OXYGEN SUPPLY AND PERFORMANCE IN PEROMYSCUS: COMPARISON OF EXERCISE WITH COLD EXPOSURE

1967 ◽  
Vol 45 (3) ◽  
pp. 543-549 ◽  
Author(s):  
Neri P. Segrem ◽  
J. S. Hart
Keyword(s):  
Heart Rate ◽  
Oxygen Consumption ◽  
Body Temperature ◽  
Oxygen Uptake ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Cold Exposure ◽  
Temperature Regulation ◽  
Oxygen Supply ◽  
And Performance

Oxygen consumption, heart rate, and body temperature were measured at temperatures ranging from 27 °C to −28 °C and at oxygen partial pressure [Formula: see text] levels from 60 to 196 mm Hg. Temperature regulation and O2 uptake were progressively limited by reduction of [Formula: see text]. Limitation of O2 consumption by O2 supply was similar to that seen during exercise. The highest oxygen uptake during exposure to cold was greater than during exercise at the higher levels of [Formula: see text].

Fish cardiorespiratory physiology in an era of climate changeThe present review is one of a series of occasional review articles that have been invited by the Editors and will feature the broad range of disciplines and expertise represented in our Editorial Advisory Board.

2009 ◽  
Vol 87 (10) ◽  
pp. 835-851 ◽  
Author(s):  
A. P. Farrell ◽  
E. J. Eliason ◽  
E. Sandblom ◽  
T. D. Clark
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Stroke Volume ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Oxygen Supply ◽  
Membrane Currents ◽  
Protective Mechanism ◽  
Optimum Temperature ◽  
Arterial Blood

This review examines selected areas of cardiovascular physiology where there have been impressive gains of knowledge and indicates fertile areas for future research. Because arterial blood is usually fully saturated with oxygen, increasing cardiac output is the only means for transferring substantially more oxygen to tissues. Consequently, any behavioural or environmental change that alters oxygen uptake typically involves a change in cardiac output, which in fishes can amount to a threefold change. During exercise, not all fishes necessarily have the same ability as salmonids to increase cardiac output by increasing stroke volume; they rely more on increases in heart rate instead. The benefits associated with increasing cardiac output via stroke volume or heart rate are unclear. Regardless, all fishes examined so far show an exquisite cardiac sensitivity to filling pressure and the cellular basis for this heightened cardiac stretch sensitivity in fish is being unraveled. Even so, a fully integrated picture of cardiovascular functioning in fishes is hampered by a dearth of studies on venous circulatory control. Potent positive cardiac inotropy involves stimulation of sarcolemmal β-adrenoceptors, which increases the peak trans-sarcolemmal current for calcium and the intracellular calcium transient available for binding to troponin C. However, adrenergic sensitivity is temperature-dependent in part through effects on membrane currents and receptor density. The membrane currents contributing to the pacemaker action potential are also being studied but remain a prime area for further study. Why maximum heart rate is limited to a low rate in most fishes compared with similar-sized mammals, even when Q10 effects are considered, remains a mystery. Fish hearts have up to three oxygen supply routes. The degree of coronary capillarization circulation is of primary importance to the compact myocardium, unlike the spongy myocardium, where venous oxygen partial pressure appears to be the critical factor in terms of oxygen delivery. Air-breathing fishes can boost the venous oxygen content and oxygen partial pressure by taking an air breath, thereby providing a third myocardial oxygen supply route that perhaps compensates for the potentially precarious supply to the spongy myocardium during hypoxia and exercise. In addition to venous hypoxemia, acidemia and hyperkalemia can accompany exhaustive exercise and acute warming, perhaps impairing the heart were it not for a cardiac protection mechanism afforded by β-adrenergic stimulation. With warming, however, a mismatch between an animal’s demand for oxygen (a Q10 effect) and the capacity of the circulatory and ventilatory systems to delivery this oxygen develops beyond an optimum temperature. At temperature extremes in salmon, it is proposed that detrimental changes in venous blood composition, coupled with a breakdown of the cardiac protective mechanism, is a potential mechanism to explain the decline in maximum and cardiac arrhythmias that are observed. Furthermore, the fall off in scope for heart rate and cardiac output is used to explain the decrease in aerobic scope above the optimum temperature, which may then explain the field observation that adult sockeye salmon ( Oncorhynchus nerka (Walbaum in Artedi, 1792)) have difficulty migrating to their spawning area at temperatures above their optimum. Such mechanistic linkages to lifetime fitness, whether they are cardiovascular or not, should assist with predictions in this era of global climate change.

OXYGEN SUPPLY AND PERFORMANCE IN PEROMYSCUS: METABOLIC AND CIRCULATORY RESPONSES TO EXERCISE

1967 ◽  
Vol 45 (3) ◽  
pp. 531-541 ◽  
Author(s):  
Neri P. Segrem ◽  
J. S. Hart
Keyword(s):  
Oxygen Consumption ◽  
Partial Pressure ◽  
Oxygen Supply ◽  
Peromyscus Leucopus ◽  
Work Rate ◽  
Air Pressure ◽  
Partial Pressure Of Oxygen ◽  
Running Speed ◽  
Adult Mice ◽  
And Performance

Adult mice, Peromyscus leucopus novaboracensis, were exercised on a treadmill at various running speeds up to the highest obtainable at levels of oxygen ranging from 60 to 196 mm Hg. Oxygen consumption was not directly proportional to work rate as found in man and dog, and declined with a fall in the partial pressure of oxygen [Formula: see text] at the same work rate. As noted in other species, dependence of oxygen consumption on oxygen supply in Peromyscus varied with the level of exertion. The uptake at the highest speed was reduced by a relatively small fall in [Formula: see text] below normal air pressure whereas the uptake in resting mice was relatively insensitive to a reduction in [Formula: see text]. Heart rates varied in proportion to running speed and to oxygen consumption and were increased by a fall in [Formula: see text] at the same running speed.

Body temperature regulation and oxygen consumption in young chicks fed thyroid hormone

1991 ◽  
Vol 69 (7) ◽  
pp. 1842-1847 ◽  
Author(s):  
Gregory K. Snyder ◽  
Joseph R. Coelho ◽  
Dalan R. Jensen
Keyword(s):  
Oxygen Consumption ◽  
Thyroid Hormone ◽  
Body Temperature ◽  
Ambient Temperature ◽  
Cold Exposure ◽  
Elevated Serum ◽  
Body Temperatures ◽  
Serum Thyroid Hormone ◽  
Regulate Body Temperature ◽  
Young Chicks

In chicks the ability to regulate body temperature to adult levels develops during the first 2 weeks of life. We examined whether the ability of young chicks to regulate body temperature is increased by elevated levels of the thyroid hormone 3,3′5-triiodothyronine. By 13 days following hatch, body temperatures of chicks were not significantly different from those expected for adult birds. Furthermore, at an ambient temperature of 10 °C, 13-day-old control chicks were able to maintain body temperature, and elevated serum thyroid hormone levels did not increase rates of oxygen consumption or body temperature above control values. Six-day-old chicks had body temperatures that were significantly lower than those of the 13-day-old chicks and were not able to regulate body temperature when exposed to an ambient temperature of 10 °C. On the other hand, 6-day-old chicks with elevated serum thyroid hormone had significantly higher rates of oxygen consumption than 6-day-old control chicks, and were able to maintain constant body temperatures during cold exposure. The increased oxygen consumption rates and improved ability to regulate body temperature during cold exposure were correlated with increased citrate synthase activity in skeletal muscle. Our results support the argument that thyroid hormones play an important role in the development of thermoregulatory ability in neonate birds by stimulating enzyme activities associated with aerobic metabolism.

Responses of cold- and warm-adapted dogs to infused norepinephrine and acute body cooling

1965 ◽  
Vol 209 (1) ◽  
pp. 227-230 ◽  
Author(s):  
Tetsuo Nagasaka ◽  
Loren D. Carlson
Keyword(s):  
Heart Rate ◽  
Oxygen Consumption ◽  
Cold Exposure ◽  
Nonshivering Thermogenesis ◽  
Mechanically Ventilated ◽  
Cold Adapted ◽  
Pentobarbital Sodium ◽  
Acute Cold Exposure ◽  
Increased Sensitivity ◽  
Body Cooling

Oxygen consumption, heart rate, and colonic, pinna, and paw temperatures were recorded continuously in warm-adapted (W-A) and cold-adapted (C-A) dogs anesthetized with pentobarbital sodium (30 mg/kg), paralyzed with Flaxedil (5 mg/kg per hr), and mechanically ventilated. The dogs were infused with norepinephrine (1.25 µg/kg per min) for 20 min at 30 C and after 45 min of acute cold exposure to 5 C. Oxygen consumption of C-A dogs increased with a slight increase in the heart rate during the initial 18–20 min of body cooling. O2 consumption decreased continuously during cold exposure in W-A dogs. Calorigenic effects of infused noradrenaline were similar in C-A and W-A dogs at 30 C and 5 C. Heart rate increased in W-A dogs at 30 and 5 C. These results show that nonshivering thermogenesis is well developed by cold acclimation in dogs, and suggest that the increase may be due to an increase in noradrenaline in blood rather than to increased sensitivity of the animals to the calorigenic effects of noradrenaline.

Body Temperature, Oxygen Consumption, and Heart Rate in Three Species of Australian Flying Foxes

1964 ◽  
Vol 37 (2) ◽  
pp. 179-198 ◽  
Author(s):  
George A. Bartholomew ◽  
Philip Leitner ◽  
John E. Nelson
Keyword(s):  
Heart Rate ◽  
Oxygen Consumption ◽  
Body Temperature ◽  
Flying Foxes

Hypergravic fields and parallel controllers for thermoregulation

1983 ◽  
Vol 55 (3) ◽  
pp. 990-995 ◽  
Author(s):  
C. B. Monson ◽  
J. M. Horowitz ◽  
B. A. Horwitz
Keyword(s):  
Oxygen Consumption ◽  
Cold Exposure ◽  
Temperature Regulation ◽  
Room Temperature ◽  
Male Rats ◽  
Nonshivering Thermogenesis ◽  
Long Evans

To test the proposal that mammals have parallel neurocontrollers for temperature regulation, Long-Evans hooded male rats were exposed to cold while in a 3-G field. When exposed to cold, these rats consumed 35% less oxygen/min at 3 G than they did when exposed to cold at 1 G. However, rats acclimated for 6 wk to 5 degrees C consumed oxygen at the same rate during cold exposure at 3 G as at 1 G. Because cold-acclimated rats generate heat primarily by nonshivering thermogenesis while rats acclimated to room temperature rely to a greater extent on shivering, the 35% decrease in oxygen consumption of cold-exposed room-temperature rats in 3-G fields may reflect an inactivation of shivering. These oxygen consumption measurements, together with measurements of core and tail temperatures of rats in 3-G fields, are consistent with the proposal that neurocontrollers for thermoregulation are arranged in parallel and can be uncoupled by hypergravic fields.

Experimental hyperthyroidism in dogs and effect of salivariectomy

1961 ◽  
Vol 201 (4) ◽  
pp. 723-728 ◽  
Author(s):  
Dorothy A. Piatnek ◽  
Robert E. Olson
Keyword(s):  
Heart Rate ◽  
Body Weight ◽  
Oxygen Consumption ◽  
Thyroid Hormone ◽  
Body Temperature ◽  
Caloric Intake ◽  
Clinical Signs ◽  
Turnover Rates ◽  
Laboratory Findings ◽  
Thyroid State

A hyperthyroid state was induced and maintained in 17 dogs for 2–10 months by the administration of massive amounts of thyroid hormone. The great tolerance of this species to such large doses was striking. The clinical signs characteristic of hyperthyroidism in other mammals were observed including significantly increased caloric intake, oxygen consumption, heart rate, and body temperature. The laboratory findings included polycythemia, markedly increased levels of protein-bound iodide (PBI), increased turnover rates of l-thyroxine, and a decreased urinary excretion of inorganic iodide. Unlike other species the hyperthyroid dogs did not demonstrate marked reductions in body weight or serum cholesterol. Salivariectomy neither hastened nor enhanced the onset of exogenous hyperthyroidism in the dog. Measurements of the rate of disappearance of I131 l-thyroxine from the plasma and the rate of appearance of radioactive iodide in the urine indicated that the salivary glands in the intact dog are effective sites of deiodination and iodide excretion. This activity, however, is not the sole regulator of the level of circulating thyroid hormone and thus of the thyroid state.

scholarly journals Reproducibility of Physiological and Performance Measures from a Squash-Specific Fitness Test

2009 ◽  
Vol 4 (1) ◽  
pp. 41-53 ◽  
Author(s):  
Michael Wilkinson ◽  
Damon Leedale-Brown ◽  
Edward M. Winter
Keyword(s):  
Heart Rate ◽  
Oxygen Uptake ◽  
Lactate Threshold ◽  
Physiological Responses ◽  
Lactate Concentration ◽  
Maximum Heart Rate ◽  
Fitness Test ◽  
Performance Time ◽  
Volitional Exhaustion ◽  
And Performance

Purpose:We examined the reproducibility of performance and physiological responses on a squash-specific incremental test.Methods:Eight trained squash players habituated to procedures with two prior visits performed an incremental squash test to volitional exhaustion on two occasions 7 days apart. Breath-by-breath oxygen uptake ( Vo2) and heart rate were determined continuously using a portable telemetric system. Blood lactate concentration at the end of 4-min stages was assessed to determine lactate threshold. Once threshold was determined, test speed was increased every minute until volitional exhaustion for assessment of maximal oxygen uptake (Vo2max), maximum heart rate (HRmax), and performance time. Economy was taken as the 60-s mean of Vo2 in the final minute of the fourth stage (below lactate threshold for all participants). Typical error of measurement (TEM) with associated 90% confidence intervals, limits of agreement, paired sample t tests, and least products regression were used to assess the reproducibility of scores.Results:Performance time (TEM 27 s, 4%, 90% CI 19 to 49 s) Vo2max (TEM 2.4 mL·kg−1·min−1, 4.7%, 90% CI 1.7 to 4.3 mL·kg−1·min−1), maximum heart rate (TEM 2 beats·min−1, 1.3%, 90% CI 2 to 4 beats·min−1), and economy (TEM 1.6 mL·kg−1·min−1, 4.1%, 90% CI 1.1 to 2.8 mL·kg−1·min−1) were reproducible.Conclusions:The results suggest that endurance performance and physiological responses to a squash-specific fitness test are reproducible.

Reduced stress- and cold-induced increase in energy expenditure in interleukin-6-deficient mice

2006 ◽  
Vol 291 (3) ◽  
pp. R551-R557 ◽  
Author(s):  
Ingrid Wernstedt ◽  
Amanda Edgley ◽  
Anna Berndtsson ◽  
Jenny Fäldt ◽  
Göran Bergström ◽  
...  
Keyword(s):  
Heart Rate ◽  
Oxygen Consumption ◽  
Energy Expenditure ◽  
Core Temperature ◽  
Cold Exposure ◽  
Interleukin 6 ◽  
Utilization Rate ◽  
Sympathetic Outflow ◽  
Wild Type ◽  
Deficient Mice

Interleukin-6 (IL-6) deficient (-/-) mice develop mature onset obesity. Pharmacological studies have shown that IL-6 has direct lipolytic effects and when administered centrally increases sympathetic outflow. However, the metabolic functions of endogenous IL-6 are not fully elucidated. We aimed to investigate the effect of IL-6 deficiency with respect to cold exposure and cage-switch stress, that is, situations that normally increase sympathetic outflow. Energy metabolism, core temperature, heart rate, and activity were investigated in young preobese IL-6−/− mice by indirect calorimetry together with telemetry. Baseline measurements and the effect of cage-switch stress were investigated at thermoneutrality (30°C) and at room temperature (20°C). The effect of cold exposure was investigated at 4°C. At 30°C, the basal core temperature was 0.6 ± 0.24°C lower in IL-6−/− compared with wild-type mice, whereas the oxygen consumption did not differ significantly. The respiratory exchange ratio at 20°C was significantly higher and the calculated fat utilization rate was lower in IL-6−/− mice. In response to cage-switch stress, the increase in oxygen consumption at both 30 and 20°C was lower in IL-6−/− than in wild-type mice. The increase in heart rate was lower in IL-6−/− mice at 30°C. At 4°C, both the oxygen consumption and core temperature were lower in IL-6−/− compared with wild-type mice, suggesting a lower cold-induced thermogenesis in IL-6−/− mice. The present results indicate that endogenous IL-6 is of importance for stress- and cold-induced energy expenditure in mice.

Microcirculatory Perfusion during Volume Therapy

1995 ◽  
Vol 82 (4) ◽  
pp. 975-982. ◽  
Author(s):  
Wolfgang Funk ◽  
Verena Baldinger
Keyword(s):  
Heart Rate ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Central Venous Pressure ◽  
Venous Pressure ◽  
Tissue Perfusion ◽  
Volume Replacement ◽  
Surface Oxygen ◽  
Tissue Oxygen ◽  
Central Venous

Background Because of the passage of water and salt molecules into the interstitial space, volume replacement with crystalloid solutions requires an amount at least four times that of lost blood. The resulting tissue edema may interfere with nutritive capillary perfusion and oxygen delivery. To prove this hypothesis, the effects of isovolemic hemodilution (hematocrit 30%) with Ringer's lactate solution or dextran 60 on tissue perfusion and oxygenation were investigated in awake Syrian golden hamsters. Methods Experiments were performed by using a chronic dorsal skinfold window giving access to skeletal muscle tissue (musculus cutaneus) with in vivo microscopy, quantitative video image analysis, and surface oxygen partial pressure electrodes. Central venous and arterial pressures were measured by means of chronically implanted jugular venous and carotid catheters. Results Isovolemic exchange of blood with dextran caused no significant changes in arterial or central venous pressure, heart rate, capillary flow velocity, functional capillary density, or surface oxygen partial pressure during the 1-h observation period. A volume of Ringer's solution equal to four times of the amount of blood lost maintained arterial pressure and heart rate when central venous pressure was kept at predilution control values. However, tissue perfusion determined by counting perfused capillaries per terminal arteriole was reduced by 62%, and mean tissue oxygen partial pressure decreased from 19 to 8 mmHg. Conclusions In this model, volume replacement with artificial colloids yielded hemodynamic stability and adequate tissue oxygen supply, whereas administration of crystalloids alone jeopardized tissue perfusion and oxygenation.

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