Postconfluent cultures of Syrian hamster embryo cell strains were exposed to /V-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or to combinations of MNNG, hydroxyurea (HU), caf feine (CF), and/or theophylline. At various intervals, [3H]thymidine incorporation into DNA was determined by autoradiography and liquid scintillation spectrometry. In parallel cultures, drugand/or carcinogen-elicited cytotox...

The production of Spirulina platensis cells resistant to 8-azaguanine or beta-(2-thienyl)-DL-alanine following mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and UV-irradiation is described. The conditions for the mutagenesis were determined by monitoring cell viability and the appearance of the two types of mutants as a function of the stage of growth of the tricomes and the leng...

In an attempt to improve the method of induction of gastric cancer in dogs, selective vagotomy without drainage procedure was performed before administration of Nmethyl-N †̃-nitmo-N-nitrosoguanidine(MNNG). Twenty dogs were divided into two groups of 10 dogs (five beagles and five mongrels). The control group received MNNG alone. Dogs of the experimental group were vagotomized 2 months before a...

The widely used drug cimetidine (Tagamet) can be nitrosated in the presence of nitrite and under mild acid conditions to form a compound, nitrosocimetidine (NC), which has a chemical structure very similar to those of the mutagens and laboratory carcinogens N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and methylnitrosourea (MNU). NC has given positive indications in several short-term tests for ...

DNA repair synthesis and posttreatment colony-forming ability were measured in six human fibroblast cell strains derived from patients with the autosomal recessive disorder, ataxia telangiectasia (AT), and five cell strains from normal individuals. All 11 cell strains showed approximately equal levels of DNA repair synthesis after methyl methanesulfonate and ultraviolet light treatments assayed...

Reports of unusual increases in transformation frequency in low density cultures of C3H/10T1/2 cells suggest that transformation occurs via an indirect multistage mechanism. The effect of surviving cell density upon subsequent focus production was examined in C3H/10T1/2 cultures treated with acetone, 12-O-tetradecanoylphorbol-13-acetate (TPA), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), MNNG p...

Isogenic variants resistant to alkylating agents have been isolated from the human lymphoblast cell line TK6. The cell lines may be divided into four classes on the basis of resistance to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). The sensitive TK6 parental line shows a 37% survival after 45-min exposure to 0.04 microM MNNG; the three classes of more resistant mutants show 37% survival after ...

Twenty-one-day-old rainbow trout Salmo gairdneri embryos were exposed to static solutions of aflatoxin B, (AFB,) (0.5 pprn for 30 min) or N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) (50 ppm for 60 min) to initiate neoplasms of the liver (AFB1 and MNNG) and other organs (MNNG). Ten weeks after the onset of feeding (14 wk after carcinogen exposure) the fish were started on diets containing 500 pp...

Rat stomach carcinomas induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) are widely used as a model for differentiated-type human stomach carcinomas. Here, we analyzed expression profiles in five MNNG-induced rat stomach carcinomas by the high-density oligonucleotide microarray containing approximately 8000 probe sets. 244 and 208 genes were up- and down-regulated, respectively, by 3-fold ...

Pretreatment of H4 (rat hepatoma) cells for 48 hr with low nontoxic doses of alkylating agents [methyl methanesulfonate (MMS), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), and N-methyl-N-nitrosourea] renders the cells more resistant to the toxic effect of these compounds. Crossreactivity for survival is also observed with the different alkylating agents tested. Pretreatment with MNNG enables th...