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Biomedical subjects

K C Light

Publications and source records attributed to K C Light.

At least 91 records · Page 5Linked to original sources
PubMed1983

Central beta adrenoceptor mediation of the antinatriuretic response to behavioral stress in conscious dogs.

This study examined the renal excretory response to behavioral stress (aversive conditioning) in conscious dogs during infusion of beta adrenoceptor antagonists that either readily cross, or that do not readily cross the blood-brain barrier. With saline infusion alone (n = 7), behavioral stress decreased sodium excretion (-47 +/- 7% from 345 microEq/min) and urine flow rate (-48 +/- 5% from 2.1 ml/min). In the same dogs, infusion of propranolol, which readily crosses the blood-brain barrier, abolished the sodium excretion and urine flow rate responses to behavioral stress (-2 +/- 6% from 527 microEq/min and -5 +/- 3% from 3.0 ml/min, respectively). In a different group of dogs (n = 5), infusion of timolol or oxprenolol, antagonists that cross the blood-brain barrier less readily than propranolol, did not abolish the excretory response to behavioral stress. Behavioral stress decreased sodium excretion and urine flow rate during timolol infusion (-38 +/- 6% from 452 microEq/min and -36 +/- 6% from 2.4 ml/min, respectively) and oxprenolol infusion (-25 +/- 9% from 328 microEq/min and -19 +/- 8% from 1.8 ml/min, respectively). With saline infusion alone in these same dogs, behavioral stress decreased sodium excretion (-48 +/- 7% from 316 microEq/min) and urine flow rate (-40 +/- 7% from 1.7 ml/min). Mean arterial pressure increased similarly among all conditions in this study. Since the three antagonists accumulate to a high degree in the kidney, but only propranolol abolished the excretory response to behavioral stress, renal beta adrenoceptors did not appear to mediate the excretory response.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1981

Beta-adrenergic influence on cardiac dynamics during shock-avoidance in dogs.

The role of beta-adrenergic receptors in the mediation of the cardiodynamic effects of a shock-avoidance task was evaluated in conscious dogs with the cardioselective beta-adrenergic antagonist practolol. The animals were chronically instrumented for the measurement of peak rate of change of left ventricular pressure (LV dP/dt), heart rate (HR), cardiac output (CO), systolic (SPB) and diastolic (DBP) blood pressure and total peripheral resistance (TPR), and were each subjected to brief bouts of shock-avoidance with and without practolol pretreatment (2-4 mg/kg). Shock-avoidance evoked reliable increases of LV dP/dt, HR, CO, SBP and DBP, and decreases of TPR. Beta-adrenergic blockade virtually eliminated LV dP/dt increases, attenuated HR and CO increase as well as the vasodilatation, diminished SBP increases in certain animals but did not affect DBP increases. Stable interindividual differences in the magnitude of LV dP/dt and HR increases during shock-avoidance were demonstrated; these differences were abolished by beta blockade. These findings indicate that a beta-adrenergic mechanism accounted for most of the rise of LV dP/dt during avoidance but contributed proportionally less to the elevations of HR and CO. Inter-individual differences in myocardial reactivity were however completely ascribable to beta-adrenergic factors.

Animals↗
PubMed1978

Effects of mild cardiovascular and cerebrovascular disorders on serial reaction time performance.

Medical examinations were used to classify 271 adults aged 18-77 into 6 groups: normotensive, treated and untreated hypertensive, coronary heart disease (CHD), transient ischemic attack (TIA), and recovered stroke. They were also divided by age into 3 groups: 18-36, 37-55, and over 55 years. Each subject completed 12 reaction time (RT) tasks which involved making 16 consecutive responses without interruption. Serial RT increased with age throughout the lifespan. RT was also increased in treated hypertensive patients; this slowing was unrelated to type of drug treatment. Patients with cerebrovascular disorders showed greater slowing and also made more errors; TIA patients showed greatest impairment. No significant performance deficits were observed in untreated hypertensive or CHD groups. However, a trend toward slowing among untreated hypertensive patients with high plasma renin activity was observed. Behavioral deficits associated with both aging and diagnosed vascular disorders were interpreted as evidence of impaired brain function.

Adolescent↗
PubMed1975

Slowing of response time in young and middle-aged hypertensive patients.

Reaction time (RT) was compared in 160 hypertensive and 43 normotensive adults. After being screened for coronary and cerebrovascular disorders, each subject completed 12 variations of a serial RT task. Subjects were blocked into normotensive, nonmedicated hypertensive, and medicated hypertensive groups, and into three age groups: 18-31; 32-45; 46-59. Response slowing was observed with increasing age. Significant slowing was also seen in the medicated but not the nonmedicated hypertensive group. Plasma renin activity (PRA) interacted with the medication factor; longest RTs were obtained for treated subjects with low and normal PRA and untreated subjects with high PRA. These results were interpreted in terms of changes in ability to autoregulate cerebral blood flow as a result of vascular damage.

Adolescent↗
PubMedDate not supplied

Effects of aerobic exercise training on hemodynamic responses during psychosocial stress in normotensive and borderline hypertensive type A men: a preliminary report.

This study assessed the effects of aerobic exercise training on cardiovascular responses to a 5-min reaction time competition task. Twenty-seven Type A men (aged 30-56) participated in this randomized study in which 14 underwent supervised aerobic training and 13 strength training, with sessions scheduled three times per week for 12 consecutive weeks. Aerobic exercise training was associated with a 13.6% increase in VO2max compared to 2.9% for the strength group. The effects of aerobic exercise training were most evident in subjects whose initial casual blood pressure readings fell in the borderline hypertensive range (N = 5). These individuals exhibited a general reduction in diastolic blood pressure (i.e., during rest, competition, and recovery) which was associated with a fall in both heart rate and total peripheral vascular resistance. Furthermore, diastolic pressure reactivity to the competition task was attenuated in borderline hypertensive subjects who underwent aerobic conditioning. These data are interpreted as preliminary findings suggesting that borderline hypertensives may be particularly responsive to the cardiovascular benefits of aerobic conditioning. For patients who have progressed to this stage of hypertensive disease, aerobic exercise may be of ameliorative value.

Adult↗
PubMedDate not supplied

Gender differences in blood pressure control during a variety of behavioral stressors.

This study assessed gender differences in hemodynamic response patterns to behavioral stressors. In addition, the extent to which gender differences in cardiovascular reactivity were a function of the type of challenge was determined by employing tasks relying on stereotypically male areas of competence and a task relying on stereotypically female areas of competence. Sixteen female and 15 male graduate, medical or dental students were exposed to two speech tasks and two math tasks. While there were no significant differences in blood pressure reactivity between the genders, females exhibited significantly greater cardiac output increases across all tasks than males, while males tended to respond with greater increases in total peripheral resistance compared with females. Furthermore, during two of the tasks, significantly more females were classified as myocardial hyperreactors (based on increases in cardiac output), while significantly more males were vascular hyperreactors (based on increases in total peripheral resistance). A post hoc analysis also indicated an apparent association between oral contraceptive use and higher cardiovascular reactivity among the females tested. This association may have been a consequence of the decision to test all women during days 10 to 14 of the menstrual cycle when reactivity in women not using oral contraceptives may be suppressed.

Adult↗
PubMedDate not supplied

Depression and type A behavior pattern in patients with coronary artery disease: relationships to painful versus silent myocardial ischemia and beta-endorphin responses during exercise.

A sample of 45 patients with a history of coronary heart disease and documented myocardial ischemia during exercise testing were evaluated in an investigation of the possible relationships between psychological factors (depression and Type A behavior pattern), plasma beta-endorphin response and pain experience during maximal exercise-induced ischemia. Depression was assessed using the MMPI-D subscale, while Type A was evaluated using the Structured Interview. All patients developed ischemia during exercise as defined by ST-segment depression; however, only 18 patients reported anginal pain. Patients with high depression scores (MMPI-D greater than or equal to 70; n = 13) showed lesser increases in plasma beta-endorphin levels, tended more often to report anginal pain and rated pain as more severe during exercise than patients with low depression scores (MMPI-D less than 60; n = 18). Hemodynamic responses and severity of ischemia (assessed by ejection fraction changes and wall-motion abnormalities) did not differ between depression groups. Even after adjustment for group differences in exercise duration, depression was significantly associated with a lesser beta-endorphin response in the sample as a whole and, among patients reporting angina, with earlier pain onset and greater pain duration and severity. In contrast, when Type A versus B/X subgroups were compared, no differences in pain experience, beta-endorphin response or measures of ischemia were obtained. These findings suggest that in patients with ischemic heart disease, there may be a relationship between depression and anginal pain which may in part involve a blunted or absent beta-endorphin response.

Aged↗
PubMedDate not supplied

Cardiovascular responses to an active coping challenge as predictors of blood pressure patterns 10 to 15 years later.

To assess the long-term predictive importance of high cardiovascular reactivity in relation to subsequent blood pressure, 51 men from a pool of 204 men originally tested at age 18 to 22 years were recruited for blood pressure assessment 10 to 15 years later. Initial testing uniformly involved monitoring of systolic pressure, diastolic pressure, and heart rate during a reaction time task involving threat of shock. In 30 of the 51 men who participated at follow-up, initial testing had also included separate visits to obtain relaxation-only baseline levels of the cardiovascular indices. At follow-up, in addition to clinic-type stethoscopic determinations, blood pressure and heart rate were assessed during work and social and leisure activities via ambulatory monitoring. Men with higher levels of systolic pressure during the task showed higher stethoscopic and ambulatory systolic pressure at follow-up. Likewise, men with higher levels of diastolic pressure during the task showed higher diastolic levels at follow-up. In the 30 men with both good task and baseline data from initial testing, those with high heart rate reactivity (task minus baseline) showed higher systolic, diastolic, and heart rate levels at follow-up than low heart rate reactors, even though their baseline blood pressures had not differed at initial testing. Similarly, men with high systolic reactivity showed higher diastolic pressure at follow-up than low systolic reactors. Multiple regression analyses also demonstrated that systolic, diastolic, and heart rate reactivity improve prediction of follow-up blood pressure when added to models incorporating the standard risk factors, baseline blood pressure, and parental history of hypertension.

Adaptation, Psychological↗
PubMedDate not supplied

Heart rate variability in patients with coronary artery disease: differences in patients with higher and lower depression scores.

OBJECTIVE: This study tested the hypothesis that coronary artery disease patients with higher depression scores have lower heart rate variability during daily life. METHOD: Thirty-three men and nine women, ranging in age from 46 to 79, with coronary artery disease and exercise-induced ischemia were studied. The standard deviation of normal R-R intervals (SDNN) and average heart rate were obtained from 24-hour ambulatory electrocardiographic monitoring. Patients were grouped by a median split of the Minnesota Multiphasic Personality Inventory (MMPI-D) score. RESULTS: SDNN was lower (p = .009) and average heart rate was higher (p = .003) in patients with higher depression scores. These relationships remained substantially unaltered after statistically adjusting for the only demographic/clinical factor that varied between the groups: gender. CONCLUSIONS: In comparison to the lower depression score group, those with higher depression scores had lower heart rate variability during daily life. These findings may be related to the reported relationship between depression and survival risk in patients with coronary artery disease.

Arousal↗
PubMedDate not supplied

Ischemic but not thermal pain sensitivity varies across the menstrual cycle.

OBJECTIVE AND METHOD: Findings from both animal and human research suggest that pain sensitivity changes across the menstrual cycle; however, among humans the nature of these menstrual cycle effects remains unclear. The present study used a repeated-measures design to evaluate changes in thermal and ischemic pain responses during three phases of the menstrual cycle, midfollicular (postmenstrual), ovulatory, and mid-to-late luteal (premenstrual), in 11 healthy women. The cycle phase during which subjects began their participation was determined randomly. Plasma levels of estrogen, progesterone, luteinizing hormone (LH), testosterone, and beta-endorphin were determined at each experimental session. Participants also completed a daily diary of physical and emotional symptoms for two complete menstrual cycles before the experimental sessions. RESULTS: The results indicated that women showed less ischemic pain sensitivity during the midfollicular compared with the ovulatory and mid-to-late luteal phases, but thermal pain responses did not vary significantly across menstrual cycle phases. Physical and emotional symptoms were minimal and did not change significantly across the menstrual cycle. CONCLUSIONS: These findings indicate greater ischemic but not thermal pain sensitivity among women after the midcycle LH surge. The practical relevance and potential mechanisms of these findings are discussed.

Adult↗