排序方式: 共有56条查询结果,搜索用时 15 毫秒
41.
Changes in ionized calcium were studied in axons isolated from living squid by measuring absorbance of the Ca binding dye Arsenazo III using multiwavelength differential absorption spectroscopy. Absorption changes measured in situ were calibrated in vitro with media of ionic composition similar to axoplasm containing CaEGTA buffers. Calcium loads of 50-2,500 μmol/kg axoplasm were induced by microinjection, by stimulation in 112 mM Ca seawater, or by soaking in choline saline with 1-10 mM Ca. Over this range of calcium loading of intact axoplasm, the ionized calcium in the axoplasm rose about 0.6 nM/μM load. Similar loading in axons preteated with carbonyl cyanide 4- trifluoromethoxyphenylhydrazone (FCCP) to inhibit the mitochondrial proton gradient increased ionized calcium by 5-7 percent of the imposed load, i.e. 93-95 percent of the calcium load was buffered by a process insensitive to FCCP. This FCCP- insensitive buffer system was not saturated by the largest calcium loads imposed, indicating a capacity of at least several millimolar. Treatment of previously loaded axons with FCCP or apyrase plus cyanide produced rises in ionized calcium which could be correlated with the extent of the load. Analysis of results indicated that, whereas only 6 percent of the endogenous calcium in fresh axons is stored in the FCCP-sensitive (presumably mitochondrial) buffer system, about 30 percent of an imposed exogenous load in the range of 50-2,500 μM is taken up by this system. 相似文献
42.
为建立鸭乙型肝炎病毒LJ-76的转染细胞系,将LJ-76病毒DNA插入到pUC19的EcoRⅠ位点上,分离得到含有双拷贝LJ-76DNA的重组质粒.通过磷酸钙沉淀方法,将经CsCl等密度离心纯化的LJ-76DNA双体导入到人肝癌细胞BEL7402中.收集转染细胞的培养液进行蔗糖密度梯度离心,所得沉淀经检测发现含有LJ-76DNA并具有特异性DHBV内源性DNA多聚酶活性;对上述样品通过DotEIA检测DHBV核心抗原及表面抗原结果为阳性.Southernblot分析表明转染细胞内存在病毒DNA复制中间体cccDNA、ssDNA和rcDNA,而cccDNA被认为是复制活动较为活跃的标志.电镜观察转染细胞的上清发现有病毒颗粒的存在. 相似文献
43.
44.
45.
Danyel GJ Jennen Addie LJ Vereijken Henk Bovenhuis Richard MPA Crooijmans Jan J van der Poel Martien AM Groenen 《遗传、选种与进化》2005,37(3):215-228
In this report we describe the analysis of an advanced intercross line (AIL) to confirm the quantitative trait locus (QTL) regions found for fatness traits in a previous study. QTL analysis was performed on chromosomes 1, 3, 4, 15, 18, and 27. The AIL was created by random intercrossing in each generation from generation 2 (G2) onwards until generation 9 (G9) was reached. QTL for abdominal fat weight (AFW) and/or percentage abdominal fat (AF%) on chromosomes 1, 3 and 27 were confirmed in the G9 population. In addition, evidence for QTL for body weight at the age of 5 (BW5) and 7 (BW7) weeks and for the percentage of intramuscular fat (IF%) were found on chromosomes 1, 3, 15, and 27. Significant evidence for QTL was detected on chromosome 1 for BW5 and BW7. Suggestive evidence was found on chromosome 1 for AFW, AF% and IF%, on chromosome 15 for BW5, and on chromosome 27 for AF% and IF%. Furthermore, evidence on the chromosome-wise level was found on chromosome 3 for AFW, AF%, and BW7 and on chromosome 27 for BW5. For chromosomes 4 and 18, test statistics did not exceed the significance threshold. 相似文献
46.
Several theories have been developed to explain why invasive species are very successful and develop into pest species in
their new area. The shifting defence hypothesis (SDH) argues that invasive plant species quickly evolve towards new defence
levels in the invaded area because they lack their specialist herbivores but are still under attack by local (new) generalist
herbivores. The SDH predicts that plants should increase their cheap, toxic defence compounds and lower their expensive digestibility
reducing compounds. As a net result resources are saved that can be allocated to growth and reproduction giving these plants
a competitive edge over the local plant species. We conducted a literature study to test whether toxic defence compounds in
general are increased in the invaded area and if digestibility reducing compounds are lowered. We specifically studied the
levels of pyrrolizidine alkaloids, a toxin which is known for its beneficial and detrimental impact against specialists and
generalists, respectively. Digestibility reducers did not show a clear trend which might be due to the small number of studies
and traits measured. The meta analysis showed that toxic compounds in general and pyrrolizidine alkaloid levels specifically,
increased significantly in the invaded area, supporting the predictions of the SDH that a fast evolution takes place in the
allocation towards defence. 相似文献
47.
48.
LJ Melchers MJAM Clausen MF Mastik L Slagter-Menkema JE van der Wal GBA Wisman JLN Roodenburg E Schuuring 《Epigenetics》2015,10(9):850-860
Hypermethylation is an important mechanism for the dynamic regulation of gene expression, necessary for metastasizing tumour cells. Our aim is to identify methylation tumour markers that have a predictive value for the presence of regional lymph node metastases in patients with oral and oropharyngeal squamous cell carcinoma (OOSCC). Significantly differentially expressed genes were retrieved from four reported microarray expression profiles comparing pN0 and pN+ head-neck tumours, and one expression array identifying functionally hypermethylated genes. Additional metastasis-associated genes were included from the literature. Thus genes were selected that influence the development of nodal metastases and might be regulated by methylation. Methylation-specific PCR (MSP) primers were designed and tested on 8 head-neck squamous cell carcinoma cell lines and technically validated on 10 formalin-fixed paraffin-embedded (FFPE) OOSCC cases. Predictive value was assessed in a clinical series of 70 FFPE OOSCC with pathologically determined nodal status. Five out of 28 methylation markers (OCLN, CDKN2A, MGMT,
MLH1 and DAPK1) were frequently differentially methylated in OOSCC. Of these, MGMT methylation was associated with pN0 status (P = 0.02) and with lower immunoexpression (P = 0.02). DAPK1 methylation was associated with pN+ status (P = 0.008) but did not associate with protein expression. In conclusion, out of 28 candidate genes, two (7%) showed a predictive value for the pN status. Both genes, DAPK1 and MGMT, have predictive value for nodal metastasis in a clinical group of OOSCC. Therefore DNA methylation markers are capable of contributing to diagnosis and treatment selection in OOSCC. To efficiently identify additional new methylation markers, genome-wide methods are needed. 相似文献
49.