Physiological Sensitivity Research Articles

Thermoregulatory strategies of songbird nestlings reveal limited capacity for cooling and high risk of dehydration

How the accelerating pace of global warming will affect animal populations depends on the effects of increasing temperature across the life cycle. Developing young are sensitive to environmental challenges, often with life-long consequences, but the risks of climate warming during this period are insufficiently understood. This may be due to limited insight into physiological sensitivity and the temperatures that represent a thermal challenge for young. Here we examined the physiological and behavioural effects of increasing temperatures by measuring metabolic rate, water loss, and heat dissipation behaviours between 25–45 °C in nestlings of a small free-living songbird of temperate SE-Australia, the superb fairy-wren. We found a high and relatively narrow thermoneutral zone from 33.1 to 42.3 °C, with metabolic rate increasing and all nestlings panting above this range. Evaporative water loss sharply increased above 33.5 °C; at the same temperature, nestlings changed their posture (extended their wings) to facilitate passive heat loss. However, at all temperatures measured, water loss was insufficient to dissipate metabolically produced heat, indicating poor cooling capabilities, which persisted even when individuals were panting. While nestlings are relatively tolerant to higher temperatures, with no evidence for hyperthermia at temperatures below 42 °C, they are at a high risk of dehydration even at lower temperatures, with limited ability to mitigate this. Thus, climate warming is likely to elevate the risk dehydration, which is concerning, since it is accompanied by drier conditions.

Patchy and Pink: Dynamics of a Chlainomonas sp. (Chlamydomonadales, chlorophyta) algal bloom on Bagley Lake, North Cascades, WA.

Snow algal blooms frequently occur throughout alpine and polar environments during spring and summer months; however, our understanding of bloom dynamics is limited. We tracked a recurrent bloom of Chlainomonas sp. on Upper Bagley Lake in the North Cascade Mountains, USA, to assess the spatiotemporal dynamics in bloom color intensity, community photophysiology, and community composition over eight weeks. We found that the algae biomass had a dynamic patchy distribution over space and time, which was decoupled from changes in community composition and life-cycle progress averaged across the bloom. The proportional representation of Chlainomonas sp. remained consistent throughout the study while the overall community composition shows a progression through the bloom. We found that community photophysiology, measured by the maximum quantum yield of PSII (Fv/Fm), decreased on average throughout the bloom. These findings suggest that the Chlainomonas sp. community on Bagley Lake is not simply an algal bloom with rapid increase in biomass followed by a population crash, as is often seen in aquatic systems, though there is a physiological trajectory and sensitivity to environmental stress. These results contribute to our understanding of the biology of Chlainomonas sp. and its response to environmental stress, specifically an extreme warming event.

Integrative ecotoxicity evaluation of Cd, Cu, Zn and Ni in aquatic animals reveals high tolerance of Artemia franciscana

Heavy metals pose a significant threat to animals in aquatic environments due to the adverse effects they exert. Species of the genus Artemia have been described as heavy metal tolerant, but the sensitivity/tolerance range for these species has not been established. In the present study, the toxicity of Cd, Cu, Zn and Ni as reported in the ECOTOX and Web of Science databases was examined for Artemia franciscana and compared with other species and taxonomic groups using an integrative ecotoxicity evaluation. The hazard concentration for 5% of the species (HC5) of acute toxicity tests (24–96 h), obtained through a species sensitivity distribution (SSD) indicated that Cu (0.02 mg/L) and Cd (0.03 mg/L) were the metals with the highest toxicity to aquatic animals followed by Zn (0.15 mg/L) and Ni (0.23 mg/L). In addition to the higher hazard of Cu and Cd to aquatic animals, the comparison of acute LC50 values for A. franciscana indicates lower toxicity of Cd followed by Cu, Zn, and Ni (200.0, 14.5, 9.5, and 0.6 mg/L, respectively). Using the SSD and physiological sensitivity (S) approaches, it was demonstrated that A. franciscana is relatively tolerant to Cd (SSD= HC99; S = 2.21), Cu (SSD= HC97; S = 2.00), Zn (SSD= HC90; S = 1.29) and Ni (SSD= HC83; S = 0.96) compared with other species and taxonomic groups. It appears that tolerance to the metals Cd, Cu, Zn and Ni is unique to the family Artemiidae within the order Anostraca, as the families Streptocephalidae and Thamnocephalidae are not tolerant (have negative S values). Our study confirmed that as expected, A. franciscana presents higher tolerance to Cd, Cu, Zn, and Ni than other aquatic animals. Our findings confirm that A. franciscana can be used as a model organism to understand mechanisms involved in tolerance to heavy metals, mainly Cd and Cu, which are considered highly toxic to other animals.

Bioaccumulation of pharmaceuticals and personal care products (PPCPs) in freshwater pearl mussels Hyriopsis cumingii in Poyang Lake

Thirty-five PPCPs were measured in representative freshwater pearl mussels (Hyriopsis cumingii) in Poyang Lake, the largest lake of China, as well as their responses to sedimentary PPCPs. We observed 32 PPCPs in soft tissues of mussels at a total concentration of 2721.5 ± 929.3 ng·g−1 dry weight (dw), much higher than those in sediments (21 PPCPs, 273.2 ± 89.4 ng·g−1 dw). Anti-inflammatories were the primary contaminants detected in both sediments and mussels. PPCP concentrations in mussels exhibited significant organ-specific characteristics, and gonads were identified as a hotspot for these contaminants. Correlation analysis showed that gonads were more likely to assimilate triclosan from sediments. Biochemical analysis revealed a higher physiological sensitivity of glutathione synthesis in gonads to sedimentary PPCPs, suggesting the long-term oxidative damage. Our findings highlight the concern on the potential effects of sedimentary PPCPs to propagation of mussels, and emphasize the necessity to formulate strategies for sedimentary PPCPs control targeting a healthy lake.

Body condition and corticosterone stress response, as markers to investigate effects of human activities on Adélie penguins (Pygoscelis adeliae)

IntroductionIn Antarctica, there is growing concern about the potential effect of anthropogenic activities (i.e., tourism, research) on wildlife, especially since human activities are developing at an unprecedented rate. Although guidelines exist to mitigate negative impacts, fundamental data are currently lacking to reliably assess impacts. Physiological tools, such as circulating corticosterone levels, appear promising to assess the potential impact of human disturbance on Antarctic vertebrates.MethodsIn this study, we compared the body condition, and the physiological sensitivity to stress (i.e., basal and stress-induced corticosterone level) of adult and chick Adélie penguins between a disturbed and an undisturbed area (i.e., 2 colonies located in the middle of a research station exposed to intense human activities and 2 colonies located on protected islands with minimal human disturbance).ResultsWe did not find any significant impact of human activities on body condition and corticosterone levels in adults (incubating adults, brooding adults). In chicks, there were significant inter-colony variations in stress-induced corticosterone levels. Specifically, the chicks from the disturbed colonies tended to have higher stress-induced corticosterone levels than the chicks from the protected areas although this difference between areas was not significant. In addition, and independently of human disturbance we also found significant differences in adult body condition, and chick corticosterone level between colonies.DiscussionOverall, our study suggests that this species is not dramatically impacted by human activities, at least when humans and penguins have cohabited for several decades. Our results support therefore the idea that this species is likely to be tolerant to human disturbance and this corroborates with the persistence of Adélie penguin colonies in the middle of the research station. However, our results also suggest that chicks might be more sensitive to human disturbance than adults and might therefore potentially suffer from human disturbance. Our study also suggests that specific individual and environmental variables outweigh the potential minor impact of human disturbance on these variables. Combining corticosterone with complementary stress-related physiological markers, such as heart rate, may strengthen further studies examining whether human disturbance may have subtle detrimental impacts on individuals.

Cardiac sensitivity to rewards in cognitively inflexible nonclinical participants.

In psychopathologies characterized by compulsive decision-making, core impairments include cognitive inflexibility and excessive sensitivity to rewards. It has been posited that traits shared by nonclinical individuals and psychiatric patients could help explain the pathogenesis of compulsive decision-making. To investigate whether cognitive inflexibility predisposes nonclinical individuals to poor choices and hyper-reactivity to reward, we recruited people with high and low scores for cognitive persistence and used the Iowa Gambling Task to assess decision-making and cardiac reactivity to monetary gains/losses. As is frequently observed in psychophysiological research, the data indicated discrepancies among self-reports, behavior, and physiology. Cognitive inflexibility was not related to worse performance; however, monetary gains, in line with the literature, prompted marked cardiac accelerations. Consistent with our research goal, only inflexible participants showed large cardiac accelerations during the largest monetary wins. Taken together, the data confirm an association between cognitive persistence and physiological reward sensitivity in a nonclinical population. The findings are in line with recent theories on the development of compulsive behaviors that consider cognitive inflexibility as a transdiagnostic impairment and predisposing factor for excessive reactivity to rewards, and might act both as a preexisting individual trait and drug-induced deficit.

Physiologically vulnerable or resilient? Tropical birds, global warming, and redistributions.

Tropical species are considered to be more threatened by climate change than those of other world regions. This increased sensitivity to warming is thought to stem from the assumptions of low physiological capacity to withstand temperature fluctuations and already living near their limits of heat tolerance under current climatic conditions. For birds, despite thorough documentation of community-level rearrangements, such as biotic attrition and elevational shifts, there is no consistent evidence of direct physiological sensitivity to warming. In this review, we provide an integrative outlook into the physiological response of tropical birds to thermal variation and their capacity to cope with warming. In short, evidence from the literature suggests that the assumed physiological sensitivity to warming attributed to tropical biotas does not seem to be a fundamental characteristic of tropical birds. Tropical birds do possess the physiological capacities to deal with fluctuating temperatures, including high-elevation species, and are prepared to withstand elevated levels of heat, even those living in hot and arid environments. However, there are still many unaddressed points that hinder a more complete understanding of the response of tropical birds to warming, such as cooling capacities when exposed to combined gradients of heat and humidity, the response of montane species to heat, and thermoregulation under increased levels of microclimatic stress in disturbed ecosystems. Further research into how populations and species from different ecological contexts handle warming will increase our understanding of current and future community rearrangements in tropical birds.

Behavioral and physiological sensitivity to natural sick faces

The capacity to rapidly detect and avoid sick people may be adaptive. Given that faces are reliably available, as well as rapidly detected and processed, they may provide health information that influences social interaction. Prior studies used faces that were manipulated to appear sick (e.g., editing photos, inducing inflammatory response); however, responses to naturally sick faces remain largely unexplored. We tested whether adults detected subtle cues of genuine, acute, potentially contagious illness in face photos compared to the same individuals when healthy. We tracked illness symptoms and severity with the Sickness Questionnaire and Common Cold Questionnaire. We also checked that sick and healthy photos were matched on low-level features. We found that participants (N = 109) rated sick faces, compared to healthy faces, as sicker, more dangerous, and eliciting more unpleasant feelings. Participants (N = 90) rated sick faces as more likely to be avoided, more tired, and more negative in expression than healthy faces. In a passive-viewing eye-tracking task, participants (N = 50) looked longer at healthy than sick faces, especially the eye region, suggesting people may be more drawn to healthy conspecifics. When making approach-avoidance decisions, participants (N = 112) had greater pupil dilation to sick than healthy faces, and more pupil dilation was associated with greater avoidance, suggesting elevated arousal to threat. Across all experiments, participants’ behaviors correlated with the degree of sickness, as reported by the face donors, suggesting a nuanced, fine-tuned sensitivity. Together, these findings suggest that humans may detect subtle threats of contagion from sick faces, which may facilitate illness avoidance. By better understanding how humans naturally avoid illness in conspecifics, we may identify what information is used and ultimately improve public health.

Seasonal variability in resilience of a coral reef fish to marine heatwaves and hypoxia.

Climate change projections indicate more frequent and severe tropical marine heatwaves (MHWs) and accompanying hypoxia year-round. However, most studies have focused on peak summer conditions under the assumption that annual maximum temperatures will induce the greatest physiological consequences. This study challenges this idea by characterizing seasonal MHWs (i.e., mean, maximum, and cumulative intensities, durations, heating rates, and mean annual occurrence) and comparing metabolic traits (i.e., standard metabolic rate (SMR), Q10 of SMR, maximum metabolic rate (MMR), aerobic scope, and critical oxygen tension (Pcrit )) of winter- and summer-acclimatized convict tang (Acanthurus triostegus) to the combined effects of MHWs and hypoxia. Fish were exposed to one of six MHW treatments with seasonally varying maximum intensities (winter: 24.5, 26.5, 28.5°C; summer: 28.5, 30.5, 32.5°C), representing past and future MHWs under IPCC projections (i.e., +0, +2, +4°C). Surprisingly, MHW characteristics did not significantly differ between seasons, yet SMR was more sensitive to winter MHWs (mean Q10=2.92) than summer MHWs (mean Q10=1.81), despite higher absolute summer temperatures. Concurrently, MMR increased similarly among winter +2 and +4°C treatments (i.e., 26.5, 28.5°C) and all summer MHW treatments, suggesting a ceiling for maximal MMR increase. Aerobic scope did not significantly differ between seasons nor among MHW treatments. While mean Pcrit did not significantly vary between seasons, warming of +4°C during winter (i.e., 28.5°C) significantly increased Pcrit relative to the winter control group. Contrary to the idea of increased sensitivity to MHWs during the warmest time of year, our results reveal heightened sensitivity to the deleterious effects of winter MHWs, and that seasonal acclimatization to warmer summer conditions may bolster metabolic resilience to warming and hypoxia. Consequently, physiological sensitivity to MHWs and hypoxia may extend across larger parts of the year than previously expected, emphasizing the importance of evaluating climate change impacts during cooler seasons when essential fitness-related traits such as reproduction occur in many species.

Long-term Xenopus laevis tadpole -heart-organ-culture: Physiological changes in cholinergic and adrenergic sensitivities of tadpole heart with thyroxine-treatment

The present study clarified changes in physiological sensitivities of cultured Nieuwkoop and Faber stage 57 Xenopus laevis tadpole-organ-heart exposed to thyroxine (T4) using acetylcholine (ACh), norepinephrine (NE) and atropine. For preliminary life span and the chemical tests, 60% minimum essential medium (MEM), two types of modified Hank's balanced salt-solution-culture-media (MHBSS-CM) I and II containing relatively lower concentrations of amino acids and collagen were prepared. In preliminary lifespan-test of cultured tadpole hearts, the hearts maintained in 60% MEM was 50 days on average, whereas that of the tadpole-hearts in MHBSS-CMs was extended by 109 days on average, showing superior effectiveness of MHBSS-CMs. 4 min-stimulation by 5 × 10−9 M T4 tended to increase the tadpole heartbeat. 10−9 M ACh decreased the tadpole heartbeat. Frog-heart at 2–4 weeks after metamorphosis completion and tadpole heart treated with 5 × 10−10 M T4 for 45 h also responded to 10−9 M ACh, and low-resting hearts were restored to the control level with the competitive muscarinic antagonist 10−8 M atropine, whereas excessive exposure of 10−5 M atropine to T4-treated tadpole heart did not increase heartbeat in spite of the increased frog heartbeat over the control. 10−14 —10−12 M NE increase the tadpole heartbeat in a concentration-dependent manner, however, 10−12 M NE did not act to stimulate adrenergic receptors on both T4-treated tadpole- and the frog-hearts. These results suggest that T4 induces the desensitization of atropine-sensitive muscarinic and adrenergic receptors in organ-cultured tadpole-heart.

RCP 기후변화 시나리오에 따른 천궁의 생장 및 생리 활성 변화

Background: Cnidium officinale Makino is a representative medicinal plant, but it is sensitive to changes in climate. The aim of this study was to investigate the growth, physiological reaction, and active compound content of C. officinale Makino in different Representative Concentration Pathway scenarios (RCP 2.6, 4.5, and 8.5).BRMethods and Results: The net photosynthesis rate of C. officinale was reduced in July and was highest in RCP 8.5 over the entire study period. The maximum carboxylation rate and maximum electron transport rate were reduced in July, therefore, photosynthetic activity also decreased. Chlorophyll a and b, total chlorophyll, and carotenoid content were significantly decreased in high-level RCP scenarios. An increased amount of light energy was captured in photosystem II, but it was lost as heat rather than being used in the electron transfer process. The decrease in the photosynthetic activity of C. officinale in RCP 8.5 was due to the accumulation of excitation energy by inactivation of the reaction center of photosystem II. The chlorogenic acid, ferulic acid, and senkyunolide A content in were significantly low in RCP 8.5.BRConclusions: CO₂ concentration significantly affects the growth, physiological sensitivity, and active compound content of C. officinale.

The Symbiodinium Proteome Response to Thermal and Nutrient Stresses.

Coral bleaching is primarily caused by high sea surface temperatures, and nutrient enrichment of reefs is associated with lower resilience to thermal stress and ecological degradation. Excess inorganic nitrogen relative to phosphate has been proposed to sensitize corals to thermal bleaching. We assessed the physiological and proteomic responses of cultures of the dinoflagellate coral symbiont Symbiodinium microadriaticum to elevated temperature under low-nutrient, high-nutrient and phosphate-limited conditions. Elevated temperature induced reductions of many chloroplast proteins, particularly the light-harvesting complexes, and simultaneously increased the abundance of many chaperone proteins. Proteomes were similar when the N:P ratio was near the Redfield ratio, regardless of absolute N and P concentrations, but were strongly affected by phosphate limitation. Very high N:P inhibited Symbiodinium cell division while increasing the abundance of chloroplast proteins. The proteome response to phosphate limitation was greater than that to elevated temperature, as measured by the number of differentially abundant proteins. Increased physiological sensitivity to high temperatures under high nutrients or imbalanced N:P ratios was not apparent; however, oxidative stress response proteins were enriched among proteins responding to thermal stress under imbalanced N:P ratios. These data provide a detailed catalog of the effects of high temperatures and nutrients on a coral symbiont proteome.

When the body knows: Interoceptive accuracy enhances physiological but not explicit differentiation between liars and truth-tellers

Recent research suggests that people experience distinct physiological reactions to lies versus truths. It is unclear, however, if this experience is incorporated into greater truth-lie judgment accuracy. We hypothesized that individuals with high interoceptive accuracy—those with greater access to bodily experiences and stronger physiological responses to emotional stimuli—might be particularly likely to accurately discriminate high-stakes, emotional lies and truths. Participants (n = 71) completed two study sessions: the first assessed their interoceptive accuracy with heartbeat detection measures, and the second assessed their deception detection ability while measuring their physiological reactivity. Interoceptive accuracy was associated with a greater difference in vasoconstriction to liars (vs. truth-tellers), suggesting that interoception was positively associated with physiological sensitivity to deception. Interoceptive accuracy, however, was unrelated to deception detection accuracy. While better interoception may enhance physiological signals that could better discriminate lies from truths, it does not improve explicit deception detection accuracy.

Size matters: Physiological sensitivity of the scallop Argopecten purpuratus to seasonal cooling and deoxygenation upwelling-driven events

Environment imposes physiological constraints which are life-stage specific as growth-maintenance and/or growth-reproduction energetic requirements are size and volume-dependent. The scallop Argopecten purpuratus, one of the most important bivalve species subjected to fishery and aquaculture along the Humboldt Current System, inhabits spaces affected by continuous changes in temperature, pH, oxygen, and food availability driven by remote and local oceanographic processes. Specifically, in Chile, this species is mainly cultured in central-north Chile where is permanently affected by upwelling events of dissimilar intensity and duration which generate local conditions of acidification, deoxygenation, and cooling with different magnitudes. However, to date, it remains unknown how this economic valuable resource is physiologically affected throughout its life cycle by the continuous environmental changes driven by upwelling events of different intensities and duration along the year. Here, for the first time, A. purpuratus life-stage physiological sensitivity was assessed at a seasonal scale through a year-field experiment where growth, calcification, and survivorship were evaluated. Our study shows how seasonal differences in the upwelling phenology (here measured as changes in temperature, dissolved oxygen, pH, and primary productivity, but also as the number, duration, and intensity of cooling and de-oxygenation events) notably impacted the A. purpuratus physiological performance from juvenile to adult life-stages. This was especially noticeable during the spring season which showed the most intense cooling and deoxygenation events driven by stronger favorable-upwelling winds and the lowest growth and gross calcification rates (the highest decalcification rates) where adult stages showed the lowest performance. On the other hand, A. purpuratus survivorship was not significantly affected by upwelling intensity which would be providing evidence of the high physiological flexibility and well-locally adapted is this species to fluctuating and occasional stressful environmental conditions. Our results are significantly relevant in the climate change context as some upwelling systems are at risk to change shortly (i.e., an upwelling intensification in frequency and intensity) as a consequence of changes in the atmospheric pressures that modulate favourable-upwelling winds. These changes may certainly increase the climate related-risks of the entire socio-ecological systems related to the fishery and aquaculture of A. purpuratus along the Humboldt Current System.

Central and peripheral nervous system responses to chronic and paced hyperventilation in anxious and healthy subjects

The aim of the present study was to examine self-report, peripheral nervous system, and central nervous system correlates of naturally-occurring, chronic hyperventilation (HV, assessed by hypocapnia or low resting state low end-tidal CO2), and to examine the additional effect of acute, experimentally-induced HV in anxious and healthy participants. By identifying the biomarkers of anxiety-related chronic HV and examining responses to acute HV, we hope to identify meaningful, mechanistic targets for further treatment development. Seventy anxious patients and 34 healthy control participants completed electroencephalogram (EEG) and peripheral nervous system recording at baseline and following a paced breathing task. Diagnosis x baseline hypnocapnia group analyses indicated that anxious/hypocapnic patients exhibited greater nonspecific skin conductance response amplitude than did anxious/normocapnic patients, and the anxious group reported greater HV-related symptoms and anxiety sensitivity than did the control group. However, no EEG abnormalities were noted as a function of anxiety group or baseline hypocapnia status. Following paced HV, anxious patients (but not controls) exhibited an increase in left-frontal alpha 1 power. Hypocapnic, but not normocapnic, participants exhibited an increase in skin conductance levels. Anxious patients reported an increase in negative cognitive appraisals of HV symptoms, and anxious/hypocapnic participants reported an increase in affective responses to HV. Thus, chronic HV is associated with greater arousal, and increased self-reported and physiological sensitivity to paced HV. Patients who chronically hyperventilate appear to be more sensitive to respiratory distress, responding with higher levels of anxiety and poorer tolerance of the physiological sensations accompanying acute HV.

99mTc /SPIO-loaded polymeric micelles as MRI and SPECT imaging, cancer-targeted nanoprobe for liver cancer detection

Magnetic resonance imaging (MRI) and single-photon emission computed tomography (SPECT) imaging are combined to diagnose cancer with high physiological, anatomical, and metabolism sensitivity. For targeting hepatoma carcinoma, a drug delivery system is employed to carry drugs or chemicals to a specific area. Galactose is one of the sugar molecules which can be bound and increase uptake with asialoglycoprotein receptor (ASGP-R). In this study, superparamagnetic iron oxide nanoparticles (SPIONs), Galactose-functionalized poly(ethylene glycol)-block-poly(lactic acid) (Gal-PEG-b-PLA) and Diethylenetriaminepentaacetic acid-functionalized poly(ethylene glycol)-block-poly(lactic acid) (DTPA-PEG-b-PLA) were successfully synthesized and constructed to DTPA/Gal/SPIO micelles (targeting micelles) and DTPA/Met/SPIO micelles (non-targeting micelles). Technetium-99 m (99mTc) formed a complex with DTPA on the micelles as 99mTc/Gal/SPIO micelles by using stannous chloride and the pH was adjusted to acidic condition. The sizes of DTPA/Gal/SPIO micelles and DTPA/Met/SPIO micelles were lower than 100 nm with a spherical shape. In vitro study with HepG2-and L929-incubated micelles showed the intensity of blue staining of Prussian blue related to the amount of SPIO. 99mTc/Gal/SPIO micelles incubated with HepG2 exhibited signal intensity (SPECT signal) and relative R2* (MRI signal) higher than 99mTc/Met/SPIO micelles at the same time. According to these results, 99mTc-labeled Galactose-functionalized SPIO micelles have the potential for specific targeting to HepG2 and can aid in the diagnosis of cancer with MRI and SPECT dual imaging.

Magnitude–duration relationships of physiological sensitivity and environmental exposure improve climate change vulnerability assessments

Integrating thermal physiology with environmental temperature is essential to understanding distributions of species and vulnerability to climate change. Warming tolerance – the difference between an organism's maximum thermal tolerance (Tmax) and maximum habitat temperature (Thab) – is frequently used to integrate organismal sensitivity and environmental exposure. Traditionally, applications of warming tolerance define Tmax and Thab as invariable magnitudes, yet tolerance magnitude depends on exposure duration, and diel temperature cycles expose organisms to a range of temperature magnitudes and durations. How traditional (i.e. acute) estimates of warming tolerance compare to estimates from prolonged exposures remains poorly understood. In this study, magnitude–duration curves for tolerances of one cold‐water, two cool‐water and one warm‐water species of freshwater fish were compiled from the literature and compared to magnitude–duration exposures from 66 streams across the eastern United States. Warming tolerances were estimated for exposure durations spanning 0.01–24 h. Current acute (0.01 h) warming tolerances ranged from median 6.30°C for the cold‐water species to 9.68°C for the warm‐water species. The lowest warming tolerances corresponded to prolonged exposures lasting median 3.85–5.30 h among species and were 2.51–4.38°C lower than acute estimates. Although acute estimates remained positive in historically occupied and unoccupied streams (6.30 versus 2.33°C), estimates based on prolonged exposure were positive at occupied streams of the cold‐water species but transitioned to negative in unoccupied streams (2.19 versus −1.12°C). Acute warming tolerances for the cold‐water species also remained positive under future climate (6.29–4.23°C) but approached zero at prolonged durations (2.19–0.09°C) and transitioned to negative for 47.2% of streams. Results demonstrate that acute measures of Tmax and Thab overestimate warming tolerances and therefore underestimate climate change vulnerability. Integrating magnitude–duration relationships into warming tolerance estimates can elucidate physiological mechanisms underlying species distributions and can improve accuracy of climate change vulnerability assessments.

Stress response during early sedation with dexmedetomidine compared with usual-care in ventilated critically ill patients

BackgroundSedative agents may variably impact the stress response. Dexmedetomidine is a sympatholytic alpha2-adrenergic agonist mainly used as a second-line sedative agent in mechanically ventilated patients. We hypothesised that early sedation with dexmedetomidine as the primary agent would result in a reduced stress response compared to usual sedatives in critically ill ventilated adults.MethodsThis was a prospective sub-study nested within a multi-centre randomised controlled trial of early sedation with dexmedetomidine versus usual care. The primary outcome was the mean group differences in plasma levels of stress response biomarkers measured over 5 days following randomisation. Other hormonal, biological and physiological parameters were collected. Subgroup analyses were planned for patients with proven or suspected sepsis.ResultsOne hundred and three patients were included in the final analysis. Baseline illness severity (APACHE II score), the proportion of patients receiving propofol and the median dose of propofol received were comparable between groups. More of the usual-care patients received midazolam (57.7% vs 33.3%; p = 0.01) and at higher dose (median (95% interquartile range) 0.46 [0.20–0.93] vs 0.14 [0.08–0.38] mg/kg/day; p < 0.01). The geometric mean (95% CI) plasma level of the stress hormones, adrenaline (0.32 [0.26–0.4] vs 0.38 [0.31–0.48]), noradrenaline (4.27 [3.12–5.85] vs 6.2 [4.6–8.5]), adrenocorticotropic hormone (17.1 [15.1–19.5] vs 18.1 [15.9–20.5]) and cortisol (515 [409–648] vs 618 [491–776)] did not differ between dexmedetomidine and usual-care groups, respectively. There were no significant differences in any other assayed biomarkers or physiological parameters Sensitivity analyses showed no effect of age or sepsis.ConclusionsEarly sedation with dexmedetomidine as the primary sedative agent in mechanically ventilated critically ill adults resulted in comparable changes in physiological and blood-borne parameters associated with the stress-response as with usual-care sedation.

Post-amputation pain: Comparing pain presentations between adults with and without increased amputated-region sensitivity.

Among adults with persistent post-amputation pain, increased amputated-region pain sensitivity may reflect peripheral sensitization or indicate underlying central sensitization. To determine whether underlying central sensitization may contribute to increased pain sensitivity in this population, this study compared clinical signs and symptoms associated with central sensitization between adults with post-amputation pain who demonstrate or lack increased amputated-region sensitivity (as compared to reference data). Cross-sectional. Ninety-nine adults (60 with a unilateral, transtibial amputation and post-amputation pain, 39 pain-free controls with intact limbs). Participants underwent pain-pressure threshold testing of amputated-region and secondary (non-amputated region) sites and completed outcome measures assessing central sensitization symptoms (Patient-Reported Outcomes Measurement Information System® pain intensity and interference domains, Central Sensitization Inventory). Among the full sample, the presence and frequency of specific central sensitization symptoms were evaluated. Participants with post-amputation pain were then grouped based on whether normalized, amputated-region pain-pressure thresholds fell below (i.e., sensitive) or above (i.e., non-sensitive) the 25th percentile of sex-specific reference data. Between-group differences in normalized secondary-site sensitivity were evaluated using a multivariate analysis of variance; central sensitization symptom scores were compared using a Kruskal-Wallis test. Noteworthy symptoms associated with central sensitization (e.g., fatigue, sleep disturbance, cognitive difficulty) were reported by 33%-62% of participants. Secondary-site pain sensitivity was greater among individuals with increased amputated-region sensitivity (n=24) compared to peers without increased amputated-region sensitivity ([n=36], mean difference > 1.33 standard deviation [SD], p < 0.001). Central sensitization symptom scores, however, were similar between groups (p > 0.187). Participants with increased amputated-region sensitivity demonstrate generalized, secondary-site pain hypersensitivity, potentially indicating underlying central sensitization. Central sensitization symptom scores, however, were similar between groups, suggesting differences in physiological pain sensitivity may not manifest in subjective post-amputation pain descriptions.

Differences in the Chloroplast Genome and Its Regulatory Network among Cathaya argyrophylla Populations from Different Locations in China.

Cathaya argyrophylla Chun et Kuang is a severely endangered, tertiary relict plant unique to China whose high physiological sensitivity to the environment, including photosensitivity, is likely closely related to its endangered status; however, the exact mechanism responsible has remained unknown due to the rarity of the plant and the difficulties involved in performing physiological studies on the molecular level. In this study, the chloroplast genomes of six C. argyrophylla populations sampled from different locations in China were characterized and compared. In addition, a gene regulatory network of the polymorphic chloroplast genes responsible for regulating genes found elsewhere in the plant genome was constructed. The result of the genome characterization and comparison showed that the genome characteristics, the gene composition, and the gene sequence of the chloroplast genes varied by location, and the gene regulatory network showed that the differences in growth location may have led to variations in the protein-coding chloroplast gene via various metabolic processes. These findings provide new insights into the relationship between chloroplasts and the sensitive metabolism of C. argyrophylla and provide additional reference materials for the conservation of this endangered plant.