Aerospace medicine and biology: A continuing bibliography with indexes, supplement 203

This bibliography lists 150 reports, articles, and other documents introduced into the NASA scientific and technical information system in January 1980

An Empirical Study Comparing Unobtrusive Physiological Sensors for Stress Detection in Computer Work.

Several unobtrusive sensors have been tested in studies to capture physiological reactions to stress in workplace settings. Lab studies tend to focus on assessing sensors during a specific computer task, while in situ studies tend to offer a generalized view of sensors' efficacy for workplace stress monitoring, without discriminating different tasks. Given the variation in workplace computer activities, this study investigates the efficacy of unobtrusive sensors for stress measurement across a variety of tasks. We present a comparison of five physiological measurements obtained in a lab experiment, where participants completed six different computer tasks, while we measured their stress levels using a chest-band (ECG, respiration), a wristband (PPG and EDA), and an emerging thermal imaging method (perinasal perspiration). We found that thermal imaging can detect increased stress for most participants across all tasks, while wrist and chest sensors were less generalizable across tasks and participants. We summarize the costs and benefits of each sensor stream, and show how some computer use scenarios present usability and reliability challenges for stress monitoring with certain physiological sensors. We provide recommendations for researchers and system builders for measuring stress with physiological sensors during workplace computer use

Eggshell appearance does not signal maternal corticosterone exposure in Japanese quail:an experimental study with brown-spotted eggs

Reproduction is a critical period for birds as they have to cope with many stressful events. One consequence of an acute exposure to stress is the release of corticosterone, the avian stress hormone. Prolonged stress can have negative impacts on the immune system, resulting in, for example, increased oxidative stress. Through maternal effects, females are known to modulate their investment in eggs content according to their own physiological condition. Less is known about maternal investment in eggshells, especially in pigments. The two main eggshell pigments may possess opposite antioxidant properties: protoporphyrin (brown) is a pro-oxidant, whereas biliverdin (blue-green) is an antioxidant. In Japanese quail, we know that the deposition of both pigments is related to female body condition. Thus, a chronic stress response may be reflected in eggshell coloration. Using female Japanese quails that lay brown-spotted eggs, we explored whether physiological exposure to corticosterone induces a change in female basal stress and antioxidant factors, and eggshell pigment concentration, spectrophotometric reflectance, and maculation coverage. We supplemented adult females over a 2 week period with either peanut oil (control) or corticosterone (treatment). We collected pre- and post-supplementation eggs and analysed the effect of corticosterone treatment on female physiology and eggshell appearance parameters. Except for corticosterone-fed birds which laid eggs with brighter spots, supplementation had no significant effect on female physiology or eggshell pigment concentration, reflectance and maculation. The change in eggshell spot brightness was not detected by a photoreceptor noise-limited color opponent model of avian visual perception. Our data confirms that eggshell reflectance in spotted eggs varies over the laying sequence, and spot reflectance may be a key factor that is affected by females CORT exposure, even if the changes are not detected by an avian visual model

Extracellular Hsp72 concentration relates to a minimum endogenous criteria during acute exercise-heat exposure

Extracellular heat-shock protein 72 (eHsp72) concentration increases during exercise-heat stress when conditions elicit physiological strain. Differences in severity of environmental and exercise stimuli have elicited varied response to stress. The present study aimed to quantify the extent of increased eHsp72 with increased exogenous heat stress, and determine related endogenous markers of strain in an exercise-heat model. Ten males cycled for 90 min at 50% O2peak in three conditions (TEMP, 20°C/63% RH; HOT, 30.2°C/51%RH; VHOT, 40.0°C/37%RH). Plasma was analysed for eHsp72 pre, immediately post and 24-h post each trial utilising a commercially available ELISA. Increased eHsp72 concentration was observed post VHOT trial (+172.4%) (P<0.05), but not TEMP (-1.9%) or HOT (+25.7%) conditions. eHsp72 returned to baseline values within 24hrs in all conditions. Changes were observed in rectal temperature (Trec), rate of Trec increase, area under the curve for Trec of 38.5°C and 39.0°C, duration Trec ≥ 38.5°C and ≥ 39.0°C, and change in muscle temperature, between VHOT, and TEMP and HOT, but not between TEMP and HOT. Each condition also elicited significantly increasing physiological strain, described by sweat rate, heart rate, physiological strain index, rating of perceived exertion and thermal sensation. Stepwise multiple regression reported rate of Trec increase and change in Trec to be predictors of increased eHsp72 concentration. Data suggests eHsp72 concentration increases once systemic temperature and sympathetic activity exceeds a minimum endogenous criteria elicited during VHOT conditions and is likely to be modulated by large, rapid changes in core temperature

Investigating the physiological underpinnings of proactive and reactive behavioural types in grey seals (Halichoerus grypus): Trial deployment of a minimally invasive data logger for recording heart rate and heart rate variability in a wild free-ranging breeding pinniped species

Individuals differ non-randomly in their responses to stressors, exhibiting consistent individual differences (CIDs) in behavioural and physiological coping mechanisms commonly referred to as coping styles. Grey seals (Halichoerus grypus) are one of the few mammal species in which CIDs in stress responses have been documented in wild populations, though evidence thus far has been purely behavioural. Physiologically, coping styles can be distinguished by differences in the autonomic regulation of cardiac activity, which can be measured using heart rate variability (HRV). The objectives of this study were two-fold. First, to assess the suitability of Polar® RS800CX monitors and H2/H3 sensors for conducting HRV analyses in grey seals. Second, to quantify inter-individual variation, repeatability, and reproductive performance correlates of baseline HRV. Polar® devices were deployed successfully during the 2013 breeding season on female grey seals (N = 15) on the Isle of May, Scotland, and were capable of recording HR patterns that characterise phocid seals at rest on land. However, artefacts were widespread and biased HRV metrics. Filtration and correction protocols were able to counteract the effects of artefacts, but severely limited the amount of data available for analysis. There were significant inter-individual differences in baseline HRV, which could not be explained by factors associated with the breeding season (e.g. percentage mass loss, day of lactation), diurnal rhythms (e.g. time of day), or stressors (e.g. days since capture). These differences in baseline HRV showed consistency across early and late lactation. Individuals appeared to separate into two groups: those with consistently lower or higher baseline HRV, characteristic of proactive and reactive coping styles, respectively. Furthermore, females with lower baseline HRV showed greater maternal transfer efficiency – though there were no associations between baseline HRV and maternal expenditure (i.e. maternal mass loss, kgday–1) or fitness outcomes (i.e. pup mass gain, kgday–1). These findings build upon previous studies on behavioural CIDs in female grey seals by providing the first preliminary evidence for physiological CIDs that are associated with maternal investment. However, due to small sample sizes, further studies are required to determine whether these findings are truly indicative of coping styles. In their current form, the use of Polar® devices requires several caveats and further studies are needed to fully realise their potential. Future research should focus on validation against simultaneously recorded ECGs to improve artefact detection and correction, and modification to minimise the occurrence of artefacts. Despite their limitations, Polar® devices have immense potential as a minimally invasive research tool for conducting HRV analyses in the field

Seasonal variation in soil and plant water potentials in a Bolivian tropical moist and dry forest

We determined seasonal variation in soil matric potentials (¿soil) along a topographical gradient and with soil depth in a Bolivian tropical dry (1160 mm y-1 rain) and moist forest (1580 mm y-1). In each forest we analysed the effect of drought on predawn leaf water potentials (¿pd) and drought response (midday leaf water potential at a standardized ¿pd of -0.98 MPa; ¿md) of saplings of three tree species, varying in shade-tolerance and leaf phenology. ¿soil changed during the dry season and most extreme in the dry forest. Crests were drier than slopes and valleys. Dry-forest top soil was drier than deep soil in the dry season, the inverse was found in the wet season. In the moist forest the drought-deciduous species, Sweetia fruticosa, occupied dry sites. In the dry forest the short-lived pioneer, Solanum riparium, occupied wet sites and the shade-tolerant species, Acosmium cardenasii drier sites. Moist-forest species had similar drought response. The dry-forest pioneer showed a larger drought response than the other two species. Heterogeneity in soil water availability and interspecific differences in moisture requirements and drought response suggest great potential for niche differentiation. Species may coexist at different topographical locations, by extracting water from different soil layers and/or by doing so at different moments in tim

Aerospace Medicine and Biology: A continuing bibliography with indexes (supplement 141)

This special bibliography lists 267 reports, articles, and other documents introduced into the NASA scientific and technical information system in April 1975

Hormones and Life Histories: An Integrative Approach

Because of their role in mediating life‐history trade‐offs, hormones are expected to be strongly associated with components of fitness; however, few studies have examined how natural selection acts on hormonal variation in the wild. In a songbird, the dark‐eyed junco (Junco hyemalis), field experiments have shown that exogenous testosterone alters individuals’ resolution of the survival‐reproduction trade‐off, enhancing reproduction at the expense of survival. Here we used standardized injections of gonadotropin‐releasing hormone (GnRH) to assay variation in the testosterone production of males. Using measurements of annual survival and reproduction, we found evidence of strong natural selection acting on GnRH‐induced increases in testosterone. Opposite to what would be predicted from the survival‐reproduction trade‐off, patterns of selection via survival and reproduction were remarkably similar. Males with GnRH‐induced testosterone production levels that were slightly above the population mean were more likely to survive and also produced more offspring, leading to strong stabilizing selection. Partitioning reproduction into separate components revealed positive directional selection via within‐pair siring success and stabilizing selection via extrapair mating success. Our data represent the most complete demonstration of natural selection on hormones via multiple fitness components, and they complement previous experiments to illuminate testosterone’s role in the evolution of life‐history trade‐offs