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Chris M Wood - One of the best experts on this subject based on the ideXlab platform.
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Drinking and water permeability in the Pacific Hagfish, Eptatretus stoutii
Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, 2017Co-Authors: Chris N. Glover, Chris M Wood, Greg G. GossAbstract:Hagfish are osmoconformers, maintaining an internal osmolality that matches their seawater habitats. Hagfish would, therefore, appear to have no physiological need to drink, but previous studies are equivocal regarding whether drinking in Hagfish occurs. The current study addressed this knowledge gap, by examining drinking and water permeability in the Pacific Hagfish, Eptatretus stoutii. One-third of analysed Hagfish were shown to accumulate radiolabelled drinking rate markers (tritiated inulin and polyethylene glycol-4000) in their gut tissues; however, this was attributed to the presence of markers in the blood perfusing the digestive tract, following absorption through paracellular pathways at the gill. No accumulation of marker was observed in Hagfish subjected to more dilute (75% seawater) or more concentrated (125% seawater) media. Diffusive water efflux, measured by tritiated water washout, was shown to be very high, with 50% of body water exchanged within 14 to 16 min, depending on exposure salinity. In full-strength seawater, the total exchangeable pool of water was 78% of Hagfish mass. We conclude that Hagfish do not drink, and their high water permeability is likely to result in rapid osmotic equilibration under circumstances where perturbations may occur.
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Effect of environmental salinity manipulation on uptake rates and distribution patterns of waterborne amino acids in the Pacific Hagfish
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2016Co-Authors: Chris N. Glover, Tamzin A. Blewett, Chris M WoodAbstract:Abstract Among vertebrates, Hagfish are the only known iono- and osmoconformers, and the only species thus far documented to absorb amino acids directly across the skin. In the current study, short-term (6 h) manipulations of exposure salinities (75–125% seawater) were conducted to determine whether changes in osmotic demands influenced the uptake and tissue distribution of waterborne amino acids (alanine, glycine and phenylalanine), in the Pacific Hagfish, Eptatretus stoutii . No changes in erythrocyte or muscle amino acid accumulation rates were noted, but the patterns of plasma amino acid accumulation were suggestive of regulation. Contrary to expectations, glycine transport across the skin in vitro was enhanced in the lowest exposure salinity, but no other salinity-dependent changes were demonstrated. Overall, this study indicates that uptake and distribution of amino acids varies with salinity, but not in a manner that is consistent with a role for the studied amino acids in maintaining osmotic balance in Hagfish.
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it s all in the gills evaluation of o2 uptake in pacific Hagfish refutes a major respiratory role for the skin
The Journal of Experimental Biology, 2016Co-Authors: Greg G. Goss, Chris M Wood, Alexander M Clifford, Alex M ZimmerAbstract:ABSTRACT Hagfish skin has been reported as an important site for ammonia excretion and as the major site of systemic oxygen acquisition. However, whether cutaneous O 2 uptake is the dominant route of uptake remains under debate; all evidence supporting this hypothesis has been derived using indirect measurements. Here, we used partitioned chambers and direct measurements of oxygen consumption and ammonia excretion to quantify cutaneous and branchial exchanges in Pacific Hagfish ( Eptatretus stoutii ) at rest and following exhaustive exercise. Hagfish primarily relied on the gills for both O 2 uptake (81.0%) and ammonia excretion (70.7%). Following exercise, both O 2 uptake and ammonia excretion increased, but only across the gill; cutaneous exchange was not increased. When branchial O 2 availability was reduced by exposure to anteriorly localized hypoxia (∼4.6 kPa O 2 ), cutaneous O 2 consumption was only slightly elevated on an absolute basis. These results refute a major role for cutaneous O 2 acquisition in the Pacific Hagfish.
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determining the functional role of waterborne amino acid uptake in Hagfish nutrition a constitutive pathway when fasting or a supplementary pathway when feeding
Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, 2016Co-Authors: Chris N. Glover, Tamzin A. Blewett, Chris M WoodAbstract:Hagfish are unique among aquatic “vertebrates” in their ability to absorb amino acids directly from the water via skin and gill epithelia, but it is unknown whether this phenomenon extends beyond a few studied substrates; what effect fed state has on absorption; and what functional role this may play in Hagfish nutrition. Using in vivo and in vitro transport assays, uptake and tissue distribution of the waterborne amino acids l-alanine, l-lysine, and l-phenylalanine were examined as a function of fed state. All three amino acids were shown to be taken up from the water (lysine and phenylalanine for the first time). Following immersion in radiolabelled solutions for 24 h, phenylalanine was the amino acid that accumulated at the highest levels in almost all tissues, with the highest accumulation noted in red blood cells and bile, followed by gill and liver. In general, tissues of fed Hagfish displayed a significantly reduced phenylalanine accumulation compared to tissues of Hagfish fasted for 3 weeks. An in vitro assay showed that phenylalanine was transported across the skin at the highest rate, with the uptake of lysine occurring at the lowest rate. Feeding status had no significant effect on in vitro transport. These data indicate that dissolved organic nutrients are a significant source of nutrition to Hagfish, and may be relatively more important during periods of fasting than during periods of feeding when immersed in decaying carcasses.
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digestion under duress nutrient acquisition and metabolism during hypoxia in the pacific Hagfish
Physiological and Biochemical Zoology, 2011Co-Authors: Chris N. Glover, Carol Bucking, Chris M WoodAbstract:AbstractHagfish feed by immersing themselves in the body cavities of decaying animals. This ensures a rich nutrient source for absorption via the gills, skin, and gut, but it may also subject Hagfish to reduced levels of dissolved oxygen and elevated levels of the products of biological degradation. This study investigated the impacts of hypoxia and ammonia on the assimilation and metabolism of selected nutrients (glycine, l-alanine, and glucose) in Pacific Hagfish (Eptatretus stoutii). Throughout exposure to hypoxia, plasma glucose levels increased. This was not accompanied by an increase in gut glucose transport, which suggests mobilization of glucose from body glycogen stores. Hypoxia preexposure enhanced glycine absorption across the gut and the gill, although l-alanine uptake was unchanged in these tissues. A 24-h period of exposure to hypoxia in Hagfish concurrently exposed to waterborne radio-labeled glycine led to a large (5.7-fold) increase in brain glycine accumulation. Preexposure to high level...
Chris N. Glover - One of the best experts on this subject based on the ideXlab platform.
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behavioural responses of the Hagfish eptatretus stoutii to nutrient and noxious stimuli
Scientific Reports, 2019Co-Authors: Chris N. Glover, Greg G. Goss, Dustin Newton, Jasmin Bajwa, Trevor J HamiltonAbstract:: The suitability of a traditional testing paradigm (e.g. choice chamber) for assessing chemosensory behaviour in the Pacific Hagfish, Eptatretus stoutii, was examined. Actively-swimming Hagfish, tested at night, showed no preference for any region of a T-maze in the absence of a stimulus, but in the presence of an olfactory food cue, spent significantly more time in the zone where the cue was placed. Conversely, Hagfish avoided spending time in the zone the fish anaesthetic 3-amino benzoic acid ethylester (MS-222) was placed, and demonstrated significantly more reversal responses in which the fish moved its body backwards. These data suggest that Hagfish are an amenable model species for laboratory testing of behaviour.
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Drinking and water permeability in the Pacific Hagfish, Eptatretus stoutii
Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, 2017Co-Authors: Chris N. Glover, Chris M Wood, Greg G. GossAbstract:Hagfish are osmoconformers, maintaining an internal osmolality that matches their seawater habitats. Hagfish would, therefore, appear to have no physiological need to drink, but previous studies are equivocal regarding whether drinking in Hagfish occurs. The current study addressed this knowledge gap, by examining drinking and water permeability in the Pacific Hagfish, Eptatretus stoutii. One-third of analysed Hagfish were shown to accumulate radiolabelled drinking rate markers (tritiated inulin and polyethylene glycol-4000) in their gut tissues; however, this was attributed to the presence of markers in the blood perfusing the digestive tract, following absorption through paracellular pathways at the gill. No accumulation of marker was observed in Hagfish subjected to more dilute (75% seawater) or more concentrated (125% seawater) media. Diffusive water efflux, measured by tritiated water washout, was shown to be very high, with 50% of body water exchanged within 14 to 16 min, depending on exposure salinity. In full-strength seawater, the total exchangeable pool of water was 78% of Hagfish mass. We conclude that Hagfish do not drink, and their high water permeability is likely to result in rapid osmotic equilibration under circumstances where perturbations may occur.
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Effect of environmental salinity manipulation on uptake rates and distribution patterns of waterborne amino acids in the Pacific Hagfish
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2016Co-Authors: Chris N. Glover, Tamzin A. Blewett, Chris M WoodAbstract:Abstract Among vertebrates, Hagfish are the only known iono- and osmoconformers, and the only species thus far documented to absorb amino acids directly across the skin. In the current study, short-term (6 h) manipulations of exposure salinities (75–125% seawater) were conducted to determine whether changes in osmotic demands influenced the uptake and tissue distribution of waterborne amino acids (alanine, glycine and phenylalanine), in the Pacific Hagfish, Eptatretus stoutii . No changes in erythrocyte or muscle amino acid accumulation rates were noted, but the patterns of plasma amino acid accumulation were suggestive of regulation. Contrary to expectations, glycine transport across the skin in vitro was enhanced in the lowest exposure salinity, but no other salinity-dependent changes were demonstrated. Overall, this study indicates that uptake and distribution of amino acids varies with salinity, but not in a manner that is consistent with a role for the studied amino acids in maintaining osmotic balance in Hagfish.
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determining the functional role of waterborne amino acid uptake in Hagfish nutrition a constitutive pathway when fasting or a supplementary pathway when feeding
Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, 2016Co-Authors: Chris N. Glover, Tamzin A. Blewett, Chris M WoodAbstract:Hagfish are unique among aquatic “vertebrates” in their ability to absorb amino acids directly from the water via skin and gill epithelia, but it is unknown whether this phenomenon extends beyond a few studied substrates; what effect fed state has on absorption; and what functional role this may play in Hagfish nutrition. Using in vivo and in vitro transport assays, uptake and tissue distribution of the waterborne amino acids l-alanine, l-lysine, and l-phenylalanine were examined as a function of fed state. All three amino acids were shown to be taken up from the water (lysine and phenylalanine for the first time). Following immersion in radiolabelled solutions for 24 h, phenylalanine was the amino acid that accumulated at the highest levels in almost all tissues, with the highest accumulation noted in red blood cells and bile, followed by gill and liver. In general, tissues of fed Hagfish displayed a significantly reduced phenylalanine accumulation compared to tissues of Hagfish fasted for 3 weeks. An in vitro assay showed that phenylalanine was transported across the skin at the highest rate, with the uptake of lysine occurring at the lowest rate. Feeding status had no significant effect on in vitro transport. These data indicate that dissolved organic nutrients are a significant source of nutrition to Hagfish, and may be relatively more important during periods of fasting than during periods of feeding when immersed in decaying carcasses.
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digestion under duress nutrient acquisition and metabolism during hypoxia in the pacific Hagfish
Physiological and Biochemical Zoology, 2011Co-Authors: Chris N. Glover, Carol Bucking, Chris M WoodAbstract:AbstractHagfish feed by immersing themselves in the body cavities of decaying animals. This ensures a rich nutrient source for absorption via the gills, skin, and gut, but it may also subject Hagfish to reduced levels of dissolved oxygen and elevated levels of the products of biological degradation. This study investigated the impacts of hypoxia and ammonia on the assimilation and metabolism of selected nutrients (glycine, l-alanine, and glucose) in Pacific Hagfish (Eptatretus stoutii). Throughout exposure to hypoxia, plasma glucose levels increased. This was not accompanied by an increase in gut glucose transport, which suggests mobilization of glucose from body glycogen stores. Hypoxia preexposure enhanced glycine absorption across the gut and the gill, although l-alanine uptake was unchanged in these tissues. A 24-h period of exposure to hypoxia in Hagfish concurrently exposed to waterborne radio-labeled glycine led to a large (5.7-fold) increase in brain glycine accumulation. Preexposure to high level...
Greg G. Goss - One of the best experts on this subject based on the ideXlab platform.
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behavioural responses of the Hagfish eptatretus stoutii to nutrient and noxious stimuli
Scientific Reports, 2019Co-Authors: Chris N. Glover, Greg G. Goss, Dustin Newton, Jasmin Bajwa, Trevor J HamiltonAbstract:: The suitability of a traditional testing paradigm (e.g. choice chamber) for assessing chemosensory behaviour in the Pacific Hagfish, Eptatretus stoutii, was examined. Actively-swimming Hagfish, tested at night, showed no preference for any region of a T-maze in the absence of a stimulus, but in the presence of an olfactory food cue, spent significantly more time in the zone where the cue was placed. Conversely, Hagfish avoided spending time in the zone the fish anaesthetic 3-amino benzoic acid ethylester (MS-222) was placed, and demonstrated significantly more reversal responses in which the fish moved its body backwards. These data suggest that Hagfish are an amenable model species for laboratory testing of behaviour.
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regulation of plasma glucose and sulfate excretion in pacific Hagfish eptatretus stoutii is not mediated by 11 deoxycortisol
General and Comparative Endocrinology, 2017Co-Authors: Nicolas R Bury, Alexander M Clifford, Aaron G Schultz, Brendan L Goss, Greg G. GossAbstract:Abstract The goal of this study was to identify whether Pacific Hagfish ( Eptatretus stoutii ) possess glucocorticoid and mineralocorticoid responses and to examine the potential role(s) of four key steroids in these responses. Pacific Hagfish were injected with varying amounts of cortisol, corticosterone or 11-deoxycorticosterone (DOC) using coconut oil implants and plasma glucose and gill total-ATPase activity were monitored as indices of glucocorticoid and mineralocorticoid responses. Furthermore, we also monitored plasma glucose and 11-deoxycortisol (11-DOC) levels following exhaustive stress (30 min of agitation) or following repeated infusion with SO 4 2− . There were no changes in gill total-ATPase following implantation with any steroid, with only very small statistical increases in plasma glucose noted in Hagfish implanted with either DOC (at 20 and 200 mg kg −1 at 7 and 4 days post-injection, respectively) or corticosterone (at 100 mg kg −1 at 7 days post-injection). Following exhaustive stress, Hagfish displayed a large and sustained increase in plasma glucose. Repeated infusion of SO 4 2− into Hagfish caused increases in both plasma glucose levels and SO 4 2− excretion rate suggesting a regulated glucocorticoid and mineralocorticoid response. However, animals under either condition did not show any significant increases in plasma 11-DOC concentrations. Our results suggest that while there are active glucocorticoid and mineralocorticoid responses in Hagfish, 11-DOC does not appear to be involved and the identity and primary function of the steroid in Hagfish remains to be elucidated.
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Drinking and water permeability in the Pacific Hagfish, Eptatretus stoutii
Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, 2017Co-Authors: Chris N. Glover, Chris M Wood, Greg G. GossAbstract:Hagfish are osmoconformers, maintaining an internal osmolality that matches their seawater habitats. Hagfish would, therefore, appear to have no physiological need to drink, but previous studies are equivocal regarding whether drinking in Hagfish occurs. The current study addressed this knowledge gap, by examining drinking and water permeability in the Pacific Hagfish, Eptatretus stoutii. One-third of analysed Hagfish were shown to accumulate radiolabelled drinking rate markers (tritiated inulin and polyethylene glycol-4000) in their gut tissues; however, this was attributed to the presence of markers in the blood perfusing the digestive tract, following absorption through paracellular pathways at the gill. No accumulation of marker was observed in Hagfish subjected to more dilute (75% seawater) or more concentrated (125% seawater) media. Diffusive water efflux, measured by tritiated water washout, was shown to be very high, with 50% of body water exchanged within 14 to 16 min, depending on exposure salinity. In full-strength seawater, the total exchangeable pool of water was 78% of Hagfish mass. We conclude that Hagfish do not drink, and their high water permeability is likely to result in rapid osmotic equilibration under circumstances where perturbations may occur.
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it s all in the gills evaluation of o2 uptake in pacific Hagfish refutes a major respiratory role for the skin
The Journal of Experimental Biology, 2016Co-Authors: Greg G. Goss, Chris M Wood, Alexander M Clifford, Alex M ZimmerAbstract:ABSTRACT Hagfish skin has been reported as an important site for ammonia excretion and as the major site of systemic oxygen acquisition. However, whether cutaneous O 2 uptake is the dominant route of uptake remains under debate; all evidence supporting this hypothesis has been derived using indirect measurements. Here, we used partitioned chambers and direct measurements of oxygen consumption and ammonia excretion to quantify cutaneous and branchial exchanges in Pacific Hagfish ( Eptatretus stoutii ) at rest and following exhaustive exercise. Hagfish primarily relied on the gills for both O 2 uptake (81.0%) and ammonia excretion (70.7%). Following exercise, both O 2 uptake and ammonia excretion increased, but only across the gill; cutaneous exchange was not increased. When branchial O 2 availability was reduced by exposure to anteriorly localized hypoxia (∼4.6 kPa O 2 ), cutaneous O 2 consumption was only slightly elevated on an absolute basis. These results refute a major role for cutaneous O 2 acquisition in the Pacific Hagfish.
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Phosphate absorption across multiple epithelia in the Pacific Hagfish (Eptatretus stoutii)
American Journal of Physiology-regulatory Integrative and Comparative Physiology, 2014Co-Authors: Aaron G Schultz, Samuel C Guffey, Alexander M Clifford, Greg G. GossAbstract:Inorganic phosphate (Pi) is an essential nutrient for all organisms, but in seawater, Pi is a limiting nutrient. This study investigated the primary mechanisms of Pi uptake in Pacific Hagfish (Eptatretus stoutii) using ex vivo physiological and molecular techniques. Hagfish were observed to have the capacity to absorb Pi from the environment into at least three epithelial surfaces: the intestine, skin, and gill. Pi uptake in all tissues was concentration dependent, and saturable Pi transport was observed in the skin and gill at
Alexander M Clifford - One of the best experts on this subject based on the ideXlab platform.
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regulation of plasma glucose and sulfate excretion in pacific Hagfish eptatretus stoutii is not mediated by 11 deoxycortisol
General and Comparative Endocrinology, 2017Co-Authors: Nicolas R Bury, Alexander M Clifford, Aaron G Schultz, Brendan L Goss, Greg G. GossAbstract:Abstract The goal of this study was to identify whether Pacific Hagfish ( Eptatretus stoutii ) possess glucocorticoid and mineralocorticoid responses and to examine the potential role(s) of four key steroids in these responses. Pacific Hagfish were injected with varying amounts of cortisol, corticosterone or 11-deoxycorticosterone (DOC) using coconut oil implants and plasma glucose and gill total-ATPase activity were monitored as indices of glucocorticoid and mineralocorticoid responses. Furthermore, we also monitored plasma glucose and 11-deoxycortisol (11-DOC) levels following exhaustive stress (30 min of agitation) or following repeated infusion with SO 4 2− . There were no changes in gill total-ATPase following implantation with any steroid, with only very small statistical increases in plasma glucose noted in Hagfish implanted with either DOC (at 20 and 200 mg kg −1 at 7 and 4 days post-injection, respectively) or corticosterone (at 100 mg kg −1 at 7 days post-injection). Following exhaustive stress, Hagfish displayed a large and sustained increase in plasma glucose. Repeated infusion of SO 4 2− into Hagfish caused increases in both plasma glucose levels and SO 4 2− excretion rate suggesting a regulated glucocorticoid and mineralocorticoid response. However, animals under either condition did not show any significant increases in plasma 11-DOC concentrations. Our results suggest that while there are active glucocorticoid and mineralocorticoid responses in Hagfish, 11-DOC does not appear to be involved and the identity and primary function of the steroid in Hagfish remains to be elucidated.
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wide scope for ammonia and urea excretion in foraging pacific Hagfish
Marine Biology, 2017Co-Authors: Alexander M Clifford, Michael P Wilkie, Susan L Edwards, Gregory G GossAbstract:Hagfish (Myxinidae) are jawless, marine vertebrates that feed on decaying carrion drops on the ocean floor. Although food consumption rates have not been measured, it is likely that Hagfish ingest large amounts of protein during such feeding bouts. Thus, they would be expected to have a high scope for amino acid catabolism which would result in high rates of post-feeding ammonia and urea excretion. Hagfish could also be exposed to high amounts of ammonia as they burrow into the decomposing carcasses during feeding. The goal of the present study was to determine if foraging Pacific Hagfish (Eptatretus stoutii) have a higher capacity than other fish species to unload the large amounts of ammonia and urea which may accumulate in their body after feeding. Accordingly, ammonia (JAmm) and urea-N (JUrea) excretion rates were measured immediately following the removal of Pacific Hagfish from cylindrical Korean cone-traps, which had been baited with decomposing hake and submerged in the Trevor Channel, off Bamfield, British Columbia. The rate of JAmm in the foraging Hagfish averaged 674 ± 210 µmol N kg−1 h−1 over the first 1 h following removal from the traps, which was 21-fold greater than measurements made in non-fed control Hagfish. By 4–6 h, JAmm was 50% lower than the 1 h post-foraging rate, before stabilizing between 48–72 h. Post-foraging JUrea was ninefold greater than in the unfed control Hagfish, averaging 116 ± 21 µmol N kg−1 h−1 during the first 2 h. Over the next 24–48 h, JUrea gradually declined, before approaching rates measured in the unfed Hagfish. Despite high post-foraging JAmm, plasma total ammonia (TAmm) concentrations were surprisingly low, averaging 114–226 µmol N L−1, but still 4.5 to 9-fold higher than in their unfed counterparts. Plasma urea-N concentrations were higher, averaging 1838 ± 376 µmol N L−1 in the unfed fish, but were unchanged following foraging. The very high factorial scope (21-fold) for JAmm compared to other fishes, suggests that Hagfish have a high capacity to excrete ammonia arising from amino acid catabolism, as well as ammonia that may be incidentally taken-up as a result of their feeding behaviour. The relatively high urea excretion capacity of Hagfish, may be important for rapidly off-loading urea which arises from the hydrolysis of dietary arginine due to the ingestion of decomposing tissue from dead fishes, or after urea is ingested from decomposing elasmobranchs or marine mammals.
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it s all in the gills evaluation of o2 uptake in pacific Hagfish refutes a major respiratory role for the skin
The Journal of Experimental Biology, 2016Co-Authors: Greg G. Goss, Chris M Wood, Alexander M Clifford, Alex M ZimmerAbstract:ABSTRACT Hagfish skin has been reported as an important site for ammonia excretion and as the major site of systemic oxygen acquisition. However, whether cutaneous O 2 uptake is the dominant route of uptake remains under debate; all evidence supporting this hypothesis has been derived using indirect measurements. Here, we used partitioned chambers and direct measurements of oxygen consumption and ammonia excretion to quantify cutaneous and branchial exchanges in Pacific Hagfish ( Eptatretus stoutii ) at rest and following exhaustive exercise. Hagfish primarily relied on the gills for both O 2 uptake (81.0%) and ammonia excretion (70.7%). Following exercise, both O 2 uptake and ammonia excretion increased, but only across the gill; cutaneous exchange was not increased. When branchial O 2 availability was reduced by exposure to anteriorly localized hypoxia (∼4.6 kPa O 2 ), cutaneous O 2 consumption was only slightly elevated on an absolute basis. These results refute a major role for cutaneous O 2 acquisition in the Pacific Hagfish.
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Phosphate absorption across multiple epithelia in the Pacific Hagfish (Eptatretus stoutii)
American Journal of Physiology-regulatory Integrative and Comparative Physiology, 2014Co-Authors: Aaron G Schultz, Samuel C Guffey, Alexander M Clifford, Greg G. GossAbstract:Inorganic phosphate (Pi) is an essential nutrient for all organisms, but in seawater, Pi is a limiting nutrient. This study investigated the primary mechanisms of Pi uptake in Pacific Hagfish (Eptatretus stoutii) using ex vivo physiological and molecular techniques. Hagfish were observed to have the capacity to absorb Pi from the environment into at least three epithelial surfaces: the intestine, skin, and gill. Pi uptake in all tissues was concentration dependent, and saturable Pi transport was observed in the skin and gill at
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extrabranchial mechanisms of systemic ph recovery in Hagfish eptatretus stoutii
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2014Co-Authors: Greg G. Goss, Alexander M Clifford, Samuel C GuffeyAbstract:Abstract This study investigates the role of branchial and extrabranchial processes in acid–base regulation in the Pacific Hagfish ( Eptatretus stoutii ). Hagfish were injected with one of the following solutions: acid saline (250 mM HCl [pH = 0.60], 250 mM NaCl), alkaline saline (250 mM NaHCO 3 , 250 mM NaCl, [pH ≈ 8.43]) or control saline (500 mM NaCl) in order to achieve an acid/alkaline/saline load of 6000 μmol·kg − 1 . Using a custom designed Hagfish compartmentalizing flux chamber, we partitioned flux of net acid or base equivalents and ammonia into the anterior (gill + skin) and posterior (skin + intestinal/renal/cloacal) components. We found that Pacific Hagfish excrete H + primarily via branchial mechanisms but base excretion occurs through extrabranchial mechanisms located in the posterior region. In addition, we demonstrate that Hagfish are able to excrete ammonia via the skin although this flux was not involved in compensation from an acid–base disturbance.
Masumi Nozaki - One of the best experts on this subject based on the ideXlab platform.
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hypothalamic pituitary gonadal endocrine system in the Hagfish
Frontiers in Endocrinology, 2013Co-Authors: Masumi NozakiAbstract:The hypothalamic-pituitary system is considered to be a seminal event that emerged prior to or during the differentiation of the ancestral agnathans (jawless vertebrates). Hagfishes as one of the only two extant members of the class of agnathans are considered the most primitive vertebrate known, living or extinct. Accordingly, studies on their reproduction are important for understanding the evolution and phylogenetic aspects of the vertebrate reproductive endocrine system. In gnathostomes (jawed vertebrates), the hormones of the hypothalamus and pituitary have been extensively studied and shown to have well-defined roles in the control of reproduction. In Hagfish, it was thought that they did not have the same neuroendocrine control of reproduction as gnathostomes, since it was not clear whether the Hagfish pituitary gland contained tropic hormones of any kind. This review highlights the recent findings of the hypothalamic-pituitary-gonadal endocrine system in the Hagfish. In contrast to gnathostomes that have two gonadotropins (GTH: luteinizing hormone and follicle-stimulating hormone), only one pituitary GTH has been identified in the Hagfish. Immunohistochemical and functional studies confirmed that this Hagfish GTH was significantly correlated with the developmental stages of the gonads and showed the presence of a steroid (estradiol) feedback system at the hypothalamic-pituitary levels. Moreover, while the identity of hypothalamic gonadotropin releasing hormone (GnRH) has not been determined, immunoreactive (ir) GnRH has been shown in the Hagfish brain including seasonal changes of ir-GnRH corresponding to gonadal reproductive stages. In addition, a Hagfish PQRFamide peptide was identified and shown to stimulate the expression of Hagfish GTH mRNA in the Hagfish pituitary. These findings provide evidence that there are neuroendocrine-pituitary hormones that share common structure and functional features compared to later evolved vertebrates.
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Glycoprotein hormone in the pituitary of Hagfish and its evolutionary implications
Fish Physiology and Biochemistry, 2012Co-Authors: Katsuhisa Uchida, Stacia A. Sower, Shunsuke Moriyama, Masumi NozakiAbstract:The pituitary gland is present in all vertebrates, from agnathans (jawless vertebrates) to mammals, but not in invertebrates. Reproduction in gnathostomes (jawed vertebrates) is controlled by two pituitary gonadotropins (GTHs), luteinizing hormone and follicle-stimulating hormone, which are part of the pituitary glycoprotein hormone (GPH) family. Hagfishes, which lack both jaws and vertebrae, are considered the most primitive vertebrate known, living or extinct. Accordingly, they are of particular importance in understanding the evolution of the pituitary GPHs and their functions related to vertebrate reproduction. Nevertheless, key elements of the reproductive endocrine system in Hagfish have yet to be elucidated. Our current report has revealed the first identification of a functional GPH composed of two subunits that possess gonadotropic action at the pituitary of brown Hagfish. It seems most likely that an ancestral GPH gave rise to only one GTH in Hagfish pituitary and that multiplicity of GPHs arose later during the early evolution of gnathostomes. This paper briefly summarizes the latest findings on the Hagfish GPH from an evolutionary point of view.
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characterization of novel rfamide peptides in the central nervous system of the brown Hagfish isolation localization and functional analysis
Endocrinology, 2011Co-Authors: Tomohiro Osugi, Katsuhisa Uchida, Masumi Nozaki, Kazuyoshi TsutsuiAbstract:RFamide (RFa) peptides play various important roles in the central nervous system in both invertebrates and vertebrates. However, there is no evidence of the existence of any RFamide peptide in the brain of Hagfish, one of the oldest lineages of vertebrates. In this study, we sought to identify novel RFamide peptides from the brains of Hagfish (Paramyxine atami). We identified four novel RFamide peptides, which had the C-terminal Pro-Gln-Arg-Phe-NH2 structure. cDNA cloning revealed that the identified RFamide peptides are encoded in two types of cDNA. Molecular phylogenetic analysis of the two precursors indicated that the Hagfish RFamide peptides belong to the PQRFamide peptide group that includes mammalian neuropeptide FF and AF. Based on immunohistochemistry and in situ hybridization, Hagfish PQRFamide peptide precursor mRNA and its translated peptides were localized in the infundibular nucleus of the hypothalamus. Immunoreactive fibers were terminated on blood vessels in the infundibular nucleus. Dens...
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evolutionary origin of a functional gonadotropin in the pituitary of the most primitive vertebrate Hagfish
Proceedings of the National Academy of Sciences of the United States of America, 2010Co-Authors: Katsuhisa Uchida, Stacia A. Sower, Shunsuke Moriyama, Hiroaki Chiba, Toyokazu Shimotani, Kaori Honda, Makoto Miki, Akiyoshi Takahashi, Masumi NozakiAbstract:Hagfish, which lack both jaws and vertebrae, are considered the most primitive vertebrate known, living or extinct. Hagfish have long been the enigma of vertebrate evolution not only because of their evolutionary position, but also because of our lack of knowledge on fundamental processes. Key elements of the reproductive endocrine system in Hagfish have yet to be elucidated. Here, the presence and identity of a functional glycoprotein hormone (GPH) have been elucidated from the brown Hagfish Paramyxine atami. The Hagfish GPH consists of two subunits, α and β, which are synthesized and colocalized in the same cells of the adenohypophysis. The cellular and transcriptional activities of Hagfish GPHα and -β were significantly correlated with the developmental stages of the gonad. The purified native GPH induced the release of gonadal sex steroids in vitro. From our phylogenetic analysis, we propose that ancestral glycoprotein α-subunit 2 (GPA2) and β-subunit 5 (GPB5) gave rise to GPHα and GPHβ of the vertebrate glycoprotein hormone family, respectively. The identified Hagfish GPHα and -β subunits appear to be the typical gnathostome GPHα and -β subunits based on the sequence and phylogenetic analyses. We hypothesize that the identity of a single functional GPH of the Hagfish, Hagfish GTH, provides critical evidence for the existence of a pituitary-gonadal system in the earliest divergent vertebrate that likely evolved from an ancestral, prevertebrate exclusively neuroendocrine mechanism by gradual emergence of a previously undescribed control level, the pituitary, which is not found in the Protochordates.
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The Hagfish pituitary gland and its putative adenohypophysial hormones.
Zoological Science, 2008Co-Authors: Masumi NozakiAbstract:Abstract The pituitary gland is present in all vertebrates, from agnathans (jawless fishes) to mammals, but not in invertebrates. Hagfishes, which lack both jaws and vertebrae, are considered the most primitive vertebrate known, living or extinct. Accordingly, studies on Hagfishes are indispensable for understanding the origin and evolution of the pituitary hormones. Nevertheless, little is known about the Hagfish adenohypophysial hormones. Our recent immunohistochemical and lectin histochemical studies have revealed that gonadotropin (GTH), adrenocorticotropin (ACTH), and growth hormone (GH) are present in the Hagfish pituitary gland. This review summarizes the latest data regarding the Hagfish adenohypophysial hormones from an evolutionary point of view.
