Journal articles on the topic 'Cellular fibers'
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1
Powers, S. K., D. Criswell, F. K. Lieu, S. Dodd, and H. Silverman. "Exercise-induced cellular alterations in the diaphragm." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 263, no. 5 (November 1, 1992): R1093—R1098. http://dx.doi.org/10.1152/ajpregu.1992.263.5.r1093.
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Limited data exist concerning the effects of exercise training on cellular oxidative capacity in the diaphragm of senescent animals. In this study we examined the changes in cellular oxidative capacity, muscle cell cross-sectional area (CSA), and capillarity within the costal diaphragm of senescent animals after a 10-wk endurance-training program. Twelve 24-mo-old female Fischer 344 rats were divided into either a sedentary control group (n = 6) or exercise training group (n = 6). The trained animals exercised on a motor-driven treadmill (60 min/day, 5 days/wk) at a work rate equal to approximately 55-65% VO2max. Capillaries were identified histologically and fiber types determined using adenosinetriphosphatase (ATPase) histochemistry. Succinate dehydrogenase (SDH) activity and CSA in individual fibers were measured using a computerized image analysis system. Exercise training did not increase (P > 0.05) the capillary-to-fiber ratio for any fiber type. However, training significantly decreased CSA (P < 0.05) and increased capillary density (capillary number/CSA) (P < 0.05) in type I, type IIa, and type IIb fibers. Furthermore, exercise training resulted in small but significant increase in SDH activity (P < 0.05) in type I and IIa fibers, whereas training did not alter SDH activity (P > 0.05) in type IIb fibers. These data demonstrate that endurance training in senescent animals results in small relative improvements in both oxidative capacity and capillary density in costal diaphragmatic type I and IIa muscle fibers. The increase in both capillary density and fiber SDH activity was largely due to a reduction in fiber CSA.
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Netsvet, Daria Dmitrievna, Alexandr L. Popov, Viktoriya Viktorovna Nelubova, and Svetlana V. Lasunova. "Properties of Microfibers of Various Compositions as a Component of Cellular Composites." Materials Science Forum 1040 (July 27, 2021): 132–38. http://dx.doi.org/10.4028/www.scientific.net/msf.1040.132.
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The paper presents studies on the properties of various types of micro-reinforcing fibers to assess their role and effectiveness in the structure formation of the cellular composite. Based on the data on the weight loss after exposure in a model medium of cement, analysis of the alkali resistance of fibers of five different types – basalt fiber, heat-treated basalt fiber, polymer fiber and glass fibers from two different manufacturers – was carried out. It is shown that the fibers have a sufficiently high durability in the medium of hardening cement, which is expressed by a relatively insignificant weight loss of the original fiber after exposure in a model medium for 28 days in ambient conditions. The weight loss for some fibers sharply increases when hardening conditions are changed to hydrothermal ones. The images of fibers exposed in a model medium of cement, obtained using scanning microscopy, were also analyzed, and the character of distribution of acidic and basic adsorption sites on the surface of fibers depending on the type was assessed. Based on the analysis of the obtained data, we can talk about a high number of active sites on the surface of basalt and glass fibers, which ensures the formation of crystalline new formations on them and makes it possible to predict their high adhesion to the cement matrix.
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Hardy, Kristin M., Richard M. Dillaman, Bruce R. Locke, and Stephen T. Kinsey. "A skeletal muscle model of extreme hypertrophic growth reveals the influence of diffusion on cellular design." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 296, no. 6 (June 2009): R1855—R1867. http://dx.doi.org/10.1152/ajpregu.00076.2009.
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Muscle fibers that power swimming in the blue crab Callinectes sapidus are <80 μm in diameter in juveniles but grow hypertrophically, exceeding 600 μm in adults. Therefore, intracellular diffusion distances become progressively greater as the animals grow and, in adults, vastly exceed those in most cells. This developmental trajectory makes C. sapidus an excellent model for characterization of the influence of diffusion on fiber structure. The anaerobic light fibers, which power burst swimming, undergo a prominent shift in organelle distribution with growth. Mitochondria, which require O2 and rely on the transport of small, rapidly diffusing metabolites, are evenly distributed throughout the small fibers of juveniles, but in the large fibers of adults they are located almost exclusively at the fiber periphery where O2 concentrations are high. Nuclei, which do not require O2, but rely on the transport of large, slow-moving macromolecules, have the inverse pattern: they are distributed peripherally in small fibers but are evenly distributed across the large fibers, thereby reducing diffusion path lengths for large macromolecules. The aerobic dark fibers, which power endurance swimming, have evolved an intricate network of cytoplasmically isolated, highly perfused subdivisions that create the short diffusion distances needed to meet the high aerobic ATP turnover demands of sustained contraction. However, fiber innervation patterns are the same in the dark and light fibers. Thus the dark fibers appear to have disparate functional units for metabolism (fiber subdivision) and contraction (entire fiber). Reaction-diffusion mathematical models demonstrate that diffusion would greatly constrain the rate of metabolic processes without these developmental changes in fiber structure.
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Luden, Nicholas, Kiril Minchev, Erik Hayes, Emily Louis, Todd Trappe, and Scott Trappe. "Human vastus lateralis and soleus muscles display divergent cellular contractile properties." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 295, no. 5 (November 2008): R1593—R1598. http://dx.doi.org/10.1152/ajpregu.90564.2008.
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The purpose of this study was to investigate potential differences in single-fiber contractile physiology of fibers with the same myosin heavy chain isoform (MHC I and MHC IIa) originating from different muscles. Vastus lateralis (VL) and soleus biopsies were obtained from 27 recreationally active females (31 ± 1 yr, 59 ± 1 kg). A total of 943 single fibers (MHC I = 562; MHC IIa = 301) were isolated and examined for diameter, peak tension (Po), shortening velocity (Vo), and power. The soleus had larger ( P < 0.05) fibers (MHC I +18%; MHC IIa +19%), higher MHC I Vo (+13%), and higher MHC I Po (+18%) compared with fibers from the VL. In contrast, fibers from the VL had higher ( P < 0.05) specific tension (MHC I +18%; MHC IIa +20%), and MHC I normalized power (+25%) compared with the soleus. There was a trend for MHC IIa soleus fibers to have higher Vo [MHC IIa +13% ( P = 0.058)], whereas VL MHC IIa fibers showed a trend for higher normalized power compared with soleus fibers [MHC IIa +33% ( P = 0.079)]. No differences in absolute power were detected between muscles. These data highlight muscle-specific differences in single-fiber contractile function that should serve as a scientific basis for consideration when extending observations of skeletal muscle tissue from one muscle of interest to other muscles of origin. This is important when examining skeletal muscle adaptation to physical states such as aging, unloading, and training.
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Hassan Nensok, Mohammed, Md Azree Othuman Mydin, and Hanizam Awang. "Optimization of mechanical properties of cellular lightweight concrete with alkali treated banana fiber." Revista de la construcción 20, no. 3 (2021): 491–511. http://dx.doi.org/10.7764/rdlc.20.3.491.
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Recent advancements in construction materials development have involved the utilization of plant-based natural fibers such as kenaf, sisal, coir and banana to replace conventional fibers such as carbon, steel, polypropylene and aramid. However, the main issue with using these fibers is the alkaline cement matrix's durability and compatibility due to high water absorption. Hence, this research focuses on the use of alkali treatment of banana fibers to enhance the mechanical properties of cellular lightweight concrete (CLC). Banana fibers were subjected to 2%, 4%, 6%, 8%, and 10% NaOH treatment before being included in 1200 kg/m3 density CLC. Plain CLC and untreated fiber composites (0% NaOH treatment) were used as the control. Results from the study indicate that compared to the untreated fibre composites and plain control CLC at 28 days, compressive, flexural and splitting tensile strengths increased simultaneously with 6% NaOH fibre treatment to peaks of 40.6% and 59.8%, 63.8% and 117.4%, and 77.4% and 157.8% respectively. The 6% NaOH treatment of BF tremendously improved the mechanical characteristics of single fibers and BFRCLC composites. It is therefore concluded that 6% NaOH treatment of banana fibre was the optimum percentage alkali treatment for use in CLC.
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Lin, Ling, Yun Neng Chen, Wen Zhong Gong, and Shan Yuan Wang. "Antibacterial Efficiency and Cellular Toxicity of PET-Based Hollow Fibers Containing Silver Particles." Advanced Materials Research 441 (January 2012): 279–83. http://dx.doi.org/10.4028/www.scientific.net/amr.441.279.
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This work focuses on antibacterial efficacy and cellular toxicity of PET-based hollow fiber with silver particles incorporated (Ag/PET hollow fiber), which was synthesized by differential pressure method. Escherichia coli (E. coli) were used to investigate the antibacterial capability of Ag/PET hollow fiber with antibacterial kinetics experiments. The antibacterial results demonstrated that Ag/PET hollow fiber had an excellent antibacterial property against E. coli and the efficacy was dependent on several aspects including fiber length, weight and silver content. The cytotoxicity of Ag/PET hollow fibers on WI-38 cells was assessed using Methyl Thiazolyl Tetrazolium (MTT) assay, and the results showed no significant toxicity to WI-38 cells. SEM images of WI-38 cells treated by Ag/PET hollow fibers showed that cells morphology was unaltered in the presence of Ag/PET hollow fiber. However, abnormal size, shrinkage and rounded appearance of cells at higher dose suggested slight toxicity of Ag/PET hollow fiber. Combining the antibacterial and cytotoxic results, it was found that there was a certain concentration of silver ions which can achieve a minimization of cytotoxicity and a maximization of antibacterial efficacy.
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Rajan, Anandi, Elin Palm, Fredrik Trulsson, Sarah Mundigl, Miriam Becker, B. David Persson, Lars Frängsmyr, and Annasara Lenman. "Heparan Sulfate Is a Cellular Receptor for Enteric Human Adenoviruses." Viruses 13, no. 2 (February 14, 2021): 298. http://dx.doi.org/10.3390/v13020298.
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Human adenovirus (HAdV)-F40 and -F41 are leading causes of diarrhea and diarrhea-associated mortality in children under the age of five, but the mechanisms by which they infect host cells are poorly understood. HAdVs initiate infection through interactions between the knob domain of the fiber capsid protein and host cell receptors. Unlike most other HAdVs, HAdV-F40 and -F41 possess two different fiber proteins—a long fiber and a short fiber. Whereas the long fiber binds to the Coxsackievirus and adenovirus receptor (CAR), no binding partners have been identified for the short fiber. In this study, we identified heparan sulfate (HS) as an interaction partner for the short fiber of enteric HAdVs. We demonstrate that exposure to acidic pH, which mimics the environment of the stomach, inactivates the interaction of enteric adenovirus with CAR. However, the short fiber:HS interaction is resistant to and even enhanced by acidic pH, which allows attachment to host cells. Our results suggest a switch in receptor usage of enteric HAdVs after exposure to acidic pH and add to the understanding of the function of the short fibers. These results may also be useful for antiviral drug development and the utilization of enteric HAdVs for clinical applications such as vaccine development.
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Straight, Chad R., Olivia R. Ringham, Jenna M. Bartley, Spencer R. Keilich, George A. Kuchel, Laura Haynes, and Mark S. Miller. "Influenza Infection has Fiber Type-Specific Effects on Cellular and Molecular Skeletal Muscle Function in Aged Mice." Journals of Gerontology: Series A 75, no. 12 (June 3, 2020): 2333–41. http://dx.doi.org/10.1093/gerona/glaa136.
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Abstract Skeletal muscle myopathies represent a common non-pulmonary manifestation of influenza infection, leading to reduced physical function and hospitalization in older adults. However, underlying mechanisms remain poorly understood. Our study examined the effects of influenza virus A pulmonary infection on contractile function at the cellular (single fiber) and molecular (myosin-actin interactions and myofilament properties) levels in soleus and extensor digitorum longus muscles of aged (20 months) C57BL/6 male mice that were healthy or flu-infected for 7 (7-days post-infection; 7-DPI) or 12 days (12-DPI). Cross-sectional area (CSA) of myosin heavy chain (MHC) IIA and IIB fibers was reduced at 12-DPI relative to 7-DPI and healthy. Maximal isometric force in MHC IIA fibers was also reduced at 12-DPI relative to 7-DPI and healthy, resulting in no change in specific force (maximal isometric force divided by CSA). In contrast, MHC IIB fibers produced greater isometric force and specific force at 7-DPI compared to 12-DPI or healthy. The increased specific force in MHC IIB fibers was likely due to greater myofilament lattice stiffness and/or an increased number or stiffness of strongly bound myosin-actin cross-bridges. At the molecular level, cross-bridge kinetics were slower in MHC IIA fibers with infection, while changes in MHC IIB fibers were largely absent. In both fiber types, greater myofilament lattice stiffness was positively related to specific force. This study provides novel evidence that cellular and molecular contractile function is impacted by influenza infection in a fiber type-specific manner, suggesting potential molecular mechanisms to help explain the impact of flu-induced myopathies.
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Biring, Manmohan S., Mario Fournier, David J. Ross, and Michael I. Lewis. "Cellular adaptations of skeletal muscles to cyclosporine." Journal of Applied Physiology 84, no. 6 (June 1, 1998): 1967–75. http://dx.doi.org/10.1152/jappl.1998.84.6.1967.
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The aim of this study was to evaluate the cellular response of the diaphragm, extensor digitorum longus (EDL), and soleus (Sol) muscles to clinically relevant doses of cyclosporine administered to male rats over 4 wk. Control rats were provided with vehicle only. Muscle fiber types, cross-sectional areas, indexes of capillarity, and succinate dehydrogenase (SDH) activity were determined by quantitative histochemistry. Myosin heavy chain isoforms were identified by SDS-PAGE, and their proportions were measured by scanning densitometry. Serum cyclosporine level, 20–24 h after the last dose of cyclosporine, was 145 ± 81 ng/ml. Final body weight and muscle mass were similar between the cyclosporine and control groups. In the diaphragm, EDL, and Sol, no differences were observed between the groups with regard to fiber type proportions, fiber cross-sectional areas, and proportions of myosin heavy chain isoforms. In the EDL, reductions, both in SDH activity in type I, IIx, and IIb fibers (−26 to −37%) and in indexes of capillarity (−18 to −37%), were noted. In the Sol, SDH activity and capillarity were similar between the groups. In the diaphragm of cyclosporine-treated rats, there was significant reduction in the number of capillaries around individual fibers (−5%), whereas levels of SDH activity tended to be lower. This suggests that activation history may in part determine muscle-specific responses to cyclosporine. We speculate that reduced oxidative activity and capillarity of some limb muscles contribute to reduced exercise capacity and the “deconditioned state” observed in patients receiving cyclosporine after successful solid-organ transplantation.
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Larkins, Noni T., Robyn M. Murphy, and Graham D. Lamb. "Absolute amounts and diffusibility of HSP72, HSP25, and αB-crystallin in fast- and slow-twitch skeletal muscle fibers of rat." American Journal of Physiology-Cell Physiology 302, no. 1 (January 2012): C228—C239. http://dx.doi.org/10.1152/ajpcell.00266.2011.
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Heat shock proteins (HSPs) are essential for normal cellular stress responses. Absolute amounts of HSP72, HSP25, and αB-crystallin in rat extensor digitorum longus (EDL) and soleus (SOL) muscle were ascertained by quantitative Western blotting to better understand their respective capabilities and limitations. HSP72 content of EDL and SOL muscle was only ∼1.1 and 4.6 μmol/kg wet wt, respectively, and HSP25 content approximately twofold greater (∼3.4 and ∼8.9 μmol/kg, respectively). αB-crystallin content of EDL muscle was ∼4.9 μmol/kg but in SOL muscle was ∼30-fold higher (∼140 μmol/kg). To examine fiber heterogeneity, HSP content was also assessed in individual fiber segments; every EDL type II fiber had less of each HSP than any SOL type I fiber, whereas the two SOL type II fibers examined were indistinguishable from the EDL type II fibers. Sarcolemma removal (fiber skinning) demonstrated that 10–20% of HSP25 and αB-crystallin was sarcolemma-associated in SOL fibers. HSP diffusibility was assessed from the extent and rate of diffusion out of skinned fiber segments. In unstressed SOL fibers, 70–90% of each HSP was readily diffusible, whereas ∼95% remained tightly bound in fibers from SOL muscles heated to 45°C. Membrane disruption with Triton X-100 allowed dispersion of HSP72 and sarco(endo)plasmic reticulum Ca2+-ATPase pumps but did not alter binding of HSP25 or αB-crystallin. The amount of HSP72 in unstressed EDL muscle is much less than the number of its putative binding sites, whereas SOL type I fibers contain large amounts of αB-crystallin, suggesting its importance in normal cellular function without upregulation.
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Ba, X., Y. Meng, Y. Huang, S. Y. Kwak, S. Ge, Y. Qin, E. DiMasi, Helga Füredi-Milhofer, N. Pernodet, and Miriam Rafailovich. "In Vitro Biomineralization Induced by Self-Assembled Extracellular Matrix Proteins." Key Engineering Materials 361-363 (November 2007): 427–30. http://dx.doi.org/10.4028/www.scientific.net/kem.361-363.427.
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Extracellular matrix (ECM) proteins play an essential role during biomineralization in bone and engineered tissues. In a previous study [1], we showed that calcite preferentially nucleated on pure elastin fibers. However, the actual cellular ECM fibers are composed of a combination of proteins, primarily collagen, fibronectin and some elastin. Here we follow the calcium carbonate- and calcium phosphate- mineralization process in vitro when these ECM proteins are combined and determine the differences between these proteins in the biomineralization process. The surface morphology and mechanical properties of the protein fibers during the early stages were probed by atomic force microscopy (AFM) and shear modulation force microscopy (SMFM). The nucleation of the mineral crystals on the protein matrices was investigated by scanning electron microscopy (SEM). Preliminary data showed that the moduli of all protein fibers increased at the early stages, with collagen having the largest increase in supersaturated calcium bicarbonate solution. In metastable calcium phosphate solutions the modulus of the mixed elastin-fibronectin fibres increased to a greater extent than the moduli of the fibers composed of the single proteins. Longer exposure in the mineral solutions led to the formation of crystals templated along the self-assembled fiber structures.
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Fournier, Mario, and Michael I. Lewis. "Influences of IGF-I gene disruption on the cellular profile of the diaphragm." American Journal of Physiology-Endocrinology and Metabolism 278, no. 4 (April 1, 2000): E707—E715. http://dx.doi.org/10.1152/ajpendo.2000.278.4.e707.
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The impact of a targeted disruption of the Igf1 gene, encoding the insulin-like growth factor I (IGF-I), on diaphragm (DIA) cellularity was studied in 2-mo-old homozygous mutant [IGF-I(−/−)] mice and their wild-type [WT; i.e., IGF-I(+/+)] littermates. DIA fiber types were classified histochemically. DIA fiber cross-sectional areas (CSA) were determined from digitized muscle sections, and fiber succinate dehydrogenase (SDH) activity was determined histochemically using a microdensitometric procedure. An acidic ATPase reaction was used to visualize capillaries. Myosin heavy chain (MyHC) isoforms were identified by SDS-PAGE, and their proportions were determined by scanning densitometry. The body weight of IGF-I(−/−) animals was 32% that of WT littermates. DIA fiber type proportions were unchanged between the groups. The CSAs of types I, IIa, and IIx DIA fibers of IGF-I(−/−) mutants were 63, 68, and 65%, respectively, those of WT animals ( P < 0.001). The DIA thickness and the number of fibers spanning its entire thickness were reduced by 36 and 25%, respectively, in IGF-I(−/−) mice ( P < 0.001). SDH activity was significantly increased in all three types of DIA fibers of IGF-I(−/−) mutants ( P< 0.05). The number of capillaries per fiber was reduced ∼30% in IGF-I(−/−) animals, whereas the capillary density was preserved. The proportions of MyHC isoforms were similar between the groups. Muscle hypoplasia likely reflects the importance of IGF-I on cell proliferation, differentiation, and apoptosis (alone or in combination) during development, although reduced cell size highlights the importance of IGF-I on rate and/or maintenance of DIA fiber growth in the postnatal state. Reduced capillarity may result from both direct and indirect influences on angiogenesis. Improved oxidative capacity likely reflects DIA compensatory mechanisms in IGF-I(−/−) mutants.
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Fitts, R. H. "Cellular mechanisms of muscle fatigue." Physiological Reviews 74, no. 1 (January 1, 1994): 49–94. http://dx.doi.org/10.1152/physrev.1994.74.1.49.
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Fatigue, defined as the failure to maintain the required or expected power output, is a complex problem, since multiple factors are clearly involved, with the relative importance of each dependent on the fiber type composition of the contracting muscles(s), and the intensity, type, and duration of the contractile activity. The primary sites of fatigue appear to be within the muscle cell itself and for the most part do not involve the central nervous system or the neuromuscular junction. The major hypotheses of fatigue center on disturbances in the surface membrane, E-C coupling, or metabolic events. The cell sites most frequently linked to the etiology of skeletal muscle fatigue are shown in Figure 1. Skeletal muscles are composed of at least four distinct fiber types (3 fast twitch and 1 slow twitch), with the slow type I and fast type IIa fibers containing the highest mitochondrial content and fatigue resistance. Despite fiber type differences in the degree of fatigability, the contractile properties undergo characteristic changes with the development of fatigue that can be observed in whole muscles, single motor units, and single fibers. The Po declines, and the contraction and relaxation times are prolonged. Additionally, there is a decrease in the peak rate of tension development and decline and a reduced Vo. Changes in Vo are more resistant to fatigue than Po and are not observed until Po has declined by at least 10% of its initial prefatigued value. However, the reduced peak power by which fatigue is defined results from both a reduction in Vo and Po. In the absence of muscle fiber damage, the prolonged relaxation time associated with fatigue causes the force-frequency curve to shift to the left, such that peak tensions are obtained at lower frequencies of stimulation. In a mechanism not clearly understood, the central nervous system senses this condition and reduces the alpha-motor nerve activation frequency as fatigue develops. In some cases, selective LFF develops that displaces the force-frequency curve to the right. Although not proven, it appears likely that this condition is associated with and likely caused by muscle injury, such that the SR releases less Ca2+ at low frequencies of activation. Alternatively, LFF could result from a reduced membrane excitability, such that the sarcolemma action potential frequency is considerably less than the stimulation frequency.(ABSTRACT TRUNCATED AT 400 WORDS)
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Ramos, Letícia Maria Alves, João Vicente de Figueiredo Latorraca, Thayanne Caroline Castor Neto, Letícia Souza Martins, and Elias Taylor Durgante Severo. "ANATOMICAL CHARACTERIZATION OF TENSION WOOD IN Hevea brasiliensis (Willd. ex A. Juss.) Mull. Arg." Revista Árvore 40, no. 6 (December 2016): 1099–107. http://dx.doi.org/10.1590/0100-67622016000600016.
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ABSTRACT Tension wood is an important anatomical structure for its participation in the orientation of the trunk and the architecture of the branches as a function of structural reinforcement. However, its presence in large amounts significantly affects the technological properties of wood, just as in the rubber tree. Nevertheless, there is still demand for information about the origin, distribution and structural features in this species. Thus, this study aims to characterize the cellular structures in tension and opposite wood in Hevea brasiliensis (rubber tree), as well as its radial and longitudinal distribution. Discs at the base and the middle of the commercial logs were collected from three trees in a commercial plantation located in Tabapoã - SP. Tangential diameter of vessels, fiber length (gelatinous and non-gelatinous fibers), microfibril angle and proportionality of cellular elements (vessels, axial parenchyma, ray, gelatinous fibers and non-gelatinous fibers) were measured, and influence of gelatinous fiber presence in vessel diameter was observed. Gelatinous fibers were observed in the two types of wood and in the two trunk heights. Both types of wood were distinguished by gelatinous fiber length and the proportion of axial parenchyma. The tension wood in mid-trunk was the most different, with long gelatinous fibers and less abundant, larger vessel diameter and vessel proportion. Moreover, smaller vessel diameter was observed in the regions with a high proportion of gelatinous fibers, suggesting that the plant invests more support than in liquid transport.
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Fournier, Mario, and Michael I. Lewis. "Functional, cellular, and biochemical adaptations to elastase-induced emphysema in hamster medial scalene." Journal of Applied Physiology 88, no. 4 (April 1, 2000): 1327–37. http://dx.doi.org/10.1152/jappl.2000.88.4.1327.
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The scalene has been reported to be an accessory inspiratory muscle in the hamster. We hypothesize that with the chronic loads and/or dynamic hyperinflation associated with emphysema (Emp), the scalene will be actively recruited, resulting in functional, cellular, and biochemical adaptations. Emp was induced in adult hamsters. Inspiratory electromyogram (EMG) activity was recorded from the medial scalene and costal diaphragm. Isometric contractile and fatigue properties were evaluated in vitro. Muscle fibers were classified histochemically and immunohistochemically. Individual fiber cross-sectional areas (CSA) and succinate dehydrogenase (SDH) activities were determined quantitatively. Myosin heavy chain (MHC) isoforms were identified by SDS-PAGE, and their proportions were determined by scanning densitometry. All Emp animals exhibited spontaneous scalene inspiratory EMG activity during quiet breathing, whereas the scalene muscles of controls (Ctl) were silent. There were no differences in contractile and fatigue properties of the scalene between Ctl and Emp. In Emp, the relative amount of MHC2Awas 15% higher whereas that of MHC2X was 14% lower compared with Ctl. Similarly, the proportion of type IIa fibers increased significantly in Emp animals with a concomitant decrease in IIx fibers. CSA of type IIx fibers were significantly smaller in Emp compared with Ctl. SDH activities of all fiber types were significantly increased by 53 to 63% in Emp. We conclude that with Emp the actively recruited scalene exhibits primary-like inspiratory activity in the hamster. Adaptations of the scalene with Emp likely relate both to increased loads and to factors intrinsic to muscle architecture and chest mechanics.
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Carey, Shawn P., Zachary E. Goldblatt, Karen E. Martin, Bethsabe Romero, Rebecca M. Williams, and Cynthia A. Reinhart-King. "Local extracellular matrix alignment directs cellular protrusion dynamics and migration through Rac1 and FAK." Integrative Biology 8, no. 8 (2016): 821–35. http://dx.doi.org/10.1039/c6ib00030d.
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Fiber alignment within tumor-mimetic engineered collagen matrices drives FAK- and Rac1-dependent cellular anisotropy that promotes protrusions along fibers and suppresses off-axis protrusions to direct cell migration.
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Efimov, Boris, Sergey Isachenko, Mukhamad-Basir Kodzoev, Gulzar Dosanova, and Ekaterina Bobrova. "Dispersed reinforcement in concrete technology." E3S Web of Conferences 110 (2019): 01032. http://dx.doi.org/10.1051/e3sconf/201911001032.
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The methods of disperse reinforcement of a concrete matrix with the help of fibers make it possible to manufacture structures of complex configuration and solve problems of frost resistance of products. Fiber replaces secondary reinforcement, reducing the volume of use of structural steel reinforcement. Cellular fibrous concrete is characterized by high performance properties, especially increased strength in bending and stretching, impact strength and crack resistance. As a reinforcing component, it is preferable to use mineral fibers or thin basalt fiber. The use of polyamide fiber is allowed, but there are difficulties in forming adhesive contacts between the fiber and the mineral matrix of cellular concrete. A feature of mineral fibers is that they are high adhesive to the cement matrix. One of the promising types of dispersed bulk reinforcement of lightweight concrete is the use of expanded vermiculite. Expanded vermiculite can simultaneously be considered as a reinforcing component of a lamellar structure, as a component that reduces the density of the material and its thermal conductivity, as well as improves the fire protection performance. Expanded vermiculite can be used both in piece cladding products and as a part of dry warm and fire retardant plaster mixes.*
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Chien, Hsi Hsin, Kung Jeng Ma, Yun Peng Yeh, and Choung Lii Chao. "Microstructure and Mechanical Properties of Air Core Polymer Photonic Crystal Fibers." Advanced Materials Research 233-235 (May 2011): 3000–3004. http://dx.doi.org/10.4028/www.scientific.net/amr.233-235.3000.
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Polymer based photonic crystal fibers with low cost manufacturability, and the mechanical and chemical flexibility offer key advantages over traditional silica based photonic crystal fibers. PMMA photonic crystal fiber was fabricated by stacking an array of PMMA capillaries to form a preform, and followed by fusing and drawing into fiber with a draw tower. The air hole diameter and fraction of photonic crystal fiber can be manipulated by the thickness of PMMA capillaries and drawing temperature. The measurement of mechanical properties was performed by universal testing machine. The air core guiding phenomena was observed in air-core PMMA photonic crystal fiber. The ultimate tensile strength of PMMA photonic crystal fiber increases with the increase of the air-hole fraction. The mechanical strengths of all the microstructured optical fibers are higher than those of traditional PMMA fibers. This can be attributed to the introduction of more cellular interfaces which hinder the crack propagation and hence improve the mechanical strength. The plastic extension of PMMA microstructured optical fiber decreases with the increase of the air-hole fraction. Overall, the mechanical flexibility of PMMA microstructured optical fiber is superior than that of traditional PMMA optical fibers.
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Liu, Gongdai, R. Ghosh, A. Vaziri, A. Hossieni, D. Mousanezhad, and H. Nayeb-Hashemi. "Biomimetic composites inspired by venous leaf." Journal of Composite Materials 52, no. 3 (May 25, 2017): 361–72. http://dx.doi.org/10.1177/0021998317707254.
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A typical plant leaf can be idealized as a composite having three principal fibers: the central mid-fiber corresponding to the mid-rib, straight parallel secondary fibers attached to the mid-fiber representing the secondary veins, and then another set of parallel fibers emanating from the secondary fibers mimicking the tertiary fibers embedded in a matrix material. This paper introduces a biomimetic composite design inspired by the morphology of venous leafs and investigates the effects of venation morphologies on the in-plane mechanical properties of the biomimetic composites using finite element method. The mechanical properties such as Young’s moduli, Poisson’s ratio, and yield stress under uniaxial loading of the resultant composite structures was studied and the effect of different fiber architectures on these properties was investigated. To this end, two broad types of architectures were used both having similar central main fiber but differing in either having only secondary fibers or additional tertiary fibers. The fiber and matrix volume fractions were kept constant and a comparative parametric study was carried out by varying the inclination of the secondary fibers. The results show that the elastic modulus of composite in the direction of main fiber increases linearly with increasing the angle of the secondary fibers. Furthermore, the elastic modulus is enhanced if the secondary fibers are closed, which mimics composites with closed cellular fibers. In contrast, the elastic modulus of composites normal to the main fiber ( x direction) exponentially decreases with the increase of the angle of the secondary fibers and it is little affected by having secondary fibers closed. Similar results were obtained for the yield stress of the composites. The results also indicate that Poisson’s ratio linearly increases with the secondary fiber angle. The results also show that for a constant fiber volume fraction, addition of various tertiary fibers may not significantly enhance the mechanical properties of the composites. The mechanical properties of the composites are mainly dominated by the secondary fibers. Finally, a simple model was proposed to predict these behaviors.
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Shenkman, Boris S., Olga E. Zinovyeva, Svetlana P. Belova, Timur M. Mirzoev, Natalia A. Vilchinskaya, Ivan M. Vikhlyantsev, Anna D. Ulanova, et al. "Cellular and molecular signatures of alcohol-induced myopathy in women." American Journal of Physiology-Endocrinology and Metabolism 316, no. 5 (May 1, 2019): E967—E976. http://dx.doi.org/10.1152/ajpendo.00513.2018.
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Alcoholic myopathy is characterized by the reduction in cross-sectional area (CSA) of muscle fibers and impaired anabolic signaling. The goal of the current study was to investigate the causes and compare the changes in CSA and fiber type composition with the modifications of anabolic and catabolic signaling pathways at the early stages of chronic alcohol consumption in women. Skeletal muscle samples from 5 female patients with alcohol abuse (AL; 43 ± 5 yr old; alcohol abuse duration 5,6 ± 0,6 yr) were compared with the muscle from the control group of 8 healthy women (C; 35 ± 4 yr old). The average daily dose of alcohol consumption was 110 ± 10 ml of pure ethanol. In women patients, a significant decrease in CSA of type I and II muscle fibers, titin and nebulin content, plasma IGF-1 level and total IRS-1, p-Akt and p-4E-BP1 in vastus lateralis was found in comparison with the control group. The p-AMPK level was found to be increased versus the control group. In women patients with chronic alcoholic myopathy 1) both fast and slow muscle fibers are subjected to atrophy; 2) impairments in IGF-I-dependent signaling and pathways controlling translation initiation (AMPK/mTOR/4E-BP1), but not translation elongation, are observed; 3) the level of calpain-1 and ubiquitinated proteins increases, unlike E3 ligases content.
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Saito, Kengo, Keishi Mizuguchi, Toshihide Horiike, Tung Anh Dinh Duong, Yohei Shinmyo, and Hiroshi Kawasaki. "Characterization of the Inner and Outer Fiber Layers in the Developing Cerebral Cortex of Gyrencephalic Ferrets." Cerebral Cortex 29, no. 10 (December 12, 2018): 4303–11. http://dx.doi.org/10.1093/cercor/bhy312.
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Abstract Changes in the cerebral cortex of mammals during evolution have been of great interest. Ferrets, monkeys, and humans have more developed cerebral cortices compared with mice. Although the features of progenitors in the developing cortices of these animals have been intensively investigated, those of the fiber layers are still largely elusive. By taking the advantage of our in utero electroporation technique for ferrets, here we systematically investigated the cellular origins and projection patterns of axonal fibers in the developing ferret cortex. We found that ferrets have 2 fiber layers in the developing cerebral cortex, as is the case in monkeys and humans. Axonal fibers in the inner fiber layer projected contralaterally and subcortically, whereas those in the outer fiber layer sent axons to neighboring cortical areas. Furthermore, we performed similar experiments using mice and found unexpected similarities between ferrets and mice. Our results shed light on the cellular origins, the projection patterns, the developmental processes, and the evolution of fiber layers in mammalian brains.
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Welle, Stephen. "Cellular and Molecular Basis of Age-Related Sarcopenia." Canadian Journal of Applied Physiology 27, no. 1 (February 1, 2002): 19–41. http://dx.doi.org/10.1139/h02-002.
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Sarcopenia, the decline in muscle bulk and performance associated with normal aging, is an important component of frailty in the elderly. The gradual loss of both motor nerves and muscle fibers during senescence appears to be the major problem. Atrophy (especially in fast-twitch fibers) and impaired function of the surviving cells also contribute to sarcopenia. Although skeletal muscle has the capacity to regenerate itself, this process is not activated by the gradual age-related loss of muscle fibers. The endocrine, autocrine, and paracrine environment in old muscle is less supportive of protein synthesis, reinnervation of muscle fibers, and satellite cell activation, proliferation, and differentiation. Lifelong exposure of DNA to free radical damage results in accumulation of somatic mutations in nerves and muscle fibers. Reduced protein synthesis leads to atrophy, and slower fractional protein turnover contributes to longer retention of proteins that may have been damaged by free radicals. Many genes are differentially expressed in young and old muscle, but additional research is needed to determine which of these genes have a significant role in the pathogenesis or adaptation to sarcopenia. Key words: muscle atrophy, motor neurons, gene expression, hormonal effects in muscle, muscle protein metabolism
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Movahedian Attar, Fakhereh, Evgeniya Kirilina, Daniel Haenelt, Kerrin J. Pine, Robert Trampel, Luke J. Edwards, and Nikolaus Weiskopf. "Mapping Short Association Fibers in the Early Cortical Visual Processing Stream Using In Vivo Diffusion Tractography." Cerebral Cortex 30, no. 8 (April 8, 2020): 4496–514. http://dx.doi.org/10.1093/cercor/bhaa049.
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Abstract Short association fibers (U-fibers) connect proximal cortical areas and constitute the majority of white matter connections in the human brain. U-fibers play an important role in brain development, function, and pathology but are underrepresented in current descriptions of the human brain connectome, primarily due to methodological challenges in diffusion magnetic resonance imaging (dMRI) of these fibers. High spatial resolution and dedicated fiber and tractography models are required to reliably map the U-fibers. Moreover, limited quantitative knowledge of their geometry and distribution makes validation of U-fiber tractography challenging. Submillimeter resolution diffusion MRI—facilitated by a cutting-edge MRI scanner with 300 mT/m maximum gradient amplitude—was used to map U-fiber connectivity between primary and secondary visual cortical areas (V1 and V2, respectively) in vivo. V1 and V2 retinotopic maps were obtained using functional MRI at 7T. The mapped V1–V2 connectivity was retinotopically organized, demonstrating higher connectivity for retinotopically corresponding areas in V1 and V2 as expected. The results were highly reproducible, as demonstrated by repeated measurements in the same participants and by an independent replication group study. This study demonstrates a robust U-fiber connectivity mapping in vivo and is an important step toward construction of a more complete human brain connectome.
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Drenckhahn, D., and J. Wagner. "Stress fibers in the splenic sinus endothelium in situ: molecular structure, relationship to the extracellular matrix, and contractility." Journal of Cell Biology 102, no. 5 (May 1, 1986): 1738–47. http://dx.doi.org/10.1083/jcb.102.5.1738.
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In the present study, we investigated structural and functional aspects of stress fibers in a cell type in situ, i.e., the sinus endothelium of the human spleen. In this cell type, stress fibers extend underneath the basal plasma membrane and are arranged parallel to the cellular long axis. Ultrastructurally, the stress fibers were found to be composed of thin actin-like filaments (5-8 nm) and thick myosin-like filaments (10-15 nm X 300 nm). Actin filaments displayed changes in polarity (determined by S-1-myosin subfragment decoration), which may allow a sliding filament mechanism. At their plasmalemmal attachment sites, actin filaments exhibited uniform polarity with the S-1-arrowhead complexes pointing away from the plasma membrane. Fluorescence microscopy showed that the stress fibers have a high affinity for phalloidin and antibodies to actin, myosin, tropomyosin, and alpha-actinin. Vinculin was confined to the cytoplasmic aspect of the plasmalemmal termination sites of stress fibers, while laminin, fibronectin, and collagens were located at the extracellular aspect of these stress fiber-membrane associations. Western blot analysis revealed polypeptide bands that contained actin, myosin, and alpha-actinin to be major components of isolated cells. Exposure of permeabilized cells to MgATP results in prominent changes in cellular shape caused by stress fiber contraction. It is concluded that the stress fibers in situ anchored to cell-to-extracellular matrix contacts can create tension that might allow the endothelium to resist the fluid shear forces of blood flow.
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Kato, Yasushi P., Michael G. Dunn, Frederick H. Silver, and Arthur J. Wasserman. "Biological and biomedical applications of collagenous biomaterials." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 3 (August 12, 1990): 856–57. http://dx.doi.org/10.1017/s0424820100161849.
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Collagenous biomaterials have been used for growing cells in vitro as well as for augmentation and replacement of hard and soft tissues. The substratum used for culturing cells is implicated in the modulation of phenotypic cellular expression, cellular orientation and adhesion. Collagen may have a strong influence on these cellular parameters when used as a substrate in vitro. Clinically, collagen has many applications to wound healing including, skin and bone substitution, tendon, ligament, and nerve replacement. In this report we demonstrate two uses of collagen. First as a fiber to support fibroblast growth in vitro, and second as a demineralized bone/collagen sponge for radial bone defect repair in vivo.For the in vitro study, collagen fibers were prepared as described previously. Primary rat tendon fibroblasts (1° RTF) were isolated and cultured for 5 days on 1 X 15 mm sterile cover slips. Six to seven collagen fibers, were glued parallel to each other onto a circular cover slip (D=18mm) and the 1 X 15mm cover slip populated with 1° RTF was placed at the center perpendicular to the collagen fibers. Fibroblast migration from the 1 x 15mm cover slip onto and along the collagen fibers was measured daily using a phase contrast microscope (Olympus CK-2) with a calibrated eyepiece. Migratory rates for fibroblasts were determined from 36 fibers over 4 days.
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Toth, Michael J., Timothy W. Tourville, Thomas B. Voigt, Rebecca H. Choquette, Bradley M. Anair, Michael J. Falcone, Mathew J. Failla, et al. "Utility of Neuromuscular Electrical Stimulation to Preserve Quadriceps Muscle Fiber Size and Contractility After Anterior Cruciate Ligament Injuries and Reconstruction: A Randomized, Sham-Controlled, Blinded Trial." American Journal of Sports Medicine 48, no. 10 (July 6, 2020): 2429–37. http://dx.doi.org/10.1177/0363546520933622.
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Background: Anterior cruciate ligament (ACL) injuries and reconstruction (ACLR) promote quadriceps muscle atrophy and weakness that can persist for years, suggesting the need for more effective rehabilitation programs. Whether neuromuscular electrical stimulation (NMES) can be used to prevent maladaptations in skeletal muscle size and function is unclear. Purpose: To examine whether early NMES use, started soon after an injury and maintained through 3 weeks after surgery, can preserve quadriceps muscle size and contractile function at the cellular (ie, fiber) level in the injured versus noninjured leg of patients undergoing ACLR. Study Design: Randomized controlled trial; Level of evidence, 1. Methods: Patients (n = 25; 12 men/13 women) with an acute, first-time ACL rupture were randomized to NMES (5 d/wk) or sham (simulated microcurrent electrical nerve stimulation; 5 d/wk) treatment to the quadriceps muscles of their injured leg. Bilateral biopsies of the vastus lateralis were performed 3 weeks after surgery to measure skeletal muscle fiber size and contractility. Quadriceps muscle size and strength were assessed 6 months after surgery. Results: A total of 21 patients (9 men/12 women) completed the trial. ACLR reduced single muscle fiber size and contractility across all fiber types ( P < .01 to P < .001) in the injured compared with noninjured leg 3 weeks after surgery. NMES reduced muscle fiber atrophy ( P < .01) through effects on fast-twitch myosin heavy chain (MHC) II fibers ( P < .01 to P < .001). NMES preserved contractility in slow-twitch MHC I fibers ( P < .01 to P < .001), increasing maximal contractile velocity ( P < .01) and preserving power output ( P < .01), but not in MHC II fibers. Differences in whole muscle strength between groups were not discerned 6 months after surgery. Conclusion: Early NMES use reduced skeletal muscle fiber atrophy in MHC II fibers and preserved contractility in MHC I fibers. These results provide seminal, cellular-level data demonstrating the utility of the early use of NMES to beneficially modify skeletal muscle maladaptations to ACLR. Clinical Relevance: Our results provide the first comprehensive, cellular-level evidence to show that the early use of NMES mitigates early skeletal muscle maladaptations to ACLR. Registration: NCT02945553 (ClinicalTrials.gov identifier)
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Bjørnsen, Thomas, Mathias Wernbom, Gøran Paulsen, James F. Markworth, Sveinung Berntsen, Randall F. D’Souza, David Cameron-Smith, and Truls Raastad. "High-frequency blood flow-restricted resistance exercise results in acute and prolonged cellular stress more pronounced in type I than in type II fibers." Journal of Applied Physiology 131, no. 2 (August 1, 2021): 643–60. http://dx.doi.org/10.1152/japplphysiol.00115.2020.
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BFRRE has been reported to preferentially stress type I muscle fibers, as evidenced by HSP responses. We extend these findings by showing that the HSP responses occur in both fiber types but more so in type I fibers and that they can still be induced after a short-term training period. Furthermore, the reductions in glycogen content of type I fibers after strenuous frequent BFRRE in unaccustomed subjects can be prolonged (≥5 days), probably due to microdamage.
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Liu, Yewei, Sarah J. Russell, and Martin F. Schneider. "Foxo1 nucleo-cytoplasmic distribution and unidirectional nuclear influx are the same in nuclei in a single skeletal muscle fiber but vary between fibers." American Journal of Physiology-Cell Physiology 314, no. 3 (March 1, 2018): C334—C348. http://dx.doi.org/10.1152/ajpcell.00168.2017.
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Foxo transcription factors promote protein breakdown and atrophy of skeletal muscle fibers. Foxo transcriptional effectiveness is largely determined by phosphorylation-dependent nucleo-cytoplasmic shuttling. Imaging Foxo1-green fluorescent protein (GFP) over time in 124 nuclei in 68 multinucleated adult skeletal muscle fibers under control culture conditions reveals large variability between fibers in Foxo1-GFP nucleo-cytoplasmic concentration ratio (N/C) and in the apparent rate coefficient ( kI′) for Foxo1-GFP unidirectional nuclear influx (measured with efflux blocked by leptomycin B). Pairs of values of N/C or of kI′ from different nuclei in the same fiber were essentially the same, but only weakly correlated in nuclei from different fibers in the same culture well. Thus, fiber to fiber variability of cellular factors, but not extracellular factors, determines Foxo1 distribution. Over all nuclei, N/C and kI′ were closely proportional, indicating that kI′ is the major determinant of Foxo1 distribution. IGF-I activation of Foxo kinase Akt reduces variability by decreasing kI′ and N/C in all fibers. However, inhibiting Akt did not drive kI′ uniformly high, indicating other pathways in Foxo1 regulation.
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Müller, Andreas, Sandra Müller, Veselin Nasufovic, Hans-Dieter Arndt, and Tilo Pompe. "Actin stress fiber dynamics in laterally confined cells." Integrative Biology 11, no. 5 (May 1, 2019): 175–85. http://dx.doi.org/10.1093/intbio/zyz016.
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Abstract Multiple cellular processes are affected by spatial constraints from the extracellular matrix and neighboring cells. In vitro experiments using defined micro-patterning allow for in-depth analysis and a better understanding of how these constraints impact cellular behavior and functioning. Herein we focused on the analysis of actin cytoskeleton dynamics as a major determinant of mechanotransduction mechanisms in cells. We seeded primary human umbilical vein endothelial cells onto stripe-like cell-adhesive micro-patterns with varying widths and then monitored and quantified the dynamic reorganization of actin stress fibers, including fiber velocities, orientation and density, within these live cells using the cell permeable F-actin marker SiR-actin. Although characteristic parameters describing the overall stress fiber architecture (average orientation and density) were nearly constant throughout the observation time interval of 60 min, we observed permanent transport and turnover of individual actin stress fibers. Stress fibers were more strongly oriented along stripe direction with decreasing stripe width, (5° on 20 μm patterns and 10° on 40 μm patterns), together with an overall narrowing of the distribution of fiber orientation. Fiber dynamics was characterized by a directed movement from the cell edges towards the cell center, where fiber dissolution frequently took place. By kymograph analysis, we found median fiber velocities in the range of 0.2 μm/min with a weak dependence on pattern width. Taken together, these data suggest that cell geometry determines actin fiber orientation, while it also affects actin fiber transport and turnover.
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Aratyn-Schaus, Yvonne, Patrick W. Oakes, and Margaret L. Gardel. "Dynamic and structural signatures of lamellar actomyosin force generation." Molecular Biology of the Cell 22, no. 8 (April 15, 2011): 1330–39. http://dx.doi.org/10.1091/mbc.e10-11-0891.
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The regulation of cellular traction forces on the extracellular matrix is critical to cell adhesion, migration, proliferation, and differentiation. Diverse lamellar actin organizations ranging from contractile lamellar networks to stress fibers are observed in adherent cells. Although lamellar organization is thought to reflect the extent of cellular force generation, understanding of the physical behaviors of the lamellar actin cytoskeleton is lacking. To elucidate these properties, we visualized the actomyosin dynamics and organization in U2OS cells over a broad range of forces. At low forces, contractile lamellar networks predominate and force generation is strongly correlated to actomyosin retrograde flow dynamics with nominal change in organization. Lamellar networks build ∼60% of cellular tension over rapid time scales. At high forces, reorganization of the lamellar network into stress fibers results in moderate changes in cellular tension over slower time scales. As stress fibers build and tension increases, myosin band spacing decreases and α-actinin bands form. On soft matrices, force generation by lamellar networks is unaffected, whereas tension-dependent stress fiber assembly is abrogated. These data elucidate the dynamic and structural signatures of the actomyosin cytoskeleton at different levels of tension and set a foundation for quantitative models of cell and tissue mechanics.
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Castorena, Carlos M., Edward B. Arias, Naveen Sharma, Jonathan S. Bogan, and Gregory D. Cartee. "Fiber type effects on contraction-stimulated glucose uptake and GLUT4 abundance in single fibers from rat skeletal muscle." American Journal of Physiology-Endocrinology and Metabolism 308, no. 3 (February 1, 2015): E223—E230. http://dx.doi.org/10.1152/ajpendo.00466.2014.
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To fully understand skeletal muscle at the cellular level, it is essential to evaluate single muscle fibers. Accordingly, the major goals of this study were to determine if there are fiber type-related differences in single fibers from rat skeletal muscle for: 1) contraction-stimulated glucose uptake and/or 2) the abundance of GLUT4 and other metabolically relevant proteins. Paired epitrochlearis muscles isolated from Wistar rats were either electrically stimulated to contract (E-Stim) or remained resting (No E-Stim). Single fibers isolated from muscles incubated with 2-deoxy-d-[3H]glucose (2-DG) were used to determine fiber type [myosin heavy chain (MHC) isoform protein expression], 2-DG uptake, and abundance of metabolically relevant proteins, including the GLUT4 glucose transporter. E-Stim, relative to No E-Stim, fibers had greater ( P < 0.05) 2-DG uptake for each of the isolated fiber types (MHC-IIa, MHC-IIax, MHC-IIx, MHC-IIxb, and MHC-IIb). However, 2-DG uptake for E-Stim fibers was not significantly different among these five fiber types. GLUT4, tethering protein containing a UBX domain for GLUT4 (TUG), cytochrome c oxidase IV (COX IV), and filamin C protein levels were significantly greater ( P < 0.05) in MHC-IIa vs. MHC-IIx, MHC-IIxb, or MHC-IIb fibers. TUG and COX IV in either MHC-IIax or MHC-IIx fibers exceeded values for MHC-IIxb or MHC-IIb fibers. GLUT4 levels for MHC-IIax fibers exceeded MHC-IIxb fibers. GLUT4, COX IV, filamin C, and TUG abundance in single fibers was significantly ( P < 0.05) correlated with each other. Differences in GLUT4 abundance among the fiber types were not accompanied by significant differences in contraction-stimulated glucose uptake.
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Callahan, Damien M., Nicholas G. Bedrin, Meenakumari Subramanian, James Berking, Philip A. Ades, Michael J. Toth, and Mark S. Miller. "Age-related structural alterations in human skeletal muscle fibers and mitochondria are sex specific: relationship to single-fiber function." Journal of Applied Physiology 116, no. 12 (June 15, 2014): 1582–92. http://dx.doi.org/10.1152/japplphysiol.01362.2013.
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Age-related loss of skeletal muscle mass and function is implicated in the development of disease and physical disability. However, little is known about how age affects skeletal muscle structure at the cellular and ultrastructural levels or how such alterations impact function. Thus we examined skeletal muscle structure at the tissue, cellular, and myofibrillar levels in young (21–35 yr) and older (65–75 yr) male and female volunteers, matched for habitual physical activity level. Older adults had smaller whole muscle tissue cross-sectional areas (CSAs) and mass. At the cellular level, older adults had reduced CSAs in myosin heavy chain II (MHC II) fibers, with no differences in MHC I fibers. In MHC II fibers, older men tended to have fewer fibers with large CSAs, while older women showed reduced fiber size across the CSA range. Older adults showed a decrease in intermyofibrillar mitochondrial size; however, the age effect was driven primarily by women (i.e., age by sex interaction effect). Mitochondrial size was inversely and directly related to isometric tension and myosin-actin cross-bridge kinetics, respectively. Notably, there were no intermyofibrillar or subsarcolemmal mitochondrial fractional content or myofilament ultrastructural differences in the activity-matched young and older adults. Collectively, our results indicate age-related reductions in whole muscle size do not vary by sex. However, age-related structural alterations at the cellular and subcellular levels are different between the sexes and may contribute to different functional phenotypes in ways that modulate sex-specific reductions in physical capacity with age.
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Vaikhanski, Lev, John J. Lesko, and Steven R. Nutt. "Cellular polymer composites based on bi-component fibers." Composites Science and Technology 63, no. 10 (August 2003): 1403–10. http://dx.doi.org/10.1016/s0266-3538(03)00087-3.
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Orwin, Donald F. G., and Joy L. Woods. "Cellular Debris in the Grease of Wool Fibers." Textile Research Journal 55, no. 2 (February 1985): 84–92. http://dx.doi.org/10.1177/004051758505500202.
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Pomp, Wim, Hedde van Hoorn, and Thomas Schmidt. "Stress-Fibers Dictate Cellular Curvature & Force Exertion." Biophysical Journal 106, no. 2 (January 2014): 361a. http://dx.doi.org/10.1016/j.bpj.2013.11.2051.
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Gouget, Cecile L. M., Yongyun Hwang, and Abdul I. Barakat. "Model of cellular mechanotransduction via actin stress fibers." Biomechanics and Modeling in Mechanobiology 15, no. 2 (June 17, 2015): 331–44. http://dx.doi.org/10.1007/s10237-015-0691-z.
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Chen, Wei, Dandan Zheng, Yanru Chen, Huitong Ruan, Yuhui Zhang, Xiuyuan Chen, Hongxing Shen, Lianfu Deng, Wenguo Cui, and Hao Chen. "Electrospun Fibers Improving Cellular Respiration via Mitochondrial Protection." Small 17, no. 46 (October 11, 2021): 2104012. http://dx.doi.org/10.1002/smll.202104012.
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Domura, Ryota, Rie Sasaki, Masami Okamoto, Minoru Hirano, Katsunori Kohda, Brett Napiwocki, and Lih-Sheng Turng. "Comprehensive study on cellular morphologies, proliferation, motility, and epithelial–mesenchymal transition of breast cancer cells incubated on electrospun polymeric fiber substrates." Journal of Materials Chemistry B 5, no. 14 (2017): 2588–600. http://dx.doi.org/10.1039/c7tb00207f.
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Gong, Ying, Guang Ting Han, Xin Ling Li, Yan Wu, Yuan Ming Zhang, Yan Zhi Xia, Chang Qing Yue, and Da Wei Wu. "Cytotoxicity and Antiviral Activity of Calcium Alginate Fibers and Zinc Alginate Fibers." Advanced Materials Research 152-153 (October 2010): 1475–78. http://dx.doi.org/10.4028/www.scientific.net/amr.152-153.1475.
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The cytotoxicity and anti-influenza virus (IFV) activity of calcium or zinc alginate fibers were investigated to explore the feasibility of them to be used as biomaterials. African Green Monkey kidney cell (Vero) and human cervical cancer cell (Hela) cultured with alginate fibres were used to screen cytotoxic effects. After 48 h, MTT (3-(4,5-dimethyl-2-thiazol)-2,5-diphenyl-2H tetrazolium bromide) assays were performed. Then cytotoxicity was evaluated with six grades according to cell relative growth rate (RGR). In anti-IFV activity assay, IFV were added to all fibers and the Vero cell survival were detected by MTT assays with calculating the percentage of protection. The cytotoxity of calcium alginate fibers on Vero were grade 0 or 1 in contrast to zinc alginate fibers which was grade 0. The cytotoxity of calcium or zinc alginate fibers on Hela were grade 0. Furthermore, partial calcium or zinc alginate fibers could promote Vero or Hela cell growth. In antiviral assay the highest percentage of protection of calcium alginate fibers was 34.42%, while that of zinc alginate fibers was 59.42%. The results showed that calcium or zinc alginate fibers had a good cellular biocompatibility and the large weight zinc alginate fibers had a better anti-IFV activity than calcium alginate fibers, which is potential for tissue engineering.
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White, G. E., and K. Fujiwara. "Expression and intracellular distribution of stress fibers in aortic endothelium." Journal of Cell Biology 103, no. 1 (July 1, 1986): 63–70. http://dx.doi.org/10.1083/jcb.103.1.63.
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Immunofluorescence microscopy was used to determine the number of endothelial cells with stress fibers for three age groups, and for three distinct anatomical locations within the descending thoracic aorta of both normotensive and spontaneously hypertensive rats. For each age group examined, hypertensive rats consistently demonstrated greater stress fiber expression than did normotensive rats. Neither age nor blood pressure was the predominant influence on stress fiber expression in aortic endothelium. In the normotensive rats, stress fiber expression remained unchanged for all age groups examined. For both strains, however, more endothelial cells with stress fibers were found in those regions where fluid shear stresses are expected to be high, when compared with those regions where the fluid shear stresses are expected to be low. This observation suggests that anatomical location, with its implied differences in fluid shear stress levels, is a major influence on stress fiber expression within this tissue. Electron microscopy was used to determine the intracellular distribution of stress fibers for both strains. Most stress fibers in both strains were located in the abluminal portion of the endothelial cells. This result is consistent with a role for stress fibers in cellular adhesion. However, the hypertensive rats had a higher proportion of stress fibers in the luminal portion of their cytoplasm than the normotensive rats. This increased presence of stress fibers in the luminal portion of the cell may be important in maintaining the structural integrity of the endothelial cell in the face of elevated hemodynamic forces in situ.
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Zheng, Qian, Elaine C. Davis, James A. Richardson, Barry C. Starcher, Tiansen Li, Robert D. Gerard, and Hiromi Yanagisawa. "Molecular Analysis of Fibulin-5 Function during De Novo Synthesis of Elastic Fibers." Molecular and Cellular Biology 27, no. 3 (February 1, 2007): 1083–95. http://dx.doi.org/10.1128/mcb.01330-06.
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ABSTRACT Elastic fibers contribute to the structural support of tissues and to the regulation of cellular behavior. Mice deficient for the fibulin-5 gene (fbln5 − / −) were used to further elucidate the molecular mechanism of elastic fiber assembly. Major elastic fiber components were present in the skin of fbln5 − / − mice despite a dramatic reduction of mature elastic fibers. We found that fibulin-5 preferentially bound the monomeric form of elastin through N-terminal and C-terminal elastin-binding regions and to a preexisting matrix scaffold through calcium-binding epidermal growth factor (EGF)-like (CB-EGF) domains. We further showed that adenovirus-mediated gene transfer of fbln5 was sufficient to regenerate elastic fibers and increase elastic fiber-cell connections in vivo. A mutant fibulin-5 lacking the first 28 amino acids of the first CB-EGF domain, however, was unable to rescue elastic fiber defects. Fibulin-5 thus serves as an adaptor molecule between monomeric elastin and the matrix scaffold to aid in elastic fiber assembly. These results also support the potential use of fibulin-5 as a therapeutic agent for the treatment of elastinopathies.
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Shinohara, Harumichi, Xiaoliang Liu, Riho Nakajima, Masashi Kinoshita, Noriyuki Ozaki, Osamu Hori, and Mitsutoshi Nakada. "Pyramid-Shape Crossings and Intercrossing Fibers Are Key Elements for Construction of the Neural Network in the Superficial White Matter of the Human Cerebrum." Cerebral Cortex 30, no. 10 (April 26, 2020): 5218–28. http://dx.doi.org/10.1093/cercor/bhaa080.
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Abstract Structural analysis of the superficial white matter is prerequisite for the understanding of highly integrated functions of the human cerebral cortex. However, the principal components, U-fibers, have been regarded as simple wires to connect adjacent gyri (inter-gyral U-fibers) but have never been thought as indispensable elements of anatomical structures to construct the cortical network. Here, we reported such novel structures made of U-fibers. Seven human cerebral hemispheres were treated with Klingler’s method and subjected to fiber dissection (FD). Additionally, tractography using diffusion spectrum imaging (DSI) was performed. Our FD and DSI tractography succeeded disclosing a new type of U-fibers that was hidden in and ran along the white matter ridge of a gyral convolution (intra-gyral U-fibers). They were distinct from inter-gyral U-fibers which paved sulcal floors. Both intra- and inter-gyral U-fibers converged from various directions into junctional areas of white matter ridges, organizing novel anatomical structures, “pyramid-shape crossings”. U-fibers to form pyramid-shape crossings also render routes for communication between crossings. There were 97 (mean, range 73–148) pyramid-shape crossings per lateral cortical surface. They are key structures to construct the neural network for intricate communications throughout the entire cerebrum. They can be new anatomical landmarks, too, for the segmentation of the cerebral cortex.
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Tabassam, Fazal H., David Y. Graham, and Yoshio Yamaoka. "Paxillin is a novel cellular target for converging Helicobacter pylori-induced cellular signaling." American Journal of Physiology-Gastrointestinal and Liver Physiology 301, no. 4 (October 2011): G601—G611. http://dx.doi.org/10.1152/ajpgi.00375.2010.
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Paxillin is involved in the regulation of Helicobacter pylori -mediated gastric epithelial cell motility. We investigated the signaling pathways regulating H. pylori -induced paxillin phosphorylation and the effect of the H. pylori virulence factors cag pathogenicity island (PAI) and outer inflammatory protein (OipA) on actin stress fiber formation, cell phenotype, and IL-8 production. Gastric cell infection with live H. pylori induced site-specific phosphorylation of paxillin tyrosine (Y) 31 and Y118 in a time- and concentration-dependent manner. Activated paxillin localized in the cytoplasm at the tips of H. pylori -induced actin stress fibers. Isogenic oipA mutants significantly reduced paxillin phosphorylation at Y31 and Y118 and reduced actin stress fiber formation. In contrast, cag PAI mutants only inhibited paxillin Y118 phosphorylation. Silencing of epidermal growth factor receptor (EGFR), focal adhesion kinase (FAK), or protein kinase B (Akt) expression by small-interfering RNAs or inhibiting kinase activity of EGFR, Src, or phosphatidylinositol 3-kinase (PI3K) markedly reduced H. pylori -induced paxillin phosphorylation and morphologic alterations. Reduced FAK expression or lack of Src kinase activity suppressed H. pylori -induced IL-8 production. Compared with infection with the wild type, infection with the cag PAI mutant and oipA mutant reduced IL-8 production by nearly 80 and 50%. OipA-induced IL-8 production was FAK- and Src-dependent, although a FAK/Src-independent pathway for IL-8 production also exists, and the cag PAI may be mainly involved in this pathway. We propose paxillin as a novel cellular target for converging H. pylori -induced EGFR, FAK/Src, and PI3K/Akt signaling to regulate cytoskeletal reorganization and IL-8 production in part, thus contributing to the H. pylori -induced diseases.
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Stallcup, William B., and Kimberlee Dahlin-Huppe. "Chondroitin sulfate and cytoplasmic domain-dependent membrane targeting of the NG2 proteoglycan promotes retraction fiber formation and cell polarization." Journal of Cell Science 114, no. 12 (June 15, 2001): 2315–25. http://dx.doi.org/10.1242/jcs.114.12.2315.
Full textAbstract:
Targeting of the NG2 proteoglycan to cellular retraction fibers was studied by expressing mutant NG2 molecules lacking specific structural elements of the proteoglycan. Both the cytoplasmic domain and the chondroitin sulfate chain of NG2 appear to have roles in sorting NG2 to subcellular microdomains destined to become retraction fibers. Neither of these structural features alone is sufficient to allow optimal targeting of NG2 to retraction fibers, but together they promote efficient localization of the proteoglycan to these sites. This pattern of NG2 sorting seems to be necessary for optimal retraction fiber formation, as cells expressing poorly targeted NG2 mutants are noticeably deficient in their ability to extend retraction fibers. Furthermore, retraction fiber formation correlates strongly with the tendency of cells to assume a polarized morphology with NG2-positive retraction fibers at one pole of the cell and actin-rich lamellipodia at the other. This polarization can be triggered either through engagement of NG2 by the substratum or by exposure to lysophosphatidic acid, a potent activator of the rho GTPase. These results suggest a possible role for NG2 in regulating rho-dependent mechanisms in the trailing processes of motile cells.
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Schuh, Rosemary A., Kathryn C. Jackson, Ramzi J. Khairallah, Christopher W. Ward, and Espen E. Spangenburg. "Measuring mitochondrial respiration in intact single muscle fibers." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 302, no. 6 (March 15, 2012): R712—R719. http://dx.doi.org/10.1152/ajpregu.00229.2011.
Full textAbstract:
Measurement of mitochondrial function in skeletal muscle is a vital tool for understanding regulation of cellular bioenergetics. Currently, a number of different experimental approaches are employed to quantify mitochondrial function, with each involving either mechanically or chemically induced disruption of cellular membranes. Here, we describe a novel approach that allows for the quantification of substrate-induced mitochondria-driven oxygen consumption in intact single skeletal muscle fibers isolated from adult mice. Specifically, we isolated intact muscle fibers from the flexor digitorum brevis muscle and placed the fibers in culture conditions overnight. We then quantified oxygen consumption rates using a highly sensitive microplate format. Peak oxygen consumption rates were significantly increased by 3.4-fold and 2.9-fold by simultaneous stimulation with the uncoupling agent, carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone (FCCP), and/or pyruvate or palmitate exposure, respectively. However, when calculating the total oxygen consumed over the entire treatment, palmitate exposure resulted in significantly more oxygen consumption compared with pyruvate. Further, as proof of principle for the procedure, we isolated fibers from the mdx mouse model, which has known mitochondrial deficits. We found significant reductions in initial and peak oxygen consumption of 51% and 61% compared with fibers isolated from the wild-type (WT) animals, respectively. In addition, we determined that fibers isolated from mdx mice exhibited less total oxygen consumption in response to the FCCP + pyruvate stimulation compared with the WT mice. This novel approach allows the user to make mitochondria-specific measures in a nondisrupted muscle fiber that has been isolated from a whole muscle.
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Sui, Kunyang, Marcello Meneghetti, Jaspreet Kaur, R. J. F. Sørensen, Rune W. Berg, and Christos Markos. "Adaptive polymer fiber neural device for drug delivery and enlarged illumination angle for neuromodulation." Journal of Neural Engineering 19, no. 1 (February 1, 2022): 016035. http://dx.doi.org/10.1088/1741-2552/ac5267.
Full textAbstract:
Abstract Objective. Optical fiber devices constitute significant tools for the modulation and interrogation of neuronal circuitry in the mid and deep brain regions. The illuminated brain area during neuromodulation has a direct impact on the spatio-temporal properties of the brain activity and depends solely on the material and geometrical characteristics of the optical fibers. In the present work, we developed two different flexible polymer optical fibers (POFs) with integrated microfluidic channels (MFCs) and an ultra-high numerical aperture (UHNA) for enlarging the illumination angle to achieve efficient neuromodulation. Approach. Three distinct thermoplastic polymers: polysulfone, polycarbonate, and fluorinated ethylene propylene were used to fabricate two step-index UHNA POF neural devices using a scalable thermal drawing process. The POFs were characterized in terms of their illumination map as well as their fluid delivery capability in phantom and adult rat brain slices. Main results. A 100-fold reduced bending stiffness of the proposed fiber devices compared to their commercially available counterparts has been found. The integrated MFCs can controllably deliver dye (trypan blue) on-demand over a wide range of injection rates spanning from 10 nl min−1 to 1000 nl min−1. Compared with commercial silica fibers, the proposed UHNA POFs exhibited an increased illumination area by 17% and 21% under 470 and 650 nm wavelength, respectively. In addition, a fluorescent light recording experiment has been conducted to demonstrate the ability of our UHNA POFs to be used as optical waveguides in fiber photometry. Significance. Our results overcome the current technological limitations of fiber implants that have limited illumination area and we suggest that soft neural fiber devices can be developed using different custom designs for illumination, collection, and photometry applications. We anticipate our work to pave the way towards the development of next-generation functional optical fibers for neuroscience.
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Hallauer, P. L., H. L. Bradshaw, and K. E. Hastings. "Complex fiber-type-specific expression of fast skeletal muscle troponin I gene constructs in transgenic mice." Development 119, no. 3 (November 1, 1993): 691–701. http://dx.doi.org/10.1242/dev.119.3.691.
Full textAbstract:
We analyzed, in transgenic mice, the cellular expression pattern of the quail fast skeletal muscle troponin I (TnIfast) gene and of a chimeric reporter construct in which quail TnIfast DNA sequences drive expression of E. coli beta-galactosidase (beta-gal). Both constructs were actively expressed in skeletal muscle and specifically in fast, as opposed to slow, muscle fibers. Unexpectedly, both constructs showed a marked differential expression among the adult fast fiber subtypes according to the pattern IIB > IIX > IIA. This expression pattern was consistent in multiple lines and differed from the endogenous mouse TnIfast pattern, which shows approximately equal expression in all fast fibers. These observations indicate that distinct regulatory mechanisms contribute to high-level expression of TnIfast in the various fast fiber subtypes and suggest that the outwardly simple pattern of equal expression in all fast fiber types shown by the endogenous mouse TnIfast gene is based on an intricate system of counterbalancing mechanisms. The adult expression pattern of the TnIfast/beta-gal construct emerged in a two-stage developmental process. Differential expression in fast versus slow fibers was evident in neonatal animals, although expression in fast fibers was relatively weak and homogeneous. During the first two weeks of postnatal life, expression in maturing IIB fibers was greatly increased whereas that in IIA/IIX fibers remained weak, giving rise to marked differential expression among fast fiber types. Thus at least two serially acting (pre- and post-natal) fiber-type-specific regulatory mechanisms contribute to high-level gene expression in adult fast muscle fibers. Unexpected similarities between TnIfast transgene expression and that of the myosin heavy chain gene family (which includes differentially expressed IIB-, IIX- and IIA-specific members) suggest that similar mechanisms may regulate adult fast muscle gene expression in a variety of unrelated muscle gene families.
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Chandra, Murali, Matthew L. Tschirgi, and Jil C. Tardiff. "Increase in tension-dependent ATP consumption induced by cardiac troponin T mutation." American Journal of Physiology-Heart and Circulatory Physiology 289, no. 5 (November 2005): H2112—H2119. http://dx.doi.org/10.1152/ajpheart.00571.2005.
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How different mutations in cardiac troponin T (cTnT) lead to distinct secondary downstream cellular remodeling in familial hypertrophic cardiomyopathy (FHC) remains elusive. To explore the molecular basis for the distinct impact of different mutations in cTnT on cardiac myocytes, we studied mechanical activity of detergent-skinned muscle fiber bundles from different lines of transgenic (TG) mouse hearts that express wild-type cTnT (WTTG), R92W cTnT, R92L cTnT, and Delta-160 cTnT (deletion of amino acid 160). The amount of mutant cTnT is ∼50% of the total myocellular cTnT in both R92W and R92L TG mouse hearts and ∼35% in Delta-160 TG mouse hearts. Myofilament Ca2+ sensitivity was enhanced in all mutant cTnT TG cardiac muscle fibers. Compared with the WTTG fibers, Ca2+ sensitivity increased significantly at short sarcomere length (SL) of 1.9 μm ( P < 0.001) in R92W TG fibers by 2.2-fold, in R92L by 2.0-fold, and in Delta-160 by 1.3-fold. At long SL of 2.3 μm, Ca2+ sensitivity increased significantly ( P < 0.01) in a similar manner (R92W, 2.5-fold; R92L, 1.9-fold; Delta-160, 1.3-fold). Ca2+-activated maximal tension remained unaltered in all TG muscle fibers. However, tension-dependent ATP consumption increased significantly in Delta-160 TG muscle fibers at both short SL (23%, P < 0.005) and long SL (37%, P < 0.0001), suggesting a mutation-induced change in cross-bridge detachment rate constant. Chronic stresses on relative cellular ATP level in cardiac myocytes may cause a strain on energy-dependent Ca2+ homeostatic mechanisms. This may result in pathological remodeling that we observed in Delta-160 TG cardiac myocytes where the ratio of sarco(endo)plasmic reticulum Ca2+-ATPase 2/phospholamban decreased significantly. Our results suggest that different types of stresses imposed on cardiac myocytes would trigger distinct cellular signaling, which leads to remodeling that may be unique to some mutants.
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Teigen, Laura E., Christopher W. Sundberg, Lauren J. Kelly, Sandra K. Hunter, and Robert H. Fitts. "Ca2+ dependency of limb muscle fiber contractile mechanics in young and older adults." American Journal of Physiology-Cell Physiology 318, no. 6 (June 1, 2020): C1238—C1251. http://dx.doi.org/10.1152/ajpcell.00575.2019.
Full textAbstract:
Age-induced declines in skeletal muscle contractile function have been attributed to multiple cellular factors, including lower peak force (Po), decreased Ca2+ sensitivity, and reduced shortening velocity (Vo). However, changes in these cellular properties with aging remain unresolved, especially in older women, and the effect of submaximal Ca2+ on contractile function is unknown. Thus, we compared contractile properties of muscle fibers from 19 young (24 ± 3 yr; 8 women) and 21 older adults (77 ± 7 yr; 7 women) under maximal and submaximal Ca2+ and assessed the abundance of three proteins thought to influence Ca2+ sensitivity. Fast fiber cross-sectional area was ~44% larger in young (6,479 ± 2,487 µm2) compared with older adults (4,503 ± 2,071 µm2, P < 0.001), which corresponded with a greater absolute Po (young = 1.12 ± 0.43 mN; old = 0.79 ± 0.33 mN, P < 0.001). There were no differences in fast fiber size-specific Po, indicating the age-related decline in force was explained by differences in fiber size. Except for fast fiber size and absolute Po, no age or sex differences were observed in Ca2+ sensitivity, rate of force development (ktr), or Vo in either slow or fast fibers. Submaximal Ca2+ depressed ktr and Vo, but the effects were not altered by age in either sex. Contrary to rodent studies, regulatory light chain (RLC) and myosin binding protein-C abundance and RLC phosphorylation were unaltered by age or sex. These data suggest the age-associated reductions in contractile function are primarily due to the atrophy of fast fibers and that caution is warranted when extending results from rodent studies to humans.
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Moré, Margret I., Frank-P. Kirsch, and Fritz G. Rathjen. "Targeted ablation of NrCAM or ankyrin-B results in disorganized lens fibers leading to cataract formation." Journal of Cell Biology 154, no. 1 (July 9, 2001): 187–96. http://dx.doi.org/10.1083/jcb.200104038.
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The NgCAM-related cell adhesion molecule (NrCAM) is an immunoglobulin superfamily member of the L1 subgroup that interacts intracellularly with ankyrins. We reveal that the absence of NrCAM causes the formation of mature cataracts in the mouse, whereas significant pathfinding errors of commissural axons at the midline of the spinal cord or of proprioceptive axon collaterals are not detected. Cataracts, the most common cause of visual impairment, are generated in NrCAM-deficient mice by a disorganization of lens fibers, followed by cellular disintegration and accumulation of cellular debris. The disorganization of fiber cells becomes histologically distinct during late embryonic development and includes abnormalities of the cytoskeleton and of connexin50-containing gap junctions. Furthermore, analysis of lenses of ankyrin-B mutant mice also reveals a disorganization of lens fibers at postnatal day 1, indistinguishable from that generated by the absence of NrCAM, indicating that NrCAM and ankyrin-B are required to maintain contact between lens fiber cells. Also, these studies provide genetic evidence of an interaction between NrCAM and ankyrin-B.