Effect of gonadectomy on age-dependent calcification of aorta and bone mineralization in rats

Effects of ovariectomy in beagle dogs

Beagle dogs 3-7 years old were ovariectomized (n = 9) or sham operated (n = 6) and followed for 48 weeks with measurements of body weight, tibial shaft bone mineral content (BMC), and serum biochemistry. Following killing, measurements were made of bone strength and histomorphometry. Ovariectomy (OX) significantly reduced serum estrone and estradiol concentrations and their variability from month to month. There was a transient decrease in cortical BMC of the OX dogs during the first 12 postoperative weeks but no difference between the groups after 48 weeks. Serum osteocalcin was elevated, but there was little effect on serum alkaline phosphatase, Ca, P, or calcitonin. OX increased the number of tetracycline-labeled osteons in cortical bone but reduced the percent trabecular surface labeled with tetracycline. OX produced no significant changes in the composition of the bones or loss of cortical area, but a statistically significant 15% trabecular bone loss occurred in the spine. However, bone strength had not been significantly affected at the time of sacrifice.

Senile osteoporosis. The effects of exercise

The available literature indicates that a high level of physical activity throughout life can result in increased skeletal mass during the fourth decade. Such a large reservoir of bone mass at midlife may delay the clinical manifestations of osteoporosis in later life. Furthermore, the published studies of animal models and humans strongly suggest that physical activity retards or prevents involutional bone loss in both recently postmenopausal and very elderly women.