Roy L. Butcher

The effects of exercise on the bones of postmenopausal women

SummaryThe effects of walking and aerobic dancing on the bones of 73 recently postmenopausal women have been compared by photon absorptiometry of the distal radius with a control group who did not exercise. The period of observation was six months. Results showed that the control group and the walking group lost statistically significant amounts of bone mineral content (1.6%, and 1.7% respectively), but that the dancing group did not (0.8%). The control group did not show a significant increase in the bone width (0.9%), but both the dancing (1.3%) and walking (1.6%) groups did. Changes in the cross-sectional moment of inertia of the radius were estimated for each subject based on bone mineral content and bone width values. Both exercise groups experienced significant increases in this variable, while the control group did not. Plasma oestrogen levels were not influenced by exercise. The results support the hypothesis that mechanical loading due to exercise may be effective in preventing postmenopausal osteoporosis.RésuméLes auteurs ont comparé, par photo-absorptiométrie de lextrémité inférieure du radius, les effets de la marche et de la danse «aerobic« sur los de 73 femmes récemment ménopausées en les comparant à un groupe de contrôle ne pratiquant aucun exercise. Lobservation a porté sur une période de six mois. Les résultats montrent que le groupe de contrôle et celui qui pratique la marche présentent une déminéralisation osseuse statistiquement significative (1,6% et 1,7% respectivement), contrairement au groupe pratiquant la danse (0,8%). Il ny a pas daugmentation significative de la largeur de los dans le groupe de contrôle (0,9%), alors quelle est importante aussi bien dans le groupe de danse (1,3%) que dans le groupe de marche (1,6%). On a calculé chez chaque sujet, à laide des mesures de la teneur en minéraux et de la largeur de los, le moment dinertie dune section horizontale du radius. Les deux groupes pratiquant un exercise présentent une augmentation significative de cette variable, tandis quil ny en a pas dans le groupe de contrôle. Le taux doestrogène plasmatique nest pas influencé par lexercise. Ces résultats confirment lhypothèse selon laquelle les contraintes mécaniques entraînées par lexercise pourraient prévenir efficacement lostéoporose post-ménopausique.

Changes in hormonal profiles during the estrous cycle in old lactating beef cows

Patterns of concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH), progesterone (P4) and estradiol-17 beta (E2) during an estrous cycle were compared between 15 lactating beef cows 5 to 7 years of age (young) and 15 cows greater than or equal to 12 years of age (old). Length of estrous cycle did not differ between young and old cows (P = .06). No differences due to age were found for LH. Patterns of concentrations of P4 during the first 15 days of the cycle, of FSH during days 6 through 12 and of E2 during the follicular phase differed with age (P less than .05). An earlier (P less than .025) midcycle elevation of FSH was associated with an earlier rise and greater concentration of E2 (P less than .05) during the follicular phase in old than in young cows. Differences in FSH and P4, although subtle, were consistent with an earlier or more advanced follicular development in old cows, leading to greater secretion of E2 from the preovulatory follicle.

Plasma concentrations of estradiol produced with two delivery systems in ovariectomized rats.

Summary Ovariectomized rats received a single sc injection of 0, 0.25, 0.5 or 1.0 μg of estradiol-17β (E2) in 0.1 ml sesame oil or sc implants of osmotic minipumps delivering 1 or 2 μg E2/24 hr. Plasma levels of E2 were determined at 2, 4, 8 and 12 hr after injections or 3, 6, 12 and 24 hr after insertion of mini-pumps. Injections produced superphysiological levels of E2 in plasma by 2 hr, but E2 was depleted from plasma in less than 12 hr. Minipumps provided constant circulating concentrations of E2. Constant release methods provide a much more logical delivery system for estrogen suppression of gonadotropin than the use of an oil vehicle.

Pre‐ovulatory and Post‐ovulatory Overripeness

Experimental work using animal models suggests that alterations of the oocyte during either a delay of ovulation or a delay of fertilization could account for a major percentage of human birth defects. The mechanism by which detrimental changes in the oocyte occur during these delays is not known. Hormonal modifications just prior to ovulation could initiate biochemical processes in the oocyte which proceed to an abnormal sequence of events when ovulation or fertilization does not take place at the optimum time. Alternately, the oocyte may be programmed earlier in its growth phase and undergo degenerative changes if ovulation or fertilization does not occur at the programmed times. A better understanding of the mechanisms involved in both pre‐ovulatory and post‐ovulatory overripeness of the oocyte could ultimately lead to a reduction in the incidence of human developmental anomalies.

RNA and protein synthesis in control and follicularly-aged rat oocytes.

Summary Autoradiographic analysis revealed that follicularly-aged oocytes show a significant reduction in RNA synthesis, but the capacity to synthesize protein was unaltered. Abnormally low amounts of RNA were synthesized by 54% of the oocytes obtained from delayed-ovulatory rats and 7% of the control oocytes. The reduced RNA synthesis characteristic of the aged oocyte could be associated with metabolic changes which are responsible for the developmental anomalies. Evaluation of RNA and protein synthesis in the cumulus cell mass, which surrounds the tubal oocyte, demonstrated that neither the percentage of cells labeled, nor the amount of RNA or protein synthesized by the cumulus cells, is altered during the follicular aging process. However, the cumulus cells which enclose the oocyte are more loosely associated with the aged oocyte.

An additional effect of yohimbine-HCl.

Summary Daily subcutaneous injections of 20 mg of yohimbine-HCl per kg of body weight from the 15th day of gestation until parturition increases the length of pregnancy in the rat by 1 day. A single injection of yohimbine on day 20 of pregnancy was without effect on gestation length. Rats which were treated with a daily dose of 20 mg of yohimbine per kg (started on day 15 and sacrified on day 21 of gestation) had significant increased pituitary and adrenal weights as well as smaller fetuses and placentas. Cold stress did not affect the weight of the fetuses or placentas. No difference in growth rate was produced by either yohimbine-HCl or formalin injections.

Endocrine Stimulating Effects of Yohimbine-HCl

Summary Daily subcutaneous injections of 20 mg of yohimbine-HCl per kg of body weight for 26 to 33 days caused pseudopregnancy, increased ovarian and adrenal weights, and produced lobulo-alveolar development in female rats. The corpora lutea formed during this treatment were active as shown by their ability to produce decidual reactions in traumatized uteri. Induction of pseudopregnancy by single injections of 20 mg of yohimbine-HCl per kg of body weight was successful when given on the day of estrus. Daily injections of yohimbine had no effect on mammary development in male rats.