Aerobic interval training partly reverse contractile dysfunction and impaired Ca2+ handling in atrial myocytes from rats with post infarction heart failure

Background: There is limited knowledge about atrial myocyte Ca2+ handling in the failing hearts. The aim of this study was to examine atrial myocyte contractile function and Ca2+ handling in rats with post-infarction heart failure (HF) and to examine whether aerobic interval training could reverse a potential dysfunction. Methods and results: Post-infarction HF was induced in Sprague Dawley rats by ligation of the left descending coronary artery. Atrial myocyte shortening was depressed (p<0.01) and time to relaxation was prolonged (p<0.01) in sedentary HF-rats compared to healthy controls. This was associated with decreased Ca2+ amplitude, decreased SR Ca2+ content, and slower Ca2+ transient decay. Atrial myocytes from HF-rats had reduced sarcoplasmic reticulum Ca2+ ATPase activity, increased Na+/Ca2+-exchanger activity and increased diastolic Ca2+ leak through ryanodine receptors. High intensity aerobic interval training in HF-rats restored atrial myocyte contractile function and reversed changes in atrial Ca2+ handling in HF. Conclusion: Post infarction HF in rats causes profound impairment in atrial myocyte contractile function and Ca2+ handling. The observed dysfunction in atrial myocytes was partly reversed after aerobic interval training.© 2013 Johnsen et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Early ontogeny of the lesser sandeel (Ammodytes marinus)

Background Lesser sandeel (Ammodytes marinus) is widely distributed in North Sea ecosystems. Sandeel acts as a critical trophic link between zooplankton and top predators (fish, mammals, sea birds). Because they live buried in the sand, sandeel may be directly affected by the rapid expansion of anthropogenic activities linked to their habitat on the sea bottom (e.g., hydrocarbon extraction, offshore renewable energy, and subsea mining). It is, therefore, important to understand the impact of cumulative environmental and anthropogenic stressors on this species. A detailed description of the ontogenetic timeline and developmental staging for this species is lacking limiting the possibilities for comparative developmental studies assessing, e.g., the impact of various environmental stressors. Results A detailed description of the morphological development of lesser sandeel and their developmental trajectory, obtained through visual observations and microscopic techniques, is presented. Methods for gamete stripping and intensive culture of the early life stages are also provided. Conclusion This work provides a basis for future research to understand the effect of cumulative environmental and anthropogenic stressors on development in the early life stages of lesser sandeel.publishedVersio

Atrial Myocyte Function and Ca2+ Handling Is Associated with Inborn Aerobic Capacity

Background: Although high aerobic capacity is associated with effective cardiac function, the effect of aerobic capacity on atrial function, especially in terms of cellular mechanisms, is not known. We aimed to investigate whether rats with low inborn maximal oxygen uptake (VO2 max) had impaired atrial myocyte contractile function when compared to rats with high inborn VO2 max. Methods and Results: Atrial myocyte function was depressed in Low Capacity Runners (LCR) relative to High Capacity Runners (HCR) which was associated with impaired Ca2+ handling. Fractional shortening was 52% lower at 2 Hz and 60% lower at 5 Hz stimulation while time to 50% relengthening was 43% prolonged and 55% prolonged, respectively. Differences in Ca2+ amplitude and diastolic Ca2+ level were observed at 5 Hz stimulation where Ca2+ amplitude was 70% lower and diastolic Ca2+ level was 11% higher in LCR rats. Prolonged time to 50% Ca2+ decay was associated with reduced sarcoplasmic reticulum (SR) Ca2+ ATPase function in LCR (39%). Na+/Ca2+ exchanger activity was comparable between the groups. Diastolic SR Ca2+ leak was increased by 109%. This could be partly explained by increased ryanodine receptors phosphorylation at the Ca2+-calmodulin-dependent protein kinase-II specific Ser-2814 site in LCR rats. T-tubules were present in 68% of HCR cells whereas only 33% LCR cells had these structures. In HCR, the significantly higher numbers of cells with T-tubules were combined with greater numbers of myocytes where Ca2+ release in the cell occurred simultaneously in central and peripheral regions, giving rise to faster and more spatial homogenous Ca2+-signal onset. Conclusion: This data demonstrates that contrasting for low or high aerobic capacity leads to diverse functional and structural remodelling of atrial myocytes, with impaired contractile function in LCR compared to HCR rats.© 2013 Johnsen et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Aerobic interval training partly reverse contractile dysfunction and impaired Ca2+ handling in atrial myocytes from rats with post infarction heart failure.

BACKGROUND: There is limited knowledge about atrial myocyte Ca(2+) handling in the failing hearts. The aim of this study was to examine atrial myocyte contractile function and Ca(2+) handling in rats with post-infarction heart failure (HF) and to examine whether aerobic interval training could reverse a potential dysfunction. METHODS AND RESULTS: Post-infarction HF was induced in Sprague Dawley rats by ligation of the left descending coronary artery. Atrial myocyte shortening was depressed (p<0.01) and time to relaxation was prolonged (p<0.01) in sedentary HF-rats compared to healthy controls. This was associated with decreased Ca(2+) amplitude, decreased SR Ca(2+) content, and slower Ca(2+) transient decay. Atrial myocytes from HF-rats had reduced sarcoplasmic reticulum Ca(2+) ATPase activity, increased Na(+)/Ca(2+)-exchanger activity and increased diastolic Ca(2+) leak through ryanodine receptors. High intensity aerobic interval training in HF-rats restored atrial myocyte contractile function and reversed changes in atrial Ca(2+) handling in HF. CONCLUSION: Post infarction HF in rats causes profound impairment in atrial myocyte contractile function and Ca(2+) handling. The observed dysfunction in atrial myocytes was partly reversed after aerobic interval training

Comparison of left versus right atrial myocardium in patients with sinus rhythm or atrial fibrillation - an assessment of mitochondrial function and microRNA expression.

Several of the cellular alterations involved in atrial fibrillation (AF) may be linked to mitochondrial function and altered microRNA (miR) expression. A majority of studies on human myocardium involve right atrial (RA) tissue only. There are indications that AF may affect the two atria differentially. This study aimed to compare interatrial differences in mitochondrial respiration and miR expression in the RA versus left atrium (LA) within patients with sinus rhythm (SR) and AF. Thirty-seven patients with AF (n = 21) or SR (n = 16), undergoing coronary artery bypass surgery and/or heart valve surgery, were included. Myocardial biopsies were obtained from RA and LA appendages. Mitochondrial respiration was assessed in situ in permeabilized myocardium. MiR array and real-time quantitative polymerase chain reaction were performed to evaluate miR expression. Mitochondrial respiratory rates were similar in RA versus LA. Expression of miR-100, -10b, -133a, -133b, -146a, -155, -199a-5p, -208b, and -30b were different between the atria in both SR and AF patients. In contrast, differential expression was observed between RA versus LA for miR-93 in patients with SR only, and for miR-1, -125b, -142-5p, -208a, and -92b within AF patients only. These results indicate that mitochondrial respiratory capacity is similar in the RA and LA of patients with SR and AF. Differences in miR expressional profiles are observed between the RA versus LA in both SR and AF, and several interatrial differences in miR expression diverge between SR and AF. These findings may contribute to the understanding of how AF pathophysiology may affect the two atria differently

Representative sample traces of cardiomyocyte fractional shortening (A) and Fura-2 ratio (D) from sham, HF-inactive and HF-trained rats.

<p>Averaged data of myocyte fractional shortening (B), time to 50% diastolic relaxation (C), Ca²⁺ amplitude (E), SR Ca²⁺ content (F), time to 50% Ca²⁺ decay (G) and diastolic Ca²⁺ (H). All averaged data presented as mean values ± SD. * <i>p<0.05</i> versus sham sedentary, <i># p<0.001</i> versus sham sedentary.</p

Averaged data of rates of decay of the twitch- and Caffeine induced Ca²⁺ transient indicating the SERCA2a function (A) and NCX function (B).

<p>All data presented as mean values ± SD. * <i>p<0.05</i> versus sham sedentary, <i># p<0.001</i> versus sham sedentary.</p

Illustration of the SR Ca²⁺ leak protocol (A), mean data of SR Ca²⁺ leak normalized to SR Ca²⁺ content (B), and mean data of SR Ca²⁺ leak after CaMKII inhibition (AIP) (C) and PKA inhibition (H89) (D).

<p>* <i>p<0.05</i> versus sham sedentary, <i># p<0.001</i> versus sham sedentary.</p

Magnetic fields generated by the DC cables of offshore wind farms have no effect on spatial distribution or swimming behavior of lesser sandeel larvae (Ammodytes marinus)

In the North Sea, the number and size of offshore wind (OW) turbines, together with the associated network of High Voltage Direct Current (HVDC) subsea cables, will increase rapidly over the coming years. HVDC cables produce magnetic fields (MFs) that might have an impact on marine animals that encounter them. One of the fish species that is at risk of exposure to MF associated with OW is the lesser sandeel (Ammodytes marinus), a keystone species of the North Sea basin. Lesser sandeel could be exposed to MF as larvae, when they drift in proximity of OW turbines. Whether MFs impact the behavior of lesser sandeel larvae, with possible downstream effects on their dispersal and survival, is unknown. We tested the behavior of 56 lesser sandeel larvae, using a setup designed to simulate the scenario of larvae drifting past a DC cable. We exposed the larvae to a MF intensity gradient (150-50 μT) that is within the range of MFs produced by HVDC subsea cables. Exposure to the MF gradient did not affect the spatial distribution of lesser sandeel larvae in a raceway tank 50 cm long, 7 cm wide and 3.5 cm deep. Nor did the MF alter their swimming speed, acceleration or distance moved. These results show that static MF from DC cables would not impact behavior of lesser sandeel larvae during the larval period of their life although it does not exclude the possibility that later life stages could be affected.publishedVersio