Biological and structural phenotypes associated with neurodevelopmental outcomes in congenital heart disease.

Neurodevelopmental disability (NDD) is recognised as one of the most common comorbidities in children with congenital heart disease (CHD) and is associated with altered brain structure and growth throughout the life course. Causes and contributors underpinning the CHD and NDD paradigm are not fully understood, and likely include innate patient factors, such as genetic and epigenetic factors, prenatal haemodynamic consequences as a result of the heart defect, and factors affecting the fetal-placental-maternal environment, such as placental pathology, maternal diet, psychological stress and autoimmune disease. Additional postnatal factors, including the type and complexity of disease and other clinical factors such as prematurity, peri-operative factors and socioeconomic factors are also expected to play a role in determining the final presentation of the NDD. Despite significant advances in knowledge and strategies to optimise outcomes, the extent to which adverse neurodevelopment can be modified remains unknown. Understanding biological and structural phenotypes associated with NDD in CHD are vital for understanding disease mechanisms, which in turn will advance the development of effective intervention strategies for those at risk. This review article summarises our current knowledge surrounding biological, structural, and genetic contributors to NDD in CHD and describes avenues for future research; highlighting the need for translational studies that bridge the gap between basic science and clinical practice.

Impacts of thermal acclimatization on fish skeletal muscle.

Thermal acclimation allows ectotherms to maintain physiological homeostasis while occupying habitats with constantly changing temperatures. This process is especially important in skeletal muscle which powers most movements necessary for life. We aimed to understand how fish skeletal muscle is impacted by acclimatization in the laboratory. To accomplish this, we compared muscle contraction kinetics of four-week lab acclimatized fish (at 20 °C) to fish taken directly from the field when sea surface temperatures were similar to lab treatment temperature (ocean temperature ranged from 17.7 to 19.9 °C in the four weeks prior to collection at 20 °C). To examine these effects, we chose to study tautog (Tautoga onitis) and cunner (Tautogolabrus adspersus) from Long Island Sound. We found that timing of contraction kinetics in cunner and tautog did not differ from the lab acclimatized and field acclimatized groups. However, lab acclimatized cunner produced greater contraction force than fish taken directly from the field. This increased force production allowed lab acclimatized cunner to produce greater power when compared to cunner from the field treatment. Furthermore, laboratory acclimatized cunner did not express any slow myosin heavy chain, suggesting that their muscle had transitioned to mostly fast twitch fibers after being held at a constant temperature in the lab. None of these effects were seen in tautog. In this work we highlight the importance of considering the impacts laboratory conditions have on experimental conditions.

Thermal acclimation leads to variable muscle responses in two temperate labrid fishes.

Temperature can be a key abiotic factor in fish distribution, as it affects most physiological processes. Specifically, temperature can affect locomotor capabilities, especially as species are exposed to temperatures nearing their thermal limits. In this study, we aimed to understand the effects of temperature on muscle in two labrids that occupy the Northwest Atlantic Ocean. When exposed to cold temperatures in autumn, cunner (Tautogolabrus adspersus) and tautog (Tautoga onitis) go into a state of winter dormancy. Transitions into dormancy vary slightly, where tautog will make short migrations to overwintering habitats while cunner overwinter in year-round habitats. To understand how muscle function changes with temperature, we held fish for 4 weeks at either 5 or 20°C and then ran muscle kinetic and workloop experiments at 5, 10 and 20°C. Following experiments, we used immunohistochemistry staining to identify acclimation effects on myosin isoform expression. Muscle taken from warm-acclimated cunner performed the best, whereas there were relatively few differences among the other three groups. Cunner acclimated at both temperatures downregulated the myosin heavy chain, suggesting a transition in fiber type from slow-oxidative to fast-glycolytic. This change did not amount to a detectable difference in muscle power production and kinetics. However, overall poor performance at cold temperatures could force these fishes into torpor to overwinter. Tautog, alternatively, retained myosin heavy chains, which likely increases locomotor capabilities when making short migrations to overwintering habitats.