Chicken embryo cells were treated with caffeine (0.5-8.0 mM) alone or combined with various chemical and physical DNA-and/or chromatin-interactive agents. Analytical procedures comprised scheduled (SDS) and unscheduled (UDS) DNA synthesis, RNA synthesis (RNS), the activities of O6-alkylguanine-DNA alkyltransferase (AT) and poly (ADP-ribose) polymerase (PARP) as well as nucleoid sedimentation. A...

For the non-clinical safety evaluation of pharmaceuticals for new drug applications (NDA), various toxicity studies must be conducted at each stage, from clinical trials to NDA. topically applied drugs, level exposure administration site is high because administered directly site. However, systemic ophthalmic drugs generally lower than that effects may not adequately assessed. The bone marrow a...

Cells of an euploid strain of the Chinese hamster synchronized in the GI phase were microirradiated in the nucIeus with a laser UV microbeam (A=257 nm) and pulse-labelled with [3H]thymidine. In autoradiographs of cells fixed immediately after the pulse unscheduled DNA synthesis (UDS) was found restricted to tbe microirradiated part of the nueleus. Tbe rate of UDS varied with the UV energy appli...

Streptonigrin (SN, CAS no. 3930-19-6) is an aminoquinone antitumor antibiotic isolated from cultures of Streptomyces flocculus. This compound is a member of a group of antitumor agents which possess the aminoquinone moiety and that includes also mitomycin C, porfiromycin, actinomycin, rifamycin and geldanamycin. Because of the potential use of SN in clinical chemotherapy, the study of its genot...

Entry into mitosis is accompanied by dramatic changes in cellular architecture, metabolism and gene expression. Many viruses have evolved cell cycle arrest strategies to prevent mitotic entry, presumably to ensure sustained, uninterrupted viral replication. Here we show for human cytomegalovirus (HCMV) what happens if the viral cell cycle arrest mechanism is disabled and cells engaged in viral ...

Styrene monomer is a commercially important chemical used extensively in the production of plastics. It has been shown to induce lung tumours in the mouse via the inhalation route. Styrene monomer has shown a low reactivity with DNA and also a lack of genotoxic response in the mouse lung in vivo. Together with the fact that the mouse lung tumours were late occurring and mostly benign, which sug...

Photoreactivating enzyme (PRE) from yeast causes a light-dependent reduction of UV-induced unscheduled DNA synthesis (UDS) when injected into the cytoplasm of repair-proficient human fibroblasts (Zwetsloot et al., 1985). This result indicates that the exogenous PRE monomerizes UV-induced dimers in these cells competing with the endogenous excision repair. In this paper we present the results of...