Proportional increment of oxygen consumption, heart rate and core body temperature in the digesting Python bivittatus.

The Burmese python has a remarkable digestive physiology with large elevations of metabolic rate and heart rate following feeding. Here, we investigated the relationship between heart rate, oxygen consumption and core body temperature during digestion in five pythons (Python bivittatus) by implantation of data loggers. The snakes were placed in respirometers at 30±0.

Temperature effects on blood gases in embryonic American alligators (Alligator mississippiensis).

Numerous studies report on the influence of temperature on blood gases in ectothermic vertebrates, but there is merely a cursory understanding of these effects in developing animals. Animals that develop in eggs are at the mercy of environmental temperature and are expected to lack the capacity to regulate gas exchange and may regulate blood gases by means of altered conductance for gas exchange. We, therefore, devised a series of studies to characterize the developmental changes in blood gases when embryonic alligators were exposed to 25, 30 and 35 °C.

The relevance of vascular adjustments to hemodynamic control in the face of temperature change in Crotalus durissus.

The presence of cardiac shunts in ectothermic tetrapods is thought to be consistent with active vascular modulations for proper hemodynamic support. Local control of blood flow modulates tissue perfusion and thus systemic conductance (Gsys) is assumed to increase with body temperature (Tb) to accommodate higher aerobic demand. However, the general increase of Gsys presses for a higher right-to-left (R-L) shunt, which reduces arterial oxygen concentration.

Impact of procedural handling on the physiological effects of alfaxalone anaesthesia in the ball python (Python regius).

To describe the cardiovascular changes following intramuscular (handled) and intravascular (undisturbed, via intraarterial catheter) alfaxalone administration, we studied 20 healthy ball pythons (Python regius) in a randomised, prospective study. The pythons were instrumented with occlusive arterial catheters to facilitate undisturbed, continuous monitoring of heart rate and blood pressure. Six pythons were administered intramuscular (IM) saline, followed by 20 mg/kg IM alfaxalone, and were manually restrained for both injections.

Specific dynamic action: the energy cost of digestion or growth?

The physiological processes underlying the post-prandial rise in metabolic rate, most commonly known as the 'specific dynamic action' (SDA), remain debated and controversial. This Commentary examines the SDA response from two opposing hypotheses: (i) the classic interpretation, where the SDA represents the energy cost of digestion, versus (ii) the alternative view that much of the SDA represents the energy cost of growth. The traditional viewpoint implies that individuals with a reduced SDA should grow faster given the same caloric intake, but experimental evidence for this effect remains scarce and inconclusive.

The pancreas does not contribute to the non-adrenergic-non-cholinergic stimulation of heart rate in digesting pythons.

Vertebrates elevate heart rate when metabolism increases during digestion. Part of this tachycardia is due to a non-adrenergic-non-cholinergic (NANC) stimulation of the cardiac pacemaker, and it has been suggested these NANC factors are circulating hormones that are released from either gastrointestinal or endocrine glands. The NANC stimulation is particularly pronounced in species with large metabolic responses to digestion, such as reptiles.

Short communication: Characterizing arterial and venous blood gases over the gas exchange surface, the chorioallantoic membrane, of embryonic American alligators (Alligator mississippiensis) at two points of development.

Assessments of arterial and venous blood gases are required to understand the function of respiratory organs in animals at different stages of development. We measured blood gases in the arteries entering and veins leaving the chorioallantoic membrane (CAM) in embryonic alligators (Alligator mississippiensis). The CAM accounts for virtually all gas exchange in these animals, and we hypothesized that the CAM vasculature would be larger in eggs incubated in hypoxia (10% O for 50% or 70% of incubation), which would be reflected in a lower partial pressure of CO (PCO).

Transesophageal echocardiography of cardiac function in Nile crocodiles - A novel tool for assessing complex hemodynamic patterns.

Background: The crocodilian heart is unique among reptiles with its four-chambered structure and complete intracardiac separation of pulmonary and systemic blood flows and pressures. Crocodiles have retained two aortic arches; one from each ventricle, that communicate via Foramen of Panizza, immediately distally from the aortic valves. Moreover, crocodiles can regulate vascular resistance in the pulmonary portion of the right ventricular outflow tract (RVOT).

The Elusive Hypertrophy of the Python Heart.

The Burmese python, one of the world's largest snakes, has reached celebrity status for its dramatic physiological responses associated with digestion of enormous meals. The meals elicit a rapid gain of mass and function of most visceral organs, particularly the small intestine. There is also a manyfold elevation of oxygen consumption that demands the heart to deliver more oxygen.

The reduction in arterial pH with increased temperature is not affected by hyperoxia in toads (Rhinella marina) and pythons (Python molurus).

It is well established that arterial pH decreases with increased temperature in amphibians and reptiles through an elevation of arterial PCO2, but the underlying regulation remains controversial. The alphastat hypothesis ascribes the pH fall to a ventilatory regulation of protein ionisation, but the pH reduction with temperature is lower than predicted by the pKa change of the imidazole group on histidine. We hypothesised that arterial pH decreases at high, but not at low, temperatures when toads (Rhinella marina) and snakes (Python molurus) are exposed to hyperoxia.

Examination of head versus body heading may help clarify the extent to which animal movement pathways are structured by environmental cues?

Understanding the processes that determine how animals allocate time to space is a major challenge, although it is acknowledged that summed animal movement pathways over time must define space-time use. The critical question is then, what processes structure these pathways? Following the idea that turns within pathways might be based on environmentally determined decisions, we equipped Arabian oryx with head- and body-mounted tags to determine how they orientated their heads - which we posit is indicative of them assessing the environment - in relation to their movement paths, to investigate the role of environment scanning in path tortuosity. After simulating predators to verify that oryx look directly at objects of interest, we recorded that, during routine movement, > 60% of all turns in the animals' paths, before being executed, were preceded by a change in head heading that was not immediately mirrored by the body heading: The path turn angle (as indicated by the body heading) correlated with a prior change in head heading (with head heading being mirrored by subsequent turns in the path) twenty-one times more than when path turns occurred due to the animals adopting a body heading that went in the opposite direction to the change in head heading.

A Novel β-Globin Variant, Hb Raklev [β 75(E19) :c.227T > A (Leu→Gln)].

We present a new hemoglobin variant, Hb Raklev, characterized by the substitution of leucine with glutamine at position 75 in the β-globin chain. This variant was discovered inadvertently during an HbA evaluation using high performance liquid chromatography in a symptomless 54-year-old Caucasian woman, with the same variant also identified in her 16-year-old daughter. Purification of the hemoglobin revealed possibly diminished 2,3-bisphosphoglycerate (2,3-BPG) sensitivity, which may result in heightened oxygen affinity.

Hypoxic incubation at 50% of atmospheric levels shifts the cardiovascular response to acute hypoxia in American alligators, Alligator mississippiensis.

We designed a series of studies to investigate whether hypoxia (10% O) from 20% of incubation to hatching, or from 20 to 50% of incubation, affects cardiovascular function when juvenile American alligators reached an age of 4-5 years compared to juveniles that were incubated in 21% O. At this age, we measured blood flows in all the major arteries as well as heart rate, blood pressure, and blood gases in animals in normoxia and acute hypoxia (10% O and 5% O). In all three groups, exposure to acute hypoxia of 10% O caused a decrease in blood O concentration and an increase in heart rate in 4-5-year-old animals, with limited effects on blood flow in the major outflow vessels of the heart.

The anti-inflammatory agent 5-ASA reduces the level of specific tsRNAs in sperm cells of high-fat fed C57BL/6J mouse sires and improves glucose tolerance in female offspring.

Introduction: The prevalence of obesity and associated comorbidities have increased to epidemic proportions globally. Paternal obesity is an independent risk factor for developing obesity and type 2 diabetes in the following generation, and growing evidence suggests epigenetic inheritance as a mechanism for this predisposition. How and why obesity induces epigenetic changes in sperm cells remain to be clarified in detail.

Special Challenges in PET Imaging of Ectothermic Vertebrates.

The bulk of biomedical positron emission tomography (PET)-scanning experiments are performed on mammals (ie, rodents, pigs, and dogs), and the technique is only infrequently applied to answer research questions in ectothermic vertebrates such as fish, amphibians, and reptiles. Nevertheless, many unique and interesting physiological characteristics in these ectothermic vertebrates could be addressed in detail through PET. The low metabolic rate of ectothermic animals, however, may compromise the validity of physiological and biochemical parameters derived from the images created by PET and other scanning modalities.

Cheap gulp foraging of a giga-predator enables efficient exploitation of sparse prey.

The giant rorqual whales are believed to have a massive food turnover driven by a high-intake lunge feeding style aptly described as the world's largest biomechanical action. This high-drag feeding behavior is thought to limit dive times and constrain rorquals to target only the densest prey patches, making them vulnerable to disturbance and habitat change. Using biologging tags to estimate energy expenditure as a function of feeding rates on 23 humpback whales, we show that lunge feeding is energetically cheap.

Exposure to hypoxia during embryonic development affects blood flow patterns and heart rate in juvenile American alligators during digestion.

The developmental environment can alter an organism's phenotype through epigenetic mechanisms. We incubated eggs from American alligators in 10% O (hypoxia) to investigate the functional plasticity of blood flow patterns in response to feeding later in life. Digestion is associated with marked elevations of metabolism, and we therefore used the feeding-induced stimulation of tissue O demand to determine whether there are lasting effects of developmental hypoxia on the cardiovascular response to digestion later in life.

Comment on "Exceptional preservation of organs in Devonian placoderms from the Gogo lagerstätte".

Trinajstic et al., (, 16 September 2022, p. 1311-1314) describe exceptionally well-preserved organs in fossilized Devonian placoderms to infer the early evolution of the vertebrate heart.

Effect of atropine and propofol on the minimum anaesthetic concentration of isoflurane in the freshwater turtle Trachemys scripta (yellow-bellied slider).

Objective: To determine if the administration of atropine would reduce the measured minimum anaesthetic concentration of isoflurane (MAC) in freshwater turtles - the yellow-bellied slider (Trachemys scripta scripta).

Study Design: Paired, blinded, randomized, prospective studies of 1) the effect of atropine in isoflurane anaesthetized freshwater turtles (T. scripta scripta) and 2) the effect of atropine in yellow-bellied sliders in which anaesthesia was induced with propofol and maintained with isoflurane.