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Karen M. Warkentin - One of the best experts on this subject based on the ideXlab platform.
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External Gills and adaptive embryo behavior facilitate synchronous development and hatching plasticity under respiratory constraint
Journal of Experimental Biology, 2008Co-Authors: Jessica R. Rogge, Karen M. WarkentinAbstract:SUMMARY Plasticity in hatching timing allows embryos to balance egg- and larval-stage risks, and depends on the ability of hatching-competent embryos to continue developing in the egg. Hypoxia can slow development, kill embryos and induce premature hatching. For terrestrial eggs of red-eyed treefrogs, the embryonic period can extend ∼50% longer than development to hatching competence, and development is synchronous across perivitelline oxygen levels ( P O 2 ) ranging from 0.5–16.5 kPa. Embryos maintain large External Gills until hatching, then Gills regress rapidly. We assessed the respiratory value of External Gills using gill manipulations and closed-system respirometry. Embryos without External Gills were oxygen limited in air and hatched at an External P O 2 of 17 kPa, whereas embryos with Gills regulated their metabolism and remained in the egg at substantially lower P O 2 . By contrast, tadpoles gained no respiratory benefit from External Gills. We videotaped behavior and manipulated embryos to test if they position Gills near the air-exposed portion of the egg surface, where P O 2 is highest. Active embryos remained stationary for minutes in Gills-at-surface positions. After manipulations and spontaneous movements that positioned Gills in the O 2 -poor region of the egg, however, they returned their Gills to the air-exposed surface within seconds. Even neural tube stage embryos, capable only of ciliary rotation, positioned their developing head in the region of highest P O 2 . Such behavior may be critical both to delay hatching after hatching competence and to obtain sufficient oxygen for normal, synchronous development at earlier stages.
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External Gills and adaptive embryo behavior facilitate synchronous development and hatching plasticity under respiratory constraint.
The Journal of experimental biology, 2008Co-Authors: Jessica R. Rogge, Karen M. WarkentinAbstract:Plasticity in hatching timing allows embryos to balance egg- and larval-stage risks, and depends on the ability of hatching-competent embryos to continue developing in the egg. Hypoxia can slow development, kill embryos and induce premature hatching. For terrestrial eggs of red-eyed treefrogs, the embryonic period can extend approximately 50% longer than development to hatching competence, and development is synchronous across perivitelline oxygen levels (PO2) ranging from 0.5-16.5 kPa. Embryos maintain large External Gills until hatching, then Gills regress rapidly. We assessed the respiratory value of External Gills using gill manipulations and closed-system respirometry. Embryos without External Gills were oxygen limited in air and hatched at an External PO2 of 17 kPa, whereas embryos with Gills regulated their metabolism and remained in the egg at substantially lower PO2. By contrast, tadpoles gained no respiratory benefit from External Gills. We videotaped behavior and manipulated embryos to test if they position Gills near the air-exposed portion of the egg surface, where PO2 is highest. Active embryos remained stationary for minutes in Gills-at-surface positions. After manipulations and spontaneous movements that positioned Gills in the O2-poor region of the egg, however, they returned their Gills to the air-exposed surface within seconds. Even neural tube stage embryos, capable only of ciliary rotation, positioned their developing head in the region of highest PO2. Such behavior may be critical both to delay hatching after hatching competence and to obtain sufficient oxygen for normal, synchronous development at earlier stages.
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Oxygen, Gills, and embryo behavior: mechanisms of adaptive plasticity in hatching.
Comparative biochemistry and physiology. Part A Molecular & integrative physiology, 2007Co-Authors: Karen M. WarkentinAbstract:Many species alter the timing of hatching in response to egg or larval predators, pathogens, or physical risks. This plasticity depends on separation between the onset of hatching competence and physiological limits to embryonic development. I present a framework based on heterokairy to categorize developmental mechanisms and identify traits contributing to and limiting hatching plasticity, then apply it to a case of predator-induced hatching. Red-eyed treefrogs have arboreal eggs, and tadpoles fall into ponds upon hatching. Egg and tadpole predators select for earlier and later hatching, respectively. Embryos hatch up to 30% early in predator attacks, and later if undisturbed. They maintain large External Gills throughout the plastic hatching period, delaying gill regression while development otherwise continues. Rapid gill regression occurs upon hatching. Prolonged embryonic development depends on External Gills; inducing gill regression causes hatching. External hypoxia retards development, kills eggs, and induces hatching. Nonetheless, embryos develop synchronously and without hatching prematurely across a broad range of perivitelline PO2, from 0.5-12.5 kPa. Embryos exploit spatial variation of PO2 within eggs by positioning Gills against patches of air-exposed surface. Respiratory plasticity and oxygen-sensitive behavior appear critical for the hatching plasticity that balances a predation risk trade-off across life stages.
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Hatching Timing, Oxygen Availability, and External Gill Regression in the Tree Frog, Agalychnis callidryas
Physiological and biochemical zoology : PBZ, 2002Co-Authors: Karen M. WarkentinAbstract:Abstract The physiological role of the embryonic External Gills in anurans is equivocal. In some species, diffusion alone is clearly sufficient to supply oxygen throughout the embryonic period. In others, morphological elaboration and environmental regulation of the External Gills suggest functional importance. Since oxygen stress is a common trigger of hatching, I examined the relationships among hatching timing, oxygen stress, and External gill loss. I worked with the red‐eyed tree frog, Agalychnis callidryas, a species with arboreal eggs and aquatic tadpoles in which gill regression is associated with hatching, and hatching timing affects posthatching survival with aquatic predators. Both exposure to a hypoxic gas mixture and submergence in water, a natural context in which hypoxic stress can occur, induced early hatching. Exposure to hyperoxic gas mixtures induced regression of External Gills, and subsequent exposure to air induced early hatching. Prostaglandin‐induced External gill regression also in...
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Do prostaglandins regulate External gill regression in anurans
The Journal of experimental zoology, 2001Co-Authors: Karen M. Warkentin, Richard J. WassersugAbstract:Although the endocrinological mechanism controlling regression of the internal, larval Gills of anurans (frogs and toads) is well understood, the mechanism regulating loss of the External, embryonic Gills is not known. Based on the homology of the mammalian ductus arteriosus with a portion of the amphibian branchial arches, and the regulation of blood flow in the mammalian ductus by prostaglandins of the E family (PGEs), we hypothesized that anuran External gill loss is also regulated by PGEs. To test this hypothesis, we topically applied both PGE2 and a synthetic analogue of PGE1, misoprostol, to embryos and young hatchlings of the red-eyed treefrog, Agalychnis callidryas. Both agents accelerated External gill regression. Furthermore, misoprostol overrode the inhibitory effect of hypoxia on gill regression in hatchlings and induced rapid loss of External Gills in embryos, which normally maintain the Gills until hatching. These observations support the hypothesis that PGEs regulate anuran External gill loss. The specific site of action for prostaglandins within the Gills is not known; however, PGEs are secreted in the oral mucus of tadpoles, and this could be a natural topical source for these agents. PGEs offer a tool for manipulation of External Gills and should facilitate tests of the physiological importance of these structures.
Jessica R. Rogge - One of the best experts on this subject based on the ideXlab platform.
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External Gills and adaptive embryo behavior facilitate synchronous development and hatching plasticity under respiratory constraint
Journal of Experimental Biology, 2008Co-Authors: Jessica R. Rogge, Karen M. WarkentinAbstract:SUMMARY Plasticity in hatching timing allows embryos to balance egg- and larval-stage risks, and depends on the ability of hatching-competent embryos to continue developing in the egg. Hypoxia can slow development, kill embryos and induce premature hatching. For terrestrial eggs of red-eyed treefrogs, the embryonic period can extend ∼50% longer than development to hatching competence, and development is synchronous across perivitelline oxygen levels ( P O 2 ) ranging from 0.5–16.5 kPa. Embryos maintain large External Gills until hatching, then Gills regress rapidly. We assessed the respiratory value of External Gills using gill manipulations and closed-system respirometry. Embryos without External Gills were oxygen limited in air and hatched at an External P O 2 of 17 kPa, whereas embryos with Gills regulated their metabolism and remained in the egg at substantially lower P O 2 . By contrast, tadpoles gained no respiratory benefit from External Gills. We videotaped behavior and manipulated embryos to test if they position Gills near the air-exposed portion of the egg surface, where P O 2 is highest. Active embryos remained stationary for minutes in Gills-at-surface positions. After manipulations and spontaneous movements that positioned Gills in the O 2 -poor region of the egg, however, they returned their Gills to the air-exposed surface within seconds. Even neural tube stage embryos, capable only of ciliary rotation, positioned their developing head in the region of highest P O 2 . Such behavior may be critical both to delay hatching after hatching competence and to obtain sufficient oxygen for normal, synchronous development at earlier stages.
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External Gills and adaptive embryo behavior facilitate synchronous development and hatching plasticity under respiratory constraint.
The Journal of experimental biology, 2008Co-Authors: Jessica R. Rogge, Karen M. WarkentinAbstract:Plasticity in hatching timing allows embryos to balance egg- and larval-stage risks, and depends on the ability of hatching-competent embryos to continue developing in the egg. Hypoxia can slow development, kill embryos and induce premature hatching. For terrestrial eggs of red-eyed treefrogs, the embryonic period can extend approximately 50% longer than development to hatching competence, and development is synchronous across perivitelline oxygen levels (PO2) ranging from 0.5-16.5 kPa. Embryos maintain large External Gills until hatching, then Gills regress rapidly. We assessed the respiratory value of External Gills using gill manipulations and closed-system respirometry. Embryos without External Gills were oxygen limited in air and hatched at an External PO2 of 17 kPa, whereas embryos with Gills regulated their metabolism and remained in the egg at substantially lower PO2. By contrast, tadpoles gained no respiratory benefit from External Gills. We videotaped behavior and manipulated embryos to test if they position Gills near the air-exposed portion of the egg surface, where PO2 is highest. Active embryos remained stationary for minutes in Gills-at-surface positions. After manipulations and spontaneous movements that positioned Gills in the O2-poor region of the egg, however, they returned their Gills to the air-exposed surface within seconds. Even neural tube stage embryos, capable only of ciliary rotation, positioned their developing head in the region of highest PO2. Such behavior may be critical both to delay hatching after hatching competence and to obtain sufficient oxygen for normal, synchronous development at earlier stages.
Minoru Uchiyama - One of the best experts on this subject based on the ideXlab platform.
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Immunohistological classification of ionocytes in the External Gills of larval Japanese black salamander, Hynobius nigrescens Stejneger
Journal of morphology, 2011Co-Authors: Minoru Uchiyama, Tomoko Kumano, Hideki Yoshizawa, Makiko Komiyama, Kouhei MatsudaAbstract:In this cytological and immunohistological study, we clarified the localization of the membrane transporters Na+, K+-ATPase (NKA), vacuolar-type H+-ATPase (VHA), and epithelial sodium channel (ENaC) and distinguished ionocyte subtypes in the gill of the Japanese salamander (Hynobius nigrescens). In larvae (IY stages 43–65), NKA immunoreactivity was observed on the basolateral plasma membrane in more than 60% cells and less than 20% cells in the primary filaments and secondary lamellae of the External Gills, respectively. VHA immunoreactivity was observed on the apical membrane of some epithelial cells in the secondary lamellae of the External Gills. High ENaCα immunoreactivity was widely observed on the apical cell membrane of a population of squamous cells, presumably pavement cells (PVCs), and mitochondria-rich cells (MRCs), in the primary filaments and secondary lamellae of the External Gills. Using double immunofluorescence microscopy, epithelial cell types involved in ionic regulation were characterized and divided into three ionocyte types: NKA-, NKA- and ENaC-, and VHA-positive cells. VHA-immunoreactive cells as well as NKA-positive cells were observed during IY stages 43–65 of the salamander larvae. During late stages of metamorphosis, NKA, VHA, and ENaCα immunoreactivities in the External Gills decreased and finally disappeared during the completion of metamorphosis (IY stage 68). PVCs and MRCs in the External Gills are probably involved in acid–base balance regulation and osmoregulation in urodele amphibian larvae. The results are discussed in relation to the ionocytes previously reported in fish Gills and the frog skin epithelium. J. Morphol., 2011. © 2011Wiley-Liss, Inc.
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Ontogeny of ENaC expression in the Gills and the kidneys of the Japanese black salamander (Hynobius nigrescens Stejneger).
Journal of experimental zoology. Part B Molecular and developmental evolution, 2010Co-Authors: Minoru Uchiyama, Tomoko Kumano, Norifumi Konno, Hideki Yoshizawa, Kouhei MatsudaAbstract:A full-length cDNA cloning and tissue distribution of epithelial sodium channel (ENaC) protein were studied during ontogeny by immunohistochemistry in the External Gills, and the kidney, pronephros and mesonephros, of the Japanese black salamander, Hynobius nigrescens (Family Hynobiidae; a primitive caudate species). The amino acid sequence of Hynobius ENaCα is 64 and 63% identical to Bufo ENaCα and Rat ENaCα, respectively. In aquatic larva salamander at the digit differentiation stage, Hynobius ENaCα mRNA was expressed in the External Gills and pronephros. In the adult, the mRNA was expressed in the skin and the mesonephros. In the larvae, juvenile, and adult specimens, Hynobius ENaCα immunoreactivity was observed at the apical cell membrane of the External Gills, late parts of the distal tubules, and mesonephric duct in the kidney. Colocalization of the apical Hynobius ENaCα and the basolateral Na(+) ,K(+) -ATPase was observed in the tubular cells of pronephros and mesonephros. These results suggest that Hynobius ENaCα plays an important role in the regulation of sodium transport in the External Gills and pronephros of aquatic larvae, and in the skin and mesonephros of terrestrial adult. This is the first study to indicate ENaC expression during ontogeny in amphibians. Since no orthologs or paralogs for ENaC have been found, so far, in databases of the genomes of teleosts, it is assumed that ENaC might have played a role in terrestriality during the evolution of early tetrapods, the origin of lissamphibians.
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Ontogeny of ENaC expression in the Gills and the kidneys of the Japanese black salamander (Hynobius nigrescens Stejneger).
Journal of Experimental Zoology, 2010Co-Authors: Minoru Uchiyama, Tomoko Kumano, Norifumi Konno, Hideki Yoshizawa, Kouhei MatsudaAbstract:A full-length cDNA cloning and tissue distribution of epithelial sodium channel (ENaC) protein were studied during ontogeny by immunohistochemistry in the External Gills, and the kidney, pronephros and mesonephros, of the Japanese black salamander, Hynobius nigrescens (Family Hynobiidae; a primitive caudate species). The amino acid sequence of Hynobius ENaCα is 64 and 63% identical to Bufo ENaCα and Rat ENaCα, respectively. In aquatic larva salamander at the digit differentiation stage, Hynobius ENaCα mRNA was expressed in the External Gills and pronephros. In the adult, the mRNA was expressed in the skin and the mesonephros. In the larvae, juvenile, and adult specimens, Hynobius ENaCα immunoreactivity was observed at the apical cell membrane of the External Gills, late parts of the distal tubules, and mesonephric duct in the kidney. Colocalization of the apical Hynobius ENaCα and the basolateral Na+,K+-ATPase was observed in the tubular cells of pronephros and mesonephros. These results suggest that Hynobius ENaCα plays an important role in the regulation of sodium transport in the External Gills and pronephros of aquatic larvae, and in the skin and mesonephros of terrestrial adult. This is the first study to indicate ENaC expression during ontogeny in amphibians. Since no orthologs or paralogs for ENaC have been found, so far, in databases of the genomes of teleosts, it is assumed that ENaC might have played a role in terrestriality during the evolution of early tetrapods, the origin of lissamphibians. J. Exp. Zool. (Mol. Dev. Evol.) 316:135–145, 2011. © 2010 Wiley-Liss, Inc.
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Cellular localization of a putative Na^+/H^+ exchanger 3 during ontogeny in the pronephros and mesonephros of the Japanese black salamander (Hynobius nigrescens Stejneger)
Cell and Tissue Research, 2008Co-Authors: Tomoko Kumano, Norifumi Konno, Tatsuya Wakasugi, Kouhei Matsuda, Hideki Yoshizawa, Minoru UchiyamaAbstract:The cloning of cDNA and an examination of the tissue distribution of Na^+/H^+ exchanger 3 (NHE3) were carried out in the Japanese black salamander, Hynobius nigrescens . The cellular localization of Hynobius NHE3 was examined by in situ hybridization and immunohistochemistry during ontogeny in the nephron of the pronephros and mesonephros of the salamander. The partial amino acid sequence of Hynobius NHE3 was 81% and 72% identical to rat NHE3 and stingray NHE3, respectively. Hynobius NHE3 mRNA and protein were exclusively expressed along the late portion of the distal tubule to the anterior part of the pronephric duct of premetamorphic larvae (IY stages 43–50). NHE3 mRNA was expressed in the pronephros but not in the External Gills in the larvae at the digit differentiation stage (IY stage 50). In the adult, mRNA was strongly expressed in the mesonephros but not in the ventral and dorsal skin. In juvenile and adult specimens, NHE3 immunoreactivity was observed at the apical membrane of the initial parts of the distal tubules of the mesonephric kidney. Immunohistochemical and in situ hybridization studies suggested that Na^+ absorption coupled with H^+ secretion via NHE3 occurred in the distal nephron of the pronephros and mesonephros. This is the first study to indicate NHE3 expression during ontogeny in amphibians.
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Cellular localization of a putative Na(+)/H (+) exchanger 3 during ontogeny in the pronephros and mesonephros of the Japanese black salamander (Hynobius nigrescens Stejneger).
Cell and tissue research, 2007Co-Authors: Tomoko Kumano, Norifumi Konno, Tatsuya Wakasugi, Kouhei Matsuda, Hideki Yoshizawa, Minoru UchiyamaAbstract:The cloning of cDNA and an examination of the tissue distribution of Na+/H+ exchanger 3 (NHE3) were carried out in the Japanese black salamander, Hynobius nigrescens. The cellular localization of Hynobius NHE3 was examined by in situ hybridization and immunohistochemistry during ontogeny in the nephron of the pronephros and mesonephros of the salamander. The partial amino acid sequence of Hynobius NHE3 was 81% and 72% identical to rat NHE3 and stingray NHE3, respectively. Hynobius NHE3 mRNA and protein were exclusively expressed along the late portion of the distal tubule to the anterior part of the pronephric duct of premetamorphic larvae (IY stages 43–50). NHE3 mRNA was expressed in the pronephros but not in the External Gills in the larvae at the digit differentiation stage (IY stage 50). In the adult, mRNA was strongly expressed in the mesonephros but not in the ventral and dorsal skin. In juvenile and adult specimens, NHE3 immunoreactivity was observed at the apical membrane of the initial parts of the distal tubules of the mesonephric kidney. Immunohistochemical and in situ hybridization studies suggested that Na+ absorption coupled with H+ secretion via NHE3 occurred in the distal nephron of the pronephros and mesonephros. This is the first study to indicate NHE3 expression during ontogeny in amphibians.
Hideki Yoshizawa - One of the best experts on this subject based on the ideXlab platform.
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Immunohistological classification of ionocytes in the External Gills of larval Japanese black salamander, Hynobius nigrescens Stejneger
Journal of morphology, 2011Co-Authors: Minoru Uchiyama, Tomoko Kumano, Hideki Yoshizawa, Makiko Komiyama, Kouhei MatsudaAbstract:In this cytological and immunohistological study, we clarified the localization of the membrane transporters Na+, K+-ATPase (NKA), vacuolar-type H+-ATPase (VHA), and epithelial sodium channel (ENaC) and distinguished ionocyte subtypes in the gill of the Japanese salamander (Hynobius nigrescens). In larvae (IY stages 43–65), NKA immunoreactivity was observed on the basolateral plasma membrane in more than 60% cells and less than 20% cells in the primary filaments and secondary lamellae of the External Gills, respectively. VHA immunoreactivity was observed on the apical membrane of some epithelial cells in the secondary lamellae of the External Gills. High ENaCα immunoreactivity was widely observed on the apical cell membrane of a population of squamous cells, presumably pavement cells (PVCs), and mitochondria-rich cells (MRCs), in the primary filaments and secondary lamellae of the External Gills. Using double immunofluorescence microscopy, epithelial cell types involved in ionic regulation were characterized and divided into three ionocyte types: NKA-, NKA- and ENaC-, and VHA-positive cells. VHA-immunoreactive cells as well as NKA-positive cells were observed during IY stages 43–65 of the salamander larvae. During late stages of metamorphosis, NKA, VHA, and ENaCα immunoreactivities in the External Gills decreased and finally disappeared during the completion of metamorphosis (IY stage 68). PVCs and MRCs in the External Gills are probably involved in acid–base balance regulation and osmoregulation in urodele amphibian larvae. The results are discussed in relation to the ionocytes previously reported in fish Gills and the frog skin epithelium. J. Morphol., 2011. © 2011Wiley-Liss, Inc.
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Ontogeny of ENaC expression in the Gills and the kidneys of the Japanese black salamander (Hynobius nigrescens Stejneger).
Journal of experimental zoology. Part B Molecular and developmental evolution, 2010Co-Authors: Minoru Uchiyama, Tomoko Kumano, Norifumi Konno, Hideki Yoshizawa, Kouhei MatsudaAbstract:A full-length cDNA cloning and tissue distribution of epithelial sodium channel (ENaC) protein were studied during ontogeny by immunohistochemistry in the External Gills, and the kidney, pronephros and mesonephros, of the Japanese black salamander, Hynobius nigrescens (Family Hynobiidae; a primitive caudate species). The amino acid sequence of Hynobius ENaCα is 64 and 63% identical to Bufo ENaCα and Rat ENaCα, respectively. In aquatic larva salamander at the digit differentiation stage, Hynobius ENaCα mRNA was expressed in the External Gills and pronephros. In the adult, the mRNA was expressed in the skin and the mesonephros. In the larvae, juvenile, and adult specimens, Hynobius ENaCα immunoreactivity was observed at the apical cell membrane of the External Gills, late parts of the distal tubules, and mesonephric duct in the kidney. Colocalization of the apical Hynobius ENaCα and the basolateral Na(+) ,K(+) -ATPase was observed in the tubular cells of pronephros and mesonephros. These results suggest that Hynobius ENaCα plays an important role in the regulation of sodium transport in the External Gills and pronephros of aquatic larvae, and in the skin and mesonephros of terrestrial adult. This is the first study to indicate ENaC expression during ontogeny in amphibians. Since no orthologs or paralogs for ENaC have been found, so far, in databases of the genomes of teleosts, it is assumed that ENaC might have played a role in terrestriality during the evolution of early tetrapods, the origin of lissamphibians.
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Ontogeny of ENaC expression in the Gills and the kidneys of the Japanese black salamander (Hynobius nigrescens Stejneger).
Journal of Experimental Zoology, 2010Co-Authors: Minoru Uchiyama, Tomoko Kumano, Norifumi Konno, Hideki Yoshizawa, Kouhei MatsudaAbstract:A full-length cDNA cloning and tissue distribution of epithelial sodium channel (ENaC) protein were studied during ontogeny by immunohistochemistry in the External Gills, and the kidney, pronephros and mesonephros, of the Japanese black salamander, Hynobius nigrescens (Family Hynobiidae; a primitive caudate species). The amino acid sequence of Hynobius ENaCα is 64 and 63% identical to Bufo ENaCα and Rat ENaCα, respectively. In aquatic larva salamander at the digit differentiation stage, Hynobius ENaCα mRNA was expressed in the External Gills and pronephros. In the adult, the mRNA was expressed in the skin and the mesonephros. In the larvae, juvenile, and adult specimens, Hynobius ENaCα immunoreactivity was observed at the apical cell membrane of the External Gills, late parts of the distal tubules, and mesonephric duct in the kidney. Colocalization of the apical Hynobius ENaCα and the basolateral Na+,K+-ATPase was observed in the tubular cells of pronephros and mesonephros. These results suggest that Hynobius ENaCα plays an important role in the regulation of sodium transport in the External Gills and pronephros of aquatic larvae, and in the skin and mesonephros of terrestrial adult. This is the first study to indicate ENaC expression during ontogeny in amphibians. Since no orthologs or paralogs for ENaC have been found, so far, in databases of the genomes of teleosts, it is assumed that ENaC might have played a role in terrestriality during the evolution of early tetrapods, the origin of lissamphibians. J. Exp. Zool. (Mol. Dev. Evol.) 316:135–145, 2011. © 2010 Wiley-Liss, Inc.
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Cellular localization of a putative Na^+/H^+ exchanger 3 during ontogeny in the pronephros and mesonephros of the Japanese black salamander (Hynobius nigrescens Stejneger)
Cell and Tissue Research, 2008Co-Authors: Tomoko Kumano, Norifumi Konno, Tatsuya Wakasugi, Kouhei Matsuda, Hideki Yoshizawa, Minoru UchiyamaAbstract:The cloning of cDNA and an examination of the tissue distribution of Na^+/H^+ exchanger 3 (NHE3) were carried out in the Japanese black salamander, Hynobius nigrescens . The cellular localization of Hynobius NHE3 was examined by in situ hybridization and immunohistochemistry during ontogeny in the nephron of the pronephros and mesonephros of the salamander. The partial amino acid sequence of Hynobius NHE3 was 81% and 72% identical to rat NHE3 and stingray NHE3, respectively. Hynobius NHE3 mRNA and protein were exclusively expressed along the late portion of the distal tubule to the anterior part of the pronephric duct of premetamorphic larvae (IY stages 43–50). NHE3 mRNA was expressed in the pronephros but not in the External Gills in the larvae at the digit differentiation stage (IY stage 50). In the adult, mRNA was strongly expressed in the mesonephros but not in the ventral and dorsal skin. In juvenile and adult specimens, NHE3 immunoreactivity was observed at the apical membrane of the initial parts of the distal tubules of the mesonephric kidney. Immunohistochemical and in situ hybridization studies suggested that Na^+ absorption coupled with H^+ secretion via NHE3 occurred in the distal nephron of the pronephros and mesonephros. This is the first study to indicate NHE3 expression during ontogeny in amphibians.
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Cellular localization of a putative Na(+)/H (+) exchanger 3 during ontogeny in the pronephros and mesonephros of the Japanese black salamander (Hynobius nigrescens Stejneger).
Cell and tissue research, 2007Co-Authors: Tomoko Kumano, Norifumi Konno, Tatsuya Wakasugi, Kouhei Matsuda, Hideki Yoshizawa, Minoru UchiyamaAbstract:The cloning of cDNA and an examination of the tissue distribution of Na+/H+ exchanger 3 (NHE3) were carried out in the Japanese black salamander, Hynobius nigrescens. The cellular localization of Hynobius NHE3 was examined by in situ hybridization and immunohistochemistry during ontogeny in the nephron of the pronephros and mesonephros of the salamander. The partial amino acid sequence of Hynobius NHE3 was 81% and 72% identical to rat NHE3 and stingray NHE3, respectively. Hynobius NHE3 mRNA and protein were exclusively expressed along the late portion of the distal tubule to the anterior part of the pronephric duct of premetamorphic larvae (IY stages 43–50). NHE3 mRNA was expressed in the pronephros but not in the External Gills in the larvae at the digit differentiation stage (IY stage 50). In the adult, mRNA was strongly expressed in the mesonephros but not in the ventral and dorsal skin. In juvenile and adult specimens, NHE3 immunoreactivity was observed at the apical membrane of the initial parts of the distal tubules of the mesonephric kidney. Immunohistochemical and in situ hybridization studies suggested that Na+ absorption coupled with H+ secretion via NHE3 occurred in the distal nephron of the pronephros and mesonephros. This is the first study to indicate NHE3 expression during ontogeny in amphibians.
Rainer R. Schoch - One of the best experts on this subject based on the ideXlab platform.
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Bystrow’s Paradox – Gills, fossils, and the fish-to-tetrapod transition
Acta Zoologica, 2010Co-Authors: Rainer R. Schoch, Florian WitzmannAbstract:Schoch, R.R. and Witzmann, F. 2011. Bystrow’s Paradox – Gills, fossils, and the fish-to-tetrapod transition. —Acta Zoologica (Stockholm) 92: 251–265. The issue of which breathing mechanism was used by the earliest tetrapods is still unsolved. Recent discoveries of stem tetrapods suggest the presence of internal Gills and fish-like underwater breathing. The same osteological features were used by Bystrow to infer a salamander-like breathing through External Gills in temnospondyl amphibians. This apparent contradiction – here called Bystrow’s Paradox – is resolved by reviewing the primary fossil evidence and the anatomy of the two gill types in extant taxa. Rather unexpectedly, we find that internal Gills were present in a range of early crown tetrapods (temnospondyls), based on the anatomy of gill lamellae and location of branchial arteries on the ventral side of gill arch elements (ceratobranchials). Although it remains to be clarified which components are homologous in External and internal Gills, both gill types are likely to have been present in Palaeozoic tetrapods – internal Gills in aquatic adults of some taxa, and External Gills in the larvae of these taxa and in larvae of numerous forms with terrestrial adults, which resorbed the External Gills after the larval phase. Future developmental studies will hopefully clarify which mechanistic pathways are involved in gill formation and how these might have evolved.
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Skeleton formation in the Branchiosauridae: a case study in comparing ontogenetic trajectories
Journal of Vertebrate Paleontology, 2004Co-Authors: Rainer R. SchochAbstract:Abstract Branchiosaurids are small Permo-Carboniferous temnospondyls that retained an immature morphology and External Gills throughout ontogeny. Their preservation of numerous size classes makes them outstanding examples for the study of ontogenetic patterns. Here, ontogenetic data of several branchiosaurids are analyzed in order to reconstruct and compare developmental trajectories. These trajectories are based on numerical changes, marked by the successive appearance of bones in the skeleton. The earliest phases in the formation of the skull are preserved only in two species, Apateon caducus and Melanerpeton humbergense. Despite being distant relatives within the clade, their ontogenetic trajectories are similar in the early formation of dentigerous elements in the jaws and palate, and a slower development of the median skull roof as compared with the smaller branchiosaurids Apateon pedestris, A. gracilis, and A. dracyi. Patterns shared by all five species are (1) the late formation and slow completion...
