Plastochrone, cycle cellulaire et teneurs en ADN nucléaire du méristème caulinaire de plants de Chrysanthemum segetum soumis à deux conditions lumineuses différentes, sous une photopériode de 16 heures

1990 ◽  
Vol 68 (11) ◽  
pp. 2389-2397 ◽  
Author(s):  
Arlette Nougarède ◽  
Maria Nicola Di Michele ◽  
Pierre Rondet ◽  
Robert Saint-Côme
Keyword(s):  
Cell Cycle ◽  
Doubling Time ◽  
Nuclear Dna ◽  
Cycle Duration ◽  
Axial Zone ◽  
Lateral Zone ◽  
Cell Doubling Time ◽  
Photon Fluence ◽  
The Mean ◽  
Chrysanthemum Segetum

Chrysanthemum segetum plants were grown from seeds under a 16-h photoperiod, at two different photon fluence rates (70 or 200 μmol m−2 s−1. At 200 μmol m−2 s−1, by comparison with 70 μmol m−2 s−1, phyllotaxy was not modified, but the plastochron decreased and the apical diameter increased by extension of the axial zone. The mean cell doubling time decreased 36.2% in the lateral zone, 29% in the axial zone, and only 13% in the rib meristem. In contrast, mitosis duration was constant. Under both light conditions, nuclei with a DNA content within the limits of the 2C range were always predominant, which means that the G1 phase of the cell cycle was the longest. At 200 μmol m−2 s−1, the shortening of the mean cell doubling time is accompanied by a reduction of the percentage of nuclei with DNA levels within the limits of the 2C range. The decrease of the latter was the most important in the axial zone and the least important in the rib meristem, showing that control of cell proliferation was obtained by means of the G1 phase of the cell cycle. Key words: Chrysanthemum segetum, cell cycle, duration of mitosis, plastochron, nuclear DNA levels, zonation.

Cycle cellulaire et teneurs en ADN nucléaire de cellules en suspension de l’Acer pseudoplatanus en phase exponentielle de croissance. Hétérogénéité de la culture

1974 ◽  
Vol 52 (7) ◽  
pp. 1535-1543 ◽  
Author(s):  
Jacques Rembur
Keyword(s):  
Cell Cycle ◽  
Doubling Time ◽  
Nuclear Dna ◽  
Cell Suspension Cultures ◽  
The Other ◽  
Acer Pseudoplatanus ◽  
Heterogeneous Cell Population ◽  
Constant Rate ◽  
Cell Groups ◽  
The Mean

The mean doubling time of Acer pseudoplatanus L. cell suspension cultures is 66 h during log-phase growth.A constant rate of proliferation and a stable mitotic index show this population to be asynchronous with little variation in the duration of the cell cycle.The results of both continuous and brief labelling show that only 84% of the cells divide. The cell cycle lasts 58 h with G1, S, G2, and M periods of 29, 21, 5.3, and 2.7 h respectively. G1 predominates while G2 is reduced.Microspectrophotometric analysis of nuclear DNA indicates a heterogeneous cell population made up of two proliferating groups, one diploid and the other tetraploid.The formation of tetraploids by endoreduplication and the possible evolution of both cell groups are discussed.

Nuclear DNA content and minimum generation time in herbaceous plants

1972 ◽  
Vol 181 (1063) ◽  
pp. 109-135 ◽  
Keyword(s):  
Cell Cycle ◽  
Dna Content ◽  
Cycle Time ◽  
Generation Time ◽  
Nuclear Dna ◽  
Nuclear Dna Content ◽  
Annual Species ◽  
Cell Cycle Time ◽  
Developmental Processes ◽  
The Mean

Many components of cell and nuclear size and mass are correlated with nuclear DNA content in plants, as also are the durations and rates of such developmental processes as mitosis and meiosis. It is suggested that the multiple effects of the mass of nuclear DNA which affect all cells and apply throughout the life of the plant can together determine the minimum generation time for each species. The durations of mitosis and of meiosis are both positively correlated with nuclear DNA content and, therefore, species with a short minimum generation time might be expected to have a shorter mean cell cycle time and mean meiotic duration, and a lower mean nuclear DNA content, than species with a long mean minimum generation time. In tests of this hypothesis, using data collated from the literature, it is shown that the mean cell cycle time and the mean meiotic duration in annual species is significantly shorter than in perennial species. Furthermore, the mean nuclear DNA content of annual species is significantly lower than for perennial species both in dicotyledons and monocotyledons. Ephemeral species have a significantly lower mean nuclear DNA content than annual species. Among perennial monocotyledons the mean nuclear DNA content of species which can complete a life cycle within one year (facultative perennials) is significantly lower than the mean nuclear DNA content of those which cannot (obligate perennials). However, the mean nuclear DNA content of facultative perennials does not differ significantly from the mean for annual species. It is suggested that the effects of nuclear DNA content on the duration of developmental processes are most obvious during its determinant stages, and that the largest effects of nuclear DNA mass are expressed at times when development is slowest, for instance, during meiosis or at low temperature. It has been suggested that DNA influences development in two ways, directly through its informational content, and indirectly by the physical-mechanical effects of its mass. The term 'nucleotype' is used to describe those conditions of the nucleus which effect the phenotype independently of the informational content of the DNA. It is suggested that cell cycle time, meiotic duration, and minimum generation time are determined by the nucleotype. In addition, it may be that satellite DNA is significant in its nucleotypic effects on developmental processes.

scholarly journals Effects of cell cycle variability on lineage and population measurements of mRNA abundance

2020 ◽  
Author(s):  
Ruben Perez-Carrasco ◽  
Casper Beentjes ◽  
Ramon Grima
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Negative Binomial ◽  
Eukaryotic Cell ◽  
Cycle Duration ◽  
Cell Cycle Duration ◽  
Monotonically Decreasing Function ◽  
Binomial Mixture ◽  
A Cell ◽  
The Mean

AbstractMany models of gene expression do not explicitly incorporate a cell cycle description. Here we derive a theory describing how mRNA fluctuations for constitutive and bursty gene expression are influenced by stochasticity in the duration of the cell cycle and the timing of DNA replication. Analytical expressions for the moments show that omitting cell cycle duration introduces an error in the predicted mean number of mRNAs that is a monotonically decreasing function of η, which is proportional to the ratio of the mean cell cycle duration and the mRNA lifetime. By contrast, the error in the variance of the mRNA distribution is highest for intermediate values of η consistent with genome-wide measurements in many organisms. Using eukaryotic cell data, we estimate the errors in the mean and variance to be at most 3% and 25%, respectively. Furthermore, we derive an accurate negative binomial mixture approximation to the mRNA distribution. This indicates that stochasticity in the cell cycle can introduce fluctuations in mRNA numbers that are similar to the effect of bursty transcription. Finally, we show that for real experimental data, disregarding cell cycle stochasticity can introduce errors in the inference of transcription rates larger than 10%.

scholarly journals MINOR COMPONENTS OF THE DNA OF PHYSARUM POLYCEPHALUM

1969 ◽  
Vol 40 (2) ◽  
pp. 484-496 ◽  
Author(s):  
Charles E. Holt ◽  
Elizabeth G. Gurney
Keyword(s):  
Cell Cycle ◽  
Physarum Polycephalum ◽  
Nuclear Dna ◽  
Buoyant Density ◽  
Cell Fractionation ◽  
Minor Components ◽  
Variable Level ◽  
The Mean ◽  
S Period ◽  
Dna Components

DNA metabolism in the slime mold Physarum polycephalum was studied by centrifugation in CsCl of lysates of cultures labeled with radioactive thymidine at various times in the cell cycle. During the G2 (premitotic) phase of the cell cycle, two components of the DNA are labeled. One component is lighter (buoyant density 1.686 g/cc) than the mean of the principal DNA (1.700 g/cc), and one is heavier (approximately 1.706 g/cc). The labeled light DNA was identified chemically by its denaturability, its susceptibility to DNase, and the recovery of its radioactivity in thymine. Cell fractionation studies showed that the heavy and the principal DNA components are located in the nucleus and that the light DNA is in the cytoplasm. The light DNA comprises approximately 10% of the DNA. About ⅓–½ of the light DNA is synthesized during the S period, and the remainder is synthesized throughout G2 (there is no G1 in Physarum). The light DNA is metabolically stable. A low, variable level of incorporation of radioactive thymidine into the principal, nuclear DNA component was observed during G2.

scholarly journals Hyperglycemia and hyperinsulinemia stimulate cervical cancer cell proliferation in vitro and in vivo study

2019 ◽  
Author(s):  
Miriam Gutiérrez-Gutiérrez ◽  
Ishell Aline Figueroa-Martínez ◽  
Rafael Jurado ◽  
Norma Uribe ◽  
Patricia García-López ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cervical Cancer ◽  
Cell Proliferation ◽  
Cancer Cell ◽  
Doubling Time ◽  
Xenograft Model ◽  
Cervical Cancer Cell ◽  
Diabetic Patients ◽  
Cell Doubling Time

Abstract Background: Diabetes mellitus and malignant tumor are the second and third causes of women death in Mexico. Hyperglycemia, insulin and insulin-like growth factor 1 are the main risk factors involved in cancer development in patient with diabetes. The aim of this study was to evaluate the effect of hyperglycemia and hyperinsulinemia over cell proliferation and tumor growth in cervical cancer. Methods: Cell proliferation, apoptosis and cell cycle of cervical cancer cell lines (HeLa, SiHa and CaSki) in presence of hyperglycemia and/or insulin were evaluated. Xenograft model for cervical cancer was done in diabetic female nu/nu mice; biochemical parameters, body weight, tumoral volume and cell doubling time were evaluated. Results: Hyperglycemia and hyperinsulinemia significantly increase cell proliferation and decreases apoptosis with no change in cell cycle. Insulin treatment increase tumor volume and diminish cell doubling time, this group also developed hyperinsulinemia and in Langerhans pancreatic islet hypertrophy; whereas, hyperglycemic groups show the same effects but in lesser degree than the insulin treated group. Conclusion: Glucose and insulin stimulates both, proliferation and tumoral growth of cervical cancer, so this should be a possible explanation for the low survival of diabetic patients with cervical cancer in compare to non-diabetic patients with cervical cancer.

scholarly journals Effects of cell cycle variability on lineage and population measurements of messenger RNA abundance

2020 ◽  
Vol 17 (168) ◽  
pp. 20200360 ◽  
Author(s):  
Ruben Perez-Carrasco ◽  
Casper Beentjes ◽  
Ramon Grima
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Messenger Rna ◽  
Negative Binomial ◽  
Eukaryotic Cell ◽  
Cycle Duration ◽  
Cell Cycle Duration ◽  
Monotonically Decreasing Function ◽  
Binomial Mixture ◽  
The Mean

Many models of gene expression do not explicitly incorporate a cell cycle description. Here, we derive a theory describing how messenger RNA (mRNA) fluctuations for constitutive and bursty gene expression are influenced by stochasticity in the duration of the cell cycle and the timing of DNA replication. Analytical expressions for the moments show that omitting cell cycle duration introduces an error in the predicted mean number of mRNAs that is a monotonically decreasing function of η , which is proportional to the ratio of the mean cell cycle duration and the mRNA lifetime. By contrast, the error in the variance of the mRNA distribution is highest for intermediate values of η consistent with genome-wide measurements in many organisms. Using eukaryotic cell data, we estimate the errors in the mean and variance to be at most 3% and 25%, respectively. Furthermore, we derive an accurate negative binomial mixture approximation to the mRNA distribution. This indicates that stochasticity in the cell cycle can introduce fluctuations in mRNA numbers that are similar to the effect of bursty transcription. Finally, we show that for real experimental data, disregarding cell cycle stochasticity can introduce errors in the inference of transcription rates larger than 10%.

scholarly journals Cell Cycle Kinetics and Development of Hydra Attenuata

1974 ◽  
Vol 16 (2) ◽  
pp. 349-358 ◽  
Author(s):  
R. D. CAMPBELL ◽  
C. N. DAVID
Keyword(s):  
Cell Cycle ◽  
Nuclear Dna ◽  
Cell Function ◽  
Control Point ◽  
Interstitial Cells ◽  
Total Cell ◽  
Cycle Duration ◽  
Cell Cycles ◽  
Cell Cycle Duration ◽  
Hydra Attenuata

The cell cycle parameters of interstitial cells in Hydra attenuata have been determined. Interstitial cells were classified according to cluster size in which they occur (1, 2, 4, 8 or 16 cells) and morphology using maceration preparations and histological sections. The lengths of G1, S, G2 and M were determined by standard methods of cell cycle analysis using pulse-chase and continuous labelling with [3H]- and [14C]thymidine. Nuclear DNA contents were measured microfluorimetrically. All classes of interstitial cells proliferate but the cell cycle of large interstitial cells occurring singly or in pairs is longer than that of interstitial cells occurring in clusters of 4, 8 and 16 cells. The S-phase is 11-12 h long and G1 is less than 1 h for all classes of interstitial cells. G2 is 3-4 h long for interstitial cells in clusters of 4, 8 and 16 cells giving these cells a total cell cycle duration of 16-17 h. In contrast, large interstitial cells occurring as singles and in clusters of 2 have G2 durations ranging from 4 to 22 h. Two subpopulations can be discerned among these cells, one having a G1 of about 6 h and a total cell cycle of about 19 h, the other having an average G2 of 14 h and a total cell cycle of about 27 h. The differences in cell cycle duration appear to be associated with interstitial cell function. Cells having a short cell cycle are probably committed to nematocyte differentiation, while large interstitial cells having long and variable cell cycles appear to be undetermined stem cells responsible for proliferating further interstitial cells. The variable length of G2 in these cells suggest it as a possible control point.

Mitotic-cycle time and the development of embryo and endosperm in compatible and incompatible crosses in tuber-bearing Solanum species

Genome ◽  
2001 ◽  
Vol 44 (3) ◽  
pp. 426-431 ◽  
Author(s):  
R W Masuelli
Keyword(s):  
Growth Rates ◽  
Doubling Time ◽  
Mitotic Cycle ◽  
Solanum Species ◽  
Endosperm Balance Number ◽  
Solanum Commersonii ◽  
Cell Doubling Time ◽  
The Mean ◽  
The Relationship ◽  
Solanum Spp

To understand the relationship between early seed development and the EBN (endosperm balance number) hypothesis, the embryo and endosperm growth rates in crosses among Solanum spp. with the same and different EBNs were analyzed. For the embryo, the differences in the mean cell-doubling time (MCDT) between the compatible species 2x Solanum gourlayi and Solanum acaule was 3.9 h, whereas the incompatible species Solanum commersonii had MCDT differences of 10 and 13.9 h with 2x S. gourlayi and S. acaule, respectively. The embryo growth rates of the 2EBN species S. acaule and S. gourlayi were almost twice as fast as that of the 1EBN species S. commersonii. Nuclei of variable sizes were observed in the endosperms resulting from incompatible crosses. The author discusses the possibility that the collapse of the endosperm in inter-EBN crosses could be caused by differences in the MCDT between the parents that produce hybrid endosperms with high levels of DNA synthesis and transcription activity, resulting in increased nuclear size. A model is proposed to explain the formation of enlarged endosperm nuclei in incompatible crosses in the genus Solanum.Key words: mean cell-doubling time, endosperm balance number, Solanum, endosperm, embryo.

scholarly journals IMAGE ANALYSIS OF CHROMATIN IN CELLS OF PREIMPLANTATION MOUSE EMBRYOS

1974 ◽  
Vol 63 (1) ◽  
pp. 227-233 ◽  
Author(s):  
Wojciech Sawicki ◽  
Jan Rowínski ◽  
Jan Abramczuk
Keyword(s):  
Cell Cycle ◽  
Image Analysis ◽  
Dna Content ◽  
Nuclear Dna ◽  
Nuclear Dna Content ◽  
Mouse Embryos ◽  
Stage Of Development ◽  
Preimplantation Mouse Embryos ◽  
Preimplantation Mouse ◽  
The Mean

Mouse two-celled embryos and blastulae were Feulgen stained and the DNA content of their nuclei was measured with an integrating microdensitometer. The cells considered on the basis of their nuclear DNA content to be in G1, S, and G2 phases of the cell cycle were selected and their total chromatin area and chromatin areas at different gray levels were measured by the image analyzing computer, Quantimet. The measurements were aimed at quantitation of several features of the chromatin morphology of cells in different functional states. The total area of chromatin was found to increase, and the mean density of chromatin to decrease, from the G1 to the G2 phase of the cell cycle in both two-celled embryos and blastulae. The area of chromatin decreased, and the mean density of chromatin increased, as embryos developed from two-celled to blastula stage. It was concluded that nuclear morphology in preimplantation mouse embryos depends on both the phase of the cell cycle and the stage of development. The method of image analysis described was found to be useful for quantitation of changes in chromatin morphology.

Variation de la durée des cycles cellulaires au cours du passage de l'état jeune à l'état adulte dans le méristème caulinaire du Polypodium vulgare

1981 ◽  
Vol 59 (10) ◽  
pp. 1811-1816 ◽  
Author(s):  
Nicole Michaux-Ferrière
Keyword(s):  
Cell Cycle ◽  
Mitotic Activity ◽  
Mitotic Index ◽  
Axial Zone ◽  
Cell Cycles ◽  
Lateral Zone ◽  
A Cell

During the development of Polypodium vulgare L. mitotic indices and duration of cell cycles have been determined for two apical zones of the meristem. In the young state, the mitotic activity of the meristem is high and uniform; the cell cycles of the axial and lateral zones are very similar. At the beginning of the adult state, the axial zone is characterized by a low mitotic index and a cell cycle which is twice that of the lateral zone.

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