摘要:

AbstractIn this paper we present some morphological observations on the morphogenesis of the hippocampus in two inbred strains of mice, C57BL/6J (C57) and DBA/2J (DBA), from day 16 (E16) to day 17 (E17) of prenatal life. At E16 some differences in the histoarchitecture of the hippocampal anlage begin to be detectable. At E17 the differences become more relevant, particularly those concerning the lamination pattern. The more relevant differences concern the differentiation of the pyramidal layer, which appears well defined in C57 mice, while in DBA mice there is no clearcut delimitation between the pyramidal layer and the intermediate zone, where numerous migrating neurons are present. These observations may be interpreted in terms of different migration rates for the neurons in the two strains.

ISSN:0736-5748    

DOI:10.1016/0736-5748(88)90001-9

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe numbers of neurons in the rat superior cervical sympathetic ganglion (SCG) differ in males and females, with the males having 30% more SCG neurons than females at 60 days of age. This sex difference arises during the early postnatal period, when testosterone administration increases the numbers of neurons and alters the nerve growth factor (NGF) content of the rat SCG. In contrast, there is no gender difference in number of neurons in the L1 dorsal root ganglion.In both males and females, the amount of NGF bound per ganglion increased between postnatal days 5 and 15 (P5 and P15) in both dorsal root ganglia (DRGs) and the SCG. There is also a gender difference in NGF binding: SCGs and DRGs of female rats at both P5 and P15 bind more NGF per ganglion than do those of males. This effect was more marked in DRGs than in the SCG. Treatment of neonatal females with testosterone reduced NGF binding in both SCGs and DRGs to levels comparable to males at P5, and in DRGs at P15. In contrast, treatment of males with testosterone from birth resulted in a 2–3 fold increase of NGF binding in both SCGs and DRGs as compared to controls at P15. At P15, testosterone treatment of females increased NGF binding in the SCG. Males and females had opposing responses to neonatal exposure to estradiol. Treatment with estradiol from birth increased NGF binding in SCGs and DRGs of females, but had no effect on NGF binding of SCGs, and reduced NGF binding in DRGs of males.These data suggest that there are more NGF receptors in sensory and sympathetic ganglia in developing females as compared to males, and that neonatal exposure to gonadal steroids affects the expression of NGF receptors.

ISSN:0736-5748    

DOI:10.1016/0736-5748(88)90002-0

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractCulture medium conditioned (CM) by embryonic chick skeletal muscle or RN22 Schwannoma cells enhanced dramatically the neuritic development of chick embryonic spinal cord slices explanted onto a collagen substratum. The addition of a mixture of bovine brain gangliosides (BBG) or the monosialoganglioside GM1 to this medium potentiated the nerve growth factor (NGF)‐independent CM‐mediated neuritogenesis. A 3–4 fold increase in spinal cord outgrowth was due to increased neurite number, length and branching. The ability of the gangliosides to potentiate the positive neuritogenic action of CM was not limited solely to spinal cord cultures since similar results were obtained in parallel studies employing organized cultures of embryonic chick ciliary ganglia. These studies demonstrate the ability of gangliosides to enhance the trophic action of factor(s) present in CM. They suggest further that gangliosides may play a modulatory role in the development of the nervous system.

ISSN:0736-5748    

DOI:10.1016/0736-5748(88)90003-2

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe early stages of myelination were examined in optic nerves of rats aged 12–15 days. The initial association between oligodendroglial processes and bare axons involves no junctional specialization, as the axoglial extracellular space remains unaltered. Following ensheathment by a collar of glial cytoplasm, at least one full rotation of mesaxon was evident before compact myelin formed. Furthermore, myelin was generally evident before a second rotation was completed. In longitudinal sections, an axoglial junction was always observed beginning on the first paranodal loop, continuing through to the last (or outermost) loop. Thus, the formation of myelin and elaboration of a junctional complex in the paranodal region follow a promyelination phase and appear to be synchronous (and possibly related) events. Although the paranodal plasmalemma and axolemma are in close apposition, there is a material in the extracellular space that precipitates phosphotungstic acid, a characteristic that appears to be featured in a number of different types of cell junctions.

ISSN:0736-5748    

DOI:10.1016/0736-5748(88)90004-4

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe fate of glial cell lines following Wallerian degeneration in the rat optic nerve was analysed after pulse labelling with [3H]thymidine. The rats were unilaterally enucleated at the key stages 2,5,8 and 20 days after birth. Three hours later, they were injected intraperitoneally with [3H]thymidine and killed after 1, 3, 5, 10 and 20 days survival. Oligodendrocytes were the most affected, being unable to differentiate after 2 days enucleation, dying rapidly or transforming into another cell type after 5, 8 and 20 days enucleation. The apparent stability of the astrocyte population is due to an equilibrium between increased differentiation from glioblasts and increased death, the latter being preponderant at the key stage 2 days. Finally, the steady increase in the number of microglia may be due to the transformation from other cells, either glioblasts for the early time intervals or oligodendrocytes later on. It appears, then, that the interrelation between glial cell lines during differentiation is more intricate than previously suspected and is closely dependent, for each line, upon the integrity of axons.

ISSN:0736-5748    

DOI:10.1016/0736-5748(88)90005-6

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractVarious natural protease inhibitors stimulate the proliferation of rat astrocytes grown in primary culture in the absence of serum. They are inactive on the proliferation of oligodendrocytes. The mean level of stimulation of the astrocyte proliferation elicited by the protease inhibitors is higher when the cells are in the growth phase, at low cell density than when they are quiescent, at high cell density. Among the protease inhibitors tested three serum proteins, α1‐antitrypsin, α2‐macroglobulin and antithrombin III were the most active. The present results, taken together with our previous finding that thrombin and some other proteases also stimulate the proliferation of astroglial cells but not of oligoden‐droglial cells, suggest that proteases and protease inhibitors participate, through still unclear mechanisms, in the control of the proliferation of astrocytes, but not in that of oligodendrocytes, during brain ontogenesis.

ISSN:0736-5748    

DOI:10.1016/0736-5748(88)90006-8

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractBipolar 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 spoor 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.

ISSN:0736-5748    

DOI:10.1016/0736-5748(88)90007-X

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractSynthesis and release of melatonin were studied in pineal expiants from 14‐ (young) and 60‐day‐old (‘maturing’) male Long‐Evans rats with or without added thyroid hormone, triiodothyronine (T3), at or near physiological levels and under light and dark conditions. Incubation for 6 hr (1200–1800) was in a synthetic medium; melatonin was measured by radioimmunoassay (RIA). In light, T3increased melatonin levels in pineal and medium of cultures from either young or maturing animals. In dark, T3decreased melatonin levels in the pineals of either age, but was without significant effect on levels in the medium. Since it is known from other work that 14‐day‐old rat pineal glands do not yet have a complete sympathetic innervation system, it is here doubly evident that T3can modulate directly pineal synthesis and release of melatonin, and may not depend upon a mature sympathetic innervation. Light in the studied conditions was permissive from the stimulatory action of T3on pineal synthesis and release of melatoninin vitro.

ISSN:0736-5748    

DOI:10.1016/0736-5748(88)90008-1

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractOligodendrocytes in primary cultures derived from rat embryo spinal cord were examined in control medium and in Trembler mouse serum (TMS)‐supplemented medium. The Oligodendrocytes were identified on the basis of the synthesis and surface expression of galactocerebrosides revealed by a monoclonal antibody directed against this component. We noticed two effects of TMS compared to control mouse serum. First, our results revealed that in TMS medium there is a mitogenic response of galactocerebroside (GalC)‐positive cells. Second, in the presence of TMS, Oligodendrocytes do not develop processes as they do in the presence of normal mouse serum. When laminin, a basal lamina component was added to TMS medium, GalC+Oligodendrocytes decreased in number and differentiation was normal. Possible explanations of the effects of TMS and laminin on oligodendrocyte proliferation and differentiation are discussed.

ISSN:0736-5748    

DOI:10.1016/0736-5748(88)90009-3

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractExtracellular recordings from raphe dorsalis neurons in rats during development were performed, and the response to iontophoretically applied β‐antagonists was analysed. In pups younger than 2 weeks, raphe dorsalis firing was totally or partially inhibited by application of β‐antagonists, while after 2 weeks of age the neurons were insensitive to the same application. The β‐receptors appeared to be involved in the control of raphe firing during a transient period of ontogenesis and thus the disappearance of β‐regulation at older ages may reflect the regression of this population of neurotransmitter receptors.

ISSN:0736-5748    

DOI:10.1016/0736-5748(88)90010-X

出版商:Wiley    

年代:2003

数据来源: WILEY