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This short review was prompted by The Physiological Society's recent online symposium on variability. It does not deal with a specific methodology, but rather with the myth that certain environmentally‐induced clinical conditions can be identified, quantified, simplified and monitored with a single methodology. Although this might be possible with some clinical conditions, others resist the prevailing reductionist approach of minimizing rather than exploring variation in pathogenesis and pathology, and will not be understood fully until the variation in cause and effect are embraced. This is likely to require comprehensive methodologies and collaboration. [ABSTRACT FROM AUTHOR]

Immobilization and hypoxemia are conditions often seen in patients suffering from severe heart insufficiency or primary pulmonary diseases (e.g. fibrosis, emphysema). In future planned long-duration and exploration class space missions (including habitats on the moon and Mars), healthy individuals will encounter such a combination of reduced physical activity and oxygen tension by way of technical reasons and the reduced gravitational forces. These overall unconventional extraterrestrial conditions can result in yet unknown consequences for the regulation of stress-permissive, psycho-neuroendocrine responses, which warrant appropriate measures in order to mitigate foreseeable risks. The Planetary Habitat Simulation Study (PlanHab) investigated these two space-related conditions: bed rest as model of reduced gravity and normobaric hypoxia, with the aim of examining their influence on psycho-neuroendocrine responses. We hypothesized that both conditions independently increase measures of psychological stress and enhance neuroendocrine markers of stress, and that these effects would be exacerbated by combined treatment. The cross-over study composed of three interventions (NBR, normobaricnormoxic horizontalbedrest; HBR, normobarichypoxic horizontalbedrest; HAMB, normobarichypoxicambulatory confinement) with 14 male subjects during three sequential campaigns separated by 4 months. The psychological state was determined through three questionnaires and principal neuroendocrine responses were evaluated by measuring cortisol in saliva, catecholamine in urine, and endocannabinoids in blood. The results revealed no effects after 3 weeks of normobaric hypoxia on psycho-neuroendocrine responses. Conversely, bed rest induced neuroendocrine alterations that were not influenced by hypoxia. [ABSTRACT FROM PUBLISHER]

This paper describes a lamination method of commercially produced silica aerogel composite and investigates its suitability for thermal insulation within protective footwear applications for severe cold and extreme high-altitude environments. A silica aerogel composite was used with a thickness of 2.7 mm and mass per unit area of 500 gm–2. Silica aerogel dust, which is generated during the crushing of brittle silica aerogel, was prevented from spreading into the environment by two-sided lamination of silica aerogel composite. A solid 5 µm thick membrane was used, reinforced with an abrasive resistant polyester knitted fabric. The thermal conductivity of laminated silica aerogel composite was comparable to that of the non-laminated one and amounted to 0.016 Wm–1K–1. Water vapor permeability of the laminated silica aerogel composite was 1.31 mgcm–2h–1. The silica aerogel composite was subjected to 30,000 cycles of flexing in order to study the impact of its irreversible crushed structure on the water vapor permeability and thermal resistances of laminated samples. It was observed that flexing did not damage the membrane of the laminated composite and had no statistically significant effect on its thermal resistance and water vapor permeability. During this study it was confirmed that the newly developed laminate has potential applications within protective footwear for extreme cold temperature environments. [ABSTRACT FROM AUTHOR]

Aim Studies in humans show global changes in mRNA and protein expression occur in human skeletal muscle during bed rest. As micro RNAs are important regulators of expression, we analysed the global micro RNA expression changes in human muscle following 10 days of sustained bed rest, with the rationale that mi RNAs play key roles in atrophy of skeletal muscle. Methods We analysed expression of mi RNA and selected target proteins before and after 10 days of bed rest in biopsies obtained from the vastus lateralis muscle of 6 healthy males. Results Fifteen of 152 mi RNAs detected in human muscle tissue were differentially expressed, and all of them with exception of two were downregulated. The downregulated mi RNAs include the following: miR-206, a myomir involved in function and maintenance of skeletal muscle; miR-23a, involved in insulin response and atrophy defence; and several members of the let-7 family involved in cell cycle, cell differentiation and glucose homeostasis. Predicted gene targets of these mi RNAs are members of the MAPK, TNF receptor, ALK1, TGF-beta receptor and SMAD signalling pathways. All of these pathways were previously indicated to be involved in skeletal muscle response to physical inactivity. We also measured protein expression of selected mi RNA targets and observed a decrease in HDAC4. Conclusion Our data demonstrate that mi RNAs in postural muscles are affected by sustained inactivity and unloading, as induced by prolonged bed rest, and hence are potentially involved in regulation of skeletal muscle adjustments to inactivity. We also propose new mi RNAs involved in regulation of biological processes in adult human muscle. [ABSTRACT FROM AUTHOR]

During increased gravitoinertial (G) load in the head-to-foot direction, pressures in dependent vascular beds are commonly raised to levels capable of distending precapillary vessels, which, in turn, may reduce arterial pressure, and hence compromise the capacity to withstand G load (G tolerance). We hypothesized that distensibility in precapillary leg vessels would be lower in a group of subjects possessing high G tolerance (H; n = 7; relaxed G tolerance = 6.6 ± 0.8 G) than in a group with low G tolerance (L; n = 8; G tolerance = 3.9 ± 0.3 G). The groups were matched with regard to gender, age, weight, height, and resting arterial pressure. Arterial pressure-distension and pressure-flow experiments were performed with the subject supine in a pressure chamber with a lower leg protruding to the outside. Increased intravascular pressure in the blood vessels of the outside leg was accomplished by stepwise increasing chamber pressure to 240 mmHg. Diameter and flow in the posterior tibial artery were measured by ultrasonographic/Doppler techniques. Pressure-induced increments in arterial diameter and flow were more pronounced (p < 0.03) in the L (14.1 ± 4.2% and 32 ± 21 ml/min respectively) than in the H (1.7 ± 5.0% and 1.6 ± 25 ml/min) group, and the pressure thresholds at which these increments commenced were lower (by 52 and 48 mmHg, respectively) in the L than in the H group (p < 0.04). Negative correlations were observed between G tolerance and the increments in diameter and flow (p < 0.02). Thus, the wall stiffness of precapillary leg vessels is greater in individuals with high relaxed G tolerance; whether a causal relationship exists remains to be established. [ABSTRACT FROM AUTHOR]

Triad person-clothing-environments set specific requirements in the development and optimization of products in the field of personal protective equipment that integrates into the transportation, living and working environments. The optimal balance in the triad as well the effectiveness of its relationship depends on the clothing, environments to which workers are exposed while performing their activities and on their performance. The aim of the present study was to determine the optimal combat clothing ensembles conducting hikes and guard duty during winter and summer months. During the trials, the subjects were instrumented to obtain skin and core temperatures, clothing microenvironment temperatures and humidity, as well as oxygen uptake and heart rate. In addition to providing data regarding thermal and evaporative resistances, the manikins also provided data for a numerical model of human temperature regulation, which was used to simulate the field trials. According to the given facts the relationship discussed in the paper is man-clothing-environment triad in terms of thermal comfort, requirements for the simulation of thermoregulation and the use of heat manikin. [ABSTRACT FROM AUTHOR]

The zone of thermal comfort was determined during normoxia and hypoxia in 15 healthy normothermic young subjects. Subjects dressed only in shorts/shorts and bikini top donned a water-perfused suit and assumed a supine position on a bench. The ambient temperature was maintained at a mean (SD) of 25.7 (0.3) degrees C. The thermal comfort zone was determined by increasing the temperature of the water perfusing the suit from cool to warm. During the heating process, subjects were instructed to report when their perception of the thermal stimulus provided by the suit changed from unpleasant to pleasant, and again from pleasant to unpleasant. The boundaries of the thermal comfort zone were assumed to be the temperatures of the water perfusing the suit at the time the subjects reported a change in the affective component of their thermal perception. In normoxia, subjects inspired room air and in hypoxia a gas mixture containing 10% O(2) in N(2). Tympanic temperature was similar in the normoxia and hypoxia conditions (P>0.05). The average (SD) lower and upper limits of the thermal comfort zone were 30.5 (1.5) and 34.7 (3.3) degrees C, respectively, during normoxia, and 30.5 (1.7) and 35.1 (3.4) degrees C, respectively, during hypoxia. No significant differences were observed between the normoxia and hypoxia conditions (P>0.05). Also, no gender-related differences were observed in the characteristics of the thermal comfort zone. The results of the present study indicate that acute hypoxic exposure simulated in the present study does not affect the zone of thermal comfort in humans. [ABSTRACT FROM AUTHOR]