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1.
Physiol Biochem Zool ; 87(4): 568-75, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24940921

RESUMO

Abstract In the undivided ventricle of noncrocodilian reptiles, the blood perfusing the systemic circulation is a controlled combination of oxygenated pulmonary blood, flowing from left to right across the heart, and relatively deoxygenated systemic blood, flowing from right to left. A clear inverse correlation has been experimentally established between metabolic demand and the magnitude of right-to-left cardiac shunt in several reptile groups. Unilateral left vagotomy renders the single effective pulmonary artery of the South American rattlesnake (Crotalus durissus) unable to adjust the magnitude of blood flow to the lung. This provides a unique model for investigation of the long-term consequences of abolition of the cardiac shunt in a squamate reptile. Rattlesnakes-vagotomized on the left or right side or sham operated-were exposed to long-term food deprivation or temperature change. Loss of control of the cardiac shunt following selective vagotomy did not change the progressive decrease in body mass or the onset of identifiable fasting stages. Resting metabolic rate and the increase in oxygen uptake measured during spontaneous or forced activity were also unchanged. The responses to reductions in temperature (from 30° to 20° or 15°C) in adult snakes or juvenile snakes were similarly unaffected by vagal transection. These data support rejection of the hypothesis that adjustment of the cardiac shunt is central to the control metabolic rate in squamate reptiles.


Assuntos
Metabolismo Basal/fisiologia , Crotalus/fisiologia , Jejum/fisiologia , Coração/fisiologia , Consumo de Oxigênio/fisiologia , Animais , Peso Corporal , Ventrículos do Coração , Hemodinâmica , Temperatura , Vagotomia
2.
J Exp Biol ; 216(Pt 10): 1881-9, 2013 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-23393283

RESUMO

The morphologically undivided ventricle of the heart in non-crocodilian reptiles permits the mixing of oxygen-rich blood returning from the lungs and oxygen-poor blood from the systemic circulation. A possible functional significance for this intra-cardiac shunt has been debated for almost a century. Unilateral left vagotomy rendered the single effective pulmonary artery of the South American rattlesnake, Crotalus durissus, unable to adjust the magnitude of blood flow to the lung. The higher constant perfusion of the lung circulation and the incapability of adjusting the right-left shunt in left-denervated snakes persisted over time, providing a unique model for investigation of the long-term consequences of cardiac shunting in a squamate. Oxygen uptake recorded at rest and during spontaneous and forced activity was not affected by removing control of the cardiac shunt. Furthermore, metabolic rate and energetic balance during the post-prandial metabolic increment, plus the food conversion efficiency and growth rate, were all similarly unaffected. These results show that control of cardiac shunting is not associated with a clear functional advantage in adjusting metabolic rate, effectiveness of digestion or growth rates.


Assuntos
Crotalus/crescimento & desenvolvimento , Crotalus/fisiologia , Coração/fisiologia , Consumo de Oxigênio/fisiologia , Nervo Vago/fisiologia , Anestesia , Animais , Metabolismo Basal/fisiologia , Peso Corporal , Estimulação Elétrica , Comportamento Alimentar/fisiologia , Reprodutibilidade dos Testes , Descanso/fisiologia , Vagotomia , Nervo Vago/cirurgia
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