Chronological changes in the cell cycle of chick neuroepithelial cells

Development ◽  
1973 ◽  
Vol 29 (3) ◽  
pp. 745-751
Author(s):  
D. B. Wilson
Keyword(s):  
Cell Cycle ◽  
Optic Tectum ◽  
Generation Time ◽  
Marked Change ◽  
Chick Embryos ◽  
Duration Of Mitosis ◽  
Neuroepithelial Cells ◽  
S Period

Radioautographic data obtained from a total of 103 chick embryos injected with [3H]thymidine suggest that the generation time of neuroepithelial cells in dorsolateral regions of the optic tectum increases from approximately 8 h at 3 days of incubation to 15 h at 6 days of incubation. The most marked change occurs between the 4th and 5th day, when the generation time increases from 9 to 13 h, respectively. Between the 3rd and 6th day of incubation the length of the DNA-synthetic (S) period and of the premitotic (G2) period remains fairly constant; however, the duration of mitosis (M) and of the postmitotic (G1) period appears to be prolonged.

scholarly journals MICRONUCLEAR RNA SYNTHESIS IN PARAMECIUM CAUDATUM

1967 ◽  
Vol 33 (2) ◽  
pp. 281-285 ◽  
Author(s):  
M. V. Narasimha Rao ◽  
David M. Prescott
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Generation Time ◽  
Rna Synthesis ◽  
Paramecium Caudatum ◽  
S Period

In a generation time of 8 hr in Paramecium caudatum, the bulk of DNA synthesis detected by thymidine-3H incorporation takes place in the latter part of the cell cycle. The micronuclear cycle includes a G1 of 3 hr followed by an S period of 3–3½ hr. G2 and division occupies the remaining period of the cycle. Macronuclear RNA synthesis detected by 5'-uridine-3H incorporation is continuous throughout the cell cycle. Micronuclear RNA synthesis is restricted to the S period. Ribonuclease removes 80–90% of the incorporated label. Pulse-chase experiments showed that part of the RNA is conserved and released to the cytoplasm during the succeeding G1 period.

scholarly journals INTERMITTENT DNA SYNTHESIS AND PERIODIC EXPRESSION OF ENZYME ACTIVITY IN THE CELL CYCLE OF WI-38

1973 ◽  
Vol 58 (3) ◽  
pp. 564-573 ◽  
Author(s):  
Robert R. Klevecz ◽  
Leon N. Kapp
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Generation Time ◽  
Chinese Hamster ◽  
S Phase ◽  
Automated System ◽  
Chinese Hamster Cells ◽  
Synchronous Cultures ◽  
Ldh Activity ◽  
S Period

Synchronous cultures of WI-38 were obtained using an automated system for detachment and partitioning of mitotic cells which operates without the use of inhibitors, altered medium, or lowered temperatures. The generation time in synchronous WI-38 is 19.5 h and the duration of S phase when determined from the percentage of labeled metaphase cells or nuclei is 12 h. DNA replication in WI-38 occurs in three temporally distinct and rapid bursts separated by intervals of greatly reduced synthesis within what is nominally described as the DNA synthetic (S) period. Lactate dehydrogenase (LDH) displayed maxima in G1 between 2 and 4 h and again at 10 and 16 h. Peaks in LDH activity were coordinated with DNA replication in a fashion similar to that reported for diploid Chinese hamster cells. Oscillations in LDH activity are more pronounced in normal diploid fibroblasts than in established and neoplastic lines.

scholarly journals CHANGES IN THE DNA SYNTHESIS PATTERN OF PARAMECIUM WITH INCREASED CLONAL AGE AND INTERFISSION TIME

1974 ◽  
Vol 61 (3) ◽  
pp. 591-598 ◽  
Author(s):  
Joan Smith-Sonneborn ◽  
Michael Klass
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Unicellular Organism ◽  
Time Intervals ◽  
Synchronized Cells ◽  
Different Ages ◽  
Self Fertilization ◽  
Autoradiographic Analysis ◽  
S Period ◽  
First Time

The clonal age in paramecia refers to the total number of vegetative divisions a clone has undergone since its origin at autogamy (self-fertilization). As clonal age increases, the interfission time usually increases. The DNA synthesis pattern of cells of different ages was compared by autoradiographic analysis of the DNA synthesis of synchronized cells at various time intervals during the cell cycle (from one division to the next). The study showed that the G1 period (the lag in DNA synthesis post division) was constant, irrespective of interfission time or clonal age; but the duration of the DNA synthesis period increased with increased interfission time or clonal age. Therefore, we have shown for the first time that the G1 period is fixed, and the S period is increased in a eukaryotic unicellular organism as a function of interfission time and clonal age.

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.

Cell proliferation in the developing wing-bud of normal and talpid3 mutant chick embryos

Development ◽  
1975 ◽  
Vol 34 (3) ◽  
pp. 589-607
Author(s):  
D. A. Ede ◽  
O. P. Flint ◽  
P. Teague
Keyword(s):  
Cell Cycle ◽  
Early Stage ◽  
Mitotic Rate ◽  
Mitotic Division ◽  
Chick Embryos ◽  
Division Rate ◽  
Cell Cycle Time ◽  
Continuous Sampling ◽  
Wing Bud ◽  
Marked Drop

Previous measurements on mitotic division rate or cell cycle time have been made on samples from a few discrete limb regions or by continuous sampling, but only down a unidimensional limb axis, disregarding morphological discontinuities such as the presence or absence of cartilage. This study presents a new analysis on normal and talpid3 mutant chick embryos, measuring mitotic rate and also cell density through the central proximo-distal axis and at the limb periphery, taking into account the development of cartilage regions. Differentiation of cartilage is correlated with a marked drop in mitotic rate, accounting for a proximo-distal gradient of mitosis in central counts which was not observed at the limb periphery. Talpid3 limbs at an early stage show a central mitotic gradient, but the reverse of that observed in normal limbs.

Growth Characteristics of Anaerobically Treated Early and Late S-Period of Ehrlich Ascites Tumor Cells after Reaeration

1983 ◽  
Vol 38 (3-4) ◽  
pp. 313-318 ◽  
Author(s):  
Rainer Merz ◽  
Friedhelm Schneider
Keyword(s):  
Cell Cycle ◽  
Flow Cytometry ◽  
Cell Cycle Progression ◽  
S Phase ◽  
Ehrlich Ascites Tumor Cells ◽  
Ascites Tumor ◽  
Cycle Progression ◽  
Ehrlich Ascites ◽  
Main Fraction ◽  
S Period

Utilizing centrifugal elutriation, early and late S-phase cells were separated from 4, 8 and 12 h anaerobically cultured Ehrlich Ascites tumor cells strain Karzel. The cytokinetic properties of these fractions after reaeration were studied by flow cytometry and the BrdU-H 33258-technique of flow cytometry. After a 4 h period of anaerobiosis, growth of early S-phase cells is not changed, 8 h deprivation of oxygen causes a delay of cell cycle progression, while the main fraction of 12 h anaerobically treated early S-populations did not divide after reaeration within 24 h. In comparison to early S-phase cells the cell cycle progression of the main fraction of late S-period is accelerated after a 4 h exclusion of oxygen. A fraction of 8 h anaerobically pretreated late S-cells continues to cycle, but a considerable number reinitiates DNA synthesis without preceeding division. Cells with DNA content up to 8 c are detected by flow cytometry. 12 h anaerobically cultured late S-cells do not divide after reaeration, a large number of these cells starts again to synthesize DNA. A considerable part of tetraploid cells retain viability, divide and enter a new cell cycle, another part of the cells disintegrates

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