An improved method for DNA alkaline gradient analysis and its application to the effect of carcinogens on mouse liver DNA

Genetic toxicity of 2-acetylaminofluorene, 2-aminofluorene and some of their metabolites and model metabolites

2-Acetylaminofluorene and 2-aminofluorene are among the most intensively studied of all chemical mutagens and carcinogens. Fundamental research findings concerning the metabolism of 2-acetylaminofluorene to electrophilic derivatives, the interaction of these derivatives with DNA, and the carcinogenic and mutagenic responses that are associated with the resulting DNA damage have formed the foundation upon which much of genetic toxicity testing is based. The parent compounds and their proximate and ultimate mutagenic and carcinogenic derivatives have been evaluated in a variety of prokaryotic and eukaryotic assays for mutagenesis and DNA damage. The reactive derivatives are active in virtually all systems, while 2-acetylaminofluorene and 2-aminofluorene are active in most systems that provide adequate metabolic activation. Knowledge of the structures of the DNA adducts formed by 2-acetylaminofluorene and 2-aminofluorene, the effects of the adducts on DNA conformation and synthesis, adduct distribution in tissues, cells and DNA, and adduct repair have been used to develop hypotheses to understand the genotoxic and carcinogenic effects of these compounds. Molecular analysis of mutations produced in cell-free, bacterial, in vitro mammalian, and intact animal systems have recently been used to extend these hypotheses.

Orellanine inhibits protein synthesis in Madin-Darby canine kidney cells, in rat liver mitochondria, and in vitro: indication for its activation prior to in vitro inhibition

Pure orellanine, a nephrotoxic compound extracted from the mushroom Cortinarius orellanus, which is known to induce severe kidney damage several days or weeks after ingestion, is found to inhibit strongly the synthesis of macromolecules (proteins, RNA and DNA) in Madin-Darby canine kidney (MDCK) cells and in rat liver mitochondria, although the uptake of labelled precursors of the above macromolecules is not significantly altered. Direct addition of orellanine to a cell-free system of rabbit reticulocyte lysate does not produce any inhibition of protein synthesis. However, when orellanine is pre-incubated with activating rat liver microsomal systems, this inhibition occurs. Thus, the in vivo inhibition of protein synthesis is most likely due to a metabolite of orellanine.

Distribution of the [3H]-label from low doses of radioactive ochratoxin A ingested by rats, and evidence for DNA single-strand breaks caused in liver and kidneys

The distribution of a single low dose of [3H]-ochratoxin A (OTA) in different tissues of male Wistar rats, after administration by intubation, was investigated after 5 h, 24 h and 48 h. This dose corresponds to concentrations encountered in naturally contaminated feed (4 ppm). The distribution of [3H]-label varied with the time elapsed after administration; at 5 h the highest specific label was found in the stomach contents and in decreasing order in: intestinal contents, lung, liver, kidney, heart, fat, intestine, testes, and the lowest in muscles, spleen and brain. With exception of brain, fat, stomach and lung, all tissues showed maximum levels at 24 h, after which time the label decreased steadily, whereas in fat it increased. After a 12-week feeding experiment, with doses of 288.8 micrograms/kg corresponding to an intake of 4 ppm in feed each 48 h, the DNA in liver and kidneys was investigated for damage. By the alkaline elution method combined with micro-spectrofluorimetric determinations of DNA, evidence for DNA single-strand breaks was obtained. These findings support reports on the carcinogenic action of OTA.

Genotoxicity of ochratoxin A in mice: DNA single-strand break evaluation in spleen, liver and kidney

Ochratoxin A, a natural contaminant of feed and food, has been shown to induce experimental liver and kidney tumours. In vitro experiments on mice spleen cells showed evidence of DNA single-strand breaks induced by ochratoxin A. We measured single-strand breaks in the DNA of spleen, liver and kidney of ochratoxin A-treated animals. Ochratoxin A induced DNA damage in vivo. This damage reversed with time. The appearance and extent of the damage varied in different tissues. Except for spleen our data correlate with the tumours induced by ochratoxin in mouse liver and kidney. With regard to the spleen, there has been no report to date of experimental leukemia induced by ochratoxin A. Thus our results indicate that this possibility has to be considered.

Induction of DNA single-strand breaks by T2 toxin, a trichothecene metabolite of fusarium: effect on lymphoid organs and liver

T2 toxin, a trichothecene metabolite produced by Fusarium species, contaminates cereals harvested and stored under damp and cold conditions. These substances are responsible for Alimentary Toxic Aleukia (ATA), a severe human disease, and numerous animal intoxications. The action of T2 toxin on DNA was studied by using Parodi's alkaline elution technique coupled with a microfluorimetric determination of DNA. In vivo the effect of the toxin was studied on liver, spleen and thymus, and in vitro on a primary culture of rat hepatocytes and on splenic and thymic lymphocytes stimulated by PHA. Under our experimental conditions, in vivo and in vitro, no damage was observed for the hepatic DNA. By contrast, the DNA of lymphoid organs was severely damaged by the toxin. In vitro, T2 toxin induced severe damage to the DNA molecule with low concentrations (5 ng/ml culture) and for short exposure (2 h). In vivo, a moderate amount of DNA breaks was observed in splenic and thymic lymphocytes 3 h after administration of T2 toxin to mice (3 mg/kg). Reversibility occurred 24 h later under these conditions in vivo, indicating DNA repair. The results agree with the preferential cytotoxicity of T2 toxin for lymphoid cells. The relation between DNA damage, mutagenicity and carcinogenic properties of T2 toxin is discussed.

Properties of human adenoviruses 5 and 7 grown in guinea-pig cells

Human adenoviruses (Ad) 5 and 7 multiplied poorly in guinea-pig cell cultures as compared to HeLa cells. Ad 7 had a modified polypeptide composition with a major 43K component. This change persisted for up to 4 passages in HeLa cells. Ad 5 was not changed by passage in guinea-pig cells.