American Journal of Physiology - Regulatory, Integrative and Comparative Physiology, 2015
The guanylin family of peptides are effective regulators of intestinal physiology in marine teleo... more The guanylin family of peptides are effective regulators of intestinal physiology in marine teleosts. In the distal intestinal segments, they inhibit or reverse fluid absorption by inhibiting the absorptive short-circuit current (ISC). The present findings demonstrate that mRNA from guanylin (GN) and uroguanylin (UGN), as well as at least one isoform of the guanylin peptide receptor, apical guanylyl cyclase-C (GC-C), was highly expressed in the intestine and rectum of the Gulf toadfish (Opsanus beta). In the posterior intestine, GC-C, as well as the cystic fibrosis transmembrane conductance regulator (CFTR) and basolateral Na(+)/K(+)/2Cl(-)-cotransporter (NKCC1), which comprise a Cl(-)-secretory pathway, were transcriptionally upregulated in 60 ppt. The present study also shows that, in intestinal tissues from Gulf toadfish held in 35 ppt, renoguanylin (RGN) expectedly causes net Cl(-) secretion, inhibits both the absorptive ISC and fluid absorption, and decreases HCO3 (-) secretion. Likewise, in intestinal tissues from Gulf toadfish acclimated to 60 ppt, RGN also inhibits the absorptive I ISC and fluid absorption, but to an even greater extent, corresponding with the mRNA expression data. In contrast, RGN does not alter Cl(-) flux and, instead, elevates HCO3 (-) secretion in the 60 ppt group, suggesting increased apical Cl(-)/HCO3 (-) exchange activity by SLC26a6. Overall, these findings reinforce the hypotheses that the guanylin peptide system is important for salinity acclimatization and that the secretory response could facilitate the removal of solids, such as CaCO3 precipitates, from the intestine.
Atlantic salmon Salmo salar smolts were exposed to one of the four different aerobic exercise reg... more Atlantic salmon Salmo salar smolts were exposed to one of the four different aerobic exercise regimens for 10 weeks followed by a 1 week final smoltification period in fresh water and a subsequent eight-day seawater transfer period. Samples of gill and intestinal tissue were taken at each time point and gene expression was used to assess the effects of exercise training on both branchial and intestinal osmoregulatory pathways. Real-time polymerase chain reaction (PCR) analysis revealed that exercise training up-regulated the expression of seawater relevant genes in the gills of S. salar smolts, including Na(+) , K(+) ATPase (nka) subunit α1b, the Na(+) , K(+) , 2 Cl(-) co-transporter (nkcc1) and cftr channel. These findings suggest that aerobic exercise stimulates expression of seawater ion transport pathways that may act to shift the seawater transfer window for S. salar smolts. Aerobic exercise also appeared to stimulate freshwater ion uptake mechanisms probably associated with an...
American journal of physiology. Regulatory, integrative and comparative physiology, 2014
The physiological effects of guanylin (GN) and uroguanylin (UGN) on fluid and electrolyte transpo... more The physiological effects of guanylin (GN) and uroguanylin (UGN) on fluid and electrolyte transport in the teleost fish intestine have yet to be thoroughly investigated. In the present study, the effects of GN, UGN, and renoguanylin (RGN; a GN and UGN homolog) on short-circuit current (Isc) and the transport of Cl-, Na+, bicarbonate (HCO3-), and fluid in the Gulf toadfish (Opsanus beta) intestine were determined using Ussing chambers, pH-stat titration, and intestinal sac experiments. GN, UGN, and RGN reversed the Isc of the posterior intestine (absorptive-to-secretory), but not of the anterior intestine. RGN decreased baseline HCO3- secretion, but increased Cl- and fluid secretion in the posterior intestine. The secretory response of the posterior intestine coincides with the presence of basolateral NKCC1 and apical cystic fibrosis transmembrane conductance regulator (CFTR), the latter of which is lacking in the anterior intestine and is not permeable to HCO3- in the posterior inte...
The Deepwater Horizon incident likely resulted in exposure of commercially and ecologically impor... more The Deepwater Horizon incident likely resulted in exposure of commercially and ecologically important fish species to crude oil during the sensitive early life stages. We show that brief exposure of a water-accommodated fraction of oil from the spill to mahi-mahi as juveniles, or as embryos/larvae that were then raised for ∼25 days to juveniles, reduces their swimming performance. These physiological deficits, likely attributable to polycyclic aromatic hydrocarbons (PAHs), occurred at environmentally realistic exposure concentrations. Specifically, a 48 h exposure of 1.2 ± 0.6 μg L(-1) ΣPAHs (geometric mean ± SEM) to embryos/larvae that were then raised to juvenile stage or a 24 h exposure of 30 ± 7 μg L(-1) ΣPAHs (geometric mean ± SEM) directly to juveniles resulted in 37% and 22% decreases in critical swimming velocities (Ucrit), respectively. Oil-exposed larvae from the 48 h exposure showed a 4.5-fold increase in the incidence of pericardial and yolk sac edema relative to control...
Cultured branchial cell epithelia from freshwater rainbow trout were incubated with ((32)P)phosph... more Cultured branchial cell epithelia from freshwater rainbow trout were incubated with ((32)P)phosphate and ((14)C)acetate as lipid precursors under both symmetrical (L15 media apical/L15 media basolateral) and asymmetrical (freshwater apical/L15 media basolateral) culture conditions. Epithelia composed of pavement cells alone, or containing both pavement cells and chloride cells, were examined. Lipids (labeled with (32)P and (14)C) were isolated and assayed by thinlayer chromatography, and fatty acids (labeled with (14)C) were isolated and assayed by paper chromatography. The main goal was to see whether the loss of a major incorporation into ((32)P)phosphatidylethanolamine [((32)P)PE], previously seen in eel gills in vivo when the fish were transferred from an osmotic steady state to more dilute media, was the result of a hormonal regulation, i.e., did it only apply to gill tissue in vivo or could it also be seen in the absence of hormonal modulation after incorporation of ((32)P)pho...
Physiological mechanisms of silver toxicity (as silver nitrate) to the sensitive rainbow trout (O... more Physiological mechanisms of silver toxicity (as silver nitrate) to the sensitive rainbow trout (Oncorhynchus mykiss) (96 h LC50: 10.2 μg silver l−1, in soft, low chloride water) and the more tolerant European eel (Anguilla anguilla)(96 h LC50: 34.4 μg silver l−1, in the same water) were investigated during acute exposure to silver, using concentrations varying from 3 to 22 μg
Adult rainbow trout were pre-exposed to a sublethal concentration of waterborne cadmium (Cd, 26.7... more Adult rainbow trout were pre-exposed to a sublethal concentration of waterborne cadmium (Cd, 26.7 nmol/l) or waterborne zinc (Zn, 2294 nmol/l) for 30 days to induce acclimation. A single dose of radiolabeled Cd (64.4 nmol/kg) or Zn (183.8 nmol/kg) was injected into the vascular system of non-acclimated and Cd- or Zn-acclimated trout through indwelling arterial catheters. Subsequently, repetitive blood samples over 10 h and terminal tissue samples (liver, heart, bile, stomach, intestine, kidney, gills, muscle, and spleen) were taken to characterize the effect of metal acclimation on clearance kinetics in vivo. Plasma clearance of Cd in Cd-acclimated fish (0.726±0.015 and 0.477±0.012 ml/min per kg for total and newly accumulated Cd, respectively), was faster than that in non-acclimated trout (0.493±0.013 and 0.394±0.009 ml/min per kg). Unlike plasma Cd, the levels of Cd in red blood cells (RBCs) were 1.2–2.2 times higher in Cd-acclimated fish than in non-acclimated fish. At 10 h post-...
American Journal of Physiology - Regulatory, Integrative and Comparative Physiology, 2015
The guanylin family of peptides are effective regulators of intestinal physiology in marine teleo... more The guanylin family of peptides are effective regulators of intestinal physiology in marine teleosts. In the distal intestinal segments, they inhibit or reverse fluid absorption by inhibiting the absorptive short-circuit current (ISC). The present findings demonstrate that mRNA from guanylin (GN) and uroguanylin (UGN), as well as at least one isoform of the guanylin peptide receptor, apical guanylyl cyclase-C (GC-C), was highly expressed in the intestine and rectum of the Gulf toadfish (Opsanus beta). In the posterior intestine, GC-C, as well as the cystic fibrosis transmembrane conductance regulator (CFTR) and basolateral Na(+)/K(+)/2Cl(-)-cotransporter (NKCC1), which comprise a Cl(-)-secretory pathway, were transcriptionally upregulated in 60 ppt. The present study also shows that, in intestinal tissues from Gulf toadfish held in 35 ppt, renoguanylin (RGN) expectedly causes net Cl(-) secretion, inhibits both the absorptive ISC and fluid absorption, and decreases HCO3 (-) secretion. Likewise, in intestinal tissues from Gulf toadfish acclimated to 60 ppt, RGN also inhibits the absorptive I ISC and fluid absorption, but to an even greater extent, corresponding with the mRNA expression data. In contrast, RGN does not alter Cl(-) flux and, instead, elevates HCO3 (-) secretion in the 60 ppt group, suggesting increased apical Cl(-)/HCO3 (-) exchange activity by SLC26a6. Overall, these findings reinforce the hypotheses that the guanylin peptide system is important for salinity acclimatization and that the secretory response could facilitate the removal of solids, such as CaCO3 precipitates, from the intestine.
Atlantic salmon Salmo salar smolts were exposed to one of the four different aerobic exercise reg... more Atlantic salmon Salmo salar smolts were exposed to one of the four different aerobic exercise regimens for 10 weeks followed by a 1 week final smoltification period in fresh water and a subsequent eight-day seawater transfer period. Samples of gill and intestinal tissue were taken at each time point and gene expression was used to assess the effects of exercise training on both branchial and intestinal osmoregulatory pathways. Real-time polymerase chain reaction (PCR) analysis revealed that exercise training up-regulated the expression of seawater relevant genes in the gills of S. salar smolts, including Na(+) , K(+) ATPase (nka) subunit α1b, the Na(+) , K(+) , 2 Cl(-) co-transporter (nkcc1) and cftr channel. These findings suggest that aerobic exercise stimulates expression of seawater ion transport pathways that may act to shift the seawater transfer window for S. salar smolts. Aerobic exercise also appeared to stimulate freshwater ion uptake mechanisms probably associated with an...
American journal of physiology. Regulatory, integrative and comparative physiology, 2014
The physiological effects of guanylin (GN) and uroguanylin (UGN) on fluid and electrolyte transpo... more The physiological effects of guanylin (GN) and uroguanylin (UGN) on fluid and electrolyte transport in the teleost fish intestine have yet to be thoroughly investigated. In the present study, the effects of GN, UGN, and renoguanylin (RGN; a GN and UGN homolog) on short-circuit current (Isc) and the transport of Cl-, Na+, bicarbonate (HCO3-), and fluid in the Gulf toadfish (Opsanus beta) intestine were determined using Ussing chambers, pH-stat titration, and intestinal sac experiments. GN, UGN, and RGN reversed the Isc of the posterior intestine (absorptive-to-secretory), but not of the anterior intestine. RGN decreased baseline HCO3- secretion, but increased Cl- and fluid secretion in the posterior intestine. The secretory response of the posterior intestine coincides with the presence of basolateral NKCC1 and apical cystic fibrosis transmembrane conductance regulator (CFTR), the latter of which is lacking in the anterior intestine and is not permeable to HCO3- in the posterior inte...
The Deepwater Horizon incident likely resulted in exposure of commercially and ecologically impor... more The Deepwater Horizon incident likely resulted in exposure of commercially and ecologically important fish species to crude oil during the sensitive early life stages. We show that brief exposure of a water-accommodated fraction of oil from the spill to mahi-mahi as juveniles, or as embryos/larvae that were then raised for ∼25 days to juveniles, reduces their swimming performance. These physiological deficits, likely attributable to polycyclic aromatic hydrocarbons (PAHs), occurred at environmentally realistic exposure concentrations. Specifically, a 48 h exposure of 1.2 ± 0.6 μg L(-1) ΣPAHs (geometric mean ± SEM) to embryos/larvae that were then raised to juvenile stage or a 24 h exposure of 30 ± 7 μg L(-1) ΣPAHs (geometric mean ± SEM) directly to juveniles resulted in 37% and 22% decreases in critical swimming velocities (Ucrit), respectively. Oil-exposed larvae from the 48 h exposure showed a 4.5-fold increase in the incidence of pericardial and yolk sac edema relative to control...
Cultured branchial cell epithelia from freshwater rainbow trout were incubated with ((32)P)phosph... more Cultured branchial cell epithelia from freshwater rainbow trout were incubated with ((32)P)phosphate and ((14)C)acetate as lipid precursors under both symmetrical (L15 media apical/L15 media basolateral) and asymmetrical (freshwater apical/L15 media basolateral) culture conditions. Epithelia composed of pavement cells alone, or containing both pavement cells and chloride cells, were examined. Lipids (labeled with (32)P and (14)C) were isolated and assayed by thinlayer chromatography, and fatty acids (labeled with (14)C) were isolated and assayed by paper chromatography. The main goal was to see whether the loss of a major incorporation into ((32)P)phosphatidylethanolamine [((32)P)PE], previously seen in eel gills in vivo when the fish were transferred from an osmotic steady state to more dilute media, was the result of a hormonal regulation, i.e., did it only apply to gill tissue in vivo or could it also be seen in the absence of hormonal modulation after incorporation of ((32)P)pho...
Physiological mechanisms of silver toxicity (as silver nitrate) to the sensitive rainbow trout (O... more Physiological mechanisms of silver toxicity (as silver nitrate) to the sensitive rainbow trout (Oncorhynchus mykiss) (96 h LC50: 10.2 μg silver l−1, in soft, low chloride water) and the more tolerant European eel (Anguilla anguilla)(96 h LC50: 34.4 μg silver l−1, in the same water) were investigated during acute exposure to silver, using concentrations varying from 3 to 22 μg
Adult rainbow trout were pre-exposed to a sublethal concentration of waterborne cadmium (Cd, 26.7... more Adult rainbow trout were pre-exposed to a sublethal concentration of waterborne cadmium (Cd, 26.7 nmol/l) or waterborne zinc (Zn, 2294 nmol/l) for 30 days to induce acclimation. A single dose of radiolabeled Cd (64.4 nmol/kg) or Zn (183.8 nmol/kg) was injected into the vascular system of non-acclimated and Cd- or Zn-acclimated trout through indwelling arterial catheters. Subsequently, repetitive blood samples over 10 h and terminal tissue samples (liver, heart, bile, stomach, intestine, kidney, gills, muscle, and spleen) were taken to characterize the effect of metal acclimation on clearance kinetics in vivo. Plasma clearance of Cd in Cd-acclimated fish (0.726±0.015 and 0.477±0.012 ml/min per kg for total and newly accumulated Cd, respectively), was faster than that in non-acclimated trout (0.493±0.013 and 0.394±0.009 ml/min per kg). Unlike plasma Cd, the levels of Cd in red blood cells (RBCs) were 1.2–2.2 times higher in Cd-acclimated fish than in non-acclimated fish. At 10 h post-...
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Papers by Martin Grosell