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61.
62.
镉对雄性小鼠生精细胞的影响 总被引:1,自引:0,他引:1
为了研究镉对小鼠生殖力和生精细胞的作用,本文对氯化镉处理后的雄性小鼠进行了交配实验,以观察其对怀孕率、每窝产仔数及子代性比的影响。测定比较了注射镉后,小鼠成熟精子的总LDH酶和LDH-X酶的活性;还用双向电泳方法分析了成熟精子的蛋白质变化。结果表明,处理组在怀孕率、每窝产仔数及子代性比方面无统计学意义的差异。成熟精子的总LDH活性经镉处理后未发现明显变化,但镉能显著地抑制与精子运动的能量有关的LDH-X酶的活性。双向电泳图谱表示,镉处理后,精子中含量较少的三组蛋白质或消失不见,或发生明显变化。 相似文献
63.
64.
通过青海锡铁山铅、锌矿区植物群落和植物中铅,锌含量特征的调查研究表明:该区植被为荒漠植被类型。矿带上的植物群落与非矿带上的相比较,群落中种属数目更少,覆盖度更低,植物生长更低矮。植物灰分中的锌含量(平均)为125.9—1144ppm。膜果麻黄(Ephedra przewalskii)含量最高,变化范围最大,为86.11—5871.88ppm。植物中的铅含量为31.32—1129.6ppm。黑柴(Sympegma regelii)含量较高,变化最大,平均为746ppm,极值为14.3—5561.70ppm。在矿带上含量最高,非矿带对照区含量最低。植物及其生长的土壤中金属元素含量之间的关系,无论是铅还是锌含量都有很好的线性关系。膜果麻黄、黑柴、优若藜(Eurotia ceratoides)和中亚紫菀木(Asterothamnus centrali-asiaticus)等植物相关系数均达显著相关水平(α≤0.05)。 这在植物地球化学勘探上是非常有用的。例如中亚紫菀木和琵琶柴(Reaumuria soongorica)中铅的植物地球化学异常,准确地圈出了铅、锌矿的位置,衬度高,异常范围与矿化区基本吻合。 相似文献
65.
A comprehensive classification of nucleic acid structural families based on strand direction and base pairing. 下载免费PDF全文
We propose a classification of DNA structures formed from 1 to 4 strands, based only on relative strand directions, base to strand orientation and base pairing geometries. This classification and its associated notation enable all nucleic acids to be grouped into structural families and bring to light possible structures which have not yet been observed experimentally. It also helps in understanding transitions between families and can assist in the design of multistrand structures. 相似文献
66.
By means of technique of cell culture, 3H-thymidine incorporation and dot blot, it was demonstrated that angiotensin II (AGT II) stimulated proliferation and c-fos oncogene expression in cultured SHR vascular smooth muscle cells (VSMC) in a dose-dependent manner. This effect of AGT II was significantly inhibited by co-incubation with ANP. The results suggest that proliferation of VSMC is regulated by some interaction between AGT II and ANP. 相似文献
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68.
The nuclear matrix is operationally defined as the structure remaining after nuclease-digested nuclei are extracted with high concentrations of salt. The nuclear matrix is thought to have a role in organizing higher order chromatin into loop domains. We determined whether specific regions of the histone H5 gene were very tightly bound to protein of erythrocyte and liver nuclear matrices in vitro. We demonstrate that DNA fragments spanning sequences 5' to the promoter and the 3' enhancer region of the histone H5 gene, but not DNA fragments spanning the promoter, were very tightly bound to protein of nuclear matrices of erythrocytes and liver. The nuclear matrix consists of internal nuclear matrix and nuclear pore-lamina complex. Recently, we demonstrated that histone deacetylase could be used as a marker enzyme of the internal nuclear matrix. We demonstrate that nuclear pore-lamina complex preparations that were depleted of histone deacetylase activity, and thus of internal nuclear matrix, retained the protein that bound very tightly to the beta-globin and histone H5 enhancers. These results provide evidence that specific regions of the histone H5 gene are very tightly bound to nuclear pore-lamina complex protein. 相似文献
69.
Although the acyl groups of phosphatidylserine in brain are uniquely enriched in docosahexaenoic acid (22:6n3), the mechanism for this enrichment is not well understood. When rat brain homogenates and microsomes were incubated in the presence of lysophosphatidylserine (LPS) together with [14C]22:6n3 and cofactors for activation to its acylCoA, very little radioactivity was incorporated into phosphatidylserine (PS). On the other hand, [14C]20:4n6 was more actively incorporated into PS. Addition of LPS (1-10 uM), however, resulted in a 2-5 fold enhancement of the transfer of labeled 22:6n3 and 20:4n6 to phosphatidic acid (PA). Kinetic analysis indicated the ability of LPS to lower the Km and increase the Vmax of the lysophosphatidic acid (LPA) acyltransferase reaction. Among other lysophospholipids tested, lysophosphatidylserine was most effective in enhancing PA biosynthesis. Since PA is an important intermediate for de novo biosynthesis of phospholipids, these results reveal a novel mechanism for promoting synthesis of PA enriched in polyunsaturated fatty acids in brain. 相似文献
70.
Conformational epitope on gp120 important in CD4 binding and human immunodeficiency virus type 1 neutralization identified by a human monoclonal antibody. 总被引:51,自引:35,他引:16 下载免费PDF全文
D D Ho J A McKeating X L Li T Moudgil E S Daar N C Sun J E Robinson 《Journal of virology》1991,65(1):489-493
A human monoclonal antibody designated 15e is reactive with the envelope glycoprotein (gp120) of multiple isolates of human immunodeficiency virus type 1 (HIV-1). Antibody 15e also neutralizes HIV-1 with broad specificity and blocks gp120 binding to CD4. Characterization of the 15e epitope shows that it is conformation dependent and is distinct from previously recognized functional domains of gp120, suggesting that this epitope represents a novel site important for HIV-1 neutralization and CD4 binding. These findings have implications for the development of a vaccine for AIDS. 相似文献