Background:The thermoregulatory ability of animals is strongly influenced by the temperature of their environment.Acclimation to cold requires a range of physiological and morphological adjustments.In this study,we te...Background:The thermoregulatory ability of animals is strongly influenced by the temperature of their environment.Acclimation to cold requires a range of physiological and morphological adjustments.In this study,we tested the hypothesis that a small passerine,the Red-billed Leiothrix(Leiothrix lutea),can maintain homeothermy in cold conditions by adjusting the physiology and biochemistry of its tissue and organs and return to its former physiological and biochemical state when moved to a warm temperature.Methods:Phenotypic variation in thermogenic activity of the Red-billed Leiothrixs(Leiothrix lutea)was investigated under warm(35℃),normal(25℃)or cold(15℃)ambient temperature conditions.Oxygen consumption was measured using an open-circuit respirometry system.Mitochondrial state-4 respiration and cytochrome-c oxidase(COX)activity in liver,kidney heart and pectoral muscle were measured with a Clark electrode.Results:Birds acclimated to an ambient temperature of 15℃ for 4 weeks significantly increased their basal metabolic rate(BMR)compared to a control group kept at 25℃.Birds acclimated to 35℃ decreased their BMR,gross energy intake(GEI)and digestible energy intake(DEI).Furthermore,birds acclimated to 15℃ increased state-4 respiration in their pectoral muscles and cytochrome-c oxidase(COX)activity in their liver and pectoral muscle,compared to the 25℃ control group.Birds acclimated to 35℃ also displayed lower state-4 respiration and COX activity in the liver,heart and pectoral muscles,compared to those kept at 25℃.There was a positive correlation between BMR and state-4 respiration,and between BMR and COX activity,in all of the above organs except the liver and heart.Conclusions:Our study illustrates that the morphological,physiological,and enzymatic changes are associated with temperature acclimation in the Red-billed Leiothrix,and supports the notion that the primary means by which small birds meet the energetic challenges of cold conditions is through metabolic adjustments.展开更多
Extreme hot weather is occurring more frequently due to global warming,posing a significant threat to species survival.Birds in particular are more likely to overheat in hot weather because they have a higher body tem...Extreme hot weather is occurring more frequently due to global warming,posing a significant threat to species survival.Birds in particular are more likely to overheat in hot weather because they have a higher body temperature.This study used a heat stress model to investigate the antioxidant defense mechanisms and changes in fatty acid catabolism in Red-billed Leiothrix(Leiothrix lutea)to gain an understanding of how birds adapt to high temperatures.The birds were divided into five groups:a control group(30℃for 0 days),1 D group(40℃for 1 day),3 D group(40℃for 3 days),14 D group(40℃for 14 days)and recovery group(40℃for 14 days,then 30℃for 14 days).Our results indicated that when Red-billed Leiothrix are subjected to heat stress,malondialdehyde(MDA)content in the liver significantly increased,as did the enzyme activities of catalase(CAT),glutathione-SH-peroxidase(GSH-PX)and total antioxidant capacity(T-AOC)in the liver.Furthermore,there was a significant increase in heat shock protein 70(HSP70)expression in the liver,while avian uncoupling protein(avUCP)expression in muscle was significantly reduced.Additionally,there was a significant reduction in fatty acid catabolism enzyme activity such as 3-hydroxyacyl-CoAdehydrogenase(HOAD)activity in the heart,and carnitine palmitoyl transferase 1(CPT-1)and citrate synthase(CS)activity in the heart and liver.Furthermore,fatty acid translocase(FAT/CD36)in the heart,heart-type fatty acid binding protein(H-FABP)and fatty acid binding protein(FABP-pm)in the liver and heart were also significantly decreased.These changes reverted after treatment,but not to the same level as the control group.Our results indicated that when Red-billed Leiothrix are exposed to heat stress their internal antioxidant defense system is activated to counteract the damage caused by high temperatures.However,even with high antioxidant levels,prolonged high temperature exposure still caused some degree of oxidative damage possibly requiring a longer recovery time.Additionally,Red-billed Leiothrix may be able to resist heat stress by reducing fatty acid transport and catabolism.展开更多
基金supported by grants from the National Natural Science Foundation of China(Grant Nos.31470472 and 31971420)the National Undergraduate “Innovation” Projectthe “Xinmiao” Project in Zhejiang Province
文摘Background:The thermoregulatory ability of animals is strongly influenced by the temperature of their environment.Acclimation to cold requires a range of physiological and morphological adjustments.In this study,we tested the hypothesis that a small passerine,the Red-billed Leiothrix(Leiothrix lutea),can maintain homeothermy in cold conditions by adjusting the physiology and biochemistry of its tissue and organs and return to its former physiological and biochemical state when moved to a warm temperature.Methods:Phenotypic variation in thermogenic activity of the Red-billed Leiothrixs(Leiothrix lutea)was investigated under warm(35℃),normal(25℃)or cold(15℃)ambient temperature conditions.Oxygen consumption was measured using an open-circuit respirometry system.Mitochondrial state-4 respiration and cytochrome-c oxidase(COX)activity in liver,kidney heart and pectoral muscle were measured with a Clark electrode.Results:Birds acclimated to an ambient temperature of 15℃ for 4 weeks significantly increased their basal metabolic rate(BMR)compared to a control group kept at 25℃.Birds acclimated to 35℃ decreased their BMR,gross energy intake(GEI)and digestible energy intake(DEI).Furthermore,birds acclimated to 15℃ increased state-4 respiration in their pectoral muscles and cytochrome-c oxidase(COX)activity in their liver and pectoral muscle,compared to the 25℃ control group.Birds acclimated to 35℃ also displayed lower state-4 respiration and COX activity in the liver,heart and pectoral muscles,compared to those kept at 25℃.There was a positive correlation between BMR and state-4 respiration,and between BMR and COX activity,in all of the above organs except the liver and heart.Conclusions:Our study illustrates that the morphological,physiological,and enzymatic changes are associated with temperature acclimation in the Red-billed Leiothrix,and supports the notion that the primary means by which small birds meet the energetic challenges of cold conditions is through metabolic adjustments.
基金This study was financially supported by grants from the National Natural Science Foundation of China(No.31971420,32171497).
文摘Extreme hot weather is occurring more frequently due to global warming,posing a significant threat to species survival.Birds in particular are more likely to overheat in hot weather because they have a higher body temperature.This study used a heat stress model to investigate the antioxidant defense mechanisms and changes in fatty acid catabolism in Red-billed Leiothrix(Leiothrix lutea)to gain an understanding of how birds adapt to high temperatures.The birds were divided into five groups:a control group(30℃for 0 days),1 D group(40℃for 1 day),3 D group(40℃for 3 days),14 D group(40℃for 14 days)and recovery group(40℃for 14 days,then 30℃for 14 days).Our results indicated that when Red-billed Leiothrix are subjected to heat stress,malondialdehyde(MDA)content in the liver significantly increased,as did the enzyme activities of catalase(CAT),glutathione-SH-peroxidase(GSH-PX)and total antioxidant capacity(T-AOC)in the liver.Furthermore,there was a significant increase in heat shock protein 70(HSP70)expression in the liver,while avian uncoupling protein(avUCP)expression in muscle was significantly reduced.Additionally,there was a significant reduction in fatty acid catabolism enzyme activity such as 3-hydroxyacyl-CoAdehydrogenase(HOAD)activity in the heart,and carnitine palmitoyl transferase 1(CPT-1)and citrate synthase(CS)activity in the heart and liver.Furthermore,fatty acid translocase(FAT/CD36)in the heart,heart-type fatty acid binding protein(H-FABP)and fatty acid binding protein(FABP-pm)in the liver and heart were also significantly decreased.These changes reverted after treatment,but not to the same level as the control group.Our results indicated that when Red-billed Leiothrix are exposed to heat stress their internal antioxidant defense system is activated to counteract the damage caused by high temperatures.However,even with high antioxidant levels,prolonged high temperature exposure still caused some degree of oxidative damage possibly requiring a longer recovery time.Additionally,Red-billed Leiothrix may be able to resist heat stress by reducing fatty acid transport and catabolism.
