摘要:

THIS study examined high affinity Na+-dependent uptake of glutamate in synaptosomal preparations from spinal cord in mice that express a dominant mutation of human copper/zinc superoxide dismutase (SOD1) and represent an animal model of amyotrophic lateral sclerosis (ALS). Their muscle strength was also monitored by a grip traction test throughout their lifespan. The high affinity Na+-dependent uptake of [3H]glutamate was decreased between 120 and 150 days of age. A marked and significant decrease in Vmax(−40.2%;p< 0.001) on whole spinal cord synaptosomes was observed at 150 days, with no change in Km. This significant decrease was reached a week before the animals died (157.2 ± 2.2 days) and corresponded to a considerable fall in muscle strength (25% loss between 120 and 140 days,p< 0.001). The FALS mouse model therefore reproduces the decrease in glutamate uptake reported in humans suffering from sporadic or familial ALS. These results are discussed in terms of a possible tardive involvement of glutamate uptake deficiency in human ALS.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE present study was designed to investigate whether a weak photic stimulus can reset the endogenous circa- dian rhythms of plasma melatonin and plasma cortisol in human subjects. A stimulus consisting of three cycles of 5 h exposures to ordinary room light (∼180 lux), centered 1.5 h after the endogenous temperature nadir, significantly phase-advanced the plasma melatonin rhythm in eight healthy young men compared with the phase delays observed in eight control subjects who underwent the same protocol but were exposed to darkness (p≤ 0.003). After light-induced phase advances, the circadian rhythms of plasma melatonin and plasma cortisol maintained stable temporal relationships with the endogenous core body temperature cycle, consistent with the conclusion that exposure to ordinary indoor room light had shifted a master circadian pacemaker.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

IN lymphocytes, the pineal hormone, melatonin, suppresses 5-lipoxygenase (5-LO) gene expression. Because circadian fluctuations in melatonin content are prominent in the pineal, we hypothesized that 5-LO mRNA level in this gland is greater when melatonin is low (day) than at night. Using the reverse transcription/polymerase chain reaction we assayed the levels of mRNAs coding for 5-LO, serotonin N-acetyltransferase (NAT), and for a constitutive gene, cyclophilin, in rat pineals obtained at 10:30–11:00 h (day) or 24:30–01:00 (night). Cyclophilin mRNA was not affected by circa- dian rhythm, whereas 5-LO and NAT were affected in an opposite manner: 5-LO mRNA was high during the day, NAT mRNA at night. We propose that circadian pineal 5-LO expression might play a role in circadian regulation of pineal functioning.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THIS study examined the relationship between orienting responses to novel events and subsequent exploratory behavior. The N2-P3 electrophysiologic component of the orienting response was found to be larger for novel than repetitive background stimuli. Across subjects, the amplitude of this N2-P3 response in frontal regions strongly predicted the proportional increase in the duration of viewing directed toward novel compared to background stimuli. Within subjects, larger N2-P3 amplitudes in response to novel stimuli were associated with longer viewing durations on those stimuli. These results suggest that the N2-P3 component of the orienting response reflects the activity of a neural system involving frontal networks that dynamically regulates the subsequent allocation of attentional resources to novel stimuli.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

TO evaluate the influence of cell type and cationic liposomal formulation on gene transfection efficiency three liposomes (lipofectin, lipofectamine and DOTAP) were used to transfect the human (A172 and MOG-GCCM) and rodent (C6 and A15A5) glioma cell lines with the Lac Z gene. Parallel studies evaluatedin vitrocytotoxicity and the neuropathological changes following intracerebral injection. The transfection efficiency and cytotoxicity of the liposomes varied both quantitatively and qualitatively between the cell lines. There were no behavioural disturbances following intrastriatal or hippocampal injection and the neuropathological changes at the injection sites were focal and similar for all liposomes. The influence of glial cell lineage on both liposomal transfection facility and cytotoxicity may have important implications forin vivogene transfection in the central nervous system.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

USING an optical recording method with a voltage-sensitive dye, we recorded activities in the primary auditory cortex (AI) of anesthetized guinea pigs in response to frequency-modulated (FM) sounds and sounds with stepwise changes in frequency (SF). Responses to the FM sound showed a spatiotemporal pattern in which a localized active spot traversed the isofrequency bands in the AI, and they differed from the band-like responses to the SF sound. These results indicate that time-varying sounds are represented as spatiotemporal activation of tonotopic organization in the AI by spectral cues with interactions between frequency bands.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE functional anatomy of the interactions between spoken language and visual mental imagery was investigated with PET in eight normal volunteers during a series of three conditions: listening to concrete word definitions and generating their mental images (CONC), listening to abstract word definitions (ABST) and silent REST. The CONC task specifically elicited activations of the bilateral inferior temporal gyri, of the left premotor and left prefrontal regions, while activations in the bilateral superior temporal gyri were smaller than during the ABST task, during which an additional activation of the anterior part of the right middle temporal gyrus was observed. No activation of the occipital areas was observed during the CONC task when compared either to the REST or to the ABST task. The present study demonstrates that a network including part of the bilateral ventral stream and the frontal working memory areas is recruited when mental imagery of concrete words is performed on the basis of continuous spoken language.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THERE is disagreement in the literature as to whether smooth pursuit latency is reduced when a temporal gap is introduced between the extinction of a central fixation target and the illumination of an eccentric moving target. This study confirms that in human subjects smooth pursuit latency is reduced by gaps and that the magnitude of the reduction is related to the duration of the gap. However, latency is not solely determined either by visual factors or by task parameters such as spatial predictability, but is affected by task context. The results suggest a role for non-visual factors such as attention in the initiation of pursuit.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

FUCOSYLATION of terminal galactose residues of brain glycoproteins in th eα(1–2) position has been shown to be crucial for neuronal plasticity, including phenomena such as long-term potentiation and long-term memory formation. We raised antibodies against the plasticity- relevant fu α(1-2)gal epitope and used them to determine the distribution of the epitope in adult rat hippocampus. To identify proteins bearing fu α(d-2)gal glycostructures antibodies against known synaptic fucoglycoproteins were used in combination with the fucα(1-2)gal antibodies. The NMDA receptor subunit NR1 and fractions of gp65 and cadherin were found to carry the epitope, while fucosylation of NCAM180 and NCAM140 obviously occurs via different linkages to the glycan chains.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

WE investigated whether electrical stimulation of the cerebellar fastigial nucleus (FN) can protect pyramidal neurons of the CA1 zone of dorsal hippocampus from delayed neuronal death caused by global ischemia. Stimulation of the FN for 1h prior to transient 4-vessel occlusion in anesthetized rats salvaged 57% (p< 0.01) of pyramidal neurons from degeneration. This effect could be preconditioned. Sham simulation of FN or stimulation of the rostral ventrolateral medulla (RVL) were without effect (p> 0.5). Excitation of intrinsic neuronal pathways represented in FN can protect central neurons from global as well as focal ischemic degeneration. The brain contains systems designed to protect it from ischemia by mechanisms of central neurogenic neuro- protection acting independently of actions on cerebral blood flow.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID