Biomedical subjects

K C Light

Publications and source records attributed to K C Light.

At least 55 records · Page 3Linked to original sources

PubMed1994

Hemodynamic stress responses in men and women examined as a function of female menstrual cycle phase.

Fifteen men and 11 normally ovulating women were each tested twice for cardiovascular stress reactivity, cognitive/behavioral performance, and mood during a variety of stressors. Each women was tested during both the follicular and luteal phase of her menstrual cycle, with men matched for number of days between testing. Although the genders did not differ in blood pressure reactivity during either phase of the cycle, during both phases of the menstrual cycle women exhibited greater heart rate reactivity and tended towards greater cardiac index increases, greater pre-ejection period decreases, and lesser vascular tone relative to men. Additionally, the menstrual cycle was observed to influence gender differences in stroke volume index responses. Specifically, stroke volume index responses for women were significantly greater in their luteal versus follicular phase resulting in a marginally significant pattern whereby women's stroke volume index responses were greater than men's luteally but less than men's follicularly. Men and women also differed in cognitive performance and mood assessment during the tasks, but the majority of these differences were unaffected by the menstrual cycle.

Adult↗

PubMed1994

Comparison of cardiac versus vascular reactors and ethnic groups in plasma epinephrine and norepinephrine responses to stress.

This study examined differences in plasma epinephrine (EPI) and norepinephrine (NOREPI) responses to stressors in 67 healthy African-American and Caucasian American men and women of the ages 18 to 49. Subjects were divided into three groups: (a) those who showed high blood pressure (BPI responses to stress associated with consistently high cardiac output (CO) increases with no substantial increases in total peripheral resistance (TPR), labeled cardiac reactors: (b) those with equally high BP increases associated with consistently higher TPR increases and lesser CO increases. labeled vascular reactors; (c) those who showed mixed hemodynamic responses or were low BP reactors. Ethnic and gender group differences in EPI and NOREPI responses were also examined. Cardiac reactors, vascular reactors and mixed + low reactors did not differ in EPI or NOREPI levels at baseline. During stressors, cardiac reactors showed greater increases in plasma EPI than vascular reactors or others during math, reaction time, and passive and active speech tasks: they also showed a weak trend toward greater NOREPI increases during these challenges as well. No differences were seen during the cold pressor: this stressor evoked the least change in EPI of all tasks, whereas the active speech elicited the greatest increases in both EPI and NOREPI of all tasks. Vascular reactors did not differ from mixed + low reactors in EPI or NOREPI reactivity, and men and women did not differ in EPI or NOREPI reactivity to any task. In contrast, Black subjects showed greater increases in NOREPI levels across all stressors compared to White subjects. These findings have implications for investigations of the role of sympathetic nervous system activity in the pathogenesis of hypertension in both African-American and Caucasian American populations.

Journal Article↗

PubMed1993

Beta-endorphin response to exercise and mental stress in patients with ischemic heart disease.

UNLABELLED: We compared symptomatic, hemodynamic and opioid responses of heart disease patients to exercise testing and a stressful public speaking task. Plasma beta-endorphins were measured at rest and immediately post stress. Nineteen of 50 patients had angina during exercise; 31 had asymptomatic ischemia. No patient had angina during the speech, but two had ECG changes and 39% had radionuclide changes indicating ischemia. Patients with asymptomatic ischemia on exercise had a significantly greater beta-endorphin response than those with angina. Public speaking elicited a significantly larger beta-endorphin increase relative to change in double product (an index of stress) than did exercise. CONCLUSIONS: (1) Patients with silent vs painful ischemia experience a greater beta-endorphin response to exercise. (2) beta-endorphin response to a speech stressor is greater than to exercise when controlled for an index of stress. (3) Increased beta-endorphin response to a speech stressor may partially explain the predominance of silent ischemia during psychological stress.

Aged↗

PubMed1993

Peripheral adrenergic receptor contributions to cardiovascular reactivity: influence of race and gender.

Ten White males, ten Black males, ten White females, and seven Black females (aged 22-48 yr) were exposed to a competitive reaction time task (enhancing beta-receptor activity), the forehead cold pressor (enhancing alpha-receptor activity), and a speech task on four separate occasions: twice under a saline placebo condition, once under a beta-blockade condition using i.v. propranolol, and once under a combined beta- and alpha-blockade condition using both i.v. propranolol and i.v. phentolamine. Order of placebo session and blockade session was counterbalanced across each race/gender group. Beta-blockade abolished the greater heart rate, cardiac index, and stroke volume index responses, and the lesser vascular tone seen under placebo in White vs. Black males. No differences between White and Black women were seen with or without beta-blockade. Gender differences in beta-receptor contribution to stress responses were restricted to the White subjects. Beta-blockade abolished the greater stroke volume index responses and less vascular tone observed in White males vs. White females. Although alpha-receptor blockade significantly decreased vascular resistance in each race/gender group, it did not differentially affect any of the subgroups. These data suggest that race and gender differences in cardiovascular stress responses of normotensive individuals are at least partly a function of differential beta-receptor activity/sensitivity. No clear support for differences in alpha-receptor activity/sensitivity was obtained.

Adult↗

PubMed1993

Laboratory reactivity assessment: effects of casual blood pressure status and choice of task difficulty.

In a study of 60 healthy young men, 26 with high and 34 with normal casual systolic pressure, blood pressure and its underlying hemodynamic determinants were measured at rest and during exposure to a series of laboratory tasks. Subjects were given a choice of performing either a difficult or an easy version of a mental arithmetic task, and then offered a similar choice of an easy or difficult stimulated public speaking task. All subjects were given the same tasks, regardless of choice, but led to believe the tasks were the ones they had chosen. During all tasks, subjects with high casual systolic pressure showed greater blood pressure, cardiac output, heart rate and myocardial contractility increases than subjects with normal casual pressure. Within the high casual pressure group, subjects who chose difficult for the mental arithmetic task exhibited greater increases in systolic pressure and heart rate during that task than subjects who chose easy. This subgroup maintained their greater responses during a subsequent mental arithmetic task in which all subjects were told that the difficulty level was the reverse of what they had initially chosen. Choosing difficult on the speaking task was associated with greater increases in cardiac output during performance on that task. Differences in cardiovascular responses associated with choice of difficulty were not evident during performance on tasks which did not pertain to the choice. For mental arithmetic, choice of difficulty was also associated with the psychological trait, fear of failure. These findings are relevant to the development of cardiovascular reactivity assessment procedures, which should attempt to detect psychological as well as physiological determinants of individual differences.

Adult↗

PubMed1993

Menstrual cycle and premenstrual syndrome: modifiers of cardiovascular reactivity in women.

Fifteen women prospectively diagnosed with PMS and 15 non-PMS women were each tested twice for cardiovascular stress reactivity and behavioral performance, once during the follicular phase and once during the luteal phase of their cycle. Although blood pressure and heart rate responses to stress did not differ across the menstrual cycle in either group of women, for the non-PMS women, differences in hemodynamic responses were observed across the 2 phases. The luteal phase was associated with greater stroke volume responses and lesser vascular tone. For the PMS women, none of their cardiovascular measures differed across their cycle. Instead, these women showed significantly attenuated blood pressure and heart rate responses compared with non-PMS women, irrespective of cycle phase.

Adult↗

PubMed1993

Race and gender comparisons: I. Hemodynamic responses to a series of stressors.

A sample of 155 adults, age 18-49 years, including nearly equal subgroups of Black and White men and women, underwent evaluation of cardiovascular reactivity during 5 behavioral stressors. Among the men, overall blood pressure increases to tasks did not differ, but Blacks showed generally higher total peripheral resistance, whereas Whites showed greater heart rate and cardiac output increases. Among the women, the same racial-group differences were evident during certain tasks, but not during others. Men showed greater overall systolic blood pressure increases than did women, and they also showed less recovery toward baseline levels in systolic and diastolic pressure and stroke volume 5 min after the stressors. Other gender differences were task specific. The possible contributions of structural changes in the myocardium and vasculature, of altered sympathetic receptor distribution, and of task-specific behavioral factors influencing task involvement are discussed.

Adolescent↗

PubMed1993

Race and gender comparisons: II. Predictions of work blood pressure from laboratory baseline and cardiovascular reactivity measures.

In 148 Black and White men and women, laboratory measures of blood pressure (BP), heart rate, stroke volume (SV), cardiac output (CO) and total peripheral resistance (TPR) during baseline and 5 stressors were examined in relationship to ambulatory systolic (SBP) and diastolic (DBP) blood pressures at work. Baseline BP strongly predicted mean work levels in all groups. For White men and Black women, higher SV and CO responses to the active speech and averaged across all tasks predicted higher work SBP individually and also when added to a model based on baseline SBP, age, and diary information. For White women, higher SBP increases to the passive speech similarly predicted mean work SBP. For Black men, higher TPR response to the cold pressor test correlated with higher work SBP but did not improve a predictor model involving baseline SBP and age. Reactivity measures did not consistently contribute to prediction of work DBP.

Adult↗

PubMed1992

Racial differences in left ventricular structure in healthy young adults.

Racial differences in cardiac structure and function were evaluated in 62 black and 71 white healthy young adults. Left ventricular (LV) mass index, relative wall thickness, fractional shortening, resting cardiac index and resting systemic vascular resistance index were estimated using M-mode echocardiography. Pulsed Doppler interrogation of transmitral flow was used to characterize LV filling. Average daytime blood pressure (BP) was determined by ambulatory monitoring during a typical work or school day. Ambulatory daytime BP averaged 127 +/- 12/80 +/- 7 mm Hg in black subjects, and 127 +/- 9/80 +/- 6 mm Hg in white subjects (p = not significant). The 2 groups were also similar in resting BP, age and gender composition. Relative wall thickness was significantly greater in black than in white subjects (0.37 +/- 0.06 vs 0.34 +/- 0.05; p less than 0.01). This difference was found in both men and women. Black subjects also had a higher resting systemic vascular resistance index (2,110 +/- 570 vs 1,920 +/- 500 dynes.s.cm-5.m2; p less than 0.05) and lower resting cardiac index (3.14 +/- 0.84 vs 3.46 +/- 0.85 L/min/m2; p less than 0.05). There were no significant differences between black and white subjects in LV mass index, fractional shortening and normalized peak filling velocity. These results suggest that racial differences in LV structure and systemic hemodynamics exist even in patients without sustained hypertension. In our study population, the greater relative wall thickness in black subjects was not accompanied by significant differences in LV systolic function or diastolic filling.

Adolescent↗

PubMed1992

Stress-induced changes in the rate of sodium excretion in healthy black and white men.

The effects of exposure to competitive mental stressors on rates of excretion of sodium (Na), potassium (K) and fluid, together with cardiovascular responses, were evaluated in 14 black and 14 white normotensive men after 3 days of controlled diet (200 mEq Na, 100 mEq K daily). In the first hour of a 5-hr protocol, subjects ingested a standard dinner and drank 1 liter of water. In hours 2-5, they voided to provide urine collections every 30 min, and drank 200 ml additional water after each collection. Hours 1-2 were for stabilization of excretion, hour 3 was baseline, hour 4 was stress and hour 5 was post-stress rest. During stress, 20 men showed faster natriuresis and 8 showed slower natriuresis than at baseline. These subgroups did not differ in any excretion measure at baseline. During stress, the slow stress natriuresis group showed slower excretion of potassium and fluid as well as sodium; slow natriuresis and kaliuresis persisted 30 min after stress. Creatinine clearance rate was also decreased, but only during the first 30 min of stress. Slow stress natriuresis subjects were found to have higher blood pressures during baseline and stress, greater heart rate and cardiac output increases during stress, and a larger percentage had hypertensive parents (63 vs 37%) compared to fast stress natriuresis subjects. Slow stress natriuresis was observed in 50 vs 17% of men with resting diastolic levels above vs below 80 mmHg, and in 43% of blacks vs 18% of whites tested. Overall, black subjects tended to excrete sodium more slowly than whites at baseline, and showed significantly lesser increases in sodium excretion rate when pressures rose during stress.

Adult↗

PubMed1992

Cardiovascular reactivity assessment: effects of choice of difficulty on laboratory task responses.

This laboratory study of cardiovascular reactivity was designed to examine how a choice of difficulty element in a mental arithmetic task would affect cardiovascular responses. 20 healthy male subjects were tested on a computer-controlled mental arithmetic task, designed to standardize performance across subjects by keeping constant the proportion of correct responses. This was achieved by automatic adjustment of problem difficulty according to ongoing performance. Subjects were led to believe that they could take either a 'difficult' or an 'easy' version of the mental arithmetic task and were asked to make a choice; in fact, all subjects were given the same task. Subjects who chose the 'difficult' mental arithmetic task (N = 10) showed significantly greater increases in myocardial contractility, cardiac output and systolic blood pressure during task performance than those who chose 'easy' (N = 10). However, subjects who chose 'difficult' were presented with more difficult problems presumably due to their exerting greater levels of effort during the task. The differences in cardiovascular responses associated with choice of difficulty were absent during testing on four subsequent tasks which did not incorporate any choice options (reaction-time, speech, mirror trace, cold pressor). These findings are interpreted as being provocative, rather than in any way conclusive. Nevertheless, they are suggestive of the possibility that choice of difficulty in laboratory tasks may be one strategy for improving the ecological validity of laboratory reactivity assessment procedures.

Adolescent↗

PubMed1992

Cognitive coping strategies and blood pressure responses to real-life stress in healthy young men.

Coping style is an important feature in the understanding of the relation between real-life stress and associated blood pressure (BP) responses. In this study, 10 high- and 10 low-"self-focused-coping" (SFC) male college students were tested with ambulatory BP monitoring on two typical schooldays, one of which included an examination. It was found that the high-SFC subjects, defined as those who tend to keep to themselves and/or blame themselves in stressful situations, showed higher BP responses than the low-SFC subjects, but only on the exam day. Further, the high-SFC subjects showed higher BP during the exam but also had BP elevations that were sustained during other activities throughout the same day, including evening rest. These results are discussed in terms of the relation between psychological and physiological responding.

Adaptation, Psychological↗

PubMed1992

Gender differences in left ventricular structure and function in young adults with normal or marginally elevated blood pressure.

Gender differences in left ventricular structure and function were evaluated in 68 male and 69 female young adults (mean age 30 +/- 7 years) with normal or marginally elevated blood pressure. Left ventricular mass index was greater in men than in women, even after controlling for blood pressure. There were no significant gender differences in left ventricular systolic function. Doppler indices of diastolic filling were also similar in men and women. Thus, men have a significantly greater left ventricular mass index than women, but this difference in ventricular size is not associated with differences in systolic or diastolic function.

Adult↗

PubMed1992

Reactivity to stress and psychological adjustment in adults with pituitary insufficiency.

OBJECTIVE: Hypopituitary adults who were affected during childhood have a below-average rate of marriage, a rate of unemployment that exceeds national norms, and often indicate dissatisfaction with their life circumstances. We undertook the present study to determine the effects of short stature versus those of pituitary hormone deficiency. DESIGN AND PATIENTS: We compared hypopituitary adults (n = 25) with normal short adults (n = 25) who were matched for height, sex, age and socioeconomic status. MEASUREMENTS: In these two groups of subjects, we compared the physiological responses to a simulated social stressor, a public speaking task, and we measured the psychometric attributes that are indicators of social assertiveness and extraversion. RESULTS: Before, during and after the stress of public speaking, patients with multiple pituitary hormone deficiencies (n = 20) had lower mean systolic and diastolic blood pressures than controls, while patients with isolated growth hormone deficiency (n = 5) were equivalent to controls. The reactivity to stress, assessed using delta scores based on changes in blood pressure and heart rate, was also decreased in multiple hormone deficient patients. Psychometric test results indicated that patients with multiple hormone deficiencies showed lower openness, lower assertiveness, greater neuroticism and a tendency towards less extraversion than did controls. The responses of patients with isolated GH deficiency on the psychometric tests were not statistically different from controls, but the number of subjects in this group (n = 5) was too small to draw conclusions. CONCLUSIONS: The impaired cardiovascular responses to stress in patients with multiple hormone deficiencies, compared to short control subjects and to patients with GH deficiency leads us to conclude that factors other than stature and GH are responsible for these observations. The differences might be related to insufficiency of catecholamines or cortisol in the patients with multiple hormone deficiencies. These hormonal deficiencies might also account for the socially inhibited behaviour of these patients. Our results suggest that more attention needs to be directed at preparing hypopituitary patients for the challenges of adulthood. Also, these patients may be helped by more intensive efforts at hormonal replacement in adulthood.

Adolescent↗

PubMed1992

Job strain and ambulatory work blood pressure in healthy young men and women.

The effect of high job strain (defined as high psychological demands plus low decision latitude at work) on blood pressure was determined in 129 healthy, nonhypertensive men (n = 65) and women (n = 64). Blood pressure measures included mean screening levels obtained in a clinical environment, mean ambulatory levels from one 8-hour workday, and the change in levels from screening to mean work levels. In male workers, men with high and low job strain showed similar blood pressures at screening, but men with high job strain showed greater increases from screening to work, resulting in higher mean work blood pressure. Occupational status was unrelated to job strain or blood pressure in men. In female workers, women with high and low job strain did not differ in any measure of blood pressure; however, there were trends for higher occupational status and greater skill discretion to be associated with higher blood pressure responses at work in women.

Adolescent↗

PubMed1991

Generalization of cardiovascular response: supportive evidence for the reactivity hypothesis.

Cardiovascular responses were monitored while 36 subjects completed a battery of laboratory stressors comprising mental arithmetic, a reaction time task, a speech task, and the forehead cold pressor. Inter-task consistency was assessed for each of 6 physiological parameters for all task pairings. Considerable inter-task consistency for reactivity scores was seen among the psychological stressors for all variables. The question of such consistency between the cold pressor and the psychological tasks was then addressed. The pattern of consistency was not as clear-cut in this case. For systolic blood pressure and pre-ejection period, reactivity scores to the cold pressor did not correlate with those to any of the psychological tasks. In contrast, cardiac output and total peripheral resistance responses showed considerable consistency. The importance of determining the nature of the relationship between psychological and physical stressors is discussed.

Adult↗

PubMed1991

Left ventricular mass index and diastolic filling. Relation to blood pressure and demographic variables in a healthy biracial sample.

The relationships of left ventricular (LV) structure and diastolic filling to ambulatory blood pressure, race, age, and gender were studied in 104 young, generally healthy, untreated subjects with normal or marginally elevated blood pressure. Average daytime systolic blood pressure (r = 0.41, P less than .001), diastolic blood pressure (r = 0.38, P less than .001), male gender (r = 0.49, P less than .001), and age (r = 0.32, P less than .001) were univariate correlates of LV mass index as measured by M-mode echocardiography. In a stepwise multiple regression model, male gender, age, and systolic blood pressure were independent predictors of LV mass index. LV filling rate normalized to mitral stroke volume, a Doppler-derived index of diastolic filling, was inversely related to age (r = -0.47, P less than .001), heart rate (r = -0.27, P less than .01), LV mass index (r = -0.32, P less than .001), and diastolic blood pressure (r = -0.20, P less than .05). Age, heart rate, and LV mass index were predictors of normalized peak filling in a stepwise regression model. Race was not significantly related to either LV mass index or diastolic filling. Our results confirm the importance of demographic variables as well as blood pressure in determining LV mass and filling characteristics in humans prior to the development of sustained essential hypertension. These variables contribute to ventricular mass and diastolic function in varying degrees. Gender is strongly correlated with LV mass, but not with filling indices.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1990

Cardiovascular responses to behavioral stressors: laboratory-field generalization and inter-task consistency.

Blood pressure and heart rate responses were monitored while 30 medical, dental or graduate students completed four laboratory tasks. On a second day, subjects wore an ambulatory blood pressure monitor, and during this day they completed the real-world challenge of presenting their research in front of a small audience. Heart rate and blood pressures correlated significantly between all four laboratory tasks for both absolute levels and reactivity scores (calculated as task level minus pre-task baseline level). However, while heart rate and blood pressure absolute levels for each task correlated significantly with those attained during the real-world stressor, correlation coefficients obtained when similarly comparing reactivity scores were uniformly non-significant. Laboratory-field generalization was thus evident only for absolute values. Consideration was then given to the fact that the laboratory tasks were undertaken in a seated position, while subjects stood during the real-world task. Activity diaries completed by subjects during the time they wore the ambulatory monitor were examined to search for readings that could be regarded as standing baselines. Such values were obtained for 12 of the subjects. Real-world reactivity scores were recalculated using these standing baselines, and compared again with reactivity scores during the laboratory tasks. Marked increases in correlation coefficients were obtained for systolic and diastolic pressure, but not for heart rate.

Adult↗