Influence of clothing and body-fat insulation on thermal adjustments to cold-water stress.

Male volunteers were divided into a low body fat (L) group (X = 10.6%, N = 5) and moderate fat (M) group (X = 18.6%, N = 5). Each was dressed in both dry suit plus medium insulation undergarment (DS-M) and dry suit plus heavy insulation (DS-H) and immersed in 10 and 15 degrees C water for 3 h. In 10 degrees C water, through not significantly different, rectal temperature (Tre) at h 3 was slightly higher in M (DS-M 36.4 degrees C, DS-H 36.5 degrees C) compared with L (DS-M 35.9 degrees C, DS-H 36.3 degrees C), whereas mean skin temperature (Tsk) and metabolic rate (MR) were in general, slightly lower for M(DS-M 23.6 degrees C, 184 W; DS-H 25.5 degrees C, 147 W, respectively). Over time the metabolic and thermal responses tended to stabilize after 120 min of immersion in both groups. Similar responses were observed in 15 degrees C water. These data suggested that despite the variation in body fatness, minimal thermal differences between groups were noted because of the attenuating effects of the insulated clothing.

Modification of Otis-McKerrow valve for measurement of respiratory water loss.

An apparatus is described that allows a continuous measurement of inspired and expired gas dew-point temperature for the calculation of water loss (Eres) during ventilation. A rapid response dew-point temperature measurement method is described which is based on a small Peltier module. The compact structure with near zero system dead space minimizes potential errors inherent in many techniques used to measure Eres. The simple design and rugged construction permit the incorporation of the apparatus into many manual or personal computer controlled oxygen consumption systems. Collection of data may be done in a variety of ambient temperatures, altitudes, and activity levels. There is also the potential for creating a portable system for field use.

Comparison of thermal responses between rest and leg exercise in water.

This study examined both the thermal and metabolic responses of individuals in cool (30 degrees C, n = 9) and cold (18 degrees C, n = 7; 20 degrees C, n = 2) water. Male volunteers were immersed up to the neck for 1 h during both seated rest (R) and leg exercise (LE). In 30 degrees C water, metabolic rate (M) remained unchanged over time during both R (115 W, 60 min) and LE (528 W, 60 min). Mean skin temperature (Tsk) declined (P less than 0.05) over 1 h during R, while Tsk was unchanged during LE. Rectal (Tre) and esophageal (Tes) temperatures decreased (P less than 0.05) during R (delta Tre, -0.5 degrees C; delta Tes, -0.3 degrees C) and increased (P less than 0.05) during LE (delta Tre, 0.4 degrees C; Tsk, 0.4 degrees C). M, Tsk, Tre, and Tes were higher (P less than 0.05) during LE compared with R. In cool water, all regional heat flows (leg, chest, and arm) were generally greater (P less than 0.05) during LE than R. In cold water, M increased (P less than 0.05) over 1 h during R but remained unchanged during LE. Tre decreased (P less than 0.05) during R (delta Tre, -0.8 degrees C) but was unchanged during LE. Tes declined (P less than 0.05) during R (delta Tes, -0.4 degrees C) but increased (P less than 0.05) during LE (delta Tes, 0.2 degrees C). M, Tre, and Tes were higher (P less than 0.05), whereas Tsk was not different during LE compared with R at 60 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Heat exchange following atropine injection before and after heat acclimation.

The effect of saline and atropine injection (2 mg, im) on eight healthy male subjects before and after heat acclimation was studied while each subject walked on a treadmill (1.34 m X s-1) in a hot-dry environment (ambient temperature = 48.4 degrees C, dew-point temperature = 20.5 degrees C). Partitional calorimetric analysis was done for the periods in which maximum sweat inhibition occurred (30 min). Mean skin temperature, rectal temperature, and heart rate were continuously observed. Evaporative loss from the skin was calculated by changes in body weight (Sauter balance); heat transfer coefficients were defined by Nishi equations. A prediction of sweat inhibition based on an analysis of heat storage and its effect on a theoretical temperature, which can be graphed on a psychrometric chart, was developed. A rational effective temperature (ET) defined as the operative temperature at the intersection of the 50% rh, which encompasses total heat exchange, was used to compare the effects of atropine before and after heat acclimation. The results show that heat acclimation reduced ET by approximately 2.5 degrees C when compared with the unacclimated state after atropine injection. Thus heat acclimation reduces the hazards of heatstroke caused by exercise in the heat with atropine injection.

Synthesis and dopamine receptor binding of exo- and endo-2-amino-6,7-dihydroxybenzonorbornene, rigid analogues of 2-amino-6,7-dihydroxytetrahydronaphthalene.

Two bridged tricyclic analogues of 2-amino-6,7-dihydroxytetrahydronaphthalene (ADTN) in which the amino group is held rigidly in an equatorial and axial conformation, respectively, and in which the catechol ring is twisted out of the plane of the ethylamine chain have been synthesized and assayed for their effects on the binding of [3H]dopamine, [3H]apomorphine, and [3H]spiperone to calf and rat striatal homogenates. Up to concentrations of 2000 nM, these exo- and endo-2-amino-6,7-dihydroxybenzonorbornenes displayed no ability to displace any of the radioligands from their receptor sites in the calf and rat brain homogenates, in contrast to measured IC50 values of 6 and 3.1 nM for racemic ADTN vs. [3H]dopamine in the two preparations, respectively. The enantiomers of the exo amine showed no specific activity vs. [3H]dopamine in the two preparations, respectively. The enantiomers of the exo amine showed no specific activity vs [3H]dopamine. Although negative, these data are informative in molecular modeling of dopaminergic receptor interactions.

Irreversible blockade of striatal dopamine receptors in vivo by a derivative of alpha-flupenthixol.

Flupenthixyl chloride (FPT-Cl), a derivative of the dopamine (DA) receptor antagonist and neuroleptic alpha-flupenthixol possessing a chloroethyl side chain, has been prepared and evaluated for use in vivo in affinity labeling of DA receptors. Binding of [3H]spiperone to rat striatal DA receptors was markedly altered up to 12 h after intraventricular injection of FPT-Cl as compared with controls, while Scatchard plots of [3H]spiperone binding obtained on rat striatal homogenates 24 and 48 h after injection of FPT-Cl had values of Bmax significantly lower than in controls. The results suggest that the administration of FPT-Cl leads to irreversible and possibly covalent blockade of a portion of the spiperone binding sites in rat striatum. A second population of receptors appears to be blocked reversibly and presumably noncovalently by FPT-Cl, and these spiperone binding sites are partially reactivated in vivo after 48 h.