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Biomedical subjects

R Lindsay

Publications and source records attributed to R Lindsay.

At least 145 records · Page 8Linked to original sources
PubMed1991

A new manual method for assessing two-dimensional cancellous bone structure: comparison between iliac crest and lumbar vertebra.

We have developed a simple method for the direct analysis of two-dimensional trabecular structure. Using this method, we have compared the structure of the left and right iliac crest and the second lumbar vertebra and studied the relationship between two-dimensional trabecular structure and the ultimate compressive stress of bone samples from the second lumbar vertebra. Transverse cores were taken from the left and right iliac crests and second lumbar vertebrae of 35 subjects (12 females) who died suddenly. The trabecular structure was subdivided into nodes (node count) and free ends (free end count), which were expressed per square millimeter of cancellous space. A node was defined as the point of junction between two or more trabeculae; a free end was defined as the end of a trabecula that was unconnected in the plane of the section to any other trabecular element. The following struts were defined by drawing a line between the nodes and the free ends: node to node, node to free end, free end to free end, and cortex-derived struts. Strut lengths were measured and expressed as a percentage of the total strut length and per square millimeter of cancellous space. Intraobserver variation was generally low, with coefficients of variation for repeat measurements in the range 3.9-17.8%. There was no statistically significant difference between left and right iliac crests for any of the variables measured. With the exception of cortex-derived struts, there was no statistically significant correlation between crests for any variable.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Radiographic absorptiometry: a simple method for determination of bone mass.

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.

Absorptiometry, Photon↗
PubMed1991

Response of the parathyroid gland to infusion of human parathyroid hormone-(1-34) [PTH-(1-34)]: demonstration of suppression of endogenous secretion using immunoradiometric intact PTH-(1-84) assay.

Alterations in the sensitivity of the parathyroid gland to both stimulative and suppressive stimuli may be partially responsible for skeletal changes that occur with age, estrogen deficiency, osteoporosis, and estrogen treatment of osteoporosis. We sought to define the changes in intact PTH-(1-84) secretion in normal premenopausal and postmenopausal, osteoporotic and estrogen-treated osteoporotic women during the infusion of human (h) PTH-(1-34). hPTH-(1-34) was infused at 0.55 U/kg.h for 24 h, with serum sampling every 4 h. Serum was analyzed for calcium (ionized and total), hPTH-(1-34), and PTH-(1-84). Basal chemistries were no different among groups, except for serum phosphorus, which was highest in osteoporotic women (1.31 vs. 1.07 mmol/L in premenopausal; P less than 0.02), and hPTH-(1-34), which was slightly higher in normal postmenopausal women (19.31 vs. 13.24 ng/L in estrogen treated; P less than 0.02). No differences in PTH-(1-84) were found among groups. hPTH-(1-34) rose similarly in all patient groups, while the calcemic response was somewhat more sluggish in estrogen-treated women, although statistically significant differences were not found. PTH-(1-84) declined rapidly in all patient groups, although estrogen-treated women had a smaller maximal decrease in PTH-(1-84), and the slope of the decremental change in PTH-(1-84) was lower in estrogen-treated women than in osteoporotic or normal postmenopausal women. Untreated osteoporotic women had less suppression of PTH-(1-84) than normal postmenopausal women at every calcium level. Estrogen treatment decreases the calcemic effects of infused hPTH-(1-34) and at the same time reduces calcium-induced suppression of parathyroid secretion. It is possible that such changes in the set-point of the gland contribute to the alterations in bone turnover that result in osteoporosis and the mechanisms by which estrogen prevents bone loss.

Calcium↗
PubMed1990

Body composition studies in premenopausal healthy women.

Body composition studies of healthy premenopausal women were performed using dual photon absorptiometry and the results compared with fat estimates obtained from skinfold measurements, body mass index, and bioelectrical impedance. Total body bone mineral did not decline with age nor did the fraction of lean body mass occupied by the skeleton, which ranged from 4-10%. DPA values for fat were significantly higher than those obtained by other techniques, in part because of calibration but also because of apparent inadequate correction for the fraction of lean body mass occupied by bone in the assumptions made for the other techniques.

Absorptiometry, Photon↗
PubMed1990

Vitamin D supplementation in elderly nursing home residents increases 25(OH)D but not 1,25(OH)2D.

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.

Aged↗
PubMed1990

Estrogen in prevention and treatment of osteoporosis.

Estrogen has clearly been shown to decrease bone loss and frequency of osteoporotic fractures. Calcitonin has been shown in several studies to reduce the rate of bone loss, although no data are yet available demonstrating a reduction in fracture frequency. Studies of osteoporosis intrinsically assume that prevention of further loss, or increments in bone mass, will be associated with declines in fracture recurrence. That may not always be the case. Recent controlled studies in which fluoride was used to increase bone mass in vertebral bodies resulted in no significant decline in fracture recurrence, and there was even a suggestion of increased fracture risk at some sites. Thus further data on calcitonin will be important, even though calcitonin is not expected to alter bone quality as does fluoride. Alternative therapies to calcitonin and estrogen are being investigated in clinical studies since both are currently limited in their use. Because calcitonin currently requires nearly daily injections, estrogen remains the principal agent available for both prevention and treatment in spite of its wide effect on multiple body systems. Bisphosphonates, given continuously or intermittently, appear to be relatively safe oral alternatives to calcitonin. The long-term effects of these agents need to be evaluated in greater detail before they can be recommended for prevention, but a role in therapy of the established disorder seems likely. The skeletal effect of bisphosphonates is also inhibition of bone remodeling and therefore prevention of further bone loss. Thus, they add nothing to the other therapeutic regimens from this perspective and as with calcitonin therapy, documentation of decreased frequency of fracture is lacking. Agents to increase bone mass are purely investigational at this time and many years may elapse before efficacy can be shown for such interventions.

Estrogen Replacement Therapy↗
PubMed1990

The histomorphometry of bone in primary hyperparathyroidism: preservation of cancellous bone structure.

To evaluate the effects of primary hyperparathyroidism (PHPT) on bone mass and structure, we have studied the iliac crest biopsies of 27 patients, 10 males (28-68 yr old) and 17 females (26-72 yr old) with mild PHPT after in vivo tetracycline labeling. All patients had mild hypercalcemia in the absence of any other cause and elevated levels of PTH without radiological evidence of bone disease. Static parameters of bone turnover (osteoid surface, osteoid volume, and eroded surface) were elevated in both men and women compared to normal values; the midmolecule RIA for PTH (PTHMM) was positively correlated with osteoid surface (r = 0.44; P less than 0.025) and eroded surface (r = 0.58; P less than 0.005). Dynamic parameters of bone turnover (mineralizing surface, expressed as double plus half single labeled surface, and bone formation rate at tissue level) were elevated compared to normal values; PTHMM was positively correlated with double plus half single labeled surfaces (r = 0.33; P less than 0.05) and with bone formation rate at the tissue level (r = 0.37; P less than 0.05). The mineral apposition rate was within the limits of normal values and positively correlated with PTHMM (r = 0.34; P less than 0.05). Histomorphometric parameters of bone structure [cancellous bone volume (BV/TV), trabecular thickness (Tb. Th), trabecular number (Tb.N), trabecular separation (Tb.Sp), cortical thickness (Ct.Th), and total bone density (TBD)] were compared to those in 20 autopsy control subjects, 12 men (33-60 yr old) and 8 women (27-75 yr old). BV/TV and Tb.N were significantly higher in PHPT patients than controls (P less than 0.02 and P less than 0.001, respectively). Tb.Sp was significantly lower in PHPT patients than controls (P less than 0.001), whereas Tb.Th was not significantly different between PHPT patients and controls. Ct.Th was significantly lower in PHPT patients than in controls (P less than 0.001), whereas TBD was not significantly different between the two groups. BV/TV was negatively correlated with age in both controls and PHPT patients. Tb.N showed a negative correlation and Tb.Sp a positive correlation with age in controls (r = -0.47; P less than 0.05 and r = 0.52; P less than 0.02, respectively), but they were not significantly dependent on age in PHPT patients. Tb.Th, while showing no significant age-related change in controls, was negatively correlated with age in PHPT patients (r = -0.42; P less than 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1990

Suppression of parathyroid hormone secretion with oral calcium in normal subjects and patients with primary hyperparathyroidism.

Exquisite sensitivity of normal parathyroid glands to small changes in ambient calcium concentrations and impaired sensitivity in primary hyperparathyroidism have been shown in vitro. Using an assay for PTH that detects rapid changes in PTH secretion (N-terminal-specific RIA; normal range, less than 3-33 pg/mL), we determined PTH suppressibility in response to a standardized dose of oral calcium in normal subjects and patients with primary hyperparathyroidism. Nine normal subjects were given oral calcium (25 mg/kg), and blood was analyzed half-hourly for 3 h for calcium and N-terminal PTH (N-PTH). Serum calcium rose by 0.34 +/- 0.06 mg/dL (0.085 +/- 0.015 mmol/L), and N-PTH levels declined rapidly from 15.3 +/- 1.4 to 4.2 +/- 1.1 pg/mL (-73 +/- 6%; P less than 0.01). In six subjects N-PTH concentrations became undetectable. Nine patients with primary hyperparathyroidism were tested in the same manner. Serum calcium rose by 0.53 +/- 0.1 mg/dL (0.13 +/- 0.025 mmol/L), and N-PTH levels declined less, from 66 +/- 14 to 52 +/- 12 pg/mL (-21 +/- 4%; P less than 0.05). In none of the patients was the PTH reduced to less than 20 pg/mL. These results illustrate in vivo that the PTH response to oral calcium in primary hyperparathyroidism is markedly different from that in normal subjects.

Administration, Oral↗
PubMed1990

Femoral head collapse associated with anorexia nervosa in a 20-year-old ballet dancer.

Femoral head collapse occurred in a 20-year-old ballet dancer with anorexia nervosa. The patient developed anorexia nervosa at the age of 11 years and had short stature. The condition never resolved, and she developed pain and stiffness in the right hip at the age of 18 years, with documentation of femoral head collapse on roentgenograms a year later. The patient had delayed pubertal maturation with a bone age of 13 years, primary amenorrhea, and hypoestrogenism. Evaluation for metabolic bone disease was negative, and dual-photon absorptiometry showed significantly decreased bone mass with a bone biopsy revealing only diffuse osteoporosis. Possible etiologic mechanisms of osteonecrosis including repetitive microtrauma and various factors predisposing to femoral head collapse in young women required further investigation.

Adult↗
PubMed1990

Functional assessment of elderly patients after percutaneous aortic balloon valvuloplasty: New York Heart Association classification versus functional status questionnaire.

Monitoring functional status in patients with cardiac disease has traditionally been done by using the New York Heart Association (NYHA) classification system. For various reasons, we found the NYHA system difficult to apply to elderly patients. We proposed that the functional status questionnaire (FSQ), which measures the ability to perform tasks, would more accurately assess the functional status of the elderly. In a study in 37 patients with a mean age of 76 years, who had aortic stenosis, we measured FSQ and NYHA scores at baseline, 1 month and 3 months. The difference in questionnaires was evident by the 3-month measurement. Individual patients were better evaluated by the FSQ. Six patients had an FSQ score of less than 72 (suggesting severe functional impairment) at 3 months but only two patients gave symptoms scored as NYHA class III or IV (cardiac disability). Five of six patients had a recurrent cardiac event subsequent to the 3-month follow-up. Changes in functional performance preceded symptomatic deterioration that was reflected only by the FSQ scores. The FSQ system more reliably predicted outcome than the NYHA system and appears to be a more useful tool in the evaluation of elderly patients with cardiac disease.

Activities of Daily Living↗