down's syndrome (ds) is the most common chromosomal abnormality in human. subjects with ds are known to be peridisposed to develop leukemia. the molecular basis of the association between ds and leukemia is unknown. the unscheduled dna synthesis (uds) test measure the ability of dna-repair in mammalian cells after excision of a stretch of dna containing the region of damage induced by chem...

Results from a recent, new assay suggest that omeprazole, a potent inhibitor of gastric acid secretion, is genotoxic. The principle of this assay is that the non-proliferating zone of surface gastric epithelial cells can be selectively removed by controlied digestion so that any incorporation of tritiated thymidine into these cells represents unscheduled DNA synthesis. Parietal cells (which are...

Repair polymerases participating in unscheduled DNA synthesis in isolated liver nuclei, bleomycin-treated permeable cells and in ultraviolet-irradiated living cells were studied using two specific inhibitors of DNA polymerases, aphidicolin and 2', 3'-dideoxythymidine-5'-triphosphate. Unscheduled, i.e., repair, DNA synthesis in rat liver nuclei, and in bleomycin-treated permeable SR-C3H/He and X...

Marked differences in the rates of de novo DNA synthesis and unscheduled DMA synthesis were observed in hepatocytes and nonparenchymal cells (NPC) isolated from Fischer 344 rats following in vivo exposure to 1,2-dimethylhydrazine (SDMH) or diethylnitrosamine (DEN) for 1.5, 4, 8, 16, and 28 days. Liver cells were labeled in vivo with bromodeoxyuridine and [3H]thymidine, following which, hepatocy...

Marked differences in the rates of de novo DNA synthesis and unscheduled DMA synthesis were observed in hepatocytes and nonparenchymal cells (NPC) isolated from Fischer 344 rats following in vivo exposure to 1,2-dimethylhydrazine (SDMH) or diethylnitrosamine (DEN) for 1.5, 4, 8, 16, and 28 days. Liver cells were labeled in vivo with bromodeoxyuridine and [3H]thymidine, following which, hepatocy...

Unscheduled DMA synthesis was induced by procarcinogens in freshly isolated suspensions and primary cul tures (6 days old) of hepatocytes on collagen membranes. Incorporation of ['HJthymidine in the presence of hydroxyurea was used to measure unscheduled DMA synthesis. When hepatocellular DNA was isolated on cesium chlo ride gradients, significant levels of unscheduled DNA synthesis were measur...

Chemical carcinogen-induced unscheduled DNA synthesis in mouse skin in vivo was demonstrated with the aid of a mechanical device. An isotonic aqueous solution containing a carcinogen and [methyl-3H]thymidine was injected s.c. into an isolated portion of the skin clamped off with ring-shaped forceps. Dose-dependent unscheduled DNA synthesis was clearly demonstrated as silver grains on the nuclei...

An unscheduled DNA synthesis has been clearly demonstrated in meiotic and postmeiotic germ cell stages of the male mouse after in vivo treatment with a 250 mg/kg dose of ethyl methanesulfonate. The germ cell stages showing unscheduled DNA synthesis range from early to middle meiotic prophase stages through early to middle spermatid stages. The initiation of this synthesis, taken to be repair of...

The ability of fibroblasts to perform unscheduled DNA synthesis (a measure of excision-repair) after UV irradiation was measured radioautographically for seven species at several times after several UV fluences. Both the initial rate and the maximum incorporation of [(3)H]dThd increased with the life-span of the species (shrew, mouse, rat, hamster, cow, elephant, man). Unscheduled DNA synthesis...

The induction of unscheduled DNA synthesis in primary cultures of urothelial cells from rats, mice, and dogs by nitrofurans and arylamines and their derivatives was examined. Electron microscopy of the culture from rat cells showed the characteristics of epithelial cells. The cultured cells were exposed to the test chemicals in a serum-free medium containing 10 mM hydroxyurea and [3H]thymidine ...