摘要:

IN order to elucidate the relationship between virus neurotropism and neuronal maturity, two experiments were performed. First, mumps virus infectivity was compared among the different developmental stages of hamster brains inoculated with mumps virus by examining the immunohistochemical distribution of mumps virus antigen. Second, brain lesions resulting from mumps virus infection during the period of neuronal migration were histologically and ultrastructurally analyzed. Three groups of Syrian hamsters, Group E12 (fetuses on the 12th day of gestation), and Groups P2 and P30 (2 and 30 days old, respectively), were injected with mumps virus intraplacentally or intracerebrally. In Group P30, mumps virus antigen was observed specifically in ependymal cells and the choroid plexus. In addition to these areas, in Group P2, some neurons in layers II and III of the cerebral cortex also showed virus antigen immunoreactivity. In Group E12, mumps virus antigen accumulated primarily in the neuroepithelial cells within the ventricular zone. Neither specific intranuclear changes related to viral replication nor the formation of complete virions and nucleocapsids was observed. We conclude that mumps virus neurotropism to hamster brains is dependent on the degree of neuronal maturity and that mumps virus can induce an abortive infection and resultant neuronal cell necrosis in the immature developing hamster brain.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

The aim was to study whether there is indication of a dissociation in processing of visuospatial and colour information in working memory in humans. Experimental subjects performed visuospatial and colour n-back tasks with and without visuospatial and colour distractive stimuli presented in the middle of the delay period to specifically affect mnemonic processing of task-related information. In the high memory-load condition, the visuospatial, but not the colour, task was selectively disrupted by visuospatial but not colour distractors. When subvocal rehearsal of the memoranda in the colour task was prevented by articulatory suppression; colour task performance was also selectively disrupted by distractors qualitatively similar to the memoranda. The results support the suggestion that visual working memory for location is processed separate from that for colour.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

We investigated binocular suppression in area 21a cells of the anaesthetized cat using drifting sinusoidal gratings presented simultaneously to each eye. The grating presented to the dominant eye was always oriented optimally and the grating presented to the non-dominant eye was either at the same orientation, but at the least effective relative spatial phase, or orthogonal. The binocular response of ∼ 80% of cells was less than the monocular dominant eye response when there was a mismatch in orientation or spatial location between stimuli. Response suppression in the two binocular stimulus conditions had a correlation coefficient (r) of 0.55. We propose a parsimonious model to account for the response facilitation and suppression by binocular stimulation of area 21a neurons.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

THE phosphorylation of cAMP response element binding protein (CREB) in the rat brain was examined immunohistochemically at 3.5 h, 12 h, 24 h and 48 h of recirculation after focal ischemia induced by occlusion of the middle cerebral artery for 1.5 h. Brain sections were stained with affinity purified anti-phosphorylated CREB antibody. The ischemic core revealed a significant, but transient increase in number of phosphorylated CREB-positive cells at 3.5 h of recirculation, followed by a rapid decrease during the subsequent period. In the peri-ischemia area, the number of phosphorylated CREB-positive cells showed a more marked increase as compared to that in the ischemic core at 3.5 h of recirculation, and the increase continued until 48 h of recirculation with a tendency for gradual decline. Persistent enhancement of CREB phosphorylation may thus be closely related to the neuronal viability and neuroprotective mechanisms, whereas rapid disappearance of CREB phosphorylation may clearly precede neuronal death.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

THE whole cell configuration of the patch clamp technique was used to study the effects of chlorpromazine (CPZ), a widely used antipsychotic drug, on miniature GABAA-mediated synaptic currents (mIPSCs) in hippocampal cells in culture. CPZ (10–30 μM) induced a clear dose-dependent increase of mIPSCs frequency that was associated with a decrease in amplitude and with an acceleration of their decay kinetics. When applied in a calcium-free medium, CPZ was less effective in enhancing mIPSCs frequency, suggesting that this effect was partially calcium dependent. While a low (10 μM) CPZ concentration induced a 2-fold increase in the total charge transfer a higher (30 μM) dose of this drug produced no changes, indicating that the presynaptic effect was counterbalanced by the postsynaptic one.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

MUTATION in the presenilin-1 (PS-1) gene at chromosome 14q24.3 is the most common cause of autosomal dominant early-onset Alzheimer's disease. Here, we report a novel missense mutation in the presenilin-1 gene found in a three-generation Danish family with autopsy-verified early-onset Alzheimer's disease. Two affected first-degree relatives in two generations were found to be heterozygous for a cytosine to adenine transversion at the second position of codon 116, which changes the amino acid at that position from threonine to asparagine. This conservative amino acid substitution occurs in an evolutionary highly conserved region of the PS-1 protein and is associated with onset of the disease between age 35 and 41 years and 4–8 years' duration of the disease. Analysis of amyloid β-protein (Aβ) deposition in brain specimens from one affected family member showed predominance of Aβ42(43). Onset and progression of the disease were very similar in two sibs homozygous for the ϵ3 allele and the ϵ4 allele, respectively, of the polymorphic apolipoprotein E locus. The lack of effect of the high risk ϵ4/ϵ4 genotype on the disease in this family corroborates and extends previous observations that the presence of one copy of the ϵ4 allele does not modulate PS-1 associated Alzheimer's disease.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

REPETITIVE stimulation of the carotid sinus nerve (CSN) elicits a short-term potentiation (STP) of the reflex response in respiratory motor output in mammals. The input-output transformation approximates a leaky integrator with a time constant of several seconds. Here, we showed that STP induced by CSN stimulation in rats was manifested in the reflex response in the amplitude of rhythmic phrenic nerve activity as well as its duration. Moreover, pharmacological blockade of NMDA receptors (NMDAR) resulted in marked increases in the time constants of the equivalent neural integrator in both the STP induction phase (by 10- to 20-fold) and recovery phase (by 1- to 5-fold). Thus, NMDAR serves as a molecular switch that facilitates the integrative processing of CSN inputs by STP.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

TO reveal the spatiotemporal characteristics of the auditory automatic discrimination process, mismatch negativity (MMN) generators were assessed with a high-resolution EEG system (128ch) and scalp current density (SCD) analysis. Ten normal volunteers participated in the study. Event-related potentials were recorded during a selective attention task. Sequential SCD mappings revealed that a current sink/source combination in the left temporal regions and a current sink in the right frontotemporal regions appeared around 200 msec irrespective of the ear of stimulation. Moreover, a parietal sink/source combination was demonstrated on the right hemisphere around 240 ms irrespective of the ear of stimulation. These findings demonstrate that the auditory automatic change detection process is, both spatially and temporally, a multiple-generated system.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

COGNITIVE impairment and dementia are common in the later stages of Parkinson's disease (PD). Neuropathological examination of demented PD (PDD) patients often reveals changes that are typical of Alzheimer's disease (AD). In AD, there is a massive reactive gliosis and increased expression of the small heat shock proteins (hsp) hsp27 and αB-crystallin. Since these proteins are characteristic for reactive astrocytes in AD, we investigated their expression in the brains of PDD patients. The results were compared with those obtained in the brains of non-demented PD patients. We found (1) no detectable expression of hsp in PD without dementia, and low expression in PD with mild dementia; (2) reactive gliosis and increased expression of hsp in the cortex of PDD brains; (3) a strong association between hsp immunoreactivity and the severity of the AD-specific changes, especially with the number of tangles in the hippocampus; (4) a distinct immunoreaction of αB-crystallin in microglia in the substantia nigra and in the hippocampus in PDD. These results indicate that astrocytes react to the disease conditions in AD and in PDD in a similar way, namely by the increased expression of small heat shock proteins, and present additional evidence for the thesis that the pathology of the dementia in PD is related to that in AD.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

IN cats, each sensorimotor cortex has bilateral corticospinal (CS) terminations during early postnatal life, with contralateral terminations denser than ipsilateral ones. Subsequent development depends on neural activity: silencing CS neurons on one side results in development of sparse terminations from that side and dense bilateral terminations from the active side. In this study we determined whether activity-dependent competition between CS terminations is important in shaping their development. We compared the effect of bilateral sensorimotor cortex activity blockade (activity deprivation alone, without competition) on CS development, with that produced by unilateral blockade (activity deprivation with competition). We found that the extent of the spinal gray matter labeled is substantially greater when the motor cortex on each side is silenced rather than when only one side is silenced. These findings support the hypothesis that competition between developing CS terminations is important in shaping the topography of CS connections.

ISSN:0959-4965    

出版商:OVID    

年代:1999

数据来源: OVID