Kasper Hansen

The specific dynamic action (SDA) of food represents the postprandial increase in metabolic rate and has often been described as the cost of digestion. However, many recent studies suggests that the SDA response primarily reflects the energetic cost of growth. Here, we estimated the contribution of growth to SDA in juvenile Burmese pythons (Python bivittatus) through simultaneous measurements of oxygen consumption (V̇O2) and growth over 50–56 days with snakes being fed at different intervals to generate variation in growth. The linear relationship between SDA (=∫(V̇O2−SMR); where SMR is standard metabolic rate) and growth was used to estimate the energetic cost of growth. This estimate was then multiplied by total growth to quantify the contribution of growth to the SDA response. Protein retention was assessed from faecal nitrogen, and changes in body composition were quantified using CT scans. Growth accounted for approximately 77% of the SDA response. The estimated contribution to the SDA response was supported by high protein retention and proportional increases in lean tissue. Together, these results strongly indicate that SDA in Burmese pythons is dominated by growth-related processes, particularly protein synthesis.

Forensic pathologists may use 3D prints as demonstrative aids when providing expert testimony in court of law, but the effects remain unclear despite many assumed benefits. In this qualitative study, the effects of using a 3D print, demonstrating a blunt force skull fracture, in court were explored by thematic analysis of interviews with judges, prosecutors, defence counsels, and forensic pathologists with the aim of improving the expert testimony. Five semi-structured focus groups and eight one-to-one interviews with a total of 29 stakeholders were transcribed ad verbatim and analysed using thematic analysis. The study found that a highly accurate 3D print of a skull demonstrated autopsy findings in detail and provided a quick overview, but sense of touch was of little benefit as the 3D print had different material characteristics than the human skull. Virtual 3D models were expected to provide all the benefits of 3D prints, be less emotionally confronting, and be logistically feasible. Both 3D prints and virtual 3D models were expected to be less emotionally confronting than autopsy photos. Regardless of fidelity, an expert witness was necessary to translate technical language and explain autopsy findings, and low-fidelity models may be equally suited as demonstrative aids. The court infrequently challenged the expert witnesses’ conclusions and, therefore, rarely had a need for viewing autopsy findings in detail, therefore rarely needing a 3D print.

Purpose Hyperpolarized C-13 MRI is a powerful technique to study dynamic metabolic processes in vivo; but it has predominantly been used in mammals, mostly humans, pigs, and rodents. Methods In the present study, we use this technique to characterize the metabolic fate of hyperpolarized [1-C-13]pyruvate in Burmese pythons (Python bivittatus), a large species of constricting snake that exhibits a four- to tenfold rise in metabolism and large growth of the visceral organs within 24-48 h of ingestion of their large meals. Results We demonstrate a fivefold elevation of the whole-body lactate-to-pyruvate ratio in digesting snakes, pointing to a large rise in lactate production from pyruvate. Consistent with the well-known metabolic stimulation of digestion, measurements of mitochondrial respiration in hepatocytes in vitro indicate a marked postprandial upregulation of mitochondrial respiration. We observed that a low SNR of the hyperpolarized C-13 produced metabolites in the python, and this lack of signal was possibly due to the low metabolism of reptiles compared with mammals, preventing quantification of alanine and bicarbonate production with the experimental setup used in this study. Spatial quantification of the [1-C-13]lactate was only possible in postprandial snakes (with high metabolism), where a statistically significant difference between the heart and liver was observed. Conclusion We confirm the large postprandial rise in the wet mass of most visceral organs, except for the heart, and demonstrated that it is possible to image the [1-C-13]pyruvate uptake and intracellular conversion to [1-C-13]lactate in ectothermic animals.

Pythons are renowned for the profound phenotypical flexibility of their visceral organs in response to ingestion of large meals following prolonged fasting. Traditionally, the phenotypic changes are studied by determining organ mass of snakes killed at different times during digestion. Here we evaluate the use of magnetic resonance imaging (MRI) for in vivo measurements of the visceral organs in fasting and digesting snakes. Twelve snakes were MRI scanned immediately before the organs were removed and weighed to provide direct comparison of the two methods. Both methods provided similar estimates for the mass of liver, gallbladder, and pancreas, whereas MRI overestimated the size of the heart and small intestine, probably because blood and digesta contributed to the volume determined by MRI. The correlations were used to derive wet organ mass from MRI-based volumes to evaluate the mass development through repeated MRI scans of five digesting snakes. MRI was performed at fasting and 24, 48, 72, 132, and 500 h after eating a meal corresponding to 25% of body mass. This observation period revealed a reversible volume upregulation of the visceral organs, supporting the view that successive MRI facilitates in vivo investigations of structural changes accompanied by digestion.