Data were compiled from the literature on the critical oxygen level (Pcrit), a hypoxia-tolerance trait, comprising 96 studies covering 151 fish species from 58 families. Salinity, temperature, body mass, and routine metabolic rate were highly correlated with Pcrit. The effects of temperature, CO2, acidification, metals and feeding are also assessed.

Background: Concussion is the most common type of TBI, yet reliable objective measures related to these injuries and associated recovery processes remain elusive, especially in military personnel. The purpose of this study was to characterize the relationship between cytokines and recovery from acute brain injury in active duty service members. Inflammatory cytokines (IL-6, IL-10, and TNFα) were measured acutely in blood samples within 8 h following a medically diagnosed concussion and then 24 h later. Methods: Participants (n = 94) were categorized into two groups: 1) military personnel who sustained providerdiagnosed concussion, without other major medical diagnosis (n = 45) and 2) healthy control participants in the same deployment environment who did not sustain concussion or other illness or injuries (n = 49). IL-6, IL-10, and TNFα concentrations were measured using an ultrasensitive single-molecule enzyme-linked immunosorbent assay. Differences in cytokine levels between concussed and healthy groups were evaluated at two time points (time point 1 ≤ 8 h after injury; time point 2 = 24 h following time point 1). Results: At time point 1, IL-6 median (IQR) concentrations were 2.62 (3.62) in the concussed group, which was greater compared to IL-6 in the healthy control group (1.03 (0.90); U = 420.00, z = − 5.12, p < 0.001). Compared to healthy controls, the concussed group did not differ at time point 1 in IL-10 or TNFα concentrations (p's > 0.05). At time point 2, no differences were detected between concussed and healthy controls for IL-6, IL-10, or TNFα (p's > 0.05). The median difference between time points 1 and 2 were compared between the concussed and healthy control groups for IL-6, IL-10, and TNFα. Change in IL-6 across time was greater for the concussed group than healthy control (− 1.54 (3.12); U = 315.00, z = − 5.96, p < 0.001), with no differences between groups in the change of IL-10 or TNFα (p's > 0.05). Conclusion: Reported here is a significant elevation of IL-6 levels in concussed military personnel less than 8 h following injury. Future studies may examine acute and chronic neurological symptomology associated with inflammatory cytokine levels, distinguish individuals at high risk for developing neurological complications, and identify underlying biological pathways to mitigate inflammation and improve outcomes.

HighlightsExposure to hypoxia resulted in acclimation by G. aculeateus, demonstrated by a reduction of their critical oxygen level.In the presence of copper, the capacity to reduce the critical oxygen tension following hypoxia was prevented.Combined exposure of copper and hypoxia resulted in an increase expression of mt1 and hif1α transcription.