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• 1. [Article] The significance of hypovolemia in dehydrational death in anurans

  The importance of hypovolemia in dehydrational death was assessed in two anuran species. Xenopus laeyis, a species which experiences a significant reduction in circulating plasma volume with dehydration, ...

  Citation × Citation Citation Abstract Copy Title: The significance of hypovolemia in dehydrational death in anurans Author: Kimmel, Peter Blair Year: 1985 The importance of hypovolemia in dehydrational death was assessed in two anuran species. Xenopus laeyis, a species which experiences a significant reduction in circulating plasma volume with dehydration, was used to evaluate the role of sympathetic reflex compensation in hypovolemia. Adrenergic blockade with propranolol or phenoxybenzamine produced no significant reduction in dehydration tolerance in this species, although β-blockade with propranolol appeared to have a minor effect. The role of hypovolemic shock in the terminal circulatory collapse that precedes death in dehydrating anurans was investigated in the toad, Bufo marinus. The activity of lysosomal proteinases (cathepsins) was used as an indicator of the shock state. An assay was developed for the determination of cathepsin activity in toad plasma and was used to demonstrate the presence of proteinases similar in pH dependence to mammalian cathepsins Bl and D. Plasma cathepsin D-type activity increased with dehydration in toads but was not significantly different from the activity in controls or in toads subjected to splanchnic artery occlusion. Toads appear to maintain plasma volume to 20% water loss at the expense of other extracellular fluids. These results do not support the hypothesis that hypovolemia is a direct cause of dehydrational death in anurans. Title: The significance of hypovolemia in dehydrational death in anurans Author: Kimmel, Peter Blair Year: 1985 The importance of hypovolemia in dehydrational death was assessed in two anuran species. Xenopus laeyis, a species which experiences a significant reduction in circulating plasma volume with dehydration, was used to evaluate the role of sympathetic reflex compensation in hypovolemia. Adrenergic blockade with propranolol or phenoxybenzamine produced no significant reduction in dehydration tolerance in this species, although β-blockade with propranolol appeared to have a minor effect. The role of hypovolemic shock in the terminal circulatory collapse that precedes death in dehydrating anurans was investigated in the toad, Bufo marinus. The activity of lysosomal proteinases (cathepsins) was used as an indicator of the shock state. An assay was developed for the determination of cathepsin activity in toad plasma and was used to demonstrate the presence of proteinases similar in pH dependence to mammalian cathepsins Bl and D. Plasma cathepsin D-type activity increased with dehydration in toads but was not significantly different from the activity in controls or in toads subjected to splanchnic artery occlusion. Toads appear to maintain plasma volume to 20% water loss at the expense of other extracellular fluids. These results do not support the hypothesis that hypovolemia is a direct cause of dehydrational death in anurans. Close

• 2. [Article] Mitochondrial Physiology of Diapausing and Developing Embryos of the Annual Killifsh Austrofundulus Limnaeus: Implications for Extreme Anoxia Tolerance

  Diapausing embryos of the annual killiWsh Austrofundulus limnaeus have the highest reported anoxia tolerance of any vertebrate and previous studies indicate modified mitochondrial physiology likely supports ...

  Citation × Citation Citation Abstract Copy Title: Mitochondrial Physiology of Diapausing and Developing Embryos of the Annual Killifsh Austrofundulus Limnaeus: Implications for Extreme Anoxia Tolerance Author: Duerr, Jeffrey M., Podrabsky, Jason E. Year: 2010 Diapausing embryos of the annual killiWsh Austrofundulus limnaeus have the highest reported anoxia tolerance of any vertebrate and previous studies indicate modified mitochondrial physiology likely supports anoxic metabolism. Functional mitochondria isolated from diapausing and developing embryos of the annual killifish exhibited VO2, respiratory control ratios (RCR), and P:O ratios consistent with those obtained from other ectothermic vertebrate species. Reduced oxygen consumption associated with dormancy in whole animal respiration rates are correlated with maximal respiration rates of mitochondria isolated from diapausing versus developing embryos. P:O ratios for developing embryos were similar to those obtained from adult liver, but were diminished in mitochondria from diapausing embryos suggesting decreased oxidative efficiency. Proton leak in adult liver corresponded with that of developing embryos but was elevated in mitochondria isolated from diapausing embryos. In metabolically suppressed diapause II embryos, over 95% of the mitochondrial oxygen consumption is accounted for by proton leak across the inner mitochondrial membrane. Decreased activity of mitochondrial respiratory chain complexes correlates with diminished oxidative capacity of isolated mitochondria, especially during diapause. Respiratory complexes exhibited suppressed activity in mitochondria with the ATP synthase exhibiting the greatest inhibition during diapause II. Mitochondria isolated from diapause II embryos are not poised to produce ATP, but rather to shuttle carbon and electrons through the Kreb’s cycle while minimizing the generation of a proton motive force. This particular mitochondrial physiology is likely a mechanism to avoid production of reactive oxygen species during large-scale changes in flux through oxidative phosphorylation pathways associated with metabolic transitions into and out of dormancy and anoxia. Title: Mitochondrial Physiology of Diapausing and Developing Embryos of the Annual Killifsh Austrofundulus Limnaeus: Implications for Extreme Anoxia Tolerance Author: Duerr, Jeffrey M., Podrabsky, Jason E. Year: 2010 Diapausing embryos of the annual killiWsh Austrofundulus limnaeus have the highest reported anoxia tolerance of any vertebrate and previous studies indicate modified mitochondrial physiology likely supports anoxic metabolism. Functional mitochondria isolated from diapausing and developing embryos of the annual killifish exhibited VO2, respiratory control ratios (RCR), and P:O ratios consistent with those obtained from other ectothermic vertebrate species. Reduced oxygen consumption associated with dormancy in whole animal respiration rates are correlated with maximal respiration rates of mitochondria isolated from diapausing versus developing embryos. P:O ratios for developing embryos were similar to those obtained from adult liver, but were diminished in mitochondria from diapausing embryos suggesting decreased oxidative efficiency. Proton leak in adult liver corresponded with that of developing embryos but was elevated in mitochondria isolated from diapausing embryos. In metabolically suppressed diapause II embryos, over 95% of the mitochondrial oxygen consumption is accounted for by proton leak across the inner mitochondrial membrane. Decreased activity of mitochondrial respiratory chain complexes correlates with diminished oxidative capacity of isolated mitochondria, especially during diapause. Respiratory complexes exhibited suppressed activity in mitochondria with the ATP synthase exhibiting the greatest inhibition during diapause II. Mitochondria isolated from diapause II embryos are not poised to produce ATP, but rather to shuttle carbon and electrons through the Kreb’s cycle while minimizing the generation of a proton motive force. This particular mitochondrial physiology is likely a mechanism to avoid production of reactive oxygen species during large-scale changes in flux through oxidative phosphorylation pathways associated with metabolic transitions into and out of dormancy and anoxia. Close