摘要:

PROLONGED blockade of glutamate reuptake by the specific inhibitor of glutamate transporters, L-transpyrrolidine-2,4-dicarboxylate (PDC), produces a dramatic decrease in NMDA-induced neurotoxicity in cerebellar granule cell cultures, and is accompanied by a down-regulation of NMDA receptors. We now report that cultured cerebellar granule cells treated with 100 μM PDC for 1, 2, 4, 8, 16 and 24 h, respectively, show increased AP-1 DNA-binding activity as measured by electrophoretic mobility shift assay. This effect was blocked by the NMDA receptor antagonist, CGP 37849, indicative of a pivotal role of NMDA receptors in the PDC-evoked enhancement of AP-1 DNA-binding. Our results suggest that AP-1 may be involved in the transcriptional regulation of neuronal adaptation initiated by prolonged inhibition of glutamate reuptake.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

IMAGING studies compared activations elicited by images of objects and scrambled versions of these same images in order to localize human brain regions involved in object recognition. Given these studies and the known role of macaque temporal cortex in object recognition, I determined the effect of image scrambling on the responses of macaque inferior temporal neurons. Images of natural objects were scrambled to different degrees. The response of most neurons decreased with increasing degrees of scrambling. In 26% of the neurons, response was reduced by ≥50% when the image was scrambled using only four parts, but most neurons tolerated higher degrees of scrambling, suggesting that these neurons code object parts instead of entire objects. These results are related to human functional imaging studies.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

ALPHA activity attenuation (blocking) over occipital regions is an electrophysiological index of cortical activation associated with visual attention and waking mental imagery. The present work focused on exploring whether the human REM background alpha activity was modulated, attending to tonic- (without rapid oculomotor activity) and phasic-REM periods (with a prominent burst of REMs). The obtained results revealed that the background alpha activity showed a decreased spectral power over occipital brain regions during phasic-REM in comparison with tonic-REM periods. This result suggests an active visual processing caused by the complex mental imagery generated during periods of oculomotor activity in human REM sleep.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

IT is widely accepted that interleukin-1β (IL-1β), a cytokine produced not only by cells of the immune system but also by cells of the central nervous system, modulates hippocampal function. Here we investigate the effect of a seizure-induced increase in hippocampal IL-1β concentration on neurotransmitter release. We report that oral administration of glycerol evoked seizure activity in BALB/c mice. Associated with these convulsions was an induction of IL-1β gene expression and a significant increase in cytokine protein in the hippocampus. Release of glutamate in synaptosomes prepared from hippocampi of these animals was reduced compared to control. These results are consistent with previous data suggesting a modulatory effect of IL-1β on glutamate release in hippocampus.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

RATS postnatally overnourished due to a reduced litter size become persistently overweight. A presumed pathophysiological mechanism consists of a change in the activity and responsiveness to neuropeptides of the neuronal system regulating feeding behavior. This study aimed to find differences in the action of neuropeptide Y, orexin-A and cholecystokinin on single unit activity of the ventromedial hypothalamic nucleus in brain slices of normal and postnatally overfed juvenile rats. NPY inhibited significantly more neurons (15 of 23) of obese than of normal rats (6 of 27;p<0.01, χ2). Orexin-A and CCK-8S mainly activated the neurons without significant differences between the groups. In conclusion, the stronger inhibition by NPY of VMN neurons which signal satiety might contribute to increased feeding behavior in postnatally overfed rats.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

GABA is a major inhibitory neurotransmitter in the vertebrate retina. Using GABABreceptor-specific antibody combined with glial fibrillary acidic protein (GFAP) antiserum, we demonstrated that primary processes, vitreal endfeet and somata of virtually all Müller glial cells in the bullfrog retina prominently showed GABABreceptor immunoreactivity by light and electron microscopy. This study provides the first evidence that glial elements in the vertebrate retina express GABABreceptors. Such receptors on Müller cells may play an important role in retinal information processing through regulating the conductance of the inward-rectifying K+channels.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

PATCH-CLAMP amplifiers (PCAs) are commonly used to characterize voltage- and current-clamp responses in the same cell. However, the cell membrane voltage response can be severely distorted by PCAs working in the current-clamp mode. Here we compare the voltage response of pigeon semicircular canal hair cellsin situ, recorded with two different PCAs, and with a classic microelectrode bridge amplifier (BA). We found that the voltage response of hair cells recorded with PCAs differed significantly from that recorded with the BA. The true hair cell membrane voltage response to positive current steps was characterized by a strongly damped oscillation, whose frequency and duration depended on hair cell location in the sensory crista ampullaris.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

A basic version of a 3-D mathematical model for simulation of otolithic control of binocular static eye position was extended by introducting excitatory commissural fibers between the vestibular nuclei, and physiological non-linearities: the force–response relationship of utricular neurons and a quadratic relationship between eye muscle innervation and force. These modifications appeared to be necessary in order to simulate the gain asymmetry of ocular counter-roll to lateral head tilt in patients with unilateral utricular loss. The current model can adequately simulate skewtorsion in patients with unilateral utricular loss, lesions of the vestibular nuclei, and central graviceptive pathway lesions. The direction of simulated skew-torsion corresponds satisfactorily to data from normals and patients with acute vestibular loss. The relatively low values of predicted eye deviations for peripheral vestibular lesions suggest that part of the effects seen in patients is caused by affection of the semicircular canals.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

APOPTOSIS of brain cells is observed in many inflammatory disorders of the central nervous system. Nitric oxide (NO) has been shown to induce apoptosis in several brain cell types, but not previously in astrocytes. In the present study, the hypothesis was examined that interleukin (IL)-1β would induce production of NO by astrocytes which, in turn, would signal apoptotic death in these glial cells. TUNEL staining demonstrated apoptosis in astrocytes treated with IL-1β. Using an ELISA method, IL-1 receptor antagonist protein completely abrogated this astrocyte apoptosis, while NG-monomethyl-L-arginine partially prevented apoptosis but almost entirely blocked NO production. Thus, IL-1β appears to signal apoptosis of astrocytes by a mechanism involving, in part, the induction of NO.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

SINCE the first identification of an association between mutations in the connexin26 (Cx26) gene and autosomal recessive non-syndromic deafness it has been shown that several mutations in this gene cause recessive, sporadic, and dominant non-syndromic deafness. Three novel mutations in the Cx26 gene were identified in four of 20 Japanese families with autosomal recessive non-syndromic deafness. Seven of 40 chromosomes contained a 233delC allele, while Tyr136Stop (408C→A) and Gly45Glu (134G→A) were detected in two of 40 chromosomes, respectively. These mutations were not found in chromosomes in cases of sporadic congenital deafness (0/60) or in control groups (0/100). This indicates that 27.5% (11/40 chromosomes) of cases of autosomal recessive non-syndromic deafness among the Japanese are caused by mutations in the Cx26 gene.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID