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Robert E Shadwick - One of the best experts on this subject based on the ideXlab platform.
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thermal dependence of contractile properties of the aerobic locomotor muscle in the leopard shark and shortfin mako shark
The Journal of Experimental Biology, 2007Co-Authors: Jeanine M Donley, Chugey A Sepulveda, Robert E Shadwick, Douglas A SymeAbstract:The work loop technique was used to examine contractile properties of the red aerobic locomotor muscle (RM) in the ectothermic leopard shark Triakis semifasciata and endothermic shortfin mako shark Isurus oxyrinchus . The effects of axial position and temperature on the twitch kinetics, and the stimulus duration and phase producing maximum net positive work and power output were investigated. Contractile performance was measured over the temperature range of 15 to 25°C for Triakis and 15 to 28°C for Isurus at cycle frequencies (analogous to tailbeat frequencies) ranging from 0.25 to 3 Hz using muscle bundles isolated from anterior (0.4 L where L is total body length) and posterior (0.6–0.65 L ) axial positions. Pairwise comparisons of twitch times for anterior and posterior muscle samples indicated that there were no significant differences related to body position, except in mako sharks at unphysiologically cool temperatures (<20°C). We found no significant differences in optimal stimulus duration, phase, net work or power output between anterior and posterior bundles in each species. With increasing cycle frequency the stimulus duration yielding maximum power decreased while optimal phase occurred earlier. The cycle frequency at which peak power was generated in leopard shark RM was only affected slightly by temperature, increasing from about 0.6 to 1.0 Hz between 15 and 25°C. In contrast, mako RM showed a much more dramatic temperature sensitivity, with the peak power frequency rising from <0.25 to 2.25 Hz between 15 and 28°C. These data support the hypothesis that the contractile properties of RM are functionally similar along the body in both species. In addition, our data identify a significant difference in the effect of temperature on net work and power output between these two shark species; at 15°C muscle from the ectothermic leopard shark performs relatively well in comparison with mako, while at higher temperatures, which reflect those normally experienced by the mako, the optimal cycle frequency for power is nearly double that of the leopard shark, suggesting that the mako may be able to maintain greater aerobic swimming speeds.
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Thermal dependence of contractile properties of the aerobic locomotor muscle in the leopard shark and shortfin mako shark
The Journal of Experimental Biology, 2007Co-Authors: Jeanine M Donley, Chugey A Sepulveda, Robert E Shadwick, Douglas A SymeAbstract:The work loop technique was used to examine contractile properties of the red aerobic locomotor muscle (RM) in the ectothermic leopard shark Triakis semifasciata and endothermic shortfin mako shark Isurus oxyrinchus . The effects of axial position and temperature on the twitch kinetics, and the stimulus duration and phase producing maximum net positive work and power output were investigated. Contractile performance was measured over the temperature range of 15 to 25°C for Triakis and 15 to 28°C for Isurus at cycle frequencies (analogous to tailbeat frequencies) ranging from 0.25 to 3 Hz using muscle bundles isolated from anterior (0.4 L where L is total body length) and posterior (0.6–0.65 L ) axial positions. Pairwise comparisons of twitch times for anterior and posterior muscle samples indicated that there were no significant differences related to body position, except in mako sharks at unphysiologically cool temperatures (
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Thermal dependence of contractile properties of the aerobic locomotor muscle in the leopard shark and shortfin mako shark.
Journal of Experimental Biology, 2007Co-Authors: Jeanine M Donley, Chugey A Sepulveda, Robert E Shadwick, Douglas A SymeAbstract:The work loop technique was used to examine contractile properties of the red aerobic locomotor muscle (RM) in the ectothermic leopard shark Triakis semifasciata and endothermic shortfin mako shark Isurus oxyrinchus. The effects of axial position and temperature on the twitch kinetics, and the stimulus duration and phase producing maximum net positive work and power output were investigated. Contractile performance was measured over the temperature range of 15 to 25 degrees C for Triakis and 15 to 28 degrees C for Isurus at cycle frequencies (analogous to tailbeat frequencies) ranging from 0.25 to 3 Hz using muscle bundles isolated from anterior (0.4 L where L is total body length) and posterior (0.6-0.65 L) axial positions. Pairwise comparisons of twitch times for anterior and posterior muscle samples indicated that there were no significant differences related to body position, except in mako sharks at unphysiologically cool temperatures (
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thermal dependence of contractile properties of the aerobic locomotor muscle in the leopard shark and shortfin mako shark
The Journal of Experimental Biology, 2007Co-Authors: Jeanine M Donley, Chugey A Sepulveda, Robert E Shadwick, Douglas A SymeAbstract:The work loop technique was used to examine contractile properties of the red aerobic locomotor muscle (RM) in the ectothermic leopard shark Triakis semifasciata and endothermic shortfin mako shark Isurus oxyrinchus. The effects of axial position and temperature on the twitch kinetics, and the stimulus duration and phase producing maximum net positive work and power output were investigated. Contractile performance was measured over the temperature range of 15 to 25 degrees C for Triakis and 15 to 28 degrees C for Isurus at cycle frequencies (analogous to tailbeat frequencies) ranging from 0.25 to 3 Hz using muscle bundles isolated from anterior (0.4 L where L is total body length) and posterior (0.6-0.65 L) axial positions. Pairwise comparisons of twitch times for anterior and posterior muscle samples indicated that there were no significant differences related to body position, except in mako sharks at unphysiologically cool temperatures (<20 degrees C). We found no significant differences in optimal stimulus duration, phase, net work or power output between anterior and posterior bundles in each species. With increasing cycle frequency the stimulus duration yielding maximum power decreased while optimal phase occurred earlier. The cycle frequency at which peak power was generated in leopard shark RM was only affected slightly by temperature, increasing from about 0.6 to 1.0 Hz between 15 and 25 degrees C. In contrast, mako RM showed a much more dramatic temperature sensitivity, with the peak power frequency rising from <0.25 to 2.25 Hz between 15 and 28 degrees C. These data support the hypothesis that the contractile properties of RM are functionally similar along the body in both species. In addition, our data identify a significant difference in the effect of temperature on net work and power output between these two shark species; at 15 degrees C muscle from the ectothermic leopard shark performs relatively well in comparison with mako, while at higher temperatures, which reflect those normally experienced by the mako, the optimal cycle frequency for power is nearly double that of the leopard shark, suggesting that the mako may be able to maintain greater aerobic swimming speeds.
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steady swimming muscle dynamics in the leopard shark Triakis semifasciata
The Journal of Experimental Biology, 2003Co-Authors: Jeanine M Donley, Robert E ShadwickAbstract:SUMMARY Patterns of red muscle strain and activation were examined at three positions along the body (0.42, 0.61 and 0.72 L , where L is total body length) and correlated with simultaneous measurements of midline kinematics during steady swimming (approx. 1.0 L s –1 ) in the leopard shark Triakis semifasciata . Analysis of lateral displacement along the body indicates that the leopard shark is a subcarangiform swimmer. Longitudinal variation in red muscle strain was observed with strain amplitudes ranging from ±3.9% in the anterior,± 6.6% in the mid, to ±4.8% in the posterior body position. Strain was in-phase with local midline curvature. In addition, strain amplitude calculated from a bending beam model closely matched strain measured using sonomicrometry at all three body positions. There is a high degree of similarity in red muscle activation patterns along the body between the leopard shark and many fish species, in that the onset of activation occurs during muscle lengthening while offset occurs during muscle shortening. However, we found no significant longitudinal variation in the EMG/strain phase relationship and duty cycles, with onset of muscle activation occurring at 51.4–61.8° and offset at 159.7–165.2° (90° is peak length). This consistent pattern of activation suggests that red muscle along the entire length of the body contributes to positive power production. Thus, sharks such as Triakis may have no regional specialization in red muscle function like that seen in many teleosts, which may indicate that the evolution of differential muscle function along the body occurred after the divergence of cartilaginous and bony fishes.
Yoshio Takei - One of the best experts on this subject based on the ideXlab platform.
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Identification of angiotensinogen genes with unique and variable angiotensin sequences in chondrichthyans
General and comparative endocrinology, 2008Co-Authors: Taro Watanabe, Koji Inoue, Yoshio TakeiAbstract:Abstract The renin–angiotensin system is an enzyme-linked hormonal cascade that plays an important role in body fluid and cardiovascular regulation. The system is initiated by the action of renin on the precursor protein, angiotensinogen (AGT), whose sequence information is scarce because of its high variability among species. In the present study, we cloned AGT in chondrichthyans (elasmobranchs: Triakis scyllium , Dasyatis akajei, Leucoraja erinacea and a holocephalan: Callorhinchus milii ). Homology was low among AGTs thus far identified; 25–28% between elasmobranchs and tetrapods and 33–61% even within chondrichthyans. All chondrichthyan angiotensin (ANG) II’s have a unique Pro 3 instead of Val 3 as seen in all other species. In addition, holocephalan ANG II has an unusual His 4 instead of Tyr 4 . In addition, and the N-terminal amino acid, which is usually Asp 1 in tetrapods and Asn 1 in fishes, was highly variable (Asp, Asn or Tyr) in chondrichthyans. Molecular phylogenetic analysis showed that chondrichthyan AGT precursors are clustered into a group separated from those of tetrapods and teleosts. The AGT gene was most abundantly expressed in the liver, followed by the kidney, interrenal tissue and rectal gland of Triakis where biological actions of ANG II have been demonstrated. Collectively, we identified diversified AGT genes for the first time in chondrichthyes and showed that their ANG II’s have unique amino acid residues at positions 1, 3 and 4. High variability of ANG II sequences in chondrichthyans is discussed in relation to their unique regulatory mechanisms such as urea-based osmoregulation.
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Neurohypophysial hormones of dogfish, Triakis scyllium: structures and salinity-dependent secretion.
General and comparative endocrinology, 2004Co-Authors: Susumu Hyodo, Takehiro Tsukada, Yoshio TakeiAbstract:Sharks and rays utilize a unique strategy for adaptation to the hyperosmotic marine environment by maintaining their plasma slightly hyperosmotic to surrounding seawater (SW) through the accumulation of urea. Since neurohypophysial hormones (NHs) are plausible candidates for osmoregulatory effectors, the synthesis and release of NHs were investigated after transfer of fish to different environmental salinities. Molecular cloning revealed three NHs from the hypothalamus of a dogfish, Triakis scyllium: vasotocin (VT), asvatocin, and a novel oxytocin-family peptide, phasitocin ([Phe3, Asn4, Ile8]vasotocin). The VT precursor consists of a signal peptide, VT, a neurophysin and a copeptin moiety. In contrast, the asvatocin and phasitocin precursors are shorter due to the lack of a copeptin moiety as is the case in oxytocin and mesotocin precursors in tetrapods and lungfish, but different from teleost isotocin precursors that have the copeptin moiety. In the hypothalamus, VT mRNA levels significantly increased after transfer to concentrated (130%) SW for 2 days, while no change was observed in mRNA levels of asvatocin and phasitocin following transfer to either 130% or diluted (60%) SW. The increase in VT mRNA was reflected in the plasma level of peptide; plasma VT concentration measured by highly sensitive and specific radioimmunoassay increased according to elevated environmental salinities. These results suggest that VT is an osmoregulatory effector in dogfish, especially when the dogfish is exposed to a hyperosmotic environment.
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a facilitative urea transporter is localized in the renal collecting tubule of the dogfish Triakis scyllia
The Journal of Experimental Biology, 2004Co-Authors: Susumu Hyodo, Toyoji Kaneko, Fumi Katoh, Yoshio TakeiAbstract:SUMMARY Reabsorption of filtered urea by the kidney tubule is essential for retaining high levels of urea in body fluids of marine elasmobranchs. To elucidate the mechanisms of urea reabsorption, we examined the distribution of a facilitative urea transporter (UT) in the kidney of the dogfish Triakis scyllia . We isolated a cDNA encoding a UT that is homologous to the facilitative UT cloned from another dogfish species, Squalus acanthias . The Triakis UT mRNA is abundantly expressed in the kidney, while low levels of expression were detected in the brain and liver. In the dogfish kidney, each nephron makes four turns and traverses repeatedly between bundle zone and sinus zone. In the bundle zone, the resulting five tubular segments are arranged in a countercurrent loop fashion. Immunohistochemistry using specific antibodies raised against the cloned UT revealed that, among the nephron segments, the UT is expressed exclusively in the final segment of the bundle zone, i.e. in the collecting tubule of the Triakis kidney. In contrast to the limited localization of UT, the transport enzyme Na + /K + -ATPase is distributed in the basolateral membrane of numerous tubular segments both in the sinus zone and the bundle zone. However, in the collecting tubule, Na + /K + -ATPase immunoreactivity was not detected. The present study suggests that the collecting tubule is responsible for the reabsorption of urea in the marine elasmobranch kidney. Other countercurrent segments may contribute to production of a driving force for facilitative diffusion of urea through the UT.
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The dipsogenic effect of the renin-angiotensin system in elasmobranch fish.
General and comparative endocrinology, 2001Co-Authors: W. Gary Anderson, Yoshio Takei, Neil HazonAbstract:Abstract This study investigated the control of drinking in elasmobranch fish through manipulation of the homologous renin–angiotensin system (RAS). The smooth muscle relaxant papaverine was found to increase basal drinking levels in the European lesser-spotted dogfish, Scyliorhinus canicula, almost 20-fold. However, this response was significantly reduced with the coadministration of the angiotensin-converting enzyme inhibitor captopril which had no effect when administered alone. Captopril was also found to block a 7-fold increase in drinking rate following administration of homologous angiotensin I in S. canicula. Finally, administration of homologous angiotensin II produced a dose-dependent response in drinking rate in two species of elasmobranchs, S. canicula and the Japanese dogfish, Triakis scyllia. These results demonstrate a central role of the RAS in the control of drinking in elasmobranch fish.
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CNP is the only Natriuretic Peptide in an Elasmobranch Fish, Triakis scyllia
Zoological Science, 2001Co-Authors: Akatsuki Kawakoshi, Susumu Hyodo, Yoshio TakeiAbstract:Abstract The natriuretic peptide (NP) family consists of endocrine ANP/BNP/VNP in the heart and paracrine CNP in the brain in vertebrates ranging from teleosts to mammals. In elasmobranchs, however, only CNP has been identified thus far in the heart and brain. To delineate the molecular evolution of this hormone family, it is essential to determine whether CNP is the only NP in this primitive fish group. In the present study, PCR cloning of all types of piscine NP was performed from the heart and brain of a dogfish, Triakis scyllia, using degenerate primers that amplified eel ANP, VNP and CNP. However, only CNP cDNA with an identical sequence was cloned from the heart and brain. Southern blot analysis showed that the CNP gene is a single copy gene, showing that endocrine CNP from the heart and paracrine CNP in the brain originate from the same gene. Since expression of the CNP gene was so high as demonstrated by Northern blot analysis, the abundantly expressed CNP mRNA could have interfered the amplificat...
Jeanine M Donley - One of the best experts on this subject based on the ideXlab platform.
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thermal dependence of contractile properties of the aerobic locomotor muscle in the leopard shark and shortfin mako shark
The Journal of Experimental Biology, 2007Co-Authors: Jeanine M Donley, Chugey A Sepulveda, Robert E Shadwick, Douglas A SymeAbstract:The work loop technique was used to examine contractile properties of the red aerobic locomotor muscle (RM) in the ectothermic leopard shark Triakis semifasciata and endothermic shortfin mako shark Isurus oxyrinchus . The effects of axial position and temperature on the twitch kinetics, and the stimulus duration and phase producing maximum net positive work and power output were investigated. Contractile performance was measured over the temperature range of 15 to 25°C for Triakis and 15 to 28°C for Isurus at cycle frequencies (analogous to tailbeat frequencies) ranging from 0.25 to 3 Hz using muscle bundles isolated from anterior (0.4 L where L is total body length) and posterior (0.6–0.65 L ) axial positions. Pairwise comparisons of twitch times for anterior and posterior muscle samples indicated that there were no significant differences related to body position, except in mako sharks at unphysiologically cool temperatures (<20°C). We found no significant differences in optimal stimulus duration, phase, net work or power output between anterior and posterior bundles in each species. With increasing cycle frequency the stimulus duration yielding maximum power decreased while optimal phase occurred earlier. The cycle frequency at which peak power was generated in leopard shark RM was only affected slightly by temperature, increasing from about 0.6 to 1.0 Hz between 15 and 25°C. In contrast, mako RM showed a much more dramatic temperature sensitivity, with the peak power frequency rising from <0.25 to 2.25 Hz between 15 and 28°C. These data support the hypothesis that the contractile properties of RM are functionally similar along the body in both species. In addition, our data identify a significant difference in the effect of temperature on net work and power output between these two shark species; at 15°C muscle from the ectothermic leopard shark performs relatively well in comparison with mako, while at higher temperatures, which reflect those normally experienced by the mako, the optimal cycle frequency for power is nearly double that of the leopard shark, suggesting that the mako may be able to maintain greater aerobic swimming speeds.
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Thermal dependence of contractile properties of the aerobic locomotor muscle in the leopard shark and shortfin mako shark
The Journal of Experimental Biology, 2007Co-Authors: Jeanine M Donley, Chugey A Sepulveda, Robert E Shadwick, Douglas A SymeAbstract:The work loop technique was used to examine contractile properties of the red aerobic locomotor muscle (RM) in the ectothermic leopard shark Triakis semifasciata and endothermic shortfin mako shark Isurus oxyrinchus . The effects of axial position and temperature on the twitch kinetics, and the stimulus duration and phase producing maximum net positive work and power output were investigated. Contractile performance was measured over the temperature range of 15 to 25°C for Triakis and 15 to 28°C for Isurus at cycle frequencies (analogous to tailbeat frequencies) ranging from 0.25 to 3 Hz using muscle bundles isolated from anterior (0.4 L where L is total body length) and posterior (0.6–0.65 L ) axial positions. Pairwise comparisons of twitch times for anterior and posterior muscle samples indicated that there were no significant differences related to body position, except in mako sharks at unphysiologically cool temperatures (
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Thermal dependence of contractile properties of the aerobic locomotor muscle in the leopard shark and shortfin mako shark.
Journal of Experimental Biology, 2007Co-Authors: Jeanine M Donley, Chugey A Sepulveda, Robert E Shadwick, Douglas A SymeAbstract:The work loop technique was used to examine contractile properties of the red aerobic locomotor muscle (RM) in the ectothermic leopard shark Triakis semifasciata and endothermic shortfin mako shark Isurus oxyrinchus. The effects of axial position and temperature on the twitch kinetics, and the stimulus duration and phase producing maximum net positive work and power output were investigated. Contractile performance was measured over the temperature range of 15 to 25 degrees C for Triakis and 15 to 28 degrees C for Isurus at cycle frequencies (analogous to tailbeat frequencies) ranging from 0.25 to 3 Hz using muscle bundles isolated from anterior (0.4 L where L is total body length) and posterior (0.6-0.65 L) axial positions. Pairwise comparisons of twitch times for anterior and posterior muscle samples indicated that there were no significant differences related to body position, except in mako sharks at unphysiologically cool temperatures (
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thermal dependence of contractile properties of the aerobic locomotor muscle in the leopard shark and shortfin mako shark
The Journal of Experimental Biology, 2007Co-Authors: Jeanine M Donley, Chugey A Sepulveda, Robert E Shadwick, Douglas A SymeAbstract:The work loop technique was used to examine contractile properties of the red aerobic locomotor muscle (RM) in the ectothermic leopard shark Triakis semifasciata and endothermic shortfin mako shark Isurus oxyrinchus. The effects of axial position and temperature on the twitch kinetics, and the stimulus duration and phase producing maximum net positive work and power output were investigated. Contractile performance was measured over the temperature range of 15 to 25 degrees C for Triakis and 15 to 28 degrees C for Isurus at cycle frequencies (analogous to tailbeat frequencies) ranging from 0.25 to 3 Hz using muscle bundles isolated from anterior (0.4 L where L is total body length) and posterior (0.6-0.65 L) axial positions. Pairwise comparisons of twitch times for anterior and posterior muscle samples indicated that there were no significant differences related to body position, except in mako sharks at unphysiologically cool temperatures (<20 degrees C). We found no significant differences in optimal stimulus duration, phase, net work or power output between anterior and posterior bundles in each species. With increasing cycle frequency the stimulus duration yielding maximum power decreased while optimal phase occurred earlier. The cycle frequency at which peak power was generated in leopard shark RM was only affected slightly by temperature, increasing from about 0.6 to 1.0 Hz between 15 and 25 degrees C. In contrast, mako RM showed a much more dramatic temperature sensitivity, with the peak power frequency rising from <0.25 to 2.25 Hz between 15 and 28 degrees C. These data support the hypothesis that the contractile properties of RM are functionally similar along the body in both species. In addition, our data identify a significant difference in the effect of temperature on net work and power output between these two shark species; at 15 degrees C muscle from the ectothermic leopard shark performs relatively well in comparison with mako, while at higher temperatures, which reflect those normally experienced by the mako, the optimal cycle frequency for power is nearly double that of the leopard shark, suggesting that the mako may be able to maintain greater aerobic swimming speeds.
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steady swimming muscle dynamics in the leopard shark Triakis semifasciata
The Journal of Experimental Biology, 2003Co-Authors: Jeanine M Donley, Robert E ShadwickAbstract:SUMMARY Patterns of red muscle strain and activation were examined at three positions along the body (0.42, 0.61 and 0.72 L , where L is total body length) and correlated with simultaneous measurements of midline kinematics during steady swimming (approx. 1.0 L s –1 ) in the leopard shark Triakis semifasciata . Analysis of lateral displacement along the body indicates that the leopard shark is a subcarangiform swimmer. Longitudinal variation in red muscle strain was observed with strain amplitudes ranging from ±3.9% in the anterior,± 6.6% in the mid, to ±4.8% in the posterior body position. Strain was in-phase with local midline curvature. In addition, strain amplitude calculated from a bending beam model closely matched strain measured using sonomicrometry at all three body positions. There is a high degree of similarity in red muscle activation patterns along the body between the leopard shark and many fish species, in that the onset of activation occurs during muscle lengthening while offset occurs during muscle shortening. However, we found no significant longitudinal variation in the EMG/strain phase relationship and duty cycles, with onset of muscle activation occurring at 51.4–61.8° and offset at 159.7–165.2° (90° is peak length). This consistent pattern of activation suggests that red muscle along the entire length of the body contributes to positive power production. Thus, sharks such as Triakis may have no regional specialization in red muscle function like that seen in many teleosts, which may indicate that the evolution of differential muscle function along the body occurred after the divergence of cartilaginous and bony fishes.
Susumu Hyodo - One of the best experts on this subject based on the ideXlab platform.
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subcellular distribution of urea transporter in the collecting tubule of shark kidney is dependent on environmental salinity
Journal of Experimental Zoology, 2009Co-Authors: Yoko Yamaguchi, Shin Takaki, Susumu HyodoAbstract:In the kidney of marine elasmobranchs, urea reabsorption from filtered urine is essential for maintaining high levels of urea in the body. In the kidney of the houndshark, Triakis scyllium, we previously found that a facilitative urea transporter (UT) is localized to a specific nephron segment, the collecting tubule, suggesting that the collecting tubule has an important role in the urea reabsorption process. To elucidate the roles of UT, we transferred T. scyllium to high (130%) and low (30%) salinity, and examined UT mRNA levels and UT distribution patterns in the kidney using real-time PCR and semi-quantitative fluorescence immunohistochemistry, respectively. Following transfer to low and high salinity, houndshark decreased and increased plasma urea concentrations, respectively, in order to control plasma osmolality. The abundance of UT mRNA did not differ among the experimental groups, whereas that of UT protein in the collecting tubule was significantly decreased in 30% seawater (SW). Furthermore, the subcellular UT distribution was dramatically changed. UT in the apical plasma membrane of collecting tubule almost disappeared in 30% SW, whereas it slightly increased in 130% SW compared with 100% SW. Conversely, reverse transfer of fish from 30 to100% SW restored UT in the apical membrane. These results indicate that the accumulation of UT to the apical plasma membrane of the collecting tubule of Triakis is an important factor for regulating urea reabsorption in the kidney. J. Exp. Zool. 311A: 705–718, 2009. © 2009 Wiley-Liss, Inc.
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Evaluation of posttranslational processing of proopiomelanocortin in the banded houndshark pituitary by combined cDNA cloning and mass spectrometry.
General and comparative endocrinology, 2008Co-Authors: Akiyoshi Takahashi, Yuki Kobayashi, Shunsuke Moriyama, Susumu HyodoAbstract:Proopiomelanocortin (POMC) is cleaved into small peptides, such as adrenocorticotropic hormone (ACTH), melanocyte-stimulating hormones (MSHs), and beta-endorphin (beta-END), by tissue-specific posttranslational processing in the corticotrophs of the pars distalis (PD) and melanotrophs of the neurointermediate lobe (NIL) of the pituitary. We examined the posttranslational processing of POMC in the pituitary of the banded houndshark Triakis scyllium by molecular cloning and subsequent mass spectrometric identification of the POMC-derived peptides in the pituitary extracts. One-fifth of the randomly selected clones from a Triakis pituitary cDNA library contained a cDNA encoding for POMC. Triakis prePOMC contained 4 MSHs and a single beta-END, as has been observed in case of other cartilaginous fish POMCs. These predicted hormonal segments were flanked by basic amino acid residues, which are the cleavage sites for the processing enzymes, i.e., protein convertases. Mass spectrometry was performed using PD (including most parts of the rostral and proximal PD) and NIL extracts to detect mass values corresponding to the POMC-derived peptides. Consequently, ACTH, beta-END, and the joining peptide (JP) were detected in the PD extract, while MSHs, processed beta-END, and some other POMC-derived peptides were identified in the NIL extract; however, neither acetylated alpha-MSH nor acetylated beta-END was detected in the latter. These tissue-specific POMC processing patterns are similar to those of the other vertebrate pituitaries; however, the absence of acetylated peptides suggests the lack of an acetylation system in the melanotrophs in the NIL of the Triakis pituitary.
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Neurohypophysial hormones of dogfish, Triakis scyllium: structures and salinity-dependent secretion.
General and comparative endocrinology, 2004Co-Authors: Susumu Hyodo, Takehiro Tsukada, Yoshio TakeiAbstract:Sharks and rays utilize a unique strategy for adaptation to the hyperosmotic marine environment by maintaining their plasma slightly hyperosmotic to surrounding seawater (SW) through the accumulation of urea. Since neurohypophysial hormones (NHs) are plausible candidates for osmoregulatory effectors, the synthesis and release of NHs were investigated after transfer of fish to different environmental salinities. Molecular cloning revealed three NHs from the hypothalamus of a dogfish, Triakis scyllium: vasotocin (VT), asvatocin, and a novel oxytocin-family peptide, phasitocin ([Phe3, Asn4, Ile8]vasotocin). The VT precursor consists of a signal peptide, VT, a neurophysin and a copeptin moiety. In contrast, the asvatocin and phasitocin precursors are shorter due to the lack of a copeptin moiety as is the case in oxytocin and mesotocin precursors in tetrapods and lungfish, but different from teleost isotocin precursors that have the copeptin moiety. In the hypothalamus, VT mRNA levels significantly increased after transfer to concentrated (130%) SW for 2 days, while no change was observed in mRNA levels of asvatocin and phasitocin following transfer to either 130% or diluted (60%) SW. The increase in VT mRNA was reflected in the plasma level of peptide; plasma VT concentration measured by highly sensitive and specific radioimmunoassay increased according to elevated environmental salinities. These results suggest that VT is an osmoregulatory effector in dogfish, especially when the dogfish is exposed to a hyperosmotic environment.
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a facilitative urea transporter is localized in the renal collecting tubule of the dogfish Triakis scyllia
The Journal of Experimental Biology, 2004Co-Authors: Susumu Hyodo, Toyoji Kaneko, Fumi Katoh, Yoshio TakeiAbstract:SUMMARY Reabsorption of filtered urea by the kidney tubule is essential for retaining high levels of urea in body fluids of marine elasmobranchs. To elucidate the mechanisms of urea reabsorption, we examined the distribution of a facilitative urea transporter (UT) in the kidney of the dogfish Triakis scyllia . We isolated a cDNA encoding a UT that is homologous to the facilitative UT cloned from another dogfish species, Squalus acanthias . The Triakis UT mRNA is abundantly expressed in the kidney, while low levels of expression were detected in the brain and liver. In the dogfish kidney, each nephron makes four turns and traverses repeatedly between bundle zone and sinus zone. In the bundle zone, the resulting five tubular segments are arranged in a countercurrent loop fashion. Immunohistochemistry using specific antibodies raised against the cloned UT revealed that, among the nephron segments, the UT is expressed exclusively in the final segment of the bundle zone, i.e. in the collecting tubule of the Triakis kidney. In contrast to the limited localization of UT, the transport enzyme Na + /K + -ATPase is distributed in the basolateral membrane of numerous tubular segments both in the sinus zone and the bundle zone. However, in the collecting tubule, Na + /K + -ATPase immunoreactivity was not detected. The present study suggests that the collecting tubule is responsible for the reabsorption of urea in the marine elasmobranch kidney. Other countercurrent segments may contribute to production of a driving force for facilitative diffusion of urea through the UT.
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CNP is the only Natriuretic Peptide in an Elasmobranch Fish, Triakis scyllia
Zoological Science, 2001Co-Authors: Akatsuki Kawakoshi, Susumu Hyodo, Yoshio TakeiAbstract:Abstract The natriuretic peptide (NP) family consists of endocrine ANP/BNP/VNP in the heart and paracrine CNP in the brain in vertebrates ranging from teleosts to mammals. In elasmobranchs, however, only CNP has been identified thus far in the heart and brain. To delineate the molecular evolution of this hormone family, it is essential to determine whether CNP is the only NP in this primitive fish group. In the present study, PCR cloning of all types of piscine NP was performed from the heart and brain of a dogfish, Triakis scyllia, using degenerate primers that amplified eel ANP, VNP and CNP. However, only CNP cDNA with an identical sequence was cloned from the heart and brain. Southern blot analysis showed that the CNP gene is a single copy gene, showing that endocrine CNP from the heart and paracrine CNP in the brain originate from the same gene. Since expression of the CNP gene was so high as demonstrated by Northern blot analysis, the abundantly expressed CNP mRNA could have interfered the amplificat...
Joseph J Cech - One of the best experts on this subject based on the ideXlab platform.
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Proteomic and physiological responses of leopard sharks (Triakis semifasciata) to salinity change
The Journal of Experimental Biology, 2010Co-Authors: W. Wesley Dowd, Joseph J Cech, Breanna N. Harris, Dietmar KültzAbstract:SUMMARY Partially euryhaline elasmobranchs may tolerate physiologically challenging, variable salinity conditions in estuaries as a trade-off to reduce predation risk or to gain access to abundant food resources. To further understand these trade-offs and to evaluate the underlying mechanisms, we examined the responses of juvenile leopard sharks to salinity changes using a suite of measurements at multiple organizational levels: gill and rectal gland proteomes (using 2-D gel electrophoresis and tandem mass spectrometry), tissue biochemistry (Na + /K + -ATPase, caspase 3/7 and chymotrypsin-like proteasome activities), organismal physiology (hematology, plasma composition, muscle moisture) and individual behavior. Our proteomics results reveal coordinated molecular responses to low salinity – several of which are common to both rectal gland and gill – including changes in amino acid and inositol (i.e. osmolyte) metabolism, energy metabolism and proteins related to transcription, translation and protein degradation. Overall, leopard sharks employ a strategy of maintaining plasma urea, ion concentrations and Na + /K + -ATPase activities in the short-term, possibly because they rarely spend extended periods in low salinity conditions in the wild, but the sharks osmoconform to the surrounding conditions by 3 weeks. We found no evidence of apoptosis at the time points tested, while both tissues exhibited proteomic changes related to the cytoskeleton, suggesting that leopard sharks remodel existing osmoregulatory epithelial cells and activate physiological acclimatory responses to solve the problems posed by low salinity exposure. The behavioral measurements reveal increased activity in the lowest salinity in the short-term, while activity decreased in the lowest salinity in the long-term. Our data suggest that physiological/behavioral trade-offs are involved in using estuarine habitats, and pathway modeling implicates tumor necrosis factor α (TNFα) as a key node of the elasmobranch hyposmotic response network.
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The influence of environmental variables on the distribution and abundance of three elasmobranchs in Tomales Bay, California
Environmental Biology of Fishes, 2003Co-Authors: Todd E. Hopkins, Joseph J CechAbstract:We tested the hypothesis that temperature, salinity, and dissolved oxygen affect elasmobranch distribution and abundance in Tomales Bay, California, with monthly longline samples over a 20 month period. We used a Poisson regression under generalized least squares and found that temperature and salinity were the most important factors determining the distribution and abundance of the three most common elasmobranch species, bat ray, Myliobatis californica, leopard shark, Triakis semifasciata, and brown smoothhound shark, Mustelis henlei. Females of all three species were more abundant than males throughout the Bay, and were most abundant in the warmer, more saline inner bay. All three species apparently left Tomales Bay in late fall as water temperatures in the bay decreased to 10° C. Three of 257 bat rays tagged in Tomales Bay were recaptured, all within 1 km of their tagging location despite having been free for up to 583 d.
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Effect of Temperature on Oxygen Consumption of the Leopard Shark, Triakis Semifasciata
Environmental Biology of Fishes, 2003Co-Authors: Paul Miklos, Shana M. Katzman, Joseph J CechAbstract:The leopard shark, Triakis semifasciata , regularly resides in California's Tomales Bay, which is characterized by thermally different regions ranging from 10°C to 26°C during the summer. Past studies have shown that leopard sharks feed on benthic invertebrate prey similar to that of the sympatric bat ray, Myliobatis californica . Fishes' metabolic (oxygen consumption) rates typically increase with temperature increases, and we measured leopard sharks' metabolic responses and sensitivity to ambient temperature, using flow-through respirometry. Leopard shark oxygen consumption rate increased with increasing temperature, over a range of 12–24°C, with a typical temperature sensitivity (Q_10 = 2.51). Whereas bat rays use a highly temperature-sensitive metabolism to efficiently feed (in warmer waters) and digest (in cooler waters) during different phases of the diel cycle, leopard sharks possess a more typical metabolic temperature sensitivity that allows for high-tide foraging, throughout the diel cycle.
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Tidal Influence on Spatial Dynamics of Leopard Sharks, Triakis semifasciata, in Tomales Bay, California
Environmental Biology of Fishes, 2000Co-Authors: Joshua T. Ackerman, Matthew C. Kondratieff, Scott A. Matern, Joseph J CechAbstract:We used ultrasonic telemetry to determine the movement directions and movement rates of leopard sharks, Triakis semifasciata , in Tomales Bay, California. To analyze tide and time of day effects, we surgically implanted transmitters in the peritoneal cavities of one male and five female leopard sharks, which we located during summer for three to five sampling sessions lasting 12 to 24 h each. All leopard sharks showed strong movement direction patterns with tide. During incoming tides, sharks moved significantly (p
