Migratory flight imposes oxidative stress in bats

Many animal species migrate over long distances, but the physiological challenges of migration are poorly understood. It has recently been suggested that increased molecular oxidative damage might be one important challenge for migratory animals. We tested the hypothesis that autumn migration imposes an oxidative challenge to bats by comparing values of 4 blood-based markers of oxidative status (oxidative damage and both enzymatic and nonenzymatic antioxidants) between Nathusius’ bats Pipistrellus nathusii that were caught during migration flights with those measured in conspecifics after resting for 18 or 24 h. Experiments were carried out at Pape Ornithological Station in Pape (Latvia) in 2016 and 2017. Our results show that flying bats have a blood oxidative status different from that of resting bats due to higher oxidative damage and different expression of both nonenzymatic and enzymatic antioxidants (glutathione peroxidase). The differences in oxidative status markers varied between sampling years and were independent from individual body condition or sex. Our work provides evidence that migratory flight might impose acute oxidative stress to bats and that resting helps animals to recover from oxidative damage accrued en route. Our data suggest that migrating bats and birds might share similar strategies of mitigating and recovering from oxidative stress

Bidirectional movements of Nathusius’ pipistrelle bats (Pipistrellus nathusii) during autumn at a major migration corridor

Migration is well documented for many species throughout the animal kingdom. Although migration is also a common behaviour in bats, it is rarely studied due to the cryptic nature of the phenomenon. Recoveries of banded individuals have shown that Nathusius' pipistrelles (Pipistrellus nathusii) can fly more than 2000 km between their summer and winter ranges in Europe, but further details of how and where they move between the endpoints of their seasonal journeys remain elusive. Here, we used three-dimensional acoustic tracking at a coastal migration corridor to elucidate the flight behaviour of Nathusius' pipistrelles during late summer. Analyzing 432 recorded flight trajectories, we show that the majority of bats followed the expected southerly direction, parallel to the coastline, on all nights, and flying at the optimal speed for long-distance travel with minimal energy expenditure. However, on one day with stronger winds, about 20 % of the bats flew in the opposite, i.e. northerly, direction. The observation of a proportion of individuals flying antiparallel to the mass of migrating conspecifics within the same movement corridor highlights that individuals may follow contrasting movement strategies at the same time and place, presumably depending on environmental conditions. We argue that it is possible for Nathusius’ pipistrelles to fly back and forth (south and north) during autumn migration, spending more time on this migration corridor than required for a straight one-way flight. This highlights the urgent need to protect migration corridors along coastlines, particularly as wind energy development continues

The immune response of bats differs between pre-migration and migration seasons

Maintaining a competent immune system is energetically costly and thus immunity may be traded against other costly traits such as seasonal migration. Here, we tested in long-distance migratory Nathusius' pipistrelles (Pipistrellus nathusii), if selected branches of immunity are expressed differently in response to the energy demands and oxidative stress of aerial migration. During the migration period, we observed higher baseline lymphocyte and lower neutrophil levels than during the pre-migration period, but no stronger response of cellular effectors to an antigen challenge. Baseline plasma haptoglobin, as a component of the humoral innate immunity, remained similar during both seasons, yet baseline plasma haptoglobin levels increased by a factor of 7.8 in migratory bats during an immune challenge, whereas they did not change during the pre-migration period. Oxidative stress was higher during migration than during pre-migration, yet there was no association between blood oxidative status and immune parameters, and immune challenge did not trigger any changes in oxidative stress, irrespective of season. Our findings suggest that humoral effectors of the acute phase response may play a stronger role in the first-line defense against infections for migrating bats compared to non-migrating bats. We conclude that Nathusius' pipistrelles allocate resources differently into the branches of their immune system, most likely following current demands resulting from tight energy budgets during migration

Why do physicians prescribe dialysis? A prospective questionnaire study

Funding Information: This study was supported by an unrestricted grant 14CECPDEU1001 from Baxter Healthcare International. Baxter Novum is the result of a grant from Baxter Healthcare Corporation to Division of Renal Medicine and Baxter Novum, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, to support research activities at Karolinska Institutet to promote the understanding and treatment of renal disease. Bengt Lindholm is employed by Baxter Healthcare Corporation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. This does not alter our adherence to PLOS ONE policies on sharing data and materials. Publisher Copyright: © 2017 Heaf 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. Copyright: Copyright 2018 Elsevier B.V., All rights reserved.Introduction.The incidence of unplanned dialysis initiation (DI) with consequent increased comorbidity, mortality and reduced modality choice remains high, but the optimal timing of dialysis initiation (DI) remains controversial, and there is a lack of studies of specific reasons for DI. We investigated why and when physicians prescribe dialysis and hypothesized that physician motivation for DI is an independent factor which may have clinical consequences. Methods In the Peridialysis study, an ongoing multicenter prospective study assessing the causes and timing of DI and consequences of unplanned dialysis, physicians in 11 hospitals were asked to describe their primary, secondary and further reasons for prescribing DI. The stated reasons for DI were analyzed in relation to clinical and biochemical data at DI, and characteristics of physicians. Results In 446 patients (median age 67 years; 38% females; diabetes 25.6%), DI was prescribed by 84 doctors who stated 23 different primary reasons for DI. The primary indication was clinical in 63% and biochemical in 37%; 23% started for life-threatening conditions. Reduced renal function accounted for only 19% of primary reasons for DI but was a primary or contributing reason in 69%. The eGFR at DI was 7.2 ±3.4 ml/min/1.73 m2, but varied according to comorbidity and cause of DI. Patients with cachexia, anorexia and pulmonary stasis (34% with heart failure) had the highest eGFR (8.2–9.8 ml/min/1.73 m2), and those with edema, “low GFR”, and acidosis, the lowest (4.6–6.1 ml/min/1.73 m2). Patients with multiple comorbidity including diabetes started at a high eGFR (8.7 ml/min/1.73 m2). Physician experience played a role in dialysis prescription. Non-specialists were more likely to prescribe dialysis for life-threatening conditions, while older and more experienced physicians were more likely to start dialysis for clinical reasons, and at a lower eGFR. Female doctors started dialysis at a higher eGFR than males (8.0 vs. 7.1 ml/min/1.73 m2). Conclusions DI was prescribed mainly based on clinical reasons in accordance with current recommendations while low renal function accounted for only 19% of primary reasons for DI. There are considerable differences in physicians´ stated motivations for DI, related to their age, clinical experience and interpretation of biochemical variables. These differences may be an independent factor in the clinical treatment of patients, with consequences for the risk of unplanned DI.publishersversionPeer reviewe

Acute effect of increasing glucocorticoid replacement dose on cardiovascular risk and insulin sensitivity in patients with adrenocorticotrophin deficiency

Context: Higher hydrocortisone doses are associated with increased overall and cardiovascular mortality in ACTH-deficient patients. The mechanisms underlying this association have not been fully defined. Objective: The aim of the study was to determine whether increasing hydrocortisone (or equivalent) to 30 mg/d in ACTH-deficient patients increased cardiovascular risk and whether a reduction in insulin sensitivity and attenuation of insulin’s hemodynamic effects was responsible for this effect. Design: We conducted an open interventional study between 2011 and 2013. Setting: The study was performed in the Endocrine Research Unit, Repatriation General Hospital, Adelaide, Australia. Patients: Seventeen ACTH-deficient subjects taking hydrocortisone (≤ 20 mg/d) for at least 6 months were studied. Intervention: Subjects were studied before and after a 7-day increase in hydrocortisone to 30 mg/d. Main Outcome Measure: The primary outcome was the change in pulse wave velocity, both fasting and after a 75-g oral glucose load. Results: Fasting and post-glucose load pulse wave velocities were not significantly different on the higher glucocorticoid dose. Fasting augmentation index (24.9 ± 2.7 vs 22.6 ± 2.6%; P=.04) and reactive hyperemia index (2.3 ± 0.2 vs 2.0 ± 0.2; P=0.04) were lower on the higher glucocorticoid dose, with no significant difference in the post-glucose load changes in these variables. There were no significant changes in insulin sensitivity or secretion on the higher glucocorticoid dose. Conclusions: Endothelial dysfunction may contribute to the increased cardiovascular mortality associated with higher glucocorticoid doses. This may be a direct glucocorticoid effect, not mediated by insulin resistance. ACTH-deficient patients should thus be prescribed the lowest safe glucocorticoid replacement dose.Carolyn J. Petersons, Brenda L. Mangelsdorf, Campbell H. Thompson, and Morton G. Bur