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排序方式: 共有397条查询结果,搜索用时 15 毫秒
101.
The Stomach, Helicobacter pylori, and Acid Secretion 总被引:1,自引:0,他引:1
102.
Dorsey DA Mascó DH Dikranian K Hyrc K Masciotra L Faddis B Soriano M Gru AA Goldberg MP de Erausquin GA 《Apoptosis : an international journal on programmed cell death》2006,11(4):535-544
Developing neuronal populations undergo significant attrition by natural cell death. Dopaminergic neurons in the substantia
nigra pars compacta undergo apoptosis during synaptogenesis. Following this time window, destruction of the anatomic target
of dopaminergic neurons results in dopaminergic cell death but the morphology is no longer apoptotic. We describe ultrastructural
changes that appear unique to dying embryonic dopaminergic neurons. In primary cultures of mesencephalon, death of dopaminergic
neurons is triggered by activation of glutamate receptors sensitive to alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic
acid (AMPA), and differs ultrastructurally from both neuronal apoptosis or typical excitotoxicity. AMPA causes morphological
changes selectively in dopaminergic neurons, without affecting other neurons in the same culture dishes. Two hours after the
onset of treatment swelling of Golgi complexes is apparent. At 3 h, dopaminergic neurons display loss of membrane asymmetry
(coinciding with commitment to die), as well as nuclear membrane invagination, irregular aggregation of chromatin, and mitochondrial
swelling. Nuclear changes continue to worsen until loss of cytoplasmic structures and cell death begins to occur after 12 h.
These changes are different from those described in neurons undergoing either apoptosis or excitotoxic death, but are similar
to ultrastructural changes observed in spontaneous death of dopaminergic neurons in the natural mutant weaver mouse. 相似文献
103.
104.
105.
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
106.
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
107.
108.
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
109.
Mark Ming-Long Hsu MD Jen-Chyi Chang Koji Yokoyama Kazuko Nishimura Makoto Miyaji 《Mycopathologia》1994,127(2):77-81
Twenty-one strains ofCryptococcus neoformans isolated from patients in Taiwan were characterized for serotypes and mating types. Slide agglutination test was performed with 8 factor-specific sera (Iatron Company, Japan) to determine the serotypes. Wheat bran agar (WBA) and malt extract agar (MEA, Wickerham) media were used for the mating tests. Twenty of the isolates were of serotype A, and one was serotype B. Except for 2 strains of serotype A, all of the serotype A strains mated withFilobasidiella neoformans var.neoformans, mating type a. The only serotype B strain mated withF. neoformans var.bacillispora mating type a in MEA medium. These data revealed the low prevalence (1/21; 4.8%) ofC. neoformans var.gattii in Taiwan, a subtropically located island. 相似文献
110.
In vitro and in vivo antifungal activities of liposomal amphotericin B,and amphotericin B lipid complex 总被引:1,自引:0,他引:1
Kotaro Mitsutake Shigeru Kohno MD Yoshitsugu Miyazaki Tetsuhiro Noda Haruko Miyazaki Takashige Miyazaki Mitsuo Kaku Hironobu Koga Kohei Hara 《Mycopathologia》1994,128(1):13-17
The in vitro and in vivo antifungal activities of liposomal amphotericin B (L-AMPH) and amphotericin B lipid complex (ABLC), which is composed of amphotericin B and the phospholipids dimyristoyl phosphatidylcholine and dimyristoyl phosphatidylglycerol, were compared with those of conventional amphotericin B (Fungizone®, AMPH). The acute intravenous toxicity was markedly lower in BALB/c mice; 50% lethal doses (LD50s) were 2.75 mg/kg in AMPH, 32.9 mg/kg in L-AMPH and >75 mg/kg in ABLC. In vitro antifungal activities againstCandida albicans, C. parapsilosis, C. tropicalis, C. glabrata, andC. krusei were evaluated by the agar plate dilution method. The activities were unchanged againstC. albicans, but MICs increased more than four fold in 18 of the 20 strains other thanC. albicans in L-AMPH and in 9 of the 20 in ABLC. L-AMPH and ABLC were as efficacious as AMPH in the treatment of mice infected withC. albicans, and at a dose of 0.5 and 1.0 mg/kg of body weight, ABLC was more efficacious on survival. A ten-times larger dose (10 mg/kg) of L-AMPH and ABLC was administered to mice with 100% survival, suggesting improved tolerability as compared to amphotericin B. 相似文献