Plasma volumes and constituents of heat-exposed men before and after acclimatization

1975 ◽  
Vol 38 (4) ◽  
pp. 570-575 ◽  
Author(s):  
L. C. Senay
Keyword(s):  
Water Movement ◽  
Venous Blood ◽  
Heat Exposure ◽  
Heat Acclimatization ◽  
Vascular Volume ◽  
Exercise Regimen ◽  
Body Weights ◽  
Before And After ◽  
Body Compartments ◽  
Considerable Loss

Five men underwent a 2-wk exercise regimen and were then exposed to 45 degrees C db, 28 degrees C wb, wind speed 1 m/s for 12 h while at rest. Body weight was maintained with 0.1% saline. One week later the exposure was repeated without rehydration. After heat acclimatization, the 12-h experiments were repeated. Frequent body weights, rectal temperatures, and venous blood samples were obtained. Results indicated that hemodilution upon acute heat exposure is partially due to protein influx into the vascular volume and the hemodilution allowed considerable loss of body water before plasma volume returned to preexposure values. Water within the vascular volume appeared to be in equilibrium with that in other body compartments before but not after acclimatization. Acclimatization altered the rate of protein transfer (and water movement) such that hemodilution was accomplished more rapidly than before acclimatization. Early hemodilution was quite labile and depended upon subject hydration during the first hour of heat exposure.

Acclimatization in a hot, humid environment: body fluid adjustments

1976 ◽  
Vol 40 (5) ◽  
pp. 786-796 ◽  
Author(s):  
L. C. Senay ◽  
D. Mitchell ◽  
C. H. Wyndham
Keyword(s):  
Plasma Volume ◽  
Water Retention ◽  
Heat Exposure ◽  
Relative Increase ◽  
Critical Event ◽  
Heat Acclimatization ◽  
Vascular Volume ◽  
Humid Environment ◽  
Maximum Aerobic Capacity ◽  
Vascular Compartment

Four trained men worked 4 h/day at 40–50% of their maximum aerobic capacity first for 3 days at 25 degrees C db, 18 degrees C wb and then for 10 consecutive days at 45 degrees C db, 32 degrees C wb. Between days 1 and 2 of heat exposure mean total circulating protein (TCP) and plasma volume (PV) increased 11.6% and 9%, respectively. Preexposure TCP and PV increased until day 6 of heat exposure. Of the protein fractions beta-globulins underwent the largest relative increase. During work movement of protein into and out of the vascular compartment was similar in control and acclimatizing subjects but the latter generally maintained a greater amount of protein and fluid within the vascular volume. There was no evidence of salt and water retention. The increase in vascualr volume was ascribed to transfer of interstitial protein and water to the vascular volume. Regression coefficients indicated significant correlations for changes in plasma volume versus heart rate, stroke volume, and cardiac output during acclimatization. It was concluded that the most critical event in heat acclimatization is the expansion of the plasma volume.

Human thermoregulatory responses during heat exposure after artificially induced sunburn

1992 ◽  
Vol 262 (4) ◽  
pp. R610-R616 ◽  
Author(s):  
K. B. Pandolf ◽  
R. W. Gange ◽  
W. A. Latzka ◽  
I. H. Blank ◽  
K. K. Kraning ◽  
...  
Keyword(s):  
Heart Rate ◽  
Venous Blood ◽  
Heat Exposure ◽  
Plasma Osmolality ◽  
Cycle Ergometer ◽  
The Body ◽  
Left Forearm ◽  
Thermoregulatory Responses ◽  
Ergometer Exercise ◽  
Before And After

Thermoregulatory responses in the heat (ambient temperature 49 degrees C, 20% relative humidity, 1 m/s wind) were investigated in 10 unacclimated men during 50 min of cycle ergometer exercise (approximately 53% of maximal aerobic power) after a 10-min rest before as well as 24 h and 1 wk after twice the minimal erythemal dose of UV-B radiation that covered approximately 85% of the body surface area. In 7 subjects esophageal temperature (Tes) was recorded while in all 10 subjects five-site skin and rectal temperatures, heart rate, and back, left forearm, and shielded (12 cm2 area) right forearm sweating rates (msw) were recorded at 15-s intervals. Venous blood was collected before and after exercise-heat stress. Mean skin temperature, Tes, rectal temperature, heart rate, and total body sweating rate were not significantly (P greater than 0.05) affected by sunburn. Pre- and postexercise values of hematocrit, hemoglobin, plasma protein, plasma volume, and plasma osmolality were also not affected (P greater than 0.05) by sunburn. Analysis of presunburn and post-sunburn data showed that the Tes intercept for sweating (degrees C) was unaffected (P greater than 0.05), but msw/Tes and final msw from the left forearm (msw/Tes 0.24 +/- 0.02 vs. 0.17 +/- 0.01 mg.cm-2.min-1. degrees C-1, P less than 0.05; msw 0.60 +/- 0.05 vs. 0.37 +/- 0.02, mg.cm-2.min-1, P less than 0.05) and back (msw/Tes 0.43 +/- 0.03 vs. 0.36 +/- 0.01 mg.cm-2.min-1. degrees C-1, P = 0.052; msw 1.08 +/- 0.09 vs. 0.74 +/- 0.05 mg.cm-2.min-1, P less than 0.05) were significantly reduced 24 h postsunburn.(ABSTRACT TRUNCATED AT 250 WORDS)

Early response of plasma contents on exposure of working men to heat

1978 ◽  
Vol 44 (2) ◽  
pp. 166-170 ◽  
Author(s):  
L. C. Senay
Keyword(s):  
Venous Blood ◽  
Heat Exposure ◽  
Early Response ◽  
Plasma Osmolarity ◽  
Vascular Volume ◽  
Group I ◽  
Conflicting Evidence ◽  
Group Protein ◽  
H Protein ◽  
Group 1

Twelve men block-stepped (35 W) 4 h/day for 12 days and were divided into two similar groups on the basis of Vo2max. All were exposed to 33.8 degrees C dry bulb, 32.7 degrees C wet bulb for 2 h (E1) while working (30% Vo2max). Venous blood was obtained at 10-min intervals during hour 1 and at 20-min intervals during hour 2. Group 1 was acclimatized to heat. Group II continued to train. The test exposure was repeated (E2). During E1 a trend toward hemodilution was evident but not significant for either group. Protein moved into the vascular volume and a decrease in plasma osmolarity was significant only after 30 min. For both groups during E2 significant hemodilution occurred during the first 10 min. Only group I remained significantly hemodiluted for 2 h. Protein movement and osmodilution again occurred in both groups. These results support earlier suggestions as to the mechanisms of hemodilution based on 1-h blood samples. Conflicting evidence as to the pressure or absence of hemodilution upon heat exposure is noted, and a hypothesis is proposed which appears to reconcile divergent results.

Effects of plasma ascorbic acid levels on heat acclimatization in man

1977 ◽  
Vol 42 (5) ◽  
pp. 711-716 ◽  
Author(s):  
H. F. Kotze ◽  
W. H. van der Walt ◽  
G. G. Rogers ◽  
N. B. Strydom
Keyword(s):  
Ascorbic Acid ◽  
Rectal Temperature ◽  
Sweat Rate ◽  
Venous Blood ◽  
Heat Exposure ◽  
Ascorbic Acid Concentration ◽  
Heat Acclimatization ◽  
Plasma Ascorbic Acid ◽  
Blood Samples ◽  
Plateau Level

Thirteen male volunteers were heat acclimatized for 4 h/day for 10 consecutive days. Three to four hours before each heat exposure, four of the subjects received an oral dose of 250 ascorbic acid, five received 500 mg ascorbic acid, and the remaining four a placebo. Rectal temperature, heart rate, and sweat rate were measured hourly during exposure. Venous blood samples were collected before each administration of drug or placebo. On days 1, 2, 3, 5, 8, and 10, blood samples were also collected just prior to heat exposure and after two and four hours of exposure. In the subjects receiving ascorbic acid, total circulating plasma ascorbic acid increased over the first three or four days to a plateau level some fourfold higher than in the subjects receiving the placebo. The plateau level was the same in the subjects receiving 250 mg and 500 mg ascorbic acid. The increased ascorbic acid concentration was shown to be associated with a reduction in total sweat output, independent of rectal temperature, and a reduction in rectal temperature, independent of total sweat output. The results indicate that ascorbic acid may be effective in reducing heat strain in unacclimatized individuals.

Sorbitol enhances the physicochemical stability of B12 vitamers

2020 ◽  
Vol 90 (5-6) ◽  
pp. 439-447 ◽  
Author(s):  
Andrew Hadinata Lie ◽  
Maria V Chandra-Hioe ◽  
Jayashree Arcot
Keyword(s):  
Ascorbic Acid ◽  
Uv Light ◽  
Heat Exposure ◽  
Water Soluble ◽  
Uv Exposure ◽  
Physicochemical Stability ◽  
Before And After ◽  
The Stability

Abstract. The stability of B12 vitamers is affected by interaction with other water-soluble vitamins, UV light, heat, and pH. This study compared the degradation losses in cyanocobalamin, hydroxocobalamin and methylcobalamin due to the physicochemical exposure before and after the addition of sorbitol. The degradation losses of cyanocobalamin in the presence of increasing concentrations of thiamin and niacin ranged between 6%-13% and added sorbitol significantly prevented the loss of cyanocobalamin (p<0.05). Hydroxocobalamin and methylcobalamin exhibited degradation losses ranging from 24%–26% and 48%–76%, respectively; added sorbitol significantly minimised the loss to 10% and 20%, respectively (p < 0.05). Methylcobalamin was the most susceptible to degradation when co-existing with ascorbic acid, followed by hydroxocobalamin and cyanocobalamin. The presence of ascorbic acid caused the greatest degradation loss in methylcobalamin (70%-76%), which was minimised to 16% with added sorbitol (p < 0.05). Heat exposure (100 °C, 60 minutes) caused a greater loss of cyanocobalamin (38%) than UV exposure (4%). However, degradation losses in hydroxocobalamin and methylcobalamin due to UV and heat exposures were comparable (>30%). At pH 3, methylcobalamin was the most unstable showing 79% degradation loss, which was down to 12% after sorbitol was added (p < 0.05). The losses of cyanocobalamin at pH 3 and pH 9 (~15%) were prevented by adding sorbitol. Addition of sorbitol to hydroxocobalamin at pH 3 and pH 9 reduced the loss by only 6%. The results showed that cyanocobalamin was the most stable, followed by hydroxocobalamin and methylcobalamin. Added sorbitol was sufficient to significantly enhance the stability of cobalamins against degradative agents and conditions.

ADRENAL 17-HYDROXYCORTICOSTEROID SECRETION IN THE DOG IN RESPONSE TO ETHANOL

1972 ◽  
Vol 70 (4) ◽  
pp. 736-740 ◽  
Author(s):  
T. Suzuki ◽  
R. Higashi ◽  
T. Hirose ◽  
H. Ikeda ◽  
K. Tamura
Keyword(s):  
Venous Blood ◽  
Secretion Rate ◽  
Conscious Dogs ◽  
Blood Samples ◽  
Before And After

ABSTRACT Conscious dogs were infused intravenously with ethanol in doses of 0.7 and 1.0 g/kg. The adrenal venous blood samples were collected before and after the infusion of ethanol and analysed for 17-hydroxycorticosteroids (17-OHCS). After the infusion of 0.7 g/kg (subanaesthetic dose) of ethanol the adrenal 17-OHCS secretion rate showed either a slight increase or no change. After the infusion of 1.0 g/kg (anaesthetic dose) of ethanol the adrenal 17-OHCS secretion rate increased markedly and reached 1.21±0.15 (mean±sem) μg/kg/min, while it was 0.09±0.023 μg/kg/min before the infusion.

Sensitivity of bioelectrical impedance to detect changes in human body composition

1989 ◽  
Vol 67 (4) ◽  
pp. 1643-1648 ◽  
Author(s):  
R. Ross ◽  
L. Leger ◽  
P. Martin ◽  
R. Roy
Keyword(s):  
Body Composition ◽  
Human Body ◽  
Correlation Coefficients ◽  
Bioelectrical Impedance ◽  
Mean Values ◽  
Significance Level ◽  
Exercise Regimen ◽  
Before And After ◽  
Hydrostatic Weighing ◽  
Human Body Composition

The purpose of this study was to compare the estimates of lean body mass (LBM) and percent body fat (%BF), as predicted by bioelectrical impedance (BIA) and sum of skinfolds (SF), with those derived by hydrostatic weighing (HW) obtained before and after a 10-wk diet and exercise regimen. The experimental (E) group consisted of 17 healthy male subjects; 20 healthy males served as the control (C) group. Post hoc Scheffe contrasts computed on E group data indicated that, for both LBM and %BF, the Lukaski and Segal BIA equations, as well as the Durnin SF equation, derived mean values that were not significantly different (0.05 significance level) from HW in both pre- and postregimen conditions. For LBM, the same equations derived the following significant (P less than 0.01) correlation coefficients for both pre- and postregimen data: Lukaski, 0.87 and 0.85; Segal, 0.89 and 0.87; and Durnin, 0.90 and 0.88. For %BF, the correlation coefficients were slightly lower but remained statistically significant (P less than 0.01). The findings of this study suggest that the BIA method, by use of either the Lukaski or Segal prediction equations, is a valid means of predicting changes in human body composition as measured by the Siri transformation of body density.

Muscle glycogen availability and temperature regulation in humans

1989 ◽  
Vol 66 (1) ◽  
pp. 72-78 ◽  
Author(s):  
L. Martineau ◽  
I. Jacobs
Keyword(s):  
Skeletal Muscle ◽  
Muscle Glycogen ◽  
Temperature Regulation ◽  
Vastus Lateralis ◽  
Water Immersion ◽  
Vastus Lateralis Muscle ◽  
Glycogen Concentration ◽  
Exercise Regimen ◽  
Before And After ◽  
Muscle Groups

The effects of intramuscular glycogen availability on human temperature regulation were studied in eight seminude subjects immersed in 18 degrees C water for 90 min or until rectal temperature (Tre) decreased to 35.5 degrees C. Each subject was immersed three times over a 3-wk period. Each immersion followed 2.5 days of a specific dietary and/or exercise regimen designed to elicit low (L), normal (N), or high (H) glycogen levels in large skeletal muscle groups. Muscle glycogen concentration was determined in biopsies taken from the vastus lateralis muscle before and after each immersion. Intramuscular glycogen concentration before the immersion was significantly different among the L, N, and H trials (P less than 0.01), averaging 247 +/- 15, 406 +/- 23, and 548 +/- 42 (SE) mmol glucose units.kg dry muscle-1, respectively. The calculated metabolic heat production during the first 30 min of immersion was significantly lower during L compared with N or H (P less than 0.05). The rate at which Tre decreased was more rapid during the L immersion than either N or H (P less than 0.05), and the time during the immersion at which Tre first began to decrease also appeared sooner during L than N or H. The results suggest that low skeletal muscle glycogen levels are associated with more rapid body cooling during water immersion in humans. Higher than normal muscle glycogen levels, however, do not increase cold tolerance.

Costal diaphragmatic O2 and lactate extraction in laryngeal hemiplegic ponies during exercise

1988 ◽  
Vol 65 (4) ◽  
pp. 1723-1728 ◽  
Author(s):  
M. Manohar ◽  
T. E. Goetz ◽  
D. Nganwa
Keyword(s):  
Maximal Exercise ◽  
Venous Blood ◽  
Lactate Concentration ◽  
Lactate Production ◽  
Hemoglobin Concentration ◽  
Insignificant Change ◽  
Resistive Breathing ◽  
O2 Extraction ◽  
Before And After ◽  
Arterial Po2

Diaphragmatic O2 and lactate extraction were examined in seven healthy ponies during maximal exercise (ME) carried out without, as well as with, inspiratory resistive breathing. Arterial and diaphragmatic venous blood were sampled simultaneously at rest and at 30-s intervals during the 4 min of ME. Experiments were carried out before and after left laryngeal hemiplegia (LH) was produced. During ME, normal ponies exhibited hypocapnia, hemoconcentration, and a decrease in arterial PO2 (PaO2) with insignificant change in O2 saturation. In LH ponies, PaO2 and O2 saturation decreased well below that in normal ponies, but because of higher hemoglobin concentration, arterial O2 content exceeded that in normal ponies. Because of their high PaCO2 during ME, acidosis was more pronounced in LH animals despite similar lactate values. Diaphragmatic venous PO2 and O2 saturation decreased with ME to 15.5 +/- 0.9 Torr and 18 +/- 0.5%, respectively, at 120 s of exercise in normal ponies. In LH ponies, corresponding values were significantly less: 12.4 +/- 1.3 Torr and 15.5 +/- 0.7% at 120 s and 9.8 +/- 1.4 Torr and 14.3 +/- 0.6% at 240 s of ME. Mean phrenic O2 extraction plateaued at 81 and 83% in normal and LH animals, respectively. Significant differences in lactate concentration between arterial and phrenic-venous blood were not observed during ME. It is concluded that PO2 and O2 saturation in the phrenic-venous blood of normal ponies do not reach their lowest possible values even during ME. Also, the healthy equine diaphragm, even with the added stress of inspiratory resistive breathing, did not engage in net lactate production.

Effect of carbohydrate ingestion on exercise metabolism

1988 ◽  
Vol 65 (4) ◽  
pp. 1553-1555 ◽  
Author(s):  
M. Hargreaves ◽  
C. A. Briggs
Keyword(s):  
Muscle Glycogen ◽  
Venous Blood ◽  
Cycle Ergometer ◽  
Strenuous Exercise ◽  
Carbohydrate Ingestion ◽  
Ergometer Exercise ◽  
Glucose Polymer ◽  
Before And After ◽  
Plasma Insulin Levels ◽  
Glycogen Utilization

Five male cyclists were studied during 2 h of cycle ergometer exercise (70% VO2 max) on two occasions to examine the effect of carbohydrate ingestion on muscle glycogen utilization. In the experimental trial (CHO) subjects ingested 250 ml of a glucose polymer solution containing 30 g of carbohydrate at 0, 30, 60, and 90 min of exercise; in the control trial (CON) they received an equal volume of a sweet placebo. No differences between trials were seen in O2 uptake or heart rate during exercise. Venous blood glucose was similar before exercise in both trials, but, on average, was higher during exercise in CHO [5.2 +/- 0.2 (SE) mmol/l] compared with CON (4.8 +/- 0.1, P less than 0.05). Plasma insulin levels were similar in both trials. Muscle glycogen levels were also similar in CHO and CON both before and after exercise; accordingly, there was no difference between trials in the amount of glycogen used during the 2 h of exercise (CHO = 62.8 +/- 10.1 mmol/kg wet wt, CON = 56.9 +/- 10.1). The results of this study indicate that carbohydrate ingestion does not influence the utilization of muscle glycogen during prolonged strenuous exercise.

Sign in / Sign up

Export Citation Format

Share Document