首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   108篇
  免费   9篇
  2023年   1篇
  2021年   1篇
  2020年   1篇
  2019年   2篇
  2018年   4篇
  2017年   3篇
  2016年   3篇
  2015年   5篇
  2014年   6篇
  2013年   14篇
  2012年   6篇
  2011年   6篇
  2010年   4篇
  2009年   2篇
  2008年   3篇
  2007年   6篇
  2006年   2篇
  2005年   8篇
  2004年   2篇
  2003年   3篇
  2002年   3篇
  2001年   1篇
  2000年   5篇
  1999年   5篇
  1998年   3篇
  1997年   4篇
  1996年   2篇
  1995年   2篇
  1994年   1篇
  1991年   2篇
  1988年   1篇
  1987年   1篇
  1984年   1篇
  1981年   1篇
  1976年   1篇
  1975年   1篇
  1908年   1篇
排序方式: 共有117条查询结果,搜索用时 15 毫秒
61.
The present study was conducted to identify polymorphisms in CACNA2D1 gene and their association with clinical mastitis and production traits. Exon 18 and its flanking regions were screened for the presence of SNPs. Statistical analysis was performed to identify association of period of birth, breed, and genotype with mastitis incidence on randomly selected 103 Sahiwal and 102 Karan Fries cattle. PCR-RFLP analysis revealed that g.38819398G?>?A mutation in exon 18 (269?bp amplicon) of CACNA2D1 gene resolved into AA, AG, and GG genotypes in Sahiwal and Karan Fries cattle. Wald chi-square analysis revealed that the period of birth, breed, and genotype were significantly associated with mastitis incidence. GG genotyped cattle were found to be less susceptible to mastitis. Least square analysis revealed that GG and AG genotype animals of G38819398A SNP of CACNA2D1 gene in Sahiwal as well as in Karan Fries cattle were associated with higher average milk yields during 1st, 2nd, and 3rd lactations (P?<?0.01). These observations and their differential association with the incidence of mastitis and production traits can be utilized as an aid to selection for simultaneous improvement of both antagonistic traits; however, validation of results on large number of animals is warranted.  相似文献   
62.
The rate at which new mutations arise in the genome is a key factor in the evolution and adaptation of species. Here we describe the rate and spectrum of spontaneous mutations for the fission yeast Schizosaccharomyces pombe, a key model organism with many similarities to higher eukaryotes. We undertook an ∼1700-generation mutation accumulation (MA) experiment with a haploid S. pombe, generating 422 single-base substitutions and 119 insertion-deletion mutations (indels) across the 96 replicates. This equates to a base-substitution mutation rate of 2.00 × 10−10 mutations per site per generation, similar to that reported for the distantly related budding yeast Saccharomyces cerevisiae. However, these two yeast species differ dramatically in their spectrum of base substitutions, the types of indels (S. pombe is more prone to insertions), and the pattern of selection required to counteract a strong AT-biased mutation rate. Overall, our results indicate that GC-biased gene conversion does not play a major role in shaping the nucleotide composition of the S. pombe genome and suggest that the mechanisms of DNA maintenance may have diverged significantly between fission and budding yeasts. Unexpectedly, CpG sites appear to be excessively liable to mutation in both species despite the likely absence of DNA methylation.  相似文献   
63.

Background  

Virus-mediated delivery of therapeutic transgenes to the inflamed colon holds a great potential to serve as an effective therapeutic strategy for inflammatory bowel disease, since local, long-term expression of the encoded therapeutic proteins in the colorectal system is potentially achievable. Viral vectors, derived from adeno-associated virus (AAV), should be very useful for such therapeutic strategies, particularly because they can establish long-term expression of transgenes. However, few studies have been carried out to investigate the ability of AAV-based vectors to transduce the inflamed colon.  相似文献   
64.
Gene expression monitoring using gene expression microarrays represents an extremely powerful technology for gene discovery in a variety of systems. We describe the results of seven experiments using Incyte GEM technology to compile a proprietary portfolio of data concerning differential gene expression in six different models of neuronal differentiation and regeneration, and recovery from injury or disease. Our first two experiments cataloged genes significantly up‐ or down‐regulated during two phases of the retinoic acid‐induced differentiation of the embryonal carcinoma line Ntera‐2. To identify genes involved in neuronal regeneration we performed three GEM experiments, which included changes in gene expression in rat dorsal root ganglia during the healing of experimentally injured sciatic nerve, in regenerating neonatal opossum spinal cord, and during lipopolysaccharide stimulation of primary cultures of rat Schwann cells. Finally we have monitored genes involved in the recovery phase of the inflammatory disease of the rat spinal cord, experimental allergic encephalomyelitis, as well as those responsible for protection from oxidative stress in a glutamate‐resistant rat hippocampal cell line. Analysis of the results of the approximately 70,000 data points collected is presented. J. Cell. Biochem. 80:171–180, 2000. © 2000 Wiley‐Liss, Inc.  相似文献   
65.
66.

Background  

The use of lactic acid bacteria as vehicles to delivery antigens to immunize animals is a promising issue. When genetically modified, these bacteria can induce a specific local and systemic immune response against selected pathogens. Gastric acid and bile salts tolerance, production of antagonistic substances against pathogenic microorganisms, and adhesive ability to gut epithelium are other important characteristics that make these bacteria useful for oral immunization.  相似文献   
67.
Endemic plants inhabiting coastal sand dunes show augmented extinction risks due to the dynamic nature of dunes and strong human pressure on coastal areas. To investigate the survival strategies and threats to long‐term survival of such species, we combined genetic, morphological and biogeographical approaches, using the example of Hieracium eriophorum (Asteraceae) and its putative cryptic sister species H. prostratum, which are endemic to the longest coastal sand dune in Europe. An analysis of amplified fragment length polymorphism revealed high within‐population genetic variability, and slight isolation by distance was the only indication of genetic population structure. Thus, no signs of genetic threats to survival were found. Furthermore, genetic and morphometric data provided no evidence for the existence of two species. Therefore, we propose to synonymize H. prostratum with H. eriophorum and provide a nomenclatural overview with typification. Finally, an analysis of historical distribution records showed that, during the last 100 years, the species was lost from its range margins, where its habitat became fragmented. Taken together, our results suggest that one successful survival strategy of narrow endemics may be the achievement of large local population sizes on a small geographical scale, thus avoiding the genetic problems inherent to small and fragmented populations. Dune management policies should thus take care that the current tendencies to allow more erosion will not result in too severe fragmentation of the remaining continuous stretches of dune habitat. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169 , 365–377.  相似文献   
68.
Late-onset Alzheimer''s disease (LOAD) is the most common form of dementia in the elderly. The National Institute of Aging-Late Onset Alzheimer''s Disease Family Study and the National Cell Repository for Alzheimer''s Disease conducted a joint genome-wide association study (GWAS) of multiplex LOAD families (3,839 affected and unaffected individuals from 992 families plus additional unrelated neurologically evaluated normal subjects) using the 610 IlluminaQuad panel. This cohort represents the largest family-based GWAS of LOAD to date, with analyses limited here to the European-American subjects. SNPs near APOE gave highly significant results (e.g., rs2075650, p = 3.2×10−81), but no other genome-wide significant evidence for association was obtained in the full sample. Analyses that stratified on APOE genotypes identified SNPs on chromosome 10p14 in CUGBP2 with genome-wide significant evidence for association within APOE ε4 homozygotes (e.g., rs201119, p = 1.5×10−8). Association in this gene was replicated in an independent sample consisting of three cohorts. There was evidence of association for recently-reported LOAD risk loci, including BIN1 (rs7561528, p = 0.009 with, and p = 0.03 without, APOE adjustment) and CLU (rs11136000, p = 0.023 with, and p = 0.008 without, APOE adjustment), with weaker support for CR1. However, our results provide strong evidence that association with PICALM (rs3851179, p = 0.69 with, and p = 0.039 without, APOE adjustment) and EXOC3L2 is affected by correlation with APOE, and thus may represent spurious association. Our results indicate that genetic structure coupled with ascertainment bias resulting from the strong APOE association affect genome-wide results and interpretation of some recently reported associations. We show that a locus such as APOE, with large effects and strong association with disease, can lead to samples that require appropriate adjustment for this locus to avoid both false positive and false negative evidence of association. We suggest that similar adjustments may also be needed for many other large multi-site studies.  相似文献   
69.
Previous studies have described the antispasmodic effect of mangiferin, a natural glucoside xanthone (2-C-β-Dgluco-pyranosyl-1,3,6,7-tetrahydroxyxanthone) that is present in mango trees and other plants, but its mechanism of action remains unknown. The aim of this study was to examine the potential contribution of the nitric oxide-cyclic GMP pathway to the antispasmodic effect of mangiferin on isolated tracheal rings preparations. The functional effect of mangiferin on allergic and non-allergic contraction of guinea pig tracheal rings was assessed in conventional organ baths. Cultured tracheal rings were exposed to mangiferin or vehicle, and nitric oxide synthase (NOS) 3 and cyclic GMP (cGMP) levels were quantified using western blotting and enzyme immunoassays, respectively. Mangiferin (0.1–10 µM) inhibited tracheal contractions induced by distinct stimuli, such as allergen, histamine, 5-hydroxytryptamine or carbachol, in a concentration-dependent manner. Mangiferin also caused marked relaxation of tracheal rings that were precontracted by carbachol, suggesting that it has both anti-contraction and relaxant properties that are prevented by removing the epithelium. The effect of mangiferin was inhibited by the nitric oxide synthase inhibitor, Nω-nitro-L-arginine methyl ester (L-NAME) (100 µM), and the soluble guanylate cyclase inhibitor, 1H-[1], [2], [4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) (10 µM), but not the adenylate cyclase inhibitor, 9-(tetrahydro-2-furyl)adenine (SQ22536) (100 µM). The antispasmodic effect of mangiferin was also sensitive to K+ channel blockers, such as tetraethylammonium (TEA), glibenclamide and apamin. Furthermore, mangiferin inhibited Ca2+-induced contractions in K+ (60 mM)-depolarised tracheal rings preparations. In addition, mangiferin increased NOS3 protein levels and cGMP intracellular levels in cultured tracheal rings. Finally, mangiferin-induced increase in cGMP levels was abrogated by co-incubation with either ODQ or L-NAME. These data suggest that the antispasmodic effect of mangiferin is mediated by epithelium-nitric oxide- and cGMP-dependent mechanisms.  相似文献   
70.

Background

Bacteria are frequently cultured from sputum samples of severe asthma patients suggesting a defect in bacterial clearance from the airway. We measured the capacity of macrophages from patients with asthma to phagocytose bacteria.

Methods

Phagocytosis of fluorescently-labelled polystyrene beads, Haemophilus influenzae or Staphylococcus aureus by broncholaveolar lavage alveolar macrophages (AM) and by monocyte-derived macrophages (MDM) from non-asthmatics, mild-moderate and severe asthmatic patients was assessed using fluorimetry.

Results

There were no differences in phagocytosis of polystyrene beads by AMs or MDMs from any of the subject groups. There was reduced phagocytosis of Haemophilus influenzae and Staphylococcus aureus in MDMs from patients with severe asthma compared to non-severe asthma (p < 0.05 and p < 0.01, respectively) and healthy subjects (p < 0.01and p < 0.001, respectively). Phagocytosis of Haemophilus influenzae and Staphylococcus aureus by AM was also reduced in severe asthma compared to normal subjects (p < 0.05). Dexamethasone and formoterol did not suppress phagocytosis of bacteria by MDMs from any of the groups.

Conclusions

Persistence of bacteria in the lower airways may result partly from a reduced phagocytic capacity of macrophages for bacteria. This may contribute to increased exacerbations, airway colonization and persistence of inflammation.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号