Perceptual strain index for heat strain assessment in an experimental study: An application to construction workers

Although the physiological strain index (PhSI) is universal and comprehensive, its restrictions are recognized in terms of invasive on-site measurements and the requirement of accurate instruments. The perceptual strain index (PeSI) has been proposed as a user-friendly and practical indicator for heat strain. However, the application of this index in assessing the heat strain of construction workers has yet to be examined and documented. This study aims to ascertain the reliability and applicability of PeSI in an experimental setting that simulates a stressful working environment (i.e., environment, work uniform, and work pace) experienced by construction workers. Ten males and two females performed intermittent exercise on a treadmill while wearing a summer work uniform at 34.5 °C and 75% relative humidity in a climatic chamber. Physiological parameters (core temperature, heart rate) and perceptual variables (thermal sensation, perceived exertion) were collated synchronously at 3 min intervals. The results of two-way repeated measures analysis of variance (clothing×time) revealed that the PeSI was useful in differentiating the heat strain levels between different work uniforms. Not only did the PeSI change in the same general manner with the PhSI, but it was also powerful in reflecting different levels of physiological strain. Thus, the PeSI offers considerable promise for heat strain assessment under simulated working conditions.     

cGMP modulates responses to queen mandibular pheromone in worker honey bees

Responses to social cues, such as pheromones, can be modified by genotype, physiology, or environmental context. Honey bee queens produce a pheromone (queen mandibular pheromone; QMP) which regulates aspects of worker bee behavior and physiology. Forager bees are less responsive to QMP than young bees engaged in brood care, suggesting that physiological changes associated with behavioral maturation modulate response to this pheromone. Since 3′,5′-cyclic guanosine monophosphate (cGMP) is a major regulator of behavioral maturation in workers, we examined its role in modulating worker responses to QMP. Treatment with a cGMP analog resulted in significant reductions in both behavioral and physiological responses to QMP in young caged workers. Treatment significantly reduced attraction to QMP and inhibited the QMP-mediated increase in vitellogenin RNA levels in the fat bodies of worker bees. Genome-wide analysis of brain gene expression patterns demonstrated that cGMP has a larger effect on expression levels than QMP, and that QMP has specific effects in the presence of cGMP, suggesting that some responses to QMP may be dependent on an individual bees’ physiological state. Our data suggest that cGMP-mediated processes play a role in modulating responses to QMP in honey bees at the behavioral, physiological, and molecular levels.     

Cardiorespiratory and subjective responses to prolonged arm and leg exercise in healthy young and older men

Ten young (aged 23–30 years) and nine older (aged 54–59 years) healthy men with a similar size of limb muscle mass performed arm crank and leg cycle exercise for 30 min at relative exercise intensities of 50% and 75% of maximal oxygen uptake for the corresponding muscle group. In the tests, heart rate, blood pressure, gas exchange variables, rating of perceived exertion and blood lactate concentration were measured. The limb muscle mass was determined by anthropometric measurements. At the 75% target exercise level, four of the older men and two of the young men could not complete the arm-cranking test, and one of the older men and two of the young men could not complete the leg-cycle test. During arm-cranking the absolute exercise intensity was similar for the young and older men because of similar maximal values during arm-cranking. But during leg-cycling the absolute excercise intensity was higher for the young men than for the older men due to the difference in corresponding maximal values. During arm-cranking there were no significant differences in the physiological responses between the age groups except that a higher ventilatory response was noted among the older compared to the young men. During leg-cycling the heart rate values were higher among the young compared to the older men. But, when the heart rate values were expressed as a percentage of maximal heart rate in the corresponding maximal tests, no significant differences between the age groups were found. The results indicated that 30-min of arm or leg exercise at the same relative submaximal excercise intensity produces a similar degree of physiological strain in healthy older compared to young men. During arm-cranking, the young and the older men exercised at the same external intensity, indicating a similar ability to perform prolonged excercise using smaller muscle groups expressed both in absolute and relative terms. Accepted: 7 October 1996     

Studies on Auxin Protectors. VII. Association of Auxin Protectors With Crown Gall Development in Sunflower Stems

Mature sunflower internodes contain only very low concentrations of auxin protectors. Wounding such internodes results in a temporary increase of protector substances. Inoculating the wounds with a virulent strain of Agrobacterium tumefaciens Conn results in a dramatic rise in protector substances, particularly the very high molecular weight protector “A”, which continues as the tumors develop. The levels attained in tumor tissue are comparable to those normally encountered in meristematic tissue. Since the auxin protectors are antioxidants which inhibit the peroxidase-catalyzed oxidation of IAA, and in view of the findings by other workers that the meristematic tissues are maintained in a relatively reduced state, the presence of such large quantities of protector substances in the tumor tissue could explain the physiological and morphological similarity of tumor tissue to young meristematic tissue.     

Heart rate monitoring on the stroke unit. What does heart beat tell about prognosis? An observational study

Background  

Guidelines recommend maintaining the heart rate (HR) of acute stroke patients within physiological limits; data on the frequency and predictors of significant deviations from these limits are scarce.     

Physiological strain due to load carrying

In an experimental study of load carrying the effects of mass (0, 5.4, 10.4 kg) and the type of support (on the shoulder or on waist) on parameters of physiological strain were quantified to determine the factor(s) which limit carrying time. Four categories of strain were investigated: metabolic (in terms of oxygen uptake), cardiovascular (in terms of heart rate), muscular (in terms of EMG activity) and skin pressure under the shoulder straps. Four young male subjects were tested on a treadmill using different combinations of load and speed. While standing, oxygen uptake was not influenced by the type or mass of the backpack, and averaged 10% maximal oxygen uptake. The heart rate increased significantly by 9 beats per min while standing wearing a backpack, independent of type of support or mass of backpack. While walking both the heart rate and the oxygen uptake were significantly influenced by the mass carried, but both types of strain remained below the tolerance limits for prolonged wear. Standing supporting a load did not significantly increase the root mean square value of the EMG signal of the trapezius pars descendens muscle. While walking, load carrying significantly increased the root mean square value, and, converted to force, the largest increase amounted to 2.7% of the maximal force for a load of 10.4 kg suspended from the shoulders. This was below levels of force producing fatigue, which was also indicated by an absence of changes in the median power frequency of the EMG signal.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of heat strain recovery in different anti-heat stress clothing ensembles after work to exhaustion

A hot environment combined with physically demanding tasks can subject workers to a higher risk of heat stress. A series of regulations and guidelines have been proposed to design appropriate anti-heat stress work uniform to reduce body heat strain. The present study aimed to examine heat strain recovery in different anti-heat stress clothing ensembles after work to exhaustion in the heat. 10 healthy males performed intermittent treadmill running/walking to exhaustion, followed by 30 min passive recovery sitting in a climatic chamber, which simulated the hot and humid outdoor environment (34 °C temperature, 60% relative humidity, 0.3 m/s air velocity, and 450 W/m² solar radiation). The participants took part in five wear trials in counter-balanced order, including Sportswear, CIC Uniform, NEW Uniform, ICEBANK Cooling Vest, and NEW Cooling Vest, which have different levels of cooling capacity. Core temperature, skin temperature, heart rate, sweat loss, ratings of perceived exertion, and thermal sensations were measured throughout the entire heat exposure period. Physiological heat strain indices, including the physiological strain index (PhSI) and the perceptual strain index (PeSI), were used as a yardstick to quantify and compare the rate of recovery. Significantly lower physiological strain was observed in the newly developed NEW Uniform and NEW Cooling Vest groups compared with the commonly worn CIC Uniform group during recovery. At the end of the recovery period, participants in NEW Cooling Vest achieved the highest recovery (42.18% in PhSI and 81.08% in PeSI), followed by ICEBANK Cooling Vest, Sportswear, NEW Uniform, and CIC Uniform. The cooling capacity of anti-heat stress clothing ensembles and the recovery time significantly affect the rate of recovery in PhSI and PeSI, which may benefit the industry by formulating the appropriate work–rest schedule by considering the clothing effect.     

The physiological and psychological relaxing effects of viewing rose flowers in office workers

Background

In recent years, the physiological relaxing effect brought by nature is becoming clear; however, many workers find it difficult to be exposed to nature in their working environment. Exposure to fresh flowers represents an opportunity to incorporate nature into their working lives. In this study, we examined the effects of exposure to roses on physiological and psychological variables (heart rate variability, pulse rate, and subjective responses) in office workers.

Results

The experimental site was Mizuho Information & Research Institute, Inc., in the Tokyo metropolitan area. Thirty-one male office workers were included in the present study. The subjects were exposed to thirty unscented pink roses (Rosa, Dekora) arranged in a cylindrical glass vase for 4 min. In the control condition, the subjects were not exposed to flowers. After the experiments, the subjects completed a questionnaire. The order of exposure was counterbalanced among subjects. Among subjects exposed to roses, the high-frequency component of heart rate variability was significantly higher than in controls. Similarly, ''comfortable,’ ''relaxed’ and ''natural’ feelings were more common in subjects exposed to roses.

Conclusions

Data from this study support the presence of physiological and psychological relaxing effects of being exposed to flowers on office workers.     

Kappa opioids modulate the arterial baroreflex control of heart rate in conscious young sheep

The present study tested the hypothesis that kappa-opioids modulate the arterial baroreflex control of heart rate in conscious young sheep. Various parameters governing the arterial baroreflex control of heart rate were assessed before and after activation of kappa-opiate receptors (KOR) by i.v. administration of the specific KOR agonist U-50488H (experiment 1) or vehicle (experiment 2) to conscious, chronically instrumented lambs aged 42 +/- 2 days (n = 6). The 2 experiments were administered in random order at minimum intervals of 48 h. Thirty min after U-50488H treatment, there was an increase in diastolic and mean arterial pressure and in heart rate, returning to control levels by 90 min. A significant increase in the arterial pressure at the midpoint of the baroreflex range and in the minimum heart rate as well as a significant decrease in the heart rate range over which the arterial baroreflex operates were also seen at 30 min after U-50488H, gradually returning to control levels over 120 min. Vehicle had no effect on any of the parameters governing the arterial baroreflex control of heart rate. These data provide the first direct evidence that under physiological conditions in young lambs, the arterial baroreflex control of heart rate is altered after administration of the specific KOR agonist U-50488H, revealing a previously unidentified role for this opioid receptor.     

A unique minute-rough colonial variant of Candida albicans

Summary A heretofore undescribed minute-rough colonial variant has been isolated from cultures of a red, adenine auxotroph ofCandida albicans, strain WC—7. The variant has been detected only in WC—7 populations which are propagated at 37° C on very low concentrations of adenine. It produces colonies much smaller than those of WC—7 at both 25° C and 37° C on defined media containing either ammonium ion or casein hydrolysate as nitrogen sources. On ammonium nitrogen, young variant colonies are smooth and contain only typical yeast cells. While colonies which grow at 37° C retain these characteristics upon extended incubation, those growing at 25° C progressively roughen due to extensive development of pseudohyphae as the glucose levels in their vicinities decline. Under comparable conditions, colonies of the parental strain WC—7 remain smooth and free of pseudohyphae, Supplementing the medium with large amounts of glucose, intermediates of the tricarboxylic acid cycle or any one of several amino acids biosynthetically derived from intermediates of oxidative respiration prevents formation of pseudohyphae by the variant without significantly affecting its growth rate. Genetically, the variant is unstable and reverts frequently to a stable, rapidly growing form apparently identical to strain WC—7. Evidence is presented indicating that, under certain circumstances, variant cells can exercise a contact-inhibition of the growth of their revertants. Possible physiological bases of the variriant's cultural properties are discussed.     

Acclimation effects on critical and lethal thermal limits of workers of the Argentine ant, Linepithema humile

For the Argentine ant Linepithema humile, bioclimatic models often predict narrower optimal temperature ranges than those suggested by behavioural and physiological studies. Although water balance characteristics of workers of this species have been thoroughly studied, gaps exist in current understanding of its thermal limits. We investigated critical thermal minima and maxima and upper and lower lethal limits following acclimation to four temperatures (15, 20, 25, 30 degrees C; 12L:12D photoperiod) in adult workers of the Argentine ant, L. humile, collected from Stellenbosch, South Africa. At an ecologically relevant rate of temperature change of 0.05 degrees Cmin(-1), CTMax varied between 38 and 40 degrees C, and CTMin varied between 0 and 0.8 degrees C. In both cases the response to acclimation was weak. A significant time by exposure temperature interaction was found for upper and lower lethal limits, with a more pronounced effect of acclimation at longer exposure durations. Upper lethal limits varied between 37 and 44 degrees C, whilst lower lethal limits varied between -4 and -10.5 degrees C, with an acclimation effect more pronounced for upper than lower lethal limits. A thermal envelope for workers of the Argentine ant is provided, demonstrating that upper thermal limits do likely contribute to distributional limits, but that lower lethal limits and limits to activity likely do not, or at least for workers who are not exposed simultaneously to the demands of load carriage and successful foraging behaviour.     

Cyclic strain inhibits acute pro-inflammatory gene expression in aortic valve interstitial cells

Mechanical in vitro preconditioning of tissue engineered heart valves is viewed as an essential process for tissue development prior to in vivo implantation. However, a number of pro-inflammatory genes are mechanosensitive and their elaboration could elicit an adverse response in the host. We hypothesized that the application of normal physiological levels of strain to isolated valve interstitial cells would inhibit the expression of pro-inflammatory genes. Cells were subjected to 0, 5, 10, 15 and 20% strain. Expression of VCAM-1, MCP-1, GM-CSF and OPN was then measured using qRT-PCR. With the exception of OPN, all genes were significantly up regulated when no strain was applied. MCP-1 expression was significantly lower in the presence of strain, although strain magnitude did not affect the expression level. VCAM-1 and GM-CSF had the lowest expression levels at 15% strain, which represent normal physiological conditions. These findings were confirmed using confocal microscopy. Additionally, pSMAD 2/3 and IκBα expression were imaged to elucidate potential mechanisms of gene expression. Data showed that 15% strain increased pSMAD 2/3 expression and prevented phosphorylation of IκBα. In conclusion, cyclic strain reduces expression of pro-inflammatory genes, which may be beneficial for the in vitro pre-conditioning of tissue engineered heart valves.     

Thermotolerance and heat acclimation may share a common mechanism in humans

Thermotolerance and heat acclimation are key adaptation processes that have been hitherto viewed as separate phenomena. Here, we provide evidence that these processes may share a common basis, as both may potentially be governed by the heat shock response. We evaluated the effects of a heat shock response-inhibitor (quercetin; 2,000 mg/day) on established markers of thermotolerance [gastrointestinal barrier permeability, plasma TNF-α, IL-6, and IL-10 concentrations, and leukocyte heat shock protein 70 (HSP70) content]. Heat acclimation reduced body temperatures, heart rate, and physiological strain during exercise/heat stress) in male subjects (n = 8) completing a 7-day heat acclimation protocol. These same subjects completed an identical protocol under placebo supplementation (placebo). Gastrointestinal barrier permeability and TNF-α were increased on the 1st day of exercise/heat stress in quercetin; no differences in these variables were reported in placebo. Exercise HSP70 responses were increased, and plasma cytokines (IL-6, IL-10) were decreased on the 7th day of heat acclimation in placebo; with concomitant reductions in exercise body temperatures, heart rate, and physiological strain. In contrast, gastrointestinal barrier permeability remained elevated, HSP70 was not increased, and IL-6, IL-10, and exercise body temperatures were not reduced on the 7th day of heat acclimation in quercetin. While exercise heart rate and physiological strain were reduced in quercetin, this occurred later in exercise than with placebo. Consistent with the concept that thermotolerance and heat acclimation are related through the heat shock response, repeated exercise/heat stress increases cytoprotective HSP70 and reduces circulating cytokines, contributing to reductions in cellular and systemic markers of heat strain. Exercising under a heat shock response-inhibitor prevents both cellular and systemic heat adaptations.     

Urine temperature as an index for the core temperature of industrial workers in hot or cold environments

Workers working in hot or cold environments are at risk for heat stroke and hypothermia. In Japan, 1718 people including 47 workers died of heat stroke in 2010 (Ministry of Health Labour and Welfare, Japan 2011). While the American Conference of Governmental Industrial Hygienists (ACGIH) recommendation lists the abnormal core temperature of workers as a criterion for halting work, no method has been established for reliably measuring core temperatures at workplaces. ISO 9886 (Ergonomics-evaluation of thermal strain by physiological measurements. ISO copyright office, Geneva, pp 3–14; 2004) recognizes urine temperature as an index of core temperature only at normal temperature. In this study we ascertained whether or not urine temperature could serve as an index for core temperature at temperatures above and below the ISO range. We measured urine temperature of 31 subjects (29.8 ± 11.9 years) using a thermocouple sensor placed in the toilet bowl at ambient temperature settings of 40, 20, and 5˚C, and compared them with rectal temperature. At all ambient temperature settings, urine temperature correlated closely with rectal temperature exhibiting small mean bias. Urine temperature changed in a synchronized manner with rectal temperature at 40˚C. A Bland and Altman analysis showed that the limits of agreement (mean bias ± 2SD) between rectal and urine temperatures were −0.39 to +0.15˚C at 40˚C (95%CI −0.44 to +0.20˚C) and −0.79 to +0.29˚C at 5˚C (−0.89 to +0.39˚C). Hence, urine temperature as measured by the present method is a practical surrogate index for rectal temperature and represents a highly reliable biological monitoring index for assessing hot and cold stresses of workers at actual workplaces.     

The effects of age and social interactions on innate immunity in a leaf-cutting ant

Both developmental and environmental factors shape investment in costly immune defences. Social insect workers have different selection pressures on their innate immune system compared to non-social insects because workers do not reproduce and their longevity affects the fitness of relatives. Furthermore, hygienic behavioural defences found in social insects can result in increased survival after fungal infection, although it is not known if there is modulation in physiological immune defence associated with group living vs. solitary living.Here we investigated whether physiological immune defence is affected by both age and the short-term presence or absence of nestmates in the leaf-cutting ant Acromyrmex octospinosus. We predicted that older ants would show immune senescence and that group living may result in prophylactic differences in immune defence compared to solitarily kept ants. We kept old and young workers alone or in nestmate groups for 48 h and assayed a key innate immune system enzyme, expressing phenoloxidase (PO) and its stored precursor (proPO), a defence that acts immediately, i.e. it is constitutive. Short-term solitary living did not affect PO or proPO levels relative to group living controls and we found no evidence for immunosenescence in proPO. However, we found a significant increase in active PO in older workers, which is consistent with two non-mutually exclusive explanations: it could be an adaptive response or indicative of immunosenescence. Our results suggest that future studies of immunosenescence should consider both active immune effectors in the body, such as PO, and the stored potential to express immune defences, such as proPO.     

Queen power in relation to age and mating status in the Argentine antIridomyrmex humilis (Mayr)

Summary Queen power inIridomyrmex humilis during six arbitrarily chosen physiological stages of queens (virgin winged queens at the time of emergence, the same 4–5 days old, mated winged queens 5–6 days old, mated queens at the time of dealation, young egg-laying queens, and old egg-laying queens) was tested with regard to workers. Tested workers and queens were nestmates. The results were as follows. 1) Power of the old queens remained rather constant throughout the reproductive season. 2) Young queens were always less attractive than older ones. No changes were observed from the time of emergence to dealation. 3) At the time of egg-laying, these young queens became markedly attractive for workers but never as much as old egg-laying queens. Therefore, insemination and dealation do not trigger the increase in queen power. In contrast, oogenesis ending by egg-laying produces a significant increase in queen power.     

The Relation of Ambulatory Heart Rate with All-Cause Mortality among Middle-Aged Men: A Prospective Cohort Study

The aim of this study was to investigate the association between average 24-hour ambulatory heart rate and all-cause mortality, while adjusting for resting clinical heart rate, cardiorespiratory fitness, occupational and leisure time physical activity as well as classical risk factors. A group of 439 middle-aged male workers free of baseline coronary heart disease from the Belgian Physical Fitness Study was included in the analysis. Data were collected by questionnaires and clinical examinations from 1976 to 1978. All-cause mortality was collected from the national mortality registration with a mean follow-up period of 16.5 years, with a total of 48 events. After adjustment for all before mentioned confounders in a Cox proportional hazards regression analysis, a significant increased risk for all-cause mortality was found among the tertile of workers with highest average ambulatory heart rate compared to the tertile with lowest ambulatory heart rate (Hazard ratio = 3.21, 95% confidence interval: 1.22–8.44). No significant independent association was found between resting clinic heart rate and all-cause mortality. The study indicates that average 24-hour ambulatory heart rate is a strong predictor of all-cause mortality independent from resting clinic heart rate, cardiorespiratory fitness, occupational and leisure time physical activity and other classical risk factors among healthy middle-aged workers.     

Fractal dynamics in circadian cardiac time series of corticotropin-releasing factor receptor subtype-2 deficient mice

Non-linear fractal analysis of circadian 24 hr heartbeat interval time series was performed in corticotropin releasing factor receptor-subtype 2 (CRFR2) deficient mice. We hypothesized that, as a result of its central as well as its peripheral expression, CRFR2 would mediate or interfere with the circadian rhythmicity. The dynamical properties of cardiac interbeat intervals were expected to be different between CRFR2 (+/+) and CRFR2 (–/–) mice when studied over an extended circadian 24 hr cycle. The dynamics of neurocardiac control were found to remain remarkably stable throughout the circadian cycle. In disagreement with the initial hypothesis, the dynamical properties underlying the cardiac control process were common to both CRFR2 (+/+) and CRFR2 (–/–) mice suggesting that control of heart rate does not rely on the elaborate interaction of the CRFR2-sensor and its intrinsic feedback arrangement. Lack of expression of CRFR2 would not compromise cardiac control and its dynamical output or is subserved by other, unknown mechanisms. Functional integrity of CRFR2 would not constitute an indispensable requirement of physiologic cardiac control. The circadian rhythm of heart rate is generated centrally and is independent of expression of CRFR2. While `normal' strain C57BL/6N mice exhibit a circadian dark/light cycle of heart rate, absence of circadian fluctuations in transgenic CRFR2-mice (both +/+ and –/–) and `normal' strain C57BL/6J mice points at the importance of other deficiencies that may be related to a common genetic background. Mutant mice that share a common 129SvJ- or C57BL/6J-derived genetic background may not present an optimal model for physiological studies of cardiovascular control.