Metabolic Rate Research Articles

Comparison and correction on calculation methods of clothing insulation based on thermal comfort

Clothing insulation is a major factor affecting human thermal comfort, and it is usually a fixed value when the clothing ensemble are determined in the standard. However, real clothing insulation is considerably affected by the environment and activity level (metabolic rate). Thus, the heat flow method for obtaining clothing insulation through thermal equilibrium between the skin layer and environment was proposed. Later, a non-contact method for easy acquisition of clothing insulation was proposed. The method was implemented via infrared imager. In this paper, above methods were compared and analysed based on experiment data. Three activity levels were considered, sedentary (1.0 met), walking at speed of 0.8 m/s (1.8 met), and 1.2 m/s (2.6 met). The feasibility and accuracy of above methods are discussed by comparing the PMV calculated by the clothing insulation with the actual thermal sensation (TSV) of the subjects obtained by questionnaire. The results showed that the non-contact method exhibited the highest prediction accuracy. Due to the sweating effect on skin temperature, the higher the activity levels, the lower the prediction accuracy. In this paper, a correction method of clothing insulation was proposed by using the temperature of face and neck and skin wettedness. After correction, the root means square error between the PMV and TSV decreased by 11 %.

Innovative approaches to assessing risk factors, diagnostics and treatment of neonatal thrombosis

Compared to children of other ages, neonates especially seriously ill and premature subjects comprise a high thrombotic risk group. A decline in the incidence of neonatal thrombosis may be accounted for by improved treatment of severe conditions in newborns and increased survival of premature infants. Neonatal and adult hemostasis exhibit distinct physiological features: difference in concentration, synthesis rate of blood coagulation factors, metabolic rate, thrombin and plasmin levels. At the same time, neonatal threshold values for natural blood coagulation inhibitors (protein C, protein S, antithrombin, heparin cofactor II) and vitamin K-dependent coagulation factors (FII, FVII, FIX, FX) are quite low, whereas that of FVIII and von Willebrand factor exceeds those found in adults. Thus, newborns have lower plasma fibrinolytic activity. The main risk factors for developing thrombotic complications are as follows: central venous catheters, altered body fluid volume, liver disease, as well as sepsis and inflammatory processes particularly COVID-19. The significance of congenital and acquired maternal and neonatal thrombophilia may pose an additional risk factor for thrombotic complications. Low-molecular weight heparins are the first-choice drugs in treatment and prevention of neonatal thrombosis.

Multiple ultradian rhythms of metabolism, body temperature and activity in Djungarian hamsters.

Djungarian hamsters (Phodopus sungorus) living at constant 15°C Ta in short photoperiod (8:16h L:D) showed pronounced ultradian rhythms (URs) of metabolic rate (MR), body temperature (Tb) and locomotor activity. The ultradian patterns differed between individuals and varied over time. The period length of URs for MR, Tb and activity was similar although not identical. Wavelet analysis showed that three different URs are existing in parallel, URs of small amplitude and short duration (URsmall), URs of medium amplitude and medium duration (URmedium) and URs of large amplitude (URlarge), superimposed on each other. URlarge were accompanied by an increase in locomotor activity, whereas URsmall and URmedium were of metabolic origin with lacking or delayed responses of activity. An energetic challenge to cold which raised total energy requirements by about 50% did not accelerate the period length of URs, but extended the amplitude of URsmall and URmedium. URlarge corresponds with the URs of activity, feeding and drinking, sleep and arousal as described in previous studies, which are related to midbrain dopaminergic signalling and hypothalamic ultradian signalling. The cause and control of URmedium and URsmall is unknown. Their periods are similar to periods of central and peripheral endocrine ultradian signalling, suggesting a link with URs of metabolism.

Insulin regulation of lysine and α-aminoadipic acid dynamics and amino metabolites in insulin-resistant and control women.

Insulin is a key regulator of amino acids (AAs) metabolism. Many plasma AAs, including lysine and its metabolite, α-aminoadipic acid (α-AA), a predictor for developing diabetes, are elevated in insulin resistance. In 18 insulin-resistant (IR) over-weight women with polycystic ovary syndrome compared to 12 lean controls, high physiological insulin during a euglycemic clamp failed to normalize many elevated AA metabolites, including branched-chain and aromatic AA, alphaamino- butyric acid, and lysine, but normalized α-AA. To understand the underpinning of differential responses of lysine and its metabolic product α-AA to high physiological insulin in IR compared to controls, we developed a kinetic model utilizing [α-15N1] lysine and [13C1] α-AA as tracers and measured the two tracers simultaneously in α-AA by innovative mass spectrometry. High insulin increased lysine conversion to α-AA in IR and controls but failed to normalize plasma lysine concentrations in IR due to a decrease in lysine metabolic clearance rate (MCR). In contrast, despite higher conversion rates of lysine to α-AA by high insulin, α-AA concentration decreased in IR because of the sustained greater MCR of α-AA. The abnormal AAs and metabolites, even while on high physiological insulin, could potentially explain many functional derangements in IR.

Nutritional Issues among Children with Duchenne Muscular Dystrophy-Incidence of Deficiency and Excess Body Mass.

The progression of Duchenne muscular dystrophy (DMD)requires the assessment of nutritional disturbances at each stage of the disease. The purpose of this study was to assess the nutritional status in various ages of boys with DMD using screening and in-depth evaluation methods. Body composition by Dual X-ray Absorptiometry (DXA), basal metabolic rate (BMR) by indirect calorimetry, a questionnaire of nutritional status-Pediatric Nutrition Screening Tool (PNST)-and laboratory parameters were performed. In the cohort of 93 boys aged 8.54 (5.9-12.6 years), inappropriate nutritional status occurred in 41.8% of boys (underweight 11.8%, overweight 16.0%, and obesity 14.0%). In the 10-13 age group, the occurrence of overweight and underweight was the highest. Based on PNST, 15.1% of patients were at nutritional risk (≥2 points)-the most in the 14-17 age group (29%). A negative correlation was identified between PNST and z-scores of body weight, BMI, and FFMI (r Spearman = -0.49, -0.46, and -0.48, respectively; p < 0.05). There were no differences between BMR results from indirect calorimetry and calculations from the Schofield formula for any age group. In obese boys, the caloric requirement in indirect calorimetry was significantly lower than that indicated by the calculations according to the Schofield formula (p < 0.028). Inappropriate nutritional status occurred in almost half of the children with DMD. The age group in which nutritional disorders were most frequently identified was 10-13 years old. PNST could be considered a tool for screening malnutrition after testing a larger group of DMD patients.

Microwave Ablation Therapy for Hepatocellular Carcinoma: The Effect of Metabolic Heat on Temperature Distribution

Hepatocellular carcinoma is the main cause of liver cancer and one of the most occurring cancers worldwide. Microwave Ablation (MWA) is a method to destroy cancer cells by heating tumors above 50°C. Cancerous tissues can have high metabolic heat rates and affect temperature gain and distribution in thermal therapies. This research clarifies the metabolic heat effects in MWA therapy of liver cancer. Using Pennes Bioheat transfer equation with finite element numerical method, this research simulates temperature distribution with metabolic heat value ranging from 368,1 W/m3 to 29000 W/m3. The heat generated by metabolic heat is lower than the MWA heat source. However, the temperature increase should be considered as it can increase healthy surrounding tissue temperature to dangerous levels.

Enhancing Liver Transplant Outcomes through Liver Precooling to Mitigate Inflammatory Response and Protect Mitochondrial Function.

Transplanted organs experience several episodes of ischemia and ischemia-reperfusion. The graft injury resulting from ischemia-reperfusion (IRI) remains a significant obstacle to the successful survival of transplanted grafts. Temperature significantly influences cellular metabolic rates because biochemical reactions are highly sensitive to temperature changes. Consequently, lowering the temperature could reduce the degradative reactions triggered by ischemia. In mitigating IRI in liver grafts, the potential protective effect of localized hypothermia on the liver prior to blood flow obstruction has yet to be explored. In this study, we applied local hypothermia to mouse donor livers for a specific duration before stopping blood flow to liver lobes, a procedure called "liver precooling". Mouse donor liver temperature in control groups was controlled at 37 °C. Subsequently, the liver donors were preserved in cold University of Wisconsin solution for various durations followed by orthotopic liver transplantation. Liver graft injury, function and inflammation were assessed at 1 and 2 days post-transplantation. Liver precooling exhibited a significant improvement in graft function, revealing more than a 47% decrease in plasma aspartate transaminase (AST) and alanine aminotransferase (ALT) levels, coupled with a remarkable reduction of approximately 50% in liver graft histological damage compared to the control group. The protective effects of liver precooling were associated with the preservation of mitochondrial function, a substantial reduction in hepatocyte cell death, and a significantly attenuated inflammatory response. Taken together, reducing the cellular metabolism and enzymatic activity to a minimum level before ischemia protects against IRI during transplantation.

Lysine Methylation and Histone Modifications during Cold Stress of Insects: Freeze-Tolerant Eurosta solidaginis and Freeze-Avoiding Epiblema scudderiana.

Overwintering survival by insects, whether of the freeze-tolerant or freeze-avoiding types, is typically associated with a strong suppression of metabolic rate (e.g., entry into diapause) that involves the differential expression of many genes with regulation at the transcriptional, translational or post-translational levels. Epigenetic modifications have been suggested to play a vital role in regulating cold responses of insects. However, knowledge of the roles of epigenetic mechanisms in modulating gene expression for winter survival of the larvae of two goldenrod gall formers, the freeze-tolerant dipteran Eurosta solidaginis and the freeze-avoiding lepidopteran Epiblema scudderiana, remain unknown. The current study evaluates the role of cold-induced lysine methylation and histone modifications, with enzymes of lysine methylation (SETD8, SETD7, SUV39H1, SMYD2 and ASH2L), as well as relative levels of histone H3 acetylation (H3K9ac, H3K18ac, H3K27ac, H3K56ac) and methylation (H3K4me1, H3K9me3, H3K36me2) examined in two insects. Significant (p < 0.05) reductions were observed in most of the targets of histone methylation/acetylation for decreasing temperatures of Ep. scudderiana larvae, whereas selected histone methylation/acetylation targets were conversely elevated (p < 0.05) in E. solidaginis, particularly under conditions of 5 °C for 4 h. Histone H3 expression was found to be variable without statistical differences in larval goldenrod gall moths and gall flies. These results provide basic information on the patterns of epigenetic regulation involved in insect cold hardiness.

Genetically engineering glycolysis in T cells increases their antitumor function

BackgroundT cells play a central role in the antitumor response. However, they often face numerous hurdles in the tumor microenvironment, including the scarcity of available essential metabolites such as glucose...

O-287 Body composition analysis and metabolic monitoring before fertility treatment: hype or hope?

Abstract The effect of body mass index on both spontaneous and assisted fertility is well known: both lower and high indexes are correlated with negative outcome including live birth rate. Asides the dysmetabolic infertility that can develop by inflammation, insulin resistance and hyperandrogenemia, psychological and social factors deserve attention: a sexual self-image dysfunction is present in up to 20% of obese people with lower sexual desire and arousal. A positive note is that ART patients want to know about the impact of diet on fertility and ART success, asides the safety of the treatment and coping strategies, when asked about research priorities. Nevertheless, research in the field of preconception weight loss in the case of obesity in non-conclusive. The difference may lay in the strategy followed: lifestyle interventions may differ in approach, new weight-losing drugs might be involved or avoided, and targets and endpoints differ between studies. A first statement is to be made: body weight is a parameter of the past. In the world of nutrition, BMI is used to describe populations but fails to give accurate information about a single person. Body composition is more refined and can be used in follow-up. Asides dual energy X-ray absorptiometry (DXA), Bio Electrical Impedance Vector Analysis (BIVA) is used to endotype patients. Magnetic Resonance Imaging can, in a whole-body approach, provides very detailed information. In general, fat mass, fat free mass, phase angle (quantitative information) and fat infiltration of muscle (qualitative aspect) are considered ‘the kg of the future’. Associations between higher amounts of fat and poorer ART outcomes are published. As body composition is the result of food intake balanced to total energy expenditure (composed from basal energy expenditure, diet induced thermogenesis and physical activity level), the knowledge of these aspects can form a basis for a personalized approach. Techniques used in clinical practice relevant to this topic are food diary analysis by specialized dietitians (quantitative and qualitative analysis of food intake) and indirect calorimetry. This device will measure oxygen consumption and carbon dioxide production and calculate the basal metabolic rate in kcal/day. The concept of nutrition intake balanced to energy expenditure is validated in critically ill patients where it reduces mortality. It also showed benefit in a cancer population during active treatment. In a tertiary, university hospital in Brussels, Belgium, the forces of the fertility clinic and the nutrition department were combined: FerMet (Fertility-Metabolism). Patients seeking ART with a BMI &amp;lt;18;5 or higher than 30 are directed. Biophysical endotyping is performed by both metabolic screening, food intake analysis and baseline testing: body composition by BIVA and metabolic measurement by indirect calorimetry. A personalized intervention plan is developed in co-operation with the patient(s) by the dietitian and the supervising MD. Psychological reference or physical activity coaching is initiated if needed. Interim results: a total of 3793 men and woman in 3,5 years. In the population with a BMI below 20, which is only 6.4% of the entire group, body composition analysis reveals: only 9% are confirmed with alarmingly low body fat mass, such as seen in eating disorders. 23% has a fat mass percentage comparable to the general population and 66% represents what is known as ‘constitutional lean’. This might open opportunities to refine criteria to withhold ART based on body weight. In the overweight population, interventions can be tailored on individual metabolic rates and eating patterns, which is unique in the setting of ART. Whole Body MRi can be used in research settings. Benefits of this Biophysical Endotype based interventions to increase fertility outcomes need to be proven by further research.

Development of Single-Nucleotide Polymorphism Markers and Population Genetic Analysis of the Hadal Amphipod Alicella gigantea across the Mariana and New Britain Trenches

Alicella gigantea, the largest amphipod scavengers found to date, play key roles in the food web of the hadal ecosystem. However, the genetic structure of A. gigantea populations among different trenches has not been reported yet. In this study, SNP (single-nucleotide polymorphism) markers were developed for three A. gigantea geographic populations collected from the southern Mariana Trench (SMT), the central New Britain Trench (CNBT), and the eastern New Britain Trench (ENBT), based on the SLAF-seq (specific locus amplified fragment sequencing) technology. A total of 570,168 filtered SNPs were screened out for subsequent population genetic analysis. Results showed that the inbreeding levels across the three geographic populations were relatively low, and the genomic inbreeding coefficients of the three populations were similar in magnitude. Based on the results of phylogenetic analysis, population structure analysis, and principal component analysis, it is believed that the three A. gigantea geographic populations belong to the same population, and the kinship relationship between the ENBT and CNBT populations is close. Moreover, the differential candidate adaptive sites on the SNPs suggest that there may be variations in metabolic rates among the three geographic populations, possibly linked to differences in food availability and sources in different trenches, ultimately resulting in different survival strategies in A. gigantea populations within distinct trenches. Compared with the Mariana Trench, the New Britain Trench has a richer organic matter input, and it is speculated that the A. gigantea Mariana Trench population may adopt a lower metabolic rate to cope with the harsher environment of nutrient deficiency.

Outcome of Neonatal Registry Through Electronic Medical Registry at Neonatal Intensive Care Units, Children's Hospital of Ain Shams University

Abstract Background The neonatal mortality rate is 19 deaths per 1000 live births worldwide. Studies have shown that neonatal registry network systems can provide the necessary data for establishing evidence- based strategies to decrease the complications in high-risk neonates and consequently reduce neonatal mortality rate. Aim of the Work To determine the frequency and distribution of neonatal critical illnesses in Neonatal Intensive Care Unit (NICU) of Ain Shams University. Patients and Methods This descriptive study was conducted in NICU, Children's Hospital, Ain Shams University. The data collected from initiated neonatal registry through electronic medical record to reach sample size number (381) patients. The current study was conducted after approval by the Department of Pediatrics, and the local Ethics and Research Committee, Faculty of Medicine, Ain Shams University. Results The mean ± (SD) age at admission was 5.52 ± 6.9 days, gestational age was 36.19 ± 2.47 weeks, more than half of our patients were males (55.6%) and females represented in (44.4%). Two- thirds (64.2%) of our participants were full term, and preterm were only (35.7%). The main etiology of NICU admission was respiratory disease (35.7%), followed by neonatal sepsis (25.2%), neonatal jaundice (21%), congenital anomalies (12.3%), CNS diseases (6.8%), inborn errors of metabolism (1%) and mortality rate was 10.5%. Four cases had inborn errors of metabolism in the form of: Maple syrup urine disease (one case), organic academia (one cases) and 2 cases referred to genetic clinic for further assessment. Congenital heart diseases in our study was reported in (7.9%) of neonates. The main etiology among them was reported in following order: PDA / pulmonary hypertension (26.7%), VSD (13.3%), Fallot tetralogy (10%), transposition of great arteries (10%), supraventricular tachycardia (6.7%) then many etiologies represented in 3.3% as Ebstein anomaly, right single ventricle, heart block, pulmonary artery stenosis, arrhythmia, tricuspid atresia and left hypoplastic heart disease. Conclusion This study showed the ability of the electronic medical record to store large amounts of data which creates a potential for information overload in the intensive care (ICU) setting. This will stimulate and facilitate research on neonatal critical illness and its management, mortality and morbidity outcomes of neonates admitted to NICUs in Children's Hospital, Ain Shams University, Egypt.

Evidence for direct CO2-mediated alterations in cerebral oxidative metabolism in humans.

How the cerebral metabolic rates of oxygen and glucose utilization (CMRO2 and CMRGlc, respectively) are affected by alterations in arterial PCO2 (PaCO2) is equivocal and therefore was the primary question of this study. This retrospective analysis involved pooled data from four separate studies, involving 41 healthy adults (35 males/6 females). Participants completed stepwise steady-state alterations in PaCO2 ranging between 30 and 60 mmHg. The CMRO2 and CMRGlc were assessed via the Fick approach (CBF × arterial-internal jugular venous difference of oxygen or glucose content, respectively) utilizing duplex ultrasound of the internal carotid artery and vertebral artery to calculate cerebral blood flow (CBF). The CMRO2 was altered by 0.5 mL × min-1 (95% CI: -0.6 to -0.3) per mmHg change in PaCO2 (p < 0.001) which corresponded to a 9.8% (95% CI: -13.2 to -6.5) change in CMRO2 with a 9 mmHg change in PaCO2 (inclusive of hypo- and hypercapnia). The CMRGlc was reduced by 7.7% (95% CI: -15.4 to -0.08, p = 0.045; i.e., reduction in net glucose uptake) and the oxidative glucose index (ratio of oxygen to glucose uptake) was reduced by 5.6% (95% CI: -11.2 to 0.06, p = 0.049) with a + 9 mmHg increase in PaCO2. Collectively, the CMRO2 is altered by approximately 1% per mmHg change in PaCO2. Further, glucose is incompletely oxidized during hypercapnia, indicating reductions in CMRO2 are either met by compensatory increases in nonoxidative glucose metabolism or explained by a reduction in total energy production.

An electrophysiological correlate of sleep in a shark.

Sleep is a prominent physiological state observed across the animal kingdom. Yet, for some animals, our ability to identify sleep can be masked by behaviors otherwise associated with being awake, such as for some sharks that must swim continuously to push oxygenated seawater over their gills to breathe. We know that sleep in buccal pumping sharks with clear rest/activity cycles, such as draughtsboard sharks (Cephaloscyllium isabellum, Bonnaterre, 1788), manifests as a behavioral shutdown, postural relaxation, reduced responsiveness, and a lowered metabolic rate. However, these features of sleep do not lend themselves well to animals that swim nonstop. In addition to video and accelerometry recordings, we tried to explore the electrophysiological correlates of sleep in draughtsboard sharks using electroencephalography (EEG), electromyography, and electrooculography, while monitoring brain temperature. The seven channels of EEG activity had a surprising level of (apparent) instability when animals were swimming, but also when sleeping. The amount of stable EEG signals was too low for replication within- and across individuals. Eye movements were not measurable, owing to instability of the reference electrode. Based on an established behavioral characterization of sleep in draughtsboard sharks, we offer the original finding that muscle tone was strongest during active wakefulness, lower in quietly awake sharks, and lowest in sleeping sharks. We also offer several critical suggestions on how to improve techniques for characterizing sleep electrophysiology in future studies on elasmobranchs, particularly for those that swim continuously. Ultimately, these approaches will provide important insights into the evolutionary confluence of behaviors typically associated with wakefulness and sleep.

How hot is too hot? Metabolic responses to temperature across life stages of a small ectotherm.

To understand how global warming will impact biodiversity, we need to pay attention to those species with higher vulnerability. However, to assess vulnerability we also need to consider the thermoregulatory mechanisms, body size and thermal tolerance of species. Studies addressing thermal tolerance on small ectotherms have mostly focused on insects, while other arthropods such as arachnids remain understudied. Here, we quantified the physiological thermal sensitivity of the pseudoscorpion Dactylochelifer silvestris using a respirometry setup with a ramping temperature increase. Overall, we found that D. silvestris has a much lower metabolic rate than other organisms of similar size. As expected, metabolic rate increased with body size, with adults having larger metabolic rates, but the overall metabolic scaling exponent was low. Both the temperature at which metabolism peaked and the critical thermal maxima were high (above 44°C) and comparable to those of other arachnids. The activation energy, which characterizes the rising portion of the thermal sensitivity curve, was 0.66 eV, consistent with predictions for insects and other taxa in general. Heat tolerances and activation energy did not differ across life stages. We conclude that D. silvestris has low metabolic rates and a high thermal tolerance, which would likely influence how all stages and sexes of this species could endure climate change.

Frequency-modulated timer regulates torpor–arousal cycles during hibernation in distinct small mammalian hibernators

Hibernation allows mammals to endure harsh seasons by reducing their basal metabolism and body temperature (Tb) to minimize energy expenditure. During hibernation in small animals such as Syrian hamsters and 13-lined ground squirrels, Tb decreases to an ambient level ( < 5 °C) and remains constant for days to weeks in a physiological condition termed deep torpor. Torpor is interrupted by periods of arousal, during which Tb recovers to a euthermic level (approximately 37 °C), and these torpor–arousal cycles are repeated multiple times during hibernation. However, little is known about the mechanisms governing Tb fluctuations during hibernation. In this study, we employed an unbiased model selection approach to Tb data and revealed that a model incorporating frequency modulation quantitatively reproduced Tb fluctuation during hibernation in Syrian hamsters. We found that an unexpectedly long period of 120–430 days modulates a shorter period of several days. In addition, the aforementioned model reproduced Tb fluctuation in 13-lined ground squirrels, which can undergo repeated hibernation according to intrinsic circannual rhythms in constant laboratory conditions. This is the first quantitative study to demonstrate the concerted action of two endogenous periods, one lasting a few days and the other lasting a year, in the torpor–arousal cycles of distinct mammalian hibernators. We anticipate that our theoretical analysis of Tb fluctuation will be a starting point for quantitative comparisons of hibernation patterns across various hibernating species. Furthermore, quantification of Tb data using models will foster our understanding of the molecular mechanisms of hibernation by revealing the biological processes operating within these periods.

Measurement ofenergy availability in highly trained male endurance athletes and examination of its associations with bone health and endocrine function.

Despite the introduction of Relative Energy Deficiency in Sport (RED-s) in 2014, there is evidence to suggest that male endurance athletes still present with a high prevalence of low energy availability (LEA). Previous findings suggest that energy availability (EA) status is strongly correlated with impairments in endocrine function such as reduced leptin, triiodothyronine (T3), and insulin, and elevated bone loss. This study aimed to report the current EA status, endocrine function and bone health of highly trained Irish male endurance athletes. In this cross-sectional study, participants (n = 3 triathletes; n = 10 runners) completed a 7-day testing period during the competition season using lab-based measures, to ascertain EA status, hormone level and rates of bone metabolism. Serum blood samples were obtained to assess hormone levels and markers of bone metabolism. Mean EA was < 30kcal/kg lean body mass (LBM)/day in 76.9% of athletes. There was a strong association between LEA and low carbohydrate intake, and lower LBM. Mean levels of insulin, IGF-1 and leptin were significantly lower than their reference ranges. Elevated mean concentrations of β-CTX and a mean P1NP: β-CTX ratio < 100, indicated a state of bone resorption. The EA level, carbohydrate intake, hormone status and bone metabolism status of highly trained male endurance athletes are a concern. Based on the findings of this study, more frequent assessment of EA across a season is recommended to monitor the status of male endurance athletes, in conjunction with nutritional education specific to EA and the associated risks.

Effects of low temperature on growth and metabolism of larval green sturgeon (Acipenser medirostris) across early ontogeny.

Southern Distinct Population Segment (sDPS) green sturgeon spawn solely in one stretch of the Sacramento River in California. Management of this spawning habitat is complicated by cold water temperature requirements for the conservation of winter-run Chinook salmon. This study assessed whether low incubation and rearing temperatures resulted in carryover effects across embryo to early juvenile life stages on scaling relationships in growth and metabolism in northern DPS green sturgeon used as a proxy for sDPS green sturgeon. Fish were incubated and reared at 11°C and 15°C, with a subset experiencing a reciprocal temperature transfer post-hatch, to assess recovery from cold incubation or to simulate a cold-water dam release which would chillrearing larvae. Growth and metabolic rate of embryos and larvae were measured to 118days post hatch. Reciprocal temperature transfers revealed a greater effect of low temperature exposure during larval rearing rather than during egg incubation. While 11°C eggs hatched at a smaller length, log-transformed length-weight relationships showed that these differences in developmental trajectory dissipated as individuals achieved juvenile morphology. However, considerable size-at-age differences persisted between rearing temperatures, with 15°C fish requiring 60days post-hatch to achieve 1g in mass, whereas 11°C fish required 120days to achieve 1g, resulting in fish of the same age at the completion of the experiment with a ca. 37-fold difference in weight. Consequently, our study suggests that cold rearing temperatures have far more consequential downstream effects than cold embryo incubation temperatures. Growth delays from 11°C rearing temperatures would greatly increase the period of vulnerability to predation in larval green sturgeon. The scaling relationship between log-transformed whole-body metabolism and mass exhibited a steeper slope and thus an increased oxygen requirement with size in 11°C reared fish, potentially indicating an energetically unsustainable situation. Understanding how cold temperatures affect green sturgeon ontogeny is necessary to refine our larval recruitment estimations for this threatened species.

Standard metabolic rate variation among New Zealand Orthoptera

Standard metabolic rates (SMR) of ectotherms reflect the energetic cost of self-maintenance and thus provide important information about life-history strategies of organisms. We examined variation in SMR among fifteen species of New Zealand orthopteran. These species represent a heterogeneous group with a wide geographic distribution, differing morphologies and life histories. Gathering original data on morphological and physiological traits of individual species is a first step towards understanding existing variability. Individual metabolic rates of ectotherms are one of the first traits to respond to climate change. Baseline SMR datasets are valuable for modeling current species distributions and their responses to a changing climate. At higher latitudes, the average environmental temperature decreases. The pattern that cold-adapted ectotherms display higher SMR at colder temperatures and greater thermal sensitivity to compensate for lower temperatures and the shorter growing and reproductive seasons is predicted from the metabolic cold adaptation (MCA) hypothesis. We predict higher SMR for the orthopteran species found at higher latitudes. We further compared the index of thermal sensitivity Q10 per species. We used closed-system respirometry to measure SMR, at two test temperatures (4 °C and 14 °C), for the fifteen species acclimated to the same conditions. As expected, we found significant differences in SMR among species. The rate of oxygen consumption was positively correlated with body mass. Our findings do not support the MCA hypothesis. In fact, we found evidence of co-gradient variation in SMR, whereby insects from higher elevations and latitudes presented lower SMR. We discuss our findings in relation to life histories and ecology of each species. The novel physiological data presented will aid in understanding potential responses of these unusual species to changing climatic conditions in Aotearoa/New Zealand.

The effects of humidity on thermoregulatory physiology of a small songbird.

Scholander-Irving curves describe the relationship between ambient temperature and metabolic rate and are fundamental to understanding the energetic demands of homeothermy. However, Scholander-Irving curves are typically measured in dry air, which is not representative of the humidity many organisms experience in nature. Consequently, it is unclear (1) whether Scholander-Irving curves (especially below thermoneutrality) are altered by humidity, given the effects of humidity on thermal properties of air, and (2) whether physiological responses associated with Scholander-Irving curves in the lab reflect organismal performance in humid field conditions. We used laboratory experiments and biophysical models to test the effects of humidity on the thermoregulatory physiology of tree swallows (Tachycineta bicolor). We also tested whether physiological responses measured under lab conditions were correlated with field body temperatures and nestling provisioning rates. We found that humidity reduced rates of evaporative water loss but did not have large effects on body temperature or metabolic rate, suggesting that swallows can decouple evaporative cooling, body temperature and metabolic rate. Although the effect of humidity on metabolic rate in the lab was small, our biophysical models indicated that energetic costs of thermoregulation were ∼8% greater in simulations that used metabolic rates from birds in humid compared with dry conditions. Finally, we found mixed evidence that physiological responses measured in the lab under humid or dry conditions were associated with body temperature and nest provisioning rates in the field. Our results help clarify the effect of humidity on endotherm thermoregulation, which may help forecast organismal responses to environmental change.