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Biomedical subjects

A Oren

Publications and source records attributed to A Oren.

At least 91 records · Page 5Linked to original sources
PubMed1986

Obstructive airway disease as a risk factor for asbestos-associated malignancy.

A case-control study of a heavily asbestos-exposed group was performed to determine if obstructive airway disorder is an independent risk factor for developing asbestos-associated malignancies. From a group of 1,500 asbestos workers who had previously undergone careful evaluation, 18 case employees were identified. Each case employee was matched by smoking status, pack-years, age, and years of asbestos exposure to a single referent, a member of the same exposed population known to be free of malignancy. The spirometry results, obtained prior to the clinical manifestation of the cancer, were compared. The FEV1/FVC ratio and the FEV1/height3 ratio were lower (P less than .05, P less than .10, respectively) in the case employees. These results suggest that obstructive airway disease may be an independent risk factor for cancer.

Adult↗
PubMed1985

Crossover comparison of captopril and propranolol as step 2 agents in hypertension.

The efficacy of captopril treatment was compared with that of propranolol in a single-blind crossover study in 14 patients with essential hypertension uncontrolled on diuretic alone. Both captopril (37.5 to 75 mg daily) and propranolol (60 to 120 mg daily), in combination with hydrochlorothiazide (50 mg daily), caused a significant fall in sitting systolic and diastolic blood pressure. Heart rate, plasma renin activity, and plasma aldosterone data were consistent with the effects of converting enzyme inhibition or beta blockade. Both drugs were well tolerated. Captopril appeared to be equivalent in efficacy and safety to propranolol when added to hydrochlorothiazide. It may be considered as an alternative step 2 antihypertensive agent, especially in patients experiencing unwanted effects on beta blockers.

Adult↗
PubMed1985

Estimation of gastric residence time of the Heidelberg capsule in humans: effect of varying food composition.

In animal and human studies, the gastric emptying of large (greater than 1 mm) indigestible solids is due to the activity of the interdigestive migrating myoelectric complex. The gastric residence time (GRT) of an orally administered, nondigestible, pH-sensitive, radiotelemetric device (Heidelberg capsule) was evaluated in three studies in healthy volunteers. In 6 subjects, the GRT of the Heidelberg capsule was compared with the half-emptying time (t1/2) of diethylenetriaminepentaacetic acid labeled with technetium 99m after a 4-ml/kg liquid fatty meal. The mean (+/-SD) GRT (4.3 +/- 1.4 h) was significantly (p less than 0.001) longer than the mean t1/2 (1.1 +/- 0.3 h); the GRT was prolonged compared with the t1/2 in each subject. In a randomized, crossover trial in 10 subjects, frequent feeding caused a dramatic prolongation in mean GRT of the capsule compared with the fasting state (greater than 14.5 vs. 0.5 h, p less than 0.005). In another crossover study in 6 subjects, the GRT of the capsule was evaluated after an overnight fast, a standard breakfast including solid food, and a liquid meal (i.e., 200 ml of diluted light cream). The mean GRT was 2.6 +/- 0.9 h after the liquid meal vs. 1.2 +/- 0.8 h after fasting (p less than 0.025). The mean GRT after the breakfast was 4.8 +/- 1.5 h, which was significantly greater than that after fasting (p less than 0.001) and after the liquid meal (p less than 0.01). These data suggest that the GRT of the Heidelberg capsule is a marker of the interdigestive migrating myoelectric complex in humans, the interdigestive migrating myoelectric complex can be markedly delayed by frequent feedings with solids, and the interdigestive migrating myoelectric complex is delayed by both liquid and solid meals.

Adult↗
PubMed1985

Lung function and exercise performance in smoking and nonsmoking asbestos-exposed workers.

Evaluation of impairment caused by exposure to an occupational toxin can be complicated by additional exposure to other injurious agents. Because cigarette smoking is common and cigarettes are implicated in obstructive lung disease and cardiovascular diseases, we assessed the contribution of smoking to functional abnormalities in a group of asbestos-exposed shipyard workers. Seventy-three workers who never smoked were paired with 73 current smokers by age and asbestos exposure. Pulmonary function and performance during cycle incremental exercise were compared between the 2 groups. Nonsmokers had significantly higher VC, FEV1, FEV1/VC, and diffusing capacity for carbon monoxide than did smokers. Only 3 of the 73 nonsmokers but 23 of the 73 smokers had a FEV1/VC below the 95% confidence limit of predicted value. The FEF25-75%, on the other hand, failed to identify additional subjects with obstruction not found by the FEV1/VC. During exercise, despite no difference in maximal heart rate, the maximal O2 uptake (VO2max) and oxygen-pulse were lower among smokers. In addition, smokers more frequently had abnormal AaPO2 at maximal exercise. Of 33 smokers who had a VO2max less than 80% of predicted, 16 were judged to have cardiac disease, whereas only 2 appeared to be limited by obstruction. Only 15 of the 73 nonsmokers had a VO2max less than 80%. We conclude that cigarette smoking was the major contributing factor to the obstructive lung disease observed in asbestos workers, and it also had a strong influence on the occurrence, nature, and magnitude of exercise limitation. The history of cigarette smoking has an important effect on the assessment of impairment from asbestos.

Aged↗
PubMed1984

Calcium oxalate kidney stones in patients on continuous ambulatory peritoneal dialysis.

Kidney stones were passed by ten out of 186 patients with endstage renal disease who were treated with continuous ambulatory peritoneal dialysis (CAPD). Stones from seven patients were examined by x-ray diffraction. In five of them the stones were composed of calcium oxalate monohydrate. The urine calcium oxalate activity product was determined in 44 CAPD patients, eight of whom were stone formers, and compared to that of 120 normal volunteers. In CAPD patients, mean urine ionic-calcium concentration was lower than in normal subjects whereas mean urine ionic-oxalate concentration was significantly higher than in normal subjects. In normal urine samples, the calcium oxalate activity product showed a significant correlation with both the urine ionic-calcium and the ionic-oxalate concentrations. In contrast, in CAPD patients the calcium oxalate activity product correlated with the ionic-calcium concentration but not with ionic-oxalate. Although the urine ionic-calcium concentration is lower in CAPD patients than in normal subjects, it is the relative increase in its concentration which appears to be associated with the increased risk of kidney stone formation in these patients. This relative hypercalciuria seems to follow 1,25(OH)2 vitamin D3 administration.

Calcitriol↗
PubMed1983

Contrasting cardiovascular and respiratory responses to exercise in mitral valve and chronic obstructive pulmonary diseases.

The role of cardiovascular and pulmonary limitation in performing maximal exercise is contrasted in patients with mitral valve disease (MVD) and chronic obstructive pulmonary disease (COPD). The ventilatory (VE) gas exchange (VO2 and VCO2) and heart rate (HR) responses to an incremental cycle ergometer exercise were measured in six patients with MVD, seven patients with COPD, and six normal subjects. The VE requirement for the work (VE-VO2 relationship) was increased in both COPD and MVD groups compared with control subjects, but the breathing reserve was significantly lower in COPD (13 percent) compared with MVD (49 percent) and control groups (44 percent). In contrast, the VO2 at the anaerobic threshold was significantly lower in MVD (12.2 +/- .5 ml/kg) compared with COPD (15.7 +/- 1.2 ml/kg) and control subjects (16.6 +/- .9 ml/kg). Also, the heart rate reserve and the VO2-HR slope were significantly reduced in MVD (9 +/- 6 percent and 6.9 +/- 1.0 ml/min/beat, respectively) compared with COPD patients (44 +/- 7 percent and 2.0 ml/min/beat, respectively). Both patient groups experienced an acidosis in their terminal work rate, but the acidosis was primarily respiratory in the COPD and totally metabolic in the MVD group. These studies indicate that at maximal work rate, MVD but not COPD patients, manifest compromised O2 delivery to the muscles, while COPD but not MVD patients were unable to increase VE sufficiently to match the exercise-induced CO2 production.

Acid-Base Equilibrium↗
PubMed1982

Renal involvement following near-drowning in the sea.

1. The metabolic changes in rats following introduction of sea water directly into the stomach were studied. The results were compared with those of a human case report of acute renal failure following swallowing of sea water. 2. In both rats and man, acute renal failure appeared within the first 24 hr. A slight improvement was found five days later. 3. There was an acute hypocalcemia. This was supposedly due to the large magnesium content of the sea water. 4. It is probable that water entering the alimentary canal, dry drowning, affects the kidneys by the initial flow of water to the intestines. This results in hemo-concentration and reduced kidney function. The abnormality is a transient one and could be due to a partial anoxia due to shrinking of the erythrocytes. 5. It is concluded that an apparently uneventful swallowing of sea water can turn into secondary drowning with transient acute renal failure.

Animals↗
PubMed1982

Cardiac output increase and gas exchange at start of exercise.

To determine the rapidity of increased gas exchange resulting from increased cardiac output (Q) following exercise onset, subjects performed multiple rest-exercise transitions on a cycle ergometer: the early dynamics of pulmonary gas exchange were measured during 1) rhythmic breathing with ventilation kept constant at the resting level (controlled ventilation) and 2) prolonged constant airflow exhalation. With controlled ventilation, PACO2 increased and PAO2 decreased, typically beginning in the first exercise breath. After 15 s, PACO2 had increased and PAO2 decreased by 4.5-6.2 and 8.7-12.1 Torr, respectively, graded within these narrow ranges as functions of work rate (0-100 W). Exercise starting during a prolonged exhalation caused the slopes of the alveolar phases for O2 and CO2 to increase immediately or within 2-5 s following exercise onset. Work rate had little effect on the delay or the change of alveolar gas tension slope during the subsequent 10-15 s. Thus, increased gas exchange due to increasing Q occurred very rapidly following exercise onset so that it would coincide with the first or second breath of exercise in free-breathing subjects.

Adult↗
PubMed1982

Effect of acid-base status on the kinetics of the ventilatory response to moderate exercise.

To determine the influence of altered carotid body drive on exercise ventilatory kinetics, five subjects performed four repetitions of constant-load cycle ergometer exercise during air and O2 breathing under each of the following conditions: 1) metabolic acidosis, (NH4Cl, 0.3 g . kg-1 . day-1); 2) metabolic alkalosis (NaHCO3, 0.7 g . kg-1 . day-1); and 3) control (CaCO3, 0.1 g . kg-1 . day-1). Ventilatory and gas exchange variables were computed, breath-by-breath, and the time constant of the ventilatory response in each condition was determined by a least-squares technique. While breathing air, metabolic acidosis caused the magnitude of the ventilatory response to increase and the time constant of the ventilatory kinetics to decrease. With metabolic alkalosis the increase in ventilation caused by exercise tended to be smaller and time constant larger although these changes were not statistically significant. Hyperoxia slowed the ventilatory response in the three acid-base conditions to a similar value. Thus hyperoxia slowed the ventilatory kinetics to a greater degree during acidosis than during control or alkalosis. We conclude that ventilatory dynamics during moderate exercise can be appreciably influenced by the acid-base status with acidosis significantly speeding the response dynamics. And, as these effects are abolished by hyperoxia, they appear to be mediated via the carotid bodies, in the human.

Acid-Base Equilibrium↗
PubMed1981

Effect of CO2 set point on ventilatory response to exercise.

The ventilatory response to exercise was determined in seven normal adults during induced chronic metabolic acidosis, chronic metabolic alkalosis, and a control state. Incremental and constant-load exercise tests were performed in each condition on a cycle ergometer. Ventilation and gas exchange variables were determined breath by breath, and CO2 partial pressure (PCO2), pH, and HCO3 were determined from arterialized venous blood (Pa-VCO2). During chronic metabolic acidosis PaVCO2 was lower than control (36.3 +/- 2.1 and 43.7 +/- 2.9 Torr, respectively) and during alkalosis it was elevated to 47.1 +/- 1.3 Torr. The new PCO2 levels caused by chronic acid-base alterations were unchanged during moderate exercise. The ventilatory response (VE) to the same metabolic rate increment was therefore larger (delta VE = 20.6 +/- 2.91/min) when PCO2 was lower than the control level (delta VE = 14.5 +/- 2.01/min. VE also increased more steeply in response to incremental exercise tests when PCO2 was reduced. Thus the hyperpnea of moderate exercise reflects the level at which arterial PCO2 is regulated at rest, as well as the metabolic load (VCO2).

Acidosis↗
PubMed1979

Sulfide inhibition of photosystem II in cyanobacteria (blue-green algae) and tobacco chloroplasts.

The present study shows that in the presence of 600 nm light, sulfide acts as a specific inhibitor of photosynthetic electron transport between water and Photosystem II in the cyanobacteria Aphanothece halophytica and Synechococcus 6311 as well as in tobacco chloroplasts. In the presence of 600 nm light sulfied affects the fast fluorescence transients as does a low concentration (10 mM) of hydroxylamine; the fluorescence yield decreases in the presence of either chemical and can be restored by the addition of 3-(3,4-dichlorophenyl)-1,1-dimethylurea. In chloroplasts, however, NH2OH, an electron donor at high concentrations (40 mM), relieves the sulfide effect. In the dark, sulfide affects the cyanobacterial fluorescence transients through decrease of oxygen tension. The fluorescence yield increases in a similar pattern to that observed under nitrogen flushing. Upon omission of sulfide in A. halophytica, the characteristic aerobic fluorescence transients return, consistent with the ease of alternation between oxygenic and sulfide-dependent anoxygenic photosynthesis in many cyanobacteria.

Aerobiosis↗
PubMed1979

Cat-scratch disease presenting as status epilepticus. A case report.

A 12-year-old Bedouin boy presented with sudden asymmetrical status epilepticus. The presence of a scalp wound, rubbery cervical lymphadenopathy and a history of contact with cats suggested the diagnosis of cat-scratch disease complicated by encephalopathy. The diagnosis was supported by histological examination of a cervical lymph node and a positive skin test with cat-scratch antigen. The rapid establishment of the diagnosis avoided the necessity of elaborate and complicated neuroradiological investigations.

Cat-Scratch Disease↗