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1.
This report describes a method by which mitotic cells were isolated from nonsynchronized Cloudman melanoma cells that had been pulse labeled with 5-bromo-2'-deoxyuridine (BrdUrd) and double-stained with a fluoresceinated monoclonal antibody to BrdUrd and with propidium iodide (PI). In initial experiments, melanoma cells were first pulse labeled with BrdUrd, treated with prostaglandin E1 (PGE1 10 micrograms/m1) or vehicle (0.1% ethanol) for up to 24 hours, then stained with anti-BrdUrd and PI. PGE1-treated cells monitored at 3-hour intervals were observed to migrate from S phase to G2 phase, then, enigmatically, back into the late S phase region of the distribution. In other experiments, cells treated with PGE1 were pulse labeled with BrdUrd at the end of the treatment period and harvested. In these experiments, there was a small, discrete subpopulation of cells within the late S phase region of the DNA distribution that was negative for anti-BrdUrd. This subpopulation of cells was sorted and examined by light microscopy. We observed that 95% of these BrdUrd-negative "S phase" cells were mitotic cells. Since mitotic cells and G2 cells have equivalent amounts of DNA, the reduced red fluorescence exhibited by these cells may be due to a greater sensitivity to denaturation, which has been described for DNA of mitotic cells, and would account for the phenomenon of cells appearing to move "backwards" in the cell cycle. This report indicates that although the BrdUrd/PI method can further define the cell cycle into four compartments, it can also lead to over-estimation of S phase cells in kinetic studies because of contaminating mitotic cells. 相似文献
2.
The effect of NAD(P) and analogs of this nucleotide on nitrogenase activity in Rhodospirillum rubrum has been studied. Addition of NAD+ to nitrogen fixing Rsp. rubrum leads to inhibition of nitrogenase. NADP+ has the same effect but NADH or analogs modified in the nicotinamide portion do not cause inhibition. In contrast to ammonium
ions, addition of NAD+ leads to inhibition of nitrogenase in cells that have been N-starved under argon. The inhibitory effect of NAD+ is more pronounced at lower light intensities. Addition of NAD+ also leads to inhibition of glutamine synthetase, a phenomenon also occurring when “switchoff” is produced by the addition
of effectors such as ammonium ions or glutamine. It is also shown that NAD+ is taken up by Rsp. rubrum cells. 相似文献
3.
Incorporation of adenine into the modifying group of inactive iron protein of nitrogenase from Rhodospirillum rubrum 总被引:5,自引:2,他引:3 下载免费PDF全文
Adenine was fed to cells of Rhodospirillum rubrum grown on glutamate. The adenine was found to be incorporated into the modifying group of the inactive form of iron protein. Adenine labelled in the 8-position ([8-3H]adenine) and the 2-position ([2-3H]adenine) was specifically incorporated into the electrophoretic 'upper-band' subunit of iron protein. Incorporation of label from the 2-position into many proteins was observed if histidine was not present in the medium. Label was removed by the activating enzyme for iron protein. 相似文献
4.
F. N. McKenzie D. P. Dhall K.-E. Arfors S. Nordlund N. A. Matheson 《BMJ (Clinical research ed.)》1969,2(5660):795-798
In view of the high incidence of thromboembolic complications after the insertion of cardiac valve prostheses, platelet adhesiveness and aggregation was measured in whole blood before, during, and for several days after this operation in 10 patients. Cardiopulmonary bypass resulted in a profound decrease in the platelet count, in the number of adhesive platelets, and in platelet aggregation. These changes returned to near preoperative levels by the sixth postoperative day. Thereafter a consistent and sustained increase in platelet count, in the number of adhesive platelets, and in platelet aggregation was observed. The results suggest that the prevalence of thromboembolism after valve replacement may be due partly to changes in platelet behaviour. 相似文献
5.
JOÃO BATISTA TAVARES DA SILVA ISAAC ROITMAN 《The Journal of eukaryotic microbiology》1990,37(6):521-523
ABSTRACT. Three strains of Phytomonas serpens two from tomatoes, Lycopersicon esculentum one from the insect Phtia picta (Hemiptera, Coreidae), were cultivated in a chemically defined medium developed from a defined medium for cultivating insect flagellates. Besides organic growth factors required by other insect trypanosomatids this flagellate requires, serine and inositol. Glutamine stimulates growth, and, surprisingly, does not require heme. 相似文献
6.
Vitiligo is a dermatological disorder characterized by hypopigmentary patches that tend to become progressive over time. There are reports of extensive familial aggregation. A genetic model for this disorder was earlier proposed by us. This model postulates that recessive alleles at multiple unlinked autosomal loci interact epistatically in the pathogenesis of vitiligo. The present family study was primarily undertaken to cross-validate the proposed genetic model. Data on 194 families from the United States were collected. Each family was ascertained through an affected proband. Analyses of these data reveal that approximately 20% of probands have at least one first-degree relative afflicted with vitiligo. All types of first-degree relatives of probands show a significant risk of developing vitiligo. Results of segregation and robustness analyses reveal that the genetic model postulated by us previously is the most parsimonious model for the present family data set. 相似文献
7.
Borrelia burgdorferi is a spirochete pathogen transmitted among warm-
blooded hosts by ixodid ticks. Frequency-dependent selection for variant
outer-surface proteins might be expected to arise in this species, since
rare variants are more likely to avoid immune surveillance in previously
infected hosts. We sequenced the OspA and OspB genes of nine North American
strains and compared them with nine strains previously described. For each
gene, the mean number of synonymous substitutions per synonymous site and
the mean number of nonsynonymous substitutions per nonsynonymous site show
only a twofold excess of silent mutations. Synonymous rates vary widely
along the OspB protein. Some regions show a significant excess of silent
substitutions, while divergence in other regions is constrained by biased
base composition or selection. The presence, in antigenically important
regions of the protein, of significant variation among strains, as well as
evidence for recombination among strains, should be considered in attempts
to develop vaccines against this disease.
相似文献
8.
M P ROBINSON G BUTCHER R H CURTIS K G DA VIES K EVANS 《The Annals of applied biology》1993,123(2):337-347
Two monoclonal antibodies, which differentially recognise the two species of potato cyst nematodes (PCN), Globodera pallida and G. rostochiensis, are described. They have been shown to have potential for quantification of these two species, recognising proteins of the same molecular weight (34 kD) in both species. Further investigation showed these proteins to have isoelectric points at pH values of 5.7 in G. pallida and 5.9 in G. rostochiensis, in common with the proteins used by Fleming & Marks (1983) to differentiate the species of PCN. They are likely to be structurally very similar, with the same physiological function (and therefore similar concentrations) in the two species. In cross-reactivity tests with a wide range of soil nematode species, the antibodies reacted strongly only with species of the genus Globodera, and thereby confirmed their potential as the basis of a quantitative immunoassay likely to be useful in management of PCN populations. 相似文献
9.
10.