Hycanthone was administered to Schistosoma mansoni-infected and non-infected Syrian golden hamsters and Swiss mice by intraperitoneal and intramuscular injection of amounts up to the maximum tolerated dose. No tumors attributable to treatment were observed in hamsters. In infected mice, the overall incidence of hepatomas and hepatocellular carcinomas increased from 3.4% in untreated mice to 10.6% in those treated with hycanthone. Non-infected control mice developed 0.8% of these tumors compared to 10.2% in mice treated with hycanthone. Despite the use of high dose levels of hycanthone, statistical significance was attained only with non-infected female mice injected intraperitoneally and intramuscularly with hycanthone and then only at confidence levels of 92 and 95% respectively.

Animals↗

PubMed1979

Food additives (natural and synthetic).

Food additives can be divided into the following categories: intentional, unintentional, contaminants, and those resulting from food processing procedures. Representative food additives from each category are discussed, with special attention being paid to the status of those suspected or proven to be toxic to humans. In addition, certain chemical components of food and methods for testing food additives are considered. Areas requiring additional testing include saccharin, cooking procedures, especially charcoal broiling, and hydrozines in mushrooms. The more recent developments in test procedures, including in vitro test methods, the transplacental exposure route, the use of maximal tolerated dose, and the initiation--promotion sequence, are evaluated.

Animals↗

PubMed1979

A carcinogenicity study of pesticide dieldrin in hamsters.

Syrian golden hamsters were fed for their lifespan a diet containing 0, 20, 60 and 180 parts per million (ppm) Dieldrin. Tumour-bearing animals totaled 13% among control females and ranged between 3-15% in treated females. Eight per cent of male controls had tumours and between 16-23% of treated males. Incidences of endocrine organ tumours were comparable in all groups. A hepatoma was found in 1 female and 1 male led 180 ppm Dieldrin. The present results show that hamsters tolerate higher doses of Dieldrin than do mice and rats. No significant tumour incidence was observed in treated versus control Syrian golden hamsters.

Animals↗

PubMed1979

Experimental induction of hepatomas, mammary tumors, and other tumors with metronidazole in noninbred Sas:MRC(WI)BR rats.

Metronidazole, a chemotherapeutic agent against trichomonas infection, was tested for carcinogenicity in noninbred Sas:MRC(WI)BR rats. Three groups were given the drug for life at dose levels of 0.6%, 0.3%, and 0.06% in a powdered diet. The incidence of mammary tumors (P less than 0.020) and hepatomas (P less than 0.050) increased significantly among females given the highest dose (0.6%). Also, the rates of Leydig cell tumors of the testes (P less than 0.040) and pituitary adenomas (P less than 0.040) were statistically significant among males given the highest dose (0.6%). Results are discussed in light of a possible hazard of this drug to humans.

Animals↗

PubMed1979

Effects of transplacental exposure to diethylstilbestrol on carcinogenic susceptibility during postnatal life in hamster progeny.

Prenatal exposure to a single dose of diethylstilbestrol (DES) produced a significant increase in carcinogenic response of hamster progeny that were subsequently subjected to the carcinogenic stimulus of 7,12-dimethylbenz(a)anthracene (DMBA) during postnatal life. The compounds were administered according to the following schedules. The pregnant animals (second group) received a single dose of DES, 10 mg/kg, on Day 14 of gestation. Postnatally, at 6 weeks of age, the progeny were given DMBA, 25 mg/kg p.o., twice weekly for 8 weeks. The first group received DMBA at 6 weeks of age, 30 mg/kg p.o., twice weekly for 18 weeks. The progeny exposed to DES prenatally and DMBA postnatally (DES-DMBA-exposed progeny) developed a greater multiplicity of tumors per tumor-bearing animal (p less than 0.001) and higher rates of neoplasms of the reproductive tract, e.g., ovarian and uterine tumors, mammary gland and forestomach tumors, and dermal melanomas. The prenatally DES-exposed progeny also had significantly higher incidences of malignant tumors, e.g., carcinomas of the mammary gland (p less than 0.001) and carcinomas of the forestomach (p less than 0.001), than did the hamsters given DMBA alone during postnatal life. Endocrine imbalance produced by exposure in utero may heighten the sensitivity of the progeny to development of neoplasms after a challenge with carcinogenic stimuli in adult life. The significance of these experimental data to the human situation is discussed.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1979

Induction of tumors by direct injection of N-ethyl-N-nitrosourea into the amniotic space of the mouse fetus.

An N-ethyl-N-nitrosourea (ENU) solution was injected into the amniotic space of Swiss mouse fetuses. Embryos 9 days old were exposed to 2 and 4 micrograms ENU and died within the first 4 weeks of life. Injection of 4 micrograms ENU into 11-day-old fetuses induced a 10% lung tumor incidence, whereas 16 micrograms injected at 12, 15, or 16 days resulted in lung tumor incidences of 42, 100, and 84%, respectively. A mortality rate of 50% and a lung tumor incidence of 89% in survivors resulted after exposure of 16-day-old fetuses to 64 micrograms ENU. Histologic examination revealed that the tumors were alveologenic adenomas 1--7 mm in diameter. Two saline-treated control groups had no tumors. The possible utilization of this biologic model in testing chemical alkylating agents similar to ENU is discussed.

Adenoma↗

PubMed1979

Kidney tumors induced in rats by the antischistosomal drug niridazole.

An increased incidence of kidney tumors was found in MRC rats fed the antischistosomal drug niridazole at four dose levels in the diet. Histologically, the adenomas and adenocarcinomas were solid papillary, clear cell, and tubular types, with the latter type predominating. Seven mesenchymal tumors were found among the 107 renal epithelial neoplasms. Severe nephrosclerosis occurred in both treated and control rats and has been suggested as important in renal carcinogenesis. Niridazole is considered a potent inducer of epithelial kidney tumors.

Adenocarcinoma↗

PubMed1978

The microcirculation in two transplantable melanomas of the hamster. I. In vivo observations in transparent chambers.

Twenty-eight transparent chambers were inserted into the cheek pouches of hamsters and daily serial observations made of the changing vasculature of transplants of 2 varieties (A-Mel-4B32, ZGYP1) of amelanotic melanomas. The tumor A-Mel-4B32 grew at a rate which covered 50% of the viewing area in 3--4 days, while the tumor ZGYP1 covered less than 10% of the viewing area at this time and did not cover 50% of the viewing area until 9.5 days after transplantation. The difference in growth rate was not reflected in any differences in the morphology of the vascular network and distribution of the venous arcades.

Animals↗

PubMed1978

The microcirculation in two transplantable melanomas of the hamster. II. Scanning electron microscopy.

Normal and tumor vessels observed in vivo on the hamster cheek pouch membrane in transparent chambers were examined by scanning electron microscopy. Large, thin walled veins were found in the reactive zone around the 2 amelanotic melanomas of the hamster. Sinusoidal vessels and channels contained red cells, which did not possess any vascular wall, were seen in the main substance of the tumors. In this system all the vessels within the central mass of the tumor transplant comprise newly formed vessels. The surfaces of the tumor cells and the lining of the tumor vessels were examined by this technique. The biological history i.e., age of the vessel and location from the growing edge of the tumor, were known. The surface of the tumor cells on cut section differed in appearance from the areolar tissue of the pouch membrane. Scanning electron microscopy of the inner aspect of newly formed tumor vessels permits much greater sampling of the tissue than transmission electron microscopy and further work should reveal aspects of the interaction of the blood with tumor stroma.

Animals↗

PubMed1978

Metastasis via the blood stream: the method of intravasation of tumor cells in a transplantable melanoma of the hamster.

Tumor cells entered the vascular compartment of transplantable amelanotic melanoma of the hasmster 3 days after transplantation, closely following vascularization of the transplant. Examination of the tortuous giant capillaries at the edge of the transplant showed tumor cells breaching the thin endothelium of these vessels. Extravasation of red cells into the surrounding tumor tissue and attempted haemostasis by small platelet aggregates attached to the vessel walls were also found.

Animals↗

PubMed1978

Carcinogenic effects of niridazole in rats.

Niridazole was administered in the diet to rats at levels of 0.1, 0.05 and 0.025%. The drug induced adenomas and adenocarcinomas of the kidneys and forestomach papillomas.

Adenocarcinoma↗

PubMed1978

Thyroid tumours in rats and hepatomas in mice after griseofulvin treatment.

Griseofulvin, an antibiotic used to treat dermatophystosis, was tested for carcinogenicity in mice, rats and hamsters. Three groups of mice and rats were given the drug in powdered diet in alternating 5-week periods for life, at dose levels of 3.0%, 1.5% and 0.3% (mice) and 2.0%, 1.0% and 0.2% (rats). A group of mice and 3 groups of hamsters received continuous daily treatment for life with griseofulvin at 3.0%, 1.5%, 0.3% and 0.1% dose levels respectively. A significant incidence of hepatic tumours was observed at the 2 higher treatment levels in mice. Also, statistically significant rates (P less than or equal to 0.001 and/or P less than or equal to 0.020) of thyroid tumours, indicating a dose-response, were recorded in male rats at the 2.0%, 1.0%, and 0.2% dose levels, and in females at the 2.0% and 1.0% dose levels. Hamsters did not develop neoplasms in response to treatment at any level.

Adenoma↗

PubMed1977

Carcinogenic activity of hexacholorobenzene in hamsters.

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Animals↗

PubMed1977

The implications of multiple tumor induction in rodent skin for the biologic nature of neoplasia.

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Animals↗