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Biomedical subjects

R Marcus

Publications and source records attributed to R Marcus.

At least 199 records · Page 11Linked to original sources
PubMed1991

Prevalence and incidence of human immunodeficiency virus among patients undergoing long-term hemodialysis. The Cooperative Dialysis Study Group.

PURPOSE: The purpose of this voluntary multicenter study was to estimate the prevalence and incidence of human immunodeficiency virus (HIV) infection and the risk of nosocomial transmission of HIV in hemodialysis patients in the United States. PATIENTS AND METHODS: In June 1986, we began collecting epidemiologic data, risk factor information, and serum for HIV antibody testing from long-term hemodialysis patients on entry into the study and 1 year later. RESULTS: Initial data and specimens were collected from 1,324 patients in 28 dialysis centers in 12 states. On entry, 26 were positive or equivocal by enzyme immunoassay; 13 of these were positive by Western blot assay (overall seroprevalence 0.98%). Seroprevalence was higher for patients tested in eight centers located in areas from which a high cumulative incidence of acquired immunodeficiency syndrome has been reported (500 or more cases per 1 million persons) than for patients in other areas (10 of 387 [2.6%] versus three of 937 [0.3%]; p = 0.00048). According to their dialysis records, all 13 of the Western blot-positive patients had received transfusions. Seropositive patients were not more likely to have received a transfusion than seronegative patients (13 of 13 versus 1,038 of 1,311; p = 0.08). The confidential risk factor questionnaire was completed by 1,206 (91%) patients including nine of 13 (69%) of the seropositive patients. A question on sharing needles for injection of drugs was answered by 1,158 patients; seropositive patients were more likely to report they had shared needles than seronegative patients (five of nine versus 17 of 1,149; p = 0.0000002). After 1 year of follow-up, data were collected from 667 patients, including 254 negative patients who underwent dialysis at centers with seropositive patients. None of the previously seronegative patients seroconverted, yielding an incidence rate of 0% (upper limit of 95% confidence interval = 0.45%). No case of possible nosocomial transmission was identified. CONCLUSION: These results suggest that use of long-standing infection control precautions is effective minimizing the risk of transmission of HIV in hemodialysis settings.

Adolescent↗
PubMed1991

Understanding osteoporosis.

Considerable progress has been achieved recently in our understanding of the normal process by which bone mass is regulated. Age-related trabecular bone loss is characterized not simply by a global loss of bone but also by cortical porosity and loss of trabecular connections. Because bone strength depends on architectural as well as material properties, bone quantity alone cannot define fracture risk with precision. Traditional therapies for osteoporosis increase bone mass, and estrogen therapy, in particular, profoundly decreases fracture risk. The pharmacologic restoration of bone quantity and quality, however, remains elusive. Modern biotechnology offers the hope that progress may come about through the development of growth factors and other osteotropic compounds for clinical use.

Bone Density↗
PubMed1990

Muscle strength as a predictor of bone mineral density in young women.

It is widely accepted that physical activity is beneficial to bone. However, the specific relationships of muscle strength to bone mineral density (BMD) are poorly understood. We examined strength and BMD in 59 women aged 18-31 years who ranged in exercise patterns from sedentary to active. Mineral density of the right proximal femur (hip) and spine (L2-4) was evaluated by dual-energy x-ray absorptiometry. BMD at the midradius was measured by single-photon absorptiometry. Dynamic strength (one repetition maximum) was measured for the following muscle groups: back, elbow flexors (biceps), leg extensors (quadriceps), and the hip flexors, extensors, adductors, and abductors. Isometric grip strength was assessed by dynamometry. Mineral density at the hip correlated independently with muscle strength and body weight, but not with age. Specifically, femoral neck BMD was significantly correlated with back strength and weight, whereas trochanter and overall hip mineral density were significantly related to biceps, back, and hip adductor strength. Hip mineral density was not related to strength of the quadriceps groups or to that of the hip flexors, extensors, or abductors. In addition, muscle strength was an independent predictor of lumbar spine and midradius mineral density. In stepwise multiple regression analysis, biceps strength proved the most robust predictor of hip BMD and grip strength best predicted bone density at the lumbar spine and radius. We conclude that muscle strength is an independent predictor of bone mineral density, accounting for 15-20% of the total variance in bone density of young women.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Effects of estrogen on daylong circulating calcium, phosphorus, 1,25-dihydroxyvitamin D, and parathyroid hormone in postmenopausal women.

We studied the effects of estrogen on daylong circulating levels of calcium, inorganic phosphorus, parathyroid hormone (PTH), and 1,25-(OH)2D3 (calcitriol) in a group of 10 postmenopausal women (68.5 +/- 1.4 years, mean +/- SEM). The study was conducted under strict dietary control, with mean calcium and phosphorus intakes of 845 and 970 mg. After treatment with conjugated equine estrogens, 1.25 mg/day, for 1 month, significant decreases in fasting (0800 h) serum levels were observed for calcium (9.09 +/- 0.08 versus 9.46 +/- 0.10 mg/dl, p less than 0.01) and phosphorus (3.38 +/- 0.10 versus 3.73 +/- 0.08 mg/dl, p less than 0.01). On the 0800 h fasting specimen, midmolecule PTH concentrations were higher (44.0 +/- 7.9 versus 34 +/- 8.2 pg/ml, p less than 0.05), but intact PTH was unchanged (28.6 +/- 2.7 versus 29.1 +/- 1.7 pg/ml) and a rise in circulating calcitriol (39.8 +/- 4.3 versus 31.6 +/- 2.1 pg/ml) was marginally significant (p = 0.07). When data represented multiple samples averaged over 7 and 15 h, significant estrogen-related reductions in serum calcium and phosphorus concentrations were observed. In addition, estrogen was associated with a significant rise in the daylong (15 h) level of calcitriol (39.4 +/- 4 versus 30.5 +/- 2.4 pg/ml, p less than 0.01). Daylong mid- and intact PTH concentrations were unchanged on estrogen compared to baseline values. No significant correlations were observed between changes in fasting calcitriol level and changes in fasting concentrations of calcium, phosphorus, or PTH. Further, the rise in daylong calcitriol concentration did not correlate significantly with changes in fasting or integrated values of calcium or PTH.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

Bilateral aortoiliac pressure measurements from a single puncture site.

Bilateral aortoiliac pressure measurements were obtained at the time of aortography by performing contralateral iliac artery catheterization in 102 patients with peripheral vascular disease. Patients studied had mild-to-moderate aortoiliac disease and in their cases the additional information was believed to be important in therapeutic decision making. Patients with severe ulcerative disease, peripheral thromboembolism, and significant aortic aneurysms were excluded. Pressure gradients out of proportion to the degree of stenosis as measured on the arteriograms were frequently found, particularly during high flow states with intraarterial injections of a vasodilator. There were two failures of catheterization and three minor complications, none embolic. We conclude that contralateral iliac artery catheterization in selected patients is both safe and generally easily performed by experienced angiographers.

Aorta, Abdominal↗
PubMed1990

Prevention of infection by ciprofloxacin in neutropenia.

Ciprofloxacin with erythromycin, each at a dose of 250 mg 12-hourly, is effective prophylaxis against Gram-negative bacteraemia in neutropenic patients. The erythromycin component may contribute little to prophylaxis and does select for erythromycin-resistant viridans streptococci which then cause bacteraemia. Ciprofloxacin prophylaxis does not prevent coagulase-negative staphylococcal bacteraemia and resistant strains are selected. Initial use of vancomycin with a ureidopenicillin in pyrexial patients is currently justified by the exclusively Gram-positive nature of breakthrough bacteraemia. In patients failing to respond to this regimen, treatment modification to include full-dose amphotericin is frequently effective. Surveillance and containment isolation of patients carrying resistant Gram-negative species is prudent to prevent the spread of such resistant bacteria in oncology/haematology units.

Ciprofloxacin↗
PubMed1990

Effects of short term administration of recombinant human growth hormone to elderly people.

We evaluated the effects of recombinant human GH (rhGH) in 16 men and women more than 60 yr of age. After 10 days of dietary equilibration and control collections, subjects were randomly assigned to receive 0.03, 0.06, or 0.12 mg/kg rhGH by daily injection for 7 days. A brisk rise in circulating somatomedin-C (insulin-like growth factor-I) occurred in all subjects, and this rise was dose dependent. rhGH produced striking changes in nitrogen retention, sodium excretion, and the parathyroid-vitamin D axis. Twenty-four-hour urinary nitrogen excretion decreased from 8.00 +/- 0.33 to 5.01 +/- 0.33 g (P less than 0.001), and sodium excretion decreased from 45.9 +/- 2.96 to 21.2 +/- 3.48 mmol/day (P less than 0.001). Serum calcium concentrations did not change, but serum inorganic phosphorus levels of 1.08 +/- 0.04 mmol/L at baseline increased significantly after rhGH treatment to 1.33 +/- 0.04 mmol/L (P less than 0.001). Increases were also observed in circulating PTH (53.2 +/- 6 vs. 39.5 +/- 4.2 ng/L; P less than 0.01) and calcitriol (82.8 vs. 65.8 pmol/L; P less than 0.05). A rise in serum osteocalcin (10.3 +/- .86 vs. 8.0 +/- 0.5 micrograms/L; P less than 0.05) was accompanied by increased urinary excretion of hydroxyproline (628 +/- 63 vs. 406 +/- 44 mumol/day; P less than 0.01). Despite the reduction in sodium excretion, marked increases were observed in urinary calcium (6.04 +/- 0.97 vs. 3.27 +/- 0.40 mmol/day; P less than 0.01). rhGH significantly impaired oral glucose tolerance and reduced insulin sensitivity, but was otherwise well tolerated and produced no systematic changes in weight or blood pressure. The results of this study indicate that rhGH requires further study as a potential agent for attenuating or reversing the loss of muscle and bone in elderly people.

Age Factors↗
PubMed1990

Decreased bone density in adolescent girls with anorexia nervosa.

Osteoporosis develops in women with chronic anorexia nervosa. To determine whether bone mass is reduced in younger patients as well, bone density was studied in a group of adolescent patients with anorexia nervosa. With single- and dual-photon absorptiometry, a comparison was made of bone mineral density of midradius, lumbar spine, and whole body in 18 girls (12 to 20 years of age) with anorexia nervosa and 25 healthy control subjects of comparable age. Patients had significantly lower lumbar vertebral bone density than did control subjects (0.830 +/- 0.140 vs 1.054 +/- 0.139 g/cm2) and significantly lower whole body bone mass (0.700 +/- 0.130 vs 0.955 +/- 0.130 g/cm2). Midradius bone density was not significantly reduced. Of 18 patients, 12 had bone density greater than 2 standard deviations less than normal values for age. The diagnosis of anorexia nervosa had been made less than 1 year earlier for half of these girls. Body mass index correlated significantly with bone mass in girls who were not anorexic (P less than .05, .005, and .0001 for lumbar, radius, and whole body, respectively). Bone mineral correlated significantly with body mass index in patients with anorexia nervosa as well. In addition, age at onset and duration of anorexia nervosa, but not calcium intake, activity level, or duration of amenorrhea correlated significantly with bone mineral density. It was concluded that important deficits of bone mass occur as a frequent and often early complication of anorexia nervosa in adolescence. Whole body is considerably more sensitive than midradius bone density as a measure of cortical bone loss in this illness.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1989

Comparison of Doppler indexes of left ventricular diastolic function with simultaneous high fidelity left atrial and ventricular pressures in idiopathic dilated cardiomyopathy.

Doppler echocardiographic indexes of ventricular inflow have been used clinically to characterize left ventricular (LV) diastolic function. The reliability of these indexes as markers for intrinsic myocardial diastolic properties has been questioned. Micro-manometer left atrial (LA) and LV pressures as well as transmitral Doppler flow velocity signals and M-mode and 2-dimensional echocardiograms were simultaneously recorded. These unique measurements were acquired in patients with dilated cardiomyopathy under baseline conditions and during infusion of high dose amrinone. The response to amrinone was chosen as a hemodynamic model because this drug has previously been described as having beneficial effects on overall LV systolic and diastolic performance. At peak amrinone effect, LV contractility increased (as assessed using load independent end-systolic indexes) and early diastolic relaxation improved whereas passive chamber stiffness, heart rate and stroke volume were unchanged. There was a significant decrease in LV end-diastolic pressure as well as a parallel downward shift of the entire LV diastolic pressure-dimension relation. These findings, which indicated an improvement in overall LV diastolic properties, probably represent the combination of more rapid early diastolic relaxation in conjunction with a reduction in venous return, the relief of pericardial restraint or the reduction in right ventricular-LV interaction. In contrast, the ratios of Doppler-determined peak transmitral early-to-late flow velocities and early-to-late diastolic flow velocity integrals decreased with amrinone infusion, thereby suggesting a drug-induced decrease in LV diastolic compliance. Thus, in patients with idiopathic dilated cardiomyopathy, administration of amrinone has a complex effect on LV diastolic properties.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Understanding and preventing osteoporosis.

Although age-related bone loss due to remodeling is basically a normal, predictable phenomenon, it is one that may be accelerated, at times quite dramatically, by dietary factors, hormonal insufficiency, or lack of exercise. Recent data regarding the long-term prophylactic efficacy of calcium supplementation, estrogen replacement therapy, and exercise are evaluated.

Adolescent↗
PubMed1989

Relationship of body composition, muscle strength, and aerobic capacity to bone mineral density in older men and women.

We evaluated the relationship of body composition, maximal aerobic capacity (VO2max), and muscle strength to bone mineral density in 91 healthy men and women, age 61-84 years. Lean body mass was estimated from two independent measures of fat mass, bioelectrical impedance and skinfold thickness. VO2max was determined by treadmill ergometry with direct measurement of oxygen consumption. Grip and back strength were measured by isometric dynamometry. Mineral density of lumbar spine and midradius were measured by dual- and single-photon absorptiometry. Men had significantly greater lean mass, muscle strength, aerobic capacity, and bone density than women. In women, grip strength correlated with forearm and spine density (r = 0.37, r = 0.28, p less than 0.05). In men, grip strength correlated with forearm density (r = 0.47, p less than 0.05), and back strength was significantly correlated with both spine (r = 0.46, p less than 0.01) and forearm density (r = 0.46, p less than 0.01). In women, neither forearm nor spine density correlated significantly with aerobic capacity. In men, midradius density did not correlate significantly with oxygen consumption, but the simple correlation between spine density and VO2max was significant (r = 0.41, p less than 0.05). Back strength and VO2max were significantly related in men (r = 0.47, p less than 0.01). By stepwise multiple regression, back strength emerged as the most robust predictor of spine mineral, accounting for 19% of the variation in bone density. Addition of VO2max to the regression did not add significant predictive value. However, when VO2max was expressed per kilogram lean body mass, both back strength and VO2max contributed significantly to the prediction of spine density in men, and the coefficient of determination R2 increased to 0.30. We conclude that body mass and grip strength, but not aerobic capacity, significantly predict bone density in elderly women. In elderly men, back strength is a more robust predictor of axial bone density than traditional expressions of aerobic capacity, but VO2max per kilogram lean mass and back strength both make significant contributions to the prediction of spine mineral density. The applicability of these results to younger men and women is uncertain.

Aged↗
PubMed1989

Identification of mononuclear cells and T cell subsets in rheumatic valvulitis.

The composition of the mononuclear cellular filtrates was investigated in 13 valve specimens from nine patients with rheumatic carditis, some of whom had clinical and laboratory evidence of acute disease at the time of surgery. In acute valvulitis (AV) as well as in chronic active valvulitis (CAV), the cellular infiltrates were primarily composed of T cells and macrophages. In AV the majority of these T cells were of the helper phenotype (Leu 3a). The T cells subsets were more heterogeneous in CAV. In five valves, the helper T cells exceeded the number of suppressor T cells, whereas in three others, helper and cytotoxic/suppressor T cells were present in equal numbers. The HLA-DR antigen was expressed by the majority of the mononuclear cells and by the vascular endothelium. These findings indicate that the valvular injury may at least in part be mediated by delayed-type hypersensitivity mechanisms. Those cells comprising the Aschoff body were primarily positive for the HLA-DR and a novel monoclonal antibody called D8/17 which identifies an antigen known to be present on the B cells of rheumatic fever patients.

Adolescent↗
PubMed1989

Rapid production of ulcerative disease of the colon in newly-weaned guinea-pigs by degraded carrageenan.

In a dose-response study, degraded carrageenan (Eucheuma spinosum) was supplied in the drinking fluid at 1.2 and 3% concentrations over two weeks to young adult guinea-pigs. Ulceration of the large bowel was produced in 100% of animals, the severity and extent of damage probably being dose-related. In a time-course study, 3% degraded carrageenan solution supplied to newly-weaned guinea-pigs produced in 100% of animals ulceration in the caecum by four days and in the ascending colon by seven days. The onset of ulceration occurred as early as the second day. This model is convenient and economic for the screening of drugs of potential therapeutic value in human ulcerative colitis.

Animals↗
PubMed1989

Effects of estrogen on circulating "free" and total 1,25-dihydroxyvitamin D and on the parathyroid-vitamin D axis in postmenopausal women.

We evaluated the effect of estrogens on "free" and total calcitriol levels and on the calcitriol response to a hypocalcemic challenge in 12 postmenopausal women, age 55-74 yr. Endogenous calcitriol production was induced by intravenous Na-EDTA before and after conjugated estrogens, 1.25 mg/d for 30 d. Free calcitriol was determined by centrifugal ultrafiltration and by the molar ratio of calcitriol to vitamin D-binding protein (DBP). Estrogen increased fasting total calcitriol from 38.5 +/- 3.8 to 62.3 +/- 7.0 pg/ml (P less than 0.05). This was accompanied by a rise in free calcitriol from 104.5 +/- 11.4 to 158.7 +/- 16.4 fg/ml (P less than 0.05). Vitamin D-binding protein increased from 348 +/- 16 to 428 +/- 12 micrograms/ml (P less than 0.001), and the ratio of calcitriol/DBP increased from 1.50 +/- 0.14 to 1.94 +/- 0.18 (P less than 0.005), confirming the rise in free calcitriol. Increases in free calcitriol and in calcitriol/DBP ratios were significantly correlated, r = 0.72. Hypocalcemia led to a rapid increase in circulating immunoreactive parathyroid hormone, and to a rise in calcitriol at 24 h. The hypocalcemia-induced rise in total and free calcitriol was similar before and after estrogen, whether expressed as increments or as percent changes. We conclude that estrogen increases circulating levels of biologically active free calcitriol in postmenopausal women, but that a 30-d period of estrogen administration does not apparently improve the renal 1 alpha-hydroxylase response to a PTH challenge.

Aged↗