ISSN:0959-4965    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

HUMAN brain evolution has resulted in a large increase in cortical folding as a result of which 60% of the cerebral cortical mantle is buried within sulci. Cortical regions within the sulci, and especially in the fundal zones (fundi) at the bottom of sulci, differ from the rest of the cortex in a number of ways with respect to anatomical and histological morphology. Although physiological implications of the fundal morphology have been discussed from time to time, and although scattered evidence hints at a special functional role for fundi, until recently there have been few empirical facts to guide the inquiry into a possibly special physiological function of fundal zones. In this article we review findings yielded by positron emission tomography studies showing that the peaks of changes in neuronal activity are frequently observed in and near fundi. We discuss, but do not accept, the possibility that these findings reflect either the partial volume effect or the course of cerebral blood vessels. Instead, because of a coarse correlation observed between fundal fraction (the proportion of fundally related activity peaks) and the apparent cognitive complexity of the tasks probed, and in light of the anatomical evidence reviewed, we propose the hypothesis that cortical sulcal and fundal regions play a distinctive role in higher cognitive processing.

ISSN:0959-4965    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

THE effects of unilateral cortical devascularization and nerve growth factor treatment on muscarinic cholinoceptors labelled with [3H]QNB were investigated in rat cerebral cortex. The lesion induced a significant ipsilateral decrease in the density (Bmax) but not in the affinity (kD) of [3H]QNB binding sites. Intraventricular infusion of 2.5 S mouse nerve growth factor (NGF) increased the density of binding sites such thatBmaxvalues of lesioned animals treated with NGF were not different from control subjects.

ISSN:0959-4965    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

INTRACELLULAR free Ca2+concentration ([Ca2+]) in spiral ganglion cells (SGC) of guinea pig was measured using the fura-2 fluorescence method. Application of high-K+external solution increased [Ca2+]i[Ca2+]ielevation was suppressed by either depletion of external Ca2+or application of the dihydropyridine Ca2+channel antagonist, nicardipine. One of the putative hair cell afferent nerve neurotransmitters, L-glutamate (Glu), induced [Ca2+]ielevation in SGC. Pharmacological studies suggested that the Glu receptor may be a non-NMDA subtype. Glu-induced response was suppressed by either depletion of external Ca2+or application of nicardipine, indicating that Glu-induced [Ca2+]ielevation is mainly carried out by the voltage-dependent Ca2+channel in SGC.

ISSN:0959-4965    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

DIFFERENT procedures to isolate the K+A-type current (IA) from other membrane currents were tested on the complex inactivating outward K+current generated in hair cells from the peripheral regions of the frog crista ampullaris. Experiments were performed in thin slices of epithelium using the whole-cell configuration of the patch-clamp technique. The conventional conditioning voltage protocol did not allow a satisfactory isolation of IA, due to the presence of other K+currents showing overlapping steady-state inactivation properties. An attempt to block other K+currents using calcium-free saline containing 50 mM TEA also failed to provide a satisfactory isolation of IA, due to contamination by a residual sustained current, probably consisting of a slow delayed outward K+current (IK). Use of the selective A-channel blocker 4-aminopyridine (4-AP) at concentrations < 12 mM was also unsatisfactory because at these concentrations 4-AP produced a voltage-dependent blockade. Conversely, use of 4-AP at concentrations of 15–20 mM allowed a good separation of an uncontaminated IA. These results indicate that IAin hair cells of vestibular epithelium can be isolated most effectively by the 4-AP procedure, provided that sufficiently high concentrations of the A-channel blocker are used.

ISSN:0959-4965    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

MICROTUBULE-associated tau proteins are hyperphosphorylated in brains from patients with Alzheimer's disease compared with normal adult human brain. At least some of the phosphorylated residues are also transiently phosphorylated in juvenile brain, but not in more mature stages. Using the monoclonal anti-tau antibodies TAU-1 and AT8, we found in cultured embryonic chicken and rat neurones a clear differential distribution of immunostaining within growing axons. Tau proteins that are phosphorylated at Ser202 (recognized by AT8) appear to be concentrated in the axonal portion that is close to the cell body and they decrease in proximal-distal direction. In contrast, tau proteins carrying an epitope that contains dephospho-Ser202 (recognized by TAU-1) are enriched in the distal axon and the growth cone. In colchicine-treated, growth-inhibited neurones there was an intense TAU-1 staining of the perikarya, but no longer any staining by AT8.

ISSN:0959-4965    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

WE assessed spatio-temporal expression of tenascin and janusin by immunocytochemistry in testosterone-treated zebra finches and in untreated controls. These cell recognition molecules and components of the extracellular matrix mediate neurone-glia interactions, which are crucial for differentiation of ordered neural structures. We describe boundaries for the spatio-temporal expression of cell recognition molecules that highly correlate with the song motor centres as defined by combined neuroanatomical and ethological studies on song vocalization. The expression of janusin is accelerated by exogenous testosterone.

ISSN:0959-4965    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

ATP evoked an increase in intracellular Ca2+concentration ([Ca]i) in hippocampal neurones in the presence of tetrodotoxin (TTX, 3 μM), hexamethonium (C6,100 μM), D-2-amino-phosphonovalerate (APV, 100 μM), 6-cyano-7-nitro quinoxalline-2,3-dione (CNQX, 30 μM), bicuculline (10 μM) and cadmium (Cd2+, 300 μM). The increase was blocked by suramin (100 μM), a P2-purinoceptor blocker. These results suggest that ATP evokes an increase in [Ca]ithrough P2-purinoceptor. As a result of measuring [Ca]iin multiple cells simultaneously, it was suggested that glutamatergic neurones connect with purinergic neurones and glutamate (10 μM) stimulated the release of ATP causing an increase in [Ca]iin postsynaptic neurones.

ISSN:0959-4965    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

THE failure of oligodendrocytes to sustain repair of demyelinated axons contributes to the cumulative neurological disability which characterizes multiple sclerosis. In the rodent, transplanted neonatal glial progenitors efficiently remyelinate gliotoxic lesions. Proliferative bipotential progenitors are also present in the adult rat, but have not hitherto been identified in adult human tissue. Here we demonstrate cells in cultures of adult human temporal lobe which are morphologically and immunocytochemically identical to rat progenitors, are bipotential, and exhibit an astrocyte-driven proliferative response. The identification of an adult human oligodendrocyte progenitor is the first step towards developing interventional strategies for promoting repair of demyelinated lesions in patients with multiple sclerosis.

ISSN:0959-4965    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

THE role of dopaminergic pathways in the retina in controlling the functional state of the pineal was investigated. Dopaminergic agents were injected into the eyes of dark-adapted chickens which were maintained in the dark. Changes in the activity ofN-acetyltransferase (NAT) in the retina and pineal were then monitored. Injection of the non-specific dopamine agonist 6,7-ADTN depressed retinal and pineal NAT. The D1-specific agonist SKF38393 did not affect retinal NAT but depressed pineal NAT. In contrast, quinpirole, a D2-specific agonist, depressed retinal NAT, but did not depress pineal NAT. Thus, D1-rather than D2-dopaminergic pathways in the retina are involved in the retinal circuits which control pineal function.

ISSN:0959-4965    

出版商:OVID    

年代:1995

数据来源: OVID