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Biomedical subjects

G A Pincomb

Publications and source records attributed to G A Pincomb.

26 records · Page 2Linked to original sources
PubMed1987

Caffeine enhances the physiological response to occupational stress in medical students.

Caffeine (3.3 mg/kg) was tested against a placebo in 20 male medical students during periods of low (no exams) versus high (final exams) work stress. On each of 8 test days, heart rate and blood pressure were measured at baseline and over a 40-min postdrug interval; immediately afterward, blood was drawn to test plasma cortisol and serum lipid concentrations. Exams increased heart rate (p less than .005) and systolic blood pressure (p less than .02). Caffeine decreased heart rate (p less than .0001) and increased systolic blood pressure (p less than .005), diastolic blood pressure (p less than .0001), plasma cortisol levels (p less than .01), and serum cholesterol levels (p less than .02). Caffeine effects were additive with those of exams, and together they increased the number of men showing systolic blood pressures in the borderline hypertensive range. Thus, caffeine use during periods of increased occupational stress may enhance the cumulative stress response.

Adult↗
PubMed1985

Effects of caffeine on vascular resistance, cardiac output and myocardial contractility in young men.

The mechanisms by which caffeine typically elevates blood pressure (BP) in humans have not been previously examined using a placebo-controlled design. Accordingly, oral caffeine (3.3 mg/kg body weight, equivalent to 2 to 3 cups of coffee) was given on 2 days and a placebo was given on 1 day to 15 healthy young men using a double-blind, crossover procedure. All 3 test sessions were held during a week of caffeine abstinence. Multiple measurements were made on subjects at rest (baseline values) and over a 45-minute interval after ingestion of caffeine for BP, heart rate, systolic time intervals and thoracic impedance measures of ventricular function. Baseline measurements were highly reliable for each subject across all sessions and yielded means for placebo vs caffeine days that were not different. Caffeine increased systolic and diastolic BP (p less than 0.01) and decreased heart rate (p less than 0.05). The pressor effect was due to progressively increased systemic vascular resistance and resulted in greater stroke work (p less than 0.01). There was no indication that caffeine increased cardiac output or contractility. These actions of caffeine were replicable when each caffeine day was tested separately against the placebo day. These results suggest that caffeine use by persons with cardiovascular diseases should be examined to determine whether caffeine's enhancement of vascular resistance may contribute to systematic hypertension and/or create excessive demands for cardiac work.

Adult↗
PubMedDate not supplied

Work pressure and the type A behavior pattern exam stress in male medical students.

The psychologic and physiologic effects of variations in occupational stress on Type A (coronary-prone) and Type B men have not previously been examined. Accordingly, 58 male medical students in two successive first-year classes (32 As, 26 Bs defined by interview) were tested for mood states, perception of work pressure, and for pituitary-adrenal and cardiovascular function during a period of minimal work pressure (no exams for 1 week) and during maximal work pressure (final exam week). All observations were made at the beginning of the school day, while the students were studying course material in the building where classes were held and study modules were located. Perceived stress and self-ratings of dysphoric moods increased significantly (ps less than 0.0005) for both groups during exams compared to no exams. Plasma cortisol concentrations increased significantly (+20%) from no exams to exams for both As and Bs. Heart rate increased significantly to exams (+8%) and did so slightly more for As (+9%) than for Bs (+7%), with As showing significantly higher rates in the work setting at both times. Systolic blood pressure increased nonsignificantly for both groups. The effect of the higher heart rate and the slight systolic blood pressure rise produced a significantly greater rate-pressure product for As than for Bs at both exams and no exams (p less than 0.005), with As showing a larger rise to exams than did Bs (+11% vs. +8%). Results indicate that the As had a higher level of tonic cardiovascular activation in the work place than the Bs, and that this was additive with the effects of increased work pressure.

Adult↗
PubMedDate not supplied

Heart rate reactivity as a predictor of neuroendocrine responses to aversive and appetitive challenges.

The present paper examines the neuroendocrine influences of aversive and reward incentives (noise and shock versus monetary bonuses) presented during reaction time tasks administered to 71 healthy men (ages 21 to 35) classified as being high (N = 30) or low (N = 41) in heart rate reactivity. High heart rate reactivity was defined as a peak heart rate increase or greater than 19 bpm to a cold pressor test administered on a different day. Independent groups of subjects worked on one of two visual reaction time tasks: either to avoid exposure to noise (115-dBA bursts) and shock (3.5 mV, 2 sec), or to earn monetary bonuses ($0.50). High heart rate reactors showed significant plasma norepinephrine rises from baseline both to aversive incentives and to reward, although they showed significant cortisol responses only during aversive incentives. In contrast, the low heart rate reactors were unresponsive in cortisol and norepinephrine during either type of incentive. These results support psychoendocrine models which view the norepinephrine response as being nonspecifically related to expenditure of effort regardless of the emotional connotations of the challenge, while cortisol is seen as being secreted primarily during periods of distress. The present data further suggest that cardiovascular reactivity is linked to neuroendocrine reactivity, possibly within the central nervous system.

Adult↗
PubMedDate not supplied

Borderline hypertensives produce exaggerated adrenocortical responses to mental stress.

Serum cortisol concentrations were compared in 18 borderline hypertensive (BH) and 20 normotensive (NT) men before and after mental stress. Two levels of demand, intermittent reaction time with brief rests and reaction time alternating continuously with mental arithmetic, were used in two consecutive protocols on different days in the laboratory. Continuous, but not intermittent, mental stress produced significant elevations in cortisol levels only in the BH subjects (p < .001). The continuous challenge produced slightly more self-reported distress in both groups than the intermittent condition, and performance on the mental arithmetic task was more strongly correlated with the cortisol response than was performance on the reaction time task, suggesting that the mental arithmetic task was a key contributor to the cortisol response. Therefore, adrenocortical activity appears sensitive to appropriate stressors in BH subjects. These results indicate the importance of including measures of adrenocortical function in studies of reactivity in subjects at high risk for hypertension.

Adrenal Cortex↗