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Biomedical subjects

S C Johnson

Publications and source records attributed to S C Johnson.

At least 109 records · Page 6Linked to original sources
PubMed1990

Aerobic capacity of older adults: a training study.

The effects of a four month aerobic conditioning program on heart rate, blood pressure, maximal oxygen consumption (VO2max), and physical work capacity of 55-70 year old sedentary individuals were evaluated. Twenty-eight men and women participated in either 4 months of supervised fast walking or jogging at a prescribed target heart rate or stretching exercises for one hour, three days per week. Gains in VO2max (ml/kg/min) obtained during a Balke maximal treadmill test in aerobic and exercise control subjects were 27% and 9%, respectively. At posttesting subjects in both groups demonstrated improved maximal work rate, increased treadmill time, and experienced lower resting and recovery heart rates, lower resting systolic blood pressure, and fewer premature ventricular depolarizations during exercise testing. In 67 physician-supervised maximal exercise tests, only one subject did not achieve VO2max due to exercise induced arrhythmias. No events of morbidity or mortality occurred as a result of the exercise testing and training. Subjects were contacted 4 years after study participation to determine if they were adhering to an exercise program. Sixty-four percent reported exercising at least 3 days per week in large muscle activities. We conclude that four months of supervised aerobic and nonaerobic exercise training is sufficient to improve aerobic capacity and other indicators of fitness in older, sedentary men and women, and that these previously sedentary people are likely to continue exercising on an individual basis once they have experienced improved physical capacity.

Aged↗
PubMed1989

Applied physiology of cross-country skiing.

Cross-country ski racing has evolved rapidly in recent years. Of particular interest has been the development and proliferation of the faster freestyle or skating techniques. In spite of changes in technique and equipment, the fact that elite cross-country ski racers have some of the highest aerobic power values reported for endurance athletes has not changed. Successful ski racers have higher percentages of slow twitch muscle fibres and higher anaerobic thresholds, but lower anaerobic power scores than Alpine skiers. Cross-country skiers are also lean, as are distance runners. The absolute bodyweight of the ski racer, however, is much more variable than that of distance runners. Since light skiers will have an advantage on steep uphill courses and heavier skiers will be favoured by level, downhill, and less steep uphill courses, the variability of courses available in international competition explains why successful skiers are so variable with respect to bodyweight. The physiological characteristics of the elite skier are a result of both genetics and adaptation to rigorous multiyear, year-round training programmes. Identification of systematic procedures for specifically challenging the physiological parameters which are requisite for ski racing are being examined. Investigation of ventilatory and lactate thresholds as well as heart rate as parameters for quantifying training intensity is of particular interest at this time.

Humans↗
PubMed1989

Constraints on priming in spatial memory: naturally learned versus experimentally learned environments.

In four experiments, we explored constraints on priming in spatial memory. In Experiments 1 and 2, subjects who were familiar with the locations of buildings on the Vanderbilt campus participated in a recognition test. The subjects' task was to decide whether or not named buildings were on the campus. Foils in this recognition test were realistic but fictional names of buildings. In principle, the subjects could have performed this task without using spatial knowledge; in fact, they must not have used spatial knowledge, because there was no evidence of priming in recognition as a function of the spatial relations between buildings on the campus. This result differs from those obtained in earlier experiments that have examined memory of spatial layouts learned in laboratory settings. In Experiment 3, the fictional foils were replaced by names of buildings in an area of the campus separated geographically from the main campus. Evidently, this change induced subjects to retrieve spatial knowledge, because the spatial priming effect materialized. A fourth experiment replicated the above findings in a single experiment and demonstrated that spatial priming could be obtained when the configuration of buildings was learned experimentally. These results are explained by appealing to the "decontextualization" that takes place in memory over time.

Adult↗
PubMed1988

Cardio-respiratory fitness of young and older active and sedentary men.

Physiological profiles are described for 30 healthy young (20-31 years) and 30 healthy older (50-62 years) men. Half of the individuals in each group reported that during the previous five years they participated frequently in strenuous physical exercises; the other half reported sedentary lifestyles. A treadmill exercise test was used to determine maximal aerobic power (VO2 max). Heart rate and blood pressure were measured during rest, maximal exercise and recovery. The active older men demonstrated significantly lower resting heart rates, lower resting systolic and diastolic blood pressures, higher VO2 max, lower maximal exercise diastolic blood pressure and lower recovery heart rates than the age-matched sedentary men. Compared with the young sedentary men, the older active men had lower resting heart rates and higher VO2 max, walked longer on the treadmill, had lower recovery heart rates and weighed less. Older active men also had higher VO2 max levels than young sedentary men. In summary, physiological profiles of the older active men more closely resembled profiles of active men who were 30 years younger than those of older sedentary men. These results emphasize the range of benefits associated with exercise.

Adult↗
PubMed1988

Danazol for the treatment of refractory autoimmune thrombocytopenia in systemic lupus erythematosus.

STUDY OBJECTIVE: to determine the efficacy of danazol therapy in patients with systemic lupus erythematosus with severe autoimmune thrombocytopenia refractory to other therapies. DESIGN: noncontrolled clinical trial, with a minimum of 8 weeks of therapy, the maximum determined by clinical response. SETTING: referral-based rheumatology clinic at an army medical center. PATIENTS: sequential sample of six patients with systemic lupus erythematosus with severe autoimmune thrombocytopenia refractory to high-dose glucocorticoids. Four patients also failed splenectomy, or cytotoxic drugs, or both. INTERVENTIONS: danazol, 200 mg four times per day, was added to the previous therapeutic regimen for at least 2 months. MEASUREMENTS AND MAIN RESULTS: all six patients had normal platelet counts within 6 weeks of starting danazol treatment. After resolution of thrombocytopenia for at least 1 month, immunosuppressive medications were tapered; one patient had a relapse. During an average follow-up of 12 months, the danazol dose was lowered in the five remaining patients but could not be discontinued without recurrence of thrombocytopenia. During danazol therapy, platelet-bound IgG antibodies and circulating immune complexes did not decrease significantly. Danazol was well tolerated. CONCLUSIONS: danazol appears to be a useful adjunctive treatment for refractory autoimmune thrombocytopenia associated with systemic lupus erythematosus.

Adult↗
PubMed1988

Pharmacologic marrow purging in murine T cell leukemia.

Deoxycoformycin in combination with deoxyadenosine was used to purge 6C3HED malignant T cells from murine marrow in vitro. Adenosine deaminase activity of 6C3HED cells was ablated by incubation with 10(-6) mol/L deoxycoformycin (dCF). During a 12-hour incubation with 10(-6) mol/L dCF and 10(-4) mol/L deoxyadenosine, tumor cells sequentially accumulated dATP, became depleted of NAD followed by ATP, then died. More than 5 logs of 6C3HED cells were killed as measured by survival of mice injected with treated tumor cells. Identical incubation of 5 x 10(6) marrow cells did not interfere with rescue of syngeneic lethally irradiated mice. Long-term survival was demonstrated in 12 of 14 mice that received marrow that had been contaminated with 5% 6C3HED cells, incubated with deoxycoformycin and deoxyadenosine, then used to rescue lethally irradiated mice. This murine model provides information not available from in vitro assays and may be useful in the development of strategies to purge malignant T cells from marrow.

5'-Nucleotidase↗
PubMed1987

Modulation of macrophage I-A expression: lack of effect of prostaglandins and glucocorticoids on macrophages that continuously express I-A.

The ability of prostaglandins, glucocorticoids and lipopolysaccharide to modulate I-A expression on macrophages that continuously or transiently express I-A was compared. We found that neither prostaglandins nor glucocorticoids affected I-A expression by macrophages that continuously expressed I-A. In contrast, prostaglandin E2 (PGE2) inhibited the lymphokine-induced maintenance of I-A on macrophages that transiently expressed I-A while glucocorticoids inhibited both the induction and expression of I-A. Lipopolysaccharide caused a loss in the expression of Class II molecules on macrophages that continuously expressed I-A by a prostaglandin-independent mechanism. The lack of effect of PGE2 and glucocorticoids may be related to our observation that continuous expression of I-A does not require its continued synthesis.

Animals↗
PubMed1987

An anthropometric estimation of body composition of older men.

This study sought to derive equations for the functions of estimating the body density (Db), lean body weight (LBW), and percentage body fat (PBF) of older men. Hydrostatic weighing was used to determine the criterion measures of 25 older men, 56 to 70 years of age (M = 62.1, SD = 4.2 years). A stepwise multiple regression analysis of these data developed equations for each variable with multiple correlation coefficients and standard error of estimates of the most practical (p less than .001) being: Db = .857, 0.0047 g/ml; LBW = .954, 2.08 kg; PBF = .842, 2.36%, respectively. The accuracy of these results are commensurate with others reported in the literature.

Aged↗
PubMed1987

Inhibition of Providencia stuartii cell envelope enzymes by chlorhexidine.

The possibility that chlorhexidine is a specific inhibitor of membrane bound bacterial adenosine triphosphatase (ATPase) was addressed. The in-vitro susceptibilities of several Providencia stuartii cell envelope enzymes, including ATPase, to chlorhexidine were compared. The following concentrations of chlorhexidine were required to cause 50% inhibition of enzyme activity in preparations from chlorhexidine-sensitive strains (MIC 50 mg chlorhexidine/l): ATPase (160 mg/l), succinic dehydrogenase (greater than 300 mg/l), penicillin binding protein 7 (300 mg/l) and beta-lactamase (45 mg/l). Fifty per cent inhibition of the ATPase from a chlorhexidine-resistant strain (MIC 1600 mg/l) was achieved at an in-vitro concentration of 225 mg chlorhexidine/l. Our observations do not support the suggestion that bacterial membrane-bound ATPases are specific targets for chlorhexidine.

Adenosine Triphosphatases↗
PubMed1987

Physical characteristics of patients with herniated intervertebral lumbar discs.

In an attempt to determine whether certain physical characteristics discriminated between people with and without herniated intervertebral lumbar discs, volunteers (N = 40) who were diagnosed as having a herniated lumbar disc were compared to control subjects (N = 40) who had been randomly selected and matched by age and sex. All subjects completed a questionnaire to determine the history of their back injury and a description of their exercise behavior patterns. Body composition was estimated by hydrostatic weighing. Maximum oxygen consumption was predicted using the Astrand-Ryhming nomogram. Strength scores were determined from a battery of cable tensiometer tests. Dependent variables were analyzed using a multiple analysis of variance (MANOVA). Using discriminant analysis, as a post hoc test, predicted maximum oxygen consumption was shown to account for the difference between the groups (P less than .002). The control subjects' values were higher than the patients' values. Subjects' exercise history indicated no differences between the groups relative to the time period preceding the onset of injury (P greater than .05). The exercise activity of patients was significantly reduced after injury (P less than .001). An average of 87 days elapsed between the onset of injury to the date of fitness testing.

Adipose Tissue↗