Determination of body heat storage in clothing: calorimetry versus thermometry

Two methods of estimating body heat storage were compared under differing conditions of clothing, training, and acclimation to heat. Six male subjects underwent 8 weeks of physical training [60–80% of maximal aerobic power ( ) for 30–45 min · day–, 3–4 days · week^–1 at < 25 °C dry bulb (db)] followed by 6 consecutive days of heat acclimation (45–55% for 60 min · day^–1 at 40°C db, 30% relative humidity)]. Nine other male subjects underwent corresponding periods of control observation followed by heat acclimation. Before and after each treatment, subjects walked continuously on a treadmill (1.34 m · s^–1, 2% grade) in a climatic chamber (40°C db, 30% relative humidity) for an average of 118 min (range 92–120 min) when wearing normal light combat clothing and for an average of 50 min (range 32–68 min) when wearing protective clothing resistant to nuclear, biological, and chemical agents. The heat storage was determined calorimetrically (by the balance of heat gains and losses) and thermometrically [by the conventional equations, using one or two set(s) of relative weightings for the rectal temperature (T _re) to mean skin temperature _sk of 4:1 and 4:1, 2:1 and 4:1, or 2:1 and 9:1 in thermoneutral and hot environments, respectively]. _sk was calculated from 12-site measurements, weighted according to the regional distribution of body surface area and the first eigenvectors of principal component analysis. There were only minor differences (< 5%) between the heat storage values calculated by given weighting factors forT _re and _sk, whether the individual coefficients were derived from estimates of regional surface area or principal component methodologies. When wearing normal clothing, no significant differences were found between the two estimates of heat storage (calorimetry vs thermometry with an invariant relative weighting of 4:1) in any experimental condition, with one specific exception: when wearing protective clothing, thermometry underestimated the heat storage by 24–31%. This underestimation was attenuated by using two sets of relative weightings of 2: 1 and 4: 1 or 2: 1 and 9: 1. The results suggest that when subjects wearing protective clothing are transferred from thermoneutral to hot environments, the accuracy of thermometric estimates of heat storage can be improved by using two sets of weighting factors forT _re and _sk     

Stress and dental caries in the rat

The stress of crowding and exposure to inescapable electric shock increased both the incidence and the severity of dental caries in rats housed in a conventional animal facility. Male Osborne-Mendel rats were inoculated intraorally with cariogenic bacteria, fed a high-sucrose diet, and housed in either a conventional or a sheltered facility. Rats in both housing conditions were subdivided into control and stress groups. At the end of the 56-day trial period, stressed rats from conventional housing had a significant increase in both incidence and severity of dental caries in comparison to their controls. In contrast, stressed rats from sheltered housing had a trend toward increased cariogenesis which reached significance in only one of five scores. These rats also failed to gain weight comparable to their controls, making it possible that stress-induced reduction in appetite partially offset stress-induced exacerbation in cariogenesis.This investigation was supported in part by the following Grants from the United States Public Health Service: CA 20093, HL 22727, and HL 07374.     

Birth factors and laterality: Effects of birth order,parental age,and birth stress on four indices of lateral preference

As an alternative to genetic theories of handedness, some theorists have offered an environmental mechanism, associated with birth stress, for the appearance of left-handedness. They suggest that brain damage as a result of birth difficulties can lead to a switch in hand preference from the right side to the left side. Consequently, one should find more left-handers in groups where the probability of the occurrence of birth stress is greater. Three studies are presented which explore the laterality of not only hand but also foot, eye, and ear, in a total of 5161 individuals, in an attempt to assess any relationship to birth stress. Maternal age seems to predict deviations from dextrality, dependent on the sex of the offspring, while paternal age and birth order do not. The use of a direct measure of conditions predisposing toward birth stress suggests that these results depend on prenatal or perinatal environmental trauma rather than chromosomal factors.This research was supported by grants from the Medical Research Council of Canada and from the Natural Sciences and Engineering Research Council of Canada, and represents an equal and shared contribution of both authors.     

A method for the collection of individual mouse urine

Behavioral research often requires urine collection. An apparatus has been developed for the collection of urine from individual or small groups of mice and is recommended for general use where urine from unstressed mice is required.     

Effect of some stressors on mitosis in the corneal epithelium and the bone marrow aneuploid cell level in adrenalectomized albino rats

It was shown previously that exposure to stressors led to a decrease in the number of mitoses in the cornea as a result of G₂–M delay. The index of labeled nuclei and level of pathological mitoses were unchanged. It is now shown that injection of pyrogenal or contact hypothermia for 1 h to 28–30°C did not cause reactive inhibition to develop in adrenalectomized rats, but led to a significant increase in the level of pathological mitoses in the cornea from 4.3–6.3% in intact and adrenalectomized rats to 10.6–12.5% in adrenalectomized rats exposed to stress. Karyotypic analysis of the bone marrow cells under these conditions revealed a significant increase in the number of aneuploid cells (both hypo- and hyperdiploid).Central Research Laboratory, Khabarovsk Medical Institute. (Presented by Academician of the Academy of Medical Sciences of the USSR A. M. Chernukh.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 88, No. 9, pp. 338–341, September, 1979.     

Heart rate reactivity and heart period variability throughout the first year after heart transplantation

Heart rate reactivity to mental stress is substantially blunted early after heart transplantation, suggesting that the loss of neural modulation limits the cardiovascular response to mental stress. We tested whether reactivity to mental stress recovers during the first year after heart transplantation. Hemodynamic and respiratory responses to mental arithmetic challenge were studied in 20 heart transplant recipients 3, 6, and 12 months after surgery. A normal comparison group was studied at equivalent intervals. Heart rate reactivity to mental arithmetic was significantly reduced in the cardiac transplant group compared to the normal subjects. This effect persisted up to 1 year after transplantation. Heart period variability in the heart transplant recipients was minimal in all three-test sessions. The findings suggest that no functional reinnervation or other compensatory adaptation occurs up to 1 year after heart transplantation.     

The sources of odors from stressed rats

Recent studies [8,9] have shown that odors from stressed Norway rats act as signals to which other rats respond primarily by overall changes in activity and exploration. At present the source of these odors is unknown. In this study odors from urine, feces and the bodies of stressed rats were delivered along a runway in which the subjects had been previously trained to run for a water reward in the presence of odors from non-stressed rats. The results indicate that odors are released from the body surface and in the urine but not the feces of stressed rats.     

Corticotropin-Releasing Hormone Modulation of a Conditioned Stress Response in the Central Amygdala of Roman High (RHA/Verh)-Avoidance and Low (RLA/Verh)-Avoidance Rats

Roman high (RHA/Verh)- and low (RLA/Verh)-avoidance rats are selected and bred for rapid versus nonacquisition of two-way, active avoidance behavior in the shuttle box. RHA/Verh rats generally show a more active coping style than do their RLA/Verh counterparts when exposed to various environmental challenges. The central nucleus of the amygdala (CeA) is known to be involved in the regulation of autonomic, neuroendocrine, and behavioral responses to stress. Its involvement in the selection of coping strategies has also been suggested. Corticotropin-releasing hormone (CRH) seems to be one of the key neurohormones in the control of CeA output. Neuroanatomical studies have revealed that the majority of CRH fibers from the CeA have direct connections with autonomic regulatory nuclei in the brain-stem, e.g. lateral parabrachial nucleus (lPB). The effects of CRH (30 ng) on modulating CeA activity were studied by infusion of CRH into the CeA during conditioned stress (inescapable foot-shocks) in RHA/Verh and RLA/Verh male rats. Heart-rate responses after CRH treatment were not changed in either line. However, distinctly different behavioral responses were seen after CRH infusion into the CeA of both rat lines. A decrease in immobility responses was seen in both RHA/Verh and RLA/Verh rats, while an increase in exploration was observed in RHA/Verh rats only in the conditioned stress situation. Rearing levels were increased in the RHA/Verh rats, whereas they were decreased in the RLA/Verh animals. As a result of CRH infusion, the number of FOS immunoreactive cells in the lPB of RLA/Verh rats was decreased, whereas an opposite response was found in RHA/Verh rats. These results indicate that the CRH system of the CeA connected with output brain-stem areas is differentially involved in the cardiovascular and behavioral responses of these rats having different coping styles.