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Biomedical subjects

William W Stringer

Publications and source records attributed to William W Stringer.

8 recordsLinked to original sources
PubMed2005

A matched comparison of serum lipids between hemodialysis patients and nondialysis morbid controls.

The high incidence of cardiac and vascular disease in maintenance hemodialysis (MHD) patients has heightened interest in many investigations concerning the serum lipid levels of these patients. The prevalence and laboratory characteristics of serum lipid concentrations in MHD patients, however, are far from clear. We hypothesized that serum lipids are significantly lower in MHD patients compared to their matched nondialysis counterparts. We compared 2-year averaged serum levels of total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoproteins (HDL), and triglycerides in 285 MHD patients to the same averaged measurements during the same period of time in 285 nondialyzed outpatients from the same geographic area, whose lipid panels were measured in the same laboratory. Matching factors were sex, race and/or ethnicity, diabetes mellitus, and age (+/- 5 years). The MHD patients and their matched controls were 55.6 +/- 13.5 (SD) and 56.3 +/- 13.0 years old, respectively. Each group contained 51% women, 31% African Americans, 52% Hispanics, and 37% diabetics; 16% of MHD patients and 38% of controls were receiving statins. Body mass index (BMI) was significantly lower in MHD patients than in controls (26.2 vs. 31.5 kg/m2; p < 0.001). Serum cholesterol levels were significantly lower in MHD patients than in control subjects including after adjustment for BMI and statin use (TC, -51; LDL, -39; and HDL, -10 mg/dL; p < 0.001). Using conditional logistic regression for matched data and after controlling for BMI and statins, all odds ratios for predetermined hypercholesterolemic, but not hypertriglyceridemic, levels were significantly and substantially lower than 1.00, indicating much lower likelihood of hypercholesterolemia in MHD patients. Total and LDL hypercholesterolemia, although very common in nondialysis ambulatory outpatients, are substantially less prevalent in the MHD population, whereas hypertriglyceridemia is approximately equally prevalent between these populations.

Adult↗
PubMed2004

Non-linear cardiac output dynamics during ramp-incremental cycle ergometry.

Published literature asserts that cardiac output (Q(.) = V(.) >O(2)x1/C((a-v))O(2)) increases as a linear function of oxygen uptake with a slope of approximately 5-6 during constant work rate exercise. However, we have previously demonstrated that C((a-v))O(2) has a linear relationship as a function of V(.)O(2) during progressively increasing work rate incremental exercise. Therefore, we hypothesized that Q(.) may indeed have a non-linear relationship with respect to V(.)O(2) during incremental, non-steady state exercise. To investigate this hypothesis, we performed five maximal progressive work rate exercise studies in healthy human subjects. Q(.) was determined every minute during exercise using measured breath-by-breath V(.) >O(2), and arterial and pulmonary artery measurements of PO(2), hemoglobin saturation, and content. Q(.) was plotted as a function of V(.) >O(2) and the linear and non-linear (first order exponential and hyperbolic) fits determined for each subject. Tests for linearity were performed by assessing the significance of the quadratic terms added to the linear relation using least squares estimation in linear regression. Linearity was inadequate in all cases (group P<0.0001). We conclude that cardiac output is a non-linear function of V(.)O(2 )during ramp-incremental exercise; the pattern of non-linearity suggests that while the kinetics of Q(.) > are faster than those of V(.) >O(2) they progressively slow as work rate (and V(.) >O(2)) increases.

Adult↗
PubMed2004

Antibodies reactive with C-terminus of the second conserved region of HIV-1gp120 as possible prognostic marker and therapeutic agent for HIV disease.

It has been reported that antibodies reactive with peptide RSANFTDNAKTIIVQLNQSVEIN (peptide NTM) derived from the C-terminus of the second conserved domain of HIV-1 envelope glycoprotein gp120 could represent an important factor in control of the HIV disease. In order to check this notion we (i) tested reactivity with peptide NTM serum samples collected from 310 consecutive HIV-1 infected patients with a CD4(+) lymphocyte count ranging from 10 to 800/microL and (ii) performed the longitudinal study that included 107 sera samples collected from 29 HIV patients. Results of these studies demonstrated correlation between presence of anti-NTM antibodies in sera of HIV patients and disease progression measured by the CD4(+) cell count. Based on these findings we proposed the anti-NTM antibodies as useful prognostic marker for HIV disease.

Biomarkers↗
PubMed2003

Partial anomalous pulmonary venous return: case report and review of the literature.

Isolated partial anomalous pulmonary venous return (APVR) is an uncommon finding. A patient with isolated APVR had pulmonary hypertension without demonstrable left-to-right shunting prior to anticoagulant treatment of pulmonary emboli. After anticoagulant therapy, with a fall in pulmonary pressures and resistance to near-normal levels, left-to-right shunting was then detected by oximetry and angiography. The anomaly was visualized on electron beam angiography and confirmed by conventional angiography after anticoagulant therapy. Contrary to the expected obligatory drainage of highly saturated blood associated with APVR, lack of detectable shunting was thought to be due to the obstruction of regional blood due to thromboembolism.

Anticoagulants↗
PubMed2002

Training improves muscle oxidative capacity and oxygenation recovery kinetics in patients with chronic obstructive pulmonary disease.

We studied 21 patients with chronic obstructive pulmonary disease aged [mean (SD)] 63 (10) years, with a mean forced expiratory volume in 1 s of 40 (6)% and a peak oxygen uptake of 67 (11)% of predicted values. Patients trained for 6 weeks on a cycle ergometer at high work-rates (WR). Near-infrared spectroscopy was used to obtain the time-constant of the deoxygenation recovery signal (tauHbO(2)) during three constant WR exercise tests, one below and two above the lactic acidosis threshold (theta(L)). Glycolytic and oxidative enzymes and lactate concentrations were assessed in muscle biopsies. The tauHbO(2) decreased significantly in all three constant WR tests: -18 (24)s, -20 (23) s and -13 (22) s, respectively. Endurance time increased in the higher WR tests, by 5.7 (4.8) min and 3.6 (2.7) min, respectively. The activity of citrate-synthase (CS) and creatine-kinase changed significantly from 20 (10) to 30 (13) micro mol x min(-1) x g(-1)and from 3.825 (950) to 3.402 (526) micro mol x min(-1) x g(-1), respectively. Training also improved significantly the mean response time of the on-transient of oxygen uptake (tau'VO(2)) of the below-theta(L) test. We found significant correlations between changes in CS and changes in tauHbO(2), tau'VO(2) and endurance time. We conclude that leg training accelerates the speed of re-oxygenation of the vastus lateralis muscle after exercise. This improvement is correlated to changes in the oxidative enzymes.

Adaptation, Physiological↗
PubMedDate not supplied

A controlled trial of the effects of leg training on breathing pattern and dynamic hyperinflation in severe COPD.

The effects of training on dynamic hyperinflation in stable chronic obstructive pulmonary disease (COPD) were investigated by using a controlled study of 28 subjects with FEV(1) = 42.5 (8.3 SD)%pred and 20 matched controls [FEV(1) = 44.9 (10.4)%pred]. Training consisted of spending 45 min/day, 4 days/week on a cycle-ergometer for six weeks. Maximal inspiratory and expiratory pressures (MIP and MEP), lung volumes, and two constant-work-rate (CWR) exercise tests (low- and high-intensity) were performed. Significant (p < 0.0l) improvements in the training group were observed in MIP [+8 (12) cmH(2)O], MEP [+18 (20) cmH(2)O], and endurance to high-intensity CWR [+7(5) min], and there were significant decreases in respiratory rate and end-expiratory lung volume (EELV) during both exercise tests. At 5 min, EELV decreased 0.1(0.08) L and 0.31(0.13) L and at end of exercise, EELV decreased by 0.09(0.07) L and 0.15(0.11) L respectively, for the moderate- and high-intensity tests. Dyspnea also decreased significantly at both exercise intensities. No changes were observed in the control group. Increased endurance showed independent significant (p < 0.05) correlation with changes in EELV, leg fatigue, and MEP. EELV changes showed a significant negative correlation with resting inspiratory capacity. We conclude that exercise training has beneficial effects on respiratory pattern and dynamic hyperinflation that may partially explain the reduction in dyspnea and the improvement in exercise tolerance.

Aged↗