[Water distribution in the organism following exposure to high environmental temperature].
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Environment↗
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Casual blood pressures and their possible relation to age, body weight, Quetelet's index, serum cholesterol, percentage of body fat and mid-arm muscle circumference in three groups of northern Nigerian residents.
Blood pressures were determined for rural outpatients, soldiers and university students. There was no consistent change of systolic blood pressure with age until the sixth decade but even here, the rise could be due to the inclusion of a relatively high number of hypertensive subjects in the sample mean. Diastolic blood pressures show a steady rise with age consistent with the decreased elasticity of arteries with age. Diastolic pressures are remarkably low and probably reflect a general vasodilation necessitated by the hot day-time temperatures of this environment to facilitate heat loss and maintain body temperature. Dietary and psychological influences may also be involved. Pulse pressures are predictably high and decrease with age. Hypertension was observed in many groups although totally absent in some. Body weight significantly correlates with systolic and diastolic pressures in 13-19-year old adolescents probably because during this period of rapid growth blood pressure changes parallel changes in body build. In most other groups blood pressures show no consistent relationship with either body weight, Quetelet's index, mid-arm muscle circumference, serum cholesterol or percentage of body fat.
Adolescent↗
The effects of different air velocities on heat storage and body temperature in humans cycling in a hot, humid environment.
AIM: The purposes of this study were to determine (i) the effects of different facing air velocities on body temperature and heat storage during exercise in hot environmental conditions and (ii) the effects of ingesting fluids at two different rates on thermoregulation during exercise in hot conditions with higher air velocities. METHODS: On five occasions nine subjects cycled for 2 h at 33.0 +/- 0.4 degrees C with a relative humidity of 59 +/- 3%. Air velocity was maintained at 0.2 km h(-1) (0 WS), 9.9 +/- 0.3 km h(-1) (10 WS), 33.3 +/-2.2 km h(-1) (100 WS) and 50.1 +/- 3.2 km h(-1) (150 WS) while subjects replaced 58.8 +/- 6.8% of sweat losses. In the fifth condition, air velocity was maintained at 33.7 +/- 2.2 km h(-1) and subjects replaced 80.0 +/- 6.8% of sweat losses (100.80 WS). RESULTS: Heat storage, body temperature and rating of perceived exertion were higher in 0 and 10 WS compared with all other conditions. There were no differences in any measured variable between 100 and 150 WS, or between 100 and 100.80 WS. Thus, the evaporative capacity of the environment is increased with higher air velocities, reducing heat storage and body temperature. At higher air velocities, a higher rate of fluid ingestion did not influence heat storage, body temperature or sweat rate. CONCLUSION: The finding of previous laboratory studies showing a beneficial effect of high rates of fluid ingestion on thermoregulation during exercise in hot, humid, windstill conditions cannot be extrapolated to out-of-doors exercise in which facing air velocities are seldom lower than the athlete's rate of forward progression.
Adult↗
Decreases in activation energy and substrate affinity in cold-adapted A4-lactate dehydrogenase: evidence from the Antarctic notothenioid fish Chaenocephalus aceratus.
Enzyme function is strongly affected by temperature, and orthologs from species adapted to different thermal environments often show temperature compensation in kinetic properties. Antarctic notothenioid fishes live in a habitat of constant, extreme cold (-1.86 +/- 2 degrees C), and orthologs of the enzyme A4-lactate dehydrogenase (A4-LDH) in these species have adapted to this environment through higher catalytic rates, lower Arrhenius activation energies (Ea), and increases in the apparent Michaelis constant for the substrate pyruvate (Km(PYR)). Here, site-directed mutagenesis was used to determine which amino acid substitutions found in A4-LDH of the notothenioid Chaenocephalus aceratus, with respect to orthologs from warm-adapted teleosts, are responsible for these adaptive changes in enzyme function. Km(PYR) was measured in eight single and two double mutants, and Ea was tested in five single and two double mutants in the temperature range 0 degrees C-20 degrees C. Of the four mutants that had an effect on these parameters, two increased Ea but did not affect Km(PYR) (Gly224Ser, Ala310Pro), and two increased both Ea and Km(PYR) (Glu233Met, Gln317Val). The double mutants Glu233Met/Ala310Pro and Glu233Met/Gln317Val increased Km(PYR) and Ea to levels not significantly different from the A4-LDH of a warm temperate fish (Gillichthys mirabilis, habitat temperature 10 degrees C-35 degrees C). The four single mutants are associated with two alpha-helices that move during the catalytic cycle; those that affect Ea but not Km(PYR) are further from the active site than those that affect both parameters. These results provide evidence that (1) cold adaptation in A4-LDH involves changes in mobility of catalytically important molecular structures; (2) these changes may alter activation energy alone or activation energy and substrate affinity together; and (3) the extent to which these parameters are affected may depend on the location of the substitutions within the mobile alpha-helices, perhaps due to differences in proximity to the active site.
Adaptation, Biological↗
Heart rate and core temperature as indicators of heat stress during deep underwater activity.
In hyperbaric environments, comfortable ambient temperatures are necessarily higher than normal room temperature, and high levels of humidity are also common. These conditions are stressful and even hazardous for an exercising diver. We monitored the heart rates and core temperatures of divers participating in deep experimental dives to pressures up to 300 msw. Accelerated heart rates (100 to 180 beats/min) and elevated core temperatures (+0.4 to 0.9 degrees C) were registered. The increase in heart rate can be explained by the rise in core temperature. Formulas are presented for the relationships between heart rate and duration of activity, between core temperature and duration of activity, and between heart rate and core temperature. These formulas allow the estimation of core temperature from the diver's pulse, and serve to prevent excessive heat stress which could lead to an accident.
Body Temperature↗
Response to selection at two temperatures for fast and slow growth from five to nine weeks of age in poultry.
Cornell Control White Leghorn chicks were grown in a common environment to five weeks of age and selected for fast and slow gain in body weight from five to nine weeks of age at two temperatures, 21.1 degrees (cold) and 32.2 degrees (hot), during which time a constant 50% relative humidity was maintained. All lines were tested each generation in both temperature environments. Selection continued for four generations, with a second replicate started six weeks after the first replicate in each generation. In the hot environment, a 20% reduction (104 g) in five-to-nine-week weight gain was found. The responses to selection for fast and slow growth were symmetrical except in the first generation, when an outbreak of bronchitis confounded selection for body weight with selection for disease resistance and allowed little gain in the slow lines. No genotype-by-environment interactions were found, indicating that selection in either direction in either selection temperature produced equal responses in either test temperature. This suggests that any interactions observed between the growth of strains in tropical vs. temperature climates must be due to some difference between these environments other than the temperature differences studied.
Animals↗
CO2/H(+) sensing: peripheral and central chemoreception.
H(+) is maintained constant in the internal environment at a given body temperature independent of external environment according to Bernard's principle of "milieu interieur". But CO2 relates to ventilation and H(+) to kidney. Hence, the title of the chapter. In order to do this, sensors for H(+) in the internal environment are needed. The sensor-receptor is CO2/H(+) sensing. The sensor-receptor is coupled to integrate and to maintain the body's chemical environment at equilibrium. This chapter dwells on this theme of constancy of H(+) of the blood and of the other internal environments. [H(+)] is regulated jointly by respiratory and renal systems. The respiratory response to [H(+)] originates from the activities of two groups of chemoreceptors in two separate body fluid compartments: (A) carotid and aortic bodies which sense arterial P(O2) and H(+); and (B) the medullary H(+) receptors on the ventrolateral medulla of the central nervous system (CNS). The arterial chemoreceptors function to maintain arterial P(O2) and H(+) constant, and medullary H(+) receptors to maintain H(+) of the brain fluid constant. Any acute change of H(+) in these compartments is taken care of almost instantly by pulmonary ventilation, and slowly by the kidney. This general theme is considered in Section 1. The general principles involving cellular CO2 reactions mediated by carbonic anhydrase (CA), transport of CO2 and H(+) are described in Section 2. Since the rest of the chapter is dependent on these key mechanisms, they are given in detail, including the role of Jacobs-Stewart Cycle and its interaction with carbonic anhydrase. Also, this section deals briefly with the mechanisms of membrane depolarization of the chemoreceptor cells because this is one mechanism on which the responses depend. The metabolic impact of endogenous CO2 appears in the section with a historical twist, in the context of acclimatization to high altitude (Section 3). Because low P(O2) at high altitude stimulates the peripheral chemoreceptors (PC) increasing ventilation, the endogenous CO2 is blown off, making the internal milieu alkaline. With acclimatization however ventilation increases. This alkalinity is compensated in the course of time by the kidney and the acidity tends to be restored, but the acidification is not great enough to increase ventilation further. The question is what drives ventilation during acclimatization when the central pH is alkaline? The peripheral chemoreceptor came to the rescue. Its sensitivity to P(O2) is increased which continues to drive ventilation further during acclimatization at high altitude even when pH is alkaline. This link of CO2 through the O2 chemoreceptor is described in Section 4 which led to hypoxia-inducible factor (HIF-1). HIF-1 is stabilized during hypoxia, including the carotid body (CB) and brain cells, the seat of CO2 chemoreception. The cells are always hypoxic even at sea level. But how CO2 can affect the HIF-1 in the brain is considered in this section. CO2 sensing in the central chemoreceptors (CC) is given in Section 5. CO(2)/H(+) is sensed by the various structures in the central nervous system but its respiratory and cardiovascular responses are restricted only to some areas. How the membranes are depolarized by CO2 or how it works through Na(+)/Ca(2+) exchange are discussed in this section. It is obvious, however, that CO2 is not maintained constant, decreasing with altitude as alveolar P(O2) decreases and ventilation increases. Rather, it is the [H(+)] that the organism strives to maintain at the expense of CO2. But then again, [H(+)] where? Perhaps it is in the intracellular environment. Gap junctions in the carotid body and in the brain are ubiquitous. What functions they perform have been considered in Section 6. CO2 changes take place in lung alveoli where inspired air mixes with the CO2 from the returning venous blood. It is the interface between the inspired and expired air in the lungs where CO2 change is most dramatic. As a result, various investigators have looked for CO2 receptors in the lung, but none have been found in the mammals. Instead, CO2/H(+) receptors were found in birds and amphibians. However, they are inhibited by increasing CO2/H(+), instead of stimulated. But the afferent impulses transmitted to the brain produced stimulation in the efferents. This reversal of afferent-efferent inputs is a curious situation in nature, and this is considered in Section 7. The NO and CO effects on CO2 sensing are interesting and have been briefly mentioned in Section 8. A model for CO2/H(+) sensing by cells, neurons and bare nerve endings are also considered. These NO effects, models for CO2/H(+) and O2-sensitive cells in the CNS have been considered in the perspectives. Finally, in conclusion, the general theme of constancy of internal environment for CO2/H(+) is reiterated, and for that CO2/H(+) sensors-receptors systems are essential. Since CO2/H(+) sensing as such has not been reviewed before, the recent findings in addition to defining basic CO2/H(+) reactions in the cells have been briefly summarized.
Animals↗
Heat tolerance in two tropically adapted Bos taurus breeds, Senepol and Romosinuano, compared with Brahman, Angus, and Hereford cattle in Florida.
Two trials were conducted with heifers to determine heat tolerance among temperate Bos taurus (Angus, Hereford), Bos indicus (Brahman), tropical Bos taurus (Senepol, Romosinuano), and the reciprocal crosses of Hereford and Senepol. Differences among breeds in temperament score, circulating concentrations of cortisol, and blood packed cell volume were also investigated. Trial 1 used 43 Angus, 28 Brahman, 12 Hereford, 23 Romosinuano, 16 Senepol, 5 Hereford x Senepol (H x S), and 5 Senepol x Hereford (S x H) heifers. Trial 2 used 36 Angus, 31 Brahman, 9 Hereford, 14 Senepol, 19 H x S, and 10 S x H heifers. On the hottest summer date in Trial 1, rectal temperature of Angus was greater (P < .001) than that of Brahman, Senepol, or Romosinuano. Rectal temperature and plasma cortisol were significantly less in Senepol than in Brahman, suggesting that the differences in rectal temperature between these breeds may be due to differences in stress response possibly related to differences in temperament. Reciprocal crosses of Hereford and Senepol had rectal temperatures nearly as low as that of Senepol and displayed substantial heterosis (-9.4%, P < .05) in log10 rectal temperature on the hottest summer date. On both the hottest and coolest dates in Trial 1, Angus heifers had significantly faster respiration rates than Brahman, Romosinuano, or Senepol heifers, and Brahman had significantly slower respiration rates than Romosinuano or Senepol. On the hottest summer date in Trial 2, rectal temperature in Angus heifers was greater (P < .001) than in Brahman or Senepol had rectal temperatures similar to that of Senepol, or heterosis for log10 rectal temperature was similar to that in Trial 1 (-9.8%, P < .05). Considering rank order among breeds, Brahman always had the slowest respiration rate and greatest packed cell volume. Brahman had significantly greater temperament scores and plasma cortisol concentrations than Angus or Senepol, except that plasma cortisol was not different between Brahman and Senepol on the hottest summer date. On this date, rectal temperature did not differ between Brahman and Senepol, which supports the hypothesis that there is a relationship between response to stress and rectal temperature that helps explain differences in rectal temperature between Brahman and Senepol. The results of these trials demonstrate heat tolerance of the Senepol and Romosinuano, two Bos taurus breeds. Furthermore, the results suggest a substantial level of dominance of the Senepol's ability to maintain constant body temperature in a hot environment as measured by rectal temperature in crosses with a non-adapted breed.
Adaptation, Physiological↗
Early age thermal conditioning immediately reduces body temperature of broiler chicks in a tropical environment.
Early age thermal conditioning (TC) durably improves resistance of broilers to heat stress and reduces body temperature (Tb). Three experiments on broiler chicks were conducted to evaluate the effects of TC at 5 d of age on Tb variation measured by thermometer between 4 and 7 d of age, under a tropical environment. Because manipulation of chickens to measure Tb with a thermometer may increase Tb, a preliminary experiment on 13 3-to-4-wk-old male broilers compared Tb measured by telemetry to Tb measured in the terminal colon during three successive periods at 22, 33, and 22 degrees C. During heat exposure, Tb rapidly increased by 0.9 degrees C and plateaued over 24 h. During the last period, seven of the broilers rapidly reduced Tb to a plateau lower than the initial Tb, although six broilers exhibited more variable Tb. Measurement by thermometer underestimated on average core Tb by 0.28 degrees C at 22 degrees C and by 0.57 degrees C at 33 degrees C, whereas Tb recorded by telemetry was not affected by manipulation of the chickens. TC reduced Tb 24 h later in the three experiments. Compared to unexposed control chicks (N), 12 h of TC at 40 degrees C did not significantly reduce Tb at 7 d of age, although 24 h did. TC at 38 and 40 degrees C over 24 h significantly reduced Tb variation from 4 to 7 d of age compared to N chicks, whereas 36 degrees C did not. Withdrawing feed from the chicks for 2 h prior to measurement did not significantly reduce Tb at 4 and 7 d of age, but Tb reduction due to TC was greater in fed chicks (0.28 degrees C) than in chicks without feed (0.05 degrees C). Early age thermal conditioning at 38 to 40 degrees C at 5 d of age for 24 h reduced body temperature of 7-d-old male broilers.
Adaptation, Physiological↗
HYPOTHALAMIC TEMPERATURES IN DOG AND MONKEY AND THERMOREGULATORY RESPONSES TO ENVIRONMENTAL FACTORS. TECHN DOCUM REP AMRL-TDR-63-5.
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Animals↗
Ambient-temperature primary nonselective enrichment for isolation of Salmonella spp. from an estuarine environment.
A primary, nonselective, ambient-temperature enrichment procedure for isolation of Salmonella spp. is described. The procedure was superior to elevated-temperature selective enrichment for Salmonella when estuarine water samples were examined. Five Chesapeake Bay stations were monitored, over an 8-month period, for the presence of salmonellae. Of 72 water and sediment samples collected, 17 (23.6%) yielded Salmonella spp. Seven serotypes were identified among the isolates. A seasonal pattern was noted for the incidence of the salmonellae. A most probable number procedure, performed by membrane filtration and nonselective enrichment, yielded Salmonella most probable number indices as high as 110 per 100 g of sediment. The results suggest that new methods, such as the one described in this report, are required for isolation of human intestinal pathogens from estuaries and coastal waters.
Bacteriological Techniques↗
Oral antibiotics reduce body temperature of healthy rabbits in a thermoneutral environment.
Nonabsorbable oral antibiotics, which reduce gut flora, decrease the daytime and night-time body temperatures of rats and mice. We investigated whether oral antibiotics would also lower the body temperature of healthy rabbits. Six rabbits received neomycin sulphate in their drinking water for ten days, and seven rabbits received a mixture of chloramphenicol and dihydroxystreptomycin for six days. Body temperatures, recorded using intra-abdominal radiotelemeters, decreased significantly, by 0.2-0.3 degree C, after three days of antibiotic treatment in both groups of rabbits. The drop in body temperature was transient; after six days body temperatures returned to pre-antibiotic levels. Antibiotic treatment had no effect on either the acrophase or the amplitude of the circadian rhythm in body temperature. Oral antibiotics therefore reduce body temperature of rabbits, without influencing the circadian rhythm in body temperature. Our results are consistent with the hypothesis that an agent arising from intestinal bacteria sustains an elevated body temperature in healthy animals.
Animals↗
Lowering of body temperature affects human platelet functions and norepinephrine release.
The effect of lowering body temperature on plasma epinephrine, norepinephrine, and platelet density distribution and volume was studied in a placebo-controlled double-blind study. Lowering of body core temperature was induced by either exposure to a cold environment at a temperature of 5 degrees C (CT) or by a single dose of the 5-HT1A agonist ipsapirone (IPS). A third group exposed to an ambient temperature of 28 degrees C was given placebo (PLAC). All of the three groups were investigated in a climate chamber. In the CT group the density distribution of blood platelet subpopulations was shifted to an increase in less dense platelets that were more sensitive towards aggregation-inducing agents. The mean platelet volume in this subpopulation was decreased. Epinephrine was not affected, whereas the increase of norepinephrine was correlated with an increase of platelets that were more sensitive to aggregation-inducing agents in the CT group but not in the PLAC and IPS groups.
Adult↗
Changes in motoneuron membrane potential and reflex activity induced by sudden cooling of isolated spinal cords: differences among cold-sensitive, cold-resistant and freeze-tolerant amphibian species.
The effects of sudden cooling of the spinal cord were studied in three species of amphibians--a cold-sensitive tropical toad (Bufo marinus), a cold-resistant, aquatic, hibernating frog (Rana pipiens, northern leopard frog) and a freeze-tolerant frog (Rana sylvatica, wood frog). Ventral root (motoneuron) potentials were recorded from isolated, hemisected spinal cords of each species mounted in a sucrose-gap recording apparatus and superfused with HCO3(-)-buffered Ringer's solution at room temperature (21 degrees C). In the toad, sudden cooling to 6-8 degrees C produced large, sustained motoneuron depolarizations that returned slowly to baseline levels and were accompanied by extensive paroxysmal activity. Larger, but shorter-lasting, motoneuron depolarizations associated with only a limited amount of paroxysmal activity were generated by rapid cooling of the leopard frog spinal cord. Small, brief motoneuron depolarizations followed by a hyperpolarization, or hyperpolarizations not preceded by depolarizations, were seen in cooled wood frog spinal cords. The wood frog displayed a large amount of spontaneous motoneuron activity, but little paroxysmal activity in response to sudden cooling. Following prolonged cooling, rewarming the spinal cords of all three species resulted in motoneuron hyperpolarizations that slowly decayed towards the baseline value. The amplitude of the rewarming-induced response was larger and longer in toad motoneurons than in leopard frog and wood frog motoneurons. At room temperature, a single supramaximal dorsal root stimulus evoked a depolarizing ventral root potential in toad and leopard frog motoneurons that was decreased in amplitude and prolonged when the spinal cords were cooled to 8 degrees C or below. In contrast, at room temperature, the ventral root reflex in the wood frog was followed by a distinct hyperpolarization. Cooling the wood frog spinal cord only slightly reduced the amplitude of the ventral root potential. In contrast, the evoked hyperpolarization was blocked by sudden cooling and also by the addition of dihydro-ouabain to the Ringer's solution. The motoneuron hyperpolarizations induced by sudden cooling in the wood frog were converted to depolarizations when Cl- in the superfusate was replaced with isethionate. The depolarizations elicited by sudden cooling were reduced by the addition of kynurenate in all three species. A dose-response curve generated by short applications of L-glutamate demonstrated that wood frog motoneurons were less sensitive than leopard frog motoneurons to L-glutamate. In summary, three species of amphibians, differing in their adaptations to the temperature of their environments, vary in their responses to sudden reductions in temperature. The relationship of these responses to their environmental adaptations remains to be determined.
Animals↗
Thermoregulation of the Japanese macaque living in a snowy mountain area.
A field investigation was conducted to study the thermoregulatory responses in nine Japanese macaques (Macaca fuscata) living in a snowy mountain area, Jigoku-Dani (Hell Valley, about 1,000 m above sea level) in Shiga Heights in central Japan in late January 1975. At about the same time, a laboratory study was made on four Japanese macaques reared in mild climate in an outdoor cage in Inuyama City. In the Hell Valley (HV) monkeys, no significant change in metabolic rate was observed at Ta between -1.4 and 28.3 degrees C, while the rectal temperature was maintained at normal level. In the cold environment, the skin temperatures of HV monkeys were significantly higher than those of the monkeys living indoors previously studied. Similar patterns of metabolic and thermal responses were observed in Inuyama monkeys living outdoors, but to a lesser degree. The hair on the back and abdomen in the HV monkeys was significantly longer than that of Iuyama monkeys living indoors. It is suggested that the thick fur of HV monkeys may account for, if not all, the thermoregulatory responses of the Japanese macaque in snowy mountain areas.
Animals↗
HUMAN SKIN TEMPERATURE AND NON-EVAPORATIVE HEAT EXCHANGE WITH THE ENVIRONMENT.
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Body Temperature Regulation↗
[Changes in the urinary excretion of gamma-glutamyltranspeptidase, leucine aminopeptidas and alkaline phosphatase in the combined action of ethylene glycol and high temperature].
Gamma-glutamyl transpeptidase (gamma--GTP), leucine aminopeptidase (LAP) and alkaline phosphatase (AP) excretion in rats is followed in dynamics (2, 8, 15, 30 and 90 days) upon isolated and combined treatment with ethylene glycol (EG) at dose 1/8 LD50 and temperature of the environment 35 degrees C. Under the effect of high temperature an increase in the excretion of enzymes in the early observation terms is noted. The independent application of the noxa causes a reduction in gamma--GTR and LAP excretion, and an increase in AP. The temperature factor attenuates the toxic effect of EG relative to the enzymes under study at the end of the observation period. Changes in gamma--GTP excretion are considered as the earliest and most sensitive sign of tubular lesions.
Alkaline Phosphatase↗
[The effect of temperature and oxygen concentration in the environment on phospholipid metabolism in isolated rat brain tissue].
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Animals↗