Child-specific thoracic gas volume prediction equations for air-displacement plethysmography.

OBJECTIVE: To develop child-specific thoracic gas volume (TGV) prediction equations for use in air-displacement plethysmography in 6- to 17-year-old children. RESEARCH METHODS AND PROCEDURES: Study 1 developed TGV prediction equations using anthropometric variables after completing a measured TGV and air-displacement plethysmography test in 224 healthy boys and girls (11.2 +/- 3.2 years, 45.3 +/- 18.7 kg, 149.9 +/- 18.5 cm). Study 2 cross-validated the prediction equations in a separate cohort of 62 healthy boys and girls (11.2 +/- 3.4 years, 44.2 +/- 15.3 kg, 149.4 +/- 19.3 cm). RESULTS: In Study 1 (development of TGV prediction equations), the quadratic relationship using height as the independent variable and the measured TGV as the dependent variable yielded the highest adjusted R(2) and the lowest SE of estimate in both genders, thus producing the following prediction equations: TGV = 0.00056 x H(2) - 0.12422 x H + 8.15194 (boys) and TGV = 0.00044 x H(2) - 0.09220 x H + 6.00305 (girls). In Study 2 (cross-validation), no significant difference between the predicted and measured TGVs (-0.018 +/- 0.377 liters) was observed. The regression between the measured TGV and the predicted TGV yielded a slope and intercept that did not significantly differ from the line of identity. Prediction accuracy was good as indicated by a high R(2) (0.862) and low SE of estimate (0.369 liters). DISCUSSION: The new child-specific TGV prediction equations accurately, precisely, and without bias estimated the actual TGV of 6- to 17-year-old children.

Bone morphogenetic protein-7 selectively enhances mechanically induced bone formation.

The responses of bone cells to skeletal loading are clearly an important factor in bone biology, but much remains to be learned about the role of these responses in skeletal development, maintenance, and tissue repair. Bone morphogenetic proteins (BMPs) are key regulators of bone formation. We examined the effect of BMP-7 on periosteal and endosteal bone formation in response to increased mechanical loading using the rat tibial bending model. Female Sprague-Dawley rats were divided into four groups of six rats each. Three groups received four point bending loading at 60 N force; the fourth group received sham loading at the same force. The right tibia received 36 cycles of loading on Monday, Wednesday, and Friday for 2 weeks; the left tibia served as a nonloaded control. Just prior to loading, the three loaded groups were injected intraperitoneally with vehicle only or 10 microg/kg or 100 microg/kg of recombinant human BMP-7. Half the sham group received vehicle, and half were given 100 microg/kg of BMP-7. Bone forming surfaces were labeled twice in vivo with calcein, and histomorphometry was performed to quantify periosteal and endosteal bone formation in the loaded and control tibiae. BMP-7 had no effect on periosteal or endosteal bone formation in control or sham-loaded tibiae. Loading produced significantly more woven bone on the periosteal surface than sham loading, but BMP-7 treatment had no effect on this response. Endosteal bone formation was entirely lamellar, and loading (but not sham loading) increased the endosteal mineral apposition and bone formation rates. The higher BMP-7 dose more than doubled the load-induced increase in endosteal lamellar bone formation rate, primarily by increasing the amount of bone forming surface.