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Biomedical subjects

S H Cohn

Publications and source records attributed to S H Cohn.

At least 37 records · Page 2Linked to original sources
PubMed1985

A model for involutional bone loss.

Bone mass of the total skeleton and distal radius were measured by in vivo neutron activation analysis and single photon absorptiometry, respectively, in 403 healthy white women and 151 healthy white men. In addition, the density of L-2 to L-4 (bone mineral content of the spine [BMCs]) was measured by dual photon absorptiometry in 159 of these women and in 56 women with the vertebral crush fracture syndrome. The rate of loss of total body calcium (TBCa) and bone mineral content of the radius (BMCr) was linear in men and was slower than in women. The best fit for TBCa and the bone mineral content of the distal radius and spine as a function of age in women was with a two-phase regression. The TBCa and BMCr could be used as well as BMCs to identify women with crush fractures. The ratios of BMCs/TBCa, BMCs/BMCr, and TBCa/BMCr did not differ among women with crush fractures and age-matched normal individuals. Our data do not support the hypothesis that women with vertebral crush fractures have preferential loss of spinal bone.

Adult↗
PubMed1984

Dose-response analysis of cadmium in man: body burden vs kidney dysfunction.

The primary objective of this study was to develop dose-response relationships of cadmium in human beings. In vivo measurements of kidney, liver, urine, and blood cadmium, and urinary levels of beta 2-microglobulin and total protein were obtained in 82 industrially exposed workers and 30 control subjects. The values of 200 micrograms/g creatinine for urinary beta 2-microglobulin and 250 mg/g creatinine for urinary total protein were used to define the upper limit for normal kidney function. Forty-one of the cadmium workers (18 active, 23 retired) were classified as having abnormal kidney function; all control subjects had normal kidney function. Most workers with Cd above 70 ppm in the liver were judged to have some evidence of kidney abnormalities. The dose-response relationship for liver cadmium for the actively employed workers could be described by a linear logistic regression model: (Formula: see text) where p is the individual's probability of having kidney dysfunction. The loss of cadmium from the kidney following dysfunction prohibited a direct logistic analysis of the kidney cadmium data. However, when the linear relationship between kidney and liver cadmium for the subjects with normal kidney function was combined with the logistic equation for the liver, a predicted-response curve was obtained for the kidney. The logistic models predict a 50% probability of having kidney dysfunction at 38.4 mg for the kidney and 42.3 ppm for the liver, respectively.

Body Burden↗
PubMed1984

An improved calibration for the in vivo determination of body nitrogen, hydrogen, and fat.

Additional investigation of the authors' original technique for measuring total body nitrogen by prompt gamma neutron activation has demonstrated the need for certain changes in the calibration procedures in order to apply the method to studies of patients with abnormal metabolism. In the present technique, total body nitrogen, hydrogen, and fat were derived, simultaneously, from data obtained by neutron capture gamma-ray analysis combined with the measurements of body weight, total body water, and total body calcium. In this improved calibration technique total body nitrogen is more accurately measured, not only in normal subjects, but also in obese subjects and in patients with marked changes in hydration, such as cancer patients. The fat values calculated do not rely on a fixed relationship of total body water or total body potassium with lean body mass as in the previous studies, but are calculated as the difference between body weight and the sum of body water, protein and bone mineral ash. This improved technique has been applied to the study of three groups of subjects, the general population with a normal weight distribution and two extremes represented by obese and cancer patients.

Adipose Tissue↗
PubMed1984

Improved models for determination of body fat by in vivo neutron activation.

In the present study, two different models of body composition, based on data obtained by nuclear techniques are used. Total body nitrogen, calcium, and chlorine were obtained by total body neutron activation. Total body chlorine was used to estimate extracellular water, and total body calcium to determine bone mineral and extracellular solids. Total body potassium was measured by whole body counting to obtain the body cell mass. In addition, total body water was measured by the tritium dilution technique. It was found that either model can be used equally well to measure total body fat in normal subjects. Estimation of body fat as the difference between body weight and the sum of total body nitrogen (protein), total body water, and bone ash (model 1) appears to have an advantage over model 2, which uses body cell mass, extracellular water, and extracellular solids, particularly for patients with metabolic disorders. This advantage is partly due to the fact that the parameter protein (total body nitrogen) is less affected in metabolic disorders than the more labile total body potassium. The closely correlated results obtained with the two models based on nuclear measurements support the conclusion that these techniques provide reliable measurements of total body fat.

Adipose Tissue↗
PubMed1984

Protracted exposure to fallout: the Rongelap and Utirik experience.

From June 1946 to August 1958, the U.S. Department of Defense and the U.S. Atomic Energy Commission (AEC) conducted nuclear weapons tests in the Northern Marshall Islands. On 1 March 1954, BRAVO, an above-ground test in the Castle series, produced high levels of radioactive material, some of which subsequently fell on Rongelap and Utirik Atolls due to an unexpected wind shift. On 3 March 1954, the inhabitants of these atolls were moved out of the affected area. They later returned to Utirik in June 1954 and to Rongelap in June 1957. Comprehensive environmental and personnel radiological monitoring programs were initiated in the mid 1950s by Brookhaven National Laboratory to ensure that body burdens of the exposed Marshallese subjects remained within AEC guidelines. Their body-burden histories and calculated activity ingestion rate patterns post-return are presented along with estimates of internal committed effective dose equivalents. External exposure data are also included. In addition, relationships between body burden or urine-activity concentration and declining continuous intake were developed. The implications of these studies are: (1) the dietary intake of 137Cs was a major component contributing to the committed effective dose equivalent for the years after the initial contamination of the atolls; (2) for persons whose diet included fish, 65Zn was a major component of committed effective dose equivalent during the first years post-return; (3) a decline in the daily activity ingestion rate greater than that resulting from radioactive decay of the source was estimated for 137Cs, 65Zn, 90Sr and 60Co; (4) the relative impact of each nuclide on the estimate of committed effective dose equivalent was dependent upon the time interval between initial contamination and rehabilitation; and (5) the internal committed effective dose equivalent exceeded the external dose equivalent by a factor of 1.1 at Utirik and 1.5 at Rongelap during the rehabitation period. Few reliable 239Pu measurements on human excreta were made. An analysis of the tentative data leads to the conclusion that a reliable estimate of committed effective dose equivalent requires further research.

Adult↗
PubMed1984

Total body phosphorus in postmenopausal women.

Total body phosphorus (TBP) and total body calcium (TBCa) were measured by neutron activation analysis and whole body counting in 82 white women who were 1-6 years postmenopausal. Mean TBP was 395 g +/- 6.3 (SE). There was no evidence for subgroups of patients with either higher or lower TBP. The TBP was significantly related to TBCa, as well as to the bone mineral content of the distal radius. Positive associations were found between TBP and urinary phosphate excretion as well as serum 1,25(OH)2D levels (r = 0.30; p = 0.017; n = 48). Serum phosphate was related to 1,25(OH)2D levels and the number of years since menopause.

Calcium↗
PubMed1983

Sodium excess in postmenopausal osteoporosis.

The sodium excess (Naes) which represents the nonexchangeable sodium compartment of bone was calculated from the total body sodium and total body chlorine of 95 women with vertebral crush fracture syndrome. No evidence was found for a subpopulation with increased or decreased Naes or Naes:TBCa ratio (TBCa is total body calcium which reflects total skeletal mass). Correlations in the osteoporotic women were found between the Naes and serum alkaline phosphatase (r = 0.31), PTH (r = 0.53), urinary hydroxyproline excretion (r = 0.42) and serum 250H vitamin D (r = -0.32). These data suggest that the state of vitamin D nutrition as well as parathyroid hormone levels may influence the quantity of sodium in bone in osteoporotic women. It is of great interest that these relationships were not observed in two control populations consisting of elderly women and women who recently underwent spontaneous menopause.

Aged↗
PubMed1983

Effects of caloric restriction on body composition and total body nitrogen as measured by neutron activation.

The purpose of this study was to compare the effects of two isocaloric diets (800 Kcals) on the changes in body composition during weight reduction. While the protein content of both diets was 70 g, the carbohydrate content of diet A was 10 g and that of diet B was 70 g. The various parameters of body composition were determined as follows: Total body potassium (TBK) by 40K counting, total body water (TBW) by the tritiated water technique, total body nitrogen (TBN) by prompt gamma neutron activation analysis (PGNAA) and total body fat was estimated by measuring the skinfold thickness. Routine serum chemistries were performed every 2 wk and serum insulin and triiodothyronine by radioimmunoassay were done at 4-wk intervals. Seventeen obese women who were at least 30% above ideal body weight volunteered for the outpatient study, (group A--10 subjects, group B--7 subjects). At the end of the 12 wk study, the percent changes in the above parameters of body composition were not significantly different for the two groups. The biochemical changes were consistent with the degree of caloric restriction. We conclude that: (1) the technique of prompt gamma neutron activation analysis can be used effectively to determine long term changes in total body nitrogen during weight reduction, (2) loss of lean tissue (water, potassium and nitrogen) as well as fat tissue occurred during weight reduction. The loss of TBN in absolute quantities was less for diet A compared to diet B; however, there was no significant difference between the two diets when the data was expressed as a percent change from the baseline values, and (3) TBK determination probably provides the best estimate of total body fat.

Adult↗
PubMed1983

Whole-body and part-body turnover of 85Sr in Paget's disease.

The whole-body and part-body retention of 85Sr has been measured over a period of 150 days in 12 patients with Paget's disease, seven of whom were treated with calcitonin, starting 60 days after the 85Sr administration. Retentions were compared with those in a group of seven control subjects. The retention data were analysed using multiple exponential, single and double power-law and combined power law and exponential functions. The mean retention of 85Sr over a long period was greater in the Paget's patients than in the controls, 1.9 times at two months. No significant effect of calcitonin treatment was demonstrated. Part-body measurements based on profile scanning demonstrated a significantly increased uptake of 85Sr in sites where disease was present. The longer-term rate of disappearance from such sites was faster than from unaffected bones.

Aged↗
PubMed1983

Evaluation of body composition and nitrogen content of renal patients on chronic dialysis as determined by total body neutron activation.

Total body protein (nitrogen), body cell mass (potassium), fat, and water were measured in 15 renal patients on maintenance hemodialysis (MHD). Total body nitrogen was measured by means of prompt gamma neutron activation analysis; total body water was determined with tritium labeled water; total body potassium was measured by whole body counting. The extracellular water was determined by a technique utilizing the measurement of total body chloride and plasma chloride. When compared with corresponding values of a control group of the same age, sex, and height, the protein content, body cell mass, and total body fat of the MHD patients were within the normal range. The only significant change was an increase in the extracellular water/body cell mass ratio in the male MHD patients compared to the controls. The lack of significant difference of the nitrogen values of the MHD patients compared to matched controls suggests that dialysis minimizes any residual effects of uremic toxicity or protein-calorie malnutrition. These findings further suggest that there is a need to reevaluate the traditional anthropometric and biochemical standards of nutritional status for MHD patients. It was concluded that it is particularly important to measure protein stores of MHD patients with low protein intake to ascertain nutritional status. Finally, in vivo measurement of total body nitrogen and potassium for determination of body composition provides a simple, direct, and accurate assessment of the nutritional status of MHD patients.

Adipose Tissue↗
PubMed1983

Indexes of body cell mass: nitrogen versus potassium.

In vivo neutron activation has provided investigators with a powerful tool for research on body composition. Total-body nitrogen (TBN), total-body potassium (TBK), and total-body water (TBW) were measured in 133 normal subjects. TBN, measured by neutron activation, is a measure of total-body protein, an index of body cell mass. TBK, also measured by a nuclear reaction, is an index of body cell mass as well as lean body mass. The mass and protein content of two compartments, muscle and nonmuscle lean tissue, were determined from the combined TBN-TBK data by compartmental analysis. In this study, nitrogen was separated into the actively metabolizing body cell mass component and the slowly metabolizing structural component. The TBK, which is 95% intracellular, was found to be more closely related to the actively metabolizing nitrogen than to TBN. The relationship of body cell mass, a concept originally proposed by Moore, to lean body mass, is shown through the relationship of TBN and TBK. The clinical significance of this study, is that TBK is the more sensitive and reliable indicator of changes in body cell mass. Maximum information on body composition, however, is obtained by the measurement of both TBK and TBN.

Adult↗
PubMed1983

Determinants of bone mass in postmenopausal women.

Eighty white women, mean age 52 years, within one to six years postmenopausal, were studied to examine the relationship of various factors to bone mass. Forty-four of the women had annual measurements of bone mass, so that the rate of bone loss could be determined. Bone mass was measured by total body neutron activation analysis and photon absorptiometry of the distal radius (total body calcium [TBCa] and bone mineral content [BMC], respectively). Breast-feeding and pregnancy were noted to be associated with higher bone mass; those with lower BMC and/or TBCa tended to have higher serum alkaline phosphatase levels, lower testosterone levels, and more years since the cessation of menses. The rate of bone loss from the radius was greater in those with higher parathyroid hormone levels; those with reduced dietary intake of calcium and lower 25-hydroxyvitamin D levels had a greater rate of loss of TBCa.

Bone and Bones↗
PubMed1983

A facility for in vivo measurement of lithium.

A facility for measurement of Li in-vivo based on measurement of exhaled HT gas has been constructed and tested. Li present in the brain of therapeutically treated individuals could be measured with a dose to the brain of 1 rem. It will be possible to locate grossly the non-uniformity of Li, left-right or front-back sides of the brain, by choosing the proper energy of neutrons. Experiments with larger animals such as sheep are planned.

Body Fluids↗
PubMed1983

Applications of nuclear technologies for in vivo elemental analysis.

The objectives of this Department of Energy sponsored program are (1) to improve existing nuclear techniques, and (2) to develop new techniques for the analysis and solution of both medical problems and those associated with environmental pollution. Measurement facilities developed, to date, include a unique whole body counter, (WBC); a total body neutron activation facility (TBNAA); and a partial body activation facility (PBNAA). A variation of the prompt gamma neutron activation technique for measuring total body nitrogen has been developed to study body composition of cancer patients and the effect of nutritional regimens on the composition. These new techniques provide data in numerous clinical studies not previously amenable to investigation. The development and perfection of these techniques provide unique applications of radiation and radioisotopes to the early diagnosis of certain diseases and the evaluation of therapeutic programs. The PBNAA technique has been developed and calibrated for in vivo measurement of metals. Development has gone forward on prompt gamma neutron activation for the measurement of cadmium, x-ray fluorescence (XRF) for measurement of lead, and nuclear resonance scattering (NRS) for measurement of iron. Other techniques are being investigated for in vivo measurement of metals such as silicon and beryllium. Cardinal to all toxicological studies of Cd and other metal pollutants is an accurate and sensitive noninvasive technique for measuring organ burdens. In keeping with the mission of Brookhaven, these facilities have been made available to qualified scientists and members of the medical community throughout the world.

Adult↗
PubMed1982

Techniques for determining the efficacy of treatment of osteoporosis.

Each of the presently available noninvasive methods used to determine the nature and degree of changes in skeletal mass has significant advantages and limitations. Dual photon absorptiometric techniques generally have a very low radiation dose. They are also less expensive to construct than other systems. However, they provide information only on a highly localized portion of the axial skeleton. Computed tomography offers significant potential advantages over other techniques, but requires further work for the solution of inherent technical problems. Similarly, considerable additional work is required for the Compton scattering technique; the technical problems associated with this are even more formidable. Neutron activation analysis permits the direct in vivo measurement of total calcium content of the body and hence, skeletal mass. However, while there is vast clinical and research experience with partial body and total body neutron activation, the techniques are generally not routinely available for application in clinical centers. The question as to whether DPA of the spine, or total body calcium measurement best reflects changes in bone mass after therapy has not been resolved.

Bone and Bones↗