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At least 649 records · Page 36Linked to original sources
PubMed2002

EphB receptors influence growth of ephrin-B1-positive statoacoustic nerve fibers.

The Eph family of receptors and ligands has been implicated in a variety of developmental processes, including the provision of inhibitory guidance cues to developing nerve fibers. A unique property of the B class of receptors is that they are able to phosphorylate ephrin-B ligands, allowing for bi-directional, or reverse signalling. While most of the studies to date have focused on central nerve fibers, little is known about the role of Eph molecules in guiding nerve fibers of the peripheral nervous system. In the present study, ephrin-B1 was found to be highly expressed on developing peripheral nerve fibers including auditory and vestibular (statoacoustic) and dorsal root ganglion nerve fibers. In vitro assays revealed that EphB-Fc receptors inhibited further growth of statoacoustic nerve fibers. In contrast, EphA7-Fc and ephrin-B2-Fc did not prevent further growth of SAG. Together, these results suggest a role for EphB receptors in providing guidance signals to ephrin-B1-positive SAG nerve fibers.

Animals↗
PubMedDate not supplied

Development of a silicone hollow fiber membrane oxygenator for ECMO application.

A new silicone hollow fiber membrane oxygenator for extracorporeal membrane oxygenation (ECMO) was developed using an ultrathin silicone hollow fiber, with a 300 microm outer diameter and a wall thickness of 50 microm. The hollow fibers were mechanically cross-wound on the flow distributor to achieve equal distribution of blood flow without changing the fiber shape. The housing, made of silicone coated acryl, was 236 mm long with an inner diameter of 60 mm. The surface area was 1.0 m2 for prototype 211, and 1.1 m2 for prototype 209. The silicone fiber length was 150 mm, and the silicone membrane packing density was 43% for prototype 211 and 36% for prototype 209. Prototype 211 has a priming volume of 208 ml, and prototype 209 has a priming volume of 228 ml. The prototype 211 oxygenator demonstrates a gas transfer rate of 120 +/- 5 ml/min (mean +/- SD) for O2 and 67 +/- 12 ml/min for CO2 under 2 L of blood flow and 4 L of O2 gas flow. Prototype 209 produced the same values. The blood side pressure drop was low compared with the silicone sheet oxygenator (Avecor, 1500ECMO). These results showed that this new oxygenator for ECMO had efficiency similar to the silicone sheet oxygenator that has a 50% larger surface area. These results suggest that the new generation oxygenator using an ultrathin silicone hollow fiber possesses sufficient gas transfer performance for long-term extracorporeal lung support.

Carbon Dioxide↗
PubMed1988

Qualitative investigation of the postnatal development of axon and nerve fiber calibers in the ventral roots of rats.

The postnatal development of the ventral spinal roots of rats was studied with optical microscopic and morphometric methods. Adult rats show a craniocaudal decrease of axon and nerve fiber diameters which cannot be detected in younger animals. The bimodal differentiation of the nerve fiber populations occurs between the 15th and 20th day. Myelinated nerve fibers show a g ratio of 0.6 for all examined age groups.

Animals↗
PubMed1996

Innervation of the chick cornea analyzed in vitro.

PURPOSE: During the early stages (embryonic day 3 [E3]) of avian corneal development, nerve fibers extend from the trigeminal ganglion to the corneal limbus. On E11, these nerve fibers enter the cornea and extend through the secondary stroma to begin innervation of the epithelium on E13. This process of innervation is concomitant with the cornea's dehydration and transition from opacity to transparency; thus, suggesting a link between innervation and the attainment of corneal function. This investigation attempts to ascertain whether the developing cornea can support its innervation in vitro and whether there is a possible developmental interrelationship between corneal innervation and dehydration, with the associated transition from opacity to transparency. METHODS: Isolated corneas from either E8 or E14 chicks were co-cultured with E8 dorsal root ganglia. After 4 days of culture, innervation was visualized by silver staining and immunohistochemistry. Changes in corneal composition and organization associated with this innervation in vitro were analyzed by measuring changes in specific hydration, thickness and compaction, and incorporation of [35S]sulfate into glycosaminoglycans during co-culture. RESULTS: The E8 and E14 corneas support extensive innervation in vitro. Developing nerve fibers extend through the secondary stroma to innervate the epithelium. In vitro innervation of E8, but not E14, corneas was associated with a decrease in corneal specific hydration, whereas control corneas (without dorsal root ganglia) failed to show any such changes. E8 corneas also showed a significant increase in compaction when innervated in vitro. Corneal innervation in vitro did not significantly change the overall incorporation of [35S]sulfate into glycosaminoglycans. Furthermore, incorporation of [35S]sulfate into corneal sulfated glycosaminoglycans (sGAG) is not influenced by either the number of nerve fibers innervating the cornea or nerve growth factor (NGF). In addition, the distribution of staining of the corneal glycosaminoglycans, chondroitin sulfate and keratan sulfate, and peanut agglutinin-binding epitopes, suggests that these molecules are not associated with inhibition of axonal development. CONCLUSIONS: The in vitro system described here is a useful model to understand the process of corneal development. Co-culture has shown that corneal innervation promotes the process of dehydration, which is dependent on the age of the cornea. However, other functionally related refinements necessary for transparency-notably proteoglycan synthesis-may not be linked to innervation or NGF production. The authors conclude that the development of transparency is dependent on corneal innervation, though not exclusively, and that other controlling factors also are required.

Animals↗
PubMedDate not supplied

Development of ultrafine polyester fiber vascular grafts with high endothelialization capability. Angiogenesis by ultrafine polyester fibers.

The authors previously showed that a vascular prosthesis made of ultrafine polyester fibers (UFPF) had high healing ability even when of low porosity. In this study, new highly porous vascular grafts fabricated from UFPF (water porosity: 3,600 ml/min/cm2, 8 mm in inner diameter and 5 cm in length), were developed and implanted in the thoracic descending aorta of dogs to evaluate their endothelialization capability. Two weeks after implantation, many colonies of endothelial cells with openings of capillary blood vessels were noted, even in the middle portion of the grafts. Numerous fibroblasts and capillary blood vessels were also observed in the synthetic walls. These results suggest that UFPF vascular grafts provide a suitable microenvironment for infiltration and proliferation of fibroblasts, which are accompanied by the capillary formation as nutrient supply; these capillaries provide multiple sources of endothelial coverage on the luminal surface. It is expected that the new, highly porous vascular grafts may have rich endothelialization capability and stable healing properties in humans.

Animals↗
PubMed1988

The synthesis of nerve growth factor (NGF) in developing skin is independent of innervation.

The arrival of sensory fibers in developing mouse skin has been demonstrated to coincide precisely with the initiation of nerve growth factor (NGF) synthesis in the skin (Davies et al., 1987). This temporal correlation suggested that the arrival of sensory fibers might initiate NGF synthesis in their target tissues. Here we have eliminated the sensory and motor neurons projecting to the chick leg by the removal of the neural primordia in 3-day-old embryos. The levels of mRNA NGF of intact and denervated leg skin were identical, indicating that the developmental regulation of NGF synthesis in the skin of chick embryos is independent of its innervation.

Animals↗
PubMed1988

An in vitro study of the effects of androgens on the cytoskeleton of ovarian granulosa cells with special reference to actin.

Ovarian granulosa cells from small antral follicles from immature rats were cultured in a serum-free medium for 1-6 days with or without the presence of 10(-5) M dehydroepiandrosterone (DHEA) or 10(-5) M-androstenedione (delta 4-A). Control cultures reveal that the cells are flattened and contain many filamentous bundles organized as stress fibers, numerous scattered cytoplasmic actin filaments, microtubules and vimentin. Alpha actinin and myosin were shown by immunocytochemistry to have a punctate pattern along the stress fibers. For the most part, cells exposed to androgens did not flatten; however, they assumed a varied shape and contained fewer stress fibers and actin filaments. Many of these cells did not develop stress fibers and those that did develop were fewer in number and displayed--actinin and myosin in a punctate pattern. Microtubules and vimentin filaments remained unaltered when compared to controls. It is believed that the deficiency of actin filaments, coupled with certain other degenerative changes which express themselves in other cellular compartments, leads to an early atresia of the granulosa cell cultured in high concentrations of androgens.

Actinin↗
PubMed2005

Transcriptional regulation of myotube fate specification and intrafusal muscle fiber morphogenesis.

Vertebrate muscle spindle stretch receptors are important for limb position sensation (proprioception) and stretch reflexes. The structurally complex stretch receptor arises from a single myotube, which is transformed into multiple intrafusal muscle fibers by sensory axon-dependent signal transduction that alters gene expression in the contacted myotubes. The sensory-derived signal transduction pathways that specify the fate of myotubes are very poorly understood. The zinc finger transcription factor, early growth response gene 3 (Egr3), is selectively expressed in sensory axon-contacted myotubes, and it is required for normal intrafusal muscle fiber differentiation and spindle development. Here, we show that overexpression of Egr3 in primary myotubes in vitro leads to the expression of a particular repertoire of genes, some of which we demonstrate are also regulated by Egr3 in developing intrafusal muscle fibers within spindles. Thus, our results identify a network of genes that are regulated by Egr3 and are involved in intrafusal muscle fiber differentiation. Moreover, we show that Egr3 mediates myotube fate specification that is induced by sensory innervation because skeletal myotubes that express Egr3 independent of other sensory axon regulation are transformed into muscle fibers with structural and molecular similarities to intrafusal muscle fibers. Hence, Egr3 is a target gene that is regulated by sensory innervation and that mediates gene expression involved in myotube fate specification and intrafusal muscle fiber morphogenesis.

Animals↗
PubMed2005

Calcineurin is necessary for the maintenance but not embryonic development of slow muscle fibers.

Skeletal muscles are a mosaic of slow and fast twitch myofibers. During embryogenesis, patterns of fiber type composition are initiated that change postnatally to meet physiological demand. To examine the role of the protein phosphatase calcineurin in the initiation and maintenance of muscle fiber types, we used a "Flox-ON" approach to obtain muscle-specific overexpression of the modulatory calcineurin-interacting protein 1 (MCIP1/DSCR1), an inhibitor of calcineurin. Myo-Cre transgenic mice with early skeletal muscle-specific expression of Cre recombinase were used to activate the Flox-MCIP1 transgene. Contractile components unique to type 1 slow fibers were absent from skeletal muscle of adult Myo-Cre/Flox-MCIP1 mice, whereas oxidative capacity, myoglobin content, and mitochondrial abundance were unaltered. The soleus muscles of Myo-Cre/Flox-MCIP1 mice fatigued more rapidly than the wild type as a consequence of the replacement of the slow myosin heavy chain MyHC-1 with a fast isoform, MyHC-2A. MyHC-1 expression in Myo-Cre/Flox-MCIP1 embryos and early neonates was normal. These results demonstrate that developmental patterning of slow fibers is independent of calcineurin, while the maintenance of the slow-fiber phenotype in the adult requires calcineurin activity.

Animals↗
PubMed2004

Development of a mammalian series-fibered muscle.

This study examines the processes by which multiply innervated, serially fibered mammalian muscles are constructed during development. We previously reported that primary myotubes of such a muscle, the guinea pig sternomastoid muscle, span from tendon to tendon and are innervated at each of the muscle's four innervation zones. Secondary myotubes form later, in association with each point of innervation (Duxson and Sheard, Dev. Dyn., 1995; 204:391-405). We now describe the further growth and development of the muscle. Secondary myotubes initially insert onto and grow along the primary myotube. However, as they reach a critical length, they encounter other secondary myotubes growing from serially adjacent innervation zones and may transfer their attachment(s) to these serially positioned secondary myotubes. Other secondary myotubes maintain attachment at one or both ends to their primary myotube. Thus, an interconnected network of primary and secondary myotubes is formed. Patterns of reactivity for cell adhesion molecules suggest that early attachment points between myotubes are the embryonic precursors of adult myomyonal junctions, characterized by the expression of alpha7Bbeta1 integrin. Finally, the results show that secondary myotubes positioned near a tendon are generally longer than those lying in the mid belly of the muscle, and we suggest that the environment surrounding the tendinous zone may somehow stimulate myotube growth.

Aging↗
PubMed1992

Development of a medical fiber-optic pH sensor based on optical absorption.

A new fiber-optic pH sensor system has been developed. The sensor uses an absorbtive indicator compound with a long wave-length absorption peak near 625 nm; change in absorption over the pH range 6.8 to 7.8 is reasonably linear. The sensor is interrogated by a pulsed, red LED. Return light signal is split into short and long wave-length components with a dichroic mirror; the respective signals are detected by photodiodes, and their photocurrents are used to form a ratiometric output signal. In laboratory tests, the sensor system provided resolution of 0.01 pH, accuracy of +/- 0.01 pH, and response time of 30-40 s. Following gamma sterilization, laboratory sensor testing with heparinized human blood yielded excellent agreement (e.g., r = 0.992 for n = 42) with a clinical blood gas analyzer. Excellent sensor performance and low cost, solid-state instrumentation are hallmarks of this sensor-system design.

Absorption↗
PubMed2002

Comparison of Lp82- and m-calpain-mediated proteolysis during cataractogenesis in Shumiya cataract rat (SCR).

PURPOSE: It is well known that m-calpain, a ubiquitous calpain, is involved in cataract formation in rodent lens. Involvement of Lp82, a lens-specific calpain, in the cataract formation is also suggested. However, the exact relationship between Lp82-mediated proteolysis and lens opacification has not yet been established. We therefore compared Lp82- and m-calpain-mediated proteolyses of alphaA-crystallin during cataractogenesis to clarify whether Lp82 is involved in cataract formation. METHODS: In order to analyze the Lp82- and m-calpain-mediated proteolyses, we developed antibodies exclusively specific to the proteolytic products of alphaA-crystallin produced by Lp82 and m-calpain actions, respectively. The proteolytic profiles of alphaA-crystallin by Lp82 and m-calpain during cataractogenesis in SCR lenses were analyzed by Western blotting and immunohistochemical staining. RESULTS: While m-calpain-mediated proteolysis was detected predominantly in cataractous lenses, Lp82-mediated proteolysis was detected not only in cataractous but in normal lenses. The m-calpain-mediated proteolysis was observed in restricted areas developing and destined to develop opacification, i.e., the nuclear and perinuclear regions of lens. On the other hand, Lp82-mediated proteolysis was observed not only in the same regions but also in the cortical region where opacity does not develop. Unlike m-calpain-mediated proteolysis, Lp82-mediated proteolysis was not inhibited by the oral administration of aminoguanidine (AG), which acts to prevent lens opacification. CONCLUSIONS: From these results, it is shown that there is no direct contribution of Lp82-mediated proteolysis to cataract formation in SCR. Rather, Lp82 may function in fiber cell development and/or fiber cell remodeling during lens maturation under physiological conditions, since Lp82-mediated proteolysis occurs in the cortical region of normal lens.

Aging↗
PubMed2003

Comparison of the mutagenic activity of XAD4 and blue rayon extracts of surface water and related drinking water samples.

The combination of mutagenicity tests and selective extraction methodologies can be useful to indicate the possible classes of genotoxic organic contaminants in water samples. Treated and source water samples from two sites were analyzed: a river under the influence of an azo dye-processing plant discharge and a reservoir not directly impacted with industrial discharges, but contaminated with untreated domestic sewage. Organic extraction was performed in columns packed with XAD4 resin, that adsorbs a broad class of mutagenic compounds like polycyclic aromatic hydrocarbons (PAHs), arylamines, nitrocompounds, quinolines, antraquinones, etc., including the halogenated disinfection by-products; and with blue rayon that selectively adsorbs polycyclic planar structures. The organic extracts were tested for mutagenicity with the Salmonella assay using TA98 and TA100 strains and the potencies were compared. A protocol for cleaning the blue rayon fibers was developed and the efficiency of the reused fibers was analyzed with spiked samples. For the river water samples under the influence of the azo-type dye-processing plant, the mutagenicity was much higher for both blue rayon and XAD4 extracts when compared to the water from the reservoir not directly impacted with industrial discharges. For the drinking water samples, although both sites showed mutagenic responses with XAD4, only samples from the site under the influence of the industrial discharge showed mutagenic activity with the blue rayon extraction, suggesting the presence of polycyclic compounds in those samples. As expected, negative results were found with the blue rayon extracts of the drinking water collected from the reservoir not contaminated with industrial discharges. In this case, it appears that using the blue rayon to extract drinking water samples and comparing the results with the XAD resin extracts we were able to distinguish the mutagenicity caused by industrial contaminants from the halogenated disinfection by-products generated during water treatment.

Cellulose↗
PubMed2004

Dispersion and current-voltage characteristics of helical polyacetylene single fibers.

To study the transport properties of individual helical polyacetylene (PA) fibers, we developed a method to extract a single fiber from tightly entangled ropes of helical PA bulk film. After a few minutes of sonication of a piece of helical PA bulk film in an organic solution containing surfactant, a droplet of solution is deposited on the pre-pattened electrode under argon atmosphere. AFM images show that extracted helical PA fibers are typically 10 mum in length and 100-200 nm in diameter. We found that the helicity of bulk materials is conserved. We present the temperature dependencies of current-voltage characteristics of individual helical PA fibers doped with iodine.

Journal Article↗
PubMed1966

Caffeine- and potassium-induced contractures of frog striated muscle fibers in hypertonic solutions.

The effect of hypertonic solutions on the caffeine- and KCl-induced contractures of isolated fibers of frog skeletal muscle was tested. Hypertonic solutions, twice the normal osmotic strength, prepared by adding NaCl or sucrose, potentiate the caffeine-induced contractures. The fibers may develop tensions of 3.6 kg/cm(2) of fiber transverse section. The same hypertonic medium reduced the peak tension of KCl-induced contractures. Thus the hypertonic condition does not affect the contractile mechanism itself. These findings give further support to the view that the differential effect of hypertonic solution is on the excitation-contraction coupling mechanism. Extracellular calcium is not essentially required for the first few of a series of caffeine-induced contractures either in hypertonic or in isotonic solutions.

Animals↗
PubMed1997

Changes in levels of mRNAs for cell wall-related enzymes in growing cotton fiber cells.

mRNAs for cell wall-related enzymes in developing cotton fiber cells were measured by reverse transcription-PCR analysis. Both endo-1,4-beta-glucanase and expansin mRNA levels were high during cell elongation but decreased when cell elongation ceased, and xyloglucan decreased. The endo-1,3-beta-glucanase mRNA level was very low in the elongating cells but increased gradually at the onset of secondary wall synthesis, accompanying the massive deposition of cellulose. Endoxyloglucan transferase and sucrose synthase mRNA levels were constant during all stages of growth.

Cell Wall↗
PubMed2001

Expression of R-cadherin and N-cadherin by cell groups and fiber tracts in the developing mouse forebrain: relation to the formation of functional circuits.

The expression of R-cadherin and N-cadherin was mapped in the postnatal forebrain of the mouse by immunohistochemistry and in situ hybridization. Results show that the two molecules are expressed in specific and restricted patterns in numerous brain nuclei, gray matter areas and cortical layers that are widely distributed throughout the mouse forebrain at postnatal day 1. The expression pattern of R-cadherin is clearly distinct from that of N-cadherin, but overlap is observed in many areas. In many cortical areas, the two cadherins have a laminar-specific distribution that varies from region to region. In addition, immunohistochemical data revealed expression of R-cadherin protein and N-cadherin protein in the neuropil of many brain regions as well as in the axons that travel in fiber tracts such as the olfactory tract, the anterior commissure, the corpus callosum, the stria terminalis and the fornix. Often, subsets of axons within the same fiber tract differentially express R-cadherin and N-cadherin, with partial overlap of expression. The targets of the cadherin-immunoreactive fiber bundles often contain neuropil as well as cell bodies of neurons that also express the same type(s) of cadherin, suggesting that R-cadherin and N-cadherin may be involved in target recognition and the establishment of connections. Specifically, the expression of R-cadherin and N-cadherin is related to the maturation of thalamocortical sensory pathways, corticofugal pathways, and pathways associated with the hippocampal complex, the piriform cortex, and the amygdala. It is also related to the development of the cell groups associated with these pathways.Together, the results from the present study indicate the possibility that the selective adhesion of neural structures that express the same type(s) of cadherin contributes to the formation of gray matter areas, neural circuits and functional connections in the postnatal forebrain of the mouse.

Aging↗