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Biomedical subjects

H Sandler

Publications and source records attributed to H Sandler.

At least 55 records · Page 3Linked to original sources
PubMed1986

Bedrest-induced peak VO2 reduction associated with age, gender, and aerobic capacity.

To compare the factors of age and gender on aerobic work capacity following bedrest-induced deconditioning, peak oxygen uptake (peak VO2), heart rate (peak HR), and exercise tolerance time were measured in 15 middle-aged men (55 +/- 2 yr) and 17 middle-aged women (55 +/- 1 yr) before and after 10 d of continuous bedrest (BR). The average body weight following BR was unchanged in both men and women. Following BR, peak VO2 decreased from 35.6 +/- 2.0 to 32.6 +/- 1.1 ml . kg-1 . min-1 (-8.4%, p less than 0.05) in the men and from 26.5 +/- 1.4 to 24.7 +/- 1.3 ml . kg-1 . min-1 (-6.8%, p less than 0.05) in the women, while total exercise tolerance time was reduced by 8.1% (p less than 0.05) and 7.3% (p less than 0.05) in the men and women, respectively. The peak HR was elevated by BR from 158 +/- 4 to 165 +/- 4 bpm (+4.4%, p less than 0.05) in the men and from 157 +/- 4 to 159 +/- 4 bpm (+1.3%, NS) in the women. The percent changes in peak VO2, peak HR, and exercise tolerance time measured in the men were not significantly different compared to those of the women. The reduction in peak VO2 in the middle-aged men and women in the present study were comparable to the reductions of 9.3% and 7.8% observed in our earlier studies with 15 young men (21 +/- 1 yr) and 8 young women (28 +/- 2 yr), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1985

Beta blockade in the compensation for bed-rest cardiovascular deconditioning: physiologic and pharmacologic observations.

Beta-adrenergic blockade using intravenous propranolol was evaluated as a countermeasure for bedrest-induced cardiovascular deconditioning. After propranolol administration, tolerance to a maximal lower body negative pressure (LBNP) test after bed rest improved to at least the -70 mm Hg level; following this, there was a sharp decrease in tolerance time. Propranolol decreased mean tolerance time by 36% (17.7 +/- 2.4 to 11.5 +/- 2.3 minutes) before bed rest, and by only half as much (16.6%) after bed rest (14.4 +/- 2.2 to 12.0 +/- 2.3 minutes). Systemic vascular resistance was maintained and even slightly increased after propranolol despite a decrease in cardiac output, indicating beta 2-adrenergic blockade. Heart rates at all levels of LBNP were lower during beta blockade, yet increases occurred with successive LBNP steps, both before and after bed rest, indicating withdrawal of parasympathetic nervous system influences. Results support the use of propranolol in small dosages as a countermeasure after bed rest, and the findings may also be extrapolated to space-flight deconditioning.

Adult↗
PubMed1985

Blockade of histamine receptors and thrombin-induced microembolic pulmonary edema in the rat.

Pulmonary edema was induced by an intravenous infusion of bovine thrombin, 500 NIH/kg b.w., given in 5 min, in rats in which fibrinolysis had been inhibited by an intraperitoneal injection of the fibrinolysis inhibitor AMCA. Ninety minutes after termination of the thrombin infusion the lung weight was increased from 1.09 +/- 0.07 to 3.14 +/- 0.12 g due to edema. A high albumin concentration in the extravascular water indicated that the edema was a consequence of increased permeability in the microcirculation. In rats injected with the H1 histamine receptor antagonist mepyramine maleate and H2 receptor antagonist cimetidine after the thrombin infusion, the lung weight was significantly lower at 90 min (2.68 +/- 0.33 g), and the amount of edema as calculated morphometrically was slightly but significantly reduced. The concentration of albumin in the extravascular water (i.e. in the edema fluid) in rats subjected to histamine receptor blockade was unchanged, indicating that the slight decrease in edema was a result of decreased filtration pressure and not of an effect on microvascular permeability.

Albumins↗
PubMed1984

Prediction of child abuse: a prospective study of feasibility.

Feasibility of identifying risk for child abuse prospectively was determined by interviewing 1400 expectant mothers and predicting that 273 were high risk. Nonaccidental child injuries were subsequently reported to authorities for 6% of these versus 1% of the remaining 1127 families. Prediction was only effective for 24 months following interview. Thus prenatal prediction was feasible although the rate of false positive high risk assignment would limit practical application of the interview we used. As a first step to improve prediction accuracy, a group of the 20 strongest predictors was selected from the interview by regression analysis. The correlation of these with abuse was .44 compared to .15 for the original interview. Important predictors included subjective impressions of interviewers, residency transience, untruthfulness, disturbed childhood nurture, unwanted pregnancy, and perhaps conditions that increased parent-child exposure.

Attitude↗
PubMed1984

VO2 kinetics of constant-load exercise following bed-rest-induced deconditioning.

The purpose of this study was to determine the effects of bed-rest-induced deconditioning on changes in O2 uptake (VO2) kinetics, O2 deficit, steady-state VO2, and recovery VO2 during the performance of constant-load exercise. Five male subjects (36-40 yr) underwent 7 days of continuous bed rest (BR) in the head-down (-6 degrees) position. Two days before (pre) and the day after (post) BR each subject performed one submaximal exercise test in the supine and one in the upright position consisting of 5 min of rest, 5 min of cycle ergometer exercise at 700 kg.m/min, and 10 min of recovery from exercise. VO2 was measured continuously in all tests from 2-liter aliquot gas samples collected every 30 s. Following BR steady-state VO2 was unchanged in supine and upright exercise. In the supine position BR did not change total exercise VO2, O2 deficit, or total recovery VO2. However, compared with pre-BR, total exercise VO2 decreased (P less than 0.05) from 7.41 +/- 0.11 to 7.23 +/- 0.17 liters, O2 deficit increased (P less than 0.05) from 1.15 +/- 0.05 to 1.41 +/- 0.07 liters, and total recovery VO2 increased (P less than 0.05) from 5.17 +/- 0.11 to 5.47 +/- 0.17 liters during the post-BR upright test. Despite the ability to attain similar steady-state VO2 within 5 min, bed-rest-induced deconditioning resulted in a reduction of total VO2 capacity and an increase in the O2 deficit during submaximal constant-load exercise. This change in VO2 kinetics is found only with exercise in the upright rather than supine position implicating orthostatic mechanisms in the delayed response to submaximal exercise.

Adult↗
PubMed1984

Effect of methysergide pretreatment on thrombin-induced pulmonary oedema in the rat.

Microembolic pulmonary oedema was induced by injection of thrombin (500 NIH units/kg body weight) i.v. in rats in which fibrinolysis had been inhibited by pretreatment with trans-4-aminomethyl-cyclohexanoid-carboxylic acid (AMCA). To evaluate the role of serotonin in this condition the effect of pretreatment with the antiserotonin compound methysergide (2.5 mg/kg body weight) on the amount of pulmonary oedema was studied. Pretreatment with methysergide resulted in a 20% decrease in lung weight in thrombin-treated rats. It caused a significant reduction of dilated lymph vessels, and of interstitial and alveolar oedema, as evaluated morphometrically. Methysergide pretreatment did not significantly alter the number of degranulated mast cells. Antiserotonin is thought to exert its effect by lowering the filtration pressure in the pulmonary microcirculation.

Animals↗
PubMed1984

Role of cardiac volume receptors in the control of ADH release during acute simulated weightlessness in man.

Hemodynamic responses and antidiuretic hormone (ADH) were measured during body position changes designed to induce central blood volume shifts in ten cardiac and one heart-lung transplant recipients to assess the contribution of cardiac volume receptors in the control of ADH release during the initial acute phase of exposure to weightlessness. Each subject underwent 15 min of a sitting-control period (C) followed by 30 min of -6 degrees headdown tilt (T) and 30 min of resumed sitting (S). Venous blood samples and cardiac dimensions were taken at 0 and 15 min of C; 5, 15, and 30 min of T; and, 5, 15, and 30 min of S. Blood samples were analyzed for hematocrit, plasma osmolality, plasma renin activity (PRA), and ADH. Heart rate (HR) and blood pressure (BP) were recorded every two min. Plasma osmolality was not altered by posture changes. Mean left ventricular end-diastolic volume increased (P < .05) from 90 ml in C to 106 ml in T and returned to 87 ml in S. Plasma ADH was reduced by 20% (P < .05) with T and returned to control levels with S. These responses were similar in six normal cardiac-innervated control subjects. These data may suggest that cardiac volume receptors are not the primary mechanism for the control of ADH release during acute central volume shifts in man.

Adult↗
PubMed1984

Oxygen uptake kinetics of constant-load work: upright vs. supine exercise.

The purpose of this study was to compare oxygen uptake (VO2), O2 deficit, steady-state VO2, and recovery VO2 during the performance of a constant-load exercise in the supine and upright position. Ten male subjects (36-40 yr) performed one submaximal exercise test in the supine and one in the upright position consisting of 5 min rest, 5 min cycle ergometer exercise at 700 kg X min-1 and 10 min of recovery from exercise. The VO2 was measured continuously in all tests from 2-L aliquot air samples collected every 30 s. Steady-state VO2 was similar during supine and upright exercise. However, total VO2 during upright exercise was 0.30 L greater (p less than 0.05) than during supine exercise while O2 deficit and recovery VO2 in the upright position were 0.64 L and 0.22 L less (p less than 0.05) compared to the supine test. The larger O2 deficit during supine exercise resulted from a significantly greater VO2 halftime compared to that of the upright response. Despite the ability to eventually attain similar steady-state VO2, supine exercise results in a reduction of total VO2 capacity associated with an increase in the O2 deficit during submaximal constant-load exercise and manifested by elevated recovery VO2.

Adult↗
PubMed1983

Cardiovascular functions during voluntary apnea in dogs.

We studied cardiovascular responses to apnea during voluntary snout immersion in conscious, chronically instrumented dogs. Voluntary snout immersion up to eye level for a duration of greater than 15 s ensured that the dog was engaged in active apnea. In a control apnea of 15-35 s, heart rate decreased by 43% from a control value of 104 beats/min. Changes in cardiac output paralleled those of heart rate. Mean aortic blood pressure did not vary during apnea, which, coupled with a reduced cardiac output, indicated a 65% increase in estimated total peripheral resistance compared with preapnea values. Treatment with atropine sulfate (0.2 mg/kg) eliminated the bradycardia response, but the peripheral vasoconstriction persisted. Treatment with propranolol (0.5 mg/kg) eliminated postapnea hypertension. Changes in myocardial contractility during apnea were observed by measuring hemodynamic parameters while maintaining a constant heart rate with cardiac pacing. Myocardial contractility was decreased during apnea as indicated by decreases in stroke volume (-13%), stroke work (-22%), cardiac output (-13%), left ventricular (dP/dt)max (-11%), and cardiac power (-24%). These changes were prevented by atropine treatment, indicating the depressed contractility was a result of vagus nerve activity. The circulatory adjustments in the dog during apnea are potential mechanisms for oxygen conservation, although the effectiveness is uncertain for the animal as a whole. It is clear that by appropriate reduction in cardiac power output, the heart itself plays an active role in conservation of limited oxygen during apnea.

Animals↗
PubMed1983

Evaluation of a Reverse Gradient Garment for prevention of bed-rest deconditioning.

A Reverse Gradient Garment (RGG) was used to intermittently induce venous pooling in the extremities of a magnitude similar to that seen in going from a lying to standing position during the course of a 15-d period of horizontal bed rest. Venous pooling failed to improve bed-rest-induced losses in +2.5 Gz and +3.0 Gz centrifugation tolerance or to prevent increased heart-rate responses to lower-body negative pressure (LBNP). Four subjects served as controls, four were treated. Tests during the 7-d recovery period showed fluid/electrolyte and body composition values to have returned to pre-bed-rest levels with continued depression of acceleration tolerance times (56% decreased at +2.5 Gz and 74% decreased at +3.0 Gz compared to pre-bed-rest levels) and exaggerated blood insulin response on glucose tolerance testing (blood insulin for treated group increased 95% at 1 h before bed rest and 465% during recovery). This study demonstrates that the physiologic changes after bed rest persist for significant periods of time. Acceleration tolerance time proved to be a sensitive test for the deconditioning process.

Acceleration↗
PubMed1982

Induced venous pooling and cardiorespiratory responses to exercise after bed rest.

The purpose of this study was to deliberately induce venous pooling the lower extremities of bed-rested subjects to determine whether such distention may reverse the reduction in maximal O2 uptake that has regularly been observed. Bed-rest deconditioning was assessed in eight healthy male subjects by measuring submaximal and maximal O2 uptake (VO2 max), ventilation, and heart rate (HRmax) before and after 15 days of bed rest. During bed rest four subjects in the experimental group received daily treatments of venous pooling for 210 min/day with a reverse gradient garment (RGG), whereas the four subjects in the control group received no treatment. Compared with prebed-rest values, VO2max was reduced by 14.0 (P less than 0.05), HRmax was increased by 4.2 (P less than 0.05), and endurance time for the exercise test was decreased by 9.2% (P less than 0.05) in the control group. In the RGG group, VO2max, HRmax, and endurance time were essentially unchanged after bed rest. The plasma volume (PV) of the control group decreased by 16.7 (P less than 0.05) after bed rest compared with a 10.3% (not significant) reduction in the RGG group. The percent delta PV was related to the percent delta VO2 max (r = 0.75, P less than 0.05) and percent delta HR max (r = 0.65, P less than 0.05). The data support the hypothesis that the lack of venous pooling and associated fluid shifts contribute the decrement in VO2 max associated with bed-rest deconditioning.

Adult↗
PubMed1982

Effects of horizontal body casting on the baroreceptor reflex control of heart rate.

The purpose of this study was to investigate the effects of long-term horizontal body position on baroreceptor reflex control of heart rate. Six male rhesus monkeys (6.2-9.4 kg) were given bolus injections of 4.0 micrograms/kg phenylephrine during each of the following conditions: awake, anesthetized (10 mg/kg ketamine HCl), and after beta-blockade (1 mg/kg propranolol HCl) before, 7, 14, and 28 days after being placed in a horizontal body cast. R-R interval vs. systolic arterial pressure was plotted, and the slope was determined by least-squares-fit linear regression. Baroreceptor slope was significantly reduced by 7 days of horizontal body position and remained attenuated throughout the 28-day restraint period both before and after beta-receptor blockade. These data are consistent with the thesis that prolonged exposure to a zero-gravity environment impairs autonomic reflex regulation of the cardiovascular system.

Animals↗
PubMed1982

Increased child abuse in families with twins.

Large families and inadequate spacing of children increase the risk of abuse. Twin births incorporate both of these factors, yet the association of twinning with subsequent abuse has not been explored. Forty-eight families with twins from St Vincent Hospital and Medical Center and Nashville General Hospital were compared with 124 single-birth families, matched for hospital of delivery, birth date, maternal age, race, and socioeconomic status. Three control (2.4%) and nine twin (18.7%) families were reported for maltreatment (P less than .001). Mothers of twins experienced greater previous parity than did control subjects (P less than .001). Twins also had significantly longer nursery stays (P less than .001), lower birth weights (P less than .001), and lower Apgar scores at one (P less than .01) and five (P less than .05) minutes. A regression analysis incorporating all of these variables, however, showed that twin status was most predictive of subsequent abuse.

Adult↗
PubMed1982

The effects of horizontal body casting on blood volume, drug responsiveness, and +Gz tolerance in the Rhesus monkey.

To simulate the weightless condition, eight rhesus monkeys, instrumented with solid-state pressure transducers, were horizontally restrained in body casts for 28 d. Blood volume decreased an average of 13% after 14 d of restraint, due mainly to a drop in plasma volume. Aortic pressure and heart rate responses to norepinephrine and phenylephrine decreased after 14 d of restraint. The monkeys did not show a statistically significant decreased tolerance to a 90 degree sudden upright tilt after horizontal restraint. During the fifth week of casting, four animals were subjected to +Gz acceleration tests on a centrifuge. The acceleration tolerance of the casted monkeys was significantly reduced compared to four similarly instrumented control animals. These findings indicate that the cardiovascular deconditioning associated with simulated weightlessness results from an inability to maintain central blood volume during orthostatic stress.

Acceleration↗