ISSN:0959-4965    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

THE aim of the present study was to determine (i) whether the centre of gravity (CG) shift resulting from the mechanical effect of arm raising in the frontal plane is minimized in standing subjects and (ii) whether this putative minimization is affected by the support conditions (unipedalvsbipedal) and/or by adding a load (3.5 kg) to the moving hand. Our results indicate first that a CG control does exist during bipedal stance (compensating for 31% of the mechanical shift), which increases markedly in unipedal stance (73%) and secondly, that an additional load is compensated for solely in the case of unipedal stance (81 %).

ISSN:0959-4965    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

THE Hu paraneoplastic antigen is an RNA binding protein important in the development and maintenance of neurons. Hu has homology with the product ofElav, a gene that is essential forDrosophilavisual system development. Using immunohistochemical staining, the Hu antigen was identified in most retinal neurons but was not detected in the photoreceptors. Hu is, therefore, not essential for the maintenance of all differentiated neurons. Hu immunolabeling was consistently found in glia in the optic nerve. The presence of the Hu antigen in a subset of glial cells emphasizes the heterogeneity of glial phenotype and raises the possibility that these cells may retain properties of undifferentiated neural stem cells.

ISSN:0959-4965    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

A combination of darkfield techniques and infrared videomicroscopy was used to measure the intrinsic optical signal (IOS) in slices of adult rat neocortex. The IOS, which reflects changes in light transmittance and scattering, provides a means of studying the spread of neuronal excitation and its modulation with high sensitivity and spatial resolution. The column-like IOS elicited by orthodromic stimulation is in accordance with models of neocortical circuitry. Blockade of synaptic transmission by the glutamate receptor antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and D-2-amino-5-phosphovaleric acid (D-APV) reduced the IOS. The GABAAagonist muscimol and the neuroactive steroid 5α-tetrahydrodeoxy-corticosterone (5α-THDOC) decreased the spread of excitation, whereas the GABAAantagonist bicuculline increased it. The present data suggest that the spatial spread of excitation in different neocortical layers is delimited by GABAergic inhibition mediated by the activation of GABAAreceptors.

ISSN:0959-4965    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

IN vitrosurvival of neurones isolated from adult mammalian brain is normally scarce and the postnatal age limit for obtaining viable cultures of cortical, hippocampal and diencephalic neurones is commonly two weeks. Here we describe a novel procedure for the establishment and long-term maintenance of cortical neurones of the adult mammalian brain in low-density cultures. Neurones isolated from the piriform cortex of 30-to 90-day-old guinea-pigs were initially grown in a chemically defined medium enriched with basic fibroblast growth factor (bFGF); later, a small quantity of foetal bovine serum (FBS) was added to facilitate cell differentiation. Under these conditions cells could be maintained in culture for at least 3 weeks, when indirect immuno-cytochemistry and whole-cell patch-clamp recordings were performed. Cells exhibiting neuronal morphology expressed the neuronal marker microtubule associated protein-2 (MAP2) and generated action potentials. Moreover, about 70% of the MAP2-immunoreactive cells were simultaneously labelled with anti-γ-aminobutyric acid (GABA) antibody. Cells expressing neuronal antigens were never labelled by antibody raised against the glial marker glial fibrillary acidic protein (GFAP). These results indicate that long-term survival ofadultneurones can be achieved under definite culture conditions.

ISSN:0959-4965    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

PYRAMIDAL neurones of the entorhinal cortex and of hippocampal areas CA1 and CA3 were acutely isolated from juvenile rats. The effect of lowering the concentration of extracellular potassium ions ([K+]0) on fast transient A-currents (IA) was studied using the whole-cell configuration of the patch-clamp technique. Upon lowering [K*]0from 5.4 to 0 mM amplitudes of IAin all pyramidal neurones were reduced only at test potentials positive to-20 mV, but were increased at potentials below-20 mV. Omission of magnesium ions from the intracellular perfusate resulted in an increase of IAin external K+-free solution at any potential tested. Moreover, when [K+]0was reduced steady-state activation and inactivation curves of IAwere shifted in the hyperpolarizing direction.

ISSN:0959-4965    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

CEREBRAL blood flow was recorded (using positron emission tomography) while middle-aged subjects viewed or visualized pictures of neutral or aversive stimuli, and then determined whether auditorily presented statements correctly described the stimuli. Visualizing aversive stimuli enhanced cerebral blood flow, relative to visualizing neutral stimuli, in areas 17 (right) and 18 (bilateral), as well as the anterior insula (bilateral) and middle frontal cortex (left). Areas 17 and 18 have been identified as supporting the representations that underlie the experience of imagery, and the anterior insula is a major cortical recipient of input from the autonomic nervous system. Perceiving aversive stimuli enhanced cerebral blood flow, relative to neutral stimuli, in area 46, the angular gyrus and area 19, area 47, and the middle temporal gyrus (all in the left hemisphere). All of these areas have previously been implicated in visual object identification. It is striking that negative emotion did not modulate activation in any areas in the same way during imagery and perception.

ISSN:0959-4965    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

VASOACTIVE intestinal polypeptide-like immunoreactive (VIP-LIR) astrocytes were found in the subcortical white matter of the human forebrain parietal lobe. Astrocytes expressing VIP-LIR represented a minority (0.97%) of the GFAP-stained astrocyte population in the white matter. The close anatomical relationship between the VIP-LIR astrocyte bodies and processes and the brain vasculature strongly suggests that they may play a role in the local control of blood flow and of the barrier properties of the vessel walls.

ISSN:0959-4965    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

WE have identified a novel Alzheimer's disease family in which affected subjects had a very young age of onset (range 29–35 years). Neuropathological confirmation of the diagnosis was obtained for one patient. Molecular analysis shows that within this family the disease results from a missense mutation at codon 235 of the presenilin 1 (PS-1) gene. Two patients had exhibited generalized tonico-clonic seizures several years before the onset of dementia. Whether this particular clinical feature is a consequence of thePS-1mutation remains to be established. The Leu235Pro mutation is, to our knowledge, thePS-1mutation associated with the youngest age of AD onset, which suggests that it has a drastic effect on PS-1 function.

ISSN:0959-4965    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

BECAUSK salicylate is known to produce tinnitus in humans and animals, the effect of salicylate on the auditory system of gerbils was investigated using [14C]2-deoxyglucose (2-DG). Salicylate treatment reduced activity in the inferior colliculus (IC), particularly in the high frequency part, whereas activation along some isofrequency contours was observed in auditory cortex. In contrast, in saline-treated controls the IC but not the auditory cortex was active. These results suggest that the sensation of subjective tinnitus may be generated within auditory brain structures. The 2-DG method may be used to measure tinnitus objectively in animals and also to evaluate tinnitus treatments.

ISSN:0959-4965    

出版商:OVID    

年代:1996

数据来源: OVID