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

{"title":"Comparative mechanisms for O₂ storage and metabolism in two Florida diving birds: the anhinga (Anhinga anhinga) and the double-crested cormorant (Nannopterum auritum).","authors":"Jeff White, Elizabeth R Schell, Neal J Dawson, Kevin G McCracken","doi":"10.1007/s00360-024-01593-x","DOIUrl":"https://doi.org/10.1007/s00360-024-01593-x","url":null,"abstract":"<p><p>Air-breathing vertebrates face many physiological challenges while breath-hold diving. In particular, they must endure intermittent periods of declining oxygen (O₂) stores, as well as the need to rapidly replenish depleted O₂ at the surface prior to their next dive. While many species show adaptive increases in the O₂ storage capacity of the blood or muscles, others increase the oxidative capacity of the muscles through changes in mitochondrial arrangement, abundance, or remodeling of key metabolic pathways. Here, we assess the diving phenotypes of two sympatric diving birds: the anhinga (Anhinga anhinga) and the double-crested cormorant (Nannopterum auritum). In each, we measured blood- and muscle-O₂ storage capacity, as well as phenotypic characteristics such as muscle fiber composition, capillarity, and mitochondrial arrangement and abundance in the primary flight (pectoralis) and swimming (gastrocnemius) muscles. Finally, we compared the maximal activities of 10 key enzymes in the pectoralis, gastrocnemius, and left ventricle of the heart to assess tissue level oxidative capacity and fuel use. Our results indicate that both species utilize enhanced muscle-O₂ stores over blood-O₂. This is most apparent in the large difference in available myoglobin in the gastrocnemius between the two species. Oxidative capacity varied significantly between the flight and swimming muscles and between the two species. However, both species showed lower oxidative capacity than expected compared to other diving birds. In particular, the anhinga exhibits a unique diving phenotype with a slightly higher reliance on glycolysis and lower aerobic ATP generation than double-crested cormorants.</p>","PeriodicalId":56033,"journal":{"name":"Journal of Comparative Physiology B-Biochemical Systems and Environmental Physiology","volume":" ","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142866538","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Whether hypoxia tolerance improved after short-term fasting is closely related to phylogeny but not to foraging mode in freshwater fish species.","authors":"Ke-Ren Huang, Qian-Ying Liu, Yong-Fei Zhang, Yu-Lian Luo, Cheng Fu, Xu Pang, Shi-Jian Fu","doi":"10.1007/s00360-024-01588-8","DOIUrl":"10.1007/s00360-024-01588-8","url":null,"abstract":"<p><p>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.</p>","PeriodicalId":56033,"journal":{"name":"Journal of Comparative Physiology B-Biochemical Systems and Environmental Physiology","volume":" ","pages":"843-853"},"PeriodicalIF":1.7,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142333104","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Metabolic effects of physical exercise on zebrafish (Danio rerio) fed a high-fat diet.","authors":"Moises Silvestre de Azevedo Martins, William Franco Carneiro, Kianne Silva Monteiro, Stefania Priscilla de Souza, André Rodrigues da Cunha Barreto Vianna, Luis David Solis Murgas","doi":"10.1007/s00360-024-01577-x","DOIUrl":"10.1007/s00360-024-01577-x","url":null,"abstract":"<p><p>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.</p>","PeriodicalId":56033,"journal":{"name":"Journal of Comparative Physiology B-Biochemical Systems and Environmental Physiology","volume":" ","pages":"793-804"},"PeriodicalIF":1.7,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141861800","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Metabolic rate and saliva cortisol concentrations in socially housed adolescent guinea pigs.","authors":"Matthias Nemeth, Susanna Fritscher, Klara Füreder, Bernard Wallner, Eva Millesi","doi":"10.1007/s00360-024-01576-y","DOIUrl":"10.1007/s00360-024-01576-y","url":null,"abstract":"<p><p>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.</p>","PeriodicalId":56033,"journal":{"name":"Journal of Comparative Physiology B-Biochemical Systems and Environmental Physiology","volume":" ","pages":"925-933"},"PeriodicalIF":1.7,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11511739/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141629379","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Oxidative stress across multiple tissues in house sparrows (Passer domesticus) acclimated to warm, stable cold, and unpredictable cold thermal treatments.","authors":"Ana Gabriela Jiménez, Chelsi Marolf, David L Swanson","doi":"10.1007/s00360-024-01572-2","DOIUrl":"10.1007/s00360-024-01572-2","url":null,"abstract":"<p><p>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.</p>","PeriodicalId":56033,"journal":{"name":"Journal of Comparative Physiology B-Biochemical Systems and Environmental Physiology","volume":" ","pages":"899-907"},"PeriodicalIF":1.7,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141592240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The effects of dissolved organic carbon and model compounds (DOC analogues) on diffusive water flux, oxygen consumption, nitrogenous waste excretion rates and gill transepithelial potential in Pacific sanddab (Citharichthys sordidus) at two salinities.","authors":"Carolyn Morris, Camila Martins, Samantha Zulian, D Scott Smith, Colin J Brauner, Chris M Wood","doi":"10.1007/s00360-024-01580-2","DOIUrl":"10.1007/s00360-024-01580-2","url":null,"abstract":"<p><p>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.</p>","PeriodicalId":56033,"journal":{"name":"Journal of Comparative Physiology B-Biochemical Systems and Environmental Physiology","volume":" ","pages":"805-825"},"PeriodicalIF":1.7,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142156767","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of in ovo supplementation of selenium (Se) and zinc (zn) on hatchability and production performance of broiler chickens.","authors":"Fazul Nabi, Muhammad Asif Arain, Mohammad Farooque Hassan, Qurban Ali Shah, Mikhlid H Almutairi, Jameel Ahmed Buzdar","doi":"10.1007/s00360-024-01578-w","DOIUrl":"10.1007/s00360-024-01578-w","url":null,"abstract":"<p><p>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.</p>","PeriodicalId":56033,"journal":{"name":"Journal of Comparative Physiology B-Biochemical Systems and Environmental Physiology","volume":" ","pages":"887-897"},"PeriodicalIF":1.7,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142001448","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microbial urea-nitrogen recycling in arctic ground squirrels: the effect of ambient temperature of hibernation.","authors":"Julita Sadowska, Karen M Carlson, C Loren Buck, Trixie N Lee, Khrystyne N Duddleston","doi":"10.1007/s00360-024-01579-9","DOIUrl":"10.1007/s00360-024-01579-9","url":null,"abstract":"<p><p>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.</p>","PeriodicalId":56033,"journal":{"name":"Journal of Comparative Physiology B-Biochemical Systems and Environmental Physiology","volume":" ","pages":"909-924"},"PeriodicalIF":1.7,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11511772/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142141828","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Common tenrecs (Tenrec ecaudatus) reduce oxygen consumption in hypoxia and in hypercapnia without concordant changes to body temperature or heart rate.","authors":"Claudia Silva Rubio, Anne B Kim, William K Milsom, Matthew E Pamenter, Gilbecca Rae Smith, Frank van Breukelen","doi":"10.1007/s00360-024-01587-9","DOIUrl":"10.1007/s00360-024-01587-9","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Common tenrecs (Tenrec ecaudatus) are fossorial mammals that use burrows during both active and hibernating seasons in Madagascar and its neighboring islands. Prevailing thought was that tenrecs hibernate for 8-9 months individually, but 13 tenrecs were removed from the same sealed burrow 1 m deep from the surface. Such group hibernation in sealed burrows presumably creates a hypoxic and/or hypercapnic environment and suggests that this placental mammal may have an increased tolerance to hypoxia and hypercapnia. Higher tolerances to hypoxia and hypercapnia have been documented for other mammals capable of hibernation and to determine if this is the case for tenrecs, we exposed them to acute hypoxia (4 h of 16 or 7% O&lt;sub&gt;2&lt;/sub&gt;), progressive hypoxia (2 h of 16, 10 and 4% O&lt;sub&gt;2&lt;/sub&gt;), or progressive hypercapnia (2 h of 2, 5 and 10% CO&lt;sub&gt;2&lt;/sub&gt;) at cold (16 °C) or warm (28 °C) ambient temperatures (T&lt;sub&gt;a&lt;/sub&gt;). Oxygen equilibrium curves were also constructed on the whole blood of tenrecs at 10, 25, and 37 °C to determine if hemoglobin (Hb)-O&lt;sub&gt;2&lt;/sub&gt; affinity contributes to hypoxia tolerance. In animals held at 16 °C, normoxic and normocapnic levels of oxygen consumption rate ( &lt;math&gt; &lt;msub&gt; &lt;mrow&gt;&lt;mover&gt;&lt;mtext&gt;V&lt;/mtext&gt; &lt;mo&gt;˙&lt;/mo&gt;&lt;/mover&gt; &lt;mtext&gt;O&lt;/mtext&gt;&lt;/mrow&gt; &lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt; &lt;/math&gt; ), body temperature (T&lt;sub&gt;b&lt;/sub&gt;), and heart rate (HR) were highly variable between individuals. This inter-individual variation was greatly reduced in animals held at 28 °C for oxygen consumption rate and body temperature. Both hypoxia (acute and progressive) and progressive hypercapnia led to decreases in &lt;math&gt; &lt;msub&gt; &lt;mrow&gt;&lt;mover&gt;&lt;mtext&gt;V&lt;/mtext&gt; &lt;mo&gt;˙&lt;/mo&gt;&lt;/mover&gt; &lt;mtext&gt;O&lt;/mtext&gt;&lt;/mrow&gt; &lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt; &lt;/math&gt; as well as the variation in &lt;math&gt; &lt;msub&gt; &lt;mrow&gt;&lt;mover&gt;&lt;mtext&gt;V&lt;/mtext&gt; &lt;mo&gt;˙&lt;/mo&gt;&lt;/mover&gt; &lt;mtext&gt;O&lt;/mtext&gt;&lt;/mrow&gt; &lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt; &lt;/math&gt; between animals held at 16 °C. The fall in oxygen consumption rate in 7% O&lt;sub&gt;2&lt;/sub&gt; independent of changes in body temperature in tenrecs held at 16 °C is unique and not consistent with the typical hypoxic metabolic response seen in other hibernating species that depends on concomitant falls in T&lt;sub&gt;b&lt;/sub&gt;. In animals held at 28 °C, exposure to O&lt;sub&gt;2&lt;/sub&gt; levels as low as 4% and CO&lt;sub&gt;2&lt;/sub&gt; levels as high as 10% had no significant effect on &lt;math&gt; &lt;msub&gt; &lt;mrow&gt;&lt;mover&gt;&lt;mtext&gt;V&lt;/mtext&gt; &lt;mo&gt;˙&lt;/mo&gt;&lt;/mover&gt; &lt;mtext&gt;O&lt;/mtext&gt;&lt;/mrow&gt; &lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt; &lt;/math&gt; , HR, or T&lt;sub&gt;b&lt;/sub&gt;, indicative of high tolerance to both hypoxia and hypercapnia. High variation in heart rate remained between individuals in all gas compositions and at all temperatures. Tenrec Hb-O&lt;sub&gt;2&lt;/sub&gt; affinity was similar to other homeothermic placental mammals and likely does not contribute to the increased hypoxia tolerance. Ultimately, our results suggest changes in T&lt;sub&gt;a&lt;/sub&gt; dictate physiological responses to hypoxia or hypercapnia in tenrecs, responses more characteristic of reptiles than of most placental ma","PeriodicalId":56033,"journal":{"name":"Journal of Comparative Physiology B-Biochemical Systems and Environmental Physiology","volume":" ","pages":"869-885"},"PeriodicalIF":1.7,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142382474","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The physiological significance of plasma-accessible carbonic anhydrase in the respiratory systems of fishes.","authors":"Till S Harter, Angelina M Dichiera, Andrew J Esbaugh","doi":"10.1007/s00360-024-01562-4","DOIUrl":"10.1007/s00360-024-01562-4","url":null,"abstract":"<p><p>Carbonic anhydrase (CA) activity is ubiquitously found in all vertebrate species, tissues and cellular compartments. Most species have plasma-accessible CA (paCA) isoforms at the respiratory surfaces, where the enzyme catalyzes the conversion of plasma bicarbonate to carbon dioxide (CO₂) that can be excreted by diffusion. A notable exception are the teleost fishes that appear to lack paCA at their gills. The present review: (i) recapitulates the significance of CA activity and distribution in vertebrates; (ii) summarizes the current evidence for the presence or absence of paCA at the gills of fishes, from the basal cyclostomes to the derived teleosts and extremophiles such as the Antarctic icefishes; (iii) explores the contribution of paCA to organismal CO₂ excretion in fishes; and (iv) the functional significance of its absence at the gills, for the specialized system of O₂ transport in most teleosts; (v) outlines the multiplicity and isoform distribution of membrane-associated CAs in fishes and methodologies to determine their plasma-accessible orientation; and (vi) sketches a tentative time line for the evolutionary dynamics of branchial paCA distribution in the major groups of fishes. Finally, this review highlights current gaps in the knowledge on branchial paCA function and provides recommendations for future work.</p>","PeriodicalId":56033,"journal":{"name":"Journal of Comparative Physiology B-Biochemical Systems and Environmental Physiology","volume":" ","pages":"717-737"},"PeriodicalIF":1.7,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141260589","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}