ISSN:0959-4965    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

SEVERAL topics in contemporary neuroscience are treated in historical perspective. These include the localizationist-connectionist model of brain function and its influence on experimental neuroscience and clinical management of brain damaged persons; brain plasticity; the accumulating evidence for non-synaptic diffusion neurotransmission (NDN) as a major mechanism of information transmission in the brain; and the co-existence of plasticity and localization as well as of synaptic and non-synaptic mechanisms. The status of theory in the neurosciences is examined.

ISSN:0959-4965    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

THE quinoxaline NBQX (2,3-dihydroxy-6-nitro-7-sulfamoylbenzo (F) quinoxaline) is a potent non-NMDA receptor antagonist, which appears to be relatively free of antagonistic action at the glycine binding site of the NMDA receptor. However, we report here that at 50 μM, NBQX significantly attenuated the inhibitory currents induced by the exogenous application of 100 μM glycine as observed using whole-cell recordings from ganglion cells in a slice preparation of the tiger salamander retina. In contrast, NBQX had no effect on GABA-mediated inhibition. This observation suggests that care should be taken when attributing the action of NBQX solely to its antagonism of non-NMDA glutamate receptors, particularly when higher concentrations are used.

ISSN:0959-4965    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

RESPIRATORY sensation was studied in European low-landers at an altitude of 4382 m after a helicopter flight in order to investigate the acute and prolonged effects of high altitude hypoxia. At rest the ability to detect four inspiratory resistive loads can be used to create a sensitivity index P(A) without taking the response bias (B) into account, based on the Sensory Decision Theory. In 6 subjects respiratory sensitivity increased significantly under acute and prolonged hypoxia after 3–4 days of high altitude exposure. The respiratory sensitivity increased with the hyperventilation and mouth pressure increase induced by hypoxia. Hypoxia might also have feedback effects on the peripheral and central nervous integration of the respiratory sensation stimuli. One subject suffering from acute mountain sickness showed a severe decrease in his sensitivity index P(A) under hypoxic conditions, while the parameters of his cardiorespiratory function evolved In the same classical way as the other subjects who adapted well to altitude hypoxia. The increase in respiratory sensation may be the first necessary step in altitude acclimatization and might serve as a useful marker of this adaptation.

ISSN:0959-4965    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

INTRACELLULAR recordings of activity in response to acoustic stimuli were obtained from units of the dentate nucleus of conscious cats. Twelve units with short latency responses to 70 dB clicks or hisses were injected intracellularly with biocytin and identified morphologically. The identified cells were small, relatively aspinous, multipolar cells with diameters <20 μm. Most had beaded dendritic varicosities. Six were located centrally, and five were on the border of the nucleus. One appeared to be an axonal process. The results provide direct evidence that small cells of the dentate nucleus can respond with short latencies of 4–14 ms to acoustic stimuli. We suggest that these cells are part of a primary ascending auditory transmission pathway between cochlear nuclei and the motor cortex.

ISSN:0959-4965    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

NITRIC oxide level in the mouse brain was estimated by determination of nitrite and nitrate using an automated flow injection analyser for NO***. Different experimental conditions were examined to determine which produced reproducible results. After pretreatment of tissue specimens by the ZnSO4-NaOH method for deproteinization, reproducible and constant values were obtained. The values were more accurate immediately after sectioning without freezing than after 24 h with freezing. Two sacrifice methods, decapitation and microwave irradiation of the head, were investigated, but there was no significant difference between the two. No substances in the mouse brain exerted a positive or negative influence on the results. These results show that our method is indeed applicable to the brain tissue.

ISSN:0959-4965    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

HYPERGLYCAEMIA impairs recovery from transient cerebral ischaemia: the importance of tissue acidification for this phenomenon has not been clarified in detail. We investigated this issue in a less complexin vitropreparation of isolated rat dorsal spinal roots exposed for 30 min to hyperglycaemic hypoxia. Peak height of compound action potentials recovered minimally in 5 mM bicarbonate. However, recovery was greatly improved by addition of the weak base trimethylamine during re-oxygenation. Addition of the weak acid propionate had no such effect. Cytoplasmic alkalinization improved recovery in a brief time window only: application of trimethylamine after 15 min of re-oxygenation was without beneficial effect. These data emphasize the importance of cytoplasmic acidification for neurophysiological recovery from hyper-glycaemic hypoxia during the initial period of re-oxygenation.

ISSN:0959-4965    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

THE syntrophins are a multigene family of proteins which bind C-terminal domains of dystrophin, utrophin and homologs thereof. We report here that antibodies specific for one isoform, β2-syntrophin, labeled only the neuro-muscular junction (NMJ) in rat skeletal muscle. Anti-α1-syntrophin antibodies gave strong labeling of the sarcolemma and NMJ in normal rat and mouse muscle, and similar but much weaker labeling in dystrophin-minus mdx muscle. β2-Syntrophin therefore appears to be specific to the NMJ in normal muscle, as is utrophin, and may be involved in acetylcholine receptor clustering. α1-Syntrophin appears to be associated mainly with dystrophin, as expected, but a small portion must be associated with another protein, possibly homologs of the electric tissue 87K protein.

ISSN:0959-4965    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

THE mRNA levels of acetylcholine receptor (AChR) and myogenic factors were followed during embryonic development ofTorpedoskeletal muscle and its homologue, the electric organ. A different developmental pattern of AChR gene expression was found in these two tissues: a slight decrease in the muscle, and a marked increase, concomitant with synapse formation, in the electric organ. However, the developmental pattern of MyoD and MRF4 mRNA levels was similar in both tissues, with no significant changes during development. This is in contrast with the sharp increase in the expression of AChR in the electric organ and may suggest that the burst in the expression of AChR during the differentiation of myotubes into electrocytes is not regulated by changes in the myogenic factor mRNA levels.

ISSN:0959-4965    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

THE serum-free mouse embryo (SFME) cell line, derived from 16-day-old mouse embryos in medium in which serum was replaced by growth factors and other supplements, has been cultured for more than 200 generations. SFME cells are nontumorigenic, lack gross chromosomal abnormalities, and display characteristics of CNS progenitor cells. SFME cells show reversible induction of the astrocyte-specific marker glial fibrillary acidic protein when cultured in the presence of TGF-β or serum. In order to determine if SFME cells exhibit further characteristics of CNS progenitor cells we investigated the expression of the gene encoding nestin, an intermediate filament protein expressed by neuroepithelial stem cells of the CNS. SFME cells express nestin in serum-free medium, and nestin expression is reversibly down-regulated by TGF-β or serum. These results demonstrate that nestin expression is regulated by factors present in serum and support the hypothesis that SFME cells represent a CNS progenitor cell.

ISSN:0959-4965    

出版商:OVID    

年代:1994

数据来源: OVID