摘要:

AbstractDNA‐polymerases α and β were studied in neuron and glial cells of mouse during developing and aging brain. Maximum activity of α‐enzyme was found to be prenatal, though a very low but significant level could be detected in aging brain. Furthermore, this pattern was found to be dependent upon cell types that shift in peak activity just before birth in glial cells in contrast to neurons. DNA‐polymerase‐β remained high throughout the period studied though a second peak of activity was also observzd at day 30 in both cell types, suggesting a possible role in DNA‐replication in addition to DNA‐repair. It was found that β‐enzyme from glial cells behaves differently than the same e

ISSN:0360-4012    

DOI:10.1002/jnr.490090102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe early postnatal development of somesthetic inputs into the pericruciate cortex of kittens was studied by intra‐ and extracellular recording and cortical surface evoked potential monitoring. Equipotent bilateral influences from the forepaw and hindpaw skin to cortical neurons during the initial postnatal weeks in kittens were revealed. During the fourth week, the functional dominance of contralateral inputs into the motor area becomes evident. Considerable reduction of the latency of postsynaptic and evoked responses only to the contralateral stimulation and the enhancement of their stability and intensity occu

ISSN:0360-4012    

DOI:10.1002/jnr.490090103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractBinding sites for [3H]spiperone were detected on membranes from primary glial cultures from neonatal rat cortex and striatum and from the C6 glioma cells. [3H]Spiperone binding was displacable by d‐butaclamol. However, competition studies suggest that [3H]spiperone binding to primary glial cultures was mainly to serotonergic sites, and binding to the C6 glioma was alpha‐adrenergic. No specific binding was detected to membranes from B104 neuroblastoma cells. Although [3H]spiperone binding to glial sites on whole striatum under generally used conditions is small (about 10%), the striatal glial hyperactivity that is often associated with neuronal degeneration could lead to an overestimation of presumed neuronal binding sites for dopaminergic liga

ISSN:0360-4012    

DOI:10.1002/jnr.490090104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractMuscarinic binding sites were measured using the radioligand [3H]quinuclidinyl benzilate (QNB) in the retina and tectum of 11‐day‐old chick embryos, after intracerebral administration of 0.02 μg of corticosterone at 8 days of incubation. This age was chosen because the hormone preferentially accumulates in retinas at 8 days of development. Hormone treatment significantly affected the affinity of3H‐QNB‐binding sites in retinas and slightly affected the affinity in treated tecta, whereas the number of binding sites remained unchanged. The specific binding was determined with either atropine or unlabeled QNB. Scatchard plot analysis of specific3H‐QNB binding revealed the presence of nonsaturable binding at high 3H‐QNB concentrations (6‐11 nM) in the treated retinas, but not in controls. It can be concluded from these data that the hormone has a primary effect on retinal cells during early growth in the chick embryo. The possibility that the hormone delays maturation of specific populations of retinal cells is considered in

ISSN:0360-4012    

DOI:10.1002/jnr.490090105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractRats were trained in an instrumental task for 2 × 25 min during 1 day and 4 days and compared with active controls with respect to membrane‐bound proteins solubilized by chloral hydrate and fractionated on polyacrylamide gels. Then 30‐μg samples of the hippocampus and entorhinal cortex were labeled by14C‐and3H‐valine. The distribution of the stained electrophoretogram was recorded by microdensitometry. The results show that the 1‐day training induced an increased synthesis of a membrane protein fraction of 50,000 mol wt already present in the brain membrane proteins of active controls. Training for 4 days resulted in an overall stimulation of the hippocampal membrane protein fractions, especially in the higher‐molecular‐weight range. The entorhinal cortex showed two stimulated membrane protein fractions, 50,000 and 120,000 mol wt. Together with previous studies, this study makes it probable that training to establish a new behavior induces a modulation of both soluble and membrane‐bound protein patterns in the hippocampus and the entorhinal cortex with a time phase retardati

ISSN:0360-4012    

DOI:10.1002/jnr.490090106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe uptake and metabolism of (U‐14C) L‐omithine by several cellular preparations was examined and compared to corresponding data for glutamine and α‐ketoglutarate. Five fractions were obtained from the cerebellum of 10‐to 14‐day‐old mice; two fractions were enriched in astrocyte cell bodies, whereas one was comprised primarily of granule cell bodies, and another was enriched in nerve terminals. Metabolic studies were also conducted on two synaptosomal preparations prepared from rat cerebral tissue.The uptake of ornithine by the cerebellar fractions was mediated by one or two saturable transport systems with apparent Kmvalues between 50 and 200 μM. Uptake inhibition experiments indicated that ornithine is transported primarily, if not exclusively, by the basic amino acid carrier(s), and that glutamine is transported in part by this carrier. Ornithine was metabolized to proline, glutamate, and to a lesser extent aspartate, glutamine and GABA. Under the conditions of our experiments, the cell bodies metabolized ornithine somewhat more readily than did the nerve terminal enriched fraction obtained from the mouse cerebellum. Our data indicate that the conversion of ornithine to GABA occurs predominantly, if not exclusively, via the pathway involving glutamate rather than putrescine. In comparison to data for glutamine and α‐ketoglutarate, the metabolism of omithine to glutamate was slow.Although the results of our study are consistent with the hypothesis that ornithine serves as a metabolic precursor of the neurotransmitter pools of glutamate and GABA, our data do not support a major role for omithine in this capacity. Based on a comparison of the availability of omithine, glutamine and α‐ketoglutarate, and the rates at which they are each transported into synaptosomes and metabolized therein to glutamate and GABA, our data suggest that glutamine and α‐ketoglutarate are used more extensively to replenish t

ISSN:0360-4012    

DOI:10.1002/jnr.490090107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe retinal uptake and metabolism of cysteine, a precursor for taurine biosynthesis, were analysed using the bull frog. The [14C] cysteine uptake into isolated retina had some specific properties: It was rather temperature independent, required Na ions, was inhibited by ouabain but not by dinitrophenol, and exhibited saturation kinetics composed of two components. When retinal homogenate was incubated with 12‐30 μM of L‐[U‐14C]cysteine, the accumulation of labeled alanine, cysteine sulfinic acid (CSA), cysteic acid (CA), hypotaurine, and taurine was detected. The metabolic conversions of [14C] cysteine to labeled alanine, hypotaurine, and taurine were linear over 90 minutes. Prolonged light adaptation (3 weeks) induced a significant reduction in the formation of labeled CA, CSA, hypotaurine, and taurine from [14C] cysteine. On the other hand, it was found that in dark‐adapted retinae, the formation of labeled taurine from [14C] cysteine increased significantly in spite of the reduction in the formation of labeled CA. These results indicate that biosynthetic pathways exist for taurine from cysteine in frog retina, and that these metabolic pathways are involved in the regulation of retinal taurine content under continuous visual ad

ISSN:0360-4012    

DOI:10.1002/jnr.490090108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractIn vitro assay of the adenylate cyclase of NB41A neuroblastoma cells in the presence of increasing concentrations of MnCI2suggested that the enzyme is modulated by both high‐ and low‐affinity sites for manganese. MnCI2in a concentration of 1 μM significantly stimulated adenylate cyclase activity, but increasing the concentration of manganese to 3 μM or 10 μM had no further effect. Raising MnCI2to 0.1 or 1 mM, however, further stimulated enzyme activity. In addition to differences in affinity for manganese, the two classes of binding sites may be distinguished by differences in their interaction with other agents that affect adenylate cyclase activity. Millimolar manganese and magnesium appeared to compete for a common site on the enzyme and the effect of manganese in this range and the effect of guanyl nucleotide were synergistic. In contrast, the stimulation of activity by micromolar manganese appeared to be additive to the effects of either increasing magnesium or the addition of guanyl nucleotide to the assay media. Comparison of the substrate dependency of the reaction measured in the presence and absence of manganese suggests that the stimulation of adenylate cyclase activity involves increases in both the apparent Vmax of the reaction and the affinity for ATP. The results raise the possibility that the interaction of Mn2+may play a role in the modulation of adenylate cyclase i

ISSN:0360-4012    

DOI:10.1002/jnr.490090109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe precise role of the nerve growth factor protein (NGF) during the growth and development of the human nervous system is not determined. Although it appears to influence a number of neural functions, its mechanism of action is poorly understood. A number of researchers have proposed that NGF may be involved in several pathological conditions including cancer. It has been shown that NGF is secreted'by certain sarcoma (23), neuroblastoma (113), and glioma (7,102,136) cell lines and can bind to neuroblastoma and metastatic melanoma cell lines (42). Neuroblastoma (136,181) and pheochromocytoma (165) cells in vitro can be induced by NGF to differentiate toward a morphologically “more benign” state and appropriate NGF treatment of rats can reduce the number of chemically induced gliomas and neurinomas (174, 178). NGF can also reduce the growth of intracerebrally inoculated anaplastic glioma cells (172). Anti‐NGF treatment of rats (178) and mice (179) can alter the tumor distribution observed following ethylnitrosourea or benzo(a)pyrene treatment (10). In humans, it has been reported that serum levels of NGF are usually elevated in persons “at risk” for neurofibromatosis (156). The precise nature of the NGF role is not known in these instances. Further understanding of the action of NGF could be of clinical i

ISSN:0360-4012    

DOI:10.1002/jnr.490090110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

ISSN:0360-4012    

DOI:10.1002/jnr.490090111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY