Robert B. Painter

Ultraviolet-induced repair replication in aging diploid human cells (WI-38)

Repair replication was measured after uv-irradiation of WI-38 cells at different passage numbers. A reduced level of DNA synthesis was found only at the last passage before cessation of cell division. This reduction was not evident two passages before this and we conclude that excision repair deficiency is not the basis for in vitro aging of diploid human cells. (auth)

The Effect of Extreme Hypoxia on the Repair of DNA Single-Strand Breaks in Mammalian Cells

About 20 percent of the single-strand breaks produced by x rays in V79 Chinese hamster cells under extremely hypoxic conditions remain unrepaired after 1 hr at 37

Effects of hyperthermia on the sedimentation of nucleoids from HeLa cells in sucrose gradients.

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LIMITATIONS IN THE USE OF CARBON-LABELED AND TRITIUM-LABELED THYMIDINE IN CELL CULTURE STUDIES.

C. The corresponding figure is only 10 percent for cells irradiated under moderately hypoxic (0.2

Are lesions induced by ionizing radiation direct blocks to DNA chain elongation

mu

Effect of Hypertonicity and X Radiation on DNA Synthesis in Normal and Ataxia-Telangiectasia Cells

M) or aerobic conditions (200

CONDITIONS AFFECTING THE EARLY THYMINELESS DEATH OCCURRING AFTER ULTRAVIOLET IRRADIATION OF ESCHERICHIA COLI B3.

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EVIDENCE FOR REPAIR OF ULTRA-VIOLET DAMAGED DEOXYRIBONUCLEIC ACID IN CULTURED MAMMALIAN CELLS.

M). The initial number of breaks produced per unit dose is identical for extremely hypoxic and moderately hypoxic cells and is about four times greater for aerobic cells. Because split-dose recovery proceeds under aerobic and moderately hypoxic conditions and is inhibited only under extremely hypoxic conditions, the split- dose recovery phenomenon may be related to the unrepaired component of single- strand breaks. (auth)

Rapid test to detect agents that damage human DNA.

ROTI ROTI, J. L., AND PAINTER, R. B. Effects of Hyperthermia on the Sedimentation of Nucleoids from HeLa Cells in Sucrose Gradients. Radiat. Res. 89, 166-175 (1982). The changes in sedimentation distance of nucleoids in neutral sucrose gradients in the presence of various concentrations of the intercalating dye ethidium bromide are believed to reflect changes in the amount of DNA supercoiling within the nucleoid. When HeLa cells were heated to 450C for 30 min before cell lysis, sedimentation of their nucleoids was markedly affected; at all concentrations of ethidium bromide in the gradient, nucleoids from heated cells sedimented farther than those from unheated cells. After cellular protein was labeled with [3H]leucine for 15 to 17 hr, approximately 4% of the total 3H radioactivity cosedimented with nucleoids from unheated cells. This percentage increased with heating time (10-70 min) and temperature (44-460C); e.g., after 20 min at 450C the fraction of 3H cosedimenting with nucleoids was 7%. The heat-induced change in nucleoid sedimentation distance was a linear function of the percentage of 3H cosedimenting with nucleoids. These results show that hyperthermia causes an increase in the protein content of nucleoids. The additional protein affects sedimentation by increasing the mass of the nucleoids and by decreasing the amount of DNA available for supercoiling and thereby the efficiency of DNA rewinding.

Bleomycin-resistant DNA synthesis in ataxia telangiectasia cells

Experiments were performed with C/sup 14/-thymidine or unlabeled thymidine added to HeLa S3 cell cultures growing in Eagles medium. The results show that thymidine in the culture medium causes a concentration-dependent inhibition of growth, with effects being significant at levels as low as 10 mu g/ ml, thymidine in the medium reduces the incorporation of H/sup 3/-uridine into both DNA and RNA, the effect on incorporation into RNA being unexpectedly great, and other nucleosides, added singly or together to the medium, cause effects similar to those induced by thymidine. Thirty-minute incubations with tritiated thymidine, at concentrations from 0.02 to 2.5 mu C/ml, and at two specific activities, did not affect the production of colonies of HeLa S3 cultures. (auth)