Exhaustive exercise training enhances aerobic capacity in American alligator (Alligator mississippiensis) (original) (raw)
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Circulatory impairment induced by exercise in the lizard Iguana iguana
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Summary Mechanical integration of the cardiac, muscular and ventilatory pumps enables mammals to vary cardiac output over a wide range to match metabolic demands. We have found this integration lacking in a lizard (Iguana iguana) that differs from mammals because blood flow from the caudal body and ventilation are maximal after, rather than during, exercise.
Eat and run: prioritization of oxygen delivery during elevated metabolic states
Respiratory Physiology & Neurobiology, 2004
The principal function of the cardiopulmonary system is the matching of oxygen and carbon dioxide transport to the metabolic requirements of different tissues. Increased oxygen demands (V O 2), for example during physical activity, result in a rapid compensatory increase in cardiac output and redistribution of blood flow to the appropriate skeletal muscles. These cardiovascular changes are matched by suitable ventilatory increments. This matching of cardiopulmonary performance and metabolism during activity has been demonstrated in a number of different taxa, and is universal among vertebrates. In some animals, large increments in aerobic metabolism may also be associated with physiological states other than activity. In particular,V O 2 may increase following feeding due to the energy requiring processes associated with prey handling, digestion and ensuing protein synthesis. This large increase inV O 2 is termed "specific dynamic action" (SDA). In reptiles, the increase inV O 2 during SDA may be 3-40-fold above resting values, peaking 24-36 h following ingestion, and remaining elevated for up to 7 days. In addition to the increased metabolic demands, digestion is associated with secretion of H + into the stomach, resulting in a large metabolic alkalosis (alkaline tide) and a near doubling in plasma [HCO 3 − ]. During digestion then, the cardiopulmonary system must meet the simultaneous challenges of an elevated oxygen demand and a pronounced metabolic alkalosis. This paper will compare and contrast the patterns of cardiopulmonary response to similar metabolic increments in these different physiological states (exercise and/or digestion) in a variety of reptiles, including the Burmese python, Python morulus, savannah monitor lizard, Varanus exanthematicus, and American alligator Alligator mississipiensis.
Journal of Comparative Physiology, 1972
Oxygen consumption and heart rate were measured during rest and activity in the lizards Varanus gouldii and Sauromalus hispidus. Oxygen debt was calculated from postactive oxygen consumption. Standard metabolic rates of the two animals are similar but Varanus consumes much more oxygen during activity than does Sauromalus (Fig. 1-3). The latter has a constant active metabolic rate above 30~ and accumulates a large oxygen debt, which is repayed slowly (Fig. 4). Varanus recovers rapidly from activity (Fig. 5), presumably because of the smaller lactacid debt incurred. Heart rate increment in Sauromalus is high (Fig. 8). This variable cannot be responsible for the limitation of active oxygen consumption; calculations of oxygen pulse suggest that an inability to increase A-V difference and/or stroke volume are implicated (Fig. 9). Varanu~ have evolved mechanisms to sustain high levels of oxygen consumption superior to those of other reptiles investigated. The role of anaerobiosis in the biology of both animals is discussed.
Journal of Experimental Biology, 2010
SUMMARY In diving animals, skeletal muscle adaptations to extend underwater time despite selective vasoconstriction include elevated myoglobin (Mb) concentrations, high acid buffering ability (β) and high aerobic and anaerobic enzyme activities. However, because cardiac muscle is perfused during dives, it may rely less heavily on Mb, β and anaerobic pathways to support contractile activity. In addition, because cardiac tissue must sustain contractile activity even before birth, it may be more physiologically mature at birth and/or develop faster than skeletal muscles. To test these hypotheses, we measured Mb levels, β and the activities of citrate synthase (CS), β-hydroxyacyl-CoA dehydrogenase (HOAD) and lactate dehydrogenase (LDH) in cardiac and skeletal muscle samples from 72 harp and hooded seals, ranging in age from fetuses to adults. Results indicate that in adults cardiac muscle had lower Mb levels (14.7%), β (55.5%) and LDH activity (36.2%) but higher CS (459.6%) and HOAD (37...
Respiration Physiology, 1983
We measured the effects of severe, short-term exercise stress on the acid base balance, the O~ transporting properties and the cofactors lk~r 02 binding in the blood of tench, Tmca tinca. Short-term severe exercise resulted in a drastic decrease in arterial blood pH which is attributed to a mixed respiratory and metabolic acidosis. Concomitantly arterial Po~ rose in apparent compensation for the detrimental effects of the acidosis on 02 transport by the blood. Acid base balance Exercise Blood lactate Fish Blood O 2 transport Red cell phosphates Swimming activity greatly increases the oxygen demand of fish (Brett, 19721. This imposes a stress on the tissue Oe supply. Adjustments to maximize the flux of O, from environment to tissues include increases in ventilation volume, cardiac output and arterio-venous O, content difference (e.g., Kiceniuk and Jones, 19771. In fish exhibiting sustained swimming activity, a steady state develops balancing O~ supply and O, demand. In vigorous swimming performance (e.g., burst activity) O, demand may, however, exceed the Oe supplying capacity (Brett, 1972). Although white myotomal muscle constitutes the major portion of fish body weight, white muscle fibres seem only to be active at high swimming speeds and during bursts of activity (e.g., Johnston el al., 1977). Extensive muscle activity is associated with decreased content of creatine phosphate and glycogen in this tissue (Driedzic et al., 1981). Both compounds are important in anaerobic ATP generation for muscle contractions. Anaerobic degradation of glycogen, however, also results in accumulation of lactate in the muscle and eventually in the blood. During .,Iccet~ted.lm" puhlicalion
Journal of Experimental Biology, 2002
SUMMARYOxygen transfer during sustained maximal exercise while locomoting on a treadmill at 0.33 m s-1 was examined in a varanid lizard Varanus mertensi at 35 °C. The rate of oxygen consumption(V̇O2) increased with locomotion from 3.49±0.75 (mean ± S.D.) to 14.0±4.0 ml O2 kg-1 min-1. Ventilation(V̇E) increased, aided by increases in both tidal volume and frequency, in direct proportion to V̇O2. The air convection requirement(V̇E/V̇O2=27)was therefore maintained, together with arterial PaCO2 and PaO2. The alveolar—arterial PO2 difference(PAO2—PaO2)also remained unchanged during exercise from its value at rest, which was approximately 20 mmHg. Pulmonary diffusion for carbon monoxide(0.116±0.027 ml kg-1 min-1 mmHg-1) was double the value previously reported in V. exanthematicus and remained unchanged with exercise. Furthermore, exercise was associated with an increase in the arterial—venous O2 content difference(CaO2—CvO2),which was assisted by a marked Bohr shift in the hemoglobin sat...
European Journal of Applied Physiology and Occupational Physiology, 1988
Aerobic and anaerobic thresholds determined by different methods in repeated exercise tests were correlated with cardiorespiratory variables and variables of muscle metabolic profile in 33 men aged 20-50 years. Aerobic threshold was determined from blood lactate, ventilation, and respiratory gas exchange by two methods (AerT1 and AerT2) and anaerobic threshold from venous lactate (AnTLa), from ventilation and gas exchange (AnTr) and by using the criterion of 4 mmol. 1-1 of venous lactate (AnT4mmo0. In addition to ordinary correlative analyses, applications of LISREL models were used. The 8 explanatory variables chosen for the regression analyses were height, relative heart volume, relative diffusing capacity of the lung, muscle fiber composition, citrate synthase (CS) and succinate dehydrogenase activities, the lactate dehydrogenase-CS ratio, and age. They explained 58% of the variation in AerT~, 73.5% that of AerT2, 71% that of AnTr, 74.5% that of AnTLa, and 67.5% that of AnT4mmol. AerT and AnT alone explained 77% of the variation in each other. Both AerT and AnT were determined mainly by a muscle metabolic profile, with the CS activity of vastus lateralis as the strongest determinant. The factor 'submaxireal endurance' which was measured with AerT and AnT seemed to be slightly more closely connected to 'muscle metabolic profile' than was 'maximal aerobic power' (= l)'o .....), but both also correlated strongly with each other (r = 0.92).