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Biomedical subjects

R N Pierson

Publications and source records attributed to R N Pierson.

At least 55 records · Page 3Linked to original sources
PubMed2000

Bone mineral in prepubertal children: gender and ethnicity.

Previous reports of gender and ethnic differences in bone mineral in prepubertal children have been inconsistent due to different methodologies, the problematic nature of bone density by dual-energy X-ray absorptiometry (DXA) calculated as the ratio of bone mineral mass to projected bone area (BA), and the generally small study populations. The aim of this study was to test the hypothesis that gender and ethnic differences in bone mineral by DXA are present in prepubertal children. The subjects were 336 healthy Asian, black, and white prepubertal children (172 females and 164 males). Total body bone mineral content (TBBMC) was adjusted for total body BA (TBBA), age, height, and weight. Adjusted mean TBBMC was greater in males than in females (p = 0.01). The gender difference was independent of ethnicity. Adjusted mean TBBMC was different for black compared with nonblack children (p = 0.001). The ethnic difference was a function of TBBA and weight. This study in a multiethnic population of prepubertal children shows (1) a gender difference in TBBMC and (2) an ethnic difference in TBBMC.

Absorptiometry, Photon↗
PubMed1999

Prolongation of primate cardiac allograft survival by treatment with ANTI-CD40 ligand (CD154) antibody.

BACKGROUND: We evaluated whether a humanized anti-CD154 antibody (hu5c8) prolongs primate cardiac allograft survival. METHODS: Heterotopic cardiac allografts were performed between MHC class II-mismatched cynomolgus monkeys. Survival was compared between groups treated with a perioperative dosing of hu5c8 (group 1; n=6), sustained dosing with hu5c8 (group 2; n=3), and control regimens (n=4). All recipients received fresh donor-specific transfusions during surgery. RESULTS: Median graft survival was 49 days (range 14 to 56) in group 1 and 106 days (range 56 to 245) in group 2, compared with 5 days (range 5 to 6) for controls (P<0.05 for all comparisons). Lymphocytic infiltrates were often present in hu5c8-treated grafts with stable contractility. Donor-specific mixed lymphocyte reaction was generally preserved. Vasculitis and cellular intimal proliferation were prevalent in rejected grafts but occurred later and were less prevalent in group 2. CONCLUSIONS: Anti-CD154 antibody markedly prolongs the survival of cardiac allografts in primates and is well tolerated. Sustained dosing with hu5c8 yielded improved survival and may be associated with a lower incidence of vascular pathology. We conclude that hu5c8 therapy is an effective approach for inhibiting acute cardiac allograft rejection in primates.

Animals↗
PubMed1999

Longitudinal analysis of fibroblast growth factor expression after transplantation and association with severity of cardiac allograft vasculopathy.

BACKGROUND: Vascular smooth muscle cell growth factors are postulated to contribute to cardiac allograft vasculopathy (CAV). Few data quantitatively address the timing, location, or stimuli for growth factor expression and relationship to CAV. METHODS AND RESULTS: Acidic fibroblast growth factor (aFGF) mRNA expression was determined in serial endomyocardial biopsies during the first year after transplantation. Patients with high levels of aFGF mRNA and elevations after the early posttransplant period had significantly more severe CAV than patients with low aFGF and no late elevations. CONCLUSIONS: Parenchymal aFGF expression varies between patients and in the same patient over time and correlates with development of CAV.

Biopsy↗
PubMed1999

Studies of body composition and fat distribution in HIV-infected and control subjects.

OBJECTIVE: Recent studies have documented alterations in body fat distribution that have been associated with protease inhibitor therapy. We compared body composition, including measurements of fat distribution, in 96 HIV-infected subjects studied since January 1996 (current HIV), subjects seen prior to January 1996 (previous HIV), and healthy controls. DESIGN: Retrospective cross-sectional studies of subjects matched by gender, race, age, and height. METHODS: Body weight, height, body cell mass by whole-body counting of 40K plus fat, fat-free mass, and body fat distribution by anthropometry were measured. RESULTS: Current HIV men weighed more (p = .025) and had more body cell mass than previous HIV men, but less than controls (p < .001). In women, the between group differences in fat were greater than the differences in body cell mass. Current and previous HIV study subjects had lower indices of subcutaneous and higher indices of visceral fat than controls. In current HIV subjects, body fat distribution was significantly associated with log plasma HIV RNA content but not with antiretroviral or protease inhibitor usage, nor with CD4+ lymphocyte counts. In 7 of 9 current HIV subjects studied, 24-hour urinary free cortisol excretion was abnormally high. CONCLUSIONS: Alterations in body fat distribution are a characteristic feature in HIV infection. The occurrence of increased visceral fat content and decreased subcutaneous fat content preceded the era of combination antiretroviral therapy. The alteration in fat distribution may be affected by plasma HIV RNA content rather than antiretroviral or protease-inhibitor therapy. The body composition alterations might be associated with endogenous hypercortisolism.

Adult↗
PubMed1999

The utility of exercise testing after cardiac transplantation in older patients.

BACKGROUND: The criteria for cardiac transplantation recipient selection, including the appropriate recipient upper age limit, continue to expand with an increasing number of recipients greater than 60 years of age. While others have reported their transplant experience in older recipients in terms of quality of life assessment, we have examined the role of exercise cardiopulmonary testing post-transplantation in older cardiac transplant recipients. METHODS: We reviewed inpatient and outpatient charts of 28 patients 60 years of age or older who underwent orthotopic heart transplantation at Vanderbilt University Medical Center. RESULTS: In this population, perioperative mortality of 7.1% and Kaplan-Meier survival at 1 and 5 years of 89 and 77%, respectively, were similar to the institutional 1-year (89%) and 5-year (75%) survival among younger adult transplant recipients. Exercise cardiopulmonary testing results were available in 22/25 patients surviving greater than 1 year. Both peak oxygen consumption and percentage of maximum VO2 were significantly greater among patients reporting NYHA Class 1 or 2 functional status, in comparison with those NYHA Class 3 or greater. CONCLUSION: Following cardiac transplantation, survival of patients greater than 60 years of age is equivalent to that of younger patients at our institution. Exercise testing provides an objective measure of performance and correlates with subjective status following heart transplantation. Most patients demonstrate good functional status, with minimal symptoms and good exercise capacity. These results, although retrospective, suggest that cardiac transplantation remains a reasonable therapeutic option for patients greater than 60 years of age with end-stage cardiomyopathy.

Aged↗
PubMed1999

Continuous loss of bone during chronic immobilization: a monozygotic twin study.

Acute immobilization is associated with rapid loss of bone. Prevailing opinion, based on population cross-sectional data, assumes that bone mass stabilizes thereafter. In order to address whole-body and regional skeletal mass in long-term immobilization, monozygotic twins were studied, one of each twin pair having chronic spinal cord injury (SCI) of a duration ranging from 3 to 26 years. The research design consisted of the co-twin control method using 8 pairs of identical male twins (mean +/- SD age, 40 +/- 10 years; range 25-58 years), one of each set with SCI. The twins were compared by paired t-tests for total and regional bone mineral content (BMC) and bone mineral density (BMD) measured by dual-energy X-ray absorptiometry. Linear regression analyses were performed to determine the associations of age or duration of injury with the differences between twin pairs for total and regional skeletal bone values. In the SCI twins, total-body BMC was significantly reduced (22% +/- 9%, p<0.001), with the predominant sites of reduction for BMC and BMD being the legs (42% +/- 14% 35% +/- 10%, p<0.0001), and pelvis (50% +/- 10% and 29% +/- 9%, p<0.0001). Duration of SCI, not age, was found to be linearly related to the degree of leg bone loss in SCI twins (BMC: r(2) = 0.60, p<0.05; BMD: r(2) = 0.70, p<0.01). Our findings suggest that pelvic and leg bone mass continues to decline throughout the chronic phase of immobilization in the individual with SCI, and this bone loss appears to be independent of age.

Absorptiometry, Photon↗
PubMed1999

Bone mineral measurements: a comparison of delayed gamma neutron activation, dual-energy X-ray absorptiometry and direct chemical analysis.

A system in vitro consisting of a femur from a cadaver and soft-tissue equivalent material was used to test the agreement between several techniques for measuring bone mineral. Calcium values measured by delayed gamma neutron activation (DGNA) and bone mineral content (BMC) by Lunar, Hologic and Norland dual-energy X-ray absorptiometers (DXA) were compared with calcium and ash content determined by direct chemical analysis. To assess the effect of soft-tissue thickness on measurements of bone mineral, we had three phantom configurations ranging from 15.0 to 26.0 cm in thickness, achieved by using soft-tissue equivalent overlays. Chemical analysis of the femur gave calcium and ash content values of 61.83 g +/- 0.51 g and 154.120 +/- 0.004 g, respectively. Calcium measured by DGNA did not differ from the ashed amount of calcium at any of the phantom configurations. The BMC measured by DXA was significantly higher, by 3-5%, than the amount determined by chemical analysis for the Lunar densitometer and significantly lower, by 3-6%, for the Norland densitometer (p<0.001-0.024), but only 1% lower (not significant) for the Hologic densitometer. DXA instruments showed a decreasing trend in BMC as the thickness increased from 20.5 to 26.0 cm (p<0.05). However, within the entire thickness range (15.0-26.0 cm), the overall influence of thickness on BMC by DXA was very small. These findings offer insight into the differences in these currently available methods for bone mineral measurement and challenge the comparability of different methods.

Absorptiometry, Photon↗
PubMed1999

Maternal body fat and water during pregnancy: do they raise infant birth weight?

OBJECTIVE: Our purpose was to determine the relation to infant birth weight of maternal fat and lean tissue during early and late pregnancy. DESIGN: Total and net maternal pregnancy weight, fat, and water were determined from measurements of total body water, body density, and bone mineral mass in 200 women, with the use of a multicompartment model for body fat estimation in early and late pregnancy. Regression modeling was used to determine the relation of maternal body composition to birth weight, with control for maternal age, height, parity, and race and for infant gestational age and sex. RESULTS: Maternal weight and body water at term were significantly associated with infant birth weight, but maternal body fat at term was not. These relations remained when maternal net values were used for weight, fat, and water to eliminate the contribution of the conceptus to these components. CONCLUSION: In well-nourished women delivering at term, maternal body fat near term does not contribute significantly to infant birth weight, but maternal body water does.

Adipose Tissue↗
PubMed1999

The effects of moderate doses of megestrol acetate on nutritional status and body composition in a hemodialysis patient.

OBJECTIVE: To determine the safety and efficacy of moderate doses of megestrol acetate (>/=320 mg/day) in a patient on hemodialysis. DESIGN: Case study. SETTING: Chronic hemodialysis facility and body composition unit in New York City. MAIN OUTCOME MEASURES: Body weight, body composition, dietary energy and protein intake, appetite assessment, serum albumin, prealbumin, serum transferrin, and quality of life. RESULTS: The patient received megestrol acetate for 24 weeks and gained little body weight. However, his fat mass increased by 7.5 kg (163%), and fat-free mass decreased by 6.8 kg (10.6%) from baseline measurements. The proportional content of total body water, extracellular water, intracellular water, body cell mass in fat-free mass, and average cell K+ concentration were maintained within normal ranges. Serum albumin was maintained, serum transferrin increased, prealbumin decreased, dietary energy and protein intakes increased, and reported appetite improved. CONCLUSIONS: Moderate doses of megestrol acetate may be an effective therapeutic agent in reversing poor appetite, increasing dietary energy and protein intakes, and improving nutritional status in some patients receiving maintenance hemodialysis. However, these changes were at the expense of altering body composition components. Further research that includes measures of body composition, nutritional status, appetite assessment, and quality of life are needed to determine the safety and effectiveness of moderate or high doses of megestrol acetate in a large number of hemodialysis patients.

Appetite Stimulants↗
PubMed1999

Immunohistologic evaluation of mechanisms mediating hyperacute lung rejection, and the effect of treatment with K76-COOH, FUT-175, and anti-Gal column immunoadsorption.

Although most investigators agree that lung dysfunction occurs rapidly in various pig-to-primate hyperacute lung rejection (HALR) models, the basic mechanisms mediating this phenomenon remain in question. Here we describe an immunohistochemical method for assessment of mechanisms driving HALR. Using an established model wherein piglet lungs are perfused ex vivo with human blood, six experimental groups (K76 COOH; FUT-175; K76 with FUT; anti-alpha-Gal column adsorption; column with FUT; and column with K76) and two control groups (unmodified human blood; autologous pig blood) were studied. Each lung was biopsied serially during perfusion, and assessed using an immunohistochemical technique, with vWF staining as an internal control to quantitate binding of human IgM, IgG, C3, C5b-9, properdin, and C1q. The effect of each treatment and subsequent lung perfusion on IgG and IgM anti-alpha-Gal titers(by ELISA) and on pig endothelial cell cytotoxicity were correlated with histologic findings. We found that [1] the classical complement activation pathway was activated, as has been shown for other pig organs in primate or human blood environments [2]; alternative complement pathway activation is also seen, which has not been described for other organs in pig-to-primate models, but only in the context of classical pathway activation; and [3] anti-Gal column absorption, pharmacologic inhibition of complement, or combination therapy each was associated with histologic evidence of partial protection, consistent with what would be predicted for each intervention. Further, immunohistologic differences correlated with physiologic outcomes [8] and with antibody assay results, and revealed that treatments used were incompletely effective. Our data suggest that more complete inhibition of antibody- and complement-driven pathways than was achieved in these experiments will be necessary to prevent the antibody and complement-mediated facets of hyperacute lung rejection. This immunohistologic technique may also help us identify additional pathogenic mechanisms important to eventual clinical application of pig-to-human lung xenografts.

Acute Disease↗
PubMed1999

Total body-calcium measurements: comparison of two delayed-gamma neutron activation facilities.

This study compares two independently calibrated delayed-gamma neutron activation (DGNA) facilities, one at the Brookhaven National Laboratory (BNL), Upton, New York, and the other at the Children's Nutrition Research Center (CNRC), Houston, Texas that measure total body calcium (TBCa). A set of BNL phantoms was sent to CNRC for neutron activation analysis, and a set of CNRC phantoms was measured at BNL. Both facilities showed high precision (< 2%), and the results were in good agreement, within 5%.

Calcium↗
PubMed1999

Relative influences of sex, race, environment, and HIV infection on body composition in adults.

BACKGROUND: The factors that control body composition in disease are uncertain. OBJECTIVE: We planned to compare the relative influences of HIV infection, sex, race, and environment on body composition. METHODS: We analyzed results of body composition studies performed by bioelectrical impedance analysis in 1415 adults from 2 cohorts: white and African American men and women from the United States, and African men and women (279 HIV-infected and 1136 control). The effects of sex and HIV infection on weight, body cell mass, and fat-free mass were analyzed by using both unadjusted and age-, weight-, and height-adjusted data. RESULTS: Control men weighed more and had more body cell mass and fat-free mass than did control women, although control women had more fat. The strongest correlates with body composition were height and weight, followed by sex. HIV infection, age, environment, and race. Control men and women weighed more and had more body cell mass, fat-free mass, and fat than did HIV-infected men. However, differences in body composition between HIV-infected and control groups were strongly influenced by sex. Of the differences in weight between HIV-infected and uninfected subjects, fat-free mass accounted for 51% in men but only 18% in women, in whom the remainder was fat. Sex effects were similar in African and American groups. CONCLUSIONS: Sex has a marked effect on the changes in body composition during HIV infection, with women losing disproportionately more fat than men. Sex-related differences in body composition were narrower in the HIV-infected groups. Race and environment had smaller effects than sex and HIV infection.

Adolescent↗
PubMed1999

Relation between body fat and age in 4 ethnic groups.

BACKGROUND: Previous studies of the relation between age and body fat reached differing conclusions concerning the question of whether body fat is lower in the elderly than in middle-aged persons. OBJECTIVE: The objectives of this study were to characterize the relation between age and body fat in 4 ethnic groups and test the hypothesis that body fat is lower in the elderly than in middle-aged persons. DESIGN: Body fat was measured in a sample of 1324 volunteers aged 20-94 y by using a 4-component model of body composition. Four ethnic groups were studied: Asians, blacks, Puerto Ricans, and whites. Regression models were developed for fat mass and fat percentage as functions of age. RESULTS: In all but one of the groups, a highly significant curvilinear relation between age and body fat was found, indicating a peak amount of body fat in late middle age and lower amounts of body fat at younger and older ages (P < 0.001). The age at which maximum body fat was predicted in the various groups ranged from 53 to 61 y for fat mass and from 55 to 71 y for fat percentage. In Puerto Rican men there was no significant relation between age and fat mass, and the relation between age and fat percentage was linear and positively correlated. CONCLUSIONS: This study provided data on the relation between age and body fat in 4 ethnic groups and supported the hypothesis that body fat is lower in the elderly than in middle-aged persons.

Adipose Tissue↗
PubMed1999

Fat distribution in HIV-infected patients reporting truncal enlargement quantified by whole-body magnetic resonance imaging.

BACKGROUND: Antiretroviral therapy has improved the prospects for people infected with HIV, but some develop a syndrome of profound body habitus and metabolic alterations that include truncal enlargement. OBJECTIVE: The purpose of this study was to define the body-composition changes associated with this syndrome by using techniques with the power to estimate regional body composition. DESIGN: We compared whole-body and regional skeletal muscle and adipose tissue contents measured by magnetic resonance imaging and dual-energy X-ray absorptiometry (DXA) in 26 HIV-infected patients and 26 matched control subjects. Twelve of the HIV-infected patients had evidence of truncal enlargement. RESULTS: HIV-infected men and women who noted truncal enlargement had similar amounts of skeletal muscle and subcutaneous adipose tissue but greater visceral adipose tissue than HIV-infected patients without truncal enlargement; these values were larger in men (P < 0.001) than in women (P = 0.08). The ratio of visceral to subcutaneous adipose tissue was greater in both men (P < 0.02) and women (P = 0.05) with truncal enlargement. Two subjects with MRI-confirmed visceral adiposity syndrome (VAS) were not taking protease inhibitors. CD4+ lymphocyte counts were higher (P < 0.001) and plasma viral burdens tended to be lower (P = 0.08) in HIV-infected patients with VAS. CONCLUSIONS: There was significantly more visceral adipose tissue in the subgroup of HIV-infected patients with truncal enlargement than in those without this sign. VAS occurs in both men and women, is associated with higher CD4+ lymphocyte counts and lower plasma HIV viral burdens, and is not limited to those receiving protease inhibitor therapy.

Absorptiometry, Photon↗
PubMed1999

Dual X-Ray absorptiometry in pediatric studies: changing scan modes alters bone and body composition measurements.

The use of dual X-ray absorptiometry (DXA) for measurement of bone mineral and body composition in pediatric subjects faces a major technical issue: body size dictates choice of scan mode. However, different scan modes change results in the same subject, thus affecting the accuracy of bone/body composition measurements and especially the capacity to measure changes owing to either growth or intervention. To evaluate the effect of scan mode selections on measurements of bone mineral and body composition, 13 children with weights at the cutoff point between the pediatric large and adult medium scan modes of Lunar DPX or DPXL (Lunar, Madison, WI) with software 3.6 g (35.3 +/- 0.9 kg or 77.7 +/- 2.0 lb) were scanned by both modes. Adult medium mode gave significantly higher results than pediatric large mode for total body fat mass (11.1%), fat% (10.5%), bone mineral content (8.1%), and bone area (1.3%) (p < 0.02). The differences between pediatric large and adult medium modes in fat measurements increased with increasing body mass index ([BMI], kg/m(2)), body surface area ([BSA], m(2)), and trunk size (mm), whereas the differences in bone mineral measurement tended to be greater only with increasing BMI and BSA. None of the differences were correlated to body weight. This study suggests that scan mode selections based on trunk size, BMI, or BSA instead of body weight may improve continuity of bone and body composition measurements by the DXA technique in pediatric subjects.

Absorptiometry, Photon↗
PubMed1999

Correlations between skeletal muscle mass and bone mass in children 6-18 years: influences of sex, ethnicity, and pubertal status.

A constant sex-specific relationship between skeletal muscle mass and bone mass was observed in healthy adults based on TBK/TBCa, using TBK (total body potassium) by 40K counting and TBCa (total body calcium) by in-vivo neutron activation analysis (Ellis and Cohn, 1975). We revisited this topic in children by studying correlations between TBK and TBCa, and by comparing TBK/TBCa between sexes, pubertal groups (prepubertal and pubertal) and ethnic groups in 141 white, 101 black, and 62 Asian healthy children, aged 6 - 18 years, living in New York City. TBK was measured by 40K counting, and TBCa by dual energy x-ray absorptiometry. TBK and TBCa were significantly correlated from 6 to 18 years (r > 0.93), but the correlation equations varied by gender and ethnicity. Boys had significantly more TBK and greater TBK/TBCa than girls at a given age and weight, reflecting greater skeletal muscle mass in boys from 6 years, the age at which the study started. TBK/TBCa in blacks was significantly smaller than whites and Asians in both sexes in prepuberty and puberty, and pubertal black girls had the smallest mean TBK/TBCa. No significant differences were found between whites and Asians. TBK/TBCa decreased as body weight increased in prepubertal girls, and decreased as body weight and age increased in pubertal girls, but did not change with body weight or age in boys of any subgroup. The inverse relationship between TBK/TBCa and age in pubertal girls suggests greater increase in TBCa compared to TBK than in other groups, while the constant TBK/TBCa in boys reflects proportional increases in TBK and TBCa. Thus TBK/TBCa can be used as an index of relative growth in skeletal muscle mass and bone mass in white, black, and Asian children according to sex, age and pubertal status.

Adolescent↗
PubMed1998

Cytochemical demonstration of sites of hydrogen peroxide generation and increased vascular permeability in isolated pig hearts after ischaemia and reperfusion.

Isolated pig hearts, subsequently perfused with pig or human blood, were prepared for the cytochemical demonstration of sites of hydrogen peroxide generation and increased vascular permeability. Oxidant stress was associated with ultrastructural changes commonly seen following myocardial reperfusion. In addition, the precipitation of cerium perhydroxide following perfusion with physiological saline containing cerium chloride suggested the vascular endothelium and leukocytes as sources of oxidants. This was associated with rapid penetration of horseradish peroxidase through the intercellular clefts of the vascular endothelium into the interstitial space, suggesting increased vascular leakiness at these sites. The rapid penetration of horseradish peroxidase was observed at all monitored periods of reperfusion with pig or human blood. This indicates that the increased permeability occurred during the ischaemic period and continued during reperfusion. Morphological damage was greatest in pig hearts reperfused with whole human blood and this was attenuated if the blood was preabsorbed to remove antibodies prior to reperfusion. We conclude that oxidant stress was initiated during ischaemia and continued during reperfusion in this model.

Animals↗