Search PubMed⌕ Search

Biomedical subjects

R R Maronpot

Publications and source records attributed to R R Maronpot.

At least 181 records · Page 10Linked to original sources
PubMed1976

Large bowel carcinogenesis in mice and rats by several intrarectal doses of methylnitrosourea and negative effect of nitrite plus methylurea.

The carcinogenic effect of several dose levels and regimens of an aqueous solution of N-methyl-N-nitrosourea (MNU) administered intrarectally to mice and rats is reported. In Ha/ICR Swiss mice, a single dose of 1.8 mg MNU induces mainly lymphomas and pulmonary tumors in less than 20 weeks. Repeated doses of 1.5 mg MNU induces lymphomas, pulmonary tumors, and also large bowel tumors in less than 20 weeks. Doses of 0.3 mg decreased the yield of lymphomas and increased large bowel neoplasms over a period of 40 to 60 weeks. Repeated doses of 0.06 mg also gave a low yield of lymphomas and large bowel tumors over a 60-week period. Thus, a maximal yield of lymphomas is seen with a brief regimen of high doses, whereas large bowel tumors occur with a more frequent lower dose rate. Male Fischer strain rats given 1.0 or 2.5 mg MNU 3 times a week for 10 weeks had a multiplicity of large bowel tumors, proportional to dose, in 25 to 30 weeks. In fact, the high dose level led to a 100% yield in less than 20 weeks. Lymphomas were seen only at the higher dose when the animals were were young, at the beginning of the test. In mice and rats the carcinomas were polypoid or plaque shaped and were well differentiated with extensive invasion but no metastases. The adenomas were pedunculated or sessile. Intrarectal administration of a mixture of methylurea and nitrite for 20 weeks and further observation of the rats for an additional 35 weeks yielded no colon tumors. Thus, there is indirect evidence of a lack of the in situ formation of carcinogenic MNU in the large bowel under physiological conditions.

Adenocarcinoma↗
PubMed1975

A study of tobacco carcinogenesis. XIII. Tumor-promoting subfractions of the weakly acidic fraction.

The weakly acidic fraction (WAF) of cigarette smoke particulate matter was fractioned by silica get chromatography. We assayed the various primary subfractions for potential tumor-promoting activity by measuring the incorporation of tritiated thymidine into mouse epidermal DNA as induced by these subfractions. Based on these results and on chemical composition, the primary subfractions, were then combined into four major subfractions and tested on initiated mouse skin for tumor-promoting activity by long-term application. Two of these subfractions (40% of WAF) were inactive, whereas the other two (18 and 35% of WAF) showed tumor-promoting activity. The two active portions were then further chromatographed and tested by the short-term bioassay. Some major components of the resulting active fractions included alkyl-2-cyclopenten-2-ol-1-ones, catechols, hydroquinone, fatty acids, and 3-hydroxypyridines. Among these components, catechol, hydroquinone, 3-hydroxypyridine, 6-methyl-3-hydroxypyridine, linolenic acid, and linoleic acid were inactive as tumor promoters in the experimental animal. The activity of the alkyl-2-cyclopenten-2-ol-1-ones is unknown. Other components remain to be identified.

Animals↗
PubMed1972

Erythrocyte glucose-6-phosphate dehydrogenase and glutathione deficiency in sheep.

Erythrocytes of 145 sheep representing six breeds were assayed for glucose-6-phosphate dehydrogenase. All sheep had erythrocyte glucose-6-phosphate dehydrogenase values similar to glucose-6-phosphate dehydrogenase deficient erythrocytes of man. Mean erythrocyte glucose-6-phosphate dehydrogenase levels ranged from 0.65 to 1.54 micromoles of reduced nicotinamide adenine dinucleotide phosphate per gram of hemoglobin per minute. Many of these sheep also had low levels and/or unstable reduced glutathione. Sheep with low levels of erythrocyte glucose-6-phosphate dehydrogenase and reduced glutathione were given large doses of oxidizing drugs or fed fresh fava beans to determine if they would develop intravascular hemolysis. No significant hemolysis was detected as a result of drug administration or fava bean ingestion.

Age Factors↗
PubMed1967

Experimental sprue-like small intestinal lesions in pigs.

The virus of transmissible gastroenteritis produced sprue-like lesions in the small intestines of young pigs. These lesions were characterized by villous shortening, fusing and blunting in the jejunum and ileum. There was decreased height of the brush border and morphologic alteration of the villous epithelial cells from simple columnar to a variable cuboidal type. Accompanying these microscopic lesions were histochemical changes characterized by decreased staining intensity of acid phosphatase, alkaline phosphatase, adenosine triphosphatase, leucine aminopeptidase, succinic dehydrogenase and malic dehydrogenase in the affected intestinal mucosa. The clinical nature of transmissible gastroenteritis in the pig together with the histopathologic and histochemical changes may provide a useful experimental model for obtaining additional basic information on enteric disturbances.

Acid Phosphatase↗
PubMedDate not supplied

Method for determining whether the number of hepatocytes in rat liver is increased after treatment with the peroxisome proliferator gemfibrozil.

A histological method has been developed for determining the absolute numbers of rodent hepatocytes after treatment with the hypolipodemic drug gemfibrozil. It can be applied to distinguish between the enlargement of the liver that commonly occurs in rodents after treatment with chemicals, due to changes in the size of cells (hypertrophy), rather than an increase in the number of cells caused by cell division (hyperplasia). In the case of gemfibrozil the liver enlargement was found to be partly due to hypertrophy and partly to hyperplasia. The induction of hyperplasia can be associated with an increased risk of eventual liver tumour formation, and the distinction of hypertrophy from hyperplasia using a purely histological method, for the determination of increases in hepatocyte cell numbers, will be useful in the assessment of compounds which cause liver enlargement that could precede neoplasia.

Animals↗
PubMedDate not supplied

Acute and subchronic toxicity of ethylenediamine in laboratory animals.

As part of a comprehensive toxicology program on ethylenediamine (EDA), acute, short-term repeated and subchronic toxicity studies were conducted. Ethylenediamine dihydrochloride (EDA X 2HCl) was used in these studies. EDA X 2HCl was slightly to moderately toxic to laboratory rats, mice or rabbits in the following acute tests: Peroral intubation, percutaneous administration, primary skin irritation and eye injury. Following dietary inclusion of EDA X 2HCl for 7 days at up to 2.70 g/kg/day to Fischer 344 rats or B6C3F1 mice, body weight gain and some organ weights of the animals were depressed in both sexes at the highest dose level. When Fischer 344 rats were fed EDA X 2HCl at 0, 0.05, 0.25, 1.00 g/kg/day for 3 months, marked decreases in body weight gain were observed in both sexes at the highest dose level. Other dose-related effects observed in either or both sexes primarily at the highest dose level, and for some at the intermediate dose level, included organ weight changes and alterations in some clinical chemistry, hematology and urinalysis parameters. No deaths occurred during the exposure period, nor were there any significant gross lesions in any of the animals. Histologic findings indicate a dose-related increase in hepatocellular pleomorphism and mild hepatocellular degeneration.

Animals↗
PubMedDate not supplied

High frequency of ras mutations in forestomach and lung tumors of B6C3F1 mice exposed to 1-amino-2,4-dibromoanthraquinone for 2 years.

1-Amino-2,4-dibromoanthraquinone (ADBAQ) is an anthraquinone-derived vat dye, and a potent carcinogen in laboratory animals. In a 2-year study with dietary exposure to 10,000 or 20,000 ppm ADBAQ, increased incidence of forestomach and lung tumors were observed in B6C3F1 mice. The present study indentified genetic alterations in H-ras and K-ras proto-oncogenes in ADBAQ-induced tumors. Point mutations in ras proto-oncogenes were identified by restriction fragment length polymorphism, single-stranded conformational polymorphism analysis and cycle sequencing of polymerase chain reaction-amplified DNA isolated from paraffin-embedded squamous cell papillomas and carcinomas in the forestomach, and alveolar/bronchiolar adenomas and carcinomas in the lung. A higher frequency of ras mutations was identified in ADBAQ-induced forestomach (23/32, 72%) and lung tumors (16/23, 70%) than in spontaneous forestomach (4/11, 36%) and lung tumors (26/86, 30%). H-ras codon 61 CTA mutations were detected in (4/8, 50%) ADBAQ-induced forestomach squamous cell papillomas and (10/24, 42%) squamous cell carcinomas, but not in the spontaneous forestomach tumors examined. H-ras codon 61 CGA mutation (6/24, 25%) was also detected in ADBAQ-induced forestomach squamous cell carcinomas. K-ras codon 61 A to T transversions and A to G transitions were prominent in ADBAQ-induced lung alveolar/bronchiolar adenomas and alveolar/bronchiolar carcinomas. The major finding of A to T transversions or A to G transitions in forestomach and lung tumors suggests that ADBAQ or its metabolites target adenine bases in the ras proto-oncogenes and that these mutations play a dominant role in multi-organ

Adenocarcinoma, Bronchiolo-Alveolar↗
PubMedDate not supplied

A retrospective analysis of background lesions and tissue accountability for male accessory sex organs in Fischer-344 rats.

Because the paired lobes (ventral, dorsal, lateral, and anterior) of the rat prostate have not been consistently sampled in many carcinogenicity and toxicity studies, comparison among different investigations has been compromised. The lack of specific site identification for prostatic lesions further lessens the value of incidences reported. We present here the lobe-specific incidences and degree of severity of background prostatic, seminal vesicular, and ampullary glandular lesions in 1768 control Fischer-344 rats from 35 recent National Toxicology Program 2-year carcinogenicity and toxicity studies conducted in 4 laboratories. The dorsal and lateral lobes were combined and considered the dorsolateral lobe where inflammation, epithelial degeneration, mucinous cysts, and edema were observed. Inflammation in the dorsolateral lobes was significantly associated with pituitary gland adenoma whose prolactin was suggested to play an important role in pathogenesis of prostatic inflammation. Epithelial degeneration, epithelial hyperplasia, inflammation, edema, and adenoma were conspicuous in the ventral lobes. Inflammation and edema occurred in the anterior lobes (coagulating glands). Inflammation, dilatation, epithelial hyperplasia, edema, and adenoma were observed in the seminal vesicles. Inflammation was also present in the ampullary glands. We suggest an optimal embedment and trimming method in rat prostate and seminal vesicle to ensure adequate, consistent sampling.

Animals↗