Temperature effects on oxygen consumption and breathing pattern in juvenile and adult Chelonoidis carbonarius (Spix, 1824).

The effects of temperature on breathing pattern and oxygen consumption are being investigated in juvenile tortoises and compared to adults, in order to understand physiological adjustments of the respiratory system as related to body size, especially regarding the energetic expenditure associated with growth. We analyzed the breathing pattern and oxygen consumption of juvenile and adult red-footed tortoises (Chelonoidis carbonarius, Cryptodira: Testudinidae). The animals (N = 9; body mass ranging from 0.

Maintained barostatic regulation of heart rate in digesting snakes (Boa constrictor).

When snakes digest large meals, heart rate is accelerated by withdrawal of vagal tone and an increased non-adrenergic-non-cholinergic tone that seems to stem from circulating blood-borne factors exerting positive chronotropic effects. To investigate whether this tonic elevation of heart rate impairs the ability for autonomic regulation of heart during digestion, we characterised heart rate responses to pharmacological manipulation of blood pressure in the snake Boa constrictor through serial injections of sodium nitroprusside and phenylephrine. Both fasting and digesting snakes responded with a robust tachycardia to hypotension induced by sodium nitroprusside, with digesting snakes attaining higher maximal heart rates than fasting snakes.

Baroreflex responses to activity at different temperatures in the South American rattlesnake, Crotalus durissus.

In humans, physical exercise imposes narrower limits for the heart rate (f) response of the baroreflex, and vascular modulation becomes largely responsible for arterial pressure regulation. In undisturbed reptiles, the baroreflex-related f alterations at the operating point (G) decreases at elevated body temperatures (T) and the vascular regulation changes accordingly. We investigated how the baroreflex of rattlesnakes, Crotalus durissus, is regulated during an activity at different T, expecting that activity would reduce the capacity of the cardiac baroreflex neural pathway to buffer arterial pressure fluctuations while being compensated by the vascular neural pathway regulation.

Effects of different levels of hypoxia and hypercarbia on ventilation and gas exchange in Boa constrictor amaralis and Crotalus durissus (Squamata: Serpentes).

Ventilation and gas exchange have been studied in relatively few species of snakes, especially regarding their response to environmental hypoxia or hypercarbia. We exposed Crotalus durissus (N = 6) and Boa constrictor (N = 6) to decreasing levels of oxygen (12, 9, 6, 3 % O) and increasing levels of carbon dioxide (1.5, 3.

Pharmacodynamics of propofol and alfaxalone in rattlesnakes (Crotalus durissus).

To characterise the effect of two common induction agents, propofol and alfaxalone, on mean arterial blood pressure (MAP) and heart rate (HR), we equipped 19 adult South American rattlesnakes (Crotalus durissus) with an indwelling arterial catheter approximately 24 h prior to recording of baseline resting values. Then, seven snakes received alfaxalone (15 mg kg) intravascularly (IV) through the catheter, while groups two and three (both n = 6) received propofol (15 mg kg IV). The first two groups were not handled, while the group 3 was manually restrained for 2 min for a mock injection of 0.

Cholinergic regulation along the pulmonary arterial tree of the South American rattlesnake: vascular reactivity, muscarinic receptors, and vagal innervation.

Vascular tone in the reptilian pulmonary vasculature is primarily under cholinergic, muscarinic control exerted via the vagus nerve. This control has been ascribed to a sphincter located at the arterial outflow, but we speculated whether the vascular control in the pulmonary artery is more widespread, such that responses to acetylcholine and electrical stimulation, as well as the expression of muscarinic receptors, are prevalent along its length. Working on the South American rattlesnake (), we studied four different portions of the pulmonary artery (truncus, proximal, distal, and branches).

Heart rate variability in the tegu lizard, Salvator merianae, its neuroanatomical basis and role in the assessment of recovery from experimental manipulation.

Using long-term, remote recordings of heart rate (f) on fully recovered, undisturbed lizards, we identified several components of heart rate variability (HRV) associated with respiratory sinus arrhythmia (RSA): 1.) A peak in the spectral representation of HRV at the frequency range of ventilation. 2.

Blood flow distribution in embryonic common snapping turtles Chelydra serpentina (Reptilia; Chelonia) during acute hypoxia and α-adrenergic regulation.

Embryonic turtles have four distinct vascular beds that separately perfuse the developing embryo's body and the extra-embryonic yolk sac, amnion and chorioallantoic membrane (CAM). The mechanisms enabling differential regulation of blood flow through these separate beds, in order to meet the varying demands of the embryo during development, is of current interest. The present investigation followed the changes in blood flow distribution during an acute exposure to hypoxia and after α-adrenergic blockade.

Hereditary angioedema: Screening of first-degree blood relatives and earlier diagnosis.

Hereditary angioedema (HAE) with C1 inhibitor (C1INH) deficiency is an inherited disease characterized by sudden, recurrent episodes of edema that involve the skin, gastrointestinal tract, respiratory tract, and other organs. Because it takes a long time from the first symptoms to diagnosis, we aimed to identify HAE in untested first-degree blood relatives among some of our patients with HAE in our outpatient clinic at Hospital Universitário Clementino Fraga (HUCFF), Federal University of Rio de Janeiro. Untested first-degree relatives of patients with HAE C1INH, even those who were asymptomatic, were identified and invited to participate.

Evaluation of the sequence method as a tool to assess spontaneous baroreflex in reptiles.

The sequence method is an alternative to the traditional pharmacological approach (i.e., the Oxford technique) used to calculate baroreflex gain (G) in mammals.

Autonomic control of cardiovascular adjustments associated with orthostasis in the scansorial snake .

Orthostatic hypotension is a phenomenon triggered by a change in the position or posture of an animal, from a horizontal to a vertical head-up orientation, characterised by a blood pooling in the lower body and a reduction in central and cranial arterial blood pressure (). This hypotension elicits systemic vasoconstriction and tachycardia, which generally reduce blood pooling and increase Little is known about the mediation and importance of such cardiovascular adjustments that counteract the haemodynamic effects of orthostasis in ectothermic vertebrates, and some discrepancies exist in the information available on this subject. Thus, we sought to expand our knowledge on this issue by investigating it in a more elaborate way, through an pharmacological approach considering temporal circulatory changes during head-up body inclinations in unanaesthetised To do so, we analysed temporal changes in , heart rate () and cardiac autonomic tone associated with 30 and 60 deg inclinations, before and after muscarinic blockade with atropine, double blockade with atropine and propranolol, and α-adrenergic receptor blockade with prazosin.

The respiratory mechanics of the yacare caiman ().

The structure and function of crocodilian lungs are unique compared with those of other reptiles. We examined the extent to which this and the semi-aquatic lifestyle of crocodilians affect their respiratory mechanics. We measured changes in intratracheal pressure in adult and juvenile caiman () during static and dynamic lung volume changes.

Are all bony fishes oxygen regulators? Evidence for oxygen regulation in a putative oxygen conformer, the swamp eel Synbranchus marmoratus.

This study investigated the oxygen consumption of the putative oxygen conformer marbled swamp eel Synbranchus marmoratus during progressive hypoxia. Earlier studies have not reached an agreement on whether S. marmoratus is a conformer or a regulator.

The electrocardiogram of vertebrates: Evolutionary changes from ectothermy to endothermy.

The electrocardiogram (ECG) reveals that heart chamber activation and repolarization are much faster in mammals and birds compared to ectothermic vertebrates of similar size. Temperature, however, affects electrophysiology of the heart and most data from ectotherms are determined at body temperatures lower than those of mammals and birds. The present manuscript is a review of the effects of temperature on intervals in the ECG of ectothermic and endothermic vertebrates rather than a hypothesis-testing original research article.

Convective oxygen transport during development in embryos of the snapping turtle .

This study investigated the maturation of convective oxygen transport in embryos of the snapping turtle (). Measurements included: mass, oxygen consumption ( ), heart rate, blood oxygen content and affinity and blood flow distribution at 50%, 70% and 90% of the incubation period. Body mass increased exponentially, paralleled by increased cardiac mass and metabolic rate.

Effects of environmental hypoxia and hypercarbia on ventilation and gas exchange in Testudines.

Background: Ventilatory parameters have been investigated in several species of Testudines, but few species have had their ventilatory pattern fully characterized by presenting all variables necessary to understand changes in breathing pattern seen under varying environmental conditions.

Methods: We measured ventilation and gas exchange at 25 °C in the semi-aquatic turtle and the terrestrial tortoise under normoxia, hypoxia, and hypercarbia and furthermore compiled respiratory data of testudine species from the literature to analyze the relative changes in each variable.

Results: During normoxia both species studied showed an episodic breathing pattern with two to three breaths per episode, but the non-ventilatory periods (T) were three to four times longer in than in .

The autonomic control of upright posture tachycardia in the arboreal lizard Iguana iguana.

In terrestrial environments, upright spatial orientation can dramatically influence animals' hemodynamics. Generally, large and elongated species are particularly sensitive to such influence due to the greater extent of their vascular beds being verticalized, favoring the establishment of blood columns in their bodies along with caudal blood pooling, and thus jeopardizing blood circulation through a cascade effect of reductions in venous return, cardiac filling, stroke volume, cardiac output, and arterial blood pressure. This hypotension triggers an orthostatic-(baroreflex)-tachycardia to normalize arterial pressure, and despite the extensive observation of this heart rate (f ) adjustment in experiments on orthostasis, little is known about its mediation and importance in ectothermic vertebrates.

The consequences of seasonal fasting during the dormancy of tegu lizards () on their postprandial metabolic response.

Tegu lizards () aestivate for up to 5 months during Brazil's winter, when they retreat to burrows and halt most activities. Dormant tegus reduce their gastrointestinal (GI) mass, which allows a substantial energy economy. This strategy, however, implies that the first post-dormancy digestion would be more costly than subsequent feeding episodes as a result of GI atrophy.

Cardiovascular effects of histamine in three widely diverse species of reptiles.

The cardiovascular system of vertebrates is regulated by a vast number of regulatory factors, including histamine. In pythons, histamine induces a strong tachycardia and dilates the systemic vasculature, which resembles the cardiovascular response to the elevated metabolic rate during digestion. In fact, there is an important role of increased histaminergic tone on the heart during the initial 24 h of digestion in pythons.

Rates of oxygen uptake increase independently of changes in heart rate in late stages of development and at hatching in the green iguana, Iguana iguana.

Oxygen consumption (VO), heart rate (f), heart mass (M) and body mass (M) were measured during embryonic incubation and in hatchlings of green iguana (Iguana iguana). Mean f and VO were unvarying in early stage embryos. VO increased exponentially during the later stages of embryonic development, doubling by the end of incubation, while f was constant, resulting in a 2.

Vagal tone regulates cardiac shunts during activity and at low temperatures in the South American rattlesnake, Crotalus durissus.

The undivided ventricle of non-crocodilian reptiles allows for intracardiac admixture of oxygen-poor and oxygen-rich blood returning via the atria from the systemic circuit and the lungs. The distribution of blood flow between the systemic and pulmonary circuits may vary, based on differences between systemic and pulmonary vascular conductances. The South American rattlesnake, Crotalus durissus, has a single pulmonary artery, innervated by the left vagus.

The Effects of Feeding on Cardiac Control of the Broad-Nosed Caiman (Caiman latirostris): The Role of the Autonomic Nervous System and NANC Factors.

The metabolic increment that occurs after feeding demands cardiovascular adjustments to be maintained, as increased heart rate (f ) and cardiac output. In mammals, postprandial tachycardia seems to be triggered by an increase in adrenergic activity and by nonadrenergic noncholinergic (NANC) factors, while in ectothermic vertebrates, this adjustment seems to be linked to a withdrawal of vagal drive as well as to NANC factors. Because the factors behind postprandial tachycardia have not yet been investigated in crocodilians, the present study sought to evaluate the postprandial tachycardia mediators in the broad-nosed caiman.

Beyond body size: muscle biochemistry and body shape explain ontogenetic variation of anti-predatory behaviour in the lizard Salvator merianae.

Anti-predatory behaviour evolves under the strong action of natural selection because the success of individuals avoiding predation essentially defines their fitness. Choice of anti-predatory strategies is defined by prey characteristics as well as environmental temperature. An additional dimension often relegated in this multilevel equation is the ontogenetic component.

Seasonal reproductive endothermy in tegu lizards.

With some notable exceptions, small ectothermic vertebrates are incapable of endogenously sustaining a body temperature substantially above ambient temperature. This view was challenged by our observations of nighttime body temperatures sustained well above ambient (up to 10°C) during the reproductive season in tegu lizards (~2 kg). This led us to hypothesize that tegus have an enhanced capacity to augment heat production and heat conservation.

Winter metabolic depression does not change arterial baroreflex control of heart rate in the tegu lizard Salvator merianae.

Baroreflex regulation of blood pressure is important for maintaining appropriate tissue perfusion. Although temperature affects heart rate (fH) reflex regulation in some reptiles and toads, no data are available on the influence of temperature-independent metabolic states on baroreflex. The South American tegu lizard Salvator merianae exhibits a clear seasonal cycle of activity decreasing fH along with winter metabolic downregulation, independent of body temperature.