SEARCH · PubMed Health

Results for “fiber development”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,189 records · Page 66Linked to original sources

PubMedDate not supplied

[Functional differentiation of the tail muscle fibers in Rana temporaria tadpoles].

Studies have been made on changes in the electrical properties of muscle membrane and lipid content of two types of myotomal fibers in the tail of tadpoles during metamorphosis. It was shown that during premetamorphosis, peripheral and inner muscle fibers do not differ with respect to their effective resistance, time constant of the membrane and lipid content; the resting membrane potential is higher in the inner fibers. During further development of the tadpoles, differentiation of muscle fibers takes place, and to the beginning of the climax the inner fibers attain lower values of the effective resistance and time constant, as well as lower content of lipids in their sarcoplasm; the difference in the level of resting membrane potential between the peripheral and inner fibers increases. The data obtained suggest that the inner fibers may be referred to as fast ones, whereas the peripheral ones--as slow. These data also reveal specific features in neurotrophic regulation of functional properties of muscle fibers in tadpoles.

Animals↗

PubMed2002

Disruption of Gja8 (alpha8 connexin) in mice leads to microphthalmia associated with retardation of lens growth and lens fiber maturation.

The development of the vertebrate lens utilizes a sophisticated cell-cell communication network via gap junction channels, which are made up of at least three connexin isoforms, alpha8 (Cx50), alpha3 (Cx46) and alpha1 (Cx43), and which are encoded by three different genes. In a previous study, we reported that, with a disruption of Gja3 (alpha3 connexin), mice developed nuclear cataracts with a normal sized lens. We show that Gja8tm1 (alpha8-/-) mice develop microphthalmia with small lenses and nuclear cataracts, while the alpha8 heterozygous (+/-) mice have relatively normal eyes and lenses. A comparative study of these alpha3 and alpha8 knockout mice showed that the protein levels of both alpha3 and alpha8 were independently regulated and there was no compensation for either the alpha3 or alpha8 protein from the wild-type allele when the other allele was disrupted. More interestingly, western blotting data indicated that the presence of alpha8 in the lens nucleus is dependent on alpha3 connexin, but not vice versa. The staining of the knock-in lacZ reporter gene showed the promoter activity of alpha8 connexin is much higher than that of alpha3 connexin in embryonic lenses and in adult lens epithelium. More importantly, a delayed denucleation process was observed in the interior fibers of the alpha8-/- lenses. Therefore, alpha8 connexin is required for proper fiber cell maturation and control of lens size.

Animals↗

PubMed1994

An immature mossy fiber innervation of hilar neurons may explain their resistance to kainate-induced cell death in 15-day-old rats.

Recent studies in adult rodents have shown that mossy fibers, the axons of hippocampal granule cells, sprout into the inner molecular layer of adult rats when hilar cell death occurs following kainate-induced seizure activity. This pattern of hilar cell death and mossy fiber sprouting is not observed in young rats at 15 postnatal days of age. Since granule cells are generated postnatally, one may assume that a lack of a mature mossy fiber input to hilar neurons at 15 days of age is a possible cause for this observed difference. Neo-Timm preparations were made from rats at 5, 10, 12, 15, 20, 21, 25, 30 and 32 postnatal days of age to study the postnatal development of mossy fibers. The adult pattern of Timm-labeled mossy fiber innervation in the granule cell layer was observed by 25 days. The Timm reaction product forms large dense granules in CA3 of 15 day old rats but the hilus at this age lacks this type of large granule. Instead, the hilus displays only small labeled boutons, suggesting that mossy terminals have not yet reached a mature size. Electron microscopic preparations of the deep hilus and the subgranular zone of the hilus at 7, 12, 15, 21 and 30 days were analyzed to study the development of synapses formed by axons of granule cells. At 7 days the deep hilus showed only a few asymmetric synapses formed by the developing mossy fibers.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

PubMed1991

Formation of the retinal ganglion cell and optic fiber layers.

The early development of retinal ganglion cell and the optic fiber layers has been studied by examining the morphology of differentiating retinal ganglion cells using immunoelectron microscopy and a monoclonal antibody against neuron-specific beta-tubulin. This antibody identified retinal ganglion cells during the stages of their most active differentiation and axonogenesis prior to maturation of other retinal neurons. The changing morphology of retinal ganglion cells during these early stages is consistent with a differentiation sequence in which axonogenesis and translocation of the cell body to the vitreal surface occur while the cell is still attached to the vitreal margin through its vitreal endfeet. Thus, the mechanism of retinal ganglion cell axon generation and soma migration to the vitreal surface appears to involve maintenance of this attachment which may act as both a focus for axon differentiation and an anchor for directed nuclear translocation to the vitreal margin.

Animals↗

PubMed1988

Ultrastructural study of calycine synaptic endings of colossal vestibular fibers in the cristae ampullares of the developing chick.

Bipolar vestibular ganglion cells give rise to the colossal vestibular fibers in the chicken. These fibers form the largest calycine endings in the cristae ampullares and also the spoon endings in the tangential vestibular nucleus of the medulla oblongata. Because these synaptic endings are two of the largest and most distinctive in the vertebrate nervous system, they are especially suitable for comparisons of the development of synapses and synaptic endings of a specific cell type. An ultrastructural study of the spoon endings and quantitative data on their synapses were available from material of 15-day-old chick embryos, hatchlings, and 3-yr-old chickens. Here we provide similar data on the large calyces. Briefly, large calyces exhibited no ultrastructural changes corresponding to the changes in the spoon endings apparent when they retract from their target cell surfaces around hatching time. However, the concentration of the ribbon synapses at the large calyces decreased around hatching, when the concentration of the chemical synapses at the spoon endings declined. Moreover, the concentration of the ribbon synapses at the large calyces corresponded closely to the concentration of the chemical synapses at the spoon endings at the same age. Thus at the developmental ages studied, there were similar concentrations in the peripheral and central synapses formed at two different synaptic endings, both derived from one cell type and participating in the same neural pathway. These findings raise the issue of how synapses are regulated locally, but also suggest the possibility for central-peripheral interactions to produce correlative changes in parallel.

Animals↗

PubMedDate not supplied

[Activation of lipid peroxidation in early degeneration of motor nerve fibers and the effect of antioxidants on its development].

It was established that early degeneration of motor fibers of the sciatic nerve of rats (24 and 48 hours after division) is marked by diminished activity of the antioxidant enzymes superoxide dismutase and glutathione reductase and activation of lipid peroxidation leading to increased accumulation of malonic dialdehyde. alpha-tocopherol acetate prevents activation of lipid peroxidation and partly suppresses the development of functional signs of degeneration (lowered amplitude of the M-response, slow restoration of the neuromuscular synapse, and decrement reaction to rhythm stimulation). OBQ2 oxidant (derivative of 4-anilino-5-methoxy-1,2-benzoquinone) had no effect on the rate of degeneration development, which is evidence of insufficiency of radical protection for realization of the anti-degeneration effect.

Animals↗

PubMed1983

Abnormal distribution of fiber types in the slow-twitch soleus muscle of the C57BL/6J dy2J/dy2J dystrophic mouse during postnatal development.

The postnatal development of extrafusal fibers in the slow-twitch soleus muscle of genetically dystrophic C57BL/6J dy2J/dy2J mice and their normal age-matched controls was investigated by histochemical and quantitative methods at selected ages of 4, 8, 12, and 32 weeks. The majority of fibers in the soleus consisted of two kinds, fast-twitch oxidative-glycolytic (FOG) and slow-twitch oxidative (SO), according to reactions for alkaline-stable and acid-stable myosin ATPase and the oxidative enzyme, NADH-tetrazolium reductase. A minor population of fibers, stable for both alkaline- and acid-preincubated ATPase, but variable in staining intensity for NADH-TR, were designated "atypical" fibers. With age, the normal soleus exhibited a gradual increase in the number and proportion of SO fibers and a reciprocal, steady decline in the percentage of FOG fibers. Atypical fibers were numerous at 4 weeks, but were substantially diminished at later ages. Since total extrafusal fiber number remained relatively constant between the periods examined, this change in relative proportions reflects an adaptive transformation of fiber types characteristic of normal postnatal growth. A striking alteration in the number and distribution of fiber types was associated with the dystrophic soleus. At 4 weeks an 18% reduction in total fiber number was already noted. Subsequently, by 32 weeks a further 22% diminution in overall fiber number had occurred. With age, the absolute number and proportion of dystrophic SO fibers were drastically reduced. In contrast, the percentage of dystrophic FOG fibers increased significantly while their absolute numbers between 4 and 32 weeks remained relatively constant. Atypical fibers in the dystrophic solei were found in elevated numbers at all age groups, particularly at 12 weeks. They may, in part, represent attempts at regeneration or an intermediate stage in fiber-type transformation. Microscopically, both of the major fiber types appeared affected, albeit differently, by the dystrophic process. We suggest that a failure or retardation in the normal postnatal conversion of fiber types within the soleus muscle occurs in this murine model for muscular dystrophy.

Animals↗

PubMed1993

Development of dopamine-beta-hydroxylase-positive fiber innervation in co-cultured hippocampus-locus coeruleus organotypic slices.

Development of the noradrenergic innervation of the rat hippocampus by the nucleus locus coeruleus was examined immunohistochemically in the roller tube organotypic cultured slice preparation. Slices of rat hippocampus and locus coeruleus were co-cultured on glass coverslips for 2-6 weeks and evaluated for the presence of dopamine-beta-hydroxylase (DBH) and tyrosine hydroxylase (TH) immunoreactive cells and fibers. Large, multipolar DBH- and TH-positive cells were visible within the locus coeruleus; an occasional cell appeared near or just within co-cultured hippocampal tissue and in connecting fiber tracts. DBH-positive cells tended to concentrate near the edges of locus coeruleus tissue. Locus coeruleus slices cultured alone showed little indication of fiber outgrowth in any direction. In co-cultures, however, beaded DBH- and TH-positive fibers were directed toward the hippocampus. The majority of these fibers entered the hippocampus in the hilar/CA3 region and formed extensive collateral branches. Light microscopy suggests that DBH-positive fiber growth was densest at or near the pyramidal cell layer in CA3b and CA3c and in the infragranular region of the dentate hilus. This pattern of noradrenergic innervation of hippocampus by co-cultured locus coeruleus in vitro appears very similar to the pattern established in vivo (see Moudy et al., companion article, this issue).

Animals↗

PubMed1996

Neuron loss, mossy fiber sprouting, and interictal spikes after intrahippocampal kainate in developing rats.

This study determined neuron losses, mossy fiber sprouting, and interictal spike frequencies in adult rats following intrahippocampal kainic acid (KA) injections during postnatal (PN) development. KA (0.4 micrograms/0.2 microliters; n = 64) was injected into one hippocampus and saline into the contralateral side between PN 7 to 30 days. Animals were sacrificed 28 to 256 days later, along with age-matched naive animals (controls; n = 20). Hippocampi were studied for: (1) Fascia dentata granule cell, hilar, and CA3c neuron counts; (2) neo-Timm's stained supragranular mossy fiber sprouting; and (3) hippocampal and intracerebral interictal spike densities (n = 13). Mossy fiber sprouting was quantified as the gray value differences between the inner and outer molecular layer. Statistically significant results (p < 0.05) showed the following: (1) Compared to controls, CA3c and hilar neuron counts were reduced in KA-hippocampi with injections at PN 7-10 and PN 12-14 respectively and counts decreased with older PN injections. Granule cell densities on the KA-side and saline injected hippocampi were not reduced compared to controls. (2) In adult rats, supragranular mossy fiber sprouting was observed in 2 of 7 PN 7 injected animals. Compared to controls, increased gray value differences, indicating mossy fiber sprouting, were found on the KA-side beginning with injuries at PN 12-14 and increasing with older PN injections. On the saline-side only PN 30 animals showed minimal sprouting. (3) Mossy fiber sprouting progressively increased on the KA-side with longer survivals in rats injured after PN 15. Sprouting correlated positively with later PN injections and longer post-injection survival intervals, and not with reduced hilar or CA3c neuron counts. (4) On the KA-side, mossy fiber gray value differences correlated positively with in vivo intrahippocampal interictal spike densities. These results indicate that during postnatal rat development intrahippocampal kainate excitotoxicity can occur as early as PN 7 and increases with older ages at injection. This rat model reproduces many of the pathologic, behavioral, and electrophysiologic features of human mesial temporal lobe epilepsy, and supports the hypothesis that hippocampal sclerosis can be the consequence of focal injury during early postnatal development that progressively evolves into a pathologic and epileptic focus.

Age Factors↗

PubMed2004

Spaceflight alters the fiber composition of the aortic nerve in the developing rat.

Hydrostatic pressure gradients due to the gravitational force in blood vessels disappear under conditions of microgravity during spaceflight, and the ability of the baroreceptor reflex to control arterial pressure and blood distribution may be altered. We hypothesized, on the basis of the results obtained in our previous experiments using the head-down tilt method in rats and rabbits, that the range of increase in arterial pressure caused by animal behavior narrows under conditions of microgravity, affecting the development of high-threshold unmyelinated fibers in the rat aortic nerve which sends signals from baroreceptors located in the aortic wall to the reflex center. We verified this hypothesis using 9-day-old rat neonates housed with their dams for 16 days on the space shuttle Columbia in outer space (STS-90, Neurolab Mission). Age-matched neonatal rats with the dams remained on the ground as controls. After breeding was carried out in the three experimental groups (FLT, spaceflight; AGC, asynchronous ground control; VIV, vivarium ground control), specimens of the 25-day-old rats were excised and five left aortic nerves in each group were examined by electron microscopy. The number of aortic unmyelinated fibers was significantly less in the FLT group than in each ground control (mean+/-S.D.; 139+/-37 in the FLT, 207+/-36 in the AGC, 283+/-121 in the VIV; P<0.05), which may be related to the weakness of the baroreceptor reflex under conditions of microgravity in space. This result may contribute to understanding of the several cardiovascular issues which occur under microgravity and after reexposure to gravity in human.

Analysis of Variance↗

PubMed1986

Triggered activity induced by combined mild hypoxia and acidosis in guinea-pig Purkinje fibers.

The effects of prolonged exposure to combined mild hypoxia (Po2 230 +/- 20 mmHg) and acidosis (pH: 6.8 +/- 0.05) were studied in guinea-pig left ventricular myocardium superfused in vitro. Only Purkinje fibers were impaled by microelectrodes. Triggered activity developed in depolarized Purkinje fibers after 48 +/- 9 min of exposure to hypoxic and acid conditions and was initiated either by short periods of rapid electrical driving or by the background slow Purkinje automaticity. Triggered activity occurred when a delayed afterdepolarization attained its threshold potential and terminated after a subthreshold afterdepolarization. Interaction between triggered activity and slow background automaticity was observed until 90 to 180 min of exposure to hypoxic and acid conditions. These effects were reversed by replacement in standard conditions (Po2 510 +/- 20 mmHg; pH 7.35 +/- 0.05). Norepinephrine (1 X 10(-6)M) significantly accelerated the rate of discharge of triggered foci and led to a stable sustained triggered activity. Increasing extracellular Ca2+ concentration aggravated the effects of combined mild hypoxia and acidosis and led to the occurrence of early afterdepolarizations initiating triggered activity. In addition abnormal automaticity developed in quiescent fibers without any triggering action potential. Lidocaine and verapamil suppressed the triggered activity following a subthreshold afterdepolarization. Their effects were reversed on wash-out. It is concluded that prolonged exposure to combined mild hypoxia and acidosis induces triggered activity by a basic mechanism common to other situations leading to a calcium overload and showing such behaviour.

Acidosis↗

PubMed1991

Distribution of myosin mRNA during development and regeneration of skeletal muscle fibers.

Myosin mRNA distribution among subcellular compartments of anterior tibialis muscles in rabbit is monitored by in situ hybridization. A high density of mRNA was widely distributed throughout myotubes from 29-day fetal muscle and from regenerating adult muscle. All cytoplasmic spaces contained mRNA except where scattered myofibrils and centrally located nuclei were found. In fibers from 22-week-old rabbits, myosin mRNA was concentrated under the sarcolemma and excluded from the consolidated myofibrils and peripheral nuclei. The dispersal of mRNA through the cytoplasm in myotubes suggests that translation of myosin is widespread and that rapid myofibril assembly can occur throughout the fiber.

Animals↗

PubMed1983

Technique for stabilizing the striation pattern in maximally calcium-activated skinned rabbit psoas fibers.

A procedure was developed for stabilizing the striation pattern of fully activated skinned rabbit psoas fibers. Inhomogeneities of the striation pattern that develop during the rise in tension and also during isometric steady state are completely reversible by this procedure. The striation pattern can be stabilized for approximately 2 h. During this period isometric tension and speed of isotonic shortening decrease less than 10-20% of their initial values.

Animals↗

PubMed1998

Prevention of colonic aberrant crypt foci and modulation of large bowel microbial activity by dietary coffee fiber, inulin and pectin.

The present experiments were aimed at developing novel dietary fibers to aid in reduction of colon cancer risk. We assessed the effects of coffee (non-fiber fraction), coffee fiber (arabino-galactose polymer) and inulin (oligo-fructose) in male F344 rats using formation of azoxymethane (AOM)-induced aberrant crypt foci (ACF) in the colon as the measure of preventive efficacy (or lack of such). At 5 weeks of age, groups of rats were fed the AIN-76A (control) and experimental diets that contained 1% coffee, 10% coffee fiber, 10% inulin, 10% pectin (positive control for fiber) or 200 p.p.m. piroxicam (a known ACF inhibitor). At 7 weeks of age, all animals were s.c injected with AOM (15 mg/kg body wt) once weekly for 2 weeks. All rats were killed 8 weeks after the last AOM injection and ACF were counted. The contents of the cecum were analyzed for bacterial beta-glucuronidase activity and short-chain fatty acids (SCFAs). Dietary administration of coffee fiber significantly suppressed AOM-induction of colonic ACF, in terms of total number, as well as crypt multiplicity and number of ACF/cm2 colon (P < 0.01-0.001). Inulin diet had no significant effect on total ACF, but had reduced the number of ACF/cm2 (P < 0.05). Whereas coffee had no effect on ACF formation, 10% pectin diet and 200 p.p.m. piroxicam significantly suppressed colonic ACF (P < 0.001) as had been expected. A significant reduction of cecal beta-glucuronidase activity was observed in the rats fed coffee, coffee fiber and pectin diets. Further, coffee fiber, inulin and pectin increased cecal SCFA levels 3- to 5-fold. These results suggest that coffee fiber can prevent colon cancer risk. Further studies are warranted to determine the full potential of this fiber in pre-clinical efficacy studies.

Animals↗

PubMed1984

Fiber-optic sensors for biomedical applications.

In this article the development of fiber-optic sensors for biomedical applications is reviewed. Light-carrying fibers are potentially useful in oximetry, dye dilution measurements, laser-Doppler velocimetry, and fluorometry; as physical sensors of temperature, pressure, and radiation; and as chemical sensors of pH, partial pressure of blood gases, and glucose. Emphasis is placed on the principles and ideas used in the various devices rather than on detailed descriptions or critical discussions.

Animals↗

PubMed1990

Human epidemiology: a review of fiber type and characteristics in the development of malignant and nonmalignant disease.

Consideration of the human epidemiology of diseases arising from exposure to naturally occurring and man-made mineral fibers encompasses the several forms of asbestos (chrysotile, crocidolite, amosite, anthophyllite, tremolite-actinolite), other naturally occurring silicates (talc, sepiolite, erionite, attapulgite, vermiculite, and wollastonite), and man-made mineral fibers (glass continuous filament, glass/rock/slag insulation wools, ceramic and other refractory fibers, and glass microfibers). The diseases arising from exposures to some of these fibers include pleural thickening (plaques, diffuse pleural thickening, and calcification), pulmonary fibrosis, lung cancers, mesothelioma of the pleura and peritoneum, and other cancers). Risk factors important in assessing these diseases include assessment of latency, duration of exposure, cumulative exposure, fiber origin and characteristics (length and diameter), other possible confounding occupational or environmental exposures, and smoking. Methodological issues commonly presenting problems in evaluation of these data include assessment of the adequacy of environmental exposures, particularly in regard to fiber identification, distribution, and concentration over the duration of exposure, and the adequacy of study design to detect health effects (disease frequency, latency, and cohort size). Research priorities include further assessment and standardization of pleural thickening relative to fiber exposure, uniform mesothelioma surveillance, further epidemiological assessment of certain silicate and man-made mineral fiber cohorts with emphasis given to assessment of tremolite and small diameter glass and ceramic fibers. Further assessment of possible health risks of the general public should await improved definition of relevant fiber exposure in ambient air.

Asbestos↗

PubMed2000

Bioartificial kidney. I. Theoretical analysis of convective flow in hollow fiber modules: application to a bioartificial hemofilter.

Analytical expressions describing convective flow in a continuous arteriovenous hollow fiber hemofilter were developed. In the lumen of the hollow fiber membrane, existing analytical expressions were applied to describe velocity profiles and pressure. For flow in the shell (the extracapillary space separating the fibers), analytical expressions for the radial and axial velocity profiles and pressure distribution were derived by first finding the stream function. The expressions are based on a similarity solution. Previous analyses of ultrafiltration have either ignored osmotic pressure or assumed constant shell pressure. In this paper, the axial variation in lumen pressure, shell pressure, and osmotic pressure were accounted for. The predicted filtration rates agree well with the experimental results. This flow model is general enough to describe flow in hollow fiber membrane systems employed as bioreactors (e.g., for cell cultures and as bioartificial organs) and as separators (e.g., ultrafiltration and microfiltration) operating in the open-shell mode. The results were applied to determine the design of an optimally functioning bioartificial hemofilter for use ex vivo or in vivo.

Hemofiltration↗

PubMed1986

Prenatal development of nucleus basalis complex and related fiber systems in man: a histochemical study.

To provide parameters for study of the "cholinergic" innervation of a human fetal cerebrum, we have analyzed the prenatal development of histochemical reactivity in the nucleus basalis complex (a magnocellular complex known to contain a high concentration of cholinergic perikarya). Brains from fetuses and premature infants ranging between 8 and 35 weeks of gestation were frozen cut and processed by the thiocholine method for the demonstration of acetylcholinesterase activity. Since no consistent results were obtained with inhibitors on the material younger than 15 weeks, the histochemical reactivity for early stages was expressed as the total cholinesterase reactivity. The first sign of histochemical differentiation of the basal telencephalon is the appearance of a dark cholinesterase reactive "spot" situated between the developing lenticular nucleus and basal telencephalon surface as early as 9 weeks of gestation. The first cholinesterase reactive bundle connects this reactive area (nucleus basalis complex anlage) with the strongly reactive fiber system situated along the dorsal side of the optic tract. During the next "stage" (10.5 weeks), there is a significant increase in the size of the nucleus basalis complex and strongly cholinesterase reactive neuropil occupies the sublenticular, diagonal and septal areas. At this stage we have seen two new cholinesterase-reactive bundles: one well developed cholinesterase reactive fiber stratum approaching (but not penetrating) the neocortical anlage through the external capsule and another minute bundle running towards the medial limbic cortex through the precommissural septum. The supraoptic fiber system can be traced now to the pregeniculate area and the tegmentum. At 15 weeks, the first acetylcholinesterase reactive perikarya appear and the nucleus basalis complex anlage becomes segregated into several strongly reactive territories, corresponding in position to the medial septal, diagonal and basal nuclei as defined on adjacent Nissl stained sections. At this stage, fibers from the nucleus basalis complex enter the "white" matter of frontal, temporal, parietal and occipital parts of the cerebral hemisphere via the external capsule. Between 15 and 18 weeks, acetylcholinesterase fibers spread throughout the "white" matter of the cerebral hemisphere. In the next "stage" (18-22 weeks), strongly reactive fibers can be followed from the nucleus basalis below the putamen and through the external capsule to the transient, synapse-rich subplate zone of frontal, temporal, parietal and occipital cortices.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetylcholinesterase↗