摘要:

AbstractResults of earlier studies clearly indicated that, during development, a number of enzymes are sequentially expressed in the brain endothelial cells correlating in time with the maturation of brain tissue. More recent data suggested that differentiation of endothelium in the intraparenchymal cerebral microvessels into one with blood‐brain barrier characteristics seems to be induced by astrocytes at a specific time of embryonic development. Details of the above‐mentioned and other important aspects of the development of the blood‐brain barrier will be discussed in the present mini review.

ISSN:0736-5748    

DOI:10.1016/0736-5748(87)90013-X

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThis study concerns the ontogeny and the cellular localization ofl‐aspartate andl‐glutamate binding sites in normal and ‘nervous’ mutant mouse cerebellar membranes. The binding kinetics revealed forl‐aspartate a single binding system (Kd= 750nM) and forl‐glutamate also a single binding component of higher affinity (Kd= 344nM). The pharmacological study, using various amino acid analogues, revealed a differential specificity for the binding sites of the two amino acids.The developmental study showed that the binding sites of both amino acids appear mainly during the second and third week of life, a period when parallel and climbing fiber synaptogenesis occurs, but they follow a slightly different developmental pattern. The study using ‘nervous’, mutant mouse cerebellum showed an age‐dependent decrease ofl‐aspartate andl‐glutamate binding, which coincides in time with the Purkinje cell degeneration in this mutant, indicating a cellular localization of these binding sites on the Purkinje cell membranes. These results suggest thatl‐aspartate andl‐glutamate binding sites may be respectively associated with the postsynaptic target of climbing and parallel fibers on the Purkinje cell dendrites. However, the decrease of specific binding in ‘nervous’ mutant mouse cerebellum was about 50% forl‐aspartate and 60% forl‐glutamate, implying that a significant number ofl‐aspartate andl‐glutamate binding sites are located on cerebellar elements other than the Purkinje cell membranes.

ISSN:0736-5748    

DOI:10.1016/0736-5748(87)90014-1

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe current studies were undertaken to determine whether males or neonatally testosterone‐treated rats of either gender have elevated endogenous levels of NGF in the SCG and one of its targets, the pineal gland. The ages studied were 5 days postnatal, which is at the peak of normal neuron death in the SCG but before a significant gender difference is present; 15 days, when normal neuron death is largely complete and males have more SCG neurons than females; and 30 days, when target innervation has matured.At 5 days, while neuron death is occurring, but before there is a significant gender difference in neuron number in the SCG, pineal glands and SCGs of males had higher NGF content than those of females. The increased NGF in the ganglia of males at the time that these neurons are undergoing neuron death may play a role in the development of the sex difference in SCG neuron numbers. At 15 days, females had more NGF in their pineal glands and SCGs than did males, even though males have significantly more SCG neurons at this age than do females. This gender difference in the developmental course of NGF content could promote the survival of different populations of neurons in males and females. By 30 days, SCG and pineal NGF content of males was almost twice that of females. This is consistent with the presence of more neurons in the SCGs of males at this age.Both the pineal gland and the SCG showed a loss of approximately 80% content of NGF during the first postnatal month. In males, this loss occurred between postnatal days 5 and 15, while in females, the drop in NGF content occurred between postnatal days 15 and 30. Treatment with testosterone from birth reduced NGF content in the SCGs of both males and females at 5 days of age. The depression of NGF levels by testosterone treatment may reflect a further acceleration of the developmental fall of NGC levels.

ISSN:0736-5748    

DOI:10.1016/0736-5748(87)90015-3

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractZinc and iron levels were studied in mice with early (pre/neonatal) exposure to phenobarbital, as the levels of these trace metals are known to be correlated with specific behaviors shown in our previous and present experiment to be affected by early phenobarbital administration. Mice were exposed to phenobarbital prenatally or neonatally. At adulthood they showed marked reduction from control in all parameters of eight‐arm maze performance (P<0.001). Since zinc is known to be correlated with this behavior, it was subsequently studied in barbiturate exposed animals. The differences between barbiturate exposed and control offspring for zinc levels in plasma, brain and hippocampus did not reach statistical significance. Our previous studies have shown that the number of dopamine receptors and the resulting apomorphine‐induced climbing behavior is altered after early exposure to phenobarbital. The effect of iron level on dopamine receptors is now well established. Subsequently, a group of mice were tested for iron levels in their brain and liver. No significant differences were found.It is suggested that deficits in the hippocampal behaviors, mainly eight‐arm maze, after early exposure to phenobarbital are not related to changes in zinc levels. Similarly, early phenobarbital‐induced alternation in dopamine receptors and the resulting dopaminergic behaviors are not related to changes in iron levels.

ISSN:0736-5748    

DOI:10.1016/0736-5748(87)90016-5

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe ganglioside metabolism of the Snell dwarf cerebrum was examined on postnatal days 15 and 20, by monitoring the rate of incorporation of radioactivity into each ganglioside species from tritiatedN‐acetyl‐d‐mannosamine. It was found that the turnover rate of the GM3ganglioside was reduced throughout the entire period of development, resulting in retardation of A pathway metabolism which becomes abundant during late cerebral development. In addition, the turnover rate of the GM4species, which is considered related to myelin formation, was also found to be reduced throughout the entire period of cerebral development.

ISSN:0736-5748    

DOI:10.1016/0736-5748(87)90017-7

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractScanning electron microscopy was used to study the surface morphology of neural retina cells from fetal rats. Dissociated cells were plated on polyornithine and examined after 1.5–3.0 hrin vitro. A quantitative analysis of the proportion of cells with and without processes was made and the former were classified according to the length and number of their processes.Treatment withp‐bromophenacyl bromide (BPB), a selective inhibitor of phospholipase A2(PLA2), induced significant changes on the early surface activity of retinal cells. An inhibitory effect on cell process formation was observed in monolayers grown for 2 hr in the presence of BPB: process formation was also inhibited when high concentrations (10−6M or more) were applied as a 30 min pulse, whereas a similar pulse of a lower concentration (10−7M) stimulated the appearance of cells with short processes. These observations suggest that PLA2or some other BPB‐reactive substance is involved in the extension of neural cell processes.

ISSN:0736-5748    

DOI:10.1016/0736-5748(87)90018-9

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe cellular localization of acetylcholinesterase (ACHE) was investigated at the electron microscope (E.M.) in a neuroblastoma and neuroblastoma × glioma hybrid line, which differ for their ability to establish synaptic contacts. Only cells of the latter line show association of AChE to the plasmamembrane, while in the former the activity is mainly intracellular. Sucrose sedimentation analysis of AChE molecular forms has shown no significant differences in the distribution of the two forms, G2and G4, between the two cell lines. On the contrary a marked difference is observed in the ability of the cell to release the enzyme in the culture medium. In fact the cells lacking AChE on their surface release in the medium a much higher proportion of their enzyme, than the cells showing AChE association to their plasmamembrane. The possible role of two alternative fates for AChE, secretion or membrane insertion, in determining the observed differences of enzyme localization is discussed.

ISSN:0736-5748    

DOI:10.1016/0736-5748(87)90019-0

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractNeural control of creatine kinase (CK, adenosine 5′‐triphosphate creatine phosphotransferase: EC 2.7.3.2) was investigated by measuring enzymatic activity and isoenzymatic representation of CK in extensor digitorum longus (EDL) muscles of adult rats during and after regeneration. Experimental models were ischemized EDLs, reversibly or permanently denervated. Results showed that, during regeneration, CK in muscle fibers was likewise modified in both reversibly and permanently denervated EDLs. After regeneration a clear dichotomy was observed between the regenerated EDLs which were innervated and recovering CK activity, and those in which innervation was prevented and were rapidly losing activity. Further to investigate the neural influence on CK turnover, merely denervated agematched EDLs were analysed and found to lose CK activity rapidly. The major conclusions are that during regeneration muscle CK is autonomously expressed, but following regeneration neural influence becomes an absolute requirement for stabilization and amplification of CK.

ISSN:0736-5748    

DOI:10.1016/0736-5748(87)90020-7

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe present experiments were designed to evaluate the effectiveness of forskolin on cAMP production, growth and morphology on cell cultures of glia, endothelium and smooth muscle derived from brain microvessels.Forskolin significantly increased formation of cAMP and decreased incorporation of thymidine in all three cell types. The thymidine incorporation was reduced dose‐dependently with maximal growth inhibition at 100 μM forskolin. A 1 hr preincubation with forskolin abolished thymidine incorporation by cells grown in fetal calf serum (FCS)‐containing media over the following 24 hr.In cerebromicrovascular endothelium and smooth muscle, forskolin caused drastic and immediate changes of cell morphology and F‐actin composition that were reversible. In glial cells, morphological changes were visible only after exposure to forskolin for more than 24 hr. These changes were accompanied by increased staining with antibodies against glial fibrillary acidic protein (GFAP).These findings support the contention of cAMP involvement in growth regulation of these cells and indicate that forskolin might be used as a tool to induce growth arrest and possible differentiation in cell cultures from mammalian brain.

ISSN:0736-5748    

DOI:10.1016/0736-5748(87)90021-9

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe effects of age and stimulation frequency (0.2/sec, 1.0/sec, 2.0/sec, or 4.0/sec) on flashevoked potentials (FEPs) were investigated in awake, unsedated, unrestrained rats. Animals were tested daily from postnatal day (PND) 8 to PND 20, and every 3 or 4 days thereafter until PND 41. On PND 9, a single negative wave (N1a) was observed following 0.2/sec flash presentation. Animals tested on PND 10 exhibited a positive wave (P2) following the return of peak N1a to baseline. On PND 13 another negative wave (N1) appeared on the leading shoulder of peak N1a. Peak N1 became the dominant negative wave on PND 14. Peak N1a merged into N1 and had disappeared by PND 19. Peak N3 was first observed as a negative shift following peak P2 on PND 15. Peaks N2 and P3 were not observed in the group average waveforms until PND 34. Peak latencies decreased through the fifth postnatal week. Peak amplitudes increased with age until after eye opening (PND 15), but were variable thereafter. No FEPs were observed following higher than 0.2/sec flash presentation until PND 13. Increasing stimulation frequency decreased N1 and P2 peak amplitudes, but had no effect on peak latencies.

ISSN:0736-5748    

DOI:10.1016/0736-5748(87)90022-0

出版商:Wiley    

年代:2003

数据来源: WILEY