ACUTE EXPOSURE OF HUMAN SUBJECTS TO AN AMBIENT TEMPERATURE OF 10 °C

1964 ◽  
Vol 42 (2) ◽  
pp. 233-243 ◽  
Author(s):  
D. A. Hurley ◽  
E. D. L. Topliff ◽  
F. Girling
Keyword(s):  
Oxygen Consumption ◽  
Ambient Temperature ◽  
Heat Production ◽  
Human Subjects ◽  
Healthy Male ◽  
Cold Acclimatization ◽  
Seasonal Acclimatization ◽  
Time Of Year ◽  
Male Subjects ◽  
Shivering Thermogenesis

Acute exposures to cold (10 °C) for 1 hour were carried out in early April on five unclothed healthy male subjects to follow their shivering responses, oxygen consumption, ventilation, skin and oral temperatures. Exposure to the cold resulted in immediate (within 5 minutes) and sustained increases in oxygen consumption, ventilation, and heat production. These subjects did not show generalized shivering, however, until after 30 minutes of exposure, even though short bursts of shivering were noted before this time. The immediate increase in heat production without shivering is indicative of a non-shivering thermogenesis which may be the result of cold-acclimatization in these subjects. Seasonal acclimatization would be maximal at the time of year during which the experiments were carried out.

METABOLIC RESPONSE OF NUDE HUMAN SUBJECTS TO ACUTE EXPOSURE AT 10 °C

1964 ◽  
Vol 42 (3) ◽  
pp. 319-327 ◽  
Author(s):  
F. Girling
Keyword(s):  
Oxygen Consumption ◽  
Heat Loss ◽  
Initial Rate ◽  
Metabolic Response ◽  
Human Subjects ◽  
Healthy Male ◽  
The Difference ◽  
Group 2 ◽  
Male Subjects ◽  
Group 1

Acute exposures to cold (10 °C) for up to 90 minutes were carried out in late April and early May on 10 unclothed healthy male subjects to follow their shivering responses, oxygen consumption, skin and oral temperatures. The 10 subjects divided into two groups with markedly different responses. Group 1 showed no increase in oxygen consumption for the initial 15 minutes of exposure. After 15 minutes the oxygen consumption increased by about 45% and appeared to be coincident with shivering. Group 2 showed an immediate increase in oxygen consumption on exposure, to about 45% above control values, and shivering in this group was delayed or absent. The difference between the two groups is explained on the basis of a greater degree of acclimatization to cold in the subjects of group 2. It is suggested that the immediate increase in oxygen consumption in group 2 is triggered by a greater initial rate of heat loss in this group.

Effects of oral glycine during cold exposure in man

1959 ◽  
Vol 14 (3) ◽  
pp. 390-392 ◽  
Author(s):  
William R. Beavers ◽  
Benjamin G. Covino
Keyword(s):  
Oxygen Consumption ◽  
Rectal Temperature ◽  
Heat Production ◽  
Cold Exposure ◽  
Human Subjects ◽  
Exposure Period ◽  
Blood Flows ◽  
Skin Temperatures ◽  
Warm Room

Six male human subjects were given 30 gm oral glycine. Oxygen consumption, skin and rectal temperatures, and forefinger blood flows were measured during an interval in a warm room and then during 75 minutes cold exposure (0°F). The same subjects receiving 30 gm glucose served as controls. Glycine increased heat production at rest in a warm room and also during cold exposure. The subjects when receiving glycine had a slightly higher rectal temperature and higher skin temperatures in areas other than fingers during the cold exposure period. Submitted on August 1, 1958

Temperature regulation and cold acclimation in the golden hamster

1965 ◽  
Vol 20 (3) ◽  
pp. 405-410 ◽  
Author(s):  
Hermann Pohl
Keyword(s):  
Oxygen Consumption ◽  
Body Temperature ◽  
Ambient Temperature ◽  
Cold Acclimation ◽  
Heat Production ◽  
Golden Hamster ◽  
Thermal Conductance ◽  
Muscular Activity ◽  
The Body ◽  
Ambient Temperatures

Characteristics of cold acclimation in the golden hamster, Mesocricetus auratus, were 1) higher metabolic rate at -30 C, 2) less shivering when related to ambient temperature or oxygen consumption, and 3) higher differences in body temperature between cardiac area and thoracic subcutaneous tissues at all ambient temperatures tested, indicating changes in tissue insulation. Cold-acclimated hamsters also showed a rise in temperature of the cardiac area when ambient temperature was below 15 C. Changes in heat distribution in cold-acclimated hamsters suggest higher blood flow and heat production in the thoracic part of the body in the cold. The thermal conductance through the thoracic and lumbar muscle areas, however, did not change notably with lowering ambient temperature. Marked differences in thermoregulatory response to cold after cold acclimation were found between two species, the golden hamster and the thirteen-lined ground squirrel, showing greater ability to regulate body temperature in the cold in hamsters. hibernator; oxygen consumption— heat production; body temperature — heat conductance; muscular activity — shivering; thermoregulation Submitted on July 6, 1964

Phase 1 clinical study of eltrombopag, an oral, nonpeptide thrombopoietin receptor agonist

Blood ◽  
2007 ◽  
Vol 109 (11) ◽  
pp. 4739-4741 ◽  
Author(s):  
Julian M. Jenkins ◽  
Daphne Williams ◽  
Yanli Deng ◽  
Joanne Uhl ◽  
Valerie Kitchen ◽  
...  
Keyword(s):  
Human Subjects ◽  
Phase 1 ◽  
Controlled Clinical Trial ◽  
Dependent Manner ◽  
Healthy Male ◽  
Once Daily ◽  
Thrombopoietin Receptor ◽  
Thrombopoietin Receptor Agonist ◽  
Dose Dependent ◽  
Male Subjects

AbstractEltrombopag (SB-497 115) is a first-in-class, oral, small-molecule, nonpeptide agonist of the thrombopoietin receptor (TpoR), being developed as a treatment for thrombocytopenia of various etiologies. In this phase 1 placebo-controlled clinical trial in 73 healthy male subjects, eltrombopag was administered as once-daily oral capsules for 10 days at doses of 5, 10, 25, 30, 50, and 75 mg. The pharmacokinetics of eltrombopag were dose dependent and linear, and eltrombopag increased platelet counts in a dose-dependent manner. There were no apparent differences in the incidence or severity of adverse events in subjects receiving active or placebo study medication. These observations indicate that eltrombopag is a once-daily, oral TpoR agonist with demonstrated thrombopoietic activity in human subjects, encouraging further studies in patients with thrombocytopenia.

Age-related thermoregulatory differences during core cooling in humans

2000 ◽  
Vol 279 (1) ◽  
pp. R349-R354 ◽  
Author(s):  
Steven M. Frank ◽  
Srinivasa N. Raja ◽  
Christian Bulcao ◽  
David S. Goldstein
Keyword(s):  
Oxygen Consumption ◽  
Heat Production ◽  
Human Subjects ◽  
Plasma Norepinephrine ◽  
Thermal Perception ◽  
Age Related ◽  
Older Subjects ◽  
Total Body ◽  
Core Cooling ◽  
Total Body Oxygen

The current study assessed sympathetic neuronal and vasomotor responses, total body oxygen consumption, and sensory thermal perception to identify thermoregulatory differences in younger and older human subjects during core cooling. Cold fluid (40 ml/kg, 4°C) was given intravenously over 30 min to decrease core temperature (Tc) in eight younger (age 18–23) and eight older (age 55–71) individuals. Compared with younger subjects, the older subjects had significantly lower Tc thresholds for vasoconstriction (35.5 ± 0.3 vs. 36.2 ± 0.2°C, P = 0.03), heat production (35.2 ± 0.4 vs. 35.9 ± 0.1°C, P = 0.04), and plasma norepinephrine (NE) responses (35.0 vs. 36.0°C, P < 0.05). Despite a lower Tc nadir during cooling, the maximum intensities of the vasoconstriction ( P = 0.03) and heat production ( P = 0.006) responses were less in the older compared with the younger subjects, whereas subjective thermal comfort scores were similar. Plasma NE concentrations increased fourfold in the younger but only twofold in the older subjects at maximal Tc cooling. The vasomotor response for a given change in plasma NE concentration was decreased in the older group ( P = 0.01). In summary, aging is associated with 1) a decreased Tc threshold and maximum response intensity for vasoconstriction, total body oxygen consumption, and NE release, 2) decreased vasomotor responsiveness to NE, and 3) decreased subjective sensory thermal perception.

SEASONAL CHANGES IN THE PHYSIOLOGICAL RESPONSE OF MAN TO AN ACUTE COLD STRESS

1967 ◽  
Vol 45 (1) ◽  
pp. 13-27 ◽  
Author(s):  
F. Girling
Keyword(s):  
Cold Stress ◽  
Heat Production ◽  
Cold Exposure ◽  
Seasonal Changes ◽  
Human Subjects ◽  
Minute Ventilation ◽  
Acute Cold Exposure ◽  
Air Temperatures ◽  
The Individual ◽  
Shivering Thermogenesis

Eight male human subjects, resting supine, and wearing swim trunks only, were exposed to an ambient temperature of 8.5 °C for 1 hour in the first week of each month from February 1964 to January 1965 inclusive. Skin, rectal, and air temperatures were measured with thermistor probes. Percentage oxygen in expired air and minute ventilation were measured, and heat production was calculated by Weir's method. Electrical activity from the muscles of all four limbs was measured to determine shivering response. Control values of resting respiration and heat production were obtained under comfortably warm conditions and showed marked seasonal variation, with minimum values in spring and maximum values in later summer. In the response to acute cold exposure, marked seasonal changes were found also which were superimposed on the seasonal changes in control values. The response to cold exposure indicated maximum acclimatization to cold in the spring and minimum in later summer. These results are discussed in terms of three modes of response to the cold stress: (i) insulative cooling, (ii) shivering thermogenesis, and (iii) nonshivering thermogenesis. The degree of acclimatization and temperature of exposure may determine the individual mode of response.

Effect of whole-body vertical vibration on respiration in human subjects

1962 ◽  
Vol 17 (6) ◽  
pp. 913-916 ◽  
Author(s):  
Lee R. Duffner ◽  
Lyle H. Hamilton ◽  
Melvin A. Schmitz
Keyword(s):  
Vital Capacity ◽  
Human Subjects ◽  
Recovery Period ◽  
Vertical Vibration ◽  
Whole Body ◽  
Breathing Frequency ◽  
Peak Acceleration ◽  
Healthy Male ◽  
Maximum Increase ◽  
Male Subjects

The respiration of ten healthy male subjects was studied during 4-min exposures to vertical whole-body vibration of 0.15 and 0.35 g peak acceleration intensities of frequencies of 2 through 7 cycle/sec. Initial hyperventilation, with a subsequent return toward normal levels, occurred during the period of vibration. The breathing frequency decreased and the end-expiratory position dropped, but the vital capacity was not changed. Vibration-induced hyperventilation was most pronounced at 4–5 cycle/sec. Oxygen consumption was increased during vibration, with a maximum increase observed at the lowest frequencies. All changes were greater at 0.35 g than at 0.15 g acceleration. Except for a decreased alveolar CO2 concentration, respiration during the 4-min recovery period did not significantly differ from the previbration levels. Submitted on May 14, 1962

Chamber cold acclimatization in man

1961 ◽  
Vol 16 (6) ◽  
pp. 1011-1015 ◽  
Author(s):  
Thomas R. A. Davis
Keyword(s):  
Oxygen Consumption ◽  
Air Temperature ◽  
Rectal Temperature ◽  
Heat Production ◽  
Cold Exposure ◽  
Technical Assistance ◽  
Exposure Period ◽  
Seasonal Difference ◽  
Nonshivering Thermogenesis ◽  
Cold Acclimatization

In March, ten nude subjects were exposed 8 hr daily for 31 days to an air temperature of 11.8 C. In September, another six subjects were similarly acclimatized to an air temperature of 13.5 C. Measurements were made of the responses of shivering, oxygen consumption, rectal temperature, and skin temperature to a standard cold exposure. By the 14th day, shivering in both groups decreased significantly. Heat production remained unchanged in the winter group but decreased in the summer group. Basal metabolism did not change in either group. In both groups, rectal temperatures were maintained at lower values after the exposure period. In the winter group extremity temperatures were unchanged; those in the summer group were lowered by a small amount. The decrease in heat production and mean surface temperature in the summer group is related to the seasonal difference in cold acclimatization. Failure of cold-elevated metabolism to decrease despite a highly significant decrease in shivering indicates the presence of nonshivering thermogenesis in man. It is concluded that man can be artificially cold acclimatized. Note: With the Technical Assistance of D. R. Johnston, F. C. Bell, W. Rawlings, and L. Lee Submitted on May 8, 1961

Effect of ambient temperature during 1st day of life on thermoregulation in lambs delivered by cesarean section

1994 ◽  
Vol 76 (4) ◽  
pp. 1481-1488 ◽  
Author(s):  
L. Clarke ◽  
C. J. Darby ◽  
M. A. Lomax ◽  
M. E. Symonds
Keyword(s):  
Cesarean Section ◽  
Ambient Temperature ◽  
Heat Production ◽  
Metabolic Response ◽  
Plasma Concentrations ◽  
Cesarean Section Delivery ◽  
Brown Adipose ◽  
Near Term ◽  
Colonic Temperature ◽  
Shivering Thermogenesis

We examined the effect of delivering near-term twin lambs by cesarean section into a warm (30 degrees C) or cool (15 degrees C) ambient temperature on the control of thermoregulation. Heat production was measured 20–30 h after birth during non-rapid-eye-movement sleep at 29 and 14 degrees C. At 29 degrees C there was no difference in heat production between groups, but at 14 degrees C cool-delivered (CD) lambs exhibited a 62% greater metabolic response. Irrespective of delivery temperature, 15 of the 18 lambs used shivering thermogenesis during cold exposure, indicating a reduction in the ability to use nonshivering thermogenesis in brown adipose tissue (BAT). Mean plasma concentrations of thyroxine and triiodothyronine were 35 and 45% greater, respectively, in CD lambs than in warm-delivered lambs. The level of guanosine 5′-diphosphate binding in BAT was lower than in normally delivered lambs and was not different between CD and warm-delivered lambs. Cesarean section delivery prevents the rise in BAT thermogenic activity, which results in an increased reliance on shivering thermogenesis to maintain colonic temperature. Under these conditions, delivery into a cool environment increases the plasma concentration of thyroid hormones, which benefits the neonate by enabling a greater thermogenic response via shivering.

The effects of shearing on the heat production and activity of sheep receiving dried grass or ground hay

1977 ◽  
Vol 24 (3) ◽  
pp. 355-361 ◽  
Author(s):  
A. W. F. Davey ◽  
C. W. Holmes
Keyword(s):  
Oxygen Consumption ◽  
Energy Expenditure ◽  
Ambient Temperature ◽  
Heat Production ◽  
Large Contribution ◽  
Maximum Increase ◽  
Respiration Chamber ◽  
The Mean ◽  
The Times ◽  
Male Sheep

SUMMARY1. Oxygen consumption was measured in two experiments using castrated Romney male sheep both shorn and unshorn. The sheep were fed either ground hay or dried grass. An ambient temperature of 13°C ± 1°C was maintained at all times. In Experiment 1, oxygen consumption was measured with eight sheep using a respiration chamber and in Experiment 2, oxygen consumption was measured with four sheep using a ventilated hood. The times spent standing, lying, eating and ruminating were measured in Experiment 2. Heat production was calculated from the measured values for oxygen consumption.2. Heat production increased following shearing in both experiments. In Experiment 1, heat production of the sheep receiving dried grass was significantly greater (P<0·05) on days 1, 8 and 16 following shearing, compared with pre-shearing values. For sheep receiving ground hay, heat production was greater on day 1 (P<0·05) and day 8 (P<0·01) following shearing, compared with pre-shearing values. The mean maximum increase in heat production following shearing was 2·3 MJ/24 hr (25% increase) for sheep receiving dried grass and 1·2 MJ (17%) for those receiving ground hay.3. The patterns of change in heat production following shearing in Experiment 2 were similar to those observed in Experiment 1 although the maximum increases were smaller: 21% for the sheep receiving dried grass and 13% for those receiving ground hay.4. The time spent standing increased considerably after shearing and this change in behaviour made a large contribution to the increase in energy expenditure after the sheep were shorn.

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