from the subclass Asteridae suggests a high diversity of phloem-loading modes†

PubMed Central

Batashev, Denis R.; Pakhomova, Marina V.; Razumovskaya, Anna V.; Voitsekhovskaja, Olga V.; Gamalei, Yuri V.

2013-01-01

The discovery of abundant plasmodesmata at the bundle sheath/phloem interface in Oleaceae (Gamalei, 1974) and Cucurbitaceae (Turgeon et al., 1975) raised the questions as to whether these plasmodesmata are functional in phloem loading and how widespread symplasmic loading would be. Analysis of over 800 dicot species allowed the definition of “open” and “closed” types of the minor vein phloem depending on the abundance of plasmodesmata between companion cells and bundle sheath (Gamalei, 1989, 1990). These types corresponded to potential symplasmic and apoplasmic phloem loaders, respectively; however, this definition covered a spectrum of diverse structures of phloem endings. Here, a review of detailed cytological analyses of minor veins in 320 species from the subclass Asteridae is presented, including data on companion cell types and their combinations which have not been reported previously. The percentage of Asteridae species with “open” minor vein cytology which also contain sieve-element-companion cell complexes with “closed” cytology, i.e., that show specialization for both symplasmic and apoplasmic phloem loading, was determined. Along with recent data confirming the dissimilar functional specialization of structurally different parts of minor vein phloem in the stachyose-translocating species Alonsoa meridionalis (Voitsekhovskaja et al., 2009), these findings suggest that apoplasmic loading is indispensable in a large group of species previously classified as putative symplasmic loaders. Altogether, this study provides formal classifications of companion cells and of minor veins, respectively, in 24 families of the Asteridae based on their structural features, opening the way to a close investigation of the relationship between structure and function in phloem loading. PMID:23970890

Photosynthetic characteristics of an amphibious plant, Eleocharis vivipara: Expression of C4 and C3 modes in contrasting environments

PubMed Central

Ueno, Osamu; Samejima, Muneaki; Muto, Shoshi; Miyachi, Shigetoh

1988-01-01

Eleocharis vivipara Link, a freshwater amphibious leafless plant belonging to the Cyperaceae can grow in both terrestrial and submersed aquatic conditions. Two forms of E. vivipara obtained from these contrasting environments were examined for the characteristics associated with C4 and C3 photosynthesis. In the terrestrial form (δ 13C values = -13.5 to -15.4‰, where ‰ is parts per thousand), the culms, which are photosynthetic organs, possess a Kranz-type anatomy typical of C4 plants, and well-developed bundle-sheath cells contain numerous large chloroplasts. In the submersed form (δ 13C value = -25.9‰), the culms possess anatomical features characteristic of submersed aquatic plants, and the reduced bundle-sheath cells contain only a few small chloroplasts. 14C pulse-12C chase experiments showed that the terrestrial form and the submersed form fix carbon by way of the C4 pathway, with aspartate (40%) and malate (35%) as the main primary products, and by way of the C3 pathway, with 3-phosphoglyceric acid (53%) and sugar phosphates (14%) as the main primary products, respectively. The terrestrial form showed photosynthetic enzyme activities typical of the NAD-malic enzyme-C4 subtype, whereas the submersed form showed decreased activities of key C4 enzymes and an increased ribulose 1,5-bisphosphate carboxylase (EC 4.1.1.39) activity. These data suggest that this species can differentiate into the C4 mode under terrestrial conditions and into the C3 mode under submersed conditions. Images PMID:16593980

Bundle Sheath Diffusive Resistance to CO2 and Effectiveness of C4 Photosynthesis and Refixation of Photorespired CO2 in a C4 Cycle Mutant and Wild-Type Amaranthus edulis1

PubMed Central

Kiirats, Olavi; Lea, Peter J.; Franceschi, Vincent R.; Edwards, Gerald E.

2002-01-01

A mutant of the NAD-malic enzyme-type C4 plant, Amaranthus edulis, which lacks phosphoenolpyruvate carboxylase (PEPC) in the mesophyll cells was studied. Analysis of CO2 response curves of photosynthesis of the mutant, which has normal Kranz anatomy but lacks a functional C4 cycle, provided a direct means of determining the liquid phase-diffusive resistance of atmospheric CO2 to sites of ribulose 1,5-bisphosphate carboxylation inside bundle sheath (BS) chloroplasts (rbs) within intact plants. Comparisons were made with excised shoots of wild-type plants fed 3,3-dichloro-2-(dihydroxyphosphinoyl-methyl)-propenoate, an inhibitor of PEPC. Values of rbs in A. edulis were 70 to 180 m2 s−1 mol−1, increasing as the leaf matured. This is about 70-fold higher than the liquid phase resistance for diffusion of CO2 to Rubisco in mesophyll cells of C3 plants. The values of rbs in A. edulis are sufficient for C4 photosynthesis to elevate CO2 in BS cells and to minimize photorespiration. The calculated CO2 concentration in BS cells, which is dependent on input of rbs, was about 2,000 μbar under maximum rates of CO2 fixation, which is about six times the ambient level of CO2. High re-assimilation of photorespired CO2 was demonstrated in both mutant and wild-type plants at limiting CO2 concentrations, which can be explained by high rbs. Increasing O2 from near zero up to ambient levels under low CO2, resulted in an increase in the gross rate of O2 evolution measured by chlorophyll fluorescence analysis in the PEPC mutant; this increase was simulated from a Rubisco kinetic model, which indicates effective refixation of photorespired CO2 in BS cells. PMID:12376660

Distribution of caspase-14 in epidermis and hair follicles is evolutionarily conserved among mammals.

PubMed

Alibardi, Lorenzo; Tschachler, Erwin; Eckhart, Leopold

2005-10-01

Caspase-14, a member of the caspase family of cysteine proteases, is almost exclusively expressed in the epidermis. Studies on human and mouse cells and tissues have implicated caspase-14 in terminal differentiation of epidermal keratinocytes and in the formation of the stratum corneum. Here we investigated evolutionary aspects of the role of caspase-14 by analyzing its distribution in the epidermis and hair follicles of representative species of placental mammals, marsupials, and monotremes. Immunocytochemical staining showed that caspase-14 is consistently expressed in the granular and corneous layer of the epidermis of all mammalian species investigated. Ultrastructural analysis using gold-labeled anticaspase-14 antibodies revealed that caspase-14 is associated preferentially with keratin bundles and amorphous material of keratohyalin granules, but is also present in nuclei of transitional cells of the granular layer and in corneocytes. In hair follicles, caspase-14 was diffusely present in cornifying cells of the outer root sheath, in the companion layer, and, most abundantly, in the inner root sheath of all mammalian species here analyzed. In Henle and Huxley layers of the inner root sheath, labeling was seen in nuclei and, more diffusely, among trichohyalin granules of cornifying cells. In summary, the tissue expression pattern and the intracellular localization of caspase-14 are highly conserved among diverse mammalian species, suggesting that this enzyme is involved in a molecular process that appeared early in the evolution of mammalian skin. The association of caspase-14 with keratohyalin and trichohyalin granules may indicate a specific role of caspase-14 in the maturation of these keratinocyte-specific structures.

Electron microscopic observations of human sperm whole-mounts after extraction for nuclear matrix and intermediate filaments (NM-IF).

PubMed

Markova, Maya Dyankova

2004-10-01

The extraction for nuclear matrix and intermediate filaments (NM-IF) is used to reveal, isolate and study these highly resistant structures in different cell types. We applied for the first time this chemical dissection to human spermatozoa and observed them as whole-mounts by unembedded electron microscopy. The general appearance of NM-IF extracted sperm cells was preserved, showing the intermediate filament-like properties of their cytoskeletal components. In most heads, a network was observed in subacrosomal position, consisting of hubs interconnected by filaments. It seemed to be overlaid on another, finer network. The neck retained its integrity, allowing observations of the three-dimensional structure of the segmented columns. More distally, axoneme and outer dense fibres were covered by submitochondrial cytoskeleton in the middle piece and fibrous sheath in the principal piece, with the annulus usually detached from the fibrous sheath. End piece microtubules were retained in most cells and showed a tendency of cohesion, remaining in a parallel bundle or forming flat sheets. In conclusion, our results provided additional structural details of human sperm cytoskeleton and demonstrated the advantages of combining different methodological approaches in ultrastructural research.

Reexcision Perineural Invasion and Epithelial Sheath Neuroma Possibly on a Spectrum of Postinjury Reactive Hyperplasia Mediated by IL-6.

PubMed

Wang, James Y; Nuovo, Gerard; Kline, Mitchell; Magro, Cynthia M

2017-01-01

Epithelial sheath neuroma is a rarely recognized but established entity in the medical literature. First described in 2000 by Requena et al, there have only been 7 published cases to date, mostly in female patients and presenting as symptomatic solitary lesions on the back without a known history of trauma. In 2006, Beer et al described and reviewed a dozen cases in which epithelial sheath neuroma-like features were seen in the advent of a surgical procedure, which was termed "re-excision perineural invasion" and attributed to possible eccrine duct implantation during surgery. Our case is a 66-year-old male patient who underwent an excision of a melanocytic neoplasm in which a reactive epithelial sheath neuroma was incidentally discovered in the excision specimen, adjacent to the biopsy site cicatrix. Histologically, there was benign cutaneous nerve hyperplasia with a proliferation of squamous epithelium in intimate apposition to the nerve bundles in the superficial dermis. We postulate that the process active in the formation of re-excision perineural invasion is the same as in epithelial sheath neuroma and that minor trauma not appreciable on histologic examination is responsible in the latter entity. We performed IL-6 staining and documented that IL-6 was upregulated at the interface of the nerve and reactive epithelium, but was absent in nerves distant from the site of surgery, suggesting that IL-6 may be essential to the lesion's development. The recognition of reactive epithelial sheath neuroma including the subcategory of re-excision perineural invasion is crucial for the dermatopathologist to prevent mislabeling this reactive entity as a perineural squamous cell carcinoma, which has clinical consequences for the patient such as wider re-excision and radiation treatment. Additionally, we have identified a potential pathophysiologic basis for this lesion.

Anatomy and ultrastructure of embryonic leaves of the C4 species Setaria viridis.

PubMed

Junqueira, Nicia E G; Ortiz-Silva, Bianca; Leal-Costa, Marcos Vinícius; Alves-Ferreira, Márcio; Dickinson, Hugh G; Langdale, Jane A; Reinert, Fernanda

2018-05-11

Setaria viridis is being promoted as a model C4 photosynthetic plant because it has a small genome (~515 Mb), a short life cycle (~60 d) and it can be transformed. Unlike other C4 grasses such as maize, however, there is very little information about how C4 leaf anatomy (Kranz anatomy) develops in S. viridis. As a foundation for future developmental genetic studies, we provide an anatomical and ultrastructural framework of early shoot development in S. viridis, focusing on the initiation of Kranz anatomy in seed leaves. Setaria viridis seeds were germinated and divided into five stages covering development from the dry seed (stage S0) to 36 h after germination (stage S4). Material at each of these stages was examined using conventional light, scanning and transmission electron microscopy. Dry seeds contained three embryonic leaf primordia at different developmental stages (plastochron 1-3 primordia). The oldest (P3) leaf primordium possessed several procambial centres whereas P2 displayed only ground meristem. At the tip of P3 primordia at stage S4, C4 leaf anatomy typical of the malate dehydrogenase-dependent nicotinamide dinucleotide phosphate (NADP-ME) subtype was evident in that vascular bundles lacked a mestome layer and were surrounded by a single layer of bundle sheath cells that contained large, centrifugally located chloroplasts. Two to three mesophyll cells separated adjacent vascular bundles and one mesophyll cell layer on each of the abaxial and adaxial sides delimited vascular bundles from the epidermis. The morphological trajectory reported here provides a foundation for studies of gene regulation during early leaf development in S. viridis and a framework for comparative analyses with other C4 grasses.

Diffusion and bulk flow in phloem loading: A theoretical analysis of the polymer trap mechanism for sugar transport in plants

NASA Astrophysics Data System (ADS)

Dölger, Julia; Rademaker, Hanna; Liesche, Johannes; Schulz, Alexander; Bohr, Tomas

2014-10-01

Plants create sugar in the mesophyll cells of their leaves by photosynthesis. This sugar, mostly sucrose, has to be loaded via the bundle sheath into the phloem vascular system (the sieve elements), where it is distributed to growing parts of the plant. We analyze the feasibility of a particular loading mechanism, active symplasmic loading, also called the polymer trap mechanism, where sucrose is transformed into heavier sugars, such as raffinose and stachyose, in the intermediary-type companion cells bordering the sieve elements in the minor veins of the phloem. Keeping the heavier sugars from diffusing back requires that the plasmodesmata connecting the bundle sheath with the intermediary cell act as extremely precise filters, which are able to distinguish between molecules that differ by less than 20% in size. In our modeling, we take into account the coupled water and sugar movement across the relevant interfaces, without explicitly considering the chemical reactions transforming the sucrose into the heavier sugars. Based on the available data for plasmodesmata geometry, sugar concentrations, and flux rates, we conclude that this mechanism can in principle function, but that it requires pores of molecular sizes. Comparing with the somewhat uncertain experimental values for sugar export rates, we expect the pores to be only 5%-10% larger than the hydraulic radius of the sucrose molecules. We find that the water flow through the plasmodesmata, which has not been quantified before, contributes only 10%-20% to the sucrose flux into the intermediary cells, while the main part is transported by diffusion. On the other hand, the subsequent sugar translocation into the sieve elements would very likely be carried predominantly by bulk water flow through the plasmodesmata. Thus, in contrast to apoplasmic loaders, all the necessary water for phloem translocation would be supplied in this way with no need for additional water uptake across the plasma membranes of the phloem.

Diffusion and bulk flow in phloem loading: a theoretical analysis of the polymer trap mechanism for sugar transport in plants.

PubMed

Dölger, Julia; Rademaker, Hanna; Liesche, Johannes; Schulz, Alexander; Bohr, Tomas

2014-10-01

Plants create sugar in the mesophyll cells of their leaves by photosynthesis. This sugar, mostly sucrose, has to be loaded via the bundle sheath into the phloem vascular system (the sieve elements), where it is distributed to growing parts of the plant. We analyze the feasibility of a particular loading mechanism, active symplasmic loading, also called the polymer trap mechanism, where sucrose is transformed into heavier sugars, such as raffinose and stachyose, in the intermediary-type companion cells bordering the sieve elements in the minor veins of the phloem. Keeping the heavier sugars from diffusing back requires that the plasmodesmata connecting the bundle sheath with the intermediary cell act as extremely precise filters, which are able to distinguish between molecules that differ by less than 20% in size. In our modeling, we take into account the coupled water and sugar movement across the relevant interfaces, without explicitly considering the chemical reactions transforming the sucrose into the heavier sugars. Based on the available data for plasmodesmata geometry, sugar concentrations, and flux rates, we conclude that this mechanism can in principle function, but that it requires pores of molecular sizes. Comparing with the somewhat uncertain experimental values for sugar export rates, we expect the pores to be only 5%-10% larger than the hydraulic radius of the sucrose molecules. We find that the water flow through the plasmodesmata, which has not been quantified before, contributes only 10%-20% to the sucrose flux into the intermediary cells, while the main part is transported by diffusion. On the other hand, the subsequent sugar translocation into the sieve elements would very likely be carried predominantly by bulk water flow through the plasmodesmata. Thus, in contrast to apoplasmic loaders, all the necessary water for phloem translocation would be supplied in this way with no need for additional water uptake across the plasma membranes of the phloem.

Biomechanics and functional morphology of a climbing monocot

PubMed Central

Hesse, Linnea; Wagner, Sarah T.; Neinhuis, Christoph

2016-01-01

Plants with a climbing growth habit possess unique biomechanical properties arising from adaptations to changing loading conditions connected with close attachment to mechanical supports. In monocot climbers, mechanical adaptation is restricted by the absence of a bifacial vascular cambium. Flagellaria indica was used to investigate the mechanical properties and adaptations of a monocot climber that, uniquely, attaches to the surrounding vegetation via leaf tendrils. Biomechanical methods such as three-point bending and torsion tests were used together with anatomical studies on tissue development, modification and distribution. In general, the torsional modulus was lower than the bending modulus; hence, torsional stiffness was less than flexural stiffness. Basal parts of mature stems showed the greatest stiffness while that of more apical stem segments levelled off. Mechanical properties were modulated via tissue maturation processes mainly affecting the peripheral region of the stem. Peripheral vascular bundles showed a reduction in the amount of conducting tissue while the proportion and density of the bundle sheath increased. Furthermore, adjacent bundle sheaths merged resulting in a dense ring of fibrous tissue. Although F. indica lacks secondary cambial growth, the climbing habit is facilitated by a complex interaction of tissue maturation and attachment. PMID:26819259

Comparison of physiological and anatomical changes of C3 (Oryza sativa [L.]) and C4 (Echinochloa crusgalli [L.]) leaves in response to drought stress

NASA Astrophysics Data System (ADS)

Hamim, Hamim; Banon, Sri; Dorly, Dorly

2016-01-01

The experiment aimed to analyse the different response of C3 (Oryza sativa L.) and C4 (Echinochloa crusgalli L.) species to drought stress based on physiological and anatomical properties. Seeds of rice (Oryza sativa) and Echinochloa (Echinochloa crusgalli) were grown in 15 cm (D) pot for 6 weeks under well-watered conditions. After 6 weeks the plants were divided into two groups, (1) well-watered which were watered daily, and (2) drought stress which were withheld from watering for 6 days. After 6 days of drought, the plants were then re-watered to analyse plant recovery. During drought period, the plants were analysed for growth, leaf relative water content (RWC), photosynthesis, and leaf anatomy. Drought stress significantly reduced leaf RWC of both species, but the reduction was bigger in rice than in Echinochloa. The maximum efficiency of photosynthesis (Fv/Fm) was decrease significantly in response to drought stress by about 48.04% in rice, while it was only 34.40% in Echinochloa. Anatomical analysis showed drought treatment tended to reduce leaf thickness in the area of bulliform cell, major- as well as intervein and xylem diameter, more in Echinochloa than in rice, suggesting that the decrease of vein and xylem diameter is among the anatomical parameters that is important to overcome from drought stress in Echinochloa. The number of chloroplast in the mesophyll cell and bundle sheath cell (BSC) was different between these two species, where in Echinochloa chloroplast was found in both mesophyll as well as BSC, while in rice it was only found in mesophyll cell, confirmed that Echinochloa is a C4 and rice is a C3 species. Interestingly, in Echinochloa, the number of chloroplast was significantly increased due to drought stress in BSC, but not in mesophyll cell. The number of starch granules also dramatically increased in response to drought in the mesophyll cells of rice and Echinochloa, and in the bundle sheath cell of Echinochloa which indicate that C3 cycle may be occurred in C4 species, at least in Echinochloa, especially during drought stress.

Postnatal development of microcyst in the anteroventral cochlear nucleus of the Mongolian gerbil: a light- and electron microscopic study.

PubMed

Yu, Shang-Ming; Ko, Tsui-Ling; Lin, Kwan-Hwa

2011-09-01

We investigated the postnatal formation and origin of the microcyst, which are not fully elucidated at present, in the cochlear nucleus of gerbils. Sixty-six Mongolian gerbils were investigated at the light microscope level, and 35 of them were observed at the electron microscopic level. Foamy structures were evidently found at 2 days of age and remained unchanged through 4-8 days. The first small vacuole, presumably the former microcyst, appeared at 8 days. Myelin sheath bundles first appeared at 13 days. Electron-dense bodies were frequently found in the junction of the superficial layer and the deep layer at 2 days. The medium-sized vacuole was found in close association with the spherical bushy cells in the anteroventral cochlear nucleus (AVCN) as early as 5 weeks. Various large and small vacuoles were presumably coalesced to form a large vacuole at 3 and 6 months. Membranous structures and red blood cells were in the budding-like vacuoles at 6 months. In addition to membranous structures, the microcyst contained distorted mitochondria and parts of myelin sheaths. The vacuole was interposed between spherical bushy cells at age of 10 months. Small vacuoles were mainly located in the flame-shaped neurons at 14 months. An internal detachment and an external protrusion of the myelin sheath into the adjacent microcyst were found. Thus, this study suggests the first appearance of microcysts at 8 days. Also, the microcyst and the blood vessel may exchange their contents through a leakage in the anteroventral cochlear nucleus.

Differences in Stylet Sheath Occurrence and the Fibrous Ring (Sclerenchyma) between xCitroncirus Plants Relatively Resistant or Susceptible to Adults of the Asian Citrus Psyllid Diaphorina citri (Hemiptera: Liviidae)

PubMed Central

Ammar, El-Desouky; Richardson, Matthew L.; Abdo, Zaid; Hall, David G.; Shatters, Robert G.

2014-01-01

The Asian citrus psyllid (ACP, Diaphorina citri, Hemiptera: Liviidae), is the principal vector of the phloem-limited bacteria strongly associated with huanglongbing (HLB), the world’s most serious disease of citrus. Host plant resistance may provide an environmentally safe and sustainable method of controlling ACP and/or HLB. Two xCitroncirus accessions (hybrids of Poncirus trifoliata and Citrus spp.), that are relatively resistant (UN-3881) or relatively susceptible (Troyer-1459) to ACP adults with regard to adult longevity, were compared in relation to ACP feeding behavior and some structural features of the leaf midrib. The settling (putative feeding/probing) sites of ACP adults on various parts of the leaf were not influenced primarily by plant accession. However, fewer ACP stylet sheaths were found in the midrib and fewer stylet sheath termini reached the vascular bundle (phloem and/or xylem) in UN-3881 compared to Troyer-1459 plants. Furthermore, in midribs of UN-3881 leaves the fibrous ring (sclerenchyma) around the phloem was significantly wider (thicker) compared to that in midribs of Troyer-1459 leaves. Our data indicate that feeding and/or probing by ACP adults into the vascular bundle is less frequent in the more resistant (UN-3881) than in the more susceptible (Troyer-1459) accessions. Our results also suggest that the thickness of the fibrous ring may be a barrier to stylet penetration into the vascular bundle, which is important for successful ACP feeding on the phloem and for transmitting HLB-associated bacteria. These results may help in the development of citrus plants resistant to ACP, which in turn could halt or slow the spread of the HLB-associated bacteria by this vector. PMID:25343712

The Role of Bundle Sheath Extensions and Life Form in Stomatal Responses to Leaf Water Status1[W][OA

PubMed Central

Buckley, Thomas N.; Sack, Lawren; Gilbert, Matthew E.

2011-01-01

Bundle sheath extensions (BSEs) are key features of leaf structure with currently little-understood functions. To test the hypothesis that BSEs reduce the hydraulic resistance from the bundle sheath to the epidermis (rbe) and thereby accelerate hydropassive stomatal movements, we compared stomatal responses with reduced humidity and leaf excision among 20 species with heterobaric or homobaric leaves and herbaceous or woody life forms. We hypothesized that low rbe due to the presence of BSEs would increase the rate of stomatal opening (V) during transient wrong-way responses, but more so during wrong-way responses to excision (Ve) than humidity (Vh), thus increasing the ratio of Ve to Vh. We predicted the same trends for herbaceous relative to woody species given greater hydraulic resistance in woody species. We found that Ve, Vh, and their ratio were 2.3 to 4.4 times greater in heterobaric than homobaric leaves and 2.0 to 3.1 times greater in herbaceous than woody species. To assess possible causes for these differences, we simulated these experiments in a dynamic compartment/resistance model, which predicted larger Ve and Ve/Vh in leaves with smaller rbe. These results support the hypothesis that BSEs reduce rbe. Comparison of our data and simulations suggested that rbe is approximately 4 to 16 times larger in homobaric than heterobaric leaves. Our study provides new evidence that variations in the distribution of hydraulic resistance within the leaf and plant are central to understanding dynamic stomatal responses to water status and their ecological correlates and that BSEs play several key roles in the functional ecology of heterobaric leaves. PMID:21459977

Nuclear Involvement in the Appearance of a Chloroplast-Encoded 32,000 Dalton Thylakoid Membrane Polypeptide Integral to the Photosystem II Complex 1

PubMed Central

Leto, Kenneth J.; Keresztes, Aron; Arntzen, Charles J.

1982-01-01

The genetic locus for the high chlorophyll fluorescent photosystem II-deficient maize mutant hcf*-3 has been definitively located to the nuclear genome. Fluorography of lamellar polypeptides labeled with [35S]methionine in vivo revealed the specific loss of a heavily labeled 32,000 dalton thylakoid membrane polypeptide as well as its chloroplast encoded precursor species at 34,000 daltons. Examination of freeze-fractured mesophyll and bundle sheath thylakoids from hcf*-3 revealed that both plastid types lacked the large EFs particles believed to consist of the photosystem II reaction center-core complex and associated light harvesting chlorophyll-proteins. The present evidence suggests that the synthesis or turnover/integration of the chloroplast-encoded 34,000 to 32,000 dalton polypeptide is under nuclear control, and that these polyipeptides are integral components of photosystem II which may be required for the assembly or structural stabilization of newly formed photosystem II reaction centers in both mesophyll and bundle sheath chloroplasts. Images PMID:16662421

In silico investigation of blast-induced intracranial fluid cavitation as it potentially leads to traumatic brain injury

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

Haniff, S.; Taylor, P. A.

In this paper, we conducted computational macroscale simulations predicting blast-induced intracranial fluid cavitation possibly leading to brain injury. To further understanding of this problem, we developed microscale models investigating the effects of blast-induced cavitation bubble collapse within white matter axonal fiber bundles of the brain. We model fiber tracks of myelinated axons whose diameters are statistically representative of white matter. Nodes of Ranvier are modeled as unmyelinated sections of axon. Extracellular matrix envelops the axon fiber bundle, and gray matter is placed adjacent to the bundle. Cavitation bubbles are initially placed assuming an intracranial wave has already produced them. Pressuremore » pulses, of varied strengths, are applied to the upper boundary of the gray matter and propagate through the model, inducing bubble collapse. Simulations, conducted using the shock wave physics code CTH, predict an increase in pressure and von Mises stress in axons downstream of the bubbles after collapse. This appears to be the result of hydrodynamic jetting produced during bubble collapse. Interestingly, results predict axon cores suffer significantly lower shear stresses from proximal bubble collapse than does their myelin sheathing. Finally, simulations also predict damage to myelin sheathing, which, if true, degrades axonal electrical transmissibility and general health of the white matter structures in the brain.« less

In silico investigation of blast-induced intracranial fluid cavitation as it potentially leads to traumatic brain injury

DOE PAGES

Haniff, S.; Taylor, P. A.

2017-10-17

In this paper, we conducted computational macroscale simulations predicting blast-induced intracranial fluid cavitation possibly leading to brain injury. To further understanding of this problem, we developed microscale models investigating the effects of blast-induced cavitation bubble collapse within white matter axonal fiber bundles of the brain. We model fiber tracks of myelinated axons whose diameters are statistically representative of white matter. Nodes of Ranvier are modeled as unmyelinated sections of axon. Extracellular matrix envelops the axon fiber bundle, and gray matter is placed adjacent to the bundle. Cavitation bubbles are initially placed assuming an intracranial wave has already produced them. Pressuremore » pulses, of varied strengths, are applied to the upper boundary of the gray matter and propagate through the model, inducing bubble collapse. Simulations, conducted using the shock wave physics code CTH, predict an increase in pressure and von Mises stress in axons downstream of the bubbles after collapse. This appears to be the result of hydrodynamic jetting produced during bubble collapse. Interestingly, results predict axon cores suffer significantly lower shear stresses from proximal bubble collapse than does their myelin sheathing. Finally, simulations also predict damage to myelin sheathing, which, if true, degrades axonal electrical transmissibility and general health of the white matter structures in the brain.« less

Functional anatomy controls ion distribution in banana leaves: significance of Na+ seclusion at the leaf margins.

PubMed

Shapira, Or; Khadka, Sudha; Israeli, Yair; Shani, Uri; Schwartz, Amnon

2009-05-01

Typical salt stress symptoms appear in banana (Musa sp., cv. 'Grand Nain' AAA) only along the leaf margins. Mineral analysis of the dry matter of plants treated with increasing concentrations of KCl or NaCl revealed significant accumulation of Na+, but not of K+ or Cl(-), in the affected leaf margins. The differential distribution of the three ions suggests that water and ion movement out of the xylem is mostly symplastic and, in contrast to K+ and Cl(-), there exists considerable resistance to the flow of Na+ from the xylem to the adjacent mesophyll and epidermis. The parallel veins of the lamina are enclosed by several layers of bundle sheath parenchyma; in contrast, the large vascular bundle that encircles the entire lamina, and into which the parallel veins merge, lacks a complete bundle sheath. Xylem sap containing a high concentration of Na+ is 'pulled' by water tension from the marginal vein back into the adjacent mesophyll without having to cross a layer of parenchyma tissue. When the marginal vein was dissected from the lamina, the pattern of Na+ distribution in the margins changed markedly. The distinct anatomy of the marginal vein plays a major role in the accumulation of Na+ in the margins, with the latter serving as a 'dumping site' for toxic molecules.

In silico investigation of blast-induced intracranial fluid cavitation as it potentially leads to traumatic brain injury

NASA Astrophysics Data System (ADS)

Haniff, S.; Taylor, P. A.

2017-11-01

We conducted computational macroscale simulations predicting blast-induced intracranial fluid cavitation possibly leading to brain injury. To further understanding of this problem, we developed microscale models investigating the effects of blast-induced cavitation bubble collapse within white matter axonal fiber bundles of the brain. We model fiber tracks of myelinated axons whose diameters are statistically representative of white matter. Nodes of Ranvier are modeled as unmyelinated sections of axon. Extracellular matrix envelops the axon fiber bundle, and gray matter is placed adjacent to the bundle. Cavitation bubbles are initially placed assuming an intracranial wave has already produced them. Pressure pulses, of varied strengths, are applied to the upper boundary of the gray matter and propagate through the model, inducing bubble collapse. Simulations, conducted using the shock wave physics code CTH, predict an increase in pressure and von Mises stress in axons downstream of the bubbles after collapse. This appears to be the result of hydrodynamic jetting produced during bubble collapse. Interestingly, results predict axon cores suffer significantly lower shear stresses from proximal bubble collapse than does their myelin sheathing. Simulations also predict damage to myelin sheathing, which, if true, degrades axonal electrical transmissibility and general health of the white matter structures in the brain.

Establishment of dermal sheath cell line from Cashmere goat and characterizing cytokeratin 13 as its novel biomarker.

PubMed

Zhu, Bing; Guo, Zhili; Jin, Muzi; Bai, Yujuan; Yang, Wenliang; Hui, Lihua

2018-05-01

To establish a dermal sheath cell line, a dermal papilla cell line and a outer root sheath cell line from Cashmere goat and clarify the similarities and differences among them. We established a dermal sheath cell line, a dermal papilla cell line and a outer root sheath cell line from the pelage skin hair follicles of Cashmere goat. The growth rate of dermal sheath cells was intermediate between that of dermal papilla cells and outer root sheath cells. Immunofluorescence experiments and reverse transcription-polymerase chain reaction analysis showed that at both the transcriptional and translational levels, the dermal sheath cells were alpha-smooth muscle actin (α-SMA) + /cytokeratin 13 + , while the dermal papilla cells were α-SMA + /cytokeratin 13 - and the outer root sheath cells were α-SMA - /cytokeratin 13 + . Patterns of cytokeratin 13 expression could distinguish the dermal sheath cells from the dermal papilla cells. These results suggest that cytokeratin 13 could serve as a novel biomarker for dermal sheath cells of Cashmere goat, and should prove useful for researchers investigating dermal stem cells or interaction of different types of cells during hair cycle.

Sperm storage, sperm translocation and genitalia formation in females of the terrestrial isopod Armadillidium vulgare (Crustacea, Peracarida, Isopoda).

PubMed

Ziegler, Andreas; Suzuki, Sachiko

2011-01-01

We investigated sperm storage, sperm transfer from the oviduct to the seminal receptacle, and formation of the cuticular genitalia in female Armadillidium vulgare using light and electron microscopy. Apolysis of the genitalia within the oviduct forms a circum-genital lumen. During insemination this space is filled with immobile spermatozoa. Sperm transfer into the seminal receptacle takes place before oviposition. Within a peculiar proximal neck region of the oviduct spermatozoa are bundled and enveloped by a folded epicuticular layer. The envelope tightly surrounds the spermatozoa probably forming a seal against the main part of the circum-genital lumen. We propose that hydrostatic pressure produced by the muscle cells surrounding the oviduct leads to sperm transfer into the seminal receptacle. Within the seminal receptacle the sperm bundle forms a ring just around the orifice to the oviduct. At one side sheath-like extensions of epithelial cells surround the ring of spermatozoa holding it in place. At the other side oocytes would have access to the sperm during oviposition, probably allowing for fertilisation when they pass right through the ring of spermatozoa. After oviposition the new genitalia are formed from epicuticular folds, and cuticle secreted by the epithelial cells. Copyright © 2010 Elsevier Ltd. All rights reserved.

Conductive cable fibers with insulating surface prepared by coaxial electrospinning of multiwalled nanotubes and cellulose.

PubMed

Miyauchi, Minoru; Miao, Jianjun; Simmons, Trevor J; Lee, Jong-Won; Doherty, Thomas V; Dordick, Jonathan S; Linhardt, Robert J

2010-09-13

Core-sheath multiwalled carbon nanotube (MWNT)-cellulose fibers of diameters from several hundreds of nanometers to several micrometers were prepared by coaxial electrospinning from a nonvolatile, nonflammable ionic liquid (IL) solvent, 1-methyl-3-methylimidazolium acetate ([EMIM][Ac]). MWNTs were dispersed in IL to form a gel solution. This gel core solution was electrospun surrounded by a sheath solution of cellulose dissolved in the same IL. Electrospun fibers were collected in a coagulation bath containing ethanol-water to remove the IL completely and dried to form core-sheath MWNT-cellulose fibers having a cable structure with a conductive core and insulating sheath. Enzymatic treatment of a portion of a mat of these fibers with cellulase selectively removed the cellulose sheath exposing the MWNT core for connection to an electrode. These MWNT-cellulose fiber mats demonstrated excellent conductivity because of a conductive pathway of bundled MWNTs. Fiber mat conductivity increased with increasing ratio of MWNT in the fibers with a maximum conductivity of 10.7 S/m obtained at 45 wt % MWNT loading.

The role of plasma membrane aquaporins in regulating the bundle sheath-mesophyll continuum and leaf hydraulics.

PubMed

Sade, Nir; Shatil-Cohen, Arava; Attia, Ziv; Maurel, Christophe; Boursiac, Yann; Kelly, Gilor; Granot, David; Yaaran, Adi; Lerner, Stephen; Moshelion, Menachem

2014-11-01

Our understanding of the cellular role of aquaporins (AQPs) in the regulation of whole-plant hydraulics, in general, and extravascular, radial hydraulic conductance in leaves (K(leaf)), in particular, is still fairly limited. We hypothesized that the AQPs of the vascular bundle sheath (BS) cells regulate K(leaf). To examine this hypothesis, AQP genes were silenced using artificial microRNAs that were expressed constitutively or specifically targeted to the BS. MicroRNA sequences were designed to target all five AQP genes from the PLASMA MEMBRANE-INTRINSIC PROTEIN1 (PIP1) subfamily. Our results show that the constitutively silenced PIP1 (35S promoter) plants had decreased PIP1 transcript and protein levels and decreased mesophyll and BS osmotic water permeability (P(f)), mesophyll conductance of CO2, photosynthesis, K(leaf), transpiration, and shoot biomass. Plants in which the PIP1 subfamily was silenced only in the BS (SCARECROW:microRNA plants) exhibited decreased mesophyll and BS Pf and decreased K(leaf) but no decreases in the rest of the parameters listed above, with the net result of increased shoot biomass. We excluded the possibility of SCARECROW promoter activity in the mesophyll. Hence, the fact that SCARECROW:microRNA mesophyll exhibited reduced P(f), but not reduced mesophyll conductance of CO2, suggests that the BS-mesophyll hydraulic continuum acts as a feed-forward control signal. The role of AQPs in the hierarchy of the hydraulic signal pathway controlling leaf water status under normal and limited-water conditions is discussed. © 2014 American Society of Plant Biologists. All Rights Reserved.

ELIGULUM-A Regulates Lateral Branch and Leaf Development in Barley1[OPEN

PubMed Central

Haaning, Allison; Bilgic, Hatice

2018-01-01

The shoot apical and axillary meristems control shoot development, effectively influencing lateral branch and leaf formation. The barley (Hordeum vulgare) uniculm2 (cul2) mutation blocks axillary meristem development, and mutant plants lack lateral branches (tillers) that normally develop from the crown. A genetic screen for cul2 suppressors recovered two recessive alleles of ELIGULUM-A (ELI-A) that partially rescued the cul2 tillering phenotype. Mutations in ELI-A produce shorter plants with fewer tillers and disrupt the leaf blade-sheath boundary, producing liguleless leaves and reduced secondary cell wall development in stems and leaves. ELI-A is predicted to encode an unannotated protein containing an RNaseH-like domain that is conserved in land plants. ELI-A transcripts accumulate at the preligule boundary, the developing ligule, leaf margins, cells destined to develop secondary cell walls, and cells surrounding leaf vascular bundles. Recent studies have identified regulatory similarities between boundary development in leaves and lateral organs. Interestingly, we observed ELI-A transcripts at the preligule boundary, suggesting that ELI-A contributes to boundary formation between the blade and sheath. However, we did not observe ELI-A transcripts at the axillary meristem boundary in leaf axils, suggesting that ELI-A is not involved in boundary development for axillary meristem development. Our results show that ELI-A contributes to leaf and lateral branch development by acting as a boundary gene during ligule development but not during lateral branch development. PMID:29440592

Sites of action of elevated CO2 on leaf development in rice: discrimination between the effects of elevated CO2 and nitrogen deficiency.

PubMed

Tsutsumi, Koichi; Konno, Masae; Miyazawa, Shin-Ichi; Miyao, Mitsue

2014-02-01

Elevated CO2 concentrations (eCO2) trigger various plant responses. Despite intensive studies of these responses, the underlying mechanisms remain obscure. In this work, we investigated when and how leaf physiology and anatomy are affected by eCO2 in rice plants. We analyzed the most recently fully expanded leaves that developed successively after transfer of the plant to eCO2. To discriminate between the effects of eCO2 and those of nitrogen deficiency, we used three different levels of N application. We found that a decline in the leaf soluble protein content (on a leaf area basis) at eCO2 was only observed under N deficiency. The length and width of the leaf blade were reduced by both eCO2 and N deficiency, whereas the blade thickness was increased by eCO2 but was not affected by N deficiency. The change in length by eCO2 became detectable in the secondly fully expanded leaf, and those in width and thickness in the thirdly fully expanded leaf, which were at the leaf developmental stages P4 and P3, respectively, at the onset of the eCO2 treatment. The decreased blade length at eCO2 was associated with a decrease in the epidermal cell number on the adaxial side and a reduction in cell length on the abaxial side. The decreased width resulted from decreased numbers of small vascular bundles and epidermal cell files. The increased thickness was ascribed mainly to enhanced development of bundle sheath extensions at the ridges of vascular bundles. These observations enable us to identify the sites of action of eCO2 on rice leaf development.

Occurrence and forms of Kranz anatomy in photosynthetic organs and characterization of NAD-ME subtype C4 photosynthesis in Blepharis ciliaris (L.) B. L. Burtt (Acanthaceae).

PubMed

Akhani, Hossein; Ghasemkhani, Maraym; Chuong, Simon D X; Edwards, Gerald E

2008-01-01

Blepharis (Acanthaceae) is an Afroasiatic genus comprising 129 species which occur in arid and semi-arid habitats. This is the only genus in the family which is reported to have some C(4) species. Blepharis ciliaris (L.) B. L. Burtt. is a semi-desert species with distribution in Iran, Oman, and Pakistan. Its form of photosynthesis was investigated by studying different organs. C(4)-type carbon isotope composition, the presence of atriplicoid type Kranz anatomy, and compartmentation of starch all indicate performance of C(4) photosynthesis in cotyledons, leaves, and the lamina part of bracts. A continuous layer of distinctive bundle sheath cells (Kranz cells) encircle the vascular bundles in cotyledons and the lateral vascular bundles in leaves. In older leaves, there is extensive development of ground tissue in the midrib and the Kranz tissue becomes interrupted on the abaxial side, and then becomes completely absent in the mature leaf base. Cotyledons have 5-6 layers, and leaves 2-3 layers, of spongy chlorenchyma beneath the veins near the adaxial side of the leaf, indicating bifacial organization of chlorenchyma. As the plant matures, bracts and spines develop and contribute to carbon assimilation through an unusual arrangement of Kranz anatomy which depends on morphology and exposure to light. Stems do not contribute to carbon assimilation, as they lack chlorenchyma tissue and Kranz anatomy. Analysis of C(4) acid decarboxylases by western blot indicates B. ciliaris is an NAD-malic enzyme type C(4) species, which is consistent with the Kranz cells having chloroplasts with well-developed grana and abundant mitochondria.

The role of gravity in leaf blade curvatures

NASA Technical Reports Server (NTRS)

Hayes, A. B.

1984-01-01

In the past year we have gained useful information on several aspects of leaf blade growth. The most important observations are as follows: The C(14)-1AA moves preferentially in a gravipositive dorsiventral direction through the blade. This movement is inhibited by inversion of the blade. The responding cells in leaf blade hyponasty are in the lower epidermis and bundle sheath cells. Two additional responses in the leaf were characterized. In addition to blade curvature, the leaf shows petiole curvature and changes in the liminal angle subtended by the pulvinus. Ethylene production was studied under a number of conditions. The blade, rather than the petiole or pulvinus, is the principal site of auxin-promoted ethylene synthesis. The effects of a variety of agents on the blade, including gibberellic acid, abscisic acid, vanadate, low pH buffers, and blue light were reviewed.

Pharmacognostic studies of the leaves and stem of Careya arborea Roxb.

PubMed Central

Gupta, Prakash Chandra; Sharma, Nisha; Rao, Ch V

2012-01-01

Objective To study detailed pharmacognostic profile of leaves and stem of Careya arborea (C. arborea) Roxb. (Lecthyidaceae), an important medicinal plant in the Indian system of medicine. Methods Leaf and stem samples of C. arborea were studied by macroscopical, microscopical, physicochemical, phytochemical, fluorescence analysis of powder of the plant and other methods for standardization recommended by WHO. Results Macroscopically, the leaves are simple, broadly obovate in shape, acuminate apex with crenate, dentate margin, petioles (0.1–1.8 cm) long. Microscopically, the leaf showed the presence of median large size vascular bundle covered with fibrous bundle sheath, arrangement of xylem in cup shape and presence of cortical vascular bundle, patches of sclerenchyma, phloem fibers in groups and brown pigment containing cells in stem are some of the diagnostic features noted from anatomical study. Powder microscopy of leaf revealed the presence of parenchyma cells, xylem with pitted vessels and epidermis with anisocytic stomata. The investigations also included leaf surface data; quantitative leaf microscopy and fluorescence analysis. Physiochemical parameters such as loss on drying, swelling index, extractive values and ash values were also determined and results showed that total ash of the stem bark was about two times higher than leaf and water soluble extractive value of leaf and stem bark was two times higher than alcohol soluble extractive value. Preliminary phytochemical screening showed the presence of triterpenoids, saponins, tannins and flavonoids. Conclusions The results of the study can serve as a valuable source of information and provide suitable standards for identification of this plant material in future investigations and applications. PMID:23569939

The influence of leaf anatomy on the internal light environment and photosynthetic electron transport rate: exploration with a new leaf ray tracing model

PubMed Central

Xiao, Yi; Tholen, Danny; Zhu, Xin-Guang

2016-01-01

Leaf photosynthesis is determined by biochemical properties and anatomical features. Here we developed a three-dimensional leaf model that can be used to evaluate the internal light environment of a leaf and its implications for whole-leaf electron transport rates (J). This model includes (i) the basic components of a leaf, such as the epidermis, palisade and spongy tissues, as well as the physical dimensions and arrangements of cell walls, vacuoles and chloroplasts; and (ii) an efficient forward ray-tracing algorithm, predicting the internal light environment for light of wavelengths between 400 and 2500nm. We studied the influence of leaf anatomy and ambient light on internal light conditions and J. The results show that (i) different chloroplasts can experience drastically different light conditions, even when they are located at the same distance from the leaf surface; (ii) bundle sheath extensions, which are strips of parenchyma, collenchyma or sclerenchyma cells connecting the vascular bundles with the epidermis, can influence photosynthetic light-use efficiency of leaves; and (iii) chloroplast positioning can also influence the light-use efficiency of leaves. Mechanisms underlying leaf internal light heterogeneity and implications of the heterogeneity for photoprotection and for the convexity of the light response curves are discussed. PMID:27702991

Consequences of C4 differentiation for chloroplast membrane proteomes in maize mesophyll and bundle sheath cells.

PubMed

Majeran, Wojciech; Zybailov, Boris; Ytterberg, A Jimmy; Dunsmore, Jason; Sun, Qi; van Wijk, Klaas J

2008-09-01

Chloroplasts of maize leaves differentiate into specific bundle sheath (BS) and mesophyll (M) types to accommodate C(4) photosynthesis. Chloroplasts contain thylakoid and envelope membranes that contain the photosynthetic machineries and transporters but also proteins involved in e.g. protein homeostasis. These chloroplast membranes must be specialized within each cell type to accommodate C(4) photosynthesis and regulate metabolic fluxes and activities. This quantitative study determined the differentiated state of BS and M chloroplast thylakoid and envelope membrane proteomes and their oligomeric states using innovative gel-based and mass spectrometry-based protein quantifications. This included native gels, iTRAQ, and label-free quantification using an LTQ-Orbitrap. Subunits of Photosystems I and II, the cytochrome b(6)f, and ATP synthase complexes showed average BS/M accumulation ratios of 1.6, 0.45, 1.0, and 1.33, respectively, whereas ratios for the light-harvesting complex I and II families were 1.72 and 0.68, respectively. A 1000-kDa BS-specific NAD(P)H dehydrogenase complex with associated proteins of unknown function containing more than 15 proteins was observed; we speculate that this novel complex possibly functions in inorganic carbon concentration when carboxylation rates by ribulose-bisphosphate carboxylase/oxygenase are lower than decarboxylation rates by malic enzyme. Differential accumulation of thylakoid proteases (Egy and DegP), state transition kinases (STN7,8), and Photosystem I and II assembly factors was observed, suggesting that cell-specific photosynthetic electron transport depends on post-translational regulatory mechanisms. BS/M ratios for inner envelope transporters phosphoenolpyruvate/P(i) translocator, Dit1, Dit2, and Mex1 were determined and reflect metabolic fluxes in carbon metabolism. A wide variety of hundreds of other proteins showed differential BS/M accumulation. Mass spectral information and functional annotations are available through the Plant Proteome Database. These data are integrated with previous data, resulting in a model for C(4) photosynthesis, thereby providing new rationales for metabolic engineering of C(4) pathways and targeted analysis of genetic networks that coordinate C(4) differentiation.

Comparative studies of C3 and C4 Atriplex hybrids in the genomics era: physiological assessments

PubMed Central

Oakley, Jason C.; Sultmanis, Stefanie; Stinson, Corey R.; Sage, Tammy L.; Sage, Rowan F.

2014-01-01

We crossed the C3 species Atriplex prostrata with the C4 species Atriplex rosea to produce F1 and F2 hybrids. All hybrids exhibited C3-like δ13C values, and had reduced rates of net CO2 assimilation compared with A. prostrata. The activities of the major C4 cycle enzymes PEP carboxylase, NAD-malic enzyme, and pyruvate-Pi dikinase in the hybrids were at most 36% of the C4 values. These results demonstrate the C4 metabolic cycle was disrupted in the hybrids. Photosynthetic CO2 compensation points (Г) of the hybrids were generally midway between the C3 and C4 values, and in most hybrids were accompanied by low, C3-like activities in one or more of the major C4 cycle enzymes. This supports the possibility that most hybrids use a photorespiratory glycine shuttle to concentrate CO2 into the bundle sheath cells. One hybrid exhibited a C4-like Г of 4 µmol mol–1, indicating engagement of a C4 metabolic cycle. Consistently, this hybrid had elevated activities of all measured C4 cycle enzymes relative to the C3 parent; however, C3-like carbon isotope ratios indicate the low Г is mainly due to a photorespiratory glycine shuttle. The anatomy of the hybrids resembled that of C3-C4 intermediate species using a glycine shuttle to concentrate CO2 in the bundle sheath, and is further evidence that this physiology is the predominant, default condition of the F2 hybrids. Progeny of these hybrids should further segregate C3 and C4 traits and in doing so assist in the discovery of C4 genes using high-throughput methods of the genomics era. PMID:24675672

77 FR 50746 - Self-Regulatory Organizations; NYSE Arca, Inc.; Order Approving a Proposed Rule Change Amending...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-22

... a single sheath can hold either one cross connect or several cross connects in multiples of six (e.g., six, twelve, eighteen or twenty-four cross connects). The Exchange proposes to charge a $500 initial... and install one cross connect between cabinets. For a bundle of six cross connects, the monthly charge...

Structural and metabolic transitions of C4 leaf development and differentiation defined by microscopy and quantitative proteomics in maize.

PubMed

Majeran, Wojciech; Friso, Giulia; Ponnala, Lalit; Connolly, Brian; Huang, Mingshu; Reidel, Edwin; Zhang, Cankui; Asakura, Yukari; Bhuiyan, Nazmul H; Sun, Qi; Turgeon, Robert; van Wijk, Klaas J

2010-11-01

C(4) grasses, such as maize (Zea mays), have high photosynthetic efficiency through combined biochemical and structural adaptations. C(4) photosynthesis is established along the developmental axis of the leaf blade, leading from an undifferentiated leaf base just above the ligule into highly specialized mesophyll cells (MCs) and bundle sheath cells (BSCs) at the tip. To resolve the kinetics of maize leaf development and C(4) differentiation and to obtain a systems-level understanding of maize leaf formation, the accumulation profiles of proteomes of the leaf and the isolated BSCs with their vascular bundle along the developmental gradient were determined using large-scale mass spectrometry. This was complemented by extensive qualitative and quantitative microscopy analysis of structural features (e.g., Kranz anatomy, plasmodesmata, cell wall, and organelles). More than 4300 proteins were identified and functionally annotated. Developmental protein accumulation profiles and hierarchical cluster analysis then determined the kinetics of organelle biogenesis, formation of cellular structures, metabolism, and coexpression patterns. Two main expression clusters were observed, each divided in subclusters, suggesting that a limited number of developmental regulatory networks organize concerted protein accumulation along the leaf gradient. The coexpression with BSC and MC markers provided strong candidates for further analysis of C(4) specialization, in particular transporters and biogenesis factors. Based on the integrated information, we describe five developmental transitions that provide a conceptual and practical template for further analysis. An online protein expression viewer is provided through the Plant Proteome Database.

Amborella trichopoda, plasmodesmata, and the evolution of phloem loading.

PubMed

Turgeon, Robert; Medville, Richard

2011-01-01

Phloem loading is the process by which photoassimilates synthesized in the mesophyll cells of leaves enter the sieve elements and companion cells of minor veins in preparation for long distance transport to sink organs. Three loading strategies have been described: active loading from the apoplast, passive loading via the symplast, and passive symplastic transfer followed by polymer trapping of raffinose and stachyose. We studied phloem loading in Amborella trichopoda, a premontane shrub that may be sister to all other flowering plants. The minor veins of A. trichopoda contain intermediary cells, indicative of the polymer trap mechanism, forming an arc on the abaxial side and subtending a cluster of ordinary companion cells in the interior of the veins. Intermediary cells are linked to bundle sheath cells by highly abundant plasmodesmata whereas ordinary companion cells have few plasmodesmata, characteristic of phloem that loads from the apoplast. Intermediary cells, ordinary companion cells, and sieve elements form symplastically connected complexes. Leaves provided with (14)CO(2) translocate radiolabeled sucrose, raffinose, and stachyose. Therefore, structural and physiological evidence suggests that both apoplastic and polymer trapping mechanisms of phloem loading operate in A. trichopoda. The evolution of phloem loading strategies is complex and may be difficult to resolve.

The influence of leaf anatomy on the internal light environment and photosynthetic electron transport rate: exploration with a new leaf ray tracing model.

PubMed

Xiao, Yi; Tholen, Danny; Zhu, Xin-Guang

2016-11-01

Leaf photosynthesis is determined by biochemical properties and anatomical features. Here we developed a three-dimensional leaf model that can be used to evaluate the internal light environment of a leaf and its implications for whole-leaf electron transport rates (J). This model includes (i) the basic components of a leaf, such as the epidermis, palisade and spongy tissues, as well as the physical dimensions and arrangements of cell walls, vacuoles and chloroplasts; and (ii) an efficient forward ray-tracing algorithm, predicting the internal light environment for light of wavelengths between 400 and 2500nm. We studied the influence of leaf anatomy and ambient light on internal light conditions and J The results show that (i) different chloroplasts can experience drastically different light conditions, even when they are located at the same distance from the leaf surface; (ii) bundle sheath extensions, which are strips of parenchyma, collenchyma or sclerenchyma cells connecting the vascular bundles with the epidermis, can influence photosynthetic light-use efficiency of leaves; and (iii) chloroplast positioning can also influence the light-use efficiency of leaves. Mechanisms underlying leaf internal light heterogeneity and implications of the heterogeneity for photoprotection and for the convexity of the light response curves are discussed. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Axonal degeneration and regeneration in sensory roots in a genital herpes model.

PubMed

Soffer, D; Martin, J R

1989-01-01

In a mouse model of genital herpes simplex virus type 2 (HSV-2) infection, roots of the lower spinal cord were examined 5 days to 6 months after inoculation. Using immunoperoxidase methods on paraffin sections, viral antigen was found in sensory ganglia, their proximal roots and distal nerves on days 5 and 6 after infection. In Epon sections, most mice had focal sensory root abnormalities in lower thoracic, lumbar or sacral levels. At days 7 and 10, lesions showed chiefly nerve fiber degeneration, particularly of large myelinated fibers. At 2 weeks, lesions contained relatively large bundles of small unmyelinated fibers with immature axon-Schwann cell relationships. From 3 to 6 weeks, lesions again contained many more small unmyelinated fibers than normal but, in increasing proportions, axons in bundles were isolated from their neighbors by Schwann cell cytoplasm, and Schwann cells having 1:1 relationships with axons showed mesaxon or thin myelin sheath formation. At later times, the proportion of small unmyelinated axons decreased in parallel with increased numbers of small myelinated axons. By 6 months, affected roots showed a relative reduction in large myelinated fibers, increased proportions of small myelinated fibers and Schwann cell nuclei. Numbers of unmyelinated fibers were reduced relative to 3- to 6-week lesions. Axonal degeneration and regeneration appears to be the chief pathological change in sensory roots in this model. If regenerated fibers arise from latently infected neurons, then establishment of latency is not a relatively silent event, but is associated with major long-lasting, morphologically detectable effects.

Hertwig's Epithelial Root Sheath Fate during Initial Cellular Cementogenesis in Rat Molars.

PubMed

Yamamoto, Tsuneyuki; Yamada, Tamaki; Yamamoto, Tomomaya; Hasegawa, Tomoka; Hongo, Hiromi; Oda, Kimimitsu; Amizuka, Norio

2015-06-29

To elucidate the fate of the epithelial root sheath during initial cellular cementogenesis, we examined developing maxillary first molars of rats by immunohistochemistry for keratin, vimentin, and tissue non-specific alkaline phosphatase (TNALP) and by TdT-mediated dUTP nick end labeling (TUNEL). The advancing root end was divided into three sections, which follow three distinct stages of initial cellular cementogenesis: section 1, where the epithelial sheath is intact; section 2, where the epithelial sheath becomes fragmented; and section 3, where initial cellular cementogenesis begins. After fragmentation of the epithelial sheath, many keratin-positive epithelial sheath cells were embedded in the rapidly growing cellular cementum. A few unembedded epithelial cells located on the cementum surface. Dental follicle cells, precementoblasts, and cementoblasts showed immunoreactivity for vimentin and TNALP. In all three sections, there were virtually no cells possessing double immunoreactivity for vimentin-keratin or TNALP-keratin and only embedded epithelial cells showed TUNEL reactivity. Taken together, these findings suggest that: (1) epithelial sheath cells divide into two groups; one group is embedded in the cementum and thereafter dies by apoptosis, and the other survives on the cementum surface as epithelial cell rests of Malassez; and (2) epithelial sheath cells do not undergo epithelial-mesenchymal transition during initial cellular cementogenesis.

Hertwig’s Epithelial Root Sheath Fate during Initial Cellular Cementogenesis in Rat Molars

PubMed Central

Yamamoto, Tsuneyuki; Yamada, Tamaki; Yamamoto, Tomomaya; Hasegawa, Tomoka; Hongo, Hiromi; Oda, Kimimitsu; Amizuka, Norio

2015-01-01

To elucidate the fate of the epithelial root sheath during initial cellular cementogenesis, we examined developing maxillary first molars of rats by immunohistochemistry for keratin, vimentin, and tissue non-specific alkaline phosphatase (TNALP) and by TdT-mediated dUTP nick end labeling (TUNEL). The advancing root end was divided into three sections, which follow three distinct stages of initial cellular cementogenesis: section 1, where the epithelial sheath is intact; section 2, where the epithelial sheath becomes fragmented; and section 3, where initial cellular cementogenesis begins. After fragmentation of the epithelial sheath, many keratin-positive epithelial sheath cells were embedded in the rapidly growing cellular cementum. A few unembedded epithelial cells located on the cementum surface. Dental follicle cells, precementoblasts, and cementoblasts showed immunoreactivity for vimentin and TNALP. In all three sections, there were virtually no cells possessing double immunoreactivity for vimentin-keratin or TNALP-keratin and only embedded epithelial cells showed TUNEL reactivity. Taken together, these findings suggest that: (1) epithelial sheath cells divide into two groups; one group is embedded in the cementum and thereafter dies by apoptosis, and the other survives on the cementum surface as epithelial cell rests of Malassez; and (2) epithelial sheath cells do not undergo epithelial-mesenchymal transition during initial cellular cementogenesis. PMID:26160988

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

Weissmann, Sarit; Ma, Fangfang; Furuyama, Koki

C 4 photosynthesis in grasses requires the coordinated movement of metabolites through two specialized leaf cell types, mesophyll (M) and bundle sheath (BS), to concentrate CO 2 around Rubisco. Despite the importance of transporters in this process, few have been identified or rigorously characterized. In maize (Zea mays), DCT2 has been proposed to function as a plastid-localizedmalate transporter and is preferentially expressed in BS cells. Here, we characterized the role of DCT2 in maize leaves using Activator-tagged mutant alleles. Our results indicate that DCT2 enables the transport of malate into the BS chloroplast. Isotopic labeling experiments show that the lossmore » of DCT2 results in markedly different metabolic network operation and dramatically reduced biomass production. In the absence of a functioning malate shuttle, dct2 lines survive through the enhanced use of the phosphoenolpyruvate carboxykinase carbon shuttle pathway that in wild-type maize accounts for ;25% of the photosynthetic activity. The results emphasize the importance of malate transport during C 4 photosynthesis, define the role of a primary malate transporter in BS cells, and support a model for carbon exchange between BS and M cells in maize.« less

C3–C4 intermediacy in grasses: organelle enrichment and distribution, glycine decarboxylase expression, and the rise of C2 photosynthesis

PubMed Central

Khoshravesh, Roxana; Stinson, Corey R.; Stata, Matt; Busch, Florian A.; Sage, Rowan F.; Ludwig, Martha; Sage, Tammy L.

2016-01-01

Photorespiratory glycine shuttling and decarboxylation in bundle sheath (BS) cells exhibited by C2 species is proposed to be the evolutionary bridge to C4 photosynthesis in eudicots. To evaluate this in grasses, we compare anatomy, cellular localization of glycine decarboxylase (GDC), and photosynthetic physiology of a suspected C2 grass, Homolepis aturensis, with these traits in known C2 grasses, Neurachne minor and Steinchisma hians, and C3 S. laxum that is sister to S. hians. We also use publicly available genome and RNA-sequencing data to examine the evolution of GDC subunits and enhance our understanding of the evolution of BS-specific GDC expression in C2 and C4 grasses. Our results confirm the identity of H. aturensis as a C2 species; GDC is confined predominantly to the organelle-enriched BS cells in H. aturensis and S. hians and to mestome sheath cells of N. minor. Phylogenetic analyses and data obtained from immunodetection of the P-subunit of GDC are consistent with the hypothesis that the BS dominant levels of GDC in C2 and C4 species are due to changes in expression of a single GLDP gene in M and BS cells. All BS mitochondria and peroxisomes and most chloroplasts in H. aturensis and S. hians are situated centripetally in a pattern identical to C2 eudicots. In S. laxum, which has C3-like gas exchange patterns, mitochondria and peroxisomes are positioned centripetally as they are in S. hians. This subcellular phenotype, also present in eudicots, is posited to initiate a facilitation cascade leading to C2 and C4 photosynthesis. PMID:27073202

C3-C4 intermediacy in grasses: organelle enrichment and distribution, glycine decarboxylase expression, and the rise of C2 photosynthesis.

PubMed

Khoshravesh, Roxana; Stinson, Corey R; Stata, Matt; Busch, Florian A; Sage, Rowan F; Ludwig, Martha; Sage, Tammy L

2016-05-01

Photorespiratory glycine shuttling and decarboxylation in bundle sheath (BS) cells exhibited by C2 species is proposed to be the evolutionary bridge to C4 photosynthesis in eudicots. To evaluate this in grasses, we compare anatomy, cellular localization of glycine decarboxylase (GDC), and photosynthetic physiology of a suspected C2 grass, Homolepis aturensis, with these traits in known C2 grasses, Neurachne minor and Steinchisma hians, and C3 S laxum that is sister to S hians We also use publicly available genome and RNA-sequencing data to examine the evolution of GDC subunits and enhance our understanding of the evolution of BS-specific GDC expression in C2 and C4 grasses. Our results confirm the identity of H aturensis as a C2 species; GDC is confined predominantly to the organelle-enriched BS cells in H aturensis and S hians and to mestome sheath cells of N minor Phylogenetic analyses and data obtained from immunodetection of the P-subunit of GDC are consistent with the hypothesis that the BS dominant levels of GDC in C2 and C4 species are due to changes in expression of a single GLDP gene in M and BS cells. All BS mitochondria and peroxisomes and most chloroplasts in H aturensis and S hians are situated centripetally in a pattern identical to C2 eudicots. In S laxum, which has C3-like gas exchange patterns, mitochondria and peroxisomes are positioned centripetally as they are in S hians This subcellular phenotype, also present in eudicots, is posited to initiate a facilitation cascade leading to C2 and C4 photosynthesis. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Functional Differentiation of Bundle Sheath and Mesophyll Maize Chloroplasts Determined by Comparative ProteomicsW⃞

PubMed Central

Majeran, Wojciech; Cai, Yang; Sun, Qi; van Wijk, Klaas J.

2005-01-01

Chloroplasts of maize (Zea mays) leaves differentiate into specific bundle sheath (BS) and mesophyll (M) types to accommodate C4 photosynthesis. Consequences for other plastid functions are not well understood but are addressed here through a quantitative comparative proteome analysis of purified M and BS chloroplast stroma. Three independent techniques were used, including cleavable stable isotope coded affinity tags. Enzymes involved in lipid biosynthesis, nitrogen import, and tetrapyrrole and isoprenoid biosynthesis are preferentially located in the M chloroplasts. By contrast, enzymes involved in starch synthesis and sulfur import preferentially accumulate in BS chloroplasts. The different soluble antioxidative systems, in particular peroxiredoxins, accumulate at higher levels in M chloroplasts. We also observed differential accumulation of proteins involved in expression of plastid-encoded proteins (e.g., EF-Tu, EF-G, and mRNA binding proteins) and thylakoid formation (VIPP1), whereas others were equally distributed. Enzymes related to the C4 shuttle, the carboxylation and regeneration phase of the Calvin cycle, and several regulators (e.g., CP12) distributed as expected. However, enzymes involved in triose phosphate reduction and triose phosphate isomerase are primarily located in the M chloroplasts, indicating that the M-localized triose phosphate shuttle should be viewed as part of the BS-localized Calvin cycle, rather than a parallel pathway. PMID:16243905

Bundle sheath lignification mediates the linkage of leaf hydraulics and venation.

PubMed

Ohtsuka, Akihiro; Sack, Lawren; Taneda, Haruhiko

2018-02-01

The lignification of the leaf vein bundle sheath (BS) has been observed in many species and would reduce conductance from xylem to mesophyll. We hypothesized that lignification of the BS in lower-order veins would provide benefits for water delivery through the vein hierarchy but that the lignification of higher-order veins would limit transport capacity from xylem to mesophyll and leaf hydraulic conductance (K leaf ). We further hypothesized that BS lignification would mediate the relationship of K leaf to vein length per area. We analysed the dependence of K leaf , and its light response, on the lignification of the BS across vein orders for 11 angiosperm tree species. Eight of 11 species had lignin deposits in the BS of the midrib, and two species additionally only in their secondary veins, and for six species up to their minor veins. Species with lignification of minor veins had a lower hydraulic conductance of xylem and outside-xylem pathways and lower K leaf . K leaf could be strongly predicted by vein length per area and highest lignified vein order (R 2  = .69). The light-response of K leaf was statistically independent of BS lignification. The lignification of the BS is an important determinant of species variation in leaf and thus whole plant water transport. © 2017 John Wiley & Sons Ltd.

Microscopic diagnosis of the leaf and stem of Piper solmsianum C.DC.

PubMed

Bertocco, A R P; Migacz, I P; Santos, V L P; Franco, C R C; Silva, R Z; Yunes, R A; Cechinel-Filho, V; Budel, J M

2017-08-01

Piper solmsianum C.DC., which is popularly known as pariparoba, is a shrub that measures 1-3 m in height and it inhabits areas with wet tropical soils. The objective of this study was to analyze the leaf and stem anatomy using light microscopy, scanning electron micrographs, and energy-dispersive X-ray spectroscopy in order to provide information for species identification. The anatomical profile showed the following main microscopic markers: hypostomatic leaf; hypodermis layer on both sides; pearl glands; biconvex midrib shape; five collateral vascular bundles in open arc with the central bundle larger than the others; circular stem shape; collateral vascular bundles arranged in two rings; sinuous sclerenchymatic sheath in the pith; secretory idioblasts; and starch grains in the mesophyll, in the ground parenchyma of the midrib, petiole, and in the stem; and six morphotypes of calcium oxalate crystals (styloids, cuneiform, tabular crystal rosettes, cuneiform crystal rosettes, elongated square dipyramids, as well as very elongated square dipyramids). © 2017 Wiley Periodicals, Inc.

A Cytochemical Study of Extracellular Sheaths Associated with Rigidoporus lignosus during Wood Decay

PubMed Central

Nicole, M.; Chamberland, H.; Rioux, D.; Lecours, N.; Rio, B.; Geiger, J. P.; Ouellette, G. B.

1993-01-01

An ultrastructural and cytochemical investigation of the development of Rigidoporus lignosus, a white-rot fungus inoculated into wood blocks, was carried out to gain better insight into the structure and role of the extracellular sheaths produced by this fungus during wood degradation. Fungal sheaths had a dense or loose fibrillar appearance and were differentiated from the fungal cell wall early after wood inoculation. Close association between extracellular fibrils and wood cell walls was observed at both early and advanced stages of wood alteration. Fungal sheaths were often seen deep in host cell walls, sometimes enclosing residual wood fragments. Specific gold probes were used to investigate the chemical nature of R. lignosus sheaths. While labeling of chitin, pectin, β-1,4- and β-1,3-glucans, β-glucosides, galactosamine, mannose, sialic acid, RNA, fucose, and fimbrial proteins over fungal sheaths did not succeed, galactose residues and laccase (a fungal phenoloxidase) were found to be present. The positive reaction of sheaths with the PATAg test indicates that polysaccharides such as β-1,6-glucans are important components. Our data suggest that extracellular sheaths produced by R. lignosus during host cell colonization play an important role in wood degradation. Transportation of lignin-degrading enzymes by extracellular fibrils indicates that alteration of plant polymers may occur within fungal sheaths. It is also proposed that R. lignosus sheaths may be involved in recognition mechanisms in fungal cell-wood surface interactions. Images PMID:16349017

New evidence for grain specific C4 photosynthesis in wheat

PubMed Central

Rangan, Parimalan; Furtado, Agnelo; Henry, Robert J

2016-01-01

The C4 photosynthetic pathway evolved to allow efficient CO2 capture by plants where effective carbon supply may be limiting as in hot or dry environments, explaining the high growth rates of C4 plants such as maize. Important crops such as wheat and rice are C3 plants resulting in efforts to engineer them to use the C4 pathway. Here we show the presence of a C4 photosynthetic pathway in the developing wheat grain that is absent in the leaves. Genes specific for C4 photosynthesis were identified in the wheat genome and found to be preferentially expressed in the photosynthetic pericarp tissue (cross- and tube-cell layers) of the wheat caryopsis. The chloroplasts exhibit dimorphism that corresponds to chloroplasts of mesophyll- and bundle sheath-cells in leaves of classical C4 plants. Breeding to optimize the relative contributions of C3 and C4 photosynthesis may adapt wheat to climate change, contributing to wheat food security. PMID:27530078

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

Emms, David M.; Covshoff, Sarah; Hibberd, Julian M.

C4 photosynthesis is considered one of the most remarkable examples of evolutionary convergence in eukaryotes. However, it is unknown whether the evolution of C4 photosynthesis required the evolution of new genes. Genome-wide gene-tree species-tree reconciliation of seven monocot species that span two origins of C4 photosynthesis revealed that there was significant parallelism in the duplication and retention of genes coincident with the evolution of C4 photosynthesis in these lineages. Specifically, 21 orthologous genes were duplicated and retained independently in parallel at both C4 origins. Analysis of this gene cohort revealed that the set of parallel duplicated and retained genes ismore » enriched for genes that are preferentially expressed in bundle sheath cells, the cell type in which photosynthesis was activated during C4 evolution. Moreover, functional analysis of the cohort of parallel duplicated genes identified SWEET-13 as a potential key transporter in the evolution of C4 photosynthesis in grasses, and provides new insight into the mechanism of phloem loading in these C4 species.« less

The BSD2 ortholog in Chlamydomonas reinhardtii is a polysome-associated chaperone that co-migrates on sucrose gradients with the rbcL transcript encoding the Rubisco large subunit.

PubMed

Doron, Lior; Segal, Na'ama; Gibori, Hadas; Shapira, Michal

2014-10-01

The expression of the CO2 -fixation enzyme ribulose-bisphosphate carboxylase/oxygenase (Rubisco), which is affected by light, involves the cysteine-rich protein bundle-sheath defective-2 (BSD2) that was originally identified in maize bundle-sheath cells. We identified the BSD2 ortholog in Chlamydomonas reinhardtii as a small protein (17 kDa) localized to the chloroplast. The algal BSD2-ortholog contains four CXXCXGXG DnaJ-like elements, but lacks the other conserved domains of DnaJ. BSD2 co-migrated with the rbcL transcript on heavy polysomes, and both BSD2 and rbcL mRNA shifted to the lighter fractions under oxidizing conditions that repress the translation of the Rubisco large subunit (RbcL). This profile of co-migration supports the possibility that BSD2 is required for the de novo synthesis of RbcL. Furthermore, BSD2 co-migrated with the rbcL transcript in a C. reinhardtii premature-termination mutant that encodes the first 60 amino acids of RbcL. In both strains, BSD2 shared its migration profile with the rbcL transcript but not with psbA mRNA. The chaperone activity of BSD2 was exemplified by its ability to prevent the aggregation of both citrate synthase (CS) and RbcL in vitro following their chemical denaturation. This activity did not depend on the presence of the thiol groups on BSD2. In contrast, the activity of BSD2 in preventing the precipitation of reduced β-chains in vitro in the insulin turbidity assay was thiol-dependent. We conclude that BSD2 combines a chaperone 'holdase' function with the ability to interact with free thiols, with both activities being required to protect newly synthesized RbcL chains. © 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.

The structure and development of the starch sheath in pea epicotyls

NASA Technical Reports Server (NTRS)

Sack, D. F.

1985-01-01

Graviperception in plant stems is thought to occur in endodermal cells differentiated as a starch sheath, but little is known about the ultrastructure of these cells in dicots. The structure of the pea starch sheath was studied with respect to gravity and to development in order to determine whether symplastic or apoplastic blockages exist and to describe any intracellular polarity. Amyloplasts increase in size towards the base of the epicotyl hook but are not consistently sedimented until the cells enter the zone exhibiting gravicurvature below the hook. The starch sheath cells are connected to each other and to cells of the cortex and the stele by plasmodesmata. A casparian strip exists in older endodermal cells but not at the stage that the endodermis is differentiated as a starch sheath. Amyloplasts were frequently observed in apparent contact with endoplasmic reticulum.

NaCl-Induced Alterations in Both Cell Structure and Tissue-Specific Plasma Membrane H+ -ATPase Gene Expression.

PubMed Central

Niu, X.; Damsz, B.; Kononowicz, A. K.; Bressan, R. A.; Hasegawa, P. M.

1996-01-01

NaCl-induced plasma membrane H+-ATPase gene expression, which occurs in roots and fully expanded leaves of the halophyte Atriplex nummularia L. (X. Niu, M.L. Narasimhan, R.A. Salzman, R.A. Bressan, P.M. Hasegawa [1993] Plant Physiol 103: 713-718), has been differentially localized to specific tissues using in situ RNA hybridization techniques. Twenty-four-hour exposure of plants to 400 mM NaCl resulted in substantial accumulation of H+ pump message in the epidermis of the root tip and the endodermis of the root elongation/differentiation zone. In expanded leaves, NaCl induction of plasma membrane H+-ATPase message accumulation was localized to bundle-sheath cells. Ultrastructural analyses indicated that significant cytological adaptations in root cells included plasmolysis that is accompanied by plasma membrane invaginations, formation of Hechtian strands and vesiculation, and vacuolation. These results identify specific tissues that are involved in the regulation of Na+ and Cl- uptake into different organs of the halophyte A. nummularia and provide evidence of the intercellular and interorgan coordination that occurs in the mediation of NaCl adaptation. PMID:12226321

NaCl-Induced Alterations in Both Cell Structure and Tissue-Specific Plasma Membrane H+ -ATPase Gene Expression.

PubMed

Niu, X.; Damsz, B.; Kononowicz, A. K.; Bressan, R. A.; Hasegawa, P. M.

1996-07-01

NaCl-induced plasma membrane H+-ATPase gene expression, which occurs in roots and fully expanded leaves of the halophyte Atriplex nummularia L. (X. Niu, M.L. Narasimhan, R.A. Salzman, R.A. Bressan, P.M. Hasegawa [1993] Plant Physiol 103: 713-718), has been differentially localized to specific tissues using in situ RNA hybridization techniques. Twenty-four-hour exposure of plants to 400 mM NaCl resulted in substantial accumulation of H+ pump message in the epidermis of the root tip and the endodermis of the root elongation/differentiation zone. In expanded leaves, NaCl induction of plasma membrane H+-ATPase message accumulation was localized to bundle-sheath cells. Ultrastructural analyses indicated that significant cytological adaptations in root cells included plasmolysis that is accompanied by plasma membrane invaginations, formation of Hechtian strands and vesiculation, and vacuolation. These results identify specific tissues that are involved in the regulation of Na+ and Cl- uptake into different organs of the halophyte A. nummularia and provide evidence of the intercellular and interorgan coordination that occurs in the mediation of NaCl adaptation.

Viral and Cellular Factors Involved in Phloem Transport of Plant Viruses

PubMed Central

Hipper, Clémence; Brault, Véronique; Ziegler-Graff, Véronique; Revers, Frédéric

2013-01-01

Phloem transport of plant viruses is an essential step in the setting-up of a complete infection of a host plant. After an initial replication step in the first cells, viruses spread from cell-to-cell through mesophyll cells, until they reach the vasculature where they rapidly move to distant sites in order to establish the infection of the whole plant. This last step is referred to as systemic transport, or long-distance movement, and involves virus crossings through several cellular barriers: bundle sheath, vascular parenchyma, and companion cells for virus loading into sieve elements (SE). Viruses are then passively transported within the source-to-sink flow of photoassimilates and are unloaded from SE into sink tissues. However, the molecular mechanisms governing virus long-distance movement are far from being understood. While most viruses seem to move systemically as virus particles, some viruses are transported in SE as viral ribonucleoprotein complexes (RNP). The nature of the cellular and viral factors constituting these RNPs is still poorly known. The topic of this review will mainly focus on the host and viral factors that facilitate or restrict virus long-distance movement. PMID:23745125

Gene Expression Profiling of the Intact Dermal Sheath Cup of Human Hair Follicles.

PubMed

Niiyama, Shiro; Ishimatsu-Tsuji, Yumiko; Nakazawa, Yosuke; Yoshida, Yuzo; Soma, Tsutomu; Ideta, Ritsuro; Mukai, Hideki; Kishimoto, Jiro

2018-04-24

Cells that constitute the dermal papillae of hair follicles might be derived from the dermal sheath, the peribulbar component of which is the dermal sheath cup. The dermal sheath cup is thought to include the progenitor cells of the dermal papillae and possesses hair inductive potential; however, it has not yet been well characterized. This study investigated the gene expression profile of the intact dermal sheath cup, and identified dermal sheath cup signature genes, including extracellular matrix components and BMP-binding molecules, as well as TGF-b1 as an upstream regulator. Among these, GREM2, a member of the BMP antagonists, was found by in situ hybridization to be highly specific to the dermal sheath cup, implying that GREM2 is a key molecule contributing to maintenance of the properties of the dermal sheath cup.

C4 plants use fluctuating light less efficiently than do C3 plants: a study of growth, photosynthesis and carbon isotope discrimination.

PubMed

Kubásek, Jiří; Urban, Otmar; Šantrůček, Jiří

2013-12-01

Plants in the field are commonly exposed to fluctuating light intensity, caused by variable cloud cover, self-shading of leaves in the canopy and/or leaf movement due to turbulence. In contrast to C3 plant species, only little is known about the effects of dynamic light (DL) on photosynthesis and growth in C4 plants. Two C4 and two C3 monocot and eudicot species were grown under steady light or DL conditions with equal sum of daily incident photon flux. We measured leaf gas exchange, plant growth and dry matter carbon isotope discrimination to infer CO2 bundle sheath leakiness in C4 plants. The growth of all species was reduced by DL, despite only small changes in steady-state gas exchange characteristics, and this effect was more pronounced in C4 than C3 species due to lower assimilation at light transitions. This was partially attributed to increased bundle sheath leakiness in C4 plants under the simulated lightfleck conditions. We hypothesize that DL leads to imbalances in the coordination of C4 and C3 cycles and increasing leakiness, thereby decreasing the quantum efficiency of photosynthesis. In addition to their other constraints, the inability of C4 plants to efficiently utilize fluctuating light likely contributes to their absence in such environments as forest understoreys. © 2013 Scandinavian Plant Physiology Society.

A mutation that eliminates bundle sheath extensions reduces leaf hydraulic conductance, stomatal conductance and assimilation rates in tomato (Solanum lycopersicum).

PubMed

Zsögön, Agustin; Negrini, Ana Clarissa Alves; Peres, Lázaro Eustáquio Pereira; Nguyen, Hoa Thi; Ball, Marilyn C

2015-01-01

Bundle sheath extensions (BSEs) are key features of leaf structure whose distribution differs among species and ecosystems. The genetic control of BSE development is unknown, so BSE physiological function has not yet been studied through mutant analysis. We screened a population of ethyl methanesulfonate (EMS)-induced mutants in the genetic background of the tomato (Solanum lycopersicum) model Micro-Tom and found a mutant lacking BSEs. The leaf phenotype of the mutant strongly resembled the tomato mutant obscuravenosa (obv). We confirmed that obv lacks BSEs and that it is not allelic to our induced mutant, which we named obv-2. Leaves lacking BSEs had lower leaf hydraulic conductance and operated with lower stomatal conductance and correspondingly lower assimilation rates than wild-type leaves. This lower level of function occurred despite similarities in vein density, midvein vessel diameter and number, stomatal density, and leaf area between wild-type and mutant leaves, the implication being that the lack of BSEs hindered water dispersal within mutant leaves. Our results comparing near-isogenic lines within a single species confirm the hypothesised role of BSEs in leaf hydraulic function. They further pave the way for a genetic model-based analysis of a common leaf structure with deep ecological consequences. © 2014 The Authors New Phytologist © 2014 New Phytologist Trust.

Liver schwannoma incidentally discovered in a patient with breast cancer.

PubMed

Akin, Murat; Bozkirli, Bahadir; Leventoglu, Sezai; Unal, Kemal; Kapucu, L Ozlem; Akyurek, Nalan; Sare, Mustafa

2009-01-01

Benign schwannomas, also referred to as neurilemomas, neurinomas, and perineural fibroblastomas, are encapsulated nerve sheath tumors. Primary schwannomas of the liver are extremely rare. We present a case of liver schwannoma, incidentally found in a patient with breast cancer. A 66-year-old female consulted her physician for a mass she palpated on her left breast. The abdominal ultrasonography (USG) revealed a 44 x 28 mm mass in the medial segment of the left lobe of her liver suspicious of a metastasis. An USG-guided biopsy was performed and the histo-pathological examination revealed a "peripheral nerve sheath tumor". Positron emission tomography (PET-CT) revealed a pathologic FDG uptake in the lesion that was previously defined in the liver. The tumor resected from the liver was 5 x 4 x 3 cm, yellowish, soft, and capsulated tumor. Microscopic examination revealed that the mass consisted of bundles of spindle cells with hypercellular and hypocellular areas. In immunohistochemistry, there was a strong positive staining for S-100. The tumor was diagnosed as benign liver schwannoma. Schwannomas are benign, encapsulated neoplasms. Symptoms and signs vary depending on the anatomical site and the size of the neoplasm; however, most schwannomas present as an asymptomatic or painless mass. Recurrence is unusual, despite of an incomplete removal, and malignant transformation is exceedingly rare (Fig. 4, Ref. 8). Full Text (Free, PDF) www.bmj.sk.

A smart core-sheath nanofiber that captures and releases red blood cells from the blood

NASA Astrophysics Data System (ADS)

Shi, Q.; Hou, J.; Zhao, C.; Xin, Z.; Jin, J.; Li, C.; Wong, S.-C.; Yin, J.

2016-01-01

A smart core-sheath nanofiber for non-adherent cell capture and release is demonstrated. The nanofibers are fabricated by single-spinneret electrospinning of poly(N-isopropylacrylamide) (PNIPAAm), polycaprolactone (PCL) and nattokinase (NK) solution blends. The self-assembly of PNIPAAm and PCL blends during the electrospinning generates the core-sheath PCL/PNIPAAm nanofibers with PNIPAAm as the sheath. The PNIPAAm-based core-sheath nanofibers are switchable between hydrophobicity and hydrophilicity with temperature change and enhance stability in the blood. When the nanofibers come in contact with blood, the NK is released from the nanofibers to resist platelet adhesion on the nanofiber surface, facilitating the direct capture and isolation of red blood cells (RBCs) from the blood above phase-transition temperature of PNIPAAm. Meanwhile, the captured RBCs are readily released from the nanofibers with temperature stimuli in an undamaged manner. The release efficiency of up to 100% is obtained while maintaining cellular integrity and function. This work presents promising nanofibers to effectively capture non-adherent cells and release for subsequent molecular analysis and diagnosis of single cells.A smart core-sheath nanofiber for non-adherent cell capture and release is demonstrated. The nanofibers are fabricated by single-spinneret electrospinning of poly(N-isopropylacrylamide) (PNIPAAm), polycaprolactone (PCL) and nattokinase (NK) solution blends. The self-assembly of PNIPAAm and PCL blends during the electrospinning generates the core-sheath PCL/PNIPAAm nanofibers with PNIPAAm as the sheath. The PNIPAAm-based core-sheath nanofibers are switchable between hydrophobicity and hydrophilicity with temperature change and enhance stability in the blood. When the nanofibers come in contact with blood, the NK is released from the nanofibers to resist platelet adhesion on the nanofiber surface, facilitating the direct capture and isolation of red blood cells (RBCs) from the blood above phase-transition temperature of PNIPAAm. Meanwhile, the captured RBCs are readily released from the nanofibers with temperature stimuli in an undamaged manner. The release efficiency of up to 100% is obtained while maintaining cellular integrity and function. This work presents promising nanofibers to effectively capture non-adherent cells and release for subsequent molecular analysis and diagnosis of single cells. Electronic supplementary information (ESI) available: Electrospinning of polymer nanofibers; FTIR spectra and XPS spectra of PCL, PNIPAAm and PCL/PNIPAAm nanofibers; SEM images of PCL/PNIPAAm nanofibers with varied composition; PNIPAAm content on the sheath of nanofibers; stability of core-sheath PCL/PNIPAAm nanofibers. Platelet adhesion on the PCL/PNIPAAm nanofibers in the presence of NK; Protein adsorption on nanofibers. See DOI: 10.1039/c5nr07070h

The Tubular Sheaths Encasing Methanosaeta thermophila Filaments Are Functional Amyloids*

PubMed Central

Dueholm, Morten S.; Larsen, Poul; Finster, Kai; Stenvang, Marcel R.; Christiansen, Gunna; Vad, Brian S.; Bøggild, Andreas; Otzen, Daniel E.; Nielsen, Per Halkjær

2015-01-01

Archaea are renowned for their ability to thrive in extreme environments, although they can be found in virtually all habitats. Their adaptive success is linked to their unique cell envelopes that are extremely resistant to chemical and thermal denaturation and that resist proteolysis by common proteases. Here we employ amyloid-specific conformation antibodies and biophysical techniques to show that the extracellular cell wall sheaths encasing the methanogenic archaea Methanosaeta thermophila PT are functional amyloids. Depolymerization of sheaths and subsequent MS/MS analyses revealed that the sheaths are composed of a single major sheath protein (MspA). The amyloidogenic nature of MspA was confirmed by in vitro amyloid formation of recombinant MspA under a wide range of environmental conditions. This is the first report of a functional amyloid from the archaeal domain of life. The amyloid nature explains the extreme resistance of the sheath, the elastic properties that allow diffusible substrates to penetrate through expandable hoop boundaries, and how the sheaths are able to split and elongate outside the cell. The archaeal sheath amyloids do not share homology with any of the currently known functional amyloids and clearly represent a new function of the amyloid protein fold. PMID:26109065

Matrix remodeling between cells and cellular interactions with collagen bundle

NASA Astrophysics Data System (ADS)

Kim, Jihan; Sun, Bo

When cells are surrounded by complex environment, they continuously probe and interact with it by applying cellular traction forces. As cells apply traction forces, they can sense rigidity of their local environment and remodel the matrix microstructure simultaneously. Previous study shows that single human carcinoma cell (MDA-MB-231) remodeled its surrounding extracellular matrix (ECM) and the matrix remodeling was reversible. In this study we examined the matrix microstructure between cells and cellular interaction between them using quantitative confocal microscopy. The result shows that the matrix microstructure is the most significantly remodeled between cells consisting of aligned, and densified collagen fibers (collagen bundle)., the result shows that collagen bundle is irreversible and significantly change micromechanics of ECM around the bundle. We further examined cellular interaction with collagen bundle by analyzing dynamics of actin and talin formation along with the direction of bundle. Lastly, we analyzed dynamics of cellular protrusion and migrating direction of cells along the bundle.

Identification of a Second Site of Pyrrolizidine Alkaloid Biosynthesis in Comfrey to Boost Plant Defense in Floral Stage1,2[OPEN

PubMed Central

Stegemann, Thomas; Sievert, Christian

2017-01-01

Pyrrolizidine alkaloids (PAs) are toxic secondary metabolites that are found in several distantly related families of the angiosperms. The first specific step in PA biosynthesis is catalyzed by homospermidine synthase (HSS), which has been recruited several times independently by duplication of the gene encoding deoxyhypusine synthase, an enzyme involved in the posttranslational activation of the eukaryotic initiation factor 5A. HSS shows highly diverse spatiotemporal gene expression in various PA-producing species. In comfrey (Symphytum officinale; Boraginaceae), PAs are reported to be synthesized in the roots, with HSS being localized in cells of the root endodermis. Here, we show that comfrey plants activate a second site of HSS expression when inflorescences start to develop. HSS has been localized in the bundle sheath cells of specific leaves. Tracer feeding experiments have confirmed that these young leaves express not only HSS but the whole PA biosynthetic route. This second site of PA biosynthesis results in drastically increased PA levels within the inflorescences. The boost of PA biosynthesis is proposed to guarantee optimal protection especially of the reproductive structures. PMID:28275146

Ultrastructural localization of hair keratins, high sulfur keratin-associated proteins and sulfhydryl oxidase in the human hair.

PubMed

Alibardi, Lorenzo

2017-03-01

Hardening of the human hair shaft during cornification results from the bonding of keratins and keratin-associated proteins. In situ hybridization and light immunocytochemical studies have shown the general distribution of different keratins and some associated proteins but not determined their ultrastructural localization. I report here the localization of hair keratins, two high-sulfur keratin-associated proteins and sulfhydryl oxidase has been studied under the transmission electron microscope in the cornification zone of the human hair. The ultrastructural study on keratin distribution in general confirms previous light microscopic studies. Sulfur-rich KAP1 is mainly cortical but the labeling disappears in fully cornified cortical cells while a diffuse labeling is also present in differentiating cuticle cells. Sulfur-rich K26 immunolocalization is only detected in the exocuticle and endocuticle. Sparse labeling for sulfhydryl oxidase occurs in differentiating cortical cells but is weak and uneven in cuticle cells and absent in medulla and inner root sheath. Labeling disappears in the upper fully cornified cortex and cuticle. The observations indicate that sulfhydryl oxidase and keratin associated proteins are initially produced in the cytoplasm among keratin bundles accumulating in cortical and cuticle cells but these proteins undergo changes during the following cornification that alter the epitopes tagged by the antibodies.

Model and particle-in-cell simulation of ion energy distribution in collisionless sheath

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

Zhou, Zhuwen, E-mail: zzwwdxy@gznc.edu.cn; Key Laboratory of Photoelectron Materials Design and Simulation in Guizhou Province, Guiyang 550018; Scientific Research Innovation Team in Plasma and Functional Thin Film Materials in Guizhou Province, Guiyang 550018

2015-06-15

In this paper, we propose a self-consistent theoretical model, which is described by the ion energy distributions (IEDs) in collisionless sheaths, and the analytical results for different combined dc/radio frequency (rf) capacitive coupled plasma discharge cases, including sheath voltage errors analysis, are compared with the results of numerical simulations using a one-dimensional plane-parallel particle-in-cell (PIC) simulation. The IEDs in collisionless sheaths are performed on combination of dc/rf voltage sources electrodes discharge using argon as the process gas. The incident ions on the grounded electrode are separated, according to their different radio frequencies, and dc voltages on a separated electrode, themore » IEDs, and widths of energy in sheath and the plasma sheath thickness are discussed. The IEDs, the IED widths, and sheath voltages by the theoretical model are investigated and show good agreement with PIC simulations.« less

Robotic positioning of standard electrophysiology catheters: a novel approach to catheter robotics.

PubMed

Knight, Bradley; Ayers, Gregory M; Cohen, Todd J

2008-05-01

Robotic systems have been developed to manipulate and position electrophysiology (EP) catheters remotely. One limitation of existing systems is their requirement for specialized catheters or sheaths. We evaluated a system (Catheter Robotics Remote Catheter Manipulation System [RCMS], Catheter Robotics, Inc., Budd Lake, New Jersey) that manipulates conventional EP catheters placed through standard introducer sheaths. The remote controller functions much like the EP catheter handle, and the system permits repeated catheter disengagement for manual manipulation without requiring removal of the catheter from the body. This study tested the hypothesis that the RCMS would be able to safely and effectively position catheters at various intracardiac sites and obtain thresholds and electrograms similar to those obtained with manual catheter manipulation. Two identical 7 Fr catheters (Blazer II; Boston Scientific Corp., Natick, Massachusetts) were inserted into the right femoral veins of 6 mongrel dogs through separate, standard 7 Fr sheaths. The first catheter was manually placed at a right ventricular endocardial site. The second catheter handle was placed in the mating holder of the RCMS and moved to approximately the same site as the first catheter using the Catheter Robotics RCMS. The pacing threshold was determined for each catheter. This sequence was performed at 2 right atrial and 2 right ventricular sites. The distance between the manually and robotically placed catheters tips was measured, and pacing thresholds and His-bundle recordings were compared. The heart was inspected at necropsy for signs of cardiac perforation or injury. Compared to manual positioning, remote catheter placement produced the same pacing threshold at 7/24 sites, a lower threshold at 11/24 sites, and a higher threshold at only 6/24 sites (p > 0.05). The average distance between catheter tips was 0.46 +/- 0.32 cm (median 0.32, range 0.13-1.16 cm). There was no difference between right atrial and right ventricular sites (p > 0.05). His-bundle electrograms were equal in amplitude and timing. Further, the remote navigation catheter was able to be disengaged, manually manipulated, then reengaged in the robot without issue. There was no evidence of perforation. The Catheter Robotics remote catheter manipulation system, which uses conventional EP catheters and introducer sheaths, appears to be safe and effective at directing EP catheters to intracardiac sites and achieving pacing thresholds and electrograms equivalent to manually placed catheters. Further clinical studies are needed to confirm these observations.

Maize development: Cell wall changes in leaves and sheaths

USDA-ARS?s Scientific Manuscript database

Developmental changes occur in maize (Zea mays L.) as it transitions from juvenile stages to the mature plant. Changes also occur as newly formed cells mature into adult cells. Maize leaf blades, including the midribs and sheaths, undergo cell wall changes as cells transition to fully mature cell ty...

The Tubular Sheaths Encasing Methanosaeta thermophila Filaments Are Functional Amyloids.

PubMed

Dueholm, Morten S; Larsen, Poul; Finster, Kai; Stenvang, Marcel R; Christiansen, Gunna; Vad, Brian S; Bøggild, Andreas; Otzen, Daniel E; Nielsen, Per Halkjær

2015-08-14

Archaea are renowned for their ability to thrive in extreme environments, although they can be found in virtually all habitats. Their adaptive success is linked to their unique cell envelopes that are extremely resistant to chemical and thermal denaturation and that resist proteolysis by common proteases. Here we employ amyloid-specific conformation antibodies and biophysical techniques to show that the extracellular cell wall sheaths encasing the methanogenic archaea Methanosaeta thermophila PT are functional amyloids. Depolymerization of sheaths and subsequent MS/MS analyses revealed that the sheaths are composed of a single major sheath protein (MspA). The amyloidogenic nature of MspA was confirmed by in vitro amyloid formation of recombinant MspA under a wide range of environmental conditions. This is the first report of a functional amyloid from the archaeal domain of life. The amyloid nature explains the extreme resistance of the sheath, the elastic properties that allow diffusible substrates to penetrate through expandable hoop boundaries, and how the sheaths are able to split and elongate outside the cell. The archaeal sheath amyloids do not share homology with any of the currently known functional amyloids and clearly represent a new function of the amyloid protein fold. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Mesophyll cells of C4 plants have fewer chloroplasts than those of closely related C3 plants.

PubMed

Stata, Matt; Sage, Tammy L; Rennie, Troy D; Khoshravesh, Roxana; Sultmanis, Stefanie; Khaikin, Yannay; Ludwig, Martha; Sage, Rowan F

2014-11-01

The evolution of C(4) photosynthesis from C(3) ancestors eliminates ribulose bisphosphate carboxylation in the mesophyll (M) cell chloroplast while activating phosphoenolpyruvate (PEP) carboxylation in the cytosol. These changes may lead to fewer chloroplasts and different chloroplast positioning within M cells. To evaluate these possibilities, we compared chloroplast number, size and position in M cells of closely related C(3), C(3) -C(4) intermediate and C(4) species from 12 lineages of C(4) evolution. All C(3) species had more chloroplasts per M cell area than their C(4) relatives in high-light growth conditions. C(3) species also had higher chloroplast coverage of the M cell periphery than C(4) species, particularly opposite intercellular air spaces. In M cells from 10 of the 12 C(4) lineages, a greater fraction of the chloroplast envelope was pulled away from the plasmalemma in the C(4) species than their C(3) relatives. C(3) -C(4) intermediate species generally exhibited similar patterns as their C(3) relatives. We interpret these results to reflect adaptive shifts that facilitate efficient C(4) function by enhancing diffusive access to the site of primary carbon fixation in the cytosol. Fewer chloroplasts in C(4) M cells would also reduce shading of the bundle sheath chloroplasts, which also generate energy required by C(4) photosynthesis. © 2014 John Wiley & Sons Ltd.

Effect of phosphorylation of myelin basic protein by MAPK on its interactions with actin and actin binding to a lipid membrane in vitro.

PubMed

Boggs, Joan M; Rangaraj, Godha; Gao, Wen; Heng, Yew-Meng

2006-01-17

Myelin basic protein (MBP) binds to negatively charged lipids on the cytosolic surface of oligodendrocyte membranes and is most likely responsible for adhesion of these surfaces in the multilayered myelin sheath. It can also polymerize actin, bundle F-actin filaments, and bind actin filaments to lipid bilayers through electrostatic interactions. MBP consists of a number of posttranslationally modified isomers of varying charge, some resulting from phosphorylation at several sites by different kinases, including mitogen-activated protein kinase (MAPK). Phosphorylation of MBP in oligodendrocytes occurs in response to various extracellular stimuli. Phosphorylation/dephosphorylation of MBP also occurs in the myelin sheath in response to electrical activity in the brain. Here we investigate the effect of phosphorylation of MBP on its interaction with actin in vitro by phosphorylating the most highly charged unmodified isomer, C1, at two sites with MAPK. Phosphorylation decreased the ability of MBP to polymerize actin and to bundle actin filaments but had no effect on the dissociation constant of the MBP-actin complex or on the ability of Ca2+-calmodulin to dissociate the complex. The most significant effect of phosphorylation on the MBP-actin complex was a dramatic reduction in its ability to bind to negatively charged lipid bilayers. The effect was much greater than that reported earlier for another charge isomer of MBP, C8, in which six arginines were deiminated to citrulline, resulting in a reduction of net positive charge of 6. These results indicate that although average electrostatic forces are the primary determinant of the interaction of MBP with actin, phosphorylation may have an additional effect due to a site-specific electrostatic effect or to a conformational change. Thus, phosphorylation of MBP, which occurs in response to various extracellular signals in both myelin and oligodendrocytes, attenuates the ability of MBP to polymerize and bundle actin and to bind it to a negatively charged membrane.

Lymphocyte migration in the micro-channel of splenic sheathed capillaries in Chinese soft-shelled turtles, Pelodiscus sinensis.

PubMed

Zhang, Qian; Ullah, Shakeeb; Liu, Yi; Yang, Ping; Chen, Bing; Waqas, Yasir; Bao, Huijun; Hu, Lisi; Li, Quanfu; Chen, Qiusheng

2016-01-01

The structural characteristics of the splenic sheathed capillary were investigated using light microscopy and transmission electron microscopy (TEM). This study mainly focused on lymphocyte migration to the splenic white pulp via micro-channels in Chinese soft-shelled turtles, Pelodiscus sinensis. The results showed that the sheathed capillaries in the turtle spleen were high endothelial venule (HEV)-like vessels. These capillaries consist of micro-channels that facilitate lymphocyte migration to the splenic white pulp. The micro-channel is a dynamic structure comprising processes of endothelial cells, supporting cells, and ellipsoid-associated cells (EACs), which provides a microenvironment for lymphocyte migration. The pattern of lymphocyte migration in the micro-channel of the turtle spleen includes the following steps: (i) lymphocyte first adheres to the endothelium of the sheathed capillary, passes through the endothelial cells, and traverses through the basement membrane of the sheathed capillary; (ii) it then enters into the ellipsoid combined with supporting cells and EACs; and (iii) lymphocyte migrates from the ellipsoid to the periellipsoidal lymphatic sheath (PELS) via the micro-channel. This study provides morphological evidence for lymphocyte migration in the micro-channels of turtle spleens and also an insight into the mechanism of lymphocyte homing to the splenic white pulp of reptiles. Copyright © 2015 Elsevier Ltd. All rights reserved.

A smart core-sheath nanofiber that captures and releases red blood cells from the blood.

PubMed

Shi, Q; Hou, J; Zhao, C; Xin, Z; Jin, J; Li, C; Wong, S-C; Yin, J

2016-01-28

A smart core-sheath nanofiber for non-adherent cell capture and release is demonstrated. The nanofibers are fabricated by single-spinneret electrospinning of poly(N-isopropylacrylamide) (PNIPAAm), polycaprolactone (PCL) and nattokinase (NK) solution blends. The self-assembly of PNIPAAm and PCL blends during the electrospinning generates the core-sheath PCL/PNIPAAm nanofibers with PNIPAAm as the sheath. The PNIPAAm-based core-sheath nanofibers are switchable between hydrophobicity and hydrophilicity with temperature change and enhance stability in the blood. When the nanofibers come in contact with blood, the NK is released from the nanofibers to resist platelet adhesion on the nanofiber surface, facilitating the direct capture and isolation of red blood cells (RBCs) from the blood above phase-transition temperature of PNIPAAm. Meanwhile, the captured RBCs are readily released from the nanofibers with temperature stimuli in an undamaged manner. The release efficiency of up to 100% is obtained while maintaining cellular integrity and function. This work presents promising nanofibers to effectively capture non-adherent cells and release for subsequent molecular analysis and diagnosis of single cells.

Characterization of Direct Current-Electrical Penetration Graph Waveforms and Correlation With the Probing Behavior of Matsumuratettix hiroglyphicus (Hemiptera: Cicadellidae), the Insect Vector of Sugarcane White Leaf Phytoplasma.

PubMed

Roddee, J; Kobori, Y; Yorozuya, H; Hanboonsong, Y

2017-06-01

The leafhopper Matsumuratettix hiroglyphicus (Matsumura) (Hemiptera: Cicadellidae) is an important vector of phytoplasma causing white leaf disease in sugarcane. Thus, the aim of our study was to understand and describe the stylet-probing activities of this vector while feeding on sugarcane plants, by using direct current (DC) electrical penetration graph (EPG) monitoring. The EPG signals were classified into six distinct waveforms, according to amplitude, frequency, voltage level, and electrical origin of the observed traces during stylet penetration into the host plant tissues (probing). These six EPG waveforms of probing behavior comprise no stylet penetration (NP); stylet pathway through epidermis, mesophyll, and parenchymal cells (waveform A); contact at the bundle sheath layer (waveform B); salivation into phloem sieve elements (waveform C); phloem sap ingestion (waveform D); and short ingestion time of xylem sap (waveform E). The above waveform patterns were correlated with histological data of salivary sheath termini in plant tissue generated from insect stylet tips. The key findings of this study were that M. hiroglyphicus ingests the phloem sap at a relatively higher rate and for longer duration from any other cell type, suggesting that M. hiroglyphicus is mainly a phloem-feeder. Quantitative comparison of probing behavior revealed that females typically probe more frequently and longer in the phloem than males. Thus, females may acquire and inoculate greater amounts of phytoplasma than males, enhancing the efficiency of phytoplasma transmission and potentially exacerbating disease spreading. Overall, our study provides basic information on the probing behavior and transmission mechanism of M. hiroglyphicus. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Ultrastructural findings in lung biopsy material from children with congenital heart defects.

PubMed Central

Meyrick, B.; Reid, L.

1980-01-01

The ultrastructural features of pulmonary arteries are described in lung biopsy material from 6 children with congenital heart defects. Right ventricular hypertrophy was found in all 6 children and increased pulmonary artery pressure in all but one. The presence of muscle in smaller and more peripheral arteries than expected for the age of the child was detected in all cases. Ultrastructural examination of the peripheral arteries revealed, for the first time, in the nonmuscular regions of human arterial walls, pericytes and intermediate cells (previously shown to be precursor smooth-muscle cells); in addition, new arterial muscle was found in the normally nonmuscular region. In the 4 cases where medial thickness of the normally muscular arteries was increased, the smooth-muscle cells were hypertrophied and the extracellular connective tissue increased. In all cases, junctions between endothelial cells and smooth-muscle cells, intermediate cells, or pericytes were found. These changes are similar to those described in the rat with hypoxia-induced pulmonary hypertension. In addition, in 2 of the 6 cases, bundles of nerve axons in Schwann cell sheaths were found in adventitial layer of small, intraacinar muscular arteries (not previously demonstrated ultrastructurally at this site in the human lung); varicosities with agranular and granular vesicles, probably adrenergic, were also identified. Images Figure 4 Figure 5 Figure 1 Figure 2 Figure 3 PMID:7446706

The endomembrane sheath: a key structure for understanding the plant cell?

NASA Technical Reports Server (NTRS)

Reuzeau, C.; McNally, J. G.; Pickard, B. G.

1997-01-01

Recent evidence suggests that integrin is abundant in endomembranes of plant cells, and the endomembranes are clad by a sheath of cytoskeleton including F-actin. A role for endomembrane integrin and the endomembrane sheath is proposed: this system might orchestrate metabolic regulation by providing and modulating loci for channelling, and might accelerate channeling as needed by dragging the endoplasmic reticulum (ER) and organelles through the cytoplasm. To accomplish this "streaming", F-actin might lever against the rest of the endomembrane sheath and the ER might also lever against adhesion sites (i.e., plasmodesmata and plasmalemmal control centers). As an important agent in the control of cellular activities, according to this model, the endomembrane sheath would play a major part in responses to diverse signals and stresses, and under extreme stress cell survival would depend on the ability of the system to maintain enough integrity to direct critical syntheses and degradations.

Espins and the actin cytoskeleton of hair cell stereocilia and sensory cell microvilli

PubMed Central

Sekerková, Gabriella; Zheng, Lili; Loomis, Patricia A.; Mugnaini, Enrico; Bartles, James R.

2008-01-01

The espins are novel actin-bundling proteins that are produced in multiple isoforms from a single gene. They are present at high concentration in the parallel actin bundle of hair cell stereocilia and are the target of deafness mutations in mice and humans. Espins are also enriched in the microvilli of taste receptor cells, solitary chemoreceptor cells, vomeronasal sensory neurons and Merkel cells, suggesting that espins play important roles in the microvillar projections of vertebrate sensory cells. Espins are potent actin-bundling proteins that are not inhibited by Ca2+. In cells, they efficiently elongate parallel actin bundles and, thereby, help determine the steady-state length of microvilli and stereocilia. Espins bind actin monomer via their WH2 domain and can assemble actin bundles in cells. Certain espin isoforms can also bind phosphatidylinositol 4,5-bisphosphate, profilins or SH3 proteins. These biological activities distinguish espins from other actin-bundling proteins and may make them well-suited to sensory cells. PMID:16909209

Interactions of C 4 Subtype Metabolic Activities and Transport in Maize Are Revealed through the Characterization of DCT2 Mutants

DOE PAGES

Weissmann, Sarit; Ma, Fangfang; Furuyama, Koki; ...

2016-01-26

C 4 photosynthesis in grasses requires the coordinated movement of metabolites through two specialized leaf cell types, mesophyll (M) and bundle sheath (BS), to concentrate CO 2 around Rubisco. Despite the importance of transporters in this process, few have been identified or rigorously characterized. In maize (Zea mays), DCT2 has been proposed to function as a plastid-localizedmalate transporter and is preferentially expressed in BS cells. Here, we characterized the role of DCT2 in maize leaves using Activator-tagged mutant alleles. Our results indicate that DCT2 enables the transport of malate into the BS chloroplast. Isotopic labeling experiments show that the lossmore » of DCT2 results in markedly different metabolic network operation and dramatically reduced biomass production. In the absence of a functioning malate shuttle, dct2 lines survive through the enhanced use of the phosphoenolpyruvate carboxykinase carbon shuttle pathway that in wild-type maize accounts for ;25% of the photosynthetic activity. The results emphasize the importance of malate transport during C 4 photosynthesis, define the role of a primary malate transporter in BS cells, and support a model for carbon exchange between BS and M cells in maize.« less

Hedgehog signaling is required for formation of the notochord sheath and patterning of nuclei pulposi within the intervertebral discs

PubMed Central

Choi, Kyung-Suk; Harfe, Brian D.

2011-01-01

The vertebrae notochord is a transient rod-like structure that produces secreted factors that are responsible for patterning surrounding tissues. During later mouse embryogenesis, the notochord gives rise to the middle part of the intervertebral disc, called the nucleus pulposus. Currently, very little is known about the molecular mechanisms responsible for forming the intervertebral discs. Here we demonstrate that hedgehog signaling is required for formation of the intervertebral discs. Removal of hedgehog signaling in the notochord and nearby floorplate resulted in the formation of an aberrant notochord sheath that normally surrounds this structure. In the absence of the notochord sheath, small nuclei pulposi were formed, with most notochord cells dispersed throughout the vertebral bodies during embryogenesis. Our data suggest that the formation of the notochord sheath requires hedgehog signaling and that the sheath is essential for maintaining the rod-like structure of the notochord during early embryonic development. As notochord cells form nuclei pulposi, we propose that the notochord sheath functions as a “wrapper” around the notochord to constrain these cells along the vertebral column. PMID:21606373

Hedgehog signaling is required for formation of the notochord sheath and patterning of nuclei pulposi within the intervertebral discs.

PubMed

Choi, Kyung-Suk; Harfe, Brian D

2011-06-07

The vertebrae notochord is a transient rod-like structure that produces secreted factors that are responsible for patterning surrounding tissues. During later mouse embryogenesis, the notochord gives rise to the middle part of the intervertebral disc, called the nucleus pulposus. Currently, very little is known about the molecular mechanisms responsible for forming the intervertebral discs. Here we demonstrate that hedgehog signaling is required for formation of the intervertebral discs. Removal of hedgehog signaling in the notochord and nearby floorplate resulted in the formation of an aberrant notochord sheath that normally surrounds this structure. In the absence of the notochord sheath, small nuclei pulposi were formed, with most notochord cells dispersed throughout the vertebral bodies during embryogenesis. Our data suggest that the formation of the notochord sheath requires hedgehog signaling and that the sheath is essential for maintaining the rod-like structure of the notochord during early embryonic development. As notochord cells form nuclei pulposi, we propose that the notochord sheath functions as a "wrapper" around the notochord to constrain these cells along the vertebral column.

Negative hair-bundle stiffness betrays a mechanism for mechanical amplification by the hair cell.

PubMed

Martin, P; Mehta, A D; Hudspeth, A J

2000-10-24

Hearing and balance rely on the ability of hair cells in the inner ear to sense miniscule mechanical stimuli. In each cell, sound or acceleration deflects the mechanosensitive hair bundle, a tuft of rigid stereocilia protruding from the cell's apical surface. By altering the tension in gating springs linked to mechanically sensitive transduction channels, this deflection changes the channels' open probability and elicits an electrical response. To detect weak stimuli despite energy losses caused by viscous dissipation, a hair cell can use active hair-bundle movement to amplify its mechanical inputs. This amplificatory process also yields spontaneous bundle oscillations. Using a displacement-clamp system to measure the mechanical properties of individual hair bundles from the bullfrog's ear, we found that an oscillatory bundle displays negative slope stiffness at the heart of its region of mechanosensitivity. Offsetting the hair bundle's position activates an adaptation process that shifts the region of negative stiffness along the displacement axis. Modeling indicates that the interplay between negative bundle stiffness and the motor responsible for mechanical adaptation produces bundle oscillation similar to that observed. Just as the negative resistance of electrically excitable cells and of tunnel diodes can be embedded in a biasing circuit to amplify electrical signals, negative stiffness can be harnessed to amplify mechanical stimuli in the ear.

Spine Patterning Is Guided by Segmentation of the Notochord Sheath.

PubMed

Wopat, Susan; Bagwell, Jennifer; Sumigray, Kaelyn D; Dickson, Amy L; Huitema, Leonie F A; Poss, Kenneth D; Schulte-Merker, Stefan; Bagnat, Michel

2018-02-20

The spine is a segmented axial structure made of alternating vertebral bodies (centra) and intervertebral discs (IVDs) assembled around the notochord. Here, we show that, prior to centra formation, the outer epithelial cell layer of the zebrafish notochord, the sheath, segments into alternating domains corresponding to the prospective centra and IVD areas. This process occurs sequentially in an anteroposterior direction via the activation of Notch signaling in alternating segments of the sheath, which transition from cartilaginous to mineralizing domains. Subsequently, osteoblasts are recruited to the mineralized domains of the notochord sheath to form mature centra. Tissue-specific manipulation of Notch signaling in sheath cells produces notochord segmentation defects that are mirrored in the spine. Together, our findings demonstrate that notochord sheath segmentation provides a template for vertebral patterning in the zebrafish spine. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

Wilms Tumor 1b defines a wound-specific sheath cell subpopulation associated with notochord repair

PubMed Central

Lopez-Baez, Juan Carlos; Zeng, Zhiqiang; Brunsdon, Hannah; Salzano, Angela; Brombin, Alessandro; Wyatt, Cameron; Rybski, Witold; Huitema, Leonie F A; Dale, Rodney M; Kawakami, Koichi; Englert, Christoph; Chandra, Tamir; Schulte-Merker, Stefan

2018-01-01

Regenerative therapy for degenerative spine disorders requires the identification of cells that can slow down and possibly reverse degenerative processes. Here, we identify an unanticipated wound-specific notochord sheath cell subpopulation that expresses Wilms Tumor (WT) 1b following injury in zebrafish. We show that localized damage leads to Wt1b expression in sheath cells, and that wt1b+cells migrate into the wound to form a stopper-like structure, likely to maintain structural integrity. Wt1b+sheath cells are distinct in expressing cartilage and vacuolar genes, and in repressing a Wt1b-p53 transcriptional programme. At the wound, wt1b+and entpd5+ cells constitute separate, tightly-associated subpopulations. Surprisingly, wt1b expression at the site of injury is maintained even into adult stages in developing vertebrae, which form in an untypical manner via a cartilage intermediate. Given that notochord cells are retained in adult intervertebral discs, the identification of novel subpopulations may have important implications for regenerative spine disorder treatments. PMID:29405914

Comparative transduction mechanisms of hair cells in the bullfrog uticulus. 2: Sensitivity and response dynamics to hair bundle displacement

NASA Technical Reports Server (NTRS)

Baird, Richard A.

1994-01-01

The present study was motivated by an interest in seeing whether hair cell types in the bullfrog utriculus might differ in their voltage responses to hair bundle displacement. Particular interest was in assessing the contributions of two factors to the responses of utricular hair cells. First, interest in examining the effect of hair bundle morphology on the sensitivity of hair cells to natural stimulation was motivated by the observation that vestibular hair cells, unlike many auditory hair cells, are not free-standing but rather linked to an accessory cupular or otolithic membrane via the tip of their kinocilium. Interest also laid in examining the contribution, if any, of adaptation to the response properties of utricular hair cells. Hair cells in auditory and vibratory inner ear endorgans adapt to maintained displacements of their hair bundles, sharply limiting their low frequency sensitivity. This adaptation is mediated by a shift in the displacement-response curve (DRC) of the hair cell along the displacement axis. Observations suggest that the adaptation process occurs within the hair bundle and precedes mechanoelectric transduction. Recent observations of time-dependent changes in hair bundle stiffness are consistent with this conclusion. Adaptation would be expected to be most useful in inner ear endorgans in which hair cells are subject to large static displacements that could potentially saturate their instantaneous response and compromise their sensitivity to high frequency stimulation. The adaptation process also permits hair cells to maintain their sensory hair bundle in the most sensitive portion of their DRC. In vestibular otolith organs in which static sensitivity is desirable, any adaptation process in the hair cells may be undesirable. The rate and extent of the decline of the voltage responses was measured of utricular hair cells to step and sinusoidal hair bundle displacements. Then for similar resting potentials and response amplitudes, the voltage responses of individual hair cells were compared to both hair bundle displacement and intracellular current.

Photovoltaic sheathing element with a flexible connector assembly

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

Langmaid, Joseph A; Keenihan, James R; Mills, Michael E

2016-07-12

The present invention is premised upon an assembly including at least a photovoltaic sheathing element capable of being affixed on a building structure, the sheathing element including at least: a photovoltaic cell assembly, a body portion attached to one or more portions of the photovoltaic cell assembly; at least a first and a second connector assembly disposed on opposing sides of the sheathing element and capable of directly or indirectly electrically connecting the photovoltaic cell assembly to at least two adjoining devices that are affixed to the building structure and wherein at least one of the connector assemblies includes amore » flexible portion; one or more connector pockets disposed in the body portion the pockets capable of receiving at least a portion of the connector assembly.« less

Analysis of the Proteome of Hair-Cell Stereocilia by Mass Spectrometry

PubMed Central

Krey, Jocelyn F.; Wilmarth, Philip A.; David, Larry L.; Barr-Gillespie, Peter G.

2017-01-01

Characterization of proteins that mediate mechanotransduction by hair cells, the sensory cells of the inner ear, is hampered by the scarcity of these cells and their sensory organelle, the hair bundle. Mass spectrometry, with its high sensitivity and identification precision, is the ideal method for determining which proteins are present in bundles and what proteins they interact with. We describe here the isolation of mouse hair bundles, as well as preparation of bundle-protein samples for mass spectrometry. We also describe protocols for data-dependent (shotgun) and parallel-reaction-monitoring (targeted) mass spectrometry that allow us to identify and quantify proteins of the hair bundle. These sensitive methods are particularly useful for comparing proteomes of wild-type and mice with deafness mutations affecting hair-bundle proteins. (120 words; maximum 250) PMID:28109437

Two Genera of Magnetococci with Bean-like Morphology from Intertidal Sediments of the Yellow Sea, China

PubMed Central

Zhang, Wen-Yan; Zhou, Ke; Pan, Hong-Miao; Yue, Hai-Dong; Jiang, Ming

2012-01-01

Magnetotactic bacteria have the unique capacity of being able to swim along geomagnetic field lines. They are Gram-negative bacteria with diverse morphologies and variable phylogenetic relatedness. Here, we describe a group of uncultivated marine magnetococci collected from intertidal sediments of Huiquan Bay in the Yellow Sea. They were coccoid-ovoid in morphology, with an average size of 2.8 ± 0.3 μm by 2.0 ± 0.2 μm. Differential interference contrast microscopy, fluorescence microscopy, and transmission electron microscopy revealed that each cell was apparently composed of two hemispheres. The cells synthesized iron oxide-type magnetosomes that clustered on one side of the cell at the interface between the two hemispheres. In some cells two chains of magnetosomes were observed across the interface. Each cell had two bundles of flagella enveloped in a sheath and displayed north-seeking helical motion. Two 16S rRNA gene sequences having 91.8% identity were obtained, and their authenticity was confirmed by fluorescence in situ hybridization. Phylogenetic analysis revealed that the magnetococci are affiliated with the Alphaproteobacteria and are most closely related to two uncultured magnetococci with sequence identities of 92.7% and 92.4%, respectively. Because they display a >7% sequence divergence to all bacteria reported, the bean-like magnetococci may represent two novel genera. PMID:22660708

Phloem loading in Verbascum phoeniceum L. depends on the synthesis of raffinose-family oligosaccharides

PubMed Central

McCaskill, Ashlee; Turgeon, Robert

2007-01-01

Phloem loading is the initial step in photoassimilate export and the one that creates the driving force for mass flow. It has been proposed that loading occurs symplastically in species that translocate carbohydrate primarily as raffinose family oligosaccharides (RFOs). In these plants, dense fields of plasmodesmata connect bundle sheath cells to specialized companion cells (intermediary cells) in the minor veins. According to the polymer trap model, advanced as a mechanism of symplastic loading, sucrose from the mesophyll diffuses into intermediary cells and is converted there to RFOs. This process keeps the sucrose concentration low and, because of the larger size of the RFOs, prevents back diffusion. To test this model, the RFO pathway was down-regulated in Verbascum phoeniceum L. by suppressing the synthesis of galactinol synthase (GAS), which catalyzes the first committed step in RFO production. Two GAS genes (VpGAS1 and VpGAS2) were cloned and shown to be expressed in intermediary cells. Simultaneous RNAi suppression of both genes resulted in pronounced inhibition of RFO synthesis. Phloem transport was negatively affected, as evidenced by the accumulation of carbohydrate in the lamina and the reduced capacity of leaves to export sugars during a prolonged dark period. In plants with severe down-regulation, additional symptoms of reduced export were obvious, including impaired growth, leaf chlorosis, and necrosis and curling of leaf margins. PMID:18048337

Fascial structures and autonomic nerves in the female pelvis: a study using macroscopic slices and their corresponding histology.

PubMed

Tamakawa, Mitsuharu; Murakami, Gen; Takashima, Ken; Kato, Tomoyasu; Hareyama, Masato

2003-12-01

We investigated the topographical anatomy of the pelvic fasciae and autonomic nerves using macroscopic slices of five decalcified female pelves. The lateral aspect of the supravaginal cervix uteri and superior-most vagina issued abundant thick fiber bundles. These visceral fibrous tissues extended dorsolaterally, joined another fibrous tissue from the rectum (the actual lateral ligament of the rectum) and attached to the parietal fibrous tissues at and around the sciatic foramina (i.e. the sacrospinous ligament, thick fasciae of the coccygeus and piriformis and dorsal end of the covering fascia of the levator ani). The inferior or ventral vagina also issued thick fiber bundles communicating with the levator ani fascia. This connection between the vagina and levator fascia, when stretched, seemed to provide a macroscopic morphology called the arcus tendineus fasciae pelvis. The overall morphology of the visceroparietal fascial bridge exhibited a bilateral wing-like shape. The fascial bridge complex was adjacent but dorso-inferior to the internal iliac vascular sheath and located slightly ventral to the pelvic splanchnic nerve. However, the pelvic plexus and its peripheral branches were embedded in the fascial complex. The hypogastric nerve ran along and beneath the uterosacral peritoneal fold, which did not contain thick fibrous tissue. During surgery, in combination with the superficially located vascular sheath, the morphology of the visceroparietal fascial bridge and associated nerves seemed to be artificially changed and developed into the so-called cardinal, uterosacral, uterovesical and/or rectal lateral ligaments. The classical and original concepts of these pelvic fascial structures may need to be altered to adjust to these surgical observations.

Hair bundles of cochlear outer hair cells are shaped to minimize their fluid-dynamic resistance.

PubMed

Ciganović, Nikola; Wolde-Kidan, Amanuel; Reichenbach, Tobias

2017-06-15

The mammalian sense of hearing relies on two types of sensory cells: inner hair cells transmit the auditory stimulus to the brain, while outer hair cells mechanically modulate the stimulus through active feedback. Stimulation of a hair cell is mediated by displacements of its mechanosensitive hair bundle which protrudes from the apical surface of the cell into a narrow fluid-filled space between reticular lamina and tectorial membrane. While hair bundles of inner hair cells are of linear shape, those of outer hair cells exhibit a distinctive V-shape. The biophysical rationale behind this morphology, however, remains unknown. Here we use analytical and computational methods to study the fluid flow across rows of differently shaped hair bundles. We find that rows of V-shaped hair bundles have a considerably reduced resistance to crossflow, and that the biologically observed shapes of hair bundles of outer hair cells are near-optimal in this regard. This observation accords with the function of outer hair cells and lends support to the recent hypothesis that inner hair cells are stimulated by a net flow, in addition to the well-established shear flow that arises from shearing between the reticular lamina and the tectorial membrane.

Characterization of C₃--C₄ intermediate species in the genus Heliotropium L. (Boraginaceae): anatomy, ultrastructure and enzyme activity.

PubMed

Muhaidat, Riyadh; Sage, Tammy L; Frohlich, Michael W; Dengler, Nancy G; Sage, Rowan F

2011-10-01

Photosynthetic pathway characteristics were studied in nine species of Heliotropium (sensu lato, including Euploca), using assessments of leaf anatomy and ultrastructure, activities of PEP carboxylase and C₄ acid decarboxylases, and immunolocalization of ribulose 1·5-bisphosphate carboxylase/oxygenase (Rubisco) and the P-subunit of glycine decarboxylase (GDC). Heliotropium europaeum, Heliotropium calcicola and Heliotropium tenellum are C₃ plants, while Heliotropium texanum and Heliotropium polyphyllum are C₄ species. Heliotropium procumbens and Heliotropium karwinskyi are functionally C₃, but exhibit 'proto-Kranz' anatomy where bundle sheath (BS) cells are enlarged and mitochondria primarily occur along the centripetal (inner) wall of the BS cells; GDC is present throughout the leaf. Heliotropium convolvulaceum and Heliotropium greggii are C₃--C₄ intermediates, with Kranz-like enlargement of the BS cells, localization of mitochondria along the inner BS wall and a loss of GDC in the mesophyll (M) tissue. These C₃--C₄ species of Heliotropium probably shuttle photorespiratory glycine from the M to the BS tissue for decarboxylation. Heliotropium represents an important new model for studying C₄ evolution. Where existing models such as Flaveria emphasize diversification of C₃--C₄ intermediates, Heliotropium has numerous C₃ species expressing proto-Kranz traits that could represent a critical initial phase in the evolutionary origin of C₄ photosynthesis. © 2011 Blackwell Publishing Ltd.

Dissociation and Re-Aggregation of Multicell-Ensheathed Fragments Responsible for Rapid Production of Massive Clumps of Leptothrix Sheaths

PubMed Central

Kunoh, Tatsuki; Nagaoka, Noriyuki; McFarlane, Ian R.; Tamura, Katsunori; El-Naggar, Mohamed Y.; Kunoh, Hitoshi; Takada, Jun

2016-01-01

Species of the Fe/Mn-oxidizing bacteria Leptothrix produce tremendous amounts of microtubular, Fe/Mn-encrusted sheaths within a few days in outwells of groundwater that can rapidly clog water systems. To understand this mode of rapid sheath production and define the timescales involved, behaviors of sheath-forming Leptothrix sp. strain OUMS1 were examined using time-lapse video at the initial stage of sheath formation. OUMS1 formed clumps of tangled sheaths. Electron microscopy confirmed the presence of a thin layer of bacterial exopolymer fibrils around catenulate cells (corresponding to the immature sheath). In time-lapse videos, numerous sheath filaments that extended from the periphery of sheath clumps repeatedly fragmented at the apex of the same fragment, the fragments then aggregated and again elongated, eventually forming a large sheath clump comprising tangled sheaths within two days. In this study, we found that fast microscopic fragmentation, dissociation, re-aggregation and re-elongation events are the basis of the rapid, massive production of Leptothrix sheaths typically observed at macroscopic scales. PMID:27490579

Independent and parallel evolution of new genes by gene duplication in two origins of C4 photosynthesis provides new insight into the mechanism of phloem loading in C4 species

DOE PAGES

Emms, David M.; Covshoff, Sarah; Hibberd, Julian M.; ...

2016-03-24

C4 photosynthesis is considered one of the most remarkable examples of evolutionary convergence in eukaryotes. However, it is unknown whether the evolution of C4 photosynthesis required the evolution of new genes. Genome-wide gene-tree species-tree reconciliation of seven monocot species that span two origins of C4 photosynthesis revealed that there was significant parallelism in the duplication and retention of genes coincident with the evolution of C4 photosynthesis in these lineages. Specifically, 21 orthologous genes were duplicated and retained independently in parallel at both C4 origins. Analysis of this gene cohort revealed that the set of parallel duplicated and retained genes ismore » enriched for genes that are preferentially expressed in bundle sheath cells, the cell type in which photosynthesis was activated during C4 evolution. Moreover, functional analysis of the cohort of parallel duplicated genes identified SWEET-13 as a potential key transporter in the evolution of C4 photosynthesis in grasses, and provides new insight into the mechanism of phloem loading in these C4 species.« less

Expression of the ribulose-1,5-bisphosphate carboxylase large subunit gene and three small subunit genes in two cell types of maize leaves

PubMed Central

Sheen, Jenq-Yunn; Bogorad, Lawrence

1986-01-01

Transcripts of three distinct ribulose-1,5-bisphosphate carboxylase (RuBPC) small subunit (SS) genes account for ∼90% of the mRNA for this protein in maize leaves. Transcripts of two of them constitute >80% of the SS mRNA in 24-h greening maize leaves. The third gene contribute ∼10%. Transcripts of all three nuclear-encoded SS genes are detectable in bundle sheath (BSC) and mesophyll cells (MC) of etiolated maize leaves. The level of mRNA for each gene is different in etioplasts of MC but all drop during photoregulated development of chloroplasts in MC and follow a pattern of transitory rise and fall in BSC. The amounts of LS and SS proteins continue to increase steadily well after the mRNA levels reach their peaks in BSC. The molar ratio of mRNA for chloroplast-encoded RuBPC large subunit (LS) to the nuclear genome encoded SS is about 10:1 although LS and SS proteins are present in about equimolar amounts. ImagesFig. 1.Fig. 2.Fig. 3.Fig. 4.Fig. 5.Fig. 6. PMID:16453739

Vesicles Are Persistent Features of Different Plastids.

PubMed

Lindquist, Emelie; Solymosi, Katalin; Aronsson, Henrik

2016-10-01

Peripheral vesicles in plastids have been observed repeatedly, primarily in proplastids and developing chloroplasts, in which they are suggested to function in thylakoid biogenesis. Previous observations of vesicles in mature chloroplasts have mainly concerned low temperature pretreated plants occasionally treated with inhibitors blocking vesicle fusion. Here, we show that such vesicle-like structures occur not only in chloroplasts and proplastids, but also in etioplasts, etio-chloroplasts, leucoplasts, chromoplasts and even transforming desiccoplasts without any specific pretreatment. Observations are made both in C3 and C4 species, in different cell types (meristematic, epidermis, mesophyll, bundle sheath and secretory cells) and different organs (roots, stems, leaves, floral parts and fruits). Until recently not much focus has been given to the idea that vesicle transport in chloroplasts could be mediated by proteins, but recent data suggest that the vesicle system of chloroplasts has similarities with the cytosolic coat protein complex II system. All current data taken together support the idea of an ongoing, active and protein-mediated vesicle transport not only in chloroplasts but also in other plastids, obviously occurring regardless of chemical modifications, temperature and plastid developmental stage. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Photovoltaic building sheathing element with anti-slide features

DOEpatents

Keenihan, James R.; Langmaid, Joseph A.; Lopez, Leonardo C.

2015-09-08

The present invention is premised` upon an assembly that includes at least a photovoltaic building sheathing element capable of being affixed on a building structure, the photovoltaic building sheathing element. The element including a photovoltaic cell assembly, a body portion attached to one or more portions of the photovoltaic cell assembly; and at feast a first and a second connector assembly capable of directly or indirectly electrically connecting the photovoltaic cell assembly to one or more adjoining devices; wherein the body portion includes one or more geometric features adapted to engage a vertically adjoining device before installation.

Steady-state stiffness of utricular hair cells depends on macular location and hair bundle structure.

PubMed

Spoon, Corrie; Moravec, W J; Rowe, M H; Grant, J W; Peterson, E H

2011-12-01

Spatial and temporal properties of head movement are encoded by vestibular hair cells in the inner ear. One of the most striking features of these receptors is the orderly structural variation in their mechanoreceptive hair bundles, but the functional significance of this diversity is poorly understood. We tested the hypothesis that hair bundle structure is a significant contributor to hair bundle mechanics by comparing structure and steady-state stiffness of 73 hair bundles at varying locations on the utricular macula. Our first major finding is that stiffness of utricular hair bundles varies systematically with macular locus. Stiffness values are highest in the striola, near the line of hair bundle polarity reversal, and decline exponentially toward the medial extrastriola. Striolar bundles are significantly more stiff than those in medial (median: 8.9 μN/m) and lateral (2.0 μN/m) extrastriolae. Within the striola, bundle stiffness is greatest in zone 2 (106.4 μN/m), a band of type II hair cells, and significantly less in zone 3 (30.6 μN/m), which contains the only type I hair cells in the macula. Bathing bundles in media that break interciliary links produced changes in bundle stiffness with predictable time course and magnitude, suggesting that links were intact in our standard media and contributed normally to bundle stiffness during measurements. Our second major finding is that bundle structure is a significant predictor of steady-state stiffness: the heights of kinocilia and the tallest stereocilia are the most important determinants of bundle stiffness. Our results suggest 1) a functional interpretation of bundle height variability in vertebrate vestibular organs, 2) a role for the striola in detecting onset of head movement, and 3) the hypothesis that differences in bundle stiffness contribute to diversity in afferent response dynamics.

Steady-state stiffness of utricular hair cells depends on macular location and hair bundle structure

PubMed Central

Spoon, Corrie; Moravec, W. J.; Rowe, M. H.; Grant, J. W.

2011-01-01

Spatial and temporal properties of head movement are encoded by vestibular hair cells in the inner ear. One of the most striking features of these receptors is the orderly structural variation in their mechanoreceptive hair bundles, but the functional significance of this diversity is poorly understood. We tested the hypothesis that hair bundle structure is a significant contributor to hair bundle mechanics by comparing structure and steady-state stiffness of 73 hair bundles at varying locations on the utricular macula. Our first major finding is that stiffness of utricular hair bundles varies systematically with macular locus. Stiffness values are highest in the striola, near the line of hair bundle polarity reversal, and decline exponentially toward the medial extrastriola. Striolar bundles are significantly more stiff than those in medial (median: 8.9 μN/m) and lateral (2.0 μN/m) extrastriolae. Within the striola, bundle stiffness is greatest in zone 2 (106.4 μN/m), a band of type II hair cells, and significantly less in zone 3 (30.6 μN/m), which contains the only type I hair cells in the macula. Bathing bundles in media that break interciliary links produced changes in bundle stiffness with predictable time course and magnitude, suggesting that links were intact in our standard media and contributed normally to bundle stiffness during measurements. Our second major finding is that bundle structure is a significant predictor of steady-state stiffness: the heights of kinocilia and the tallest stereocilia are the most important determinants of bundle stiffness. Our results suggest 1) a functional interpretation of bundle height variability in vertebrate vestibular organs, 2) a role for the striola in detecting onset of head movement, and 3) the hypothesis that differences in bundle stiffness contribute to diversity in afferent response dynamics. PMID:21918003

Multiple pass gas absorption cell utilizing a spherical mirror opposite one or more pair of obliquely disposed flat mirrors

NASA Technical Reports Server (NTRS)

Pearson, Richard (Inventor); Lynch, Dana H. (Inventor); Gunter, William D. (Inventor)

1995-01-01

A method and apparatus for passing light bundles through a multiple pass sampling cell is disclosed. The multiple pass sampling cell includes a sampling chamber having first and second ends positioned along a longitudinal axis of the sampling cell. The sampling cell further includes an entrance opening, located adjacent the first end of the sampling cell at a first azimuthal angular position. The entrance opening permits a light bundle to pass into the sampling cell. The sampling cell also includes an exit opening at a second azimuthal angular position. The light exit permits a light bundle to pass out of the sampling cell after the light bundle has followed a predetermined path.

Flow cytometry apparatus

DOEpatents

Pinkel, D.

1987-11-30

An obstruction across the flow chamber creates a one-dimensional convergence of a sheath fluid. A passageway in the obstruction directs flat cells near to the area of one-dimensional convergence in the sheath fluid to provide proper orientation of flat cells at fast rates. 6 figs.

Spatially Resolved Distribution of Fe Species around Microbes at the Submicron Scale in Natural Bacteriogenic Iron Oxides.

PubMed

Suga, Hiroki; Kikuchi, Sakiko; Takeichi, Yasuo; Miyamoto, Chihiro; Miyahara, Masaaki; Mitsunobu, Satoshi; Ohigashi, Takuji; Mase, Kazuhiko; Ono, Kanta; Takahashi, Yoshio

2017-09-27

Natural bacteriogenic iron oxides (BIOS) were investigated using local-analyzable synchrotron-based scanning transmission X-ray microscopy (STXM) with a submicron-scale resolution. Cell, cell sheath interface (EPS), and sheath in the BIOS were clearly depicted using C-, N-, and O- near edge X-ray absorption fine structure (NEXAFS) obtained through STXM measurements. Fe-NEXAFS obtained from different regions of BIOS indicated that the most dominant iron mineral species was ferrihydrite. Fe(II)- and/or Fe(III)-acidic polysaccharides accompanied ferrihydrite near the cell and EPS regions. Our STXM/NEXAFS analysis showed that Fe species change continuously between the cell, EPS, and sheath under several 10-nm scales.

Thermal hydraulic design and decay heat removal of a solid target for a spallation neutron source

NASA Astrophysics Data System (ADS)

Takenaka, N.; Nio, D.; Kiyanagi, Y.; Mishima, K.; Kawai, M.; Furusaka, M.

2005-08-01

Thermal hydraulic design and thermal stress calculations were conducted for a water-cooled solid target irradiated by a MW-class proton beam for a spallation neutron source. Plate type and rod bundle type targets were examined. The thickness of the plate and the diameter of the rod were determined based on the maximum and the wall surface temperature. The thermal stress distributions were calculated by a finite element method (FEM). The neutronics performance of the target is roughly proportional to its average density. The averaged densities of the designed targets were calculated for tungsten plates, tantalum clad tungsten plates, tungsten rods sheathed by tantalum and Zircaloy and they were compared with mercury density. It was shown that the averaged density was highest for the tungsten plates and was high for the tantalum cladding tungsten plates, the tungsten rods sheathed by tantalum and Zircaloy in order. They were higher than or equal to that of mercury for the 1 2 MW proton beams. Tungsten target without the cladding or the sheath is not practical due to corrosion by water under irradiation condition. Therefore, the tantalum cladding tungsten plate already made successfully by HIP and the sheathed tungsten rod are the candidate of high performance solid targets. The decay heat of each target was calculated. It was low enough low compared to that of ISIS for the target without tantalum but was about four times as high as that of ISIS when the thickness of the tantalum cladding was 0.5 mm. Heat removal methods of the decay heat with tantalum were examined. It was shown that a special cooling system was required for the target exchange when tantalum was used for the target. It was concluded that the tungsten rod target sheathed with stainless steel or Zircaloy was the most reliable from the safety considerations and had similar neutronics performance to that of mercury.

Electromagnetic Particle-In-Cell simulation on the impedance of a dipole antenna surrounded by an ion sheath

NASA Astrophysics Data System (ADS)

Miyake, Y.; Usui, H.; Kojima, H.; Omura, Y.; Matsumoto, H.

2008-06-01

We have newly developed a numerical tool for the analysis of antenna impedance in plasma environment by making use of electromagnetic Particle-In-Cell (PIC) plasma simulations. To validate the developed tool, we first examined the antenna impedance in a homogeneous kinetic plasma and confirmed that the obtained results basically agree with the conventional theories. We next applied the tool to examine an ion-sheathed dipole antenna. The results confirmed that the inclusion of the ion-sheath effects reduces the capacitance below the electron plasma frequency. The results also revealed that the signature of impedance resonance observed at the plasma frequency is modified by the presence of the sheath. Since the sheath dynamics can be solved by the PIC scheme throughout the antenna analysis in a self-consistent manner, the developed tool has feasibility to perform more practical and complicated antenna analyses that will be necessary in real space missions.

Synchronization of Spontaneous Active Motility of Hair Cell Bundles

PubMed Central

Zhang, Tracy-Ying; Ji, Seung; Bozovic, Dolores

2015-01-01

Hair cells of the inner ear exhibit an active process, believed to be crucial for achieving the sensitivity of auditory and vestibular detection. One of the manifestations of the active process is the occurrence of spontaneous hair bundle oscillations in vitro. Hair bundles are coupled by overlying membranes in vivo; hence, explaining the potential role of innate bundle motility in the generation of otoacoustic emissions requires an understanding of the effects of coupling on the active bundle dynamics. We used microbeads to connect small groups of hair cell bundles, using in vitro preparations that maintain their innate oscillations. Our experiments demonstrate robust synchronization of spontaneous oscillations, with either 1:1 or multi-mode phase-locking. The frequency of synchronized oscillation was found to be near the mean of the innate frequencies of individual bundles. Coupling also led to an improved regularity of entrained oscillations, demonstrated by an increase in the quality factor. PMID:26540409

Human dermal papilla cells and outer root sheath cells: no follicular differentiation in nude mice and chicken embryos.

PubMed

Chiu, H C; Chang, C H; Jee, S H; Chang, C C; Wu, Y C

1994-09-01

Human scalp specimens were incubated in 5 U/ml dispase solution at 4 degrees C overnight before the isolation of dermal papillae and follicle epithelium. This pretreatment not only facilitated the attachment and cell outgrowth of dermal papillae but also made it easier to pluck out hairs with intact follicle epithelium. The outer root sheath cells were released from the follicle epithelium and grown on a feeder layer of mitomycin C-treated human dermal fibroblasts. The subcultured outer root sheath cells were grown in a serum-free medium. When the mixtures of early-passage dermal papilla cells and outer root sheath cells were injected into the subcutis of nude mice, an epidermal cyst surrounded by layers of fibrous tissue was found in three weeks. No hair follicles were found when the mixtures were implanted onto the chorioallantoic membrane of nine-day-old chicken embryos. A keratinized mass lying on the chorionic epithelium with or without smaller similar masses in the chorioallantoic membrane was found in eight days. No hair follicle-like structure could be found. Possible factors contributing to the failure to undergo follicular differentiation in this study are discussed.

Stimulation of hair cells with ultraviolet light

NASA Astrophysics Data System (ADS)

Azimzadeh, Julien B.; Fabella, Brian A.; Hudspeth, A. J.

2018-05-01

Hair bundles are specialized organelles that transduce mechanical inputs into electrical outputs. To activate hair cells, physiologists have resorted to mechanical methods of hair-bundle stimulation. Here we describe a new method of hair-bundle stimulation, irradiation with ultraviolet light. A hair bundle illuminated by ultraviolet light rapidly moves towards its tall edge, a motion typically associated with excitatory stimulation. The motion disappears upon tip-link rupture and is associated with the opening of mechanotransduction channels. Hair bundles can be induced to move sinusoidally with oscillatory modulation of the stimulation power. We discuss the implications of ultraviolet stimulation as a novel hair-bundle stimulus.

The role of the parenchyma sheath and PCD during the development of oil cavities in Pterodon pubescens (Leguminosae-Papilionoideae).

PubMed

Rodrigues, Tatiane Maria; Santos, Daniela Carvalho Dos; Machado, Silvia Rodrigues

2011-07-01

Pterodon pubescens cavities are constituted by lumen and uniseriated epithelium surrounded by multiseriate parenchyma sheath. We studied the development of secretory cavities, including the role of parenchyma sheath, using light and transmission electron microscopy. A Tunel assay was performed to verify whether programmed cell death (PCD) occurs during the process. The lumen is formed by schizogeny and lysigeny occur in later developmental stages of the secretory cavities. Ultrastructurally, epithelial cells in later developmental stages become dark and with sinuous walls; the protoplast becomes retracted and the cytoplasm shows low organelle definition. Degenerated cells are released toward the lumen. Our results showed that PCD occurs during later developmental stages of cavities and plays a critical role in functioning of these glands. New cells originated from the parenchyma sheath differentiate into secretory cells and replace those degenerated ones. This fact associated to PCD guarantees epithelium renovation during the secretory cycle and the maintenance of secretory activity of cavities. Copyright © 2011 Académie des sciences. Published by Elsevier SAS. All rights reserved.

From cell differentiation to cell collectives: Bacillus subtilis uses division of labor to migrate.

PubMed

van Gestel, Jordi; Vlamakis, Hera; Kolter, Roberto

2015-04-01

The organization of cells, emerging from cell-cell interactions, can give rise to collective properties. These properties are adaptive when together cells can face environmental challenges that they separately cannot. One particular challenge that is important for microorganisms is migration. In this study, we show how flagellum-independent migration is driven by the division of labor of two cell types that appear during Bacillus subtilis sliding motility. Cell collectives organize themselves into bundles (called "van Gogh bundles") of tightly aligned cell chains that form filamentous loops at the colony edge. We show, by time-course microscopy, that these loops migrate by pushing themselves away from the colony. The formation of van Gogh bundles depends critically on the synergistic interaction of surfactin-producing and matrix-producing cells. We propose that surfactin-producing cells reduce the friction between cells and their substrate, thereby facilitating matrix-producing cells to form bundles. The folding properties of these bundles determine the rate of colony expansion. Our study illustrates how the simple organization of cells within a community can yield a strong ecological advantage. This is a key factor underlying the diverse origins of multicellularity.

Faster Rubisco Is the Key to Superior Nitrogen-Use Efficiency in NADP-Malic Enzyme Relative to NAD-Malic Enzyme C4 Grasses1

PubMed Central

Ghannoum, Oula; Evans, John R.; Chow, Wah Soon; Andrews, T. John; Conroy, Jann P.; von Caemmerer, Susanne

2005-01-01

In 27 C4 grasses grown under adequate or deficient nitrogen (N) supplies, N-use efficiency at the photosynthetic (assimilation rate per unit leaf N) and whole-plant (dry mass per total leaf N) level was greater in NADP-malic enzyme (ME) than NAD-ME species. This was due to lower N content in NADP-ME than NAD-ME leaves because neither assimilation rates nor plant dry mass differed significantly between the two C4 subtypes. Relative to NAD-ME, NADP-ME leaves had greater in vivo (assimilation rate per Rubisco catalytic sites) and in vitro Rubisco turnover rates (kcat; 3.8 versus 5.7 s−1 at 25°C). The two parameters were linearly related. In 2 NAD-ME (Panicum miliaceum and Panicum coloratum) and 2 NADP-ME (Sorghum bicolor and Cenchrus ciliaris) grasses, 30% of leaf N was allocated to thylakoids and 5% to 9% to amino acids and nitrate. Soluble protein represented a smaller fraction of leaf N in NADP-ME (41%) than in NAD-ME (53%) leaves, of which Rubisco accounted for one-seventh. Soluble protein averaged 7 and 10 g (mmol chlorophyll)−1 in NADP-ME and NAD-ME leaves, respectively. The majority (65%) of leaf N and chlorophyll was found in the mesophyll of NADP-ME and bundle sheath of NAD-ME leaves. The mesophyll-bundle sheath distribution of functional thylakoid complexes (photosystems I and II and cytochrome f) varied among species, with a tendency to be mostly located in the mesophyll. In conclusion, superior N-use efficiency of NADP-ME relative to NAD-ME grasses was achieved with less leaf N, soluble protein, and Rubisco having a faster kcat. PMID:15665246

Encapsulation of Anticancer Drugs (5-Fluorouracil and Paclitaxel) into Polycaprolactone (PCL) Nanofibers and In Vitro Testing for Sustained and Targeted Therapy

PubMed Central

Iqbal, Sakib; Rashid, Mohammad H.; Arbab, Ali S.; Khan, Mujibur

2017-01-01

We report a continuous nanoscale encapsulation of cancer drugs 5-Fluorouracil (FU) and Paclitaxel into biocompatible polycaprolactone (PCL) nanofibers (NFs) using core-sheath electrospinning process. A high potential electric field of 19–23.2 kV was used to draw a compound solution jet from a specialized coaxial spinneret. Using of DMF in both core and Sheath resulted in NFs within 50–160 nm along with large beaded structures. Addition of Trichloromethane (TCM) or Trifluoroethanol (TFE) in sheath turned NFs in more uniform and thin fiber structure. The diameter range for paclitaxel encapsulated fibers was 22–90 nm with encapsulation efficiency of 77.5% and the amount of drug was only 4 to 5% of sheath polymer. Addition of PVA within core resulted drug nanocrystal formation outside of sheath and poor encapsulation efficiency (52%) with rapid initial release (52–53%) in first 3 days. Drug release test of NFs in different pH exhibited increase of release rate with the decrease of media pH. In-vitro cell viability test with FU encapsulated NFs in human prostatic cancer PC3 cells exhibited 38% alive cells at 5 μM concentration while in pristine FU 43% cells were alive. Paclitaxel encapsulated NFs with breast cancer cells also exhibited increased efficacy in comparison to pristine anticancer drugs. Continuous decrease of cell density indicated the slow release of cancer drugs from the NFs. Both PCL+Paclitaxel and PCL+5FU treated conditions caused breast cancer cell death between 40% to 50%. PMID:28845137

Encapsulation of Anticancer Drugs (5-Fluorouracil and Paclitaxel) into Polycaprolactone (PCL) Nanofibers and In Vitro Testing for Sustained and Targeted Therapy.

PubMed

Iqbal, Sakib; Rashid, Mohammad H; Arbab, Ali S; Khan, Mujibur

2017-04-01

We report a continuous nanoscale encapsulation of cancer drugs 5-Fluorouracil (FU) and Paclitaxel into biocompatible polycaprolactone (PCL) nanofibers (NFs) using core-sheath electrospinning process. A high potential electric field of 19-23.2 kV was used to draw a compound solution jet from a specialized coaxial spinneret. Using of DMF in both core and Sheath resulted in NFs within 50-160 nm along with large beaded structures. Addition of Trichloromethane (TCM) or Trifluoroethanol (TFE) in sheath turned NFs in more uniform and thin fiber structure. The diameter range for paclitaxel encapsulated fibers was 22-90 nm with encapsulation efficiency of 77.5% and the amount of drug was only 4 to 5% of sheath polymer. Addition of PVA within core resulted drug nanocrystal formation outside of sheath and poor encapsulation efficiency (52%) with rapid initial release (52-53%) in first 3 days. Drug release test of NFs in different pH exhibited increase of release rate with the decrease of media pH. In-vitro cell viability test with FU encapsulated NFs in human prostatic cancer PC3 cells exhibited 38% alive cells at 5 μM concentration while in pristine FU 43% cells were alive. Paclitaxel encapsulated NFs with breast cancer cells also exhibited increased efficacy in comparison to pristine anticancer drugs. Continuous decrease of cell density indicated the slow release of cancer drugs from the NFs. Both PCL+Paclitaxel and PCL+5FU treated conditions caused breast cancer cell death between 40% to 50%.

Microtubule bundling plays a role in ethylene-mediated cortical microtubule reorientation in etiolated Arabidopsis hypocotyls.

PubMed

Ma, Qianqian; Sun, Jingbo; Mao, Tonglin

2016-05-15

The gaseous hormone ethylene is known to regulate plant growth under etiolated conditions (the 'triple response'). Although organization of cortical microtubules is essential for cell elongation, the underlying mechanisms that regulate microtubule organization by hormone signaling, including ethylene, are ambiguous. In the present study, we demonstrate that ethylene signaling participates in regulation of cortical microtubule reorientation. In particular, regulation of microtubule bundling is important for this process in etiolated hypocotyls. Time-lapse analysis indicated that selective stabilization of microtubule-bundling structures formed in various arrays is related to ethylene-mediated microtubule orientation. Bundling events and bundle growth lifetimes were significantly increased in oblique and longitudinal arrays, but decreased in transverse arrays in wild-type cells in response to ethylene. However, the effects of ethylene on microtubule bundling were partially suppressed in a microtubule-bundling protein WDL5 knockout mutant (wdl5-1). This study suggests that modulation of microtubule bundles that have formed in certain orientations plays a role in reorienting microtubule arrays in response to ethylene-mediated etiolated hypocotyl cell elongation. © 2016. Published by The Company of Biologists Ltd.

SYNTHETIC STRANDS OF CARDIAC MUSCLE

PubMed Central

Purdy, Joyce E.; Lieberman, Melvyn; Roggeveen, Anne E.; Kirk, R. Gary

1972-01-01

Spontaneously active bundles of cardiac muscle (synthetic strands) were prepared from isolated cells of 11–13-day old embryonic chick hearts which were disaggregated with trypsin. Linear orientation of the cells was obtained by plating them on agar-coated culture dishes in which either grooves were cut in the agar film or a thin line of palladium was deposited over the agar. The influence of cell-to-cell and cell-to-substrate interactions was observed with time lapse cinematography and the formation of the synthetic strand was shown to involve both random and guided cell movements, enlargement of aggregates by accretion and coalescence, and the compact linear arrangement of cells along paths of preferential adhesion. Electron microscope investigations of these strands showed that a dispersed population of heart cells organized into an inner core of muscle cells and an outer sheath of fibroblast-like cells. The muscle cells contained well-developed, but widely spaced myofibrils, a developing sarcoplasmic reticulum associated in part with the myofibrils and in part with the sarcolemma, an abundance of nonmembrane bound ribosomes and glycogen, and a prominent Golgi complex. Numerous specialized contacts were observed between the muscle cells in the strand, e.g., fasciae adherentes, desmosomes, and nexuses. A distinct type of muscle cell characterized by its pale appearance was regularly observed in the strand and was noted to be similar to Purkinje cells described in the adult avian conduction system and in developing chick myocardium. The present findings were compared with other observations of the developing myocardium, in situ, and it was concluded that, by a number or criteria, the muscle cells of the strand were differentiating normally and suitably organized for electrophysiological studies. PMID:4656702

Biosorption of metal elements by exopolymer nanofibrils excreted from Leptothrix cells.

PubMed

Kunoh, Tatsuki; Nakanishi, Makoto; Kusano, Yoshihiro; Itadani, Atsushi; Ando, Kota; Matsumoto, Syuji; Tamura, Katsunori; Kunoh, Hitoshi; Takada, Jun

2017-10-01

Leptothrix species, aquatic Fe-oxidizing bacteria, excrete nano-scaled exopolymer fibrils. Once excreted, the fibrils weave together and coalesce to form extracellular, microtubular, immature sheaths encasing catenulate cells of Leptothrix. The immature sheaths, composed of aggregated nanofibrils with a homogeneous-looking matrix, attract and bind aqueous-phase inorganics, especially Fe, P, and Si, to form seemingly solid, mature sheaths of a hybrid organic-inorganic nature. To verify our assumption that the organic skeleton of the sheaths might sorb a broad range of other metallic and nonmetallic elements, we examined the sorption potential of chemically and enzymatically prepared protein-free organic sheath remnants for 47 available elements. The sheath remnants were found by XRF to sorb each of the 47 elements, although their sorption degree varied among the elements: >35% atomic percentages for Ti, Y, Zr, Ru, Rh, Ag, and Au. Electron microscopy, energy dispersive x-ray spectroscopy, electron and x-ray diffractions, and Fourier transform infrared spectroscopy analyses of sheath remnants that had sorbed Ag, Cu, and Pt revealed that (i) the sheath remnants comprised a 5-10 nm thick aggregation of fibrils, (ii) the test elements were distributed almost homogeneously throughout the fibrillar aggregate, (iii) the nanofibril matrix sorbing the elements was nearly amorphous, and (iv) these elements plausibly were bound to the matrix by ionic binding, especially via OH. The present results show that the constitutive protein-free exopolymer nanofibrils of the sheaths can contribute to creating novel filtering materials for recovering and recycling useful and/or hazardous elements from the environment. Copyright © 2017. Published by Elsevier Ltd.

Daple coordinates organ-wide and cell-intrinsic polarity to pattern inner-ear hair bundles

PubMed Central

Siletti, Kimberly; Hudspeth, A. J.

2017-01-01

The establishment of planar polarization by mammalian cells necessitates the integration of diverse signaling pathways. In the inner ear, at least two systems regulate the planar polarity of sensory hair bundles. The core planar cell polarity (PCP) proteins coordinate the orientations of hair cells across the epithelial plane. The cell-intrinsic patterning of hair bundles is implemented independently by the G protein complex classically known for orienting the mitotic spindle. Although the primary cilium also participates in each of these pathways, its role and the integration of the two systems are poorly understood. We show that Dishevelled-associating protein with a high frequency of leucine residues (Daple) interacts with PCP and cell-intrinsic signals. Regulated by the cell-intrinsic pathway, Daple is required to maintain the polarized distribution of the core PCP protein Dishevelled and to position the primary cilium at the abneural edge of the apical surface. Our results suggest that the primary cilium or an associated structure influences the domain of cell-intrinsic signals that shape the hair bundle. Daple is therefore essential to orient and pattern sensory hair bundles. PMID:29229865

Dimerization and actin-bundling properties of villin and its role in the assembly of epithelial cell brush borders.

PubMed

George, Sudeep P; Wang, Yaohong; Mathew, Sijo; Srinivasan, Kamalakkannan; Khurana, Seema

2007-09-07

Villin is a major actin-bundling protein in the brush border of epithelial cells. In this study we demonstrate for the first time that villin can bundle actin filaments using a single F-actin binding site, because it has the ability to self-associate. Using fluorescence resonance energy transfer, we demonstrate villin self-association in living cells in microvilli and in growth factor-stimulated cells in membrane ruffles and lamellipodia. Using sucrose density gradient, size-exclusion chromatography, and matrix-assisted laser desorption ionization time-of-flight, the majority of villin was identified as a monomer or dimer. Villin dimers were also identified in Caco-2 cells, which endogenously express villin and Madin-Darby canine kidney cells that ectopically express villin. Using truncation mutants of villin, site-directed mutagenesis, and fluorescence resonance energy transfer, an amino-terminal dimerization site was identified that regulated villin self-association in parallel conformation as well as actin bundling by villin. This detailed analysis describes for the first time microvillus assembly by villin, redefines the actin-bundling function of villin, and provides a molecular mechanism for actin bundling by villin, which could have wider implications for other actin cross-linking proteins that share a villin-like headpiece domain. Our study also provides a molecular basis to separate the morphologically distinct actin-severing and actin-bundling properties of villin.

Distinct cytoskeleton populations and extensive crosstalk control Ciona notochord tubulogenesis.

PubMed

Dong, Bo; Deng, Wei; Jiang, Di

2011-04-01

Cell elongation is a fundamental process that allows cells and tissues to adopt new shapes and functions. During notochord tubulogenesis in the ascidian Ciona intestinalis, a dramatic elongation of individual cells takes place that lengthens the notochord and, consequently, the entire embryo. We find a novel dynamic actin- and non-muscle myosin II-containing constriction midway along the anteroposterior aspect of each notochord cell during this process. Both actin polymerization and myosin II activity are required for the constriction and cell elongation. Discontinuous localization of myosin II in the constriction indicates that the actomyosin network produces local contractions along the circumference. This reveals basal constriction by the actomyosin network as a novel mechanism for cell elongation. Following elongation, the notochord cells undergo a mesenchymal-epithelial transition and form two apical domains at opposite ends. Extracellular lumens then form at the apical surfaces. We show that cortical actin and Ciona ezrin/radixin/moesin (ERM) are essential for lumen formation and that a polarized network of microtubules, which contributes to lumen development, forms in an actin-dependent manner at the apical cortex. Later in notochord tubulogenesis, when notochord cells initiate a bi-directional crawling movement on the notochordal sheath, the microtubule network rotates 90° and becomes organized as parallel bundles extending towards the leading edges of tractive lamellipodia. This process is required for the correct organization of actin-based protrusions and subsequent lumen coalescence. In summary, we establish the contribution of the actomyosin and microtubule networks to notochord tubulogenesis and reveal extensive crosstalk and regulation between these two cytoskeleton components.

Anterior uveal spindle cell tumor in a cat.

PubMed

Evans, Paige M; Lynch, Gwendolyn L; Dubielzig, Richard R

2010-11-01

To describe a case of anterior uveal spindle cell tumor in a cat with features similar to spindle cell tumor of blue eyed dogs. A 10-year-old female spayed domestic short-haired cat was referred for an iris mass OS. The mass was solitary, nodular, nonpigmented, located medially, and causing dyscoria. A diagnosis of a benign epithelial tumor was suggested by a FNA of the mass. The cat was lost to follow-up for 2 years, after which time she re-presented with glaucoma, blindness and grossly evident iridal mass enlargement OS. Transconjunctival enucleation was performed and the globe submitted for histopathology. Histopathology of the enucleated globe revealed the superior iris to be infiltrated and effaced by a large population of neoplastic spindle cells. The cells were arranged in streams and bundles and exhibited Antoni-A and Antoni-B tissue patterns, which are characteristic of Schwann cell tumors. Mitotic figures were rare and cellular pleomorphism moderate. Immunohistochemical staining was positive for S-100 protein and glial fibrillary acidic protein (GFAP), and negative for Melan-A. Interestingly, there was no histological evidence of glaucoma. Based on its histopathologic characteristics, this iris tumor was diagnosed as a Schwann cell variant of a peripheral nerve sheath tumor (PNST) closely resembling the spindle cell tumor of blue-eyed dogs. Anterior uveal PNST has not been previously reported in cats to the authors' knowledge. The presence of Antoni type A and type B tissue patterns along with immunohistochemical staining may facilitate a diagnosis of PNST and rule out malignant melanoma. © 2010 American College of Veterinary Ophthalmologists.

Rubisco small subunit, chlorophyll a/b-binding protein and sucrose:fructan-6-fructosyl transferase gene expression and sugar status in single barley leaf cells in situ. Cell type specificity and induction by light.

PubMed

Lu, Chungui; Koroleva, Olga A; Farrar, John F; Gallagher, Joe; Pollock, Chris J; Tomos, A Deri

2002-11-01

We describe a highly efficient two-step single-cell reverse transcriptase-polymerase chain reaction technique for analyzing gene expression at the single-cell level. Good reproducibility and a linear dose response indicated that the technique has high specificity and sensitivity for detection and quantification of rare RNA. Actin could be used as an internal standard. The expression of message for Rubisco small subunit (RbcS), chlorophyll a/b-binding protein (Cab), sucrose (Suc):fructan-6-fructosyl transferase (6-SFT), and Actin were measured in individual photosynthetic cells of the barley (Hordeum vulgare) leaf. Only Actin was found in the non-photosynthetic epidermal cells. Cab, RbcS, and 6-SFT genes were expressed at a low level in mesophyll and parenchymatous bundle sheath (BS) cells when sampled from plants held in dark for 40 h. Expression increased considerably after illumination. The amount of 6-SFT, Cab, and RbcS transcript increased more in mesophyll cells than in the parenchymatous BS cells. The difference may be caused by different chloroplast structure and posttranscriptional control in mesophyll and BS cells. When similar single-cell samples were assayed for Suc, glucose, and fructan, there was high correlation between 6-SFT gene expression and Suc and glucose concentrations. This is consistent with Suc concentration being the trigger for transcription. Together with earlier demonstrations that the mesophyll cells have a higher sugar threshold for fructan polymerization, our data may indicate separate control of transcription and enzyme activity. Values for the sugar concentrations of the individual cell types are reported.

Continuous cell introduction and rapid dynamic lysis for high-throughput single-cell analysis on microfludic chips with hydrodynamic focusing.

PubMed

Xu, Chun-Xiu; Yin, Xue-Feng

2011-02-04

A chip-based microfluidic system for high-throughput single-cell analysis is described. The system was integrated with continuous introduction of individual cells, rapid dynamic lysis, capillary electrophoretic (CE) separation and laser induced fluorescence (LIF) detection. A cross microfluidic chip with one sheath-flow channel located on each side of the sampling channel was designed. The labeled cells were hydrodynamically focused by sheath-flow streams and sequentially introduced into the cross section of the microchip under hydrostatic pressure generated by adjusting liquid levels in the reservoirs. Combined with the electric field applied on the separation channel, the aligned cells were driven into the separation channel and rapidly lysed within 33ms at the entry of the separation channel by Triton X-100 added in the sheath-flow solution. The maximum rate for introducing individual cells into the separation channel was about 150cells/min. The introduction of sheath-flow streams also significantly reduced the concentration of phosphate-buffered saline (PBS) injected into the separation channel along with single cells, thus reducing Joule heating during electrophoretic separation. The performance of this microfluidic system was evaluated by analysis of reduced glutathione (GSH) and reactive oxygen species (ROS) in single erythrocytes. A throughput of 38cells/min was obtained. The proposed method is simple and robust for high-throughput single-cell analysis, allowing for analysis of cell population with considerable size to generate results with statistical significance. Copyright © 2010 Elsevier B.V. All rights reserved.

Evolution of myelin sheaths: both lamprey and hagfish lack myelin.

PubMed

Bullock, T H; Moore, J K; Fields, R D

1984-07-27

Modern views of agnathan phylogeny consider Petromyzoniformes and Myxiniformes to belong to distinct classes that diverged from a common ancestor at a remote period, perhaps in the lower Cambrian, greater than 600 million years ago. Both are more primitive than elasmobranchs, holocephalans and bony fishes. Myelin is well developed in elasmobranchs and other fishes but was reported to be lacking in the spinal cord of lampreys. In order to search further for possible early myelin in some part of the nervous system of one of the agnathan stems, or for further evidence that it first appeared in chondrichthians, we extended the sampling to many parts of the brain and cord of hagfish. Transmission electron microscopy was used as a nearly ideal criterion. We find no trace or forerunner of the spiral, multilaminate glial wrapping. Many axons are embedded within one or more glial cells, like unmyelinated fibers in other vertebrates, or lie contiguously in bundles without an obviously complete glial investment. True myelin must be presumed to have been invented within the vertebrates, in ancestors of the living cartilaginous fishes after the agnathans branched from the vertebrate stem.

FGF signaling supports Drosophila fertility by regulating development of ovarian muscle tissues

PubMed Central

Irizarry, Jihyun; Stathopoulos, Angelike

2015-01-01

The thisbe (ths) gene encodes a Drosophila fibroblast growth factor (FGF), and mutant females are viable but sterile suggesting a link between FGF signaling and fertility. Ovaries exhibit abnormal morphology including lack of epithelial sheaths, muscle tissues that surround ovarioles. Here we investigated how FGF influences Drosophila ovary morphogenesis and identified several roles. Heartless (Htl) FGF receptor was found expressed within somatic cells at the larval and pupal stages, and phenotypes were uncovered using RNAi. Differentiation of terminal filament cells was affected, but this effect did not alter ovariole number. In addition, proliferation of epithelial sheath progenitors, the apical cells, was decreased in both htl and ths mutants, while ectopic expression of the Ths ligand led to these cells’ over-proliferation suggesting that FGF signaling supports ovarian muscle sheath formation by controlling apical cell number in the developing gonad. Additionally, live imaging of adult ovaries was used to show that htl RNAi mutants, hypomorphic mutants in which epithelial sheaths are present, exhibit abnormal muscle contractions. Collectively, our results demonstrate that proper formation of ovarian muscle tissues is regulated by FGF signaling in the larval and pupal stages through control of apical cell proliferation and is required to support fertility. PMID:25958090

Micro sized implantable ball lens-based fiber optic probe design

NASA Astrophysics Data System (ADS)

Cha, Jaepyeong; Kang, Jin U.

2014-02-01

A micro sized implantable ball lens-based fiber optic probe design is described for continuous monitoring of brain activity in freely behaving mice. A prototype uses a 500-micron ball lens and a highly flexible 350-micron-diameter fiber bundle, which are enclosed by a 21G stainless steel sheath. Several types and thickness of brain tissue, consisting of fluorescent probes such as GFP, GCaMP3 calcium indicator, are used to evaluate the performance of the imaging probe. Measured working distance is approximately 400-μm, but is long enough to detect neural activities from cortical and cerebellar tissues of mice brain.

Map-based Cloning and Characterization of the BPH18 Gene from Wild Rice Conferring Resistance to Brown Planthopper (BPH) Insect Pest

PubMed Central

Ji, Hyeonso; Kim, Sung-Ryul; Kim, Yul-Ho; Suh, Jung-Pil; Park, Hyang-Mi; Sreenivasulu, Nese; Misra, Gopal; Kim, Suk-Man; Hechanova, Sherry Lou; Kim, Hakbum; Lee, Gang-Seob; Yoon, Ung-Han; Kim, Tae-Ho; Lim, Hyemin; Suh, Suk-Chul; Yang, Jungil; An, Gynheung; Jena, Kshirod K.

2016-01-01

Brown planthopper (BPH) is a phloem sap-sucking insect pest of rice which causes severe yield loss. We cloned the BPH18 gene from the BPH-resistant introgression line derived from the wild rice species Oryza australiensis. Map-based cloning and complementation test revealed that the BPH18 encodes CC-NBS-NBS-LRR protein. BPH18 has two NBS domains, unlike the typical NBS-LRR proteins. The BPH18 promoter::GUS transgenic plants exhibited strong GUS expression in the vascular bundles of the leaf sheath, especially in phloem cells where the BPH attacks. The BPH18 proteins were widely localized to the endo-membranes in a cell, including the endoplasmic reticulum, Golgi apparatus, trans-Golgi network, and prevacuolar compartments, suggesting that BPH18 may recognize the BPH invasion at endo-membranes in phloem cells. Whole genome sequencing of the near-isogenic lines (NILs), NIL-BPH18 and NIL-BPH26, revealed that BPH18 located at the same locus of BPH26. However, these two genes have remarkable sequence differences and the independent NILs showed differential BPH resistance with different expression patterns of plant defense-related genes, indicating that BPH18 and BPH26 are functionally different alleles. These findings would facilitate elucidation of the molecular mechanism of BPH resistance and the identified novel alleles to fast track breeding BPH resistant rice cultivars. PMID:27682162

Map-based Cloning and Characterization of the BPH18 Gene from Wild Rice Conferring Resistance to Brown Planthopper (BPH) Insect Pest.

PubMed

Ji, Hyeonso; Kim, Sung-Ryul; Kim, Yul-Ho; Suh, Jung-Pil; Park, Hyang-Mi; Sreenivasulu, Nese; Misra, Gopal; Kim, Suk-Man; Hechanova, Sherry Lou; Kim, Hakbum; Lee, Gang-Seob; Yoon, Ung-Han; Kim, Tae-Ho; Lim, Hyemin; Suh, Suk-Chul; Yang, Jungil; An, Gynheung; Jena, Kshirod K

2016-09-29

Brown planthopper (BPH) is a phloem sap-sucking insect pest of rice which causes severe yield loss. We cloned the BPH18 gene from the BPH-resistant introgression line derived from the wild rice species Oryza australiensis. Map-based cloning and complementation test revealed that the BPH18 encodes CC-NBS-NBS-LRR protein. BPH18 has two NBS domains, unlike the typical NBS-LRR proteins. The BPH18 promoter::GUS transgenic plants exhibited strong GUS expression in the vascular bundles of the leaf sheath, especially in phloem cells where the BPH attacks. The BPH18 proteins were widely localized to the endo-membranes in a cell, including the endoplasmic reticulum, Golgi apparatus, trans-Golgi network, and prevacuolar compartments, suggesting that BPH18 may recognize the BPH invasion at endo-membranes in phloem cells. Whole genome sequencing of the near-isogenic lines (NILs), NIL-BPH18 and NIL-BPH26, revealed that BPH18 located at the same locus of BPH26. However, these two genes have remarkable sequence differences and the independent NILs showed differential BPH resistance with different expression patterns of plant defense-related genes, indicating that BPH18 and BPH26 are functionally different alleles. These findings would facilitate elucidation of the molecular mechanism of BPH resistance and the identified novel alleles to fast track breeding BPH resistant rice cultivars.

The Actions of Calcium on Hair Bundle Mechanics in Mammalian Cochlear Hair Cells

PubMed Central

Beurg, Maryline; Nam, Jong-Hoon; Crawford, Andrew; Fettiplace, Robert

2008-01-01

Sound stimuli excite cochlear hair cells by vibration of each hair bundle, which opens mechanotransducer (MT) channels. We have measured hair-bundle mechanics in isolated rat cochleas by stimulation with flexible glass fibers and simultaneous recording of the MT current. Both inner and outer hair-cell bundles exhibited force-displacement relationships with a nonlinearity that reflects a time-dependent reduction in stiffness. The nonlinearity was abolished, and hair-bundle stiffness increased, by maneuvers that diminished calcium influx through the MT channels: lowering extracellular calcium, blocking the MT current with dihydrostreptomycin, or depolarizing to positive potentials. To simulate the effects of Ca2+, we constructed a finite-element model of the outer hair cell bundle that incorporates the gating-spring hypothesis for MT channel activation. Four calcium ions were assumed to bind to the MT channel, making it harder to open, and, in addition, Ca2+ was posited to cause either a channel release or a decrease in the gating-spring stiffness. Both mechanisms produced Ca2+ effects on adaptation and bundle mechanics comparable to those measured experimentally. We suggest that fast adaptation and force generation by the hair bundle may stem from the action of Ca2+ on the channel complex and do not necessarily require the direct involvement of a myosin motor. The significance of these results for cochlear transduction and amplification are discussed. PMID:18178649

Localization of polyhydroxybutyrate in sugarcane using Fourier-transform infrared microspectroscopy and multivariate imaging

DOE PAGES

Lupoi, Jason S.; Smith-Moritz, Andreia; Singh, Seema; ...

2015-07-10

Background: Slow-degrading, fossil fuel-derived plastics can have deleterious effects on the environment, especially marine ecosystems. The production of bio-based, biodegradable plastics from or in plants can assist in supplanting those manufactured using fossil fuels. Polyhydroxybutyrate (PHB) is one such biodegradable polyester that has been evaluated as a possible candidate for relinquishing the use of environmentally harmful plastics. Results: PHB, possessing similar properties to polyesters produced from non-renewable sources, has been previously engineered in sugarcane, thereby creating a high-value co-product in addition to the high biomass yield. This manuscript illustrates the coupling of a Fourier-transform infrared microspectrometer, equipped with a focalmore » plane array (FPA) detector, with multivariate imaging to successfully identify and localize PHB aggregates. Principal component analysis imaging facilitated the mining of the abundant quantity of spectral data acquired using the FPA for distinct PHB vibrational modes. PHB was measured in the chloroplasts of mesophyll and bundle sheath cells, acquiescent with previously evaluated plant samples. Conclusion: This study demonstrates the power of IR microspectroscopy to rapidly image plant sections to provide a snapshot of the chemical composition of the cell. While PHB was localized in sugarcane, this method is readily transferable to other value-added co-products in different plants.« less

Localization of polyhydroxybutyrate in sugarcane using Fourier-transform infrared microspectroscopy and multivariate imaging

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

Lupoi, Jason S.; Smith-Moritz, Andreia; Singh, Seema

Background: Slow-degrading, fossil fuel-derived plastics can have deleterious effects on the environment, especially marine ecosystems. The production of bio-based, biodegradable plastics from or in plants can assist in supplanting those manufactured using fossil fuels. Polyhydroxybutyrate (PHB) is one such biodegradable polyester that has been evaluated as a possible candidate for relinquishing the use of environmentally harmful plastics. Results: PHB, possessing similar properties to polyesters produced from non-renewable sources, has been previously engineered in sugarcane, thereby creating a high-value co-product in addition to the high biomass yield. This manuscript illustrates the coupling of a Fourier-transform infrared microspectrometer, equipped with a focalmore » plane array (FPA) detector, with multivariate imaging to successfully identify and localize PHB aggregates. Principal component analysis imaging facilitated the mining of the abundant quantity of spectral data acquired using the FPA for distinct PHB vibrational modes. PHB was measured in the chloroplasts of mesophyll and bundle sheath cells, acquiescent with previously evaluated plant samples. Conclusion: This study demonstrates the power of IR microspectroscopy to rapidly image plant sections to provide a snapshot of the chemical composition of the cell. While PHB was localized in sugarcane, this method is readily transferable to other value-added co-products in different plants.« less

Independent and Parallel Evolution of New Genes by Gene Duplication in Two Origins of C4 Photosynthesis Provides New Insight into the Mechanism of Phloem Loading in C4 Species.

PubMed

Emms, David M; Covshoff, Sarah; Hibberd, Julian M; Kelly, Steven

2016-07-01

C4 photosynthesis is considered one of the most remarkable examples of evolutionary convergence in eukaryotes. However, it is unknown whether the evolution of C4 photosynthesis required the evolution of new genes. Genome-wide gene-tree species-tree reconciliation of seven monocot species that span two origins of C4 photosynthesis revealed that there was significant parallelism in the duplication and retention of genes coincident with the evolution of C4 photosynthesis in these lineages. Specifically, 21 orthologous genes were duplicated and retained independently in parallel at both C4 origins. Analysis of this gene cohort revealed that the set of parallel duplicated and retained genes is enriched for genes that are preferentially expressed in bundle sheath cells, the cell type in which photosynthesis was activated during C4 evolution. Furthermore, functional analysis of the cohort of parallel duplicated genes identified SWEET-13 as a potential key transporter in the evolution of C4 photosynthesis in grasses, and provides new insight into the mechanism of phloem loading in these C4 species. C4 photosynthesis, gene duplication, gene families, parallel evolution. © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Distinguishing the Chinese materia medica Tiepishihu from similar Dendrobium species of the same genus using histological and microscopic method.

PubMed

Yu, Kun-Zi; Yan, Hua; Tai, Hai-Chuan; Zhang, Nan-Ping; Cheng, Xian-Long; Guo, Zeng-Xi; Ma, Shuang-Cheng; Wei, Feng

2017-07-01

The Chinese Materia Medica, Tiepishihu, used as a tonic for over one thousand years, is a well-known precious medicine in China. According to the Chinese Pharmacopoeia, its source is the species Dendrobium officinale Kimura et Migo, which is distinguished from other species in Dendrobium genus. However, these species from the same genus are similar with Tiepishihu and caused confusion in the market. To find a quick and simple method to distinguish Tiepishihu from other similar species, histologic and microscopic methods were combined together to investigate the transverse section of stem of Tiepishihu and other similar species. Phloroglucinol test solution with hydrochloric acid was used to reveal the lignified tissue by staining the transverse section of Tiepishihu and similar species. Results revealed the unique identification characteristics to distinguish Tiepishihu from similar species, which were difficult to distinguish by other methods. The identification characteristics of Tiepishihu include the cells of vascular bundle sheath were stained red, parenchyma cells were not stained red. What's more, other species can be distinguished from each other with microscopic and histological characteristics. These characteristics proved stable and can be easily observed by normal light microscopic examination. This method is rapid, accurate, stable, and inexpensive. © 2017 Wiley Periodicals, Inc.

[Screening and identification of endophytic fungi with growth promoting effect on Dendrobium officinale].

PubMed

Hou, Xiao-qiang; Guo, Shun-xing

2014-09-01

The endophytic fungi with plant growth promoting effects were screened by co-culture of each endophytic fungus and seedlings of Dendrobium officinale. Anatomical features of the inoculated roots were studied by paraffin sectioning. Morphological characteristics and rDNA ITS1-5. 8S-ITS2 sequences were applied for the taxonomy of endophytic fungi. The results showed that 8 strains inoculated to D. officinale seedlings greatly enhanced plant height, stem diameter, new roots number and biomass. According to the anatomical features of the inoculated roots, each fungus could infect the velamina of seedlings. The hyphae or pelotons were existed in the exodermis passage cells and cortex cells. The effective fungi could not infect the endodermis and vascular bundle sheath, but which was exception for other fungi with harmful to seedlings. Combined with classic morphologic classification, 2 effective strains were identified which were subjected to Pestalotiopsis and Eurotium. Six species of fungi without conidiophore belonged to Pyrenochaeta, Coprinellus, Pholiota, Alternaria, Helotiales, which were identified by sequencing the PCR-amplified rDNA ITS1-5. 8S-ITS2 regions. The co-culture technology of effective endophytic fungi and plant can apply to cultivate the seedlings of D. officinale. It is feasible to shorten growth cycle of D. officinale and increase the resource of Chinese herbs.

Whole-Mount Adult Ear Skin Imaging Reveals Defective Neuro-Vascular Branching Morphogenesis in Obese and Type 2 Diabetic Mouse Models.

PubMed

Yamazaki, Tomoko; Li, Wenling; Yang, Ling; Li, Ping; Cao, Haiming; Motegi, Sei-Ichiro; Udey, Mark C; Bernhard, Elise; Nakamura, Takahisa; Mukouyama, Yoh-Suke

2018-01-11

Obesity and type 2 diabetes are frequently associated with peripheral neuropathy. Though there are multiple methods for diagnosis and analysis of morphological changes of peripheral nerves and blood vessels, three-dimensional high-resolution imaging is necessary to appreciate the pathogenesis with an anatomically recognizable branching morphogenesis and patterning. Here we established a novel technique for whole-mount imaging of adult mouse ear skin to visualize branching morphogenesis and patterning of peripheral nerves and blood vessels. Whole-mount immunostaining of adult mouse ear skin showed that peripheral sensory and sympathetic nerves align with large-diameter blood vessels. Diet-induced obesity (DIO) mice exhibit defective vascular smooth muscle cells (VSMCs) coverage, while there is no significant change in the amount of peripheral nerves. The leptin receptor-deficient db/db mice, a severe obese and type 2 diabetic mouse model, exhibit defective VSMC coverage and a large increase in the amount of smaller-diameter nerve bundles with myelin sheath and unmyelinated nerve fibers. Interestingly, an increase in the amount of myeloid immune cells was observed in the DIO but not db/db mouse skin. These data suggest that our whole-mount imaging method enables us to investigate the neuro-vascular and neuro-immune phenotypes in the animal models of obesity and diabetes.

Subcellular-level resolution MALDI-MS imaging of maize leaf metabolites by MALDI-linear ion trap-Orbitrap mass spectrometer

DOE PAGES

Korte, Andrew R.; Yandeau-Nelson, Marna D.; Nikolau, Basil J.; ...

2015-01-25

A significant limiting factor in achieving high spatial resolution for matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS) imaging is the size of the laser spot at the sample surface. We present modifications to the beam-delivery optics of a commercial MALDI-linear ion trap-Orbitrap instrument, incorporating an external Nd:YAG laser, beam-shaping optics, and an aspheric focusing lens, to reduce the minimum laser spot size from ~50 μm for the commercial configuration down to ~9 μm for the modified configuration. This improved system was applied for MALDI-MS imaging of cross sections of juvenile maize leaves at 5-μm spatial resolution using an oversampling method. Theremore » are a variety of different metabolites including amino acids, glycerolipids, and defense-related compounds were imaged at a spatial resolution well below the size of a single cell. Such images provide unprecedented insights into the metabolism associated with the different tissue types of the maize leaf, which is known to asymmetrically distribute the reactions of C4 photosynthesis among the mesophyll and bundle sheath cell types. The metabolite ion images correlate with the optical images that reveal the structures of the different tissues, and previously known and newly revealed asymmetric metabolic features are observed.« less

Independent and Parallel Evolution of New Genes by Gene Duplication in Two Origins of C4 Photosynthesis Provides New Insight into the Mechanism of Phloem Loading in C4 Species

PubMed Central

Emms, David M.; Covshoff, Sarah; Hibberd, Julian M.; Kelly, Steven

2016-01-01

C4 photosynthesis is considered one of the most remarkable examples of evolutionary convergence in eukaryotes. However, it is unknown whether the evolution of C4 photosynthesis required the evolution of new genes. Genome-wide gene-tree species-tree reconciliation of seven monocot species that span two origins of C4 photosynthesis revealed that there was significant parallelism in the duplication and retention of genes coincident with the evolution of C4 photosynthesis in these lineages. Specifically, 21 orthologous genes were duplicated and retained independently in parallel at both C4 origins. Analysis of this gene cohort revealed that the set of parallel duplicated and retained genes is enriched for genes that are preferentially expressed in bundle sheath cells, the cell type in which photosynthesis was activated during C4 evolution. Furthermore, functional analysis of the cohort of parallel duplicated genes identified SWEET-13 as a potential key transporter in the evolution of C4 photosynthesis in grasses, and provides new insight into the mechanism of phloem loading in these C4 species. Key words: C4 photosynthesis, gene duplication, gene families, parallel evolution. PMID:27016024

Measurement of leaf hydraulic conductance and stomatal conductance and their responses to irradiance and dehydration using the Evaporative Flux Method (EFM).

PubMed

Sack, Lawren; Scoffoni, Christine

2012-12-31

Water is a key resource, and the plant water transport system sets limits on maximum growth and drought tolerance. When plants open their stomata to achieve a high stomatal conductance (gs) to capture CO2 for photosynthesis, water is lost by transpiration(1,2). Water evaporating from the airspaces is replaced from cell walls, in turn drawing water from the xylem of leaf veins, in turn drawing from xylem in the stems and roots. As water is pulled through the system, it experiences hydraulic resistance, creating tension throughout the system and a low leaf water potential (Ψ(leaf)). The leaf itself is a critical bottleneck in the whole plant system, accounting for on average 30% of the plant hydraulic resistance(3). Leaf hydraulic conductance (K(leaf) = 1/ leaf hydraulic resistance) is the ratio of the water flow rate to the water potential gradient across the leaf, and summarizes the behavior of a complex system: water moves through the petiole and through several orders of veins, exits into the bundle sheath and passes through or around mesophyll cells before evaporating into the airspace and being transpired from the stomata. K(leaf) is of strong interest as an important physiological trait to compare species, quantifying the effectiveness of the leaf structure and physiology for water transport, and a key variable to investigate for its relationship to variation in structure (e.g., in leaf venation architecture) and its impacts on photosynthetic gas exchange. Further, K(leaf) responds strongly to the internal and external leaf environment(3). K(leaf) can increase dramatically with irradiance apparently due to changes in the expression and activation of aquaporins, the proteins involved in water transport through membranes(4), and K(leaf) declines strongly during drought, due to cavitation and/or collapse of xylem conduits, and/or loss of permeability in the extra-xylem tissues due to mesophyll and bundle sheath cell shrinkage or aquaporin deactivation(5-10). Because K(leaf) can constrain gs and photosynthetic rate across species in well watered conditions and during drought, and thus limit whole-plant performance they may possibly determine species distributions especially as droughts increase in frequency and severity(11-14). We present a simple method for simultaneous determination of K(leaf) and gs on excised leaves. A transpiring leaf is connected by its petiole to tubing running to a water source on a balance. The loss of water from the balance is recorded to calculate the flow rate through the leaf. When steady state transpiration (E, mmol • m(-2) • s(-1)) is reached, gs is determined by dividing by vapor pressure deficit, and K(leaf) by dividing by the water potential driving force determined using a pressure chamber (K(leaf)= E /- Δψ(leaf), MPa)(15). This method can be used to assess K(leaf) responses to different irradiances and the vulnerability of K(leaf) to dehydration(14,16,17).

Unity in diversity: a survey of muscular systems of ctenostome Gymnolaemata (Lophotrochozoa, Bryozoa).

PubMed

Schwaha, Thomas F; Wanninger, Andreas

2018-01-01

Myoanatomical studies of adult bryozoans employing fluorescent staining and confocal laser scanning microscopy (CLSM) have been chiefly conducted on freshwater bryozoans. The diversity of muscular systems in the marine bryozoans is currently not well known with only two species being studied in more detail. The aim of this study is to unravel the diversity of muscle systems of 15 ctenostome bryozoans by phalloidin-coupled fluorescence stainings combined with CLSM. In general, the myoanatomy of the selected ctenostomes shows significant similarities and consists of 1) muscles associated with the body wall, 2) apertural muscles, 3) lophophoral muscles, 4) tentacle sheath muscles, 5) digestive tract muscles and 6) the prominent retractor muscles. Differences are present in the arrangement of the apertural muscles from generally three muscles sets of four bundles, which in some species can be partially reduced or modified into a bilateral arrangement. The cardiac region of the digestive tract shows a distinct sphincter in four of the six studied clades. In some cases the cardiac region forms a prominent proventriculus or gizzard. Tentacle sheath muscles in victorelloideans and walkerioideans are arranged diagonally and differ from the simple longitudinal muscle arrangements common to all other taxa. Lophophoral base muscles consist of four sets that vary in the size of the sets and in the shape of the inner lophophoral ring, which either forms a complete ring or separate, intertentacular muscle bundles. The stolon-forming walkeridiodean ctenostomes show prominent transverse muscles in their stolons. These are always present in the shorter side stolons, but their occurrence in the main stolon seems to depend on the colony form, being present in creeping but absent in erect colony forms. This study represents the first broad survey of muscular systems in adult ctenostome bryozoans and shows a certain degree of conservation in a series of diverse colony forms belonging to five major clades. However, several myoanatomical features such as the cardiac sphincter, basal (possibly transitory) cystid muscles, tentacle sheath muscles or apertural muscle arrangement vary across taxa and thus show a high potential for the assessment of character evolution within ctenostomes. As such, this study represents an essential contribution towards determining and reconstructing the character states of the bryozoan ground pattern once a reliable phylogenetic tree of the whole phylum becomes available.

Endothelial cells in the oral mucosa of Bufo marinus.

PubMed Central

Loo, S K; Yeo, B C; Kovac, H

1980-01-01

The oral mucosa of the cane toad (Bufo marinus) is lined by a pseudostratified columnar ciliated epithelium containing an intraepithelial network of capillaries, which penetrates it to the bases of the distal layer of cells. The capillaries are lined by fenestrated endothelium lying on a complete basal lamina. A connective tissue sheath, approximately 1 micrometer thick, surrounds the capillaries and separates them from the surrounding epithelial cells. Endothelial cells resemble those in lymphatic capillaries in that they show microvillus-like processes or folds projecting into the lumen and also have extremely attenuated and fenestrated cytoplasm except in the nuclear region. Numerous pinocytotic vesicles, bundles of filaments and many electrondense granules occur in the cytoplasm. These granules are oval or round in shape and approximately 250-400 micrometer in diameter. Histochemical tests on the endothelial cells show that the granules do not contain pigment, as both the Schmorl and argentaffin reactions are negative. Both the Sudan black B and Luxol fast blue reactions are also negative showing the lack of stainable lipids. The formaldehyde-induced fluorescence, the argentaffin reactions and lead haematoxylin reactions are negative, indicating that they do not have the characteristics of endocrine cells. The acid phosphatase reaction gives a positive result, localized to the site of the granules by electron microscopy and suggesting that these granules in amphibian capillaries may have a lysosomal function. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 Fig. 13 Fig. 14 Fig. 15 Fig. 16 PMID:6773911

Emilin3 is required for notochord sheath integrity and interacts with Scube2 to regulate notochord-derived Hedgehog signals.

PubMed

Corallo, Diana; Schiavinato, Alvise; Trapani, Valeria; Moro, Enrico; Argenton, Francesco; Bonaldo, Paolo

2013-11-01

The notochord is a transient and essential structure that provides both mechanical and signaling cues to the developing vertebrate embryo. In teleosts, the notochord is composed of a core of large vacuolated cells and an outer layer of cells that secrete the notochord sheath. In this work, we have identified the extracellular matrix glycoprotein Emilin3 as a novel essential component of the zebrafish notochord sheath. The development of the notochord sheath is impaired in Emilin3 knockdown embryos. The patterning activity of the notochord is also affected by Emilin3, as revealed by the increase of Hedgehog (Hh) signaling in Emilin3-depleted embryos and the decreased Hh signaling in embryos overexpressing Emilin3 in the notochord. In vitro and in vivo experiments indicate that Emilin3 modulates the availability of Hh ligands by interacting with the permissive factor Scube2 in the notochord sheath. Overall, this study reveals a new role for an EMILIN protein and reinforces the concept that structure and function of the notochord are strictly linked.

Some Observations on the Fine Structure of the Giant Nerve Fibers of the Earthworm, Eisenia foetida

PubMed Central

Hama, Kiyoshi

1959-01-01

Sectioned dorsal giant fibers of the earthworm Eisenia foetida have been studied with the electron microscope. The giant axon is surrounded by a Schwannian sheath in which the lamellae are arranged spirally. They can be traced from the outer surface of the Schwann cell to the axon-Schwann membranes. Irregularities in the spiral arrangement are frequently observed. Desmosome-like attachment areas occur on the giant fiber nerve sheath. These structures appear to be arranged bilaterally in columns which are oriented slightly obliquely to the long axis of the giant fiber and aligned linearly from the axon to the periphery of the sheath. At these sites they bind together apposing portions of Schwann cell membrane comprising the sheath. Longitudinal or oblique sections of the nerve sheath attachment areas are reminiscent of the Schmidt-Lantermann clefts of vertebrate peripheral nerve. Septa of the giant fibers have been examined. They are symmetrical or non-polarized and consist of the two plasma membranes of adjacent nerve units. Characteristic vesicular and tubular structures are associated with both cytoplasmic surfaces of these septa. PMID:13673048

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

Duenas, Maria Emilia; Klein, Adam T.; Alexander, Liza E.

Metabolism in plants is compartmentalized among different tissues, cells and subcellular organelles. Mass spectrometry imaging (MSI) with matrix-assisted laser desorption ionization (MALDI) has recently advanced to allow for the visualization of metabolites at single-cell resolution. Here we applied 5- and 10 μm high spatial resolution MALDI-MSI to the asymmetric Kranz anatomy of Zea mays (maize) leaves to study the differential localization of two major anionic lipids in thylakoid membranes, sulfoquinovosyldiacylglycerols (SQDG) and phosphatidylglycerols (PG). The quantification and localization of SQDG and PG molecular species, among mesophyll (M) and bundle sheath (BS) cells, are compared across the leaf developmental gradient frommore » four maize genotypes (the inbreds B73 and Mo17, and the reciprocal hybrids B73 × Mo17 and Mo17 × B73). SQDG species are uniformly distributed in both photosynthetic cell types, regardless of leaf development or genotype; however, PG shows photosynthetic cell-specific differential localization depending on the genotype and the fatty acyl chain constituent. Overall, 16:1-containing PGs primarily contribute to the thylakoid membranes of M cells, whereas BS chloroplasts are mostly composed of 16:0-containing PGs. Furthermore, PG 32:0 shows genotype-specific differences in cellular distribution, with preferential localization in BS cells for B73, but more uniform distribution between BS and M cells in Mo17. Maternal inheritance is exhibited within the hybrids, such that the localization of PG 32:0 in B73 × Mo17 is similar to the distribution in the B73 parental inbred, whereas that of Mo17 × B73 resembles the Mo17 parent. As a result, this study demonstrates the power of MALDI-MSI to reveal unprecedented insights on metabolic outcomes in multicellular organisms at single-cell resolution.« less

Comparative cell-specific transcriptomics reveals differentiation of C4 photosynthesis pathways in switchgrass and other C4 lineages

PubMed Central

Rao, Xiaolan; Lu, Nan; Li, Guifen; Nakashima, Jin; Tang, Yuhong; Dixon, Richard A.

2016-01-01

Almost all C4 plants require the co-ordination of the adjacent and fully differentiated cell types, mesophyll (M) and bundle sheath (BS). The C4 photosynthetic pathway operates through two distinct subtypes based on how malate is decarboxylated in BS cells; through NAD-malic enzyme (NAD-ME) or NADP-malic enzyme (NADP-ME). The diverse or unique cell-specific molecular features of M and BS cells from separate C4 subtypes of independent lineages remain to be determined. We here provide an M/BS cell type-specific transcriptome data set from the monocot NAD-ME subtype switchgrass (Panicum virgatum). A comparative transcriptomics approach was then applied to compare the M/BS mRNA profiles of switchgrass, monocot NADP-ME subtype C4 plants maize and Setaria viridis, and dicot NAD-ME subtype Cleome gynandra. We evaluated the convergence in the transcript abundance of core components in C4 photosynthesis and transcription factors to establish Kranz anatomy, as well as gene distribution of biological functions, in these four independent C4 lineages. We also estimated the divergence between NAD-ME and NADP-ME subtypes of C4 photosynthesis in the two cell types within C4 species, including differences in genes encoding decarboxylating enzymes, aminotransferases, and metabolite transporters, and differences in the cell-specific functional enrichment of RNA regulation and protein biogenesis/homeostasis. We suggest that C4 plants of independent lineages in both monocots and dicots underwent convergent evolution to establish C4 photosynthesis, while distinct C4 subtypes also underwent divergent processes for the optimization of M and BS cell co-ordination. The comprehensive data sets in our study provide a basis for further research on evolution of C4 species. PMID:26896851

Transduction channels' gating can control friction on vibrating hair-cell bundles in the ear.

PubMed

Bormuth, Volker; Barral, Jérémie; Joanny, Jean-François; Jülicher, Frank; Martin, Pascal

2014-05-20

Hearing starts when sound-evoked mechanical vibrations of the hair-cell bundle activate mechanosensitive ion channels, giving birth to an electrical signal. As for any mechanical system, friction impedes movements of the hair bundle and thus constrains the sensitivity and frequency selectivity of auditory transduction. Friction is generally thought to result mainly from viscous drag by the surrounding fluid. We demonstrate here that the opening and closing of the transduction channels produce internal frictional forces that can dominate viscous drag on the micrometer-sized hair bundle. We characterized friction by analyzing hysteresis in the force-displacement relation of single hair-cell bundles in response to periodic triangular stimuli. For bundle velocities high enough to outrun adaptation, we found that frictional forces were maximal within the narrow region of deflections that elicited significant channel gating, plummeted upon application of a channel blocker, and displayed a sublinear growth for increasing bundle velocity. At low velocity, the slope of the relation between the frictional force and velocity was nearly fivefold larger than the hydrodynamic friction coefficient that was measured when the transduction machinery was decoupled from bundle motion by severing tip links. A theoretical analysis reveals that channel friction arises from coupling the dynamics of the conformational change associated with channel gating to tip-link tension. Varying channel properties affects friction, with faster channels producing smaller friction. We propose that this intrinsic source of friction may contribute to the process that sets the hair cell's characteristic frequency of responsiveness.

Disruption of SorCS2 reveals differences in the regulation of stereociliary bundle formation between hair cell types in the inner ear

PubMed Central

Taylor, Ruth R.; Lovett, Michael; Jagger, Daniel J.

2017-01-01

Behavioural anomalies suggesting an inner ear disorder were observed in a colony of transgenic mice. Affected animals were profoundly deaf. Severe hair bundle defects were identified in all outer and inner hair cells (OHC, IHC) in the cochlea and in hair cells of vestibular macular organs, but hair cells in cristae were essentially unaffected. Evidence suggested the disorder was likely due to gene disruption by a randomly inserted transgene construct. Whole-genome sequencing identified interruption of the SorCS2 (Sortilin-related VPS-10 domain containing protein) locus. Real-time-qPCR demonstrated disrupted expression of SorCS2 RNA in cochlear tissue from affected mice and this was confirmed by SorCS2 immuno-labelling. In all affected hair cells, stereocilia were shorter than normal, but abnormalities of bundle morphology and organisation differed between hair cell types. Bundles on OHC were grossly misshapen with significantly fewer stereocilia than normal. However, stereocilia were organised in rows of increasing height. Bundles on IHC contained significantly more stereocilia than normal with some longer stereocilia towards the centre, or with minimal height differentials. In early postnatal mice, kinocilia (primary cilia) of IHC and of OHC were initially located towards the lateral edge of the hair cell surface but often became surrounded by stereocilia as bundle shape and apical surface contour changed. In macular organs the kinocilium was positioned in the centre of the cell surface throughout maturation. There was disruption of the signalling pathway controlling intrinsic hair cell apical asymmetry. LGN and Gαi3 were largely absent, and atypical Protein Kinase C (aPKC) lost its asymmetric distribution. The results suggest that SorCS2 plays a role upstream of the intrinsic polarity pathway and that there are differences between hair cell types in the deployment of the machinery that generates a precisely organised hair bundle. PMID:28346477

Inner hair cell stereocilia movements captured in-situ by a high-speed camera with subpixel image processing

NASA Astrophysics Data System (ADS)

Wang, Yanli; Puria, Sunil; Steele, Charles R.; Ricci, Anthony J.

2018-05-01

Mechanical stimulation of the stereocilia hair bundles of the inner and outer hair cells (IHCs and OHCs, respectively) drives IHC synaptic release and OHC electromotility. The modes of hair-bundle motion can have a dramatic influence on the electrophysiological responses of the hair cells. The in vivo modes of motion are, however, unknown for both IHC and OHC bundles. In this work, we are developing technology to investigate the in situ hair-bundle motion in excised mouse cochleae, for which the hair bundles of the OHCs are embedded in the tectorial membrane but those of the IHCs are not. Motion is generated by pushing onto the stapes at 1 kHz with a glass probe coupled to a piezo stack, and recorded using a high-speed camera at 10,000 frames per second. The motions of individual IHC stereocilia and the cell boundary are analyzed using 2D and 1D Gaussian fitting algorithms, respectively. Preliminary results show that the IHC bundle moves mainly in the radial direction and exhibits a small degree of splay, and that the stereocilia in the second row move less than those in the first row, even in the same focal plane.

Strong fascin expression promotes metastasis independent of its F-actin bundling activity.

PubMed

Heinz, Lisa S; Muhs, Stefanie; Schiewek, Johanna; Grüb, Saskia; Nalaskowski, Marcus; Lin, Yuan-Na; Wikman, Harriet; Oliveira-Ferrer, Leticia; Lange, Tobias; Wellbrock, Jasmin; Konietzny, Anja; Mikhaylova, Marina; Windhorst, Sabine

2017-12-15

High expression of the actin bundling protein Fascin increases the malignancy of tumor cells. Here we show that fascin expression is up-regulated in more malignant sub-cell lines of MDA-MB-231 cells as compared to parental cells. Since also parental MDA-MB-231 cells exhibit high fascin levels, increased fascin expression was termed as "hyperexpression". To examine the effect of fascin hyperexpression, fascin was hyperexpressed in parental MDA-MB-231 cells and metastasis was analyzed in NOD scid gamma (NSG) mice. In addition, the effect of fascin mutants with inactive or constitutively active actin bundling activity was examined. Unexpectedly, we found that hyperexpression of both, wildtype (wt) and mutant fascin strongly increased metastasis in vivo , showing that the effect of fascin hyperexpression did not depend on its actin bundling activity. Cellular assays revealed that hyperexpression of wt and mutant fascin increased adhesion of MDA-MB-231 cells while transmigration and proliferation were not affected. Since it has been shown that fascin controls adhesion by directly interacting with microtubules ( MTs), we analyzed if fascin hyperexpression affects MT dynamics. We found that at high concentrations fascin significantly increased MT dynamics in cells and in cell-free approaches. In summary our data show that strong expression of fascin in breast cancer cells increases metastasis independent of its actin bundling activity. Thus, it seems that the mechanism of fascin-stimulated metastasis depends on its concentration.

Study of cell-differentiation and assembly of photosynthetic proteins during greening of etiolated Zea mays leaves using confocal fluorescence microspectroscopy at liquid-nitrogen temperature.

PubMed

Shibata, Yutaka; Katoh, Wataru; Tahara, Yukari

2013-04-01

Fluorescence microspectroscopy observations were used to study the processes of cell differentiation and assemblies of photosynthesis proteins in Zea mays leaves under the greening process. The observations were done at 78K by setting the sample in a cryostat to avoid any undesired progress of the greening process during the measurements. The lateral and axial spatial resolutions of the system were 0.64μm and 4.4μm, respectively. The study revealed the spatial distributions of protochlorophyllide (PChld) in both the 632-nm-emitting and 655-nm-emitting forms within etiolated Zea mays leaves. The sizes of the fluorescence spots attributed to the former were larger than those of the latter, validating the assignment of the former and latter to the prothylakoid and prolamellar bodies, respectively. In vivo microspectroscopy observations of mature Zea mays leaves confirmed the different photosystem II (PS I)/photosystem I (PS II) ratio between the bundle sheath (BS) and mesophyll (MS) cells, which is specific for C4-plants. The BS cells in Zea mays leaves 1h after the initiation of the greening process tended to show fluorescence spectra at shorter wavelength side (at around 679nm) than the MS cells (at around 682nm). The 679-nm-emitting chlorophyll-a form observed mainly in the BS cells was attributed to putative precursor complexes to PS I. The BS cells under 3-h greening showed higher relative intensities of the PS I fluorescence band at around 735nm, suggesting the reduced PS II amount in the BS cells in this greening stage. Copyright © 2013 Elsevier B.V. All rights reserved.

Genomic and Expression Profiling of Benign and Malignant Nerve Sheath Tumors in Neurofibromatosis Patients

DTIC Science & Technology

2008-05-01

DAMD17-03-1-0297 Title: Genomic and Expression Pr ofiling of Benign and Malignant Nerve Sheath Tumors in Neurofibromatosis Patients...have determined the gene expression signature for benign and malignant peripheral nerve sheath tumors and found that the major trend in transformation...However, EGFR data in soft tissue neoplasms is limited. Using a variety of benign and malignant spindle cell neoplasms, we assessed EGFR status by

Effects of Mechanical Loading on the Dynamics of Hair-Cell Stereociliary Bundles

NASA Astrophysics Data System (ADS)

Fredrickson, Lea

Hearing is remarkably sensitive and still not entirely understood. Hair cells of the inner ear are the mechano-electrical transducers of sound and understanding how they function is essential to the understanding of hearing in general. Spontaneous oscillations exhibited by stereociliary bundles of the bullfrog sacculus provide a useful probe for the study of the hair cells' internal dynamic state. In this work we study the effects of mechanical loading on these hair-cell bundles in order to study their dynamics. When applying stiffness loads, we find that the spontaneous oscillation profile changes from multimode to single mode with light loading, and decreases in amplitude and increases in frequency with stiffer loads. We also find that tuning decreases with increasing load such that at loads comparable to in vivo conditions the tuning is flat. We further explore loading via deflections to hair cell bundles, both in the form of steady-state offsets and slow ramps. We find that steady state offsets lead to significant modulation of the characteristic frequency of response, decreasing the frequency in the channels closed direction (negative) and increasing it in the channels open direction (positive). Attachment to the overlying membrane was found, in vitro, to affect bundle offset position in hair cells of the bullfrog sacculus. Application of similar offsets on free-standing, spontaneously oscillating hair bundles shows modulation of their dynamic state, i.e. oscillation profile, characteristic frequency, and response to stimulus. Large offsets are found to arrest spontaneous oscillations, which recover upon reversal of the stimulus. The dynamical state of the hair bundle is dependent on both the history and direction of the offset stimulus. Oscillation suppression occurs much more readily in the negative direction and the bundle behavior approaching quiescence is distinct from that in the positive direction. With the change in spontaneous oscillation frequency and profile comes a change in the phase-locked response amplitude, dependent on bundle offset, winch extends the range of detection frequencies of the hair cell. We explore the broadband phase-locked response of spontaneously oscillating saccular hair cell bundles subject to time-dependent mechanical deflections. The experimental phase-locked amplitude shows an Arnold Tongue, consistent with theoretically predicted dynamical behavior. An offset that steadily increases in time, imposed on the position of the bundle to explore its dynamics at the zero frequency limit, is observed to progressively suppress spontaneous oscillations in a transition that displays strong frequency modulation, with the frequency vanishing at the critical point. When deflected at a faster rate and when allowed to recover to the oscillatory regime, the bundles also displayed a modulation in the amplitude of oscillation. We propose the dynamics of this transition to be dominated by a multi-critical region such that slight variations of a control parameter can produce either an infinite-period, supercritical Hopf, or Bogdanov-Takens bifurcation.

Leaf blade structure of Verbesina macrophylla (Cass.) F. S. Blake (Asteraceae): ontogeny, duct secretion mechanism and essential oil composition.

PubMed

Bezerra, L D A; Mangabeira, P A O; de Oliveira, R A; Costa, L C D B; Da Cunha, M

2018-05-01

Secretory structures are common in Asteraceae, where they exhibit a high degree of morphological diversity. The species Verbesina macrophylla, popularly known as assa-peixe, is native to Brazil where it is widely used for medicinal purposes. Despite its potential medical importance, there have been no studies of the anatomy of this species, especially its secretory structures and secreted compounds. This study examined leaves of V. macrophylla with emphasis on secretory structures and secreted secondary metabolites. Development of secretory ducts and the mechanism of secretion production are described for V. macrophylla using ultrastructure, yield and chemical composition of its essential oils. Verbesina macrophylla has a hypostomatic leaf blade with dorsiventral mesophyll and secretory ducts associated with vascular bundles of schizogenous origin. Histochemistry identified the presence of lipids, terpenes, alkaloids and mucopolysaccharides. Ultrastructure suggests that the secretion released into the duct lumen is produced in plastids of transfer cells, parenchymal sheath cells and stored in vacuoles in these cells and duct epithelial cells. The essential oil content was 0.8%, and its major components were germacrene D, germacrene D-4-ol, β-caryophyllene, bicyclogermacrene and α-cadinol. Secretory ducts of V. macrophylla are squizogenous. Substances identified in tissues suggest that both secretions stored in the ducts and in adjacent parenchyma cells are involved in chemical defence. The essential oil is rich in sesquiterpenes, with germacrene D and its derivatives being notable components. © 2018 German Society for Plant Sciences and The Royal Botanical Society of the Netherlands.

Mechanisms of graviperception and response in pea seedlings

NASA Technical Reports Server (NTRS)

Galston, A. W.

1984-01-01

A new method for the mass isolation and purification of multigranular amyloplasts from the bundle sheath parenchyma of etiolated pa epicotyls was presented. These bodies, which displace within 2+3 minutes of exposure to 1 x g, are probably the gravity receptors (statoliths) in this plant. These amyloplasts were characterized as having a doublemembrane with a surface-localized ATPase, a high calcium content, and their own genomic DNA. These amyloplasts are investigated as to (a) the reasons for their especially high density, probable related to their starch content, (b) the possible identity of their DNA with the DNA of chloroplasts and unigranular amyloplasts, and (c) possible importance of their high calcium content.

From Cell Differentiation to Cell Collectives: Bacillus subtilis Uses Division of Labor to Migrate

PubMed Central

van Gestel, Jordi; Vlamakis, Hera; Kolter, Roberto

2015-01-01

The organization of cells, emerging from cell–cell interactions, can give rise to collective properties. These properties are adaptive when together cells can face environmental challenges that they separately cannot. One particular challenge that is important for microorganisms is migration. In this study, we show how flagellum-independent migration is driven by the division of labor of two cell types that appear during Bacillus subtilis sliding motility. Cell collectives organize themselves into bundles (called “van Gogh bundles”) of tightly aligned cell chains that form filamentous loops at the colony edge. We show, by time-course microscopy, that these loops migrate by pushing themselves away from the colony. The formation of van Gogh bundles depends critically on the synergistic interaction of surfactin-producing and matrix-producing cells. We propose that surfactin-producing cells reduce the friction between cells and their substrate, thereby facilitating matrix-producing cells to form bundles. The folding properties of these bundles determine the rate of colony expansion. Our study illustrates how the simple organization of cells within a community can yield a strong ecological advantage. This is a key factor underlying the diverse origins of multicellularity. PMID:25894589

Cell wall and enzyme changes during the graviresponse of the leaf-sheath pulvinus of oat (Avena sativa)

NASA Technical Reports Server (NTRS)

Gibeaut, David M.; Karuppiah, Nadarajah; Chang, S.-R.; Brock, Thomas G.; Vadlamudi, Babu; Kim, Donghern; Ghosheh, Najati S.; Rayle, David L.; Carpita, Nicholas C.; Kaufman, Peter B.

1990-01-01

The graviresponse of the leaf-sheath pulvinus of oat (Avena sativa) involves an asymmetric growth response and asymmetric processes involving degradation of starch and cell wall synthesis. Cellular and biochemical events were studied by investigation of the activities of related enzymes and changes in cell walls and their constituents. It is suggested that an osmotic potential gradient acts as the driving factor for growth, while wall extensibility is a limiting factor in pulvinus growth.

Self-consistent simulation of high-frequency driven plasma sheaths

NASA Astrophysics Data System (ADS)

Shihab, Mohammed; Eremin, Denis; Mussenbrock, Thomas; Brinkmann, Ralf

2011-10-01

Low pressure capacitively coupled plasmas are widely used in plasma processing and microelectronics industry. Understanding the dynamics of the boundary sheath is a fundamental problem. It controls the energy and angular distribution of ions bombarding the electrode, which in turn affects the surface reaction rate and the profile of microscopic features. In this contribution, we investigate the dynamics of plasma boundary sheaths by means of a kinetic self-consistent model, which is able to resolve the ion dynamics. Asymmetric sheath dynamics is observed for the intermediate RF regime, i.e., in the regime where the ion plasma frequency is equal to the driving frequency. The ion inertia causes an additional phase difference between the expansion and the contraction phase of the plasma sheath and an asymmetry for the ion energy distribution bimodal shape. A comparison with experimental results and particle in cell simulations is performed. Low pressure capacitively coupled plasmas are widely used in plasma processing and microelectronics industry. Understanding the dynamics of the boundary sheath is a fundamental problem. It controls the energy and angular distribution of ions bombarding the electrode, which in turn affects the surface reaction rate and the profile of microscopic features. In this contribution, we investigate the dynamics of plasma boundary sheaths by means of a kinetic self-consistent model, which is able to resolve the ion dynamics. Asymmetric sheath dynamics is observed for the intermediate RF regime, i.e., in the regime where the ion plasma frequency is equal to the driving frequency. The ion inertia causes an additional phase difference between the expansion and the contraction phase of the plasma sheath and an asymmetry for the ion energy distribution bimodal shape. A comparison with experimental results and particle in cell simulations is performed. The financial support from the Federal Ministry of Education and Research within the frame of the project ``Plasma-Technology-Grid'' and the support of the DFG via the collaborative research center SFB-TR87 is gratefully acknowledged.

Actin-binding proteins sensitively mediate F-actin bundle stiffness

NASA Astrophysics Data System (ADS)

Claessens, Mireille M. A. E.; Bathe, Mark; Frey, Erwin; Bausch, Andreas R.

2006-09-01

Bundles of filamentous actin (F-actin) form primary structural components of a broad range of cytoskeletal processes including filopodia, sensory hair cell bristles and microvilli. Actin-binding proteins (ABPs) allow the cell to tailor the dimensions and mechanical properties of the bundles to suit specific biological functions. Therefore, it is important to obtain quantitative knowledge on the effect of ABPs on the mechanical properties of F-actin bundles. Here we measure the bending stiffness of F-actin bundles crosslinked by three ABPs that are ubiquitous in eukaryotes. We observe distinct regimes of bundle bending stiffness that differ by orders of magnitude depending on ABP type, concentration and bundle size. The behaviour observed experimentally is reproduced quantitatively by a molecular-based mechanical model in which ABP shearing competes with F-actin extension/compression. Our results shed new light on the biomechanical function of ABPs and demonstrate how single-molecule properties determine mesoscopic behaviour. The bending mechanics of F-actin fibre bundles are general and have implications for cytoskeletal mechanics and for the rational design of functional materials.

Unique photosynthetic phenotypes in Portulaca (Portulacaceae): C3-C4 intermediates and NAD-ME C4 species with Pilosoid-type Kranz anatomy.

PubMed

Voznesenskaya, Elena V; Koteyeva, Nuria K; Edwards, Gerald E; Ocampo, Gilberto

2017-01-01

Portulacaceae is a family that has considerable diversity in photosynthetic phenotypes. It is one of 19 families of terrestrial plants where species having C 4 photosynthesis have been found. Most species in Portulaca are in the alternate-leaved (AL) lineage, which includes one clade (Cryptopetala) with taxa lacking C 4 photosynthesis and three clades having C 4 species (Oleracea, Umbraticola and Pilosa). All three species in the Cryptopetala clade lack Kranz anatomy, the leaves have C 3 -like carbon isotope composition and they have low levels of C 4 cycle enzymes. Anatomical, biochemical and physiological analyses show they are all C 3 -C 4 intermediates. They have intermediate CO 2 compensation points, enrichment of organelles in the centripetal position in bundle sheath (BS) cells, with selective localization of glycine decarboxylase in BS mitochondria. In the three C 4 clades there are differences in Kranz anatomy types and form of malic enzyme (ME) reported to function in C 4 (NAD-ME versus NADP-ME): Oleracea (Atriplicoid, NAD-ME), Umbraticola (Atriplicoid, NADP-ME) and Pilosa (Pilosoid, NADP-ME). Structural and biochemical analyses were performed on Pilosa clade representatives having Pilosoid-type leaf anatomy with Kranz tissue enclosing individual peripheral vascular bundles and water storage in the center of the leaf. In this clade, all species except P. elatior are NADP-ME-type C 4 species with grana-deficient BS chloroplasts and grana-enriched M chloroplasts. Surprisingly, P. elatior has BS chloroplasts enriched in grana and NAD-ME-type photosynthesis. The results suggest photosynthetic phenotypes were probably derived from an ancestor with NADP-ME-type C 4 , with two independent switches to NAD-ME type. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Regulation of leaf hydraulics: from molecular to whole plant levels.

PubMed

Prado, Karine; Maurel, Christophe

2013-01-01

The water status of plant leaves is dependent on both stomatal regulation and water supply from the vasculature to inner tissues. The present review addresses the multiple physiological and mechanistic facets of the latter process. Inner leaf tissues contribute to at least a third of the whole resistance to water flow within the plant. Physiological studies indicated that leaf hydraulic conductance (K leaf) is highly dependent on the anatomy, development and age of the leaf and can vary rapidly in response to physiological or environmental factors such as leaf hydration, light, temperature, or nutrient supply. Differences in venation pattern provide a basis for variations in K leaf during development and between species. On a short time (hour) scale, the hydraulic resistance of the vessels can be influenced by transpiration-induced cavitations, wall collapses, and changes in xylem sap composition. The extravascular compartment includes all living tissues (xylem parenchyma, bundle sheath, and mesophyll) that transport water from xylem vessels to substomatal chambers. Pharmacological inhibition and reverse genetics studies have shown that this compartment involves water channel proteins called aquaporins (AQPs) that facilitate water transport across cell membranes. In many plant species, AQPs are present in all leaf tissues with a preferential expression in the vascular bundles. The various mechanisms that allow adjustment of K leaf to specific environmental conditions include transcriptional regulation of AQPs and changes in their abundance, trafficking, and intrinsic activity. Finally, the hydraulics of inner leaf tissues can have a strong impact on the dynamic responses of leaf water potential and stomata, and as a consequence on plant carbon economy and leaf expansion growth. The manipulation of these functions could help optimize the entire plant performance and its adaptation to extreme conditions over short and long time scales.

Regulation of leaf hydraulics: from molecular to whole plant levels

PubMed Central

Prado, Karine; Maurel, Christophe

2013-01-01

The water status of plant leaves is dependent on both stomatal regulation and water supply from the vasculature to inner tissues. The present review addresses the multiple physiological and mechanistic facets of the latter process. Inner leaf tissues contribute to at least a third of the whole resistance to water flow within the plant. Physiological studies indicated that leaf hydraulic conductance (Kleaf) is highly dependent on the anatomy, development and age of the leaf and can vary rapidly in response to physiological or environmental factors such as leaf hydration, light, temperature, or nutrient supply. Differences in venation pattern provide a basis for variations in Kleaf during development and between species. On a short time (hour) scale, the hydraulic resistance of the vessels can be influenced by transpiration-induced cavitations, wall collapses, and changes in xylem sap composition. The extravascular compartment includes all living tissues (xylem parenchyma, bundle sheath, and mesophyll) that transport water from xylem vessels to substomatal chambers. Pharmacological inhibition and reverse genetics studies have shown that this compartment involves water channel proteins called aquaporins (AQPs) that facilitate water transport across cell membranes. In many plant species, AQPs are present in all leaf tissues with a preferential expression in the vascular bundles. The various mechanisms that allow adjustment of Kleaf to specific environmental conditions include transcriptional regulation of AQPs and changes in their abundance, trafficking, and intrinsic activity. Finally, the hydraulics of inner leaf tissues can have a strong impact on the dynamic responses of leaf water potential and stomata, and as a consequence on plant carbon economy and leaf expansion growth. The manipulation of these functions could help optimize the entire plant performance and its adaptation to extreme conditions over short and long time scales. PMID:23874349

Visualization of Live Cochlear Stereocilia at a Nanoscale Resolution Using Hopping Probe Ion Conductance Microscopy

PubMed Central

Vélez-Ortega, A. Catalina; Frolenkov, Gregory I.

2016-01-01

The mechanosensory apparatus that detects sound-induced vibrations in the cochlea is located on the apex of the auditory sensory hair cells and it is made up of actin-filled projections, called stereocilia. In young rodents, stereocilia bundles of auditory hair cells consist of 3 to 4 rows of stereocilia of decreasing height and varying thickness. Morphological studies of the auditory stereocilia bundles in live hair cells have been challenging because the diameter of each stereocilium is near or below the resolution limit of optical microscopy. In theory, scanning probe microscopy techniques, such as atomic force microscopy, could visualize the surface of a living cell at a nanoscale resolution. However, their implementations for hair cell imaging have been largely unsuccessful because the probe usually damages the bundle and disrupts the bundle cohesiveness during imaging. We overcome these limitations by using hopping probe ion conductance microscopy (HPICM), a non-contact scanning probe technique that is ideally suited for the imaging of live cells with a complex topography. Organ of Corti explants are placed in a physiological solution and then a glass nanopipette –which is connected to a 3D-positioning piezoelectric system and to a patch clamp amplifier– is used to scan the surface of the live hair cells at nanometer resolution without ever touching the cell surface. Here we provide a detailed protocol for the imaging of mouse or rat stereocilia bundles in live auditory hair cells using HPICM. We provide information about the fabrication of the nanopipettes, the calibration of the HPICM setup, the parameters we have optimized for the imaging of live stereocilia bundles and, lastly, a few basic image post-processing manipulations. PMID:27259929

Visualization of Live Cochlear Stereocilia at a Nanoscale Resolution Using Hopping Probe Ion Conductance Microscopy.

PubMed

Vélez-Ortega, A Catalina; Frolenkov, Gregory I

2016-01-01

The mechanosensory apparatus that detects sound-induced vibrations in the cochlea is located on the apex of the auditory sensory hair cells and it is made up of actin-filled projections, called stereocilia. In young rodents, stereocilia bundles of auditory hair cells consist of 3-4 rows of stereocilia of decreasing height and varying thickness. Morphological studies of the auditory stereocilia bundles in live hair cells have been challenging because the diameter of each stereocilium is near or below the resolution limit of optical microscopy. In theory, scanning probe microscopy techniques, such as atomic force microscopy, could visualize the surface of a living cell at a nanoscale resolution. However, their implementations for hair cell imaging have been largely unsuccessful because the probe usually damages the bundle and disrupts the bundle cohesiveness during imaging. We overcome these limitations by using hopping probe ion conductance microscopy (HPICM), a non-contact scanning probe technique that is ideally suited for the imaging of live cells with a complex topography. Organ of Corti explants are placed in a physiological solution and then a glass nanopipette-which is connected to a 3D-positioning piezoelectric system and to a patch clamp amplifier-is used to scan the surface of the live hair cells at nanometer resolution without ever touching the cell surface.Here, we provide a detailed protocol for the imaging of mouse or rat stereocilia bundles in live auditory hair cells using HPICM. We provide information about the fabrication of the nanopipettes, the calibration of the HPICM setup, the parameters we have optimized for the imaging of live stereocilia bundles and, lastly, a few basic image post-processing manipulations.

Spontaneous Oscillation by Hair Bundles of the Bullfrog's Sacculus

PubMed Central

Martin, Pascal; Bozovic, D.; Choe, Y.; Hudspeth, A. J.

2007-01-01

One prominent manifestation of mechanical activity in hair cells is spontaneous otoacoustic emission, the unprovoked emanation of sound by an internal ear. Because active hair-bundle motility probably constitutes the active process of non-mammalian hair cells, we investigated the ability of hair bundles in the bullfrog's sacculus to produce oscillations that might underlie spontaneous otoacoustic emissions. When maintained in the ear's normal ionic milieu, many bundles oscillated spontaneously through distances as great as 80 nm at frequencies of 5-50 Hz. Whole-cell recording disclosed that the positive phase of movement was associated with the opening of transduction channels. Gentamicin, which blocks transduction channels, reversibly arrested oscillation; drugs that affect the cAMP phosphorylation pathway and might influence myosin's activity altered the rate of oscillation. Increasing the Ca2+ concentration rendered oscillations faster and smaller until they were suppressed; lowering the Ca2+ concentration moderately with chelators had the opposite effect. When a bundle was offset with a stimulus fiber, oscillations were transiently suppressed but gradually resumed. Loading a bundle by partial displacement clamping, which simulated the presence of the accessory structures to which a bundle is ordinarily attached, increased the frequency and diminished the magnitude of oscillation. These observations accord with a model in which oscillations arise from the interplay of the hair bundle's negative stiffness with the activity of adaptation motors and with Ca2+-dependent relaxation of gating springs. PMID:12805294

Real-Time Dynamics of Emerging Actin Networks in Cell-Mimicking Compartments

PubMed Central

Deshpande, Siddharth; Pfohl, Thomas

2015-01-01

Understanding the cytoskeletal functionality and its relation to other cellular components and properties is a prominent question in biophysics. The dynamics of actin cytoskeleton and its polymorphic nature are indispensable for the proper functioning of living cells. Actin bundles are involved in cell motility, environmental exploration, intracellular transport and mechanical stability. Though the viscoelastic properties of actin-based structures have been extensively probed, the underlying microstructure dynamics, especially their disassembly, is not fully understood. In this article, we explore the rich dynamics and emergent properties exhibited by actin bundles within flow-free confinements using a microfluidic set-up and epifluorescence microscopy. After forming entangled actin filaments within cell-sized quasi two-dimensional confinements, we induce their bundling using three different fundamental mechanisms: counterion condensation, depletion interactions and specific protein-protein interactions. Intriguingly, long actin filaments form emerging networks of actin bundles via percolation leading to remarkable properties such as stress generation and spindle-like intermediate structures. Simultaneous sharing of filaments in different links of the network is an important parameter, as short filaments do not form networks but segregated clusters of bundles instead. We encounter a hierarchical process of bundling and its subsequent disassembly. Additionally, our study suggests that such percolated networks are likely to exist within living cells in a dynamic fashion. These observations render a perspective about differential cytoskeletal responses towards numerous stimuli. PMID:25785606

Spermatogenesis and sperm ultrastructure in the polychaete genus Ophryotrocha (Dorvilleidae)

NASA Astrophysics Data System (ADS)

Pfannenstiel, Hans-Dieter; Grünig, Charlotte

1990-06-01

The details of spermatogenesis and spermiogenesis are described for Ophryotrocha puerilis. The ultrastructure of mature sperm is shown for O. puerilis, O. hartmanni, O. gracilis, O. diadema, O. labronica, and O. notoglandulata. Clusters of sixteen cells each are proliferated by two stem cells in each setigerous segment of O. puerilis representing the very early stages of both oogenesis and spermatogenesis. In each spermatocyte-I cluster, the cells are interconnected by cytoplasmic bridges. Early, clusters are enveloped by peritoneal sheath cells. These transient gonad walls break down prior to meiosis. The meiotic processes may start in the clusters with the cells still interconnected, or during breakdown of the original cluster, giving rise to smaller subclusters of both spermatocytes I and spermatocytes II with various numbers of cells. Finally, spermatid tetrads are present. As spermiogenesis progresses, the tetrads disintegrate. Golgi vesicles in both spermatocytes and spermatids contain electron-dense material, presumably preacrosomal. The acrosome is formed by such vesicles. In the six species studied here, the acrosomes appear to be of a similar overall structure but are of different shape. Centrioles are usually located beneath the acrosome. The distal centriole forms the basal body of a flagellum-like cytoplasmic process. The microtubules of these flagellar equivalents do not show a normal ciliar arrangement. The flagellar equivalent appears to be non-motile. In O. hartmanni and in O. notoglandulata, a flagellar equivalent is missing. Microtubules originating from the proximal end of the distal centriole stretch to the nuclear envelope. This feature appears to be especially conspicuous in O. puerilis and in O. labronica. In O. labronica and in O. notoglandulata, bundles of microtubules paralleling the cell perimeter appear to stabilise the sperm. Various numbers of mitochondria are either randomly distributed around the nucleus or accumulate on one side, often directly under the acrosome.

A STRUCTURAL ANALYSIS OF THE MYELIN SHEATH IN THE CENTRAL NERVOUS SYSTEM

PubMed Central

Hirano, Asao; Dembitzer, Herbert M.

1967-01-01

The cerebral white matter of rats subjected to a variety of noxious experimental conditions was examined in the electron microscope. Several unusual configurations of the myelin sheath are identified in addition to the usual configuration. These variations include the presence of (a) formed organelles within the inner and outer loops, (b) isolated islands of cytoplasm in unfused portions of the major dense lines, (c) apparently unconnected cell processes between the sheath and the axon, and (d) concentric, double myelin sheaths. A generalized model of the myelin sheath based on a hypothetical unrolling of the sheath is described. It consists of a shovel-shaped myelin sheet surrounded by a continuous thickened rim of cytoplasm. Most of the unusual myelin configurations are explained as simple variations on this basic theme. With the help of this model, an explanation of the formation of the myelin sheath is offered. This explanation involves the concept that myelin formation can occur at all cytoplasmic areas adjacent to the myelin proper and that adjacent myelin lamellae can move in relation to each other. PMID:6035645

Influence of the axial magnetic field on sheath development after current zero in a vacuum circuit breaker

NASA Astrophysics Data System (ADS)

Chen, Yi; Yang, Fei; Sun, Hao; Wu, Yi; Niu, Chunping; Rong, Mingzhe

2017-06-01

After current zero, which is the moment when the vacuum circuit breaker interrupts a vacuum arc, sheath development is the first process in the dielectric recovery process. An axial magnetic field (AMF) is widely used in the vacuum circuit breaker when the high-current vacuum arc is interrupted. Therefore, it is very important to study the influence of different AMF amplitudes on the sheath development. The objective of this paper is to study the influence of different AMF amplitudes on the sheath development from a micro perspective. Thus, the particle in cell-Monte Carlo collisions (PIC-MCC) method was adopted to develop the sheath development model. We compared the simulation results with the experimental results and then validated the simulation. We also obtained the speed of the sheath development and the energy density of the ions under different AMF amplitudes. The results showed that the larger the AMF amplitudes are, the faster the sheath develops and the lower the ion energy density is, meaning the breakdown is correspondingly more difficult.

Photovoltaic sheathing element with one or more tabs

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

Keenihan, James R; Langmaid, Joseph A; Lopez, Leonardo C.

2017-02-07

The present invention is premised upon an assembly that includes at least a photovoltaic sheathing element capable of being affixed on a building structure. The shingle including at least a photovoltaic cell assembly, a body portion attached to one or more portions of the photovoltaic cell assembly. Wherein the body portion includes one or more top peripheral tabs each capable of fitting under one or more vertically adjoining devices.

* Hierarchically Structured Electrospun Scaffolds with Chemically Conjugated Growth Factor for Ligament Tissue Engineering.

PubMed

Pauly, Hannah M; Sathy, Binulal N; Olvera, Dinorath; McCarthy, Helen O; Kelly, Daniel J; Popat, Ketul C; Dunne, Nicholas J; Haut Donahue, Tammy Lynn

2017-08-01

The anterior cruciate ligament (ACL) of the knee is vital for proper joint function and is commonly ruptured during sports injuries or car accidents. Due to a lack of intrinsic healing capacity and drawbacks with allografts and autografts, there is a need for a tissue-engineered ACL replacement. Our group has previously used aligned sheets of electrospun polycaprolactone nanofibers to develop solid cylindrical bundles of longitudinally aligned nanofibers. We have shown that these nanofiber bundles support cell proliferation and elongation and the hierarchical structure and material properties are similar to the native human ACL. It is possible to combine multiple nanofiber bundles to create a scaffold that attempts to mimic the macroscale structure of the ACL. The goal of this work was to develop a hierarchical bioactive scaffold for ligament tissue engineering using connective tissue growth factor (CTGF)-conjugated nanofiber bundles and evaluate the behavior of mesenchymal stem cells (MSCs) on these scaffolds in vitro and in vivo. CTGF was immobilized onto the surface of individual nanofiber bundles or scaffolds consisting of multiple nanofiber bundles. The conjugation efficiency and the release of conjugated CTGF were assessed using X-ray photoelectron spectroscopy, assays, and immunofluorescence staining. Scaffolds were seeded with MSCs and maintained in vitro for 7 days (individual nanofiber bundles), in vitro for 21 days (scaled-up scaffolds of 20 nanofiber bundles), or in vivo for 6 weeks (small scaffolds of 4 nanofiber bundles), and ligament-specific tissue formation was assessed in comparison to non-CTGF-conjugated control scaffolds. Results showed that CTGF conjugation encouraged cell proliferation and ligament-specific tissue formation in vitro and in vivo. The results suggest that hierarchical electrospun nanofiber bundles conjugated with CTGF are a scalable and bioactive scaffold for ACL tissue engineering.

Erk regulation of actin capping and bundling by Eps8 promotes cortex tension and leader bleb-based migration

PubMed Central

Logue, Jeremy S; Cartagena-Rivera, Alexander X; Baird, Michelle A; Davidson, Michael W; Chadwick, Richard S; Waterman, Clare M

2015-01-01

Within the confines of tissues, cancer cells can use blebs to migrate. Eps8 is an actin bundling and capping protein whose capping activity is inhibited by Erk, a key MAP kinase that is activated by oncogenic signaling. We tested the hypothesis that Eps8 acts as an Erk effector to modulate actin cortex mechanics and thereby mediate bleb-based migration of cancer cells. Cells confined in a non-adhesive environment migrate in the direction of a very large ‘leader bleb.’ Eps8 bundling activity promotes cortex tension and intracellular pressure to drive leader bleb formation. Eps8 capping and bundling activities act antagonistically to organize actin within leader blebs, and Erk mediates this effect. An Erk biosensor reveals concentrated kinase activity within leader blebs. Bleb contents are trapped by the narrow neck that separates the leader bleb from the cell body. Thus, Erk activity promotes actin bundling by Eps8 to enhance cortex tension and drive the bleb-based migration of cancer cells under non-adhesive confinement. DOI: http://dx.doi.org/10.7554/eLife.08314.001 PMID:26163656

Optical Imaging of Neuronal Activity and Visualization of Fine Neural Structures in Non-Desheathed Nervous Systems

PubMed Central

Stein, Wolfgang

2014-01-01

Locating circuit neurons and recording from them with single-cell resolution is a prerequisite for studying neural circuits. Determining neuron location can be challenging even in small nervous systems because neurons are densely packed, found in different layers, and are often covered by ganglion and nerve sheaths that impede access for recording electrodes and neuronal markers. We revisited the voltage-sensitive dye RH795 for its ability to stain and record neurons through the ganglion sheath. Bath-application of RH795 stained neuronal membranes in cricket, earthworm and crab ganglia without removing the ganglion sheath, revealing neuron cell body locations in different ganglion layers. Using the pyloric and gastric mill central pattern generating neurons in the stomatogastric ganglion (STG) of the crab, Cancer borealis, we found that RH795 permeated the ganglion without major residue in the sheath and brightly stained somatic, axonal and dendritic membranes. Visibility improved significantly in comparison to unstained ganglia, allowing the identification of somata location and number of most STG neurons. RH795 also stained axons and varicosities in non-desheathed nerves, and it revealed the location of sensory cell bodies in peripheral nerves. Importantly, the spike activity of the sensory neuron AGR, which influences the STG motor patterns, remained unaffected by RH795, while desheathing caused significant changes in AGR activity. With respect to recording neural activity, RH795 allowed us to optically record membrane potential changes of sub-sheath neuronal membranes without impairing sensory activity. The signal-to-noise ratio was comparable with that previously observed in desheathed preparations and sufficiently high to identify neurons in single-sweep recordings and synaptic events after spike-triggered averaging. In conclusion, RH795 enabled staining and optical recording of neurons through the ganglion sheath and is therefore both a good anatomical marker for living neural tissue and a promising tool for studying neural activity of an entire network with single-cell resolution. PMID:25062029

Contribution of actin filaments to the global compressive properties of fibroblasts.

PubMed

Ujihara, Yoshihiro; Nakamura, Masanori; Miyazaki, Hiroshi; Wada, Shigeo

2012-10-01

Actin filaments are often regarded as tension-bearing components. Here, we examined the effects of actin filaments on global compressive properties of cells experimentally and numerically. Fibroblasts were harvested from the patellar tendon of a mature Japanese white rabbit and treated with cytochalasin D to depolymerize the actin filaments. Intact cells and cells with disrupted actin filaments were subjected to the compressive tests. Each floating cell was held between the cantilever and compressive plates and compressed by moving the compressive plate with a linear actuator to obtain a load-deformation curve under quasi-static conditions. The experimental results demonstrated that the initial stiffness of a cell with disrupted actin filaments decreased by 51%. After the experiments, we simulated the compressive test of cells with/without bundles of actin filaments. A bundle of actin filaments was modeled as a tension-bearing component that generates a force based on Hooke's law only when it was elongated. By contrast, if it was shortened, it was assumed to exert no force. The computational results revealed that the alignment of bundles of actin filaments significantly affected the cell stiffness. In addition, the passive reorientation of bundles of actin filaments perpendicular to the compression induced an increase in the resistance to the vertical elongation of a cell and thereby increased the cell stiffness. These results clearly indicated that bundles of actin filaments contribute to the compressive properties of a cell, even if they are tension-bearing components. Copyright © 2012 Elsevier Ltd. All rights reserved.

Mutations in cadherin 23 affect tip links in zebrafish sensory hair cells.

PubMed

Söllner, Christian; Rauch, Gerd-Jörg; Siemens, Jan; Geisler, Robert; Schuster, Stephan C; Müller, Ulrich; Nicolson, Teresa

2004-04-29

Hair cells have highly organized bundles of apical projections, or stereocilia, that are deflected by sound and movement. Displacement of stereocilia stretches linkages at the tips of stereocilia that are thought to gate mechanosensory channels. To identify the molecular machinery that mediates mechanotransduction in hair cells, zebrafish mutants were identified with defects in balance and hearing. In sputnik mutants, stereociliary bundles are splayed to various degrees, with individuals displaying reduced or absent mechanotransduction. Here we show that the defects in sputnik mutants are caused by mutations in cadherin 23 (cdh23). Mutations in Cdh23 also cause deafness and vestibular defects in mice and humans, and the protein is present in hair bundles. We show that zebrafish Cdh23 protein is concentrated near the tips of hair bundles, and that tip links are absent in homozygous sputnik(tc317e) larvae. Moreover, tip links are absent in larvae carrying weak alleles of cdh23 that affect mechanotransduction but not hair bundle integrity. We conclude that Cdh23 is an essential tip link component required for hair-cell mechanotransduction.

Comparative transduction mechanisms of hair cells in the bullfrog utriculus. II. Sensitivity and response dynamics to hair bundle displacement

NASA Technical Reports Server (NTRS)

Baird, R. A.

1994-01-01

1. Hair cells in whole-mount in vitro preparations of the utricular macula of the bullfrog (Rana catesbeiana) were selected according to their macular location and hair bundle morphology. The sensitivity and response dynamics of selected hair cells to natural stimulation were examined by recording their voltage responses to step and sinusoidal hair bundle displacements applied to their longest stereocilia. 2. The voltage responses of 31 hair cells to sinusoidal hair bundle displacements were characterized by their gains and phases, taken with respect to peak hair bundle displacement. The gains of Type B and Type C cells at both 0.5 and 5.0 Hz were markedly lower than those of Type F and Type E cells. Phases, with the exception of Type C cells, lagged hair bundle displacement at 0.5 Hz. Type C cells had phase leads of 25-40 degrees. At 5.0 Hz, response phases in all cells were phase lagged with respect to those at 0.5 Hz. Type C cells had larger gains and smaller phase leads at 5.0 Hz than at 0.5 Hz, suggesting the presence of low-frequency adaptation. 3. Displacement-response curves, derived from the voltage responses to 5.0-Hz sinusoids, were sigmoidal in shape and asymmetrical, with the depolarizing response having a greater magnitude and saturating less abruptly than the hyperpolarizing response. When normalized to their largest displacement the linear ranges of these curves varied from < 0.5 to 1.25 microns and were largest in Type B and smallest in Type F and Type E cells. Sensitivity, defined as the slope of the normalized displacement-response curve, was inversely correlated with linear range. 4. The contribution of geometric factors associated with the hair bundle to linear range and sensitivity were predicted from realistic models of utricular hair bundles created using morphological data obtained from light and electron microscopy. Three factors, including 1) the inverse ratio of the lengths of the kinocilium and longest stereocilia, representing the lever arm between kinociliary and stereociliary displacement; 2) tip link extension/linear displacement, largely a function of stereociliary height and separation; and 3) stereociliary number, an estimate of the number of transduction channels, were considered in this analysis. The first of these factors was quantitatively more important than the latter two factors and their total contribution was largest in Type B and Type C cells. Theoretical models were also used to calculate the relation between rotary and linear displacement.(ABSTRACT TRUNCATED AT 400 WORDS).

Carbon dioxide and water vapor high temperature electrolysis

NASA Technical Reports Server (NTRS)

Isenberg, Arnold O.; Verostko, Charles E.

1989-01-01

The design, fabrication, breadboard testing, and the data base obtained for solid oxide electrolysis systems that have applications for planetary manned missions and habitats are reviewed. The breadboard tested contains sixteen tubular cells in a closely packed bundle for the electrolysis of carbon dioxide and water vapor. The discussion covers energy requirements, volume, weight, and operational characteristics related to the measurement of the reactant and product gas compositions, temperature distribution along the electrolyzer tubular cells and through the bundle, and thermal energy losses. The reliability of individual cell performance in the bundle configuration is assessed.

Particle-in-cell study of the ion-to-electron sheath transition

DOE PAGES

Scheiner, Brett; Baalrud, Scott D.; Hopkins, Matthew M.; ...

2016-08-09

The form of a sheath near a small electrode, with bias changing from below to above the plasma potential, is studied using 2D particle-in-cell simulations. When the electrode is biased within T e/2 e below the plasma potential, the electron velocity distribution functions (EVDFs) exhibit a loss-cone type truncation due to fast electrons overcoming the small potential difference between the electrode and plasma. No sheath is present in this regime, and the plasma remains quasineutral up to the electrode. The EVDF truncation leads to a presheath-like density and flow velocity gradients. Once the bias exceeds the plasma potential, an electronmore » sheath is present. In this case, the truncation driven behavior persists, but is accompanied by a shift in the maximum value of the EVDF that is not present in the negative bias cases. In conclusion, the flow moment has significant contributions from both the flow shift of the EVDF maximum, and the loss-cone truncation.« less

Stationary organization of the actin cytoskeleton in Vallisneria: the role of stable microfilaments at the end walls.

PubMed

Ryu, J H; Takagi, S; Nagai, R

1995-04-01

In mesophyll cells of the aquatic angiosperm Vallisneria gigantea, bundles of microfilaments (MFs) serve as tracks for the rotational streaming of the cytoplasm, which occurs along the two longer side walls and the two shorter end walls. The stationary organization of these bundles has been shown to depend on the association of the bundles with the plasma membrane at the end walls. To identify the sites of such association, the effects of cytochalasin B (CB) on the configuration of the bundles of MFs were examined. In the case of the side walls, MFs were completely disrupted after treatment with CB at 100 micrograms/ml for 24 hours. By contrast, in the case of the end walls, a number of partially disrupted MFs remained even after 48 hours of treatment. After removal of CB, a completely normal arrangement of bundles of MFs was once again evident within 24 hours after a rather complicated process of reassembly. When reassembly had been completed, the direction of cytoplasmic streaming was reversed only in a small fraction of the treated cells, suggesting that bundles of MFs are anchored and stabilized at the end walls of each cell and that the polarity of reorganized bundles and, therefore, the direction of the cytoplasmic streaming is determined in a manner that depends on the original polarity of MFs that remained in spite of the disruptive action of CB. By contrast, the direction of reinitiated cytoplasmic streaming was reversed in 50% of cells in which the bundles of MFs had been completely disrupted by exogenously applied trypsin prior treatment with CB.(ABSTRACT TRUNCATED AT 250 WORDS)

Synovial hemangioma in an adult horse.

PubMed

Holzhausen, Lars; Nowak, Michael; Junginger, Johannes; Puff, Christina

2012-03-01

A 15-year-old gelding presented with a progressive lameness of the left forelimb of 2.5 months duration. Clinically, a dilation of the deep flexor tendon sheath with a firm elastic consistency and a pronounced tenderness was noted. Ultrasonically, a marked swelling of the flexor tendon sheath with an irregular density of the mesotendineum was observed. The white, firm material forming a nodular distension of the flexor tendon sheath with a diameter of approximately 1 cm was excised and sent for histopathological examination. Biopsies of the deep flexor tendon and corresponding tendon sheath were sent for histopathological evaluation. Histologically, the mass consisted of clefts and numerous anastomosing vascular channels extending between the collagen fibers of the deep flexor tendon. These capillary-like spaces were lined by neoplastic cells that were flattened to polygonal and contained few erythrocytes. There was 0 to 1 mitotic figure per 10 high power fields (400×). Immunohistochemically, the neoplastic cells stained positive for vimentin and factor VIII-related antigen. Adjacent to the neoplastic endothelial cells located pericytes expressed α-smooth muscle actin antigen. Based on the histopathological and immunohistochemical features, synovial hemangioma was diagnosed. One year after surgery, the horse has shown no lameness.

Generator module architecture for a large solid oxide fuel cell power plant

DOEpatents

Gillett, James E.; Zafred, Paolo R.; Riggle, Matthew W.; Litzinger, Kevin P.

2013-06-11

A solid oxide fuel cell module contains a plurality of integral bundle assemblies, the module containing a top portion with an inlet fuel plenum and a bottom portion receiving air inlet feed and containing a base support, the base supports dense, ceramic exhaust manifolds which are below and connect to air feed tubes located in a recuperator zone, the air feed tubes passing into the center of inverted, tubular, elongated, hollow electrically connected solid oxide fuel cells having an open end above a combustion zone into which the air feed tubes pass and a closed end near the inlet fuel plenum, where the fuel cells comprise a fuel cell stack bundle all surrounded within an outer module enclosure having top power leads to provide electrical output from the stack bundle, where the fuel cells operate in the fuel cell mode and where the base support and bottom ceramic air exhaust manifolds carry from 85% to all 100% of the weight of the stack, and each bundle assembly has its own control for vertical and horizontal thermal expansion control.

ECM remodeling and its plasticity

NASA Astrophysics Data System (ADS)

Feng, Jingchen; Jones, Christopher A. R.; Cibula, Matthew; Mao, Xiaoming; Sander, Leonard M.; Levine, Herbert; Sun, Bo

The mechanical interactions between cells and Extracellular Matrix (ECM) are of great importance in many cellular processes. These interactions are reciprocal, i.e. contracting cells pull and reorganize the surrounding matrix, while the remodeled matrix feeds back to regulate cell activities. Recent experiments show in collagen gels with densely distributed cells, aligned fiber bundles are formed in the direction between neighboring cells. Fibers flow into the center region between contracting cell pairs in this process, which causes the concentration of fibers in the fiber bundles to become significantly enhanced. Using an extended lattice-based model, we show that viscoelasticity plays an essential role in ECM remodeling and contributes to the enhanced concentration in fiber bundles. We further characterize ECM plasticity within our model and verify our results with rheometer experiments.

Light-regulated phosphorylation of maize phosphoenolpyruvate carboxykinase plays a vital role in its activity.

PubMed

Chao, Qing; Liu, Xiao-Yu; Mei, Ying-Chang; Gao, Zhi-Fang; Chen, Yi-Bo; Qian, Chun-Rong; Hao, Yu-Bo; Wang, Bai-Chen

2014-05-01

Phosphoenolpyruvate carboxykinase (PEPCK)-the major decarboxylase in PEPCK-type C4 plants-is also present in appreciable amounts in the bundle sheath cells of NADP-malic enzyme-type C4 plants, such as maize (Zea mays), where it plays an apparent crucial role during photosynthesis (Wingler et al., in Plant Physiol 120(2):539-546, 1999; Furumoto et al., in Plant Mol Biol 41(3):301-311, 1999). Herein, we describe the use of mass spectrometry to demonstrate phosphorylation of maize PEPCK residues Ser55, Thr58, Thr59, and Thr120. Western blotting indicated that the extent of Ser55 phosphorylation dramatically increases in the leaves of maize seedlings when the seedlings are transferred from darkness to light, and decreases in the leaves of seedlings transferred from light to darkness. The effect of light on phosphorylation of this residue is opposite that of the effect of light on PEPCK activity, with the decarboxylase activity of PEPCK being less in illuminated leaves than in leaves left in the dark. This inverse relationship between PEPCK activity and the extent of phosphorylation suggests that the suppressive effect of light on PEPCK decarboxylation activity might be mediated by reversible phosphorylation of Ser55.

Correlations between axial stiffness and microstructure of a species of bamboo

PubMed Central

Mannan, Sayyad; Paul Knox, J.

2017-01-01

Bamboo is a ubiquitous monocotyledonous flowering plant and is a member of the true grass family Poaceae. In many parts of the world, it is widely used as a structural material especially in scaffolding and buildings. In spite of its wide use, there is no accepted methodology for standardizing a species of bamboo for a particular structural purpose. The task of developing structure–property correlations is complicated by the fact that bamboo is a hierarchical material whose structure at the nanoscopic level is not very well explored. However, we show that as far as stiffness is concerned, it is possible to obtain reliable estimates of important structural properties like the axial modulus from the knowledge of certain key elements of the microstructure. Stiffness of bamboo depends most sensitively on the size and arrangement of the fibre sheaths surrounding the vascular bundles and the arrangement of crystalline cellulose microfibrils in their secondary cell walls. For the species of bamboo studied in this work, we have quantitatively determined the radial gradation that the arrangement of fibres renders to the structure. The arrangement of the fibres gives bamboo a radially graded property variation across its cross section. PMID:28280545

Increasing leaf vein density by mutagenesis: laying the foundations for C4 rice.

PubMed

Feldman, Aryo B; Murchie, Erik H; Leung, Hei; Baraoidan, Marietta; Coe, Robert; Yu, Su-May; Lo, Shuen-Fang; Quick, William P

2014-01-01

A high leaf vein density is both an essential feature of C4 photosynthesis and a foundation trait to C4 evolution, ensuring the optimal proportion and proximity of mesophyll and bundle sheath cells for permitting the rapid exchange of photosynthates. Two rice mutant populations, a deletion mutant library with a cv. IR64 background (12,470 lines) and a T-DNA insertion mutant library with a cv. Tainung 67 background (10,830 lines), were screened for increases in vein density. A high throughput method with handheld microscopes was developed and its accuracy was supported by more rigorous microscopy analysis. Eight lines with significantly increased leaf vein densities were identified to be used as genetic stock for the global C4 Rice Consortium. The candidate population was shown to include both shared and independent mutations and so more than one gene controlled the high vein density phenotype. The high vein density trait was found to be linked to a narrow leaf width trait but the linkage was incomplete. The more genetically robust narrow leaf width trait was proposed to be used as a reliable phenotypic marker for finding high vein density variants in rice in future screens.

The role of photorespiration during the evolution of C4 photosynthesis in the genus Flaveria.

PubMed

Mallmann, Julia; Heckmann, David; Bräutigam, Andrea; Lercher, Martin J; Weber, Andreas P M; Westhoff, Peter; Gowik, Udo

2014-06-16

C4 photosynthesis represents a most remarkable case of convergent evolution of a complex trait, which includes the reprogramming of the expression patterns of thousands of genes. Anatomical, physiological, and phylogenetic and analyses as well as computational modeling indicate that the establishment of a photorespiratory carbon pump (termed C2 photosynthesis) is a prerequisite for the evolution of C4. However, a mechanistic model explaining the tight connection between the evolution of C4 and C2 photosynthesis is currently lacking. Here we address this question through comparative transcriptomic and biochemical analyses of closely related C3, C3-C4, and C4 species, combined with Flux Balance Analysis constrained through a mechanistic model of carbon fixation. We show that C2 photosynthesis creates a misbalance in nitrogen metabolism between bundle sheath and mesophyll cells. Rebalancing nitrogen metabolism requires anaplerotic reactions that resemble at least parts of a basic C4 cycle. Our findings thus show how C2 photosynthesis represents a pre-adaptation for the C4 system, where the evolution of the C2 system establishes important C4 components as a side effect.

Active Coupled Oscillators in the Inner Ear

NASA Astrophysics Data System (ADS)

Strimbu, Clark Elliott

Auditory and vestibular systems are endowed with an active process that enables them to detect signals as small as a few Angstroms; they also exhibit frequency selectivity; show strong nonlinearities; and can exhibit as spontaneous activity. Much of this active process comes from the sensory hair cells at the periphery of the auditory and vestibular systems. Each hair cell is capped by an eponymous hair bundle, a specialized structure that transduces mechanical forces into electrical signals. Experiments on mechanically decoupled cells from the frog sacculus have shown that individual hair bundles behave in an active manner analogous to an intact organ suggesting a common cellular basis for the active processes seen in many species. In particular, mechanically decoupled hair bundles show rapid active movements in response to transient stimuli and exhibit spontaneous oscillations. However, a single mechanosensitive hair cell is unable to match the performance of an entire organ. In vivo, hair bundles are often coupled to overlying membranes, gelatinous extracellular matrices. We used an in vitro preparation of the frog sacculus in which the otolithic membrane has been left intact. Under natural coupling conditions, there is a strong degree of correlation across the saccular epithelium, suggesting that the collective response of many cells contributes to the extreme sensitivity of this organ. When the membrane is left intact, the hair bundles do not oscillate spontaneously, showing that the natural coupling and loading tunes them into a quiescent regime. However, when stimulated by a pulse, the bundles show a rapid biphasic response that is abolished when the transduction channels are blocked. The active forces generated by the bundles are sufficient to move the overlying membrane.

Mineralized remains of morphotypes of filamentous cyanobacteria in carbonaceous meteorites

NASA Astrophysics Data System (ADS)

Hoover, Richard B.

2005-09-01

The quest for conclusive evidence of microfossils in meteorites has been elusive. Abiotic microstructures, mineral grains, and even coating artifacts may mimic unicellular bacteria, archaea and nanobacteria with simple spherical or rod morphologies (i.e., cocci, diplococci, bacilli, etc.). This is not the case for the larger and more complex microorganisms, colonies and microbial consortia and ecosystems. Microfossils of algae, cyanobacteria, and cyanobacterial and microbial mats have been recognized and described from many of the most ancient rocks on Earth. The filamentous cyanobacteria and sulphur-bacteria have very distinctive size ranges, complex and recognizable morphologies and visibly differentiated cellular microstructures. The taphonomic modes of fossilization and the life habits and processes of these microorganisms often result in distinctive chemical biosignatures associated with carbonization, silicification, calcification, phosphatization and metal-binding properties of their cell-walls, trichomes, sheaths and extracellular polymeric substances (EPS). Valid biogenicity is provided by the combination of a suite of known biogenic elements (that differ from the meteorite matrix) found in direct association with recognizable and distinct biological features and microstructures (e.g., uniseriate or multiseriate filaments, trichomes, sheaths and cells of proper size/size range); specialized cells (e.g., basal or apical cells, hormogonia, akinetes, and heterocysts); and evidence of growth characteristics (e.g., spiral filaments, robust or thin sheaths, laminated sheaths, true or false branching of trichomes, tapered or uniform filaments) and evidence of locomotion (e.g. emergent cells and trichomes, coiling hormogonia, and hollow or flattened and twisted sheaths). Since 1997 we have conducted Environmental and Field Emission Scanning Electron Microscopy (ESEM and FESEM) studies of freshly fractured interior surfaces of carbonaceous meteorites, terrestrial rocks, living, cryopreserved and fossilized extremophiles and cyanobacteria. These studies have resulted in the detection of mineralized remains of morphotypes of filamentous cyanobacteria, mats and consortia in many carbonaceous meteorites. These well-preserved and embedded microfossils are consistent with the size, morphology and ultra-microstructure of filamentous trichomic prokaryotes and degraded remains of microfibrils of cyanobacterial sheaths. EDAX elemental studies reveal that the forms in the meteorites often have highly carbonized sheaths in close association with permineralized filaments, trichomes, and microbial cells. The eextensive protocols and methodologies that have been developed to protect the samples from contamination and to distinguish recent contaminants from indigenous microfossils are described recent bio-contaminants. Ratios of critical bioelements (C:O, C:N, C:P, and C:S) reveal dramatic differences between microfossils in Earth rocks and meteorites and in the cells, filaments, trichomes, and hormogonia of recently living cyanobacteria. The results of comparative optical, ESEM and FESEM studies and EDAX elemental analyses of recent cyanobacteria (e.g. Calothrix, Oscillatoria, and Lyngbya) of similar size, morphology and microstructure to microfossils found embedded in the Murchison CM2 and the Orgueil CI1 carbonaceous meteorites are presented

OsNIP3;1, a rice boric acid channel, regulates boron distribution and is essential for growth under boron-deficient conditions.

PubMed

Hanaoka, Hideki; Uraguchi, Shimpei; Takano, Junpei; Tanaka, Mayuki; Fujiwara, Toru

2014-06-01

Boron is an essential micronutrient for higher plants. Boron deficiency is an important agricultural issue because it results in loss of yield quality and/or quantity in cereals and other crops. To understand boron transport mechanisms in cereals, we characterized OsNIP3;1, a member of the major intrinsic protein family in rice (Oryza sativa L.), because OsNIP3;1 is the most similar rice gene to the Arabidopsis thaliana boric acid channel genes AtNIP5;1 and AtNIP6;1. Yeast cells expressing OsNIP3;1 imported more boric acid than control cells. GFP-tagged OsNIP3;1 expressed in tobacco BY2 cells was localized to the plasma membrane. The accumulation of OsNIP3;1 transcript increased fivefold in roots within 6 h of the onset of boron starvation, but not in shoots. Promoter-GUS analysis suggested that OsNIP3;1 is expressed mainly in exodermal cells and steles in roots, as well as in cells around the vascular bundles in leaf sheaths and pericycle cells around the xylem in leaf blades. The growth of OsNIP3;1 RNAi plants was impaired under boron limitation. These results indicate that OsNIP3;1 functions as a boric acid channel, and is required for acclimation to boron limitation. Boron distribution among shoot tissues was altered in OsNIP3;1 knockdown plants, especially under boron-deficient conditions. This result demonstrates that OsNIP3;1 regulates boron distribution among shoot tissues, and that the correct boron distribution is crucial for plant growth. © 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.

Transduction channels’ gating can control friction on vibrating hair-cell bundles in the ear

PubMed Central

Bormuth, Volker; Barral, Jérémie; Joanny, Jean-François; Jülicher, Frank; Martin, Pascal

2014-01-01

Hearing starts when sound-evoked mechanical vibrations of the hair-cell bundle activate mechanosensitive ion channels, giving birth to an electrical signal. As for any mechanical system, friction impedes movements of the hair bundle and thus constrains the sensitivity and frequency selectivity of auditory transduction. Friction is generally thought to result mainly from viscous drag by the surrounding fluid. We demonstrate here that the opening and closing of the transduction channels produce internal frictional forces that can dominate viscous drag on the micrometer-sized hair bundle. We characterized friction by analyzing hysteresis in the force–displacement relation of single hair-cell bundles in response to periodic triangular stimuli. For bundle velocities high enough to outrun adaptation, we found that frictional forces were maximal within the narrow region of deflections that elicited significant channel gating, plummeted upon application of a channel blocker, and displayed a sublinear growth for increasing bundle velocity. At low velocity, the slope of the relation between the frictional force and velocity was nearly fivefold larger than the hydrodynamic friction coefficient that was measured when the transduction machinery was decoupled from bundle motion by severing tip links. A theoretical analysis reveals that channel friction arises from coupling the dynamics of the conformational change associated with channel gating to tip-link tension. Varying channel properties affects friction, with faster channels producing smaller friction. We propose that this intrinsic source of friction may contribute to the process that sets the hair cell’s characteristic frequency of responsiveness. PMID:24799674

High-order synchronization of hair cell bundles

NASA Astrophysics Data System (ADS)

Levy, Michael; Molzon, Adrian; Lee, Jae-Hyun; Kim, Ji-Wook; Cheon, Jinwoo; Bozovic, Dolores

2016-12-01

Auditory and vestibular hair cell bundles exhibit active mechanical oscillations at natural frequencies that are typically lower than the detection range of the corresponding end organs. We explore how these noisy nonlinear oscillators mode-lock to frequencies higher than their internal clocks. A nanomagnetic technique is used to stimulate the bundles without an imposed mechanical load. The evoked response shows regimes of high-order mode-locking. Exploring a broad range of stimulus frequencies and intensities, we observe regions of high-order synchronization, analogous to Arnold Tongues in dynamical systems literature. Significant areas of overlap occur between synchronization regimes, with the bundle intermittently flickering between different winding numbers. We demonstrate how an ensemble of these noisy spontaneous oscillators could be entrained to efficiently detect signals significantly above the characteristic frequencies of the individual cells.

High-order synchronization of hair cell bundles

PubMed Central

Levy, Michael; Molzon, Adrian; Lee, Jae-Hyun; Kim, Ji-wook; Cheon, Jinwoo; Bozovic, Dolores

2016-01-01

Auditory and vestibular hair cell bundles exhibit active mechanical oscillations at natural frequencies that are typically lower than the detection range of the corresponding end organs. We explore how these noisy nonlinear oscillators mode-lock to frequencies higher than their internal clocks. A nanomagnetic technique is used to stimulate the bundles without an imposed mechanical load. The evoked response shows regimes of high-order mode-locking. Exploring a broad range of stimulus frequencies and intensities, we observe regions of high-order synchronization, analogous to Arnold Tongues in dynamical systems literature. Significant areas of overlap occur between synchronization regimes, with the bundle intermittently flickering between different winding numbers. We demonstrate how an ensemble of these noisy spontaneous oscillators could be entrained to efficiently detect signals significantly above the characteristic frequencies of the individual cells. PMID:27974743

Receptor Tyrosine Kinases as Targets for Treatment of Peripheral Nerve Sheath Tumors in NF 1 Patients

DTIC Science & Technology

2007-03-01

EGFR patterns by interphase cytogenetics (FISH) in malignant peripheral nerve sheath tumor (MPNST) and morphologically similar spindle cell neoplasms ...Armstrong,F., Delsol,G., Dastugue,N. and Brousset,P. (2003) Chronic myeloproliferative disorders with rearrangement of the platelet-derived growth

Pathology in practice: Peripheral nerve sheath tumor in a Shubunkin goldfish

USDA-ARS?s Scientific Manuscript database

Peripheral nerve sheath tumors (PNSTs) have been detected in many fish species, including goldfish, several species of snapper, coho salmon, the bicolor damselfish, and rainbow smelt. They originate from neural crest cells and generally occur along the subcutaneous nerves. A viral etiology has bee...

Verticillium Infection Triggers VASCULAR-RELATED NAC DOMAIN7–Dependent de Novo Xylem Formation and Enhances Drought Tolerance in Arabidopsis[W

PubMed Central

Reusche, Michael; Thole, Karin; Janz, Dennis; Truskina, Jekaterina; Rindfleisch, Sören; Drübert, Christine; Polle, Andrea; Lipka, Volker; Teichmann, Thomas

2012-01-01

The soilborne fungal plant pathogen Verticillium longisporum invades the roots of its Brassicaceae hosts and proliferates in the plant vascular system. Typical aboveground symptoms of Verticillium infection on Brassica napus and Arabidopsis thaliana are stunted growth, vein clearing, and leaf chloroses. Here, we provide evidence that vein clearing is caused by pathogen-induced transdifferentiation of chloroplast-containing bundle sheath cells to functional xylem elements. In addition, our findings suggest that reinitiation of cambial activity and transdifferentiation of xylem parenchyma cells results in xylem hyperplasia within the vasculature of Arabidopsis leaves, hypocotyls, and roots. The observed de novo xylem formation correlates with Verticillium-induced expression of the VASCULAR-RELATED NAC DOMAIN (VND) transcription factor gene VND7. Transgenic Arabidopsis plants expressing the chimeric repressor VND7-SRDX under control of a Verticillium infection-responsive promoter exhibit reduced de novo xylem formation. Interestingly, infected Arabidopsis wild-type plants show higher drought stress tolerance compared with noninfected plants, whereas this effect is attenuated by suppression of VND7 activity. Together, our results suggest that V. longisporum triggers a tissue-specific developmental plant program that compensates for compromised water transport and enhances the water storage capacity of infected Brassicaceae host plants. In conclusion, we provide evidence that this natural plant–fungus pathosystem has conditionally mutualistic features. PMID:23023171

An rbcL mRNA-binding protein is associated with C3 to C4 evolution and light-induced production of Rubisco in Flaveria.

PubMed

Yerramsetty, Pradeep; Agar, Erin M; Yim, Won C; Cushman, John C; Berry, James O

2017-07-20

Nuclear-encoded RLSB protein binds chloroplastic rbcL mRNA encoding the Rubisco large subunit. RLSB is highly conserved across all groups of land plants and is associated with positive post-transcriptional regulation of rbcL expression. In C3 leaves, RLSB and Rubisco occur in all chlorenchyma cell chloroplasts, while in C4 leaves these accumulate only within bundle sheath (BS) chloroplasts. RLSB's role in rbcL expression makes modification of its localization a likely prerequisite for the evolutionary restriction of Rubisco to BS cells. Taking advantage of evolutionarily conserved RLSB orthologs in several C3, C3-C4, C4-like, and C4 photosynthetic types within the genus Flaveria, we show that low level RLSB sequence divergence and modification to BS specificity coincided with ontogeny of Rubisco specificity and Kranz anatomy during C3 to C4 evolution. In both C3 and C4 species, Rubisco production reflected RLSB production in all cell types, tissues, and conditions examined. Co-localization occurred only in photosynthetic tissues, and both proteins were co-ordinately induced by light at post-transcriptional levels. RLSB is currently the only mRNA-binding protein to be associated with rbcL gene regulation in any plant, with variations in sequence and acquisition of cell type specificity reflecting the progression of C4 evolution within the genus Flaveria. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Distinct patterns of notochord mineralization in zebrafish coincide with the localization of Osteocalcin isoform 1 during early vertebral centra formation

PubMed Central

2012-01-01

Background In chondrichthyans, basal osteichthyans and tetrapods, vertebral bodies have cartilaginous anlagen that subsequently mineralize (chondrichthyans) or ossify (osteichthyans). Chondrocytes that form the vertebral centra derive from somites. In teleost fish, vertebral centrum formation starts in the absence of cartilage, through direct mineralization of the notochord sheath. In a second step, the notochord is surrounded by somite-derived intramembranous bone. In several small teleost species, including zebrafish (Danio rerio), even haemal and neural arches form directly as intramembranous bone and only modified caudalmost arches remain cartilaginous. This study compares initial patterns of mineralization in different regions of the vertebral column in zebrafish. We ask if the absence or presence of cartilaginous arches influences the pattern of notochord sheath mineralization. Results To reveal which cells are involved in mineralization of the notochord sheath we identify proliferating cells, we trace mineralization on the histological level and we analyze cell ultrastructure by TEM. Moreover, we localize proteins and genes that are typically expressed by skeletogenic cells such as Collagen type II, Alkaline phosphatase (ALP) and Osteocalcin (Oc). Mineralization of abdominal and caudal vertebrae starts with a complete ring within the notochord sheath and prior to the formation of the bony arches. In contrast, notochord mineralization of caudal fin centra starts with a broad ventral mineral deposition, associated with the bases of the modified cartilaginous arches. Similar, arch-related, patterns of mineralization occur in teleosts that maintain cartilaginous arches throughout the spine. Throughout the entire vertebral column, we were able to co-localize ALP-positive signal with chordacentrum mineralization sites, as well as Collagen II and Oc protein accumulation in the mineralizing notochord sheath. In the caudal fin region, ALP and Oc signals were clearly produced both by the notochord epithelium and cells outside the notochord, the cartilaginous arches. Based on immunostaining, real time PCR and oc2:gfp transgenic fish, we identify Oc in the mineralizing notochord sheath as osteocalcin isoform 1 (Oc1). Conclusions If notochord mineralization occurs prior to arch formation, mineralization of the notochord sheath is ring-shaped. If notochord mineralization occurs after cartilaginous arch formation, mineralization of the notochord sheath starts at the insertion point of the arches, with a basiventral origin. The presence of ALP and Oc1, not only in cells outside the notochord, but also in the notochord epithelium, suggests an active role of the notochord in the mineralization process. The same may apply to Col II-positive chondrocytes of the caudalmost haemal arches that show ALP activity and Oc1 accumulation, since these chondrocytes do not mineralize their own cartilage matrix. Even without cartilaginous preformed vertebral centra, the cartilaginous arches may have an inductive role in vertebral centrum formation, possibly contributing to the distinct mineralization patterns of zebrafish vertebral column and caudal fin vertebral fusion. PMID:23043290

Distinct patterns of notochord mineralization in zebrafish coincide with the localization of Osteocalcin isoform 1 during early vertebral centra formation.

PubMed

Bensimon-Brito, Anabela; Cardeira, João; Cancela, Maria Leonor; Huysseune, Ann; Witten, Paul Eckhard

2012-10-09

In chondrichthyans, basal osteichthyans and tetrapods, vertebral bodies have cartilaginous anlagen that subsequently mineralize (chondrichthyans) or ossify (osteichthyans). Chondrocytes that form the vertebral centra derive from somites. In teleost fish, vertebral centrum formation starts in the absence of cartilage, through direct mineralization of the notochord sheath. In a second step, the notochord is surrounded by somite-derived intramembranous bone. In several small teleost species, including zebrafish (Danio rerio), even haemal and neural arches form directly as intramembranous bone and only modified caudalmost arches remain cartilaginous. This study compares initial patterns of mineralization in different regions of the vertebral column in zebrafish. We ask if the absence or presence of cartilaginous arches influences the pattern of notochord sheath mineralization. To reveal which cells are involved in mineralization of the notochord sheath we identify proliferating cells, we trace mineralization on the histological level and we analyze cell ultrastructure by TEM. Moreover, we localize proteins and genes that are typically expressed by skeletogenic cells such as Collagen type II, Alkaline phosphatase (ALP) and Osteocalcin (Oc). Mineralization of abdominal and caudal vertebrae starts with a complete ring within the notochord sheath and prior to the formation of the bony arches. In contrast, notochord mineralization of caudal fin centra starts with a broad ventral mineral deposition, associated with the bases of the modified cartilaginous arches. Similar, arch-related, patterns of mineralization occur in teleosts that maintain cartilaginous arches throughout the spine.Throughout the entire vertebral column, we were able to co-localize ALP-positive signal with chordacentrum mineralization sites, as well as Collagen II and Oc protein accumulation in the mineralizing notochord sheath. In the caudal fin region, ALP and Oc signals were clearly produced both by the notochord epithelium and cells outside the notochord, the cartilaginous arches. Based on immunostaining, real time PCR and oc2:gfp transgenic fish, we identify Oc in the mineralizing notochord sheath as osteocalcin isoform 1 (Oc1). If notochord mineralization occurs prior to arch formation, mineralization of the notochord sheath is ring-shaped. If notochord mineralization occurs after cartilaginous arch formation, mineralization of the notochord sheath starts at the insertion point of the arches, with a basiventral origin. The presence of ALP and Oc1, not only in cells outside the notochord, but also in the notochord epithelium, suggests an active role of the notochord in the mineralization process. The same may apply to Col II-positive chondrocytes of the caudalmost haemal arches that show ALP activity and Oc1 accumulation, since these chondrocytes do not mineralize their own cartilage matrix. Even without cartilaginous preformed vertebral centra, the cartilaginous arches may have an inductive role in vertebral centrum formation, possibly contributing to the distinct mineralization patterns of zebrafish vertebral column and caudal fin vertebral fusion.

Mammalian Auditory Hair Cell Bundle Stiffness Affects Frequency Tuning by Increasing Coupling along the Length of the Cochlea.

PubMed

Dewey, James B; Xia, Anping; Müller, Ulrich; Belyantseva, Inna A; Applegate, Brian E; Oghalai, John S

2018-06-05

The stereociliary bundles of cochlear hair cells convert mechanical vibrations into the electrical signals required for auditory sensation. While the stiffness of the bundles strongly influences mechanotransduction, its influence on the vibratory response of the cochlear partition is unclear. To assess this, we measured cochlear vibrations in mutant mice with reduced bundle stiffness or with a tectorial membrane (TM) that is detached from the sensory epithelium. We found that reducing bundle stiffness decreased the high-frequency extent and sharpened the tuning of vibratory responses obtained postmortem. Detaching the TM further reduced the high-frequency extent of the vibrations but also lowered the partition's resonant frequency. Together, these results demonstrate that the bundle's stiffness and attachment to the TM contribute to passive longitudinal coupling in the cochlea. We conclude that the stereociliary bundles and TM interact to facilitate passive-wave propagation to more apical locations, possibly enhancing active-wave amplification in vivo. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

Plant 115-kDa actin-filament bundling protein, P-115-ABP, is a homologue of plant villin and is widely distributed in cells.

PubMed

Yokota, Etsuo; Vidali, Luis; Tominaga, Motoki; Tahara, Hiroshi; Orii, Hidefumi; Morizane, Yosuke; Hepler, Peter K; Shimmen, Teruo

2003-10-01

In many cases, actin filaments are arranged into bundles and serve as tracks for cytoplasmic streaming in plant cells. We have isolated an actin-filament bundling protein, which is composed of 115-kDa polypeptide (P-115-ABP), from the germinating pollen of lily, Lilium longiflorum [Nakayasu et al. (1998) BIOCHEM: Biophys. Res. Commun. 249: 61]. P-115-ABP shared similar antigenicity with a plant 135-kDa actin-filament bundling protein (P-135-ABP), a plant homologue of villin. A full-length cDNA clone (ABP115; accession no. AB097407) was isolated from an expression cDNA library of lily pollen by immuno-screening using antisera against P-115-ABP and P-135-ABP. The amino acid sequence of P-115-ABP deduced from this clone showed high homology with those of P-135-ABP and four villin isoforms of Arabidopsis thaliana (AtVLN1, AtVLN2, AtVLN3 and AtVLN4), especially AtVLN4, indicating that P-115-ABP can also be classified as a plant villin. The P-115-ABP isolated biochemically from the germinating lily pollen was able to arrange F-actin filaments with uniform polarity into bundles and this bundling activity was suppressed by Ca2+-calmodulin (CaM), similar to the actin-filament bundling properties of P-135-ABP. The P-115-ABP type of plant villin was widely distributed in plant cells, from algae to land plants. In root hair cells of Hydrocharis dubia, this type of plant villin was co-localized with actin-filament bundles in the transvacuolar strands and the sub-cortical regions. Microinjection of the antiserum against P-115-ABP into living root hair cells caused the disappearance of transvaculor strands and alteration of the route of cytoplasmic streaming. In internodal cells of Chara corallina in which the P-135-ABP type of plant villin is lacking, the P-115-ABP type showed co-localization with actin-filament cables anchored on the intracellular surface of chloroplasts. These results indicated that plant villins are widely distributed and involved in the organization of actin filaments into bundles throughout the plant kingdom.

Covisualization in living onion cells of putative integrin, putative spectrin, actin, putative intermediate filaments, and other proteins at the cell membrane and in an endomembrane sheath

NASA Technical Reports Server (NTRS)

Reuzeau, C.; Doolittle, K. W.; McNally, J. G.; Pickard, B. G.; Evans, M. L. (Principal Investigator)

1997-01-01

Covisualizations with wide-field computational optical-sectioning microscopy of living epidermal cells of the onion bulb scale have evidenced two major new cellular features. First, a sheath of cytoskeletal elements clads the endomembrane system. Similar elements clad the inner faces of punctate plasmalemmal sites interpreted as plasmalemmal control centers. One component of the endomembrane sheath and plasmalemmal control center cladding is anti-genicity-recognized by two injected antibodies against animal spectrin. Immunoblots of separated epidermal protein also showed bands recognized by these antibodies. Injected phalloidin identified F-actin with the same cellular distribution pattern, as did antibodies against intermediate-filament protein and other cytoskeletal elements known from animal cells. Injection of general protein stains demonstrated the abundance of endomembrane sheath protein. Second, the endomembrane system, like the plasmalemmal puncta, contains antigen recognized by an anti-beta 1 integrin injected into the cytoplasm. Previously, immunoblots of separated epidermal protein were shown to have a major band recognized both by this antibody prepared against a peptide representing the cytosolic region of beta 1 integrin and an antibody against the matrix region of beta 1 integrin. The latter antiboby also identified puncta at the external face of protoplasts. It is proposed that integrin and associated transmembrane proteins secure the endomembrane sheath and transmit signals between it and the lumen or matrix of the endoplasmic reticulum and organellar matrices. This function is comparable to that proposed for such transmembrane linkers in the plasmalemmal control centers, which also appear to bind cytoskeleton and a host of related molecules and transmit signals between them and the wall matrix. It is at the plasmalemmal control centers that the endoplasmic reticulum, a major component of the endomembrane system, attaches to the plasma membrane.

Hair cell regeneration in the bullfrog vestibular otolith organs following aminoglycoside toxicity

NASA Technical Reports Server (NTRS)

Baird, R. A.; Torres, M. A.; Schuff, N. R.

1993-01-01

Adult bullfrog were given single intraotic injections of the aminoglycoside antibiotic gentamicin sulfate and sacrificed at postinjection times ranging from 0.5 to 9 days. The saccular and utricular maculae of normal and injected animals were examined in wholemount and cross-section. Intraotic 200 microM gentamicin concentrations resulted in the uniform destruction of the hair bundles and, at later times, the cell bodies of saccular hair cells. In the utriculus, striolar hair cells were selectively damaged while extrastriolar hair cells were relatively unaffected. Regenerating hair cells, identified in sectioned material by their small cell bodies and short, well-formed hair bundles, were seen in the saccular and utricular maculae as early as 24-48 h postinjection. Immature versions of mature hair cell types in both otolith organs were recognized by the presence or absence of a bulbed kinocilia and the relative lengths of their kinocilia and longest stereocilia. Utricular hair cell types with kinocilia longer than their longest stereocilia were observed at earlier than hair cell types with shorter kinocilia. In the sacculus, the hair bundles of gentamicin-treated animals, even at 9 days postinjection, were significantly smaller than those of normal animals. The hair bundles of utricular hair cells, on the other hand, reached full maturity within the same time period.

Hair cell regeneration in the bullfrog vestibular otolith organs following aminoglycoside toxicity

NASA Technical Reports Server (NTRS)

Baird, Richard A.; Torres, M. A.; Schuff, N. R.

1994-01-01

Adult bullfrogs were given single intraotic injections of the aminoglycoside antibiotic gentamicin sulfate and sacrificed at postinjection times ranging from 0.5 to 9 days. The saccular and utricular maculae of normal and injected animals were examined in wholemount and cross-section. Intraotic 200 (mu) M gentamicin concentrations resulted in the uniform destruction of the hair bundles and, at later times, the cell bodies of saccular hair cells. In the utriculus, striolar hair cells were selectively damaged while extrastriolar hair cells were relatively unaffected. Regenerating hair cells, identified in sectioned material by their small cell bodies and short, well-formed hair bundles, were seen in the saccular and utricular maculae as early as 24-48 h postinjection. Immature versions of mature hair cell types in both otolith organs were recognized by the presence of absence of a bulbed kinocilia and the relative lengths of their kinocilia and longest sterocilia. Utricular hair cell types with kinocilia longer than their longest stereocilia were observed at earlier times than hair cell types with shorter kinocilia. In the same sacculus, the hair bundles of gentamicin-treated animals, even at 9 days postinjection, were significantly smaller than those of normal animals. The hair bundles of utricular hair cells, on the other hand, reached full maturity within the same time period.

Stability of the Tonks–Langmuir discharge pre-sheath

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

Tskhakaya, D. D.; Kos, L.; Tskhakaya, D.

The article formulates the stability problem of the plasma sheath in the Tonks–Langmuir discharge. Using the kinetic description of the ion gas, i.e., the stability of the potential shape in the quasi-neutral pre-sheath regarding the high and low frequency, the perturbations are investigated. The electrons are assumed to be Maxwell–Boltzmann distributed. Regarding high-frequency perturbations, the pre-sheath is shown to be stable. The stability problem regarding low-frequency perturbations can be reduced to an analysis of the “diffusion like” equation, which results in the instability of the potential distribution in the pre-sheath. By means of the Particle in Cell simulations, also themore » nonlinear stage of low frequency oscillations is investigated. Comparing the figure obtained with the figure for linear stage, one can find obvious similarity in the spatial-temporal behavior of the potential.« less

Observation of an abrupt electron heating mode transition in capacitive single radio frequency discharges

NASA Astrophysics Data System (ADS)

Wilczek, Sebastian; Trieschmann, Jan; Schulze, Julian; Brinkmann, Ralf Peter; Mussenbrock, Thomas; Derzsi, Aranka; Korolov, Ihor; Donkó, Zoltan

2013-09-01

The electron heating in capacitive discharges at very low pressures (~1 Pa) is dominated by stochastic heating. In this regime electrons are accelerated by the oscillating sheaths, traverse through the plasma bulk and interact with the opposite sheath. By varying the driving frequency or the gap size of the discharge, energetic electrons reach the sheath edge at different temporal phases, i.e., the collapsing or expanding phase, or the moment of minimum sheath width. This work reports numerical experiments based on Particle-In-Cell simulations which show that at certain frequencies the discharge switches abruptly from a low density mode in a high density mode. The inverse transition is also abrupt, but shows a significant hysteresis. This behavior is explained by the complex interaction of the bulk and the sheath. This work is supported by the German Research Foundation in the frame of TRR 87.

The Architecture of Iron Microbial Mats Reflects the Adaptation of Chemolithotrophic Iron Oxidation in Freshwater and Marine Environments

PubMed Central

Chan, Clara S.; McAllister, Sean M.; Leavitt, Anna H.; Glazer, Brian T.; Krepski, Sean T.; Emerson, David

2016-01-01

Microbes form mats with architectures that promote efficient metabolism within a particular physicochemical environment, thus studying mat structure helps us understand ecophysiology. Despite much research on chemolithotrophic Fe-oxidizing bacteria, Fe mat architecture has not been visualized because these delicate structures are easily disrupted. There are striking similarities between the biominerals that comprise freshwater and marine Fe mats, made by Beta- and Zetaproteobacteria, respectively. If these biominerals are assembled into mat structures with similar functional morphology, this would suggest that mat architecture is adapted to serve roles specific to Fe oxidation. To evaluate this, we combined light, confocal, and scanning electron microscopy of intact Fe microbial mats with experiments on sheath formation in culture, in order to understand mat developmental history and subsequently evaluate the connection between Fe oxidation and mat morphology. We sampled a freshwater sheath mat from Maine and marine stalk and sheath mats from Loihi Seamount hydrothermal vents, Hawaii. Mat morphology correlated to niche: stalks formed in steeper O2 gradients while sheaths were associated with low to undetectable O2 gradients. Fe-biomineralized filaments, twisted stalks or hollow sheaths, formed the highly porous framework of each mat. The mat-formers are keystone species, with nascent marine stalk-rich mats comprised of novel and uncommon Zetaproteobacteria. For all mats, filaments were locally highly parallel with similar morphologies, indicating that cells were synchronously tracking a chemical or physical cue. In the freshwater mat, cells inhabited sheath ends at the growing edge of the mat. Correspondingly, time lapse culture imaging showed that sheaths are made like stalks, with cells rapidly leaving behind an Fe oxide filament. The distinctive architecture common to all observed Fe mats appears to serve specific functions related to chemolithotrophic Fe oxidation, including (1) removing Fe oxyhydroxide waste without entombing cells or clogging flow paths through the mat and (2) colonizing niches where Fe(II) and O2 overlap. This work improves our understanding of Fe mat developmental history and how mat morphology links to metabolism. We can use these results to interpret biogenicity, metabolism, and paleoenvironmental conditions of Fe microfossil mats, which would give us insight into Earth's Fe and O2 history. PMID:27313567

One-dimensional particle-in-cell simulation on the influence of electron and ion temperature on the sheath expansion process in the post-arc stage of vacuum circuit breaker

NASA Astrophysics Data System (ADS)

Mo, Yongpeng; Shi, Zongqian; Jia, Shenli; Wang, Lijun

2015-02-01

The inter-contact region of vacuum circuit breakers is filled with residual plasma at the moment when the current is zero after the burning of metal vapor arc. The residual plasma forms an ion sheath in front of the post-arc cathode. The sheath then expands towards the post-arc anode under the influence of a transient recovery voltage. In this study, a one-dimensional particle-in-cell model is developed to investigate the post-arc sheath expansion. The influence of ion and electron temperatures on the decrease in local plasma density at the post-arc cathode side and post-arc anode side is discussed. When the decay in the local plasma density develops from the cathode and anode sides into the high-density region and merges, the overall plasma density in the inter-contact region begins to decrease. Meanwhile, the ion sheath begins to expand faster. Furthermore, the theory of ion rarefaction wave only explains quantitatively the decrease in the overall plasma density at relatively low ion temperatures. With the increase of ion temperature to certain extent, another possible reason for the decrease in the overall plasma density is proposed and results from the more active thermal diffusion of plasma.

Increased dermal collagen bundle alignment in systemic sclerosis is associated with a cell migration signature and role of Arhgdib in directed fibroblast migration on aligned ECMs

PubMed Central

Lafyatis, Robert; Burkly, Linda C.

2017-01-01

Systemic sclerosis (SSc) is a devastating disease affecting the skin and internal organs. Dermal fibrosis manifests early and Modified Rodnan Skin Scores (MRSS) correlate with disease progression. Transcriptomics of SSc skin biopsies suggest the role of the in vivo microenvironment in maintaining the pathological myofibroblasts. Therefore, defining the structural changes in dermal collagen in SSc patients could inform our understanding of fibrosis pathogenesis. Here, we report a method for quantitative whole-slide image analysis of dermal collagen from SSc patients, and our findings of more aligned dermal collagen bundles in diffuse cutaneous SSc (dcSSc) patients. Using the bleomycin-induced mouse model of SSc, we identified a distinct high dermal collagen bundle alignment gene signature, characterized by a concerted upregulation in cell migration, adhesion, and guidance pathways, and downregulation of spindle, replication, and cytokinesis pathways. Furthermore, increased bundle alignment induced a cell migration gene signature in fibroblasts in vitro, and these cells demonstrated increased directed migration on aligned ECM fibers that is dependent on expression of Arhgdib (Rho GDP-dissociation inhibitor 2). Our results indicate that increased cell migration is a cellular response to the increased collagen bundle alignment featured in fibrotic skin. Moreover, many of the cell migration genes identified in our study are shared with human SSc skin and may be new targets for therapeutic intervention. PMID:28662216

A Model for Amplification of Hair-Bundle Motion by Cyclical Binding of Ca2+ to Mechanoelectrical-Transduction Channels

NASA Astrophysics Data System (ADS)

Choe, Yong; Magnasco, Marcelo O.; Hudspeth, A. J.

1998-12-01

Amplification of auditory stimuli by hair cells augments the sensitivity of the vertebrate inner ear. Cell-body contractions of outer hair cells are thought to mediate amplification in the mammalian cochlea. In vertebrates that lack these cells, and perhaps in mammals as well, active movements of hair bundles may underlie amplification. We have evaluated a mathematical model in which amplification stems from the activity of mechanoelectrical-transduction channels. The intracellular binding of Ca2+ to channels is posited to promote their closure, which increases the tension in gating springs and exerts a negative force on the hair bundle. By enhancing bundle motion, this force partially compensates for viscous damping by cochlear fluids. Linear stability analysis of a six-state kinetic model reveals Hopf bifurcations for parameter values in the physiological range. These bifurcations signal conditions under which the system's behavior changes from a damped oscillatory response to spontaneous limit-cycle oscillation. By varying the number of stereocilia in a bundle and the rate constant for Ca2+ binding, we calculate bifurcation frequencies spanning the observed range of auditory sensitivity for a representative receptor organ, the chicken's cochlea. Simulations using prebifurcation parameter values demonstrate frequency-selective amplification with a striking compressive nonlinearity. Because transduction channels occur universally in hair cells, this active-channel model describes a mechanism of auditory amplification potentially applicable across species and hair-cell types.

Zebrafish Models for the Mechanosensory Hair Cell Dysfunction in Usher Syndrome 3 Reveal That Clarin-1 Is an Essential Hair Bundle Protein.

PubMed

Gopal, Suhasini R; Chen, Daniel H-C; Chou, Shih-Wei; Zang, Jingjing; Neuhauss, Stephan C F; Stepanyan, Ruben; McDermott, Brian M; Alagramam, Kumar N

2015-07-15

Usher syndrome type III (USH3) is characterized by progressive loss of hearing and vision, and varying degrees of vestibular dysfunction. It is caused by mutations that affect the human clarin-1 protein (hCLRN1), a member of the tetraspanin protein family. The missense mutation CLRN1(N48K), which affects a conserved N-glycosylation site in hCLRN1, is a common causative USH3 mutation among Ashkenazi Jews. The affected individuals hear at birth but lose that function over time. Here, we developed an animal model system using zebrafish transgenesis and gene targeting to provide an explanation for this phenotype. Immunolabeling demonstrated that Clrn1 localized to the hair cell bundles (hair bundles). The clrn1 mutants generated by zinc finger nucleases displayed aberrant hair bundle morphology with diminished function. Two transgenic zebrafish that express either hCLRN1 or hCLRN1(N48K) in hair cells were produced to examine the subcellular localization patterns of wild-type and mutant human proteins. hCLRN1 localized to the hair bundles similarly to zebrafish Clrn1; in contrast, hCLRN1(N48K) largely mislocalized to the cell body with a small amount reaching the hair bundle. We propose that this small amount of hCLRN1(N48K) in the hair bundle provides clarin-1-mediated function during the early stages of life; however, the presence of hCLRN1(N48K) in the hair bundle diminishes over time because of intracellular degradation of the mutant protein, leading to progressive loss of hair bundle integrity and hair cell function. These findings and genetic tools provide an understanding and path forward to identify therapies to mitigate hearing loss linked to the CLRN1 mutation. Mutations in the clarin-1 gene affect eye and ear function in humans. Individuals with the CLRN1(N48K) mutation are born able to hear but lose that function over time. Here, we develop an animal model system using zebrafish transgenesis and gene targeting to provide an explanation for this phenotype. This approach illuminates the role of clarin-1 and the molecular mechanism linked to the CLRN1(N48K) mutation in sensory hair cells of the inner ear. Additionally, the investigation provided an in vivo model to guide future drug discovery to rescue the hCLRN1(N48K) in hair cells. Copyright © 2015 the authors 0270-6474/15/3510188-14$15.00/0.

A macroscopic scale model of bacterial flagellar bundling

NASA Astrophysics Data System (ADS)

Kim, Munju; Bird, James C.; van Parys, Annemarie J.; Breuer, Kenneth S.; Powers, Thomas R.

2003-12-01

Escherichia coli and other bacteria use rotating helical filaments to swim. Each cell typically has about four filaments, which bundle or disperse depending on the sense of motor rotation. To study the bundling process, we built a macroscopic scale model consisting of stepper motor-driven polymer helices in a tank filled with a high-viscosity silicone oil. The Reynolds number, the ratio of viscous to elastic stresses, and the helix geometry of our experimental model approximately match the corresponding quantities of the full-scale E. coli cells. We analyze digital video images of the rotating helices to show that the initial rate of bundling is proportional to the motor frequency and is independent of the characteristic relaxation time of the filament. We also determine which combinations of helix handedness and sense of motor rotation lead to bundling.

Spatial confinement of active microtubule networks induces large-scale rotational cytoplasmic flow

PubMed Central

Suzuki, Kazuya; Miyazaki, Makito; Takagi, Jun; Itabashi, Takeshi; Ishiwata, Shin’ichi

2017-01-01

Collective behaviors of motile units through hydrodynamic interactions induce directed fluid flow on a larger length scale than individual units. In cells, active cytoskeletal systems composed of polar filaments and molecular motors drive fluid flow, a process known as cytoplasmic streaming. The motor-driven elongation of microtubule bundles generates turbulent-like flow in purified systems; however, it remains unclear whether and how microtubule bundles induce large-scale directed flow like the cytoplasmic streaming observed in cells. Here, we adopted Xenopus egg extracts as a model system of the cytoplasm and found that microtubule bundle elongation induces directed flow for which the length scale and timescale depend on the existence of geometrical constraints. At the lower activity of dynein, kinesins bundle and slide microtubules, organizing extensile microtubule bundles. In bulk extracts, the extensile bundles connected with each other and formed a random network, and vortex flows with a length scale comparable to the bundle length continually emerged and persisted for 1 min at multiple places. When the extracts were encapsulated in droplets, the extensile bundles pushed the droplet boundary. This pushing force initiated symmetry breaking of the randomly oriented bundle network, leading to bundles aligning into a rotating vortex structure. This vortex induced rotational cytoplasmic flows on the length scale and timescale that were 10- to 100-fold longer than the vortex flows emerging in bulk extracts. Our results suggest that microtubule systems use not only hydrodynamic interactions but also mechanical interactions to induce large-scale temporally stable cytoplasmic flow. PMID:28265076

Does the peritumoral stroma of basal cell carcinoma recapitulate the follicular connective tissue sheath?

PubMed

Sellheyer, Klaus; Krahl, Dieter

2011-07-01

There are compelling embryologic and anatomic relationships within adnexal tumors. However, these are mostly perceived within the epithelial component while the stromal component of the tumors is frequently overlooked. In postnatal skin, nestin is almost exclusively expressed in the perifollicular mesenchyme. This study examines the expression of this neuroepithelial stem cell protein in trichoblastoma/trichoepithelioma and in basal cell carcinoma (BCC), which is increasingly being viewed as follicular in nature. We employed standard immunohistochemical methods with three different antibodies to examine the expression of nestin in 25 BCCs and compared the staining pattern with that of 7 trichoblastomas and 11 trichoepitheliomas. Nestin is expressed in the peritumoral stroma of all tumors examined and is limited to the immediate layer of mesenchymal cells surrounding the tumor epithelium. In BCC, nestin-immunoreactive cells are found as a sheath of thin, spindled fibroblasts, while reactive cells are plump in trichoepitheliomas/trichoblastomas. We postulate that the peritumoral stroma of BCC imitates the perifollicular connective tissue sheath, while in contrast that of trichoepithelioma/trichoblastoma is similar to the papillary and immediate peripapillary follicular mesenchyme. Further functional and animal experimental studies are needed to test this hypothesis. Copyright © 2011 John Wiley & Sons A/S.

Magnetic actuation of hair cells

NASA Astrophysics Data System (ADS)

Rowland, David; Roongthumskul, Yuttana; Lee, Jae-Hyun; Cheon, Jinwoo; Bozovic, Dolores

2011-11-01

The bullfrog sacculus contains mechanically sensitive hair cells whose stereociliary bundles oscillate spontaneously when decoupled from the overlying membrane. Steady-state offsets on the resting position of a hair bundle can suppress or modulate this native motility. To probe the dynamics of spontaneous oscillation in the proximity of the critical point, we describe here a method for mechanical actuation that avoids loading the bundles or contributing to the viscous drag. Magnetite beads were attached to the tips of the stereocilia, and a magnetic probe was used to impose deflections. This technique allowed us to observe the transition from multi-mode to single-mode state in freely oscillating bundles, as well as the crossover from the oscillatory to the quiescent state.

Evolutionary Convergence of Cell-Specific Gene Expression in Independent Lineages of C4 Grasses1[W][OPEN

PubMed Central

John, Christopher R.; Smith-Unna, Richard D.; Woodfield, Helen; Covshoff, Sarah; Hibberd, Julian M.

2014-01-01

Leaves of almost all C4 lineages separate the reactions of photosynthesis into the mesophyll (M) and bundle sheath (BS). The extent to which messenger RNA profiles of M and BS cells from independent C4 lineages resemble each other is not known. To address this, we conducted deep sequencing of RNA isolated from the M and BS of Setaria viridis and compared these data with publicly available information from maize (Zea mays). This revealed a high correlation (r = 0.89) between the relative abundance of transcripts encoding proteins of the core C4 pathway in M and BS cells in these species, indicating significant convergence in transcript accumulation in these evolutionarily independent C4 lineages. We also found that the vast majority of genes encoding proteins of the C4 cycle in S. viridis are syntenic to homologs used by maize. In both lineages, 122 and 212 homologous transcription factors were preferentially expressed in the M and BS, respectively. Sixteen shared regulators of chloroplast biogenesis were identified, 14 of which were syntenic homologs in maize and S. viridis. In sorghum (Sorghum bicolor), a third C4 grass, we found that 82% of these trans-factors were also differentially expressed in either M or BS cells. Taken together, these data provide, to our knowledge, the first quantification of convergence in transcript abundance in the M and BS cells from independent lineages of C4 grasses. Furthermore, the repeated recruitment of syntenic homologs from large gene families strongly implies that parallel evolution of both structural genes and trans-factors underpins the polyphyletic evolution of this highly complex trait in the monocotyledons. PMID:24676859

Initial Events during the Evolution of C4 Photosynthesis in C3 Species of Flaveria1[W][OPEN

PubMed Central

Sage, Tammy L.; Busch, Florian A.; Johnson, Daniel C.; Friesen, Patrick C.; Stinson, Corey R.; Stata, Matt; Sultmanis, Stefanie; Rahman, Beshar A.; Rawsthorne, Stephen; Sage, Rowan F.

2013-01-01

The evolution of C4 photosynthesis in many taxa involves the establishment of a two-celled photorespiratory CO2 pump, termed C2 photosynthesis. How C3 species evolved C2 metabolism is critical to understanding the initial phases of C4 plant evolution. To evaluate early events in C4 evolution, we compared leaf anatomy, ultrastructure, and gas-exchange responses of closely related C3 and C2 species of Flaveria, a model genus for C4 evolution. We hypothesized that Flaveria pringlei and Flaveria robusta, two C3 species that are most closely related to the C2 Flaveria species, would show rudimentary characteristics of C2 physiology. Compared with less-related C3 species, bundle sheath (BS) cells of F. pringlei and F. robusta had more mitochondria and chloroplasts, larger mitochondria, and proportionally more of these organelles located along the inner cell periphery. These patterns were similar, although generally less in magnitude, than those observed in the C2 species Flaveria angustifolia and Flaveria sonorensis. In F. pringlei and F. robusta, the CO2 compensation point of photosynthesis was slightly lower than in the less-related C3 species, indicating an increase in photosynthetic efficiency. This could occur because of enhanced refixation of photorespired CO2 by the centripetally positioned organelles in the BS cells. If the phylogenetic positions of F. pringlei and F. robusta reflect ancestral states, these results support a hypothesis that increased numbers of centripetally located organelles initiated a metabolic scavenging of photorespired CO2 within the BS. This could have facilitated the formation of a glycine shuttle between mesophyll and BS cells that characterizes C2 photosynthesis. PMID:24064930

Initial events during the evolution of C4 photosynthesis in C3 species of Flaveria.

PubMed

Sage, Tammy L; Busch, Florian A; Johnson, Daniel C; Friesen, Patrick C; Stinson, Corey R; Stata, Matt; Sultmanis, Stefanie; Rahman, Beshar A; Rawsthorne, Stephen; Sage, Rowan F

2013-11-01

The evolution of C4 photosynthesis in many taxa involves the establishment of a two-celled photorespiratory CO2 pump, termed C2 photosynthesis. How C3 species evolved C2 metabolism is critical to understanding the initial phases of C4 plant evolution. To evaluate early events in C4 evolution, we compared leaf anatomy, ultrastructure, and gas-exchange responses of closely related C3 and C2 species of Flaveria, a model genus for C4 evolution. We hypothesized that Flaveria pringlei and Flaveria robusta, two C3 species that are most closely related to the C2 Flaveria species, would show rudimentary characteristics of C2 physiology. Compared with less-related C3 species, bundle sheath (BS) cells of F. pringlei and F. robusta had more mitochondria and chloroplasts, larger mitochondria, and proportionally more of these organelles located along the inner cell periphery. These patterns were similar, although generally less in magnitude, than those observed in the C2 species Flaveria angustifolia and Flaveria sonorensis. In F. pringlei and F. robusta, the CO2 compensation point of photosynthesis was slightly lower than in the less-related C3 species, indicating an increase in photosynthetic efficiency. This could occur because of enhanced refixation of photorespired CO2 by the centripetally positioned organelles in the BS cells. If the phylogenetic positions of F. pringlei and F. robusta reflect ancestral states, these results support a hypothesis that increased numbers of centripetally located organelles initiated a metabolic scavenging of photorespired CO2 within the BS. This could have facilitated the formation of a glycine shuttle between mesophyll and BS cells that characterizes C2 photosynthesis.

A Common histone modification code on C4 genes in maize and its conservation in Sorghum and Setaria italica.

PubMed

Heimann, Louisa; Horst, Ina; Perduns, Renke; Dreesen, Björn; Offermann, Sascha; Peterhansel, Christoph

2013-05-01

C4 photosynthesis evolved more than 60 times independently in different plant lineages. Each time, multiple genes were recruited into C4 metabolism. The corresponding promoters acquired new regulatory features such as high expression, light induction, or cell type-specific expression in mesophyll or bundle sheath cells. We have previously shown that histone modifications contribute to the regulation of the model C4 phosphoenolpyruvate carboxylase (C4-Pepc) promoter in maize (Zea mays). We here tested the light- and cell type-specific responses of three selected histone acetylations and two histone methylations on five additional C4 genes (C4-Ca, C4-Ppdk, C4-Me, C4-Pepck, and C4-RbcS2) in maize. Histone acetylation and nucleosome occupancy assays indicated extended promoter regions with regulatory upstream regions more than 1,000 bp from the transcription initiation site for most of these genes. Despite any detectable homology of the promoters on the primary sequence level, histone modification patterns were highly coregulated. Specifically, H3K9ac was regulated by illumination, whereas H3K4me3 was regulated in a cell type-specific manner. We further compared histone modifications on the C4-Pepc and C4-Me genes from maize and the homologous genes from sorghum (Sorghum bicolor) and Setaria italica. Whereas sorghum and maize share a common C4 origin, C4 metabolism evolved independently in S. italica. The distribution of histone modifications over the promoters differed between the species, but differential regulation of light-induced histone acetylation and cell type-specific histone methylation were evident in all three species. We propose that a preexisting histone code was recruited into C4 promoter control during the evolution of C4 metabolism.

Electrolytic/fuel cell bundles and systems including a current collector in communication with an electrode thereof

DOEpatents

Hawkes, Grant L.; Herring, James S.; Stoots, Carl M.; O& #x27; Brien, James E.

2013-03-05

Electrolytic/fuel cell bundles and systems including such bundles include an electrically conductive current collector in communication with an anode or a cathode of each of a plurality of cells. A cross-sectional area of the current collector may vary in a direction generally parallel to a general direction of current flow through the current collector. The current collector may include a porous monolithic structure. At least one cell of the plurality of cells may include a current collector that surrounds an outer electrode of the cell and has at least six substantially planar exterior surfaces. The planar surfaces may extend along a length of the cell, and may abut against a substantially planar surface of a current collector of an adjacent cell. Methods for generating electricity and for performing electrolysis include flowing current through a conductive current collector having a varying cross-sectional area.

Theoretical and computational studies of the sheath of a planar wall

NASA Astrophysics Data System (ADS)

Giraudo, Martina; Camporeale, Enrico; Delzanno, Gian Luca; Lapenta, Giovanni

2012-03-01

We present an investigation of the stability and nonlinear evolution of the sheath of a planar wall. We focus on the electrostatic limit. The stability analysis is conducted with a fluid model where continuity and momentum equations for the electrons and ions are coupled through Poisson's equation. The effect of electron emission from the wall is studied parametrically. Our results show that a sheath instability associated with the emitted electrons can exist. Following Ref. [1], it is interpreted as a Rayleigh-Taylor instability driven by the favorable combination of the sheath electron density gradient and electric field. Fully kinetic Particle-In-Cell (PIC) simulations will also be presented to investigate whether this instability indeed exists and to study the nonlinear effect of electron emission on the sheath profiles. The simulations will be conducted with CPIC, a new electrostatic PIC code that couples the standard PIC algorithm with strategies for generation and adaptation of the computational grid. [4pt] [1] G.L. Delzanno, ``A paradigm for the stability of the plasma sheath against fluid perturbations,'' Phys. Plasmas 18, 103508 (2011).

Dual mTORC1/2 inhibition induces anti-proliferative effect in NF1-associated plexiform neurofibroma and malignant peripheral nerve sheath tumor cells

PubMed Central

Hivelin, Mikael; Nusbaum, Patrick; Hubas, Arnaud; Laurendeau, Ingrid; Lantieri, Laurent; Wolkenstein, Pierre; Vidaud, Michel; Pasmant, Eric; Chapuis, Nicolas; Parfait, Béatrice

2016-01-01

Approximately 30-50% of individuals with Neurofibromatosis type 1 develop benign peripheral nerve sheath tumors, called plexiform neurofibromas (PNFs). PNFs can undergo malignant transformation to highly metastatic malignant peripheral nerve sheath tumors (MPNSTs) in 5-10% of NF1 patients, with poor prognosis. No effective systemic therapy is currently available for unresectable tumors. In tumors, the NF1 gene deficiency leads to Ras hyperactivation causing the subsequent activation of the AKT/mTOR and Raf/MEK/ERK pathways and inducing multiple cellular responses including cell proliferation. In this study, three NF1-null MPNST-derived cell lines (90-8, 88-14 and 96-2), STS26T sporadic MPNST cell line and PNF-derived primary Schwann cells were used to test responses to AZD8055, an ATP-competitive “active-site” mTOR inhibitor. In contrast to rapamycin treatment which only partially affected mTORC1 signaling, AZD8055 induced a strong inhibition of mTORC1 and mTORC2 signaling in MPNST-derived cell lines and PNF-derived Schwann cells. AZD8055 induced full blockade of mTORC1 leading to an efficient decrease of global protein synthesis. A higher cytotoxic effect was observed with AZD8055 compared to rapamycin in the NF1-null MPNST-derived cell lines with IC50 ranging from 70 to 140 nM and antiproliferative effect was confirmed in PNF-derived Schwann cells. Cell migration was impaired by AZD8055 treatment and cell cycle analysis showed a G0/G1 arrest. Combined effects of AZD8055 and PD0325901 MEK inhibitor as well as BRD4 (BromoDomain-containing protein 4) inhibitors showed a synergistic antiproliferative effect. These data suggest that NF1-associated peripheral nerve sheath tumors are an ideal target for AZD8055 as a single molecule or in combined therapies. PMID:26840085

Cytology of long-term desiccation in the desert cyanobacterium Chroococcidiopsis (Chroococcales)

NASA Technical Reports Server (NTRS)

Caiola, M. G.; Ocampo-Friedmann, R.; Friedmann, E. I.

1993-01-01

Young and old cultures (up to 66 months) of two Chroococcidiopsis sp. strains isolated from the Negev desert, Israel, were examined by epifluorescence and electron microscopy. In old cultures, cell viability and autofluorescence were lower than in young cultures. An increase was seen with age in the polysaccharide content of the sheaths of nanocytes and nanocyte mother cells, and a decrease of phycobiliproteins was also seen. In the oldest cultures most of the cells were dead and in various stages of degeneration. Single living cells were scattered among the dead ones. No resting cells were formed in the oldest cultures, but many cell groups showed highly electron-dense sheaths and, in the cytoplasm, ribosomes and glycogen. These changes in cell structure may have a role in preventing water loss from the cell.

Characterization of active hair-bundle motility by a mechanical-load clamp

NASA Astrophysics Data System (ADS)

Salvi, Joshua D.; Maoiléidigh, Dáibhid Ó.; Fabella, Brian A.; Tobin, Mélanie; Hudspeth, A. J.

2015-12-01

Active hair-bundle motility endows hair cells with several traits that augment auditory stimuli. The activity of a hair bundle might be controlled by adjusting its mechanical properties. Indeed, the mechanical properties of bundles vary between different organisms and along the tonotopic axis of a single auditory organ. Motivated by these biological differences and a dynamical model of hair-bundle motility, we explore how adjusting the mass, drag, stiffness, and offset force applied to a bundle control its dynamics and response to external perturbations. Utilizing a mechanical-load clamp, we systematically mapped the two-dimensional state diagram of a hair bundle. The clamp system used a real-time processor to tightly control each of the virtual mechanical elements. Increasing the stiffness of a hair bundle advances its operating point from a spontaneously oscillating regime into a quiescent regime. As predicted by a dynamical model of hair-bundle mechanics, this boundary constitutes a Hopf bifurcation.

Synthetic peptides that cause F-actin bundling and block actin depolymerization

DOEpatents

Sederoff, Heike [Raleigh, NC; Huber, Steven C [Savoy, IL; Larabell, Carolyn A [Berkeley, CA

2011-10-18

Synthetic peptides derived from sucrose synthase, and having homology to actin and actin-related proteins, sharing a common motif, useful for causing acting bundling and preventing actin depolymerization. Peptides exhibiting the common motif are described, as well as specific synthetic peptides which caused bundled actin and inhibit actin depolymerization. These peptides can be useful for treating a subject suffering from a disease characterized by cells having neoplastic growth, for anti-cancer therapeutics, delivered to subjects solely, or concomitantly or sequentially with other known cancer therapeutics. These peptides can also be used for stabilizing microfilaments in living cells and inhibiting growth of cells.

Elevated temperature triggers human respiratory syncytial virus F protein six-helix bundle formation

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

Yunus, Abdul S.; Jackson, Trent P.; Crisafi, Katherine

2010-01-20

Human respiratory syncytial virus (RSV) is a major cause of severe lower respiratory tract infection in infants, immunocompromised patients, and the elderly. The RSV fusion (F) protein mediates fusion of the viral envelope with the target cell membrane during virus entry and is a primary target for antiviral drug and vaccine development. The F protein contains two heptad repeat regions, HR1 and HR2. Peptides corresponding to these regions form a six-helix bundle structure that is thought to play a critical role in membrane fusion. However, characterization of six-helix bundle formation in native RSV F protein has been hindered by themore » fact that a trigger for F protein conformational change has yet to be identified. Here we demonstrate that RSV F protein on the surface of infected cells undergoes a conformational change following exposure to elevated temperature, resulting in the formation of the six-helix bundle structure. We first generated and characterized six-helix bundle-specific antibodies raised against recombinant peptides modeling the RSV F protein six-helix bundle structure. We then used these antibodies as probes to monitor RSV F protein six-helix bundle formation in response to a diverse array of potential triggers of conformational changes. We found that exposure of 'membrane-anchored' RSV F protein to elevated temperature (45-55 deg. C) was sufficient to trigger six-helix bundle formation. Antibody binding to the six-helix bundle conformation was detected by both flow cytometry and cell-surface immunoprecipitation of the RSV F protein. None of the other treatments, including interaction with a number of potential receptors, resulted in significant binding by six-helix bundle-specific antibodies. We conclude that native, untriggered RSV F protein exists in a metastable state that can be converted in vitro to the more stable, fusogenic six-helix bundle conformation by an increase in thermal energy. These findings help to better define the mechanism of RSV F-mediated membrane fusion and have important implications for the identification of therapeutic strategies and vaccines targeting RSV F protein conformational changes.« less

Theory of the electron sheath and presheath

DOE PAGES

Scheiner, Brett; Baalrud, Scott D.; Yee, Benjamin T.; ...

2015-12-30

Here, electron sheaths are commonly found near Langmuir probes collecting the electron saturation current. The common assumption is that the probe collects the random flux of electrons incident on the sheath, which tacitly implies that there is no electron presheath and that the flux collected is due to a velocity space truncation of the electron velocity distribution function (EVDF). This work provides a dedicated theory of electron sheaths, which suggests that they are not so simple. Motivated by EVDFs observed in particle-in-cell(PIC) simulations, a 1D model for the electron sheath and presheath is developed. In the model, under low temperaturemore » plasma conditions (T e >> T i), an electron pressure gradient accelerates electrons in the presheath to a flow velocity that exceeds the electron thermal speed at the sheath edge. This pressure gradient generates large flow velocities compared to what would be generated by ballistic motion in response to the electric field. It is found that in many situations, under common plasma conditions, the electron presheath extends much further into the plasma than an analogous ion presheath. PIC simulations reveal that the ion density in the electron presheath is determined by a flow around the electron sheath and that this flow is due to 2D aspects of the sheath geometry. Simulations also indicate the presence of ion acoustic instabilities excited by the differential flow between electrons and ions in the presheath, which result in sheath edge fluctuations. The 1D model and time averaged PIC simulations are compared and it is shown that the model provides a good description of the electron sheath and presheath.« less

High spatial resolution mass spectrometry imaging reveals the genetically programmed, developmental modification of the distribution of thylakoid membrane lipids among individual cells of maize leaf

DOE PAGES

Duenas, Maria Emilia; Klein, Adam T.; Alexander, Liza E.; ...

2016-11-17

Metabolism in plants is compartmentalized among different tissues, cells and subcellular organelles. Mass spectrometry imaging (MSI) with matrix-assisted laser desorption ionization (MALDI) has recently advanced to allow for the visualization of metabolites at single-cell resolution. Here we applied 5- and 10 μm high spatial resolution MALDI-MSI to the asymmetric Kranz anatomy of Zea mays (maize) leaves to study the differential localization of two major anionic lipids in thylakoid membranes, sulfoquinovosyldiacylglycerols (SQDG) and phosphatidylglycerols (PG). The quantification and localization of SQDG and PG molecular species, among mesophyll (M) and bundle sheath (BS) cells, are compared across the leaf developmental gradient frommore » four maize genotypes (the inbreds B73 and Mo17, and the reciprocal hybrids B73 × Mo17 and Mo17 × B73). SQDG species are uniformly distributed in both photosynthetic cell types, regardless of leaf development or genotype; however, PG shows photosynthetic cell-specific differential localization depending on the genotype and the fatty acyl chain constituent. Overall, 16:1-containing PGs primarily contribute to the thylakoid membranes of M cells, whereas BS chloroplasts are mostly composed of 16:0-containing PGs. Furthermore, PG 32:0 shows genotype-specific differences in cellular distribution, with preferential localization in BS cells for B73, but more uniform distribution between BS and M cells in Mo17. Maternal inheritance is exhibited within the hybrids, such that the localization of PG 32:0 in B73 × Mo17 is similar to the distribution in the B73 parental inbred, whereas that of Mo17 × B73 resembles the Mo17 parent. As a result, this study demonstrates the power of MALDI-MSI to reveal unprecedented insights on metabolic outcomes in multicellular organisms at single-cell resolution.« less

[Determination of Hair Shafts by InnoTyper® 21 Kit].

PubMed

Li, F; Zhang, M; Wang, Y X; Shui, J J; Yan, M; Jin, X P; Zhu, X J

2017-12-01

To explore the application value of InnoTyper® 21 kit in forensic practice. Samples of hair shafts and saliva were collected from 8 unrelated individuals. Template DNA was extracted by AutoMate Express™ forensic DNA automatic extraction system. DNA was amplified by InnoTyper® 21 kit and AmpFℓSTR™ Identifiler™ Plus kit, respectively, and then the results were compared. After the amplification by InnoTyper® 21 kit, complete specific genotyping could be detected from the saliva samples, and the peak value of genotyping profiles of hair shafts without sheath cells was 57-1 219 RFU. Allelic gene deletion could be found sometimes. When amplified by AmpFℓSTR™ Identifiler™ Plus kit, complete specific genotyping could be detected from the saliva samples, and the specific fragment was not detected in hair shafts without sheath cells. The InnoTyper® 21 kit has certain application value in the cases of hair shafts without sheath cells. Copyright© by the Editorial Department of Journal of Forensic Medicine

Anatomical characteristics of fusoid cells and vascular bundles in Fargesia yunnanensis leaves

Treesearch

Shuguang Wang; Hui Zhang; Shuyan Lin; Chungyun Hse; Yulong Ding

2016-01-01

As of today, the functions of fusoid cell, and the transport and loading pathways of photoassimilate in bamboo leaves are still not clear. In this paper, the leaves of Fargesia yunnanensis from a greenhouse and the wild were respectively used as samples to analyze the anatomical characteristics of fusoid cells and vascular bundles. The results showed that the bamboo...

Time-Domain Modeling of RF Antennas and Plasma-Surface Interactions

NASA Astrophysics Data System (ADS)

Jenkins, Thomas G.; Smithe, David N.

2017-10-01

Recent advances in finite-difference time-domain (FDTD) modeling techniques allow plasma-surface interactions such as sheath formation and sputtering to be modeled concurrently with the physics of antenna near- and far-field behavior and ICRF power flow. Although typical sheath length scales (micrometers) are much smaller than the wavelengths of fast (tens of cm) and slow (millimeter) waves excited by the antenna, sheath behavior near plasma-facing antenna components can be represented by a sub-grid kinetic sheath boundary condition, from which RF-rectified sheath potential variation over the surface is computed as a function of current flow and local plasma parameters near the wall. These local time-varying sheath potentials can then be used, in tandem with particle-in-cell (PIC) models of the edge plasma, to study sputtering effects. Particle strike energies at the wall can be computed more accurately, consistent with their passage through the known potential of the sheath, such that correspondingly increased accuracy of sputtering yields and heat/particle fluxes to antenna surfaces is obtained. The new simulation capabilities enable time-domain modeling of plasma-surface interactions and ICRF physics in realistic experimental configurations at unprecedented spatial resolution. We will present results/animations from high-performance (10k-100k core) FDTD/PIC simulations of Alcator C-Mod antenna operation.

Estimating biozone hydraulic conductivity in wastewater soil-infiltration systems using inverse numerical modeling.

PubMed

Bumgarner, Johnathan R; McCray, John E

2007-06-01

During operation of an onsite wastewater treatment system, a low-permeability biozone develops at the infiltrative surface (IS) during application of wastewater to soil. Inverse numerical-model simulations were used to estimate the biozone saturated hydraulic conductivity (K(biozone)) under variably saturated conditions for 29 wastewater infiltration test cells installed in a sandy loam field soil. Test cells employed two loading rates (4 and 8cm/day) and 3 IS designs: open chamber, gravel, and synthetic bundles. The ratio of K(biozone) to the saturated hydraulic conductivity of the natural soil (K(s)) was used to quantify the reductions in the IS hydraulic conductivity. A smaller value of K(biozone)/K(s,) reflects a greater reduction in hydraulic conductivity. The IS hydraulic conductivity was reduced by 1-3 orders of magnitude. The reduction in IS hydraulic conductivity was primarily influenced by wastewater loading rate and IS type and not by the K(s) of the native soil. The higher loading rate yielded greater reductions in IS hydraulic conductivity than the lower loading rate for bundle and gravel cells, but the difference was not statistically significant for chamber cells. Bundle and gravel cells exhibited a greater reduction in IS hydraulic conductivity than chamber cells at the higher loading rates, while the difference between gravel and bundle systems was not statistically significant. At the lower rate, bundle cells exhibited generally lower K(biozone)/K(s) values, but not at a statistically significant level, while gravel and chamber cells were statistically similar. Gravel cells exhibited the greatest variability in measured values, which may complicate design efforts based on K(biozone) evaluations for these systems. These results suggest that chamber systems may provide for a more robust design, particularly for high or variable wastewater infiltration rates.

Coupling and Elastic Loading Affect the Active Response by the Inner Ear Hair Cell Bundles

PubMed Central

Strimbu, Clark Elliott; Fredrickson-Hemsing, Lea; Bozovic, Dolores

2012-01-01

Active hair bundle motility has been proposed to underlie the amplification mechanism in the auditory endorgans of non-mammals and in the vestibular systems of all vertebrates, and to constitute a crucial component of cochlear amplification in mammals. We used semi-intact in vitro preparations of the bullfrog sacculus to study the effects of elastic mechanical loading on both natively coupled and freely oscillating hair bundles. For the latter, we attached glass fibers of different stiffness to the stereocilia and observed the induced changes in the spontaneous bundle movement. When driven with sinusoidal deflections, hair bundles displayed phase-locked response indicative of an Arnold Tongue, with the frequency selectivity highest at low amplitudes and decreasing under stronger stimulation. A striking broadening of the mode-locked response was seen with increasing stiffness of the load, until approximate impedance matching, where the phase-locked response remained flat over the physiological range of frequencies. When the otolithic membrane was left intact atop the preparation, the natural loading of the bundles likewise decreased their frequency selectivity with respect to that observed in freely oscillating bundles. To probe for signatures of the active process under natural loading and coupling conditions, we applied transient mechanical stimuli to the otolithic membrane. Following the pulses, the underlying bundles displayed active movement in the opposite direction, analogous to the twitches observed in individual cells. Tracking features in the otolithic membrane indicated that it moved in phase with the bundles. Hence, synchronous active motility evoked in the system of coupled hair bundles by external input is sufficient to displace large overlying structures. PMID:22479461

Establishment and characterization of outer root sheath (ORS) cell line from Jining grey goat.

PubMed

Cui, Zhifeng; Hu, Yanxia; Wang, Hui; Zeng, Yongqing; Dong, Bin; Zhu, Houshun; Dong, Zhongdian; Liu, Zhiyuan

2012-03-01

A new line of outer root sheath (ORS) cells was established from hair follicles of Jining grey goat by using a mechanical separation combined with enzyme digestion. Cell morphology is described at different phases. The chromosome analysis of ORS cells, identification of the ORS cells and morphological reversion test were detected at the 4th and 40th passages. The ORS cells were healthy and the growth characteristics were stable with a population doubling time of 52 h. Chromosome analysis showed that >58% of cells were diploid. Test for ORS cell line CK19 expression was positive. This newly established ORS cell line not only lays the foundation for further studying on the growth, regeneration, development law of goat hair follicle but also provides a mirror for the research of human hair in medical field.

Actin filament bundling by fimbrin is important for endocytosis, cytokinesis, and polarization in fission yeast.

PubMed

Skau, Colleen T; Courson, David S; Bestul, Andrew J; Winkelman, Jonathan D; Rock, Ronald S; Sirotkin, Vladimir; Kovar, David R

2011-07-29

Through the coordinated action of diverse actin-binding proteins, cells simultaneously assemble actin filaments with distinct architectures and dynamics to drive different processes. Actin filament cross-linking proteins organize filaments into higher order networks, although the requirement of cross-linking activity in cells has largely been assumed rather than directly tested. Fission yeast Schizosaccharomyces pombe assembles actin into three discrete structures: endocytic actin patches, polarizing actin cables, and the cytokinetic contractile ring. The fission yeast filament cross-linker fimbrin Fim1 primarily localizes to Arp2/3 complex-nucleated branched filaments of the actin patch and by a lesser amount to bundles of linear antiparallel filaments in the contractile ring. It is unclear whether Fim1 associates with bundles of parallel filaments in actin cables. We previously discovered that a principal role of Fim1 is to control localization of tropomyosin Cdc8, thereby facilitating cofilin-mediated filament turnover. Therefore, we hypothesized that the bundling ability of Fim1 is dispensable for actin patches but is important for the contractile ring and possibly actin cables. By directly visualizing actin filament assembly using total internal reflection fluorescence microscopy, we determined that Fim1 bundles filaments in both parallel and antiparallel orientations and efficiently bundles Arp2/3 complex-branched filaments in the absence but not the presence of actin capping protein. Examination of cells exclusively expressing a truncated version of Fim1 that can bind but not bundle actin filaments revealed that bundling activity of Fim1 is in fact important for all three actin structures. Therefore, fimbrin Fim1 has diverse roles as both a filament "gatekeeper" and as a filament cross-linker.

A salivary sheath protein essential for the interaction of the brown planthopper with rice plants.

PubMed

Huang, Hai-Jian; Liu, Cheng-Wen; Cai, Ye-Fang; Zhang, Min-Zhu; Bao, Yan-Yuan; Zhang, Chuan-Xi

2015-11-01

Salivary secretions, including gel saliva and watery saliva, play crucial roles in the interaction between the insect and plant during feeding. In this study, we identified a salivary gland-specific gene encoding a salivary sheath protein (NlShp) in Nilaparvata lugens. NlShp has two alternative splicing variants; both are expressed at high levels during the nymph and adult stages. Immunohistochemical staining showed that the NlShp were synthesized in the principal gland cells of the salivary gland. LC-MS/MS and western blot analysis confirmed that NlShp was one of the components of the salivary sheath. Simultaneously knocking down the two NlShp variants by RNA interference inhibited both salivary flange and salivary sheath formation and resulted in a lethal phenotype within four days for the brown planthopper (BPH) feeding on rice plants, indicating that the salivary sheath and salivary flanges were essential for plant-associated feeding. Despite the salivary sheath deficiency, no obvious phenotype was observed in the NlShp-knockdown BPHs fed on artificial diet. The electrical penetration graph (EPG) results showed that salivary sheath-deficient BPHs exhibited a prolonged nonpenetration period, scarce sap period, and increased stylet movement on rice plants and eventually starved to death. Our results provided evidence that the interaction between the salivary sheath and host plant might be a critical step in successful BPH feeding. According to present research, we propose a salivary sheath required feeding model for piercing-sucking insects and provide a potential target for rice planthopper management. Copyright © 2015 Elsevier Ltd. All rights reserved.

Fibrin Sheath Angioplasty: A Technique to Prevent Superior Vena Cava Stenosis Secondary to Dialysis Catheters

PubMed Central

Hacker, Robert I.; Garcia, Lorena De Marco; Chawla, Ankur; Panetta, Thomas F.

2012-01-01

Fibrin sheaths are a heterogeneous matrix of cells and debris that form around catheters and are a known cause of central venous stenosis and catheter failure. A total of 50 cases of central venous catheter fibrin sheath angioplasty (FSA) after catheter removal or exchange are presented. A retrospective review of an outpatient office database identified 70 eligible patients over a 19-month period. After informed consent was obtained, the dialysis catheter exiting the skin was clamped, amputated, and a wire was inserted. The catheter was then removed and a 9-French sheath was inserted into the superior vena cava, a venogram was performed. If a fibrin sheath was present, angioplasty was performed using an 8 × 4 or 10 × 4 balloon along the entire length of the fibrin sheath. A completion venogram was performed to document obliteration of the sheath. During the study, 50 patients were diagnosed with a fibrin sheath, and 43 had no pre-existing central venous stenosis. After FSA, 39 of the 43 patient's (91%) central systems remained patent without the need for subsequent interventions; 3 patients (7%) developed subclavian stenoses requiring repeat angioplasty and stenting; 1 patent (2.3%) developed an occlusion requiring a reintervention. Seven patients with prior central stenosis required multiple angioplasties; five required stenting of their central lesions. Every patient had follow-up fistulograms to document long-term patency. We propose that FSA is a prudent and safe procedure that may help reduce the risk of central venous stenosis from fibrin sheaths due to central venous catheters. PMID:23997555

Giant cell tumour of tendon sheath and synovial membrane: A review of 26 cases.

PubMed

Kant, Kumar Shashi; Manav, Ajoy Kumar; Kumar, Rakesh; Abhinav; Sinha, Vishvendra Kumar; Sharma, Akshat

2017-11-01

Aim of our study is to highlight the incidence and benign nature of Giant cell tumour of tendon sheath and need for complete removal, thus minimizing the chances of recurrence. A total of 26 cases of Giant cell tumour of tendon sheath operated in the department of Orthopaedics, Patna Medical College & Hospital, Patna from 2003 to 2010 were included in this study. The surgery was performed after clinical evaluation of the lesion and Fine Needle Aspiration Cytology (FNAC). The tumour underwent en bloc marginal excision. The patients were followed up for minimum two year. Our study population consisted of 18 females and 8 males. The mean age at the time of surgery was 38.3 years (range, 18-62 years). Twenty three cases were found in the 3rd and 4th decade. Twenty two cases involved upper extremity and only 4 cases in lower extremity. MRI was done in 2 cases where diagnosis was in doubt. Bony indentation on X-ray film was found in 7 cases and thorough curettage of cortical shell was done. All the cases were treated by marginal excision. Three cases developed post-operative stiffness but regained full range of movement with physiotherapy. Sensory impairment was seen in 3 cases. Recurrence occurred in 2 case and they were treated by repeat marginal excision. Meticulous en-masse marginal excision of the giant cell tumour of tendon sheath in blood less field using magnification is the treatment of choice.

One-dimensional particle-in-cell simulation on the influence of electron and ion temperature on the sheath expansion process in the post-arc stage of vacuum circuit breaker

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

Mo, Yongpeng; Shi, Zongqian; Jia, Shenli

2015-02-15

The inter-contact region of vacuum circuit breakers is filled with residual plasma at the moment when the current is zero after the burning of metal vapor arc. The residual plasma forms an ion sheath in front of the post-arc cathode. The sheath then expands towards the post-arc anode under the influence of a transient recovery voltage. In this study, a one-dimensional particle-in-cell model is developed to investigate the post-arc sheath expansion. The influence of ion and electron temperatures on the decrease in local plasma density at the post-arc cathode side and post-arc anode side is discussed. When the decay inmore » the local plasma density develops from the cathode and anode sides into the high-density region and merges, the overall plasma density in the inter-contact region begins to decrease. Meanwhile, the ion sheath begins to expand faster. Furthermore, the theory of ion rarefaction wave only explains quantitatively the decrease in the overall plasma density at relatively low ion temperatures. With the increase of ion temperature to certain extent, another possible reason for the decrease in the overall plasma density is proposed and results from the more active thermal diffusion of plasma.« less

Plant-based torsional actuator with memory

Treesearch

Nayomi Plaza; Samuel L. Zelinka; Don S. Stone; Joseph E. Jakes

2013-01-01

A bundle of a few loblolly pine (Pinus taeda) cells are moisture-activated torsional actuators that twist multiple revolutions per cm length in direct proportion to moisture content. The bundles generate 10 N m kg􀀀1 specific torque during both twisting and untwisting, which is higher than an electric motor. Additionally, the bundles exhibit a moisture-...

Photosystem II efficiency of the palisade and spongy mesophyll in Quercus coccifera using adaxial/abaxial illumination and excitation light sources with wavelengths varying in penetration into the leaf tissue.

PubMed

Peguero-Pina, José Javier; Gil-Pelegrín, Eustaquio; Morales, Fermín

2009-01-01

The existence of major vertical gradients within the leaf is often overlooked in studies of photosynthesis. These gradients, which involve light heterogeneity, cell composition, and CO(2) concentration across the mesophyll, can generate differences in the maximum potential PSII efficiency (F (V)/F (M) or F (V)/F (P)) of the different cell layers. Evidence is presented for a step gradient of F (V)/F (P) ratios across the mesophyll, from the adaxial (palisade parenchyma, optimal efficiencies) to the abaxial (spongy parenchyma, sub-optimal efficiencies) side of Quercus coccifera leaves. For this purpose, light sources with different wavelengths that penetrate more or less deep within the leaf were employed, and measurements from the adaxial and abaxial sides were performed. To our knowledge, this is the first report where a low photosynthetic performance in the abaxial side of leaves is accompanied by impaired F (V)/F (P) ratios. This low photosynthetic efficiency of the abaxial side could be related to the occurrence of bundle sheath extensions, which facilitates the penetration of high light intensities deep within the mesophyll. Also, leaf morphology (twisted in shape) and orientation (with a marked angle from the horizontal plane) imply direct sunlight illumination of the abaxial side. The existence of cell layers within leaves with different photosynthetic efficiencies makes appropriate the evaluation of how light penetrates within the mesophyll when using Chl fluorescence or gas exchange techniques that use different wavelengths for excitation and/or for driving photosynthesis.

Comparative anatomy, morphology, and molecular phylogenetics of the African genus Satanocrater (Acanthaceae).

PubMed

Tripp, Erin A; Fatimah, Siti

2012-06-01

Anatomical and morphological features of Satanocrater were studied to test hypotheses of xeric adaptations in the genus, which is endemic to arid tropical Africa. These features, together with molecular data, were used to test the phylogenetic placement of Satanocrater within the large plant family Acanthaceae. We undertook a comparative study of four species of Satanocrater. Carbon isotope ratios were generated to test a hypothesis of C(4) photosynthesis. Molecular data from chloroplast (trnG-trnS, trnG-trnR, psbA-trnH) and nuclear (Eif3E) loci were used to test the placement of Satanocrater within Acanthaceae. Anatomical features reflecting xeric adaptations of species of Satanocrater included a thick-walled epidermis, thick cuticle, abundant trichomes and glandular scales, stomata overarched by subsidiary cells, tightly packed mesophyll cells, and well-developed palisade parenchyma on both leaf surfaces. Although two species had enlarged bundle sheath cells, a feature often implicated in C(4) photosynthesis, isotope ratios indicated all species of Satanocrater use the C(3) pathway. Molecular data resolved Satanocrater within tribe Ruellieae with strong support. Within Ruellieae, our data suggest that pollen morphology of Satanocrater may represent an intermediate stage in a transition series. Anatomical and morphological features of Satanocrater reflect adaptation to xeric environments and add new information about the biology of xerophytes. Morphological and molecular data place Satanocrater in the tribe Ruellieae with confidence. This study adds to our capacity to test hypotheses of broad evolutionary and ecological interest in a diverse and important family of flowering plants.

[Lipomatosis of nerve: a clinicopathologic analysis of 15 cases].

PubMed

MAO, Rong-jun; YANG, Ke-fei; WANG, Jian

2011-03-01

To study the clinicopathologic features of lipomatosis of nerve (NLS). The clinical, radiologic and pathologic features were analyzed in 15 cases of NLS. There were a total of 10 males and 5 females. The age of patients ranged from 4 to 42 years (mean age = 22.4 years). Eleven cases were located in the upper limbs and 4 cases in the lower limbs. The median nerve was the most common involved nerve. The patients typically presented before 30 years of age (often at birth or in early childhood) with a soft and slowly enlarging mass in the limb, with or without accompanying motor and sensory deficits. Some cases also had macrodactyly and carpal tunnel syndrome. MRI showed the presence of fatty tissue between nerve fascicles, resembling coaxial cable in axial plane and assuming a spaghetti-like appearance in coronal plane. On gross examination, the affected nerve was markedly increased in length and diameter. It consisted of a diffusely enlarged greyish-yellow lobulated fusiform beaded mass within the epineural sheath. Histologically, the epineurium was infiltrated by fibrofatty tissue which separated, surrounded and compressed the usually normal-appearing nerve fascicles, resulting in perineural septation of nerve fascicles and microfascicle formation. The infiltration sometimes resulted in concentric arrangement of perineural cells and pseudo-onion bulb-like hypertrophic changes. The perineurial cells might proliferate, with thickening of collagen fibers, degeneration and atrophic changes of nerve bundles. Immunohistochemical study showed that the nerve fibers expressed S-100 protein, neurofilament and CD56 (weak). The endothelial cells and dendritic fibers were highlighted by CD34. The intravascular smooth muscle cells were positive for muscle-specific actin. NLS is a rare benign soft tissue tumor of peripheral nerve. The MRI findings are characteristic. A definitive diagnosis can be made with histologic examination of tissue biopsy.

Integration of Tmc1/2 into the mechanotransduction complex in zebrafish hair cells is regulated by Transmembrane O-methyltransferase (Tomt)

PubMed Central

Erickson, Timothy; Morgan, Clive P; Olt, Jennifer; Hardy, Katherine; Busch-Nentwich, Elisabeth; Maeda, Reo; Clemens, Rachel; Krey, Jocelyn F; Nechiporuk, Alex; Barr-Gillespie, Peter G; Marcotti, Walter; Nicolson, Teresa

2017-01-01

Transmembrane O-methyltransferase (TOMT/LRTOMT) is responsible for non-syndromic deafness DFNB63. However, the specific defects that lead to hearing loss have not been described. Using a zebrafish model of DFNB63, we show that the auditory and vestibular phenotypes are due to a lack of mechanotransduction (MET) in Tomt-deficient hair cells. GFP-tagged Tomt is enriched in the Golgi of hair cells, suggesting that Tomt might regulate the trafficking of other MET components to the hair bundle. We found that Tmc1/2 proteins are specifically excluded from the hair bundle in tomt mutants, whereas other MET complex proteins can still localize to the bundle. Furthermore, mouse TOMT and TMC1 can directly interact in HEK 293 cells, and this interaction is modulated by His183 in TOMT. Thus, we propose a model of MET complex assembly where Tomt and the Tmcs interact within the secretory pathway to traffic Tmc proteins to the hair bundle. DOI: http://dx.doi.org/10.7554/eLife.28474.001 PMID:28534737

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

Miller, William A; Railkar, Sudhir; Shiao, Ming C

Field studies in a hot, humid climate were conducted to investigate the thermal and hygrothermal performance of ventilated attics and non-ventilated semi-conditioned attics sealed with open-cell and with closed-cell spray polyurethane foam insulation. Moisture pin measurements made in the sheathing and absolute humidity sensor data from inside the foam and from the attic air show that moisture is being stored in the foam. The moisture in the foam diffuses to and from the sheathing dependent on the pressure gradient at the foam-sheathing interface which is driven by the irradiance and night-sky radiation. Ventilated attics in the same hot, humid climatemore » showed less moisture movement in the sheathing than those sealed with either open- or closed-cell spray foam. In the ventilated attics the relative humidity drops as the attic air warms; however, the opposite was observed in the sealed attics. Peaks in measured relative humidity in excess of 80 90% and occasionally near saturation (i.e., 100%) were observed from solar noon till about 8 PM on hot, humid days. The conditioned space of the test facility is heated and cooled by an air-to-air heat pump. Therefore the partial pressure of the indoor air during peak irradiance is almost always less than that observed in the sealed attics. Field data will be presented to bring to light the critical humidity control issues in sealed attics exposed to hot, humid climates.« less

ACF7 is a hair-bundle antecedent, positioned to integrate cuticular plate actin and somatic tubulin.

PubMed

Antonellis, Patrick J; Pollock, Lana M; Chou, Shih-Wei; Hassan, Ahmed; Geng, Ruishuang; Chen, Xi; Fuchs, Elaine; Alagramam, Kumar N; Auer, Manfred; McDermott, Brian M

2014-01-01

The precise morphology of the mechanosensitive hair bundle requires seamless integration of actin and microtubule networks. Here, we identify Acf7a (actin crosslinking family protein 7a) as a protein positioned to bridge these distinct cytoskeletal networks in hair cells. By imaging Acf7a-Citrine fusion protein in zebrafish and immunolabeling of vestibular and cochlear mouse hair cells, we show that Acf7a and ACF7 circumscribe, underlie, and are interwoven into the cuticular plate (CP), and they also encircle the basal body of the kinocilium. In cochlear hair cells, ACF7 localization is graded, with the highest concentration near each fonticulus--an area free of F-actin in the region of the CP that contains the basal body. During hair-cell development and regeneration, Acf7a precedes formation of the hair bundle and CP. Finally, electron tomography demonstrates that the ends of microtubules insert into the CP and are decorated with filamentous linkers connecting microtubules to the CP. These observations are consistent with ACF7 being a linker protein, which may shape the cytoskeleton of the hair cell early during hair-bundle genesis.

ACF7 Is a Hair-Bundle Antecedent, Positioned to Integrate Cuticular Plate Actin and Somatic Tubulin

PubMed Central

Antonellis, Patrick J.; Pollock, Lana M.; Chou, Shih-Wei; Hassan, Ahmed; Geng, Ruishuang; Chen, Xi; Fuchs, Elaine; Alagramam, Kumar N.; Auer, Manfred

2014-01-01

The precise morphology of the mechanosensitive hair bundle requires seamless integration of actin and microtubule networks. Here, we identify Acf7a (actin crosslinking family protein 7a) as a protein positioned to bridge these distinct cytoskeletal networks in hair cells. By imaging Acf7a–Citrine fusion protein in zebrafish and immunolabeling of vestibular and cochlear mouse hair cells, we show that Acf7a and ACF7 circumscribe, underlie, and are interwoven into the cuticular plate (CP), and they also encircle the basal body of the kinocilium. In cochlear hair cells, ACF7 localization is graded, with the highest concentration near each fonticulus—an area free of F-actin in the region of the CP that contains the basal body. During hair-cell development and regeneration, Acf7a precedes formation of the hair bundle and CP. Finally, electron tomography demonstrates that the ends of microtubules insert into the CP and are decorated with filamentous linkers connecting microtubules to the CP. These observations are consistent with ACF7 being a linker protein, which may shape the cytoskeleton of the hair cell early during hair-bundle genesis. PMID:24381291

Radiation Therapy With or Without Combination Chemotherapy or Pazopanib Hydrochloride Before Surgery in Treating Patients With Newly Diagnosed Non-rhabdomyosarcoma Soft Tissue Sarcomas That Can Be Removed by Surgery

ClinicalTrials.gov

2018-06-20

Adult Fibrosarcoma; Alveolar Soft Part Sarcoma; Angiomatoid Fibrous Histiocytoma; Atypical Fibroxanthoma; Clear Cell Sarcoma of Soft Tissue; Epithelioid Malignant Peripheral Nerve Sheath Tumor; Epithelioid Sarcoma; Extraskeletal Myxoid Chondrosarcoma; Extraskeletal Osteosarcoma; Fibrohistiocytic Neoplasm; Glomus Tumor of the Skin; Inflammatory Myofibroblastic Tumor; Intimal Sarcoma; Leiomyosarcoma; Liposarcoma; Low Grade Fibromyxoid Sarcoma; Low Grade Myofibroblastic Sarcoma; Malignant Cutaneous Granular Cell Tumor; Malignant Peripheral Nerve Sheath Tumor; Malignant Triton Tumor; Mesenchymal Chondrosarcoma; Myxofibrosarcoma; Myxoid Chondrosarcoma; Myxoinflammatory Fibroblastic Sarcoma; Nerve Sheath Neoplasm; PEComa; Pericytic Neoplasm; Plexiform Fibrohistiocytic Tumor; Sclerosing Epithelioid Fibrosarcoma; Stage IB Soft Tissue Sarcoma AJCC v7; Stage IIB Soft Tissue Sarcoma AJCC v7; Stage III Soft Tissue Sarcoma AJCC v7; Stage IV Soft Tissue Sarcoma AJCC v7; Synovial Sarcoma; Undifferentiated (Embryonal) Sarcoma; Undifferentiated High Grade Pleomorphic Sarcoma of Bone

Progress on the Development of the hPIC Particle-in-Cell Code

NASA Astrophysics Data System (ADS)

Dart, Cameron; Hayes, Alyssa; Khaziev, Rinat; Marcinko, Stephen; Curreli, Davide; Laboratory of Computational Plasma Physics Team

2017-10-01

Advancements were made in the development of the kinetic-kinetic electrostatic Particle-in-Cell code, hPIC, designed for large-scale simulation of the Plasma-Material Interface. hPIC achieved a weak scaling efficiency of 87% using the Algebraic Multigrid Solver BoomerAMG from the PETSc library on more than 64,000 cores of the Blue Waters supercomputer at the University of Illinois at Urbana-Champaign. The code successfully simulates two-stream instability and a volume of plasma over several square centimeters of surface extending out to the presheath in kinetic-kinetic mode. Results from a parametric study of the plasma sheath in strongly magnetized conditions will be presented, as well as a detailed analysis of the plasma sheath structure at grazing magnetic angles. The distribution function and its moments will be reported for plasma species in the simulation domain and at the material surface for plasma sheath simulations. Membership Pending.

Segmentation of the zebrafish axial skeleton relies on notochord sheath cells and not on the segmentation clock

PubMed Central

Lleras Forero, Laura; Narayanan, Rachna; Huitema, Leonie FA; VanBergen, Maaike; Apschner, Alexander; Peterson-Maduro, Josi; Logister, Ive; Valentin, Guillaume

2018-01-01

Segmentation of the axial skeleton in amniotes depends on the segmentation clock, which patterns the paraxial mesoderm and the sclerotome. While the segmentation clock clearly operates in teleosts, the role of the sclerotome in establishing the axial skeleton is unclear. We severely disrupt zebrafish paraxial segmentation, yet observe a largely normal segmentation process of the chordacentra. We demonstrate that axial entpd5+ notochord sheath cells are responsible for chordacentrum mineralization, and serve as a marker for axial segmentation. While autonomous within the notochord sheath, entpd5 expression and centrum formation show some plasticity and can respond to myotome pattern. These observations reveal for the first time the dynamics of notochord segmentation in a teleost, and are consistent with an autonomous patterning mechanism that is influenced, but not determined by adjacent paraxial mesoderm. This behavior is not consistent with a clock-type mechanism in the notochord. PMID:29624170

Bypassing Iron Storage in Endodermal Vacuoles Rescues the Iron Mobilization Defect in the natural resistance associated-macrophage protein3natural resistance associated-macrophage protein4 Double Mutant1[OPEN

PubMed Central

Mary, Viviane; Schnell Ramos, Magali; Gillet, Cynthia; Socha, Amanda L.; Giraudat, Jérôme; Agorio, Astrid; Merlot, Sylvain; Clairet, Colin; Kim, Sun A.; Punshon, Tracy; Guerinot, Mary Lou; Thomine, Sébastien

2015-01-01

To improve seed iron (Fe) content and bioavailability, it is crucial to decipher the mechanisms that control Fe storage during seed development. In Arabidopsis (Arabidopsis thaliana) seeds, most Fe is concentrated in insoluble precipitates, with phytate in the vacuoles of cells surrounding the vasculature of the embryo. NATURAL RESISTANCE ASSOCIATED-MACROPHAGE PROTEIN3 (AtNRAMP3) and AtNRAMP4 function redundantly in Fe retrieval from vacuoles during germination. When germinated under Fe-deficient conditions, development of the nramp3nramp4 double mutant is arrested as a consequence of impaired Fe mobilization. To identify novel genes involved in seed Fe homeostasis, we screened an ethyl methanesulfonate-mutagenized population of nramp3nramp4 seedlings for mutations suppressing their phenotypes on low Fe. Here, we report that, among the suppressors, two independent mutations in the VACUOLAR IRON TRANSPORTER1 (AtVIT1) gene caused the suppressor phenotype. The AtVIT1 transporter is involved in Fe influx into vacuoles of endodermal and bundle sheath cells. This result establishes a functional link between Fe loading in vacuoles by AtVIT1 and its remobilization by AtNRAMP3 and AtNRAMP4. Moreover, analysis of subcellular Fe localization indicates that simultaneous disruption of AtVIT1, AtNRAMP3, and AtNRAMP4 limits Fe accumulation in vacuolar globoids. PMID:26232490

Numerically bridging lamellipodial and filopodial activity during cell spreading reveals a potentially novel trigger of focal adhesion maturation.

PubMed

Loosli, Y; Vianay, B; Luginbuehl, R; Snedeker, J G

2012-05-01

We present a novel approach to modeling cell spreading, and use it to reveal a potentially central mechanism regulating focal adhesion maturation in various cell phenotypes. Actin bundles that span neighboring focal complexes at the lamellipodium-lamellum interface were assumed to be loaded by intracellular forces in proportion to bundle length. We hypothesized that the length of an actin bundle (with the corresponding accumulated force at its adhesions) may thus regulate adhesion maturation to ensure cell mechanical stability and morphological integrity. We developed a model to test this hypothesis, implementing a "top-down" approach to simplify certain cellular processes while explicitly incorporating complexity of other key subcellular mechanisms. Filopodial and lamellipodial activities were treated as modular processes with functional spatiotemporal interactions coordinated by rules regarding focal adhesion turnover and actin bundle dynamics. This theoretical framework was able to robustly predict temporal evolution of cell area and cytoskeletal organization as reported from a wide range of cell spreading experiments using micropatterned substrates. We conclude that a geometric/temporal modeling framework can capture the key functional aspects of the rapid spreading phase and resultant cytoskeletal complexity. Hence the model is used to reveal mechanistic insight into basic cell behavior essential for spreading. It demonstrates that actin bundles spanning nascent focal adhesions such that they are aligned to the leading edge may accumulate centripetal endogenous forces along their length, and could thus trigger focal adhesion maturation in a force-length dependent fashion. We suggest that this mechanism could be a central "integrating" factor that effectively coordinates force-mediated adhesion maturation at the lamellipodium-lamellum interface.

Correlation between the distribution of lignin and pectin and distribution of sorbed metal ions (lead and zinc) on coir (Cocos nucifera L.).

PubMed

Conrad, Kathrine

2008-11-01

Plant fibres are capacious for sorption of metal ions, and can be used in water cleaning. Knowledge about the sorption will help in selection of the fibre and optimisation of its chemical modification, if any. The aim of this paper is to investigate the connection, if any, between the distribution of lignin and pectin and the loading of Pb and Zn on coir (mesocarp fibres from Cocos nucifera L.). The coir consisted mainly of xylem and a fibre sheath. The lignin was evenly distributed in the cell walls of the fibre sheath, but in the xylem, there was no detectable content in the compound middle lamella, and a smaller content of lignin in the secondary walls than in the walls of the fibre sheath. The only detectable content of pectin in the fibre sheath walls was in the middle lamella, cell corners and extracellular matrix, while in the xylem, the pectin was almost evenly distributed in the wall, with a higher concentration in the middle lamella and cell corners. All cell walls facing the lacuna had a high content of pectin. The metal ions were mainly loaded on the xylem and cell walls facing the lacuna, maybe with an additional trend to be loaded on the large fibres. Lead was distributed on and across the whole secondary wall. Zinc was loaded on the secondary walls, but there was no information about the distribution across the wall. If there is a simple correlation between the loading of metal ions and the distribution of lignin or pectin, these investigations point at no correlation with lignin and a positive correlation with pectin. It has to be stressed that these conclusions are made on limited material and are therefore preliminary in nature.

A transmission and scanning electron microscopic study of the saccule in five species of catfishes.

PubMed

Jenkins, D B

1979-01-01

The sacculi of five species of catfishes were studied by transmission and scanning electron microscopy. In four species, the sagitta exhibited a multifluted anterior part and a tapered posterior part; in Corydoras aeneus, however, the fluted part was absent, and a vertical component extended dorsally to terminate near the opening of the transverse canal. In all species, the otoliths had a laminar structure. An otolithic membrane was present, and hair cell bundles projected into cavities on the macular surface of the membrane. Attachments of the otolithic membrane to the neuroepithelium included short extensions of the membrane to the tallest components of the hair cell bundles of the peripheral cells and more delicate connections to the kinocilium and taller stereocilia of central cells; in addition, attachments to the microvilli of supporting cells were present. In both hair cells and supporting cells single microtubules and bundles of microtubules were present; the bundles had an orderly arrangement and were associated with cytoplasmic densities surrounding the desmosomes. The hair cells were innervated by both afferent and efferent nerve endings. Studies of the polarization of the hair cells in all species (except C. aeneus) showed that there was a single longitudinal axis that divided dorsally polarized cells from those oriented ventrally. In Doras spinosissimus and Bunocephalus bicolor, an additional line of polarization was evident in a small area in the anterior part of the macula; therefore, in these forms there was a double bipolar orientation.

The role of photorespiration during the evolution of C4 photosynthesis in the genus Flaveria

PubMed Central

Mallmann, Julia; Heckmann, David; Bräutigam, Andrea; Lercher, Martin J; Weber, Andreas PM; Westhoff, Peter; Gowik, Udo

2014-01-01

C4 photosynthesis represents a most remarkable case of convergent evolution of a complex trait, which includes the reprogramming of the expression patterns of thousands of genes. Anatomical, physiological, and phylogenetic and analyses as well as computational modeling indicate that the establishment of a photorespiratory carbon pump (termed C2 photosynthesis) is a prerequisite for the evolution of C4. However, a mechanistic model explaining the tight connection between the evolution of C4 and C2 photosynthesis is currently lacking. Here we address this question through comparative transcriptomic and biochemical analyses of closely related C3, C3–C4, and C4 species, combined with Flux Balance Analysis constrained through a mechanistic model of carbon fixation. We show that C2 photosynthesis creates a misbalance in nitrogen metabolism between bundle sheath and mesophyll cells. Rebalancing nitrogen metabolism requires anaplerotic reactions that resemble at least parts of a basic C4 cycle. Our findings thus show how C2 photosynthesis represents a pre-adaptation for the C4 system, where the evolution of the C2 system establishes important C4 components as a side effect. DOI: http://dx.doi.org/10.7554/eLife.02478.001 PMID:24935935

A mutation in the melon Vacuolar Protein Sorting 41prevents systemic infection of Cucumber mosaic virus.

PubMed

Giner, Ana; Pascual, Laura; Bourgeois, Michael; Gyetvai, Gabor; Rios, Pablo; Picó, Belén; Troadec, Christelle; Bendahmane, Abdel; Garcia-Mas, Jordi; Martín-Hernández, Ana Montserrat

2017-09-05

In the melon exotic accession PI 161375, the gene cmv1, confers recessive resistance to Cucumber mosaic virus (CMV) strains of subgroup II. cmv1 prevents the systemic infection by restricting the virus to the bundle sheath cells and impeding viral loading to the phloem. Here we report the fine mapping and cloning of cmv1. Screening of an F2 population reduced the cmv1 region to a 132 Kb interval that includes a Vacuolar Protein Sorting 41 gene. CmVPS41 is conserved among plants, animals and yeast and is required for post-Golgi vesicle trafficking towards the vacuole. We have validated CmVPS41 as the gene responsible for the resistance, both by generating CMV susceptible transgenic melon plants, expressing the susceptible allele in the resistant cultivar and by characterizing CmVPS41 TILLING mutants with reduced susceptibility to CMV. Finally, a core collection of 52 melon accessions allowed us to identify a single amino acid substitution (L348R) as the only polymorphism associated with the resistant phenotype. CmVPS41 is the first natural recessive resistance gene found to be involved in viral transport and its cellular function suggests that CMV might use CmVPS41 for its own transport towards the phloem.

Effect of Ethanol Stress on Fermentation Performance of Saccharomyces cerevisiae Cells Immobilized on Nypa fruticans Leaf Sheath Pieces

PubMed Central

Nguyen, Hoang Phong; Du Le, Hoang

2015-01-01

Summary The yeast cells of Saccharomyces cerevisiae immobilized on Nypa fruticans leaf sheath pieces were tested for ethanol tolerance (0, 23.7, 47.4, 71.0 and 94.7 g/L). Increase in the initial ethanol concentration from 23.7 to 94.7 g/L decreased the average growth rate and concentration of ethanol produced by the immobilized yeast by 5.2 and 4.1 times, respectively. However, in the medium with initial ethanol concentration of 94.7 g/L, the average growth rate, glucose uptake rate and ethanol formation rate of the immobilized yeast were 3.7, 2.5 and 3.5 times, respectively, higher than those of the free yeast. The ethanol stress inhibited ethanol formation by Saccharomyces cerevisiae cells and the yeast responded to the stress by changing the fatty acid composition of cellular membrane. The adsorption of yeast cells on Nypa fruticans leaf sheath pieces of the growth medium increased the saturated fatty acid (C16:0 and C18:0) mass fraction in the cellular membrane and that improved alcoholic fermentation performance of the immobilized yeast. PMID:27904338

From Biological Cilia to Artificial Flow Sensors: Biomimetic Soft Polymer Nanosensors with High Sensing Performance

NASA Astrophysics Data System (ADS)

Asadnia, Mohsen; Kottapalli, Ajay Giri Prakash; Karavitaki, K. Domenica; Warkiani, Majid Ebrahimi; Miao, Jianmin; Corey, David P.; Triantafyllou, Michael

2016-09-01

We report the development of a new class of miniature all-polymer flow sensors that closely mimic the intricate morphology of the mechanosensory ciliary bundles in biological hair cells. An artificial ciliary bundle is achieved by fabricating bundled polydimethylsiloxane (PDMS) micro-pillars with graded heights and electrospinning polyvinylidenefluoride (PVDF) piezoelectric nanofiber tip links. The piezoelectric nature of a single nanofiber tip link is confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Rheology and nanoindentation experiments are used to ensure that the viscous properties of the hyaluronic acid (HA)-based hydrogel are close to the biological cupula. A dome-shaped HA hydrogel cupula that encapsulates the artificial hair cell bundle is formed through precision drop-casting and swelling processes. Fluid drag force actuates the hydrogel cupula and deflects the micro-pillar bundle, stretching the nanofibers and generating electric charges. Functioning with principles analogous to the hair bundles, the sensors achieve a sensitivity and threshold detection limit of 300 mV/(m/s) and 8 μm/s, respectively. These self-powered, sensitive, flexible, biocompatibale and miniaturized sensors can find extensive applications in navigation and maneuvering of underwater robots, artificial hearing systems, biomedical and microfluidic devices.

From Biological Cilia to Artificial Flow Sensors: Biomimetic Soft Polymer Nanosensors with High Sensing Performance.

PubMed

Asadnia, Mohsen; Kottapalli, Ajay Giri Prakash; Karavitaki, K Domenica; Warkiani, Majid Ebrahimi; Miao, Jianmin; Corey, David P; Triantafyllou, Michael

2016-09-13

We report the development of a new class of miniature all-polymer flow sensors that closely mimic the intricate morphology of the mechanosensory ciliary bundles in biological hair cells. An artificial ciliary bundle is achieved by fabricating bundled polydimethylsiloxane (PDMS) micro-pillars with graded heights and electrospinning polyvinylidenefluoride (PVDF) piezoelectric nanofiber tip links. The piezoelectric nature of a single nanofiber tip link is confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Rheology and nanoindentation experiments are used to ensure that the viscous properties of the hyaluronic acid (HA)-based hydrogel are close to the biological cupula. A dome-shaped HA hydrogel cupula that encapsulates the artificial hair cell bundle is formed through precision drop-casting and swelling processes. Fluid drag force actuates the hydrogel cupula and deflects the micro-pillar bundle, stretching the nanofibers and generating electric charges. Functioning with principles analogous to the hair bundles, the sensors achieve a sensitivity and threshold detection limit of 300 mV/(m/s) and 8 μm/s, respectively. These self-powered, sensitive, flexible, biocompatibale and miniaturized sensors can find extensive applications in navigation and maneuvering of underwater robots, artificial hearing systems, biomedical and microfluidic devices.

Structural and experimental investigations of the functional anatomy and the turgor of the notochord in the larval tail of anuran tadpoles.

PubMed

Platz, Franz

2006-07-01

The premetamorphotic morphology and metamorphotic degeneration of the tail notochord of anuran tadpoles has been investigated. For this purpose the functional anatomy and origin of the notochord turgor was analysed in 10 species macroscopically and using light, transmission and scanning electron microscopic techniques. The notochord consists of the fibrous notochord sheath, which surrounds the notochord cells. Within the sheath these cells form a net-like unit. The inner cells are derived from the marginal notochord cells (chordoblasts). They are protected from mechanical overload by intracellular filaments and desmosomes. Due to their vacuoles, which are filled with a hyaline liquid, they have a constant volume but are deformable. Dissolved substances may pass from the vascularized fin to the notochord cells. The transport from marginal to inner cells occurs via cytopempsis and micropinocytosis. The morphological correlation of this process consists of multiple membrane invaginations and intracellular vesicles. Within the notochord cells a high turgor pressure has been observed. During metamorphosis the membrane vesiculation persists and the notochord cells degenerate. Due to the loss of turgor pressure the tight consistency of the notochord is lost. The collagen filaments and the elastic membrane of the notochord sheath dissolve. Notochord cells with their filaments, high turgor pressure and their central vacuole can function as a combined mechanical and physiological system, which is adaptable to the needs of pressure, compression, tensile and bending forces.

Sperm fibrous sheath proteins: a potential new class of target antigens for use in human therapeutic cancer vaccines

PubMed Central

Chiriva-Internati, Maurizio; Cobos, Everardo; Da Silva, Diane M.

2008-01-01

Cancer vaccines have been demonstrated to be a promising strategy for treating human neoplastic disease, but one of the limitations of these vaccines remains the paucity of target antigens to which to direct an effective immune response. We hypothesize that sperm fibrous sheath proteins may be a new class of useful antigens for developing successful cancer vaccines. This hypothesis is supported by the expression of two sperm fibrous sheath proteins, called sperm protein 17 and calcium-binding tyrosine-phosphorylation regulated protein, in tumors of unrelated histological origin and their capability to induce T cell-based immune responses. PMID:18433090

Preferential soft-tissue preservation in the Hot Creek carbonate spring deposit, British Columbia, Canada

NASA Astrophysics Data System (ADS)

Rainey, Dustin K.; Jones, Brian

2010-05-01

The relict Holocene Hot Creek carbonate spring deposit in southeast British Columbia is characterized by excellent preservation of soft-tissue organisms (e.g. cyanobacteria), but poor preservation of organisms with hard-tissue (e.g. wood, diatoms). The deposit is formed mainly of calcified cyanobacteria, with fewer mineralized macrophytes (plants), bryophytes (mosses), wood, and diatoms. Cyanobacteria grew as solitary filaments ( Lyngbya) and as radiating hemispherical colonies ( Rivularia). Both were preserved by encrustation and encapsulation while alive, and as casts after filament death and decay. Sheath impregnation was rare to absent. Filament encrustation, whereby calcite crystals nucleated on, and grew away from the sheath exterior, produced moulds that replicated external filament morphology, but hastened filament decay. Filament encapsulation, whereby calcite nucleated in the vicinity of, and grew towards the encapsulated filament, promoted sheath preservation even after trichome decay. Subsequent calcite precipitation inside the hollow sheath generated sheath casts. The inability of mineralizing spring water to penetrate durable cell walls meant that bryophytes, macrophytes, and most wood was preserved by encrustation. Some wood resisted complete decay for several thousand years, and its lignified cell walls allowed rare permineralizations. Diatoms were not preserved in the relict deposit because the frustules were dissolved by the basic spring water. Amorphous calcium carbonate produced by photosynthetic CO 2 removal may have acted as nucleation sites for physicochemically precipitated calcite. Thus, metabolic activities of floral organisms probably initiated biotic mineralization, but continuous inorganic calcite precipitation on and in flora ensured that soft tissues were preserved.

Novel everting urologic access sheath: potential advantages of decreased cellular advancement.

PubMed

Camargo, Affonso H L A; Rubenstein, Jonathan N; Sozen, Sinan; Ershoff, Brent D; Stoller, Marshall L

2006-02-01

Axial forces are imposed on the urothelium during advancement of instruments across the urinary tract, potentially transferring cellular debris, bacteria, or urothelial carcinoma from one anatomic location to another. A prototype access sheath (Cystoglide; Percutaneous Systems, Mountain View, CA) was created that everts and radially dilates but does not provide axial forces during deployment that can be used in a variety of anatomic systems. We created a urinary-tract model to evaluate the in-vitro advancement of cells to compare this technology with using instruments alone. Blocks of sterile agar were created with 17F tracts of three lengths (2.7, 5.5, and 11 cm) with 5 mL of Luria-Bertani broth/ampicillin solution in a well at the end. The tips of a Cystoglide sheath and a traditional urologic instrument of the same diameter were dipped into a suspension of ampicillin-resistant Escherichia coli and advanced through the tracts. After a 10-second exposure, 4 mL of broth was collected and cultured. Bacterial growth was compared by measuring the optical density (OD) of the broth at multiple time points. The mean overall OD of the broth was significantly lower (P < 0.001) in the novel-sheath cultures than with a traditional instrument for all advancements at all tract lengths. The Cystoglide sheath significantly reduces the advancement of cells within an artificial urinary tract compared with a non-everting instrument. Clinical studies are needed to assess the utility of this technology in vivo.

Bundling of elastic filaments induced by hydrodynamic interactions

NASA Astrophysics Data System (ADS)

Man, Yi; Page, William; Poole, Robert J.; Lauga, Eric

2017-12-01

Peritrichous bacteria swim in viscous fluids by rotating multiple helical flagellar filaments. As the bacterium swims forward, all its flagella rotate in synchrony behind the cell in a tight helical bundle. When the bacterium changes its direction, the flagellar filaments unbundle and randomly reorient the cell for a short period of time before returning to their bundled state and resuming swimming. This rapid bundling and unbundling is, at its heart, a mechanical process whereby hydrodynamic interactions balance with elasticity to determine the time-varying deformation of the filaments. Inspired by this biophysical problem, we present in this paper what is perhaps the simplest model of bundling whereby two or more straight elastic filaments immersed in a viscous fluid rotate about their centerline, inducing rotational flows which tend to bend the filaments around each other. We derive an integrodifferential equation governing the shape of the filaments resulting from mechanical balance in a viscous fluid at low Reynolds number. We show that such equation may be evaluated asymptotically analytically in the long-wavelength limit, leading to a local partial differential equation governed by a single dimensionless bundling number. A numerical study of the dynamics predicted by the model reveals the presence of two configuration instabilities with increasing bundling numbers: first to a crossing state where filaments touch at one point and then to a bundled state where filaments wrap along each other in a helical fashion. We also consider the case of multiple filaments and the unbundling dynamics. We next provide an intuitive physical model for the crossing instability and show that it may be used to predict analytically its threshold and adapted to address the transition to a bundling state. We then use a macroscale experimental implementation of the two-filament configuration in order to validate our theoretical predictions and obtain excellent agreement. This long-wavelength model of bundling will be applicable to other problems in biological physics and provides the groundwork for further, more realistic, models of flagellar bundling.

Application of Spray Foam Insulation Under Plywood and OSB Roof Sheathing (Fact Sheet)

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

None, None

2013-11-01

Spray polyurethane foams (SPFs) have advantages over alternative insulation methods because they provide air sealing in complex assemblies, particularly roofs. Spray foam can provide the thermal, air, and vapor control layers in both new and retrofit construction. Unvented roof strategies with open cell and closed cell SPF insulation sprayed to the underside of roof sheathing have been used since the mid-1990s to provide durable and efficient building enclosures. However, there have been isolated incidents of failures (either sheathing rot or SPF delamination) that raise some general concerns about the hygrothermal performance and durability of these systems. The primary risks formore » roof systems are rainwater leaks, condensation from diffusion and air leakage, and built-in construction moisture. This project directly investigated rain and indirectly investigated built-in construction moisture and vapor drives. Research involved both hygrothermal modeling of a range of rain water leakage scenarios and field evaluations of in-service residential roofs. Other variables considered were climate zone, orientation, interior relative humidity, and the vapor permeance of the coating applied to the interior face of open cell SPF.« less

Five vicarious genera from Gondwana: the Velloziaceae as shown by molecules and morphology

PubMed Central

Mello-Silva, Renato; Santos, Déborah Yara A. C.; Salatino, Maria Luiza F.; Motta, Lucimar B.; Cattai, Marina B.; Sasaki, Denise; Lovo, Juliana; Pita, Patrícia B.; Rocini, Cintia; Rodrigues, Cristiane D. N.; Zarrei, Mehdi; Chase, Mark W.

2011-01-01

Background and Aims The amount of data collected previously for Velloziaceae neither clarified relationships within the family nor helped determine an appropriate classification, which has led to huge discordance among treatment by different authors. To achieve an acceptable phylogenetic result and understand the evolution and roles of characters in supporting groups, a total evidence analysis was developed which included approx. 20 % of the species and all recognized genera and sections of Velloziaceae, plus outgroups representatives of related families within Pandanales. Methods Analyses were undertaken with 48 species of Velloziaceae, representing all ten genera, with DNA sequences from the atpB-rbcL spacer, trnL-trnF spacer, trnL intron, trnH-psbA spacer, ITS ribosomal DNA spacers and morphology. Key Results Four groups consistently emerge from the analyses. Persistent leaves, two phloem strands, stem cortex divided in three regions and violet tepals support Acanthochlamys as sister to Velloziaceae s.s., which are supported mainly by leaves with marginal bundles, transfusion tracheids and inflorescence without axis. Within Velloziaceae s.s., an African Xerophyta + Talbotia clade is uniquely supported by basal loculicidal capsules; an American clade, Barbacenia s.l. + Barbaceniopsis + Nanuza + Vellozia, is supported by only homoplastic characters. Barbacenia s.l. (= Aylthonia + Barbacenia + Burlemarxia + Pleurostima) is supported by a double sheath in leaf vascular bundles and a corona; Barbaceniopsis + Nanuza + Vellozia is not supported by an unambiguous character, but Barbaceniopsis is supported by five characters, including diclinous flowers, Nanuza + Vellozia is supported mainly by horizontal stigma lobes and stem inner cortex cells with secondary walls, and Vellozia alone is supported mainly by pollen in tetrads. Conclusions The results imply recognition of five genera (Acanthochlamys (Xerophyta (Barbacenia (Barbaceniopsis, Vellozia)))), solving the long-standing controversies among recent classifications of the family. They also suggest a Gondwanan origin for Velloziaceae, with a vicariant pattern of distribution. PMID:21693665

Association of a new type of gliding, filamentous, purple phototrophic bacterium inside bundles of Microcoleus chthonoplastes in hypersaline cyanobacterial mats

NASA Technical Reports Server (NTRS)

D'Amelio, E. D.; Cohen, Y.; Des Marais, D. J.

1987-01-01

An unidentified filamentous purple bacterium, probably belonging to a new genus or even a new family, is found in close association with the filamentous, mat-forming cyanobacterium Microcoleus chthonoplastes in a hypersaline pond at Guerrero Negro, Baja California Sur, Mexico, and in Solar Lake, Sinai, Egypt. This organism is a gliding, segmented trichome, 0.8-0.9 micrometer wide. It contains intracytoplasmic stacked lamellae which are perpendicular and obliquely oriented to the cell wall, similar to those described for the purple sulfur bacteria Ectothiorhodospira. These bacteria are found inside the cyanobacterial bundle, enclosed by the cyanobacterial sheath. Detailed transmission electron microscopical analyses carried out in horizontal sections of the upper 1.5 mm of the cyanobacterial mat show this cyanobacterial-purple bacterial association at depths of 300-1200 micrometers, corresponding to the zone below that of maximal oxygenic photosynthesis. Sharp gradients of oxygen and sulfide are established during the day at this microzone in the two cyanobacterial mats studied. The close association, the distribution pattern of this association and preliminary physiological experiments suggest a co-metabolism of sulfur by the two-membered community. This probable new genus of purple bacteria may also grow photoheterotrophically using organic carbon excreted by the cyanobacterium. Since the chemical gradients in the entire photic zone fluctuate widely in a diurnal cycle, both types of metabolism probably take place. During the morning and afternoon, sulfide migrates up to the photic zone allowing photoautotrophic metabolism with sulfide as the electron donor. During the day the photic zone is highly oxygenated and the purple bacteria may either use oxidized species of sulfur such as elemental sulfur and thiosulfate in the photoautotrophic mode or grow photoheterotrophically using organic carbon excreted by M. chthonoplastes. The new type of filamentous purple sulfur bacteria is not available yet in pure culture, and its taxonomical position cannot be fully established. This organism is suggested to be a new type of gliding, filamentous, purple phototroph.

Mechanical properties and cellular response of novel electrospun nanofibers for ligament tissue engineering: Effects of orientation and geometry.

PubMed

Pauly, Hannah M; Kelly, Daniel J; Popat, Ketul C; Trujillo, Nathan A; Dunne, Nicholas J; McCarthy, Helen O; Haut Donahue, Tammy L

2016-08-01

Electrospun nanofibers are a promising material for ligamentous tissue engineering, however weak mechanical properties of fibers to date have limited their clinical usage. The goal of this work was to modify electrospun nanofibers to create a robust structure that mimics the complex hierarchy of native tendons and ligaments. The scaffolds that were fabricated in this study consisted of either random or aligned nanofibers in flat sheets or rolled nanofiber bundles that mimic the size scale of fascicle units in primarily tensile load bearing soft musculoskeletal tissues. Altering nanofiber orientation and geometry significantly affected mechanical properties; most notably aligned nanofiber sheets had the greatest modulus; 125% higher than that of random nanofiber sheets; and 45% higher than aligned nanofiber bundles. Modifying aligned nanofiber sheets to form aligned nanofiber bundles also resulted in approximately 107% higher yield stresses and 140% higher yield strains. The mechanical properties of aligned nanofiber bundles were in the range of the mechanical properties of the native ACL: modulus=158±32MPa, yield stress=57±23MPa and yield strain=0.38±0.08. Adipose derived stem cells cultured on all surfaces remained viable and proliferated extensively over a 7 day culture period and cells elongated on nanofiber bundles. The results of the study suggest that aligned nanofiber bundles may be useful for ligament and tendon tissue engineering based on their mechanical properties and ability to support cell adhesion, proliferation, and elongation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Vertical-probe-induced asymmetric dust oscillation in complex plasma.

PubMed

Harris, B J; Matthews, L S; Hyde, T W

2013-05-01

A complex plasma vertical oscillation experiment which modifies the bulk is presented. Spherical, micron-sized particles within a Coulomb crystal levitated in the sheath above the powered lower electrode in a GEC reference cell are perturbed using a probe attached to a Zyvex S100 Nanomanipulator. By oscillating the probe potential sinusoidally, particle motion is found to be asymmetric, exhibiting superharmonic response in one case. Using a simple electric field model for the plasma sheath, including a nonzero electric field at the sheath edge, dust particle charges are found by employing a balance of relevant forces and emission analysis. Adjusting the parameters of the electric field model allowed the change predicted in the levitation height to be compared with experiment. A discrete oscillator Green's function is applied using the derived force, which accurately predicts the particle's motion and allows the determination of the electric field at the sheath edge.

Sheath oscillation characteristics and effect on near-wall conduction in a krypton Hall thruster

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

Zhang, Fengkui, E-mail: fengkuizhang@163.com; Kong, Lingyi; Li, Chenliang

2014-11-15

Despite its affordability, the krypton Hall-effect thruster in applications always had problems in regard to performance. The reason for this degradation is studied from the perspective of the near-wall conductivity of electrons. Using the particle-in-cell method, the sheath oscillation characteristics and its effect on near-wall conduction are compared in the krypton and xenon Hall-effect thrusters both with wall material composed of BNSiO{sub 2}. Comparing these two thrusters, the sheath in the krypton-plasma thruster will oscillate at low electron temperatures. The near-wall conduction current is only produced by collisions between electrons and wall, thereby causing a deficiency in the channel current.more » The sheath displays spatial oscillations only at high electron temperature; electrons are then reflected to produce the non-oscillation conduction current needed for the krypton-plasma thruster. However, it is accompanied with intensified oscillations.« less

A segmental pattern of alkaline phosphatase activity within the notochord coincides with the initial formation of the vertebral bodies.

PubMed

Grotmol, Sindre; Nordvik, Kari; Kryvi, Harald; Totland, Geir K

2005-05-01

This study shows that segmental expression of alkaline phosphatase (ALP) activity by the notochord of the Atlantic salmon (Salmo salar L.) coincides with the initial mineralization of the vertebral body (chordacentrum), and precedes ALP expression by presumed somite-derived cells external to the notochordal sheath. The early expression of ALP indicates that the notochord plays an instructive role in the segmental patterning of the vertebral column. The chordacentra form segmentally as mineralized rings within the notochordal sheath, and ALP activity spreads within the chordoblast layer from ventral to dorsal, displaying the same progression and spatial distribution as the mineralization process. No ALP activity was observed in sclerotomal mesenchyme surrounding the notochordal sheath during initial formation of the chordacentra. Our results support previous findings indicating that the chordoblasts initiate a segmental differentiation of the notochordal sheath into chordacentra and intervertebral regions.

Magnetic field generation in core-sheath jets via the kinetic Kelvin-Helmholtz instability

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

Nishikawa, K.-I.; Hardee, P. E.; Duţan, I.

2014-09-20

We have investigated magnetic field generation in velocity shears via the kinetic Kelvin-Helmholtz instability (kKHI) using a relativistic plasma jet core and stationary plasma sheath. Our three-dimensional particle-in-cell simulations consider plasma jet cores with Lorentz factors of 1.5, 5, and 15 for both electron-proton and electron-positron plasmas. For electron-proton plasmas, we find generation of strong large-scale DC currents and magnetic fields that extend over the entire shear surface and reach thicknesses of a few tens of electron skin depths. For electron-positron plasmas, we find generation of alternating currents and magnetic fields. Jet and sheath plasmas are accelerated across the shearmore » surface in the strong magnetic fields generated by the kKHI. The mixing of jet and sheath plasmas generates a transverse structure similar to that produced by the Weibel instability.« less

Pulsed laser activated cell sorter (PLACS) for high-throughput fluorescent mammalian cell sorting

NASA Astrophysics Data System (ADS)

Chen, Yue; Wu, Ting-Hsiang; Chung, Aram; Kung, Yu-Chung; Teitell, Michael A.; Di Carlo, Dino; Chiou, Pei-Yu

2014-09-01

We present a Pulsed Laser Activated Cell Sorter (PLACS) realized by exciting laser induced cavitation bubbles in a PDMS microfluidic channel to create high speed liquid jets to deflect detected fluorescent samples for high speed sorting. Pulse laser triggered cavitation bubbles can expand in few microseconds and provide a pressure higher than tens of MPa for fluid perturbation near the focused spot. This ultrafast switching mechanism has a complete on-off cycle less than 20 μsec. Two approaches have been utilized to achieve 3D sample focusing in PLACS. One is relying on multilayer PDMS channels to provide 3D hydrodynamic sheath flows. It offers accurate timing control of fast (2 m sec-1) passing particles so that synchronization with laser bubble excitation is possible, an critically important factor for high purity and high throughput sorting. PLACS with 3D hydrodynamic focusing is capable of sorting at 11,000 cells/sec with >95% purity, and 45,000 cells/sec with 45% purity using a single channel in a single step. We have also demonstrated 3D focusing using inertial flows in PLACS. This sheathless focusing approach requires 10 times lower initial cell concentration than that in sheath-based focusing and avoids severe sample dilution from high volume sheath flows. Inertia PLACS is capable of sorting at 10,000 particles sec-1 with >90% sort purity.

Signal detection by active, noisy hair bundles

NASA Astrophysics Data System (ADS)

O'Maoiléidigh, Dáibhid; Salvi, Joshua D.; Hudspeth, A. J.

2018-05-01

Vertebrate ears employ hair bundles to transduce mechanical movements into electrical signals, but their performance is limited by noise. Hair bundles are substantially more sensitive to periodic stimulation when they are mechanically active, however, than when they are passive. We developed a model of active hair-bundle mechanics that predicts the conditions under which a bundle is most sensitive to periodic stimulation. The model relies only on the existence of mechanotransduction channels and an active adaptation mechanism that recloses the channels. For a frequency-detuned stimulus, a noisy hair bundle's phase-locked response and degree of entrainment as well as its detection bandwidth are maximized when the bundle exhibits low-amplitude spontaneous oscillations. The phase-locked response and entrainment of a bundle are predicted to peak as functions of the noise level. We confirmed several of these predictions experimentally by periodically forcing hair bundles held near the onset of self-oscillation. A hair bundle's active process amplifies the stimulus preferentially over the noise, allowing the bundle to detect periodic forces less than 1 pN in amplitude. Moreover, the addition of noise can improve a bundle's ability to detect the stimulus. Although, mechanical activity has not yet been observed in mammalian hair bundles, a related model predicts that active but quiescent bundles can oscillate spontaneously when they are loaded by a sufficiently massive object such as the tectorial membrane. Overall, this work indicates that auditory systems rely on active elements, composed of hair cells and their mechanical environment, that operate on the brink of self-oscillation.

Potential of boron neutron capture therapy (BNCT) for malignant peripheral nerve sheath tumors (MPNST).

PubMed

Fujimoto, Takuya; Andoh, Tooru; Sudo, Tamotsu; Fujita, Ikuo; Fukase, Naomasa; Takeuchi, Tamotsu; Sonobe, Hiroshi; Inoue, Masayoshi; Hirose, Tkanori; Sakuma, Toshiko; Moritake, Hiroshi; Sugimoto, Tohru; Kawamoto, Teruya; Fukumori, Yoshinobu; Yamamoto, Satomi; Atagi, Shinji; Sakurai, Yoshinori; Kurosaka, Masahiro; Ono, Koji; Ichikawa, Hideki; Suzuki, Minoru

2015-12-01

Malignant peripheral nerve sheath tumors (MPNST) are relatively rare neoplasms with poor prognosis. At present there is no effective treatment for MPNST other than surgical resection. Nonetheless, the anti-tumor effect of boron neutron capture therapy (BNCT) was recently demonstrated in two patients with MPNST. Subsequently, tumor-bearing nude mice subcutaneously transplanted with a human MPNST cell line were injected with p-borono-L-phenylalanine (L-BPA) and subjected to BNCT. Pathological studies then revealed that the MPNST cells were selectively destroyed by BNCT. Copyright © 2015 Elsevier Ltd. All rights reserved.

An operating principle of the turtle utricle to detect wide dynamic range.

PubMed

Nam, Jong-Hoon

2018-03-01

The utricle encodes both static information such as head orientation, and dynamic information such as vibrations. It is not well understood how the utricle can encode both static and dynamic information for a wide dynamic range (from <0.05 to >2 times the gravitational acceleration; from DC to > 1000 Hz vibrations). Using computational models of the hair cells in the turtle utricle, this study presents an explanation on how the turtle utricle encodes stimulations over such a wide dynamic range. Two hair bundles were modeled using the finite element method-one representing the striolar hair cell (Cell S), and the other representing the medial extrastriolar hair cell (Cell E). A mechano-transduction (MET) channel model was incorporated to compute MET current (i MET ) due to hair bundle deflection. A macro-mechanical model of the utricle was used to compute otoconial motions from head accelerations (a Head ). According to known anatomical data, Cell E has a long kinocilium that is embedded into the stiff otoconial layer. Unlike Cell E, the hair bundle of Cell S falls short of the otoconial layer. Considering such difference in the mechanical connectivity between the hair cell bundle and the otoconial layer, three cases were simulated: Cell E displacement-clamped, Cell S viscously-coupled, and Cell S displacement-clamped. Head accelerations at different amplitude levels and different frequencies were simulated for the three cases. When a realistic head motion was simulated, Cell E was responsive to head orientation, while the viscously-coupled Cell S was responsive to fast head motion imitating the feeding strike of a turtle. Copyright © 2017 Elsevier B.V. All rights reserved.

The acquisition of mechano-electrical transducer current adaptation in auditory hair cells requires myosin VI.

PubMed

Marcotti, Walter; Corns, Laura F; Goodyear, Richard J; Rzadzinska, Agnieszka K; Avraham, Karen B; Steel, Karen P; Richardson, Guy P; Kros, Corné J

2016-07-01

The transduction of sound into electrical signals occurs at the hair bundles atop sensory hair cells in the cochlea, by means of mechanosensitive ion channels, the mechano-electrical transducer (MET) channels. The MET currents decline during steady stimuli; this is termed adaptation and ensures they always work within the most sensitive part of their operating range, responding best to rapidly changing (sound) stimuli. In this study we used a mouse model (Snell's waltzer) for hereditary deafness in humans that has a mutation in the gene encoding an unconventional myosin, myosin VI, which is present in the hair bundles. We found that in the absence of myosin VI the MET current fails to acquire its characteristic adaptation as the hair bundles develop. We propose that myosin VI supports the acquisition of adaptation by removing key molecules from the hair bundle that serve a temporary, developmental role. Mutations in Myo6, the gene encoding the (F-actin) minus end-directed unconventional myosin, myosin VI, cause hereditary deafness in mice (Snell's waltzer) and humans. In the sensory hair cells of the cochlea, myosin VI is expressed in the cell bodies and along the stereocilia that project from the cells' apical surface. It is required for maintaining the structural integrity of the mechanosensitive hair bundles formed by the stereocilia. In this study we investigate whether myosin VI contributes to mechano-electrical transduction. We report that Ca(2+) -dependent adaptation of the mechano-electrical transducer (MET) current, which serves to keep the transduction apparatus operating within its most sensitive range, is absent in outer and inner hair cells from homozygous Snell's waltzer mutant mice, which fail to express myosin VI. The operating range of the MET channels is also abnormal in the mutants, resulting in the absence of a resting MET current. We found that cadherin 23, a component of the hair bundle's transient lateral links, fails to be downregulated along the length of the stereocilia in maturing Myo6 mutant mice. MET currents of heterozygous littermates appear normal. We propose that myosin VI, by removing key molecules from developing hair bundles, is required for the development of the MET apparatus and its Ca(2+) -dependent adaptation. © 2016 The Authors. The Journal of Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society.

Magnetic Bead Actuation of Saccular Hair Cells

NASA Astrophysics Data System (ADS)

Rowland, David; Ramunno-Johnson, Damien; Lee, Jae-Hyun; Cheon, Jinwoo; Bozovic, Dolores

2011-11-01

When decoupled from the overlying membrane, hair bundles of the amphibian sacculus exhibit spontaneous oscillation. To explore the dynamics of this innate motility without an imposed external load, we recorded their oscillations with a high-speed CMOS camera, and applied mechanical manipulation that minimally alters the geometry of an individual hair bundle. We present a technique that utilizes micron-sized magnetic particles to actuate the stereociliary bundle with a magnetized probe. Quasi-steady-state displacements were imposed on freely oscillating bundles. Our data indicate that deflection of the bundle affects both the frequency and the amplitude of the oscillations, with a crossing of the bifurcation that is dependent on the direction and speed of the applied offset.

Thalamic reticular nucleus in Caiman crocodilus: Relationship with the dorsal thalamus.

PubMed

Pritz, M B

2016-05-13

The thalamic reticular nucleus was investigated in one group of crocodilians, Caiman crocodilus. This neuronal aggregate is composed of two parts: a compact portion and a diffuse region made up of scattered cells within the forebrain bundles. In Caiman, both the lateral and medial forebrain bundles project to the telencephalon and the thalamic reticular nucleus is associated with each fiber tract. In the lateral forebrain bundle, the compact area is termed the nucleus of the dorsal peduncle (dorsal peduncular nucleus) while the diffuse part is called the perireticular area. In the medial forebrain bundle, the interstitial nucleus comprises one part of the compact area while another region without a specific neuronal label is also present. Similar to the perireticular cells of the lateral forebrain bundle, scattered cells are also present in the medial forebrain bundle. Morphological features of the thalamic reticular nucleus are revealed with stains for the following: fibers; cells; succinic acid dehydrogenase; and acetylcholinesterase. Regardless of which dorsal thalamic nucleus was injected, a localized region of the thalamic reticular nucleus contained retrogradely labeled cells and anterogradely labeled axons and terminals. This grouping was termed clusters and was felt to represent the densest interconnection between the dorsal thalamus and the reticular nucleus. Using clusters as an index of interconnections, the reticular nucleus was divided into sectors, each of which was associated with a specific dorsal thalamic nucleus. An organization similar to that found in Caiman is present in other sauropsids as well as in mammals. These data suggest that a thalamic reticular nucleus is present in all amniotes and has morphological properties similar to those described in this analysis. Lastly, a hypothesis is presented to explain how the external shape of the reticular nucleus in Caiman might be transformed into the homologous area in a representative bird and mammal. Copyright © 2016 IBRO. Published by Elsevier Ltd. All rights reserved.

Amino group in Leptothrix sheath skeleton is responsible for direct deposition of Fe(III) minerals onto the sheaths.

PubMed

Kunoh, Tatsuki; Matsumoto, Syuji; Nagaoka, Noriyuki; Kanashima, Shoko; Hino, Katsuhiko; Uchida, Tetsuya; Tamura, Katsunori; Kunoh, Hitoshi; Takada, Jun

2017-07-26

Leptothrix species produce microtubular organic-inorganic materials that encase the bacterial cells. The skeleton of an immature sheath, consisting of organic exopolymer fibrils of bacterial origin, is formed first, then the sheath becomes encrusted with inorganic material. Functional carboxyl groups of polysaccharides in these fibrils are considered to attract and bind metal cations, including Fe(III) and Fe(III)-mineral phases onto the fibrils, but the detailed mechanism remains elusive. Here we show that NH 2 of the amino-sugar-enriched exopolymer fibrils is involved in interactions with abiotically generated Fe(III) minerals. NH 2 -specific staining of L. cholodnii OUMS1 detected a terminal NH 2 on its sheath skeleton. Masking NH 2 with specific reagents abrogated deposition of Fe(III) minerals onto fibrils. Fe(III) minerals were adsorbed on chitosan and NH 2 -coated polystyrene beads but not on cellulose and beads coated with an acetamide group. X-ray photoelectron spectroscopy at the N1s edge revealed that the terminal NH 2 of OUMS1 sheaths, chitosan and NH 2 -coated beads binds to Fe(III)-mineral phases, indicating interaction between the Fe(III) minerals and terminal NH 2 . Thus, the terminal NH 2 in the exopolymer fibrils seems critical for Fe encrustation of Leptothrix sheaths. These insights should inform artificial synthesis of highly reactive NH 2 -rich polymers for use as absorbents, catalysts and so on.

Medical and Scientific Evaluations aboard the KC-135. Microgravity-Compatible Flow Cytometer

NASA Technical Reports Server (NTRS)

Crucian, Brian; Nelman-Gonzalez, Mayra; Sams, Clarence

2005-01-01

A spaceflight-compatible flow cytometer would be useful for the diagnosis of astronaut illness during long duration spaceflight and for conducting in-flight research to evaluate the effects of microgravity on human physiology. Until recently, the primary limitations preventing the development of a spaceflight compatible flow cytometer have been largely mechanical. Standard commercially available flow cytometers are large, complex instruments that use high-energy lasers and require significant training to operate. Standard flow cytometers function by suspending the particles to be analyzed inside a sheath fluid for analysis. This requires the presence of several liters of sheath fluid for operation, and generates a corresponding amount of liquid hazardous waste. The particles are then passed through a flow cell which uses the fluid mechanical property of hydrodynamic focusing to place the cells in single-file (laminar flow) as they pass through a laser beam for scanning and evaluation. Many spaceflight experiments have demonstrated that fluid physics is dramatically altered in microgravity (MSF [Manned Space Flight] Fluid Physics Data Sheet-August 1997) and previous studies have shown that sheath-fluid based hydrodynamic focusing may also be altered during microgravity (Crucian et al, 2000). For these reasons it is likely that any spaceflight compatible design for a flow cytometer would abandon the sheath fluid requirement. The elimination of sheath fluid would remove both the problems of weight associated with large volumes of liquids as well as the large volume of liquid waste generated. It would also create the need for a method to create laminar particle flow distinct from the standard sheath-fluid based method. The spaceflight prototype instrument is based on a recently developed commercial flow cytometer possessing a novel flow cell design that creates single-particle laser scanning and evaluation without the need for sheath-fluid based hydrodynamic focusing. This instrument also possesses a number of design advances that make it conditionally microgravity compatible: it is highly miniaturized and lightweight, uses a low energy diode laser, has a small number of moving parts, does not use sheath fluid and does not generate significant liquid waste. Although possessing certain limitations, the commercial cytometer functions operationally like a standard bench top laboratory flow cytometer, aspirating liquid particle samples and generating histogram or dot-plot data in standard FCS file format. In its current configuration however, the cytometer is limited to three parameter/two-color capability (two color PMTs + forward scatter), does not allow compensation between colors, does not allow linear analysis and is operated by rather inflexible software with limited capabilities. This is due to the fact that the cytometer has been designed and marketed as an instrument specific to a few particular assays, not as a multipurpose cytometer.

3-D Imaging Reveals Participation of Donor Islet Schwann Cells and Pericytes in Islet Transplantation and Graft Neurovascular Regeneration.

PubMed

Juang, Jyuhn-Huarng; Kuo, Chien-Hung; Peng, Shih-Jung; Tang, Shiue-Cheng

2015-02-01

The primary cells that participate in islet transplantation are the endocrine cells. However, in the islet microenvironment, the endocrine cells are closely associated with the neurovascular tissues consisting of the Schwann cells and pericytes, which form sheaths/barriers at the islet exterior and interior borders. The two cell types have shown their plasticity in islet injury, but their roles in transplantation remain unclear. In this research, we applied 3-dimensional neurovascular histology with cell tracing to reveal the participation of Schwann cells and pericytes in mouse islet transplantation. Longitudinal studies of the grafts under the kidney capsule identify that the donor Schwann cells and pericytes re-associate with the engrafted islets at the peri-graft and perivascular domains, respectively, indicating their adaptability in transplantation. Based on the morphological proximity and cellular reactivity, we propose that the new islet microenvironment should include the peri-graft Schwann cell sheath and perivascular pericytes as an integral part of the new tissue.

The structure of the conus arteriosus of the sturgeon (Acipenser naccarii) heart: II. The myocardium, the subepicardium, and the conus-aorta transition.

PubMed

Icardo, José M; Colvee, Elvira; Cerra, Maria C; Tota, Bruno

2002-12-01

Sturgeons constitute a family of living "fossil" fish whose heart is related to that of other ancient fish and the elasmobranches. We have undertaken a systematic study of the structure of the sturgeon heart aimed at unraveling the relationship between the heart structure and the adaptive evolutionary changes. In a related paper, data were presented on the conus valves and the subendocardium. Here, the structure of the conus myocardium, the subepicardial tissue, and the conus-aorta transition were studied by conventional light, transmission, and scanning electron microscopy. In addition, actin localization by fluorescent phalloidin was used. The conus myocardium is organized into bundles whose spatial organization changes along the conus length. The variable orientation of the myocardial cell bundles may be effective in emptying the conus lumen during contraction and in preventing reflux of blood. Myocardial cell bundles are separated by loose connective tissue that contains collagen and elastin fibers, vessels, and extremely flat cells separating the cell bundles and enclosing blood vessels and collagen fibers. The ultrastructure of the myocardial cells was found to be very similar to that of other fish groups, suggesting that it is largely conservative. The subepicardium is characterized by the presence of nodular structures that contain lympho-hemopoietic (thymus-like) tissue in the young sturgeons and a large number of lymphocytes after the sturgeons reach sexual maturity. This tissue is likely implicated in the establishment and maintenance of the immune responses. The intrapericardial ventral aorta shows a middle layer of circumferentially oriented cells and internal and external layers with cells oriented longitudinally. Elastin fibers completely surround each smooth muscle cell, and the spaces between the different layers are occupied by randomly arranged collagen bundles. The intrapericardial segment of the ventral aorta is a true transitional segment whose structural characteristics are different from those of both the conus subendocardium and the rest of the ventral aorta. Copyright 2002 Wiley-Liss, Inc.

3D pulsed laser-triggered high-speed microfluidic fluorescence-activated cell sorter

PubMed Central

Chen, Yue; Wu, Ting-Hsiang; Kung, Yu-Chun; Teitell, Michael A.; Chiou, Pei-Yu

2014-01-01

We report a 3D microfluidic pulsed laser-triggered fluorescence-activated cell sorter capable of sorting at a throughput of 23,000 cells sec−1 with 90% purity in high-purity mode and at a throughput of 45,000 cells sec−1 with 45% purity in enrichment mode in one stage and in a single channel. This performance is realized by exciting laser-induced cavitation bubbles in a 3D PDMS microfluidic channel to generate high-speed liquid jets that deflect detected fluorescent cells and particles focused by 3D sheath flows. The ultrafast switching mechanism (20 μsec complete on-off cycle), small liquid jet perturbation volume, and three-dimensional sheath flow focusing for accurate timing control of fast (1.5 m sec−1) passing cells and particles are three critical factors enabling high-purity sorting at high-throughput in this sorter. PMID:23844418

Insulin-induced upregulation of lipoprotein lipase in Schwann cells during diabetic peripheral neuropathy.

PubMed

Rachana, Kuruvanthe S; Manu, Mallahalli S; Advirao, Gopal M

2018-03-17

Diabetic peripheral neuropathy (DPN) is one of the major complications associated with diabetes. It is characterized by the degeneration of the myelin sheath around axons, referred to as demyelination. Such demyelinations are often caused by reduced lipid component of the myelin sheath. Since, lipoprotein lipase (LPL) provides the lipid for myelin sheath by hydrolysing the triglyceride rich lipoproteins, and also helps in the uptake of lipids by the Schwann cells (SCs) for its utilization, LPL is considered as the important factor in the regeneration of myelin sheath during diabetic neuropathy. Earlier reports from our laboratory have provided the insights of insulin and its receptor in SCs during diabetic neuropathy. In order to evaluate the long term effect of insulin on lipid metabolism during diabetic neuropathy, in this study, we analyzed the expression of LPL in SCs under normal, high glucose and insulin treated conditions. A decrease in the expression of LPL was observed in SCs of high glucose condition and it was reversed upon insulin treatment. Histochemical observations of sciatic nerve of insulin treated neuropathy subjects showed the improved nerve morphology, signifying the importance of insulin in restoring the pathophysiology of diabetic neuropathy. Copyright © 2018 Diabetes India. Published by Elsevier Ltd. All rights reserved.

The plasma-wall transition layers in the presence of collisions with a magnetic field parallel to the wall

NASA Astrophysics Data System (ADS)

Moritz, J.; Faudot, E.; Devaux, S.; Heuraux, S.

2018-01-01

The plasma-wall transition is studied by means of a particle-in-cell (PIC) simulation in the configuration of a parallel to the wall magnetic field (B), with collisions between charged particles vs. neutral atoms taken into account. The investigated system consists of a plasma bounded by two absorbing walls separated by 200 electron Debye lengths (λd). The strength of the magnetic field is chosen such as the ratio λ d / r l , with rl being the electron Larmor radius, is smaller or larger than unity. Collisions are modelled with a simple operator that reorients randomly ion or electron velocity, keeping constant the total kinetic energy of both the neutral atom (target) and the incident charged particle. The PIC simulations show that the plasma-wall transition consists in a quasi-neutral region (pre-sheath), from the center of the plasma towards the walls, where the electric potential or electric field profiles are well described by an ambipolar diffusion model, and in a second region at the vicinity of the walls, called the sheath, where the quasi-neutrality breaks down. In this peculiar geometry of B and for a certain range of the mean-free-path, the sheath is found to be composed of two charged layers: the positive one, close to the walls, and the negative one, towards the plasma and before the neutral pre-sheath. Depending on the amplitude of B, the spatial variation of the electric potential can be non-monotonic and presents a maximum within the sheath region. More generally, the sheath extent as well as the potential drop within the sheath and the pre-sheath is studied with respect to B, the mean-free-path, and the ion and electron temperatures.

Tin-oxide-coated single-walled carbon nanotube bundles supporting platinum electrocatalysts for direct ethanol fuel cells.

PubMed

Hsu, Ryan S; Higgins, Drew; Chen, Zhongwei

2010-04-23

Novel tin-oxide (SnO(2))-coated single-walled carbon nanotube (SWNT) bundles supporting platinum (Pt) electrocatalysts for ethanol oxidation were developed for direct ethanol fuel cells. SnO(2)-coated SWNT (SnO(2)-SWNT) bundles were synthesized by a simple chemical-solution route. SnO(2)-SWNT bundles supporting Pt (Pt/SnO(2)-SWNTs) electrocatalysts and SWNT-supported Pt (Pt/SWNT) electrocatalysts were prepared by an ethylene glycol reduction method. The catalysts were physically characterized using TGA, XRD and TEM and electrochemically evaluated through cyclic voltammetry experiments. The Pt/SnO(2)-SWNTs showed greatly enhanced electrocatalytic activity for ethanol oxidation in acid medium, compared to the Pt/SWNT. The optimal SnO(2) loading of Pt/SnO(2)-SWNT catalysts with respect to specific catalytic activity for ethanol oxidation was also investigated.

Conditional ablation of osteoblasts in medaka.

PubMed

Willems, Bernd; Büttner, Anita; Huysseune, Ann; Renn, Joerg; Witten, P Eckhard; Winkler, Christoph

2012-04-15

Different from tetrapods, teleost vertebral centra form without prior establishment of a cartilaginous scaffold, in two steps: First, mineralization of the notochord sheath establishes the vertebral centra. Second, sclerotome derived mesenchymal cells migrate around the notochord sheath. These cells differentiate into osteoblasts and deposit bone onto the mineralized notochord sheath in a process of intramembranous bone formation. In contrast, most skeletal elements of the cranial skeleton arise by chondral bone formation, with remarkably similar mechanisms in fish and tetrapods. To further investigate the role of osteoblasts during formation of the cranial and axial skeleton, we generated a transgenic osx:CFP-NTR medaka line which enables conditional ablation of osterix expressing osteoblasts. By expressing a bacterial nitroreductase (NTR) fused to Cyan Fluorescent Protein (CFP) under control of the osterix promoter these cells become sensitive towards Metronidazole (Mtz). Mtz treatment of stable osx:CFP-NTR transgenic medaka for several consecutive days led to significant loss of osteoblasts by apoptosis. Live staining of mineralized bone matrix revealed reduced ossification in head skeletal elements such as cleithrum and operculum, as well as in the vertebral arches. Interestingly in Mtz treated larvae, intervertebral spaces were missing and the notochord sheath was often continuously mineralized resulting in the fusion of centra. We therefore propose a dual role for osx-positive osteoblasts in fish. Besides a role in bone deposition, we suggest an additional border function during mineralization of the chordal centra. After termination of Mtz treatment, osteoblasts gradually reappeared, indicating regenerative properties in this cell lineage. Taken together, the osx:CFP-NTR medaka line represents a valuable tool to study osteoblast function and regeneration at different stages of development in whole vertebrate specimens in vivo. Copyright © 2012 Elsevier Inc. All rights reserved.

From Biological Cilia to Artificial Flow Sensors: Biomimetic Soft Polymer Nanosensors with High Sensing Performance

PubMed Central

Asadnia, Mohsen; Kottapalli, Ajay Giri Prakash; Karavitaki, K. Domenica; Warkiani, Majid Ebrahimi; Miao, Jianmin; Corey, David P.; Triantafyllou, Michael

2016-01-01

We report the development of a new class of miniature all-polymer flow sensors that closely mimic the intricate morphology of the mechanosensory ciliary bundles in biological hair cells. An artificial ciliary bundle is achieved by fabricating bundled polydimethylsiloxane (PDMS) micro-pillars with graded heights and electrospinning polyvinylidenefluoride (PVDF) piezoelectric nanofiber tip links. The piezoelectric nature of a single nanofiber tip link is confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Rheology and nanoindentation experiments are used to ensure that the viscous properties of the hyaluronic acid (HA)-based hydrogel are close to the biological cupula. A dome-shaped HA hydrogel cupula that encapsulates the artificial hair cell bundle is formed through precision drop-casting and swelling processes. Fluid drag force actuates the hydrogel cupula and deflects the micro-pillar bundle, stretching the nanofibers and generating electric charges. Functioning with principles analogous to the hair bundles, the sensors achieve a sensitivity and threshold detection limit of 300 mV/(m/s) and 8 μm/s, respectively. These self-powered, sensitive, flexible, biocompatibale and miniaturized sensors can find extensive applications in navigation and maneuvering of underwater robots, artificial hearing systems, biomedical and microfluidic devices. PMID:27622466

Particle-in-cell simulation of an electronegative plasma under direct current bias studied in a large range of electronegativity

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

Oudini, N.; Laboratoire des plasmas de Decharges, Centre de Developement des Technologies Avancees, Cite du 20 Aout BP 17 Baba Hassen, 16081 Algiers; Raimbault, J.-L.

2013-04-15

A one-dimensional electronegative plasma situated between two symmetrical parallel electrodes under DC bias is studied by Particle-In-Cell simulation with Monte Carlo Collisions. By varying the electronegativity {alpha}{identical_to}n{sub -}/n{sub e} from the limit of electron-ion plasmas (negative ion free) to ion-ion plasmas (electron free), the sheaths formation, the negative ion flux flowing towards the electrodes, and the particle velocities at the sheath edges are investigated. Depending on {alpha}, it is shown that the electronegative plasma behavior can be described by four regimes. In the lowest regime of {alpha}, i.e., {alpha} < 50, negative ions are confined by two positive sheaths withinmore » the plasma, while in the higher regimes of {alpha}, a negative sheath is formed and the negative ion flux can be extracted from the bulk plasma. In the two intermediate regimes of {alpha}, i.e., 50 < {alpha} < 10{sup 5}, both the electron and the negative ion fluxes are involved in the neutralization of the positive ions flux that leaves the plasma. In particular, we show that the velocity of the negative ions entering the negative sheath is affected by the presence of the electrons, and is not given by the modified Bohm velocity generally accepted for electronegative plasmas. For extremely high electronegativity, i.e., {alpha} > 10{sup 5}, the presence of electrons in the plasma is marginal and the electronegative plasma can be considered as an ion-ion plasma (electron free).« less

Invited Lectures from a Spatial Orientation Symposium in Honor of Frederick Guedry, Day 1

DTIC Science & Technology

2014-01-01

111  Computational Fluid Dynamics Model of Endolymph Flow around Hair Cell Bundle ̶ Wallace Grant...Wallace Grant: Computational Fluid Dynamics Model of Endolymph Flow around Hair Cell Bundle  Ian Curthoys: Update from Sydney  Discussion Tactile...usefulness of preserving free- flowing scholarly discussion. It is in the spirit of those fascinating early discussions among vestibular researchers1

Segmentation of the zebrafish axial skeleton relies on notochord sheath cells and not on the segmentation clock.

PubMed

Lleras Forero, Laura; Narayanan, Rachna; Huitema, Leonie Fa; VanBergen, Maaike; Apschner, Alexander; Peterson-Maduro, Josi; Logister, Ive; Valentin, Guillaume; Morelli, Luis G; Oates, Andrew C; Schulte-Merker, Stefan

2018-04-06

Segmentation of the axial skeleton in amniotes depends on the segmentation clock, which patterns the paraxial mesoderm and the sclerotome. While the segmentation clock clearly operates in teleosts, the role of the sclerotome in establishing the axial skeleton is unclear. We severely disrupt zebrafish paraxial segmentation, yet observe a largely normal segmentation process of the chordacentra. We demonstrate that axial entpd5+ notochord sheath cells are responsible for chordacentrum mineralization, and serve as a marker for axial segmentation. While autonomous within the notochord sheath, entpd5 expression and centrum formation show some plasticity and can respond to myotome pattern. These observations reveal for the first time the dynamics of notochord segmentation in a teleost, and are consistent with an autonomous patterning mechanism that is influenced, but not determined by adjacent paraxial mesoderm. This behavior is not consistent with a clock-type mechanism in the notochord. © 2018, Lleras Forero et al.

Two-dimensional particle-in-cell plasma source ion implantation of a prolate spheroid target

NASA Astrophysics Data System (ADS)

Liu, Cheng-Sen; Han, Hong-Ying; Peng, Xiao-Qing; Chang, Ye; Wang, De-Zhen

2010-03-01

A two-dimensional particle-in-cell simulation is used to study the time-dependent evolution of the sheath surrounding a prolate spheroid target during a high voltage pulse in plasma source ion implantation. Our study shows that the potential contour lines pack more closely in the plasma sheath near the vertex of the major axis, i.e. where a thinner sheath is formed, and a non-uniform total ion dose distribution is incident along the surface of the prolate spheroid target due to the focusing of ions by the potential structure. Ion focusing takes place not only at the vertex of the major axis, where dense potential contour lines exist, but also at the vertex of the minor axis, where sparse contour lines exist. This results in two peaks of the received ion dose, locating at the vertices of the major and minor axes of the prolate spheroid target, and an ion dose valley, staying always between the vertices, rather than at the vertex of the minor axis.

Intercellular Distribution of Glutathione Synthesis in Maize Leaves and Its Response to Short-Term Chilling1

PubMed Central

Gómez, Leonardo D.; Vanacker, Hélène; Buchner, Peter; Noctor, Graham; Foyer, Christine H.

2004-01-01

To investigate the intercellular control of glutathione synthesis and its influence on leaf redox state in response to short-term chilling, genes encoding γ-glutamylcysteine synthetase (γ-ECS) and glutathione synthetase (GSH-S) were cloned from maize (Zea mays) and specific antibodies produced. These tools were used to provide the first information on the intercellular distribution of γ-ECS and GSH-S transcript and protein in maize leaves, in both optimal conditions and chilling stress. A 2-d exposure to low growth temperatures (chill) had no effect on leaf phenotype, whereas return to optimal temperatures (recovery) caused extensive leaf bleaching. The chill did not affect total leaf GSH-S transcripts but strongly induced γ-ECS mRNA, an effect reversed during recovery. The chilling-induced increase in γ-ECS transcripts was not accompanied by enhanced total leaf γ-ECS protein or extractable activity. In situ hybridization and immunolocalization of leaf sections showed that γ-ECS and GSH-S transcripts and proteins were found in both the bundle sheath (BS) and the mesophyll cells under optimal conditions. Chilling increased γ-ECS transcript and protein in the BS but not in the mesophyll cells. Increased BS γ-ECS was correlated with a 2-fold increase in both leaf Cys and γ-glutamylcysteine, but leaf total glutathione significantly increased only in the recovery period, when the reduced glutathione to glutathione disulfide ratio decreased 3-fold. Thus, while there was a specific increase in the potential contribution of the BS cells to glutathione synthesis during chilling, it did not result in enhanced leaf glutathione accumulation at low temperatures. Return to optimal temperatures allowed glutathione to increase, particularly glutathione disulfide, and this was associated with leaf chlorosis. PMID:15047902

Stress response and tolerance of Zea mays to CeO2 nanoparticles: cross talk among H2O2, heat shock protein, and lipid peroxidation.

PubMed

Zhao, Lijuan; Peng, Bo; Hernandez-Viezcas, Jose A; Rico, Cyren; Sun, Youping; Peralta-Videa, Jose R; Tang, Xiaolei; Niu, Genhua; Jin, Lixin; Varela-Ramirez, Armando; Zhang, Jian-ying; Gardea-Torresdey, Jorge L

2012-11-27

The rapid development of nanotechnology will inevitably release nanoparticles (NPs) into the environment with unidentified consequences. In addition, the potential toxicity of CeO(2) NPs to plants and the possible transfer into the food chain are still unknown. Corn plants (Zea mays) were germinated and grown in soil treated with CeO(2) NPs at 400 or 800 mg/kg. Stress-related parameters, such as H(2)O(2), catalase (CAT), and ascorbate peroxidase (APX) activity, heat shock protein 70 (HSP70), lipid peroxidation, cell death, and leaf gas exchange were analyzed at 10, 15, and 20 days post-germination. Confocal laser scanning microscopy was used to image H(2)O(2) distribution in corn leaves. Results showed that the CeO(2) NP treatments increased accumulation of H(2)O(2), up to day 15, in phloem, xylem, bundle sheath cells and epidermal cells of shoots. The CAT and APX activities were also increased in the corn shoot, concomitant with the H(2)O(2) levels. Both 400 and 800 mg/kg CeO(2) NPs triggered the up-regulation of the HSP70 in roots, indicating a systemic stress response. None of the CeO(2) NPs increased the level of thiobarbituric acid reacting substances, indicating that no lipid peroxidation occurred. CeO(2) NPs, at both concentrations, did not induce ion leakage in either roots or shoots, suggesting that membrane integrity was not compromised. Leaf net photosynthetic rate, transpiration, and stomatal conductance were not affected by CeO(2) NPs. Our results suggest that the CAT, APX, and HSP70 might help the plants defend against CeO(2) NP-induced oxidative injury and survive NP exposure.

Stress Response and Tolerance of Zea mays to CeO2 Nanoparticles: Cross Talk among H2O2, Heat Shock Protein and Lipid Peroxidation

PubMed Central

Zhao, Lijuan; Peng, Bo; Hernandez-Viezcas, Jose A.; Rico, Cyren; Sun, Youping; Peralta-Videa, Jose R.; Tang, Xiaolei; Niu, Genhua; Jin, Lixin; Varela-Ramirez, Armando; Zhang, Jian-ying; Gardea-Torresdey, Jorge L.

2014-01-01

The rapid development of nanotechnology will inevitably release nanoparticles (NPs) into the environment with unidentified consequences. In addition, the potential toxicity of CeO2 NPs to plants, and the possible transfer into the food chain, are still unknown. Corn plants (Zea mays) were germinated and grown in soil treated with CeO2 NPs at 400 or 800 mg/kg. Stress related parameters, such as: H2O2, catalase (CAT) and ascorbate peroxidase (APX) activity, heat shock protein 70 (HSP 70), lipid peroxidation, cell death and leaf gas exchange were analyzed at 10, 15, and 20 days post germination. Confocal laser scanning microscopy was used to image H2O2 distribution in corn leaves. Results showed that the CeO2 NP treatments increased accumulation of H2O2, up to day 15, in phloem, xylem, bundle sheath cells, and epidermal cells of shoots. The CAT and APX activities were also increased in the corn shoot, concomitant with the H2O2 levels. Both 400 and 800 mg/kg CeO2 NPs triggered the up regulation of the HSP 70 in roots, indicating a systemic stress response. None of the CeO2 NPs increased the level of thiobarbituric acid reacting substances, indicating that no lipid peroxidation occurred. CeO2 NPs, at both concentrations, did not induce ion leakage in either roots or shoots, suggesting membrane integrity was not compromised. Leaf net photosynthetic rate, transpiration, and stomatal conductance were not affected by CeO2 NPs. Our results suggest that the CAT, APX and HSP 70 might help the plants defend against CeO2 NPs induced oxidative injury and survive NP exposure. PMID:23050848

The effects of rearing light level and duration differences on the optic nerve, brain, and associated structures in developing zebrafish larvae: a light and transmission electron microscope study.

PubMed

Chapman, George B; Tarboush, Rania; Connaughton, Victoria P

2012-03-01

The ultrastructure of the optic nerve, brain, and some associated structures of larval zebrafish, grown under three different light regimens were studied. Fish grown under cyclic light (control), constant dark (CD), and constant light (CL) were studied for 4 and 8 days postfertilization (dpf). We also studied the control and CD fish at 15 dpf. The brains of the control and CL fish were larger at 4 dpf than at 8 dpf. In all 4 dpf fish, the brain occupied the entire expanse between the two retinas and the optic nerve extended the shortest distance between the retina and the brain. The 15 dpf zebrafish had the smallest brain size. Groups of skeletal muscle cells associated with the optic nerves became visible in all older larvae. In the 15 dpf larvae, bulges and dilations in the optic nerve occurred as it reached the brain and optic chiasms occurred proximal to the brain. Electron microscopy yielded information about myelinated and unmyelinated axons in the optic nerve, the dimensions of neurotubules, neurofilaments, and myofilaments, including a unique variation in actin myofilaments, and a confirmation of reported myosin myofilament changes (but with dimensions). We also describe the ultrastructure of a sheath-like structure that is confluent over the optic nerve and the brain, which has not been described before in zebrafish. Also presented are images of associated fibroblasts, epithelial cells lining the mouth, cartilage plates, blood vessels, nerve bundles, and skeletal muscle cells, most of which have not been previously described in the literature. Copyright © 2012 Wiley Periodicals, Inc.

The Brassicaceae species Heliophila coronopifolia produces root border-like cells that protect the root tip and secrete defensin peptides.

PubMed

Weiller, Florent; Moore, John P; Young, Philip; Driouich, Azeddine; Vivier, Melané A

2017-03-01

Root border cells and border-like cells (BLCs), the latter originally described in Arabidopsis thaliana , have been described as cells released at the root tips of the species in which they occur. BLCs are thought to provide protection to root meristems similar to classical root border cells. In addition, four defensin peptides (Hc-AFP1-4) have previously been characterized from Heliophila coronopifolia , a South African semi-desert flower, and found to be strongly antifungal. This provided an opportunity to evaluate if the BLCs of H. coronopifolia indeed produce these defensins, which would provide evidence towards a defence role for BLCs. Fluorescence microscopy, using live-cell-imaging technology, was used to characterize the BLCs of H. coronopifolia . Quantitative real-time PCR (qRT-PCR) analysis and immunofluorescence microscopy was used to characterize these defensin peptides. BLCs originated at the root apical meristem and formed a protective sheath at the tip and along the sides as the root elongated in solid medium. BLCs have a cellulose-enriched cell wall, intact nuclei and are embedded in a layer of pectin-rich mucilage. Pectinase treatments led to the dissolution of the sheath and dissociation of the root BLCs. Hc-AFP1-4 genes were all expressed in root tissues, but Hc-AFP3 transcripts were the most abundant in these tissues as measured by qRT-PCR. A polyclonal antibody that was cross-reactive with all four defensins, and probably recognizing a general plant defensin epitope, was used in fluorescence microscopy analysis to examine the presence of the peptides in the root tip and BLCs. Data confirmed the peptides present in the root tip tissues, the mucilage sheath and the BLCs. This study provides a link between defensin peptides and BLCs, both embedded in a protective pectin mucilage sheath, during normal plant growth and development. The presence of the Hc-AFP3 defensin peptides in the BLCs suggests a role for these cells in root protection. © The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com

The Brassicaceae species Heliophila coronopifolia produces root border-like cells that protect the root tip and secrete defensin peptides

PubMed Central

Weiller, Florent; Young, Philip; Driouich, Azeddine; Vivier, Melané A.

2017-01-01

Background and Aims Root border cells and border-like cells (BLCs), the latter originally described in Arabidopsis thaliana, have been described as cells released at the root tips of the species in which they occur. BLCs are thought to provide protection to root meristems similar to classical root border cells. In addition, four defensin peptides (Hc-AFP1–4) have previously been characterized from Heliophila coronopifolia, a South African semi-desert flower, and found to be strongly antifungal. This provided an opportunity to evaluate if the BLCs of H. coronopifolia indeed produce these defensins, which would provide evidence towards a defence role for BLCs. Methods Fluorescence microscopy, using live-cell-imaging technology, was used to characterize the BLCs of H. coronopifolia. Quantitative real-time PCR (qRT-PCR) analysis and immunofluorescence microscopy was used to characterize these defensin peptides. Key Results BLCs originated at the root apical meristem and formed a protective sheath at the tip and along the sides as the root elongated in solid medium. BLCs have a cellulose-enriched cell wall, intact nuclei and are embedded in a layer of pectin-rich mucilage. Pectinase treatments led to the dissolution of the sheath and dissociation of the root BLCs. Hc-AFP1–4 genes were all expressed in root tissues, but Hc-AFP3 transcripts were the most abundant in these tissues as measured by qRT-PCR. A polyclonal antibody that was cross-reactive with all four defensins, and probably recognizing a general plant defensin epitope, was used in fluorescence microscopy analysis to examine the presence of the peptides in the root tip and BLCs. Data confirmed the peptides present in the root tip tissues, the mucilage sheath and the BLCs. Conclusions This study provides a link between defensin peptides and BLCs, both embedded in a protective pectin mucilage sheath, during normal plant growth and development. The presence of the Hc-AFP3 defensin peptides in the BLCs suggests a role for these cells in root protection. PMID:27481828

Temporal Evolution of the Plasma Sheath Surrounding Solar Cells in Low Earth Orbit

NASA Technical Reports Server (NTRS)

Willis, Emily M.; Pour, Maria Z. A.

2017-01-01

High voltage solar array interactions with the space environment can have a significant impact on array performance and spacecraft charging. Over the past 10 years, data from the International Space Station has allowed for detailed observations of these interactions over long periods of time. Some of the surprising observations have been floating potential transients, which were not expected and are not reproduced by existing models. In order to understand the underlying processes producing these transients, the temporal evolution of the plasma sheath surrounding the solar cells in low Earth orbit is being investigated. This study includes lumped element modeling and particle-in-cell simulation methods. This presentation will focus on recent results from the on-going investigations.

Characterization of midrib vascular bundles of selected medicinal species in Rubiaceae

NASA Astrophysics Data System (ADS)

Nurul-Syahirah, M.; Noraini, T.; Latiff, A.

2016-11-01

An anatomical study was carried out on mature leaves of five selected medicinal species of Rubiaceae from Peninsular Malaysia. The chosen medicinal species were Aidia densiflora, Aidia racemosa, Chasallia chartacea, Hedyotis auricularia and Ixora grandifolia. The objective of this study is to determine the taxonomic value of midrib anatomical characteristics. Leaves samples were collected from Taman Paku Pakis, Universiti Kebangsaan Malaysia, Bangi, Selangor and Kledang Saiong Forest Reserve, Perak, Malaysia. Leaves samples then were fixed in spirit and acetic acid (3:1), the midrib parts then were sectioned using sliding microtome, cleared using Clorox, stained in Safranin and Alcian blue, mounted in Euparal and were observed under light microscope. Findings in this study have shown all species have collateral bundles. The midrib vascular bundles characteristics that can be used as tool to differentiate between species or genus are vascular bundles system (opened or closed), shape and arrangement of main vascular bundles, presence of both additional and medullary vascular bundles, position of additional vascular bundles, shape of medullary vascular bundles, presence of sclerenchyma cells ensheathed the vascular bundles. As a conclusion, midrib anatomical characteristics can be used to identify and discriminate medicinal plants species studied in the Rubiaceae.

Direct visualization of membrane architecture of myelinating cells in transgenic mice expressing membrane-anchored EGFP.

PubMed

Deng, Yaqi; Kim, BongWoo; He, Xuelian; Kim, Sunja; Lu, Changqing; Wang, Haibo; Cho, Ssang-Goo; Hou, Yiping; Li, Jianrong; Zhao, Xianghui; Lu, Q Richard

2014-04-01

Myelinogenesis is a complex process that involves substantial and dynamic changes in plasma membrane architecture and myelin interaction with axons. Highly ramified processes of oligodendrocytes in the central nervous system (CNS) make axonal contact and then extrapolate to wrap around axons and form multilayer compact myelin sheathes. Currently, the mechanisms governing myelin sheath assembly and axon selection by myelinating cells are not fully understood. Here, we generated a transgenic mouse line expressing the membrane-anchored green fluorescent protein (mEGFP) in myelinating cells, which allow live imaging of details of myelinogenesis and cellular behaviors in the nervous systems. mEGFP expression is driven by the promoter of 2'-3'-cyclic nucleotide 3'-phosphodiesterase (CNP) that is expressed in the myelinating cell lineage. Robust mEGFP signals appear in the membrane processes of oligodendrocytes in the CNS and Schwann cells in the peripheral nervous system (PNS), wherein mEGFP expression defines the inner layers of myelin sheaths and Schmidt-Lanterman incisures in adult sciatic nerves. In addition, mEGFP expression can be used to track the extent of remyelination after demyelinating injury in a toxin-induced demyelination animal model. Taken together, the membrane-anchored mEGFP expression in the new transgenic line would facilitate direct visualization of dynamic myelin membrane formation and assembly during development and process remodeling during remyelination after various demyelinating injuries.

The role of a Sertoli cell actin-myosin system in sperm bundle formation in the ratfish, Hydrolagus colliei (Chondrichthyes, Holocephali).

PubMed

Stanley, H P; Lambert, C C

1985-11-01

Sertoli cells in the ratfish entirely surround a clone of spermatids to form a spermatocyst. As spermiogenesis proceeds within the cyst cavity, the acrosome areas become apposed to the Sertoli cell plasma membrane lining the spermatocyst. The spermatids elongate and are gathered into an increasingly compact bundle oriented with acrosomal tips directed toward the Sertoli cell base. As all acrosome areas move closer together, Sertoli cell microfilaments oriented parallel to the long spermatid axis appear and increase in concentration. Actin and myosin were demonstrated in the microfilament area with fluorescent antibodies and NBD-Phallacidin. Simultaneously, endocytosis of Sertoli cell membrane between spermatid attachment sites removes the intervening membrane and allows the latter sites to approach each other. Sertoli cell endocytosis is spatially and temporally related to a unique projection at the basal rim of each acrosome. During midspermiogenesis, structured intercellular material appears between the Sertoli cell and the acrosomal region of each spermatid. Its periodicity is closely related to periodic arrangement of Sertoli cell actin and material within the spermatids. These attachment sites move together upon endocytosis, gathering a clone of spermatids into a closely packed bundle.

Size effects of single-walled carbon nanotubes on in vivo and in vitro pulmonary toxicity

PubMed Central

Fujita, Katsuhide; Fukuda, Makiko; Endoh, Shigehisa; Maru, Junko; Kato, Haruhisa; Nakamura, Ayako; Shinohara, Naohide; Uchino, Kanako; Honda, Kazumasa

2015-01-01

Abstract To elucidate the effect of size on the pulmonary toxicity of single-wall carbon nanotubes (SWCNTs), we prepared two types of dispersed SWCNTs, namely relatively thin bundles with short linear shapes (CNT-1) and thick bundles with long linear shapes (CNT-2), and conducted rat intratracheal instillation tests and in vitro cell-based assays using NR8383 rat alveolar macrophages. Total protein levels, MIP-1α expression, cell counts in BALF, and histopathological examinations revealed that CNT-1 caused pulmonary inflammation and slower recovery and that CNT-2 elicited acute lung inflammation shortly after their instillation. Comprehensive gene expression analysis confirmed that CNT-1-induced genes were strongly associated with inflammatory responses, cell proliferation, and immune system processes at 7 or 30 d post-instillation. Numerous genes were significantly upregulated or downregulated by CNT-2 at 1 d post-instillation. In vitro assays demonstrated that CNT-1 and CNT-2 SWCNTs were phagocytized by NR8383 cells. CNT-2 treatment induced cell growth inhibition, reactive oxygen species production, MIP-1α expression, and several genes involved in response to stimulus, whereas CNT-1 treatment did not exert a significant impact in these regards. These results suggest that SWCNTs formed as relatively thin bundles with short linear shapes elicited delayed pulmonary inflammation with slower recovery. In contrast, SWCNTs with a relatively thick bundle and long linear shapes sensitively induced cellular responses in alveolar macrophages and elicited acute lung inflammation shortly after inhalation. We conclude that the pulmonary toxicity of SWCNTs is closely associated with the size of the bundles. These physical parameters are useful for risk assessment and management of SWCNTs. PMID:25865113

ELMOD1 Stimulates ARF6-GTP Hydrolysis to Stabilize Apical Structures in Developing Vestibular Hair Cells.

PubMed

Krey, Jocelyn F; Dumont, Rachel A; Wilmarth, Philip A; David, Larry L; Johnson, Kenneth R; Barr-Gillespie, Peter G

2018-01-24

Sensory hair cells require control of physical properties of their apical plasma membranes for normal development and function. Members of the ADP-ribosylation factor (ARF) small GTPase family regulate membrane trafficking and cytoskeletal assembly in many cells. We identified ELMO domain-containing protein 1 (ELMOD1), a guanine nucleoside triphosphatase activating protein (GAP) for ARF6, as the most highly enriched ARF regulator in hair cells. To characterize ELMOD1 control of trafficking, we analyzed mice of both sexes from a strain lacking functional ELMOD1 [roundabout ( rda )]. In rda/rda mice, cuticular plates of utricle hair cells initially formed normally, then degenerated after postnatal day 5; large numbers of vesicles invaded the compromised cuticular plate. Hair bundles initially developed normally, but the cell's apical membrane lifted away from the cuticular plate, and stereocilia elongated and fused. Membrane trafficking in type I hair cells, measured by FM1-43 dye labeling, was altered in rda/rda mice. Consistent with the proposed GAP role for ELMOD1, the ARF6 GTP/GDP ratio was significantly elevated in rda/rda utricles compared with controls, and the level of ARF6-GTP was correlated with the severity of the rda/rda phenotype. These results suggest that conversion of ARF6 to its GDP-bound form is necessary for final stabilization of the hair bundle. SIGNIFICANCE STATEMENT Assembly of the mechanically sensitive hair bundle of sensory hair cells requires growth and reorganization of apical actin and membrane structures. Hair bundles and apical membranes in mice with mutations in the Elmod1 gene degenerate after formation, suggesting that the ELMOD1 protein stabilizes these structures. We show that ELMOD1 is a GTPase-activating protein in hair cells for the small GTP-binding protein ARF6, known to participate in actin assembly and membrane trafficking. We propose that conversion of ARF6 into the GDP-bound form in the apical domain of hair cells is essential for stabilizing apical actin structures like the hair bundle and ensuring that the apical membrane forms appropriately around the stereocilia. Copyright © 2018 the authors 0270-6474/18/380843-15$15.00/0.

Morphology of the bryozoan Cinctipora elegans (Cyclostomata, Cinctiporidae) with first data on its sexual reproduction and the cyclostome neuro-muscular system.

PubMed

Schwaha, Thomas F; Handschuh, Stephan; Ostrovsky, Andrew N; Wanninger, Andreas

2018-06-14

Cyclostome bryozoans are an ancient group of marine colonial suspension-feeders comprising approximately 700 extant species. Previous morphological studies are mainly restricted to skeletal characters whereas data on soft tissues obtained by state-of-the-art methods are still lacking. In order to contribute to issues related to cyclostome ground pattern reconstruction, we analyzed the morphology of the neuromuscular system Cinctipora elegans by means of immunocytochemical staining, confocal laser scanning microscopy, histological sections and microCT imaging. Polypides of C. elegans are located in elongated tubular skeletal cystids. Distally, the orifice leads into a prominent vestibulum which is lined by an epithelium that joins an almost complete perimetrical attachment organ, both containing radially arranged neurite bundles and muscles. Centrally, the prominent atrial sphincter separates the vestibulum from the atrium. The latter is enclosed by the tentacle sheath which contains few longitudinal muscle fibers and two principal neurite bundles. These emerge from the cerebral ganglion, which is located at the lophophoral base. Lateral ganglia are located next to the cerebral ganglion from which the visceral neurite bundles emerge that extend proximally towards the foregut. There are four tentacle neurite bundles that emerge from the ganglia and the circum-oral nerve ring, which encompasses the pharynx. The tentacles possess two striated longitudinal muscles. Short buccal dilatators are situated at the lophophoral base and short muscular sets are present at the abfrontal and frontal side of the tentacle base. The pharynx is myoepithelial and triradiate in cross-section. Oocytes are found inside the pharyngeal myoepithelium. The digestive tract contains dense circular musculature and few longitudinal muscles. The membranous sac contains regular, thin, circular and diagonal muscles and neurites in its epithelial lining. The general structure of the neuro-muscular system is more reminiscent of the condition found in Gymnolaemata rather than Phylactolaemata, which supports a close relationship between Cyclostomata and Gymnolaemata. Several characters of C. elegans such as the lateral ganglia or loss of the cardia are probably apomorphic for this species. For the first time, oocytes that surprisingly develop in the pharyngeal wall are reported for this species.

Ontogeny of the sheathing leaf base in maize (Zea mays).

PubMed

Johnston, Robyn; Leiboff, Samuel; Scanlon, Michael J

2015-01-01

Leaves develop from the shoot apical meristem (SAM) via recruitment of leaf founder cells. Unlike eudicots, most monocot leaves display parallel venation and sheathing bases wherein the margins overlap the stem. Here we utilized computed tomography (CT) imaging, localization of PIN-FORMED1 (PIN1) auxin transport proteins, and in situ hybridization of leaf developmental transcripts to analyze the ontogeny of monocot leaf morphology in maize (Zea mays). CT imaging of whole-mounted shoot apices illustrates the plastochron-specific stages during initiation of the basal sheath margins from the tubular disc of insertion (DOI). PIN1 localizations identify basipetal auxin transport in the SAM L1 layer at the site of leaf initiation, a process that continues reiteratively during later recruitment of lateral leaf domains. Refinement of these auxin transport domains results in multiple, parallel provascular strands within the initiating primordium. By contrast, auxin is transported from the L2 toward the L1 at the developing margins of the leaf sheath. Transcripts involved in organ boundary formation and dorsiventral patterning accumulate within the DOI, preceding the outgrowth of the overlapping margins of the sheathing leaf base. We suggest a model wherein sheathing bases and parallel veins are both patterned via the extended recruitment of lateral maize leaf domains from the SAM. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

Hydrodynamic Assists Magnetophoreses Rare Cancer cells Separation in Microchannel Simulation and Experimental Verifications

NASA Astrophysics Data System (ADS)

Saeed, O.; Duru, L.; Yulin, D.

2018-05-01

A proposed microfluidic design has been fabricated and simulated using COMSOL Multiphysics software, based on two physical models included in this design. The device’s ability to create a narrow stream of the core sample by controlling the sheath flow rates Qs1 and Qs2 in both peripheral channels was investigated. The main target of this paper is to study the possibility of combing the hydrodynamic and magnetic techniques, in order to achieve a high rate of cancer cells separation from a cell mixture and/or buffer sample. The study has been conducted in two stages, firstly, the effects of the sheath flow rates (Qs1 and Qs2) on the sample stream focusing were studied, to find the proposed device effectiveness optimal conditions and its capability in cell focusing, and then the magnetic mechanism has been utilized to finalize the pre-labelled cells separation process.

Structured Post-IQ Domain Governs Selectivity of Myosin X for Fascin-Actin Bundles*

PubMed Central

Nagy, Stanislav; Rock, Ronald S.

2010-01-01

Without guidance cues, cytoskeletal motors would traffic components to the wrong destination with disastrous consequences for the cell. Recently, we identified a motor protein, myosin X, that identifies bundled actin filaments for transport. These bundles direct myosin X to a unique destination, the tips of cellular filopodia. Because the structural and kinetic features that drive bundle selection are unknown, we employed a domain-swapping approach with the nonselective myosin V to identify the selectivity module of myosin X. We found a surprising role of the myosin X tail region (post-IQ) in supporting long runs on bundles. Moreover, the myosin X head is adapted for initiating processive runs on bundles. We found that the tail is structured and biases the orientation of the two myosin X heads because a targeted insertion that introduces flexibility in the tail abolishes selectivity. Together, these results suggest how myosin motors may manage to read cellular addresses. PMID:20538587

[Giant cell tumor of the tendon sheath: characteristic findings of the bone scintigraphy and correlation with MRI].

PubMed

Mena, E; Martín-Miramon, J C; Bernà, L; Veintemillas, M; Marín, A; Valls, R; Melloni, P

2009-01-01

We report 3 cases of an unusual tumor, that is, the giant cell tumor of the tendon sheath. The patients consulted due to the appearance of a well-defined, painless, soft tissue mass with mild-to-moderate inflammation located in the thumbs or toes. These clinical data, together with the bone scan findings, oriented the diagnostic suspicion that was confirmed by a pathology study of the tumor after resection. This work has aimed to review the characteristics of the bone scan (BS) image of this tumor and its correlation with the conventional X-ray imaging and magnetic resonance imaging (MRI).

Technology Solutions Case Study: Application of Spray Foam Insulation Under Plywood and OSB Roof Sheathing

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

None

2013-11-01

Spray polyurethane foams (SPFs) have advantages over alternative insulation methods because they provide air sealing in complex assemblies, particularly roofs. Spray foam can provide the thermal, air, and vapor control layers in both new and retrofit construction. Unvented roof strategies with open cell and closed cell SPF insulation sprayed to the underside of roof sheathing have been used since the mid-1990s to provide durable and efficient building enclosures. However, there have been isolated incidents of failures (either sheathing rot or SPF delamination) that raise some general concerns about the hygrothermal performance and durability of these systems. The primary risks formore » roof systems are rainwater leaks, condensation from diffusion and air leakage, and built-in construction moisture. In this project, Building Science Corporation investigated rain and built-in construction moisture and vapor drives. Research involved both hygrothermal modeling of a range of rain water leakage scenarios and field evaluations of in-service residential roofs. Other variables considered were climate zone, orientation, interior relative humidity, and the vapor permeance of the coating applied to the interior face of open cell SPF.« less

Convection-Enhanced Delivery (CED) in an Animal Model of Malignant Peripheral Nerve Sheath Tumors and Plexiform Neurofibromas

DTIC Science & Technology

2013-02-01

successfully establish the xenograft within the sciatic nerve. Convection-Enhanced Delivery ( CED ), Malignant Peripheral Nerve Sheath ( MPNST ), Plexiform...intraneural PNs and MPNST via CED . Design: Orthotopic xenograft models of sciatic intraneural NF1 MPNST and PNs in scid mice as described by Perrin et...using convection-enhanced delivery ( CED ). Relative Growth of MPNST cells in vivo treated with rapamycin, imatinib or erlotinib: Elotinib

Influence of residual plasma drift velocity on the post-arc sheath expansion of vacuum circuit breakers

NASA Astrophysics Data System (ADS)

Mo, Yongpeng; Shi, Zongqian; Bai, Zhibin; Jia, Shenli; Wang, Lijun

2016-05-01

The residual plasma in the inter-contact region of a vacuum circuit breaker moves towards the post-arc cathode at current zero, because the residual plasma mainly comes from the cathode spots during the arc burning process. In the most previous theoretical researches on the post-arc sheath expansion process of vacuum circuit breakers, only the thermal motion of residual plasma was taken into consideration. Alternately, the residual plasma was even assumed to be static at the moment of current zero in some simplified models. However, the influence of residual plasma drift velocity at current zero on the post-arc sheath expansion process was rarely investigated. In this paper, this effect is investigated by a one-dimensional particle-in-cell model. Simulation results indicate that the sheath expands slower with higher residual plasma drift velocity in the initial sheath expansion stage. However, with the increase of residual plasma drift velocity, the overall plasma density in the inter-contact region decreases faster, and the sheath expansion velocity increases earlier. Consequently, as a whole, it needs shorter time to expel the residual plasma from the inter-contact region. Furthermore, if the residual plasma drift velocity is high enough, the sheath expansion process ceases before it develops to the post-arc anode. Besides, the influence of the collisions between charges and neutrals is investigated as well in terms of the density of metal vapor. It shows that the residual plasma drift velocity takes remarkable effect only if the density of the metal vapor is relatively low, which corresponds to the circumstance of low-current interruptions.

Fuel cell integral bundle assembly including ceramic open end seal and vertical and horizontal thermal expansion control

DOEpatents

Zafred, Paolo R [Murrysville, PA; Gillett, James E [Greensburg, PA

2012-04-24

A plurality of integral bundle assemblies contain a top portion with an inlet fuel plenum and a bottom portion containing a base support, the base supports a dense, ceramic air exhaust manifold having four supporting legs, the manifold is below and connects to air feed tubes located in a recuperator zone, the air feed tubes passing into the center of inverted, tubular, elongated, hollow electrically connected solid oxide fuel cells having an open end above a combustion zone into which the air feed tubes pass and a closed end near the inlet fuel plenum, where the open end of the fuel cells rest upon and within a separate combination ceramic seal and bundle support contained in a ceramic support casting, where at least one flexible cushion ceramic band seal located between the recuperator and fuel cells protects and controls horizontal thermal expansion, and where the fuel cells operate in the fuel cell mode and where the base support and bottom ceramic air exhaust manifolds carry from 85% to all of the weight of the generator.

Regional variations in the distribution and colocalization of extracellular matrix proteins in the juvenile bovine meniscus

PubMed Central

Vanderploeg, Eric J; Wilson, Christopher G; Imler, Stacy M; Ling, Carrie Hang-Yin; Levenston, Marc E

2012-01-01

A deeper understanding of the composition and organization of extracellular matrix molecules in native, healthy meniscus tissue is required to fully appreciate the degeneration that occurs in joint disease and the intricate environment in which an engineered meniscal graft would need to function. In this study, regional variations in the tissue-level and pericellular distributions of collagen types I, II and VI and the proteoglycans aggrecan, biglycan and decorin were examined in the juvenile bovine meniscus. The collagen networks were extensively, but not completely, colocalized, with tissue-level organization that varied with radial position across the meniscus. Type VI collagen exhibited close association with large bundles composed of type I and II collagen and, in contrast to type I and II collagen, was further concentrated in the pericellular matrix. Aggrecan was detected throughout the inner region of the meniscus but was restricted to the pericellular matrix and sheaths of collagen bundles in the middle and outer regions. The small proteoglycans biglycan and decorin exhibited regional variations in staining intensity but were consistently localized in the intra- and/or peri-cellular compartments. These results provide insight into the complex hierarchy of extracellular matrix organization in the meniscus and provide a framework for better understanding meniscal degeneration and disease progression and evaluating potential repair and regeneration strategies. PMID:22703476

A Common Histone Modification Code on C4 Genes in Maize and Its Conservation in Sorghum and Setaria italica1[W][OA

PubMed Central

Heimann, Louisa; Horst, Ina; Perduns, Renke; Dreesen, Björn; Offermann, Sascha; Peterhansel, Christoph

2013-01-01

C4 photosynthesis evolved more than 60 times independently in different plant lineages. Each time, multiple genes were recruited into C4 metabolism. The corresponding promoters acquired new regulatory features such as high expression, light induction, or cell type-specific expression in mesophyll or bundle sheath cells. We have previously shown that histone modifications contribute to the regulation of the model C4 phosphoenolpyruvate carboxylase (C4-Pepc) promoter in maize (Zea mays). We here tested the light- and cell type-specific responses of three selected histone acetylations and two histone methylations on five additional C4 genes (C4-Ca, C4-Ppdk, C4-Me, C4-Pepck, and C4-RbcS2) in maize. Histone acetylation and nucleosome occupancy assays indicated extended promoter regions with regulatory upstream regions more than 1,000 bp from the transcription initiation site for most of these genes. Despite any detectable homology of the promoters on the primary sequence level, histone modification patterns were highly coregulated. Specifically, H3K9ac was regulated by illumination, whereas H3K4me3 was regulated in a cell type-specific manner. We further compared histone modifications on the C4-Pepc and C4-Me genes from maize and the homologous genes from sorghum (Sorghum bicolor) and Setaria italica. Whereas sorghum and maize share a common C4 origin, C4 metabolism evolved independently in S. italica. The distribution of histone modifications over the promoters differed between the species, but differential regulation of light-induced histone acetylation and cell type-specific histone methylation were evident in all three species. We propose that a preexisting histone code was recruited into C4 promoter control during the evolution of C4 metabolism. PMID:23564230

Review of ion energy and angular distributions in capacitively coupled RF plasma reactors

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

Kawamura, E.; Lieberman, M.A.; Birdsall, C.K.

1995-12-31

The authors present a historical review and discussion of previous works on ion energy and angular distributions (IED and IAD) arriving at the target in the collisionless regime. This regime is of great interest to experimentalists and modelers studying the new generation of high density sources in which the sheath is much thinner than in the conventional RIE systems. The purpose of the review is to asses what has been done so far, and to clarify some issues about sheaths in high density systems. Having determined the important parameters, the authors show some particle-in-cell simulation results of a dually excitedmore » capacitively coupled plasma in which the sheath ions roughly see the scaling as in high density sources. The results show that when {tau}{sub ion}/{tau}{sub rf} < 1, the oscillating voltage and width of the rf sheath significantly affect the IEDs, where {tau}{sub ion} is the ion transit-time and {tau}{sub rf} is rf period.« less

Effect of lignin content and subunit composition on digestibility in clones of timothy (Phleum pratense L.).

PubMed

Kärkönen, Anna; Tapanila, Tarja; Laakso, Tapio; Seppänen, Mervi M; Isolahti, Mika; Hyrkäs, Maarit; Virkajärvi, Perttu; Saranpää, Pekka

2014-07-02

Lignin amount and subunit composition were analyzed from stems and leaf sheaths of timothy (Phleum pratense L.) clones of different in vitro digestibility. Lignin concentration in stems and leaf sheaths was higher in clones of low digestibility than those of high digestibility. No change in lignin concentration occurred in stems as digestibility decreased. Intriguingly, the lignin concentration was lower and the syringyl/guaiacyl (S/G) ratio was higher in stems compared to leaf sheaths at all developmental stages studied. The developmental-associated decrease in digestibility correlated with the increase in S units in lignin in stems and leaf sheaths and in the amounts of p-coumaric acid and ferulic acid residues in the cell wall of stems. Yields of copper oxidation products increased in stems during maturation indicating qualitative changes in the lignin structure. This correlated strongly with the developmentally linked decrease in digestibility. The information obtained is valuable for breeding and for DNA marker development.

Enhanced target normal sheath acceleration based on the laser relativistic self-focusing

NASA Astrophysics Data System (ADS)

Zou, D. B.; Zhuo, H. B.; Yang, X. H.; Shao, F. Q.; Ma, Y. Y.; Yu, T. P.; Wu, H. C.; Yin, Y.; Ge, Z. Y.; Li, X. H.

2014-06-01

The enhanced target normal sheath acceleration of ions in laser target interaction via the laser relativistic self-focusing effect is investigated by theoretical analysis and particle-in-cell simulations. The temperature of the hot electrons in the underdense plasma is greatly increased due to the occurrence of resonant absorption, while the electron-betatron-oscillation frequency is close to its witnessed laser frequency [Pukhov et al., Phys. Plasma 6, 2847 (1999)]. While these hot electrons penetrate through the backside solid target, a stronger sheath electric field at the rear surface of the target is induced, which can accelerate the protons to a higher energy. It is also shown that the optimum length of the underdense plasma is approximately equal to the self-focusing distance.

Malate decarboxylases: evolution and roles of NAD(P)-ME isoforms in species performing C(4) and C(3) photosynthesis.

PubMed

Maier, Alexandra; Zell, Martina B; Maurino, Veronica G

2011-05-01

In the C(4) pathway of photosynthesis two types of malate decarboxylases release CO(2) in bundle sheath cells, NADP- and NAD-dependent malic enzyme (NADP-ME and NAD-ME), located in the chloroplasts and the mitochondria of these cells, respectively. The C(4) decarboxylases involved in C(4) photosynthesis did not evolve de novo; they were recruited from existing housekeeping isoforms. NADP-ME housekeeping isoforms would function in the control of malate levels during hypoxia, pathogen defence responses, and microspore separation, while NAD-ME participates in the respiration of malate in the tricarboxylic acid cycle. Recently, the existence of three enzymatic NAD-ME entities in Arabidopsis, occurring by alternative association of two subunits, was described as a novel mechanism to regulate NAD-ME activity under changing metabolic environments. The C(4) NADP-ME is thought to have evolved from a C(3) chloroplastic ancestor, which in turn would have evolved from an ancient cytosolic enzyme. In this way, the C(4) NADP-ME would have emerged through gene duplication, acquisition of a new promoter, and neo-functionalization. In contrast, there would exist a unique NAD-ME in C(4) plants, which would have been adapted to perform a dual function through changes in the kinetic and regulatory properties of the C(3) ancestors. In addition to this, for the evolution of C(4) NAD-ME, insertion of promoters or enhancers into the single-copy genes of the C(3) ancestors would have changed the expression without gene duplication.

Overexpression of gene encoding the key enzyme involved in proline-biosynthesis (PuP5CS) to improve salt tolerance in switchgrass (Panicum virgatum L.).

PubMed

Guan, Cong; Huang, Yan-Hua; Cui, Xin; Liu, Si-Jia; Zhou, Yun-Zhuan; Zhang, Yun-Wei

2018-05-25

Genetic improvement through overexpressing PuP5CS in switchgrass is feasible for enhancing plant salt stress tolerance. Switchgrass (Panicum virgatum L.) has developed into a dedicated bioenergy crop. To improve the biomass production of switchgrass grown on different types of soil, abiotic stress tolerance traits are considered for its genetic improvement. Proline accumulation is a widespread response when plants are subjected to abiotic stresses such as drought, cold and salinity. In plants, P5CS gene encodes the key regulatory enzyme that plays a crucial role in proline biosynthesis. Here, we introduced the PuP5CS gene (from Puccinellia chinampoensis) into switchgrass by Agrobacterium-mediated transformation. Transgenic lines overexpressing the PuP5CS gene showed phenotypic advantages, in leaf width, internode diameter, internode length, tiller numbers and precocious flowering under normal conditions, and the transgenic lines displayed better regenerative capacity in forming more tillers after harvest. Moreover, the PuP5CS gene enhanced the salt tolerance of transgenic switchgrass by altering a wide range of physiological responses. In accordance with the physiological results, histological analysis of cross sections through the leaf blade showed that the areas of bulliform cells and bundle sheath cells were significantly increased in PuP5CS-overexpressing leaves. The expression levels of ROS scavenging-associated genes in transgenic plants were higher than in control plants under salt stress. The results show that genetic improvement through overexpressing PuP5CS in switchgrass is feasible for enhancing plant stress tolerance.

The End of the Line: Can Ferredoxin and Ferredoxin NADP(H) Oxidoreductase Determine the Fate of Photosynthetic Electrons?

PubMed Central

Goss, Tatjana; Hanke, Guy

2014-01-01

At the end of the linear photosynthetic electron transfer (PET) chain, the small soluble protein ferredoxin (Fd) transfers electrons to Fd:NADP(H) oxidoreductase (FNR), which can then reduce NADP+ to support C assimilation. In addition to this linear electron flow (LEF), Fd is also thought to mediate electron flow back to the membrane complexes by different cyclic electron flow (CEF) pathways: either antimycin A sensitive, NAD(P)H complex dependent, or through FNR located at the cytochrome b6f complex. Both Fd and FNR are present in higher plant genomes as multiple gene copies, and it is now known that specific Fd iso-proteins can promote CEF. In addition, FNR iso-proteins vary in their ability to dynamically interact with thylakoid membrane complexes, and it has been suggested that this may also play a role in CEF. We will highlight work on the different Fd-isoproteins and FNR-membrane association found in the bundle sheath (BSC) and mesophyll (MC) cell chloroplasts of the C4 plant maize. These two cell types perform predominantly CEF and LEF, and the properties and activities of Fd and FNR in the BSC and MC are therefore specialized for CEF and LEF respectively. A diversity of Fd isoproteins and dynamic FNR location has also been recorded in C3 plants, algae and cyanobacteria. This indicates that the principles learned from the extreme electron transport situations in the BSC and MC of maize might be usefully applied to understanding the dynamic transition between these states in other systems. PMID:24678667

Absence of bundle structure in the neocortex of the reeler mouse at the embryonic stage. Studies by scanning electron microscopic fractography.

PubMed

Mikoshiba, K; Nishimura, Y; Tsukada, Y

The reeler mutant mouse is characterized by a derangement of the cerebral cortical structure due to abnormalities during the migration step at the embryonic stage. We have analyzed both the control and reeler cerebral cortex by means of scanning electron microscopic fractography. In the control cerebral cortex, the bundle formation was composed of fine fibers on which the migrating neuroblasts were attached perpendicular to the pial surface, whereas no bundle formation was observed in the reeler; instead, there was a fine meshwork of fibers surrounding the neuroblasts. The possible role of bundle formation in the normal cerebral cortex and the correlation between the inability of cells to migrate and the absence of bundle formation in the reeler is discussed.

Engineering biomimetic hair bundle sensors for underwater sensing applications

NASA Astrophysics Data System (ADS)

Kottapalli, Ajay Giri Prakash; Asadnia, Mohsen; Karavitaki, K. Domenica; Warkiani, Majid Ebrahimi; Miao, Jianmin; Corey, David P.; Triantafyllou, Michael

2018-05-01

We present the fabrication of an artificial MEMS hair bundle sensor designed to approximate the structural and functional principles of the flow-sensing bundles found in fish neuromast hair cells. The sensor consists of micro-pillars of graded height connected with piezoelectric nanofiber "tip-links" and encapsulated by a hydrogel cupula-like structure. Fluid drag force actuates the hydrogel cupula and deflects the micro-pillar bundle, stretching the nanofibers and generating electric charges. These biomimetic sensors achieve an ultrahigh sensitivity of 0.286 mV/(mm/s) and an extremely low threshold detection limit of 8.24 µm/s. A complete version of this paper has been published [1].

Tau mediates microtubule bundle architectures mimicking fascicles of microtubules found in the axon initial segment

DOE PAGES

Chung, Peter J.; Song, Chaeyeon; Deek, Joanna; ...

2016-07-25

Tau, an intrinsically disordered protein confined to neuronal axons, binds to and regulates microtubule dynamics. Although there have been observations of string-like microtubule fascicles in the axon initial segment (AIS) and hexagonal bundles in neurite-like processes in non-neuronal cells overexpressing Tau, cell-free reconstitutions have not replicated either geometry. Here we map out the energy landscape of Tau-mediated, GTP-dependent ‘active’ microtubule bundles at 37°C, as revealed by synchrotron SAXS and TEM. Widely spaced bundles (wall-to-wall distance D w–w≈25–41nm) with hexagonal and string-like symmetry are observed, the latter mimicking bundles found in the AIS. A second energy minimum (D w–w≈16–23nm) is revealedmore » under osmotic pressure. The wide spacing results from a balance between repulsive forces, due to Tau’s projection domain (PD), and a stabilizing sum of transient sub-k BT cationic/anionic charge–charge attractions mediated by weakly penetrating opposing PDs. In the end, we find that this landscape would be significantly affected by charge-altering modifications of Tau associated with neurodegeneration.« less

A specialized outer layer of the primary cell wall joins elongating cotton fibers into tissue-like bundles.

PubMed

Singh, Bir; Avci, Utku; Eichler Inwood, Sarah E; Grimson, Mark J; Landgraf, Jeff; Mohnen, Debra; Sørensen, Iben; Wilkerson, Curtis G; Willats, William G T; Haigler, Candace H

2009-06-01

Cotton (Gossypium hirsutum) provides the world's dominant renewable textile fiber, and cotton fiber is valued as a research model because of its extensive elongation and secondary wall thickening. Previously, it was assumed that fibers elongated as individual cells. In contrast, observation by cryo-field emission-scanning electron microscopy of cotton fibers developing in situ within the boll demonstrated that fibers elongate within tissue-like bundles. These bundles were entrained by twisting fiber tips and consolidated by adhesion of a cotton fiber middle lamella (CFML). The fiber bundles consolidated via the CFML ultimately formed a packet of fiber around each seed, which helps explain how thousands of cotton fibers achieve their great length within a confined space. The cell wall nature of the CFML was characterized using transmission electron microscopy, including polymer epitope labeling. Toward the end of elongation, up-regulation occurred in gene expression and enzyme activities related to cell wall hydrolysis, and targeted breakdown of the CFML restored fiber individuality. At the same time, losses occurred in certain cell wall polymer epitopes (as revealed by comprehensive microarray polymer profiling) and sugars within noncellulosic matrix components (as revealed by gas chromatography-mass spectrometry analysis of derivatized neutral and acidic glycosyl residues). Broadly, these data show that adhesion modulated by an outer layer of the primary wall can coordinate the extensive growth of a large group of cells and illustrate dynamic changes in primary wall structure and composition occurring during the differentiation of one cell type that spends only part of its life as a tissue.

Pathologic changes in the cytokeratin pericanalicular sheath in experimental cholestasis and alcoholic fatty liver.

PubMed

Ohta, M; Marceau, N; French, S W

1988-07-01

The architectural framework of the pericanalicular sheath composed of cytokeratin intermediate filaments (IFs) was examined after phalloidin treatment, bile duct ligation, and alcoholic fatty liver in rats to assess the role of IFs in experimental cholestasis. Electron microscopy examination of whole mount unembedded extracted liver slices was employed to visualize the cytoskeleton. Immunofluorescence staining and immunoelectron microscopy of the sheath were also performed using monoclonal antibodies to rat hepatocyte cytokeratins CK49 and CK55. The thickness of the wall and the diameter of the lumens were measured. In the phalloidin-treated rats, the pericanalicular sheath was markedly dilated and thickened. Immunofluorescence staining showed that the CK49 and CK55 IFs were localized in the pericanalicular region, particularly in the pericentral area. Immunoelectron microscopy documented that the IFs at the thickened pericanalicular sheath consisted of both CK49 and CK55, which means that the thickening of the bile canaliculus was in part due to an increase of IFs and not just due to an increase in actin filaments. In the livers where the bile duct was ligated, the pericanalicular sheath was irregularly dilated and some parts of the sheath appeared thinned out or missing. The belt desmosome also appeared absent focally in the pericanalicular sheath. Immunofluorescence studies showed that the staining for CK49 and CK55 was reduced focally in the pericanalicular region. The CK55 antibody stained the cytoplasm of hepatocytes in the periportal area more intensely when compared with the controls. These results indicated that the pericanalicular sheath and the belt desmosome were focally disrupted in response to extrahepatic bile duct obstruction. In the ethanol-fed rats, the pericanalicular sheath was dilated, thickened and tortuous, and appeared focally flattened by large fat droplets. IFs in the cytoplasm were pushed to the cell periphery and were compressed against each other by the fat droplets. CK55 and CK49 appeared increased as indicated by the observed immunofluorescence at the pericanalicular region. Immunoelectron microscopy showed that IFs of the thickened pericanalicular sheath were composed of CK55 and CK49. It is suggested that the pericanalicular sheath functions to mechanically provide a scaffolding for the bile canaliculus which is vulnerable to the different forces involved in cholestasis of different pathogenesis such as focal compression and distortion by fat, hypertrophy in response to increased F actin and focal destruction by increased intracanalicular pressure.

The new vestibular stimuli: sound and vibration-anatomical, physiological and clinical evidence.

PubMed

Curthoys, Ian S

2017-04-01

The classical view of the otoliths-as flat plates of fairly uniform receptors activated by linear acceleration dragging on otoconia and so deflecting the receptor hair bundles-has been replaced by new anatomical and physiological evidence which shows that the maculae are much more complex. There is anatomical spatial differentiation across the macula in terms of receptor types, hair bundle heights, stiffness and attachment to the overlying otolithic membrane. This anatomical spatial differentiation corresponds to the neural spatial differentiation of response dynamics from the receptors and afferents from different regions of the otolithic maculae. Specifically, receptors in a specialized band of cells, the striola, are predominantly type I receptors, with short, stiff hair bundles and looser attachment to the overlying otoconial membrane than extrastriolar receptors. At the striola the hair bundles project into holes in the otolithic membrane, allowing for fluid displacement to deflect the hair bundles and activate the cell. This review shows the anatomical and physiological evidence supporting the hypothesis that fluid displacement, generated by sound or vibration, deflects the short stiff hair bundles of type I receptors at the striola, resulting in neural activation of the irregular afferents innervating them. So these afferents are activated by sound or vibration and show phase-locking to individual cycles of the sound or vibration stimulus up to frequencies above 2000 Hz, underpinning the use of sound and vibration for clinical tests of vestibular function.

Immunocytochemical and autoradiographic studies on the process of keratinization in avian epidermis suggests absence of keratohyalin.

PubMed

Alibardi, Lorenzo

2004-02-01

The process of keratinization in apteric avian epidermis and in scutate scales of some avian species has been studied by autoradiography for histidine and immunohistochemistry for keratins and other epidermal proteins. Acidic or basic alpha-keratins are present in basal, spinosus, and transitional layers, but are not seen in the corneous layer. Keratinization-specific alpha-keratins (AE2-positive) are observed in the corneous layer of apteric epidermis but not in that of scutate scales, which contain mainly beta-keratin. Alpha-keratin bundles accumulate along the plasma membrane of transitional cells of apteric epidermis. In contrast to the situation in scutate scales, in the transitional layer and in the lowermost part of the corneous layer of apteric epidermis, filaggrin-like, loricrin-like, and transglutaminase immunoreactivities are present. The lack of isopeptide bond immunoreactivity suggests that undetectable isopeptide bonds are present in avian keratinocytes. Using immunogold ultrastructural immunocytochemistry a low but localized loricrin-like and, less, filaggrin-like labeling is seen over round-oval granules or vesicles among keratin bundles of upper spinosus and transitional keratinocytes of apteric epidermis. Filaggrin-and loricrin-labeling are absent in alpha-keratin bundles localized along the plasma membrane and in the corneous layer, formerly considered keratohyalin. Using ultrastructural autoradiography for tritiated histidine, occasional trace grains are seen among these alpha-keratin bundles. A different mechanism of redistribution of matrix and corneous cell envelope proteins probably operates in avian keratinocytes as compared to that of mammals. Keratin bundles are compacted around the lipid-core of apteric epidermis keratinocytes, which do not form complex chemico/mechanical-resistant corneous cell envelopes as in mammalian keratinocytes. These observations suggest that low amounts of matrix proteins are present among keratin bundles of avian keratinocytes and that keratohyalin granules are absent. Copyright 2003 Wiley-Liss, Inc.

The mechanosensory structure of the hair cell requires clarin-1, a protein encoded by Usher syndrome III causative gene.

PubMed

Geng, Ruishuang; Melki, Sami; Chen, Daniel H-C; Tian, Guilian; Furness, David N; Oshima-Takago, Tomoko; Neef, Jakob; Moser, Tobias; Askew, Charles; Horwitz, Geoff; Holt, Jeffrey R; Imanishi, Yoshikazu; Alagramam, Kumar N

2012-07-11

Mutation in the clarin-1 gene (Clrn1) results in loss of hearing and vision in humans (Usher syndrome III), but the role of clarin-1 in the sensory hair cells is unknown. Clarin-1 is predicted to be a four transmembrane domain protein similar to members of the tetraspanin family. Mice carrying null mutation in the clarin-1 gene (Clrn1(-/-)) show loss of hair cell function and a possible defect in ribbon synapse. We investigated the role of clarin-1 using various in vitro and in vivo approaches. We show by immunohistochemistry and patch-clamp recordings of Ca(2+) currents and membrane capacitance from inner hair cells that clarin-1 is not essential for formation or function of ribbon synapse. However, reduced cochlear microphonic potentials, FM1-43 [N-(3-triethylammoniumpropyl)-4-(4-(dibutylamino)styryl) pyridinium dibromide] loading, and transduction currents pointed to diminished cochlear hair bundle function in Clrn1(-/-) mice. Electron microscopy of cochlear hair cells revealed loss of some tall stereocilia and gaps in the v-shaped bundle, although tip links and staircase arrangement of stereocilia were not primarily affected by Clrn1(-/-) mutation. Human clarin-1 protein expressed in transfected mouse cochlear hair cells localized to the bundle; however, the pathogenic variant p.N48K failed to localize to the bundle. The mouse model generated to study the in vivo consequence of p.N48K in clarin-1 (Clrn1(N48K)) supports our in vitro and Clrn1(-/-) mouse data and the conclusion that CLRN1 is an essential hair bundle protein. Furthermore, the ear phenotype in the Clrn1(N48K) mouse suggests that it is a valuable model for ear disease in CLRN1(N48K), the most prevalent Usher syndrome III mutation in North America.

The Fysics of Filopodia (or The Physics of Philopodia)

NASA Astrophysics Data System (ADS)

Schwarz, Jen; Gopinathan, Ajay; Lee, Kun-Chun; Liu, Andrea; Yang, Louise

2006-03-01

Cell motility is driven by the dynamic reorganization of the cellular cytoskeleton which is composed of actin. Monomeric actin assembles into filaments that grow, shrink, branch and bundle. Branching generates new filaments that form a mesh-like structure that protrudes outward allowing the cell to move somewhere. But how does it know where to move? It has been proposed that filopodia serve as scouts for the cell. Filopodia are bundles of actin filaments that extend out ahead of the rest of the cell to probe its upcoming environment. Recent in vitro experiments [Vignjevic et al., J. Ce ll Bio. 160, 951 (2003)] determine the minimal ingredients required for such a process. We model these experiments analytically and via Monte Carlo simulations to estimate the typical bundle size and length. We also estimate the size of the mesh-like structure from which the filopodia emerge and explain the observed nonmonotonicity of this size as a function of capping protein concentration, which inhibits filament growth.

Engineered Herpes Simplex Viruses for the Treatment of Malignant Peripheral Nerve Sheath Tumors

DTIC Science & Technology

2012-09-01

sheath tumors ( MPNST ), which occur in patients with neurofibromatosis type-1, to oncolytic HSV (oHSVs). We have demonstrated that many of the MPNSTs ...there ability to maintain late viral protein synthesis in the infected MPNST cells. This is an unanticipated finding that could have been...productive and has led to new information regarding the susceptibility of MPNST to oHSVs. We are currently testing 2 new hypotheses developed based upon

Flagellar Hook Flexibility Is Essential for Bundle Formation in Swimming Escherichia coli Cells

PubMed Central

Brown, Mostyn T.; Steel, Bradley C.; Silvestrin, Claudio; Wilkinson, David A.; Delalez, Nicolas J.; Lumb, Craig N.; Obara, Boguslaw; Berry, Richard M.

2012-01-01

Swimming Escherichia coli cells are propelled by the rotary motion of their flagellar filaments. In the normal swimming pattern, filaments positioned randomly over the cell form a bundle at the posterior pole. It has long been assumed that the hook functions as a universal joint, transmitting rotation on the motor axis through up to ∼90° to the filament in the bundle. Structural models of the hook have revealed how its flexibility is expected to arise from dynamic changes in the distance between monomers in the helical lattice. In particular, each of the 11 protofilaments that comprise the hook is predicted to cycle between short and long forms, corresponding to the inside and outside of the curved hook, once each revolution of the motor when the hook is acting as a universal joint. To test this, we genetically modified the hook so that it could be stiffened by binding streptavidin to biotinylated monomers, impeding their motion relative to each other. We found that impeding the action of the universal joint resulted in atypical swimming behavior as a consequence of disrupted bundle formation, in agreement with the universal joint model. PMID:22522898

Myosin IIA/IIB restrict adhesive and protrusive signaling to generate front-back polarity in migrating cells.

PubMed

Vicente-Manzanares, Miguel; Newell-Litwa, Karen; Bachir, Alexia I; Whitmore, Leanna A; Horwitz, Alan Rick

2011-04-18

Migratory front-back polarity emerges from the cooperative effect of myosin IIA (MIIA) and IIB (MIIB) on adhesive signaling. We demonstrate here that, during polarization, MIIA and MIIB coordinately promote localized actomyosin bundling, which generates large, stable adhesions that do not signal to Rac and thereby form the cell rear. MIIA formed dynamic actomyosin proto-bundles that mark the cell rear during spreading; it also bound to actin filament bundles associated with initial adhesion maturation in protrusions. Subsequent incorporation of MIIB stabilized the adhesions and actomyosin filaments with which it associated and formed a stable, extended rear. These adhesions did not turn over and no longer signal to Rac. Microtubules fine-tuned the polarity by positioning the front opposite the MIIA/MIIB-specified rear. Decreased Rac signaling in the vicinity of the MIIA/MIIB-stabilized proto-bundles and adhesions was accompanied by the loss of Rac guanine nucleotide exchange factor (GEFs), like βPIX and DOCK180, and by inhibited phosphorylation of key residues on adhesion proteins that recruit and activate Rac GEFs. These observations lead to a model for front-back polarity through local GEF depletion.

Calbindin and parvalbumin are early markers of non-mitotically regenerating hair cells in the bullfrog vestibular otolith organs

NASA Technical Reports Server (NTRS)

Steyger, P. S.; Burton, M.; Hawkins, J. R.; Schuff, N. R.; Baird, R. A.

1997-01-01

Earlier studies have demonstrated hair cell regeneration in the absence of cell proliferation, and suggested that supporting cells could phenotypically convert into hair cells following hair cell loss. Because calcium-binding proteins are involved in gene up-regulation, cell growth, and cell differentiation, we wished to determine if these proteins were up-regulated in scar formations and regenerating hair cells following gentamicin treatment. Calbindin and parvalbumin immunolabeling was examined in control or gentamicin-treated (GT) bullfrog saccular and utricular explants cultured for 3 days in amphibian culture medium or amphibian culture medium supplemented with aphidicolin, a blocker of nuclear DNA replication in eukaryotic cells. In control cultures, calbindin and parvalbumin immunolabeled the hair bundles and, less intensely, the cell bodies of mature hair cells. In GT or mitotically-blocked GT (MBGT) cultures, calbindin and parvalbumin immunolabeling was also seen in the hair bundles, cuticular plates, and cell bodies of hair cells with immature hair bundles. Thus, these antigens were useful markers for both normal and regenerating hair cells. Supporting cell immunolabeling was not seen in control cultures nor in the majority of supporting cells in GT cultures. In MBGT cultures, calbindin and parvalbumin immunolabeling was up-regulated in the cytosol of single supporting cells participating in scar formations and in supporting cells with hair cell-like characteristics. These data provide further evidence that non-mitotic hair cell regeneration in cultures can be accomplished by the conversion of supporting cells into hair cells.

Directional selectivity of afferent neurons in zebrafish neuromasts is regulated by Emx2 in presynaptic hair cells

PubMed Central

Ji, Young Rae; Warrier, Sunita; Jiang, Tao

2018-01-01

The orientation of hair bundles on top of sensory hair cells (HCs) in neuromasts of the lateral line system allows fish to detect direction of water flow. Each neuromast shows hair bundles arranged in two opposing directions and each afferent neuron innervates only HCs of the same orientation. Previously, we showed that this opposition is established by expression of Emx2 in half of the HCs, where it mediates hair bundle reversal (Jiang et al., 2017). Here, we show that Emx2 also regulates neuronal selection: afferent neurons innervate either Emx2-positive or negative HCs. In emx2 knockout and gain-of-function neuromasts, all HCs are unidirectional and the innervation patterns and physiological responses of the afferent neurons are dependent on the presence or absence of Emx2. Our results indicate that Emx2 mediates the directional selectivity of neuromasts by two distinct processes: regulating hair bundle orientation in HCs and selecting afferent neuronal targets. PMID:29671737

Paleobiology of the Mesoproterozoic-Neoproterozoic transition: the Sukhaya Tunguska Formation, Turukhansk Uplift, Siberia

NASA Technical Reports Server (NTRS)

Sergeev, V. N.; Knoll, A. H.

1997-01-01

Silicified carbonates of the latest Mesoproterozoic Sukhaya Tunguska Formation, northwestern Siberia, contain abundant and diverse permineralized microfossils. Peritidal environments are dominated by microbial mats built by filamentous cyanobacteria comparable to modern species of Lyngbya and Phormidium. In subtidal to lower intertidal settings, mat-dwelling microbenthos and possible coastal microplankton are abundant. In contrast, densely woven mat populations with few associated taxa characterize more restricted parts of tidal flats; the preservation of vertically oriented sheath bundles and primary fenestrae indicates that in these mats carbonate cementation was commonly penecontemporaneous with mat growth. Eoentophysalis mats are limited to restricted environments where microlaminated carbonate precipitates formed on or just beneath the sediment surface. Most microbenthic populations are cyanobacterial, although eukaryotic microfossils may occur among the simple spheroidal cells interpreted as coastal plankton. Protists are more securely represented by large (up to 320 micrometers in diameter) but poorly preserved acritarchs in basinal facies. The Sukhaya Tunguska assemblage contains 27 species in 18 genera. By virtue of their stratigraphic longevity and their close and predictable association with specific paleoenvironmental conditions, including substrates, Proterozoic cyanobacteria support a model of bacterial evolution in which populations adapt rapidly to novel environments and, thereafter, resist competitive replacement. The resulting evolutionary pattern is one of accumulation and stasis rather than the turnover and replacement characteristic of Phanerozoic plants and animals.

Urea retranslocation from senescing Arabidopsis leaves is promoted by DUR3-mediated urea retrieval from leaf apoplast

PubMed Central

Bohner, Anne; Kojima, Soichi; Hajirezaei, Mohammad; Melzer, Michael; von Wirén, Nicolaus

2015-01-01

In plants, urea derives either from root uptake or protein degradation. Although large quantities of urea are released during senescence, urea is mainly seen as a short-lived nitrogen (N) catabolite serving urease-mediated hydrolysis to ammonium. Here, we investigated the roles of DUR3 and of urea in N remobilization. During natural leaf senescence urea concentrations and DUR3 transcript levels showed a parallel increase with senescence markers like ORE1 in a plant age- and leaf age-dependent manner. Deletion of DUR3 decreased urea accumulation in leaves, whereas the fraction of urea lost to the leaf apoplast was enhanced. Under natural and N deficiency-induced senescence DUR3 promoter activity was highest in the vasculature, but was also found in surrounding bundle sheath and mesophyll cells. An analysis of petiole exudates from wild-type leaves revealed that N from urea accounted for >13% of amino acid N. Urea export from senescent leaves further increased in ureG-2 deletion mutants lacking urease activity. In the dur3 ureG double insertion line the absence of DUR3 reduced urea export from leaf petioles. These results indicate that urea can serve as an early metabolic marker for leaf senescence, and that DUR3-mediated urea retrieval contributes to the retranslocation of N from urea during leaf senescence. PMID:25440717

Paleobiology of the Mesoproterozoic-Neoproterozoic transition: the Sukhaya Tunguska Formation, Turukhansk Uplift, Siberia.

PubMed

Sergeev, V N; Knoll, A H; Petrov PYu

1997-12-01

Silicified carbonates of the latest Mesoproterozoic Sukhaya Tunguska Formation, northwestern Siberia, contain abundant and diverse permineralized microfossils. Peritidal environments are dominated by microbial mats built by filamentous cyanobacteria comparable to modern species of Lyngbya and Phormidium. In subtidal to lower intertidal settings, mat-dwelling microbenthos and possible coastal microplankton are abundant. In contrast, densely woven mat populations with few associated taxa characterize more restricted parts of tidal flats; the preservation of vertically oriented sheath bundles and primary fenestrae indicates that in these mats carbonate cementation was commonly penecontemporaneous with mat growth. Eoentophysalis mats are limited to restricted environments where microlaminated carbonate precipitates formed on or just beneath the sediment surface. Most microbenthic populations are cyanobacterial, although eukaryotic microfossils may occur among the simple spheroidal cells interpreted as coastal plankton. Protists are more securely represented by large (up to 320 micrometers in diameter) but poorly preserved acritarchs in basinal facies. The Sukhaya Tunguska assemblage contains 27 species in 18 genera. By virtue of their stratigraphic longevity and their close and predictable association with specific paleoenvironmental conditions, including substrates, Proterozoic cyanobacteria support a model of bacterial evolution in which populations adapt rapidly to novel environments and, thereafter, resist competitive replacement. The resulting evolutionary pattern is one of accumulation and stasis rather than the turnover and replacement characteristic of Phanerozoic plants and animals.

Assessing the Metabolic Impact of Nitrogen Availability Using a Compartmentalized Maize Leaf Genome-Scale Model1[C][W][OPEN

PubMed Central

Simons, Margaret; Saha, Rajib; Amiour, Nardjis; Kumar, Akhil; Guillard, Lenaïg; Clément, Gilles; Miquel, Martine; Li, Zhenni; Mouille, Gregory; Lea, Peter J.; Hirel, Bertrand; Maranas, Costas D.

2014-01-01

Maize (Zea mays) is an important C4 plant due to its widespread use as a cereal and energy crop. A second-generation genome-scale metabolic model for the maize leaf was created to capture C4 carbon fixation and investigate nitrogen (N) assimilation by modeling the interactions between the bundle sheath and mesophyll cells. The model contains gene-protein-reaction relationships, elemental and charge-balanced reactions, and incorporates experimental evidence pertaining to the biomass composition, compartmentalization, and flux constraints. Condition-specific biomass descriptions were introduced that account for amino acids, fatty acids, soluble sugars, proteins, chlorophyll, lignocellulose, and nucleic acids as experimentally measured biomass constituents. Compartmentalization of the model is based on proteomic/transcriptomic data and literature evidence. With the incorporation of information from the MetaCrop and MaizeCyc databases, this updated model spans 5,824 genes, 8,525 reactions, and 9,153 metabolites, an increase of approximately 4 times the size of the earlier iRS1563 model. Transcriptomic and proteomic data have also been used to introduce regulatory constraints in the model to simulate an N-limited condition and mutants deficient in glutamine synthetase, gln1-3 and gln1-4. Model-predicted results achieved 90% accuracy when comparing the wild type grown under an N-complete condition with the wild type grown under an N-deficient condition. PMID:25248718

Recruitment of pre-existing networks during the evolution of C4 photosynthesis.

PubMed

Reyna-Llorens, Ivan; Hibberd, Julian M

2017-09-26

During C 4 photosynthesis, CO 2 is concentrated around the enzyme RuBisCO. The net effect is to reduce photorespiration while increasing water and nitrogen use efficiencies. Species that use C 4 photosynthesis have evolved independently from their C 3 ancestors on more than 60 occasions. Along with mimicry and the camera-like eye, the C 4 pathway therefore represents a remarkable example of the repeated evolution of a highly complex trait. In this review, we provide evidence that the polyphyletic evolution of C 4 photosynthesis is built upon pre-existing metabolic and genetic networks. For example, cells around veins of C 3 species show similarities to those of the C 4 bundle sheath in terms of C 4 acid decarboxylase activity and also the photosynthetic electron transport chain. Enzymes of C 4 photosynthesis function together in gluconeogenesis during early seedling growth of C 3 Arabidopsis thaliana Furthermore, multiple C 4 genes appear to be under control of both light and chloroplast signals in the ancestral C 3 state. We, therefore, hypothesize that relatively minor rewiring of pre-existing genetic and metabolic networks has facilitated the recurrent evolution of this trait. Understanding how these changes are likely to have occurred could inform attempts to install C 4 traits into C 3 crops.This article is part of the themed issue 'Enhancing photosynthesis in crop plants: targets for improvement'. © 2017 The Author(s).

Involvement of microtubules and 10-nm filaments in the movement and positioning of nuclei in syncytia

PubMed Central

1979-01-01

Previous studies (Holmes, K.V., and P.W. Choppin. J. Exp. Med. 124:501- 520; J. Cell Biol. 39:526-543) showed that infection of baby hamster kidney (BHK21-F) cells with the parainfluenza virus SV5 causes extensive cell fusion, that nuclei migrate in the syncytial cytoplasm and align in tightly-packed rows, and that microtubules are involved in nuclear movement and alignment. The role of microtubules, 10-nm filaments, and actin-containing microfilaments in this process has been investigated by immunofluorescence microscopy using specific antisera, time-lapse cinematography, and electron microscopy. During cell fusion, micro tubules and 10-nm filaments from many cells form large bundles which are localized between rows of nuclei. No organized bundles of actin fibers were detected in these areas, although actin fibers were observed in regions away from the aligned nuclei. Although colchicine disrupts microtubules and inhibits nuclear movement, cytochalasin B (CB; 20-50 microgram/ml) does not inhibit cell fusion or nuclear movement. However, CB alters the shape of the syncytium, resulting in long filamentous processes extending from a central region. When these processes from neighboring cells make contact, fusion occurs, and nuclei migrate through the channels which are formed. Electron and immunofluorescence microscopy reveal bundles of microtubules and 10-nm filaments in parallel arrays within these processes, but no bundles of microfilaments were detected. The effect of CB on the structural integrity of microfilaments at this high concentration (20 microgram/ml) was demonstrated by the disappearance of filaments interacting with heavy meromyosin. Cycloheximide (20 microgram/ml) inhibits protein synthesis but does not affect cell fusion, the formation of microtubules and 10-nm filament bundles, or nuclear migration and alignment; thus, continued protein synthesis is not required. The association of microtubules and 10-nm filaments with nuclear migration and alignment suggests that microtubules and 10-nm filaments are two components in a system which serves both cytoskeletal and force-generating functions in intracellular movement and position of nuclei. PMID:227913

Stimulus dependent properties of mammalian cochlear hair cell mechanoelectrical transduction

NASA Astrophysics Data System (ADS)

Scharr, A. L.; Ricci, Anthony

2018-05-01

Cochlear hair cell stereocilia move semi-independently, shaping the force transfer to mechanoelectrical transduction (MET) channels, as indicated by the MET current response. Semi-independent movement of stereocilia was evoked by stimulating inner hair cell (IHC) bundles from acutely dissected rat cochlea with stiff probes ranging in size from 1 to 10 µm. MET current responses were recorded using whole-cell patch-clamp electrophysiology. Small probes directly displaced stereocilia they contacted, and recruited adjacent stereocilia depending on stimulus magnitude. We inferred that the recruitment of stereocilia resulted in less uniform and less synchronous movement. Step displacements using smaller probes resulted in smaller current responses (from 1 nA for large probes to 0.3 nA for small, p <.0001), slower rate of current activation, as measured from the linear portion (from 4 nA/ms to 1 nA/ms, p <.0001), slower time constants of adaptation, as measured from double exponential fits from peak to steady state current (fast component: from 0.6 to 1.2 ms, p =.004; slow component: from 8 ms to 12 ms, p =.001) and less complete adaptation (from 95% to 30%, p <.0001). These results indicate that the mechanical properties of less coherent bundles greatly affect force transfer to MET channels as indicated by the electrical response of the cell. Thus, outer hair cells (OHCs), with their bundles embedded in the tectorial membrane, may exhibit synchronous MET activation and therefore time-dependent adaptation where fast adaptation provides a high pass filter. Hair cells with free standing bundles, like inner hair cells (IHC), may exhibit more asynchronous MET activation and adaptation, in which case adaptation would not provide this additional filter.

Exploring the membrane fusion mechanism through force-induced disassembly of HIV-1 six-helix bundle

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

Gao, Kai; Beijing Key Laboratory of Noncoding RNA, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101; University of Chinese Academy of Sciences, Beijing 100049

Enveloped virus, such as HIV-1, employs membrane fusion mechanism to invade into host cell. HIV-1 gp41 ectodomain uses six-helix bundle configuration to accomplish this process. Using molecular dynamic simulations, we confirmed the stability of this six-helix bundle by showing high occupancy of hydrogen bonds and hydrophobic interactions. Key residues and interactions important for the bundle integration were characterized by force-induced unfolding simulations of six-helix bundle, exhibiting the collapse order of these groups of interactions. Moreover, our results in some way concerted with a previous theory that the formation of coiled-coil choose a route which involved cooperative interactions between the N-terminalmore » and C-terminal helix. -- Highlights: •Unfolding of HIV-1 gp41 six-helix bundle is studied by molecular dynamics simulations. •Specific interactions responsible for the stability of HIV-1 envelope post-fusion conformation were identified. •The gp41 six-helix bundle transition inducing membrane fusion might be a cooperative process of the three subunits.« less

Pigmented villonodular bursitis/diffuse giant cell tumor of the pes anserine bursa: a report of two cases and review of literature.

PubMed

Maheshwari, Aditya V; Muro-Cacho, Carlos A; Pitcher, J David

2007-10-01

Pigmented villonodular synovitis (PVNS) is a benign but potentially aggressive lesion, characterized by synovial villonodular proliferation with hemosiderin pigmentation and stromal infiltration of histiocytes and giant cells. This consists of a common family of lesions, including localized and diffuse forms of pigmented villonodular synovitis, giant cell tumor of the tendon sheath (nodular tenosynovitis) and the very rare cases of extra-articular pigmented villonodular synovitis arising from the bursa (pigmented villonodular bursitis or diffuse giant cell tumor of the tendon sheath). The purpose of this paper is to present two rare cases of pigmented villonodular bursitis arising from the pes anserinus bursa. The various differentials along with a review of literature of similar lesions are also being discussed. However, as with other lesions, clinicoradiographic features along with close histological correlation is essential for diagnosis.

Reconstitution of the NF1 GAP-related domain in NF1-deficient human Schwann cells

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

Thomas, Stacey L.; Neuroscience Program, Loyola University Medical Center, Maywood, IL; Department of Anatomy and Cell Biology, University of Illinois Chicago, Chicago, IL

Schwann cells derived from peripheral nerve sheath tumors from individuals with Neurofibromatosis Type 1 (NF1) are deficient for the protein neurofibromin, which contains a GAP-related domain (NF1-GRD). Neurofibromin-deficient Schwann cells have increased Ras activation, increased proliferation in response to certain growth stimuli, increased angiogenic potential, and altered cell morphology. This study examined whether expression of functional NF1-GRD can reverse the transformed phenotype of neurofibromin-deficient Schwann cells from both benign and malignant peripheral nerve sheath tumors. We reconstituted the NF1-GRD using retroviral transduction and examined the effects on cell morphology, growth potential, and angiogenic potential. NF1-GRD reconstitution resulted in morphologic changes,more » a 16-33% reduction in Ras activation, and a 53% decrease in proliferation in neurofibromin-deficient Schwann cells. However, NF1-GRD reconstitution was not sufficient to decrease the in vitro angiogenic potential of the cells. This study demonstrates that reconstitution of the NF1-GRD can at least partially reverse the transformation of human NF1 tumor-derived Schwann cells.« less

Experimental Study of Convective Cells and RF Sheaths Excited by a Fast Wave Antenna in the LAPD

NASA Astrophysics Data System (ADS)

Martin, Michael; Gekelman, Walter; Pribyl, Patrick; van Compernolle, Bart; Carter, Troy; van Eester, Dirk; Crombé, Kristel

2016-10-01

Ion cyclotron resonance heating (ICRH) will be essential for ITER where it is planned to couple 20 MW to the plasma. During ICRH, radio frequency (RF) sheaths may form on the antenna or farther away, and convective cells are suspected to form adjacent to ICRH antennas, negatively affecting both machine and plasma performance. The LAPD (ne 10 12 - 13cm-3 , Te 1-10 eV, B0 0.4 to 2 kG, diameter 60 cm, length 17m) is an ideal device for performing detailed experiments to fully diagnose these phenomena. A 200 kW RF system capable of pulsing at the 1 Hz. rep. rate of the LAPD and operating from 2 to 2.5 MHz has been constructed to perform such studies. B0 can be adjusted so that this encompasses the 1st to 7th harmonic of fci in H plasmas. Emissive, Mach, Langmuir, and B-field probes measured plasma potential, bulk plasma flows, wave patterns, ne, and Te in 2D planes at various axial locations from the antenna. Plasma potential enhancements of up to 90 V along magnetic field lines connected to the antenna and induced ExB flows consistent in structure with convective cells were observed. Details of these observations along with power scaling of RF sheath voltage and convective cell flows will be presented.

Influence of residual plasma drift velocity on the post-arc sheath expansion of vacuum circuit breakers

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

Mo, Yongpeng; Shi, Zongqian; Jia, Shenli

The residual plasma in the inter-contact region of a vacuum circuit breaker moves towards the post-arc cathode at current zero, because the residual plasma mainly comes from the cathode spots during the arc burning process. In the most previous theoretical researches on the post-arc sheath expansion process of vacuum circuit breakers, only the thermal motion of residual plasma was taken into consideration. Alternately, the residual plasma was even assumed to be static at the moment of current zero in some simplified models. However, the influence of residual plasma drift velocity at current zero on the post-arc sheath expansion process wasmore » rarely investigated. In this paper, this effect is investigated by a one-dimensional particle-in-cell model. Simulation results indicate that the sheath expands slower with higher residual plasma drift velocity in the initial sheath expansion stage. However, with the increase of residual plasma drift velocity, the overall plasma density in the inter-contact region decreases faster, and the sheath expansion velocity increases earlier. Consequently, as a whole, it needs shorter time to expel the residual plasma from the inter-contact region. Furthermore, if the residual plasma drift velocity is high enough, the sheath expansion process ceases before it develops to the post-arc anode. Besides, the influence of the collisions between charges and neutrals is investigated as well in terms of the density of metal vapor. It shows that the residual plasma drift velocity takes remarkable effect only if the density of the metal vapor is relatively low, which corresponds to the circumstance of low-current interruptions.« less

Sheathless Size-Based Acoustic Particle Separation

PubMed Central

Guldiken, Rasim; Jo, Myeong Chan; Gallant, Nathan D.; Demirci, Utkan; Zhe, Jiang

2012-01-01

Particle separation is of great interest in many biological and biomedical applications. Flow-based methods have been used to sort particles and cells. However, the main challenge with flow based particle separation systems is the need for a sheath flow for successful operation. Existence of the sheath liquid dilutes the analyte, necessitates precise flow control between sample and sheath flow, requires a complicated design to create sheath flow and separation efficiency depends on the sheath liquid composition. In this paper, we present a microfluidic platform for sheathless particle separation using standing surface acoustic waves. In this platform, particles are first lined up at the center of the channel without introducing any external sheath flow. The particles are then entered into the second stage where particles are driven towards the off-center pressure nodes for size based separation. The larger particles are exposed to more lateral displacement in the channel due to the acoustic force differences. Consequently, different-size particles are separated into multiple collection outlets. The prominent feature of the present microfluidic platform is that the device does not require the use of the sheath flow for positioning and aligning of particles. Instead, the sheathless flow focusing and separation are integrated within a single microfluidic device and accomplished simultaneously. In this paper, we demonstrated two different particle size-resolution separations; (1) 3 μm and 10 μm and (2) 3 μm and 5 μm. Also, the effects of the input power, the flow rate, and particle concentration on the separation efficiency were investigated. These technologies have potential to impact broadly various areas including the essential microfluidic components for lab-on-a-chip system and integrated biological and biomedical applications. PMID:22368502

Coevolution of the ATPase ClpV, the Sheath Proteins TssB and TssC, and the Accessory Protein TagJ/HsiE1 Distinguishes Type VI Secretion Classes*

PubMed Central

Förster, Andreas; Planamente, Sara; Manoli, Eleni; Lossi, Nadine S.; Freemont, Paul S.; Filloux, Alain

2014-01-01

The type VI secretion system (T6SS) is a bacterial nanomachine for the transport of effector molecules into prokaryotic and eukaryotic cells. It involves the assembly of a tubular structure composed of TssB and TssC that is similar to the tail sheath of bacteriophages. The sheath contracts to provide the energy needed for effector delivery. The AAA+ ATPase ClpV disassembles the contracted sheath, which resets the systems for reassembly of an extended sheath that is ready to fire again. This mechanism is crucial for T6SS function. In Vibrio cholerae, ClpV binds the N terminus of TssC within a hydrophobic groove. In this study, we resolved the crystal structure of the N-terminal domain of Pseudomonas aeruginosa ClpV1 and observed structural alterations in the hydrophobic groove. The modification in the ClpV1 groove is matched by a change in the N terminus of TssC, suggesting the existence of distinct T6SS classes. An accessory T6SS component, TagJ/HsiE, exists predominantly in one of the classes. Using bacterial two-hybrid approaches, we showed that the P. aeruginosa homolog HsiE1 interacts strongly with ClpV1. We then resolved the crystal structure of HsiE1 in complex with the N terminus of HsiB1, a TssB homolog and component of the contractile sheath. Phylogenetic analysis confirmed that these differences distinguish T6SS classes that resulted from a functional co-evolution between TssB, TssC, TagJ/HsiE, and ClpV. The interaction of TagJ/HsiE with the sheath as well as with ClpV suggests an alternative mode of disassembly in which HsiE recruits the ATPase to the sheath. PMID:25305017

A palladium-doped ceria@carbon core-sheath nanowire network: a promising catalyst support for alcohol electrooxidation reactions

NASA Astrophysics Data System (ADS)

Tan, Qiang; Du, Chunyu; Sun, Yongrong; Du, Lei; Yin, Geping; Gao, Yunzhi

2015-08-01

A novel palladium-doped ceria and carbon core-sheath nanowire network (Pd-CeO2@C CSNWN) is synthesized by a template-free and surfactant-free solvothermal process, followed by high temperature carbonization. This hierarchical network serves as a new class of catalyst support to enhance the activity and durability of noble metal catalysts for alcohol oxidation reactions. Its supported Pd nanoparticles, Pd/(Pd-CeO2@C CSNWN), exhibit >9 fold increase in activity toward the ethanol oxidation over the state-of-the-art Pd/C catalyst, which is the highest among the reported Pd systems. Moreover, stability tests show a virtually unchanged activity after 1000 cycles. The high activity is mainly attributed to the superior oxygen-species releasing capability of Pd-doped CeO2 nanowires by accelerating the removal of the poisoning intermediate. The unique interconnected one-dimensional core-sheath structure is revealed to facilitate immobilization of the metal catalysts, leading to the improved durability. This core-sheath nanowire network opens up a new strategy for catalyst performance optimization for next-generation fuel cells.A novel palladium-doped ceria and carbon core-sheath nanowire network (Pd-CeO2@C CSNWN) is synthesized by a template-free and surfactant-free solvothermal process, followed by high temperature carbonization. This hierarchical network serves as a new class of catalyst support to enhance the activity and durability of noble metal catalysts for alcohol oxidation reactions. Its supported Pd nanoparticles, Pd/(Pd-CeO2@C CSNWN), exhibit >9 fold increase in activity toward the ethanol oxidation over the state-of-the-art Pd/C catalyst, which is the highest among the reported Pd systems. Moreover, stability tests show a virtually unchanged activity after 1000 cycles. The high activity is mainly attributed to the superior oxygen-species releasing capability of Pd-doped CeO2 nanowires by accelerating the removal of the poisoning intermediate. The unique interconnected one-dimensional core-sheath structure is revealed to facilitate immobilization of the metal catalysts, leading to the improved durability. This core-sheath nanowire network opens up a new strategy for catalyst performance optimization for next-generation fuel cells. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03023d

Transmission properties and physical mechanisms of X-ray communication for blackout mitigation during spacecraft reentry

NASA Astrophysics Data System (ADS)

Liu, Yunpeng; Li, Huan; Li, Yanlong; Hang, Shuang; Tang, Xiaobin

2017-11-01

Recent advances in X-ray science have witnessed the X-ray communication (XCOM), a new revolutionary technology first proposed by NASA since 2007. In combination with the advanced modulated X-ray source, XCOM shows a promising prospect for helping to alleviate the occurrence of inevitable blackout communication by using the regular radio frequency (RF) signal, paving the way towards realizing real-time communication during spacecraft reentry into atmosphere. Here, we acquired the detailed information of electron density distribution of plasma sheath encountered during vehicle reentry through Computational Fluid Dynamics simulation. Based on these derived parameters, Finite-difference Time-domain method was employed to investigate the transmission properties of X-rays through the plasma sheath, and the results indicated that X-ray transmission was not influenced by the reentry plasma sheath at different reentry altitudes and spacecraft surface positions compared with RF signal. In addition, 2D Particle-In-Cell simulation was also adopted to provide deeper insight into the transmission properties and physical mechanisms of X-ray carrier propagating through the plasma sheath, and results showed that the transmission coefficient was over 0.994 and the observation of plasma channel effect was also an important signature, which was of great importance to X-ray propagating through the plasma sheath.

C4GEM, a Genome-Scale Metabolic Model to Study C4 Plant Metabolism1[W][OA

PubMed Central

de Oliveira Dal’Molin, Cristiana Gomes; Quek, Lake-Ee; Palfreyman, Robin William; Brumbley, Stevens Michael; Nielsen, Lars Keld

2010-01-01

Leaves of C4 grasses (such as maize [Zea mays], sugarcane [Saccharum officinarum], and sorghum [Sorghum bicolor]) form a classical Kranz leaf anatomy. Unlike C3 plants, where photosynthetic CO2 fixation proceeds in the mesophyll (M), the fixation process in C4 plants is distributed between two cell types, the M cell and the bundle sheath (BS) cell. Here, we develop a C4 genome-scale model (C4GEM) for the investigation of flux distribution in M and BS cells during C4 photosynthesis. C4GEM, to our knowledge, is the first large-scale metabolic model that encapsulates metabolic interactions between two different cell types. C4GEM is based on the Arabidopsis (Arabidopsis thaliana) model (AraGEM) but has been extended by adding reactions and transporters responsible to represent three different C4 subtypes (NADP-ME [for malic enzyme], NAD-ME, and phosphoenolpyruvate carboxykinase). C4GEM has been validated for its ability to synthesize 47 biomass components and consists of 1,588 unique reactions, 1,755 metabolites, 83 interorganelle transporters, and 29 external transporters (including transport through plasmodesmata). Reactions in the common C4 model have been associated with well-annotated C4 species (NADP-ME subtypes): 3,557 genes in sorghum, 11,623 genes in maize, and 3,881 genes in sugarcane. The number of essential reactions not assigned to genes is 131, 135, and 156 in sorghum, maize, and sugarcane, respectively. Flux balance analysis was used to assess the metabolic activity in M and BS cells during C4 photosynthesis. Our simulations were consistent with chloroplast proteomic studies, and C4GEM predicted the classical C4 photosynthesis pathway and its major effect in organelle function in M and BS. The model also highlights differences in metabolic activities around photosystem I and photosystem II for three different C4 subtypes. Effects of CO2 leakage were also explored. C4GEM is a viable framework for in silico analysis of cell cooperation between M and BS cells during photosynthesis and can be used to explore C4 plant metabolism. PMID:20974891

Continuum-kinetic approach to sheath simulations

NASA Astrophysics Data System (ADS)

Cagas, Petr; Hakim, Ammar; Srinivasan, Bhuvana

2016-10-01

Simulations of sheaths are performed using a novel continuum-kinetic model with collisions including ionization/recombination. A discontinuous Galerkin method is used to directly solve the Boltzmann-Poisson system to obtain a particle distribution function. Direct discretization of the distribution function has advantages of being noise-free compared to particle-in-cell methods. The distribution function, which is available at each node of the configuration space, can be readily used to calculate the collision integrals in order to get ionization and recombination operators. Analytical models are used to obtain the cross-sections as a function of energy. Results will be presented incorporating surface physics with a classical sheath in Hall thruster-relevant geometry. This work was sponsored by the Air Force Office of Scientific Research under Grant Number FA9550-15-1-0193.

Study on plasma sheath and plasma transport properties in the azimuthator

NASA Astrophysics Data System (ADS)

Zhenyu, WANG; Binhao, JIANG; N, A. STROKIN; A, N. STUPIN

2018-04-01

A physical model of transport in an azimuthator channel with the sheath effect resulting from the interaction between the plasma and insulation wall is established in this paper. Particle in cell simulation is carried out by the model and results show that, besides the transport due to classical and Bohm diffusions, the sheath effect can significantly influences the transport in the channel. As a result, the ion density is larger than the electron density at the exit of azimuthator, and the non-neutral plasma jet is divergent, which is unfavorable for mass separation. Then, in order to improve performance of the azimuthator, a cathode is designed to emit electrons. Experiment results have demonstrated that the auxiliary cathode can obviously compensate the space charge in the plasma.

Multiple sort flow cytometer

DOEpatents

Van den Engh, Ger; Esposito, Richard J.

1996-01-01

A flow cytometer utilizes multiple lasers for excitation and respective fluorescence of identified dyes bonded to specific cells or events to identify and verify multiple events to be sorted from a sheath flow and droplet stream. Once identified, verified and timed in the sheath flow, each event is independently tagged upon separation from the flow by an electrical charge of +60, +120, or +180 volts and passed through oppositely charged deflection plates with ground planes to yield a focused six way deflection of at least six events in a narrow plane.

Scanning Electron Microscope Examination of Cotton Linters and Wood Pulp Fibers before and after Nitration and Gun Propellant Manufacture

DTIC Science & Technology

1983-03-01

both types of cellulose , the cell walls are still intact with the microfibrils showing little damage. The cellulose microfibrils consist of long chains...25 2. Model of Cellulose Microfibril ... S............. .............. .26 3. Model of Plant Cell Wall Bonding of Microfibril Bundles...molecules protrude above and below the plane of the cellulose ribbon.J’ (See Figures 2 and 3,) Bundles of these cellulose ribbons are called microfibrils

Malignant peripheral nerve sheath tumor of the uterine cervix expressing both S-100 protein and HMB-45.

PubMed

Kim, Na Rae; Chung, Dong-Hae; Park, Chan Yong; Ha, Seung Yeon

2009-12-01

A 50-year-old woman presented with a large cervical polypoid mass. Grossly, the mass occupied a substantial proportion of the cervical canal, measuring 6 cm. Histologically, the mass showed a spindle cell malignancy arranged in large fascicles that penetrated deeply into the fibromuscular wall of the cervix. The spindle cells were immunoreactive for both S-100 protein and HMB-45 antigen, but were negative for Melan-A. Electron microscopy showed that cytoplasmic processes of the spindle to oval tumor cells contained microtubules and were lined by basal lamina and abundant intercellular collagen spacing with no melanosomes in any stage. As far as we are aware, this is the ninth reported case of cervical malignant peripheral nerve sheath tumor (MPNST), and the second reported case of MPNST expressing HMB-45 antigen.

The Mechanosensory Structure of the Hair Cell Requires Clarin-1, a Protein Encoded by Usher Syndrome III Causative Gene

PubMed Central

Geng, Ruishuang; Melki, Sami; Chen, Daniel H.-C.; Tian, Guilian; Furness, David; Oshima-Takago, Tomoko; Neef, Jakob; Moser, Tobias; Askew, Charles; Horwitz, Geoff; Holt, Jeffrey; Imanishi, Yoshikazu; Alagramam, Kumar N.

2012-01-01

Mutation in the clarin-1 gene results in loss of hearing and vision in humans (Usher syndrome III), but the role of clarin-1 in the sensory hair cells is unknown. Clarin-1 is predicted to be a four transmembrane domain protein similar to members of the tetraspanin family. Mice carrying null mutation in the clarin-1 (Clrn1−/−) gene show loss of hair cell function and a possible defect in ribbon synapse. We investigated the role of clarin-1 using various in vitro and in vivo approaches. We show by immunohistochemistry and patch-clamp recordings of Ca2+ currents and membrane capacitance from IHCs that clarin-1 is not essential for formation or function of ribbon synapse. However, reduced cochlear microphonic potentials, FM1-43 loading and transduction currents pointed to diminished cochlear hair bundle function in Clrn1−/− mice. Electron microscopy of cochlear hair cells revealed loss of some tall stereocilia and gaps in the v-shaped bundle, although tip-links and staircase arrangement of stereocilia were not primarily affected by Clrn1−/− mutation. Human clarin-1 protein expressed in transfected mouse cochlear hair cells localized to the bundle; however, the pathogenic variant, p.N48K, failed to localize to the bundle. The mouse model generated to study the in vivo consequence of p. N48K in clarin-1 (Clrn1N48K) supports our in vitro and Clrn1−/− mouse data and the conclusion that CLRN1 is an essential hair bundle protein. Further, the ear phenotype in the Clrn1N48K mouse suggests that it is a valuable model for ear disease in CLRN1N48K, the most prevalent Usher III mutation in North America. PMID:22787034

Mechanical properties of sensory hair bundles are reflected in their Brownian motion measured with a laser differential interferometer.

PubMed Central

Denk, W; Webb, W W; Hudspeth, A J

1989-01-01

By optically probing with a focused, low-power laser beam, we measured the spontaneous deflection fluctuations of the sensory hair bundles on frog saccular hair cells with a sensitivity of about 1 pm/square root of Hz. The preparation was illuminated by two orthogonally polarized laser beams separated by only about 0.2 microns at their foci in the structure under investigation. Slight movement of the object from one beam toward the other caused a change of the phase difference between the transmitted beams and an intensity modulation at the detector where the beams interfered. Maintenance of the health of the cells and function of the transduction mechanism were occasionally confirmed by measuring the intracellular resting potential and the sensitivity of transduction. The root-mean-square (rms) displacement of approximately 3.5 nm at a hair bundle's tip suggests a stiffness of about 350 microN/m, in agreement with measurements made with a probe attached to a bundle's tip. The spectra resemble those of overdamped harmonic oscillators with roll-off frequencies between 200 and 800 Hz. Because the roll-off frequencies depended strongly on the viscosity of the bathing medium, we conclude that hair-bundle motion is mainly damped by the surrounding fluid. PMID:2787510

Enhanced signal-to-noise ratios in frog hearing can be achieved through amplitude death

PubMed Central

Ahn, Kang-Hun

2013-01-01

In the ear, hair cells transform mechanical stimuli into neuronal signals with great sensitivity, relying on certain active processes. Individual hair cell bundles of non-mammals such as frogs and turtles are known to show spontaneous oscillation. However, hair bundles in vivo must be quiet in the absence of stimuli, otherwise the signal is drowned in intrinsic noise. Thus, a certain mechanism is required in order to suppress intrinsic noise. Here, through a model study of elastically coupled hair bundles of bullfrog sacculi, we show that a low stimulus threshold and a high signal-to-noise ratio (SNR) can be achieved through the amplitude death phenomenon (the cessation of spontaneous oscillations by coupling). This phenomenon occurs only when the coupled hair bundles have inhomogeneous distribution, which is likely to be the case in biological systems. We show that the SNR has non-monotonic dependence on the mass of the overlying membrane, and find out that the SNR has maximum value in the region of amplitude death. The low threshold of stimulus through amplitude death may account for the experimentally observed high sensitivity of frog sacculi in detecting vibration. The hair bundles' amplitude death mechanism provides a smart engineering design for low-noise amplification. PMID:23883956

A nano-microstructured artificial-hair-cell-type sensor based on topologically graded 3D carbon nanotube bundles

NASA Astrophysics Data System (ADS)

Yilmazoglu, O.; Yadav, S.; Cicek, D.; Schneider, J. J.

2016-09-01

A design for a unique artificial-hair-cell-type sensor (AHCTS) based entirely on 3D-structured, vertically aligned carbon nanotube (CNT) bundles is introduced. Standard microfabrication techniques were used for the straightforward micro-nano integration of vertically aligned carbon nanotube arrays composed of low-layer multi-walled CNTs (two to six layers). The mechanical properties of the carbon nanotube bundles were intensively characterized with regard to various substrates and CNT morphology, e.g. bundle height. The CNT bundles display excellent flexibility and mechanical stability for lateral bending, showing high tear resistance. The integrated 3D CNT sensor can detect three-dimensional forces using the deflection or compression of a central CNT bundle which changes the contact resistance to the shorter neighboring bundles. The complete sensor system can be fabricated using a single chemical vapor deposition (CVD) process step. Moreover, sophisticated external contacts to the surroundings are not necessary for signal detection. No additional sensors or external bias for signal detection are required. This simplifies the miniaturization and the integration of these nanostructures for future microsystem set-ups. The new nanostructured sensor system exhibits an average sensitivity of 2100 ppm in the linear regime with the relative resistance change per micron (ppm μm-1) of the individual CNT bundle tip deflection. Furthermore, experiments have shown highly sensitive piezoresistive behavior with an electrical resistance decrease of up to ˜11% at 50 μm mechanical deflection. The detection sensitivity is as low as 1 μm of deflection, and thus highly comparable with the tactile hair sensors of insects, having typical thresholds on the order of 30-50 μm. The AHCTS can easily be adapted and applied as a flow, tactile or acceleration sensor as well as a vibration sensor. Potential applications of the latter might come up in artificial cochlear systems. In particular, the stable mechanical bending of the sensor up to 90° opens up unique application opportunities.

A palladium-doped ceria@carbon core-sheath nanowire network: a promising catalyst support for alcohol electrooxidation reactions.

PubMed

Tan, Qiang; Du, Chunyu; Sun, Yongrong; Du, Lei; Yin, Geping; Gao, Yunzhi

2015-08-28

A novel palladium-doped ceria and carbon core-sheath nanowire network (Pd-CeO2@C CSNWN) is synthesized by a template-free and surfactant-free solvothermal process, followed by high temperature carbonization. This hierarchical network serves as a new class of catalyst support to enhance the activity and durability of noble metal catalysts for alcohol oxidation reactions. Its supported Pd nanoparticles, Pd/(Pd-CeO2@C CSNWN), exhibit >9 fold increase in activity toward the ethanol oxidation over the state-of-the-art Pd/C catalyst, which is the highest among the reported Pd systems. Moreover, stability tests show a virtually unchanged activity after 1000 cycles. The high activity is mainly attributed to the superior oxygen-species releasing capability of Pd-doped CeO2 nanowires by accelerating the removal of the poisoning intermediate. The unique interconnected one-dimensional core-sheath structure is revealed to facilitate immobilization of the metal catalysts, leading to the improved durability. This core-sheath nanowire network opens up a new strategy for catalyst performance optimization for next-generation fuel cells.

Infrared imaging spectrometry by the use of bundled chalcogenide glass fibers and a PtSi CCD camera

NASA Astrophysics Data System (ADS)

Saito, Mitsunori; Kikuchi, Katsuhiro; Tanaka, Chinari; Sone, Hiroshi; Morimoto, Shozo; Yamashita, Toshiharu T.; Nishii, Junji

1999-10-01

A coherent fiber bundle for infrared image transmission was prepared by arranging 8400 chalcogenide (AsS) glass fibers. The fiber bundle, 1 m in length, is transmissive in the infrared spectral region of 1 - 6 micrometer. A remote spectroscopic imaging system was constructed with the fiber bundle and an infrared PtSi CCD camera. The system was used for the real-time observation (frame time: 1/60 s) of gas distribution. Infrared light from a SiC heater was delivered to a gas cell through a chalcogenide fiber, and transmitted light was observed through the fiber bundle. A band-pass filter was used for the selection of gas species. A He-Ne laser of 3.4 micrometer wavelength was also used for the observation of hydrocarbon gases. Gases bursting from a nozzle were observed successfully by a remote imaging system.

Theory and Simulation of Electron Sheaths and Anode Spots in Low Pressure Laboratory Plasmas

NASA Astrophysics Data System (ADS)

Scheiner, Brett Stanford

Electrodes in low pressure laboratory plasmas have a multitude of possible sheath structures when biased at a large positive potential. When the size of the electrode is small enough the electrode bias can be above the plasma potential. When this occurs an electron-rich sheath called an electron sheath is present at the electrode. Electron sheaths are most commonly found near Langmuir probes and other electrodes collecting the electron saturation current. Such electrodes have applications in the control of plasma parameters, dust confinement and circulation, control of scrape off layer plasmas, RF plasmas, and in plasma contactors and tethered space probes. The electron sheaths in these various systems most directly influence the plasma by determining how electron current is lost from the system. An understanding of how the electron sheath interfaces with the bulk plasma is necessary for understanding the behavior induced by positively biased electrodes in these plasmas. This thesis provides a dedicated theory of electron sheaths. Motivated by electron velocity distribution functions (EVDFs) observed in particle-in-cell (PIC) simulations, a 1D model for the electron sheath and presheath is developed. In the presheath model, an electron pressure gradient accelerates electrons to near the electron thermal speed by the sheath edge. This pressure gradient generates large flow velocities compared to what would be generated by ballistic motion in response to the electric field. Using PIC simulations, the form of a sheath near a small electrode with bias near the plasma potential is also studied. When the electrode is biased near the plasma potential, the EVDFs exhibit a loss-cone type truncation due to fast electrons overcoming the small potential difference between the electrode and plasma. No sheath is present in this regime, instead the plasma remains quasineutral up to the electrode. Once the bias exceeds the plasma potential an electron sheath is present. In this case, 2D EVDFs indicate that the flow moment has comparable contributions from the flow shift and loss-cone truncation. The case of an electrode at large positive bias relative to the plasma potential is also studied. Here, the rate of electron impact ionization of neutrals increases near the electrode. If this ionization rate is great enough a double layer forms. This double layer can move outward separating a high potential plasma at the electrode surface from the bulk plasma. This phenomenon is known as an anode spot. Informed by observations from the first PIC simulations of an anode spot, a model has been developed describing the onset in which ionization leads to the buildup of positive space charge and the formation of a potential well that traps electrons near the electrode surface. A model for steady-state properties based on current loss, power, and particle balance of the anode spot plasma is also presented.

Morphology, Growth, and Size Limit of Bacterial Cells

NASA Astrophysics Data System (ADS)

Jiang, Hongyuan; Sun, Sean X.

2010-07-01

Bacterial cells utilize a living peptidoglycan network (PG) to separate the cell interior from the surroundings. The shape of the cell is controlled by PG synthesis and cytoskeletal proteins that form bundles and filaments underneath the cell wall. The PG layer also resists turgor pressure and protects the cell from osmotic shock. We argue that mechanical influences alter the chemical equilibrium of the reversible PG assembly and determine the cell shape and cell size. Using a mechanochemical approach, we show that the cell shape can be regarded as a steady state of a growing network under the influence of turgor pressure and mechanical stress. Using simple elastic models, we predict the size of common spherical and rodlike bacteria. The influence of cytoskeletal bundles such as crescentin and MreB are discussed within the context of our model.

Quantitative Analysis of Statics and Dynamics of Actin Cables in Fission Yeast

NASA Astrophysics Data System (ADS)

Yusuf, Eddy; Wu, Jian-Qiu; Vavylonis, Dimitrios

2010-03-01

The assembly of actin and tubulin proteins into long filaments and bundles, i.e. closely-packed filaments, underlies important cellular processes such as cell motility, intracellular transport, and cell division. Recent theoretical and experimental work has addressed the nonequilibrium dynamics of single microtubules within live cells [1]. Actin filaments usually form dense networks that prevents microscopic imaging of individual filaments or bundles. Here, we studied actin dynamics using fission yeast that has low-density actin cytoskeleton consisting of actin cables (actin bundles aligned along the long axis of the cell) and ``actin patches.'' Yeast cells expressing GFP-CHD were imaged by 3D confocal microscopy. Stretching open active contours [2] were used to segment and track individual actin cables. We analyzed their curvature distribution, the tangent correlation, and the temporal bending amplitude fluctuations. We contrast our findings to equilibrium fluctuating semiflexible polymers and to microtubules in cells. We calculate the important time and length scales for the actin cables. We also discuss our findings within the broad context of understanding actin assembly in cells. [1] C. P. Brangwynne et. al., Phys. Rev. Lett. 100, 118104 (2008) [2] H. Li et. al., Proc. of the IEEE Int'l Symposium on Biomedical Imaging: From Nano to Macro, ISBI'09

Microscopic Analysis of Bacterial Motility at High Pressure

PubMed Central

Nishiyama, Masayoshi; Sowa, Yoshiyuki

2012-01-01

The bacterial flagellar motor is a molecular machine that converts an ion flux to the rotation of a helical flagellar filament. Counterclockwise rotation of the filaments allows them to join in a bundle and propel the cell forward. Loss of motility can be caused by environmental factors such as temperature, pH, and solvation. Hydrostatic pressure is also a physical inhibitor of bacterial motility, but the detailed mechanism of this inhibition is still unknown. Here, we developed a high-pressure microscope that enables us to acquire high-resolution microscopic images, regardless of applied pressures. We also characterized the pressure dependence of the motility of swimming Escherichia coli cells and the rotation of single flagellar motors. The fraction and speed of swimming cells decreased with increased pressure. At 80 MPa, all cells stopped swimming and simply diffused in solution. After the release of pressure, most cells immediately recovered their initial motility. Direct observation of the motility of single flagellar motors revealed that at 80 MPa, the motors generate torque that should be sufficient to join rotating filaments in a bundle. The discrepancy in the behavior of free swimming cells and individual motors could be due to the applied pressure inhibiting the formation of rotating filament bundles that can propel the cell body in an aqueous environment. PMID:22768943

Particle-in-cell and global simulations of α to γ transition in atmospheric pressure Penning-dominated capacitive discharges

NASA Astrophysics Data System (ADS)

Kawamura, E.; Lieberman, M. A.; Lichtenberg, A. J.; Chabert, P.; Lazzaroni, C.

2014-06-01

Atmospheric pressure radio-frequency (rf) capacitive micro-discharges are of interest due to emerging applications, especially in the bio-medical field. A previous global model did not consider high-power phenomena such as sheath multiplication, thus limiting its applicability to the lower power range. To overcome this, we use one-dimensional particle-in-cell (PIC) simulations of atmospheric He/0.1% N2 capacitive discharges over a wide range of currents and frequencies to guide the development of a more general global model which is also valid at higher powers. The new model includes sheath multiplication and two classes of electrons: the higher temperature ‘hot’ electrons associated with the sheaths, and the cooler ‘warm’ electrons associated with the bulk. The electric field and the electron power balance are solved analytically to determine the time-varying hot and warm temperatures and the effective rate coefficients. The particle balance equations are integrated numerically to determine the species densities. The model and PIC results are compared, showing reasonable agreement over the range of currents and frequencies studied. They indicate a transition from an α mode at low power characterized by relatively high electron temperature Te with a near uniform profile to a γ mode at high power with a Te profile strongly depressed in the bulk plasma. The transition is accompanied by an increase in density and a decrease in sheath widths. The current and frequency scalings of the model are confirmed by the PIC simulations.

Influence of carbon nanotubes on the buckling of microtubule bundles in viscoelastic cytoplasm using nonlocal strain gradient theory

NASA Astrophysics Data System (ADS)

Farajpour, A.; Rastgoo, A.

Carbon nanotubes are a new class of microtubule-stabilizing agents since they interact with protein microtubules in living cells, interfering with cell division and inducing apoptosis. In the present work, a modified beam model is developed to investigate the effect of carbon nanotubes on the buckling of microtubule bundles in living cell. A realistic interaction model is employed using recent experimental data on the carbon nanotube-stabilized microtubules. Small scale and surface effects are taken into account applying the nonlocal strain gradient theory and surface elasticity theory. Pasternak model is used to describe the normal and shearing effects of enclosing filament matrix on the buckling behavior of the system. An exact solution is obtained for the buckling growth rates of the mixed bundle in viscoelastic surrounding cytoplasm. The present results are compared with those reported in the open literature for single microtubules and an excellent agreement is found. Finally, the effects of different parameters such as the size, chirality, position and surface energy of carbon nanotubes on the buckling growth rates of microtubule bundles are studied. It is found that the buckling growth rate may increase or decrease by adding carbon nanotubes, depending on the diameter and chirality of carbon nanotubes.

Class III myosins shape the auditory hair bundles by limiting microvilli and stereocilia growth

PubMed Central

Lelli, Andrea; Michel, Vincent; Boutet de Monvel, Jacques; Cortese, Matteo; Bosch-Grau, Montserrat; Aghaie, Asadollah; Perfettini, Isabelle; Dupont, Typhaine; Avan, Paul

2016-01-01

The precise architecture of hair bundles, the arrays of mechanosensitive microvilli-like stereocilia crowning the auditory hair cells, is essential to hearing. Myosin IIIa, defective in the late-onset deafness form DFNB30, has been proposed to transport espin-1 to the tips of stereocilia, thereby promoting their elongation. We show that Myo3a−/−Myo3b−/− mice lacking myosin IIIa and myosin IIIb are profoundly deaf, whereas Myo3a-cKO Myo3b−/− mice lacking myosin IIIb and losing myosin IIIa postnatally have normal hearing. Myo3a−/−Myo3b−/− cochlear hair bundles display robust mechanoelectrical transduction currents with normal kinetics but show severe embryonic abnormalities whose features rapidly change. These include abnormally tall and numerous microvilli or stereocilia, ungraded stereocilia bundles, and bundle rounding and closure. Surprisingly, espin-1 is properly targeted to Myo3a−/−Myo3b−/− stereocilia tips. Our results uncover the critical role that class III myosins play redundantly in hair-bundle morphogenesis; they unexpectedly limit the elongation of stereocilia and of subsequently regressing microvilli, thus contributing to the early hair bundle shaping. PMID:26754646

The very large G-protein-coupled receptor VLGR1: a component of the ankle link complex required for the normal development of auditory hair bundles.

PubMed

McGee, Joann; Goodyear, Richard J; McMillan, D Randy; Stauffer, Eric A; Holt, Jeffrey R; Locke, Kirsten G; Birch, David G; Legan, P Kevin; White, Perrin C; Walsh, Edward J; Richardson, Guy P

2006-06-14

Sensory hair bundles in the inner ear are composed of stereocilia that can be interconnected by a variety of different link types, including tip links, horizontal top connectors, shaft connectors, and ankle links. The ankle link antigen is an epitope specifically associated with ankle links and the calycal processes of photoreceptors in chicks. Mass spectrometry and immunoblotting were used to identify this antigen as the avian ortholog of the very large G-protein-coupled receptor VLGR1, the product of the Usher syndrome USH2C (Mass1) locus. Like ankle links, Vlgr1 is expressed transiently around the base of developing hair bundles in mice. Ankle links fail to form in the cochleae of mice carrying a targeted mutation in Vlgr1 (Vlgr1/del7TM), and the bundles become disorganized just after birth. FM1-43 [N-(3-triethylammonium)propyl)-4-(4-(dibutylamino)styryl) pyridinium dibromide] dye loading and whole-cell recordings indicate mechanotransduction is impaired in cochlear, but not vestibular, hair cells of early postnatal Vlgr1/del7TM mutant mice. Auditory brainstem recordings and distortion product measurements indicate that these mice are severely deaf by the third week of life. Hair cells from the basal half of the cochlea are lost in 2-month-old Vlgr1/del7TM mice, and retinal function is mildly abnormal in aged mutants. Our results indicate that Vlgr1 is required for formation of the ankle link complex and the normal development of cochlear hair bundles.

Trial of Dasatinib in Advanced Sarcomas

ClinicalTrials.gov

2017-03-20

Rhabdomyosarcoma; Malignant Peripheral Nerve Sheath Tumors; Chondrosarcoma; Sarcoma, Ewing's; Sarcoma, Alveolar Soft Part; Chordoma; Epithelioid Sarcoma; Giant Cell Tumor of Bone; Hemangiopericytoma; Gastrointestinal Stromal Tumor (GIST)

Multiple Giant Cell Tumor of Tendon Sheath Involving Both Flexor and Extensor Tendons in a Single Digit: A Case Report and Review of the Literatures.

PubMed

Min, Hak Jin; Kim, Jeong Hwan; Kim, Jae Woo; Yeom, Jae Woo

2018-06-01

Giant cell tumor of the tendon sheath (GCTTS) is a common neoplasm of the hand. This tumor is usually solitary. Multi focal origin of the tumor is considered unusual and very few cases of multiple GCTTS have been reported. We report a 48-year-old female patient who presented with three separate painless nodules in same index finger since three years. The two masses located on dorsal aspect, and the other one located on volar aspect. The imaging studies revealed three separated masses without any connection. We performed excisional biopsy and found multiple tumors, attached to flexor and extensor tendon. The final histopathologic diagnosis was GCTTS.

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

Chung, Peter J.; Song, Chaeyeon; Deek, Joanna

Tau, an intrinsically disordered protein confined to neuronal axons, binds to and regulates microtubule dynamics. Although there have been observations of string-like microtubule fascicles in the axon initial segment (AIS) and hexagonal bundles in neurite-like processes in non-neuronal cells overexpressing Tau, cell-free reconstitutions have not replicated either geometry. Here we map out the energy landscape of Tau-mediated, GTP-dependent ‘active’ microtubule bundles at 37°C, as revealed by synchrotron SAXS and TEM. Widely spaced bundles (wall-to-wall distance D w–w≈25–41nm) with hexagonal and string-like symmetry are observed, the latter mimicking bundles found in the AIS. A second energy minimum (D w–w≈16–23nm) is revealedmore » under osmotic pressure. The wide spacing results from a balance between repulsive forces, due to Tau’s projection domain (PD), and a stabilizing sum of transient sub-k BT cationic/anionic charge–charge attractions mediated by weakly penetrating opposing PDs. In the end, we find that this landscape would be significantly affected by charge-altering modifications of Tau associated with neurodegeneration.« less

Electrostatic interaction between stereocilia: I. Its role in supporting the structure of the hair bundle.

PubMed

Dolgobrodov, S G; Lukashkin, A N; Russell, I J

2000-12-01

This paper provides theoretical estimates for the forces of electrostatic interaction between adjacent stereocilia in auditory and vestibular hair cells. Estimates are given for parameters within the measured physiological range using constraints appropriate for the known geometry of the hair bundle. Stereocilia are assumed to possess an extended, negatively charged surface coat, the glycocalyx. Different charge distribution profiles within the glycocalyx are analysed. It is shown that charged glycocalices on the apical surface of the hair cells can support spatial separation between adjacent stereocilia in the hair bundles through electrostatic repulsion between stereocilia. The charge density profile within the glycocalyx is a crucial parameter. In fact, attraction instead of repulsion between adjacent stereocilia will be observed if the charge of the glycocalyx is concentrated near the membrane of the stereocilia, thereby making this type of charge distribution unlikely. The forces of electrostatic interaction between stereocilia may influence the mechanical properties of the hair bundle and, being strongly non-linear, contribute to the non-linear phenomena that have been recorded from the periphery of the auditory and vestibular systems.

Epithelioid variant of malignant peripheral nerve sheath tumor (malignant schwannoma) of the urinary bladder.

PubMed

Eltoum, I A; Moore, R J; Cook, W; Crowe, D R; Rodgers, W H; Siegal, G P

1999-10-01

Sarcoma represents less than 2% of all neoplasms diagnosed or recognized in effusions. Epithelioid peripheral nerve sheath tumor is a rare tumor that is difficult to differentiate from other epithelioid tumors without the use of ancillary studies. A 39-year-old paraplegic man presented with hematuria and a bladder mass that extended to involve the pelvic peritoneum. Light microscopy using hematoxylin-eosin, Papanicolaou, and immunohistochemical stains as well as transmission electron microscopy showed features of epithelioid malignant peripheral nerve sheath tumor with rhabdoid features and an accompanying eosinophilic infiltrate. Cytologic smears confirmed the similarities between the primary tumor in the bladder and the cells in the pelvic fluid and excluded the possibility of reactive changes related to postsurgical radiation. Ancillary studies were critical in narrowing the differential diagnoses and reaching the final conclusion.

High-resolution imaging of the retinal nerve fiber layer in normal eyes using adaptive optics scanning laser ophthalmoscopy.

PubMed

Takayama, Kohei; Ooto, Sotaro; Hangai, Masanori; Arakawa, Naoko; Oshima, Susumu; Shibata, Naohisa; Hanebuchi, Masaaki; Inoue, Takashi; Yoshimura, Nagahisa

2012-01-01

To conduct high-resolution imaging of the retinal nerve fiber layer (RNFL) in normal eyes using adaptive optics scanning laser ophthalmoscopy (AO-SLO). AO-SLO images were obtained in 20 normal eyes at multiple locations in the posterior polar area and a circular path with a 3-4-mm diameter around the optic disc. For each eye, images focused on the RNFL were recorded and a montage of AO-SLO images was created. AO-SLO images for all eyes showed many hyperreflective bundles in the RNFL. Hyperreflective bundles above or below the fovea were seen in an arch from the temporal periphery on either side of a horizontal dividing line to the optic disc. The dark lines among the hyperreflective bundles were narrower around the optic disc compared with those in the temporal raphe. The hyperreflective bundles corresponded with the direction of the striations on SLO red-free images. The resolution and contrast of the bundles were much higher in AO-SLO images than in red-free fundus photography or SLO red-free images. The mean hyperreflective bundle width around the optic disc had a double-humped shape; the bundles at the temporal and nasal sides of the optic disc were narrower than those above and below the optic disc (P<0.001). RNFL thickness obtained by optical coherence tomography correlated with the hyperreflective bundle widths on AO-SLO (P<0.001) AO-SLO revealed hyperreflective bundles and dark lines in the RNFL, believed to be retinal nerve fiber bundles and Müller cell septa. The widths of the nerve fiber bundles appear to be proportional to the RNFL thickness at equivalent distances from the optic disc.

Micro-PIXE investigation of bean seeds to assist micronutrient biofortification

NASA Astrophysics Data System (ADS)

Cvitanich, Cristina; Przybyłowicz, Wojciech J.; Mesjasz-Przybyłowicz, Jolanta; Blair, Matthew W.; Astudillo, Carolina; Orłowska, Elżbieta; Jurkiewicz, Anna M.; Jensen, Erik Ø.; Stougaard, Jens

2011-10-01

This study compares the distribution and concentrations of micro- and macronutrients in different bean cultivars with the aim of optimizing the biofortification, a sustainable approach towards improving dietary quality. Micro-PIXE was used to reveal the distribution of Fe, Zn, Mn, Ca, P, S in seeds of common beans (Phaseolus vulgaris) and runner beans (Phaseolus coccineus). Average concentrations of elements in different tissues were obtained using ICP-AES. The highest concentrations of Zn in the studied beans were found in the embryonic axis, but an increased concentration of this element was also detected in the provascular bundles of the cotyledons. The first layer of cells surrounding provascular bundles accumulated high concentrations of Fe, while the next cell layer had an increased concentration of Mn. The analysis showed that the provascular bundles and the first cell layers surrounding them could have a significant role in the storage of important seed micronutrients - Zn, Fe, and Mn. This information has important implications for molecular biology studies aimed at seed biofortification.

Artificial hair cell integrated with an artificial neuron: Interplay between criticality and excitability

NASA Astrophysics Data System (ADS)

Lee, Woo Seok; Jeong, Wonhee; Ahn, Kang-Hun

2014-12-01

We provide a simple dynamical model of a hair cell with an afferent neuron where the spectral and the temporal responses are controlled by the hair bundle's criticality and the neuron's excitability. To demonstrate that these parameters, indeed, specify the resolution of the sound encoding, we fabricate a neuromorphic device that models the hair cell bundle and its afferent neuron. Then, we show that the neural response of the biomimetic system encodes sounds with either high temporal or spectral resolution or with a combination of both resolutions. Our results suggest that the hair cells may easily specialize to fulfil various roles in spite of their similar physiological structures.

Histochemical studies on protease formation in the cotyledons of germinating bean seeds.

PubMed

Yomo, H; Taylor, M P

1973-03-01

Protease formation in Phaseolus vulgaris L. cotyledons during seed germination was studied histochemically using a gelatin-film-substrate method. Protease activity can be detected by this method on the 5th day of germination, at approximately the same time that a rapid increase of activity was observed by a test-tube assay with casein as a substrate. At the early stage of germination, protease activity was observed throughout the cotyledon except in two or three cell layers below the cotyledon surface and in several cell layers around the vascular bundles. A highly active cell layer surrounding the protease-inactive cells near the vascular bundles is suggested to be a source of the protease.

Identification of Maize Silicon Influx Transporters

PubMed Central

Mitani, Namiki; Yamaji, Naoki; Ma, Jian Feng

2009-01-01

Maize (Zea mays L.) shows a high accumulation of silicon (Si), but transporters involved in the uptake and distribution have not been identified. In the present study, we isolated two genes (ZmLsi1 and ZmLsi6), which are homologous to rice influx Si transporter OsLsi1. Heterologous expression in Xenopus laevis oocytes showed that both ZmLsi1 and ZmLsi6 are permeable to silicic acid. ZmLsi1 was mainly expressed in the roots. By contrast, ZmLsi6 was expressed more in the leaf sheaths and blades. Different from OsLsi1, the expression level of both ZmLsi1 and ZmLsi6 was unaffected by Si supply. Immunostaining showed that ZmLsi1 was localized on the plasma membrane of the distal side of root epidermal and hypodermal cells in the seminal and crown roots, and also in cortex cells in lateral roots. In the shoots, ZmLsi6 was found in the xylem parenchyma cells that are adjacent to the vessels in both leaf sheaths and leaf blades. ZmLsi6 in the leaf sheaths and blades also exhibited polar localization on the side facing towards the vessel. Taken together, it can be concluded that ZmLsi1 is an influx transporter of Si, which is responsible for the transport of Si from the external solution to the root cells and that ZmLsi6 mainly functions as a Si transporter for xylem unloading. PMID:18676379

Sperm dynamics in spiders (Araneae): ultrastructural analysis of the sperm activation process in the garden spider Argiope bruennichi (Scopoli, 1772).

PubMed

Vöcking, Oliver; Uhl, Gabriele; Michalik, Peter

2013-01-01

Storage of sperm inside the female genital tract is an integral phase of reproduction in many animal species. The sperm storage site constitutes the arena for sperm activation, sperm competition and female sperm choice. Consequently, to understand animal mating systems information on the processes that occur from sperm transfer to fertilization is required. Here, we focus on sperm activation in spiders. Male spiders produce sperm whose cell components are coiled within the sperm cell and that are surrounded by a proteinaceous sheath. These inactive and encapsulated sperm are transferred to the female spermathecae where they are stored for later fertilization. We analyzed the ultrastructural changes of sperm cells during residency time in the female genital system of the orb-web spider Argiope bruennichi. We found three clearly distinguishable sperm conditions: encapsulated sperm (secretion sheath present), decapsulated (secretion sheath absent) and uncoiled sperm (cell components uncoiled, presumably activated). After insemination, sperm remain in the encapsulated condition for several days and become decapsulated after variable periods of time. A variable portion of the decapsulated sperm transforms rapidly to the uncoiled condition resulting in a simultaneous occurrence of decapsulated and uncoiled sperm. After oviposition, only decapsulated and uncoiled sperm are left in the spermathecae, strongly suggesting that the activation process is not reversible. Furthermore, we found four different types of secretion in the spermathecae which might play a role in the decapsulation and activation process.

Proteome Analysis of Watery Saliva Secreted by Green Rice Leafhopper, Nephotettix cincticeps

PubMed Central

Hattori, Makoto; Komatsu, Setsuko; Noda, Hiroaki; Matsumoto, Yukiko

2015-01-01

The green rice leafhopper, Nephotettix cincticeps, is a vascular bundle feeder that discharges watery and gelling saliva during the feeding process. To understand the potential functions of saliva for successful and safe feeding on host plants, we analyzed the complexity of proteinaceous components in the watery saliva of N. cincticeps. Salivary proteins were collected from a sucrose diet that adult leafhoppers had fed on through a membrane of stretched parafilm. Protein concentrates were separated using SDS-PAGE under reducing and non-reducing conditions. Six proteins were identified by a gas-phase protein sequencer and two proteins were identified using LC-MS/MS analysis with reference to expressed sequence tag (EST) databases of this species. Full -length cDNAs encoding these major proteins were obtained by rapid amplification of cDNA ends-PCR (RACE-PCR) and degenerate PCR. Furthermore, gel-free proteome analysis that was performed to cover the broad range of salivary proteins with reference to the latest RNA-sequencing data from the salivary gland of N. cincticeps, yielded 63 additional protein species. Out of 71 novel proteins identified from the watery saliva, about 60 % of those were enzymes or other functional proteins, including GH5 cellulase, transferrin, carbonic anhydrases, aminopeptidase, regucalcin, and apolipoprotein. The remaining proteins appeared to be unique and species- specific. This is the first study to identify and characterize the proteins in watery saliva of Auchenorrhyncha species, especially sheath-producing, vascular bundle-feeders. PMID:25909947

Morphological and functional characteristics of the kidney of cartilaginous fishes: with special reference to urea reabsorption.

PubMed

Hyodo, Susumu; Kakumura, Keigo; Takagi, Wataru; Hasegawa, Kumi; Yamaguchi, Yoko

2014-12-15

For adaptation to high-salinity marine environments, cartilaginous fishes (sharks, skates, rays, and chimaeras) adopt a unique urea-based osmoregulation strategy. Their kidneys reabsorb nearly all filtered urea from the primary urine, and this is an essential component of urea retention in their body fluid. Anatomical investigations have revealed the extraordinarily elaborate nephron system in the kidney of cartilaginous fishes, e.g., the four-loop configuration of each nephron, the occurrence of distinct sinus and bundle zones, and the sac-like peritubular sheath in the bundle zone, in which the nephron segments are arranged in a countercurrent fashion. These anatomical and morphological characteristics have been considered to be important for urea reabsorption; however, a mechanism for urea reabsorption is still largely unknown. This review focuses on recent progress in the identification and mapping of various pumps, channels, and transporters on the nephron segments in the kidney of cartilaginous fishes. The molecules include urea transporters, Na(+)/K(+)-ATPase, Na(+)-K(+)-Cl(-) cotransporters, and aquaporins, which most probably all contribute to the urea reabsorption process. Although research is still in progress, a possible model for urea reabsorption in the kidney of cartilaginous fishes is discussed based on the anatomical features of nephron segments and vascular systems and on the results of molecular mapping. The molecular anatomical approach thus provides a powerful tool for understanding the physiological processes that take place in the highly elaborate kidney of cartilaginous fishes. Copyright © 2014 the American Physiological Society.

Myelin

MedlinePlus

... and fatty substances. This myelin sheath allows electrical impulses to transmit quickly and efficiently along the nerve cells. If myelin is damaged, these impulses slow down. This can cause diseases such as ...

Development of the nervous system in Phoronopsis harmeri (Lophotrochozoa, Phoronida) reveals both deuterostome- and trochozoan-like features

PubMed Central

2012-01-01

Background Inferences concerning the evolution of invertebrate nervous systems are often hampered by the lack of a solid data base for little known but phylogenetically crucial taxa. In order to contribute to the discussion concerning the ancestral neural pattern of the Lophotrochozoa (a major clade that includes a number of phyla that exhibit a ciliated larva in their life cycle), we investigated neurogenesis in Phoronopsis harmeri, a member of the poorly studied Phoronida, by using antibody staining against serotonin and FMRFamide in combination with confocal microscopy and 3D reconstruction software. Results The larva of Phoronopsis harmeri exhibits a highly complex nervous system, including an apical organ that consists of four different neural cell types, such as numerous serotonin-like immunoreactive flask-shaped cells. In addition, serotonin- and FMRFamide-like immunoreactive bi- or multipolar perikarya that give rise to a tentacular neurite bundle which innervates the postoral ciliated band are found. The preoral ciliated band is innervated by marginal serotonin-like as well as FMRFamide-like immunoreactive neurite bundles. The telotroch is innervated by two neurite bundles. The oral field is the most densely innervated area and contains ventral and ventro-lateral neurite bundles as well as several groups of perikarya. The digestive system is innervated by both serotonin- and FMRFamide-like immunoreactive neurites and perikarya. Importantly, older larvae of P. harmeri show a paired ventral neurite bundle with serial commissures and perikarya. Conclusions Serotonin-like flask-shaped cells such as the ones described herein for Phoronopsis harmeri are found in the majority of lophotrochozoan larvae and therefore most likely belong to the ground pattern of the last common lophotrochozoan ancestor. The finding of a transitory paired ventral neurite bundle with serially repeated commissures that disappears during metamorphosis suggests that such a structure was part of the “ur-phoronid” nervous system, but was lost in the adult stage, probably due to its acquired sessile benthic lifestyle. PMID:22827441

Visible red light enhances physiological anagen entry in vivo and has direct and indirect stimulative effects in vitro.

PubMed

Sheen, Yi-Shuan; Fan, Sabrina Mai-Yi; Chan, Chih-Chieh; Wu, Yueh-Feng; Jee, Shiou-Hwa; Lin, Sung-Jan

2015-01-01

Hair follicles are located at the interface of the external and internal environments and their cycling has been shown to be regulated by intra- and extra-follicular factors. The aim of this study is to examine whether or how hair follicles respond to visible light. We examined the effect of 3 mW red (630 nm, 1 J/cm(2)), 2 mW green (522 nm, 1 J/cm(2)), and 2 mW blue light (463 nm, 1 J/cm(2)) on telogen in mice for 3 weeks. The photobiologic effects of red light on cell proliferation of outer root sheath keratinocytes and dermal papilla cells were studied in vitro. We found that red light accelerated anagen entry faster than green and blue light in mice. Red light irradiation stimulated the proliferation of both outer root sheath keratinocytes and dermal papilla cells in a dose-dependent manner by promoting cell cycle progression. This stimulative effect was mediated via extracellular signal-regulated kinase phosphorylation in both cells. In a co-culture condition, dermal papilla cells irradiated by red light further enhanced keratinocyte proliferation, suggesting enhanced epithelial-mesenchymal interaction. In search for factors that mediated this paracrine effect, we found fibroblast growth factor 7 was upregulated in both mRNA and protein levels. The stimulative paracrine effect on keratinocytes was significantly inhibited by neutralizing antibody against fibroblast growth factor 7. These results suggest that hair follicles respond to visible light in vivo. Red light may promote physiological telogen to anagen transition by directly stimulating outer root sheath keratinocytes and indirectly by enhancing epithelial-mesenchymal interaction in vitro. © 2014 Wiley Periodicals, Inc.

IGFBP-7 inhibits the differentiation of oligodendrocyte precursor cells via regulation of Wnt/β-Catenin signaling.

PubMed

Li, Nan; Han, Jinfeng; Tang, Jing; Ying, Yanqin

2018-06-01

Oligodendrocytes (OLs) are glial cells that form myelin sheaths in the central nervous system. Myelin sheath plays important role in nervous system and loss of it in neurodegenerative diseases can lead to impairment of movement. Understanding the signals and factors that regulate OL differentiation can help to address novel strategies for improving myelin repair in neurodegenerative diseases. The aim of this study was to investigate the role of insulin-like growth factor-binding proteins 7 (IGFBP-7) in differentiating OL precursor cells (OPCs). It was found that oligodendrocyte precursors undergoing differentiation were accompanied by selective expression of IGFBP-7. In addition, knockdown of IGFBP-7 promoted differentiation of oligodendrocytes and increased formation of myelin in cultured cells. In contrast, excessive expression of IGFBP-7 inhibited differentiation of oligodendrocytes. Furthermore, overexpression of IGFBP-7 in oligodendrocyte precursor cells increased transcription of Wnt target genes and promoted β-Catenin nuclear translocation. These findings suggest that IGFBP-7 negatively regulates differentiation of oligodendrocyte precursor cells via regulation of Wnt/β-Catenin signaling. © 2017 Wiley Periodicals, Inc.

TssA forms a gp6-like ring attached to the type VI secretion sheath.

PubMed

Planamente, Sara; Salih, Osman; Manoli, Eleni; Albesa-Jové, David; Freemont, Paul S; Filloux, Alain

2016-08-01

The type VI secretion system (T6SS) is a supra-molecular bacterial complex that resembles phage tails. It is a killing machine which fires toxins into target cells upon contraction of its TssBC sheath. Here, we show that TssA1 is a T6SS component forming dodecameric ring structures whose dimensions match those of the TssBC sheath and which can accommodate the inner Hcp tube. The TssA1 ring complex binds the T6SS sheath and impacts its behaviour in vivo In the phage, the first disc of the gp18 sheath sits on a baseplate wherein gp6 is a dodecameric ring. We found remarkable sequence and structural similarities between TssA1 and gp6 C-termini, and propose that TssA1 could be a baseplate component of the T6SS Furthermore, we identified similarities between TssK1 and gp8, the former interacting with TssA1 while the latter is found in the outer radius of the gp6 ring. These observations, combined with similarities between TssF and gp6N-terminus or TssG and gp53, lead us to propose a comparative model between the phage baseplate and the T6SS. © 2016 The Authors. Published under the terms of the CC BY 4.0 license.

Multiple sort flow cytometer

DOEpatents

Engh, G. van den; Esposito, R.J.

1996-01-09

A flow cytometer utilizes multiple lasers for excitation and respective fluorescence of identified dyes bonded to specific cells or events to identify and verify multiple events to be sorted from a sheath flow and droplet stream. Once identified, verified and timed in the sheath flow, each event is independently tagged upon separation from the flow by an electrical charge of +60, +120, or +180 volts and passed through oppositely charged deflection plates with ground planes to yield a focused six way deflection of at least six events in a narrow plane. 8 figs.

Localization of cells containing sedimented amyloplasts in the shoots of normal and lazy rice seedlings.

PubMed

Abe, K; Takahashi, H; Suge, H

1994-12-01

We have examined the localization of the cells containing sedimented amyloplasts (putative statocytes) and its relation to the graviresponding sites in the shoots of normal and lazy rice seedlings. All graviresponsive organs of the shoots of normal rice seedlings, the mesocotyl, the coleoptile and the leaf-sheath base, were found to possess the statocytes. This is the first indication that mesocotyl senses gravity by its own cells in inducing gravitropic bending in rice seedlings. In lazy-Kamenoo, although the shoots lost their gravitropic response with the advance of age, sedimentation of amyloplasts itself might not be attributable to the agravitropic growth of the shoots, because, including those of the leaf-sheath bases that had lost their response to gravity, sedimented amyloplasts appeared to be identical to those of normal Kamenoo and of younger seedlings of lazy-Kamenoo whose gravitropism is still apparent.

Meningioma-like tumor of the skin. An ultrastructural and immunohistochemical study.

PubMed

Barr, R J; Yi, E S; Jensen, J L; Wuerker, R B; Liao, S Y

1993-08-01

Three unusual cutaneous tumors are described along with ultrastructural and immunohistochemical studies. All lesions were asymptomatic red-brown papulonodules. Light microscopic examination revealed a whorled configuration of spindle-shaped cells, some concentrically arranged around blood vessels. Immunohistochemical panels exhibited positive staining only with antibody to vimentin and negative staining with antibodies against S-100 protein, muscle markers, cytokeratin, epithelial membrane antigen, Leu 7, type IV collagen, and factor XIIIa, ruling out obvious nevomelanocytic, nerve sheath, meningothelial, smooth muscle, and perithelial differentiation. Electron microscopic examination demonstrated cells producing poorly formed collagen fibrils, sparse collagen fibers, and possessing occasional ill-defined intercellular junctions between their elongated cell processes. This rare tumor is considered to be either an immature fibrohistiocytic or possibly a nerve sheath neoplasm with striking similarities to so-called canine hemangiopericytoma. Because the prominent whorled pattern was reminiscent of meningioma, the lesion was referred to as meningioma-like tumor of the skin.

Structural abnormalities of corpus callosum and cortical axonal tracts accompanied by decreased anxiety-like behavior and lowered sociability in spock3- mutant mice.

PubMed

Yamamoto, Ayako; Uchiyama, Koji; Nara, Tomoka; Nishimura, Naomichi; Hayasaka, Michiko; Hanaoka, Kazunori; Yamamoto, Tatsuro

2014-01-01

Spock3/Testican-3 is a nervous system-expressed heparan sulfate proteoglycan belonging to a subgroup of the BM-40/SPARC/osteonectin family, the role of which in brain development is unclear. Because Spock1, a member of the Spock family, inhibits their attachment to substrates and the neurite outgrowth of cultured neuronal cells, Spock3 is also thought to be similarly involved in the neuronal development. In the present study, we established a Spock3-mutant mouse harboring a deletion extending from the presumptive upstream regulatory region to exon 4 of the Spock3 locus and performed histological and behavioral studies on these mutant mice. In wild-type (WT) mice, all Spock members were clearly expressed during brain development. In adults, intense Spock1 and Spock2 expressions were observed throughout the entire brain; whereas, Spock3 expression was no longer visible except in the thalamic nuclei. Thus, Spock3 expression is mostly confined to the developmental stage of the brain. In adult mutant mice, the cells of all cortical layers were swollen. The corpus callosum was narrowed around the central region along the rostral-caudal axis and many small spaces were observed without myelin sheaths throughout the entire corpus callosum. In addition, the cortical input and output fibers did not form into thick bundled fibers as well as the WT counterparts did. Moreover, a subpopulation of corticospinal axonal fibers penetrated into the dorsal striatum with moderately altered orientations. Consistent with these modifications of brain structures, the mutant mice exhibited decreased anxiety-like behavior and lowered sociability. Together, these results demonstrate that Spock3 plays an important role in the formation or maintenance of major neuronal structures in the brain. © 2014 S. Karger AG, Basel.

Effects of an inhibitor of phosphoenolpyruvate carboxylase on photosynthesis of the terrestrial forms of amphibious Eleocharis species.

PubMed

Ueno, Osamu; Ishimaru, Ken

2002-01-01

The leafless amphibious sedge Eleocharis vivipara develops culms with C(4) traits and Kranz anatomy under terrestrial conditions, but develops culms with C(3) traits and non-Kranz anatomy under submerged conditions. The culms of the terrestrial form have high C(4) enzyme activities, while those of the submerged form have decreased C(4) enzyme activities. The culms accumulate ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in the mesophyll cells (MC) and the bundle sheath cells. The Rubisco in the MC may be responsible for the operation of the C(3) pathway in the submerged form. To verify the presence of the C(3) cycle in the MC, we examined the effects of 3,3-dichloro-2-(dihydroxyphosphinoylmethyl) -propenoate (DCDP), an inhibitor of phosphoenolpyruvate carboxylase (PEPC), on photosynthesis in culms of the terrestrial forms of E. vivipara and related amphibious species, E. baldwinii and E. retroflexa ssp. chaetaria. When 1 mM DCDP was fed via the transpiration stream to excised leaves, photosynthesis was inhibited completely in Fimbristylis dichotoma (C(4) control), but by only 20% in potato (C(3) control). In the terrestrial Eleocharis plants, the degree of inhibition of photosynthesis by DCDP was intermediate between those of the C(4) and C(3) plants, at 58-81%. These results suggest that photosynthesis under DCDP treatment in the terrestrial Eleocharis plants is due mainly to fixation of atmospheric CO(2) by Rubisco and probably the C(3) cycle in the MC. These features are reminiscent of those in C(4)-like plants. Differential effects of DCDP on photosynthesis of the 3 Eleocharis species are discussed in relation to differences in the degree of Rubisco accumulation and C(3) activity in the MC.

Immunolocalization of a Histidine-Rich Epidermal Differentiation Protein in the Chicken Supports the Hypothesis of an Evolutionary Developmental Link between the Embryonic Subperiderm and Feather Barbs and Barbules

PubMed Central

Alibardi, Lorenzo; Holthaus, Karin Brigit; Sukseree, Supawadee; Hermann, Marcela; Tschachler, Erwin

2016-01-01

The morphogenesis of feathers is a complex process that depends on a tight spatiotemporal regulation of gene expression and assembly of the protein components of mature feathers. Recent comparative genomics and gene transcription studies have indicated that genes within the epidermal differentiation complex (EDC) encode numerous structural proteins of cornifying skin cells in amniotes including birds. Here, we determined the localization of one of these proteins, termed EDMTFH (Epidermal Differentiation Protein starting with a MTF motif and rich in Histidine), which belongs to a group of EDC-encoded proteins rich in aromatic amino acid residues. We raised an antibody against an EDMTFH-specific epitope and performed immunohistochemical investigations by light microscopy and immunogold labeling by electron microscopy of chicken embryos at days 14–18 of development. EDMTFH was specifically present in the subperiderm, a transient layer of the embryonic epidermis, and in barbs and barbules of feathers. In the latter, it partially localized to bundles of so-called feather beta-keratins (corneous beta-proteins, CBPs). Cells of the embryonic periderm, the epidermis proper, and the feather sheath were immunonegative for EDMTFH. The results of this study indicate that EDMTFH may contribute to the unique mechanical properties of feathers and define EDMTFH as a common marker of the subperiderm and the feather barbules. This expression pattern of EDMTFH resembles that of epidermal differentiation cysteine-rich protein (EDCRP) and feather CBPs and is in accordance with the hypothesis that a major part of the cyclically regenerating feather follicle is topologically, developmentally and evolutionarily related to the embryonic subperiderm. PMID:27936131

Optical imaging of neural and hemodynamic brain activity

NASA Astrophysics Data System (ADS)

Schei, Jennifer Lynn

Optical imaging technologies can be used to record neural and hemodynamic activity. Neural activity elicits physiological changes that alter the optical tissue properties. Specifically, changes in polarized light are concomitant with neural depolarization. We measured polarization changes from an isolated lobster nerve during action potential propagation using both reflected and transmitted light. In transmission mode, polarization changes were largest throughout the center of the nerve, suggesting that most of the optical signal arose from the inner nerve bundle. In reflection mode, polarization changes were largest near the edges, suggesting that most of the optical signal arose from the outer sheath. To overcome irregular cell orientation found in the brain, we measured polarization changes from a nerve tied in a knot. Our results show that neural activation produces polarization changes that can be imaged even without regular cell orientations. Neural activation expends energy resources and elicits metabolic delivery through blood vessel dilation, increasing blood flow and volume. We used spectroscopic imaging techniques combined with electrophysiological measurements to record evoked neural and hemodynamic responses from the auditory cortex of the rat. By using implantable optics, we measured responses across natural wake and sleep states, as well as responses following different amounts of sleep deprivation. During quiet sleep, evoked metabolic responses were larger compared to wake, perhaps because blood vessels were more compliant. When animals were sleep deprived, evoked hemodynamic responses were smaller following longer periods of deprivation. These results suggest that prolonged neural activity through sleep deprivation may diminish vascular compliance as indicated by the blunted vascular response. Subsequent sleep may allow vessels to relax, restoring their ability to deliver blood. These results also suggest that severe sleep deprivation or chronic sleep disturbances could push the vasculature to critical limits, leading to metabolic deficit and the potential for tissue trauma.

Motility of vestibular hair cells in the chick.

PubMed

Ogata, Y; Sekitani, T

1993-01-01

Recent studies of the outer hair cells in cochlea have demonstrated active motilities. However, very little study has been done on the vestibular hair cells (VHCs). The present study shows the motile response of the VHCs induced by application of Ca2+/ATP promoting contraction. Reversible cell shape changes could be shown in 10 of 16 isolated type I hair cells and 9 of 15 isolated type II hair cells by applying the contraction solution. Furthermore, the sensory hair bundles in the utricular epithelium pivoted around the base and stood perpendicularly to the apical borderline of the epithelium in response to the application of the same solution. It is suggested that the contraction of the isolated VHCs may be transferred to tension which causes the sensory hair bundles to restrict their motion in normal tissue, instead of changing the cell shape.

Implantation of autogenous meniscal fragments wrapped with a fascia sheath enhances fibrocartilage regeneration in vivo in a large harvest site defect.

PubMed

Kobayashi, Yasukazu; Yasuda, Kazunori; Kondo, Eiji; Katsura, Taro; Tanabe, Yoshie; Kimura, Masashi; Tohyama, Harukazu

2010-04-01

Concerning meniscal tissue regeneration, many investigators have studied the development of a tissue-engineered meniscus. However, the utility still remains unknown. Implantation of autogenous meniscal fragments wrapped with a fascia sheath into the donor site meniscal defect may significantly enhance fibrocartilage regeneration in vivo in the defect. Controlled laboratory study. Seventy-five mature rabbits were used in this study. In each animal, an anterior one-third of the right medial meniscus was resected. Then, the animals were divided into the following 3 groups of 25 rabbits each: In group 1, no treatment was applied to the meniscal defect. In group 2, the defect was covered with a fascia sheath. In group 3, after the resected meniscus was fragmented into small pieces, the fragments were grafted into the defect. Then, the defect with the meniscal fragments was covered with a fascia sheath. In each group, 5 rabbits were used for histological evaluation at 3, 6, and 12 weeks after surgery, and 5 rabbits were used for biomechanical evaluation at 6 and 12 weeks after surgery. Histologically, large round cells in group 3 were scattered in the core portion of the meniscus-shaped tissue, and the matrix around these cells was positively stained by safranin O and toluisin blue at 12 weeks. The histological score of group 3 was significantly higher than that of group 1 and group 2. Biomechanically, the maximal load and stiffness of group 3 were significantly greater than those of groups 1 and 2. This study clearly demonstrated that implantation of autogenous meniscal fragments wrapped with a fascia sheath into the donor site meniscal defect significantly enhanced fibrocartilage regeneration in vivo in the defect at 12 weeks after implantation in the rabbit. This study proposed a novel strategy to treat a large defect after a meniscectomy.

Inhibition of OsSWEET11 function in mesophyll cells improves resistance of rice to sheath blight disease.

PubMed

Gao, Yue; Zhang, Chong; Han, Xiao; Wang, Zi Yuan; Ma, Lai; Yuan, De Peng; Wu, Jing Ni; Zhu, Xiao Feng; Liu, Jing Miao; Li, Dao Pin; Hu, Yi Bing; Xuan, Yuan Hu

2018-04-16

Pathogen-host interaction is a complicated process; pathogens mainly infect host plants to acquire nutrients, especially sugars. Rhizoctonia solani, the causative agent of sheath blight disease, is a major pathogen of rice. However, it is not known, as to how this pathogen obtains sugar from rice plants. In this study, we found that the rice sugar transporter, OsSWEET11 is involved in the pathogenesis of sheath blight disease. qRT-PCR and β-d-glucuronidase expression analyses showed that R. solani infection significantly enhanced OsSWEET11 expression in leaves among the clade III SWEET members. The analyses of transgenic plants revealed that Ossweet11 mutants were less susceptible, whereas plants overexpressing OsSWEET11 were more susceptible to sheath blight compared to wild-type controls, but the yield of OsSWEET11 mutants and overexpressors was reduced. SWEETs become active upon oligomerization. Split-ubiquitin yeast two-hybrid, bimolecular fluorescence complementation, and coimmunoprecipitation assays showed that mutated-OsSWEET11 interacted with normal OsSWEET11. In addition, expressing conserved residue mutated-AtSWEET1 inhibits normal AtSWEET1 activity. To analyze whether inhibition of OsSWEET11 function in mesophyll cells is related to defense against this disease, mutated- OsSWEET11 was expressed under the control of Rubisco promoter, which is specific for green tissues. The resistance of transgenic plants to sheath blight disease, but not other disease was improved, while yield production was not evidently affected. Overall, these results suggest that R. solani might acquire sugar from rice leaves by activating OsSWEET11 expression. The plants can be protected from infection by manipulating the expression of OsSWEET11 without affecting the crop yield. This article is protected by copyright. All rights reserved. © 2018 BSPP and John Wiley & Sons Ltd.

Formation of compact myelin is required for maturation of the axonal cytoskeleton

NASA Technical Reports Server (NTRS)

Brady, S. T.; Witt, A. S.; Kirkpatrick, L. L.; de Waegh, S. M.; Readhead, C.; Tu, P. H.; Lee, V. M.

1999-01-01

Although traditional roles ascribed to myelinating glial cells are structural and supportive, the importance of compact myelin for proper functioning of the nervous system can be inferred from mutations in myelin proteins and neuropathologies associated with loss of myelin. Myelinating Schwann cells are known to affect local properties of peripheral axons (de Waegh et al., 1992), but little is known about effects of oligodendrocytes on CNS axons. The shiverer mutant mouse has a deletion in the myelin basic protein gene that eliminates compact myelin in the CNS. In shiverer mice, both local axonal features like phosphorylation of cytoskeletal proteins and neuronal perikaryon functions like cytoskeletal gene expression are altered. This leads to changes in the organization and composition of the axonal cytoskeleton in shiverer unmyelinated axons relative to age-matched wild-type myelinated fibers, although connectivity and patterns of neuronal activity are comparable. Remarkably, transgenic shiverer mice with thin myelin sheaths display an intermediate phenotype indicating that CNS neurons are sensitive to myelin sheath thickness. These results indicate that formation of a normal compact myelin sheath is required for normal maturation of the neuronal cytoskeleton in large CNS neurons.

Mechanism of Methane Transport from the Rhizosphere to the Atmosphere through Rice Plants 1

PubMed Central

Nouchi, Isamu; Mariko, Shigeru; Aoki, Kazuyuki

1990-01-01

To clarify the mechanisms of methane transport from the rhizosphere into the atmosphere through rice plants (Oryza sativa L.), the methane emission rate was measured from a shoot whose roots had been kept in a culture solution with a high methane concentration or exposed to methane gas in the gas phase by using a cylindrical chamber. No clear correlation was observed between change in the transpiration rate and that in the methane emission rate. Methane was mostly released from the culm, which is an aggregation of leaf sheaths, but not from the leaf blade. Micropores which are different from stomata were newly found at the abaxial epidermis of the leaf sheath by scanning electron microscopy. The measured methane emission rate was much higher than the calculated methane emission rate that would result from transpiration and the methane concentration in the culture solution. Rice roots could absorb methane gas in the gas phase without water uptake. These results suggest that methane dissolved in the soil water surrounding the roots diffuses into the cell-wall water of the root cells, gasifies in the root cortex, and then is mostly released through the micropores in the leaf sheaths. Images Figure 7 PMID:16667719

Wood as inspiration for new stimuli-responsive structures and materials

Treesearch

Joseph E. Jakes; Nayomi Plaza-Rodriguez; Samuel L. Zelinka; Donald S. Stone; Sophie-Charlotte Gleber; Stefan Vogt

2014-01-01

Nature has often provided inspiration for new smart structures and materials. Recently, we showed a bundle of a few wood cells are moisture-activated torsional actuators that can reversibly twist multiple revolutions per centimeter of length. The bundles produce specific torque higher than that produced by electric motors and possess shape memory twist capabilities....

Determination of the turbulence integral model parameters for a case of a coolant angular flow in regular rod-bundle

NASA Astrophysics Data System (ADS)

Bayaskhalanov, M. V.; Vlasov, M. N.; Korsun, A. S.; Merinov, I. G.; Philippov, M. Ph

2017-11-01

Research results of “k-ε” turbulence integral model (TIM) parameters dependence on the angle of a coolant flow in regular smooth cylindrical rod-bundle are presented. TIM is intended for the definition of efficient impulse and heat transport coefficients in the averaged equations of a heat and mass transfer in the regular rod structures in an anisotropic porous media approximation. The TIM equations are received by volume-averaging of the “k-ε” turbulence model equations on periodic cell of rod-bundle. The water flow across rod-bundle under angles from 15 to 75 degrees was simulated by means of an ANSYS CFX code. Dependence of the TIM parameters on flow angle was as a result received.

Comparative transduction mechanisms of hair cells in the bullfrog utriculus. 1: Responses to intracellular current

NASA Technical Reports Server (NTRS)

Baird, Richard A.

1994-01-01

Hair cells in the bullfrog sacculus are specifically adapted to sense small-amplitude, high-frequency linear accelerations. These hair cells display many properties that are undesirable or inappropriate for hair cells that must provide static gravity sensitivity. This study resulted in part due to an interest in seeing how the transduction mechanisms of hair cells in a gravity-sensing otolith endorgan would differ from those in the bullfrog sacculus. The bullfrog utriculus is an appropriate model for these studies, because its structure is representative of higher vertebrates in general and its function as a sensor of static gravity and dynamic linear acceleration is well known. Hair cells in the bullfrog utriculus, classifiable as Type 2 by cell body and synapse morphology, differ markedly in hair bundle morphology from those in the bullfrog sacculus. Moreover, the hair bundle morphologies of utricular hair cells, unlike those in the sacculus, differ in different membrane regions.

Kinesins have a dual function in organizing microtubules during both tip growth and cytokinesis in Physcomitrella patens.

PubMed

Hiwatashi, Yuji; Sato, Yoshikatsu; Doonan, John H

2014-03-01

Microtubules (MTs) play a crucial role in the anisotropic deposition of cell wall material, thereby affecting the direction of growth. A wide range of tip-growing cells display highly polarized cell growth, and MTs have been implicated in regulating directionality and expansion. However, the molecular machinery underlying MT dynamics in tip-growing plant cells remains unclear. Here, we show that highly dynamic MT bundles form cyclically in the polarized expansion zone of the moss Physcomitrella patens caulonemal cells through the coalescence of growing MT plus ends. Furthermore, the plant-specific kinesins (KINID1) that are is essential for the proper MT organization at cytokinesis also regulate the turnover of the tip MT bundles as well as the directionality and rate of cell growth. The plus ends of MTs grow toward the expansion zone, and KINID1 is necessary for the stability of a single coherent focus of MTs in the center of the zone, whose formation coincides with the accumulation of KINID1. We propose that KINID-dependent MT bundling is essential for the correct directionality of growth as well as for promoting growth per se. Our findings indicate that two localized cell wall deposition processes, tip growth and cytokinesis, previously believed to be functionally and evolutionarily distinct, share common and plant-specific MT regulatory components.

Enhanced target normal sheath acceleration of protons from intense laser interaction with a cone-tube target

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

Xiao, K. D.; Huang, T. W.; Zhou, C. T., E-mail: zcangtao@iapcm.ac.cn

2016-01-15

Laser driven proton acceleration is proposed to be greatly enhanced by using a cone-tube target, which can be easily manufactured by current 3D-print technology. It is observed that energetic electron bunches are generated along the tube and accelerated to a much higher temperature by the combination of ponderomotive force and longitudinal electric field which is induced by the optical confinement of the laser field. As a result, a localized and enhanced sheath field is produced at the rear of the target and the maximum proton energy is about three-fold increased based on the two-dimentional particle-in-cell simulation results. It is demonstratedmore » that by employing this advanced target scheme, the scaling of the proton energy versus the laser intensity is much beyond the normal target normal sheath acceleration (TNSA) case.« less

Imaging extracellular calcium in endolymph

NASA Astrophysics Data System (ADS)

Strimbu, C. Elliott; Fridberger, Anders

2018-05-01

Hair cell mechanoelectrical transduction and adaptation are believed to be regulated by extracellular calcium. However, the majority of experiments addressing calcium's role have been performed on reduced preparations in conditions that do not mimic those present in vivo. We used confocal microscopy and a low affinity (kd ˜11 µM) ratiometric fluorescent indicator to measure the extracellular calcium concentration in scala media in an in vitro preparation of the guinea pig cochlea. Microelectrodes were used to measure the cochlear microphonic potential during acoustic stimulation. The mean calcium concentration is significantly higher in the tectorial membrane (TM) than the surrounding endolymph, suggesting that the membrane acts as a calcium sink. We also observe calcium hot spots along the underside of the TM, near the outer hair cell bundles and near Hensens stripe close to the inner hair cell bundle. This suggests that the local calcium concentration near the hair bundles exceeds 100 µM, significantly higher than the bulk endolymph. These results were corroborated with fluorescence correlation spectroscopy using a second calcium sensitive dye, Oregon Green 488-BAPTA. Following a brief exposure to loud sound, TM calcium drops dramatically and shows recovery on a similar timescale as the microphonic potential. Our results suggest that the extracellular calcium concentration near the hair bundles is much higher than previously believed and may also serve as a partial control parameter for temporary threshold shifts.

Characterisation of myofibroblasts in fibrovascular tissues of primary and recurrent pterygia

PubMed Central

Touhami, A; Di Pascuale, M A; Kawatika, T; Valle, M Del; Rosa, R H; Dubovy, S; Tseng, S C G

2005-01-01

Aims: To determine the presence and origin of myofibroblasts in pterygia. Methods: 86 specimens including head, body, and fibrovascular tissue from 52 primary and 34 recurrent pterygia and five exenterated eyes without pterygia were searched for the origin of myofibroblasts. All tissues were subjected to haematoxylin and eosin staining, immunohistochemistry using antibodies against alpha smooth muscle actin (α-SMA), desmin, vimentin, and caldesmon, and transmission electron microscopy (TEM). The phenotype of fibroblasts subcultured in a serum free medium from pterygium fibrovascular tissues was characterised by the above antibodies. Bundles of dense fibrous tissues were noted in 86% of the fibrovascular tissue specimens evaluated. Cells within these bundles were characterised as myofibroblasts based on positive staining to α-SMA, but negative to desmin and caldesmon, markers for smooth muscle cells. Interestingly, positive α-SMA staining was also found in the periorbital fibroadipose tissue posterior to Tenon’s capsule near the nasal conjunctiva in all exenterated specimens. All first passage fibroblasts expressed vimentin, some were positive to α-SMA, but all were negative to desmin or caldesmon. Cells in pterygium fibrovascular tissues showed ultrastructural features of intracytoplasmic bundles of microfilaments, consistent with myofibroblastic differentiation. Conclusion: These studies collectively demonstrate the presence of contractile myofibroblasts bundle in pterygia and in the periorbital fibroadipose tissue posterior to Tenon’s capsule of exenterated eyes without pterygium. PMID:15722301

Formation of biogenic sheath-like Fe oxyhydroxides in a near-neutral pH hot spring: Implications for the origin of microfossils in high-temperature, Fe-rich environments

NASA Astrophysics Data System (ADS)

Peng, Xiaotong; Chen, Shun; Xu, Hengchao

2013-12-01

small hot spring that is informally called "Fe-waterfall spring" and is located in the Rehai geothermal area discharges hot (42 to 73°C), near-neutral (pH = 7.65) Fe-rich water. Submerged reddish precipitates are composed largely of ferrihydrite, goethite, lepidocrocite, opal-A, quartz, and anorthite, as revealed by X-ray diffraction (XRD) and Mössbauer spectroscopy. Molecular phylogenetic analysis demonstrates that the bacterial community in these precipitates is mainly composed of Cyanobacteria, Planctomycetes, β-proteobacteria, Deinococci-Thermus, and Chlorobi. Scanning electron microscopy and high-resolution transmission electron microscopy examinations show that abundant sheath-like Fe oxyhydroxides, which exhibit different morphologies and sizes, are present in Fe-rich precipitates. These sheath-like structures are composed of ferrihydrite rather than more crystalline lepidocrocite or goethite. Energy-dispersive X-ray spectrometer, scanning transmission electron microscopy, and nano secondary ion mass spectrometry reveal that they are mainly composed of Fe, Si, and O, together with some trace elements. Most of the sheath-like structures are not morphologically comparable to biogenic Fe oxyhydroxides produced by known chemolithotrophic Fe oxidizers, which is consistent with the fact that no chemolithotrophic Fe oxidizers were identified by molecular analysis in the precipitates. We suggest that the sheath-like Fe oxyhydroxides are formed through passive Fe sorption and nucleation onto the cell walls of various thermophiles rather than by the direct metabolic activities of chemolithotrophic Fe oxidizers. Biogenic sheath-like Fe oxyhydroxides in Fe-waterfall spring have important implications for geochemical cycles driven by microorganisms, the origin of microfossils, and the formation of banded iron formations (BIFs) in the Archean ocean.

Trafficking of Aminoglycosides Into Endolymph in Vivo

NASA Astrophysics Data System (ADS)

Wang, Qi; Steyger, Peter S.

2009-02-01

In vitro, aminoglycosides increase the stiffness of cochlear hair cell stereocilia, altering bundle motion and transduction kinetics. Aminoglycosides also permeate the mechanosensitive transduction channel and rapidly initiate cytotoxicity in hair cells. If these effects occur in vivo, aminoglycosides would need to enter endolymph. The most direct route for systemically-administered aminoglycosides to enter endolymph is by trafficking from strial capillaries across the stria vascularis. An as-yet-unidentified active transporter is required to translocate aminoglycosides from the intra-strial space into the cytoplasm of marginal cells. Once in marginal cells, aminoglycosides would passively flow down the electrochemical gradient into endolymph. We present data that support a trans-strial trafficking route of aminoglycosides into endolymph, where they can then interfere with the mechanosensitive hair bundles.

Investigation of particle lateral migration in sample-sheath flow of viscoelastic fluid and Newtonian fluid.

PubMed

Yuan, Dan; Zhang, Jun; Yan, Sheng; Peng, Gangrou; Zhao, Qianbin; Alici, Gursel; Du, Hejun; Li, Weihua

2016-08-01

In this work, particle lateral migration in sample-sheath flow of viscoelastic fluid and Newtonian fluid was experimentally investigated. The 4.8-μm micro-particles were dispersed in a polyethylene oxide (PEO) viscoelastic solution, and then the solution was injected into a straight rectangular channel with a deionised (DI) water Newtonian sheath flow. Micro-particles suspended in PEO solution migrated laterally to a DI water stream, but migration in the opposite direction from a DI water stream to a PEO solution stream or from one DI water stream to another DI water stream could not be achieved. The lateral migration of particles depends on the viscoelastic properties of the sample fluids. Furthermore, the effects of channel length, flow rate, and PEO concentration were studied. By using viscoelastic sample flow and Newtonian sheath flow, a selective particle lateral migration can be achieved in a simple straight channel, without any external force fields. This particle lateral migration technique could be potentially used in solution exchange fields such as automated cell staining and washing in microfluidic platforms, and holds numerous biomedical applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Espins are multifunctional actin cytoskeletal regulatory proteins in the microvilli of chemosensory and mechanosensory cells

PubMed Central

Sekerková, Gabriella; Zheng, Lili; Loomis, Patricia A.; Changyaleket, Benjarat; Whitlon, Donna S.; Mugnaini, Enrico; Bartles, James R.

2010-01-01

Espins are associated with the parallel actin bundles of hair cell stereocilia and are the target of mutations that cause deafness and vestibular dysfunction in mice and humans. Here, we report that espins are also concentrated in the microvilli of a number of other sensory cells: vomeronasal organ sensory neurons, solitary chemoreceptor cells, taste cells and Merkel cells. Moreover, we show that hair cells and these other sensory cells contain novel espin isoforms that arise from a different transcriptional start site and differ significantly from other espin isoforms in their complement of ligand-binding activities and their effects on actin polymerization. The novel espin isoforms of sensory cells bundled actin filaments with high affinity in a Ca2+-resistant fashion, bound actin monomer via a WASP homology 2 domain, bound profilin via a single proline-rich peptide, and caused a dramatic elongation of microvillus-type parallel actin bundles in transfected epithelial cells. In addition, the novel espin isoforms of sensory cells differed from other espin isoforms in that they potently inhibited actin polymerization in vitro, did not bind the Src homology 3 domain of the adapter protein insulin receptor substrate p53 and did not bind the acidic, signaling phospholipid phosphatidylinositol 4,5- bisphosphate. Thus, the espins constitute a family of multifunctional actin cytoskeletal regulatory proteins with the potential to differentially influence the organization, dimensions, dynamics and signaling capabilities of the actin filament-rich, microvillus-type specializations that mediate sensory transduction in a variety of mechanosensory and chemosensory cells. PMID:15190118

Multiscale Metabolic Modeling of C4 Plants: Connecting Nonlinear Genome-Scale Models to Leaf-Scale Metabolism in Developing Maize Leaves

PubMed Central

Bogart, Eli; Myers, Christopher R.

2016-01-01

C4 plants, such as maize, concentrate carbon dioxide in a specialized compartment surrounding the veins of their leaves to improve the efficiency of carbon dioxide assimilation. Nonlinear relationships between carbon dioxide and oxygen levels and reaction rates are key to their physiology but cannot be handled with standard techniques of constraint-based metabolic modeling. We demonstrate that incorporating these relationships as constraints on reaction rates and solving the resulting nonlinear optimization problem yields realistic predictions of the response of C4 systems to environmental and biochemical perturbations. Using a new genome-scale reconstruction of maize metabolism, we build an 18000-reaction, nonlinearly constrained model describing mesophyll and bundle sheath cells in 15 segments of the developing maize leaf, interacting via metabolite exchange, and use RNA-seq and enzyme activity measurements to predict spatial variation in metabolic state by a novel method that optimizes correlation between fluxes and expression data. Though such correlations are known to be weak in general, we suggest that developmental gradients may be particularly suited to the inference of metabolic fluxes from expression data, and we demonstrate that our method predicts fluxes that achieve high correlation with the data, successfully capture the experimentally observed base-to-tip transition between carbon-importing tissue and carbon-exporting tissue, and include a nonzero growth rate, in contrast to prior results from similar methods in other systems. PMID:26990967

Localization and subcellular association of Grapevine Pinot Gris Virus in grapevine leaf tissues.

PubMed

Tarquini, Giulia; Ermacora, Paolo; Bianchi, Gian Luca; De Amicis, Francesca; Pagliari, Laura; Martini, Marta; Loschi, Alberto; Saldarelli, Pasquale; Loi, Nazia; Musetti, Rita

2018-05-01

Despite the increasing impact of Grapevine Pinot gris disease (GPG-disease) worldwide, etiology about this disorder is still uncertain. The presence of the putative causal agent, the Grapevine Pinot Gris Virus (GPGV), has been reported in symptomatic grapevines (presenting stunting, chlorotic mottling, and leaf deformation) as well as in symptom-free plants. Moreover, information on virus localization in grapevine tissues and virus-plant interactions at the cytological level is missing at all. Ultrastructural and cytochemical investigations were undertaken to detect virus particles and the associated cytopathic effects in field-grown grapevine showing different symptom severity. Asymptomatic greenhouse-grown grapevines, which tested negative for GPGV by real time RT-PCR, were sampled as controls. Multiplex real-time RT-PCR and ELISA tests excluded the presence of viruses included in the Italian certification program both in field-grown and greenhouse-grown grapevines. Conversely, evidence was found for ubiquitous presence of Grapevine Rupestris Stem Pitting-associated Virus (GRSPaV), Hop Stunt Viroid (HSVd), and Grapevine Yellow Speckle Viroid 1 (GYSVd-1) in both plant groups. Moreover, in every field-grown grapevine, GPGV was detected by real-time RT-PCR. Ultrastructural observations and immunogold labelling assays showed filamentous flexuous viruses in the bundle sheath cells, often located inside membrane-bound organelles. No cytological differences were observed among field-grown grapevine samples showing different symptom severity. GPGV localization and associated ultrastructural modifications are reported and discussed, in the perspective of assisting management and control of the disease.

C/sub 4/ photosynthesis in Euphorbia degeneri and E. remyi: a comparison of photosynthetic carbon metabolism in leaves, callus cultures and regenerated plants

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

Ruzin, S.E.

1984-04-01

Based on analysis of /sup 14/CO/sub 2/ fixation kinetics and assays of enzymes related to C/sub 4/ metabolism (NAD-ME, NADP-ME, NAD-MDH, NADP-MDH, AST, ALT), leaves and regenerated plants of Euphorbia degeneri exhibit a modified NADP-ME-type photosynthesis. Apparently, both aspartate and malate are used for transport of CO/sub 2/ to bundle sheath cells. Callus grown on either non-shoot-forming or shoot-forming media fixes CO/sub 2/ into RPP-cycle intermediates and sucrose, as well as malate and aspartate. /sup 14/CO/sub 2/ pulse/chase kinetics show no significant loss of label from C/sub 4/ acids throughout a one minute chase. Analysis of PEPCase revealed the presencemore » of 2 isoenzymes in both leaf and regenerated plant tissues (K/sub m/ (PEP) = 0.080 and 0.550) but only one isoenzyme in callus (K/sub m/ = 0.100). It appears that C/sub 4/ photosynthesis does not occur in callus derived from this C/sub 4/ dicot but is regenerated concomitant with shoot regeneration, and ..beta..-carboxylation of PEP in callus, mediated by the low K/sub m/ isoenzyme of PEPCase, produces C/sub 4/ acids that are not involved in the CO/sub 2/ shuttle mechanism characteristic of C/sub 4/ photosynthesis. 161 references, 19 figures, 12 tables.« less

Combining genetic and evolutionary engineering to establish C4 metabolism in C3 plants.

PubMed

Li, Yuanyuan; Heckmann, David; Lercher, Martin J; Maurino, Veronica G

2017-01-01

To feed a world population projected to reach 9 billion people by 2050, the productivity of major crops must be increased by at least 50%. One potential route to boost the productivity of cereals is to equip them genetically with the 'supercharged' C 4 type of photosynthesis; however, the necessary genetic modifications are not sufficiently understood for the corresponding genetic engineering programme. In this opinion paper, we discuss a strategy to solve this problem by developing a new paradigm for plant breeding. We propose combining the bioengineering of well-understood traits with subsequent evolutionary engineering, i.e. mutagenesis and artificial selection. An existing mathematical model of C 3 -C 4 evolution is used to choose the most promising path towards this goal. Based on biomathematical simulations, we engineer Arabidopsis thaliana plants that express the central carbon-fixing enzyme Rubisco only in bundle sheath cells (Ru-BSC plants), the localization characteristic for C 4 plants. This modification will initially be deleterious, forcing the Ru-BSC plants into a fitness valley from where previously inaccessible adaptive steps towards C 4 photosynthesis become accessible through fitness-enhancing mutations. Mutagenized Ru-BSC plants are then screened for improved photosynthesis, and are expected to respond to imposed artificial selection pressures by evolving towards C 4 anatomy and biochemistry. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Auditory Mechanics of the Tectorial Membrane and the Cochlear Spiral

PubMed Central

Gavara, Núria; Manoussaki, Daphne; Chadwick, Richard S.

2012-01-01

Purpose of review This review is timely and relevant since new experimental and theoretical findings suggest that cochlear mechanics from the nanoscale to the macroscale are affected by mechanical properties of the tectorial membrane and the spiral shape. Recent findings Main tectorial membrane themes covered are i) composition and morphology, ii) nanoscale mechanical interactions with the outer hair cell bundle, iii) macroscale longitudinal coupling, iv) fluid interaction with inner hair cell bundles, v) macroscale dynamics and waves. Main cochlear spiral themes are macroscale low-frequency energy focusing and microscale organ of Corti shear gain. Implications Findings from new experimental and theoretical models reveal exquisite sensitivity of cochlear mechanical performance to tectorial membrane structural organization, mechanics, and its positioning with respect to hair bundles. The cochlear spiral geometry is a major determinant of low frequency hearing. Suggestions are made for future research directions. PMID:21785353

Mineralized Remains of Morphotypes of Filamentous Cyanobacteria in Carbonaceous Meteorites

NASA Technical Reports Server (NTRS)

Hoover, Richard B.

2005-01-01

The quest for conclusive evidence of microfossils in meteorites has been elusive. One difficulty arises from the fact than many abiotic or inorganic microstructures, mineral grains, and coating artifacts can mimic the smaller representatives of the microbial world that possess very simple morphologies (unicellular cocci or bacilli). However, there exist a wide variety of large, filamentous trichomic prokaryotic microorganisms (cyanobacteria and sulfur bacteria) with sufficiently well known and complex morphologies that they can be recognized and are known to be of unquestionable biogenic origin. The taphonomic modes of fossilization and their of their life habits and processes frequently result in distinctive chemical biosignatures associated with carbonization, silicification, calcification, phosphatization and metal-binding properties of their cell-walls, trichomes, sheaths and extracellular polymeric substances (EPS). Strong differences of mineral concentrations in closely associated and visibly differentiated cellular microstructures provide strong evidence of biogenicity. This evidence is further enhanced by the detection of recognizable and distinct microstructures (e.g., uniseriate or multiseriate filaments, trichomes, sheaths, cells of proper sizes and size distributions) and growth characteristics (e.g., basal or apical cells, true or false branching of trichomes, tapered or uniform filaments, robust or thin sheaths) and reproductive and nitrogen fixation habits (e.g., baeocytes, hormogonia, akinetes and heterocysts), Microfossils of cyanobacteria and cyanobacterial mats and stromatolites have been recognized a described from many of the most ancient rocks on Earth. The crucial problem lies in developing valid protocols and methodologies for establishing that the putative microfossils are truly indigenous and not merely recent microbial contaminants. During the past several years, we have conducted Field Emission Scanning Electron Microscopy (FESEM) investigations of freshly fractured interior surfaces of carbonaceous meteorites, terrestrial rocks, and recent microbial extremophiles and filamentous cyanobacteria. These studies have resulted in the detection in a several carbonaceous meteorites of the mineralized remains of a wide variety of complex filamentous trichomic microorganisms. These embedded forms are consistent in size and microstructure with well-preserved morphotypes of mat- forming filamentous trichomic cyanobacteria and the degraded remains of microfibrils of cyanobacterial sheaths. We present the results of comparative imaging studies and EDAX elemental analyses of recent cyanobacteria (e.g. Calothrix, Oscillatoria, and Lyngbya) that are similar in size, morphology and microstructure to morphotypes found embedded in meteorites. EDAX elemental studies reveal that forms found in carbonaceous meteorites often have highly carbonized sheaths in close association with permineralized filaments, trichomes and microbial cells. Ratios of critical bioelements (C:O, C:N, C:P, and C:S) reveal dramatic differences between microfossils in Earth rocks and meteorites and in filaments, trichomes, hormogonia, and cells of recent cyanobacteria.

Soft Tissue Sarcoma

MedlinePlus

... begins in the lining of blood vessels, while liposarcoma arises from fat cells. Some types of soft ... sarcoma Gastrointestinal stromal tumor (GIST) Kaposi's sarcoma Leiomyosarcoma Liposarcoma Malignant peripheral nerve sheath tumor Myxofibrosarcoma Rhabdomyosarcoma Solitary ...

Multilamellar Structures and Filament Bundles Are Found on the Cell Surface during Bunyavirus Egress

PubMed Central

Sanz-Sánchez, Laura; Risco, Cristina

2013-01-01

Inside cells, viruses build specialized compartments for replication and morphogenesis. We observed that virus release associates with specific structures found on the surface of mammalian cells. Cultured adherent cells were infected with a bunyavirus and processed for oriented sectioning and transmission electron microscopy. Imaging of cell basal regions showed sophisticated multilamellar structures (MLS) and extracellular filament bundles with attached viruses. Correlative light and electron microscopy confirmed that both MLS and filaments proliferated during the maximum egress of new viruses. MLS dimensions and structure were reminiscent of those reported for the nanostructures on gecko fingertips, which are responsible for the extraordinary attachment capacity of these lizards. As infected cells with MLS were more resistant to detachment than control cells, we propose an adhesive function for these structures, which would compensate for the loss of adherence during release of new virus progeny. PMID:23799021

Ulnar malignant peripheral nerve sheath tumour diagnosis in a mixed-breed dog as a model to study human: histologic, immunohistochemical, and clinicopathologic study

PubMed Central

2013-01-01

Canine Malignant Peripheral Nerve Sheath Tumors (MPNSTs) are uncommonly reported in the ulnar, since they are underestimated relative to the more common spindle cell tumours of soft tissue. In dogs, MPNST accounts for 27% of nervous system tumours. In man, MPNST represents 5-10% of all soft tissue sarcomas and is often associated with neurofibromatosis type 1 (NF-1).An 8-year-old, 9 kg, female mixed-breed dog with a subcutaneous mass on the upper right side of the ulnar region was presented to the small animal research and teaching hospital of Tehran University. The dog was anorexic with general weakness. The mass (7 × 4 cm) was removed surgically and processed routinely. Microscopically, the mass was composed of highly cellular areas with a homogeneous population of round or spindle cells, high cellular pleomorphism, high mitotic index and various morphologic patterns. Furthermore, spindle cells arranged in densely or loosely sweeping fascicles, interlacing whorls, or storiform patterns together with wavy cytoplasm, nuclear palisades, and round cells were arranged in sheets or cords with a meshwork of intratumoral nerve fibers. In addition, in this case the presence of neoplastic cells within the blood vessels was observed. Immunohistochemically, tumor was positive for vimentin and S-100 protein. The histopathologic features coupled with the S-100 and vimentin immunoreactivity led to a diagnosis of malignant neurofibroma. To the best of our knowledge, primary ulnar MPNST has not been reported in animals. This is the first documentation of an ulnar malignant peripheral nerve sheath tumour in a dog. Virtual slides The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1310907815984587 PMID:23688209

The Mechanical Properties of Hydrated Intermediate Filaments: Insights from Hagfish Slime Threads

PubMed Central

Fudge, Douglas S.; Gardner, Kenn H.; Forsyth, V. Trevor; Riekel, Christian; Gosline, John M.

2003-01-01

Intermediate filaments (IFs) impart mechanical integrity to cells, yet IF mechanics are poorly understood. It is assumed that IFs in cells are as stiff as hard α-keratin, F-actin, and microtubules, but the high bending flexibility of IFs and the low stiffness of soft α-keratins suggest that hydrated IFs may be quite soft. To test this hypothesis, we measured the tensile mechanics of the keratin-like threads from hagfish slime, which are an ideal model for exploring the mechanics of IF bundles and IFs because they consist of tightly packed and aligned IFs. Tensile tests suggest that hydrated IF bundles possess low initial stiffness (Ei = 6.4 MPa) and remarkable elasticity (up to strains of 0.34), which we attribute to soft elastomeric IF protein terminal domains in series with stiffer coiled coils. The high tensile strength (180 MPa) and toughness (130 MJ/m3) of IF bundles support the notion that IFs lend mechanical integrity to cells. Their long-range elasticity suggests that IFs may also allow cells to recover from large deformations. X-ray diffraction and congo-red staining indicate that post-yield deformation leads to an irreversible α→β conformational transition in IFs, which leads to plastic deformation, and may be used by cells as a mechanosensory cue. PMID:12944314

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

Barber, Laura Jeaneen

The purpose of the L’Innovator is to assemble unique, state-of-the-art IP bundles developed at the national labs that aggregate synergistic technologies in furtherance of the emerging hydrogen and fuel cell market. The first L’Innovator IP bundle consists of Oxygen Reduction Reaction (ORR) Catalyst technology developed at Brookhaven National Laboratory (BNL), combined with Membrane Electrode Assembly (MEA) technology developed at Los Alamos National Laboratory (LANL).

Characterization of the Chicken Ovarian Cancer Model

DTIC Science & Technology

2005-08-01

Typical staining of tumor in an area of stromal hyperplasia . Figure 5. Adenocarcinoma, Ovary, Chicken, Her2/neu. Intense staining of tumor cells in...variable amounts of interstitial fibrovascular tissue and/or smooth muscle bundles, which accounted for their scirrhous nature grossly. 22...Figure 25). Figure 25. Peritoneum, Adenocarcinoma. Interstitial fibrovascular tissue and/or smooth muscle bundles account for the scirrhous

The chromokinesin Kid is required for maintenance of proper metaphase spindle size.

PubMed

Tokai-Nishizumi, Noriko; Ohsugi, Miho; Suzuki, Emiko; Yamamoto, Tadashi

2005-11-01

The human chromokinesin Kid/kinesin-10, a plus end-directed microtubule (MT)-based motor with both microtubule- and DNA-binding domains, is required for proper chromosome alignment at the metaphase plate. Here, we performed RNA interference experiments to deplete endogenous Kid from HeLa cells and confirmed defects in metaphase chromosome arm alignment in Kid-depleted cells. In addition, we noted a shortening of the spindle length, resulting in a pole-to-pole distance only 80% of wild type. The spindle microtubule-bundles with which Kid normally colocalize became less robust. Rescue of the two Kid deficiency phenotypes-imprecise chromosome alignment at metaphase and shortened spindles- exhibited distinct requirements. Mutants lacking either the DNA-binding domain or the MT motor ATPase failed to rescue the former defect, whereas rescue of the shortened spindle phenotype required neither activity. Kid also exhibits microtubule bundling activity in vitro, and rescue of the shortened spindle phenotype and the bundling activity displayed similar domain requirements, except that rescue required a coiled-coil domain not needed for bundling. These results suggest that distinct from its role in chromosome movement, Kid contributes to spindle morphogenesis by mediating spindle microtubules stabilization.

The Chromokinesin Kid Is Required for Maintenance of Proper Metaphase Spindle SizeD⃞

PubMed Central

Tokai-Nishizumi, Noriko; Ohsugi, Miho; Suzuki, Emiko; Yamamoto, Tadashi

2005-01-01

The human chromokinesin Kid/kinesin-10, a plus end-directed microtubule (MT)-based motor with both microtubule- and DNA-binding domains, is required for proper chromosome alignment at the metaphase plate. Here, we performed RNA interference experiments to deplete endogenous Kid from HeLa cells and confirmed defects in metaphase chromosome arm alignment in Kid-depleted cells. In addition, we noted a shortening of the spindle length, resulting in a pole-to-pole distance only 80% of wild type. The spindle microtubule-bundles with which Kid normally colocalize became less robust. Rescue of the two Kid deficiency phenotypes—imprecise chromosome alignment at metaphase and shortened spindles— exhibited distinct requirements. Mutants lacking either the DNA-binding domain or the MT motor ATPase failed to rescue the former defect, whereas rescue of the shortened spindle phenotype required neither activity. Kid also exhibits microtubule bundling activity in vitro, and rescue of the shortened spindle phenotype and the bundling activity displayed similar domain requirements, except that rescue required a coiled-coil domain not needed for bundling. These results suggest that distinct from its role in chromosome movement, Kid contributes to spindle morphogenesis by mediating spindle microtubules stabilization. PMID:16176979

Rheological alteration of erythrocytes exposed to carbon nanotubes.

PubMed

Heo, Yujin; Li, Cheng-Ai; Kim, Duckjong; Shin, Sehyun

2017-01-01

Single-walled carbon nanotubes (SWNTs) have been increasingly used in a variety of biomedical applications, such as in vivo delivery of drugs and tumor imaging. Potential exposure of SWNTs to human red blood cells (RBCs) may cause serious toxicity including alteration of mechanical properties of cells. The present study investigated the cellular response to exposure of SWNTs with measuring rheological characteristics of RBCs, including hemolysis, deformability, aggregation, and morphological changes. RBCs were exposed to two different dispersion-state samples (i.e. individual SWNTs and bundled SWNTs) in chitosan hydroxyphenyl acetamide (CHPA) solutions. The concentrations of SWNTs were carefully chosen to avoid any hemorheological alterations due to hemolysis. Rheological characteristics were measured using microfluidic-laser diffractometry and aggregometry. Our results show that the bundled SWNTs had higher hemolytic activity than did the individual SWNTs. RBC aggregation apparently decreased as the concentration of SWNTs or incubation time increased. Additionally, bundled SWNTs caused significant alterations in the shape and fusion of RBCs. In conclusion, bundled SWNTs were found to be more toxic than individual SWNTs. These results provide important insights into the interactions between RBCs and SWNTs and will facilitate assessment of the risk of nanomaterial toxicity of blood.

Patients affected by endemic pemphigus foliaceus in Colombia, South America exhibit autoantibodies to optic nerve sheath envelope cell junctions.

PubMed

Abreu-Velez, Ana Maria; Gao, Wendy; Howard, Michael S

2018-01-01

The majority of the patients affected by a new variant of endemic pemphigus foliaceus in El Bagre, Colombia (El Bagre EPF or pemphigus Abreu-Manu), have experienced vision problems; we have previously reported several ocular abnormalities. Here, we aimed to investigate reactivity to optic nerves in these patients. We utilized bovine, rat and mouse optic nerves, and performed immunofluorescence and confocal microscopy to test for optical nerve autoreactivity. We tested 45 patients affected by this disease and 45 controls from the endemic area matched by age, sex and work activity. Overall, 37 of the 45 patient sera reacted to the optic nerve envelope that is composed of leptomeninges; the reactivity was polyclonal and present mostly at the cell junctions (P < 0.001). The immune response was directed against optic nerve sheath cell junctions and the vessels inside it, as well as other molecules inside the nerve. No control cases were positive. Of interest, all the patient autoantibodies co-localized with commercial antibodies to desmoplakins I-II, myocardium-enriched zonula occludens-1- associated protein (MYZAP), armadillo repeat gene deleted in velo-cardio-facial syndrome (ARVCF), and plakophilin-4 (p0071) from Progen Biotechnik (P < 0.001). We conclude that the majority of the patients affected by pemphigus Abreu-Manu have autoantibodies to optic nerve sheath envelope cell junctions. These antibodies also co-localize with armadillo repeat gene deleted in velo-cardio-facial syndrome, p0071 and desmoplakins I-II. The clinical significance of our findings remains unknown.

Immunohistochemical study of calretinin in normal skin and cutaneous adnexal proliferations.

PubMed

González-Guerra, Elena; Kutzner, Heinz; Rutten, Arno; Requena, Luis

2012-07-01

Calretinin is a calcium-binding protein member of the EF-hand family. The presence of calretinin has been demonstrated in certain stages of the cellular cycle in a wide variety of normal and neoplastic tissues. The main aims of our study were (1) to investigate what structures of the normal skin and cutaneous adnexal proliferations express immunoreactivity for calretinin and (2) to determine the value of immunohistochemical expression for calretinin as a marker for follicular, sebaceous, apocrine, and eccrine differentiation in cutaneous adnexal proliferations. We studied 139 biopsy specimens, including 10 cases of normal skin of different locations and 129 benign and malignant cutaneous adnexal proliferations. In normal skin, we found that calretinin is expressed in the innermost cell layer of the outer root sheath in anagen hair follicle, in both the duct and sebolemma of the sebaceous gland, in the secretory portion of eccrine glands, and in mast cells of the stroma. In cutaneous adnexal proliferations, we found strong immunoreactivity for calretinin in tricholemmal cysts, tricholemmomas/inverted follicular keratoses, tumors of follicular infundibulum, and in some basal cell carcinomas. Focal positivity was also seen in trichoadenomas, trichoblastomas/trichoepitheliomas, pilomatricomas, proliferating tricholemmal tumors, pilar sheath acanthomas, trichofolliculomas, follicular hybrid cysts, cutaneous mixed tumors, steatocystomas, sebaceous hyperplasias, and sebaceomas. These results demonstrate that immunohistochemical study for calretinin may be helpful to identify the innermost cell layer of the outer root sheath in anagen hair follicle and the cutaneous adnexal proliferations showing differentiation toward this structure. Calretinin immunoreactivity supports eccrine differentiation in some sweat gland neoplasms, and it is also useful in identifying neoplasms with ductal sebaceous differentiation.

A finite element procedure for radio-frequency sheath–plasma interactions based on a sheath impedance model

DOE PAGES

Kohno, H.; Myra, J. R.

2017-07-24

A finite element code that solves self-consistent radio-frequency (RF) sheath-plasma interaction problems is improved by incorporating a generalized sheath boundary condition in the macroscopic solution scheme. This sheath boundary condition makes use of a complex sheath impedance including both the sheath capacitance and resistance, which enables evaluation of not only the RF voltage across the sheath but also the power dissipation in the sheath. The newly developed finite element procedure is applied to cases where the background magnetic field is perpendicular to the sheath surface in one- and two-dimensional domains filled by uniform low- and high-density plasmas. The numerical resultsmore » are compared with those obtained by employing the previous capacitive sheath model at a typical frequency for ion cyclotron heating used in fusion experiments. It is shown that for sheaths on the order of 100 V in a high-density plasma, localized RF power deposition can reach a level which causes material damage. It is also shown that the sheath-plasma wave resonances predicted by the capacitive sheath model do not occur when parameters are such that the generalized sheath impedance model substantially modifies the capacitive character of the sheath. Here, possible explanations for the difference in the maximum RF sheath voltage depending on the plasma density are also discussed.« less

A finite element procedure for radio-frequency sheath–plasma interactions based on a sheath impedance model

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

Kohno, H.; Myra, J. R.

A finite element code that solves self-consistent radio-frequency (RF) sheath-plasma interaction problems is improved by incorporating a generalized sheath boundary condition in the macroscopic solution scheme. This sheath boundary condition makes use of a complex sheath impedance including both the sheath capacitance and resistance, which enables evaluation of not only the RF voltage across the sheath but also the power dissipation in the sheath. The newly developed finite element procedure is applied to cases where the background magnetic field is perpendicular to the sheath surface in one- and two-dimensional domains filled by uniform low- and high-density plasmas. The numerical resultsmore » are compared with those obtained by employing the previous capacitive sheath model at a typical frequency for ion cyclotron heating used in fusion experiments. It is shown that for sheaths on the order of 100 V in a high-density plasma, localized RF power deposition can reach a level which causes material damage. It is also shown that the sheath-plasma wave resonances predicted by the capacitive sheath model do not occur when parameters are such that the generalized sheath impedance model substantially modifies the capacitive character of the sheath. Here, possible explanations for the difference in the maximum RF sheath voltage depending on the plasma density are also discussed.« less

Selective pH-Responsive Core-Sheath Nanofiber Membranes for Chem/Bio/Med Applications: Targeted Delivery of Functional Molecules.

PubMed

Han, Daewoo; Steckl, Andrew J

2017-12-13

Core-sheath fibers using different Eudragit materials were successfully produced, and their controlled multi-pH responses have been demonstrated. Core-sheath fibers made of Eudragit L 100 (EL100) core and Eudragit S 100 (ES100) sheath provide protection and/or controlled release of core material at pH 6 by adjusting the sheath thickness (controlled by the flow rate of source polymer solution). The thickest sheath (∼250 nm) provides the least core release ∼1.25%/h, while the thinnest sheath (∼140 nm) provides much quicker release ∼16.75%/h. Furthermore, switching core and sheath material dramatically altered the pH response. Core-sheath fibers made of ES100 core and EL100 sheath can provide a consistent core release rate, while the sheath release rate becomes higher as the sheath layer becomes thinner. For example, the thinnest sheath (∼120 nm) provides a core and sheath release ratio of 1:2.5, while the thickest sheath (∼200 nm) shows only a ratio of 1:1.7. All core-sheath Eudragit fibers show no noticeable release at pH 5, while they are completely dissolved at pH 7. Extremely high surface area in the porous network of the fiber membranes provides much faster (>30 times) response to external pH changes as compared to that of equivalent cast films.

Thick Filament Length and Isoform Composition Determine Self-Organized Contractile Units in Actomyosin Bundles

PubMed Central

Thoresen, Todd; Lenz, Martin; Gardel, Margaret L.

2013-01-01

Diverse myosin II isoforms regulate contractility of actomyosin bundles in disparate physiological processes by variations in both motor mechanochemistry and the extent to which motors are clustered into thick filaments. Although the role of mechanochemistry is well appreciated, the extent to which thick filament length regulates actomyosin contractility is unknown. Here, we study the contractility of minimal actomyosin bundles formed in vitro by mixtures of F-actin and thick filaments of nonmuscle, smooth, and skeletal muscle myosin isoforms with varied length. Diverse myosin II isoforms guide the self-organization of distinct contractile units within in vitro bundles with shortening rates similar to those of in vivo myofibrils and stress fibers. The tendency to form contractile units increases with the thick filament length, resulting in a bundle shortening rate proportional to the length of constituent myosin thick filament. We develop a model that describes our data, providing a framework in which to understand how diverse myosin II isoforms regulate the contractile behaviors of disordered actomyosin bundles found in muscle and nonmuscle cells. These experiments provide insight into physiological processes that use dynamic regulation of thick filament length, such as smooth muscle contraction. PMID:23442916

Xyloside primed glycosaminoglycans alter hair bundle micromechanical coupling and synaptic transmission: Pharmacokinetics

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

Holman, Holly A.; Nguyen, Lynn Y.; Tran, Vy M.

Glycosaminoglycans (GAGs) are ubiquitous in the inner ear, and disorders altering their structure or production often result in debilitating hearing and balance deficits. The specific mechanisms responsible for loss of hair-cell function are not well understood. We recently reported that introduction of a novel BODIPY conjugated xyloside (BX) into the endolymph primes fluorescent GAGs in vivo [6, 15]. Confocal and two-photon fluorescence imaging revealed rapid turnover and assembly of a glycocalyx enveloping the kinocilia and extending into the cupula, a structure that presumably serves as a mechanical link between the hair bundle and the cupula. Extracellular fluorescence was also observedmore » around the basolateral surface of hair cells and surrounding afferent nerve projections into the crista. Single unit afferent recordings during mechanical hair bundle stimulation revealed temporary interruption of synaptic transmission following BX administration followed by recovery, demonstrating an essential role for GAGs in function of the hair cell synapse. In the present work we present a pharmacokinetic model to quantify the time course of BX primed GAG production and turnover in the ear.« less

Xyloside primed glycosaminoglycans alter hair bundle micromechanical coupling and synaptic transmission: Pharmacokinetics

NASA Astrophysics Data System (ADS)

Holman, Holly A.; Tran, Vy M.; Nguyen, Lynn Y.; Arungundram, Sailaja; Kalita, Mausam; Kuberan, Balagurunathan; Rabbitt, Richard D.

2015-12-01

Glycosaminoglycans (GAGs) are ubiquitous in the inner ear, and disorders altering their structure or production often result in debilitating hearing and balance deficits. The specific mechanisms responsible for loss of hair-cell function are not well understood. We recently reported that introduction of a novel BODIPY conjugated xyloside (BX) into the endolymph primes fluorescent GAGs in vivo [6, 15]. Confocal and two-photon fluorescence imaging revealed rapid turnover and assembly of a glycocalyx enveloping the kinocilia and extending into the cupula, a structure that presumably serves as a mechanical link between the hair bundle and the cupula. Extracellular fluorescence was also observed around the basolateral surface of hair cells and surrounding afferent nerve projections into the crista. Single unit afferent recordings during mechanical hair bundle stimulation revealed temporary interruption of synaptic transmission following BX administration followed by recovery, demonstrating an essential role for GAGs in function of the hair cell synapse. In the present work we present a pharmacokinetic model to quantify the time course of BX primed GAG production and turnover in the ear.

Progressive trichodysplasia spinulosa in a patient with chronic lymphocytic leukaemia in remission.

PubMed

Lee, Joyce S-S; Frederiksen, Peter; Kossard, Steven

2008-02-01

A 70-year old Caucasian man with chronic lymphocytic leukaemia developed trichodysplasia spinulosa 2 months after ceasing chemotherapy. Histological features characteristic to this condition include dilated and enlarged hair follicles, hyperplastic hair bulbs, hyperplasia of inner root sheath cells with numerous large, eosinophilic, trichohyaline granules, and hypercornification. Although he was in remission for chronic lymphocytic leukaemia, lesions were slowly progressive 15 months after cessation of chemotherapy. We also describe a painless pull-test where spicules can be easily plucked and assessed microscopically for inner root sheath keratinization, or observed with surface microscopy in a clinic setting.

Control of target-normal-sheath-accelerated protons from a guiding cone

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

Zou, D. B.; Institut für Theoretische Physik I, Heinrich-Heine-Universität Düsseldorf, Düsseldorf 40225; Zhuo, H. B., E-mail: hongbin.zhuo@gmail.com

2015-06-15

It is demonstrated through particle-in-cell simulations that target-normal-sheath-accelerated protons can be well controlled by using a guiding cone. Compared to a conventional planar target, both the collimation and number density of proton beams are substantially improved, giving a high-quality proton beam which maintained for a longer distance without degradation. The effect is attributed to the radial electric field resulting from the charge due to the hot target electrons propagating along the cone surface. This electric field can effectively suppress the spatial spread of the protons after the expansion of the hot electrons.

Modeling fluid diffusion in cerebral white matter with random walks in complex environments

NASA Astrophysics Data System (ADS)

Levy, Amichai; Cwilich, Gabriel; Buldyrev, Sergey V.; Weeden, Van J.

2012-02-01

Recent studies with diffusion MRI have shown new aspects of geometric order in the brain, including complex path coherence within the cerebral cortex, and organization of cerebral white matter and connectivity across multiple scales. The main assumption of these studies is that water molecules diffuse along myelin sheaths of neuron axons in the white matter and thus the anisotropy of their diffusion tensor observed by MRI can provide information about the direction of the axons connecting different parts of the brain. We model the diffusion of particles confined in the space of between the bundles of cylindrical obstacles representing fibrous structures of various orientations. We have investigated the directional properties of the diffusion, by studying the angular distribution of the end point of the random walks as a function of their length, to understand the scale over which the distribution randomizes. We will show evidence of qualitative change in the behavior of the diffusion for different volume fractions of obstacles. Comparisons with three-dimensional MRI images will be illustrated.

Prospects for improving CO2 fixation in C3-crops through understanding C4-Rubisco biogenesis and catalytic diversity.

PubMed

Sharwood, Robert E; Ghannoum, Oula; Whitney, Spencer M

2016-06-01

By operating a CO2 concentrating mechanism, C4-photosynthesis offers highly successful solutions to remedy the inefficiency of the CO2-fixing enzyme Rubisco. C4-plant Rubisco has characteristically evolved faster carboxylation rates with low CO2 affinity. Owing to high CO2 concentrations in bundle sheath chloroplasts, faster Rubisco enhances resource use efficiency in C4 plants by reducing the energy and carbon costs associated with photorespiration and lowering the nitrogen investment in Rubisco. Here, we show that C4-Rubisco from some NADP-ME species, such as maize, are also of potential benefit to C3-photosynthesis under current and future atmospheric CO2 pressures. Realizing this bioengineering endeavour necessitates improved understanding of the biogenesis requirements and catalytic variability of C4-Rubisco, as well as the development of transformation capabilities to engineer Rubisco in a wider variety of food and fibre crops. Copyright © 2016 Elsevier Ltd. All rights reserved.

Rumen Protozoal Degradation of Structurally Intact Forage Tissues

PubMed Central

Amos, Henry E.; Akin, Danny E.

1978-01-01

The association with and digestion of intact leaf sections of cool- and warm-season grasses by cattle rumen protozoa were investigated by light and scanning electron microscopy and by in vitro dry matter disappearance studies. Within extensively degraded areas of mesophyll tissue in cool-season forages, almost all protozoa were Epidinium ecaudatum form caudatum, with maximum numbers at 4 to 10 h of incubation. However, few protozoa were found inside warm-season forage leaves. In in vitro dry matter disappearance studies of a series of incubations with and without 1.6 mg of streptomycin per ml, which inhibited the cellulolytic activity of the bacteria, and in comparison with uninoculated controls, rumen protozoa degraded 11.0 and 3.7 percentage units of orchardgrass and bermuda-grass, respectively. Scanning electron microscopy showed that the tissues degraded in orchardgrass consisted of large amounts of mesophyll and portions of the parenchyma bundle sheath and epidermis; no tissue loss due to the protozoa was observed in bermudagrass. The relationship of these observations to forage digestion is discussed. Images PMID:16345315

New flexible endoscope for otologic application

NASA Astrophysics Data System (ADS)

Marchan, Mark L.

1993-07-01

Endoscopy has become an important procedure in many medical specialties. For the Otologist, however, space limitations within the ear have restricted development of endoscopic procedures. The desire for minimally invasive techniques in Otology has demonstrated itself through the work of numerous physicians who have performed procedures ranging from diagnostic inspection of the middle ear to viewing the interior of the cochlea. To assist in performing such endoscopic procedures, Xomed-Treace has developed a line of flexible fiberoptic endoscopes for use by the Otologist. These scopes combine illumination and imaging fiber bundles within a small diameter unit ranging in size from 0.8 mm to 1.2 mm. The 1.2 mm scope is produced with an angled, rigid stainless steel sheath. The 0.8 mm scope is flexible with the ability to articulate 120 degree(s) in one direction. The fiberscopes have been designed for the Otologist to produce a good resolution image while allowing ease of operation through ergonomics and consideration of the surgical anatomy.

Regulation of Polysaccharide- and Protein- Specific Antibody Responses to Intact Extracellular Bacteria

DTIC Science & Technology

2016-03-11

50, Immunology. 26 | P a g e blood-borne antigens. The white pulp consists of the periarteriolar lymphoid sheath (PALS) which contain T cells ...and CD8α+ dendritic (DC), and adjacent lymphoid follicles containing mainly circulating B cells , known as follicular B cells (FB). The outer boundary...complexes, for initial priming within the T cell zones of secondary lymphoid organs followed by migration of T cells to the T cell -B cell border. B

Composition of the sheath produced by the green alga Chlorella sorokiniana.

PubMed

Watanabe, K; Imase, M; Sasaki, K; Ohmura, N; Saiki, H; Tanaka, H

2006-05-01

To investigate the chemical characterization of the mucilage sheath produced by Chlorella sorokiniana. Algal mucilage sheath was hydrolysed with NaOH, containing EDTA. The purity of the hydrolysed sheath was determined by an ATP assay. The composition of polysaccharide in the sheath was investigated by high-performance anion-exchange chromatography with pulsed amperometric detection. Sucrose, galacturonic acid, xylitol, inositol, ribose, mannose, arabinose, galactose, rhamnose and fructose were detected in the sheath as sugar components. Magnesium was detected in the sheath as a divalent cation using inductively coupled argon plasma. The sheath matrix also contained protein. It appears that the sheath is composed of sugars and metals. Mucilage sheath contains many kinds of saccharides that are produced as photosynthetic metabolites and divalent cations that are contained in the culture medium. This is the first report on chemical characterization of the sheath matrix produced by C. sorokiniana.

MicroRNA Gene Regulatory Networks in Peripheral Nerve Sheath Tumors

DTIC Science & Technology

2012-09-01

chondrosarcoma are identified based on the unique histology, cell of origin, clinical features and site distribution. The following are the major... Chondrosarcoma Chondrosarcoma is a cancer composed of cells derived from transformed cells that produce cartilage. Peripheral chondrosarcoma is a malignant...biosynthesis. This is in line with gene expression analyses previously performed in osteochondroma and chondrosarcoma samples showing modulation of

Repair of traumatized mammalian hair cells via sea anemone repair proteins.

PubMed

Tang, Pei-Ciao; Smith, Karen Müller; Watson, Glen M

2016-08-01

Mammalian hair cells possess only a limited ability to repair damage after trauma. In contrast, sea anemones show a marked capability to repair damaged hair bundles by means of secreted repair proteins (RPs). Previously, it was found that recovery of traumatized hair cells in blind cavefish was enhanced by anemone-derived RPs; therefore, the ability of anemone RPs to assist recovery of damaged hair cells in mammals was tested here. After a 1 h incubation in RP-enriched culture media, uptake of FM1-43 by experimentally traumatized murine cochlear hair cells was restored to levels comparable to those exhibited by healthy controls. In addition, RP-treated explants had significantly more normally structured hair bundles than time-matched traumatized control explants. Collectively, these results indicate that anemone-derived RPs assist in restoring normal function and structure of experimentally traumatized hair cells of the mouse cochlea. © 2016. Published by The Company of Biologists Ltd.

Enhanced Expansion and Sustained Inductive Function of Skin‐Derived Precursor Cells in Computer‐Controlled Stirred Suspension Bioreactors

PubMed Central

Agabalyan, Natacha A.; Borys, Breanna S.; Sparks, Holly D.; Boon, Kathryn; Raharjo, Eko W.; Abbasi, Sepideh; Kallos, Michael S.

2016-01-01

Abstract Endogenous dermal stem cells (DSCs) reside in the adult hair follicle mesenchyme and can be isolated and grown in vitro as self‐renewing colonies called skin‐derived precursors (SKPs). Following transplantation into skin, SKPs can generate new dermis and reconstitute the dermal papilla and connective tissue sheath, suggesting they could have important therapeutic value for the treatment of skin disease (alopecia) or injury. Controlled cell culture processes must be developed to efficiently and safely generate sufficient stem cell numbers for clinical use. Compared with static culture, stirred‐suspension bioreactors generated fivefold greater expansion of viable SKPs. SKPs from each condition were able to repopulate the dermal stem cell niche within established hair follicles. Both conditions were also capable of inducing de novo hair follicle formation and exhibited bipotency, reconstituting the dermal papilla and connective tissue sheath, although the efficiency was significantly reduced in bioreactor‐expanded SKPs compared with static conditions. We conclude that automated bioreactor processing could be used to efficiently generate large numbers of autologous DSCs while maintaining their inherent regenerative function. Stem Cells Translational Medicine 2017;6:434–443 PMID:28191777

Giant cell tumour of tendon sheath: A 10-year study from a tertiary care centre.

PubMed

Kumar, R; Bharani, V; Gupta, N; Gupta, K; Dey, P; Srinivasan, R; Rajwanshi, A

2018-06-01

Cytology of giant cell tumour of tendon sheath (GCTTS) is often sufficient to diagnose this lesion and has been previously described in small series. The present study was undertaken to evaluate detailed cytomorphological features and differential diagnostic entities and pitfalls in the diagnosis. All the cases of GCTTS reported on FNAC were retrieved from July 2007 to June 2017. The cases were reviewed for various cytomorphological features, which were correlated with follow-up histopathology wherever available. A total of 72 cases of GCTTS were retrieved, follow-up histopathology was available in 20 cases. The common sites of involvement were fingers and palm followed by wrists, elbow, knee, ankle and shoulder. The characteristic cytomorphology consisted of mononuclear cells, multinucleated giant cells and pigment laden macrophages in variable numbers. There were four discordant cases that were confirmed on histopathology as sarcoidosis, melanoma, fibrous histiocytoma and eumycetoma. GCTTS can be confused cytologically with giant cell rich lesions of bone and soft tissue and pigment containing lesions including melanoma. Ladybird cell is a characteristic feature seen in this lesion. Proper clinicoradiological correlation is essential before offering a diagnosis of GCTTS on cytology. © 2018 John Wiley & Sons Ltd.

In-Depth Analysis of the Structure and Properties of Two Varieties of Natural Luffa Sponge Fibers

PubMed Central

Chen, Yuxia; Su, Na; Zhang, Kaiting; Zhu, Shiliu; Zhao, Lei; Fang, Fei; Ren, Linyan; Guo, Yong

2017-01-01

The advancement in science and technology has led to luffa sponge (LS) being widely used as a natural material in industrial application because of its polyporous structure and light texture. To enhance the utility of LS fibers as the reinforcement of lightweight composite materials, the current study investigates their water absorption, mechanical properties, anatomical characteristics and thermal performance. Hence, moisture regain and tensile properties of LS fiber bundles were measured in accordance with American Society for Testing and Materials (ASTM) standards while their structural characteristics were investigated via microscopic observation. Scanning electron microscopy (SEM) was used to observe the surface morphology and fractured surface of fiber bundles. The test results show that the special structure where the phloem tissues degenerate to cavities had a significant influence on the mechanical properties of LS fiber bundles. Additionally, the transverse sectional area occupied by fibers in a fiber bundle (SF), wall thickness, ratio of wall to lumen of fiber cell, and crystallinity of cellulose had substantial impact on the mechanical properties of LS fiber bundles. Furthermore, the density of fiber bundles of LS ranged within 385.46–468.70 kg/m3, significantly less than that of jute (1360.40 kg/m3) and Arenga engleri (950.20 kg/m3). However, LS fiber bundles demonstrated superior specific modulus than Arenga engleri. PMID:28772838

Tension and Elasticity Contribute to Fibroblast Cell Shape in Three Dimensions.

PubMed

Brand, Christoph A; Linke, Marco; Weißenbruch, Kai; Richter, Benjamin; Bastmeyer, Martin; Schwarz, Ulrich S

2017-08-22

The shape of animal cells is an important regulator for many essential processes such as cell migration or division. It is strongly determined by the organization of the actin cytoskeleton, which is also the main regulator of cell forces. Quantitative analysis of cell shape helps to reveal the physical processes underlying cell shape and forces, but it is notoriously difficult to conduct it in three dimensions. Here we use direct laser writing to create 3D open scaffolds for adhesion of connective tissue cells through well-defined adhesion platforms. Due to actomyosin contractility in the cell contour, characteristic invaginations lined by actin bundles form between adjacent adhesion sites. Using quantitative image processing and mathematical modeling, we demonstrate that the resulting shapes are determined not only by contractility, but also by elastic stress in the peripheral actin bundles. In this way, cells can generate higher forces than through contractility alone. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Cixutumumab and Doxorubicin Hydrochloride in Treating Patients With Unresectable, Locally Advanced, or Metastatic Soft Tissue Sarcoma

ClinicalTrials.gov

2016-05-16

Adult Angiosarcoma; Adult Desmoplastic Small Round Cell Tumor; Adult Epithelioid Sarcoma; Adult Extraskeletal Myxoid Chondrosarcoma; Adult Extraskeletal Osteosarcoma; Adult Fibrosarcoma; Adult Leiomyosarcoma; Adult Liposarcoma; Adult Malignant Mesenchymoma; Adult Malignant Peripheral Nerve Sheath Tumor; Adult Rhabdomyosarcoma; Adult Synovial Sarcoma; Adult Undifferentiated High Grade Pleomorphic Sarcoma of Bone; Childhood Angiosarcoma; Childhood Desmoplastic Small Round Cell Tumor; Childhood Epithelioid Sarcoma; Childhood Fibrosarcoma; Childhood Leiomyosarcoma; Childhood Liposarcoma; Childhood Malignant Mesenchymoma; Childhood Malignant Peripheral Nerve Sheath Tumor; Childhood Pleomorphic Rhabdomyosarcoma; Childhood Rhabdomyosarcoma With Mixed Embryonal and Alveolar Features; Childhood Synovial Sarcoma; Dermatofibrosarcoma Protuberans; Malignant Adult Hemangiopericytoma; Malignant Childhood Hemangiopericytoma; Metastatic Childhood Soft Tissue Sarcoma; Previously Treated Childhood Rhabdomyosarcoma; Recurrent Adult Soft Tissue Sarcoma; Recurrent Childhood Rhabdomyosarcoma; Recurrent Childhood Soft Tissue Sarcoma; Stage III Adult Soft Tissue Sarcoma; Stage IV Adult Soft Tissue Sarcoma; Untreated Childhood Rhabdomyosarcoma

Aphidicolin-induced nuclear elongation in tobacco BY-2 cells.

PubMed

Yasuhara, Hiroki; Kitamoto, Kazuki

2014-05-01

Plant nuclei are known to differentiate into various shapes within a single plant. However, little is known about the mechanisms of nuclear morphogenesis. We found that nuclei of tobacco BY-2 cells were highly elongated on long-term treatment with 5 mg l⁻¹ aphidicolin, an inhibitor of DNA polymerase α. In aphidicolin-treated cells, the nuclear length was correlated with the cell length. During culture in the presence of aphidicolin, the nuclei were elongated in parallel with cell elongation. Nuclear elongation was inhibited by the inhibition of cell elongation with 2,6-dichlorobenzonitrile, a cellulose synthesis inhibitor. However, cell elongation induced in the auxin-depleted medium in the absence of aphidicolin did not cause nuclear elongation, indicating that cell elongation alone is not sufficient for nuclear elongation. Treatment with either latrunculin B or propyzamide inhibited the aphidicolin-induced nuclear elongation, indicating that both actin filaments and microtubules (MTs) are required for nuclear elongation. Observations using BY-YTHCLR2 cells, in which actin filaments, MTs and nuclei were simultaneously visualized, revealed that the longitudinally arranged MT bundles associated with the nucleus play an important role in nuclear elongation, and that actin filaments affect the formation of these MT bundles. In aphidicolin-treated cells, the nuclear DNA contents of the elongated nuclei exceeded 4C, and the nuclear length was highly correlated with the nuclear DNA content. In cells treated with 50 mg l⁻¹ aphidicolin, cells were elongated and nucleus-associated longitudinal MT bundles were formed, but the nuclear DNA contents did not exceed 4C and the nuclei did not elongate. These results indicate that an increase in the nuclear DNA content above 4C is also required for nuclear elongation.

Fast wave experiments in LAPD: RF sheaths, convective cells and density modifications

NASA Astrophysics Data System (ADS)

Carter, T. A.; van Compernolle, B.; Martin, M.; Gekelman, W.; Pribyl, P.; van Eester, D.; Crombe, K.; Perkins, R.; Lau, C.; Martin, E.; Caughman, J.; Tripathi, S. K. P.; Vincena, S.

2017-10-01

An overview is presented of recent work on ICRF physics at the Large Plasma Device (LAPD) at UCLA. The LAPD has typical plasma parameters ne 1012 -1013 cm-3, Te 1 - 10 eV and B 1000 G. A new high-power ( 150 kW) RF system and fast wave antenna have been developed for LAPD. The source runs at a frequency of 2.4 MHz, corresponding to 1 - 7fci , depending on plasma parameters. Evidence of rectified RF sheaths is seen in large increases ( 10Te) in the plasma potential on field lines connected to the antenna. The rectified potential scales linearly with antenna current. The rectified RF sheaths set up convective cells of local E × B flows, measured indirectly by potential measurements, and measured directly with Mach probes. At high antenna powers substantial modifications of the density profile were observed. The plasma density profile initially exhibits transient low frequency oscillations (10 kHz). The amplitude of the fast wave fields in the core plasma is modulated at the same low frequency, suggesting fast wave coupling is affected by the density rearrangement. Work performed at the Basic Plasma Science Facility, supported jointly by the National Science Foundation and the Department of Energy.

Expression of the Intermediate Filament Nestin in Gastrointestinal Stromal Tumors and Interstitial Cells of Cajal

PubMed Central

Tsujimura, Tohru; Makiishi-Shimobayashi, Chiaki; Lundkvist, Johan; Lendahl, Urban; Nakasho, Keiji; Sugihara, Ayako; Iwasaki, Teruo; Mano, Masayuki; Yamada, Naoko; Yamashita, Kunihiro; Toyosaka, Akihiro; Terada, Nobuyuki

2001-01-01

It has recently been proposed that gastrointestinal stromal tumors (GISTs) originate from stem cells that differentiate toward a phenotype of interstitial cells of Cajal (ICCs). Nestin is a newly identified intermediate filament protein, and is predominantly expressed in immature cells, such as neuroectodermal stem cells and skeletal muscle progenitor cells, and tumors originating from these cells. In this study, we examined, using immunohistochemistry, the nestin expression in GISTs and ICCs to clarify the origin of GISTs. Strong immunoreactivity for nestin was observed in all 18 GISTs, and its expression was confirmed by Western blot and Northern blot analyses. In contrast, three leiomyomas and a schwannoma that developed in the gastrointestinal tract showed no apparent immunoreactivity for nestin. Among 17 mesenchymal tumors (seven leiomyosarcomas, five malignant peripheral nerve sheath tumors, and five fibrosarcomas) that occurred in sites other than the gastrointestinal tract, only two malignant peripheral nerve sheath tumors were moderately immunoreactive for nestin. Furthermore, with fluorescence double immunostaining of the normal small intestine, nestin expression was demonstrated in ICCs. These results show that nestin may be a useful marker for diagnosis of GISTs, and support the current hypothesis that GISTs are tumors of stem cells that differentiate toward an ICC phenotype. PMID:11238030

Numerical Model of the Plasma Sheath Generated by the Plasma Source Instrument Aboard the Polar Satellite

NASA Technical Reports Server (NTRS)

Singh, N.; Leung, W. C.; Moore, T. E.; Craven, P. D.

2001-01-01

The plasma sheath generated by the operation of the Plasma Source Instrument (PSI) aboard the Polar satellite is studied by using a three-dimensional particle-in-cell (PIC) code. When the satellite passes through the region of low-density plasma, the satellite charges to positive potentials as high as 40-50 V, owing to the photoelectron emission. In such a case, ambient core ions cannot accurately be measured or detected. The goal of the onboard PSI is to reduce the floating potential of the satellite to a sufficiently low value so that the ions in the polar wind become detectable. When the PSI is operated, ion-rich xenon plasma is ejected from the satellite, such that the floating potential of the satellite is reduced and is maintained at approximately 2 V. Accordingly, in our three-dimensional PIC simulation we considered that the potential of the satellite is 2 V as a fixed bias. Considering the relatively high density of the xenon plasma in the sheath (10-10(exp 3)/cc), the ambient plasma of low density (<1/cc) is neglected. In the simulations the electric fields and plasma dynamics are calculated self-consistently. We found that an 'apple'-shape positive potential sheath forms surrounding the satellite. In the region near the PSI emission a high positive potential hill develops. Near the Thermal Ion Dynamics Experiment detector away from the PSI, the potentials are sufficiently low for the ambient polar wind ions to reach it. In the simulations it takes only about a couple of tens of electron gyroperiods for the sheath to reach a quasi steady state. This time is approximately the time taken by the heavy Xe(+) ions to expand up to about one average Larmor radius of electrons from the satellite surface. After this time the expansion of the sheath in directions transverse to the ambient magnetic field slows down because the electrons are magnetized. Using the quasi steady sheath, we performed trajectory calculations to characterize the detector response to a highly supersonic polar wind flow. The detected ions' velocity distribution shows significant deviations from a shifted Maxwellian in the ambient polar wind population. The deviations are caused by the effects of electric fields on the ions' motion as they traverse the sheath.

Morphological study of the atrioventricular conduction system and Purkinje fibers in yak.

PubMed

Duan, Deyong; Yu, Sijiu; Cui, Yan; Li, Chaoxu

2017-07-01

We studied the morphology of the atrioventricular conduction system (AVCS) and Purkinje fibers of the yak. Light and transmission electron microscopy were used to study the histological features of AVCS. The distributional characteristics of the His-bundle, the left bundle branch (LBB), right bundle branch (RBB), and Purkinje fiber network of yak hearts were examined using gross dissection, ink injection, and ABS casting. The results showed that the atrioventricular node (AVN) of yak located in the right side of interatrial septum and had a flattened ovoid shape. The AVN of yak is composed of the slender, interweaving cells formed almost entirely of the transitional cells (T-cells). The His-bundle extended from the AVN, and split into left LBB and RBB at the crest of the interventricular septum. The LBB descended along the left side of interventricular septum. At approximately the upper 1/3 of the interventricular septum, the LBB typically divided into three branches. The RBB ran under the endocardium of the right side of interventricular septum, and extended to the base of septal papillary muscle, passed into the moderator band, crossed the right ventricular cavity to reach the base of anterior papillary muscle, and divided into four fascicles under the subendocardial layer. The Purkinje fibers in the ventricle formed a complex spatial network. The distributional and cellular component characteristics of the AVCS and Purkinje fibers ensured normal cardiac function. © 2017 Wiley Periodicals, Inc.

Apparatus for measuring resistance change only in a cell analyzer and method for calibrating it

DOEpatents

Hoffman, Robert A.

1980-01-01

The disclosure relates to resistance only monitoring and calibration in an electrical cell analyzer. Sample and sheath fluid flows of different salinities are utilized, the sample flow being diameter modulated to produce a selected pattern which is compared to the resistance measured across the flows.

RF sheaths for arbitrary B field angles

NASA Astrophysics Data System (ADS)

D'Ippolito, Daniel; Myra, James

2014-10-01

RF sheaths occur in tokamaks when ICRF waves encounter conducting boundaries and accelerate electrons out of the plasma. Sheath effects reduce the efficiency of ICRF heating, cause RF-specific impurity influxes from the edge plasma, and increase the plasma-facing component damage. The rf sheath potential is sensitive to the angle between the B field and the wall, the ion mobility and the ion magnetization. Here, we obtain a numerical solution of the non-neutral rf sheath and magnetic pre-sheath equations (for arbitrary values of these parameters) and attempt to infer the parametric dependences of the Child-Langmuir law. This extends previous work on the magnetized, immobile ion regime. An important question is how the rf sheath voltage distributes itself between sheath and pre-sheath for various B field angles. This will show how generally previous estimates of the rf sheath voltage and capacitance were reasonable, and to improve the RF sheath BC. Work supported by US DOE grants DE-FC02-05ER54823 and DE-FG02-97ER54392.

Assembly kinetics determine the architecture of α-actinin crosslinked F-actin networks.

PubMed

Falzone, Tobias T; Lenz, Martin; Kovar, David R; Gardel, Margaret L

2012-05-29

The actin cytoskeleton is organized into diverse meshworks and bundles that support many aspects of cell physiology. Understanding the self-assembly of these actin-based structures is essential for developing predictive models of cytoskeletal organization. Here we show that the competing kinetics of bundle formation with the onset of dynamic arrest arising from filament entanglements and crosslinking determine the architecture of reconstituted actin networks formed with α-actinin crosslinks. Crosslink-mediated bundle formation only occurs in dilute solutions of highly mobile actin filaments. As actin polymerization proceeds, filament mobility and bundle formation are arrested concomitantly. By controlling the onset of dynamic arrest, perturbations to actin assembly kinetics dramatically alter the architecture of biochemically identical samples. Thus, the morphology of reconstituted F-actin networks is a kinetically determined structure similar to those formed by physical gels and glasses. These results establish mechanisms controlling the structure and mechanics in diverse semiflexible biopolymer networks.

Microtubules and epithem-cell morphogenesis in hydathodes of Pilea cadierei.

PubMed

Galatis, B

1988-12-01

When cell divisions have ceased, the epithem of the hydathodes of Pilea cadierei Gagnep. et Guill. consists of small polyhedral cells exhibiting a meristematic appearance, and completely lacks intercellular spaces. The cortical microtubules in epithem cells exhibit a unique organization: they are not scattered along the whole wall surface but form groups lying at some distance from each other. In sections, from two to eight groups of microtubules can be observed, each lining a wall region averaging between 0.5 and 1.5 μm in length. These groups represent sections of microtubule bundles girdling a major part or the whole of the cell periphery. They are connected to one another by anastomoses, forming a microtubular reticulum. The assembly of microtubule bundles is followed by the appearance of distinct local thickenings in the adjacent wall areas. The cellulose microfibrils in the thickenings are deposited in parallel to the underlying microtubules. Gradually, the vacuolating epithem cells undergo swelling, except for the areas bounded by the wall thickenings. Since the latter, and actually their constituent bundles of cellulose microfibrils, cannot extend in length the differential cell growth results in schizogenous formation of intercellular spaces between contiguous cell walls at their thickened regions. The spaces then broaden and merge to become an extensive intercellular space system. As a result of the above processes, the epithem cells become constricted and finally deeply lobed. The observations show that (i) the cortical microtubules are intimately involved in the morphogenesis of the epithem cells and (ii) the initiation and development of the epithem intercellular spaces is a phenomenon directly related to cell morphogenesis and therefore to the cortical microtubule cytoskeleton. The sites of initiation of these spaces are highly predictable.

The actin-binding proteins eps8 and gelsolin have complementary roles in regulating the growth and stability of mechanosensory hair bundles of mammalian cochlear outer hair cells.

PubMed

Olt, Jennifer; Mburu, Philomena; Johnson, Stuart L; Parker, Andy; Kuhn, Stephanie; Bowl, Mike; Marcotti, Walter; Brown, Steve D M

2014-01-01

Sound transduction depends upon mechanosensitive channels localized on the hair-like bundles that project from the apical surface of cochlear hair cells. Hair bundles show a stair-case structure composed of rows of stereocilia, and each stereocilium contains a core of tightly-packed and uniformly-polarized actin filaments. The growth and maintenance of the stereociliary actin core are dynamically regulated. Recently, it was shown that the actin-binding protein gelsolin is expressed in the stereocilia of outer hair cells (OHCs) and in its absence they become long and straggly. Gelsolin is part of a whirlin scaffolding protein complex at the stereocilia tip, which has been shown to interact with other actin regulatory molecules such as Eps8. Here we investigated the physiological effects associated with the absence of gelsolin and its possible overlapping role with Eps8. We found that, in contrast to Eps8, gelsolin does not affect mechanoelectrical transduction during immature stages of development. Moreover, OHCs from gelsolin knockout mice were able to mature into fully functional sensory receptors as judged by the normal resting membrane potential and basolateral membrane currents. Mechanoelectrical transducer current in gelsolin-Eps8 double knockout mice showed a profile similar to that observed in the single mutants for Eps8. We propose that gelsolin has a non-overlapping role with Eps8. While Eps8 is mainly involved in the initial growth of stereocilia in both inner hair cells (IHCs) and OHCs, gelsolin is required for the maintenance of mature hair bundles of low-frequency OHCs after the onset of hearing.

Noise alters hair-bundle mechanics at the cochlear apex

NASA Astrophysics Data System (ADS)

Strimbu, C. Elliott; Fridberger, Anders

2015-12-01

Exposure to loud sounds can lead to both permanent and short term changes in auditory sensitivity. Permanent hearing loss is often associated with gross changes in cochlear morphology including the loss of hair cells and auditory nerve fibers while the mechanisms of short term threshold shifts are much less well understood and may vary at different locations across the cochlea. Previous reports suggest that exposure to loud sounds leads to a decrease in the cochlear microphonic potential and in the stiffness of the organ of Corti. Because the cochlear microphonic reflects changes in the membrane potential of the hair cells, this suggests that hair-bundle motion should be reversibly altered following exposure to loud sounds. Using an in vitro preparation of the guinea pig temporal bone we investigate changes in the micro-mechanical response near the cochlear apex following a brief (up to 10 - 20 minutes) exposure to loud (˜ 120 dB) tones near the best frequency at this location. We use time-resolved confocal imaging to record the motion of outer hair cell bundles before and after acoustic overstimulation. We have also recorded larger-scale structural views of the organ of Corti before and after exposure to the loud sound. Conventional electrophysiological techniques are used measure the cochlear microphonic potential. As has been previously reported, following acoustic overexposure the cochlear microphonic declines in value and typically recovers on the order of 30 - 60 minutes. Hair-bundle trajectories are affected following the loud sound and typically recover on a somewhat faster time scale than the microphonic potential, although the results vary considerably across preparations. Preliminary results also suggest reversible changes in the hair cell's resting potential following the loud sound.

Numerical Model of the Plasma Sheath Generated by the Plasma Source Instrument Aboard the Polar Satellite

NASA Technical Reports Server (NTRS)

Leung, Wing C.; Singh, Nagendra; Moore, Thomas E.; Craven, Paul D.

2000-01-01

The plasma sheath generated by the operation of the Plasma Source Instrument (PSI) aboard the POLAR satellite is studied by using a 3-dimensional Particle-In-Cell (PIC) code. When the satellite passes through the region of low density plasma, the satellite charges to positive potentials as high as 4050Volts due to the photoelectrons emission. In such a case, ambient core ions cannot accurately be measured or detected. The goal of the onboard PSI is to reduce the floating potential of the satellite to a sufficiently low value so that the ions in the polar wind become detectable. When the PSI is operated, an ion-rich Xenon plasma is ejected from the satellite, such that the floating potential of the satellite is reduced and is maintained at about 2Volts. Accordingly, in our 3-dimensional PIC simulation, we considered that the potential of the satellite is 2Volts as a fixed bias. Considering the relatively high density of the Xenon plasma in the sheath (approx. 10 - 10(exp 3)/cc), the ambient plasma of low density (less than 1/cc) is neglected. In the simulations, the electric fields and plasma dynamics are calculated self-consistently. We found that an "Apple" shape positive potential sheath forms surrounding the satellite. In the region near the PSI emission, a high positive potential hill develops. Near the Thermal Ion Detection Experiment (TIDE) detector away from the PSI, the potentials are sufficiently low for the ambient polar wind ions to reach it. In the simulations, it takes about a hundred electron gyroperiods for the sheath to reach a quasi-steady state. This time is approximately the time taken by the heavy Xe(+) ions to expand up to about one average Larmor radius of electrons from the satellite surface. Using the steady state sheath, we performed trajectory calculations to characterize the detector response to a highly supersonic polar wind flow. The detected ions' velocity distribution shows significant deviations from a shifted Maxwellian in the ambient polar wind population. The deviations are caused by the effects of electric fields on the ions' motion as they traverse the sheath.

Behavior of collisional sheath in electronegative plasma with q-nonextensive electron distribution

NASA Astrophysics Data System (ADS)

Borgohain, Dima Rani; Saharia, K.

2018-03-01

Electronegative plasma sheath is addressed in a collisional unmagnetized plasma consisting of q-nonextensive electrons, Boltzmann distributed negative ions and cold fluid positive ions. Considering the positive ion-neutral collisions and ignoring the effects of ionization and collisions between negative species and positive ions (neutrals), a modified Bohm sheath criterion and hence floating potential are derived by using multifluid model. Using the modified Bohm sheath criterion, the sheath characteristics such as spatial profiles of density, potential and net space charge density have been numerically investigated. It is found that increasing values of q-nonextensivity, electronegativity and collisionality lead to a decrease of the sheath thickness and an increase of the sheath potential and the net space charge density. With increasing values of the electron temperature to negative ion temperature ratio, the sheath thickness increases and the sheath potential as well as the net space charge density in the sheath region decreases.