摘要:

APOPTOSIS is a controlled form of cell death involving cascades of degradative events. Proteolysis during apoptosis is largely due to the activity of a family of cysteine proteases called caspases. In recent years different roles for members of this family have been revealed. In the central nervous system caspase-2 is highly expressed in the brain during development although many caspases are expressed at low levels in the adult. However, an involvement of caspases in apoptosis of mature neurons has been demonstratedin vivo, where specific inhibitors of caspases are found to protect against ischemic injury. We have reviewed the evidence for the existence of caspases in the central nervous system and their activation during neuronal cell death.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

TWO types of calcium current (ICa) have been identified in the bipolar cell of the mouse retina: a transient (T-) type current and a long lasting (L-) type current. It has been suggested that the former is present in the soma and the latter in the axon terminal. To establish the cellular localization of the two types of ICa, bipolar cells of the mouse retina was studied electrophysiologically in a slice preparation, and immunocytochemically by staining specific calcium channels in isolated cells. The dihydropyridine-sensitive L-type ICawas recorded in the axon terminal, and the T-type current was recorded in the somatic region. Strong immunoreactivity to a polyclonal antibody against the L-type calcium channel was found in the axon terminal. These observations suggest that the L-type ICais generated at the axon terminal and contributes to the transmission of sustained depolarization.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

WE put forward the hypothesis that synchronous muscle activation would be less frequent with increasingly more complex grip tasks. Six subjects performed a visuo-motor step-tracking task using the precision and the power grip. During the experiment transcranial magnetic stimuli were applied. Electromyographic activity was recorded from the hand muscles active in both tasks. Muscle synchronization was found to be enhanced during the power grip as compared to the precision grip. Magnetic stimulation had a stronger effect during the precision grip than during the power grip. Our findings are in favour of a variable organization of muscle activation in hand muscles during various tasks and support the stronger contribution of the corticomotoneuronal system in the precision than the power grip.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

NITRIC oxide (NO) involvement has been demonstrated in mechanisms of synaptic plasticity, particularly in hippocampal long-term potentiation, a mechanism that underlies certain forms of learning and memory. Several findings suggest that NO production may be decreased in the aged rats. Changes in the nNOS-containing neurons with ageing were demonstrated by immunocytochemistry. NOS-immunoreactive (IR) cells in aged rats were present in all cortical areas and the hippocampus, and the pattern of distribution was similar to that of the control group. The number of NOS-IR cells in the cerebral cortex was significantly decreased in the aged rats, but the extent of changes was variable in each area, and ranged from mild decrease (< 30 %) to severe decrease (> 50%). Severely decreased areas were the cingulate cortex, parietal cortex area 1, temporal cortex area 1, 2, 3, medial part of occipital cortex area 2, monocular and binocular part of occipital cortex area 1, entorhinal cortex, hippocampus proper, dentate gyrus and subiculum. Morphologically, the number of dendritic branches seemed to be decreased in aged group and the length of dendrites of NOS-IR neurons showed a tendency to shorten. These results indicate the involvement of neuronal system containing NOS in the ageing brain, and provide the first morphological evidence for the loss of NOS neurons in the cerebral cortex of the aged rats by immunocytochemistry.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE aim of the present study was to investigate the effects of ageing on optokinetic function in labyrinthineintact human subjects. Subjects aged 18–39 years, 40–59 years and ≥ 60 years were tested for sensitivity to optokinetic stimulation using latency to the illusion of circularvection in an optokinetic drum. The latency to circularvection significantly increased with increasing age. These results suggest a decline in optokinetic sensitivity with increasing age, which may be related to agerelated deterioration in the optokinetic visual pathways.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE aim of this study was to investigate whether the neuroprotective properties of magnesium in cerebral ischaemia involve suppression of repetitive tissue depolarizations. Cortical spreading depressions (CSDs), evoked by cortical KCl application, and cardiac arrestinduced anoxic depolarization (AD) were measured by extracellular DC recording on intact rat brain. At 90 min after onset of CSDs saline, MK-801 (3 mg/kg) or MgSO4(90 mg/kg) was given i.v. Latency time to AD was measured after 4h. The frequency of CSDs was significantly reduced in animals treated with MgSO4or MK-801. AD was significantly delayed by MgSO4but not by MK-801. Our results suggest that suppression of depolarization by magnesium may play a role in its neuroprotective properties in cerebral ischaemia.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

GLIAL-DERIVED neurotrophic factor (GDNF) was tested for its ability to prevent hearing and sensory cell loss in guinea pigs exposed to acoustic trauma. Hearing was measured prior to any treatment. Animals were exposed to damaging levels of noise either before or after local application of GDNF to one ear. Four weeks later, hearing and sensory cell loss was greater in the control ear than in the ear receiving GDNF before acoustic trauma or 2 h after trauma, but not 4 or 6 h after trauma. The results indicate that GDNF treatmentin vivocan prevent cochlear sensory cell damage and hearing loss if present during or shortly after acoustic trauma.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

HALOPERIDOL (HP) can block both the motor stimulation and the neurotoxic vacuolization of MK-801, suggesting that the two drugs have antagonistic brain actions. However, we show here that the modest EEG slowing produced by HP and MK-801 individually is massively potentiated when the drugs are combined. This finding challenges the argument for the PCP model of schizophrenia that assumes a general antagonism of neuroleptics and NMDA channel blockers. It further suggests that blockade of MK-801 motor effects is an inadequate test for antipsychotic drug actions. Our data indicate that intact function of D2 receptors (or other HP targets) is required to prevent generalized EEG slowing in the presence of NMDA channel blockade, a possibility of potential clinical interest.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE average duration of eye fixations in reading places constraints on the time for lexical processing. Data from event related potential (ERP) studies of word recognition can illuminate stages of processing within a single fixation on a word. In the present study, high and low frequency regular and exception words were used as targets in an eye movement reading experiment and a high-density electrode ERP lexical decision experiment. Effects of lexicality (wordvspseudowordvsconsonant strings), word frequency (highvslow frequency) and word regularity (regularvsexception spelling-sound correspondence) were examined. Results suggest a very early time-course for these aspects of lexical processing within the context of a single eye fixation.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

WE describe the use of an immunoblotting technique to investigate the potential role of reaction oxygen species in the pathogenesis of Duchenne muscular dystrophy. Quadriceps femoris muscle biopsy samples were obtained from six patients with Duchenne and six with Becker muscular dystrophy, and from six control subjects. These were analysed for the presence of protein carbonyl moieties (indicative of oxidation to protein) by SDS–polyacrylamide gel electrophoresis and Western blotting, using a commercially available antibody. In all Duchenne and Becker patient samples analysed, a heavily oxidized protein species was identified migrating at 125 kDa. This oxidized species was not present (or was present at very low levels) in normal control samples. Use of the present technique also identified that the various muscle proteins in Duchenne and Becker muscular dystrophy muscle are oxidized to varying degrees, supporting the hypothesis of a differential susceptibility of proteins to oxidation in these disorders. Work from the present study further supports the hypothesis that reactive oxygen species play a role in dystrophic muscle cell pathogenesis.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID