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Biomedical subjects

R M David

Publications and source records attributed to R M David.

30 records · Page 2Linked to original sources
PubMed1983

Induction of mouse liver glutathione S-transferase by ethanol.

The induction of hepatic glutathione S-transferase by ethanol was investigated in male Swiss-Webster mice using a liquid diet. After a 7-day feeding period, mice that received 18, 27 or 36% of their calories as ethanol exhibited significant increases in the specific activity of glutathione S-transferase when 1,2-dichloro-4-nitrobenzene (DCNB), p-nitrobenzylchloride (NBC) and 1,2-epoxy-3-(p-nitrophenoxy)propane (ENP) were used as substrates. The observed increases in activity appeared to be related to the concentration of ethanol in the diet. Thus, mice fed a diet with 36% of the calories as ethanol exhibited the greatest increase in specific activity (DCNB, 75%; NBC, 60%, ENP, 34%). Pair-fed mice demonstrated similar changes in enzymatic activity. A time-course study indicated a 4-day feeding period was not sufficient to elicit significant induction, but a significant increase was apparent by day 7. This increase was maintained or increased through day 14. By comparison, 0.5 mg of phenobarbital/ml of diet produced a greater increase in enzymatic activity (DCNB, 449%; NBC, 227%; ENP, 219%). These results suggest that ethanol does induce glutathione S-transferase, but it is a relatively poor inducer of this enzyme.

Animals↗
PubMed1983

Localization of 1,6-[14C]diaminohexane (HMDA) in the prostate and the effects of HMDA on early gestation in Fischer-344 rats.

Following oral administration of 1,6-[14C]diaminohexane (hexamethylenediamine, HMDA) to male Fischer-344 rats, approx. 20% of the administered dose was recovered as 14CO2 after 72 h. Urinary and fecal excretion accounted for 47% and 27% of the administered radioactivity, respectively. Of several tissues examined, the highest concentrations of residual radioactivity were found in the prostate at 24 and 72 h post-administration. Daily administration of HMDA (200 mg/kg/day) by gavage to pregnant female rats for 2 weeks starting on gestation day 0 did not affect litter size in these animals.

Animals↗
PubMedDate not supplied

Subchronic inhalation toxicity study of a water-dispersible polyester in rats.

AQ55 is a high molecular weight, water-dispersible, amorphous polyester used in applications where the exclusion of solvents and conventional surfactants is desirable, such as water-based adhesives, coatings, emulsions, paint primers, cosmetics and detergents. Potential health effects were evaluated in rats exposed by inhalation for about 13 wk to mean concentrations of 0, 2.4, 19.6 or 199 mg/m3 AQ55 polymer. No mortality occurred and body weights were unaffected. Mean relative liver weights in all treated male groups were slightly higher than control weights, but were not judged to be treatment related. Absolute liver weights and all other organ weights except lung weights were normal. Haematology, clinical chemistries and gross pathology were unremarkable. Exposure-related changes in the 199 mg/m3 groups included increased mean absolute and relative lung weights, accumulations of macrophages and acute inflammatory cells in alveolar and bronchial lumina, and increased numbers of macrophages in sinusoids of peribronchial lymph nodes. Minor accumulation of macrophages in alveolar lumina was the only exposure-related change in the 19.6 mg/m3 group. No exposure-related effects were seen in the 2.4 mg/m3 group. AQ55 produced no systemic toxicity, and aerosols of AQ55 do not appear to be toxic to pulmonary tissues following subchronic inhalation exposure.

Administration, Inhalation↗
PubMedDate not supplied

Reversibility of the chronic effects of di(2-ethylhexyl)phthalate.

Fischer-344 rats treated with 12,500 ppm (728 and 879 mg/kg/d for male and females, respectively) and B6C3F1 mice treated with 6,000 ppm (1,227 and 1,408 mg/kg/d, respectively) di(2-ethylhexyl)phthalate (DEHP) in the diet for 78 weeks were allowed to recover for an additional 26 weeks on control diet. Blood was analyzed at weeks 78 and 104 from 10 animals per sex per group; animals were sacrificed at weeks 79 and 105 for histopathologic examination. The results are compared with data from animals continuously exposed to these dietary levels for 104 weeks (10, 11). Body weights and food consumption were measured monthly. BUN, albumin, and globulin that were significantly different for rats exposed to DEHP throughout 104 weeks, were comparable to controls for the recovery group. Reversibility of chronic effects on erythrocyte count, hemoglobin, and hematocrit values was apparent only for female rats. Chronic exposure demonstrated effects on liver, kidney, and testes weights. All organ weight effects except for testes for the Recovery group of rats, and all organ weight effects for mice, were reversible. Pigmentation of Kupffer cells and renal tubules present in chronically treated rats were not observed for the Recovery group. Lesions in the testes and pituitary gland were not reversible in rats. This may be a reflection of the senescence of the hypothalamic-gonad axis in rats. Cessation of exposure for mice resulted in amelioration of effects in the kidneys, liver, and testes. The extent of reversibility suggests that many chronic effects may be associated with a metabolic phenomenon such as peroxisome proliferation, which also reverted to control levels after 26 weeks of recovery.

Administration, Oral↗