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21.
A 5.1-kb plasmid, designated pSCS12, isolated from a naturally occurring Staphylococcus sciuri conferred resistance to chloramphenicol (CmR) and streptomycin (SmR). Restriction endonuclease analyses of pSCS12 revealed partial structural homologies to the CmR-plasmids pC221 from S. aureus and pSCS1 from S. intermedius, to the SmR-plasmids pSAI-1 from S. hyicus and pS194 from S. aureus, as well as to the CmR/SmR plasmid pSK68 from S. aureus. Southern-blot hybridization with specific CmR- and SmR-gene probes confirmed these similarities and allowed the mapping of the CmR- and SmR-determinants in the S. sciuri plasmid pSCS12. These observations lead to the suggestion that CmR/SmR-plasmids, such as pSCS12, may have evolved from CmR- and SmR-plasmids by interplasmidic recombination. 相似文献
22.
Experimental Evaluation of Conversion Factors for the [3H]Thymidine Incorporation Assay of Bacterial Secondary Productivity
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The relationship between bacterial growth and incorporation of [methyl-3H]thymidine in oligotrophic lake water cultures was investigated. Prescreening, dilution, and addition of organic and inorganic nutrients were treatments used to prevent bacterivory and stimulate bacterial growth. Growth in unmanipulated samples was estimated through separate measurements of grazing losses. Both bacterial number and biovolume growth responses were measured, and incorporation of [3H]thymidine in both total macromolecules and nucleic acids was assayed. The treatments had significant effects on conversion factors used to relate thymidine incorporation to bacterial growth. Cell number-based factors ranged from 1.1 × 1018 to 38 × 1018 cells mol of total thymidine incorporation−1 and varied with treatment up to 10-fold for the same initial bacterial assemblage. In contrast, cell biovolume-based conversion factors were similar for two treatment groups across a 16-fold range of [3H]thymidine incorporation rates: 5.54 × 1017 μm3 mol of total thymidine incorporation−1 and 15.2 × 1017 μm3 mol of nucleic acid incorporation−1. Much of the variation in cell number-based conversion factors was related to changes in apparent mean cell volume of produced bacteria. Phosphorus addition stimulated [3H]thymidine incorporation more than it increased bacterial growth, which resulted in low conversion factors. 相似文献
23.
Daniel Chappard Christian Alexandre Sabine Palle George Riffat 《Biotechnic & histochemistry》1986,61(2):93-96
Polyester fibers are not dissolved by either glycol methacrylate or methyl methacrylate. Commercial polyester wadding is consequently an advantageous material to use in getting precise orientation of tissue specimens during embedding in methacrylate. 相似文献
24.
Daniel Chappard Christian Alexandre Sabine Palle Georges Riffat 《Biotechnic & histochemistry》1986,61(3):145-149
A one-step clearing and embedding procedure for alizarin red S stained skeletons is described. Embryos are fixed in formalin, skinned and eviscerated. After staining in a 10 mg/liter solution of alizarin red S in 5% aqueous KOH, specimens are dehydrated in a graded series of acetone-polyester monomer solutions. Finally, the specimens are embedded at room temperature in the polyester resin. A special reusable metallic mold is described for embedment of large fetuses. Specimens previously cleared in glycerol can be processed with this method. 相似文献
25.
Summary Labeling cells with bromodeoxyuridine (BrdU) permits the differentiation of mitoses of the first, second, and third generation after the addition of BrdU. The term second mitoses is used for those cells which have incorporated BrdU for two-S-phases and which exhibit sister chromatid differentiation (SCD). However, SCD can also be obtained if the cell was in S-phase at the time of BrdU-addition and had already replicated part of its DNA. Such cells with incomplete BrdU-substitution in the first S-phase can only be differentiated from completely substituted ones by the quality of the SCD and are usually also grouped as second mitoses in the evaluation of experiments. Due to the heterogeneity of the evaluated second mitoses, the determination of proliferation delay and the incidence of sister chromatid exchange-induction can depend on the time of chromosome preparation. 相似文献
26.
Cyanophora paradoxa Korshikov synchronized autotrophically in a light-dark regime of 14 h light and 10 h dark divides in the last two hours of the dark period. The division rate of the free-living blue-green alga, Synechococcus leopoliensis Raciborski, at identical culture conditions (24°C; 32 W m−2 ) is only slightly lowered in the light period. The comparison of thylakoid differentiation in the endocyanelles of Cyanophora paradoxa and in Synechococcus leopoliensis during the light-dark regime yields (1) the same ensemble of pigment-protein complexes in both organisms, (2) comparable syntheses of chlorophyll and phycobilins of Cyanophora paradoxa grown under 32 W m−2 and of Synechococcus leopoliensis grown under light intensities below 9.2 W m−2 , and (3) identical photosynthetic oxygen evolution during the light period of the light-dark regime with minima at the beginning, in the middle (6th–7th h), and at the end of the light period. In both organisms this stage-specific oxygen evolution is inhibited by treatment with chloroamphenicol. Cycloheximide, however, causes no significant alterations. Results are discussed in view of the endosymbiotic theory. 相似文献
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M. Klinkowski H. Lange Fabig M. Schmidt K. Wuttky J. Helm Hagemann F. Mechelke Buder Reinmuth Alfred Lein W. Laube A. Wetzel 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1960,30(6):258-264
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