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91.
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小鼠Lewis肺癌组织中层粘连蛋白受体的分离及其性质的研究 总被引:2,自引:2,他引:0
层粘连蛋白(Laminin,LN)是基膜(basement membrane)中的一种主要大分子糖蛋白。一些研究资料表明肿瘤细胞的浸润转移可能与LN有关。肿瘤细胞与LN的作用可能是通过细胞表面LN受体进行的。本文采用亲和层析法从小鼠Lewis肺癌组织中分离LN受体并对其理化性质进行研究。Lewis肺癌LN受体的表观分子量为70,000,还原后SDS电泳图为一条较宽的条带。氨基酸组成中疏水氨基酸占38%,苏氨酸、絲氨酸、门冬氨酸(包括门冬酰胺)占23.5%,通过硝酸纤维素膜片法用HRP-LN测定受体与LN的结合特性,证明具有配基结合专一性,饱和性及高亲和性(Kd=0.95×10~(-9)mol/L)。 相似文献
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Summary Substructured populations exhibit an overall deficiency of heterozygosity whose proportional magnitude depends on the nature of substructuring, i.e., the number of subpopulations (s), their time of divergence (t) from the ancestral population, and the rate of gene flow amongst them (m). Since apparent heterozygote deficiency could be caused by many factors other than population substructuring, one must examine the nature of substructuring that could produce the observed extent of heterozygote deficiency, in order to infer the substructuring from an observed heterozygote deficiency. Using the equivalence of proportional heterozygote deficiency and the coefficient of gene differentiation (G
ST), we can generate isolines of G
ST as functions of s, t (in units of 2N
e generations, N
e being the effective population size) and m. Analytical results suggest that large G
ST values cannot be reached by substructuring alone, unless the number of subpopulations are large and they remain isolated over a long period of time. Application of the theory to population data on six variable number of tandem repeats (VNTR) loci in US Caucasians and US Blacks demonstrates that the observed heterozygote deficiencies at these loci cannot be explained by substructuring within these populations alone. This is so because such large values of G
ST (3%–10%) would require an absence of gene exchange between the subpopulations and a divergence time from each other of at least 25000 years ago, neither of which is compatible with the demography and ethnohistory of US Caucasians and Blacks. In contrast, the inability to detect extreme-sized alleles and/or incomplete resolution of nearly similar-sized alleles following Southern gel electrophoresis could easily explain the observed heterozygote deficiencies. The implications of these results are discussed in the context of the forensic use of DNA-typing data, and justify the employment of population genetic principles in forensic genetics. 相似文献
96.
A simple and efficient method for the oligodeoxyribonucleotide-directed mutagenesis of double-stranded plasmid DNA. 总被引:4,自引:0,他引:4
A method for the oligodeoxyribonucleotide-directed mutagenesis of double-stranded DNA without the necessity for phenotypic selection is described. Plasmids denatured with alkali and purified by adsorption to and elution from nitrocellulose have single-stranded regions where primers can hybridize and serve as templates for a T7 DNA polymerase-catalyzed synthesis of complementary mutant DNA strands. When this procedure was carried out such that the original nonmutant strand contained uracil [method of Kunkel, Proc. Natl. Acad. Sci. USA 82(1985)488-492], mutation frequencies of between 30% and 40% were obtained. The technique has been used to generate mutant genes in plasmids of a wide variety of sizes. The largest plasmid manipulated and successfully mutagenized was 22 kb. The method is rapid and efficient and is not dependent upon either f1 phage vectors or the presence of restriction sites in the vicinity of the sequence targeted for mutation. 相似文献
97.
Application of automated DNA sizing technology for genotyping microsatellite loci. 总被引:21,自引:0,他引:21
J S Ziegle Y Su K P Corcoran L Nie P E Mayrand L B Hoff L J McBride M N Kronick S R Diehl 《Genomics》1992,14(4):1026-1031
Highly polymorphic microsatellite loci offer great promise for gene mapping studies, but fulfillment of this potential will require substantial improvements in methods for accurate and efficient genotyping. Here, we report a genotyping method based on fluorescently labeled PCR primers and size characterization of PCR products using an automated DNA fragment analyzer. We capitalize on the availability of three distinct fluorescent dyes to label uniquely loci that overlap in size, and this innovation increases by threefold the number of loci that can be analyzed simultaneously. We label size standards with a fourth dye and combine these with the microsatellite PCR products in each gel lane. Computer programs provide very rapid and accurate sizing of microsatellite alleles and efficient data management. In addition, fluorescence signals are linear over a much greater range of intensity than conventional autoradiography. This facilitates multiplexing of loci (since signal intensities often vary greatly) and helps distinguish major peaks from artifacts, thereby improving genotyping accuracy. 相似文献
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99.
Species-specific diversity among simian immunodeficiency viruses from African green monkeys 总被引:23,自引:16,他引:7
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J S Allan M Short M E Taylor S Su V M Hirsch P R Johnson G M Shaw B H Hahn 《Journal of virology》1991,65(6):2816-2828
The prevalence, natural history, and genetic characteristics of simian immunodeficiency virus (SIV) infections in most feral African monkey species are presently unknown, yet this information is essential to elucidate their origin and relationship to other simian and human immunodeficiency viruses. In this study, a combination of classical and molecular approaches were used to identify and characterize SIV isolates from West African green monkeys (Cercopithecus sabaeus) (SIVagm isolates). Four SIVagm viruses from wild-caught West African green monkeys were isolated and analyzed biologically and molecularly. Amplification, cloning, and sequencing of a 279-bp polymerase fragment directly from uncultured peripheral blood mononuclear cells was facilitated by the use of nested polymerase chain reaction. The results indicated that West African green monkeys are naturally infected with SIVs which are closely related to East African SIVagm isolates. However, structural, antigenic, and genetic differences were observed which strongly suggest that the West African green monkey viruses comprise a phylogenetically distinct subgroup of SIVagm. These findings support our previous hypothesis that SIVagm viruses may have evolved and diverged coincident with the evolution and divergence of their African green monkey host. In addition, this study describes a polymerase chain reaction-based approach that allows the identification and molecular analysis of divergent SIV strains directly from primary monkey tissue. This approach, which does not depend on virus isolation methods, should facilitate future studies aimed at elucidating the origins and natural history of SIVs in feral African green monkey populations. 相似文献
100.
A conserved coronavirus epitope, critical in virus neutralization, mimicked by internal-image monoclonal anti-idiotypic antibodies.
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Monoclonal antibody (MAb) 6A.C3 neutralizes transmissible gastroenteritis coronavirus (TGEV) and is specific for a conserved epitope within subsite Ac of the spike (S) glycoprotein of TGEV. Six hybridomas secreting anti-idiotypic (Ab2) MAbs specific for MAb 6A.C3 (Ab1) have been selected. All six MAbs inhibited the binding of Ab1 to TGEV and specifically cross-linked MAb1-6A.C3. Four of these hybridomas secreted gamma-type anti-idiotypic MAbs. The other two Ab2s (MAbs 9A.G3 and 9C.E11) were recognized by TGEV-specific antiserum induced in two species. This binding was inhibited by viruses of the TGEV group but not by serologically unrelated coronaviruses. These results indicate that MAb2-9A.G3 and MAb2-9C.E11 mimic an antigenic determinant present on the TGEV surface, and they were classified as beta-type ("internal-image") MAbs. TGEV-binding Ab3 antiserum was induced in 100% of mice immunized with the two beta-type MAb2s and in 25 to 50% of mice immunized with gamma-type MAb2. Both beta- and gamma-type Ab2s induced neutralizing Ab3 antibodies in mice that were mainly directed to antigenic subsite Ac of the S protein. 相似文献