Bone mass measurements have been shown to be useful determinants of the risk of development of osteoporotic fractures and may help identify individuals who are most likely to benefit from both primary and secondary prevention of osteoporosis. As standard bone density measurements are not available to all physicians, there is a need for a fast, inexpensive, and widely available technique to measure bone mass. Radiographic absorptiometry of the phalanges requires only routine radiography with processing of the films done at a special off-site laboratory. We performed a preliminary investigation to see whether this simple technique could be used to predict a low bone mass as defined by dual- and single-photon absorptiometry. Correlations between radiographic absorptiometry. Correlations between radiographic absorptiometry and the standard techniques were as good as those among the standard techniques themselves (r = 0.58-0.9). Radiographic absorptiometry measurements predicted low bone mass of the lumbar spine and femoral neck with 90% and 82% sensitivity respectively. If further evaluation supports these initial conclusions, radiographic absorptiometry may be useful as a screening technique for primary care physicians and in research settings where dual-photon or dual-energy X-ray absorptiometry are impossible.

Vitamin D metabolism in elderly individuals can be compromised by several mechanisms. We previously described reduced concentrations of 1,25-dihydroxyvitamin D [1,25(OH)2D] in 30% of elderly nursing home residents. The present study assesses the effect of vitamin D supplementation on 25-hydroxyvitamin D [25(OH)D] and 1,25(OH)2D. We performed a double-blind study in which 30 elderly nursing home residents were randomly given either 50 micrograms vitamin D or a placebo daily for 6 wk. Vitamin D metabolites, immunometrically assayed parathyroid hormone (IRMA-PTH), ionized calcium, and bone Gla hormone (BGP) were measured in serum at baseline and biweekly for 6 wk. Serum 25(OH)D concentrations increased significantly (P less than 0.0001) over the 6 wk in the treatment group but were unchanged in the placebo group. Serum 1,25(OH)2D, ionized calcium, BGP, and PTH were not significantly altered by the supplement. We conclude that vitamin D supplementation results in an increase in circulating 25(OH)D but not 1,25(OH)2D; however, the long-term effect on bone mineral metabolism remains unclear.

The interrelationships between measurements of bone mass and total-body bone mineral were examined in a cross-sectional study of normal healthy women aged 17-82 years. In addition we evaluated the relationship between measures of body composition, estimated by four independent techniques, and bone mass in the same population. Considering the group as a whole, bone mass at all sites correlated with each other and with total-body bone mineral (TBBM). Cancellous and cortical sites could predict TBBM equally well. As expected, all measurements of bone mass were significantly lower in postmenopausal women in comparison to premenopausal women. Declines in bone mass were only seen in premenopausal women in the femoral neck and Ward's triangle, not in lumbar spine, radius, or skeleton as a whole. In postmenopausal women bone mass correlated negatively with age and years from menopause equally at all sites. TBBM was significantly related to height and weight in both premenopausal and postmenopausal women. In premenopausal and postmenopausal women TBBM also correlated with fat mass, but TBBM was much better correlated with percentage body fat in premenopausal than postmenopausal women. TBBM was a constant proportion of lean body mass in premenopausal women, but the fraction of lean mass occupied by the skeleton declined with age in postmenopausal women. Correction of TBBM for lean mass did not change the relationship between TBBM and percentage fat in premenopausal women but eliminated the relationship in postmenopausal women. Regional measurements, which are at least partially corrected for body size by dividing mass by area, correlated less well with height and weight and with any index of obesity, especially in postmenopausal women.

A B S T R A C T Addition of HCOi-to the serosal side (S) of the isolated turtle bladder results in a HCO0-flow from S to the mucosal side (M) which markedly reduces the net rate of acid secretion. To characterize the driving forces for this downhill HCO3-flow, the effects of metabolic inhibitors and substrates were examined. In short-circuited bladders with the M pH lowered to the point of zero net H+ secretion, the rate of HCO-entry into M in response to a 20-mM HCO3-gradient was measured by pH stat titration. Deoxygenation reduced the HC03-flux from 1.24±0.1 gM/h/8 cm2 (SEM) to 0.50±0.1 tM/h with glucose (2 X 10' M) and from 1.32±0.1 to 0.47±0.1 iAM/h without glucose.A similar reduction (61%) was observed in the presence of 1% C02. Dinitrophenol (10' M), cyanide (10' M), and deoxyglucose (10-' M) inhibited the HCO3-flux by 39%, 37%, and 38%, respectively. The combination of any of these inhibitors with N2 caused the same inhibition as Ns alone. In bladders depleted of substrate, pyruvate (5 X 10-' M) increased the HCOs-flux from 0.36 ±0.05 to 0.58±0.01 ,M/h (P < 0.005); the increment was abolished by deoxygenation.The results indicate that the bulk of the downhill HCOi-flow in this system is dependent on metabolic energy derived primarily from oxidative sources, and that this energy-dependent flow approximates the electroneutral component of HCO3-secretion that is coupled to Cl-absorption.

The present study was designed to provide further information on the enduring cognitive effects of experimental phenylketonuria (PKU) in rats, produced by the administration of alpha-methylphenylalanine and phenylalanine on postnatal days 3-21. These rats evidenced: (1) impaired learning set formation, (2) stimulus perseveration, particularly after an error, and (3) difficulty in utilizing the less salient features of their environment in mastering discrimination problems. In contrast, long-term memory function and the ability to form simple associations did not differ from controls. This pattern of intact and impaired cognitive functions bears remarkable similarity to that of mentally retarded humans and neonatally hyperphenylalaninemic rhesus monkeys, thus affirming the use of rats to study mental retardation. In addition, possible reasons for the mildness of the impairments commonly observed in animal models of severe mental retardation syndromes are discussed. We suggest that transfer of learning paradigms that assess the animal's ability to use information acquired in other problems are more likely to uncover significant cognitive impairments in such models than are procedures that test only the animals' ability to solve a single problem.