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991.
992.
Substance abuse and dependence is the most common psychiatric problem. Alcohol is the most commonly abused substance and most people who abuse other substance(s) abuse alcohol at the same time. Accumulating evidence suggests that neurophysiological and pathological effects of ethanol are mediated to a considerable extent via the glutamatergic system. Ethanol disrupts glutamatergic neurotransmission by inhibiting the response of the N-methyl-D-aspartate (NMDA) receptor and by promoting neuronal toxicity through upregulation of the NMDA receptor density. Therefore, short-term/acute ethanol treatment results in a blockade of NMDA receptor-mediated neurotransmission and apoptotic cell death by inhibiting the trophic effect mediated by the NMDA receptor whereas chronic ethanol treatment and withdrawal results in an enhanced toxic response toward glutamate. The neurobiology of human alcoholism such as ethanol intoxication, dependence, withdrawal seizures, delirium tremens, Wernicke-Korsakoff syndrome, and fetal alcohol syndrome can be better understood as a spectrum of consequences of ethanol's effect on the NMDA glutamatergic system. 相似文献
993.
Toshifumi Noguchi MD PhD Naoto Yamada Miyuki Sadamatsu Nobumasa Kato 《Journal of biomedical science》1998,5(3):221-225
We assayed the diurnal concentrations of growth hormone (GH) and prolactin (PRL) in 6 healthy male volunteers to evaluate the self-similar features in the time series of each hormone on the basis of fractal theory and to determine the fractal dimension as an index of the complexity of the diurnal variation. In addition, we assessed the effects of a 6-hour delay in the sleep period on the complexity of the diurnal variaton of these hormones. There was a statistically significant fractal feature in the serum levels of GH both under the nocturnal-sleep and delayed-sleep conditions in all subjects. The time series of the serum PRL concentrations also showed a statistically significant fractal feature under the nocturnal-sleep and delayed-sleep conditions in all subjects. The fractal dimensions of the patterns of the GH or PRL levels were 1.879 and 1.929 or 1.754 and 1.785 under the nocturnal-sleep and delayed-sleep conditions, respectively. Two-way ANOVA revealed no significant difference in the fractal dimension between the two sleep conditions but did reveal a significant difference between the fractal dimensions of the GH and PRL levels. These results showed (1) that delayed sleep had no significant effect on the complexity of the diurnal pattern of these hormones, and (2) that the diurnal pattern of the GH levels was more complex than that of the PRL levels. 相似文献
994.
A comprehensive screen for TWIST mutations in patients with craniosynostosis identifies a new microdeletion syndrome of chromosome band 7p21.1. 总被引:4,自引:0,他引:4 下载免费PDF全文
995.
996.
Microsatellite variation in Drosophila melanogaster and Drosophila simulans: a reciprocal test of the ascertainment bias hypothesis 总被引:2,自引:1,他引:1
Interspecific comparisons of microsatellite loci have repeatedly shown that
the loci are longer and more variable in the species from which they are
derived (the focal species) than are homologous loci in other (nonfocal)
species. There is debate as to whether this is due to directional evolution
or to an ascertainment bias during the cloning and locus selection
processes. This study tests these hypotheses by performing a reciprocal
study. Eighteen perfect dinucleotide microsatellite loci identified from a
Drosophila simulans library screen and 18 previously identified in an
identical Drosophila melanogaster library screen were used to survey
natural populations of each species. No difference between focal and
nonfocal species was observed for mean PCR fragment length. However,
heterozygosity and number of alleles were significantly higher in the focal
species than in the nonfocal species. The most common allele in the
Zimbabwe population of both species was sequenced for 31 of the 36 loci.
The length of the longest stretch of perfect repeat units is, on average,
longer in the focal species than in the non-focal species. There is a
positive correlation between the length of the longest stretch of perfect
repeats and heterozygosity. The difference in heterozygosity can thus be
explained by a reduction in the length of the longest stretch of perfect
repeats in the nonfocal species. Furthermore, flanking-sequence length
difference was noted between the two species at 58% of the loci sequenced.
These data do not support the predictions of the directional-evolution
hypothesis; however, consistent with the ascertainment bias hypothesis, the
lower variability in nonfocal species is an artifact of the microsatellite
cloning and isolation process. Our results also suggest that the magnitude
of ascertainment bias for repeat unit length is a function of the
microsatellite size distribution in the genomes of different species.
相似文献
997.
Suspensions of Kluveromyces marxianus var. marxianus NRRLy2415 and active dry bakers' yeast were dead-end filtered in the range 30–500kPa. In all cases, the specific cake resistance, , could be related to pressure, P, through the expression = 0 (1 kcP) where 0 and kc are empirical constants. For K. marxianus, the values of kc were 1.67 × 10–5 Pa–1 and 2.39 × 10×5 Pa–1 for suspensions with mean cell aspect ratios of 2.98 and 7.33 respectively. Values of kcfor active dry yeast were 10.56 × 10–5 Pa–1 in the case of unwashed cells with a mean aspect ratio of 1.21 and 7.94 × 10–5 Pa–1 for washed cells with a mean aspect ratio of 1.20. © Rapid Science Ltd. 1998 相似文献
998.
V Walsh A Ellison L Battelli A Cowey 《Proceedings. Biological sciences / The Royal Society》1998,265(1395):537-543
Transcranial magnetic stimulation (TMS) can be used to simulate the effects of highly circumscribed brain damage permanently present in some neuropsychological patients, by reversibly disrupting the normal functioning of the cortical area to which it is applied. By using TMS we attempted to recreate deficits similar to those reported in a motion-blind patient and to assess the specificity of deficits when TMS is applied over human area V5. We used six visual search tasks and showed that subjects were impaired in a motion but not a form ''pop-out'' task when TMS was applied over V5. When motion was present, but irrelevant, or when attention to colour and form were required, TMS applied to V5 enhanced performance. When attention to motion was required in a motion-form conjunction search task, irrespective of whether the target was moving or stationary, TMS disrupted performance. These data suggest that attention to different visual attributes involves mutual inhibition between different extrastriate visual areas. 相似文献
999.
The condition of grey mullet from the urbanized Coliigan estuary was higher than that of mullet from the rural Barnawee estuary and those of several other samples described in the literature (P<0·05). It is suggested that their better condition was due to dietary supplementation from creamery and tannery effluent in the urbanized estuary. As a result of their distinctive condiiion, indirect evidence is provided for homing in this species, at this site. 相似文献
1000.
K. van Dam N. Jansen P. Postma P. Richard G. Ruijter M. Rutgers H. P. Smits B. Teusink J. van der Vlag M. Walsh H. V. Westerhoff 《Antonie van Leeuwenhoek》1993,63(3-4):315-321
The control of enzymes and substrates on the flux through microbial metabolic pathways can be quantified in terms of flux control coefficients. In pathways involving group transfer, the summation theorem for flux control by the enzymes has to be modified: the sum of control by all enzymes is between 1 and 2. The phosphoenolpyruvate:glucose phosphotransferase system is such a pathway. Experimental determination of the control by the enzymes in this pathway is under way. The control of the enzymes on the glycolytic flux in yeast is low, with the possible exception of the uptake step. InKlebsiella pneumoniae potassium and ammonium ions can simultaneously be limiting, (i.e. have significant control on growth) at pH 6, but not at pH 8. This may be due to the fact that at pH 8 the high-affinity potassium uptake system is absent. 相似文献