共查询到20条相似文献,搜索用时 0 毫秒
1.
Dimeric distribution of the cell number of Saccharomyces cerevisiae is analysed according to the volume and content of volutin in them. Dynamics of the age composition of the population in time when changing the medium limiting growth for the balanced one is considered. The data obtained indicate that volutin may serve as a regulator when the yeast cells pass the starting point in the division cycle, however, this event has no contrary effect on volutin accumulation. 相似文献
2.
3.
Intracellular Na+, K+, and Mg2+ concentrations have been measured during the HeLa cell cycle and compared with changes in oxygen utilization and macromolecular synthesis. Cell water content remains relatively constant at 79 +/- 1% during the cell cycle. A biphasic change in intracellular Na+ occurs with low values as cells reach peak S phase and again in early G1. The decrease in S coincides with an increase in cell volume during increased macromolecular synthesis. The fall in intracellular Na+ during mitosis/early G1 coincides with decreased energy utilization as macromolecular synthesis decreases with a continued decrease in [Na+]i in G1 corresponding to a period of increasing cell volume and an increase in protein synthesis. Intracellular Na+ is relatively high during late S/G2 when phosphate incorporation into protein and phospholipid is maximal. Intracellular K+ concentrations largely parallel intracellular Na+ levels although the intracellular K+:Na+ ratio is significantly lower as the cell volume increases during late G2/mitosis. Additions of a Na+-pump inhibitor (strophanthidin) not only caused a rise in [Na+]i and fall in [K+]i but also inhibited protein synthesis. Conversely, addition of a protein synthesis inhibitor (cycloheximide) blocked amino acid incorporation and produces a fall in intracellular Na+ levels. These findings indicate that intracellular Na+ and K+ play an important role in regulating cell hydration during the cell cycle and that changes in Na+, K+-ATPase activity, synthesis and/or utilization of high energy phosphate compounds, fluid phase turnover (endocytosis), Na+:H+ exchange (pHi), Donnan forces, and ionic adsorption may all be involved. 相似文献
4.
We investigated whether the levels of adrenomedullin, a novel peptide produced by several tissues, including the pituitary gland, change during the ovarian cycle. We studied 13 healthy women with regular menstrual cycles. Plasma samples were collected at 7, 14, 21 and 28 days of the ovarian cycle and assayed for adrenomedullin 1-52 using a specific RIA. LH, FSH, 17beta-estradiol, and progesterone concentrations were also determined. The adrenomedullin profile during ovarian cycle was similar to that of LH; plasma adrenomedullin increased from 10.9 pg/ml at the 7th day to 15.1 pg/ml at the 14th, and decreased to 8.5 pg/ml in the subsequent menses. The changes in plasma adrenomedullin were related to changes in LH and 17beta-estradiol. The cause of the increase in adrenomedullin levels during the late follicular phase of the menstrual cycle is not clear. Since it has been demonstrated that adrenomedullin is involved in the regulation of hypothalamus-pituitary-adrenal gland and its secretion is regulated by sex hormones we speculate that adrenomedullin could also play a role in regulating the hypothalamus-pituitary-ovary feedback. Alternatively it may be involved in the regulation of fluid and electrolyte homeostasis during the menstrual cycle. 相似文献
5.
Changes in membrane potential during the cell cycle 总被引:4,自引:0,他引:4
The membrane potential of isolated synchronized Chinese hamster lung cells (V79) has been determined as a function of their position in the cell cycle. During G 1 the cells exhibit a low but increasing membrane potential which rises sharply at the onset of the S phase. The elevated membrane potential is maintained throughout S and G 2 and declines again when the cells enter mitosis. Membrane potentials in an unsynchronized culture, which was recorded from both mitotic and interphase cells physically associated in groups and clusters, were similar to the plateau level obtained during S and G 2 in isolated synchronized cells, and exhibited little variation. It is concluded that although the membrane potential of isolated cells fluctuates during the cell cycle, it plays no causal role as a regulator of mitotic activity. 相似文献
6.
Changes in protein phosphorylation during the cell cycle of Chinese hamster ovary cells 总被引:10,自引:0,他引:10
The phosphorylation patterns of proteins were examined during the cell cycle of Chinese hamster ovary cells. This was accomplished by labeling synchronized cells at various times with [32P]orthophosphate and separating the proteins by both isoelectric focusing and nonequilibrium pH gradient two-dimensional gel electrophoresis. The most dramatic changes occurred during late G2/M when approximately eight proteins (including vimentin, lamin B, and histones 1 and 3) showed increased phosphorylation. Ten other proteins appeared to be uniquely phosphorylated during late G2/M. Of these 10 proteins, seven were no longer phosphorylated shortly after mitosis. There is also at least one protein which showed a relative decrease in phosphorylation during late G2/M. 相似文献
7.
Olle Heby Joe W. Gray Patricia A. Lindl Laurence J. Marton Charles B. Wilson 《Biochemical and biophysical research communications》1976,71(1):99-105
The activity of L-ornithine decarboxylase (L-ornithine carboxy-lyase; EC 4.1.1.17), the enzyme that catalyzes the initial and rate-limiting step in polyamine biosynthesis, has been studied in Chinese hamster ovary fibroblasts synchronized by selective detachment of mitotic cells. At various times after plating the distribution of cells among the G1, S and G2+M phases of the cell cycle was calculated from DNA distributions obtained by high-speed flow cytometric analysis. At these same times determination of the cellular L-ornithine decarboxylase activity showed that polyamine (putrescine) synthesis was initiated in mid-G1, that the rate of synthesis was maximal prior to DNA synthesis, and that it decreased during the S phase. A second increase in enzyme activity occurred before mitosis. 相似文献
8.
UDP-sugar contents were measured using high performance liquid chromatography and gas chromatography during the cell cycle in a synchronous culture of Catharanthus roseus (L.) G. Don. UDP-glucose, UDP-galactose, UDP-glucuronic acid, UDP-xylose and UDP-arabinose could be determined, and 75–90% of the UDP-sugars were UDP-glucose. The contents of UDP-glucose and UDP-galactose increased in the late G2-M and the late S-M phases, respectively, whereas UDP-glucoronic acid and UDP-arabinose increased in amount in the G1 phase. These changes in the levels of UDP-sugars during the cell cycle generally correlated well with the changes in cell wall constituents and in the activities of the enzyme involved in synthesis and interconversion of UDP-sugars reported by S. Amino et al. (Physiol. Plant. 1985. 64: 111–117). 相似文献
9.
C P Muller D A Stephany J R Wunderlich 《Journal of immunology (Baltimore, Md. : 1950)》1986,136(1):17-22
This study was directed at correlating the expression of class I MHC determinants with different segments of the cell cycle by using dual laser flow microfluorometry to measure levels of both DNA and cell surface H-2Kd or H-2Dd determinants for single cells. Con A-treated mouse spleen cells were identified as being in the G2/M or G0/G1 phases of the cell cycle on the basis of propidium iodide or Hoechst 33342 dye bound to DNA. Monoclonal anti-H-2 antibodies, indirectly fluoresceinated with goat anti-mouse IgG, were used to detect MHC determinants. The average level of both Kd and Dd determinants expressed by G2/M cells was about 1.6-fold higher than that expressed by G0/G1 cells. These observations indicate that the average-size G0/G1 and G2/M cells have the same apparent surface density of Kd and Dd determinants, insofar as we estimate that these cells differ in surface area by a factor of about 1.5. We also analyzed the expression of Kd and Dd determinants by measuring how they changed as a function of the intensity of forward light scatter from cells. For both G2/M and G0/G1 cells, changes in light scatter intensity were associated with parallel changes in levels of Dd and Kd determinants, indicating a common mechanism(s) that controls their cell surface expression. 相似文献
10.
Cell cycle studies, using PLM analysis, were carried out on a mouse-Chinese hamster cell hybrid and its derivatives which stably retained all parental chromosomes during the year of study. Parameter estimates were obtained from the PLM curves, using conjugate gradient curve fitting procedures. The hybrid initially grew very slowly, and all phases (especially G1) were longer than those of either parent. During propagation, mean generation time decreased progressively, and the phase times approached those of the mouse parent (which had the longer G1 and S). DNA replication could be scored separately in mouse and hamster chromosome sets; initially termination was highly asynchronous, but during growth asynchrony was progressively reduced as DNA synthesis in the hamster set was prolonged. We conclude that cell hybrids may undergo progressive modifications of the cell cycle, even in the absence of significant chromosome segregation, and suggest that such changes may at least partly account for the great variety of relationships between the growth rates and phase times of parent and hybrid cells which have been reported. Because of the complexity of these changes in the cycles of interspecific cell hybrids, we believe that somatic cell genetic analysis of the regulation of the cell cycle would be more usefully applied to intraspecific hybrids whose parents differ in only one specific cycle characteristic. 相似文献
11.
Changes in nuclear protein during the cell cycle in cultured mast cells separated by zonal centrifugation 总被引:1,自引:0,他引:1
Margaret E. Cross 《The Biochemical journal》1972,128(5):1213-1219
1. Exponentially grown mouse mast cells (cell line P815, strain Y) were separated by zonal centrifugation on a Ficoll gradient. Fractions were allocated to different phases of the cell cycle according to the specific radioactivity of their DNA. 2. Histones were extracted and their thiol content was analysed. The proportion of reduced thiol increased in S phase, decreasing subsequently. 3. The phosphate content of histone F1 and of the other histones reached a peak in early and later S phase respectively. The incorporation of (32)P into these fractions showed a corresponding increase. 4. The timing of histone synthesis was examined. Incorporation of (14)C-labelled amino acids into the histone fractions took place at the same times as phosphorylation. 5. Acid nuclear proteins differ from the histones in incorporating labelled amino acids and (32)P fairly constantly through the cell cycle. 相似文献
12.
In this study, we employed a surface-specific antibody against the large ribosome subunit to investigate the distribution of ribosomes in cells during the cell cycle. The antibody, anti-L7n, was raised against an expansion segment (ES) peptide from the large subunit ribosomal protein L7, and its ribosome-surface specificity was evident from the positive immuno-reactivity of ribosome particles and the detection of 60 S immune-complex formation by an immuno-electron microscopy. Using immunofluorescent staining, we have microscopically revealed that ribosomes are dispersed in the cytoplasm of cells throughout all phases of the cell cycle, except at the G2 phase where ribosomes show a tendency to gather toward the nuclear envelope. The finding in G2 cells was confirmed by electron microscopy using a morphometric assay and paired t test. Furthermore, further observations have shown that ribosomes are not distributed immune-fluorescently with nuclear envelope markers including the nuclear pore complex, the integral membrane protein gp210, the inner membrane protein lamin B2, and the endoplasm reticulum membrane during cell division we propose that the mechanism associated with ribosome segregation into daughter cells could be independent of the processes of disassembly and reassembly of the nuclear envelope. 相似文献
13.
14.
The amino acid and muropeptide compositions of murein (peptidoglycan) isolated from populations of Caulobacter crescentus predominantly composed of swarmer or stalked cells were determined and compared with the structure of murein sacculi obtained from a population of unsegregated cells. It appears that in spite of vast morphological alterations in the course of the cell cycle, the murein composition of the various cell types is not markedly different. 相似文献
15.
In order to analyze the fluctuation of the poly ADP-ribosylation level during the cell cycle of synchronously growing He La S3 cells, we have developed three different assay systems; intact and disrupted nuclear systems, and poly(ADP-ribose) polymerase in vitro system. The optimum conditions for poly ADP-ribosylation in each assay system were similar except the pH optimum. Under the conditions favoring poly ADP-ribosylation, little radioactivity incorporated into poly(ADP-ribose) was lost after termination of the poly ADP-ribosylation by addition of nicotinamide which inhibits the reactions by more than 90% in any system. In the intact nuclear system, the level of poly ADP-ribosylation increased slightly subsequent to late G2 phase with a peak at M phase. The high level of poly ADP-ribosylation in M phase was also confirmed by using selectively collected mitotic cells which were arrested in M phase by Colcemid. The level in mitotic chromosomes was 5.1-fold higher than that in the nuclei from logarithmically growing cells. Colcemid has no effect on the poly ADP-ribosylation. In the disrupted nuclear system, a relatively high level of poly ADP-ribosylation was observed during mid S-G2 phase. When poly(ADP-ribose) polymerase was extracted from the nuclei with a buffer solution containing 0.3 M KCl, more than 90% of the enzyme activity was recovered. The poly(ADP-ribose) polymerase in vitro system was dependent on both DNA and histone—10 μg each. In the enzyme system, enzyme activity was detected throughout the cell cycle and was observed to be highest in G2 phase. The high level at M phase observed in the intact nuclear system was not seen in the other two systems. Under the assay conditions, little influence of poly(ADP-ribose) degrading enzymes was noted on the level of poly ADP-ribosylation in any of the three systems. This was confirmed at various stages during the cell cycle through pulse-labeling and “chasing” by adding nicotinamide. 相似文献
16.
17.
18.
The relationship between the sporulation ability and the stage of the vegetative cell cycle was studied. The ability of mature cells to sporulate was the highest just before bud initiation and decreased rapidly as soon as detectable buds appeared. The mitotic DNA synthesis was competitive with the premeiotic one. 相似文献
19.
Extensive measurements of steady-state populations of several Escherichia coli strains have consistently indicated that cell diameter decreases with increasing cell length. This was observed both after electron microscopy of air-dried cells and after phase-contrast microscopy of living cells. The analysis was made by considering separately the unconstricted cells and three classes (slight, medium, and deep) of constricted cells in the population. During slow growth, cells with the average newborn length were up to 8% thicker than unconstricted cells twice as long. This decrease in diameter is less at higher growth rates. Despite the small changes and the large variation of the diameter in any particular length class, significant negative correlations between diameter and length were obtained. Cell diameter increases again at the end of the cell cycle as indicated by an increase of average diameter in the three consecutive classes of constriction. 相似文献
20.
By using chromosome conformation capture technology, a recent study has revealed two alternative three-dimensional folding states of the human genome during the cell cycle. 相似文献