ISSN:0736-5748    

DOI:10.1016/0736-5748(90)90001-I

出版商:Wiley    

年代:2003

数据来源: WILEY

ISSN:0736-5748    

DOI:10.1016/0736-5748(90)90002-J

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractA quantitative morphometric study of the development of myelinated fibres in the optic and trochlear nerves has been made in growth‐retarded fetal sheep at 140 days gestation (term = 146 days). Intrauterine growth retardation was induced as a result of the reduction of placental mass, by prior removal of placentation sites in six ewes. In the optic nerve (central nervous system) the mean diameter of myelinated fibres was not significantly reduced but the thickness of the myelin sheath relative to axon diameter was disproportionately reduced. In the trochlear nerve (peripheral nervous system) there was a significant reduction of 23% (p<0.01) in the mean diameter of myelinated fibres; however the normal axon:myelin ratio was maintained. The total number of myelinated fibres in the trochlear nerve did not differ between the normal and growth‐retarded group, indicating that there was not a greater than normal incidence of cell death during intrauterine growth retardation in the nucleus of the trochlear nerve.The differential effect of intrauterine growth retardation on myelination in the central and peripheral nervous systems suggests that chronic intrauterine deprivation affects oligodendrocyte activity but does not markedly affect the capacity of Schwann cells to produce myelin.

ISSN:0736-5748    

DOI:10.1016/0736-5748(90)90003-K

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractTo establish inherent potential for the induction of neural tube defects the ability of selected anticonvulsant agents to interfere with cell division has been establishedin vitrousing an antiproliferative assay in clonal cell lines and a cytotoxicity assay using primary cultures of cerebral cortex neurons at different stages of development. In order to evaluate the relative toxicities of these agents theirin vitroeffects were determined at 2–3 times the plasma therapeutic level. By these procedures valproate and the benzodiazepines, diazepam and clonazepam, exerted a potent antiproliferative action which could not be attributed to increased cytotoxicity. In contrast phenytoin was markedly cytotoxic but was without an antiproliferative action. This cytotoxicity was most pronounced during the periods of extensive fibre outgrowth. When compared to epidemiological and animal study data, agents which inhibited cell proliferation within twice therapeutic concentration were consistently associated with major neural tube malformations. However phenytoin, found to be positive in the cell cytotoxicity assay, is not associated with neural tube malformations but rather is primarily associated with mental retardation. Thus assessment of antiproliferative activity of anticonvulsant drugs may be one criterion for identification of teratogenic potential during neurulation.

ISSN:0736-5748    

DOI:10.1016/0736-5748(90)90004-L

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractCortical brain cells from 14‐day‐old mouse embryos were seeded on various substrates and cultivated in serum‐free medium with or without conditioned medium from astrocytes or C6 glioma cells. Poly‐l‐lysine was shown to be the best substrate for cell attachment followed by Concanavalin A (ConA) and adhesion particles derived from glia cells. Cells grown on ConA sprouted rapidly and formed large networks. Survival of neurons was greatly prolonged when glia‐conditioned medium (GCM) was present in the culture medium. Cells grown on ConA were then viable for more than 4 weeks. Without GCM, neurons survived in culture for about 2 weeks, regardless of the substrate. Endothelial cell growth supplement or acidic fibroblast growth factor increased survival of neurons but also stimulated proliferation of astrocytes.

ISSN:0736-5748    

DOI:10.1016/0736-5748(90)90005-M

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractNeurotransmitter‐related (choline acetyltransferase, acetylcholinesterase, glutamate decarboxylase,l‐glutamate and GABA high affinity uptake) and glial neurochemical markers (glutamine synthetase, β‐alanine uptake and 2′,3′ cyclic nucleotide phosphohydrolase) have been quantitatively assayed in various regions of the rat CNS during normal postnatal development: spinal cord, cerebellum, superior colliculus, hippocampus, striatum, visual cortex, frontal sensory‐motor cortex and prefrontal cortex. In general, neurochemical markers show an obvious trend toward increasing levels in parallel with brain maturation. However, some relevant exceptions have been observed and discussed. Detailed knowledge of regional neurochemical brain maturation is important since it gives us information concerning some key events of brain development. In addition, this knowledge is the essential pre‐requisite for studies aimed at the alteration of specific regional and temporal parameters through experimental manipulation.

ISSN:0736-5748    

DOI:10.1016/0736-5748(90)90006-N

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractPost‐translational modifications of chromatin‐bound proteins play an important role in the regulation of eukaryotic gene expression. Processes such as acetylation, methylation, phosphorylation and ADP‐ribosylation may alter the interaction of these proteins with DNA and consequently affect chromatin conformation and the binding of enzymes and other molecules involved in the regulation of gene expression.In the present study the process of ADP‐ribosylation of chromosomal proteins (histone and nonhistone proteins) in some rat brain regions during postnatal development was investigated; also the effect of epidermal growth factor (EGF) on this process in fetal brain slices was studied.It has been found that the process of ADP‐ribosylation of total histones extracted from rat cerebral cortex and cerebellum at 1, 10 and 30 days of age, increases from 1 to 10 days of age (i.e. the period of maximal cell proliferation) and decreases thereafter, while the process of ADP‐ribosylation of nonhistone proteins (NHPs) sharply decreases during the same developmental period.The addition of EGF to fetal brain slices causes a significant increase of ADP‐ribosylation of total histones (particularly of the histone H1fraction) and also of NHPs and microsomal proteins. This result is in agreement with the effect of EGF as a mitogen factor, previously shown in astroglial cell cultures.

ISSN:0736-5748    

DOI:10.1016/0736-5748(90)90007-O

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractLocalization of dipeptidylpeptidase IV was studied in the spinal cord meninges and peripheral nerve coverings of fetal and postnatal rats. In the same sections, the localization of alkaline phosphatase was monitored.In the prenatal period, dipeptidylpeptidase (DPP) IV activity in the differentiating meninges appeared at the time of cerebrospinal fluid spaces formation (on day 16 in the cervical region and on day 18 in the lumbar region).In adult animals DPP IV was found in cells of those meningeal lamellae which delineated the cerebrospinal fluid spaces (the outer, intermediate and inner lamellae), in the perineurium, in Schwann cells and in some fibroblasts of the bulk of dura mater. It is suggested that DPP IV plays a role in the metabolism of neuropeptides by their interaction with cerebrospinal fluid.Alkaline phosphatase activity was detectable earlier than DPP IV activity. Positivity was first observed in some cells of the meninx primitiva and, later on, in the ectomeninx and also in the differentiating endomeninx where it disappeared postnatally.The developing ectomeninx exhibited activities of both enzymes. Alkaline phosphatase occupied its external layers, while DPP IV was localized in its inner layers. This enzymatic heterogeneity of the ectomeningeal layers suggests that the ectomeninx gives rise not only to dura mater (which in adult animals exhibits alkaline phosphatase activity) but also to the outer arachnoid layer (positive for DPP IV in adult rats).

ISSN:0736-5748    

DOI:10.1016/0736-5748(90)90008-P

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractCharacterizing the last phases of embryonic avian brain development are increased brain activity and increased absorption of shell calcium. The calcium‐binding protein, calmodulin, regulates many activities of calcium. In neural tissue, calmodulin modulates neural transmission, and is required for the phosphorylation of synaptosomal proteins. Therefore, the objective was to compare levels of brain calcium and calmodulin in the Japanese quail. Brain extracts from embryonic days 11, 15, hatch, and 5 days post‐hatch (n= 7/group) were analysed for calcium, protein and calmodulin. Despite increases in protein between embryonic (x―= 0.126 and 0.145 mg/mg wet wt) and hatched groups (x―= 0.183 and 0.221 mg), no significant increases in calmodulin were observed (237–279 ng/mg protein). Calcium levels in the brain were U‐shaped with low levels at embryonic day 1 (341 μg/mg wet wt) and post‐hatch day 5 (315 μg/mg wet wt) with higher levels on embryonic day 15 (425 μg/mg wet wt) and at hatch (433 μg/mg wet wt). Calmodulin levels do not show a developmental pattern similar to calcium and protein levels or with reports of brain activity.

ISSN:0736-5748    

DOI:10.1016/0736-5748(90)90009-Q

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe aim of the present study was to elucidate whether the endothelial cells, besides providing the structural basis for the blood‐brain barrier (M. Bradbury,Concept for a Blood‐Brain Barrier, 1979; F. Joó,Nature321, 197–198, 1986) can also produce laminin and, via its release, regulate the growth of neuntes of neurons originating from the central nervous system (CNS). In immunohistochemical investigations, the presence of laminin‐like immunoreactivity could be detected in the cytoplasm and on the surface of endothelial cells derived from brain microvessels. Further, the neurite‐promoting effect of laminin on CNS neurons was also noted in a co‐culture system designed especially for conditioning nerve cell cultures continuously with materials released from the cerebral endothelial cells. It is suggested that the endothelial cells may be involved via their laminin secretion in the regulation of axonal growth and guidance in the CNS.

ISSN:0736-5748    

DOI:10.1016/0736-5748(90)90010-Y

出版商:Wiley    

年代:2003

数据来源: WILEY