Ageing, depression, anxiety, social support and the diurnal rhythm and awakening response of salivary cortisol

The present study compared the cortisol awakening response and diurnal rhythm in 24 young healthy students and 48 community-dwelling older adults. The associations with diurnal cortisol and depression, anxiety and social support were also examined in relation to age. Salivary cortisol was measured over the course of one day: immediately upon awakening, 30 min later, and then 3 h, 6 h, 9 h and 12 h post-awakening. Participants completed a questionnaire measuring symptoms of anxiety and depression and social support was assessed. Older adults exhibited a significantly reduced awakening response, overall cortisol levels, area under the curve (AUC) and diurnal slopes than younger adults, resulting in a flatter diurnal rhythm. Younger adults with higher depression scores had significantly higher overall cortisol and higher levels upon awakening and 30 min post-awakening. In the younger adults, anxiety and depression correlated positively with AUC and the cortisol awakening response (CAR). Older adults with lower social support had a reduced AUC where younger adults with lower social support displayed a larger AUC. These findings suggest that the diurnal rhythm and awakening response of salivary cortisol are significantly reduced in older adults and the associations between anxiety, depression and social support and diurnal cortisol vary with age.\ud \u

Blunted cardiac reactions to acute psychological stress predict symptoms of depression five years later: Evidence from a large community study

We recently reported a cross-sectional negative relationship between cardiovascular reactivity and depressive symptoms. The present analyses examined the prospective association between reactivity and symptoms of depression five years later. At the earlier time point depressive symptoms, using the Hospital Anxiety and Depression Scale (HADS), and cardiovascular reactions to a standard mental stress were measured in 1608 adults comprising three distinct age cohorts: 24-, 44-, and 63-year olds. Depression was re-assessed using the HADS five years later. Heart rate reactions to acute psychological stress were negatively associated with subsequent depressive symptoms; the lower the reactivity the higher the depression scores. This association withstood adjustment for symptom scores at the earlier time point, and for socio-demographic factors and medication status. The mechanisms underlying this prospective relationship remain to be determined

Altered Human Neutrophil Function in Response to Acute Psychological Stress

Objective: To examine the effects of an acute laboratory psychological stress task on neutrophil function, specifically phagocytosis of Escherichia coli and stimulated superoxide production in human neutrophils. There is mounting evidence that acute stress is associated with short-term increases in a number of immune indices. \ud \ud Methods: Participants were 40 (n = 20 females) university students (mean age, 25.9 ± 4.56 years). Blood samples to determine neutrophil function by flow cytometry were taken at the end of resting baseline, during an acute stress task, and during recovery. The stress task was a 10-minute time-pressured mental arithmetic challenge with social evaluation. \ud \ud Results: There was an acute increase in phagocytic ability, $\rho$ = .047, η2p = 0.076, and a reduction of superoxide production, p = .026, η2p = 0.101, associated with the stress task relative to baseline. \ud \ud Conclusion: These findings suggest that neutrophil bactericidal function may be sensitive to mental challenge tasks that provoke acute psychological stress. Further research is needed to replicate the observed psychological stress-induced changes in neutrophil function. \ud \u

Life events and acute cardiovascular reactions to mental stress: a cohort study

Objective: This study addressed the issue of whether frequent exposure to life events is associated with aggravation or blunting of cardiovascular reactions to acute mental stress. Methods: In a substantial cohort of 585 healthy young adults, systolic and diastolic blood pressure and pulse rate were recorded at rest and in response to a mental arithmetic stress task. Participants indicated, from a list of 50 events, those they had experienced in the last year. Results: There was an overall association between life events and blunted cardiovascular reactivity that was driven by variations in the frequency of exposure to desirable events. The total number of events and the number of personal events were negatively associated with systolic blood pressure and pulse rate reactions to acute stress, whereas the number of work-related events was negatively associated with diastolic blood pressure and pulse rate reactivity. The negative association between total events and systolic blood pressure reactivity was stronger for women than men, whereas men exposed to frequent undesirable events showed enhanced diastolic blood pressure reactivity. The blunting of pulse rate reactivity associated with frequent personal life events was evident particularly for those who had a relatively large number of close friends. Conclusions: The nature and extent of the association between life events exposure and stress reactivity in young adults depends on the valence of the events together with the sex of the individual and their social network size

Design and implementation of robust decentralized control laws for the ACES structure at Marshall Space Flight Center

Many large space system concepts will require active vibration control to satisfy critical performance requirements such as line-of-sight accuracy. In order for these concepts to become operational it is imperative that the benefits of active vibration control be practically demonstrated in ground based experiments. The results of the experiment successfully demonstrate active vibration control for a flexible structure. The testbed is the Active Control Technique Evaluation for Spacecraft (ACES) structure at NASA Marshall Space Flight Center. The ACES structure is dynamically traceable to future space systems and especially allows the study of line-of-sight control issues

The association between life events, social support, and antibody status following thymus-dependent and thymus-independent vaccinations in healthy young adults

This study determined whether stressful life events and social support were related to antibody status following both thymus-dependent and thymus-independent vaccinations. Life events in the previous year and customary social support were measured in 57 healthy students at baseline. Antibody status was also assessed at baseline and at five weeks and five months following vaccination with the trivalent influenza vaccine and the meningococcal A+C polysaccharide vaccine. Taking into account baseline antibody titre, high life events scores prior to vaccination were associated with lower responses to the B/Shangdong influenza strain at both five weeks and five months and meningococcal C at five weeks. Life events scores were not associated with response to the other two influenza viral strains nor response to meningococcal A. Those with high social support scores had stronger 5-week and 5-month antibody responses to the A/Panama influenza strain, but not to any of the other strains. These associations could not be accounted for by demographic or health behaviour factors, and also emerged from analyses comparing those who exhibited a four-fold increase in antibody titre from baseline with those who did not. Life events and social support were related to antibody status following influenza vaccination in distinctive ways that may be partly determined by vaccine novelty and prior naturalistic exposure. Life events also predicted poor antibody response to meningococcal C polysaccharide vaccination after previous meningococcal C conjugate vaccination. Neither psychosocial factor was associated with response to primary meningococcal A polysaccharide vaccination

Negative life events and symptoms of depression and anxiety: stress causation and/or stress generation

Background and Objectives: Stressful life events are known to contribute to development of depression; however, it is possible this link is bidirectional. The present study examined whether such stress generation effects are greater than the effects of stressful life events on depression, and whether stress generation is also evident with anxiety. Design: Participants were two large age cohorts (N = 732 aged 44 years; N = 705 aged 63 years) from the West of Scotland Twenty-07 study. Methods: Stressful life events, depression, and anxiety symptoms were measured twice five years apart. Cross-lagged panel analysis examined the mutual influences of stressful life events on depression and on anxiety over time. Results: Life events predicted later depressive symptomatology (p = .01), but the depression predicting life events relationship was less strong (p = .06), whereas earlier anxiety predicted life events five years later (p = .001). There was evidence of sex differences in the extent to which life events predicted later anxiety. Conclusions: This study provides evidence of stress causation for depression and weaker evidence for stress generation. In contrast, there was strong evidence of stress generation for anxiety but weaker evidence for stress causation, and that differed for men and women

High performance, accelerometer-based control of the Mini-MAST structure at Langley Research Center

Many large space system concepts will require active vibration control to satisfy critical performance requirements such as line of sight pointing accuracy and constraints on rms surface roughness. In order for these concepts to become operational, it is imperative that the benefits of active vibration control be shown to be practical in ground based experiments. The results of an experiment shows the successful application of the Maximum Entropy/Optimal Projection control design methodology to active vibration control for a flexible structure. The testbed is the Mini-Mast structure at NASA-Langley and has features dynamically traceable to future space systems. To maximize traceability to real flight systems, the controllers were designed and implemented using sensors (four accelerometers and one rate gyro) that are actually mounted to the structure. Ground mounted displacement sensors that could greatly ease the control design task were available but were used only for performance evaluation. The use of the accelerometers increased the potential of destabilizing the system due to spillover effects and motivated the use of precompensation strategy to achieve sufficient compensator roll-off

Mechanosensitive channels: what can they do and how do they do it?

While mechanobiological processes employ diverse mechanisms, at their heart are force-induced perturbations in the structure and dynamics of molecules capable of triggering subsequent events. Among the best characterized force-sensing systems are bacterial mechanosensitive channels. These channels reflect an intimate coupling of protein conformation with the mechanics of the surrounding membrane; the membrane serves as an adaptable sensor that responds to an input of applied force and converts it into an output signal, interpreted for the cell by mechanosensitive channels. The cell can exploit this information in a number of ways: ensuring cellular viability in the presence of osmotic stress and perhaps also serving as a signal transducer for membrane tension or other functions. This review focuses on the bacterial mechanosensitive channels of large (MscL) and small (MscS) conductance and their eukaryotic homologs, with an emphasis on the outstanding issues surrounding the function and mechanism of this fascinating class of molecules