Biomedical subjects

S K Oviatt

Publications and source records attributed to S K Oviatt.

10 recordsLinked to original sources

PubMed1994

Testosterone influences spatial cognition in older men.

Testosterone plays a role in the organization of behavior during development. The authors examined whether testosterone could play a maintenance role in behavior as well. In a double-blind manner, verbal and visual memory, spatial cognition, motor speed, cognitive flexibility, and mood in a group of healthy older men who were supplemented for 3 months with testosterone were assessed. The increase in testosterone levels to 150% of baseline levels resulted in a significant enhancement of spatial cognition, but no change in any other cognitive domain was found. Testosterone supplementation influenced the endogenous production of estradiol, and estradiol was found to have an inverse relationship to spatial cognitive performance. These results suggest that testosterone supplementation can modify spatial cognition in older men; however, it is likely that this occurs through testosterone's influence on estrogen.

Administration, Cutaneous↗

PubMed1993

Precision of dual-energy x-ray absorptiometry: development of quality control rules and their application in longitudinal studies.

In research settings, longitudinal measurements of bone mineral density have become an integral part of the assessment of patients with metabolic skeletal disorders. To adequately utilize longitudinal measures, confidence in the long-term precision of the measurement technique must be very high. Dual-energy x-ray absorptiometry (DXA) has become commonly utilized in this context, and to better understand its long-term precision and to develop quality assurance protocols for its use, we examined the performance of eight DXA machines over a 3 year period. Anthropomorphic spine phantoms were measured frequently on each machine during the period of observation, and precision was estimated from the consistency of these determinations. Overall precision was excellent (mean longitudinal coefficient of variation, 0.4%). Nevertheless, by using a series of objective quality control criteria, small alterations in the performance of each machine were identified (mean number of changes, 4.6 in 3 years; mean magnitude, 0.0039 g/cm2, or 0.4%). The cumulative effects of those changes were sufficient to cause a significant (albeit minor) change in the regression slopes (phantom mineral density versus time) of most machines. The same quality control rules were also used to quantitate the magnitude of change and to adjust retrospectively machine performance during the period of observation, such that alterations were minimal and regression slopes were not significantly different from zero. Although the precision of DXA is excellent, alterations in machine function must be anticipated during longitudinal use. The development of quality control protocols provides the means to detect change objectively and to adjust for alterations in performance during the course of longitudinal evaluations.

Absorptiometry, Photon↗

PubMed1992

Vertebral deformity in men.

Vertebral fracture is the most prevalent manifestation of osteoporosis in women, but there is very little information concerning vertebral fracture in men. These studies begin to determine the prevalence, radiographic character, and relationship to bone mineral density of vertebral deformity in men. A group of 144 white men aged 34-94 years (83% between 50 and 80 years) were studied. Thoracic and lumbar spine radiographs were obtained using standardized techniques, and morphometric measures of vertebrae (T6-L5) were obtained using a computerized digitization pad. Vertebral deformities (wedge, midbody, and crush) were identified using several criteria. In addition, a skeletal radiologist independently identified vertebral deformities, as well as vertebrae affected by epiphysitis (Scheuermann's disease), using classic radiographic criteria. Bone mineral density was measured at lumbar spine and proximal femoral sites using dual-photon absorptiometry. The prevalence of vertebral deformity was related to the criteria used for their identification. Utilizing vertebral-specific criteria (anterior/posterior or midbody/posterior vertebral height more than 3 SD below vertebral specific mean), 10% of subjects had vertebral deformity. Wedge deformity occurred primarily in thoracic vertebrae and were more common than midbody deformity, which occurred more commonly in lumbar vertebrae. Crush deformities were not observed. Evidence of vertebral epiphysitis was present in 9% of subjects but was not responsible for vertebral deformity sufficient to be falsely identified using the more than -3 SD criterion. Bone mineral density in subjects with vertebral deformity was clearly reduced at both vertebral (p = 0.003) and proximal femoral (p = 0.002) measurements sites. The number of vertebral deformities was negatively correlated with vertebral bone mineral density.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1991

Longitudinal precision of dual-energy x-ray absorptiometry in a multicenter study. The Nafarelin/Bone Study Group.

Reproducibility is a key issue in both clinical and research applications of bone mineral density (BMD) measurements. To examine the longitudinal precision of dual-energy x-ray absorptiometry (DEXA) for the measurement of mineral density in vivo and in vitro, the performance of a group of instruments in the course of a multicenter longitudinal clinical trial was monitored. Measures were performed on eight identical machines (Hologic QDR1000) and analyzed using the same automated software program. Short-term precision was good in vitro, [anthropomorphic spine phantoms; mean intrasite coefficient of variation (CV) 0.42 +/- 0.1% (SD)] and in vivo (lumbar spine; CV 1.1 +/- 0.5%). Intersite measures of a single spine phantom (specified mineral content -57.8 g) revealed a range of 57.3-58.4 g (CV 0.7%). In two subjects intersite CV in vivo were 3.7 and 2.1% (spine) and 1.8 and 3.2% (femoral neck). At five sites frequent phantom measures were performed over a 1 year period (mean number of measures 196) and revealed a mean all-point CV of 0.43% (range 0.35-0.53%). Longitudinal precision in vivo was somewhat less (mean CV of spinal measures 1.1%, femoral neck 1.2%, trochanter 1.3%, and Ward's area 2.4%). At one additional site large variations in phantom measures heralded repeated mechanical failures that eventually required machine replacement. In summary, DEXA demonstrates good in vitro and in vivo longitudinal precision, providing the basis for expanded clinical and research usefulness. Nevertheless, stringent quality assurance measures are required to detect and respond to system malfunctions.

Absorptiometry, Photon↗

PubMed1990

The rate of bone mineral loss in normal men and the effects of calcium and cholecalciferol supplementation.

OBJECTIVE: To determine the rate of bone loss in normal men, and to examine the effects of dietary calcium and cholecalciferol supplementation on bone loss in men. DESIGN: Double-blinded, placebo-controlled 3-year trial of supplementation with calcium (1000 mg/d) and cholecalciferol (25 micrograms/d). SETTING: Clinical research center at a university medical facility. SUBJECTS: Normal men 30 to 87 years old, recruited from the Portland community. MEASUREMENTS AND MAIN RESULTS: Radial bone mineral content (assessed by single-photon absorptiometry) fell by 1.0%/y (95% CI, -1.3% to 0.7%) at a proximal radial site and 1.0%/y (95% CI, -1.4% to -0.6%) at a distal radial site. Vertebral bone mineral content (assessed by dual-energy quantitative computed tomography) declined by 2.3%/y (95% CI, -2.8% to -1.8%). In these healthy men with a high basal dietary calcium intake (1159 mg/d), calcium and cholecalciferol supplementation did not affect bone loss at any site. CONCLUSIONS: Normal men experience a substantial bone loss at both axial and appendicular sites that is not prevented by calcium and vitamin D supplementation in a well-nourished population.

Adult↗

PubMed1990

The impact of osteophytic and vascular calcifications on vertebral mineral density measurements in men.

To evaluate the influence of extravertebral calcification on spinal bone density determinations, we measured lumbar vertebral density in 71 hospitalized and 58 normal men using dual photon absorptiometry. The extent of vascular and osteophytic calcification was graded from lateral lumbar radiographs. Fifty-five (43%) of the subjects had identifiable osteophytes, and 86 (67%) had vascular calcifications. Despite similar ages and weights in subjects with and without ostephytes, those with osteophytes had greater spinal density (1.34 vs. 1.17 g/cm2; P less than 0.001), and there was a strong correlation between osteophyte severity and spinal density (r = 0.41; P less than 0.00001). Proximal femoral density was not different in those with and without osteophytes. The distribution of osteophytes in this population was not random, and as a result, the presence of osteophytes obscured the the relationship of bone density to age as well as the comparison of hospitalized to normal men. Vascular calcification had a minimal effect on vertebral density. In summary, osteophytic calcification exerted an important influence on the measurement of spinal bone density in men. This effect should be considered in both clinical and research applications of integral vertebral density measures.

Absorptiometry, Photon↗

PubMed1989

Histomorphometric effects of calcium or calcium plus 25-hydroxyvitamin D3 therapy in senile osteoporosis.

To evaluate the effects of calcium and 25-OHD in the therapy of senile osteoporosis, we studied a group of 39 women aged 69 +/- 7 (standard deviation, SD) years with severe osteoporosis. The group was characterized histomorphometrically by depressed bone remodeling rates without hyperosteoidosis. No subject had risk factors for osteopenia other than their age and postmenopausal status, and no subject was receiving therapy for bone disease at the onset of the study. Subjects were followed for 2 years after randomization to receive either 1200 mg/day of calcium (as calcium carbonate) and 40 micrograms/day of 25-OHD (calcium-25-OHD group), or 1200 mg/day of calcium plus placebo (calcium-placebo group). Calcium-25-OHD resulted in a clear increase in 25-OHD levels (p less than 0.001) and an increase in calcium absorption as indicated by urinary calcium excretion. Nevertheless, there was no significant change in fasting serum calcium, phosphorus, alkaline phosphatase, PTH, or 1,25-(OH)2D in either group. Radial and phalangeal bone mineral content and trabecular bone volume in the biopsied patients remained stable in both groups over the 2 year period. Unexpectedly, repeat bone biopsies revealed a clear improvement in the rate of mineralization in both groups, presumably as a result of the calcium supplementation alone. In summary, calcium-placebo and calcium-25-OHD treatment were both associated with stable appendicular bone mineral content in women with senile osteopenia. The finding of an effect of calcium supplementation on the rate of mineralization indicates that relative calcium deficiency may impair the mineralization phase of remodeling.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1989

The relationship of swimming exercise to bone mass in men and women.

Exercise appears to be capable of exerting a positive effect on bone mass, but how exercise can be used to best advantage in the prevention and therapy of osteopenia is unclear. Weight-bearing activity has been commonly considered to be essential for the beneficial effects of exercise on the skeleton, and, therefore, swimming has been considered valueless in the maintenance of bone mass. To examine this issue we measured radial and vertebral bone mineral density in a group of subjects aged 40 to 85 years who had been swimming regularly for at least 3 years as well as in a similar group of nonexercising control subjects. The swimmers engaged in no other forms of regular exercise, and no subject had other conditions known to affect bone or mineral metabolism. Dietary calcium and protein intakes were similar in the two groups. At both radial (0.84 +/- 0.08 vs 0.81 +/- 0.09 g/cm2) and vertebral (123 +/- 27 vs 108 +/- 31 mg/cm3) sites the male swimmers had significantly greater bone mineral density than did the nonexercisers. In women, however, no relationship of swimming to bone mineral density could be identified. These results suggest that swimming exercise may be beneficial in the prevention or therapy of osteopenia and that its usefulness in this regard should be further investigated.

Adult↗

PubMed1988

Calcium and cholecalciferol: effects of small supplements in normal men.

The effect of small calcium and vitamin D supplements on mineral metabolism in normal persons is unclear. To investigate the biochemical response to these medications, we administered 1000 mg Ca and 25 micrograms cholecalciferol per day or a placebo to 92 normal men for 1 y. The Ca and cholecalciferol were tolerated well. 25-Hydroxycholecalciferol [25-(OH)D] and 24,25-dihydroxycholecalciferol [24,25-(OH)2D] levels rose in treated subjects; there was no definite change in 1,25-(OH)2D concentrations. The average difference in 25-(OH)D levels between treated and untreated subjects was 30 nmol/L at 1 y. Fasting serum Ca, alkaline phosphatase, creatinine, and parathyroid hormone levels and the fasting urinary excretion of Ca, phosphorus and cAMP, were not affected. However, 24-h urinary Ca excretion was higher in the supplemented group (3.5 +/- 1.9 vs 4.7 +/- 1.7 mmol/d, p = 0.006). Serum P concentrations were slightly higher in the supplemented group at 1 y. In normal men small calcium and cholecalciferol supplements are safe, provide adequate vitamin D nutrition and apparently increase net gastrointestinal Ca absorption.

Adult↗

PubMed1987

Serum protein concentrations and bone mineral content in aging normal men.

Low serum protein levels and low dietary protein intakes possibly influence bone metabolism. To evaluate the relationships among serum protein concentrations, protein intakes, and bone mineral content (BMC), we have examined two populations of normal men. BMC was measured at two radial sites and a vertebral site. Aging was associated with a fall in BMC at all sites. Serum albumin levels also fell with age and were related to BMC. Albumin concentrations were associated with BMC when other variables (calcium and protein intake, vitamin D levels, parathyroid hormone, and urinary calcium) also were considered. Thus, alterations in protein metabolism may affect BMC and may play a role in the genesis of senile osteopenia.

Adult↗