Lung Protective Ventilation (ARDSNet) versus APRV: Ventilatory Management in a Combined Model of Acute Lung and Brain Injury

BACKGROUND: Concomitant lung/brain traumatic injury, results in significant morbidity and mortality. Lung protective ventilation (ARDSNet) has become the standard for managing acute respiratory distress syndrome (ARDS); however, the resulting permissive hypercapnea may compound traumatic brain injury (TBI). Airway pressure release ventilation (APRV) offers an alternative strategy for management of this patient population. APRV was hypothesized to retard the progression of acute lung/brain injury to a greater degree than ARDSNet in a swine model. METHODS: Yorkshire swine were randomized to ARDSNet, APRV, or sham. Ventilatory settings and pulmonary parameters, vitals, blood gases, quantitative histopathology, and cerebral microdialysis were compared between groups using chi-square, Fisher’s exact, Student’s t-test, Wilcoxon rank-sum, and mixed effects repeated measures modeling. RESULTS: 22 swine (17 male, 5 female), weighing 25±6.0kg, were randomized to APRV (n=9), ARDSNet (n=12), or sham (n=1). PaO(2)/FiO(2) (P/F) ratio dropped significantly while intracranial pressure increased significantly for all three groups immediately following lung and brain injury. Over time, peak inspiratory pressure, mean airway pressure, and P/F ratio significantly increased, while total respiratory rate significantly decreased within the APRV group compared to the ARDSNet group. Histopathology did not show significant differences between groups in overall brain or lung tissue injury; however, cerebral microdialysis trends suggested increased ischemia within the APRV group compared to ARDSNet over time. CONCLUSION: Previous studies have not evaluated the effects of APRV in this population. While our macroscopic parameters and histopathology did not observe a significant difference between groups, microdialysis data suggest a trend toward increased cerebral ischemia associated with APRV over time. Additional and future studies should focus on extending the time interval for observation to further delineate differences between groups. LEVEL OF EVIDENCE: II STUDY TYPE: Therapeuti

Disease and the Extended Phenotype: Parasites Control Host Performance and Survival through Induced Changes in Body Plan

BACKGROUND: By definition, parasites harm their hosts. However, some forms of parasite-induced alterations increase parasite transmission between hosts, such that manipulated hosts can be considered extensions of the parasite's phenotype. While well accepted in principle, surprisingly few studies have quantified how parasite manipulations alter host performance and survival under field and laboratory conditions. METHODOLOGY/PRINCIPAL FINDINGS: By interfering with limb development, the trematode Ribeiroia ondatrae causes particularly severe morphological alterations within amphibian hosts that provide an ideal system to evaluate parasite-induced changes in phenotype. Here, we coupled laboratory performance trials with a capture-mark-recapture study of 1388 Pacific chorus frogs (Pseudacris regilla) to quantify the effects of parasite-induced malformations on host locomotion, foraging, and survival. Malformations, which affected ~50% of metamorphosing frogs in nature, caused dramatic reductions in all measures of organismal function. Malformed frogs exhibited significantly shorter jumping distances (41% reduction), slower swimming speeds (37% reduction), reduced endurance (66% reduction), and lower foraging success relative to infected hosts without malformations. Furthermore, while normal and malformed individuals had comparable survival within predator-free exclosures, deformed frogs in natural populations had 22% lower biweekly survival than normal frogs and rarely recruited to the adult population over a two-year period. CONCLUSIONS/SIGNIFICANCE: Our results highlight the ability of parasites to deeply alter multiple dimensions of host phenotype with important consequences for performance and survival. These patterns were best explained by malformation status, rather than infection per se, helping to decouple the direct and indirect effects of parasitism on host fitness.Brett A. Goodman and Pieter T. J. Johnso

A many-analysts approach to the relation between religiosity and well-being

The relation between religiosity and well-being is one of the most researched topics in the psychology of religion, yet the directionality and robustness of the effect remains debated. Here, we adopted a many-analysts approach to assess the robustness of this relation based on a new cross-cultural dataset (N=10,535 participants from 24 countries). We recruited 120 analysis teams to investigate (1) whether religious people self-report higher well-being, and (2) whether the relation between religiosity and self-reported well-being depends on perceived cultural norms of religion (i.e., whether it is considered normal and desirable to be religious in a given country). In a two-stage procedure, the teams first created an analysis plan and then executed their planned analysis on the data. For the first research question, all but 3 teams reported positive effect sizes with credible/confidence intervals excluding zero (median reported β=0.120). For the second research question, this was the case for 65% of the teams (median reported β=0.039). While most teams applied (multilevel) linear regression models, there was considerable variability in the choice of items used to construct the independent variables, the dependent variable, and the included covariates

A Many-analysts Approach to the Relation Between Religiosity and Well-being

The relation between religiosity and well-being is one of the most researched topics in the psychology of religion, yet the directionality and robustness of the effect remains debated. Here, we adopted a many-analysts approach to assess the robustness of this relation based on a new cross-cultural dataset (N = 10, 535 participants from 24 countries). We recruited 120 analysis teams to investigate (1) whether religious people self-report higher well-being, and (2) whether the relation between religiosity and self-reported well-being depends on perceived cultural norms of religion (i.e., whether it is considered normal and desirable to be religious in a given country). In a two-stage procedure, the teams first created an analysis plan and then executed their planned analysis on the data. For the first research question, all but 3 teams reported positive effect sizes with credible/confidence intervals excluding zero (median reported β = 0.120). For the second research question, this was the case for 65% of the teams (median reported β = 0.039). While most teams applied (multilevel) linear regression models, there was considerable variability in the choice of items used to construct the independent variables, the dependent variable, and the included covariates

Selective Photochemical Oxidation of Reduced Dissolved Organic Sulfur to Inorganic Sulfate.

The chemical nature and stability of reduced dissolved organic sulfur (DOSRed) have implications on the biogeochemical cycling of trace and major elements across fresh and marine aquatic environments, but the underlying processes governing DOSRed stability remain obscure. Here, dissolved organic matter (DOM) was isolated from a sulfidic wetland, and laboratory experiments quantified dark and photochemical oxidation of DOSRed using atomic-level measurement of sulfur X-ray absorption near-edge structure (XANES) spectroscopy. DOSRed was completely resistant to oxidation by molecular oxygen in the dark and underwent rapid and quantitative oxidation to inorganic sulfate (SO42-) in the presence of sunlight. The rate of DOSRed oxidation to SO42- greatly exceeded that of DOM photomineralization, resulting in a 50% loss of total DOS and 78% loss of DOSRed over 192 h of irradiance. Sulfonates (DOSSO3) and other minor oxidized DOS functionalities were not susceptible to photochemical oxidation. The observed susceptibility of DOSRed to photodesulfurization, which has implications on carbon, sulfur, and mercury cycling, should be comprehensively evaluated across diverse aquatic environments of differing DOM composition

Permafrost Hydrology Drives the Assimilation of Old Carbon by Stream Food Webs in the Arctic

Permafrost thaw in the Arctic is mobilizing old carbon (C) from soils to aquatic ecosystems and the atmosphere. Little is known, however, about the assimilation of old C by aquatic food webs in Arctic watersheds. Here, we used C isotopes (d13C, D14C) to quantify C assimilation by biota across 12 streams in arctic Alaska. Streams spanned watersheds with varying permafrost hydrology, from ice-poor bedrock to ice-rich loess (that is, yedoma). We measured isotopic content of (1) C sources including dissolved organic C (DOC), dissolved inorganic C (DIC), and soil C, and (2) stream biota, including benthic biofilm and macroinvertebrates, and resident fish species (Arctic Grayling (Thymallus arcticus) and Dolly Varden (Salvelinus malma)). Findings document the assimilation of old C by stream biota, with depleted D14C values observed at multiple trophic levels, including benthic biofilm (14C ages = 5255 to 265 years before present (y BP)), macroinverte- brates (4490 y BP to modern), and fish (3195 y BP to modern). Mixing model results indicate that DOC and DIC contribute to benthic biofilm composition, with relative contributions differing across streams draining ice-poor and ice-rich terrain. DOC originates primarily from old terrestrial C sources, including deep peat horizons (39–47%; 530 y BP) and near-surface permafrost (12–19%; 5490 y BP). DOC also accounts for approximately half of fish isotopic composition. Analyses suggest that as the contribution of old C to fish increases, fish growth and nutritional status decline. We anticipate increases in old DOC delivery to streams under projected warming, which may further alter food web function in Arctic watersheds

Effects of Iron on Optical Properties of Dissolved Organic Matter

Iron is a source of interference in the spectroscopic analysis of dissolved organic matter (DOM); however, its effects on commonly employed ultraviolet and visible (UV–vis) light adsorption and fluorescence measurements are poorly defined. Here, we describe the effects of iron­(II) and iron­(III) on the UV–vis absorption and fluorescence of solutions containing two DOM fractions and two surface water samples. In each case, regardless of DOM composition, UV–vis absorption increased linearly with increasing iron­(III). Correction factors were derived using iron­(III) absorption coefficients determined at wavelengths commonly used to characterize DOM. Iron­(III) addition increased specific UV absorbances (SUVA) and decreased the absorption ratios (<i>E</i>₂:<i>E</i>₃) and spectral slope ratios (<i>S</i>_R) of DOM samples. Both iron­(II) and iron­(III) quenched DOM fluorescence at pH 6.7. The degree and region of fluorescence quenching varied with the iron:DOC concentration ratio, DOM composition, and pH. Regions of the fluorescence spectra associated with greater DOM conjugation were more susceptible to iron quenching, and DOM fluorescence indices were sensitive to the presence of both forms of iron. Analyses of the excitation–emission matrices using a 7- and 13-component parallel factor analysis (PARAFAC) model showed low PARAFAC sensitivity to iron addition

Seasonal Dynamics and Interannual Variability in Mercury Concentrations and Loads through a Three-Reservoir Complex.

The Hells Canyon Complex (HCC) along the Snake River (Idaho-Oregon border, U.S.A.) encompasses three successive reservoirs that seasonally stratify, creating anoxic conditions in the hypolimnion that promote methylmercury (MeHg) production. This study quantified seasonal dynamics and interannual variability in mercury concentrations (inorganic divalent mercury (IHg) and MeHg) and loads at four reservoir inflow and outflow locations through the HCC (2014-2017). We observed (1) that the HCC is a net sink for both IHg and MeHg, (2) interannual variability in IHg and MeHg loads largely reflecting streamflow conditions, and (3) seasonal variability in particulate IHg loading at the inflow (greatest from February to April) and MeHg export from the outflow (greatest from September to December) of the HCC. Seasonal export of MeHg was evidenced by increases in monthly mean concentrations of unfiltered MeHg (approximately 2-fold) and the percentage of total mercury (THg) as MeHg (≥4-fold) coincident with reservoir destratification. Despite evidence of seasonal export of MeHg from the HCC, annual loads indicate a 42% decrease in unfiltered MeHg from HCC inflow to outflow. Results from this study improve the understanding of seasonal variability in mercury transport through and transformation within a reservoir complex

Permafrost Hydrology Drives the Assimilation of Old Carbon by Stream Food Webs in the Arctic

Permafrost thaw in the Arctic is mobilizing old carbon (C) from soils to aquatic ecosystems and the atmosphere. Little is known, however, about the assimilation of old C by aquatic food webs in Arctic watersheds. Here, we used C isotopes (d13C, D14C) to quantify C assimilation by biota across 12 streams in arctic Alaska. Streams spanned watersheds with varying permafrost hydrology, from ice-poor bedrock to ice-rich loess (that is, yedoma). We measured isotopic content of (1) C sources including dissolved organic C (DOC), dissolved inorganic C (DIC), and soil C, and (2) stream biota, including benthic biofilm and macroinvertebrates, and resident fish species (Arctic Grayling (Thymallus arcticus) and Dolly Varden (Salvelinus malma)). Findings document the assimilation of old C by stream biota, with depleted D14C values observed at multiple trophic levels, including benthic biofilm (14C ages = 5255 to 265 years before present (y BP)), macroinverte- brates (4490 y BP to modern), and fish (3195 y BP to modern). Mixing model results indicate that DOC and DIC contribute to benthic biofilm composition, with relative contributions differing across streams draining ice-poor and ice-rich terrain. DOC originates primarily from old terrestrial C sources, including deep peat horizons (39–47%; 530 y BP) and near-surface permafrost (12–19%; 5490 y BP). DOC also accounts for approximately half of fish isotopic composition. Analyses suggest that as the contribution of old C to fish increases, fish growth and nutritional status decline. We anticipate increases in old DOC delivery to streams under projected warming, which may further alter food web function in Arctic watersheds