Replicon sizes in mammalian cells as estimated by an x-ray plus bromodeoxyuridine photolysis method. [Comparative estimation of replicon size in human diploid fibroblasts, HeLa cells, and Chinese hamster ovary cells]
A new method is described for estimating replicon sizes in mammalian cells. Cultures were pulse labeled with (/sup 3/H)thymidine ((/sup 3/H)TdR) and bromodeoxyuridine (BrDUrd) for up to 1 h. The lengths of the resulting labeled regions of DNA, L/sub obs/, were estimated by a technique wherein the change in molecular weight of nascent DNA strands, induced by 313 nm light, is measured by velocity sedimentation in alkaline sucrose gradients. If cells are exposed to 1,000 rads of x rays immediately before pulse labeling, initiation of replicon operation is blocked, although chain elongation proceeds almost normally. Under these conditions L/sub obs/ continues to increase only until operating replicons have completed their replication. This value for L/sub obs/ then remains constant as long as the block to initiation remains and represents an estimate for the average size of replicons operating in the cells before x irradiation. For human diploid fibroblasts and human HeLa cells this estimated average size is approximately 17 ..mu..M, whereas for Chinese hamster ovary cells, the average replicon size is about 42 ..mu..M.
- Research Organization:
- Univ. of California, San Francisco
- OSTI ID:
- 6469915
- Journal Information:
- Biophys. J.; (United States), Journal Name: Biophys. J.; (United States) Vol. 24:3; ISSN BIOJA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400500 -- Photochemistry
560121* -- Radiation Effects on Cells-- External Source-- (-1987)
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ANIMAL CELLS
ANIMALS
ANTIMETABOLITES
ANTIMITOTIC DRUGS
AZINES
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
BODY
BROMOURACILS
BUDR
CELL CULTURES
CHEMICAL REACTIONS
COMPARATIVE EVALUATIONS
CONNECTIVE TISSUE CELLS
DECOMPOSITION
DNA
DRUGS
ELECTROMAGNETIC RADIATION
FEMALE GENITALS
FIBROBLASTS
GONADS
HAMSTERS
HELA CELLS
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
IONIZING RADIATIONS
IRRADIATION
LABELLED COMPOUNDS
LABELLING
MAMMALS
MAN
NUCLEIC ACIDS
NUCLEOSIDES
NUCLEOTIDES
ORGANIC BROMINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
OVARIES
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
PRIMATES
PYRIMIDINES
RADIATION EFFECTS
RADIATIONS
RIBOSIDES
RODENTS
SOMATIC CELLS
THYMIDINE
TRITIUM COMPOUNDS
ULTRAVIOLET RADIATION
URACILS
VERTEBRATES
X RADIATION