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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
3.
Physical and Chemical Correlates of Microbial Activity and Biomass in Composting Municipal Sewage Sludge 总被引:8,自引:2,他引:6 下载免费PDF全文
Various physical and chemical parameters were monitored to evaluate their influence on the microbial communities present in composting municipal sewage sludge. Temperature, moisture content, depth, pH, protein content, total nitrogen, total carbon, lipid phosphate biomass, and the rates of microbial incorporation of substrates into lipids were measured at several times throughout the 17- to 19-day composting runs. Temperature was found to have the most consistent and dramatic effect on microbial activity and biomass. When temperatures exceeded 55 to 60°C, microbial activity fell dramatically, usually by more than 1 order of magnitude. Microbial activity was generally greatest in samples taken from the 35 to 50°C areas of the composting piles. Changes in the composition of the compost over time included increased pH, increased protein content, and decreased total organic content. The changes in these parameters appeared to reflect the microbial activity and biomass present. The results of this study indicate that the rate of composting may best be optimized by controlling the composting temperatures, provided that the other parameters fall within reasonable limits in the starting material. 相似文献
4.
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
5.
Improvements in and Environmental Applications of Double-Vial Radiorespirometry for the Study of Microbial Mineralization 总被引:4,自引:3,他引:1 下载免费PDF全文
Several variations in the scintillation mixture and the filter paper arrangements for double-vial radiorespirometry were compared. Improved efficiencies (44%) and shorter response times were found by adding wetting agents and methanolic NaOH to the scintillation mixture in the filter paper. The scintillation chemicals used did not contain dioxane and were found to be nontoxic to the test microbiota in this system. Covering the inner reaction vial with aluminum foil minimized the reduction in counting efficiency when testing colored or dense environmental samples. Mineralization rates were determined with 14C-labeled glucose, acetate, and glutamate and [14C]cellulose- and [14C]lignin-labeled lignocellulose for composting cow manure, forest soil, and arctic lake sediment microbiota. This improved method can be used in a variety of procedures involving the measurement of microbial mineralizations of organic compounds. Since no liquid scintillation cocktail is used for counting, the radioactive wastes are aqueous or can be incinerated, making disposal easy. 相似文献
6.
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
7.
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
8.
9.
Bombesin: potential integrative peptide for feeding and satiety 总被引:1,自引:0,他引:1
The neuropeptide bombesin (BBS) is examined with regard to possible designation as an integrative peptide. The term integrative peptide has been proposed to distinguish a subset of regulatory peptides. These peptides, distributed in the body and the brain, may function as hormones and neurotransmitters to integrate physiological and psychological functions. It is suggested that BBS may function as a peripheral and central satiety-inducing agent. The specific topics with regard to BBS include: feeding, satiety, and aversion; peripheral and central effects; learning, memory, and reward; route of injection; taste modulation; gastrointestinal activity; neurotransmitter status; mechanism and neuroanatomical site of action; and neural and humoral transmission. 相似文献
10.
The effects of daily supplemental chromium (200 μg) complexed with 1.8 mg nicotinic acid on plasma glucose and lipids, including
total cholesterol, HDL cholesterol, LDL cholesterol, and triglycerides, were assessed in 14 healthy adults and 5 adults with
noninsulin-dependent diabetes mellitus (NIDDM) using a double-blind crossover study with 8-wk experimental periods. Eight
of the 14 healthy subjects and all 5 subjects with NIDDM also underwent an oral glucose tolerance test with assessment of
90 min postprandial plasma glucose and insulin concentrations. No statistically significant effects of chromium nicotinic
acid supplementation were found on plasma insulin, glucose, or lipid concentrations, although chromium nicotinic acid supplementation
slightly lowered fasting plasma total and LDL cholesterol, triglycerides, and glucose concentrations, and 90-min postprandial
glucose concentrations in individuals with NIDDM. 相似文献