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Biomedical subjects

T G Pickering

Publications and source records attributed to T G Pickering.

At least 289 records · Page 16Linked to original sources
PubMedDate not supplied

Effects of exercise on plasma viscosity in athletes and sedentary normal subjects.

To assess the immediate and long-term effects of exercise on factors regulating blood flow, we measured plasma viscosity (eta p) and plasma renin activity (PRA) in 17 trained runners and 16 sedentary healthy subjects before and 10 min after graded treadmill exercise. Resting eta p was lower in runners primarily because of significantly lower fibrinogen concentration. Compared to nonrunners with similar 24-h urine electrolyte excretion rates, runners were characterized by lower PRA at rest. In view of the overall correlation between heart rate and PRA before exercise, reduced adrenergic tone was probably a major factor contributing to the lower PRA in runners. After exercise, plasma viscosity and PRA exceeded control levels, and were similar in magnitude in runners and sedentary subjects. Changes in plasma viscosity were less than expected from the degree of hemoconcentration, primarily because enhanced fibrinolysis maintained fibrinogen level constant. To the extent that plasma viscosity affects viscous flow resistance, the results suggest that tissue perfusion and oxygen delivery rate at rest are greater in trained runners than in sedentary subjects, but these variables become similar after maximum exertion.

Adult↗
PubMedDate not supplied

An historical context for behavioral models of hypertension.

OBJECTIVE: The purpose of this study is provide an historical context for current behavioral models of hypertension. METHODS: A selective sample of the cardiovascular reactivity literature was reviewed, from 1932 to present. RESULTS: In the earliest model, cardiovascular reactivity was regarded as a marker of disease risk; however, in later models, reactivity came to be viewed as a causal influence in the development of hypertension. As the models evolved, the underlying assumptions changed. Thus, the risk marker model assumed that cardiovascular responses to stress were a stable, generalized characteristic of the individual, and therefore the eliciting stimuli were arbitrary. The later models, however, assume that the nature of the eliciting stimulus is a determinant of the cardiovascular response. We describe the increasing complexity of the four models, and contrast their underlying assumptions and the implications of these assumptions. CONCLUSION: We provide an overview of study designs and variables that should be incorporated into studies seeking to understand the ways in which cardiovascular responses to stress may influence the development of hypertension.

Blood Pressure↗
PubMedDate not supplied

Psychologic differences between high-, normal-, and low-renin hypertensives.

Sixty-one male subjects with mild untreated essential hypertension were classified by renin-sodium profiling as high renin (HR--13 Subjects), normal renin (NR--33 Subjects), or low renin (LR--15 Subjects). The HR subjects reported significantly more symptoms of sensitivity, depression, anxiety, hostility, paranoia, and psychotic thought than LR subjects on the Symptom Checklist (SCL-90). The NR subjects also reported more symptomatology than LR subjects. Similar differences between HR and LR subjects were found with the Cattell 16 Personality Factor Questionnaire (16PF).

Adult↗
PubMedDate not supplied

The influence of happiness, anger, and anxiety on the blood pressure of borderline hypertensives.

Differences in blood pressure associated with reported happiness, anger, and anxiety are examined among 90 borderline hypertensives during 24-hr blood pressure monitoring. There were 1152 individual ambulatory blood pressure readings for which subjects classified their emotional state as happy (n = 628), angry (n = 67), or anxious (n = 457) on scales from one (low) to ten (high). Pressures were transformed to z-scores using the subject's 24-hr mean and standard deviation to assess relative elevation during reported emotional arousal. The results show that emotional arousal significantly increases systolic and diastolic pressure (p less than 0.00001), an effect independent of posture and location of subject during measurement (at work, home, or elsewhere). On average, pressures during reported angry or anxious states were higher than those during a happy state (p less than 0.01). Examination of arousal intensity showed that scores on the happiness scale were inversely related to systolic pressure (p less than 0.01) whereas the degree of anxiety was positively associated with diastolic pressure (p less than 0.02). Emotional effects were also related to the degree of individual daily pressure variation such that the greater the variability, the larger the blood pressure change associated with the emotions. The results suggest that happiness, anger, and anxiety increase blood pressure to differing degrees and that emotional effects may be greater in individuals with more labile blood pressure.

Adolescent↗
PubMedDate not supplied

Social support in social interaction: a moderator of cardiovascular reactivity.

This study examines the possibility that social support operates as a moderator of cardiovascular reactivity, which may be a factor in the development of heart disease and hypertension. An experiment was performed in which each of 40 subjects was the object of verbal attack in a discussion of a controversial issue. In each session, one subject and three confederates participated. Two of the confederates argued with the subject; in half the groups, a third confederate defended the subject's position (social support condition); in the other half, the third confederate sat quietly (no support condition). The subject's blood pressure and heart rate were continuously monitored. Subjects in the social support condition showed significantly smaller increases in cardiovascular measures than subjects in the no support condition. The results are discussed in terms of small group dynamics and Social Comparison Theory.

Adaptation, Psychological↗
PubMedDate not supplied

The multi-dimensional nature of active coping: differential effects of effort and enhanced control on cardiovascular reactivity.

Some studies show that enhanced control increases cardiovascular reactivity; other studies show decreases. This disparity may be due to a confound: enhanced control may reduce reactivity, but effort accompanying active coping may increase it. The present study was designed to vary level of control and availability of active coping responses, while maintaining effort constant. Sixty female undergraduates performed word-search puzzles while blood pressure and heart rate were monitored. They were divided into three groups: In condition 1, reinforcement was contingent on the subjects' performance only; in conditions 2 and 3, reinforcement was contingent on the joint performance of the subject and a poorly performing confederate. In condition 2, subjects could help their partners (active coping); in condition 3, they could not (passive coping). Effort was constant across groups. Cardiovascular responses were significantly greater in the passive coping condition than in the other two, indicating that with effort held constant, enhanced control diminishes reactivity.

Achievement↗
PubMedDate not supplied

The association between daily blood pressure and catecholamine variability in normotensive working women.

Using ambulatory blood pressure monitors and timed urine collection techniques, blood pressure and the rates of urinary catecholamine excretion were compared across the work, home, and sleep environments of 45 women who perceived their work environment as most stressful (work stressed) and 35 women who perceived their home environment as equally or more stressful (home stressed) on the day of monitoring. The work-stressed women had higher systolic pressure at work (121 vs. 115; p < 0.05). There were no significant differences in diastolic pressure or the absolute levels of the catecholamines between the groups. However, the percent changes in blood pressure and catecholamines from work or home to sleep were significantly correlated in the work-stressed but not the home-stressed women (r values from 0.25 to 0.45, p < 0.05). The work-stressed and home-stressed women differed in their proportional make-up of several demographic characteristics, including having children (percentage of home-stressed women with children > work-stressed) (p < 0.05), ethnicity (percent of black home-stressed > work-stressed) (p < 0.01), and family history of hypertension (percentage of work-stressed > home-stressed) (0.05 < p < 0.10). These differences, in part, may have determined the daily patterns of perceived stress in the two groups of women. Overall, these findings suggest that work stress and/or the sociodemographic characteristics that may influence the perception of work stress may drive a daylong sympathetic response that increases blood pressure in working women.

Adult↗
PubMedDate not supplied

A test of generalizability of cardiovascular reactivity using a controlled ambulatory procedure.

This study tested the hypothesis that reports of poor generalizability of cardiovascular reactivity measured in the laboratory to changes observed during everyday life are due to a lack of standardization of activities and position (sitting, standing) in the latter situation. Thirty-seven subjects engaged in reactivity testing, and then in a 4-hour series of standardized activities outside the laboratory (controlled ambulatory phase), accompanied by the experimenter, on each of 2 days. The controlled ambulatory activities included alphabetizing, an editing task, a brisk walk, solving word puzzles, and eating lunch. Two measures of field variability were examined: the standard deviation and the root mean square of successive differences, of all ambulatory measurements. Associations between laboratory changes scores and measures of field variability were poor (highest r = .23). We conclude that evidence for generalizability of reactivity change scores remains poor, and cannot be solely attributed to the uncontrolled nature of activities in the field.

Adolescent↗
PubMedDate not supplied

Social support as a moderator of cardiovascular reactivity in women: a test of the direct effects and buffering hypotheses.

This study examines the possibility that social support operates as a moderator of cardiovascular reactivity in women. Two models by which social support may operate were examined: the direct effects and buffering models. Twenty-six subjects were exposed to four conditions while playing a video game: two levels of stress (low, high) and two levels of social support (alone, together). Blood pressure and heart rate were monitored continuously. Ratings of stress were obtained for each condition. Results indicated that the support manipulation produced significant main effects for diastolic blood pressure and stress ratings, with lower diastolic blood pressure and ratings observed in the "together" condition, and that the interaction between support and stress produced lower reactivity for the cardiovascular measures in the high stress (but not the low stress) condition. No interaction was found for the stress ratings. We conclude that the results provide support for both the buffering and direct effects models. Implications concerning the (within-subjects) design of the study and the stress ratings are discussed.

Adolescent↗
PubMedDate not supplied

Self-efficacy as a moderator of perceived control effects on cardiovascular reactivity: is enhanced control always beneficial?

We have found that enhanced control has an attenuating effect on cardiovascular reactivity when effort of responding is maintained constant; however, not all individuals will react to increased control in the same manner. In the present study, 40 subjects engaged in a mental arithmetic task under high control (self-paced) and low control (externally paced) conditions. Subjects' self-efficacy concerning this task was assessed. As expected, significant main effects were found for control condition, with high control producing smaller blood pressure and heart rate changes than low control (11.4 vs. 20.4 mm Hg (systolic blood pressure), 4.4 vs. 11.4 mm Hg (diastolic blood pressure), and 6.2 vs. 7.9 beats per minute (heart rate)). No main effects were found for self-efficacy. However, the interaction between control and self-efficacy was significant for systolic blood pressure and heart rate and marginally significant for diastolic blood pressure; post hoc tests showed that this was due to the effect of self-efficacy classification under high control conditions; subjects with low self-efficacy for the mental arithmetic task evidenced cardiovascular changes that were significantly greater than those of the high self-efficacy group (8.0 vs. 14.8 mm Hg (systolic blood pressure), 2.7 vs. 6.1 mm Hg (diastolic blood pressure), and 5.2 vs. 7.1 beats per minute (heart rate). The data suggest that the reactivity observed during active coping is due in part to the effort of responding and in part to the match between the demands of the task and certain mastery-related attributes of the individual.

Adolescent↗