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排序方式: 共有91条查询结果,搜索用时 15 毫秒
81.
Nuno A Fonseca Cristina P Vieira Peter WH Holland Jorge Vieira 《BMC evolutionary biology》2008,8(1):200
Background
Although homeobox genes have been the subject of many studies, little is known about the main amino acid changes that occurred early in the evolution of genes belonging to different classes. 相似文献82.
83.
Tamasi G Curci M Berrettini F Justice N Sega A Chiasserini L Cini R 《Journal of inorganic biochemistry》2008,102(10):1874-1884
The reaction of RuCl(3)(NO).H(2)O with 4-methylpyrimidine (MePYM) and ethylisonicotinate (EINT), in absolute ethanol at 40-55 degrees C afforded crystalline trans-[RuCl(3)(NO)L(2)] complexes. Structural studies via X-ray diffraction, and spectroscopic methods (NMR, IR, UV-visible (UV-Vis)) revealed that the molecular structures have the two Ls in trans positions (axial) and the chloride anions and the NO(+) cation as equatorial ligands; pyrimidine...pyrimidine pairing pattern via two weak C-H...N interactions occur. The molecular structures for the EINT derivative was inferred from spectroscopy and computations. Under irradiation at 366 nm several solutions of the title compounds deliver NO via first order processes. Visible light (420-700 nm) does not produce significant NO release from CH(2)Cl(2) and CH(3)CN solutions within 24h. 相似文献
84.
Combined analysis from eleven linkage studies of bipolar disorder provides strong evidence of susceptibility loci on chromosomes 6q and 8q 总被引:4,自引:1,他引:3
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McQueen MB Devlin B Faraone SV Nimgaonkar VL Sklar P Smoller JW Abou Jamra R Albus M Bacanu SA Baron M Barrett TB Berrettini W Blacker D Byerley W Cichon S Coryell W Craddock N Daly MJ Depaulo JR Edenberg HJ Foroud T Gill M Gilliam TC Hamshere M Jones I Jones L Juo SH Kelsoe JR Lambert D Lange C Lerer B Liu J Maier W Mackinnon JD McInnis MG McMahon FJ Murphy DL Nothen MM Nurnberger JI Pato CN Pato MT Potash JB Propping P Pulver AE Rice JP Rietschel M Scheftner W Schumacher J Segurado R 《American journal of human genetics》2005,77(4):582-595
Several independent studies and meta-analyses aimed at identifying genomic regions linked to bipolar disorder (BP) have failed to find clear and consistent evidence of linkage regions. Our hypothesis is that combining the original genotype data provides benefits of increased power and control over sources of heterogeneity that outweigh the difficulty and potential pitfalls of the implementation. We conducted a combined analysis using the original genotype data from 11 BP genomewide linkage scans comprising 5,179 individuals from 1,067 families. Heterogeneity among studies was minimized in our analyses by using uniform methods of analysis and a common, standardized marker map and was assessed using novel methods developed for meta-analysis of genome scans. To date, this collaboration is the largest and most comprehensive analysis of linkage samples involving a psychiatric disorder. We demonstrate that combining original genome-scan data is a powerful approach for the elucidation of linkage regions underlying complex disease. Our results establish genomewide significant linkage to BP on chromosomes 6q and 8q, which provides solid information to guide future gene-finding efforts that rely on fine-mapping and association approaches. 相似文献
85.
The consumption of fermented foods contaminated with aflatoxin B1 is linked to aflatoxicosis. Aflatoxicosis is a serious problem in developing countries with environmental conditions appropriate for the biosynthesis of AFB1 byAspergillus flavus andAspergillus parasiticus. In Africa, especially in Ghana and Nigeria, there is a very high risk of liver cancer which is caused by the consumption of AFB1-intoxicated, traditionally fermented maize and sorghum products. It is suggested that one way to diminish this health risk might be the reduction of the AFB1 concentration in foods by bacteria. Especially bacteria used for food fermentation processes are of great importance, with a special emphasis on lactic acid bacteria which are involved in traditionally fermented African foods based on maize and sorghum.Most publications dealing with aflatoxin degradation by microorganisms describe a phosphate buffer test system for the performance of degradation experiments. In contrast to that, a test system based on physiological active bacterial and yeast cells has been developed, to assess food fermentation organisms for their ability to reduce the AFB1 concentration in vitro. The aflatoxin B1 concentration in test samples was quatitatively determined by HPLC.The assessment of lactic acid bacteria originating from different German and other European culture collections only showed a very slight reduction of the AFB1 concentration from 3% to 12%. Screening experiments in which other bacterial genera and lactic acid bacteria, isolated from different African foods have been assessed, in most cases showed the same results. However, some bacterial strains, e.g. strains of the genusBacillus derived from European culture collections and strains of the genusLactobacillus isolated from African foods, caused a release of AFB1 which was chemically bound before to components of the test medium and which therefore could not be extracted with chloroform.A process quite similar to that may happen during food fermentations. Different experiments showed that e.g. cellulose can bind AFB1 very effectively. Cellulose and different other food components are well known to absorb AFB1. During fermentation the cellulose and other AFB1-absorbing components may be degraded and the AFB1 will be released again.The only bacterial strain known as yet which is able to reduce the AFB1 concentration in vitro and in different food comodities isNocardia corynebacteroides (formerFlavobacterium aurantiacum). Nevertheless the mechanism of this AFB1 reduction is actually not well understood, it still has to be investigated. In the meantime several other bacterial strains, presumably from the taxonomic group of theActinomycetes could be proved to be effective reducers of the AFB1 concentration in our in vitro test system. Because as yet no food relevant microorganism could be found, which is able to degrade AFB1, these new strains in general offer the possibility for a genetic modification of food relevant microorganisms. This seems to be the way to come to starter cultures which are able to degrade AFB1 during food fermentations. 相似文献
86.
87.
Altered neuregulin 1-erbB4 signaling contributes to NMDA receptor hypofunction in schizophrenia 总被引:24,自引:0,他引:24
Hahn CG Wang HY Cho DS Talbot K Gur RE Berrettini WH Bakshi K Kamins J Borgmann-Winter KE Siegel SJ Gallop RJ Arnold SE 《Nature medicine》2006,12(7):824-828
Recent molecular genetics studies implicate neuregulin 1 (NRG1) and its receptor erbB in the pathophysiology of schizophrenia. Among NRG1 receptors, erbB4 is of particular interest because of its crucial roles in neurodevelopment and in the modulation of N-methyl-D-aspartate (NMDA) receptor signaling. Here, using a new postmortem tissue-stimulation approach, we show a marked increase in NRG1-induced activation of erbB4 in the prefrontal cortex in schizophrenia. Levels of NRG1 and erbB4, however, did not differ between schizophrenia and control groups. To evaluate possible causes for this hyperactivation of erbB4 signaling, we examined the association of erbB4 with PSD-95 (postsynaptic density protein of 95 kDa), as this association has been shown to facilitate activation of erbB4. Schizophrenia subjects showed substantial increases in erbB4-PSD-95 interactions. We found that NRG1 stimulation suppresses NMDA receptor activation in the human prefrontal cortex, as previously reported in the rodent cortex. NRG1-induced suppression of NMDA receptor activation was more pronounced in schizophrenia subjects than in controls, consistent with enhanced NRG1-erbB4 signaling seen in this illness. Therefore, these findings suggest that enhanced NRG1 signaling may contribute to NMDA hypofunction in schizophrenia. 相似文献
88.
89.
90.
Retention of cryptic genes in microbial populations 总被引:5,自引:0,他引:5
Cryptic genes are silenced genes that can still be reactivated by mutation.
Since they can make no positive contribution to the fitness of their
carriers, it is not clear why many cryptic genes in microbial populations
have not degenerated into useless DNA sequences. Hall et al. (1983) have
suggested that cryptic genes have persisted because of occasional strong
environmental selection for reactivated genes. The present mathematical
study supports their suggestion. It shows that a cryptic gene can be
retained without having any selective advantage over a useless DNA
sequence, if selection for the reactivated gene occasionally occurs for a
substantially long time.
相似文献