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bioRxiv2023

When the tap runs dry: The physiological effects of acute experimental dehydration in Peromyscus eremicus

Desert organisms have evolved physiological, biochemical, and genomic mechanisms to survive the extreme aridity of desert environments. Studying desert-adapted species provides a unique opportunity to investigate the survival strategies employed by organisms in some of the harshest habitats on Earth. Two of the primary challenges faced in desert environments are maintaining water balance and thermoregulation. We collected data in a simulated desert environment and a captive colony of cactus mice (Peromyscus eremicus) and used lab-based experiments with real time physiological measurements to characterize the response to water-deprivation. Mice without access to water had significantly lower energy expenditures and in turn, reduced water loss compared to mice with access to water after the first 24 hours of the experiment. Additionally, we observed significant weight loss likely related to dehydration-associated anorexia a response to limit fluid loss by reducing waste and the solute load as well as allowing water reabsorption from the kidneys and gastrointestinal tract. Finally, we observed body temperature correlated with sex, with males without access to water maintaining body temperature when compared to hydrated males while body temperature decreased for females without access to water compared to hydrated, suggesting daily torpor in females.

physiology↗

bioRxiv2023

Behavioral Thermoregulation in Captive Fish: Molecular, Physiological, and Welfare Implications

Environmental Enrichment (EE) serves as a cornerstone in the attempt to emulate natural habitats for captive organisms. While substantial strides have been made in this field, current methodologies still grapple with discrepancies between recreated habitats and the innate conditions vital for maintaining biological homeostasis in captive species. Our study highlights the pivotal role of behavioral thermoregulation in modulating molecular and physiological outcomes in captive fish. Collective evidence suggests that enabling fish to autonomously regulate temperature confers numerous beneficial cellular and systemic effects. Specifically, introducing a thermal gradient within the EE paradigm correlated with increased survival metrics, enhanced physiological parameters, and improved welfare indices, establishing the criticality of thermoregulation in captivity. In contrast, the lack of a thermoregulatory framework resulted in the emergence of transient free radicals, a clear marker of temperature-induced oxidative stress. Persistent disruptions in free radical equilibrium, especially in uniform temperature settings, were linked to DNA damage, heightened cellular apoptosis, tissue anomalies, and metabolic deviations. In conclusion, this research underscores the significance of behavioral thermoregulation as an integral feature of EE, especially related to fish in controlled environments. Our data present key biomarkers valuable for optimizing fish welfare and highlight the necessity for sustained research into their adaptability and survival benchmarks. Such insights aim to enhance EE protocols, fortifying their efficacy in mirroring natural habitats and, in turn, advancing the welfare benchmarks of captive organisms.

physiology↗

bioRxiv2024

Non-physiologic interaction of MG53 with insulin receptor and lack of evidence for MG53's role in controlling insulin-stimulated Akt phosphorylation in muscle, heart and liver tissues.

RationaleMG53s known function in facilitating tissue repair and anti-inflammation has broad applications to regenerative medicine. There is controversy regarding MG53s role in the development of type 2 diabetes mellitus (T2DM). ObjectiveThis study aims to address this controversy - whether MG53s myokine function contributes to inhibition of insulin signaling in muscle, heart, and liver tissues. Study DesignWe determined the binding affinity of the recombinant human MG53 (rhMG53) to the insulin receptor extracellular domain (IR-ECD) and found low affinity of interaction with Kd (>480 nM). Using cultured C2C12 myotubes and HepG2 cells, we found no effect of rhMG53 on insulin-stimulated Akt phosphorylation (p-Akt). We performed in vivo assay with C57BL/6J mice subjected to insulin stimulation (1 U/kg, intraperitoneal injection) and observed no effect of rhMG53 on insulin-stimulated p-Akt in muscle, heart and liver tissues. ConclusionOverall, our data suggest that rhMG53 can bind to the IR-ECD, however has a low likelihood of a physiologic role, as the Kd for binding is [~]10,000 higher than the physiologic level of MG53 present in the serum of rodents and humans ([~]10 pM). Our findings question the notion proposed by Xiao and colleagues - whether targeting circulating MG53 opens a new therapeutic avenue for T2DM and its complications.

physiology↗

bioRxiv2024

Cardiomyocyte PGC-1α enables physiological adaptations to endurance exercise through suppression of GDF15 and cardiac atrophy

Exercise training induces physiological cardiac hypertrophy, enhanced mitochondrial biogenesis and myocardial contractility. In skeletal muscle, the transcriptional coactivator PGC-1 is a key orchestrator of these responses. The heart expresses abundant and exercise-responsive PGC-1, but it is unclear whether cardiomyocyte PGC-1 is necessary for cardiac adaptation to endurance training. Here we demonstrate that cardiomyocyte PGC-1 is required for physiological cardiac hypertrophy during exercise training in mice. In the absence of cardiomyocyte PGC-1, voluntary wheel running does not improve exercise capacity and instead confers immune-fibrotic-atrophic heart failure after just 6 weeks of training. We identify cardiomyocyte PGC-1 as a negative regulator of stress-responsive senescence gene expression. The most enriched of these is the myomitokine GDF15. GDF15 is secreted locally but not systemically in PGC-1-deficient mouse hearts and reduces cardiomyocyte size. Cardiomyocyte-specific reduction of GDF15 expression preserves exercise tolerance and cardiac contractility in PGC-1-deficient mice during endurance training. Finally, we show that cardiomyocyte PPARGC1A expression correlates with cardiomyocyte number and negatively with GDF15 expression in human cardiomyopathies through single nucleus RNA sequencing. Our data implicate cardiomyocyte PGC-1 as a vital safeguard against stress-induced atrophy and local GDF15-induced dysfunction during exercise.

physiology↗

bioRxiv2024

Comparing physiological impacts of positive pressure ventilation versus self-breathing via a versatile cardiopulmonary model incorporating a novel alveoli opening mechanism

Mathematical models can be used to generate high-fidelity simulations of the cardiopulmonary system. Such models, when applied to real patients, can provide valuable insights into underlying physiological processes that are hard for clinicians to observe directly. In this work, we propose a novel modelling strategy capable of generating scenario-specific cardiopulmonary simulations to replicate the vital physiological signals clinicians use to determine the state of a patient. This model is composed of a tree-like pulmonary system that features a novel, non-linear alveoli opening strategy, based on the dynamics of balloon inflation, that interacts with the cardiovascular system via the thorax. A baseline simulation of the model is performed to measure the response of the system during spontaneous breathing which is subsequently compared to the same system under mechanical ventilation. To test the new lung opening mechanics and systematic recruitment of alveolar units, a positive end-expiratory pressure (PEEP) test is performed and its results are then compared to simulations of a deep spontaneous breath. The system displays a marked decrease in tidal volume as PEEP increases, replicating a sigmoidal curve relationship between volume and pressure. At high PEEP, cardiovascular function is shown to be visibly impaired, in contrast to the deep breath test where normal function is maintained.

physiology↗

bioRxiv2024

Coral long-term recovery after bleaching: implications for sexual reproduction and physiology.

This study examined the long-term impacts of coral bleaching on the reproduction and physiology of Montipora capitata, a dominant reef-building coral in Hawaii. We monitored bleached and non-bleached colonies during and after a natural coral bleaching event in 2014 and analyzed reproductive traits and transcriptomic signatures eight months later. Our study shows that non-bleached and bleached colonies successfully produced gametes. Colonies that bleached had smaller oocytes, and development was slower than in colonies that did not bleach. Corals with different vulnerabilities to bleaching exhibited distinct transcriptomic responses eight months after a bleaching event. Those more prone to bleaching showed suppression of transcripts associated with sperm motility, calcification, and immunity. We found distinct transcriptomic signatures between fringing and patch reefs, suggesting local adaptation and/or acclimatization. To conserve coral reefs and better understand how they will be affected by future heat stress, we need to track which colonies survive and examine how their physiological and reproductive processes are impacted in the short- and long-term. This is critical as consecutive bleaching events become more frequent, and corals have less time to recover. Our study provides valuable molecular and reproductive data that can be used for conservation and management purposes. This information can help us identify signs of coral vulnerability and resilience to bleaching, project how future bleaching events will affect coral reproduction, determine which traits are most at risk, and assess which sites are more likely to be compromised.

physiology↗

bioRxiv2024

Control of Physiologic Glucose Homeostasis via the Hypothalamic Modulation of Gluconeogenic Substrate Availability

The brain augments glucose production during fasting, but the mechanisms are poorly understood. Here, we show that Cckbr-expressing neurons in the ventromedial hypothalamic nucleus (VMNCckbr cells) prevent low blood glucose during fasting through sympathetic nervous system (SNS)-mediated augmentation of adipose tissue lipolysis and substrate release. Activating VMNCckbr neurons mobilized gluconeogenic substrates without altering glycogenolysis or gluconeogenic enzyme expression. Silencing these cells (CckbrTetTox animals) reduced fasting blood glucose, impaired lipolysis, and decreased circulating glycerol (but not other gluconeogenic substrates) despite normal insulin, counterregulatory hormones, liver glycogen, and liver gluconeogenic gene expression. Furthermore, {beta}3-adrenergic adipose tissue stimulation in CckbrTetTox animals restored lipolysis and blood glucose. Hence, VMNCckbr neurons impact blood glucose not by controlling islet or liver physiology, but rather by mobilizing gluconeogenic substrates. These findings establish a central role for hypothalamic and SNS signaling during normal glucose homeostasis and highlight the importance of gluconeogenic substrate mobilization during physiologic fasting.

physiology↗

bioRxiv2025

When Stopping Requires Going; Physiological Similarities Between Action Cancellation and the Cancellation of Action Cancellation

The reactive cancellation of real-world actions typically requires complex combinations of both muscle contraction and/or muscle suppression. However, current experimental paradigms solely examine contexts in which action cancellation requires muscle suppression. To provide fundamental insights into inhibitory control mechanisms, we directly compared the latency of action cancellation in novel paradigms where stopping required either suppression of planned activation or reinstatement of ongoing activity. 20 healthy adults (mean age = 32.2 years) completed novel variants of the stop signal task (SST) in which each trial began with tonic force production to depress two buttons. When a go signal appeared, participants were required to release these buttons. On a subset of trials, a stop signal occurred after a brief delay, and participants were required to cancel the release of one of the buttons. Data in these variants were compared to conventional response-selective SSTs, in which the go signal required bilateral button presses and stop signals necessitated cancellation of one of these responses. Electromyographic (EMG) recordings allowed detailed comparison of the characteristics of muscle contraction and suppression (i.e., stopping speed) across these tasks. When physiological evidence of synchronous action cancellation in both hands was observed (supporting recent models of complex stopping), EMG measures of action cancellation speed did not differ (p = 0.863, BF01 = 8.49) between cancellation of releases and cancellation of presses conditions. This result suggests that response inhibition may broadly characterise reactive control to maintain a current physiological state rather than specific cancellation of a voluntary response.

physiology↗

bioRxiv2025

Impact of a standardized Tetradesmus obliquus Mi175.B1.a extract on gut function and physiology in inflammatory conditions: in vitro and in vivo insights

Microalgae have emerged as a promising source of natural nutraceuticals, which may play a critical role in maintaining the structural integrity of the gut mucosal barrier and modulating immune responses. Extracts from Tetradesmus obliquus have demonstrated potential benefits for gut health in humans. This study aimed to evaluate the efficacy of Tetradesmus obliquus Mi175.B1.a through two complementary approaches: (1) an in vitro model using the HT-29 cell line to assess cytotoxicity, intestinal permeability, immunomodulatory properties, and gut barrier function, and (2) an in vivo mouse model of dextran sodium sulfate (DSS)-induced colitis to examine parameters relevant to digestive physiology. In the in vitro model, HT-29 cells were pretreated with two selected doses of T. obliquus (Mi175.B1.a) extract for 72 hours prior to stress induction with lipopolysaccharide (LPS). Parameters assessed included gene expression, paracellular permeability, and immunomodulatory properties. For the in vivo model, forty (40) male mice were randomly allocated to receive daily oral administration of either vehicle or T. obliquus extract at two different doses for 21 days. Colitis was induced from Day 14 to Day 21 using 3% DSS, and macroscopic and gut motility parameters were subsequently evaluated. Key findings revealed that T. obliquus (Mi175.B1.a) significantly reduced FITC-dextran permeability, restored physiological expression of Zonula occludens-1 (a tight junction protein), and attenuated TNF- release and Cox2 gene expression in comparison to the LPS-only condition. In the in vivo model, T. obliquus extract significantly reduced the daily disease activity index and colitis score compared to DSS-only condition. Importantly, the two evaluated doses of T. obliquus (Mi175.B1.a) were well-tolerated, demonstrating no toxic effects. These results highlight the potential of T. obliquus extract to enhance intestinal barrier integrity by regulating inflammatory and oxidative stress pathways opening promising research perspectives to determine the benefits in human application.

physiology↗

bioRxiv2025

Expert drummers replicate neuromechanical signatures of physiological tremor at extreme movement frequencies.

This study investigates the neuromechanical characteristics associated with expert drummers ability to achieve unilateral ankle oscillation frequencies of up to 10 Hz, surpassing known limits for lower-body movements. Eighteen experienced drummers performed trials at various frequencies, using a protocol combining H-reflex measurement, motion analysis, and electromyography. Our findings closely parallel neuromechanical signatures observed in ankle tremors, with an average movement frequency of 6.3 Hz (SD: 0.5 Hz), and a modulation range of 5.5-7.3 Hz. Oscillatory behavior may result from the interplay between muscle-tendon mechanics and stretch reflex loops. At 6.3 Hz, soleus activation lasts 56.2 ms, shortening by 2.5 ms/Hz (p < 0.001), while tibialis anterior activation lasts 52.7 ms, decreasing by 5.3 ms/Hz (p < 0.001). The latency between ankle dorsiflexion and soleus activation is 48.5 ms at 6.3 Hz, matching the short-latency stretch reflex, and decreases by 11 ms/Hz (p<0.001). Limiting factors for the drummers maximal frequency are soleus and tibialis anterior co-activation, reducing ankle movement, and high levels of activation in hip and back muscles, associated with discomfort and pain. Drummers with higher maximal frequencies (above 7.5 Hz, n = 6) show shorter tibialis anterior activation durations (34.3 ms vs. 53.2 ms, p = 0.0013) and reduced tensor fascia latae activation (6.2% vs. 21.0%, p = 0.0135). These findings highlight phenomenological similarities between the ankle technique and physiological tremors, in terms of neuromechanical timing and oscillatory patterns. Precise tibialis anterior timing and relaxed proximal muscle activation are critical for performance, while injury prevention strategies remain essential. Significance StatementThis study provides a neuromechanical analysis of expert metal drummers producing exceptionally high-frequency ankle movements--up to 10 Hz--that surpass known limits for lower-body movements, and draws parallels with physiological action tremors. By comparing their motor patterns to those reported in tremor literature, this work highlights the role of neuromuscular timing and mechanical adaptations, such as stretch reflex dynamics and muscle-tendon interactions. The findings demonstrate that precise tibialis anterior timing and relaxed proximal muscles are critical for performance, while stabilization demands increase the risk of musculoskeletal disorders in the lower back and hips. These insights bridge performance science, biomechanics, and injury prevention, offering valuable perspectives for optimizing high-frequency movements in music, sports, and rehabilitation.

physiology↗

bioRxiv2025

Evidence of physiological assortment and movement dynamics among social groups of a coral reef fish

The trade-offs of group living are modulated by the phenotypes of individual members of a social group, particularly in dynamic and diverse habitats like coral reefs. Little is known about the patterns of physiological traits among fishes within social groups and the mechanisms that promote these patterns, which could elucidate the drivers of group composition and their downstream ecological and evolutionary impacts. Here, in the gregarious damselfish species Chromic viridis, we examined inter-group differences in whole-animal physiological traits and the tendency for fish to move either within sites (i.e., sections of continuous reef) or among habitats (i.e., reefs separated by sandy substratum) to a new social group. Using oxygen uptake as a proxy for aerobic metabolic rate, we found significant differences in maximum metabolic rate (MMR) and aerobic scope (AS) among schools from different habitats, with these traits higher in habitats with faster water flow rates. However, we found no differences in any metabolic traits (standard metabolic rate, SMR, MMR, AS) between groups from the same site. These trends could stem from a range of mechanisms, as mark-recapture studies of this species indicated a willingness to migrate to a new social group in over 30% of recollected fish. However, there were no effects of either body size or perceived habitat risk on the distance moved or movement type (i.e., over coral or sand). Our results indicate that, in social species, a combination of mechanisms may influence phenotypic differences among groups over different spatial scales.

physiology↗

bioRxiv2025

Questioning the utility of oxidative stress measurements as biomarkers of physiological condition and fitness

Markers of oxidative stress are widely used as indicators of physiological state, but their utility for ecological and evolutionary inference remains uncertain due to high intraindividual variation masking associations with environmental conditions, fitness, and other physiological indicators such as telomere length. Although numerous longitudinal studies exist, individual repeatability of oxidative stress measurements is rarely reported explicitly. Here, we present the first meta-analysis assessing individual repeatability of oxidative stress markers, comprising 123 repeatability estimates from 22 studies. Overall, oxidative stress markers exhibited low repeatability on average (Intraclass correlation = 0.164), although repeatability estimates were highly heterogenous across biomarkers, study systems, and ecological contexts. Repeatability was generally low across taxa, sexes, study designs, and environments, although some markers, particularly lipid peroxidation quantified with HPLC, exhibited moderate repeatability in specific contexts. To illustrate the statistical consequences of low repeatability, we used heuristic simulations examining associations between oxidative stress and telomere length under different biological scenarios. These simulations demonstrate how low repeatability substantially reduces statistical power, but this is somewhat mitigated by taking repeated measurements. More broadly, our findings highlight the value of greater cross-disciplinary dialogue, as ecological and biomedical studies often use oxidative stress biomarkers in different ways and may benefit from shared perspectives.

physiology↗

bioRxiv2018

Effects of different load on physiological, hematological, biochemical, cytokines indices of Zanskar ponies at high altitude

High altitude people required high endurance pack animals for load carrying and riding at prevalent mountainous terrains and rugged region. So far no studies have been taken to evaluate effect of loads on physiology of ponies in high altitude region. So, in this view we evaluated variation in physiological, hematological, biochemical, and cytokines indices of Zanskar ponies during load carrying at high altitude. Total twelve (12) numbers of Zanskar ponies, mare, age 4-6 years, were divided into three groups; group-A (without load), group-B (60 kg), and group-C (80 kg) of back pack loads. Track was very narrow and slippery with gravel, uneven with rocky surface and has a steep gradient of 4 km uphill at altitude 3291 to 3500 m. When we evaluate these parameters, it is understood that the heart rate, pulse rate and respiration rate was significantly (p<0.05) increased in 80 kg group among the three groups. The hematology parameters viz. hemoglobin, PCV, lymphocytes, monocytes%, ESR and eosinophil% significantly (p<0.05) changed in 80 kg group after load carrying among the three groups which was followed by control and 60 kg group. In biochemical parameters viz. LA, LDH, TP, HK, CORT, T3, CRT, AST, CK-MB, GPx, FRAP and IL-6 significantly (p<0.05) changed in 80 kg group after load carrying among the three groups which was followed by control and 60 kg group. The ALT, ALB, GLB, UR and UA significantly (p<0.05) changed in 80 kg group before and after load carrying among the three groups which was followed by control and 60 kg group. It has been concluded that, this result has revealed strong correlation of change in biomarkers level with performance in ponies during load carry. Hence, these parameters might be use for performance of endurance of Zanskar ponies in high mountain region.

physiology↗

bioRxiv2018

Association of physiological variables with football subconcussive head impacts: Why measure?

Subconcussive head impacts, defined as impacts to the cranium that do not result in clinical symptoms of concussion, are gaining traction as a major public health concern. Researchers begin to suggest subconcussive impact-dependent changes in various neurological measures. However, a contribution of physiological factors such as physical exertion and muscle damage has never been accounted. We conducted a prospective longitudinal study during a high school American football season to examine the association between physiological factors and subconcussive head impact kinematics. Fifteen high-school American football players volunteered in the study. A sensor-installed mouthguard recorded the number of head impacts, peak linear (PLA: g) and peak rotational (PRA: rad/s2) head accelerations from every practice and game. Serum samples were collected at 12 time points (pre-season baseline, five in-season pre-post games, and post-season) and assessed for the creatine kinase skeletal muscle-specific isoenzyme (CK-MM), as a surrogate for skeletal muscle damage. Physical exertion was estimated in the form of excess post-exercise oxygen consumption (EPOC) from heart rate data captured during five games via a wireless heart rate monitor. A total of 9,700 hits, 214,492 g, and 19,885,037 rad/s2 were recorded from 15 players across the study period. Mixed-effect regression models indicated that head impact kinematics (frequency, PLA, and PRA) were significantly and positively associated with CK-MM increase, but not with EPOC. There was a significant and positive association between CK-MM and EPOC. These data suggest that skeletal muscle damage effects should be considered when using outcome measures that may have an interaction with muscle damage, including inflammatory biomarkers and vestibular/balance tests.

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bioRxiv2019

Molecular physiology of chemical defenses in a poison frog

Poison frogs sequester small molecule lipophilic alkaloids from their diet of leaf litter arthropods for use as chemical defenses against predation. Although the dietary acquisition of chemical defenses in poison frogs is well-documented, the physiological mechanisms of alkaloid sequestration has not been investigated. Here, we used RNA sequencing and proteomics to determine how alkaloids impact mRNA or protein abundance in the Little Devil Frog (Oophaga sylvatica) and compared wild caught chemically defended frogs to laboratory frogs raised on an alkaloid-free diet. To understand how poison frogs move alkaloids from their diet to their skin granular glands, we focused on measuring gene expression in the intestines, skin, and liver. Across these tissues, we found many differentially expressed transcripts involved in small molecule transport and metabolism, as well as sodium channels and other ion pumps. We then used proteomic approaches to quantify plasma proteins, where we found several protein abundance differences between wild and laboratory frogs, including the amphibian neurotoxin binding protein saxiphilin. Finally, because many blood proteins are synthesized in the liver, we used thermal proteome profiling as an untargeted screen for soluble proteins that bind the alkaloid decahydroquinoline. Using this approach, we identified several candidate proteins that interact with this alkaloid, including saxiphilin. These transcript and protein abundance patterns suggest the presence of alkaloids influences frog physiology and that small molecule transport proteins may be involved in toxin bioaccumulation in dendrobatid poison frogs.\n\nResumenLas ranas venenosas obtienen moleculas lipofilicas a partir de su dieta de artropodos que luego usan como una defensa quimica contra depredadores. Mientras que la acumulacion de toxinas dieteticas ha sido bien documentada, el mecanismo fisiologico de obtencion de alcaloides no ha sido investigado. En este estudio usamos secuenciacion de RNA y proteomica para determinar como la presencia de alcaloides afecta la abundancia de mRNA y proteinas en ranas diablito (Oophaga sylvatica) silvestres con defensas quimicas en comparacion a ranas diablito criadas en laboratorio con una dieta sin alcaloides. Para entender como las ranas venenosas mueven los alcaloides de su dieta a las glandulas granulares en su piel, nos enfocamos en medir la expresion de genes en tres tejidos: intestinos, piel e higado. En estos tejidos, encontramos varios transcriptomas regulados diferencialmente que tienen actividades involucradas con el transporte y metabolismo de pequenas moleculas, ademas de canales de sodio y bombas de iones. Luego usamos metodos proteomicos para cuantificar proteinas en plasma, donde encontramos varias diferencias en abundancia de proteinas entre las ranas silvestres y de laboratorio, incluyendo la proteina anfibia de fijacion de toxinas, saxifilina. Finalmente, debido a que muchas proteinas encontradas en la sangre se sintetizan en el higado, usamos la tecnica de perfilacion proteomica termal para seleccionar imparcialmente las proteinas solubles que fijan el alcaloide decahydroquinolina. Usando este metodo, identificamos varias posibles proteinas que interactuan con este alcaloide, incluyendo saxifilina. Estos patrones de cambios en abundancia de transcriptomas y proteinas en ranas con y sin defensas quimicas sugieren que la presencia de alcaloides influye en la fisiologia de las ranas y que moleculas proteicas pequenas de transporte podrian estar involucradas en la bioacumulacion de toxinas en ranas venenosas dendrobatidos.\n\nSummary StatementChemically defended wild poison frogs have gene expression and protein abundance differences across several tissue systems compared to poison frogs reared on an alkaloid-free diet.

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bioRxiv2019

Physiological response to slalom water skiing: A case study of a sit-skier with paraplegia

Recreational and competitive slalom waterskiing is popular among those with spinal cord injuries. People with paraplegia can practice on the slalom course using a sit-ski. A slalom run consists of a boat towing the sit-skier through a set of buoys and normally begins with a deep-water start. Despite its popularity, very little is known about the physiological aspects of the sit-skier's preparation. We examined the internal training load (TL) experienced by a sit-skier with paraplegia while learning and improving the slalom deep-water starts, executed with both the traditional technique and an alternative method. The TL was determined by means of heart rate (HR) and session rating of perceived exertion (sRPE) methods. The percentage of maximal heart rate values ranged from from 63.2% to 81.3% during deep-water starts. Training sessions were performed most of the time below the ventilatory threshold and tended to be qualitatively described as hard. A moderate but non-significant correlation existed between HR and sRPE-based methods. We also found a significant decrement in handgrip strength after practice. These findings indicate that the intensity of training experienced by our sit-skier was moderate in terms of physiological internal load during an adaptive slalom waterskiing training program.

physiology↗

bioRxiv2019

Atrial natriuretic peptide orchestrates a coordinated physiological response to fuel non shivering thermogenesis

Atrial natriuretic peptide (ANP) is a cardiac hormone controlling blood volume and arterial pressure in mammals. It is unclear whether and how ANP controls cold-induced thermogenesis in vivo. Here we show that acute cold exposure induces cardiac ANP secretion in mice and humans. Genetic inactivation of ANP promotes cold intolerance and suppresses about half of cold-induced brown adipose tissue (BAT) activation in mice. While white adipocytes are resistant to ANP-mediated lipolysis at thermoneutral temperature in mice, cold exposure renders white adipocytes fully responsive to ANP to activate lipolysis and a thermogenic program, a physiological response which is dramatically suppressed in ANP null mice. ANP deficiency also blunts liver triglycerides and glycogen metabolism thus impairing fuel availability for BAT thermogenesis. ANP directly increases mitochondrial uncoupling and thermogenic genes expression in human white and brown adipocytes. Together, these results indicate that ANP is a major physiological trigger of BAT thermogenesis upon cold exposure in mammals.

physiology↗

bioRxiv2026

Metabolomic and lipidomic shifts underpin physiological acclimation to thermal stress in the European green crab (Carcinus maenas)

Many marine invertebrates are characterized by broad and highly plastic thermal limits, though the dynamic molecular mechanisms that enable extended thermal acclimation remain poorly understood. A classic example is the green crab (Carcinus maenas), which is a prolific and damaging non-indigenous species. Using a 22-day thermal exposure to cold (5{degrees}C), ambient (13{degrees}C), or warm (30{degrees}C) temperatures, we characterized plastic shifts in C. maenas performance using respirometry and time-to-right. We then used untargeted metabolomics and lipidomics analysis of heart tissues from days 4 and 22 to identify the molecular mechanisms underpinning plastic responses over time. Crabs at 30{degrees}C exhibited higher oxygen consumption rates than counterparts at 5{degrees}C. Interestingly, oxygen consumption rate increased over time at both temperatures, indicating thermal plasticity of aerobic respiration. Temperature-dependent metabolic reprogramming was employed by crabs to sustain aerobic respiration across temperature. Catabolism of branched-chain amino acids was important for energy production at elevated temperatures, while catabolism of arginine may have sustained the minimal energy needs of crabs exhibiting metabolic depression at cold temperatures. Righting response was positively correlated with temperature, and did not exhibit any changes over time. Lipidome remodeling consistent with homeoviscous adaptation could have enabled motor activity across temperature. Higher abundances of saturated and monounsaturated lipids likely provided structural integrity to cell membranes at 30{degrees}C, while lower abundances of these compounds may have enabled membrane fluidity at 5{degrees}C. Our work demonstrates the importance of ongoing molecular reprogramming in long-term acclimation, even when whole-animal physiology remains relatively stable. Summary StatementThis study demonstrates how the highly invasive green crab regulates metabolite and lipid pathways over time to maintain physiological performance across different temperatures.

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