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Thiourea (TU) fails to enhance the incidence of foci deficient in adenosine-5'-triphosphatase (ATPase) either by initiation or by promotion in a rat liver foci bioassay. To weanling female Sprague-Dawley rats, 3 x 200 or 3 x 500 mg/kg body wt of TU, respectively, were applied for initiation. One week later Clophen A 50, a technical mixture of(More)
Aldrin epoxidation was studied in rat liver microsomes. The assay is very sensitive; amounts of less than 1 microgram of microsomal protein were sufficient for activity determination. The very low background, stability of the metabolite, and the complete separation of substrate and metabolite permit estimation of mono-oxygenase activities of less than 1(More)
The promoting activity of the commercial PCB mixture Clophen A 50 on preneoplastic, enzymealtered islands in rat liver was investigated. Female Sprague-Dawley rats, 3 and 6 weeks old, were pretreated with nitrosamines for island initiation. There-after Clophen A 50 was administered repeatedly. Island development was examined between 2 and 12 weeks. Clophen(More)
The nuclear morphology of preneoplastic and unaltered hepatocytes in diethylnitrosamine-treated rats was investigated. Two-micrometer-thick sections of methacrylate-embedded liver were scanned with a TV camera and evaluated in a computer using multivariate analysis methods. The preneoplastic cell populations (islands) were distinguished from unaltered(More)
The expression of the insulin-like growth factor II (IGF-II) gene (Igf2) in rodents is completely abrogated in almost all adult tissues. A prominent exception are neoplasms in which IGF-II frequently serves as an autocrine growth factor. We have investigated the potential role of Igf2 expression during liver carcinogenesis. After application of(More)
The promoting effect of Clophen A 50, a commercial mixture of polychlorinated biphenyls (PCBs) on preneoplastic islands, initiated by diethylnitrosamine (DEN), was studied in male and female Sprague-Dawley rats. The islands were identified histochemically by loss of adenosine-5'-triphosphatase (ATPase) and/or emergence of gamma-glutamyltranspeptidase(More)
Treatment of adult female rats with a single dose of benzo[a]pyrene (BaP) fails to initiate preneoplastic enzyme-altered islands in their livers. Treatment with polychlorinated biphenyls (PCBs) at a dose which strongly induces aryl hydrocarbon(BaP)hydroxylase prior to BaP application and followed by promotion with PCBs causes the appearance of about 9(More)
The formation of foci with loss of ATPase and emergence of γ-GTase was studied histochemically in livers of male and female Wistar and Sprague-Dawley rats of 3–4 and 6–7 weeks of age, respectively, after application of diethylnitrosamine. A single dose of 8 mg/kg body weight induced a considerable island formation in weanlings of both sexes. Island(More)
The presence of glutathione was demonstrated histochemically in livers of rats treated with diethylnitrosamine or N-nitrosomorpholine. Glutathione content was markedly elevated in adenosine triphosphatase-deficient, gamma-glutamyltranspeptidase-positive hyperplastic cell islands. This finding may partly explain the increased resistance of hyperplastic cells(More)