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Characteristic changes in the secreted polypeptides of Kirsten murine sarcoma virus (KiMSV) transformed mouse and rat cell lines could be detected 48 hours after infection of phenotypically normal cells with this virus and correlated with detection of the KiMSV encoded polypeptide p21. 相似文献
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Summary Chromosomes and their relationship to nuclear components during various phases of the cell cycle were studied with different fixation, embedding, and enzyme techniques. The results showed that interphase chromosomes may have oriented in such a way that a given locus became associated with the nuclear membrane. Some chromosomes also appeared to interact with the nucleolus. The nuclear matrix materials, however, were distributed between the chromosomes and formed a delineating boundary for the chromosomes. These matrix materials, furthermore, formed channel-like structures within the nucleus and towards the cytoplasm through their interaction with nuclear pore complexes. During mitosis, chromosomes were encapsulated with material that appeared to be derived from the matrix, disintegrated residues and fragments of the nuclear envelope, the lamina, and nucleolar material. These chromosome-associated materials seen in mitosis appeared to serve as foci for formation of new nuclear components in subsequent interphase. 相似文献
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Fusayuki Kanda Sei-ichi Matsui Donald E. Sykes Avery A. Sandberg 《Biochemical and biophysical research communications》1984,122(3):1296-1306
Isopeptidase is a novel eukaryotic enzyme that cleaves a structural chromatin protein, A24, stoichiometrically into H2A and ubiquitin. To understand the rapid turnover of ubiquitin in mitosis as wells as the high specific activity of the enzyme associated with metaphase chromosomes, attempts were made to determine chromatin constituents that show high affinity for this enzyme. Endogenous protease-free isopeptidase was prepared from calf thymus and applied to a Sepharose 4B affinity column on which histones, DNA, NHCP and ubiquitin were respectively immobilized. The enzyme proved to bind only histones. To further determine which of the histone fractions is involved, affinity columns with each histone fraction were also used. The enzyme showed affinity for all histone fractions. However, the strength of affinity varied in the order H2A>H3 H2B≥H4?H1, being inversely correlated with the ratio of basic/acidic amino acids in these molecules. These results suggest that the turnover of A24 in mitosis is controlled, at least in part, by the affinity of enzyme for histones, and also that such affinity is caused by a mechanism which cannot be explained simply by the electrostatic interaction between negatively charged enzyme molecules and positively charged histones. 相似文献
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J Richards S Hamamoto S Smith D Pasco R Guzman S Nandi 《Experimental cell research》1983,147(1):95-109
End buds from 4- to 5-week-old rat mammary glands were isolated and cultured within a rat tail tendon collagen gel matrix. Media containing equine serum or porcine serum and cholera toxin promoted growth, but not the production of casein or thioesterase II, nor did they induce a state of differentiation as assessed by cell ultrastructure. Medium supplemented with only 5% porcine serum, insulin and cholera toxin did not support growth or differentiation. However, when prolactin, estradiol, progesterone and hydrocortisone were added to this medium, growth was stimulated greatly and a differentiated state was induced as assessed by the production of casein and thioesterase and by the appearance of a highly secretory ultrastructure. 相似文献
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Pasco David Smith Stuart Quan Albert Richards James Nandi Satyabrata 《Cell and tissue research》1983,234(1):57-70
The avidin-biotin-peroxidase complex immunoperoxidase technique was employed to determine the intercellular distribution of thioesterase II in rat mammary glands. This enzyme is responsible for shifting the product specificity of the fatty-acid synthetase enzyme complex from long to medium chain fatty acids. Thioesterase II was found exclusively in the cells lining the lumen of the ductal and alveolar structures in glands from mature virgin (150 days old) and pregnant rats. The ductal cell staining intensity was considerably less than that of the alveolar cells in the mature virgin rat glands. No immunoreactive thioesterase II was found in the stromal, adipose, vascular, or myoepithelial components of the gland in the developmental stages examined. In the glands from immature virgin rats (40-45 days old) thioesterase II was again found only in the epithelial cells lining the lumen of the ductal and end-bud structures although this layer was usually more than one cell thick. Quantitative determination of thioesterase II activity in cytosol preparations revealed similar levels in mammary fragments from enzymatically-dissociated glands obtained from mature virgins and in end buds derived from immature virgins, but somewhat higher levels in mammary structures derived from late-pregnant animals. These immunohistological and biochemical results demonstrate thioesterase II's usefulness as a mammary epithelial cell-specific marker. 相似文献
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An analysis of the ribosomal ribonucleic acids of Escherichia coli by hybridization techniques 总被引:6,自引:3,他引:3
From analyses of the hybridization of Escherichia coli rRNA (ribosomal RNA) to homologous denatured DNA, the following conclusions were drawn. (1) When a fixed amount of DNA was hybridized with increasing amounts of RNA, only 0.35+/-0.02% of E. coli DNA was capable of binding (16s+23s) rRNA. Although preparations of 16s and 23s rRNA were virtually free from cross-contamination, the hybridization curves for purified 16s or 23s rRNA were almost identical with that of the parent specimen containing 1 weight unit of 16s rRNA mixed with 2 weight units of 23s rRNA. The 16s and 23s rRNA also competed effectively for the same specific DNA sites. It appears that these RNA species each possess all hybridizing species typical of the parent (16s+23s) rRNA specimen, though probably in different relative amounts. (2) By using hybridization-efficiency analysis of DNA-RNA hybridization curves (Avery & Midgley, 1969) it was found that (a) 0.45% of the DNA would hybridize total rRNA and (b) when so little RNA was added to unit weight of DNA that the DNA sites were not saturated, only 70-75% of the input RNA would form hybrids. The reasons for the discrepancy between the results obtained by the two alternative analytical approaches were discussed. (3) For either 16s or 23s rRNA, hybridization analysis indicated that two principal weight fractions of rRNA may exist, hybridizing to two distinct groups of DNA sites. However, these groups seem to be incompletely divided between the 16s and 23s fractions. Analysis suggested that (a) 85% of the 16s rRNA was hybridized to about half the DNA that specifically binds rRNA (0.23% of the total DNA). (b) 70% of the 23s rRNA hybridized to a further 0.23% of the DNA and (c) the minor fraction (15%) of 16s rRNA may be competitive with the major fraction (70%) of 23s rRNA. Conversely, the minor fraction (30%) of the 23s rRNA may compete with the major fraction (85%) of 16s rRNA. Models were proposed to explain the apparent lack of segregation of distinct RNA species in the two subfractions of rRNA. (4) If protein synthesis and ribosome maturation were inhibited in cells of an RC(rel) mutant, E. coli W 1665, by depriving them of an amino acid (methionine) essential for growth, the inhibition had no discernible effect on the relative rates of synthesis of rRNA species. The rRNA that accumulates in RC(rel) strains of E. coli after amino acid deprivation is apparently identical in its content of RNA species with that of the pre-existing mature RNA in the ribosomes. On the other hand, the messenger RNA is stabilized, and accumulates as about 15% of the RNA formed after withdrawal of the amino acid. 相似文献
10.
CHROMOSOME PULVERIZATION IN HUMAN BINUCLEATE CELLS FOLLOWING COLCEMID TREATMENT 总被引:2,自引:2,他引:0 下载免费PDF全文
Under the influence of Colcemid, a substantial number of binucleate human cells from a line infected with herpes-like virus was found to possess pulverized chromosomes. Although this abnormality was also detected in untreated binucleate cells, the increase in the number of pulverized cells after the addition of Colcemid was too striking to be explained by accumulation of spontaneously occurring cells in response to the mitotic inhibition by Colcemid. Furthermore, the induction of pulverization may be dependent upon Colcemid concentration. These findings imply an involvement of Colcemid in the mechanism of pulverization induction in the system studied. When tritiated thymidine was added to the culture medium simultaneously with Colcemid, the majority of binucleate cells with an intact and a pulverized chromosome set incorporated this isotope into the pulverized set only. This obviously suggests that the nuclei in the binucleate cell are asynchronous in DNA synthesis, and that this asynchrony is intimately related to the induction of the pulverization phenomenon. It seems very probable that the late S phase in the late synthesizing nuclei represents a critical stage at which damage to the chromosomes most readily occurs. 相似文献