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41.
42.
Nuclear genome characterization of the carrageenophyteAgardhiella subulata (Rhodophyta) 总被引:2,自引:0,他引:2
Donald F. Kapraun Julie A. Dutcher Juan Lopez-Bautista 《Journal of applied phycology》1992,4(2):129-137
DNA reassociation kinetics were used to determine nuclear genome organization and complexity inAgardhiella subulata (Gigartinales, Rhodophyta). Results indicate the presence of three second-order components corresponding to fast (22%), intermediate
(68%) and slow (10%) fractions. Thus, the genome consists of 90% repetitive sequences. Microspectrophotoometry with the DNA-localizing
fluorochrome DAPI was used to confirm ploidy level differences in the gametophytic and tetrasporophytic phases. Results indicate
that meiosis occurs during tetrasporogenesis. Comparison of mean nuclear DNA (If) values to chicken erythrocytes (RBC) resulted in an estimate of 0.9 pg/2C genome forAgardhiella. Karyological studies using aceto-orcein revealed a chromosome complement of 2N = 44 in carposporangia and the presence of 22 bivalents during diakinesis of tetraspore mother cells. 相似文献
43.
44.
The malmö polymorphism of coagulation factor IX, an immunologic polymorphism due to dimorphism of residue 148 that is in linkage disequilibrium with two other F.IX polymorphisms
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![点击此处可从《American journal of human genetics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
John B. Graham Dennis B. Lubahn Susan T. Lord Julie Kirshtein Inga Marie Nilsson Anders Wallmark Rolf Ljung L. D. Frazier Jerry L. Ware Shu Wah Lin Darrell W. Stafford John Bosco 《American journal of human genetics》1988,42(4):573-580
A mouse monoclonal antibody (MAB 9.9) to coagulation factor IX (F.IX) detects a polymorphism in the plasma of normal people. Its epitope has been narrowed down to <6 amino acids in the activation peptide of the X-linked F.IX protein. The activation peptide contains a dimorphism—Thr:Ala—at position 148 of the protein. Using synthetic oligonucleotides, we have demonstrated that (1) the F.IX which reacts with 9.9 has Thr at position 148 and (2) that which does not has Ala. Positive reactors (148thr) are designated Malmö A, and negative reactors (148ala) are designated Malmö B. The plasma levels of AA women are indistinguishable from those of A men, and both B men and BB women are null against MAB 9.9. The plasma level of Malmö A in AB women is approximately half that of AA women, and “lyonization” is clearly operating in the heterozygotes. The dimorphism is in strong linkage disequilibrium with two other intragenic RFLPs, TaqI and XmnI. Furthermore, intragenic crossing-over—including double crossing-over—appears to have occurred between the three sites. Seven of the eight possible haplotypes have been identified, five in men and two others in women. The immunoassay that identifies ~50% of the AB women in the pool of Malmö A females with 95% confidence identifies men unambiguously as A or B. The assay would be very useful for population-genetic studies of the Malmö epitope if the studies were limited to men. 相似文献
45.
A simplified methylcoenzyme M methylreductase assay with artificial electron donors and different preparations of component C from Methanobacterium thermoautotrophicum delta H. 总被引:1,自引:0,他引:1
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![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
P L Hartzell J C Escalante-Semerena T A Bobik R S Wolfe 《Journal of bacteriology》1988,170(6):2711-2715
Different preparations of the methylreductase were tested in a simplified methylcoenzyme M methylreductase assay with artificial electron donors under a nitrogen atmosphere. ATP and Mg2+ stimulated the reaction. Tris(2,2'-bipyridine)ruthenium (II), chromous chloride, chromous acetate, titanium III citrate, 2,8-diaminoacridine, formamidinesulfinic acid, cob(I)alamin (B12s), and dithiothreitol were tested as electron donors; the most effective donor was titanium III citrate. Methylreductase (component C) was prepared by 80% ammonium sulfate precipitation, 70% ammonium sulfate precipitation, phenyl-Sepharose chromatography, Mono Q column chromatography, DEAE-cellulose column chromatography, or tetrahydromethanopterin affinity column chromatography. Methylreductase preparations which were able to catalyze methanogenesis in the simplified reaction mixture contained contaminating proteins. Homogeneous component C obtained from a tetrahydromethanopterin affinity column was not active in the simplified assay but was active in a methylreductase assay that contained additional protein components. 相似文献
46.
A deoxyribonuclease was partially purified from the free-living nematodeCaenorhabditis elegans. The DNase functioned as an endonuclease and introduced both single-strand nicks and double-strand breaks into DNA. The enzyme
hydrolyzed double-stranded DNA seven times more rapidly than single-stranded DNA. DNase activity was not affected by the addition
of divalent cations below 1mm but was inhibited at higher ionic concentrations. In addition, the enzyme was not inhibited in the presence of 10mm EDTA. The enzyme was inhibited by salt concentrations greater than 20mm. Three independent mutations in thenuc-1 gene were shown to reduce nuclease activity to less than 1% of that seen in wild-type organisms.
This work was supported by National Institutes of Health Grant AG03161 and a TCU Research Foundation Grant. Some stocks used
in these experiments were obtained from theCaenorhabditis Genetics Center, which is supported by Contract NOI-AG-9-2113 between the NIH and the curators of the University of Missouri. 相似文献
47.
Indoxyl-beta-D-glucuronide, a novel chromogenic reagent for the specific detection and enumeration of Escherichia coli in environmental samples 总被引:7,自引:0,他引:7
About 97% of Escherichia coli strains produce beta-glucuronidase, but almost all other Enterobacteriaceae lack this enzyme. A D-glucopyranosiduronic acid (glucuronide) possessing a readily detectable beta-linked aglycone should, therefore, constitute a specific reagent for the detection of this organism. For this purpose, the title compound has been synthesized for the first time. The synthesis proceeds in eight steps from readily available D-glucuronolactone, anthranilic acid, and chloroacetic acid and can be carried out on a large scale. The compound has the predicted properties: when included in the standard membrane filter test for the analysis of water, indoxyl-beta-D-glucuronide allows specific detection of E. coli through the formation of blue colonies that are the result of rapid conversion of the liberated aglycone to indigo. The recovery of E. coli is easily measured and almost quantitative. 相似文献
48.
In situ hybridization methods for the detection of somatostatin mRNA in tissue sections using antisense RNA probes 总被引:23,自引:0,他引:23
H Hoefler H Childers M R Montminy R M Lechan R H Goodman H J Wolfe 《The Histochemical journal》1986,18(11-12):597-604
In situ hybridization studies with [32P] and [3H] labelled antisense RNA probes were undertaken to determine optimal methods of tissue fixation, tissue sectioning, and conditions of hybridization, and to compare the relative merits of the two different radioactive labels. The distribution of somatostatin mRNA in neurons of rat brain using a labelled antisense somatostatin RNA probe was employed as a model for these studies. The highest degree of sensitivity for in situ hybridization was obtained using paraformaldehyde fixation and vibratome sectioning. Optimal autoradiographic localization of mRNA was obtained within 7 days using [32P] labelled probes. However, due to the high energy emittance of [32P], precise intracellular localization of hybridization sites was not possible. [3H] labelled RNA probes gave more precise cellular localization but required an average of 18-20 days autoradiographic exposure. The addition of the scintillator, PPO, decreased the exposure time for the localization of [3H] labelled probes to seven days. We also report a method for combined in situ hybridization and immunocytochemistry for the simultaneous localization of somatostatin in mRNA and peptide in individual neurons. 相似文献
49.
Improved Agar Bottle Plate for Isolation of Methanogens or Other Anaerobes in a Defined Gas Atmosphere 总被引:7,自引:4,他引:3
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A bottle plate for the cultivation of methanogens or other organisms in a defined pressurized-gas atmosphere was developed. The bottle provides the convenience of an agar streak plate, solves the problem of the water exudate from agar medium, and provides a convenient way of adding or sampling a defined gas atmosphere. 相似文献
50.
Evidence for H-2-linked control of retrovirus production in Friend virus-induced tumor cell lines.
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![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In Friend leukemia virus-induced tumor cell lines derived from mice congenic with respect to the H-2 complex, most cell lines expressing the H-2k haplotype continuously produced infectious exogenous virus in culture, whereas most cell lines expressing the H-2b or H-2d haplotype stopped producing virus during in vitro passage. This apparent H-2-linked control of virus production did not appear to be the result of alteration of the provirus or resistance to superinfection. The implications of this finding with respect to virus-induced leukemogenesis are discussed. 相似文献