ISSN:0736-5748    

DOI:10.1016/0736-5748(88)90024-X

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractMyelinated axons are highly differentiated in the vicinity of the node of Ranvier, both structurally and with respect to ion channel distribution. Evidence is reviewed showing that axonal differentiation depends upon two distinct types of interaction between glial cells and the axolemma, one at the node itself, with astrocyte processes, and the second, more extensive one, in the paranodal region, with oligodendrocyte processes. In the peripheral nervous system, Schwann cells fulfill both roles. Glial or Schwann cell abnormalities, due to genetic deficiencies, diseases or experimental procedures, result in corresponding abnormalities in the axolemma and can have devastating effects on nerve fiber function. An example, the myelin‐deficient mutant rat, is presented, and the defects underlying the profound and ultimately lethal neurological abnormalities seen in this mutant are discussed in relation to abnormalities in its axoglial interactions.

ISSN:0736-5748    

DOI:10.1016/0736-5748(88)90025-1

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractTo ascertain whether there is a mutual influence on the structure of their cell membranes, brain endothelial cells and their closest neighbor, astrocytes, were grown alone or togetherin vitroand freeze‐fractured. When cultured separately, the brain endothelial cells had a low frequency of short, fragmented tight junctions. Many gap junctions, which are absent from mature brain capillariesin vivo, intercalated among the tight junctional strands, or were separate from them. The separately cultured astrocytes had low concentrations of randomly distributed assemblies (1–30/μm2) in their membranes. When the two cell types were co‐cultured, the endothelial tight junctions were greatly enhanced in frequency, length, width and complexity, and the gap junctional area enclosed by the tight junctional strands were markedly reduced. Thus, thein vitroendothelial junctional complex resembled theirin vivocounterpart, the tight junctions of brain capillaries, when co‐cultured with astrocytes. Reciprocally, brain endothelial cells induced the astrocytic membrane assemblies to increase in concentrations by 5̃ fold, and sometimes to form aggregates with very high concentrations (400/μm2) which approached the concentration of the perivascular astrocytic membranesin vivo. Substituting astrocytes with fibroblasts or smooth muscle cells in co‐cultures did not enhance the tight junctions in the brain endothelium. On the other hand, substituting brain endothelium with endothelium from pulmonary artery or aorta in cocultures did not increase the concentration or induce aggregation of the assemblies in the astrocytes. Thus, the two close neighborsin vivo, brain endothelium and astrocytes, interact specificallyin vitroto induce development of membrane specializations which resemble those at the site of the blood‐brain barrier.

ISSN:0736-5748    

DOI:10.1016/0736-5748(88)90026-3

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractGliosis is a common phenomenon which occurs in many human diseases and in experimentally altered nervous tissue. The factors activating astrocytes to respond are still unclear but recent evidence suggests that diverse substances can provoke a gliotic response. This paper describes the nature of the gliosis in the myelin deficient jimpy and relates these findings to other recent studies of experimentally induced demyelination in which gliosis is a prominent feature of the disorder.In jimpy males, an astroglial hypertrophy which consists of an increase in the number of cell processes can be demonstrated by both electron microscopy and immunocytochemistry using antibodies to glial fibrillary acidic protein. Increased glial fibrillary acidic protein staining in the white matter of jimpy males correlates with the normal time of myelination in different tracts. The immunostaining is not, however, restricted to white matter. Increased staining can be demonstrated in spinal cord grey matter when hardly any myelinated fibers are present, it is especially prominent around blood vessels of both white and grey matter, and is found in the corpus callosum and in the underlying subventricular zone shortly before or at the time myelination begins in this tract. These observations suggest that the hypertrophy is not simply a response by the astrocyte to the absence of myelin sheaths.While an astroglial hypertrophy is dramatic in jimpy males, quantitative counts of astrocytes and electron microscopic autoradiograms do not reveal an increase in the total number of this cell type. These findings suggest that hyperplasia and hypertrophy of astrocytes may be under separate regulatory control with different factors involved in each phenomenon.In the female carriers of the jimpy gene, myelination is temporarily delayed during postnatal development but after several months, the amount of myelin, whether measured morphometrically or biochemically, reaches normal levels. In the white matter of the young female carrier, staining for glial fibrillary acidic protein is increased in terms of the number of processes and the total volume of neuropil but a normal pattern of staining is observed within a year. These and other observations suggest that the glial hypertrophy in the young mosaic is temporary and that regression and reorganization of glial processes takes place as myelination proceeds.

ISSN:0736-5748    

DOI:10.1016/0736-5748(88)90027-5

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe developing neural substrate in dorsal lateral geniculate nucleus of human fetuses and premature, full‐term and postnatal infants, has been analysed using rapid Golgi impregnation, computerized image analysis, electronmicroscopy, and immunocytochemical method for localization of γ‐aminobutyric acid. Nuclear and cytoplasmic neuronal maturation is observed to extend over the entire period studied. Axodendritic synapses, presumably of retinal origin, are occasionally seen at 13–14 fetal weeks. They become increasingly apparent at 18–19 weeks. Dendrodendritic contacts are visualized at 15 weeks. Cortical terminals and occasional triadic contacts are evident around 21 weeks. The inhibitory interneurons containing γ‐aminobutyric acid are present in small numbers at 15–16 weeks; their numerical density increases considerably at 17 weeks but decreases thereafter. The presence of γ‐aminobutyric acid containing nerve cells and synaptic triads is indicative of the formation of inhibitory circuitry. At 15–16 weeks neurons are mostly bipolar although different forms of multipolar cells may be seen. By 24 weeks the radiated and bitufted multipolar neurons, neurons with beaded dendrites and neurons with axon‐like dendritic processes are identifiable. There are no apparent differences in differentiation of neurons between the cranial and caudal parts of dorsal lateral geniculate nucleus. At 15–16 weeks, however, the cells of prospective magnocellular zone appear to be more mature than do the cells in the parvocellular zone. The neuronal soma increases continuously in size. Dendrite development starts at 15–16 weeks of gestation, thereafter the increase in number of their branches and their length is observed. Between 15–16 and 24 weeks, spines and filiform processes appear first on the proximal shafts of the dendrites and subsequently on their distal portion. There is increase in the number of filiform processes and hair‐like appendages on geniculate neurons of premature infants born at 32 and 37 weeks of gestation and of a 4‐day postnatal infant. Computerized quantitative data substantiate the progressive increase in growth parameters. The significance of comparative and functional aspect of the data is discussed.

ISSN:0736-5748    

DOI:10.1016/0736-5748(88)90028-7

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractNSE immunoreactivity has been studied in the organ of Corti of the developing mouse from birth to 21 days. NSE immunohistochemical stain is observed in spiral ganglion cells, in nerve fibers and in nerve endings of inner and outer hair cells, and in both populations of sensory cells. Spiral ganglion cells in lower and central parts of the ganglion stain for NSE at birth, but all nerve cells are stained by day 4. Radial and spiral fibers and the endings on inner hair cells stain at birth, but the nerve endings on outer hair cells develop NSE between days 3 and 6. The inner and outer hair cells are NSE‐positive at day 2 but the NSE immunoreactivity in the outer hair cells decreases at the end of the second week until the cells become negative. The NSE stain in the neuronal pathways of the inner and outer hair cell regions increases for about 19 days, showing a predominant accumulation in neuronal endings. The data suggest that the development of NSE expression in the organ of Corti reflects the nascence and maturation of the synaptic contacts.Spiral neurons, their fibers and endings as well as inner and outer hair cells express NSE in the isolated organ of Corti in culture. Variability of stain among the different cell populations indicates a role of local factors in the regulation of NSE expression.

ISSN:0736-5748    

DOI:10.1016/0736-5748(88)90029-9

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractWe compared neuronal growth patterns in primary cultures prepared by dissociating 3‐day‐old chick embryos, either whole embryo (E3WE) or head only (E3H) and plating the dispersed cells onto Petri dishes coated with either poly‐l‐lysine, collagen or laminin. The culture medium was Dulbecco's Modified Eagle's Medium (DMEM), supplemented with either 5 or 10% fetal bovine calf serum (FCS). As we have previously described, in E3WE cultures on poly‐l‐lysine the neuronal primary growth patterns were aggregation with neuritic fasciculation, presence of growth cones with microspikes and very few flat cells. In contrast with cultures grown on poly‐l‐lysine, in cultures grown on collagen or laminin the distinct growth pattern was extensive networks of isolated and differentiated neurons lying on acquired monolayers of flat cells. When 5% PCS was used, as compared to 10% PCS, neuronal aggregates were fewer and smaller on poly‐l‐lysine; on collagen or laminin a tendency to aggregate was observed. Several differences were observed in the E3H cultures when compared to E3WE: (a) aggregates were less numerous with the prevailing pattern being a web‐like, self‐contained aggregate; (b) aggregates connected with other aggregates or flat cells were rare and the aggregate adhesivity was minimized; (c) neurons on collagen or laminin formed networks with the exception of a few, small aggregates displaying no fasciculation; (d) flat cells did not form a monolayer but islets which hosted the neuronal meshy networks. We attribute these differences in the growth patterns between the various types of cultures to be the combined result of a variety of environmental signals, derived from the provided substrata, the serum and the nonneuronal cell factors and cell surface, all primarily regulating neuronal adhesivity.

ISSN:0736-5748    

DOI:10.1016/0736-5748(88)90030-5

出版商:Wiley    

年代:2003

数据来源: WILEY

ISSN:0736-5748    

DOI:10.1016/0736-5748(88)90031-7

出版商:Wiley    

年代:2003

数据来源: WILEY

ISSN:0736-5748    

DOI:10.1016/0736-5748(88)90032-9

出版商:Wiley    

年代:2003

数据来源: WILEY

ISSN:0736-5748    

DOI:10.1016/0736-5748(88)90023-8

出版商:Wiley    

年代:2003

数据来源: WILEY