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At least 559 records · Page 31Linked to original sources

PubMed1989

Dynamic structure of the radial glial fiber system of the developing murine cerebral wall. An immunocytochemical analysis.

Dramatic changes occur in the radial glial fiber system of the murine forebrain in the course of neocortical histogenesis. Initially, prior to substratification of cortical and subcortical anlagen between E13 and E14, the system is uniformly radial in alignment. It appears to achieve maximum density and to be highly uniform in structure throughout its radial span, both in terms of apparent fiber density and the pattern of arrangement of fibers in fascicles. Subsequent to E14, concurrently with rapid growth of the cerebral wall and with the differentiation of the cortical substrata and intermediate zone, the subcortical segment of the system becomes laterally arced while the transcortical span of the system remains radially aligned. Although the spacing between fascicles changes little, there is an apparent general drop in fiber density associated with a progressive reduction in the number of fibers per fascicle. The changes in relative positioning of the fibers and the apparent decline in fiber density are most dramatic within the developing cortical plate and subplate and may be of specific significance for the migration and radial assembly of the neurons in the supragranular neocortical layers.

Animals↗

PubMed1988

Strain-specific development of the mossy fiber system in organotypic cultures of the mouse hippocampus.

The postnatal development of the hippocampus of the inbred mice strains BALB/c, C57BL/6, and DBA/2 was studied in organotypic explant cultures using the roller-tube technique. In vivo, mice exhibit strain-specific mossy fiber distribution patterns. As a main result we found, that after cultivation of 3-4 weeks, similar strain-specific patterns became apparent in vitro, as visualized by a modified Timm staining. From this experiment we can conclude that a postnatal extrinsic influence cannot be the cause of the strain-specific hippocampal features.

Animals↗

PubMedDate not supplied

A new method of determining the solute permeability of hollow-fiber dialysis membranes by means of laser lights traveling along optic fibers.

To develop a new method of determining solute permeability more simply and accurately, the authors employed light from a laser traveling along quartz optic fibers. Dialysis experiments at 310 K were made with a single hollow fiber containing aqueous test solutes. A membrane tube was sealed at either end with quartz optic fibers. Helium-neon and helium-cadmium laser lights emitted from one of these optic fibers into the test solution at wavelengths of 543 and 442 nm for vitamin B12 and cytochrome-C, respectively, were caught by the other optic fiber and detected with a silicon photodiode. The solute permeability for cytochrome-C obtained by this method was almost in agreement with that for beta-2-microglobulin by the radioisotope method. This study demonstrates the usefulness of light from a laser traveling along quartz optic fibers in determining the solute permeability of hollow-fiber dialysis membranes.

Cytochrome c Group↗

PubMed1976

The development and maturation of the supracrestal fibers in nonhuman primates.

The transseptal fibers appear to develop independently in adjacent teeth and course toward each other meeting at the midline. Correction of rotations should be accomplished if possible before the teeth are in clinical occlusion. The thickness of the band of transeptal fibers depends on the anatomy of the interproximal space. The fibers are not continuous but interlace at the midline. In disease the transseptal fibers are destroyed first at the midline and appear to reorganize at that point. A thick fiber bundle was demonstrated to run buccolingually in the interdental space which served to connect the buccal and lingual gingiva. It was independent of the dentogingival fibersfibers. Circumferential fibers which extend from the interproximal to the labial and lingual gingiva were also noted. Poor hygiene which contributes to the formation of gingivitis and in extreme cases periodontitis causes the lysing of the gingival fibers. This study does not answer the problem of why certain rotations reoccur even after surgical transsection of the fibers. Further morphologic studies in a time sequence during rotation correction and retention are needed to determine which fibers play an exact role in the rotational relapse phenomenon.

Animals↗

PubMed2002

Molecular characterization of the cotton GhTUB1 gene that is preferentially expressed in fiber.

Each fiber of cotton (Gossypium hirsutum) is a single epidermal cell that rapidly elongates to 2.5 to 3.0 cm from the ovule surface within about 16 d after anthesis. A large number of genes are required for fiber differentiation and development, but so far, little is known about how these genes control and regulate the process of fiber development. To investigate gene expression patterns in fiber, a cDNA, GhTUB1, encoding beta-tubulin was isolated from a cotton fiber cDNA library. The analyses of RNA northern-blot hybridization and reverse transcriptase-polymerase chain reaction demonstrated that GhTUB1 transcripts preferentially accumulated at high levels in fiber, at low levels in ovules at the early stage of cotton boll development, and at very low levels in other tissues of cotton. The corresponding GhTUB1 gene including the promoter region was isolated by screening a cotton genomic DNA library. To demonstrate the specificity of the GhTUB1 promoter, the 5'-flanking region including the promoter and 5'-untranslated region was fused with the beta-glucuronidase reporter gene. The expression of the reporter chimera was examined in a large number of transgenic cotton plants. Histochemical assays demonstrated that GhTUB1::beta-glucuronidase fusion genes were expressed preferentially at high levels in fiber and primary root tip of 1- to 3-d-old seedlings and at low levels in other tissues such as ovule, pollen, seedling cotyledon, and root basal portion. The results suggested that the GhTUB1 gene may play a distinct and required role in fiber development. In addition, the GhTUB1 promoter may have great potential for cotton improvement by genetic engineering.

Arabidopsis Proteins↗

PubMed1999

Postnatal development of cytochrome oxidase activity in fiber tracts of the rat brain.

This paper describes postnatal changes in cytochrome oxidase (C.O.) activity in developing fiber tracts. Quantitative histochemistry was used to measure changes in C.O. activity in nine white matter regions at postnatal days (P) 7, 12, 17, 30, and 60 in the rat. At P7, enzyme activity was maximal in the spinal trigeminal tract, medial longitudinal fasciculus, and cerebellar white matter. At P12, maximal levels were measured in the medial lemniscus and cerebral peduncle. C.O. activity increased from low levels at P7 to maximal levels by P17 in the hippocampal commissure, posterior and anterior corpus callosum, and anterior commissure. In all nine regions, C.O. activity decreased by P60. Thus, peaks in C.O. activity shifted as a function of postnatal age in a caudo-rostral direction. The regional heterogeneity in the age of onset in C.O. fluctuations suggests that vulnerability to injury and metabolic dysfunction during the perinatal period will differentially affect white matter structures, depending on the age of onset of such disruptions.

Aging↗

PubMed1989

Development of elastic-system fibers in human vocal cords.

The morphogenesis of elastic fibers in human, fetal and adult vocal cords was studied by light microscopy and transmission electron microscopy. The elastic system includes elastic, elaunin and oxytalan fibers at different stages. The development of elastic-system fibers in human vocal cord is characterized by every stage of maturation, whether normal, stifled or accelerated, according to areas.

Aged↗

PubMed1989

The different effects of type I and IV collagens on the survival and proliferation of cultured BSC-1 cells.

The effects of type I and IV collagens on the survival and proliferation of cells were investigated to clarify a possible involvement of the substratum in the regulation of cell function. BSC-1 cells attached, spread and sustained their viability in the absence of calf serum on culture dishes coated with type IV collagen, but were unable to spread and survive on untreated culture dishes. The effects of adding type IV collagen in solution were similar to those of type IV coating. The fraction of the solution of type IV collagen with molecular mass of more than 100 kDa enhanced spreading and survival of cells, but the fraction of less than 100 kDa did not. Type I collagen did not support cell viability in the absence of calf serum. Moreover, coating of culture dishes with type I collagen, but not with type IV collagen, inhibited DNA synthesis and cell proliferation in the presence of calf serum. The cells grown on type I collagen were long, thin and spindle-shaped, and their stress fibers were not well developed, but the cells grown on type IV collagen, as well as those grown on untreated culture dishes, were polygonal in shape with well-developed stress fibers. These results indicate that the interactions of BSC-1 cells with the substratum, when it is derived from type I and IV collagens, differentially modulate the survival and proliferation of BSC-1 cells.

Animals↗

PubMed1989

Development of the nerve fiber layer in the olfactory bulb of mouse embryos.

The purpose of this study was to provide an ultrastructural description of the development of the olfactory nerve fiber layer (ONL) in the olfactory bulbs of mouse embryos. The developmental age of each embryo was determined by means of the Theiler staging system. During stages 17 and 18, the olfactory axons grew through the mesenchyme toward the cerebral vesicle; they were accompanied by a group of electron-dense cells which were referred to as peripheral glial progenitor cells (GPCs) because they ensheathed the adjacent axons. In Theiler stage 19-21 embryos, the axons and the peripheral GPCs grew dorsocaudally along the external surface of the bulb primordium forming a presumptive ONL immediately superficial to its glia limitans. Through small breaks in this glia limitans, the axons, but not the peripheral GPCs, penetrated into the marginal zone of the bulb primordium. Even though by the first half of stage 21 there were only short stretches of glia limitans separating the presumptive ONL from the marginal zone, there was no intermingling of the perikarya between the two layers. A definitive ONL could be identified by the second half of Theiler stage 21, by which time the glia limitans of the bulb primordium had totally disappeared. However, up to Theiler stage 24 of development the only cells to be found in this definitive ONL were the peripheral GPCs. Although in Theiler stage 25 and 26 embryos there was an additional population of less-electron-dense GPCs within the definitive ONL, these cells were likely derived from the previous group of peripheral GPCs rather than from cells newly emigrated from the deeper layers of the developing bulb. This developmental data necessitated a reevaluation of the cell lineages of the two glial cell types that reside within the ONL of the adult olfactory bulb.

Aging↗

PubMed2002

Mechanisms by which discharge modulates diastolic depolarization in sheep and dog Purkinje fibers.

For reasons unknown, a fast drive is prone to induce overdrive excitation in sheep Purkinje fibers under conditions that still induce overdrive suppression in dog Purkinje fibers. Our aim was to study by means of a microelectrode technique diastolic depolarization (DD) and its changes with overdrive in sheep and dog Purkinje fibers perfused in vitro under identical conditions. The major results are: (a) At a slow rate, diastolic depolarization is much faster and larger in sheep than in dog Purkinje fibers. (b) Faster rates increase DD slope and amplitude in sheep and decrease them in dog Purkinje fibers. (c) DD slope and amplitude increase in sheep and decrease in dog if the same number of action potentials are separated by a shorter diastole. (d) The change in DD slope and amplitude induced by a fast drive persists after a subsequent slow drive of approximately 20 s. (e) The fastest drives can induce an oscillatory potential superimposed on early DD in sheep. (f) In both species, high [Ca(2+)](o) increases and low [Ca(2+)](o) decreases DD slope and amplitude. (g) Neither high nor low [Ca(2+)](o) change the DD rate-dependence patterns peculiar to either species. (h) DD amplitude in dog in high [Ca(2+)](o) is still smaller than that in sheep in Tyrode solution. (i) Caffeine prevents the steepening of early DD by drive, but not the subsequent increase which can lead to overdrive excitation in both species. (j) TTX decreases DD slope and amplitude in both species. (k) Cs(+) markedly reduces DD slope and amplitude and more so at faster rates, especially in the sheep. We conclude that the differences in diastolic depolarization and the different behavior of DD with overdrive in the two species account for the propensity of sheep Purkinje fibers to develop overdrive excitation and for that of dog Purkinje fibers to develop overdrive suppression.

Animals↗

PubMed1998

Temporal expression of elastic fiber components in bladder development.

Fetal and postnatal bovine bladders were examined for expression of elastic fiber components by immunohistochemistry as well as by measurement of steady state mRNA levels. Expression of fibrillin-1, microfibril-associated glycoprotein (MAGP) and elastin during the fetal period were compared with that of postnatal two year old animals (heifers) and adults. Each bladder was separated into two distinct tissue samples: 1) the outer smooth muscle layer (detrusor) and 2) the inner epithelium (urothelium) lined lamina propria (urotherial-lamina propria). Each of these samples was analyzed separately. Distribution of the elastic fiber components, determined by immunohistochemistry with matrix-specific antibodies, was different depending upon the region of the bladder wall examined and its developmental stage. In particular, MAGP and fibrillin-1 were conspicuously present in the urothelium during the later fetal stages. RNA products of elastic fiber genes were detectable both in the detrusor smooth muscle and urothelial-lamina propria fractions. The highest level of expression occurred in the urothelial-lamina propria fraction during the late second-early third trimester. Elastin expression was different from that of MAGP and fibrillin-1. The highest levels of steady-state elastin mRNA occurred at the earliest developmental stages examined and then progressively decreased through term. A high level of elastin expression occurred within the inner or lamina propria layer of the bladder. Since this layer is the functional capacitance layer within the bladder, its flexibility is likely related to the structural integration of elastin and associated microfibrillar components.

Animals↗

PubMed2005

Postnatal development of ectopic sensory fibers containing endomorphin-2 in the white matter of the spinal cord of a transgenic mouse expressing nerve growth factor in oligodendrocytes.

Transgenic mice ectopically expressing nerve growth factor in oligodendrocytes have high levels of nerve growth factor immunoreactivity in the white matter of the spinal cord from birth until 2 months of age. The nerve growth factor over-expression leads to the appearance of ectopic substance P containing sensory fibers in the white matter of the spinal cord that persist throughout the life of the animal. These transgenic mice have been found to display hypersensitivity to a thermal stimulus following a sensitizing pinch stimulus known to release endogenous substance P. Surprisingly, this hypersensitivity is completely reversed following the administration of morphine, to the extent that transgenic mice become less sensitive to pain than the wild type mice given morphine. Endomorphin-2, an endogenous opioid peptide, has been found co-localized with substance P in primary sensory fibers in the spinal cord. In this study, we show that the ectopic fibers also express endomorphin-2, and describe the postnatal development of such expression, as detected by immunocytochemistry. We confirmed that endomorphin-2 expression starts later in the postnatal period than substance P. Surprisingly, transgenic animals had delayed appearance of endomorphin-2 in the superficial dorsal horn, compared with wild type, and expressed particularly high levels of endomorphin-2 immunoreactivity in the ectopic fibers from postnatal days 10-30, coinciding with the peak of nerve growth factor expression in oligodendrocytes. Endomorphin-2 immunoreactivity was still readily detected in ectopic fibers of 120-day-old animals. Furthermore, we detected immunoreactivity for the mu-opioid receptor in the ectopic fibers, where it was co-localized with endomorphin-2 immunoreactivity. In the superficial dorsal horn, there were no apparent differences in the distribution and intensity of mu-opioid receptor immunoreactivity between wild type and transgenic animals. Taken together, these data could provide an explanation for the enhanced effect of opioid analgesics in transgenic mice, when compared with control mice, as well as provide the basis for studies of the postnatal development of the hyperalgesia and allodynia demonstrated by these animals.

Animals↗

PubMed1995

Capillary supply during development of individual regenerating muscle fibers.

This study describes the capillary supply of individual regenerating muscle fiber during three stages of its development. Regeneration was induced by the injection of mepivacaine in the anterior tibial muscle of rats. Muscle fiber capillarization during regeneration was analysed in semithin sections, employing the following parameters: the number of capillaries around a fiber and the number of capillaries per fiber cross-sectional area. The results revealed that during development of regenerating fibers, the fiber cross-sectional area increased, the number of capillaries around each fiber increased and the number of capillaries per fiber cross-sectional area decreased. These data indicated a greater capillary supply of the individual regenerating muscle fiber during its early stage of maturation.

Animals↗

PubMed2003

Sodium imaging of climbing fiber innervation fields in developing mouse Purkinje cells.

Maturation of specific neuronal connections in the mature nervous system includes elimination of redundant synapses formed earlier during development. In the cerebellum of adult animals, each Purkinje cell (PC) is innervated by a single climbing fiber (CF). In early postnatal development each PC is innervated by multiple CFs and elimination of synapses formed by supernumerary CFs occurs until monoinnervation is established at around postnatal day 20 (P20) in mice. It is not clear whether multiple CFs, or only a single CF, translocate from the cell body of immature PCs to the developing dendrite and, in case several CFs translocate, whether they share or segregate their innervation fields. To localize CF innervation fields, we imaged changes in postsynaptic sodium concentration resulting from CF-mediated postsynaptic currents. We found that more than one CF translocates from an innervation field on the cell body of the PC to the developing dendrite and that these CFs share rather than segregate their innervation fields. We concluded that both the soma and the proximal dendrite of the PC are territories of competition for the developing CFs and that the overlapping of their termination fields may be the prerequisite for a local process of elimination of all but one CF, as previously demonstrated in the developing neuromuscular junction.

Aging↗

PubMed2004

Development of a novel polyimide hollow-fiber oxygenator.

We have developed a membrane oxygenator using a novel asymmetric polyimide hollow fiber. The hollow fibers are prepared using a dry/wet phase-inversion process. The gas transfer rates of O(2) and CO(2) through the hollow fibers are investigated in gas-gas and gas-liquid systems. The polyimide hollow fiber has an asymmetric structure characterized by the presence of macrovoids, and the outer diameter of the hollow fiber is 330 microm. It is found that the polyimide hollow-fiber oxygenator can enhance the gas transfer rates of O(2) and CO(2), and that the hollow fiber provides excellent blood compatibility in vitro and in vivo.

Animals↗

PubMed2000

Dispersive multiplexing in multimode optical fiber

Recently developed ideas in the field of wireless communications suggest that the presence of scattering can be used to enhance, rather than degrade, the total information capacity of a transmission system. This concept is applied to data transmission over multimode optical fiber, and the result is an optical multiplexing that can increase the capacity of such fiber. Experimental results demonstrate the feasibility of this approach. The technique may play an important role in future high-bandwidth local area networking applications.

Journal Article↗

PubMed1985

The development of central cores in both fiber types in tenotomized muscle.

Using the histochemical reaction for myosin adenosine triphosphatase (ATPase), a study of the rat soleus muscle following tenotomy was undertaken. It was demonstrated that both type 2A and 2C fibers undergo degenerative changes following tenotomy. All previous studies have stated that only type 1 fibers were affected and developed central core lesions and that type 2 fibers were somehow protected from the degenerative process. The results of this experiment illustrate that central core lesions will develop in all three fiber types (types 1, 2A, and 2C) of the soleus following tenotomy.

Adenosine Triphosphatases↗

PubMed1987

[Amplitude of the tension developed by glycerinated muscle fibers during rigidity depends on the nature of the structural reorganizations in F-actin induced by formation of the actomyosin complex].

Dependence between the amplitude of tension, developed by glycerinated muscle fibers during rigidity, and the character of structural changes in F-actin, induced by the formation of actomyosin complex, was studied by polarized microfluorimetry and tensiometry. It is shown that during rigidity the anisotropy of intrinsic tryptophan residues as well as of rhodamine phalloidin bound to F-actin, and amplitude of tension depend on pH (6-8) and ionic strength (mu = 0.07 M-0.14 M) of solution. Greater changes in polarized fluorescence and in amplitude of tension were registered during rigidity in solutions with low ionic strength (mu = 0.07 M) and pH 8. It suggested that the amplitude of muscle fibre tension depends on the relative quantity of actin monomers, being in the "switched on" state.

Actins↗