Due to the higher energy requirements of birds during winter, it is predicted that the activities of metabolic enzymes （e.g., citrate synthase, CS and cytochrome C oxidase, COX） should increase in tandem with increa...Due to the higher energy requirements of birds during winter, it is predicted that the activities of metabolic enzymes （e.g., citrate synthase, CS and cytochrome C oxidase, COX） should increase in tandem with increases in rates of energy expendi ture （e.g., basal metabolic rate, BMR）. However, there is mixed support for the hypothesis of enzymatic acclimatization. Fur thermore, there is little information about the effect of ambient temperature on energetics and tissue enzyme activity levels in passerines inhabiting seasonal Mediterranean environments. In this study we evaluated the interplay between BMR and enzyme activities of freshly caught individuals of the passerine Zonotrichia capensis in winter and summer in a Mediterranean environment from central Chile, and also in warm （30℃） and cold （15℃） labacclimated birds. The results revealed a lack of seasonal variation in BMR, thermal conductance and in the activity of CS and COX. However, we found higher BMR and lower thermal conductance in coldacclimated than in warmacclimated birds. Also, total CS activity was higher in the flight muscles of coldacclimated than in warmacclimated birds. We found also a significant correlation between BMR and total CS activity in pectoral muscle. Although some authors have suggested that BMR mainly depends on the metabolic intensity and mass of internal organs, our results revealed that skeletal muscles such as the flight muscles may also affect BMR. Finally, differences in the accli mation and acclimatization responses in Rufouscollared sparrows suggest that largescale oscillations in the physical environment might maintain the capacity for flexibility in thermogenic traits through generations .展开更多
During vertebrate development,the immune function is inefficient and is mainly controlled by innate defense.While there have been detailed studies of various aspects of innate immune function,the effects of this func&...During vertebrate development,the immune function is inefficient and is mainly controlled by innate defense.While there have been detailed studies of various aspects of innate immune function,the effects of this function in the growth of vertebrates is still not well known.Similarly,there is little information regarding how early endotoxin exposure would affect juvenile phenotypes,specifically in a non-model mammal like a precocial rodent.We evaluated the response to an antigen and its cost in offspring of the rodent Octodon degus.We inoculated pups at 4 different ages(8,15,22 and 30 days after birth)with an antigen to determine the ontogeny and costs of the response to an endotoxin.We assessed changes in body mass,body temperature,sickness behavior and the levels of a key mediator of the inflammatory response,the cytokine interleukin-1β.We also determined the effects of early endotoxin exposure on the resting metabolic rate of juvenile animals(i.e.90 days after birth).The cytokine levels,body mass and body temperature were unaffected by time of inoculation and treatment.However,pups subjected to inoculation at 22 days after birth with the antigen showed reduced locomotion.Juvenile resting metabolic rate was not affected by early endotoxin exposure.These results suggest that the magnitude of O.degus responses would not change with age.We discuss whether the lack of effect of the response on body mass or body condition is caused by environmental variables or by the precocial characteristics of O.degus.展开更多
文摘Due to the higher energy requirements of birds during winter, it is predicted that the activities of metabolic enzymes （e.g., citrate synthase, CS and cytochrome C oxidase, COX） should increase in tandem with increases in rates of energy expendi ture （e.g., basal metabolic rate, BMR）. However, there is mixed support for the hypothesis of enzymatic acclimatization. Fur thermore, there is little information about the effect of ambient temperature on energetics and tissue enzyme activity levels in passerines inhabiting seasonal Mediterranean environments. In this study we evaluated the interplay between BMR and enzyme activities of freshly caught individuals of the passerine Zonotrichia capensis in winter and summer in a Mediterranean environment from central Chile, and also in warm （30℃） and cold （15℃） labacclimated birds. The results revealed a lack of seasonal variation in BMR, thermal conductance and in the activity of CS and COX. However, we found higher BMR and lower thermal conductance in coldacclimated than in warmacclimated birds. Also, total CS activity was higher in the flight muscles of coldacclimated than in warmacclimated birds. We found also a significant correlation between BMR and total CS activity in pectoral muscle. Although some authors have suggested that BMR mainly depends on the metabolic intensity and mass of internal organs, our results revealed that skeletal muscles such as the flight muscles may also affect BMR. Finally, differences in the accli mation and acclimatization responses in Rufouscollared sparrows suggest that largescale oscillations in the physical environment might maintain the capacity for flexibility in thermogenic traits through generations .
基金This study was funded by FONDECYT 3160133 to NRO and Millennium Institute of Immunology and Immunotherapy,Pontificia Universidad Católica de Chile。
文摘During vertebrate development,the immune function is inefficient and is mainly controlled by innate defense.While there have been detailed studies of various aspects of innate immune function,the effects of this function in the growth of vertebrates is still not well known.Similarly,there is little information regarding how early endotoxin exposure would affect juvenile phenotypes,specifically in a non-model mammal like a precocial rodent.We evaluated the response to an antigen and its cost in offspring of the rodent Octodon degus.We inoculated pups at 4 different ages(8,15,22 and 30 days after birth)with an antigen to determine the ontogeny and costs of the response to an endotoxin.We assessed changes in body mass,body temperature,sickness behavior and the levels of a key mediator of the inflammatory response,the cytokine interleukin-1β.We also determined the effects of early endotoxin exposure on the resting metabolic rate of juvenile animals(i.e.90 days after birth).The cytokine levels,body mass and body temperature were unaffected by time of inoculation and treatment.However,pups subjected to inoculation at 22 days after birth with the antigen showed reduced locomotion.Juvenile resting metabolic rate was not affected by early endotoxin exposure.These results suggest that the magnitude of O.degus responses would not change with age.We discuss whether the lack of effect of the response on body mass or body condition is caused by environmental variables or by the precocial characteristics of O.degus.
