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81.
氟化物对桑蚕幼虫中肠ATP酶活性影响的电镜细胞化学定位 总被引:2,自引:1,他引:1
氟化物对桑蚕幼虫中肠ATP酶活性影响的电镜细胞化学定位陈玉银,包焕盛,吴玉澄(浙江农业大学杭州3100N)桑蚕Bombyxmori(L.)氟中毒导致蚕茧严重减产是目前蚕业界最为关切的问题,有关桑蚕幼虫氟中毒的机理研究也从各方面展开[11]。已知桑蚕氟... 相似文献
82.
Adherence Patterns and DNA Probe Types of Escherichia coli Isolated from Diarrheal Patients in China
Jian-Guo Xu Bo-Qun Cheng Yan-Ping Wu Li-Bao Huang Xin-He Lai Bing-Yang Liu Xing-Zu Lo Hun-Fen Li 《Microbiology and immunology》1996,40(2):89-97
One hundred and seventy-two strains of Escherichia coli isolated from diarrheal patients in Beijing, P. R. China, were analyzed for plasmid DNA profile, HEp-2 cell adherence ability and reactivity to 10 previously described DNA probes. They had not been recognized as pathogenic E. coli in China. Of the 110 strains tested, 76 (69%) contained one or multiple large plasmids. Of the 71 strains with the large plasmids 64 could adhere to HEp-2 cells. Of the 172 strains, 102 (59.3%) were hybridized with at least one of the 10 probes. Of those, seven strains hybridized with enteroaggregative E. coli (EAggEC) probe. Their serotypes were O128 (two strains), O6 (one strain), and O111 (one strain). Three strains were untypable. Six and three strains were hybridized with enteropathogenic E. coli (EPEC) attaching and effacing genes (eae) or EPEC adherence factor (EAF) probe, respectively. Two non-O157: H7 strains hybridized with enterohemorrhagic E. coli (EHEC) probe. Seventy-two strains (41.9%) hybridized with shiga-like toxin 2 or 1 (SLT2 or SLT1) probes. Among the SLT1 or SLT2 probe-positive strains, 54 hybridized with invasive (INV) plasmid probe developed for identification of enteroinvasive E. coli (EIEC) and Shigella species. The INV and SLT probe-positive strains might represent a new variety of verotoxin-producing E. coli (VTEC). 相似文献
83.
中国貂祝蛾属研究及二新种记述(鳞翅目:祝蛾科)武春生(中国科学院动物研究所北京100080)貂祝蛾属AthymorisMeyrick,1935曾一直是瘤祝蛾亚科(Torodorinae)中的一个单型属,分布于我国和日本。其前翅的M2+3合并,且靠近共... 相似文献
84.
85.
Zhao Rongrui Wang Wenze Wu Bowei Hoebeke Johan Hjalmarson Åke Fu Michael L. X. 《Molecular and cellular biochemistry》1996,163(1):185-193
The effects of anti-peptide antibodies against the second extracellular loop of human M2 muscarinic receptor on transmembrane potentials and currents in guinea pig single ventricular cells were analyzed using whole-cell patch clamp technique. These effects were compared with those of the muscarinic receptor agonists carbachol and acetylcholine. The antibodies shortened the action potential duration in a dose-dependent manner. By using a ramp or step rectangular pulse protocol, it was found that the antibodies increased the outward K+ current and decreased the inward basal I Ca significantly. The reversal potential of both carbachol-and antibody-induced extra currents were close to –80 mV, being in proximity to the calculated Ek of –90 mV. A -adrenergic receptor agonist, isoprenaline, prolonged the action potential and increased the overshoot which could be inhibited by both antibody and carbachol. Isoprenaline increased inward Ica and outward Ik simultaneously. Both antibody and carbachol could significantly reduce the isoprenaline-stimulated ICa but not the isoprenaline-stimulated Ik. The antibody- or carbachol-induced outward K+ current and the depressant effects of antibody and carbachol on isoprenaline-stimulated Ica were partially antagonized by atropine. These results suggest that the anti-M2 muscarinic receptor antibodies display a stimulatory activity similar to muscarinic receptor agonist on the receptor-mediated electrophysiological events. 相似文献
86.
The intrinsic chlorophyll-protein CP 47 is a component of photosystem II which functions in both light-harvesting and oxygen evolution. Using site-directed mutagenesis we have produced the mutant W167S which lies in loop C of CP 47. This strain exhibited a 75% loss in oxygen evolution activity and grew extremely slowly in the absence of glucose. Examination of normalized oxygen evolution traces indicated that the mutant was susceptible to photoinactivation. Analysis of the variable fluorescence yield indicated that the mutant accumulated very few functional PS II reaction centers. This was confirmed by immunoblotting experiments. Interestingly, when W167S was grown in the presence of 20 M DCMU, the mutant continued to exhibit these defects. These results indicate that tryptophan 167 in loop C of CP 47 is important for the assembly and stability of the PS II reaction center. 相似文献
87.
Previous work on the growth biophysics of maize (Zea mays L.) primary roots suggested that cell walls in the apical 5 mm of the elongation zone increased their yielding ability as an adaptive response to low turgor and water potential (psi w). To test this hypothesis more directly, we measured the acid-induced extension of isolated walls from roots grown at high (-0.03 MPa) or low (-1.6 MPa) psi w using an extensometer. Acid-induced extension was greatly increased in the apical 5 mm and was largely eliminated in the 5- to 10-mm region of roots grown at low psi w. This pattern is consistent with the maintenance of elongation toward the apex and the shortening of the elongation zone in these roots. Wall proteins extracted from the elongation zone possessed expansin activity, which increased substantially in roots grown at low psi w. Western blots likewise indicated higher expansin abundance in the roots at low psi w. Additionally, the susceptibility of walls to expansin action was higher in the apical 5 mm of roots at low psi w than in roots at high psi w. The basal region of the elongation zone (5-10 mm) did not extend in response to expansins, indicating that loss of susceptibility to expansins was associated with growth cessation in this region. Our results indicate that both the increase in expansin activity and the increase in cell-wall susceptibility to expansins play a role in enhancing cell-wall yielding and, therefore, in maintaining elongation in the apical region of maize primary roots at low psi w. 相似文献
88.
The p21WAF-1 gene is positively regulated by the wild-type p53 protein. p21WAF-1 has been shown to interact with several cyclin-dependent kinase complexes and block the activity of G1 cyclin-dependent kinases (cdks). Mutational analysis with the p21WAF-1 gene localized a site, at amino acid residues 21 and 24 in the amino terminus of the protein, for p21WAF-1 binding to cyclins D and E. This region of the protein is conserved (residues 21 to 26) in other p21WAF-1 family members, p27kip-1 and p57kip-2. The same p21WAF-121,24 mutant also fails to bind to cyclin D1-cdk 4 or cyclin E-cdk 2 complexes in vitro, suggesting that amino acid residues 21 and 24 are important for p21WAF-1-cdk-cyclin trimeric complex interactions. The p21WAF-1 wild-type protein will suppress tumor cell growth in culture while p21WAF-1 mutant proteins with defects in residues 21 and 24 fail to suppress tumor cell growth. The overexpression of cyclin D or E in these cells will partially overcome the growth suppression of wild-type p21WAF-1 protein in cells. These results provide evidence that p21WAF-1 acts through cyclin D1-cdk4 and cyclin E-cdk2 complexes in vivo to induce the growth suppression. The p21WAF-1 binding sites for cyclins (residues 21 to 26), cdk2 (residues 49 to 71), and proliferating-cell nuclear antigen (residues 124 to 164) have all been mapped to discrete sites on the protein. 相似文献
89.
90.
自养黄杆菌合成羟基丁酸和羟基戊酸共聚体的发酵研究 总被引:14,自引:2,他引:12
采用本实验室从土壤中分离到的一株自养黄杆菌进行了羟基丁酸和羟基戊酸共聚体〔P(HB-co-HV)〕的发酵试验。实验结果表明,该菌株是自养黄杆菌葡萄糖运输突变株,可以葡萄糖、果糖、蔗糖、麦芽糖、乙酸盐、乳酸盐和苹果酸盐作为唯一碳源,尤以葡萄糖和果糖效果最佳。硫酸铵、氯化铵和蛋白胨等不同氮源不影响其生长,却影响细胞中P(HB-co-HV)的含量和P(HB-co-HV)中HV/HB的比例。应用两阶段控制方式,经42h的补料分批发酵,细胞浓度达34.9g·L~(-1),P(HB-co-HV)浓度达25.28g·L~(-1)。细胞和P(HB-co-HV)生产速率系数分别为0.83g·L~(-1)”·h~(-1)和0.61g·L~(-1)·h~(-1)。以基质为基准的细胞得率系数(Yx/s)、产物得率系数(Yp/s)和以干细胞为基准的产物得率系数(Yp/x)分别为0.283(g/g)、0.174(g/g)和0.73(g/g)。改变培养基中碳氮源组分可将P(HB-co-HV)中HB的含量调节在24%~78%之间。 相似文献