Relationship of sex, exercise, and growth rate of life span in the Wistar rat: a multivariate correlational approach

Age-related levels of GABA/benzodiazepine binding sites in cerebrum of F-344 rats: effects of exercise

We examined gamma-aminobutyric acid (GABA), benzodiazepine and convulsant sites of postsynaptic GABA/benzodiazepine receptors (GBZR) in cerebral membranes of inbred Fischer 344 male rats as a function of age. In aged rats (23 to 24 months), the benzodiazepine binding site as determined by [3H]flunitrazepam was 47% and 43% lower than corresponding values in young adult (3 to 4 months) and mature (10 to 12 months) rats, respectively. The decrease was due to the loss of binding density rather than a change in affinity. No statistically significant age-related changes in [3H]muscimol binding were observed when 5 nM or 40 nM labeled muscimol were used. GABA produced a dose-dependent stimulation of flunitrazepam binding in all age groups, but the maximum stimulation in aged animals was significantly higher (24%) than in young and mature animals. The [35S]TBPS binding site, the convulsant site of GABA/benzodiazepine receptors, was unaffected with age. We also studied the effects of exercise on GBZR binding sites of aged rats. The decline of flunitrazepam binding sites and the high sensitivity of flunitrazepam binding to regulation by GABA in aged animals were reversed by 8 to 10 weeks of endurance exercise. Endurance exercise did not have any significant effect on muscimol or TBPS binding sites. Results suggest that there are aged-related alterations of GBZR binding sites and that these modifications can be reversed by exercise.

Food restriction in female Wistar rats. I. survival characteristics, membrane microviscosity and proliferative response in lymphocytes

The effect of food restriction on the survival characteristics, membrane microviscosity and proliferative response in lymphocytes of female Wistar undernourished rats has been evaluated. Diet restriction was applied starting from the age of 3.5 months by feeding the animals on an every-other-day schedule (EOD). Diet restricted animals showed an increase of both mean, median and maximal life span as compared to the rats fed ad libitum (AL). Analyzing the survival curves by a parametric model, it emerged that undernutrition increased the individual resistance to environmental insults. In particular, it could be speculated that the positive influence was more pronounced in individuals with the lowest physiological capacities. The membrane microviscosity of lymphocytes was lower in EOD animals as compared to the AL ones even if one assumes a decrease in body temperature of 1-2 degrees C in EOD groups. The improvement of membrane microviscosity due to diet restriction may in part explain the improvement of proliferative response of lymphocytes from EOD groups.

A return to time, cells, systems, and aging: III. Gompertzian models of biological aging and some possible roles for critical elements

In this paper, I continue my investigation into the modeling of senescence in biological hierarchies. Making use of my previous discussion on non-reestablishable biological components, I derive a mathematical model which has Gompertzian-like dynamics. I show how this model may be approximated, in certain instances, by a Gompertzian equation. I then demonstrate how our approach yields a biological interpretation for the parameters in the Gompertzian equation. I then demonstrate how changes in the parameter values may be interpreted in light of the biology. Subsequently, I review the literature on the allometry of aging, and I demonstrate how my reliability model may be used to obtain--in a qualitative manner--some of the lifespan curves found in the literature. I close my discussion by constructing a more complex reliability model which incorporates the deterministic failure of biological components with stochastic aspects of senescence.

Effect of exercise on longevity, body weight, locomotor performance, and passive-avoidance memory of C57BL/6J mice

Studies of human and animal subjects have suggested that exercise may retard aging, help prevent age-related diseases, and prolong life span. Earlier studies focused on the effects of exercise on the heart, skeletal muscles, lungs, metabolism, and longevity. Researchers recently have begun to direct their attention to possible benefits of exercise on the brain. The goals of this study were to examine the effects of voluntary wheel-running exercise on life span, body weight, food and water intake, locomotor performance, and one-trial passive-avoidance memory of mature (10-14 month), middle-aged (20-24 month), and old (28-30 month) C57BL/6J male mice. No significant differences in life span, expressed in months, were found between control and exercised mice when exercise was carried out during maturity, senescence, intermittently across both periods, or continuously throughout maturity and senescence. Exercised adult mice maintained body weight compared to adult controls, an effect not apparent in old mice. Locomotor performance was reduced in old mice, and exercise increased performance much more in adult than in old mice. In the passive avoidance test of recent memory, exercise significantly increased latency, that is, it improved retention, in adult, middle-aged, and old mice. The effect was greatest in middle-aged, next in old, and lowest in adult mice. The findings indicate that exercise may be an important modulator of the rate of aging.

Open-field behaviour, growth rate and life span in the black-hooded rat

The life span of the black-hooded rat has been studied in relation to two behavioural variables: (1) habituated level of responding; and (2) emotional reactivity in the open-field arena. The results indicate a relationship between the open-field measures and life span and also with growth rate measures.

Effects of intermittent feeding upon growth, activity, and lifespan in rats allowed voluntary exercise

From weaning until death, male Wistar rats were housed in activity-wheel cages with one group maintained on an ad libitum (AL) diet and another provided the diet every-other-day (EOD). EOD-fed rats had a mean lifespan of 124 weeks compared to 103 weeks for AL-fed rats. While post-weaning body weight and growth rates were reduced among the EOD-fed animals compared to AL-fed animals, there was no significant difference in growth duration. Positive correlations were observed between lifespan and estimates of growth rate and duration in the AL group but not in the EOD group; thus, little evidence was produced to support the hypothesis that growth rate is inversely related to longevity. While the EOD feeding regimen resulted in higher activity levels later in life, wheel activity levels were actually lower in this group in early life compared to the AL group. The observation of reduced wheel activity among young rats fed EOD was replicated in a second experiment. Thus, little support was obtained for the hypothesis that increased activity mediates the beneficial effects of dietary restriction on longevity, unless this mechanism is active late in the lifespan.