Static bone histomorphometry in preterm and term babies.

The nature and pathophysiology of the bone loss which occurs in term and especially preterm neonates are poorly understood, and it is unclear whether this neonatal osteopenia results from impaired bone formation or increased bone resorption. This study compared the static bone histomorphometry of preterm and term babies, employing iliac crest bone biopsy specimens obtained postmortem. All the babies died within the first 6 days of life and none had any clinical, biochemical or radiologic evidence of metabolic bone disease. The trabecular bone volume, as well as static parameters of bone formation (OV/TV, OV/BV, OS/BS, OB.S/BS) did not differ significantly in preterm and term babies. Although time-spaced tetracycline labelling could not be employed in the present study, evidence of rickets was not apparent. Parameters of bone resorption in preterm babies were, however, significantly higher (p = 0.01) than those of term babies, suggesting that increased bone resorption and not impaired formation, underlies the development of osteopenia in the preterm neonate.

Effect of exercise on the development of osteoporosis in adult rats.

The role of moderate exercise in the prevention of high-turnover osteoporosis was investigated by the use of an animal model. The effect of chronic training on gravimetric, mineral, physical, and histological parameters of normal bone was also examined. Fifty-six adult female Long-Evans rats were divided into four groups: sedentary (C) and exercising controls (E) and sedentary (O) and exercising osteoporotics (EO). Exercising animals ran 4 h/wk for 1 yr. Two percent NH4Cl added to drinking water induced osteoporosis as shown by significantly lower femoral density and breaking strength and histomorphometrically quantified tibial trabecular bone volume but a normal mineral-to-matrix ratio in the O rats. The development of high-turnover osteoporosis in O rats was confirmed by significantly higher alkaline phosphatase activity (P less than 0.05), urinary hydroxyproline content (P less than 0.01), resorption surfaces (P less than 0.01), and histological parameters of bone formation (P less than 0.01). Exercise prevented all these biochemical, biophysical, and histological abnormalities in the EO group. Exercise had no influence on the density of normal femurs but tended to increase their breaking strength (by 11%) compared with femurs of C rats (P = 0.11).