Biomedical subjects

D L McCormick

Publications and source records attributed to D L McCormick.

58 records · Page 4Linked to original sources

PubMedDate not supplied

Chronic toxicity/oncogenicity evaluation of 60 Hz (power frequency) magnetic fields in F344/N rats.

A 2-yr whole-body exposure study was conducted to evaluate the chronic toxicity and possible oncogenicity of 60 Hz (power frequency) magnetic fields in rats. Groups of 100 male and 100 female F344/N rats were exposed continuously to pure, linearly polarized, transient-free 60 Hz magnetic fields at flux densities of 0 Gauss (G) (sham control), 20 milligauss (mG), 2 G, and 10 G; an additional group of 100 male and 100 female F344/N rats received intermittent (1 hr on/1 hr off) exposure to 10 G fields. Mortality patterns, body weight gains throughout the study, and the total incidence and number of malignant and benign tumors in all groups exposed to magnetic fields were similar to those found in sex-matched sham controls. Statistically significant increases in the combined incidence of C-cell adenomas and carcinomas of the thyroid were seen in male rats chronically exposed to 20 mG and 2 G magnetic fields. These increases were not seen in male rats exposed continuously or intermittently to 10 G fields or in female rats at any magnetic field exposure level. No increases in the incidence of neoplasms, which have been identified in epidemiology studies as possible targets of magnetic field action (leukemia, breast cancer, and brain cancer), were found in any group exposed to magnetic fields. There was a decrease in leukemia in male rats exposed to 10 G intermittent fields. The occurrence of C-cell tumors at the 2 lower field intensities in male rats is interpreted as equivocal evidence of carcinogenicity; data from female rats provides no evidence of carcinogenicity in that sex. These data, when considered as a whole, are interpreted as indicating that chronic exposure to pure linearly polarized 60 Hz magnetic fields has little or no effect on cancer development in the F344/N rat.

Adenoma↗

PubMedDate not supplied

Chronic toxicity/oncogenicity evaluation of 60 Hz (power frequency) magnetic fields in B6C3F1 mice.

A 2-yr whole-body exposure study was conducted to evaluate the chronic toxicity and possible oncogenicity of 60 Hz (power frequency) magnetic fields in mice. Groups of 100 male and 100 female B6C3F1 mice were exposed to pure, linearly polarized, transient-free 60 Hz magnetic fields at flux densities of 0 Gauss (G) (sham control), 20 milligauss (mG), 2 G, and 10 G; an additional group of 100 male and 100 female B6C3F1 mice received intermittent (1 hr on/1 hr off) exposure to 10 G fields. A small but statistically significant increase in mortality was observed in male mice exposed continuously to 10 G fields; mortality patterns in all other groups of mice exposed to magnetic fields were comparable to those found in sex-matched sham controls. Body weight gains and the total incidence and number of malignant and benign tumors were similar in all groups. Magnetic field exposure did not increase the incidence of neoplasia in any organ, including those sites (leukemia, breast cancer, and brain cancer) that have been identified in epidemiology studies as possible targets of magnetic field action. A statistically significant decrease in the incidence of malignant lymphoma was observed in female mice exposed continuously to 10 G fields, and statistically significant decreases in the incidence of lung tumors were seen in both sexes exposed continuously to 2 G fields. These data do not support the hypothesis that chronic exposure to pure, linearly polarized 60 Hz magnetic fields is a significant risk factor for neoplastic development in mice.

Adenoma↗

PubMedDate not supplied

Distribution and metabolism of the retinoid, N-(4-methoxyphenyl)-all-trans-retinamide, the major metabolite of N-(4-hydroxyphenyl)-all-trans-retinamide, in female mice.

The metabolism and disposition of N-(4-methoxyphenyl)-all-trans-retinamide (MPR), the major metabolite of N-(4-hydroxyphenyl)-all-trans-retinamide (4-HPR), were investigated in female B6D2F1 (BDF) mice. Following a single oral dose of 10 mg/kg, MPR distributed to the serum, liver, mammary gland, urinary bladder, and skin. The highest levels of MPR were detected in the liver and mammary gland, and the largest values for AUC were in the mammary gland followed by the skin and liver. The t1/2 for MPR was 5.1 hr in liver, 5.6 hr in serum, 18.7 hr in urinary bladder, 23.1 hr in skin, and 26.6 hr in mammary gland. MPR and five metabolites were detected; levels varied between tissues. One metabolite was 4-HPR; the other four, which eluted at 7, 12, 13, and 18 min, remain unidentified. The major metabolite of MPR was the 18-min metabolite and comprised 17% of total retinoid in skin and 14% in mammary gland. 4-HPR was only a minor metabolite of MPR; 4-HPR was not detectable in serum or urinary bladder and accounted for less than 4% of total retinoid in the other tissues. In mice dosed with 10 mg/kg 4-HPR, the parent compound, MPR, a putative 4-HPR ester, and three of the MPR metabolites (7, 13, and 18 min) were found. These data suggest that the interconversion of 4-HPR and MPR greatly favors formation of MPR.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

Effects of pretreatment with the retinoid N-(4-hydroxyphenyl)-all-trans-retinamide and phenobarbital on the disposition and metabolism of N-(4-hydroxyphenyl)-all-trans-retinamide in mice.

The effects of pretreatment with N-(4-hydroxyphenyl)-all-trans-retinamide (4-HPR) and phenobarbital (PB) on the distribution and metabolism of 4-HPR, and on the levels of hepatic cytochromes, were investigated in female BDF mice. Pretreatment of mice for 3 days with 10 mg/kg 4-HPR had no effect on the disposition of 4-HPR in the serum, liver, mammary gland, or urinary bladder. 4-HPR pretreatment also had no effect on the pharmacokinetics of any of its metabolites in the liver, or on the levels of hepatic cytochromes P450 or b5. By contrast, pretreatment of mice for 3 days with 80 mg/kg PB had a significant effect on the disposition of 4-HPR in all the tissues examined; the areas under the concentration-time curves for PB-pretreated mice were half those for vehicle-pretreated mice. PB pretreatment also significantly reduced the levels of four metabolites of 4-HPR in the liver and increased the levels of hepatic cytochromes P450 and b5. These data suggest that prior or concomitant administration of drugs that induce the mixed function oxidase system could result in changes in retinoid disposition and metabolism; such changes may alter retinoid chemopreventive activity.

Animals↗