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To determine a concentration of 5-bromo-2-deoxyuridine (BrdU) sufficient for sister chromatid differentiation (SCD), and yet having a minimal effect on the number of sister chromatid exchanges (SCEs), we assessed the effect produced on the number of SCEs by low concentrations (1, 3, and 10 micrograms/mL) of BrdU. SCD was not obtained in 19% of the 31 subjects with 1 microgram/mL of BrdU, while the differentiation was adequate for all samples treated with 3 and 10 micrograms/mL. We statistically analysed the effects of these three different doses and found no significant difference in the number of SCEs obtained with the doses of 1 and 3 micrograms/mL, but a significant difference was observed between these two concentrations and 10 micrograms/mL. We therefore suggest that the dose of 3 micrograms/mL, while sufficient to produce reliable differential staining, still permits an adequate evaluation of the base line of SCEs and appears to enhance the sensitivity of the test to evaluate between-individual variations. Our experiments also underline that SCE counts should include the centromere exchanges. 相似文献
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The uptake of cholesterol from high-density lipoproteins (HDL) labeled with 125I and [3H]cholesterol was examined in cultured rat luteal cells. Luteal cells were incubated with labeled HDL, following which the metabolic fate of the apolipoproteins and cholesterol moieties of the receptor-bound HDL were examined. About 50% of the originally bound HDL apolipoproteins were released into the medium in 24 h by a temperature-dependent process while only 5% of the HDL cholesterol was released unmetabolized. Inclusion of unlabeled HDL in the chase incubation resulted in increased release of apolipoprotein-derived radioactive products without significant change in the release of unmetabolized cholesterol. 60% of the apolipoprotein-derived radioactivity could be precipitated with trichloroacetic acid; the remaining trichloroacetic acid-soluble radioactive fraction was identified as [125I]iodotyrosine. Gel filtration chromatography of the chase-released material showed that the trichloroacetic acid-precipitable products, which contained no detectable amounts of cholesterol, eluted over a range of molecular sizes (9-80 kDa). No intact HDL was retroendocytosed. About 80% of trichloroacetic acid-precipitable products could be immunoadsorbed on anti-apolipoprotein A-I antibody immobilized on CNBr-activated Sepharose, suggesting the presence of fragments containing apolipoprotein A-I. This material was also capable of reassociating with native HDL. Lysosomal inhibitors were partially effective in inhibiting the amount of trichloroacetic acid-soluble products formed. The lysosomal degradation appeared to have no role in the uptake of HDL-derived cholesterol. These studies demonstrate preferential and total uptake of HDL cholesterol by luteal cells, with concomitant degradation of the lipoprotein. 相似文献
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Cooperative binding of Agrobacterium tumefaciens VirE2 protein to single-stranded DNA. 总被引:13,自引:5,他引:8
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The VirE2 protein of Agrobacterium tumefaciens Ti plasmid pTiA6 is a single-stranded-DNA-binding protein. Density gradient centrifugation studies showed that it exists as a tetramer in solution. Monomeric VirE2 active in DNA binding could also be obtained by using a different protein isolation procedure. VirE2 was found to be thermolabile; brief incubation at 37 degrees C abolished its DNA-binding activity. It was insensitive to the sulfhydryl-specific reagent N-ethylmaleimide. Removal of the carboxy-terminal 37 residues of the 533-residue VirE2 polypeptide led to complete loss of DNA-binding activity; however, chimeric fusion proteins containing up to 125 residues of the VirE2 C terminus were inactive in DNA binding. In nuclease protection studies, VirE2 protected single-stranded DNA against degradation by DNase I. Analysis of the DNA-VirE2 complex by electron microscopy demonstrated that VirE2 coats a single-stranded DNA molecule and that the binding of VirE2 to its substrate is cooperative. 相似文献
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Yuzuru Mikami Sen Feng Yu Katsukiyo Yazawa Kazutaka Fukushima Akio Maeda Jun Uno Kiyoshi Terao Naoki Saito Akinori Kubo Ken -ichiro Suzuki 《Mycopathologia》1990,112(2):113-118
During our studies on toxic substances from clinically isolated Nocarida, a new isolate identified as Nocardia otitidiscaviarum from cutaneous nocardiosis was found to produce a toxic substance called HS-6 that had strong in vitro as well as in vivo toxicity. The mouse intraperitoneal LD50 value was 1.25 mg/kg and the ED50 value for L1210 cultured cells was 0.3 ng/ml. The structure of HS-6 was determined and found to belong to the 16-membered macrocyclic group with a molecular formula of C43H68O12. HS-6 also showed activity against pathogenic fungi such as Cryptococcus neoformans. 相似文献
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Mesophyll protoplasts from leaves of aseptically grown shoot tips of Diplotaxis muralis were isolated (6.2–7.1×105 protoplasts/g fresh weight of tissue) using one step enzyme digestion. The protoplasts (71% viability) underwent divisions (4.2+0.1%) on plating in M8PS2 medium and ultimately formed calli with 0.45+0.03% plating efficiency. Plant regeneration could be achieved both through embryogenesis and organogenesis. The efficiency of plant regeneration through organogenesis was 9 times higher than embryogenesis. Forty eight out of 52 plants regenerated so far from 3 independent experiments were normal with respect to fertility and meiotic chromosomal behavior.Abbreviations BAP
6-benzylaminopurine
- GA3
Gibberellic acid
- A
Kao and Michayluk, 1981
- KM
Kao and Michayluk, 1975
- MK3
Modified K3
- M8P
Modified 8P
- MS
Murashige and Skoog, 1962
- NAA
1-naphthalene acetic acid
- PE
Plating efficiency 相似文献
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