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排序方式: 共有6209条查询结果,搜索用时 750 毫秒
971.
972.
van den Berg MA Albang R Albermann K Badger JH Daran JM Driessen AJ Garcia-Estrada C Fedorova ND Harris DM Heijne WH Joardar V Kiel JA Kovalchuk A Martín JF Nierman WC Nijland JG Pronk JT Roubos JA van der Klei IJ van Peij NN Veenhuis M von Döhren H Wagner C Wortman J Bovenberg RA 《Nature biotechnology》2008,26(10):1161-1168
973.
Murphy J 《Journal of applied animal welfare science : JAAWS》2008,11(3):228-231
There is an inherent element of risk associated with "backing" and riding the previously unbroken horse. If training proceeds too quickly, conflict behaviors may result from the simultaneous application of too many cues. Automated horse walkers (AHW) facilitate the exercising of several horses concurrently at walk or trot for warm-up, cool-down, fitness programs, and rehabilitation purposes. The objective of this study was to investigate if backing the horse within the AHW was an appropriate training method. Ten horses (3-year-olds) took part in this study. They began training within the AHW with a simple bridle and protective boots. A handler subsequently long-reined the horses within the AHW when they wore rollers, side reins, and a saddle. When considered appropriate, the handler went from jumping beside the horse to lying over the saddle to sitting astride the horse within the AHW. The horses habituated to this innovative approach quickly without evidence of conflict behavior. The handler rode the horses from the AHW after approximately 4 riding episodes of this innovative training system. 相似文献
974.
Wood A Ogawa M Portier RJ Schexnayder M Shirley M Losso JN 《Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology》2008,151(3):246-249
Acid-soluble collagen (ASC) and pepsin solubilized collagen (PSC) isolated and purified from alligator (Alligator mississippiensis) bone were studied for molecular size, amino acid profile, secondary structure, and denaturation temperature by SDS-PAGE, HPLC, circular dichroism, and viscometry. Two collagen subunits, alpha1 and alpha2 were identified by SDS-PAGE. The molecular masses for alpha1 and alpha2 chains of ASC were 124 kDa and 111 kDa, respectively. The molecular masses were 123 kDa for alpha1 and 110 kDa for alpha2 chains of the PSC preparation. The molecular masses for ([alpha1](2) alpha2) of ASC and PSC were 359 kDa and 356 kDa, respectively. The major composition of alligator bone ASC and PSC was found to be typical type I collagen. The amino acid profiles of alligator ASC and PSC were similar to amino acid profile of subtropical fish black drum (Pogonias cromis, Sciaenidae) bone. Comparison of amino acid profiles with shark cartilage PSC, showed differences in alanine, hydroxylysine, lysine, and histidine contents. The denaturation temperatures (T(d)) of alligator ASC and PSC collagen measured by viscometry were 38.1 and 38.2 degrees C, respectively. Thermal denaturation temperatures, measured by melting point using circular dichroism, were 37.6 and 37.9 degrees C, respectively. Taken together, these results suggest that alligator bone collagen may find a wide range of applications in biological research, functional foods and nutraceuticals, and biomedical and pharmaceutical research. 相似文献
975.
Nedea E Nalbant D Xia D Theoharis NT Suter B Richardson CJ Tatchell K Kislinger T Greenblatt JF Nagy PL 《Molecular cell》2008,29(5):577-587
Glc7, the yeast protein phosphatase 1, is a component of the cleavage and polyadenylation factor (CPF). Here we show that downregulation of Glc7, or its dissociation from CPF in the absence of CPF subunits Ref2 or Swd2, results in similar snoRNA termination defects. Overexpressing a C-terminal fragment of Sen1, a superfamily I helicase required for snoRNA termination, suppresses the growth and termination defects associated with loss of Swd2 or Ref2, but not Glc7. Suppression by Sen1 requires nuclear localization and direct interaction with Glc7, which can dephosphorylate Sen1 in vitro. The suppressing fragment, and in a similar manner full-length Sen1, copurifies with the snoRNA termination factors Nrd1 and Nab3, suggesting loss of Glc7 from CPF can be compensated by recruiting Glc7 to Nrd1-Nab3 through Sen1. Swd2 is also a subunit of the Set1c histone H3K4 methyltransferase complex and is required for its stability and optimal methyltransferase activity. 相似文献
976.
Influenza A virus (IAV) strains are denoted by the subtype of their hemagglutinin (HA) and neuraminidase (NA) virion surface proteins. Major changes in HA subtype among strains circulating in humans are referred to as "antigenic shift". Antigenic shift can occur by two means: direct transmission of a zoonotic strain to humans or through reshuffling of the segmented genome in cells co-infected with animal and human strains. The lack of circulating anti-HA antibodies in human populations to a novel IAV results in extremely high frequency of illness and the potential for severe morbidity and mortality on a world-wide basis; the dreaded pandemic. Such pandemics could be partially controlled by developing a vaccine that generates effective heterosubtypic immunity (HSI) based on immune recognition of IAV antigens conserved across all viral strains. While it has long been known that T cells exhibit such broad cross-reactive specificity that could provide effective HSI, recent animal studies suggest a potential role for antibodies as well. Here we review current knowledge of the mechanisms contributing to HSI to influenza and speculate on the potential for this approach to contribute to public health. 相似文献
977.
The role of human ribosomal proteins in the maturation of rRNA and ribosome production 总被引:2,自引:0,他引:2
Robledo S Idol RA Crimmins DL Ladenson JH Mason PJ Bessler M 《RNA (New York, N.Y.)》2008,14(9):1918-1929
Production of ribosomes is a fundamental process that occurs in all dividing cells. It is a complex process consisting of the coordinated synthesis and assembly of four ribosomal RNAs (rRNA) with about 80 ribosomal proteins (r-proteins) involving more than 150 nonribosomal proteins and other factors. Diamond Blackfan anemia (DBA) is an inherited red cell aplasia caused by mutations in one of several r-proteins. How defects in r-proteins, essential for proliferation in all cells, lead to a human disease with a specific defect in red cell development is unknown. Here, we investigated the role of r-proteins in ribosome biogenesis in order to find out whether those mutated in DBA have any similarities. We depleted HeLa cells using siRNA for several individual r-proteins of the small (RPS6, RPS7, RPS15, RPS16, RPS17, RPS19, RPS24, RPS25, RPS28) or large subunit (RPL5, RPL7, RPL11, RPL14, RPL26, RPL35a) and studied the effect on rRNA processing and ribosome production. Depleting r-proteins in one of the subunits caused, with a few exceptions, a decrease in all r-proteins of the same subunit and a decrease in the corresponding subunit, fully assembled ribosomes, and polysomes. R-protein depletion, with a few exceptions, led to the accumulation of specific rRNA precursors, highlighting their individual roles in rRNA processing. Depletion of r-proteins mutated in DBA always compromised ribosome biogenesis while affecting either subunit and disturbing rRNA processing at different levels, indicating that the rate of ribosome production rather than a specific step in ribosome biogenesis is critical in patients with DBA. 相似文献
978.
The process of mRNA localization typically utilizes cis-targeting elements and trans-recognition factors to direct the compartmental organization of translationally suppressed mRNAs. mRNA localization to the endoplasmic reticulum (ER), in contrast, occurs via a co-translational, signal sequence/signal recognition particle (SRP)-dependent mechanism. We have utilized cell fractionation/cDNA microarray analysis, shRNA-mediated suppression of SRP expression, and mRNA reporter construct studies to define the role of the SRP pathway in ER-directed mRNA localization. Cell fractionation studies of mRNA partitioning between the cytosol and ER demonstrated the expected enrichment of cytosolic/nucleoplasmic protein-encoding mRNAs and secretory/integral membrane protein-encoding mRNAs in the cytosol and ER fractions, respectively, and identified a subpopulation of cytosolic/nucleoplasmic protein-encoding mRNAs in the membrane-bound mRNA pool. The latter finding suggests a signal sequence-independent pathway of ER-directed mRNA localization. Extending from these findings, mRNA partitioning was examined in stable SRP54 shRNA knockdown HeLa cell lines. shRNA-directed reductions in SRP did not globally alter mRNA partitioning patterns, although defects in membrane protein processing were observed, further suggesting the existence of multiple pathways for mRNA localization to the ER. ER localization of GRP94-encoding mRNA was observed when translation was disabled by mutation of the start codon/insertion of a 5'UTR stem-loop structure or upon deletion of the encoded signal sequence. Combined, these data indicate that the mRNA localization to the ER can be conferred independent of the signal sequence/SRP pathway and suggest that mRNA localization to the ER may utilize cis-encoded targeting information. 相似文献
979.
Matthew D. Robbins Michael D. Casler Jack E. Staub 《Molecular breeding : new strategies in plant improvement》2008,22(1):131-139
Multiple lateral branching (MLB) is a quantitatively inherited trait associated with yield in cucumber (Cucumis sativus L.; 2n = 2x = 14). Although quantitative trait loci (QTL) have been identified for MLB and QTL-marker associations have been verified
by marker-assisted selection, the individual effects of these QTL have not been characterized. To test the effects of pyramiding
QTL for MLB, molecular genotyping was utilized to create two sets (standard- and little-leaf types) of inbred backcross (IBC)
lines possessing various numbers of QTL that promote branching. These IBC lines were evaluated for lateral branch number in
two Wisconsin environments at three plant densities. Highly significant differences in the number of primary lateral branches
were detected between spacings, leaf types, and lines, but not between locations. Lateral branch number decreased at higher
plant densities in all genotypes, while genotype by environment and QTL by environment interactions were marginally non-significant.
As the number of QTL increased among IBC lines, the number of branches did not generally change in the little-leaf lines,
but decreased in the standard-leaf lines, demonstrating an epistatic effect related to genetic background during lateral branch
development. The genomic location with the greatest effect on MLB was confirmed as the QTL that was previously mapped near
the little-leaf locus (ll), while the addition of one specific QTL consistently decreased the number of lateral branches in standard-leaf lines. Although
pyramiding QTL for MLB did not uniformly increase the number of lateral branches, pyramiding QTL in IBC lines allowed further
characterization of individual QTL involved in MLB. Our results, coupled with those of previous studies indicate that lateral
branch development in cucumber is determined by growing environment (i.e., plant spacing), genetic background, and QTL composition. 相似文献
980.
Around the world in 10 million years: biogeography of the nearly cosmopolitan true toads (Anura: Bufonidae) 总被引:2,自引:0,他引:2
Jennifer B. Pramuk Tasia Robertson Jack W. Sites Jr Brice P. Noonan 《Global Ecology and Biogeography》2008,17(1):72-83
Aim The species‐rich family of true toads (Anura: Bufonidae) has been the focus of several earlier studies investigating the biogeography of geographically widespread taxa. Herein, we employ newly developed Bayesian divergence estimate methods to investigate the biogeographical history of this group. Resulting age estimates are used to test several key temporal hypotheses including that the origin of the bufonid clade pre‐dates Gondwanan vicariance (~105 million years ago, Ma). Area cladograms are also invoked to investigate the geographical origin of the family. Location Worldwide, except the Australia–New Guinea plate, Madagascar and the Antarctic. Methods A phylogenetic hypothesis of the relationships among true toads was derived from analysis of 2521 bp of DNA data including fragments from three mitochondrial (12S, tRNAval, 16S) and two nuclear (RAG‐1, CXCR‐4) genes. Analysis of multiple, unlinked loci with a Bayesian method for estimating divergence times allowed us to address the timing and biogeographical history of Bufonidae. Resulting divergence estimates permitted the investigation of alternative vicariance/dispersal scenarios that have been proposed for true toads. Results Our area cladogram resulting from phylogenetic analysis of DNA data supports a South American origin for Bufonidae. Divergence estimates indicate that the family originated earlier than had been suggested previously (78–99 Ma). The age of the enigmatic Caribbean clade was dated to the late Palaeocene–early Eocene. A return of bufonids to the New World in the Eocene was followed by rapid diversification and secondary expansion into South America by the early Oligocene (Rupelian). Main conclusions The South American origin of Bufonidae in the Upper Cretaceous was followed by relatively rapid expansion and radiation around the globe, ending with a return to the Americas via a Eurasian/North American land bridge in the Eocene. Though the exact route of this dispersal (Beringia or North Atlantic) remains unclear, an argument is made for the less frequently invoked North Atlantic connection. The origin of the enigmatic Caribbean lineage was found to be consistent with colonization following the bolide impact at the K/T boundary. These findings provide the first, firm foundation for understanding true toad divergence times and their truly remarkable and global radiation. 相似文献