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Chris M Wood - One of the best experts on this subject based on the ideXlab platform.
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the effects of digesting a urea rich meal on north pacific spiny Dogfish squalus acanthias suckleyi
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2020Co-Authors: Lisa J Hoogenboom, Gary W Anderson, Chris M Wood, Alyssa M WeinrauchAbstract:Abstract Marine elasmobranchs are nitrogen-limited owing to the requirement of nitrogen for both somatic growth and urea-based osmoregulation, and due to the loss of urea across the gills and kidney as nitrogenous waste. In this study we used in vitro stomach and intestinal gut sacs to investigate the effects of consuming a urea-rich meal (700 mM within a 2% body-mass ration of food-slurry) on nitrogen movement across the gastrointestinal (GI) tract of North Pacific spiny Dogfish (Squalus acanthias suckleyi). Plasma urea concentrations did not differ between fasted (359 ± 19 mM), urea-poor fed (340 ± 16 mM), and urea-rich fed (332 ± 24 mM) Dogfish. Interestingly, in vitro gut sacs of urea-rich fed Dogfish showed no net urea absorption from the lumen over 3 h incubation, which contrasts previously published data on urea-poor fed Dogfish that absorb urea from the lumen. In addition, ammonium (NH4+) concentration within the gut sac intestinal lumen significantly increased from 0.62 to 4.35 mM over 3 h. This is likely due to a combination of tissue production and microbial urease activity in the intestine. The overall results highlight the ability of S. a. suckleyi to regulate and maintain internal nitrogen concentrations despite the addition of excess dietary urea.
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examining urea flux across the intestine of the spiny Dogfish squalus acanthias
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2015Co-Authors: Gary W Anderson, Chris M Wood, Christopher Mccabe, Catherine BrandtAbstract:Abstract Recent examination of urea flux in the intestine of the spiny Dogfish shark, Squalus acanthias , has shown that feeding significantly enhances urea uptake across the intestine, and this was significantly inhibited following mucosal addition of phloretin. The present study examined potential mechanisms of urea uptake across the Dogfish intestine in starved and fed Dogfish. Unidirectional flux chambers were used to examine the kinetics of urea uptake, and to determine the influence of sodium, ouabain, competitive urea analogues, and phloretin on urea uptake across the gut of fed Dogfish. Intestinal epithelial preparations from starved and fed Dogfish were mounted in Ussing chambers to examine the effect of phloretin on bidirectional solute transport across the intestine. In the unidirectional studies, the maximum uptake rate of urea was found to be 35.3 ± 6.9 μmol.cm -2 .h -1 and K m was found to be 291.8 ± 9.6 mM in fed fish, and there was a mild inhibition of urea uptake following mucosal addition of competitive agonists. Addition of phloretin, Na-free Ringers and ouabain to the mucosal side of intestinal epithelia also led to a significant reduction in urea uptake in fed fish. In the Ussing chamber studies there was a net influx of urea in fed fish and a small insignificant efflux in starved fish. Addition of phloretin blocked urea uptake in fed fish when added to the mucosal side. Furthermore, phloretin had no effect on ion transport across the intestinal epithelia with the exception of the divalent cations, magnesium and calcium.
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body fluid osmolytes and urea and ammonia flux in the colon of two chondrichthyan fishes the ratfish hydrolagus colliei and spiny Dogfish squalus acanthias
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2012Co-Authors: Gary W Anderson, Michele C Nawata, Chris M Wood, Michele D Pierceynormore, Dirk WeihrauchAbstract:Abstract The present study has examined the role of the colon in regulating ammonia and urea nitrogen balance in two species of chondrichthyans, the ratfish, Hydrolagus colliei (a holocephalan) and the spiny Dogfish, Squalus acanthias (an elasmobranch). Stripped colonic tissue from both the Dogfish and ratfish was mounted in an Ussing chamber and in both species bi-directional urea flux was found to be negligible. Urea uptake by the mucosa and serosa of the isolated colonic epithelium through accumulation of 14C-urea was determined to be 2.8 and 6.2 fold greater in the mucosa of the Dogfish compared to the serosa of the Dogfish and the mucosa of the ratfish respectively. Furthermore, there was no difference between serosal and mucosal accumulation of 14C-urea in the ratfish. Through the addition of 2 mM NH4Cl to the mucosal side of each preparation the potential for ammonia flux was also examined. This was again found to be negligible in both species suggesting that the colon is an extremely tight epithelium to the movement of both urea and ammonia. Plasma, chyme and bile fluid samples were also taken from the agastric ratfish and were compared with solute concentrations of equivalent body fluids in the Dogfish. Finally molecular analysis revealed expression of 3 isoforms of the urea transport protein (UT) and an ammonia transport protein (Rhbg) in the gill, intestine, kidney and colon of the ratfish. Partial nucleotide sequences of the UT-1, 2 and 3 isoforms in the ratfish had 95, 95 and 92% identity to the equivalent UT isoforms recently identified in another holocephalan, the elephantfish, Callorhinchus milii. Finally, the nucleotide sequence of the Rhbg identified in the ratfish had 73% identity to the Rhbg protein recently identified in the little skate, Leucoraja erinacea.
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is the alkaline tide a signal to activate metabolic or ionoregulatory enzymes in the Dogfish shark squalus acanthias
Physiological and Biochemical Zoology, 2008Co-Authors: Chris M Wood, Makiko Kajimura, Thomas P Mommsen, Patrick J WalshAbstract:Abstract Experimental metabolic alkalosis is known to stimulate whole‐animal urea production and active ion secretion by the rectal gland in the Dogfish shark. Furthermore, recent evidence indicates that a marked alkaline tide (systemic metabolic alkalosis) follows feeding in this species and that the activities of the enzymes of the ornithine‐urea cycle (OUC) for urea synthesis in skeletal muscle and liver and of energy metabolism and ion transport in the rectal gland are increased at this time. We therefore evaluated whether alkalosis and/or NaCl/volume loading (which also occurs with feeding) could serve as a signal for activation of these enzymes independent of nutrient loading. Fasted Dogfish were infused for 20 h with either 500 mmol L−1 NaHCO3 (alkalosis + volume expansion) or 500 mmol L−1 NaCl (volume expansion alone), both isosmotic to Dogfish plasma, at a rate of 3 mL kg−1 h−1. NaHCO3 infusion progressively raised arterial pH to 8.28 ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfo...
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copper toxicity in the spiny Dogfish squalus acanthias urea loss contributes to the osmoregulatory disturbance
Aquatic Toxicology, 2007Co-Authors: G De Boeck, Chris M Wood, Patrick J Walsh, Jasper Hattink, Natasha M Franklin, C P Bucking, Sylvia L R WoodAbstract:Abstract Previous research showed that the spiny Dogfish, Squalus acanthias, is much more sensitive to silver exposure than typical marine teleosts. The aim of the present study was to investigate if spiny Dogfish were equally sensitive to copper exposure and whether the toxic mechanisms were the same. We exposed cannulated and non-cannulated spiny Dogfish to measured concentrations of Cu (nominally 0, 500, 1000 and 1500 μg L−1 Cu) for 72–96 h. All Cu exposures induced acidosis and lactate accumulation of either a temporary (500 μg L−1) or more persistent nature (1000 and 1500 μg L−1). At the two highest Cu concentrations, gill Na+/K+-ATPase activities were reduced by 45% (1000 μg L−1) and 62% (1500 μg L−1), and plasma Na+ and Cl− concentrations increased by approximately 50 mM each. At the same time urea excretion doubled and plasma urea dropped by ∼100 mM. Together with plasma urea, plasma TMAO levels dropped proportionally, indicating that the general impermeability of the gills was compromised. Overall plasma osmolarity did not change. Cu accumulation was limited with significant increases in plasma Cu and elevated gill and kidney Cu burdens at 1000 and 1500 μg L−1. We conclude that Cu, like Ag, exerts toxic effect on Na+/K+-ATPase activities in the shark similar to those of teleosts, but there is an additional toxic action on elasmobranch urea retention capacities. With a 96 h LC50 in the 800–1000 μg L−1 range, overall sensitivity of spiny Dogfish for Cu is, in contrast with its sensitivity to Ag, only slightly lower than in typical marine teleosts.
Gary W Anderson - One of the best experts on this subject based on the ideXlab platform.
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the effects of digesting a urea rich meal on north pacific spiny Dogfish squalus acanthias suckleyi
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2020Co-Authors: Lisa J Hoogenboom, Gary W Anderson, Chris M Wood, Alyssa M WeinrauchAbstract:Abstract Marine elasmobranchs are nitrogen-limited owing to the requirement of nitrogen for both somatic growth and urea-based osmoregulation, and due to the loss of urea across the gills and kidney as nitrogenous waste. In this study we used in vitro stomach and intestinal gut sacs to investigate the effects of consuming a urea-rich meal (700 mM within a 2% body-mass ration of food-slurry) on nitrogen movement across the gastrointestinal (GI) tract of North Pacific spiny Dogfish (Squalus acanthias suckleyi). Plasma urea concentrations did not differ between fasted (359 ± 19 mM), urea-poor fed (340 ± 16 mM), and urea-rich fed (332 ± 24 mM) Dogfish. Interestingly, in vitro gut sacs of urea-rich fed Dogfish showed no net urea absorption from the lumen over 3 h incubation, which contrasts previously published data on urea-poor fed Dogfish that absorb urea from the lumen. In addition, ammonium (NH4+) concentration within the gut sac intestinal lumen significantly increased from 0.62 to 4.35 mM over 3 h. This is likely due to a combination of tissue production and microbial urease activity in the intestine. The overall results highlight the ability of S. a. suckleyi to regulate and maintain internal nitrogen concentrations despite the addition of excess dietary urea.
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examining urea flux across the intestine of the spiny Dogfish squalus acanthias
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2015Co-Authors: Gary W Anderson, Chris M Wood, Christopher Mccabe, Catherine BrandtAbstract:Abstract Recent examination of urea flux in the intestine of the spiny Dogfish shark, Squalus acanthias , has shown that feeding significantly enhances urea uptake across the intestine, and this was significantly inhibited following mucosal addition of phloretin. The present study examined potential mechanisms of urea uptake across the Dogfish intestine in starved and fed Dogfish. Unidirectional flux chambers were used to examine the kinetics of urea uptake, and to determine the influence of sodium, ouabain, competitive urea analogues, and phloretin on urea uptake across the gut of fed Dogfish. Intestinal epithelial preparations from starved and fed Dogfish were mounted in Ussing chambers to examine the effect of phloretin on bidirectional solute transport across the intestine. In the unidirectional studies, the maximum uptake rate of urea was found to be 35.3 ± 6.9 μmol.cm -2 .h -1 and K m was found to be 291.8 ± 9.6 mM in fed fish, and there was a mild inhibition of urea uptake following mucosal addition of competitive agonists. Addition of phloretin, Na-free Ringers and ouabain to the mucosal side of intestinal epithelia also led to a significant reduction in urea uptake in fed fish. In the Ussing chamber studies there was a net influx of urea in fed fish and a small insignificant efflux in starved fish. Addition of phloretin blocked urea uptake in fed fish when added to the mucosal side. Furthermore, phloretin had no effect on ion transport across the intestinal epithelia with the exception of the divalent cations, magnesium and calcium.
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body fluid osmolytes and urea and ammonia flux in the colon of two chondrichthyan fishes the ratfish hydrolagus colliei and spiny Dogfish squalus acanthias
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2012Co-Authors: Gary W Anderson, Michele C Nawata, Chris M Wood, Michele D Pierceynormore, Dirk WeihrauchAbstract:Abstract The present study has examined the role of the colon in regulating ammonia and urea nitrogen balance in two species of chondrichthyans, the ratfish, Hydrolagus colliei (a holocephalan) and the spiny Dogfish, Squalus acanthias (an elasmobranch). Stripped colonic tissue from both the Dogfish and ratfish was mounted in an Ussing chamber and in both species bi-directional urea flux was found to be negligible. Urea uptake by the mucosa and serosa of the isolated colonic epithelium through accumulation of 14C-urea was determined to be 2.8 and 6.2 fold greater in the mucosa of the Dogfish compared to the serosa of the Dogfish and the mucosa of the ratfish respectively. Furthermore, there was no difference between serosal and mucosal accumulation of 14C-urea in the ratfish. Through the addition of 2 mM NH4Cl to the mucosal side of each preparation the potential for ammonia flux was also examined. This was again found to be negligible in both species suggesting that the colon is an extremely tight epithelium to the movement of both urea and ammonia. Plasma, chyme and bile fluid samples were also taken from the agastric ratfish and were compared with solute concentrations of equivalent body fluids in the Dogfish. Finally molecular analysis revealed expression of 3 isoforms of the urea transport protein (UT) and an ammonia transport protein (Rhbg) in the gill, intestine, kidney and colon of the ratfish. Partial nucleotide sequences of the UT-1, 2 and 3 isoforms in the ratfish had 95, 95 and 92% identity to the equivalent UT isoforms recently identified in another holocephalan, the elephantfish, Callorhinchus milii. Finally, the nucleotide sequence of the Rhbg identified in the ratfish had 73% identity to the Rhbg protein recently identified in the little skate, Leucoraja erinacea.
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purification characterization and biological activity of insulins from the spotted Dogfish scyliorhinus canicula and the hammerhead shark sphyrna lewini
General and Comparative Endocrinology, 2002Co-Authors: Gary W Anderson, Lauge Schaffer, Ingibjörg Eir Einarsdottir, Neil Hazon, Michael J ConlonAbstract:Abstract Insulin was purified from pancreatic extracts of two elasmobranch species belonging to different families in the order Carcharhiniformes, the European spotted Dogfish, Scyliorhinus canicula (Scyliorhinidae), and the hammerhead shark, Sphyrna lewini (Carcharhinidae). The amino acid sequence of Dogfish insulin was established as A-chain GIVDHCCRNT 10 CSLYDLEGYC 20 NQ and B-chain LPSQHLCGSH 10 LVETLYFVCG 20 QKGFYYVPKV 30 . The primary structure of hammerhead shark insulin was similar to that of Dogfish insulin with only 2 amino acid substitutions at A8 (R → H) and B30 (V → I). The elasmobranch insulins were markedly different from human insulin (17 amino acid substitutions) but all the residues in human insulin that are believed to be important in determining the receptor binding conformation (B6, B8, B11, B13, B23, B24, B25, A2, A3, and A19) have been conserved in the elasmobranch insulins with the exception of the conservative substitution Phe → Tyr at B25. Consistent with this, Dogfish and human insulin showed almost identical binding affinity to the recombinant solubilized human insulin receptor ( K D values of 14.0 and 18.6 pM, respectively; relative potency 133%). Previous studies have shown that bovine insulin produces severe and sustained hypoglycemia in elasmobranchs but the effect is of slow onset. Bolus arterial injections of Dogfish insulin (10 nmol · kg −1 ) into unanesthetized, fasting Dogfish ( n = 9) produced no changes in blood glucose, 3-hydroxybutyrate, and acetoacetate concentrations over a 4-h period. In a second series of experiments ( n = 7), Dogfish insulin (10 nmol · kg −1 ) produced a significant (P
Pascal Sourdaine - One of the best experts on this subject based on the ideXlab platform.
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Maintenance of Potential Spermatogonial Stem Cells In Vitro by GDNF Treatment in a Chondrichthyan Model (Scyliorhinus canicula L.)1
2016Co-Authors: Aude Gautier, Pierrïck Auvray, Adrien Bosseboeuf, Pascal SourdaineAbstract:Previous work in Dogfish, Scyliorhinus canicula, has identified the testicular germinative area as the spermatogonial stem cell niche. In the present study, an in vitro co-culture system of spermatogonia and somatic cells from the germinative area was developed. Long-term maintenance of spermatogonia has been successful, and addition of GDNF has promoted the develop-ment of clones of spermatogonia expressing stem cell charac-teristics such as alkaline phosphatase activity and has allowed maintenance of self-renewal in spermatogonia for at least 5 mo under culture conditions, notably by decreasing cell apoptosis. Furthermore, clones of spermatogonia expressed the receptor of GDNF, GFRalpha1, which is consistent with the effect of GDNF on cells despite the lack of identification of a GDNF sequence in the Dogfish’s transcriptome. However, a sequence homologous to artemin has been identified, and in silico analysis supports the hypothesis that artemin could replace GDNF in the germinative area in Dogfish. This study, as the first report on long-term in vitro maintenance of spermatogonia in a chondrichthyan species, suggests that the GFRalpha1 signaling function in self-renewal of spermatogonial stem cells is probably conserved in gnathostomes. culture, Dogfish, GDNF, self-renewal, spermatogonial stem cell
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Characterization of spermatogonial markers in the mature testis of the Dogfish (Scyliorhinus canicula L.)
Reproduction, 2014Co-Authors: Adrien Bosseboeuf, Aude Gautier, Pierrïck Auvray, Sylvie Mazan, Pascal SourdaineAbstract:In Dogfish, spermatogenesis progresses from a restricted germinative zone, which lines the dorsal testicular vessel. Single spermatogonia (As), including the spermatogonial stem cells (SSCs), produce successively paired (Ap), undifferentiated (Au4 to Au512), and differentiated (Ad1 to Ad8) spermatogonia and preleptotene (PL) spermatocytes through 13 mitoses. Dogfish spermatogonial subpopulations present classical morphological characteristics but cannot be distinguished on the basis of molecular markers. This characterization has been initiated in mammals despite the difficulty to separate each spermatogonial subpopulation. For instance, both glial cell-derived neurotrophic factor family receptor alpha 1 (GFRα1) and promyelocytic leukemia zinc finger protein (PLZF) are markers of undifferentiated spermatogonia, whereas receptor tyrosine kinase C-kit is a marker of differentiated spermatogonia. The aim of this study is to characterize spermatogonial markers and to differentiate several spermatogonial subpopulations. Dogfish cDNA sequences have been identified and validated by phylogenetic analyses for gfrα1, plzf, pou2, as well as for high-mobility group box proteins 2 and 3 (hmgb2 and 3) and for mini-chromosome maintenance protein 6 (mcm6). We have used the anatomical advantage of the polarized Dogfish testis to analyze the expression of those markers by RT-PCR and in situ hybridization. gfrα1, pou2, and plzf have been detected in the testicular germinative zone, suggesting that spermatogonial markers are relatively well conserved among vertebrates but with a less restricted expression for plzf. Moreover, hmgb3 and mcm6 have been identified as new markers of differentiated spermatogonia. Finally, this first molecular characterization of spermatogonial subpopulations in a chondrichthyan model will be useful for further studies on the SSC niche evolution.
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stage specific gene expression during spermatogenesis in the Dogfish scyliorhinus canicula
Reproduction, 2010Co-Authors: Emma Redon, Adrien Bosseboeuf, Sylvie Mazan, Claire Rocancourt, Corinne Da Silva, Patrick Wincker, Pascal SourdaineAbstract:In the Dogfish testis, the cystic arrangement and polarization of germ cell stages make it possible to observe all stages of spermatogenesis in a single transverse section. By taking advantage of the zonation of this organ, we have used suppressive subtractive libraries construction, real-time PCR, and in situ hybridization to identify 32 Dogfish genes showing differential expressions during spermatogenesis. These include homologs of genes already known to be expressed in the vertebrate testis, but found here to be specifically expressed either in pre-meiotic and/or meiotic zones (ribosomal protein S8, high-mobility group box 3, ubiquitin carboxyl-terminal esterase L3, 20beta-hydroxysteroid dehydrogenase, or cyclophilin B) or in post-meiotic zone (speriolin, Soggy, zinc finger protein 474, calreticulin, or phospholipase c-zeta). We also report, for the first time, testis-specific expression patterns for Dogfish genes coding for A-kinase anchor protein 5, ring finger protein 152, or F-box only protein 7. Finally, the study highlights the differential expression of new sequences whose identity remains to be assessed. This study provides the first molecular characterization of spermatogenesis in a chondrichthyan, a key species to gain insight into the evolution of this process in gnathostomes.
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Study of the potential spermatogonial stem cell compartment in Dogfish testis, Scyliorhinus canicula L.
Cell and Tissue Research, 2008Co-Authors: Géraldine Loppion, Pierrïck Auvray, Amélie Crespel, Anne-sophie Martinez, Pascal SourdaineAbstract:In the lesser-spotted Dogfish (Scyliorhinus canicula), spermatogenesis takes place within spermatocysts made up of Sertoli cells associated with stage-synchronized germ cells. As shown in testicular cross sections, cysts radiate in maturational order from the germinative area, where they are formed, to the opposite margin of the testis, where spermiation occurs. In the germinative zone, which is located in a specific area between the tunica albuginea of the testis and the dorsal testicular vessel, individual large spermatogonia are surrounded by elongated somatic cells. The aim of this study has been to define whether these spermatogonia share characteristics with spermatogonial stem cells described in vertebrate and non-vertebrate species. We have studied their ultrastructure and their mitotic activity by 5′-bromo-2′-deoxyuridine (BrdU) incorporation and proliferating cell nuclear antigen (PCNA) immunodetection. Additionally, immunodetection of c-Kit receptor, a marker of differentiating spermatogonia in rodents, and of α- and β-spectrins, as constituents of the spectrosome and the fusome, has been performed. Ultrastructurally, nuclei of stage I spermatogonia present the same mottled aspect in Dogfish as undifferentiated spermatogonia nuclei in rodents. Moreover, intercellular bridges are not observed in Dogfish spermatogonia, although they are present in stage II spermatogonia. BrdU and PCNA immunodetection underlines their low mitotic activity. The presence of a spectrosome-like structure, a cytological marker of the germline stem cells in Drosophila, has been observed. Our results constitute the first step in the study of spermatogonial stem cells and their niche in the Dogfish.
Greg G Goss - One of the best experts on this subject based on the ideXlab platform.
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time course of the acute response of the north pacific spiny Dogfish shark squalus suckleyi to low salinity
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2014Co-Authors: Samuel C Guffey, Greg G GossAbstract:Abstract Dogfish are considered stenohaline sharks but are known to briefly enter estuaries. The acute response of North Pacific spiny Dogfish ( Squalus suckleyi ) to lowered salinity was tested by exposing sharks to 21‰ salinity for 48 h. Temporal trends in blood pH, plasma osmolality, CO 2 , HCO 3 − , Na + , Cl − , K + , and urea concentrations, and in the rates of urea efflux and O 2 consumption, were quantified. The rate of O 2 consumption exhibited cyclic variation and was significantly depressed by lowered salinity. After 9 h, plasma [Cl − ] stabilized at 9% below initial levels, while plasma [Na + ] decreased by more than 20% within the first 12 h. Plasma [urea] dropped by 15% between 4 and 6 h, and continued to decrease. The rate of urea efflux increased over time, peaking after 36 h at 72% above the initial rate. Free-swimming sharks subjected to the same salinity challenge survived over 96 h and differed from cannulated sharks with respect to patterns of Na + and urea homeostasis. This high-resolution study reveals that Dogfish exposed to 21‰ salinity can maintain homeostasis of Cl − and pH, but Na + and urea continue to be lost, likely accounting for the inability of the Dogfish to fully acclimate to reduced salinity.
Patrick J Walsh - One of the best experts on this subject based on the ideXlab platform.
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is the alkaline tide a signal to activate metabolic or ionoregulatory enzymes in the Dogfish shark squalus acanthias
Physiological and Biochemical Zoology, 2008Co-Authors: Chris M Wood, Makiko Kajimura, Thomas P Mommsen, Patrick J WalshAbstract:Abstract Experimental metabolic alkalosis is known to stimulate whole‐animal urea production and active ion secretion by the rectal gland in the Dogfish shark. Furthermore, recent evidence indicates that a marked alkaline tide (systemic metabolic alkalosis) follows feeding in this species and that the activities of the enzymes of the ornithine‐urea cycle (OUC) for urea synthesis in skeletal muscle and liver and of energy metabolism and ion transport in the rectal gland are increased at this time. We therefore evaluated whether alkalosis and/or NaCl/volume loading (which also occurs with feeding) could serve as a signal for activation of these enzymes independent of nutrient loading. Fasted Dogfish were infused for 20 h with either 500 mmol L−1 NaHCO3 (alkalosis + volume expansion) or 500 mmol L−1 NaCl (volume expansion alone), both isosmotic to Dogfish plasma, at a rate of 3 mL kg−1 h−1. NaHCO3 infusion progressively raised arterial pH to 8.28 ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfo...
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copper toxicity in the spiny Dogfish squalus acanthias urea loss contributes to the osmoregulatory disturbance
Aquatic Toxicology, 2007Co-Authors: G De Boeck, Chris M Wood, Patrick J Walsh, Jasper Hattink, Natasha M Franklin, C P Bucking, Sylvia L R WoodAbstract:Abstract Previous research showed that the spiny Dogfish, Squalus acanthias, is much more sensitive to silver exposure than typical marine teleosts. The aim of the present study was to investigate if spiny Dogfish were equally sensitive to copper exposure and whether the toxic mechanisms were the same. We exposed cannulated and non-cannulated spiny Dogfish to measured concentrations of Cu (nominally 0, 500, 1000 and 1500 μg L−1 Cu) for 72–96 h. All Cu exposures induced acidosis and lactate accumulation of either a temporary (500 μg L−1) or more persistent nature (1000 and 1500 μg L−1). At the two highest Cu concentrations, gill Na+/K+-ATPase activities were reduced by 45% (1000 μg L−1) and 62% (1500 μg L−1), and plasma Na+ and Cl− concentrations increased by approximately 50 mM each. At the same time urea excretion doubled and plasma urea dropped by ∼100 mM. Together with plasma urea, plasma TMAO levels dropped proportionally, indicating that the general impermeability of the gills was compromised. Overall plasma osmolarity did not change. Cu accumulation was limited with significant increases in plasma Cu and elevated gill and kidney Cu burdens at 1000 and 1500 μg L−1. We conclude that Cu, like Ag, exerts toxic effect on Na+/K+-ATPase activities in the shark similar to those of teleosts, but there is an additional toxic action on elasmobranch urea retention capacities. With a 96 h LC50 in the 800–1000 μg L−1 range, overall sensitivity of spiny Dogfish for Cu is, in contrast with its sensitivity to Ag, only slightly lower than in typical marine teleosts.