Establishing the validity of a novel passive stress task

Laboratory tasks used to elicit a cardiovascular stress response in the laboratory can involve either active or passive coping. However, in previous work, passive stress tasks often incorporate a distinct physical stress element, such as the handgrip or cold pressor task, meaning observed changes in cardiovascular parameters may be the result of the physical element of the stressor rather than truly reflecting psychological stress. The present study aimed to establish the validity of a psychological passive stressor; one more analogous to active tasks than those previously employed in laboratory studies. Twenty-six young, healthy adults completed a speech task in the laboratory following a resting baseline period. Twelve months later, they were invited back to the laboratory and watched the video recording of their speech. Analyses confirmed that while both tasks elicited significant SBP and DBP change (all ps < .001), only the active task was associated with HR and CO reactivity (both ps < .001), while only the passive task was associated with TPR reactivity (p = .028). Furthermore, the passive stressor was associated with a mixed hemodynamic profile, whereas the active stressor was associated with a clear myocardial profile. This study confirms that watching a video recording of oneself complete a speech task is associated with a more vascular response profile, a response associated with passive coping contexts.     

Relation between beta-adrenergic receptor density and lymphocyte proliferation associated with acute stress

The relations between acute changes in beta-adrenoreceptor density on lymphocytes and lymphocyte proliferation to a laboratory speech stressor were examined. Male participants either prepared and delivered a challenging speech task or read from a list of words. Participants engaged in the speech task, but not those involved in reading, exhibited significant increases in systolic blood pressure (an index of sympathetic nervous system arousal) and beta-adrenoreceptor density, accompanied by significant decreases in lymphocyte proliferation to pokeweed mitogen (PWM) but not concanavalin A (Con A). Increases in adrenoreceptor density significantly predicted decreases in lymphocyte activity in response to both mitogens. The increases in beta-adrenoreceptor density in the speech task condition occurred within 5 min after the baseline period, when participants were preparing for the speech task, but not yet speaking. These findings suggest that an acute stressor eliciting sympathetic nervous system activity can evoke rapid changes in beta-adrenoreceptor activity and decreases in mitogenic responses.     

Aerobic Fitness Affects Cardiovascular and Catecholamine Responses to Stressors

Subjects of varying degrees of aerobic fitness were subjected to four laboratory stressors in a test of the hypothesis that aerobic fitness is associated with decreased responsiveness to stressors other than exercise. Blood pressure, heart rate, norepinephrine, epinephrine, and psychological responses to a film of industrial accidents (passive psychological stressor), the Stroop word color task (active psychological stressor), the cold pressor test (passive physical stressor), and running to exhaustion on a treadmill (active physical stressor) were measured. Baseline systolic blood pressure and relative diastolic responses to the film, Stroop task, and exercise were smaller in fit subjects over 40 than in less fit subjects of the same age group. Heart rates were lower in fit subjects at most times, except during and after maximal exercise. Norepinephrine was lower after 9 min of exercise in fit subjects, but was much higher at exhaustion, after these subjects had accomplished more work. Norepinephrine levels fell rapidly and were not different among groups 3 and 10 min after exercise. There was no preferential generalization of the “fitness effect” to the active psychological task.     

Immunological Marker Analysis of Mitogen-Induced Proliferating Lymphocytes Using Brd U Incorporation or Screening of Metaphases

The proliferative effects of the mitogens phytohaemagglutinin (PHA), concanavalin A (Con A), pokeweed mitogen (PWM), and staphylococcal protein A (SpA) were investigated using two different methods which enable immunological marker analysis of proliferating cells: either surface marker labelling followed by BrdU incorporation or screening of metaphases after surface marker labelling. Therefore peripheral blood mononuclear cells from six healthy volunteers were stimulated with these four mitogens. Both PHA and Con A gave rise to more CD8+ than CD4+ proliferating cells. PHA, but not Con A, induced B-cell proliferation as well. PWM mainly caused T-cell proliferation. SpA also appeared to be a potent T-cell mitogen in addition to its capacity to induce B-cell proliferation. However, in contrast to the other mitogens SpA predominantly stimulated CD4+ cells.     

The effect of laboratory stressors on glycemic control and gastrointestinal transit time

This study compared effects of an active coping task (computerized stressors involving arithmetic, anagrams, and Atari games) and a passive coping task (cold pressor) on gastrointestinal transit time and glycemic response to an oral glucose load. Eleven normal weight males were studied; subjects participated in three counterbalanced sessions, each including a 45-minute baseline, 20-minute experimental period (active coping, passive coping, or nonstress control) and 2.5-hour recovery period. The stressors produced different cardiovascular and catecholamine responses; systolic and diastolic blood pressure were highest during cold pressor (p less than 0.001), heart rate was highest during computer stressor (p less than 0.001), and norepinephrine excretion was greatest during cold pressor (p less than 0.002). However, both stressors delayed gastrointestinal transit time compared with the control condition (p less than 0.009 and p less than 0.026 for cold pressor and computerized stressor, respectively) and both delayed the time of peak glucose response (p less than 0.002 and p less than 0.05, respectively). Implications of these findings for patients with diabetes and for effects of stress on eating behavior are discussed.     

Hemodynamic profile of stress-induced anticipation and recovery.

Systolic and diastolic blood pressure, heart rate, stroke volume, cardiac output, and total peripheral resistance were measured in 100 healthy men and women with the aim of investigating hemodynamic profile during anticipation of, and recovery from, exposure to active and passive laboratory stressors. A 5-min anticipatory period preceded two tasks, both of which lasted 2.5 min. The tasks were mental arithmetic ('beta-adrenergic' stress) and the cold pressor test ('alpha-adrenergic' stress). Each task was followed by a 5-min recovery period. Blood pressure and heart rate were measured with a FinaPres 2300e, and stroke volume, cardiac output, and total peripheral resistance were computed from these parameters. Salivary cortisol was measured in relation to both tasks, and participants completed tests of state and trait anxiety, locus of control, and hostility. As expected, mental arithmetic and the cold pressor test elicited myocardial and vascular patterns of reactivity, respectively. However, contrary to expectations, anticipatory and recovery hemodynamic profile involved essentially vascular responding for both stressors. Salivary cortisol increased in response to both tasks but only weakly correlated with hemodynamic changes. None of the subjective measurements was a strong predictor of physiological reactivity. The findings suggest that stress-induced anticipatory and recovery reactivity may be generally vascular rather than myocardial. This could have important implications in light of suggestions that anticipatory and recovery responses may be better predictors of subsequent cardiovascular disease than direct stress-induced reactivity.     

Airflow and autonomic responses to stress and relaxation in asthma: the impact of stressor type.

The impact of stress on respiratory airflow in asthmatics is unclear. Part of the uncertainty may spring from the different physiological effects of different stressors. Given their potential to elicit increases in parasympathetic vagal activity, stressful situations that present few opportunities for coping (passive coping stressors) may be particularly problematic for people with asthma. Thirty-one adult asthmatics participated in a protocol including a widely used passive coping stressor (the cold pressor test), an active coping stressor (mental arithmetic), an interview about an upsetting asthma-related incident (viewed as a potential passive coping stressor given the exposure to unpleasant memories), and progressive muscle relaxation. Repeated measurements of airflow (via peak expiratory flow), vagal tone (via heart rate variability), and other variables were obtained. The cold pressor test, asthma interview and progressive muscle relaxation produced significant decreases in airflow compared to the baseline period. The cold pressor test and progressive muscle relaxation produced significant, complementary increases in vagal tone. These results suggest that passive coping stressors and other stimuli (e.g., certain forms of relaxation) that elicit increased vagal tone may be associated with poorer asthma control, a view consistent with a significant negative correlation between the participant's mean vagal tone response to the tasks and score on a measure of asthma self-efficacy.     

Parental History of Essential Hypertension, Active Coping, and Cardiovascular Reactivity

Differences in cardiovascular reactivity to stress between individuals with and without a family history of essential hypertension (EH) may be affected by stimulus characteristics and/or individual differences in behavioral response. Twenty-four male students with a parental history of EH and 24 without a parental history of EH participated in two laboratory sessions during which two “active’ (mental arithmetic and the Stroop word-color interference test) stressors and one “non-active’ (isometric hand-grip) stressor were presented. Family history subjects exhibited greater systolic blood pressure responses than non-family history subjects only to the two active stressors in Session 2, despite the fact that, overall, isometric hand-grip elicited the largest responses. High-performing Stroop subjects with a parental history of EH displayed greater heart rate responses to the task than high-performing subjects without a parental history of EH in both sessions. No group differences appeared among poor performers. The degree to which a stressor encourages active coping behavior appears to be one determinant of differences in cardiovascular response between individuals with and without a family history of EH.     

Lymphocyte stimulation and plasma inhibition in patients with malignant neoplasms. A comparative study with three mitogens.

The blastogenic response of lymphocytes from patients with malignant neoplasms was evaluated by stimulation with three phytomitogens (PHA, PWM, and Con A). The response of patient lymphocytes to all three mitogens was significantly lower than that of control lymphocytes, and most patients with abnormal PHA responses also responded abnormally to PWM and Con A. However, a few patients with normal PHA responses were abnormal to Con A, suggesting the suppression of a Con A-sensitive population. The observation that PWM responses were abnormal in patients with lowered PHA lymphocyte stimulation indicates that both T and B lymphocyte mitogen responses were suppressed in these patients. Plasma from patients was capable of either inhibiting or enhancing lymphocyte mitogen stimulation. However, inhibitory plasmas were generally from patients with abnormal mitogen responses.     

Depressive symptoms and attenuated physiological reactivity to laboratory stressors

There is evidence that depressive symptoms are associated with attenuated physiological reactivity to active stressors. However, it is not known whether blunted reactivity in depressed individuals is stressor-specific. We examined cardiovascular and electrodermal reactivity in non-clinical participants with varying levels of depressive symptoms to different active and passive stressors. Depressive symptoms were inversely related to both blood pressure and skin conductance reactivity during a public speaking task and the viewing of the speech video. However, no effects were found during a cold pressor task. Together these findings suggest that depressive symptoms are related to attenuated sympathetic nervous system reactivity in response to self-relevant stressors.     

Lymphocyte Transformation with Mitogens and Antigens during Normal Human Pregnancy: a Longitudinal Study

In a longitudinal analysis of immunological changes in normal human pregnancy, twenty-two pregnant women were studied, with blood samples taken before pregnancy, during its course, at delivery, and 3–5 months after delivery. The blood samples were frozen successively, using a cryobiological freezing system, and were stored until the whole longitudinal series was obtained. The collected material for a longitudinal series was then thawed and tested in one seance. Lymphocyte transformation tests were performed with stimulation with the mitogens phytohae-magglutinin (PHA), pokeweed mitogen (PWM), concanavalin A (Con A) and the specific antigens tuberculin purified protein derivative (PPD), Candida albicans (CA), Staphylococcus aureus (SA) and streptokinase/streptodornase (SK/SD). No changes were found in PHA or in PWM responses, whereas there were significant changes in the Con A response, with lowest values in the middle of pregnancy. PPD, CA, SA and SK/SD responses all reached lowest values towards the end of pregnancy, with increases subsequently, after delivery. These findings seem to show that T suppressor function is increased and B-lymphocyte function decreases during the course of pregnancy.     

Hemodynamics of Blood Pressure Responses During Active and Passive Coping

This laboratory study was designed to address a number of interrelated issues regarding cardiovascular reactivity to psychological stress. One objective was to extend the previous research comparing cardiovascular responses during active versus passive coping, by comparing responses to two task conditions designed to be similar in all ways except the opportunity to make a response influencing the task's outcome. A second objective was to compare responses to two different passive film tasks, which differed in outcome uncertainty and the degree of vicarious active coping achieved through identification with the role portrayed by the actors. A third objective was to evaluate whether individuals are predisposed to exhibit a particular hemodynamic pattern underlying their blood pressure adjustments, independently of the task demands imposed. Ninety healthy young adult male subjects were tested in pairs on a series of tasks that included a competitive reaction-time task, an active as well as a passive phase of a team reaction-time task, and passive viewing of two film segments. The tasks demanding active coping responses tended to raise blood pressure due primarily to an increase in cardiac output, while vascular resistance fell. During passive coping demands cardiac output increased to a lesser extent, but vascular resistance also tended to increase, thereby raising blood pressure by their synergistic effects. However, these patterns were not typical of all participating subjects. On the basis of their cardiac output and vascular resistance responses to the competitive reaction-time task, one third of the subjects were categorized as being high myocardial reactors (n = 30) and another third high vascular reactors (n = 31). Post-hoc analyses of responses to the other tasks, based on these categorizations, indicated that the hemodynamic basis of reactivity is an individual characteristic only partially modified by coping demands. The active/passive coping dimension is discussed both conceptually and in relation to the role of stress in the etiology of hypertension.     

Lesions of the medial septal nucleus produce a long-lasting inhibition of T lymphocyte proliferation

The influence of the central cholinergic system on the immune system was studied in Wistar rats by lesioning the medial septal nucleus. This lesion inhibited T cell proliferation of splenocytes and thymocytes induced by the mitogens concanavalin A (Con A), phytohemagglutinin (PHA) and pokeweed mitogen (PWM) up to 25 days and did not affect proliferation at 40 days after lesioning. In contrast, the response to the B cell mitogen lipopolysaccharide from E. coli (LPS) was not affected at any time. These findings suggest a regulatory role of the cholinergic medial septal nucleus on T lymphocyte proliferation.     

The influence of organic acids on the proliferation of human peripheral lymphocytes activated by concanavalin a and pokeweed mitogen

The present study was undertaken to assess the influence of 25 organic acids, which appear in high concentrations in tissues of patients with various organic acidaemias, on the proliferation of human peripheral lymphocytes stimulated with concanavalin A (Con A) (a T-cell activator) and pokeweed mitogen (PWM) (predominantly a B-cell activator). Mononuclear cells were cultivated in flat-bottomed 96-well microplates at 37°C for 96 (Con A) or 144h (PWM) in the presence of one mitogen at different concentrations and of one acid at doses ranging from 1 to 5 mM. Control cultures did not contain any acid. Cell reactivity was measured by the incorporation of tritiated thymidine into cellular DNA. We observed that, among the 25 acids tested, aminoadipic (AAD), 2-hydroxy-3-methylvaleric (HMV), 2-ketoisocaproic (KIC), 2-methylbutyric (MBA), propionic (PPA) and tiglic (TIG) acids strongly suppressed lymphocyte DNA synthesis in Con A-supplemented cultures, whereas in cultures stimulated with PWM, 2-ketoisovaleric (KIV) and PPA acids presented the same effect. In contrast, lactic (LAC) and pyruvic (PYR) acids activated lymphocyte DNA synthesis in cultures treated with Con A, the same effect occurring with LAC acid for PWM-stimulated lymphocytes. The most inhibitory or stimulatory acids were added to cultures at different times after the beginning of the incubation period when mitogens were added. Except for HMV, KIC, PPA and LAC acids, whose actions persisted even after 24 h from the beginning of culture, the others only exerted their effects when added at time zero. The present study therefore demonstrated that some organic acids modulate DNA synthesis in Con A- and PWM-stimulated human lymphocytes.     

Seasonal Differences in the Rhythmicity of Human Male and Female Lymphocyte Blastogenic Responses

To test the hypothesis that there are circannual differences in mitotic activity in males and females, normal human peripheral blood lymphocytes were stimulated with suboptimal concentrations of Phytohemagglutinin (PHA), Concanavalin A (Con A) and Poke weed mitogen (PWM) over two summer/winter cycles. Lymphocyte responses for the entire population were significantly higher in the summer than in the winter. The same results were observed when responses were compared between a summer and a successive winter. However, when male and child-bearing age female responses were compared, females showed a higher significant difference for PHA and Con A between summer and winter, but not for PWM. These different responses due to season may reflect a relationship between the neuroendocrine and immune systems. At the cell level, these results suggest that an inherent difference exists between female and male lymphocytes and that these lymphocytes are sensitive to seasonal changes.     

Seasonal Differences in the Rhythmicity of Human Male and Female Lymphocyte Blastogenic Responses

To test the hypothesis that there are circannual differences in mitotic activity in males and females, normal human peripheral blood lymphocytes were stimulated with suboptimal concentrations of Phytohemagglutinin (PHA), Concanavalin A (Con A) and Poke weed mitogen (PWM) over two summer/winter cycles. Lymphocyte responses for the entire population were significantly higher in the summer than in the winter. The same results were observed when responses were compared between a summer and a successive winter. However, when male and child-bearing age female responses were compared, females showed a higher significant difference for PHA and Con A between summer and winter, but not for PWM. These different responses due to season may reflect a relationship between the neuroendocrine and immune systems. At the cell level, these results suggest that an inherent difference exists between female and male lymphocytes and that these lymphocytes are sensitive to seasonal changes.     

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.     

Antigen and Unspecific Mitogen Stimulation of Lymphocytes Eluted from Rheumatoid Inflammatory Tissue

Lymphocytes were eluted from synovial tissues of 17 patients with classical rheumatoid arthritis, using a procedure previously reported. Stimulation was obtained wit h the unspecific mitogens phytohemaggalutinin (PHA), pokeweed mitogen (PWM), and concanavalin A (Con A) as well as with purified protein derivative of tuberculin (PPD) and mitomycin-C-treated allogeneic lymphocytes, whereas Candida antigen usually gave a low response. The pattern of reactivity o t unspecific mitogens was similar to that obtained with lymphocytes from peripheral blood of rheumatoid arthritis patients. Two different PPD preparations usually gave transformation of the same magnitude as seen with PHA. This was in contrast to the reactivity of the peripheral blood lymphocytes. It could be demonstrated that the elution procedure initiated some degree of lymphocyte transformation, mainly potentiating the responses to PHA and Con A.     

Physiologic responses to cognitive challenge during pregnancy: effects of task and repeat testing.

Physiological responses to stress during pregnancy are believed to influence birth outcomes. Researchers have studied pregnant women in laboratory stressor paradigms to investigate these associations, yet normative data on cardiovascular and respiratory responses to laboratory challenge during pregnancy are not yet established. To begin to establish such normative data, this study examined the effects of task and repeat stressor exposure on reactivity in third-trimester pregnant women. Thirty-one healthy pregnant women (mean age=27 years; range 18-36) between the 33rd and 39th week of pregnancy, were instrumented for continuous electrocardiography, blood pressure (BP), and respiration data. Subjects rested quietly for a 5-min baseline and then performed both a mental arithmetic stressor and a Stroop color-word-matching task, each 5 min in length and each followed by a 5-min recovery period. The order of the tasks was counterbalanced. After each 5-min period, subjects rated the period on a 10-point stress scale. Averaged across task type and challenge period, systolic and diastolic BP and respiration rate increased significantly in response to cognitive challenge, but heart rate (HR) did not. When data were examined for task and period effects, the following results emerged: the Stroop task elicited significantly greater systolic BP and HR reactivity than the arithmetic task, yet subjects rated the arithmetic task as more stressful. Averaged across task type, subjects showed greater systolic BP reactivity during the second challenge period compared to the first. Finally, women's BP tended to drift upward and did not return to baseline during the first recovery period. These findings indicate that averaging data across tasks and periods can obscure the time course of response patterns that may be important in the study of associations between maternal stress and perinatal development, as well as in other research on reactivity to repeat stress exposure.     

PPD and mitogen responsiveness of lymphocytes from patients with atopic dermatitis.

Lymphocytes from twenty-five patients with atopic dermatitis were investigated for their in vitro reactivity to stimulation with tuberculin (PPD), lipopolysaccharide (LPS), phytohaemagglutinin (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM). The response to a low dose of Con A was increased, and the reactivity in unstimulated cultures tended to be lower than similar cultures from the control group. Addition of inactivated autologous plasma to the cultures had an inhibitory effect, when the plasma came from patients with high levels of IgE. The patients' in vitro reactivity to PPD in a leucocyte migration test was equal to that found in normal persons and no effect was observed after addition of autologous serum. The mean percentage of E rosette forming cells was significantly reduced in patients with high levels of IgE. The number of EAC rosette forming cells was within normal range. It is hypothesized that the observations could reflect the existence of suppressor mechanisms in patients where the immune system is strongly stimulated.