Subchromosomal DNA Synthesis in Synchronous V-79 Chinese Hamster Cells after X Irradiation

1984 ◽  
Vol 100 (2) ◽  
pp. 273 ◽  
Author(s):  
P. J. Meechan ◽  
J. G. Carpenter ◽  
T. D. Griffiths
Keyword(s):  
Dna Synthesis ◽  
Chinese Hamster ◽  
Chinese Hamster Cells ◽  
X Irradiation

scholarly journals CELL KILLING BY ACTINOMYCIN D IN RELATION TO THE GROWTH CYCLE OF CHINESE HAMSTER CELLS

1969 ◽  
Vol 42 (2) ◽  
pp. 366-376 ◽  
Author(s):  
M. M. Elkind ◽  
E. Kano ◽  
H. Sutton-Gilbert
Keyword(s):  
Dna Synthesis ◽  
Functional Capacity ◽  
Response Pattern ◽  
Actinomycin D ◽  
Chinese Hamster ◽  
Growth Cycle ◽  
S Phase ◽  
Chinese Hamster Cells ◽  
X Irradiation ◽  
A Cell

Using Chinese hamster cells in culture, we have measured the effectiveness of actinomycin D to suppress division as a function of the position, or age, of a cell in its growth cycle. Cells were first exposed to millimolar concentrations of hydroxyurea in order to produce a synchronized population just before the onset of DNA synthesis. Thereafter, the survival response after 30 min exposures to actinomycin D was measured. Cells become resistant as they enter the S phase and then sensitive again in the latter part of S. When they reach G2 (or G2-mitosis) they are maximally resistant; at 1.0 µg/ml, for example, the survival in G2 is 30-fold greater than it is in G1. These results, plus measurements reported earlier on the interaction of damage in S cells due to actinomycin D and X-irradiation, suggest that the age-response pattern of the toxic effects of this drug probably reflects both the functional capacity of DNA-actinomycin complexes and the ability of this antibiotic to penetrate chromatin and bind to DNA.

scholarly journals SYNCHRONIZATION OF MITOCHONDRIAL DNA SYNTHESIS IN CHINESE HAMSTER CELLS (LINE CHO) DEPRIVED OF ISOLEUCINE

1973 ◽  
Vol 58 (2) ◽  
pp. 340-345 ◽  
Author(s):  
Kenneth D. Ley ◽  
Marilyn M. Murphy
Keyword(s):  
Cell Cycle ◽  
Mitochondrial Dna ◽  
Dna Synthesis ◽  
Cell Cycle Progression ◽  
Time Course ◽  
Nuclear Dna ◽  
Tritiated Thymidine ◽  
Chinese Hamster ◽  
Chinese Hamster Cells ◽  
In Cells

Mitochondrial DNA (mit-DNA) synthesis was compared in suspension cultures of Chinese hamster cells (line CHO) whose cell cycle events had been synchronized by isoleucine deprivation or mitotic selection. At hourly intervals during cell cycle progression, synchronized cells were exposed to tritiated thymidine ([3H]TdR), homogenized, and nuclei and mitochondria isolated by differential centrifugation. Mit-DNA and nuclear DNA were isolated and incorporation of radioisotope measured as counts per minute ([3H]TdR) per microgram DNA. Mit-DNA synthesis in cells synchronized by mitotic selection began after 4 h and continued for approximately 9 h. This time-course pattern resembled that of nuclear DNA synthesis. In contrast, mit-DNA synthesis in cells synchronized by isoleucine deprivation did not begin until 9–12 h after addition of isoleucine and virtually all [3H]TdR was incorporated during a 3-h interval. We have concluded from these results that mit-DNA synthesis is inhibited in CHO cells which are arrested in G1 because of isoleucine deprivation and that addition of isoleucine stimulates synchronous synthesis of mit-DNA. We believe this method of synchronizing mit-DNA synthesis may be of value in studies of factors which regulate synthesis of mit-DNA.

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