Increased reliance on coronary perfusion for cardiorespiratory performance in seawater-acclimated rainbow trout

Salmonid ventricles are composed of spongy and compact myocardium, the latter being perfused via a coronary circulation. Rainbow trout (Oncorhynchus mykiss) acclimated to sea water have higher proportions of compact myocardium and display stroke volume-mediated elevations in resting cardiac output relative to freshwater-acclimated trout, probably to meet the higher metabolic needs of osmoregulatory functions. Here, we tested the hypothesis that cardiorespiratory performance of rainbow trout in sea water is more dependent on coronary perfusion by assessing the effects of coronary ligation on cardiorespiratory function in resting and exhaustively exercised trout acclimated to fresh water or sea water. While ligation only had minor effects on resting cardiorespiratory function across salinities, cardiac function after chasing to exhaustion was impaired, presumably as a consequence of atrioventricular block. Ligation reduced maximum O2 consumption rate by 33% and 17% in fish acclimated to sea water and fresh water, respectively, which caused corresponding 41% and 17% reductions in aerobic scope. This was partly explained by different effects on cardiac performance, as maximum stroke volume was only significantly impaired by ligation in sea water, resulting in 38% lower maximum cardiac output in seawater compared with 28% in fresh water. The more pronounced effect on respiratory performance in sea water was presumably also explained by lower blood O2 carrying capacity, with ligated seawater-acclimated trout having 16% and 17% lower haemoglobin concentration and haematocrit, respectively, relative to ligated freshwater trout. In conclusion, we show that the coronary circulation allows seawater-acclimated trout to maintain aerobic scope at a level comparable to that in fresh water

Dissecting the Shared Genetic Architecture of Suicide Attempt, Psychiatric Disorders, and Known Risk Factors

Background Suicide is a leading cause of death worldwide, and nonfatal suicide attempts, which occur far more frequently, are a major source of disability and social and economic burden. Both have substantial genetic etiology, which is partially shared and partially distinct from that of related psychiatric disorders. Methods We conducted a genome-wide association study (GWAS) of 29,782 suicide attempt (SA) cases and 519,961 controls in the International Suicide Genetics Consortium (ISGC). The GWAS of SA was conditioned on psychiatric disorders using GWAS summary statistics via multitrait-based conditional and joint analysis, to remove genetic effects on SA mediated by psychiatric disorders. We investigated the shared and divergent genetic architectures of SA, psychiatric disorders, and other known risk factors. Results Two loci reached genome-wide significance for SA: the major histocompatibility complex and an intergenic locus on chromosome 7, the latter of which remained associated with SA after conditioning on psychiatric disorders and replicated in an independent cohort from the Million Veteran Program. This locus has been implicated in risk-taking behavior, smoking, and insomnia. SA showed strong genetic correlation with psychiatric disorders, particularly major depression, and also with smoking, pain, risk-taking behavior, sleep disturbances, lower educational attainment, reproductive traits, lower socioeconomic status, and poorer general health. After conditioning on psychiatric disorders, the genetic correlations between SA and psychiatric disorders decreased, whereas those with nonpsychiatric traits remained largely unchanged. Conclusions Our results identify a risk locus that contributes more strongly to SA than other phenotypes and suggest a shared underlying biology between SA and known risk factors that is not mediated by psychiatric disorders.Peer reviewe

The impact of aerobic fitness on functioning in chronic back pain

Despite lack of convincing evidence that reduced aerobic fitness is associated with chronic back pain (CBP), exercise programs are regarded as being effective for persons with non-specific CBP. It is unsure whether gain in aerobic fitness following intervention is associated with functioning improvement in persons with CBP. The objective of this prospective cohort study was to study the impact of aerobic fitness on functioning in persons with CBP, at baseline and following 3-week intensive interdisciplinary intervention. This study included persons who had passed 8 weeks of sick-listing because of back pain (n = 94) and were referred to a 3-week intensive biopsychosocial rehabilitation program. Aerobic fitness was assessed with a sub-maximal bicycle test at baseline, at admission to and discharge from the rehabilitation program, and at 6 months follow-up. Contextual factors, body function, activity and participation were evaluated before and after intervention. In addition, working ability was recorded at 3-years follow-up. At baseline aerobic fitness was reduced in most subjects, but improved significantly following intervention. Baseline measurements and intervention effects did not differ among the diagnostic sub-groups. Neither contextual factors nor functioning at baseline were associated with aerobic fitness. Increase in aerobic fitness was not associated with improvements in functioning and contextual factors and work-return following intervention either. From this study we conclude that improvement of aerobic fitness seems of limited value as goal of treatment outcome for patients with CBP