Lack of effect of age and dietary restriction on DNA single-stranded breaks in brain, liver, and kidney of (C3H x C57BL/10)F1 mice

Single-stranded DNA breaks in brain, liver, and kidney of (C3H x C57BL/10)F1 mice 6 and 25 months of age on two dietary regimens (isonutrient diets at 85 and 50 kcal/week) were investigated by means of fluorometric analysis of DNA unwinding in alkaline solutions. No age-dependent alterations were found for either control or dietary restricted groups. Except for possible differences for liver in the young age groups, there were no significant differences in the amount of single-stranded DNA breaks between control and dietary restricted mice. These results suggest that the antiaging effects of dietary restriction in rodents are not mediated by a change in the number of accumulated nuclear DNA stranded breaks in internal organs.

Dietary restriction alone and in combination with oral ethoxyquin/2-mercaptoethylamine in mice

To investigate effects of dietary caloric restriction (DR) combined with antioxidant feeding, long-lived hybrid mice were divided into four dietary groups at weaning, and followed until natural death. Groups "C" and "R" received control (97 kcal/wk) and restricted (56 kcal/wk) diets respectively. Groups "C+ alpha ox" and "R+ alpha ox" received C or R diets supplemented with an antioxidant mixture (2-mercaptoethylamine plus ethoxyquin). R mice (mean life span 41 months) significantly outlived the other three groups (mean life span 30-34 months). Hepatic degeneration and increased hepatoma in the R+ alpha ox group suggested unusual hepatotoxicity of this regimen. Antioxidants had little effect on splenic cell mitogen response in similarly fed mice sacrificed at 12-15 months. Gompertz analysis suggests that the beneficial effect of DR may be due to reductions in initial vulnerability or rate-of-aging parameters, or both, and that the relative influence of each factor may vary with animal strain and DR protocol used.

Fetal effects of inhalation exposure to cyclohexanone vapor in pregnant rats

Cyclohexanone (CH), a solvent and thinner that has extensive use in industry, was investigated for developmental effects using pregnant Sprague-Dawley rats exposed to 100, 250 or 500 ppm concentrations in an inhalation chamber for seven hours per day from days 5 through 20 of pregnancy. Controls were exposed to room air. Maternal weight gain at 250 and 500 ppm CH was only slightly lower than in the control dams, and a grey mottling of the lungs was seen in a few of the CH-exposed dams. There were no significant differences between the CH and control groups in fetal weight, resorption sites, fetal death or sex ratio. External and soft tissue examinations revealed no significant incidence of malformations or variations in CH-exposed animals. A slight increase in the mean percent of rudimentary ribs per litter was observed in the 250 and 500 ppm CH-exposed groups. However, no significant numbers of skeletal malformations were noticed in either the CH or room air control groups. It was concluded that respiratory exposure of rats to as much as 500 ppm CH during organogenesis was unlikely to be developmentally toxic.

Inhalation developmental toxicity study of propylene oxide in Fischer 344 rats

The developmental toxicity potential of propylene oxide (PO) was evaluated in Fischer 344 rats following inhalation exposure. Four groups of 25 mated female rats were exposed to 0, 100, 300, and 500 ppm of PO for 6 hr per day on Gestation Days 6 through 15, inclusive. Cesarean sections were performed on all females on Gestation Day 20 and the fetuses removed for morphological evaluation. Exposure to propylene oxide did not adversely affect survival, appearance, or behavior at any of the exposure levels tested. Maternal body weight gain and food consumption were reduced significantly among the females at the 500 ppm level during the exposure period. No exposure-related effects were noted with respect to maternal water consumption, organ weights, cesarean section, or fetal morphological observations with the sole exception of increased frequency of seventh cervical ribs in fetuses at the maternally toxic exposure level of 500 ppm. In summation, the no-observable-adverse-effect level (NOAEL) of propylene oxide, when administered to Fischer 344 rats via whole-body inhalation exposure, was considered to be 300 ppm.

Dietary restriction and aging: historical phases, mechanisms and current directions

Energy intake restriction (ER) without essential nutrient deficiency retards aging and extends life span in all species tested so far, and across wide phylogenetic differences. Historical phases of this model system for studying aging have included modulation of the survival curve, effects on disease susceptibility and effects on physiological indices of aging; the current phase focuses upon possible mechanisms whereby ER influences such widely diverse phenomena. Mechanistic possibilities include effects on the immune system, on basal state and proliferation potential, metabolic rate, DNA repair, levels of free radical scavengers, chromatin structure and protein synthesis and turnover. The ER model may also be useful in analyzing unifactorial versus multifactorial theories of aging, and in clarifying the possible significance of physiological markers that correlate with differences in maximum life spans between species.

Reproductive and teratogenic effects of nitrous oxide, halothane, isoflurane, and enflurane in Sprague-Dawley rats

A total of 305 timed-pregnant Sprague-Dawley rats were exposed for 6 h a day on each of three consecutive days in one of three periods, i.e., pregnancy days 14-16, 11-13, or 8-10, either to 0.55 times the minimum alveolar concentration (MAC) of nitrous oxide (75%) or to 0.75 MAC of halothane (0.8%), isoflurane (1.05%) or enflurane (1.65%); an additional 232 positive-control (retinoic acid) and air control rats were studied. Reproductive indices were determined, and the 5178 offspring delivered at cesarean section were examined for external, internal, and skeletal abnormalities. There were no major or minor teratologic effects in anesthetic treated groups, although several developmental variants were observed in halothane- and enflurane-treated groups. Nitrous oxide exposure on days 14-16 resulted in a three-fold increase in fetal resorptions. The results suggest that the volatile anesthetics are not teratogenic and confirm that nitrous oxide may be associated with increased reproductive loss.

Influence of intrauterine position on fetal weight in Dutch belted rabbits

The influence of intrauterine position on fetal body weight was statistically evaluated for 199 Dutch belted rabbit litters from does receiving various treatments during teratological studies. The data consisted of the number, type (live, dead, resorbed), and position of implantation sites in the left and right uterine horns. Body weights of live fetuses were also recorded. No statistically significant relation was found between the number of live, dead, or resorbed fetuses and intrauterine position. An effect related to differences in position between the left and right uterine horns for the proportions of largest fetuses was statistically significant. This uterine horn effect was not seen for the proportions of smallest fetuses. Positional differences within the uterine horns were significant and indicated a decrease in the proportion of largest fetuses and an increase in the proportion of smallest fetuses with increasing position number (ovarian to cervical end). Mean fetal weights differed significantly between the two uterine horns and among positions. There was a monotonic decrease in fetal weight with increasing position number. There were no significant associations between uterine horn or position and mean weight for the largest fetuses, but statistical evidence of the position effect was seen for weights of the smallest fetuses.

Correlation of cytotoxicity and mitotic spindle dissolution by vinblastine in mammalian cells

In two hamster cell lines that differed 100-fold in their vinblastine sensitivity, dissolution of the mitotic spindle by vinblastine in living cells correlated with cytotoxicity from vinblastine expressed as suppression of colony formation. The effect on the spindle apparatus occurred in 30 sec or less and thus provides a rapid assay for determining the cytotoxic effects of the Vinca alkaloids, as well as the potential for quantitative assay of solutions of Vinca derivatives.

Teratology and percutaneous toxicity studies on hair dyes

Twelve hair dye formulations were tested for systemic toxicity by topical application twice weekly for 13 wk to groups of 12 New Zealand white rabbits and for teratologic effects following applications to groups of 20 pregnant Charles River CD rats on days 1, 4, 7, 10, 13, 16, and 19 of gestation. The three semipermanent formulations were applied as is, and the nine oxidation dyes were mixed 1:1 with 6% hydrogen peroxide just prior to application, as in normal use. The formulations induced a broad spectrum of dyes and dye intermediates used or considered useful in oxidative and semipermanent hair color products. In the teratology study no biologically significant soft tissue or skeletal changes were noted. Similarly, the mean numbers of corpora lutea, implantation sites, live fetuses, and resorptions per pregnancy, as well as numbers of litters with resporptions, were not significantly affected by the dye treatment. In the percutaneous toxicity study there was no evidence of compound-induced systemic effects. Microscopic examination of 25 tissues from each animal gave no indication of histomorphologic evidence of toxicity. No dye discoloration of urine was seen at any time during the test or at necropsy. Some of the dye groups showed epidermal hyperplasia, which was probably a reflection of slight irritation due to the frequency of application of the oxidation formulations.