摘要:

AbstractThe expression of polysialylated neurons in the dentate gyrus of the hippocampal formation of young (postnatal day 40), mature (postnatal day 80) and aged (postnatal day 540) male Wistar rats has been investigated by immunohistochemical techniques employing a monoclonal antibody specific for neural cell adhesion molecule‐linked α2,8 polysialic acid. A strong immunoreactivity was found on the cell bodies, dendrites and axons of granule‐like neuronal cells at the border between the hilar region and the granule cell layer of the young rat. In the mature animal the number of immunoreactive neurons declined dramatically and were virtually absent in the aged group. Using an alternative fixation procedure, glial fibrillary acidic protein‐positive and polysialylated astroglia processes were found in close proximity to the dendrites of the polysialylated granule‐like cells. The number of astroglial processes traversing the granule cell layer showed a similar age‐dependent decline to that observed with the polysialylated neurons. Glial fibrillary acidic protein‐positive and polysialylated stellate astroglia were present throughout the hippocampal formation, but did not show the marked age‐dependent decline observed with the astroglial processes in the granule cell layer.The neuronal dendrites and astroglial processes exhibited a strict numerical ratio in the young and mature animal and, in double immunofluorescence studies with anti‐polysialic acid and anti‐glial fibrillary acidic protein, the astroglial processes exhibited apparent points of cell and/or dendritic contact. These findings suggest that loss of polysialylated astroglial processes precedes the decline in polysialylated dentate neurons.

ISSN:0736-5748    

DOI:10.1016/0736-5748(95)00067-4

出版商:Wiley    

年代:1999

数据来源: WILEY

摘要:

AbstractRat dorsal root ganglia (DRG) were cultured from different stages of development ranging from embryonic day‐14 to adult. The expression of eight neurotransmitter phenotypes was examined with immunocytochemical detection and the percentages of each phenotype were calculated with reference to the whole neuronal population defined by the expression of neuron‐specific enolase (NSE). The expression of peptides, calcitonin gene‐related peptide (CGRP), substance P (SP), cholecystokinin (CCK) and neuropeptide Y (NPY) was always present whatever the age at onset of the cultures. Although the percentage of CGRP remained stable, that of the other peptides declined progressively. Theirin‐vitroexpression did not differ marked from that foundin vivo. Another group of neurotransmiiters, including 5‐hydroxytryptamine (5‐HT), thyrotropin‐releasing hormone (TRH) and gamma‐aminobutyric acid (GABA) was never expressedin situin DRG neurons. In culture, they were expressed in a high percentage of neurons, especially for 5‐HT and TRH, and they showed a similar evolution, with a decrease at early postnatal ages followed by a further increase. This profile suggests that the expression of these transmitters is strongly environment‐dependent and may be repressedin situ. Finally, somatostatin (SOM) was found only in cultures prepared from adult tissues, whereas it was presentin situfrom the embryo onwards. The expression of this peptide would thus require a stabilization by a long exposure to environmental factors.We can conclude that the great diversity of phenotypic expression found in DRG neuronsin situis the result of a wide variety of influences occurring at different stages of development in a large potential repertory present in these neurons.

ISSN:0736-5748    

DOI:10.1016/0736-5748(95)00066-6

出版商:Wiley    

年代:1999

数据来源: WILEY

摘要:

AbstractWe have used primary cultures of rat striatum to study the effects of ATP analogues on the elongation of astrocytic processes, a parameter of astroglial cell differentiation. Parallel studies were performed with basic fibroblast growth factor, a known regulator of astroglial cell function. After three days in culture, both the growth factor and αβ‐methylene‐ATP induced dramatic increases in the mean length of astrocytic processes/cell. For both agents, effects were dose‐dependent. The effect of αβ‐methylene‐ATP was antagonized by the trypanoside suramin and mimicked by 2‐methyl‐thio‐ATP, suggesting the involvement of a suramin‐sensitive P2‐purinoceptor. Neither an additive nor a synergistic effect between αβ‐methylene‐ATP and basic fibroblast growth factor on the elongation of processes was detected in cultures exposed to both agents. Indeed, an inhibition with respect to the effects induced by either agent alone was recorded, suggesting that the growth factor and the purine analogue can modulate astrocytic differentiation by activation of common intracellular pathways.It is concluded that, like basic fibroblast growth factor, ATP can promote the maturation of astrocytes towards a more differentiated phenotype characterized by the presence of longer astrocytic processes. These findings might have interesting implications for astroglial cell differentiation during brain development and for ischemia‐ and trauma‐associated hypergliosis.

ISSN:0736-5748    

DOI:10.1016/0736-5748(95)00064-X

出版商:Wiley    

年代:1999

数据来源: WILEY

摘要:

AbstractThisin vivostudy concerns developmental differences in the sensitivity of striatal neurons toN‐methyl‐d‐aspartate (NMDA). Changes in calcium homeostatis in adult vs immature rats at postnatal days 8–10, evoked by NMDA, were evaluated by measurements of45Ca efflux and of Ca2+taurine and phosphoethanolamine concentrations in striatal microdialysates. The efflux of [14C]sucrose was employed in order to measure changes in extracellular space volume. In adult rats the addition of 5 mM NMDA for 20 min to the perfusion medium resulted in a 30–40% increase in45Ca efflux, and in a 15% increase in [14C]sucrose efflux. Ten minutes after NMDA perfusion,45Ca and [14C]sucrose efflux returned to the baseline. No significant changes in Ca2+or amino acid concentrations were observed in the dialysate of the adult rat striatum. NMDA perfusion in the striatum of immature rats initially induced a transient (5 min) increase in the efflux of45Ca (by 13%) and [14C]sucrose (by 9%). This was followed by a prolonged (lasting 45–50 min) 45% decrease in45Ca efflux, an 80% reduction of Ca2+concentration, and increases in taurine and phosphoethanolamine concentrations in the dialysate, whereas [14C]sucrose efflux recovered within 10 min.These data illustrate differences in the NMDA response between developing and adult rat striatum. Only in developing rats did NMDA induce a large and prolonged influx of extracellular calcium to neurons that may explain the enhanced NMDA neurotoxicity in immature rats.

ISSN:0736-5748    

DOI:10.1016/0736-5748(95)00061-5

出版商:Wiley    

年代:1999

数据来源: WILEY

摘要:

AbstractNeurotransmitters such as acetylcholine can control neuritogenesis of hippocampal cells. The timing of its receptors expression consequently may influence synaptogenesis and neuronal activity in the developing hippocampus. We investigated the mRNA expression of the nicotinic acetylcholine‐gated ion channel receptor (nAChR) α4 subunit in the embryonic and postnatal hippocampal formation. Although its expression level is low in the adult hippocampus, this protein consitutes the major nAChR subunit in the central nervous system. We carried outin‐situhybridization experiments to determine whether or not the α4 AChR subunit mRNA distributions show evidence of regional and developmental regulation during hippocampal maturation. Our studies reveal that α4 AChR mRNA expression was low at the embryonic stage, but increased transiently during postnatal development reaching a maximum during the second week of life and decreasing thereafter, to a minimum at adulthood. In hippocampal regions, the peak values of α4 AChR expression were between 400 and 800% of adult α4 messenger levels. In the postnatal hippocampus, most of the cells from the pyramidal layer of the CA3 and CA2 areas displayed a strong hybridization signal for the α4 AChR subunit. In the hilus and the CA1 regions, the localization of the α4 transcripts seemed to be restricted to some interneurons and pyramidal cells, respectively. Moderate and uniformin‐situhybridization signals were observed in granular cells from the dentate gyrus. The transient profile of α4 expression suggests that nAChRs may participate in the early postnatal maturation of hippocampal circuity.

ISSN:0736-5748    

DOI:10.1016/0736-5748(95)00062-3

出版商:Wiley    

年代:1999

数据来源: WILEY

摘要:

AbstractWe have examined motor control in normal and shiverer mutant mice using the rotarod assay, a forced motor activity which tests for balance and co‐ordination. Shiverer mice carry a deletion of the myelin basic protein (MBP) gene, resulting in CNS dysmyelination and characteristics motor dysfunction. Homozygous mutant mice had a significant increase in cumulative falls from the rotatod relative to heterozygous mice. Non‐acclimated animals of both genotypes showed progressive improvement in performance when tested on successive days. The rotarod test also discriminited shiverer mutants from animals that received gene therapy intervention. Shiverer animals carrying an MBP transgene showed gene‐dosage‐dependent improvements in motor function, and mutants which received thalamic transplants of wild type oligodendrocyte precursor cells showed improvement relative to sham operated and non‐transplanted controls. Thus the rotarod is a sensitive measure of motor function in hypomyelinated mice, and may be useful for assessing the results of experimental manipulations including transgenic gene therapy and cell transplantation.

ISSN:0736-5748    

DOI:10.1016/0736-5748(96)81215-9

出版商:Wiley    

年代:1999

数据来源: WILEY

摘要:

AbstractRat hippocampal neurons in culture extended their neurites until day 5in vitro(DIV). Then, the mean neuritic length slightly decreased. Excitatory amino acid (EAA)‐elicited inositol phosphate (IP) formation increased from 0.5 to 2 DIV, reached a plateau between 2 and 4–5 DIV, and then gradually decreased until 10 DIV. This decrease was likely not due to neuronal death. This developmental pattern was observed forN‐methyl‐d‐aspartate, kainate, glutamate, ibotenate and quisqualate (QA). Interestingly, the 1S,3R‐aminocyclopentane dicarboxylate (1S,3R‐ACPD) response slightly increased during neuronal culture development. At 3 DIV, the ionotropic antagonists 6,7‐dinitro‐quinoxalin‐2,3‐dion andd‐2‐amino‐5‐phosphonopentanoate efficiently blockedN‐methyl‐d‐aspartate and kainate‐elicited IP formation, and partially inhibited glutamate and ibotenate responses. QA and 1S,3R‐ACPD responses were not affected, suggesting a metabotropic action for these two compounds. Furthermore, QA and 1S,3R‐ACPD potencies significantly increased between 3 and 10 DIV.The transient high activity periods induced by EAA, except for 1S,3R‐ACPD, are not observed for norepinephrine, carbachol and potassium chloride responses.Taken together, these data suggest that: (i) QA and 1S,3R‐ACPD can act on two different glutamate metabotropic receptors subtypes during development; and (ii) the EAA‐induced transient peaks of IP stimulation, which are specific with respect to other neuroactive substances profiles, could be involved in the development of hippocampal neurons. Indeed, these transient high activities take plase when the neuritic length regularly increasesin vitro.

ISSN:0736-5748    

DOI:10.1016/0736-5748(95)00058-5

出版商:Wiley    

年代:1999

数据来源: WILEY

摘要:

AbstractIn this paper, we report that pure cultures of human microglia were obtained from long‐term astrocytic cultures of human fetal brain. After five to six months and repeated cell passages, macrophage‐like cells started to spontaneously formin vitro, so that in two to three weeks the whole culture was populated by them. These cells were grown up to over 50 passages in culture and analyzed for morphology, specific marker positivity, growth rate and major histocompatibility complex (MHC) antigen expression with or without gamma‐interferon (IFN) stimulation. We found that, regardless of embryonic age of original cultures (10–15 weeks of gestation), cultures showed a remarkable homogeneity and purity and over 90 stained for typical microglial markers. Under basal conditions, two cell subpopulations similar to those describedin vivo, we observed: the reactive ‘ameboid’ type and the resting ‘ramified’ one, the latter increasing with timein vitroand cell passages. Both cell subpopulations were capable of active phagocytosis and of high‐rate proliferation. They spontaneously expressed low levels of MHC class II antigens, but were negative for MHC class I. Stimulation with gamma‐interferon lymphokine upregulated the MHC class II expression as well as the MHC class I heavy chain form in ameboid, ‘reactive’ cells but not in the ramified ones. We also found thatβ2microglobulin, already expressed in basal conditions, was dissociated from HLA A‐B‐C molecules in lymphokine‐stimulated cells at early passages. The physiological significance of these data, as well as the possible correlation within vivoontogenetic modifications, are also discussed.

ISSN:0736-5748    

DOI:10.1016/0736-5748(95)00059-3

出版商:Wiley    

年代:1999

数据来源: WILEY

摘要:

AbstractTreatment of PC12 cells or dorsal root ganglion neurons with the protease inhibitor,N‐Acetyl‐Leu‐Leu‐norleucinal, stimulated phosphorylation of the mid‐sized and heavy neurofilament subunits and caused the heavy subunit in the perikarya of dorsal root ganglion neurons to become hyperphosphorylated. The closely related inhibitor,N‐Acetyl‐Leu‐Leu‐methioninal, did not produce a similar effect. Okadaic acid increased the phosphorylation state of the heavy neurofilament subunit in PC12 cells in a fashion similar toN‐Acetyl‐Leu‐Leu‐norleucinal and the effect of both compounds together was greater than for either one alone. There was no increase in cyclin‐dependent kinase 5‐immunoprecitable histone H1 kinase activity in PC12 cells treated withN‐Acetyl‐Leu‐Leu‐norleucinal despite the presence of enzyme protein.The present study demonstrates that a protease inhibitor can induce the hyperphosphorylation of neurofilament subunits to a level normally seen only in axons. This suggests that perturbations in intracellular proteolysis may lead to the accumulation of phosphorylated neurofilament epitopes in neuronal perikarya in certain pathological states. The results also show that the carboxy‐terminal tail domains of the two largest neurofilament subunits are phosphorylated even when cyclin dependent kinase 5 is inactive, indicating that other neuronal kinases are involved in the phosphorylation of Lys‐Ser‐Pro repeats.

ISSN:0736-5748    

DOI:10.1016/0736-5748(95)00060-7

出版商:Wiley    

年代:1999

数据来源: WILEY

摘要:

AbstractPolyamines and their related monoacetyl derivatives were studied in rod outer segment (ROS) and cone outer segment (COS) of photoreceptor cells from chick embryo retina during eye development (7th–18th days). Putrescine was found to be necessary, in the second phase of retinogenesis, to sustain both ROS and COS differentiation and, after acetylation, γ‐aminobutyric acid synthesis. On the other hand, spermidine and even more spermine intervene in the third phase of development when photoreceptors mature. Moreover, the presence ofN1‐acetylspermidine already at the 7th day indicates that in the outer segment of photoreceptor cells too, as in the whole retina, putrescine synthesis comes about by two pathways. One pathway involves ornithine decarboxylase; the other, spermidine/spermineN1‐acetyltransferase and FAD‐dependent polyamine oxidase activities that convert spermidine to putrescine viaN1‐acetylspermidine. These different biosynthetic pathways are probably also decisive in permitting γ‐aminobutyric acid synthesis, which is very important in the ripening process of neural retina.

ISSN:0736-5748    

DOI:10.1016/0736-5748(95)00056-9

出版商:Wiley    

年代:1999

数据来源: WILEY