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Biomedical subjects

R J Barnard

Publications and source records attributed to R J Barnard.

At least 127 records · Page 7Linked to original sources
PubMed1981

Symptomatic renal angiomyolipoma.

Two cases of symptomatic renal angiomyolipoma not associated with tuberous sclerosis are presented. The clinical and radiological features, the pathology and the management of these rare but well documented tumours are briefly discussed. They pose problems in diagnosis and controversy still exists regarding their management. Recent radiological techniques such as CT may help in the diagnosis. When conservative surgery is not possible, or when an adenocarcinoma cannot be confidently excluded, nephrectomy should be performed.

Adult↗
PubMed1981

Influence of exercise on excitation-contraction coupling in rat myocardium.

The present studies were conducted to investigate further the mechanisms by which the myocardium adapts to exercise training. Sixty female rats were randomly divided into sedentary control (group C) and trained (group T) groups. Group T was progressively trained for 12 wk. After the rats were killed, left ventricular papillary muscles were mounted in a tissue bath for mechanical studies. Muscles from group T generated greater peak isometric twitch tension per unit cross-sectional area than muscles from group C with [Ca2+]o ranging from 0.25 to 3.5 mM. Analyses of these data indicated that the Km for Ca2+ was not different but that the predicted number of sarcolemmal Ca2+ binding sites was 63% higher in group T. The ATPase activity of the purified cardiac myofibrils was not different between the two groups in the pCa range of 8.53-4.42. Action potentials were recorded with microelectrodes impaled into left ventricular muscle fibers of the subendocardium. Although there was no difference in the resting membrane potential, overshoot, or 90% duration, there was a significant prolongation of the action potential at 0 mV (20.2 +/- 1.0 vs 30.0 +/- 1.3 ms) in group T. These data further support the hypothesis that treadmill exercise enhances cardiac performance by increasing Ca2+ availability to the contractile element. This adaptation is mediated, at least in part, by a sarcolemmal adaptation induced by the exercise paradigm.

Action Potentials↗
PubMed1981

Effect of exhaustive exercise on myocardial performance.

Several investigators have reported ultrastructural changes in hearts of animals exercised to exhaustion. The present study was designed to determine whether functional changes occur in the intact heart at exhaustion. Adult mongrel dogs (n = 8) were chronically instrumented to measure cardiac output, coronary blood flow, aortic blood pressure, left ventricular pressure, +dP/dtmax, and -dP/dtmax. After recovery, the dogs were run to exhaustion at a constant work load, eliciting approximately 70% of maximum heart rate. The exhaustive bouts were terminated when the animals either refused or were unable to continue running, at which time their rectal temperatures approaches 42.2 degree C. The mean exhaustion time was 76.7 +/- 11.8 min. All parameters increased from rest to steady state with the exception of stroke volume (23.2 +/- 4.9 vs. 20.5 +/- 1.6 ml), which remained constant. In the transition from steady state to exhaustion, only +dP/dtmax (6,652 +/- 291 vs. 7,689 +/- 479 Torr/s) and -dP/dtmax (4,110 +/- 227 vs. 4,890 +/- 215 Torr/s) increased significantly; all other values exhibited no significant change. Similarly, when maximum cardiovascular parameters were measured before and after exhaustion, no significant changes were found. These data show that cardiac contractile function is not depressed in dogs as a result of exhaustive exercise.

Animals↗
PubMed1981

Elevation of hemoglobin and work tolerance in iron-deficient subjects.

Selected parameters related to work tolerance were measured in 31 adult subjects with hemoglobin (Hb) concentration from 2.5 to 14.0 g/100 ml. Work tolerance was closely related to Hb concentration (r = 0.74) regardless of the adequacy of storage iron level. One male and six females with a mean Hb of 3.5 g/ml (27-55 years old) were studied before and 24h after transfusing 570ml of whole blood. The mean maximal work load tolerated increased 83% within 24h after transfusion in these seven subjects. Post-exercise venous blood lactate was markedly lower after transfusion. Work tolerance of these subjects within 24h after transfusion was the same as in other subjects who had had the equivalent Hb level as the post-transfusion subjects presumably for at least several weeks. These data suggest that the decrement in work performance capacity in iron-deficient and anemic subjects is, in a large part, a reflection of the level of anemia rather than other non-Hb related biochemical changes that could accompany prolonged iron deficiency anemia.

Adult↗
PubMed1981

A clinical and morphological evaluation of the trabeculated urinary bladder.

In a group of 28 patients the microscopic appearance of bladder biopsy samples has been correlated with a careful clinical assessment of each case. This assessment consisted of a detailed history and clinical examination including cystoscopy and urodynamic investigation using videocystourethrography. The results have shown that, in the presence of outflow obstruction, an association exists between the severity of trabeculation observed endoscopically and the degree of histological change in the bladder wall (involving infiltration of detrusor muscle bundles by connective tissue). In patients with no apparent outflow obstruction mild or moderate trabeculation as assessed cystoscopically was not accompanied by structural alterations in the bladder wall.

Female↗
PubMed1980

Effects of intensive exercise training on myocardial performance and coronary blood flow.

Five instrumented and eight noninstrumented dogs were progressively trained for 12-18 wk on a motor-driven treadmill. Data were compared with 14 instrumented and 8 noninstrumented control dogs. Gastrocnemius malate dehydrogenase activity was significantly increased in the trained dogs (887 +/- 75 vs. 667 +/- 68 mumol . g-1 . min-1). The trained dogs also showed significant increases in maximum work capacity, cardiac output (7.1 +/- 0.5 vs. 9.1 +/- 0.7 1/min), stroke volume (25.9 +/- 2.0 vs. 32.0 +/- 2.0 ml/beat), and left ventricular (LV) positive dP/dtmax (9,242 +/- 405 vs. 11,125 +/- 550 Torr/s). Negative dP/dtmax was not significantly different. Peak LV systolic pressure increased with exercise, but there was no significant difference between the trained and control dogs. LV end-diastolic pressure did not change with exercise and was the same in both groups. Tension-time index was lower in the trained dogs at rest and submaximum exercise (9.7 km/h, 10%) but was not different at maximum exercise. Diastolic pressure-time index was significantly higher in the trained dogs at rest and during submaximum exercise but was not different at maximum exercise. LV coronary blood flow was significantly reduced at rest (84 +/- 4 vs. 67 +/- 6 mo . min-1 . 100 g-1) and during submaximum exercise (288 +/- 24 vs. 252 +/- 8 ml . min-1 . 100 g-1). During maximum exercise flow was not significantly different (401 +/- 22 vs. 432 +/- 11 ml . min-1 . 100 g-1) between the control and trained groups. The maximum potential for subendocardial flow was unchanged with training despite the development of mild hypertrophy.

Animals↗
PubMed1979

Work capacity, heart rate and blood lactate responses to iron treatment.

Changes in haemoglobin (Hb), work performance, heart rate and postexercise blood lactate were studied in iron deficient, anaemic subjects for 16 d following total dosage infusion of iron dextran, i.v. (30-50 ml). Six adult men and 14 women were subjects with initial Hb levels of 6.6 +/- 0.6 g/dl (mean +/- SEM) for the iron treatment group (n=10) and 8.0 +/- 0.7 for the placebo group (saline infusion, n=10). Serum levels were 0.51 +/- 0.15 and 0.67 +/- 0.12 mg/l for the two groups, respectively. Haemoglobin and maximal work time increased significantly within 4 d after iron treatment and continued to increase up to 16 d. No changes were found in the placebo subjects. Heart rates at a given exercise intensity were lower in the iron treatment group than in control subjects who had the same Hb levels but had not been treated with iron. Post-exercise venous blood lactate was similar on succeeding days after iron treatment even though the subjects reached higher work loads. These results demonstrate the treatment of iron deficient, anaemic subjects with iron dextran results in improved work capacity within 4 d and a lower heart rate at a given work load after treatment which cannot be accounted for totally by the elevation of Hb concentration.

Adult↗
PubMed1979

Diuresis renography and the results of pyeloplasty for idiopathic hydronephrosis.

Eighty-six kidneys in 82 patients have been assessed by diuresis renography after pyeloplasty. A non-obstructed diuresis renogram was found in 64% of kidneys. Ninety per cent of patients were clinically improved by surgery and 51% of cases studied had improved urographic features. Thirty kidneys (29 patients) were assessed both before and after pyeloplasty. An improvement in the diuresis renogram was found in 89% of cases postoperatively. Standard renography demonstrated improved drainage in only 33% of kidneys. These findings are discussed in relation to the value of diuresis renography after pyeloplasty.

Adolescent↗
PubMed1979

Physiological characteristics of sprint and endurance Masters runners.

Data were obtained from 13 sprint (age range 41-58) and 13 distance (age range 4-78) Masters track athletes. The mean VO2max value for the distance runners was 54.4 +/- 3 ml kg min compared with 47.2 +/- 2 ml kg min for the sprinters. The highest VO2max (71.0 ml kg min) was obtained on a 45-year-old distance runner while the lowest (27.3 ml kg min) was obtained on the oldest (78 years) distance runner. VO2max decreased by 34.5% from age 40 to 70 in the distance runner in spite of continued training that ranged from 40 to 120 miles/week. Maximum ventilation rates were 122.5 +/- 6.8 and 116.8 +/- 7.0 1 min for the sprint and distance runners, respectively. Percentage of body fat was 16.5 +/- 0.5 for the sprinters and 18.0 +/- 1.1 for the distance runners. Serum cholesterol values were 218.7 +/- 8.7 and 203.0 +/- 13.8 ml/dl, while triglyceride values were 101.5 +/- 8.2 and 84.1 +/- 9.3 mg/dl for the sprint and distance groups, respectively. These data indicate that, VO2max decreases significantly with aging despite the continuation of long distance training. Percent body fat and serum lipid levels were significantly lower in these athletes compared to those for sedentary adults, suggesting a protective effect against coronary heart disease. Only one subject had S-T segment depression during the exercise test.

Adult↗
PubMed1978

Adaptation of the rat myocardium to endurance training.

The purpose of this study was to assess cardiac adaptation to endurance training in rats. After 11 wk of progressive treadmill exercise (1 h/day), gastrocnemius cytochrome c oxidase activity was 38% higher (P less than 0.01) in the trained (n = 20) as compared to control (n = 20) rats. Cardiac Mg2+-stimulated myofibril ATPase activity (0.308 +/- 0.012 vs. 0.324 +/- 0.006 micrometer.mg-1.min-1) did not change nor was there any change in myofibril protein concentration (60.0 +/- 1.12 vs. 59.9 +/- 0.85 mg.g-1). The isolated left ventricular papillary muscle showed no significant change in time-to-peak tension (TPT) or half-relaxation time. Tension output, however, was significantly increased with training, 2.2 +/- 0.3 vs. 1.5 +/- 0.1 g.mm-2 (P less than 0.025). Furthermore, when the papillary preparations were perfused with 0.5 mM lanthanum (La3+) to displace membrane-bound Ca2+, the time course for tension decay was significantly prolonged in the trained muscles (P less than 0.001). We conclude that endurance running of this type does not necessarily increase myofibril ATPase activity or the time course of the isometric twitch of rat papillary muscle. However, tension output per unit area does increase and this appears to be due to a greater amount of Ca2+ being made available to the contractile apparatus.

Adaptation, Physiological↗
PubMed1978

Optimizing myocardial supply/demand balance with alpha-adrenergic drugs during cardiopulmonary resuscitation.

In 14 dogs the determinants of myocardial blood supply and metabolic demands were assessed during cardiopulmonary resuscitation (CPR) and under steady-state conditions in fibrillating hearts on cardiopulmonary bypass. During open chest cardiac massage (nine dogs), coronary diastolic blood pressure and blood flow were low. Vasopressor infusion (methoxamine or epinephrine) raised diastolic pressure from 33 +/- 3 to 55 +/- 3 mm. Hg and increased coronary blood flow (CBF) 124 percent (from 38 +/- 3 to 85 +/- 11 c.c. per 100 Gm. per minute. Comparison of these drugs in fibrillating hearts on cardiopulmonary bypass showed that epinephrine increased the "vigor of fibrillation" (intraventricular balloon pressure rose 24 percent and oxygen uptake increased 42%) but impeded subendocardial flow 53% (endocardial/epicardial flow ratio fell from 0.79 to 0.48). In contrast, methoxamine did not significantly change intraventricular balloon pressure, oxygen uptake, coronary flow, or its distribution. We conclude that augmentation of diastolic pressure with alpha adrenergic drugs during CPR improves coronary perfusion and that inotropic drugs may worsen myocardial ischemia during CPR by raising oxygen demands while simultaneously impeding subendocardial blood supply.

Animals↗
PubMed1977

Sexually dimorphic effects of forced exercise on food intake and body weight in the rat.

The food intake (FI), body weight (BWt) and water intake (WI) of adult male and female rats were compared during a seven day period of forced exercise in a treadmill. Work loads for the exercised groups were gradually increased across the seven-day test period, whereas work loads for the sedentary controls were maintained at the same level used during a previous three-day training period. Relative to their respective control groups, male rats showed a decrease in FI and BWt in response to the exercise challenge, but female rats showed an increase in FI sufficient to maintain their BWt at control levels. Both male and female rats showed a reliable increase in WI during the period of forced exercise. These sexually dimorphic changes in FI and BWt in response to forced exercise indicate that female rats are capable of demonstrating a more vigorous defense of BWt than are male rats and suggest that there is a sex difference in the long-term control of feeding behavior in the rat.

Animals↗