摘要:

THE impact of oxidative stress (H2O2) was observed using purified rat motoneuron cultures and H2O2-induced dose-dependent motoneuron death was demonstrated. The apoptotic characteristics of cell death were studied morphologically and using the TUNEL technique. This H2O2-induced motoneuron death was inhibited by the poly ADP ribosyl synthetase (PARS) inhibitors benzamide and nicotinamide. These findings suggest the potential utility of PARS inhibitors in the treatment of neurodegenerative disorders such as amyotrophic lateral sclerosis, in which oxidative stress has been suspected to play an important etiopathogenic role.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

ACUTE hypovolaemia evokes abrupt, life-threatening hypotension and bradycardia. Hypotension can be evoked also by excitation of the caudal midline medulla (CMM). This study investigated the possible contribution of the CMM depressor area to hypotension evoked by acute hypovolaemia. Inactivation of the CMM, with either lignocaine or cobalt chloride did not alter resting arterial pressure. However lignocaine injections blocked the fall in arterial pressure, and cobalt chloride injections delayed the onset and significantly attenuated the size of hypovolaemic-evoked hypotension. These findings suggest that the CMM is a key region triggering hypo-tension after blood loss, and that the brain areas mediating cardiovascular response to challenges such as acute hypovolaemia are not the same areas that regulate resting arterial pressure.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

ELECTRIC charge has long been hypothesized to be the effective stimulus variable that determines loudness evoked by directly stimulating the auditory nerve. This ‘equal-charge, equal-loudness’ hypothesis predicts that stimulus amplitude and duration can be traded linearly to produce equal loudness. Loudness sensations from threshold to maximum loudness were measured systematically as a function of stimulus amplitude and duration in cochlear implant listeners. The measured data do not support the equal-charge, equal-loudness hypothesis: an increment in stimulus amplitude produces a significantly louder sensation than the same change in stimulus duration. Instead of the linear equal-charge model, a power-function model successfully predicts the measured data and should be used to encode loudness in electric hearing.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE effect of the neuroprotective drug, vinpocetine on the veratridine-evoked [Na+]iand [Ca2+]irise in isolated nerve terminals was studied. Vinpocetine, in a pharmacologically relevant concentration range (0.4–10 μM)ireduced the increase of [Na+]iinduced by veratridine (100 μM). The effect of the drug was concentration-dependent with 10 μM vinpocetine completely preventing the increase of [Na+]i. The [Ca2plus;]irise in response to veratridine was also prevented by vinpocetine. In addition, the [Ca2+]isignal induced by depolarization with 20 mM K+was reduced by vinpocetine (1–20 μM). This effect was not influenced by preincubation with 1 μM TTX and was also observed when Na+was replaced byN-methyl glucamine in the medium. It is concluded that vinpocetine is capable of inhibiting voltage-dependent Na+and Ca2+channels, respectively, and these effects might contribute to the neuroprotection exerted by the drug.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE present experiments examined the effects of excitotoxic lesions of anterior perirhinal cortex (PRH) on the expression of fear conditioned to an explicit olfactory CS and to the context in which CS–US pairing took place. Animals with anterior PRH lesions exhibited an attenuation of fear conditioned to the explicit CS, but no attenuation of fear conditioned to the training context. These data replicate previous findings in our laboratory examining the effects of aspirative lesions of anterior PRH, and are consistent with the notion that this cortical region comprises a critically important component of the neural system mediating the acquisition and/or expression of associations between olfactory cues and footshock.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

WE used fMRI to compare the ipsilateral activation in the sensorimotor region (SMR) during dominant and non-dominant hand motor tasks between right and left handers. In right handers, the ipsilateral activation was significantly greater during non-dominant (left) hand task than dominant (right) hand task, while in left handers, it showed no significant difference. The ipsilateral activation was most pronounced in the precentral subregion (presumably corresponding to the premotor area) during either hand task in both groups. We conclude that the different patterns of ipsilateral activation might be mainly explained by the hemispheric dominance. The skill of the hand and complexity of tasks may be related to the predominant activation of the premotor area.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE apparent preservation of word priming effects in amnesia has been interpreted as supporting the view that implicit memory depends on brain systems that are independent of mesial temporal lobe structures which are in part responsible for explicit memory disorders. Nevertheless, a number of studies have demonstrated word priming deficits in amnesic patients relatively to normal subjects, suggesting that such structures may also be involved in implicit memory. To determine whether one such structure, the hippocampal formation, is a component of the brain system subserving word priming, a 3-D PET study was carried out in 13 normal individuals. Encoding was carried out using the brief multiple presentation technique, a procedure that allows one to effectively circumvent contamination of implicit memory tasks by explicit memory strategies. Results revealed that word priming was indeed associated with an activation of the right hippocampal formation. This finding of an hippocampal involvement in word priming calls into question the notion of absolute dissociability between the brain systems underlying performance on various explicit and implicit memory tasks.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

TRANSIENT forebrain ischemia causes selective neuronal death in the hippocampal CA1 neurons. A short sublethal ischemic episode preceding ischemia of longer duration is known to increase tolerance against cell death. The mechanisms of this ischemic tolerance are still poorly understood. Here we show, using Ca2+imaging, that intracellular calcium ([Ca2+]i) elevation in CA1 neurons after an anoxic-aglycemic episode is markedly inhibited in the ischemia-tolerant gerbil. The hippocampus of gerbils which did not acquire tolerance showed a high [Ca2+]ielevation during the anoxicaglycemic episode, similar to controls. Since hypoxia/ischemia-induced neurodegeneration can be triggered by cytoplasmic Ca2+overload, the tolerant gerbil may regulate calcium and keep [Ca2+]ibelow the critical level for initiating neuronal death.NeuroReport9: 1875–1878 © 1998 Rapid Science Ltd.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

HEAD injury is one of the potential environmental factors in Alzheimer's disease (AD). To study the chronic stage of concussive brain injury, histological analyses were performed 2–6 months after right lateral fluid percussion (FP) brain injury (3.6–4.8 atm) in rats. Six months after injury, numerous normal-looking neurons in the telencephalon and brain stem were immunoreactive with either antibody to phosphorylated tau or with four antibodies to β-amyloid protein. Neuronal counts in the cortices were gradually decreased after injury, up to 42% loss at 6 months after injury. These neuropathological changes suggest that this animal model could serve as a good animal model of neurodegenerative diseases such as AD.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

IN adults, neural networks for phonological processing distinct from those involved in acoustical processing are located in the left temporal lobe. We now report that by the age of 3 months, infants display phonological processing devices analogous to those found in adults. Within a stream of identical syllables, acoustic deviants were introduced, either crossing a phonetic boundary or remaining within the same category. Event-related potentials were recorded using a 64-electrode net. Although the acoustical change was of similar amplitude in the two deviants, the electrophysiological response was larger for a phonological change and involved a more posterior and dorsal temporal region than for an acoustical change. These results demonstrate that infants, like adults, already possess a dedicated neuronal network for phonetic processing.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID