Comparative developmental and phenotypic properties of altered hepatocyte foci and hepatic tumors in rats.

Previous investigations in this laboratory have provided evidence that histochemically detectable altered hepatocyte foci and hepatic tumors appearing in rats given a single neonatal treatment with a low dose of carcinogen followed by chronic dietary phenobarbital administration are developmentally independent. The present investigation further evaluates developmental relationships among these lesions. Altered hepatocyte foci were divided into two subclasses consisting of foci that were detectable by histochemical as well as by hematoxylin-eosin staining [designated hist(+)/morph(+) foci] and those foci that were detectable solely by histochemical staining [designated hist(+)/morph(-) foci].

Effects of separate and combined treatments with gamma radiation and diethylnitrosamine in neonatal rats on the induction of altered hepatocyte foci and hepatic tumors.

To characterize the effects of combined treatments with gamma radiation and diethylnitrosamine (DEN) on the induction of histochemically detectable altered hepatocyte foci and hepatic tumors, we assessed the yields of these lesions in the livers of 150-day-old rats that had been treated neonatally with a single dose of gamma radiation (75 rad, whole body) and i.p.-injected DEN (0.

Effects of rat strain, diet composition, and phenobarbital on hepatic gamma-glutamyl transpeptidase histochemistry and on the induction of altered hepatocyte foci and hepatic tumors by diethylnitrosamine.

To extend our ongoing characterization of modulatory influences on hepatic tumorigenesis, we examined effects of rat strain (Sprague-Dawley versus Fischer), diet composition (semipurified diet versus standard nonpurified laboratory chow), and dietary phenobarbital on the production of gamma-glutamyl transpeptidase (GGT)-positive hepatocyte foci and hepatic tumors initiated by diethylnitrosamine. In addition to GGT-positive foci, we observed, under certain conditions, the appearance of extensive hepatic GGT staining not associated with focal lesions. This elevated nonfocal GGT was found in rats of both strains fed the nonpurified rather than the purified diet, but the level of staining was higher in Fischer than in Sprague-Dawley rats.

Characterization of histochemically detectable altered hepatocyte foci and their relationship to hepatic tumorigenesis in rats treated once with diethylnitrosamine or benzo(a)pyrene within one day after birth.

A new experimental system was used to examine the stages of chemically induced hepatic neoplasia in the rat. The treatment protocol involved the i.p.

Relationship of histochemically detectable altered hepatocyte foci to hepatic tumorigenesis.

A new experimental system was used to examine the stages of chemically induced hepatic neoplasia in the rat. The treatment protocol involved the intraperitoneal injection of a single non-necrogenic dose of carcinogen [N-nitrosodiethylamine (NDEA) or benzo[a]pyrene (BP)] into male and female rats within one day after birth, followed by dietary exposure to promoter (0.05% phenobarbital) from weaning.

Early appearance of histochemically altered hepatocyte foci and liver tumors in female rats treated with carcinogens one day after birth.

A single i.p. injection of diethylnitrosamine (DEN) or benzo[a]pyrene (BAP) in 1-day-old female rats produced a high incidence of gamma-glutamyltranspeptidase-(GGT)-positive hepatocyte foci within 4 weeks after the rats were weaned onto a 0.

Evaluation of Myrothecium verrucaria as a nutrient source for ruminants.

The soil saprophytic fungus Myrothecium verrucaria was cultivated from glucose, starch, or xylan as the carbon source, and the biomass was compared with three selected feedstuffs. Fungal biomass was analyzed for nitrogen, protein, lipid, water soluble fraction, hemicellulose, cellulose, lignin, and residual ash, and the in vitro dry matter disappearance was determined. The chemical composition of M.

Odontomas in Peromyscus leucopus.

A colony of Peromyscus leucopus was established 15 years ago from animals trapped in the deciduous forest at Argonne National Laboratory, Argonne, Illinois. A roentgenographic survey of the skeletons of 189 of these untreated animals dying during a 13-month period disclosed 48 odontogenic growths in 21 of the mice. These growths were diagnosed on histopathologic examination as complex odontomas, the incidence of which was higher in males than in females.

Comparative effects of aminotriazole on normal and acatalasemic mice.

Some pharmacological and toxicological effects of dietary 3-amino-1,2,4-triazole (AT), a known catalase inhibitor, antithyroid agent, and carcinogen, have been examined, using acatalasemic (Csb) and normal catalase, "wild-type" (Csa) substrains of highly inbred C3H and C57BL mice. It was found that (a) the acatalasemic substrains are more resistant to weight loss and death on the AT diet than are their normal catalase counterparts; (b) Csb and Csa substrains of C57BL mice are more resistant to weight loss and death on the AT diet than are the Csb and Csa substrains of the C3H mouse; (c) the liver catalase, as well as the whole body catalase, of the two C57BL substrains is less inhibited by the AT diet than is that of the C3H substrains; (d) mice consuming the same quantity of either normal or AT-containing diet gain much more weight on the normal diet; (e) temporary consumption of the AT diet causes a considerable increase in thyroid weight, with an extremely slow, and only partial, return toward normal weight; and (f) the C3H/Csa mouse on an AT diet develops a scaly, necrotic tail very similar in appearance to the so-called rodent ringtail; this lesion is never observed in the acatalasemic mouse on the same diet.

Carcinogenic and antitumor effects of aminotriazole on acatalasemic and normal catalase mice.

Dietary 3-amino-1H-1,2,4-triazole (AT), although carcinogenic when administered alone, was an antitumor agent when combined with certain other carconogenic stimuli. The carcinogenic effect was prominent in the livers of C3H mice; thyroid tumors were less common because they required a longer period of development, and the life-span of the animal was shortened by the AT diet. The antitumor effects of AT included: delay in appearance of mammary tumors, striking reduction in gamma-radiation-induced lymphomas, and sharp reduction in neutron radiation-induced harderian gland and ovarian tumors.

Comparative enhancing effects of phenobarbital, amobarbital, diphenylhydantoin, and dichlorodiphenyltrichloroethane on 2-acetylaminofluorene-induced hepatic tumorigenesis in the rat.

Earlier studies showed that phenobarbital feeding enhanced hepatic tumorigenesis in rats previously fed 2-acetylaminofluorene for a brief period. As part of an investigation of the mechanism of this enhancement, the present study evaluated the relative enhancing abilities of amobarbital, diphenylhydantoin, and dichlorodiphenyltrichloroethane (DDT), agents that resemble phenobarbital to varying degrees in their effects on liver structure and metabolism. A comparison of hepatic tumor yields in rats fed 2-acetylaminofluorene, followed by the test substance (sequential treatment), showed that amobarbital and diphenylhydantoin had no enhancing activity, whereas the enhancing effect of DDT was similar to that of phenobarbital.