Comparative Biochemistry and Physiology A-Molecular & Integrative Physiology最新文献

The ability to endure a wide range of body temperatures, called heterothermy, offers many species worldwide the possibility to survive times of malnourishment by lowering metabolic rate and body temperature. During development, facultative hypothermia and therefore lowered body temperatures might have disadvantages. Our study aimed at identifying potential trade-offs between the use of facultative hypothermia and investment into growth, immunity, and nutritional physiology in chicks of an Antarctic seabird, the Wilson's Storm-petrel (Oceanites oceanicus). To answer these questions, we used the irregular occurrence of facultative hypothermia of chicks from a free-living colony breeding on the South Shetland Islands, Antarctica. Our study showed that chicks experiencing lower body temperatures or snowstorms had slower growth, fewer circulating leukocytes, and lower triglyceride concentrations. These findings suggest reduced investment into physiology and growth during events of facultative hypothermia. Patterns of wing growth following facultative hypothermia suggest that chicks may recover within little time after feeding and rewarming. For other parameters, more data of intervals with facultative hypothermic body temperatures followed by normothermy are needed to allow similar conclusions. Our results suggest that while heterothermy seems a beneficial strategy for chick survival in this species, it incurs partially reversible trade-offs with other physiological traits.

Climate change increases fluctuations in water salinity and temperature, which affects osmoregulation, energy metabolism, and the immune response in milkfish (Chanos chanos). Milkfish, an important economic species in Southeast Asia, can tolerate a wide range of salinity levels. However, sudden winter cold snaps often result in high mortality among cultured milkfish. Cold-inducible RNA-binding protein (Cirp), a well-known multi-stress indicator in mammals, is inducible by environmental stressors. However, studies on Cirp in teleost fish remain scarce, and most existing work has focused primarily on transcriptomic analyses. This study aimed to assess Cirp expression as a potential indicator of acute environmental stress in milkfish. Two cirp genes, cirpa and cirpb, were previously identified in milkfish; and both are widely distributed among tissues; notably, cirpa expression in the gills is approximately 3-fold higher in fresh water (FW)- than in seawater (SW)-acclimated milkfish. Quantitative real-time PCR revealed that cirpa expression in the gills was upregulated approximately 2-fold, while cirpb expression increased more than 2-fold in the liver and gills of milkfish at 24 h of hypothermal stress across salinity conditions. Furthermore, cirpb expression in the gills increased (approximately 1.8-fold) at 12 and 24 h after exposure to a hyperosmotic challenge and at 6 h after transferring to a hypoosmotic environment, whereas cirpa expression was induced about 2-fold only after hypothermal challenge at 12 h. Overall, cirpb expression was consistently upregulated by both salinity and hypothermal stress in the gills and liver of milkfish, whereas cirpa showed a more limited response, indicating that cirpb is a more sensitive molecular indicator of hypothermal and osmotic stress.

Insulin-like growth factor binding protein 3 (IGFBP3), an important member of the IGFBP family, is involved in growth, reproduction and metabolic regulation. In the present study, we isolated and characterized two IGFBP3 subtypes, namely IGFBP3a and IGFBP3b from turbot through rapid amplification of cDNA ends-polymerase chain reaction (RACE-PCR) cloning. The deduced amino acid sequences of turbot IGFBP3a and IGFBP3b showed high homology to those of other teleosts, particularly with Atlantic halibut (Hippoglossus hippoglossus). Turbot IGFBP3a and IGFBP3b contained two conserved motifs in the IGFBP domain (GCGCCXXC) and thyroglobulin type 1 domain (CWCV) as well as conserved cysteines. Molecular docking analysis predicted that IGFBP3a preferentially bound to IGF3, whereas IGFBP3b preferentially bound to IGF1. Both proteins localized in the cytoplasm and nucleus. The igfbp3a mRNA was most abundant in the livers of males and the pituitary of females, followed by the pituitary and heart in males, and the ovaries in females. However, igfbp3b was abundant in the hearts of males and females. igfbp3a and igfbp3b mRNAs significantly increased from the two-cell stage to the gastrula stage, peaked at gastrulation, and sharply decreased at the hatched larval stage. Moreover, the mRNA level of igfbp3a was significantly higher than that of igfbp3b throughout turbot embryonic development. These findings suggested functional divergence between IGFBP3a and IGFBP3b, IGFBP3a may play a key role during embryonic development and tissue-specific modulation in turbot.

Melatonin (Mel; N-acetyl-5-methoxytryptamine) is recognized in fish as both a biological time-keeper and regulator of many physiological processes, including reproduction. Beyond its endocrine functions, Mel acts as an antioxidant, either by directly scavenging reactive radicals and forming N¹-acetyl-N²-formyl-5-methoxykynuramine (AFMK), or by influencing the activity of antioxidant enzymes. This study examined whether Mel contributes to the protection of post-ovulated eggs of farmed rainbow trout against oxidative stress. Mel and AFMK levels were measured in plasma, ovarian fluid, and eggs, while the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione-S-transferase (GST) were determined in eggs. Plasma Mel concentrations did not significantly differ among pre-ovulation, ovulation, and post-ovulation stages, nor did they correlate with ovarian fluid levels. AFMK was undetectable in both plasma and ovarian fluid, whereas both Mel and AFMK were consistently present and positively correlated in eggs. This suggests that Mel directly reacts with reactive oxygen species within the eggs, resulting in AFMK formation. Mel concentrations in eggs did not correlate with the activities of SOD, CAT, or GST, implying that Mel primarily contributes to the antioxidant defense of post-ovulated eggs through non-enzymatic radical scavenging. Mel and AFMK levels were lower in eggs from four-year-old females compared to three-year-old, whereas SOD activity showed the opposite trend, suggesting a compensatory upregulation of enzymatic defense mechanisms in response to an age-related Mel decline. The concentration of Mel in eggs was approximately three times higher than in plasma or ovarian fluid, suggesting possible local synthesis within oocytes.

Pathogen-induced high mortality is a severe problem in turtle cultures. Increasing evidence indicates that pathogenic infection may disrupt iron homeostasis, thereby creating a vicious cycle of iron imbalance-inflammation-oxidative stress. However, the effects of infection on iron metabolism and related physiological traits in turtles remain unclear. This study aimed to investigate the response of iron metabolism in juvenile soft-shelled turtles (Pelodiscus sinensis) under acute bacterial challenge and its association with inflammation and oxidative stress. We intraperitoneally injected juvenile P. sinensis (108 ± 2.5 g) with the recently identified pathogen Elizabethkingia anophelis at concentrations of 0, 3.24 × 10⁷, 8.10 × 10⁷, and 1.62 × 10⁸ colony-forming units per millilitre (CFU/mL) in a volume of 0.2 mL. We sampled at 6, 24, and 120 h postinjection to assess the physiological responses to bacterial invasion. The results revealed that haemolysis developed as time progressed and the bacterial dose increased, accompanied by a decrease in plasma iron concentration. Moreover, the expression levels of iron metabolism-related genes in the liver and spleen-hepcidin, transferrin, TFR1, and FTH1-increased, whereas FPN1 expression decreased, concurrent with elevated tissue iron levels. Oxidative stress levels and the expression of proinflammatory cytokine genes were positively correlated with tissue iron accumulation. Overall, acute E. anophelis infection disrupts iron homeostasis in P. sinensis in a dose- and time-dependent manner, promotes the redistribution of iron from the circulation to storage tissues, exacerbates tissue inflammatory responses, and reduces antioxidant capacity. These findings indicate that dysregulated iron homeostasis plays a central role in infection-associated tissue injury and that restoring iron balance may aid in the treatment of bacterial infections in P. sinensis.

With global climate warming increasingly threatening aquatic ecosystems, prolonged exposure to high temperatures has become a major environmental stressor for both wild and cultured fish. However, the long-term effects of chronic heat stress on blood physiology and hematopoietic processes remain poorly understood. To assess the long-term impacts of chronic heat stress on hematopoiesis in largemouth bass (Micropterus salmoides), we conducted a 180-day acclimation experiment at 34 °C. Hematological analyses showed significant reductions in red blood cell counts and hemoglobin concentrations, indicating impaired oxygen transport capacity. Blood cell morphology was altered, with erythrocytes exhibiting a lower major-to-minor axis ratio and leukocytes (lymphocytes and granulocytes) showing increased volumes. Histological and ultrastructural observations of the head kidney revealed tissue loosening, hemosiderin deposition, mitochondrial damage, and elevated apoptosis. Furthermore, transcriptomic analysis combined with GO and KEGG enrichment revealed that pathways involved in vascular development, stress response, and fatty acid metabolism were significantly activated under heat stress. Notably, key genes associated with angiogenesis, lipid metabolism, stimuli response, apoptosis and immunity, including mmp9, angptl4, abca1 and stab2, were markedly upregulated, suggesting their crucial roles in vascular remodeling and thermotolerance. Together, these results provide the first integrative cellular and molecular characterization of hematopoietic responses to prolonged high temperature in M. salmoides. The findings enhance understanding of fish physiological plasticity under environmental stress and have implications for aquaculture management and the development of heat-resilient strains.

Amphibians possess intricate biochemical and physiological adaptations that enable survival in oxygen-deprived environments. Our study investigated metabolic and oxidative responses in the brain, skeletal muscle, liver, and plasma of the subtropical tree frog Boana pulchella exposed to 30 min of anoxia followed by normoxic recovery. Adult males were divided into control, anoxia, and recovery groups (n = 5 each). Key parameters measured included gluconeogenesis from lactate, catalase (CAT) and superoxide dismutase (SOD) activities, thiobarbituric acid reactive substances (TBARS), glucose oxidation, glycogen synthesis, and plasma and tissue metabolite levels. Plasma glucose, urea, and hemoglobin concentrations were stable, whereas plasma lactate increased significantly during anoxia (65% vs. control; 41% vs. recovery), confirming activation of anaerobic metabolism. In skeletal muscle, protein and urea concentrations were significantly higher in the recovery group compared to anoxia, indicating post-stress metabolic reactivation. In the liver, glucose oxidation increased by ∼66% and glycogen synthesis by ∼70% during anoxia, suggesting anticipatory energy storage, while brain gluconeogenesis from lactate declined nearly twofold, pointing to preferential lactate utilization as fuel. Antioxidant enzyme activities remained stable across tissues; however, hepatic TBARS increased ∼3.6-fold during anoxia compared to control, although this difference was not statistically significant, indicating a possible tendency toward oxidative imbalance. Principal component analyses revealed tissue-specific metabolic signatures: plasma responses driven by lactate and hemoglobin, liver by protein and TBARS, muscle by protein and urea, and brain by protein and urea. Together, these findings demonstrate that Boana pulchella maintains systemic stability under short-term anoxia through tissue-specific metabolic adjustments, with the liver acting as a central hub for energy regulation and the brain displaying metabolic flexibility to sustain function during oxygen deprivation.