Journal of Comparative Physiology B-Biochemical Systems and Environmental Physiology最新文献

The combined stresses of fasting and hypoxia are common events during the life history of freshwater fish species. Hypoxia tolerance is vital for survival in aquatic environments, which requires organisms to down-regulate their maintenance energetic expenditure while simultaneously preserving physiological features such as oxygen supply capacity under conditions of food deprivation. Generally, infrequent-feeding species who commonly experience food shortages might evolve more adaptive strategies to cope with food deprivation than frequent-feeding species. Thus, the present study aimed to test whether the response of hypoxia tolerance in fish to short-term fasting (2 weeks) varied with different foraging modes. Fasting resulted in similar decreases in maintenance energetic expenditure and similar decreases in P_crit and P_loe between fishes with different foraging modes, whereas it resulted in decreased oxygen supply capacity only in frequent-feeding fishes. Furthermore, independent of foraging mode, fasting decreased P_crit and P_loe in all Cypriniformes and Siluriformes species but not in Perciformes species. The mechanism for decreased P_crit and P_loe in Cypriniformes and Siluriformes species is at least partially due to the downregulated metabolic demand and/or the maintenance of a high oxygen supply capacity while fasting. The present study found that the effect of fasting on hypoxia tolerance depends upon phylogeny in freshwater fish species. The information acquired in the present study is highly valuable in aquaculture industries and can be used for species conservation in the field.

The present study aimed to establish zebrafish as an experimental model for investigations into obesity and physical exercise, as well as to assess the effects of these factors on metabolism. The experiment spanned twelve weeks, comprising a feeding trial during which the last four weeks incorporated a physical exercise protocol. This protocol involved placing fifteen animals in a five-liter aquarium, where they were subjected to swimming at an approximate speed of 0.08 m/s for 30 min daily. Throughout the experiment, histological analyses of visceral, subcutaneous, and hepatic adipose tissues were conducted, along with biochemical analyses of total cholesterol and its fractions, triglycerides, glucose, lactate, and alanine aminotransferase (ALT) levels. Additionally, oxidative stress markers, such as reactive oxygen species (ROS) levels, superoxide dismutase (SOD) activity, and catalase activity and the formation of thiobarbituric acid-reactive substances, were investigated. The results revealed that the group fed a high-fat diet exhibited an increase in ROS production and SOD activity. In contrast, the group administered the high-fat diet and subjected to physical exercise demonstrated a notable reduction in visceral adipocyte area, hepatic steatosis levels, ALT levels, and SOD activity. These findings indicate that physical exercise has a positive effect on obesity and oxidative stress in zebrafish, providing promising evidence for future investigations in this field.

An individual's energetic demands and hence metabolic rate can strongly change during adolescence, a phase characterized by profound morphological, physiological, and endocrine changes. Glucocorticoid hormones (e.g. cortisol) are released in response to hypothalamic-pituitary-adrenal-axis activity, modulate several metabolic processes, and can also be linked to increased metabolic rate. In domestic guinea pigs (Cavia aperea f. porcellus) housed in same-sex groups, cortisol concentrations increase during adolescence in males but remain stable in females, which was suggested to be related to different energetic demands by age. We therefore measured metabolic rate through oxygen (O₂) consumption over 2.5 h in male and female guinea pigs housed in same-sex groups during adolescence at ages of 60, 120, and 180 days, which was paralleled by analyses of saliva cortisol concentrations before and after the measurement. The statistical analyses involved whole body metabolic rate (ml O₂/h), body mass-corrected metabolic rate (ml O₂/h/kg), and body mass-independent metabolic rate (ml O₂/h statistically corrected for body mass). We found increasing cortisol concentrations with age in males only, but none of the three metabolic rate analyses revealed a sex difference by age. On the individual level, repeatability across ages was found in metabolic rate as well as in body mass and cortisol concentrations after the measurement, but not in "basal" cortisol concentrations. Our results suggest no sex-specific changes in metabolic rate and hence equal energetic demands in male and female guinea pigs during adolescence. Moreover, metabolic rate clearly represents a highly stable physiological trait already early in a guinea pig's life irrespective of rather fluctuating cortisol concentrations.

With climate change increasing not just mean temperatures but the frequency of cold snaps and heat waves, animals occupying thermally variable areas may be faced with thermal conditions for which they are not prepared. Studies of physiological adaptations of temperate resident birds to such thermal variability are largely lacking in the literature. To address this gap, we acclimated winter-phenotype house sparrows (Passer domesticus) to stable warm, stable cold, and fluctuating cold temperatures. We then measured several metrics of the oxidative stress (OS) system, including enzymatic and non-enzymatic antioxidants and lipid oxidative damage, in brain (post-mitotic), kidney (mitotic), liver (mitotic) and pectoralis muscle (post-mitotic). We predicted that high metabolic flexibility could be linked to increases in reactive oxygen damage. Alternatively, if variation in ROS production is not associated with metabolic flexibility, then we predict no antioxidant compensation with thermal variation. Our data suggest that ROS production is not associated with metabolic flexibility, as we found no differences across thermal treatment groups. However, we did find differences across tissues. Brain catalase activity demonstrated the lowest values compared with kidney, liver and muscle. In contrast, brain glutathione peroxidase (GPx) activities were higher than those in kidney and liver. Muscle GPx activities were intermediate to brain and kidney/liver. Lipid peroxidation damage was lowest in the kidney and highest in muscle tissue.

Many flatfish species are partially euryhaline, such as the Pacific sanddab which spawn and feed in highly dynamic estuaries ranging from seawater to near freshwater. With the rapid increase in saltwater invasion of freshwater habitats, it is very likely that in these estuaries, flatfish will be exposed to increasing levels of dissolved organic carbon (DOC) of freshwater origin at a range of salinities. As salinity fluctuations often coincide with changes in DOC concentration, two natural freshwater DOCs [Luther Marsh (LM, allochthonous) and Lake Ontario (LO, autochthonous) were investigated at salinities of 30 and 7.5 ppt. Optical characterization of the two natural DOC sources indicate salinity-dependent differences in their physicochemistry. LO and LM DOCs, as well as three model compounds [tannic acid (TA), sodium dodecyl sulfate (SDS) and bovine serum albumin (BSA)] representing key chemical moieties of DOC, were used to evaluate physiological effects on sanddabs. In the absence of added DOC, an acute decrease in salinity resulted in an increase in diffusive water flux (a proxy for transcellular water permeability), ammonia excretion and a change in TEP from positive (inside) to negative (inside). The effects of DOC (10 mg C L^-1) were salinity and source-dependent, with generally more pronounced effects at 30 than 7.5 ppt, and greater potency of LM relative to LO. Both LM DOC and SDS increased diffusive water flux at 30 ppt but only SDS had an effect at 7.5 ppt. TA decreased ammonia excretion at 7.5 ppt. LO DOC decreased urea-N excretion at both salinities whereas the stimulatory effect of BSA occurred only at 30 ppt. Likewise, the effects of LM DOC and BSA to reduce TEP were present at 30 ppt but not 7.5 ppt. None of the treatments affected oxygen consumption rates. Our results demonstrate that DOCs and salinity interact to alter key physiological processes in marine flatfish, reflecting changes in both gill function and the physicochemistry of DOCs between 30 and 7.5 ppt.

The current research was conducted to assess the effect of in ovo feeding (IOF) of selenium (Se) and zinc (Zn) on hatchability, production performance, liver, intestinal morphology, antioxidant levels and expression levels of immune-related genes in broiler chickens. A total of 400 fertilized eggs were equally divided into four groups: control (non-injected), sham (in ovo injection of 0.75% NaCl), Se (@ 1.5 µg/egg in ovo injection) and Zn (500 µg/egg in ovo injection) groups respectively. On the seventeenth day of incubation, treatment solutions were administered into amniotic fluid of fertilized eggs. The results revealed that Se and Zn supplementation significantly (P < 0.05) enhanced hatchability, post-hatch growth, organ development, and liver antioxidant capability. Histopathological examination revealed a typical hepatocyte morphology, well-arranged cells, and a significant (P < 0.05) decrease in apoptosis in both selenium and zinc groups. Additionally, selenium and zinc produced auspicious effects on intestinal epithelium and villi surface area. Interestingly, our results revealed that IOF of Se and Zn modulated the expression of immune-related genes in comparison to the control and sham groups. Conclusively, IOF of Se and Zn augmented health and productivity by enhancing the cellular immunity in the broiler chickens, thus IOF can be utilized as an effective strategy to promote health and immunity in broiler chickens.

Energy conservation associated with hibernation is maximized at the intersection of low body temperature (T_b), long torpor bouts, and few interbout arousals. In the arctic ground squirrel (Urocitellus parryii), energy conservation during hibernation is best achieved at ambient temperatures (T_a) around 0 °C; however, they spend the majority of hibernation at considerably lower T_a. Because arctic ground squirrels switch to mixed fuel metabolism, including protein catabolism, at extreme low T_a of hibernation, we sought to investigate how microbial urea-nitrogen recycling is used under different thermal conditions. Injecting squirrels with isotopically labeled urea (¹³C/¹⁵N) during hibernation at T_a's of - 16 °C and 2 °C and while active and euthermic allowed us to assess the ureolytic activity of gut microbes and the amount of liberated nitrogen incorporated into tissues. We found greater incorporation of microbially-liberated nitrogen into tissues of hibernating squirrels. Although ureolytic activity appears higher in euthermic squirrels, liberated nitrogen likely makes up a smaller percentage of the available nitrogen pool in active, fed animals. Because non-lipid fuel is a limiting factor for torpor at lower T_a in this species, we hypothesized there would be greater incorporation of liberated nitrogen in animals hibernating at - 16 °C. However, we found higher microbial-ureolytic activity and incorporation of microbially-liberated nitrogen, particularly in the liver, in squirrels hibernating at 2 °C. Likely this is because squirrels hibernating at 2 °C had higher T_b and longer interbout arousals, a combination of factors creating more favorable conditions for gut microbes to thrive and maintain greater activity while giving the host more time to absorb microbial metabolites.

The Australian brushtail possum (Trichosurus vulpecula) is adapted to a wide range of food plants across its range and is exposed to numerous physiological challenges. Populations that are resistant to the plant toxin sodium fluoroacetate are of particular interest as this compound has been used since the 1940s for vertebrate pest management around the world. Candidate gene identification is an important first step in understanding how spatial populations have responded to local selection resulting in local physiological divergence. We employ differential gene expression of liver samples from wild-caught brushtail possums from toxin-resistant and toxin-susceptible populations to identify candidate genes that might be involved in metabolic pathways associated with toxin-resistance. This allowed us to identify genetic pathways involved in resistance to the plant toxin sodium fluoroacetate in Western Australian possums but not those originally from south eastern Australia. We identified differentially expressed genes in the liver that are associated with cell signalling, encapsulating structure, cell mobility, and tricarboxylic acid cycle. The gene expression differences detected indicate which metabolic pathways are most likely to be associated with sodium fluoroacetate resistance in these marsupials and we provide a comprehensive list of candidate genes and pathways to focus on for future studies.

Sleep deprivation (SD) can affect the adaptive thermogenesis in laboratory rodents, but the molecular mechanism and the crosstalk with other organs remain largely unknown. In order to investigate the effects and mechanisms of SD on thermoregulation and energy metabolism, here we measured the changes of body weight, body fat mass, body temperature, resting metabolic rate (RMR), and thermogenic gene expression in brown adipose tissue (BAT), white adipose tissue (WAT), skeleton muscle and liver in C57BL/6J mice during 7-day SD with rotating rod sleep deprivation device. Results showed that compared with the control group, the body weight and body fat mass of SD mice were decreased and RMR of SD mice increased. The gene expression of Ampk, Pgc1α and Ucp1 which related to thermogenesis in BAT and WAT were significantly increased, and the expression of Ampk, Serca1, Serca2 and Ucp3 which related to thermogenesis in skeletal muscle were significantly increased in SD mice. Taken together, these data demonstrated that 7-day SD enhanced the adaptive thermogenesis in mice by activating AMPK, including the upregulation of the AMPK - PGC1α - UCP1 pathway in BAT, and the AMPK - UCP3 and SLN - SERCA pathway in skeleton muscle. Our data provide the molecular evidence for SD-stimulated adaptive thermogenesis and energy metabolism in small mammals.