Wall thickness, a major determinant of trabecular thickness, falls with age and falls further in osteoporosis. To estimate the importance of defective osteoblast recruitment in the pathogenesis of this defect, we compared various histologic indices of bone formation in iliac bone biopsies in three groups of subjects--healthy premenopausal women, healthy postmenopausal women, and patients with postmenopausal osteoporosis and at least one non-traumatic vertebral compression fracture. Indices that reflect the frequency of activation of bone remodeling and consequent birth rate of new teams of osteoblasts (osteoid surface, mineralizing surface, osteoblast surface, and bone formation rate, all expressed per unit of bone surface) were each higher in healthy subjects who were postmenopausal than in those who were premenopausal, but lower in osteoporotic than in normal postmenopausal women. In each group, the primary surface measurements were significantly correlated with each other, but the correlation was less close in those with osteoporosis. Indices that reflect the average collective performance of individual teams of osteoblasts (mineralizing surface and osteoblast surface per unit of osteoid surface, mineral apposition rate, adjusted apposition rate, and wall thickness) were all lower in postmenopausal than in premenopausal normal subjects, and even lower in those with postmenopausal osteoporosis. The parameters of the regression lines relating bone formation rate to osteoblast surface were essentially the same in each group, indicating that bone formation rate per unit of osteoblast surface was unaffected by age or menopause, and was the same in osteoporosis as in healthy subjects of similar age.(ABSTRACT TRUNCATED AT 250 WORDS)

Nubian bone recovered from an X-group cemetery (A.D. 350 to 550) exhibits a pattern of fluorescence identical to that of modern tetracycline-labeled bone. When it is viewed under ultraviolet light at 490 angstroms, fluorophors are visible as a characteristic yellow-green fluorescence on surfaces that were actively mineralizing at the time of exposure. Contamination of stored grains provided the proper environment for cultivation of tetracycline-producing Streptomycetes. Evidence for exposure to antibiotics in an archeological population is relevant to studies of the evolution of R factors and to the interpretation of health and disease within the population.

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We examined the relationships between the changes in bone mineral deficit in the radius, determined by single-energy photon absorptiometry at standard proximal and distal sites, and in the ilium, determined by bone histomorphometry, during the treatment of osteomalacia of diverse etiology in 28 patients. In the ilium, relative osteoid volume decreased by 75-80% in both cortical bone (from 6.0% to 1.5%) and trabecular bone (from 30.1% to 6.6%) during a mean treatment duration of 2 yr. There was also a significant fall in iliac cortical porosity from 10.3% to 7.8%. As a result, mineralized bone volume increased by 7.5% in cortical and by 40.1% in trabecular bone; the cortical and trabecular increments were correlated (r = 0.69, P < 0.001). The properly weighted increase for the entire tissue sample was 18.6%. By contrast, there was no change in bone mineral at either radial site, although there was a 2% increase at both sites when allowance was made for age-related bone loss during treatment. The proximal and distal age-adjusted increments were correlated (r = 0.76, P < 0.001), but there was no correlation between the changes in any photon absorptiometric and any histomorphometric index. In that iliac cortical bone turnover in normal subjects was 7.2%/yr, we estimated the rate of bone turnover to be <2%/yr at both proximal and distal radial sites, including any trabecular bone present at the distal site. Compared to appropriate control subjects, the bone mineral deficits fell during treatment from 19.2% to 17.1% at the proximal radius (>95% cortical bone) and from 20.5% to 18.5% at the distal radius (>75% cortical bone). In the ilium the deficits, assuming attainment of normal values for osteoid volume and cortical porosity, fell from 41.7% to 36.1% in cortical and from 31.5% to 6.3% in trabecular bone, the properly weighted combined deficit falling from 38.6% to 27.7%. The irreversible iliac cortical deficit was entirely due to cortical thinning because of increased net endosteal resorption; the resultant expansion of the marrow cavity offset the modest loss of fractional trabecular mineralized bone. We conclude: (a) in osteomalacia there is a large irreversible and a small reversible bone mineral deficit at both proximal and distal radial sites, in similar proportion to the iliac cortex but of smaller This work was presented in part at the Third International Workshop

Absence of leucine in an essential amino acid supplement reduces activation of mTORC1 signalling following resistance exercise in young females.. were not significantly altered after 3h recovery from exercise. In conclusion, the presence of leucine in the supplement enhances the stimulatory effect on mTORC1 signaling and reduces the level of tyrosine and the sum of the EAA in muscle and plasma, suggesting a stimulation of protein synthesis and/or inhibition of breakdown, leading to improvement in net protein balance.