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.

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.

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 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 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.

The cell cycle during the vegetative stage of Dictyostelium discoideum and its response to temperature change

1978 ◽  
Vol 32 (1) ◽  
pp. 1-20
Author(s):  
I.M. Zada-Hames ◽  
J.M. Ashworth
Keyword(s):  
Cell Cycle ◽  
Stationary Phase ◽  
Dictyostelium Discoideum ◽  
Doubling Time ◽  
Nuclear Dna ◽  
Cell Number ◽  
Cell Cycle Time ◽  
Optimum Growth Temperature ◽  
Cell Cycle Phases ◽  
Response To Temperature

The cell cycle in amoebae of Dictyostelium discoideum has been analysed in cells growing asynchronously in axenic medium. For cells growing at the optimum growth temperature of 22 degrees C with a culture doubling time of 8 h the average times for the cell cycle phases are as follows: G1, 1.5 h; S, 2.1 h; G2, 4.4 h; M, 15.2 min. When amoebae are grown at temperatures below 22 degrees C, culture doubling time increases and the cell cycle phases are altered in ways characteristic for each phase. G2 is the most variable period and may occupy up to 70% of the total cell cycle time; S and G1 are the least affected, increasing by only 20% when the cell generation time is doubled. When cells which have reached the stationary phase of growth in liquid medium are washed and reinoculated into fresh medium they divide synchronously after a lag period of 5 h. By following cell number increase and nuclear DNA synthesis in these cultures we have shown that stationary phase cells are arrested in the G2 phase of the cell cycle. Finally, although more than 97% of amoebae grown on a bacterial food source are uninucleate, when grown axenically up to 35% of the cell population may become multinucleate. Our results suggest that these cells probably arise through the failure of cytokinesis to follow karyokinesis. Multinucleate cells appear to have a slightly longer G2 period than mononucleate cells.

scholarly journals Cell Cycle Analysis and Stimulation of Rat Kangaroo Cells (PtK2) after Pulse Labeling

1971 ◽  
Vol 26 (7) ◽  
pp. 722-724 ◽  
Author(s):  
Peter R. Lorenz ◽  
John W. Ainsworth
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Doubling Time ◽  
Tritiated Thymidine ◽  
Cell Counts ◽  
The Mean ◽  
Gap Phase ◽  
Potorous Tridactylus ◽  
Stimulation Of

The phases of the cell cycle of Potorous tridactylus (PtK2) cells were determined in vitro by analysis of labeled mitoses for 37-½ hours after a tritiated thymidine pulse. The mean duration of DNA synthesis (tS) was 8 h. The mean duration of the gap phase before appearance of labeled mitoses was 5 h. Whereas the duration of the cell cycle (tC) based on analysis of labeled mitoses was 30 h, the doubling time (tD) derived from cell counts in the same cultures was only about 23 h. The analysis of the indices of labeled nuclei and mitoses suggests a stimulation of cells at the time of pulse labeling, which was maximal after beginning of the gap phase before DNA-synthesis, and possibly caused the observed difference between tC and tD.

scholarly journals Pattern of DNA increase in macronuclear anlagen of Tetrahymena

1986 ◽  
Vol 83 (1) ◽  
pp. 155-164
Author(s):  
J. Roth ◽  
G. Cleffmann
Keyword(s):  
Cell Cycle ◽  
Dna Content ◽  
Nuclear Dna ◽  
Nuclear Dna Content ◽  
S Phase ◽  
The Mean

By combining cytophotometry with autoradiography, five stages of macronuclear anlagen can be discriminated by their DNA content until the end of the first cell cycle after conjugation in Tetrahymena. DNA increases from 2C to about 32C. Each S-phase is followed by a non-synthetic period. Comparing the mean nuclear DNA content after and before each S-phase revealed that 16C anlagen contain significantly less DNA than twice the amount of 8C anlagen. This is unlike the situation in other S-phases during which the amount of DNA is precisely doubled. In the second cell cycle after conjugation some of the cells increase their macronuclear G2 DNA content beyond the 64C stage, while the majority show a mean G2 content of about 64C.

Multi-Center Study of Thromboplastin Calibration Precision – Influence of Reagent Species, Composition, and International Sensitivity Index (ISI)

1993 ◽  
Vol 69 (01) ◽  
pp. 035-040 ◽  
Author(s):  
A M H P van den Besselaar ◽  
R M Bertina
Keyword(s):  
Oral Anticoagulants ◽  
International Normalized Ratio ◽  
The Other ◽  
World Health ◽  
Rabbit Brain ◽  
Sensitivity Index ◽  
Bovine Plasma ◽  
Significant Difference ◽  
The Mean ◽  
International Sensitivity Index

SummaryFour thromboplastin reagents were tested by 18 laboratories in Europe, North-America, and Australasia, according to a detailed protocol. One thromboplastin was the International Reference Preparation for ox brain thromboplastin combined with adsorbed bovine plasma (coded OBT/79), and the second was a certified reference material for rabbit brain thromboplastin, plain (coded CRM 149R). The other two thromboplastin reagents were another rabbit plain brain thromboplastin (RP) with a lower ISI than CRM 149R and a rabbit brain thromboplastin combined with adsorbed bovine plasma (RC). Calibration of the latter two reagents was performed according to methods recommended by the World Health Organization (W. H. O.).The purpose of this study was to answer the following questions: 1) Is the calibration of the RC reagent more precise against the bovine/combined (OBT/79) than against the rabbit/plain reagent (CRM 149R)? 2) Is the precision of calibration influenced by the magnitude of the International Sensitivity Index (ISI)?The lowest inter-laboratory variation of ISI was observed in the calibration of the rabbit/plain reagent (RP) against the other rabbit/plain reagent (CRM 149R) (CV 1.6%). The highest interlaboratory variation was obtained in the calibration of rabbit/plain (RP) against bovine/combined (OBT/79) (CV 5.1%). In the calibration of the rabbit/combined (RC) reagent, there was no difference in precision between OBT/79 (CV 4.3%) and CRM 149R (CV 4.2%). Furthermore, there was no significant difference in the precision of the ISI of RC obtained with CRM 149R (ISI = 1.343) and the rabbit/plain (RP) reagent with ISI = 1.14. In conclusion, the calibration of RC could be performed with similar precision with either OBT/79 or CRM 149R, or RP.The mean ISI values calculated with OBT/79 and CRM 149R were practically identical, indicating that there is no bias in the ISI of these reference preparations and that these reference preparations have been stable since their original calibration studies in 1979 and 1987, respectively.International Normalized Ratio (INR) equivalents were calculated for a lyophilized control plasma derived from patients treated with oral anticoagulants. There were small but significant differences in the mean INR equivalents between the bovine and rabbit thromboplastins. There were no differences in the interlaboratory variation of the INR equivalents, when the four thromboplastins were compared.

Prothrombin Time Standardization: Report of the Expert Panel on Oral Anticoagulant Control

1979 ◽  
Vol 42 (04) ◽  
pp. 1073-1114 ◽  
Keyword(s):  
Prothrombin Time ◽  
Expert Panel ◽  
The Other ◽  
Rabbit Brain ◽  
Calibration Constant ◽  
Freeze Dried ◽  
The Mean ◽  
Point Of Intersection ◽  
And Control ◽  
Standardization Report

SummaryIn collaborative experiments in 199 laboratories, nine commercial thromboplastins, four thromboplastins held by the National Institute for Biological Standards and Control (NIBS & C), London and the British Comparative Thromboplastin were tested on fresh normal and coumarin plasmas, and on three series of freeze-dried plasmas. One of these was made from coumarin plasmas and the other two were prepared from normal plasmas; in each series, one plasma was normal and the other two represented different degrees of coumarin defect.Each thromboplastin was calibrated against NIBS&C rabbit brain 70/178, from the slope of the line joining the origin to the point of intersection of the mean ratios of coumarin/normal prothrombin times when the ratios obtained with the two thromboplastins on the same fresh plasmas were plotted against each other. From previous evidence, the slopes were calculated which would have been obtained against the NIBS&C “research standard” thromboplastin 67/40, and termed the “calibration constant” of each thromboplastin. Values obtained from the freeze-dried coumarin plasmas gave generally similar results to those from fresh plasmas for all thromboplastins, whereas values from the artificial plasmas agreed with those from fresh plasmas only when similar thromboplastins were being compared.Taking into account the slopes of the calibration lines and the variation between laboratories, precision in obtaining a patient’s prothrombin time was similar for all thromboplastins.

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