Hemodynamic responses to 6 degree head-down rest in dogs: effect of aerobic conditioning.

The -6 degree head-down position is used in humans to produce fluid shifts that resemble those occurring in microgravity. Alternative animal models of microgravity may be helpful for extensive exploration of this unique condition. The dog may be a viable candidate. Sixteen dogs were assigned to one of three conditions: anesthetized open chest, anesthetized closed chest, and awake. Dogs in groups 1 (N = 6) and 2 (N = 6) were divided into an exercise or a sedentary treatment, and dogs in group 3 (N = 4) served as their own controls. Following instrumentation the dogs were put in the head-down position for 1 h. Measurements included right atrial pressure, heart rate, and mean arterial pressure for all groups, left ventricular pressure and LV dp/dt for group 1, and cardiac output and iliac flow for group 2. Right atrial pressure increased for all groups. Heart rate demonstrated non-significant changes over time or group. Significant differences were noted for mean arterial pressure, left ventricular pressure and LV dp/dt for exercise condition in response to HDR. It appears that -6 degrees of head-down rest produces similar cardiovascular responses in dogs as those observed in humans and that exercise has a minor effect on those responses.

Body composition alterations consequent to an exercise program for pre and postmenopausal women.

The purposes of this study were: (a) to evaluate the effects of an exercise program upon the body composition of premenopausal (no. 43) and postmenopausal (no. 66) women, aged 35-70 years, and (b) to compare exercise Ss with age matched control Ss. Body composition was assessed by skinfold measurement and hydrostatic weighing. Exercise Ss walked or jogged and performed light resistive exercise for 60 minutes per day three times per week for 24 weeks. Control Ss remained sedentary. ANOVAs revealed: (a) no significant (p greater than or equal to .05) differences in exercise training effects between premenopausal and postmenopausal Ss, and (b) exercise Ss exhibited less body fatness while control Ss possessed more body fat as represented by significant changes (p less than or equal to .05) for the exercise and control Ss, respectively in: body density (+.002 g/cc, -.001 g/cc); % fat (-1.2%, +.6%); fat weight (-.4 kg, +1.1 kg); suprailiac skinfold (-.3 mm, +7 mm); and abdominal skinfold (-.3 mm, +1.5 mm). It was concluded that: (a) menopausal status did not alter the effects of exercise in this study, and (b) exercise training produced a positive effect in the exercise Ss by reversing body composition trends associated with a sedentary lifestyle.

The effect of high level physical activity (8.5 METs or greater) and estrogen replacement therapy upon bone mass in postmenopausal females, aged 50-68 years.

The purpose of this study was to assess the effect of physical activity (PA) and estrogen therapy (ET) upon bone mass at the 1/3 and 4 mm distal radial sites in 50 postmenopausal females. The Ss (means age = 57.4 +/- 5.4 yrs) completed: 1) activity and gynecological surveys, 2) Balke treadmill tests (85% of age determined HR), and 3) single photon absorptiometry measurements of the radius. The activity surveys and treadmill tests were used to categorize Ss into high (8.5 METs or greater, n = 27) and low (6.0 METs or less, n = 23) physical activity groups (HPA/LPA), and the gynecological surveys were used to distinguish Ss who were on estrogen therapy (n = 17) and those who had never been on estrogen therapy (n = 33). Data revealed the HPA group had significantly higher BMC (g/cm) and BMC/BW (g/cm2) at the 1/3 distal radial site than the LPA group (.834 g/cm to .721 g/cm, p less than .01; and .698 g/cm2 to .653 g/cm2, p less than .06, respectively) but were not significantly different at the 4 mm distal site. The ET group had a significantly higher bone mass than the never on ET group for BMC/BW at the 4 mm site (.907 g/cm to .809 g/cm p less than .027). It was concluded that high level physical activity (8.5 METs or greater) or estrogen therapy was helpful in reducing the risk of bone loss in postmenopausal women.

Alterations in physiological and perceptual variables during exhaustive endurance work while wearing a pressure-demand respirator.

The purpose of this investigation was to describe the time course of changes in physiological and perceptual variables during exhaustive endurance work with and without an air-supplied, full-facepiece, pressure-demand respirator. Thirty-eight healthy subjects (24 to 51 years of age) volunteered for this study. Treadmill speed was set at 5.5 kph (3.4 mph) and elevation was set at a level calculated to elicit 70% of a previously determined maximal aerobic capacity (VO2max). Subjects continued at this rate to exhaustion. Despite a constant work rate, VO2 and %VO2max increased during exercise and were significantly greater with the respirator (34.4 +/- 1.1 mL/kg.min; 84% VO2max) than without the respirator (31.9 +/- 1.1 mL/kg.min; 76% VO2max) at the "final" measurement point prior to termination of exercise by each subject. The final values for ventilation volume (VE) also were significantly greater with the respirator (89.2 +/- 3.4 L/min) than without (73.4 +/- 3.7 L/min). At the conclusion of the endurance walk, dyspnea index (VE/MMV.25) remained well below maximal values (with = 58.6 +/- 2%; without = 44.6 +/- 2%; p less than 0.001). Also, at the final period, no significant differences occurred in the subjects' perceptual ratings of work of breathing, yet work performance time was significantly reduced (p less than 0.0001) from 69.1 +/- 4.4 min (without) to 55.6 +/- 3.8 min (with). A significantly greater swing in peak pressure (maximum pressure measured within the facepiece of respirator), however, from inspired (PPi) to expired (PPe) occurred with the respirator (13.42 cmH2O) than without the respirator (9.25 cmH2O).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of pressure-demand respirator wear on physiological and perceptual variables during progressive exercise to maximal levels.

Current regulations governing the certification of respiratory protective devices are based on data published in the early 1950s. The limited data base of this early work and documented increases in the average height of the population underscore the need for additional information concerning the parameters of certification. In the present study, a protocol using an inclined treadmill (0.5% grade every 12 sec) was used to test a heterogeneous population (n = 38). Through submaximal up to and including maximal exercise levels with and without respirator wear, maximal oxygen uptake (VO2max) was significantly greater (p less than 0.01) with the respirator (44.11 +/- 1.3 mL/kg.min) than without the respirator (42.18 +/- 1.4 mL/kg.min) while maximal ventilation volumes (VEmax) were not significantly different (with = 118.7 +/- 4 L/min; without 119.6 +/- 5 L/min). While peak inspired flows (PFI) with the respirator (268 +/- 7 L/min) were less than without the respirator (281 +/- 9 L/min), p greater than 0.05, the lower peak expired flow (PFE) with the respirator (289 +/- 12 L/min) than without the respirator (324 +/- 13 L/min), p less than 0.01, indicated a significant blunting effect of the respiratory flows by the expired resistance during exercise to maximal levels. Peak inspired pressures (PPi) with and without the respirator were not significantly different (p greater than 0.05). The negative values obtained within the facepiece of the respirator (-7.65 +/- 0.8 cmH2O), however, indicate that the positive pressure within the facepiece was lost, and respiratory protection may be compromised. Peak expired pressure with the respirator (13.05 +/- 0.7 cmH2O) was significantly greater than without the respirator (10.7 +/- 0.5 cmH2O) indicating that, despite a lower PFE, greater force was required to overcome the resistances of the respirator on expiration. The dyspnea index, an index of physiological effort; suggests that the subjects were working at a higher percentage of their respiratory reserve with the respirator (p less than 0.05) than without. Perceptually, subjects also felt that breathing with the respirator was more difficult (p less than 0.05). The maximum heart rate and the ratings of perceived exertion were not significantly different between the two tests at maximal exercise levels. Maximum oxygen uptake was considered reached when subjects attained a respiratory exchange ratio of at least 1.15, when a heart rate response at or greater than age-predicted maximum was achieved, when ratings of perceived exertion indicated exhaustion, and/or when the measure of VO2 had plateaued during the final minute of exercise.(ABSTRACT TRUNCATED AT 400 WORDS)

Exercise conditioning in the rehabilitation of patients with chronic obstructive pulmonary disease.

Fifty-nine patients with severe chronic obstructive pulmonary disease (COPD) performed pulmonary function and exercise tests before and after participation in a 12-day pulmonary rehabilitation inpatient program. Postdischarge follow-ups were performed at three months. Training consisted of twice daily aerobic exercise of 30 to 40 minutes' duration. Intensity of training was determined after exercise testing and approached the maximal limits of ventilation. In general, the program failed to demonstrate significant changes in pulmonary function. Exceptions were mid-expiratory flow rate (FEF25-75) (p less than .02) and peak flow rate (p less than .05). Evaluation of exercise capacity via maximal exercise testing yielded significant increases in caloric expenditure (p less than .001), peak exercise oxygen consumption (p less than .001), and work output (p less than .0001). Peak exercise ventilation increased significantly (p less than .005) due to an increase in tidal volume (p less than .002). Work efficiency improved with training, but the change was not statistically significant. Resting oxygen consumption and carbon dioxide production were decreased (p less than .05); tidal volume was increased (p less than .005). However, the significant increase noted in tidal volume did not alter minute ventilation. In general, the changes noted at 12 days were maintained at three months postdischarge. These data support the hypothesis that a short-term, in-hospital program of general exercise conditioning can improve work output, gas exchange, and mechanical efficiency without significantly affecting spirometric indices. These changes may translate into improved performance of activities of daily living and a sense of general well-being.

Use of a semi-automatic image analyser in directly determining mean linear intercepts.

A direct method for measuring mean linear intercepts (Lm) was tested. A semi-automatic image analysis system (Zeiss, Videoplan) and an overlay of parallel lines were employed in determining Lm in intravascularly perfused guinea pig lungs. Actual chord lengths were recorded and the data was immediately processed. Spurious intercepts and manual data manipulation were avoided. This direct method of measurement proved to be simple, rapid and very consistent across three trials for each animal. Analysis of variance revealed no significant differences between the three trials (p = 0.22).

Racial contrasts in hemoglobin levels and dietary patterns related to hematopoiesis in children: the Bogalusa Heart Study.

Racial differences in hemoglobin (Hgb) levels were explored in two groups of children at different maturational stages, the pre-adolescent (10-year-olds: Whites n = 160, Blacks n = 56,) and the adolescent (15-year-olds; Whites n = 60, Blacks n = 44). Mean Hgb levels were higher for Whites than Blacks in both age groups. When all the dietary components (i.e., iron, zinc, copper, folacin, ascorbic acid and vitamins B12, E and B6) were considered as a group, they accounted for 8.4 per cent of the Hgb variance in 10-year-olds and 10.1 per cent of variance in 15-year-olds. However, even after controlling for the variations in dietary patterns of the adolescents and pre-adolescents, race still accounted for a notable proportion of Hgb variance in both age groups (9.1 per cent in 10-year-olds and 7.0 per cent in 15-year-olds). Within each race, gender accounted for a greater percentage of the Hgb variance in the adolescents than in the pre-adolescents. Our results indicate that in all likelihood racial differences in Hgb levels during childhood exist independent of racial differences in intake of specific "blood building" nutrients and maturational changes.

Lower respiratory tract abnormalities in rheumatoid interstitial lung disease. Potential role of neutrophils in lung injury.

Although the etiology of rheumatoid interstitial lung disease (RILD) remains unknown, bronchoalveolar lavage (BAL) has been useful in studying potentially pathogenic mechanisms in this disorder. Previous investigations in patients with rheumatoid arthritis (RA) and RILD revealed abnormal BAL T-lymphocyte subpopulations and a significant elevation in BAL neutrophils. Because neutrophils have been implicated as important effector cells in inflammatory disorders such as ARDS and idiopathic pulmonary fibrosis, we evaluated BAL fluid in patients with RA for neutrophil chemotactic and activating properties and for evidence of neutrophil activation. The BAL fluid from patients with RILD contained significant neutrophil chemotactic activity derived from both lipid and nonlipid components. Evidence for neutrophil stimulation in the lower respiratory tract of patients with RILD was suggested by elevations in both myeloperoxidase activity and immunologically determined levels of human neutrophil elastase in BAL fluid. Free uninhibited elastolytic activity, however, was not demonstrated, suggesting that adequate protease inhibitor levels were present to inhibit active elastase activity. In addition to elevated myeloperoxidase activity, a potential role for neutrophil-derived oxidant injury was indirectly suggested by the enhanced release of superoxide anion (O2-) from resting normal human blood neutrophils challenged with concentrated BAL fluid from patients with RA and interstitial lung disease. Significant correlations were found between physiologic parameters and the percentage of BAL neutrophils, as well as levels of neutrophil-derived mediators. For example, levels of human neutrophil elastase were strongly correlated with diminished diffusion capacity (r = -0.73, p less than 0.001) and reduced forced vital capacity (r = -0.63, p less than 0.006).(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of a comprehensive type A measure for children in a biracial community: the Bogalusa Heart Study.

To evaluate the development of Type A-like behavior in children, responses to the Hunter-Wolf Instrument were studied in 2128 children in Bogalusa, Louisiana, a biracial community. Test-retest reliability measures were generated by retesting a random subsample of 387 children 2 weeks after the initial testing. Norms were tabulated for each of the age, race, and sex groups. Increases in total and subscale scores with age were noted except for the Hostility subscale, which decreased dramatically in the older groups. White males had higher average scores during the entire period than other groups and scored significantly higher than other groups on subscales, created from principal-components analysis, measuring Eagerness and Hostility. Low test-retest correlations were observed in children younger than 13 years of age. Of the four race-sex groups studied, white males appear to accrue the highest risk for coronary heart disease from type A-like behavior.

Predicting maximal exercise ventilation in patients with chronic obstructive pulmonary disease.

Shortness of breath is a chief complaint of many individuals with cardiopulmonary diseases. Exercise testing is often used to help differentiate cardiac from pulmonary involvement. In assessing pulmonary dysfunction during exercise it is essential to know the point at which ventilatory limitation will occur. Numerous authors have presented regression equations based on the FEV1 for predicting either MVV or VEmax. Resting pulmonary function studies were obtained from 53 patients with COPD. Symptom-limited maximal exercise testing was completed on a cycle ergometer using increments of 10 watts/min. Each regression equation for predicting MVV or VEmax was then applied to the data set. Results showed that the FEV1 correlated with the measured VEmax (r = .81) as did PEF (r = .81), MVV (r = .78), IC (r = .78), DCO (r = .68), VA (r = .67), VE (r = .65) and FVC (r = .64). Single post-bronchodilator FEV1 measurements ranged from 0.56 to 1.64 L (mean 1.0 L) while VEmax ranged from 16 to 78 L/min (mean 37.69 L/min). The equation VEmax = 37.5 X FEV1 was the most robust equation found in the literature for predicting VEmax in this sample. This equation was not statistically different from the line of identity when predicted VEmax was plotted against the measured VEmax. The intercept was 0.91 with a slope of 0.98. In addition, this equation had a smaller mean square error in predicting VEmax than those of the other equations investigated.

Sources of error in measurement of children's blood pressure in a large epidemiologic study: Bogalusa Heart Study.

Accurate and reliable measurement of blood pressure is essential in the determination of early hypertensive disease. Multiple blood pressure measures were determined by well trained field observers on a large number of children representing a total pediatric community. Changes in children's blood pressure levels with multiple measurements, as well as differences between field observers, were examined. A random effects analysis of variance model was used to determine specific contributors to blood pressure variability in an epidemiologic survey of children. Observer differences were found to be the largest preventable contributor to blood pressure variation. In addition, systolic blood pressure levels decreased approx. 2.5 mmHg from the first to the third blood pressure station. More than 86% of systolic blood pressure readings and 90% of diastolic blood pressure readings by two different observers on the same child were within 15 mmHg. These data emphasize the importance of both adequate training of field observers and the use of replicate blood pressure measurements by multiple observers to determine blood pressure levels accurately in an epidemiologic survey.

Patterns of recall in schizophrenics and normal subjects.

In two experiments it was demonstrated that the patterns of recall exhibited by schizophrenics qualitatively changed as the amount of structure present in the encoding and retrieval environments changed. When the encoding environment was structured and the retrieval environment was left unstructured (experiment 1), the schizophrenics' recall was not only lower than that of the normal subjects, but the patterns of recall of the two groups qualitatively differed. When encoding and retrieval environments were both structured (experiment 2), the patterns of recall exhibited by both groups were identical, although the schizophrenics continued to exhibit a recall deficit. This pattern of performance is more consistent with the notion that the recall deficit is caused by disease-induced depression of attentional capacity rather than by irreversible defects in ability to process information.

Decreased arterial elasticity associated with cardiovascular disease risk factors in the young. Bogalusa Heart Study.

Noninvasive ultrasonic examinations were performed in 1984 on a biracial sample of 109 10- to 17-year-old adolescents to determine whether elastic properties of the carotid arteries are associated with cardiovascular disease risk factors in the young. The subjects examined were in either the upper (high risk) or lower (low risk) race-, sex-, and age-specific tertile for both serum total cholesterol (TC) and systolic blood pressure (SBP) during a 1981-82 community survey. The pressure-strain elastic modulus (Ep), a measure of stiffness, for the carotid arteries was calculated by dividing the pulse pressure by the fractional diameter increase in the carotid artery during the cardiac cycle, as measured by ultrasonic techniques. Repeat studies on 20 randomly selected subjects demonstrated high reproducibility of the elasticity measurements (intraclass correlation coefficient = 0.84). The mean Ep in the high risk group was 5.1 kPa higher than in the low risk group, after controlling for race, sex, and age (one-sided p value = 0.03). Furthermore, a positive parental history of myocardial infarction was related to increased Ep levels (p less than 0.05), independently of race, sex, age, TC, and SBP. The results indicate that ultrasonic techniques can detect functional differences in the carotid arteries of children and adolescents that are associated with the risk of cardiovascular disease as adults.

Hemodynamic effects of oral smokeless tobacco in dogs and young adults.

Oral smokeless tobacco (snuff) is increasingly used among the young male population. To determine cardiovascular effects of an oral smokeless tobacco product, 10 anesthetized dogs were instrumented to measure blood pressure, heart rate, left ventricular end diastolic pressure, and circumflex coronary, renal, and femoral flows. After a 5-min baseline, a 2.5-g, approximately 1.2% nicotine bolus dose was placed in the buccal space, and measurements were made for 20 min. Significant increases were seen in heart rate, blood pressure, left ventricular pressure, left ventricular end diastolic pressure, and left ventricular dP/dt. Significant decreases in flow were noted in the coronary circumflex, renal, and femoral arteries. The flow reduction was thought to have been mediated by an alpha-adrenergic mechanism. Additionally, 20 human males, mean age 20 years, without nicotine exposure for 72 hr, were given a 2.5-g dose of the same oral smokeless product. From baseline to 20 min, heart rate increased from 69 to 88 beats/min (P less than 0.05), blood pressure from 118/72 to 126/78 mm Hg (P less than 0.05). Thus, oral smokeless tobacco use can produce significant hemodynamic changes in both dogs and normal humans.