The Synthesis of DNA Through the Cell Cycle of Amoeba Proteus

1968 ◽  
Vol 3 (4) ◽  
pp. 483-491
Author(s):  
M. J. ORD
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Amoeba Proteus ◽  
Pulse Labelling ◽  
Two Peaks ◽  
Second Peak

DNA synthesis has been investigated in Amoeba proteus by pulse-labelling cells of known age with [3H]thymidine. Ninety per cent of the DNA so labelled was synthesized during the first quarter of the cell cycle. Synthesis was in two peaks: the first occurring between 0.5 and 4 h after division and the second at about 10 h. All cells labelled at both peaks. The authenticity of the second peak was proved statistically. Considerable variation was observed among amoebae of similar age. In experiments in which daughter amoebae underwent different treatments, differences in the rates of incorporation of [3H]thymidine due to differences in the nutrition of the cells were found to be a predominant cause of variation. Heavy feeding reduced labelling; starvation increased labelling while at the same time reducing variability.

Differences in cell cycle between human adult aortic and Vena Cava SMC In Cell Culture. A Impuls-Cytophotometric Study

1981 ◽  
Author(s):  
D G S Thilo ◽  
D Heinrich ◽  
E Peifer ◽  
P Rudloff
Keyword(s):  
Cell Cycle ◽  
Cell Culture ◽  
Vena Cava ◽  
Growth Curves ◽  
Large Cell ◽  
Human Adult ◽  
Cytophotometric Study ◽  
A Minor ◽  
Two Peaks ◽  
Second Peak

Human aortic and vena cava SMCs show different growth pattern and proliferation rates in cell culture. We further tried to substantiate these differences by examination of the cell cycle phases with the impuls-cytophotometry(ICP). As reported in the previous abstract SMCs were established from explant cultures of human adult aortic and vena cava. After sufficient outgrowth the SMCs were subcultivated and used for cell cycle analysis at different intervals. Acridine orange(AO), ethidium bromide(Eb) and mithramycin(M) were used for nucleic acid staining followed by fluorescence microscopy. For ICP a nucleus suspension was prepared and stained with Eb/M.DNA-histogramms of SMC were recorded in a ICP 22 in combination with a 500-channel distribution analyzer. Results:Clear DNA-histogramms of SMC-suspension could not be obtained because of the large cell size and their tendency to form aggregates in suspension. Therefore, a nucleus suspension of the appropiate culture was prepared. The AO-stained SMCs show a green and red staining of the nucleus. In Eb/M-stained SMCs a uniformly staining was observed. Histogramms of proliferating art. SMC show a peak at 4N(about 50%), a second peak at 2N (about 40%) and a minor one at 8N (about 10%). In contrast we found only two peaks in the vena cava SMCs at 2 N (about 85%) and at 4N (about 15%).Summary: Again these results show that there a marked differences between the art and venous SMCs. These results fit with the microscopic examinations and the growth curves for both types of SMCs. These differences have to be considered of the effect of drugs on functions of SMCs are examined.

Effects of Ginsenosides Rg1 and Rb1 of Panax Ginseng on Mitosis in Root Tip Cells of Allium Cepa

1981 ◽  
Vol 09 (02) ◽  
pp. 119-133 ◽  
Author(s):  
Wan-yee Ng ◽  
Chuan-ying Chao
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Panax Ginseng ◽  
Time Course ◽  
Mitotic Cell ◽  
Root Tip ◽  
Pulse Labelling ◽  
Promoting Effect ◽  
Tip Cells ◽  
Root Tip Cells

The effects of ginsenosides Rg1 and Rb1 of Panax ginseng on mitosis in the onion root tip cells as well as on the rate of DNA synthesis in onion seedlings were studied. Results obtained from the concentration and time course study in bulb and seedling root tip cells indicate that Rg1 promotes and Rb1 inhibits mitosis, both being dose-dependent. The promoting effect of Rg1 on the rate of DNA synthesis was observed at the peak hour which occurs at the same time as that of the control. Rb1 was found to shift the peak hour of DNA synthesis to a later period of the experiment. These results are in agreement with the results obtained from the study of the cell cycle by pulse labelling and auto-radiography, which show that Rg1 shortens the mitotic cell cycle and S period while Rb1 lengthens them. They in turn increase and decrease the mitotic indices respectively.

scholarly journals The study of multipeaked type-I X-ray bursts in the neutron star low-mass X-ray binary 4U 1636 − 536 with RXTE

2020 ◽  
Vol 501 (1) ◽  
pp. 168-178
Author(s):  
Chen Li ◽  
Guobao Zhang ◽  
Mariano Méndez ◽  
Jiancheng Wang ◽  
Ming Lyu
Keyword(s):  
Neutron Star ◽  
Flux Ratio ◽  
Light Curves ◽  
Type I ◽  
X Ray ◽  
Soft State ◽  
Peak Flux ◽  
Low Mass ◽  
Two Peaks ◽  
Second Peak

ABSTRACT We have found and analysed 16 multipeaked type-I bursts from the neutron-star low-mass X-ray binary 4U 1636 − 53 with the Rossi X-ray Timing Explorer (RXTE). One of the bursts is a rare quadruple-peaked burst that was not previously reported. All 16 bursts show a multipeaked structure not only in the X-ray light curves but also in the bolometric light curves. Most of the multipeaked bursts appear in observations during the transition from the hard to the soft state in the colour–colour diagram. We find an anticorrelation between the second peak flux and the separation time between two peaks. We also find that in the double-peaked bursts the peak-flux ratio and the temperature of the thermal component in the pre-burst spectra are correlated. This indicates that the double-peaked structure in the light curve of the bursts may be affected by enhanced accretion rate in the disc, or increased temperature of the neutron star.

The Chromatin Extrusion Phenomenon in Amoeba proteus Cell Cycle

2019 ◽  
Vol 67 (2) ◽  
pp. 203-208 ◽  
Author(s):  
Andrew V. Goodkov ◽  
Mariia A. Berdieva ◽  
Yuliya I. Podlipaeva ◽  
Sergei Yu. Demin
Keyword(s):  
Cell Cycle ◽  
Amoeba Proteus

scholarly journals High-intensity Raf signal causes cell cycle arrest mediated by p21Cip1.

1997 ◽  
Vol 17 (9) ◽  
pp. 5588-5597 ◽  
Author(s):  
A Sewing ◽  
B Wiseman ◽  
A C Lloyd ◽  
H Land
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Cell Cycle Arrest ◽  
Expression Patterns ◽  
Cellular Responses ◽  
Specific Cell ◽  
Cyclin D ◽  
Inhibition Of Proliferation ◽  
Cycle Arrest ◽  
Signal Specificity

Activated Raf has been linked to such opposing cellular responses as the induction of DNA synthesis and the inhibition of proliferation. However, it remains unclear how such a switch in signal specificity is regulated. We have addressed this question with a regulatable Raf-androgen receptor fusion protein in murine fibroblasts. We show that Raf can cause a G1-specific cell cycle arrest through induction of p21Cip1. This in turn leads to inhibition of cyclin D- and cyclin E-dependent kinases and an accumulation of hypophosphorylated Rb. Importantly, this behavior can be observed only in response to a strong Raf signal. In contrast, moderate Raf activity induces DNA synthesis and is sufficient to induce cyclin D expression. Therefore, Raf signal specificity can be determined by modulation of signal strength presumably through the induction of distinct protein expression patterns. Similar to induction of Raf, a strong induction of activated Ras via a tetracycline-dependent promoter also causes inhibition of proliferation and p21Cip1 induction at high expression levels. Thus, p21Cip1 plays a key role in determining cellular responses to Ras and Raf signalling. As predicted by this finding we show that Ras and loss of p21 cooperate to confer a proliferative advantage to mouse embryo fibroblasts.

scholarly journals Primase p49 mRNA expression is serum stimulated but does not vary with the cell cycle.

1989 ◽  
Vol 9 (5) ◽  
pp. 1940-1945 ◽  
Author(s):  
B Y Tseng ◽  
C E Prussak ◽  
M T Almazan
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Mammalian Cells ◽  
Cell Cycle Progression ◽  
Small Subunit ◽  
Mrna Levels ◽  
Proliferating Cells ◽  
Restriction Point ◽  
Serum Stimulation ◽  
G1 Cells

Expression of the small-subunit p49 mRNA of primase, the enzyme that synthesizes oligoribonucleotides for initiation of DNA replication, was examined in mouse cells stimulated to proliferate by serum and in growing cells. The level of p49 mRNA increased approximately 10-fold after serum stimulation and preceded synthesis of DNA and histone H3 mRNA by several hours. Expression of p49 mRNA was not sensitive to inhibition by low concentrations of cycloheximide, which suggested that the increase in mRNA occurred before the restriction point control for cell cycle progression described for mammalian cells and was not under its control. p49 mRNA levels were not coupled to DNA synthesis, as observed for the replication-dependent histone genes, since hydroxyurea or aphidicolin had no effect on p49 mRNA levels when added before or during S phase. These inhibitors did have an effect, however, on the stability of p49 mRNA and increased the half-life from 3.5 h to about 20 h, which suggested an interdependence of p49 mRNA degradation and DNA synthesis. When growing cells were examined after separation by centrifugal elutriation, little difference was detected for p49 mRNA levels in different phases of the cell cycle. This was also observed when elutriated G1 cells were allowed to continue growth and then were blocked in M phase with colcemid. Only a small decrease in p49 mRNA occurred, whereas H3 mRNA rapidly decreased, when cells entered G2/M. These results indicate that the level of primase p49 mRNA is not cell cycle regulated but is present constitutively in proliferating cells.

Effects of BD-40, an ellipticine analogue (aza-ellipticine) on cell cycle traverse and DNA synthesis in cultures of synchronized mouse fibroblasts

Biochimie ◽  
1984 ◽  
Vol 66 (9-10) ◽  
pp. 591-599 ◽  
Author(s):  
Marie-José Vilarem ◽  
Marie-Pierre Gras ◽  
Florence Primaux ◽  
Christian-Jacques Larsen
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Mouse Fibroblasts

scholarly journals CYTOPLASMIC DNA SYNTHESIS IN AMOEBA PROTEUS

1962 ◽  
Vol 15 (3) ◽  
pp. 535-540 ◽  
Author(s):  
M. Rabinovitch ◽  
W. Plaut
Keyword(s):  
Nucleic Acid ◽  
Dna Synthesis ◽  
Acridine Orange ◽  
Particle Number ◽  
Amoeba Proteus ◽  
Acridine Orange Staining ◽  
Particle Population ◽  
Cell Age ◽  
Cytoplasmic Dna ◽  
Number Of Particles

Nucleic acid-containing particles in the cytoplasm of Amoeba proteus (cf. reference 1) were counted after acridine orange staining. The number of particles per ameba was found to be correlated with cell age and size. Fresh daughters had a mean particle number of 5400, whereas predivision amebae contained around 11,000 particles. Amebae from two other strains contained similar particles. The particles were found to be clustered in fasted cells and redispersed after feeding. A marked increase in the particle population was noted in anucleate fragments. These results, together with those previously presented, suggest that the particles multiply intracellularly. Their nature and their relationship to previous work on nucleic acid labeling in Amoeba are discussed.

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