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991.
Deoxyribozymes that could catalyze the formation of an internucleotide phosphorothioester linkage were selected from a random
sequence pool. During the course of the selection, the pool was successively challenged with five oligonucleotide substrates,
each of which terminated in the same hexanucleotide sequence. Selected deoxyribozyme ligases could use all five substrates,
albeit to different degrees, and appeared to form secondary structures that allow differential pairing between the deoxyribozyme
and each substrate. These results suggest that early replicases may have been able to bind a variety of oligonucleotide substrates
while catalyzing ligation via a common junction.
Received: 12 December 2000 / Accepted: 28 June 2001 相似文献
992.
Melamed‐Frank Meira Terzic Andre Carrasco Antonio J. Nevo Eviatar Avivi Aaron Levy Andrew P. 《Molecular and cellular biochemistry》2001,225(1-2):145-150
The ATPsensitive potassium (KATP) channel is thought to play an important role in the protection of heart and brain against tissue hypoxia. The genetic regulation of the components of the channel by hypoxia has not been previously described. Here, we investigated the regulation of the two poreforming channel proteins, Kir6.1 and Kir6.2, in response to hypoxia in vivo and in vitro. We find that these two structurallyrelated inwardly-rectifying potassium channel proteins are reciprocally regulated by hypoxia in vivo, with upregulation of Kir6.1 and downregulation of Kir6.2, thereby resulting in a significant change in the composition of the channel complex in response to hypoxia. In vitro we describe neuronal and cardiac cell lines in which Kir6.1 is upregulated by hypoxia, demonstrating that Kir6.1 is a hypoxiainducible gene. We conclude that the heart and brain display genetic plasticity in response to hypoxic stress through specific genetic reprograming of cytoprotective channel genes. 相似文献
993.
Modulation of intestinal and liver fatty acid-binding proteins in Caco-2 cells by lipids, hormones and cytokines 总被引:5,自引:0,他引:5
Dubé N Delvin E Yotov W Garofalo C Bendayan M Veerkamp JH Levy E 《Journal of cellular biochemistry》2001,81(4):613-620
Intestinal and liver fatty acid binding proteins (I- and L-FABP) are thought to play a role in enterocyte fatty acid (FA) trafficking. Their modulation by cell differentiation and various potential effectors was investigated in the human Caco-2 cell line. With the acquisition of enterocytic features, Caco-2 cells seeded on plastic progressively increased L-FABP quantities, whereas I-FABP was not detectable even very late in the maturation process. On permeable filters that improved differentiation markers (sucrase, alkaline phosphatase, transepithelial resistance), Caco-2 cells furthered their L-FABP content and expressed I-FABP. Western blot analysis showed a significant increase in I- and L-FABP expression following an 8-hour incubation period with butyric acid, oleic acid, and phosphatidylcholine. However, in all cases, I-FABP levels were higher than L-FABP concentrations regardless of the lipid substrates added. Similarly, hydrocortisone and insulin enhanced the cellular content of I- and L-FABP whereas leptin triggered I-FABP expression only after an 8-hour incubation. Finally, tumor necrosis factor-alpha was more effective in increasing the cytosolic amount of I-FABP levels. In conclusion, our data demonstrate that I-FABP expression is limited to fully differentiated Caco-2 cells and can be more easily regulated than L-FABP by lipids, hormones, and cytokines. 相似文献
994.
Due to the difficulty to crystallize membrane proteins, there is a considerable interest to intensify research topics aimed at developing new methods of crystallization. In this context, the lipid layer crystallization at the air/water interface, used so far for soluble proteins, has been recently adapted successfully to produce two-dimensional (2D) crystals of membrane proteins, amenable to structural analysis by electron crystallography. Besides to represent a new alternative strategy, this approach gains the advantage to decrease significantly the amount of material needed in incubation trials, thus opening the field of crystallization to those membrane proteins difficult to surexpress and/or purify. The systematic studies that have been performed on different classes of membrane proteins are reviewed and the physico-chemical processes that lead to the production of 2D crystals are addressed. The different drawbacks, advantages and perspectives of this new strategy for providing structural information on membrane proteins are discussed. 相似文献
995.
A genomewide scan for loci predisposing to type 2 diabetes in a U.K. population (the Diabetes UK Warren 2 Repository): analysis of 573 pedigrees provides independent replication of a susceptibility locus on chromosome 1q 总被引:19,自引:0,他引:19 下载免费PDF全文
Wiltshire S Hattersley AT Hitman GA Walker M Levy JC Sampson M O'Rahilly S Frayling TM Bell JI Lathrop GM Bennett A Dhillon R Fletcher C Groves CJ Jones E Prestwich P Simecek N Rao PV Wishart M Bottazzo GF Foxon R Howell S Smedley D Cardon LR Menzel S McCarthy MI 《American journal of human genetics》2001,69(3):553-569
Improved molecular understanding of the pathogenesis of type 2 diabetes is essential if current therapeutic and preventative options are to be extended. To identify diabetes-susceptibility genes, we have completed a primary (418-marker, 9-cM) autosomal-genome scan of 743 sib pairs (573 pedigrees) with type 2 diabetes who are from the Diabetes UK Warren 2 repository. Nonparametric linkage analysis of the entire data set identified seven regions showing evidence for linkage, with allele-sharing LOD scores > or =1.18 (P< or =.01). The strongest evidence was seen on chromosomes 8p21-22 (near D8S258 [LOD score 2.55]) and 10q23.3 (near D10S1765 [LOD score 1.99]), both coinciding with regions identified in previous scans in European subjects. This was also true of two lesser regions identified, on chromosomes 5q13 (D5S647 [LOD score 1.22] and 5q32 (D5S436 [LOD score 1.22]). Loci on 7p15.3 (LOD score 1.31) and 8q24.2 (LOD score 1.41) are novel. The final region showing evidence for linkage, on chromosome 1q24-25 (near D1S218 [LOD score 1.50]), colocalizes with evidence for linkage to diabetes found in Utah, French, and Pima families and in the GK rat. After dense-map genotyping (mean marker spacing 4.4 cM), evidence for linkage to this region increased to a LOD score of 1.98. Conditional analyses revealed nominally significant interactions between this locus and the regions on chromosomes 10q23.3 (P=.01) and 5q32 (P=.02). These data, derived from one of the largest genome scans undertaken in this condition, confirm that individual susceptibility-gene effects for type 2 diabetes are likely to be modest in size. Taken with genome scans in other populations, they provide both replication of previous evidence indicating the presence of a diabetes-susceptibility locus on chromosome 1q24-25 and support for the existence of additional loci on chromosomes 5, 8, and 10. These data should accelerate positional cloning efforts in these regions of interest. 相似文献
996.
997.
998.
The gene transfer technique, transgenesis, has permitted the transfer of genes from one organism to another to create new lineages of organisms with improvement in traits important to aquaculture. Genetically modified organisms (GMOs), therefore, hold promise for producing genetic improvements, such as enhanced growth rate, increased production and efficiency, disease resistance and expanded ecological ranges. The basic procedure to generate transgenic fish for aquaculture includes: (1) design and construction of transgenic DNA; (2) transfer of the gene construct into fish germ cells; (3) screening for transgenic fish; (4) determination of transgene expression and phenotype; (5) study of inheritance; and (6) selection of stable lines of transgenics.GMOs offer economic benefits, but also pose environmental threats. Optimising the mix of benefits and risks is of fundamental importance. The potential economic benefits of transgenic technology to aquaculture are obvious. Transgenic fish production has the goal of producing food for human consumption; thus the design of genetic constructs must take into consideration the potential risks to consumer health, as well as marketing strategies and product acceptance in the market. 相似文献
999.
Natural and anthropogenic disturbances may fragment stony reef corals, but few quantitative data exist on the impacts of
skeletal fragmentation on sexual reproduction in corals. We experimentally fragmented colonies of the branching coral Pocillopora damicornis and determined the number and size of planula larvae released during one lunar reproductive cycle. Partially fragmented colonies
significantly delayed both the onset and peak period of planula release compared with intact control colonies. Most fragments
removed from the corals died within 11–18 days, and released few planulae. The total number of planulae released per coral
colony varied exponentially with remaining tissue volume, and was significantly lower in damaged versus undamaged colonies.
However, the number of planulae produced per unit tissue volume, and planula size, did not vary with damage treatment. We
conclude that even partial fragmentation of P. damicornis colonies (<25% of tissue removed) decreases their larval output by reducing reproductive tissue volume. Repeated breakage
of corals, such as caused by intensive diving tourism or frequent storms, may lead to substantially reduced sexual reproduction.
Therefore, reef management should limit human activities that fracture stony corals and lead to decreases in colony size and
reproductive output.
Accepted: 2 February 2000 相似文献
1000.