Sink or Swim: Ions and Organics at the Ice-Air Interface.

The ice-air interface is an important locus of environmental chemical reactions. The structure and dynamics of the ice surface impact the uptake of trace gases and kinetics of reactions in the atmosphere and snowpack. At tropospheric temperatures, the ice surface is partially premelted. Experiments indicate that ions increase the liquidity of the ice surface but hydrophilic organics do not. However, it is not yet known the extent of the perturbation solutes induce at the ice surface and what is the role of the disordered liquid-like layer in modulating the interaction between solutes and their mobility and aggregation at the ice surface. Here we use large-scale molecular simulations to investigate the effect of ions and glyoxal, one of the most abundant oxygenated volatile organic compounds in the atmosphere, on the structure, dynamics, and solvation properties of the ice surface. We find that the premelted surface of ice has unique solvation properties, different from those of liquid water. The increase in surface liquidity resulting from the hydration of ions leads to a water-mediated attraction of ions at the ice surface. Glyoxal molecules, on the other hand, perturb only slightly the surface of ice and do not experience water-driven attraction. They nonetheless accumulate as dry agglomerates at the ice surface, driven by direct interactions between the organic molecules. The enhanced attraction and clustering of ions and organics at the ice surface may play a significant role in modulating the mechanism and rate of heterogeneous chemical reactions occurring at the surface of atmospheric ice particles.

Adaptive style and physiological reactivity during a laboratory stress paradigm in children with cancer and healthy controls.

Repressive adaptation has been conceptualized as one pathway to psychological resilience in children with cancer, but the physiological costs of maintaining a repressive adaptive style are currently unknown. The goal of this study was to examine physiological functioning as a function of adaptive style in children with cancer (N = 120) and healthy controls (N = 120). Children completed self-report measures of state anxiety and defensiveness prior to participating in three verbal stress tasks while monitoring blood pressure, electrocardiogram, and electrodermal response, and rated their anxiety following each task. Findings indicated no consistent differences in baseline indices and physiological reactivity as a function of adaptive style or health status (cancer vs. control). In addition, children identified as having a repressive adaptive style did not exhibit greater verbal-autonomic discrepancy than low-anxious children. In contrast to findings with adults, children with a repressive adaptive style do not appear to experience adverse effects of this coping style in terms of physiological reactivity.

The effects of race on peak oxygen consumption and survival in patients with systolic dysfunction.

BACKGROUND: The relationship of peak exercise oxygen consumption (VO(2)) to survival in black heart failure (HF) patients is not well established. We examined the effects of race on peak VO(2) values and survival in HF patients with systolic dysfunction. METHODS AND RESULTS: This study evaluated consecutive ambulatory HF patients who underwent symptom-limited stress tests with breath-by-breath expired gas analyses using ramped treadmill protocols. The relationship between cardiopulmonary exercise parameters and patient transplant-free survival was assessed by race. This study included 580 HF patients (mean age 52 +/- 12 years; 28% females; 22% blacks; mean left ventricular ejection fraction 26 +/- 12%; mean body mass index 28.7 +/- 5.4; 73% on beta-blocker). Black patients had a significantly lower peak VO(2) than white patients (14.2 +/- 5.2 versus 16.4 +/- 7.0; P < .0001), despite adjusting for identified covariates. However, there was no significant difference in the 1-year transplant-free survival between black and white HF patients (87% versus 85%; P = NS). Peak VO(2) was significantly associated with survival in both racial groups. CONCLUSIONS: Black HF patients had significantly lower peak VO(2), but yet had equivalent survival rates at 1 year. Further study is warranted to clarify the impact of these racial differences on the timing of cardiac transplantation black HF patients.

Bovine Arch and Stroke Laterality.

Background Left-hemispheric strokes are more frequent and often have a worse outcome than their right-hemispheric counterparts. This study aimed to evaluate whether cardioembolic stroke laterality is affected by anatomical characteristics of the aortic arch. We hypothesized that laterality varies between patients with bovine versus standard arch. Methods and Results We retrospectively identified 1598 acute cardioembolic strokes in patients with atrial fibrillation from our institutional stroke database (2009-2017). Inclusion criteria were acute anterior circulation ischemic infarct and availability of both arch and brain imaging (magnetic resonance imaging or computed tomography). Alternative causes of stroke and anomalous arch were excluded. Imaging was reviewed for stroke characterization and laterality and arch branching pattern. Bovine arch denotes a common origin of the brachiocephalic trunk and left common carotid artery. Strokes were classified as bilateral (left or right). Univariate analysis was performed using chi-square tests. The final cohort comprised 615 patients, mean age 77 years (SD 11.8 years) with 376 women (61%) and 33% white, 30% black, and the remainder mixed/Hispanic. Standard arch (n=424) stroke distribution was left 43.6% (185), right 45.1% (191), and bilateral 11.3% (48). Bovine arch (n=191) stroke distribution was left 51.3% (98), right 35.6% (68), and bilateral 13.1% (25). Bovine arches were associated with more left-sided strokes compared with standard arches (P=0.018). There was an association between black race and bovine arch (P=0.0001). Conclusions Bovine aortic arch configuration is associated with left hemispheric laterality of cardioembolic stroke. This study enriches the understanding that arch anatomy influences stroke laterality and highlights the need for further research into the causative hemodynamic factors.

Cardiorespiratory Response to Moderate Hypercapnia in Female College Students Expressing Behaviorally Inhibited Temperament.

Behaviorally inhibited (BI) temperament is marked by heightened behavioral sensitivity to environmental threats. The degree to which threat sensitivity is reflected in cardiorespiratory responses has been relatively unexplored. Female college students were exposed to modest hypercapnia (7.0% CO2) or ambient air (AA) while engaging in a computerized task with cued reinforcement features. All physiological variables except for blood pressure were processed in 4 min epochs corresponding to pre-exposure, exposure, and post-exposure. Primary respiratory measures were respiratory frequency (fb), tidal volume (VT), and minute ventilation (VE). Electrocardiograms (ECGs) were processed using ARTiiFACT software with resultant heart rate variability (HRV) measures in the frequency domain and time domain. Consistent with the literature, modest hypercapnia increased VT, Fb, and VE. No differences in respiratory parameters were detected between BI and non-behaviorally inhibited individuals (NI). For HRV in the time domain, RMSSD and NN50 values increased during CO2 inhalation which then returned to pre-exposure levels after CO2 cessation. Hypercapnia increased high frequency (HF) power which then recovered. BI exhibited reduced low frequency (LF) power during the pre-exposure period. For NI, LF power reduced over the subsequent phases ameliorating differences between BI and NI. Hypercapnia improved the task performance of BI. This is the largest study of female reactivity to hypercapnia and associated HRV to date. In general, hypercapnia increased time domain HRV and HF power, suggesting a strong vagal influence. Those expressing BI exhibited similar respiratory and HRV reactivity to NI despite inherently reduced LF power. Although 7% CO2 represents a mild challenge to the respiratory and cardiovascular systems, it is nonetheless sufficient to explore inherent difference in stress reactivity in those vulnerable to develop anxiety disorders.

Intolerance of uncertainty in opioid dependency - Relationship with trait anxiety and impulsivity.

Intolerance of uncertainty (IU) is the tendency to interpret ambiguous situations as threatening and having negative consequences, resulting in feelings of distress and anxiety. IU has been linked to a number of anxiety disorders, and anxiety felt in the face of uncertainty may result in maladaptive behaviors such as impulsive decision making. Although there is strong evidence that anxiety and impulsivity are risk factors for addiction, there is a paucity of research examining the role of IU in this disorder. The rate of opioid addiction, in particular, has been rising steadily in recent years, which necessitates deeper understanding of risk factors in order to develop effective prevention and treatment methods. The current study tested for the first time whether opioid-dependent adults are less tolerant of uncertainty compared to a healthy comparison group. Opioid dependent patients undergoing methadone maintenance therapy (n = 114) and healthy comparisons (n = 69) completed the following scales: Intolerance of Uncertainty Scale, the Barrett Impulsivity Scale, and the State Trait Anxiety Inventory. Analysis revealed that these measures were positively correlated with each other and that opioid-dependent patients had significantly higher IU scores. Regression analysis revealed that anxiety mediated the relationship between IU and impulsivity. Hierarchical moderation regression found an interaction between addiction status and impulsivity on IU scores in that the relationship between these variables was only observed in the patient group. Findings suggest that IU is a feature of addiction but does not necessarily play a unique role. Further research is needed to explore the complex relationship between traits and how they may contribute to the development and maintenance of addiction.

Cardiovascular reactivity to stress predicts future blood pressure in adolescence.

OBJECTIVE: This study evaluated the prospective relationship between cardiovascular reactivity to psychological stress and increases in resting blood pressure across a 3-year period among a multiethnic pediatric sample (N = 149). METHODS: Systolic and diastolic blood pressure; EKG heart rate, pre-ejection period, and mean successive difference of R to R intervals; and impedance-derived measures of cardiac output, stroke volume, and total peripheral resistance were collected during performance of four tasks that elicited different hemodynamic response patterns. Changes from baseline to each task were standardized and averaged to form eight composite scores. Analyses adjusted for time 1 baseline blood pressure and age, body mass index at baseline and change to follow-up, and duration of follow-up. RESULTS: Rises in SBP over the follow-up period were independently predicted by SBP (beta = 0.161, p =.009), DBP (beta = 0.132, p =.02), and CO (beta = 0.144, p =.02) composite measures of reactivity. Rises in DBP over the follow-up period were predicted by DBP (beta = 0.292, p =.003, respectively), and MSD (beta = -0.176, p <.03) composite measures of reactivity. TPR reactivity was not related prospectively to blood pressure rises. CONCLUSIONS: This study adds to the pediatric literature documenting an association between cardiovascular reactivity to stress and subsequent risk for hypertension. It is the first to show that impedance-derived measures of myocardial function during stress are related to future blood pressure levels.

Bupropion and paroxetine differentially influence cardiovascular and neuroendocrine responses to stress in depressed patients.

BACKGROUND: There exists a need to identify safe and effective treatments for depression in patients with coronary heart disease (CHD). METHODS: Using a cross-sectional design, 17 depressed patients being treated with bupropion (200-450 mg/day) were compared with 17 depressed patients being treated with paroxetine (10-50 mg/day) and with a group of 15 unmedicated, non-depressed controls for cardiovascular, neuroendocrine and heart rate variability (HRV) measures at rest and in response to mental and physical stressors. RESULTS: Regardless of treatment, both treated groups exhibited blunted plasma cortisol, plasma epinephrine, systolic blood pressure, cardiac output, and pre-ejection period responses to mental stressors relative to controls. Bupropion treated individuals exhibited greater total peripheral resistance (TPR) increases than either the paroxetine or control groups, and greater plasma norepinephrine (NE) increases to mental stressors than the paroxetine group. The bupropion group also displayed reduced HRV at rest relative to the controls and during orthostatic challenge relative to both the control and paroxetine groups. LIMITATIONS: Despite the fact that the treated groups were well matched for depression and other psychiatric histories, lack of randomization into treatment arms may be associated with a selection bias in the two treated groups. CONCLUSIONS: Although both pharmacological treatments were associated with a blunting of some cardiovascular and neuroendocrine responses to stress relative to controls, which may be reflective of their therapeutic mechanisms of action, the results of our study also suggest that bupropion is associated with a more detrimental autonomic profile than paroxetine, as reflected in increased TPR and NE, and reduced HRV. The results of this study may have implications for the pharmacological treatment of depression in CHD patients.

Stress task specific impairments of cardiovascular functioning in obese participants.

The role that excess adipose tissue plays in chronic inflammation gives rise to its importance as an independent risk factor in cardiovascular dysfunction. Operationalizing chronic stress as obesity, we sought to explore the relationship between obesity, perceived stress and cardiovascular reactivity and recovery from laboratory stressors. Cardiovascular function was assessed using blood pressure and heart rate. Two stress tasks (mental arithmetic and cold pressor) were employed to examine potential differences between type of stress and cardiovascular response. Body mass index (BMI) was able to predict dysfunction in both cardiovascular reactivity and recovery. Participants with a higher BMI exhibited blunted systolic blood pressure and heart rate reactivity to the mental arithmetic task. In contrast, BMI has an incongruent effect on blood pressure reactivity to the cold pressor task that is dependent on the level of perceived stress. This suggests that in some instances the effect of BMI on cardiovascular response to acute stress may be moderated by perceived stress. Further, we found greater adiposity was related to delayed heart rate recovery following both stress tasks.

Integrative commentary: implications of blunted reactivity.

The previous issue of the International Journal of Psychophysiology was a special issue that collected some of the latest emerging evidence on blunted reactivity and its relationships with a variety of negative health outcomes. This commentary on the special issue briefly reviews each of the contributions and then provides some thoughts on the general themes that run through these papers. The findings from the special issue suggest that both lower and higher than expected cardiovascular and neuroendocrine responses to active psychological challenges may be maladaptive and differentially associated with adverse health sequelae.

Gender differences and the relationships of perceived background stress and psychological distress with cardiovascular responses to laboratory stressors.

The primary aim of this study was to evaluate the relationships of perceived background stress and self-reported psychological distress on cardiovascular reactivity during acute laboratory stressors. The Perceived Stress Scale (PSS) was used as the measure of perceived background stress, and the General Health Questionnaire (GHQ) was used as the measure of psychological distress. A secondary aim was to examine whether background stress and psychological distress affected the susceptibility to induction of a negative mood using music. Heart rate (HR) and blood pressure (BP) were measured in 149 female and male college students at rest and during a stressful mental arithmetic (MA) task and a mood induction procedure. Higher scores on the GHQ were associated with lower systolic BP reactivity during the MA task by all participants. Higher scores on the PSS and GHQ were also associated with lower diastolic BP and HR reactivity, but only in females. Thus, higher self-reports of background stress and psychological distress tended to result in blunted reactivity to an acute laboratory challenge. Higher levels of background stress and psychological distress were not associated with greater susceptibility to a negative mood induction. This study adds to the growing literature indicating that potentially negative health outcomes may be associated with diminished cardiovascular reactivity under certain conditions.

The relationships of impulsivity and cardiovascular responses: the role of gender and task type.

The present study was conducted to assess the relationships of impulsivity with both baseline cardiovascular levels and reactivity during two laboratory stressors in both female and male young adults. Heart rate (HR), blood pressure (BP), and heart rate variability (HRV) were measured at rest and during a reaction time and speech task in one hundred and one undergraduate students. Impulsivity was measured using the Barratt Impulsiveness Scale-11 and Block's Ego-Undercontrol Scale. Males and females responded similarly to both laboratory tasks and also did not differ on the impulsivity scales. For males, higher scores on impulsivity were associated with higher systolic BP levels at rest but decreased systolic BP and HR reactivity during the preparation of the speech task; females showed no relationships of resting cardiovascular levels with impulsivity, but more impulsive females did show decreased HR response during speech preparation. No significant relationships were found between impulsivity and either HRV levels or reactivity. It is speculated that tasks involving a degree of planning may be important to find relationships between impulsivity and cardiovascular reactivity, especially in males.

Effects of gender on peak oxygen consumption and the timing of cardiac transplantation.

OBJECTIVES: This study examines the gender effects on peak exercise oxygen consumption (VO2) and survival in heart failure (HF) patients and their implications for cardiac transplantation. BACKGROUND: The predictive value of peak VO2 in women HF patients is poorly established but is one of the indicators used to optimally time cardiac transplantation in women. METHODS: A total of 594 ambulatory HF patients (mean age 52 +/- 12 years, 28% women, mean left ventricular ejection fraction 26 +/- 12%, 73% on beta-blocker) underwent symptom-limited exercise tests with breath-by-breath expired gas analyses using ramped treadmill protocols. Kaplan-Meier survival curves were generated for each gender and compared using log-rank tests. RESULTS: Women had a significantly lower peak VO2 than men (14.0 +/- 4.9 ml/kg/min vs. 16.6 +/- 7.1 ml/kg/min; p < 0.0001), despite being younger (48.9 +/- 11.5 years vs. 53.2 +/- 12.4 years; p < 0.0001) and having a higher left ventricular ejection fraction (29 +/- 13% vs. 25 +/- 11%; p < 0.0003). However, the one-year transplant-free survival was significantly lower for men than for women (81% vs. 94%, p < 0.0001), a finding seen across each Weber class. Cox regression analyses confirmed the protective effects of female gender on transplant-free survival when controlling for peak VO2, age, race, beta-blocker use, and type of cardiomyopathy. The peak VO2 associated with 85% one-year transplant-free survival was significantly higher in men than in women (11.5 vs. 10.0 ml/kg/min). CONCLUSIONS: Women had a significantly lower peak Vo(2) than men, but had better survival at all levels of exercise capacity. The current practice of uniform application of peak VO2 as an aid to determine cardiac transplantation timing should be re-examined.

Stability of children's and adolescents' hemodynamic responses to psychological challenge: a three-year longitudinal study of a multiethnic cohort of boys and girls.

This report evaluated (a) the temporal stability of hemodynamic responses to three tasks using impedance cardiography, and (b) the influence of aging on stress responses in a multi-ethnic pediatric sample. One hundred children 8 to 10 years old and 49 adolescents 15 to 17 years old were tested at study entry and on average 3 years later. Results showed that the composite task-induced changes in stroke volume (SV), cardiac output (CO), total peripheral resistance (TPR), and pre-ejection period (PEP) were moderately stable across 3 years (rs = .36 to .51), with children showing greater stability in task-induced CO change than did adolescents. However, the magnitude of the participant's stress responses changed over time, varied by task, age group, and gender. These results suggest that hemodynamic responses to stress change with aging during childhood and adolescence and that they can be measured reliably.