scholarly journals SYNTHESIS OF RNA IN MAMMALIAN CELLS DURING MITOSIS AND INTERPHASE

1967 ◽  
Vol 33 (2) ◽  
pp. 265-272 ◽  
Author(s):  
Donald W. King ◽  
M. L. Barnhisel
Keyword(s):  
Tissue Culture ◽  
Nucleic Acid ◽  
Linear Relationship ◽  
Cell Population ◽  
Mammalian Cells ◽  
Short Pulse ◽  
Chinese Hamster ◽  
Growth Cycle ◽  
Chinese Hamster Cells ◽  
Number Of Cells

Chinese hamster cells in the mitotic and G1 phases of the growth cycle were incubated for 30 or 60 min in suspension tissue culture and pulse-labeled with tritiated uridine. After appropriate chases, washes, and extractions, it was found that all incorporation into the nucleic acid may be accounted for by those cells in interphase. An average of 410 counts was found for incorporation into the cell population (approximately 2.0 x 105 cells) of which over 80% of the cells was initially in mitosis. The increasing number of cells leaving mitosis and entering interphase during the 30 min incubation was theoretically able to account for 470 counts. In addition, short-pulse labeling experiments have shown a consistent linear relationship between the percentage of cells in division and the incorporation of the isotope, which strongly suggests that, if 100% of the cells were in mitosis, the counts would be essentially zero. Thus, the entire label may be attributed to those cells in interphase where portions of the chromosomal material are known to be already extended.

scholarly journals 8-AZAGUANINE RESISTANCE IN MAMMALIAN CELLS I. HYPOXANTHINE-GUANINE PHOSPHORIBOSYLTRANSFERASE

Genetics ◽  
1972 ◽  
Vol 72 (2) ◽  
pp. 239-252 ◽  
Author(s):  
F D Gillin ◽  
D J Roufa ◽  
A L Beaudet ◽  
C T Caskey
Keyword(s):  
Nucleic Acid ◽  
Mammalian Cells ◽  
Chinese Hamster ◽  
Acid Synthesis ◽  
Ethyl Methanesulfonate ◽  
Nucleic Acid Synthesis ◽  
Wild Type ◽  
Chinese Hamster Cells ◽  
Hypoxanthine Guanine Phosphoribosyltransferase

ABSTRACT Chinese hamster cells were treated with ethyl methanesulfonate or N-methyl-N'-nitro-N-nitrosoguanidine, and mutants resistant to 8-azaguanine were selected and characterized. Hypoxanthine-guanine phosphoribosyltransferase activity of sixteen mutants is extremely negative, making them suitable for reversion to HGPRTase+. Ten of the extremely negative mutants revert at a frequency higher than 10-7 suggesting their point mutational character. The remaining mutants have demonstrable HGPRTase activity and are not useful for reversion analysis. Five of these mutants have < 2% HGPRTase and are presumably also HGPRTase point mutants. The remaining 14 mutants utilize exogenous hypoxanthine for nucleic acid synthesis poorly, and possess 20-150% of wild-type HGPRTase activity in in vitro. Their mechanism of 8-azaguanine resistance is not yet defined.

Correction of Genetic Defects in Mammalian Cells by the Input of Small Amounts of Foreign Genetic Material

1973 ◽  
Vol 13 (3) ◽  
pp. 841-861
Author(s):  
YVONNE L. BOYD ◽  
H. HARRIS
Keyword(s):  
Thymidine Kinase ◽  
Mammalian Cells ◽  
Hybrid Cell ◽  
Genetic Material ◽  
Chinese Hamster ◽  
Heat Sensitivity ◽  
Chinese Hamster Cells ◽  
Inosinic Acid ◽  
Mouse Cells

Chinese hamster cells lacking inosinic acid pyrophosphorylase and mouse cells lacking thymidine kinase were fused with chick erythrocytes. The resultant heterokaryons were cultivated in a selective medium in which possession of these enzymes was essential for cell survival and growth. Clones of cells able to grow in this medium were isolated and studied. A detailed karyological analysis of these clones failed to reveal any chick chromosomes; nor could any chick-specific antigens be detected on the surface of the cells. Nonetheless, clones arising from the fusion of chick erythrocytes with Chinese hamster cells were shown to possess an inosinic acid pyrophosphorylase which had the electrophoretic characteristics of chick inosinic acid pyrophosphorylase. However, the clones arising from the fusion of the chick erythrocytes with the mouse cells had a thymidine kinase with the electrophoretic mobility and heat sensitivity of murine, not chick, thymidine kinase. Both types of hybrid cell have now been cultivated in vitro for 18 months without the loss of thymidine kinase or inosinic acid pyrophosphorylase activity.

Metabolic Co-Operation Between Biochemically Marked Mammalian Cells in Tissue Culture

1969 ◽  
Vol 4 (2) ◽  
pp. 353-367
Author(s):  
H. SUBAK-SHARPE ◽  
R. R. BÜRK ◽  
J. D. PITTS
Keyword(s):  
Tissue Culture ◽  
Nucleic Acid ◽  
Mixed Culture ◽  
Molecular Basis ◽  
Mammalian Cells ◽  
Genetic Variant ◽  
Cell Contact ◽  
Metabolic Function ◽  
Indirect Contact ◽  
Fibroblast Line

Cells of a genetic variant of the hamster fibroblast line BHK 21 which lack inosinic pyrophosphorylase activity (IPP- cells) and therefore cannot normally incorporate [3H]hypoxanthine were grown in mixed culture with cells of BHK 21 sublines which have inosinic pyrophosphorylase activity (IPP+ cells). If not in contact with IPP+ cells, IPP- cells do not incorporate added [3H]hypoxanthine into nucleic acid. IPP+ cells always do incorporate [3H]hypoxanthine and IPP- cells when in direct or indirect contact with IPP+ cells also incorporate the isotope. Cell to cell contact appears to be essential for this gain of a metabolic function by IPP- cells. The possible molecular basis and general implications of the phenomenon are discussed.

scholarly journals STUDIES OF DNA-INDUCED HERITABLE ALTERATION OF MAMMALIAN CELLS

1970 ◽  
Vol 132 (6) ◽  
pp. 1071-1089 ◽  
Author(s):  
Ellen Borenfreund ◽  
Yuji Honda ◽  
Mildred Steinglass ◽  
Aaron Bendich
Keyword(s):  
Mammalian Cells ◽  
Chinese Hamster ◽  
Ascites Tumor ◽  
Intercellular Interaction ◽  
Oncogenic Potential ◽  
Chinese Hamster Cells ◽  
Direct Microscopic Examination ◽  
Ehrlich Ascites ◽  
Specific Antigens

An intercellular interaction between mouse Ehrlich ascites tumor and non-malignant Chinese hamster cells occurred when these were co-cultured. That the intercellular processes which formed had emanated from the EA cells was revealed by immunofluoroscopy using anti-EA antiserum, and by direct microscopic examination. A passage of DNA from the EA to the CH cells was also observed. On long-term co-culture, new cell forms arose which were isolated, cloned, and propagated. They showed a CH karyotype and had acquired oncogenic potential and the ability to synthesize murine-specific antigens. These same heritable properties were also acquired by CH cells following their exposure to DNA isolated from EA cells.

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.

Mutagenesis in cultured mammalian cells I. Spontaneous gene mutations in human and Chinese hamster cells

1972 ◽  
Vol 15 (2) ◽  
pp. 203-214 ◽  
Author(s):  
N.I. Shapiro ◽  
A.E. Khalizev ◽  
Eugeny V. Luss ◽  
Marina I. Marshak ◽  
Olga N. Petrova ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Chinese Hamster ◽  
Gene Mutations ◽  
Chinese Hamster Cells

scholarly journals TEMPORAL ORDER IN MAMMALIAN CELLS

1969 ◽  
Vol 43 (2) ◽  
pp. 207-219 ◽  
Author(s):  
Robert R. Klevecz
Keyword(s):  
Enzyme Activity ◽  
Mammalian Cells ◽  
Temporal Order ◽  
Actinomycin D ◽  
Chinese Hamster ◽  
Enzyme Synthesis ◽  
S Phase ◽  
Selection System ◽  
Enzyme Protein ◽  
Chinese Hamster Cells

Chinese hamster cells were synchronized by the Colcemid-selection system. In cells with a division cycle time of 11.5–12 hr, the activity of the enzyme lactate dehydrogenase (LDH) underwent marked oscillations with a 3.5-hr period. Precipitation of labeled LDH enzyme with specific antibody indicated that the enzyme activity changes were the result of intermittent enzyme synthesis and relatively constant degradation. Inhibition of normal DNA replication with 4 mM of thymidine, while reducing the amount of new enzyme synthesized, did not prevent oscillations from occurring. Similarly, actinomycin D (AcD) added at the time of synchronization allowed some new enzyme synthesis to proceed in an oscillatory manner. LDH synthesis went on at nearly normal rates when AcD was added in the middle of S phase. However, addition of cycloheximide to cultures at any time in the cycle caused an immediate drop in levels of activity and in enzyme protein. The half-life of LDH, calculated either from loss of enzyme activity or precipitable radioactivity in cycloheximide-treated cultures, was between 2 and 2.5 hr.

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