A study of newborn rats exposed to the cold

1968 ◽  
Vol 46 (6) ◽  
pp. 865-871 ◽  
Author(s):  
G. E. Thompson ◽  
R. E. Moore
Keyword(s):  
Cardiac Output ◽  
Oxygen Consumption ◽  
Heat Production ◽  
Environmental Temperature ◽  
Maximum Oxygen Consumption ◽  
Maximum Heat ◽  
Endogenous Noradrenaline ◽  
Old Rats ◽  
Environmental Temperatures ◽  
Oxygen Difference

The purpose of this investigation was to study heat production in the newborn rat, and the factors which may be limiting maximum heat production in the cold. Rats of varying ages between 1 and 30 days were exposed to various environmental temperatures. The minimum oxygen consumption in the warm, and maximum oxygen consumption in the cold, increased with age. The critical environmental temperature, and the environmental temperature at which oxygen consumption was maximal, fell with increase in age. Exogenous noradrenaline raised the oxygen consumption of 6-day-old but not of 12-day-old rats above the maximum oxygen consumption found with cold exposure. The cardiac output and arteriovenous oxygen difference of 12-day-old rats was increased in the cold. These results are consistent with the view that oxygen consumption in the cold is limited in 6-day-old rats by the release of endogenous noradrenaline and in 12-day-old rats by cardiac output and the supply of oxygen to the heat-producing tissues.

EXERCISE AND TEMPERATURE REGULATION IN LEMMINGS AND RABBITS

1955 ◽  
Vol 33 (1) ◽  
pp. 428-435 ◽  
Author(s):  
J. S. Hart ◽  
O. Heroux
Keyword(s):  
Oxygen Consumption ◽  
Body Temperature ◽  
Heat Production ◽  
Temperature Regulation ◽  
Thermal Equilibrium ◽  
Environmental Temperature ◽  
Body Temperatures ◽  
Temperature Changes ◽  
Extreme Cold ◽  
Environmental Temperatures

Oxygen consumption and body temperatures were determined in lemmings at environmental temperatures from 20 °C. to −10 °C. and in rabbits from 20 °C. to −50 °C. Body insulation indices were estimated as the ratio [Formula: see text]. In both species, increase in activity and decrease in temperature led to increases in oxygen consumption that were additive over the temperature range. Oxygen increments of work were independent of environmental temperature in the absence of progressive hypothermia. Work led to increases in body temperature at the upper environmental temperatures and to decreases in body temperature at the lower temperatures. In extreme cold, rabbits became progressively hypothermic during work and there was a decline in oxygen consumption. Body temperatures started to fall at environmental temperatures 18 °C. higher in working than in resting rabbits. Insulation was lower in working than in resting animals. During exercise there appears to be a readjustment of body temperature, insulation, and heat loss until thermal equilibrium is established. The regulation of heat production, within limits, seems to be independent of body-temperature changes during exercise.

EXERCISE AND TEMPERATURE REGULATION IN LEMMINGS AND RABBITS

1955 ◽  
Vol 33 (3) ◽  
pp. 428-435 ◽  
Author(s):  
J. S. Hart ◽  
O. Heroux
Keyword(s):  
Oxygen Consumption ◽  
Body Temperature ◽  
Heat Production ◽  
Temperature Regulation ◽  
Thermal Equilibrium ◽  
Environmental Temperature ◽  
Body Temperatures ◽  
Temperature Changes ◽  
Extreme Cold ◽  
Environmental Temperatures

Oxygen consumption and body temperatures were determined in lemmings at environmental temperatures from 20 °C. to −10 °C. and in rabbits from 20 °C. to −50 °C. Body insulation indices were estimated as the ratio [Formula: see text]. In both species, increase in activity and decrease in temperature led to increases in oxygen consumption that were additive over the temperature range. Oxygen increments of work were independent of environmental temperature in the absence of progressive hypothermia. Work led to increases in body temperature at the upper environmental temperatures and to decreases in body temperature at the lower temperatures. In extreme cold, rabbits became progressively hypothermic during work and there was a decline in oxygen consumption. Body temperatures started to fall at environmental temperatures 18 °C. higher in working than in resting rabbits. Insulation was lower in working than in resting animals. During exercise there appears to be a readjustment of body temperature, insulation, and heat loss until thermal equilibrium is established. The regulation of heat production, within limits, seems to be independent of body-temperature changes during exercise.

Regulation of the Circulation During Exercise

1956 ◽  
Vol 184 (3) ◽  
pp. 613-623 ◽  
Author(s):  
A. C. Barger ◽  
V. Richards ◽  
J. Metcalfe ◽  
B. Günther
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Oxygen Consumption ◽  
Steady State ◽  
Rest Period ◽  
Moderate Exercise ◽  
Work Intensity ◽  
Short Bout ◽  
Graded Exercise ◽  
Oxygen Difference

Oxygen consumption and cardiac output (direct Fick) have been measured in normal dogs at rest and during graded exercise on the treadmill up to a work intensity of 5 mph and 10°. Systemic and pulmonary artery pressures have also been recorded. The changes in cardiac output produced ‘at rest’ by excitement were frequently as large as those induced by moderate exercise. A short bout of exercise followed by a rest period was far more efficacious in producing lower and more uniform results during rest and subsequent exercise than a prolonged rest period alone. Under such conditions the ‘steady state’ was reached in 3 minutes or less of exercise. The linear relation between oxygen consumption and cardiac output during exercise in the dog is similar to that observed in man, and in the horse. The possible significance of this similarity is discussed and it is suggested that the data are consistent with the hypothesis that the increase in blood flow during exercise is largely the increase in muscle flow with a constant arteriovenous oxygen difference of approximately 14 vol. %.

Effect of Hypothermia of 2 to 24 Hours on Oxygen Consumption and Cardiac Output in the Dog

1957 ◽  
Vol 188 (3) ◽  
pp. 473-476 ◽  
Author(s):  
Bernard Fisher ◽  
Clem Russ ◽  
E. J. Fedor
Keyword(s):  
Cardiac Output ◽  
Oxygen Consumption ◽  
Body Temperature ◽  
The Body ◽  
Anesthetic Agent ◽  
Oxygen Utilization ◽  
Pentobarbital Sodium ◽  
Initial Decrease ◽  
Physiologic Parameters ◽  
Oxygen Difference

The changes occurring in cardiac output and oxygen consumption in short periods of hypothermia are the same when either ether or pentobarbital sodium is used as the anesthetic agent during the induction of hypothermia. Following an initial decrease in oxygen consumption, no further change occurred as long as the body temperature was maintained at a constant level. Cardiac output, arterial-venous oxygen difference, and coefficient of oxygen utilization remain unchanged for longer periods of time than most physiologic parameters studied during prolonged hypothermia at constant temperatures. After about 14 hours they also begin to alter so that by 24 hours the changes are profound. Stagnant anoxemia and marked increased in the coefficient of O2 utilization resulting from the markedly lowered cardiac output, which was 5% of the precooled controls, occurred.

scholarly journals Effect of environmental temperature on muscle protein turnover and heat production in tube-fed broiler chickens

1997 ◽  
Vol 77 (6) ◽  
pp. 897-909 ◽  
Author(s):  
Vitus D. Yunianto ◽  
K. Hayashit ◽  
S. Kaiwda ◽  
A. Ohtsuka ◽  
Y. Tomita
Keyword(s):  
Heat Production ◽  
Protein Turnover ◽  
Broiler Chickens ◽  
Environmental Temperature ◽  
Muscle Protein ◽  
Plasma Concentrations ◽  
Abdominal Fat ◽  
Fat Content ◽  
Muscle Protein Turnover ◽  
Environmental Temperatures

The present experiments4 were undertaken to investigate the effects of environmental temperatures on growth, abdominal fat content, rate of muscle protein turnover, and heat production in tube-fed intact male broiler chickens. Plasma concentrations of thyroxine (T4), triiodothyronine (T3), and corticosterone (CTC) were also examined. Chicks (15d old) were kept at different environmental temperatures (16,19,22,25,28,31, and 34°) and given the experimental diet (200g crude protein/kg, 13·;57M/kg metabolizable energy) by tube three times daily throughout the 12d experimental period. In the hot conditions, except for 34°, body-weight gain was significantly higher than in the cold conditions. Thus, food conversion ratios (food: gain ratios) were lower when the birds were exposed to the hot conditions other than 34°. Likewise, abdominal fat content was significantly increased, and heat production was lower in the groups kept under the hot conditions other than 34°. The rate of skeletal muscle protein turnover and plasma concentration of CTC were decreased when the birds were exposed to hot conditions other than 34°. suggesting a role of CTC in the regulation of muscle protein turnover. Plasma concentrations of T4 and T3 were significantly decreased as environmental temperature increased. These results clearly show that plasma concentrations of thyroid hormones and CTC are associated with accelerated muscle protein turnover and heat production.

The effect of environmental conditions on food utilisation by sheep

1959 ◽  
Vol 1 (1) ◽  
pp. 1-12 ◽  
Author(s):  
D. G. Armstrong ◽  
K. L. Blaxter ◽  
N. McC. Graham ◽  
F. W. Wainman
Keyword(s):  
Critical Temperature ◽  
Heat Loss ◽  
Heat Production ◽  
Environmental Conditions ◽  
Environmental Temperature ◽  
Heat Losses ◽  
The Body ◽  
Food Utilisation ◽  
Metabolisable Energy ◽  
Environmental Temperatures

1. A series of calorimetric experiments was conducted with sheep which had fleeces ranging in thickness from 0·1 cm. to 12 cm. at environmental temperatures between 8 and 32° C. Heat production, heat loss by radiation, by convection and conduction, by vaporisation of water and due to warming food and water to body temperature were measured together with losses of energy in faeces, in urine and as methane.2. The effects of a rise in environmental temperature on digestion of the food and on the loss of energy in urine or as methane resulted in a slight rise in the metabolisable energy of the ration by 6 Cal./° C.3. Environmental temperature had a marked effect on heat production, particularly when the fleece was short. The critical temperature (i.e. the environmental temperature at which heat production was minimal) of the closely-clipped sheep varied from 24° C. at a high level of feeding to 38°C. at a sub-maintenance level of feeding. These critical temperatures are similar to that of naked, resting man but much higher than that of the pig when fed similarly.4. As the fleece grew the critical temperature fell. Thus, on a maintenance level of feeding, a sheep with a fleece of 0·1 cm. had a critical temperature of 32° C.; when the fleece had grown to 2·5 cm. the critical temperature was 13° C. while with a 12 cm. fleece the critical temperature was 0° C.5. Below the critical temperature heat losses increase more rapidly in sheep with light fleeces. Thus a heavy fleece not only depresses the critical temperature but also reduces the rate of increase of heat loss with falling temperature under sub-critical conditions.6. At environmental temperatures well below the critical, the heat losses of the sheep per unit surface were identical. Under such conditions, when the whole of the metabolisable energy of the food is used to keep the animal warm, the criterion of ration adequacy is a high content of meta-bolisable energy in small bulk.7. At environmental temperatures above 32° C. the heat production on a constant ration increased, the rise being greatest with the highest level of feeding. Consequently the net energy value of the food declined at these high environmental temperatures.8. The calorimetric experiments were supplemented by two comparative feeding trials in which the effects of normal outdoor environmental conditions on the body weight of groups of Cheviot and Blackface sheep were measured. Control groups were kept indoors in heated pens.9. During the mild winter of 1956-7 the out-wintered Blackface wethers i n full fleece did not loose any more weight than those fed the same rations indoors.10. During the more severe winter of 1957-8, Cheviot, in-lamb ewes kept on a maintenance diet gained 2·3 lb.; those kept outside on the same ration lost 3·3 lb. With Blackface, in·lamb ewes the difference between the two groups was 0·3 lb. in favour of the indoor group.11. The food utilisation of sheep is affected considerably by environmental conditions. With little fleece the critical temperature is high and even when in full fleece an effect of cold can be demonstrated under practical conditions.

Cardiac output response and peripheral oxygen extraction during exercise among symptomatic hypertrophic cardiomyopathy patients with and without left ventricular outflow tract obstruction

Heart ◽  
2014 ◽  
Vol 100 (8) ◽  
pp. 639-646 ◽  
Author(s):  
Christopher H Critoph ◽  
Vimal Patel ◽  
Bryan Mist ◽  
Perry M Elliott
Keyword(s):  
Cardiac Output ◽  
Oxygen Consumption ◽  
Hypertrophic Cardiomyopathy ◽  
Cardiac Index ◽  
Left Ventricular Outflow Tract ◽  
Ventricular Outflow Tract ◽  
Left Ventricular ◽  
Non Invasive ◽  
Left Ventricular Outflow ◽  
Oxygen Difference

ObjectiveReduction of left ventricular outflow tract obstruction (LVOTO) often improves symptoms in hypertrophic cardiomyopathy (HCM), but the correlation between exercise performance and measured LVOT gradients is weak. We investigated the relationship between LVOTO and cardiorespiratory responses during exercise.MethodsThe study cohort included 70 patients with HCM (32 with LVOTO, 55 male, age 47±13) attending a dedicated cardiomyopathy clinic and 28 normal volunteers. All underwent cardiopulmonary exercise testing with simultaneous non-invasive haemodynamic assessment using finger plethysmography. Main outcome measures were peak oxygen consumption, cardiac index and arteriovenous oxygen difference.ResultsWhen compared with controls, patients had reduced peak exercise oxygen consumption (22.4±6.1 vs 34.7±7.7 mL/kg/min, p<0.0001) and cardiac index (5.5±1.9 vs 9.4±2.9 L/min/m2, p<0.0001). At all workloads, stroke volume index (SVI) was lower and arteriovenous oxygen difference greater in patients. During all stages of exercise, LVOTO in patients was associated with failure to augment SVI and higher oxygen consumption; cardiac reserve (4.4±2.7 vs 6.3±3.6 L/min, p=0.025) and peak mean arterial pressure (104±16 vs 112±16 mm Hg, p=0.033) were lower. Multivariable predictors of cardiac output response were age (β: −0.11; CI −0.162 to −0.057; p<0.0001), peak LVOT gradient (β: −0.018; CI −0.034 to −0.002; p=0.031) and gender (β: −2.286; CI −0.162 to −0.577; p=0.01). Within the obstructive cohort, different patterns of SV response were elicited in patients with similar clinical features.ConclusionsCardiac reserve is reduced in HCM because of failure of SV augmentation. LVOTO exacerbates this abnormal response, but haemodynamic responses vary significantly. Non-invasive exercise haemodynamic assessment may improve understanding of symptoms and help tailor therapy.

The effect of environmental temperature on the energy metabolism of cattle

1960 ◽  
Vol 55 (3) ◽  
pp. 359-364 ◽  
Author(s):  
A. Rogerson
Keyword(s):  
Food Intake ◽  
Heat Production ◽  
Environmental Temperature ◽  
Energy Losses ◽  
Net Energy ◽  
Retention Data ◽  
Respiration Chamber ◽  
Energy Retention ◽  
Environmental Temperatures ◽  
Different Levels

1. A relatively inexpensive closed-circuit respiration chamber for cattle is described.2. Experiments with two steers are reported in which heat production and energy retention data were measured at different levels of food intake and at different environmental temperatures.3. The energy lost in faeces increased with improving plane of nutrition but was not significantly affected by the environmental temperature. Urine energy losses fell with increasing environmental temperature at low planes of nutrition. Methane losses increased with improving nutritional plane but were reduced by high environmental temperatures at high levels of food intake.4. The heat production of fasting animals, or animals on low planes of nutrition was not influenced by the environmental temperature in the range 20–40° C. On higher planes of nutrition an increasing environmental temperature increased the animals' heat production.5. The major factor determining energy retention in different environments is the heat production of the animal. Net energy values consequently vary with temperature.

The Effect of Massage on Oxygen Consumption at Rest

1995 ◽  
Vol 23 (01) ◽  
pp. 37-41 ◽  
Author(s):  
Tommy Boone ◽  
Rae Cooper
Keyword(s):  
Cardiac Output ◽  
Oxygen Consumption ◽  
Healthy Adult ◽  
Statistical Significance ◽  
Lower Extremities ◽  
Treatment Session ◽  
Adult Males ◽  
Significant Difference ◽  
Metabolic Measurement ◽  
Oxygen Difference

This study determined the effect of massage on oxygen consumption at rest. Ten healthy, adult males (mean age = 28 years) volunteered to serve as subjects. During the Control Session, each subject was placed in the supine position on a massage table to remain motionless for 30 minutes. During the Treatment Session, each subject received a 30-minute sports massage of the lower extremities. Oxygen consumption was determined via the Beckman Metabolic Measurement Cart, which was upgraded to estimate cardiac output using the CO 2 rebreathing (equilibrium) method. Paired t-tests were used for all tests of statistical significance. There was no significant difference in the subjects' oxygen consumption with the massage. Also, there were no significant differences in heart rate, stroke volume, cardiac output, and arteriovenous oxygen difference during the massage. These findings indicate (1) that massaging the lower extremities results in neither an increase nor a decrease in the subjects' expenditure of energy at rest and (2) that the energy cost of metabolism at rest is determined by the same central and/or peripheral adjustments.

Evidence favoring a cardiac mechanism in irreversible hemorrhagic shock

1961 ◽  
Vol 201 (5) ◽  
pp. 893-896 ◽  
Author(s):  
Jack W. Crowell ◽  
Arthur C. Guyton
Keyword(s):  
Cardiac Output ◽  
Oxygen Consumption ◽  
Pulmonary Artery ◽  
Hemorrhagic Shock ◽  
Left Atrial ◽  
Peripheral Resistance ◽  
Arterial System ◽  
Operating Parameters ◽  
The Right ◽  
Oxygen Difference

Shock was induced in 55 dogs by removing blood until the arterial pressure had fallen to 30 mm Hg. The pressure was kept at this level for as long as 10 hr by constantly adding additional blood to the reservoir. The hematocrit was kept constant to prevent large variations in the viscosity. Mean pressures of the right and left atrium, the pulmonary artery, and the systemic arterial system were recorded as well as oxygen consumption and A-V oxygen difference. Total peripheral resistance and cardiac output were calculated. That period of time during which the animal passed from a reversible stage of shock to an irreversible stage of shock was studied. It was found that no significant change occurred in oxygen consumption, cardiac output, or peripheral resistance during this transition phase. However, changes did occur in the operating parameters of the heart. The left atrial pressure began rising with the transition from reversible to irreversible shock and continued rising until death of the animal. It is suggested that irreversible hemorrhagic shock is due to acute cardiac failure.

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