Search PubMed⌕ Search

Biomedical subjects

R N Pierson

Publications and source records attributed to R N Pierson.

At least 109 records · Page 6Linked to original sources
PubMed1995

Low spinal and pelvic bone mineral density among individuals with Down syndrome.

The bone mineral density of 15 adults with Down syndrome was compared to 25 control subjects without Down syndrome. Bone mineral density was measured by dual x-ray absorptiometry with a Lunar DPX scanner. Arm, leg, pelvic, and spine bone mineral density was tested. Analysis of covariance was conducted for each variable; Down syndrome was the independent variable, and the covariates were height, lean body mass, fat mass, age, and gender. No significant group differences were found for arm or leg bone mineral density. Individuals with Down syndrome had significantly lower pelvic and spinal bone mineral density. Before adjustment for covariates, percentage difference between group means for spine was 14.5% and for pelvis, 11.6%. Adjusted percentage was 11.1% and 13.9%, respectively. Suggestions for further research were made.

Adult↗
PubMed1994

A comparison of the performance of pig hearts perfused with pig or human blood using an ex-vivo working heart model.

The pathophysiology of xenograft hyperacute rejection is still poorly understood although it is believed to involve complement fixation to vascular endothelium, probably as a result of the presence of naturally occurring anti-species antibodies. Hyperacute rejection of pig hearts by human blood was studied in an ex-vivo working heart model. Cardiac performance and immunological reactions occurring in the perfusing blood were studied. Stroke work performed by pig hearts perfused with human blood and their survival (median 47 min: n = 10) was significantly reduced compared to survival (median 158 min: n = 10) and stroke work performed by pig hearts perfused with pig blood. Decomplementation of human blood resulted in improved performance and duration of the action (median survival > 240 min: n = 10) of hearts. Quantitative differences were seen in complement fixation between the groups. Our data demonstrate the central role of complement in the destruction of pig-to-man xenografts.

Animals↗
PubMed1994

Asians have lower body mass index (BMI) but higher percent body fat than do whites: comparisons of anthropometric measurements.

We studied the correlations between body mass index (BMI) and percent body fat (fat%) measured by dual-photon absorptiometry (DPA) in 445 white and 242 Asian adults aged 18-94 y. In addition, comparisons in six circumferences and eight skinfold-thickness measurements between whites and Asians were made to explain the discrepancies. Although Asians had lower BMI, they were fatter than whites of both sexes. The correlations between fat% and BMI varied by BMI and sex and race. Comparisons in anthropometry show that Asians had more subcutaneous fat than did whites and had different fat distributions from whites. Asians had more upper-body subcutaneous fat than did whites. The magnitude of differences between the two races was greater in females than in males. Prediction equations developed for each sex and race, based on BMI alone, gave SEEs ranging from 4.4% to 5.7%. All were significantly improved to the range of 3.5-4.4% when age and several skinfold-thickness measurements were added.

Adipose Tissue↗
PubMed1994

Differences between young and old females in the five levels of body composition and their relevance to the two-compartment chemical model.

BACKGROUND: Body composition differs between young and old females, although the magnitude of these age-related changes remains uncertain. This uncertainty persists because methodology applied in earlier studies required assumptions that may be age-dependent and also because studies included young and old subjects who differed substantially in body size and health status. METHODS: To resolve these earlier concerns we examined components at the atomic, molecular, cellular, tissue-system, and whole body levels of body composition in 19 weight- and height-matched pairs of young (age 19-35 yrs) and old (age > 65 yrs) healthy White females. Isotope dilution, dual photon, whole-body counting, hydrodensitometry, and anthropometric methods were used either alone or in combination to produce multicomponent models. RESULTS: Old females had significantly more fat, greater truncal skinfolds and circumferences, and significantly less fat-free body mass (FFM), total body potassium (TBK), total body water (TBW), and bone mineral than did their young matched counterparts. Skeletal muscle mass was less in the old females, although the magnitude of the difference from young females varied between the three indices examined. The main assumptions (i.e., TBW/FFM = 0.73 kg/kg and density of FFM = 1.100 g/cc) which the widely used two-compartment TBW and hydrodensitometry methods are based on were not significantly different in young and old females. In contrast, the main assumed steady-state value for the two-compartment TBK method (TBK/FFM = 64.2 mmol/kg) was significantly lower (p < .001) in the old females. CONCLUSION: New approaches thus allow for a critical reexamination of body composition in elderly subjects, and these methods also give new insight into less complex widely used body composition techniques.

Adipose Tissue↗
PubMed1993

Bone mineral density and mass in a cross-sectional study of white and Asian women.

The literature suggests that Asians have lower bone mineral density and mass than whites. It has been proposed that these differences may be due to differences in height, weight, and factors other than ethnicity, but no study has made the appropriate direct comparisons. We compared total-body bone mineral density and mass between Asian and white women while controlling for factors known to be associated with bone mineral density and mass. Measurements were made in 129 Asian (primarily of Chinese ancestry) and 274 white women. A subgroup was formed of women who did not have a history of alcoholism, premenopausal amenorrhea, kidney disease, estrogen use, birth control pill use, thyroid disease, steroid use, hysterectomy, or smoking. In both the main group and the subgroups, bone mineral mass was significantly lower in Asian than in white women, but after analysis of covariance with body weight, height, and age (or years since menopause) as covariates, the differences between ethnic groups disappeared, except in the large group of premenopausal women, in whom average bone mineral density in Asians actually exceeded (p < 0.04) that in whites. The data set was also searched for Asian-white pairs who matched on 17 characteristics related to bone mineral density and mass. In the resulting 16 matched pairs, bone mineral density and mass were not different between ethnic groups. Although Asian women have lower bone mineral mass than white women, when weight, height, and other factors are controlled, bone mineral density and mass do not differ between Asian and white women.

Absorptiometry, Photon↗
PubMed1993

Biological homogeneity and precision of measurement: the boundary conditions for normal in body composition.

For compartments most urgently important to clinical medicine we have satisfactory levels of measurement precision, and the clinical considerations now are the availability of the methods, and the collection of data for normal subjects. Our colleagues in physics and imaging will improve measurement precisions, but the work most needed is to refine the biological side of the measurement equation. Large numbers of measurements, carefully done with carefully calibrated and unchanging systems, exist only for the special case of measuring body calcium in women, in the large cohort of approximately 2,500 women, studied by Aloia and Cohn with neutron activation, and for body potassium, in these women, and in the larger numbers of diverse age, sex, race, and size in the Rosetta study in our laboratory. Can we benefit from the "orthogonal measurements" and "orthogonal physiologic constraints" approaches, in which triangulation is used to combine measurements from several techniques to establish upper-lower bounds estimates by different techniques, with convergence on a "best fit" result? We have noted that the intrinsic homeostatic mechanisms of the body function with great precision to control body temperature, osmotic and ionic concentrations in the water phase, hypertrophy of muscle with exercise, and remodeling of bone by stress. We consider it unlikely that the control mechanisms are more loosely hinged for such secondary parameters as K/FFM and bone density.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1993

Body fat topography as an independent predictor of fatty liver.

Abdominal (truncal) fat distribution reflected by an elevated waist to hip ratio (WHR) predicts metabolic abnormalities such as diabetes and dyslipidemia as well as hypertension and stroke, all of which are associated with obesity. The pathogenesis is not known, although elevated splanchnic serum free fatty acid levels and reduced hepatic insulin clearance have been implicated. WHR and body fat (BF) by 40K-counting and 3H2O were measured before liver biopsy during antiobesity surgery in 68 severely obese women (body mass index [BMI], 48.9 +/- 1.1 SEM) and 15 men (BMI, 49.0 +/- 3.1) without histories of liver disease, diabetes, or hepatotoxic exposure. Biopsies were graded for fat content semiquantitatively (0 to 4+) by the hepatologist who was blinded to the patients' clinical characteristics. All 15 men had fatty infiltration (score, 2.5 +/- 0.3 v 1.4 +/- 0.1 in women; P < .001). The correlation between WHR and liver fat was .44 (P < .0005), while BF (-.16), weight (.15), or BMI (.04) did not correlate significantly with steatosis (all NS). As expected, percentage body fat (BF%) was greater in women than in men (40.3 +/- 0.8 kg v 33.9 +/- 2.0, P < .007), and accordingly liver fat was inversely related to BF% (r = -.32, P < .002). Steatosis was significantly greater in 14 men (2.5 +/- 0.3) than in 20 women (1.7 +/- 0.3, P < .04) matched for BF%. In multiple regression analysis R2 = .49, P < .0001), WHR and sex accounted for the variance in liver fat content without any further contribution from weight, BMI, BF, or BF%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1993

Calibration for measuring total body nitrogen with a newly upgraded prompt gamma neutron activation facility.

A description is given of the calibration and performance of the upgraded facility at Brookhaven National Laboratory (BNL) for measuring total body nitrogen using the technique of prompt gamma neutron activation analysis. With the improved calibration, total body nitrogen can be more accurately measured not only in normal subjects but also in obese and wasted patients. Body hydrogen is used as an internal standard. We examined the effect of a heavy-water premoderator on the uniformity of composite sensitivity, nitrogen and hydrogen measurement statistics, and dose to the subject. The calibration technique corrects the ratio of nitrogen-to-hydrogen counts measured from the subject for body size. Additionally, a correction for subcutaneous adipose tissue on the nitrogen-to-hydrogen count ratio is introduced. The newly upgraded BNL facility provides precision in counting statistics using a Remcal anthropomorphic phantom filled with a tissue-equivalent solution of 2.1% for a body dose of 0.35 mSv using a 2.5 cm D2O premoderator. The measurements were made at five 20 cm sections, counting for 200 s per section.

Calibration↗