摘要:

AbstractThe cytotoxic effects ofN‐ethyl‐N‐nitrosourea (ENU) and the potential for recovery from this damage in the developing rat spinal cord was investigated. Emphasis was placed on determining the severity and location of initial cell necrosis and the subsequent reorganizational changes in the damaged tissues. Pregnant rats were injected i.v. with a single dose of ENU (60 mg/kg) on one of days 12–16 of gestation. At 6, 12, 24 and 48 h post‐injection one pregnant rat from each gestational stage was anesthetized, the embryos were removed, fixed and processed for embedding in paraplast or epon‐araldite. Transverse sections from embryos killed at 6 h revealed extensive necrosis throughout the neuroepithelium in accordance with the temporal‐spatial patterns of neurogenesis. At this dose level the post‐mitotic neuroblasts appeared unaffected. Regeneration of the damaged neural tissue as defined by the restoration of the neuroepithelial cell layer and removal of necrotic debris proceeded quickly, and within 48 h a near‐normal cytoarchitecture was observed. The embryonic age at time of ENU injection had no apparent influence on the actual sequence of tissue repair in the spinal cords although the events were slightly delayed within embryos exposed to ENU on days 12 or 13 of gestation.

ISSN:0736-5748    

DOI:10.1016/0736-5748(84)90054-6

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe developmental patterns of three ganglioside glycosyltransferases were determined in the embryonic rat cerebral hemispheres from day 14 of gestation until birth. Considering the values of day 14 of gestation as 100%, the activity per μg of DNA at birth of the CMP‐NeuAc:GM3 sialosyltransferase decreased to 40%, that of UDP‐GalNAc:GM3N‐acetylgalactosaminyltransferase increased to 230% and that of UDP‐Gal:GM2 galactosyltransferase showed minor variations. The changes in the activities of these enzymes correlated with the changes occurring in this embryonic period in the complexity of the oligosaccharide chain of gangliosides which result in a relative increase of gangliosides having the gangliotetraosyl backbone.

ISSN:0736-5748    

DOI:10.1016/0736-5748(84)90055-8

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe myelin content of the anterior commissure in female carriers of the jimpy gene (X+Xjp) and in normal male mice (X+Y) was determined using morphometric methods. Young jimpy heterozygotes (X+Xjp), 42–43 days old, exhibit a 33% reduction in myelin area fraction in the anterior limb of the anterior commissure. At older ages (⩾ 145 days), the myelin area fraction in the heterozygotes is not different from control values in the anterior limb and the posterior limb of the anterior commissure. In comparing the young and old jimpy heterozygotes, a significant increase occurs in the myelin area fraction after 43 days of age.The increase in the myelin area fraction in the anterior limb of the heterozygote may occur in response to the myelin deficit caused by the jimpy mutation and may involve the formation of new myelin. A further study of cellular interactions in the central nervous system of the jimpy heterozygote may provide new insight into mechanisms of myelin formation and remyelination.

ISSN:0736-5748    

DOI:10.1016/0736-5748(84)90056-X

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

Abstract[3H]5‐HT specific binding sites have been characterized in the rat spinal cord. Experimental conditions allowed us to study a single class of sites possibly related to the postsynaptic receptor for 5‐HT. Binding constants (KDandBmax) are described for adult and developing animals. No substantial changes in affinity were observed but the number of receptors increased from birth up to day 20 postnatally, stabilizing thereafter. The developmental pattern of a presynaptic marker, tryptophan‐5‐hydroxylase, was similar to that of binding sites.

ISSN:0736-5748    

DOI:10.1016/0736-5748(84)90057-1

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractChronic experimental hyperphenylalaninemia in suckling rats causes a depletion of amino acids in the blood and in the brain, and an accumulation of amino acids in the peripheral tissues. The amino acid depletion in the blood is greater than that in the brain. The amino acid accumulating potency of all body tissues is increased by the excess of phenylalanine, most pronounced in the gut, least pronounced in the brain. All body tissues compete for the amino acids circulating in the blood. This competition is enhanced in hyperphenylalaninemia. The brain is at a disadvantage in the competition of the various body tissues for the amino acids available from the common pool. Brain tissue is increasingly depleted of amino acids as the accumulation of amino acids in the peripheral tissues is stimulated in hyperphenylalaninemia.The depletion of amino acids in the blood and the simultaneous rise of the free amino acid concentrations in the various developing tissues indicates tissue‐specific shifts in the balance between protein synthesis and protein degradation in hyperphenylalaninemia.There is no indication that amino acid competition at the blood‐brain barrier contributes importantly to the depletion of amino acids in the brain tissue in hyperphenylalaninemic rats. Instead, brain amino acid pools underin vivosteady‐state conditions appear to be primarily regulated by the rate of amino acid utilization by the peripheral tissues.

ISSN:0736-5748    

DOI:10.1016/0736-5748(84)90058-3

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe developmental pattern of glutamine synthetase (GS) in rat brain has been studied with respect to that of the cells involved in the synthesis of the enzyme. GS activity is very low until day 13 after birth, rises sharply between days 13 and 15, and slowly thereafter. In contrast, more than half of the total number of protoplasmic astrocytes—the cells involved in synthesis of GS—are formed by day 12, following which the rate of proliferation declines considerably. GS is precociously inducible by cortisol in purified protoplasmic astrocytes, in organ cultures of 6–13 day rat brain and in the brains of cortisoladministered 12 day rats. These results and the temporal coincidence of the period of increase of GS with the onset of the function of adrenal cortex suggest that GS activity in the developing rat brain is under steroidal control.

ISSN:0736-5748    

DOI:10.1016/0736-5748(84)90059-5

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractAdult rats whose dopamine receptor number was reduced via prenatal haloperidol exposure were less resistant than controls to pentobarbital narcosis. This altered resistance was functional (CNS) and not metabolic, as shown by pentobarbital brain levels. These results are consistent with our previous experiments, indicating that changes in the number of dopamine receptors may underlie relative susceptibility to barbiturates.

ISSN:0736-5748    

DOI:10.1016/0736-5748(84)90060-1

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractA fluorescence microscopical study has been performed in the pre‐ and postnatal development of the sympathetic superior cervical ganglion of Sprague‐Dawley rat. Ganglia from 10.5‐ to 21.5‐day‐old embryos and newborn to 90‐day‐old postnatal rats were freeze‐dried and the catecholamine‐containing cells were demonstrated by formaldehyde‐induced fluorescence.The first catecholamine‐containing cells appeared on day 11.5 of gestation. The ganglia of 11.5‐ to 12.5‐day‐old embryos contained a continuous range of cells showing weak to bright fluorescence intensities. In the ganglia of 13.5‐ to 14.5‐day‐old embryos few solitary cells or small groups of cells showing bright fluorescence were discernible among weakly fluorescent developing principal nerve cells. The cell numbers of both types markedly increased during the prenatal period while the mean diameter of the brightly fluorescent cells significantly decreased. In the late prenatal ganglia clusters were observed in which a large brightly fluorescent cell was surrounded by other intensely fluorescent cells of various sizes.There were about 300 small intensely fluorescent (SIF) cells in the ganglia of newborn rats. This number decreased by about 50% during postnatal week 1 and again increased during postnatal week 4 reaching the adult value of about 500 cells/ganglion. During the postnatal development the SIF cells formed clusters, the largest of which contained several hundred cells.Occurrence of large intensely fluorescent cells during a limited period suggests that this cell type represents a transitional form. It is possible that in the rat the primitive sympathetic cells continue their development along two lines: some cells remain weakly fluorescent and give rise to the principal nerve cells, and others accumulate catecholamine(s) and are transformed, possibly after mitotic divisions, into smaller brightly fluorescent cells which mature into SIF cells late postnatally.

ISSN:0736-5748    

DOI:10.1016/0736-5748(84)90061-3

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractSex differences in the growth and dendritic development of neurons in the sexually dimorphic nucleus of the preoptic area were examined with quantitative Golgi techniques during early postnatal life in rats. Neuronal size and dendritic extent were found to increase more in males than in females during the first 10 postnatal days, while the numbers of primary and terminal dendrites were similar in the two sexes. The onset of greater dendritic growth in males occurs just after the volume of the nucleus begins to exhibit sexual dimorphism, between 24 and 26 days after fertilization. Growth of dendrites in this region may be related to the presence of sex hormones during the critical period of sexual brain differentiation.

ISSN:0736-5748    

DOI:10.1016/0736-5748(84)90062-5

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe distribution of immunoreactivity to basement membrane components in cultures of rat skeletal myotubes was compared to acetylcholine receptor distribution by fluorescence microscopy. Laminin occurred in patches on the myotube surface, and most laminin patches coincided or overlapped with acetylcholine receptor aggregates. Almost all receptor aggregates coincided with laminin patches. Most of the heparan sulfate proteoglycan and fibronectin was associated with non‐muscle cells, but some patches coincided with receptor aggregates on myotubes. In cultures treated withl‐ascorbate, collagen types IV and V covered much of the myotube surface and receptor aggregates often coincided with intense collagen patches. When receptor aggregation was induced by treatment of cultures with soluble neural factors, the newly formed receptor aggregates coincided with laminin patches.The results suggest that each of the basement membrane components studied has a distinct distribution pattern in primary rat muscle cell cultures. The striking association of laminin immunoreactivity with receptor aggregates, together with the enhancement of receptor aggregation by laminin reported previously (Vogelet al., J. Neurosci.3, 1058–1068, 1983) suggests that laminin could have a role in the organization of acetylcholine receptors on developing muscle fibers.

ISSN:0736-5748    

DOI:10.1016/0736-5748(84)90063-7

出版商:Wiley    

年代:2003

数据来源: WILEY