The Experts below are selected from a list of 4824 Experts worldwide ranked by ideXlab platform
Martin Grosell - One of the best experts on this subject based on the ideXlab platform.
-
salt water acclimation of the estuarine crocodile crocodylus porosus involves enhanced ion transport properties of the urodaeum and rectum
The Journal of Experimental Biology, 2020Co-Authors: Martin Grosell, Rebecca L. Cramp, Ross G Dwyer, Rachael M Heuer, Nicholas C Wu, Yadong Wang, Edward M Mager, Craig E FranklinAbstract:Estuarine crocodiles, Crocodylus porosus, inhabit freshwater, estuarine and marine environments. Despite being known to undertake extensive movements throughout and between hypo-osmotic and hyperosmotic environments, little is known about the role of the cloaca in coping with changes in salinity. We report here that, in addition to the well-documented functional plasticity of the lingual salt glands, the middle of the three cloacal segments (i.e. the urodaeum) responds to increased ambient salinity to enhance solute-coupled water absorption. This post-renal modification of urine serves to conserve water when exposed to hyperosmotic environments and, in conjunction with lingual salt gland secretions, enables C. porosus to maintain salt and water balance and thereby thrive in hyperosmotic environments. Isolated epithelia from the urodaeum of 70% seawater-acclimated C. porosus had a strongly enhanced short-circuit current (an indicator of active ion transport) compared with freshwater-acclimated crocodiles. This enhanced active ion absorption was driven by increased Na/K-ATPase activity, and possibly enhanced proton pump activity, and was facilitated by the apical epithelial Na channel (ENaC) and/or the apical Na/H exchanger (NHE2), both of which are expressed in the urodaeum. NHE3 was expressed at very low levels in the urodaeum and probably does not contribute to solute-coupled water absorption in this cloacal segment. As C. porosus does not appear to drink water of salinities above 18 ppt, observations of elevated short-circuit current in the rectum as well as a trend for increased NHE2 expression in the oesophagus, the Anterior Intestine and the rectum suggest that dietary salt intake may stimulate salt and possibly water absorption by the gastrointestinal tract of C. porosus living in hyperosmotic environments.
-
salt water acclimation of the estuarine crocodile crocodylus porosus involves enhanced ion transport properties of the urodaeum and rectum
The Journal of Experimental Biology, 2020Co-Authors: Martin Grosell, Rebecca L. Cramp, Ross G Dwyer, Rachael M Heuer, Yadong Wang, Edward M Mager, Craig E FranklinAbstract:Estuarine crocodiles Crocodylus porosus inhabit freshwater, estuarine and marine environments. Despite being known to undertake extensive movements throughout and between hypo- and hyperosmotic environments, little is known on the role of the cloaca in coping with changes in salinity. In addition to the well-documented functional plasticity of the lingual salt glands, we report here that the middle of the three cloacal segments (i.e. the urodaeum), responds to increased ambient salinity to enhance solute-coupled water absorption. This post-renal modification of urine serves to conserve water when exposed to hyperosmotic environments and, in conjunction with lingual salt gland secretions, enables C. porosus to maintain salt and water balance and thereby thrive in hyperosmotic environments. Isolated epithelia from the urodaeum of 70% seawater-acclimated C. porosus had a strongly enhanced short circuit current (indicator of active ion transport) compared to freshwater-acclimated crocodiles. This enhanced active ion absorption was driven by increased Na+/K+-ATPase activity, and possibly enhanced proton pump activity, and was facilitated by the apical epithelial Na+ channel (ENaC) and/or the apical Na+/H+ exchanger (NHE2), both of which are expressed in the urodaeum. NHE3 was expressed at very low levels in the urodaeum and likely does not contribute to solute-coupled water absorption in this cloacal segment. Since C. porosus does not appear to drink water of salinities above 18 ppt, observations of elevated short circuit current in the rectum as well as a trend for increased NHE2 expression in the esophagus, the Anterior Intestine, and the rectum, suggests that dietary salt intake may stimulate salt, and possibly water absorption by the gastro-intestinal tract of C. porosus living in hyperosmotic environments.
-
interrogation of the gulf toadfish intestinal proteome response to hypersalinity exposure provides insights into osmoregulatory mechanisms and regulation of carbonate mineral precipitation
Comparative Biochemistry and Physiology Part D: Genomics and Proteomics, 2018Co-Authors: Kevin L Schauer, Aalekhya Reddam, Lisa M Wolfe, Martin GrosellAbstract:Abstract Marine bony fish live in a hyperosmotic environment and maintain osmotic homeostasis by drinking seawater, and absorbing salt and water across their gastrointestinal tract. Although the ion and water transport mechanisms in the Intestine have been the subject of much study, numerous questions remain unanswered. To address some of these questions, a shotgun proteomics methodology employing isobaric tandem mass tags (TMT) was used to interrogate the Anterior Intestine, posterior Intestine, and intestinal fluid proteomes of Gulf toadfish (Opsanus beta) acclimated to normal (35 ppt) or hypersaline (60 ppt) seawater. Relative protein abundance between tissues was also investigated using label free quantitation. Protein products from nearly 3000 unique toadfish loci were identified and quantified between the tissues, and pathway analysis was performed to gain insight into biological significance. Numerous proteins potentially involved in ion transport, digestion, nutrient absorption, and intestinal CaCO3 precipitation were found to respond to changing salinity, providing additional insight into the molecular mechanisms behind these processes. Intestinal protein heterogeneity was also observed with proteins involved in ion transport responding to hypersalinity exposure primarily in the Anterior Intestine, and proteins involved in digestion and nutrient absorption showing higher abundance in the Anterior Intestine, regardless of salinity.
-
mechanisms of transepithelial ammonia excretion and luminal alkalinization in the gut of an intestinal air breathing fish misgurnus anguilliacaudatus
The Journal of Experimental Biology, 2013Co-Authors: Jonathan M. Wilson, Joana Moreirasilva, Ines L S Delgado, Sue C Ebanks, Mathilakath M Vijayan, Joao Coimbra, Martin GrosellAbstract:The weatherloach, Misgurnus angulliacaudatus, is an intestinal air-breathing, freshwater fish that has the unique ability to excrete ammonia through gut volatilization when branchial and cutaneous routes are compromised during high environmental ammonia or air exposure. We hypothesized that transepithelial gut NH(4)(+) transport is facilitated by an apical Na(+)/H(+) (NH(4)(+)) exchanger (NHE) and a basolateral Na(+)/K(+)(NH(4)(+))-ATPase, and that gut boundary layer alkalinization (NH(4)(+) → NH(3) + H(+)) is facilitated by apical HCO(3)(-) secretion through a Cl(-)/HCO(3)(-) anion exchanger. This was tested using a pharmacological approach with Anterior (digestive) and posterior (respiratory) Intestine preparations mounted in pH-stat-equipped Ussing chambers. The Anterior Intestine had a markedly higher conductance, increased short-circuit current, and greater net base (J(base)) and ammonia excretion rates (J(amm)) than the posterior Intestine. In the Anterior Intestine, HCO(3)(-) accounted for 70% of J(base). In the presence of an imposed serosal-mucosal ammonia gradient, inhibitors of both NHE (EIPA, 0.1 mmol l(-1)) and Na(+)/K(+)-ATPase (ouabain, 0.1 mmol l(-1)) significantly inhibited J(amm) in the Anterior Intestine, although only EIPA had an effect in the posterior Intestine. In addition, the anion exchange inhibitor DIDS significantly reduced J(base) in the Anterior Intestine although only at a high dose (1 mmol l(-1)). Carbonic anhydrase does not appear to be associated with gut alkalinization under these conditions as ethoxzolamide was without effect on J(base). Membrane fluidity of the posterior Intestine was low, suggesting low permeability, which was also reflected in a lower mucosal-serosal J(amm) in the presence of an imposed gradient, in contrast to that in the Anterior Intestine. To conclude, although the posterior Intestine is highly modified for gas exchange, it is the Anterior Intestine that is the likely site of ammonia excretion and alkalinization leading to ammonia volatilization in the gut.
-
intestinal transport following transfer to increased salinity in an anadromous fish oncorhynchus mykiss
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2011Co-Authors: Janet Genz, Andrew J Esbaugh, Martin GrosellAbstract:The ability to transition from freshwater to seawater environments is an intrinsic requirement of the life history of some fish species, including the anadromous rainbow trout (Oncorhynchus mykiss). The differences between hyper- and hypoosmoregulation are developed quickly (in hours to days), and at all scales, from gene expression to organ function. In this study, intestinal ion and water transport was examined in O. mykiss following acute transfer from freshwater (FW) to 70% seawater (SW). Plasma [Mg²+] increased at 24h post-transfer but recovered by 72 h. In the intestinal fluids, total CO₂ was found to increase with SW exposure/acclimation, while [Na+] decreased after 24h of SW exposure. Overall, in vitro experiments demonstrated the importance of base secretion to epithelial water uptake, and suggested that the primary physiological adjustments occurred 24-72 h after acute SW transfer. The mRNA expression of ion transporters important for intestinal osmoregulation and maintenance of acid-base balance was also investigated. A Na+/H+ exchanger (NHE2) and anion exchanger (SLC26a6) were hypothesized to be involved in the transport of acid-base equivalents, Na+, and Cl⁻, but were not uniformly expressed across tissue samples, and expression, where present, did not change following salinity transfer. NHE1, however, was expressed in all examined tissues (gill, kidney, Anterior Intestine, and pyloric cecae), but exhibited no changes in expression following acute salinity transfer.
John H. Youson - One of the best experts on this subject based on the ideXlab platform.
-
an immunohistochemical study of the endocrine cells within the pancreas Intestine and stomach of the gar lepisosteus osseusl
General and Comparative Endocrinology, 1997Co-Authors: Karen E Groff, John H. YousonAbstract:Abstract The distribution and identity of the various endocrine cell types were examined in the pancreas, stomach, and Anterior Intestine of the phylogenetically ancient actinopterygian, the gar ( Lepisosteus osseus L.), using immunohistochemistry. Antisera used were directed against several insulins (INSs) and somatostatins (SSTs), and members of the pancreatic polypeptide (PP, aPY, NPY) and glucagon (GLUC, GLP) families. In the gar pancreas the most pronounced aggregation of islet tissue is among the exocrine acini near the union of extrahepatic common bile duct with the gastrointestinal junction. Four immunoreactive cell types were identified within well-defined islets (A, B, D, and F cells) but immunoreactive cell types were also seen isolated among the exocrine acini. Centrally located B cells were immunoreactive with mammalian and lamprey INS antisera whereas the widely dispersed D cells immunostained with anti-SST-14, -25, and -34. SST was also localized in the epithelium of the pancreatic ducts. There was a colocalization of immunoreactivity for each member of the PP and GLU families at the periphery of each islet to identify F and A cells, respectively. However, colocalization of peptides from both families is suspected for at least some cells. Although the gastric and intestinal mucosae showed a similar pattern of immunoreactivity to GLP and not GLU, they had contrasting immunoreactivity with the two INS antisera. SST immunoreactivity was restricted to the stomach, whereas three of the four PP-family peptides were only immunoreactive in the Intestine. Immunoreactivity to the various antisera used in the study imply that there may be an organ-specific processing of preproinsulin, that the gar SST profile may be more similar to agnathan and bowfin rather than either elasmobranch or teleost SSTs, and that only the GLP portion of the preproglucagon gene is expressed in the gastrointestinal mucosa. Our results are consistent with other recent endocrine studies showing that the gar is a widely distinct actinopterygian.
-
An immunohistochemical study of enteropancreatic endocrine cells in larvae and juveniles of the southern-hemisphere lampreys Geotria australis and Mordacia mordax
General and Comparative Endocrinology, 1993Co-Authors: John H. Youson, Ian C. PotterAbstract:The cell types within the endocrine pancreatic tissue and Anterior Intestine of larvae and juveniles of representatives of the two southern- hemisphere families (Mordaciidae and Geotriidae) were compared, using immunohistochemistry and antisera against insulin (lamprey, bovine), two somatostatins (SST-14, -34), two PP-family peptides (aPY, NPY), and salmon glucagon and glucagon-like peptide (GLP). Cells of the islets and some Anterior intestinal cells in larval Mordacia mordax showed intense immunoreactivity (IR) to the two insulin antisera. In contrast, immunoreactivity to these antisera in the islets of larval Geotria australis was restricted to antibovine insulin and even then the staining was weak. The islet cells did not IR with other antisera, but IR to aPY and NPY antisera was noted in a few intestinal cells of both species and cells in the Intestine of G. australis were positively stained with antiSST-14 and/or - 34. The single islet organ of adults of both species consisted only of antiinsulin-IR, B cells, and D cells, which were IR with only antiSST-14. Although IR was not seen in islet tissue to antisera against aPY, NPY, glucagon, and GLP, four cell types were identified in the intestinal epithelium in both species based on their IR to these antisera and the two antiSSTs. A fifth cell type IR to the two insulin antisera was recognized in adult M. mordax. The types and IR of endocrine cells in the enteropancreatic system of two southern-hemisphere lamprey families are compared with those of the Petromyzontidae, the single family of holarctic lampreys. Differences are discussed in relation to variations in hormone processing and whether they are a consequence of varied ontogenic and phylogenetic history among the extant Petromyzontiformes.
-
immunoreactivity to peptides belonging to the pancreatic polypeptide family npy apy pp pyy and to glucagon like peptide in the endocrine pancreas and Anterior Intestine of adult lampreys petromyzon marinus an immunohistochemical study
General and Comparative Endocrinology, 1991Co-Authors: Richard Y Cheung, Erika M Plisetskaya, P C Andrews, John H. YousonAbstract:Abstract Immunoreactivity of antisera directed against human neuropeptide Y (NPY), anglerfish polypeptide YG (aPY), bovine pancreatic polypeptide (bPP), salmon pancreatic polypeptide (sPP), porcine peptide tyrosine tyrosine (PYY), and salmon glucagon-like peptide (GLP) was investigated in the endocrine pancreas and Anterior Intestine of adult lampreys, Petromyzon marinus , by immunohistochemical analysis. There was no immunoreactivity to anti-sPP and anti-bPP in any tissue and anti-GLP immunostaining was only present in the Anterior Intestine. The immunoreactivity to antisera raised against NPY, aPY, and PYY was colocalized within the same small number of cells in the caudal and cranial pancreas of juveniles and the caudal pancreas of upstream migrant adults. These antibodies did not immunostain B- or D-cells and thus, NPY, aPY, and PYY were likely localized in a third cell type (3a) in the lamprey pancreas. Immunostaining of a few cells with only anti-aPY suggested the possibility of a fourth cell type (3b). Immunoreactivity was similar in the cranial and caudal pancreas of male upstream migrants; however, in the female cranial pancreas, a few cells demonstrated intense immunoreaction to anti-aPY, while weaker immunostaining with this antiserum was observed in B-cells. In the Intestine of juvenile and upstream migrant lampreys, positive immunostaining to GLP, NPY, aPY, and PYY antibodies was colocalized within the same cell. We believe that this cell may contain PYY/glucagon family peptides. Other intestinal cells immunostained with either GLP or somatostatin-34 antiserum.
Juan Fuentes - One of the best experts on this subject based on the ideXlab platform.
-
dietary butyrate helps to restore the intestinal status of a marine teleost sparus aurata fed extreme diets low in fish meal and fish oil
PLOS ONE, 2016Co-Authors: Itziar Estensoro, Juan Fuentes, Gabriel F Ballesterlozano, Laura Beneditopalos, Fabian Grammes, Juan Antonio Martossitcha, Liv Torunn Mydland, Josep A Calduchginer, Vasileios Karalazos, Alvaro OrtizAbstract:There is a constant need to find feed additives that improve health and nutrition of farmed fish and lessen the intestinal inflammation induced by plant-based ingredients. The objective of this study was to evaluate the effects of adding an organic acid salt to alleviate some of the detrimental effects of extreme plant-ingredient substitution of fish meal (FM) and fish oil (FO) in gilthead sea bream diet. Three experiments were conducted. In a first trial (T1), the best dose (0.4%) of sodium butyrate (BP-70 ®NOREL) was chosen after a short (9-weeks) feeding period. In a second longer trial (T2) (8 months), four diets were used: a control diet containing 25% FM (T2-D1) and three experimental diets containing 5% FM (T2-D2, T2-D3, T2-D4). FO was the only added oil in D1, while a blend of plant oils replaced 58% and 84% of FO in T2-D2, and T2-D3 and T2-D4, respectively. The latter was supplemented with 0.4% BP-70. In a third trial (T3), two groups of fish were fed for 12 and 38 months with D1, D3 and D4 diets of T2. The effects of dietary changes were studied using histochemical, immunohistochemical, molecular and electrophysiological tools. The extreme diet (T2-D3) modified significantly the transcriptomic profile, especially at the Anterior Intestine, up-regulating the expression of inflammatory markers, in coincidence with a higher presence of granulocytes and lymphocytes in the submucosa, and changing genes involved in antioxidant defences, epithelial permeability and mucus production. Trans-epithelial electrical resistance (Rt) was also decreased (T3-D3). Most of these modifications were returned to control values with the addition of BP-70. None of the experimental diets modified the staining pattern of PCNA, FABP2 or ALPI. These results further confirm the potential of this additive to improve or reverse the detrimental effects of extreme fish diet formulations.
-
Adaptation to different salinities exposes functional specialization in the Intestine of the sea bream (Sparus aurata L.).
Journal of Experimental Biology, 2012Co-Authors: Sílvia F. Gregório, Edison S.m. Carvalho, Sandra Encarnação, Jonathan M. Wilson, Deborah M. Power, Adelino V.m. Canario, Juan FuentesAbstract:The processing of intestinal fluid, in addition to a high drinking rate, is essential for osmoregulation in marine fish. This study analyzed the long-term response of the sea bream (Sparus aurata L.) to relevant changes of external salinity (12, 35 and 55 p.p.t.), focusing on the Anterior Intestine and in the less-often studied rectum. Intestinal water absorption, epithelial HCO(3)(-) secretion and gene expression of the main molecular mechanisms (SLC26a6, SLC26a3, SLC4a4, atp6v1b, CFTR, NKCC1 and NKCC2) involved in Cl(-) and HCO(3)(-) movements were examined. The anion transporters SLC26a6 and SLC26a3 are expressed severalfold higher in the Anterior Intestine, while the expression of Atp6v1b (V-type H(+)-ATPase β-subunit) is severalfold higher in the rectum. Prolonged exposure to altered external salinity was without effect on water absorption but was associated with concomitant changes in intestinal fluid content, epithelial HCO(3)(-) secretion and salinity-dependent expression of SLC26a6, SLC26a3 and SLC4a4 in the Anterior Intestine. However, the most striking response to external salinity was obtained in the rectum, where a 4- to 5-fold increase in water absorption was paralleled by a 2- to 3-fold increase in HCO(3)(-) secretion in response to a salinity of 55 p.p.t. In addition, the rectum of high salinity-acclimated fish shows a sustained (and enhanced) secretory current (I(sc)), identified in vitro in Ussing chambers and confirmed by the higher expression of CFTR and NKCC1 and by immunohistochemical protein localization. Taken together, the present results suggest a functional Anterior-posterior specialization with regard to intestinal fluid processing and subsequently to salinity adaptation of the sea bream. The rectum becomes more active at higher salinities and functions as the final controller of intestinal function in osmoregulation.
-
water absorption and bicarbonate secretion in the Intestine of the sea bream are regulated by transmembrane and soluble adenylyl cyclase stimulation
Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, 2012Co-Authors: Edison S.m. Carvalho, Sílvia F. Gregório, Deborah M. Power, Adelino V.m. Canario, Juan FuentesAbstract:In the marine fish Intestine luminal, HCO3 − can remove divalent ions (calcium and magnesium) by precipitation in the form of carbonate aggregates. The process of epithelial HCO3 − secretion is under endocrine control, therefore, in this study we aimed to characterize the involvement of transmembrane (tmACs) and soluble (sACs) adenylyl cyclases on the regulation of bicarbonate secretion (BCS) and water absorption in the Intestine of the sea bream (Sparus aurata). We observed that all sections of sea bream Intestine are able to secrete bicarbonate as measured by pH–Stat in Ussing chambers. In addition, gut sac preparations reveal net water absorption in all segments of the Intestine, with significantly higher absorption rates in the Anterior Intestine that in the rectum. BCS and water absorption are positively correlated in all regions of the sea bream intestinal tract. Furthermore, stimulation of tmACs (10 μM FK + 500 μM IBMX) causes a significant decrease in BCS, bulk water absorption and short circuit current (Isc) in a region dependent manner. In turn, stimulation of sACs with elevated HCO3 − results in a significant increase in BCS, and bulk water absorption in the Anterior Intestine, an action completely reversed by the sAC inhibitor KH7 (200 μM). Overall, the results reveal a functional relationship between BCS and water absorption in marine fish Intestine and modulation by tmACs and sAC. In light of the present observations, it is hypothesized that the endocrine effects on intestinal BCS and water absorption mediated by tmACs are locally and reciprocally modulated by the action of sACs in the fish enterocyte, thus fine-tuning the process of carbonate aggregate production in the intestinal lumen.
Brent B. Nickol - One of the best experts on this subject based on the ideXlab platform.
-
Emigration of Leptorhynchoides thecatus (Acanthocephala) in Green Sunfish (Lepomis cyanellus)
Comparative Parasitology, 2008Co-Authors: Kristen E. Richardson, Dennis J. Richardson, Brent B. NickolAbstract:Leptorhynchoides thecatus, an acanthocephalan of centrarchid fishes, occurs in the pyloric ceca and the Anterior Intestine of green sunfish, Lepomis cyanellus. One wk post-laboratory infection, L. thecatus is found in the pyloric ceca and the Anterior portion of the Intestine of green sunfish, but by 3 wk postinfection, worms are present only in the pyloric ceca. This study investigated whether differential mortality (higher mortality in the Intestine than in the ceca) or anteriad emigration is responsible for localization in the ceca. Chi-square analysis was performed on data obtained from 149 1-worm laboratory infections. No significant difference was found in the number of worms recovered during the course of the study; therefore, differential mortality as a mechanism for worm localization is unlikely. Furthermore, there was a decrease in prevalence of intestinal worms with a concurrent increase in prevalence of cecal worms. It is concluded that L. thecatus is localized in the pyloric ceca of green sunfish due to anteriad emigration. This emigration appears to be complete by day 2 post infection.
-
experimental investigation of physiological factors that may influence microhabitat specificity exhibited by leptorhynchoides thecatus acanthocephala in green sunfish lepomis cyanellus
Journal of Parasitology, 2000Co-Authors: Dennis J. Richardson, Brent B. NickolAbstract:Representatives of Leptorhynchoides thecatus (Acanthocephala) inhabit ceca of green sunfish but cannot survive in the Anterior Intestine. The influence of elevated cecal protein concentrations, pH, and amounts of lumenal materials on the microhabitat specificity of L. thecatus was investigated. An attempt was made to alter the distribution of worms in starved fish, in fish of which cecal pH was reduced, and in fish of which intestinal protein concentration was elevated. Protein concentration and pH showed no effect on worm distribution. Starving hosts had no effect on worm number or distribution but resulted in retardation of worm growth and development, providing a mechanism by which worms may overwinter and by which peak egg production may coincide with abundance of the amphipod intermediate host. None of the factors investigated is solely responsible for the microhabitat specificity of L. thecatus. It is suggested that helminth site specificity is characterized by long histories of adaptation to specific habitats with many physiological adaptations being facilitated synergistically. Maximization of sexual congress may exert an important selective pressure favoring this establishment of microhabitat specificity.
-
physiological attributes of the pyloric caeca and Anterior Intestine of green sunfish lepomis cyanellus potentially influencing microhabitat specificity of leptorhynchoides thecatus acanthocephala
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 1999Co-Authors: Dennis J. Richardson, Brent B. NickolAbstract:Abstract Pyloric caeca are present in some species of fish and serve as a habitat for many helminth parasites. Physiological and biochemical attributes of luminal contents of the caeca and proximal Intestine of green sunfish, Lepomis cyanellus, were compared to determine factors that could account for localization of Leptorhynchoides thecatus (Acanthocephala) in caeca after initial establishment in caeca and Anterior portion of the Intestine. Caecal protein concentrations were significantly higher. The Anterior Intestine exhibited significantly higher levels of proteolytic activity; however, caeca exhibited higher levels of aminopeptidase activity. The pH of caeca was significantly higher than that of the proximal portion of the Intestine. Caeca contained greater total amounts of materials, and therefore contained greater total amounts of proteins, free amino acids, lipids, carbohydrates, and bile salts. A significant time–place interaction was detected regarding total free amino acids, suggesting that enzymatic activity in the caeca was responsible for increased amounts of intestinal amino acids. Physiological factors that might influence microhabitat specificity of L. thecatus include inadequate levels of intestinal protein, different levels of proteolytic activity (perhaps resulting from differences in pH), such as aminopeptidase activity, and lack of sufficient quantities of Anterior intestinal nutrients to sustain worms. These results demonstrate subtle spatial and temporal complexities intrinsic to the environment of helminths inhabiting the teleost enteric system.
Craig E Franklin - One of the best experts on this subject based on the ideXlab platform.
-
salt water acclimation of the estuarine crocodile crocodylus porosus involves enhanced ion transport properties of the urodaeum and rectum
The Journal of Experimental Biology, 2020Co-Authors: Martin Grosell, Rebecca L. Cramp, Ross G Dwyer, Rachael M Heuer, Nicholas C Wu, Yadong Wang, Edward M Mager, Craig E FranklinAbstract:Estuarine crocodiles, Crocodylus porosus, inhabit freshwater, estuarine and marine environments. Despite being known to undertake extensive movements throughout and between hypo-osmotic and hyperosmotic environments, little is known about the role of the cloaca in coping with changes in salinity. We report here that, in addition to the well-documented functional plasticity of the lingual salt glands, the middle of the three cloacal segments (i.e. the urodaeum) responds to increased ambient salinity to enhance solute-coupled water absorption. This post-renal modification of urine serves to conserve water when exposed to hyperosmotic environments and, in conjunction with lingual salt gland secretions, enables C. porosus to maintain salt and water balance and thereby thrive in hyperosmotic environments. Isolated epithelia from the urodaeum of 70% seawater-acclimated C. porosus had a strongly enhanced short-circuit current (an indicator of active ion transport) compared with freshwater-acclimated crocodiles. This enhanced active ion absorption was driven by increased Na/K-ATPase activity, and possibly enhanced proton pump activity, and was facilitated by the apical epithelial Na channel (ENaC) and/or the apical Na/H exchanger (NHE2), both of which are expressed in the urodaeum. NHE3 was expressed at very low levels in the urodaeum and probably does not contribute to solute-coupled water absorption in this cloacal segment. As C. porosus does not appear to drink water of salinities above 18 ppt, observations of elevated short-circuit current in the rectum as well as a trend for increased NHE2 expression in the oesophagus, the Anterior Intestine and the rectum suggest that dietary salt intake may stimulate salt and possibly water absorption by the gastrointestinal tract of C. porosus living in hyperosmotic environments.
-
salt water acclimation of the estuarine crocodile crocodylus porosus involves enhanced ion transport properties of the urodaeum and rectum
The Journal of Experimental Biology, 2020Co-Authors: Martin Grosell, Rebecca L. Cramp, Ross G Dwyer, Rachael M Heuer, Yadong Wang, Edward M Mager, Craig E FranklinAbstract:Estuarine crocodiles Crocodylus porosus inhabit freshwater, estuarine and marine environments. Despite being known to undertake extensive movements throughout and between hypo- and hyperosmotic environments, little is known on the role of the cloaca in coping with changes in salinity. In addition to the well-documented functional plasticity of the lingual salt glands, we report here that the middle of the three cloacal segments (i.e. the urodaeum), responds to increased ambient salinity to enhance solute-coupled water absorption. This post-renal modification of urine serves to conserve water when exposed to hyperosmotic environments and, in conjunction with lingual salt gland secretions, enables C. porosus to maintain salt and water balance and thereby thrive in hyperosmotic environments. Isolated epithelia from the urodaeum of 70% seawater-acclimated C. porosus had a strongly enhanced short circuit current (indicator of active ion transport) compared to freshwater-acclimated crocodiles. This enhanced active ion absorption was driven by increased Na+/K+-ATPase activity, and possibly enhanced proton pump activity, and was facilitated by the apical epithelial Na+ channel (ENaC) and/or the apical Na+/H+ exchanger (NHE2), both of which are expressed in the urodaeum. NHE3 was expressed at very low levels in the urodaeum and likely does not contribute to solute-coupled water absorption in this cloacal segment. Since C. porosus does not appear to drink water of salinities above 18 ppt, observations of elevated short circuit current in the rectum as well as a trend for increased NHE2 expression in the esophagus, the Anterior Intestine, and the rectum, suggests that dietary salt intake may stimulate salt, and possibly water absorption by the gastro-intestinal tract of C. porosus living in hyperosmotic environments.