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h-flux: an interactive program for the analysis of acid-base efflux.h-flux is an interactive computer program designated to facilitate the calculation of acid or base efflux from a tissue or organism into the surrounding media. it will accept data derived from different experimental protocols and allows for a high level of experimental flexibility. an example calculation of acid efflux from the marine fish opsanus beta is given.19827083833
sound production and other behavioral effects of midbrain stimulation in free-swimming toadfish, opsanus beta. 19744858823
sound production evoked by electrical stimulation of the brain in toadfish (opsanus beta). 19724574756
effects of feeding and confinement on nitrogen metabolism and excretion in the gulf toadfish opsanus betain order to elucidate further the cues for, and the biochemical mechanisms of, the transition to ureogenesis in the gulf toadfish opsanus beta, experiments on the effects of feeding (i.e. nitrogen loading) were carried out. baseline nitrogen excretion rates were first measured on solitary toadfish in large water volumes (i.e. unconfined conditions). these nitrogen excretion rates were higher, and had a higher proportion as ammonia (61 %), than previously published 'control' measurements. feeding ...19959319462
pulsatile urea excretion in the toadfish (opsanus beta) is due to a pulsatile excretion mechanism, not a pulsatile production mechanismwhen subjected to a crowding/confinement protocol in the laboratory, toadfish become facultatively ureotelic, excreting approximately 90 % of their nitrogenous waste as urea-nitrogen (urea-n). the great majority of this excretion occurs via large, irregular pulses from the head region which occur on average once per day, with a duration of 3 h or less. pulses measured chemically by the appearance of urea-n in the external water were identical to those measured by assaying [14c]urea appearance in ...19979318847
subcellular localization and biochemical properties of the enzymes of carbamoyl phosphate and urea synthesis in the batrachoidid fishes opsanus beta, opsanus tau and porichthys notatusthe subcellular localization and biochemical properties of the enzymes of carbamoyl phosphate and urea synthesis were examined in three representatives of fishes of the family batrachoididae, the gulf toadfish (opsanus beta), the oyster toadfish (opsanus tau) and the plainfin midshipman (porichthys notatus). the primary objective of the study was to compare the biochemical characteristics of these fishes, which represent a range between ammoniotelism and ureotelism (o. beta being facultatively u ...19959318521
urea transport by hepatocytes and red blood cells of selected elasmobranch and teleost fishesalthough urea transport is receiving increased attention in mammalian systems, very little is known about urea transport in fish tissues. this study examined mechanisms of urea transport in red blood cells and hepatocytes from the lesser spotted dogfish (scyliorhinus canicula), atlantic stingray (dasyatis sabina), turbot (scopthalmus maximus), redfish (scianops ocellatus), gulf toadfish (opsanus beta) and oyster toadfish (opsanus tau). urea appeared to be passively distributed in both tissues (i ...19949317893
effects of confinement/crowding on ureogenesis in the gulf toadfish opsanus betain order to elucidate the cues for, and the biochemical mechanisms of, the transition to ureogenesis in the gulf toadfish opsanus beta, experiments on the effects of confinement/crowding were carried out. confinement of toadfish to small volumes of water initiated a switch to nearly complete reliance on ureogenesis for nitrogen excretion within 24­48 h. further experiments suggested that this switch was probably due to the physical confinement per se, rather than to a measurable build-up of ...19949317620
evolution and regulation of urea synthesis and ureotely in (batrachoidid) fishes.selected teleostean (bony) fish species of the family batrachoididae (toadfishes and midshipmen) possess high titers of all enzymes of the ornithine-urea cycle in their livers. these species have proven valuable in understanding the short-term regulation of urea synthesis, urea permeability, and transport across epithelial tissues, and how urea synthesis and excretion have evolved among vertebrates. one species in particular, the gulf toadfish (opsanus beta), has been shown to rapidly switch fro ...19979074766
brevetoxin: tissue distribution and effect on cytochrome p450 enzymes in fish.as part of our investigation of the metabolism of brevetoxin (pbtx) in fish, we initiated a two-part study to determine the toxin's tissue distribution and its ability to induce xenobiotic metabolizing enzymes. in the first study, gulf toadfish (opsanus beta) were administered 14c-pbtx-3 orally in a fishmeal slurry and sacrificed 72 hr later. radioactivity was greatest in the hepatobiliary system (40% of body burden), representing the key role this system plays in the detoxification and eliminat ...19947940587
localization and analysis of natriuretic peptide receptors in the gills of the toadfish, opsanus beta (teleostei).the distribution and nature of natriuretic peptide binding sites was determined in the gills of the toadfish, opsanus beta. specific 125i-labeled rat atrial natriuretic peptide (ranp) and 125i-labeled porcine c-type natriuretic peptide (pcnp) binding sites were observed on the afferent and efferent filamental arteries and lamellar arterioles, and on the marginal channels of the secondary lamellae. in both section autoradiography and competition assays, the binding of both ligands was completely ...19947810750
interactions of cortisol and nitrogen metabolism in the ureogenic gulf toadfish opsanus beta.we examined the relationship between plasma cortisol levels, hepatic glutamine synthetase (gns) activity and the form of nitrogen excreted (e.g. urea, ammonia) in undisturbed versus confined/crowded (acutely stressed) gulf toadfish. specifically, we tested the hypothesis that acute increases in plasma cortisol levels are required to trigger the increase in gns activity induced by the confinement/crowding stress. toadfish responded to the stress of confinement/crowding with an initial cortisol su ...19957500006
pulsatile urea excretion in the ureagenic toadfish opsanus beta: an analysis of rates and routesthis study focused on the rates and routes of urea-n and ammonia-n excretion in the ureagenic toadfish and on the possibility that urea-n excretion occurs in pulses. experimental approaches included the following: confinement in small individual containers with automated hourly sampling of water to follow temporal excretion patterns; divided chambers to separate excretion from the anterior and posterior parts of the fish; collection of urine and rectal fluid via chronic indwelling catheters; and ...19959319637
physiological and molecular characterization of urea transport by the gills of the lake magadi tilapia (alcolapia grahami).the lake magadi tilapia (alcolapia grahami) is an unusual fish, excreting all its nitrogenous waste as urea because of its highly alkaline and buffered aquatic habitat. here, using both physiological and molecular studies, we describe the mechanism of branchial urea excretion in this species. in vivo, repeated short-interval sampling revealed that urea excretion is continuous. the computed urea permeability of a. grahami gill is 4.74x10(-)(5)+/-0.38x10(-)(5 )cm s(-)(1) (mean +/- s.e.m., n=11), s ...200111171302
intestinal base excretion in the seawater-adapted rainbow trout: a role in acid-base balance?a potential role for the intestine of seawater-adapted teleosts in acid­base regulation was investigated following earlier reports of highly alkaline rectal fluids in the gulf toadfish opsanus beta. rectal samples taken from starved seawater-adapted rainbow trout had a high fluid ph (8.90±0.03; mean ± s.e.m., n=13) and base (hco3-+2co32-) content of 157±26 mequiv kg-1 (n=11). in trout fitted with rectal catheters, rectal fluid was voided at a rate of 0.47±0.11 ml ...19969320250
reexamination of metabolic potential in the toadfish sonic muscle.activities of eight enzymes were measured in the sonic muscle of the gulf toadfish, opsanus beta, to determine the metabolic poise of this unique tissue and to evaluate potential sex related differences in metabolism. in contrast to a prior study (pennypacker et al., '85, j. exp. zool., 239: 259-264), we observed substantial activities of m4-lactate dehydrogenase, 333 to 482 units/g wet sonic muscle weight. this observation and the presence of high activities of other enzymes of glycolytic and a ...19873559499
acoustic nuclei in the medulla and midbrain of the vocalizing gulf toadfish (opsanus beta).the organization of the descending and secondary octaval nuclei in the hindbrain of the gulf toadfish, opsanus beta, was revealed following the injection of biotin compounds into a physiologically identified auditory region of the torus semicircularis. the results show retrogradely-filled neurons mainly in a dorsomedial division of the descending octaval nucleus, and dorsal and ventral divisions of a secondary octaval nucleus; minor labeling also appeared in dorsolateral and rostromedial interme ...200111435667
immunoreactive atriopeptin in plasma of fishes: its potential role in gill hemodynamics.with the use of antibodies raised against human atriopeptin (ap), immunoreactive ap (apir) was quantified in the plasma of five species of marine fishes, including members of the agnatha, chondrichthyes, and osteichthyes. concentrations of apir in fish plasma are in the same range as those described for mammalian species, indicating that ap was present in the earliest vertebrates and has retained at least partial structural similarity during the course of vertebrate evolution. acclimation of two ...19892529787
acoustic competition in the gulf toadfish opsanus beta: acoustic tagging.nesting male gulf toadfish opsanus beta produce a boatwhistle advertisement call used in male-male competition and to attract females and an agonistic grunt call. the grunt is a short-duration pulsatile call, and the boatwhistle is a complex call typically consisting of zero to three introductory grunts, a long tonal boop note, and zero to three shorter boops. the beginning of the boop note is also gruntlike. anomalous boatwhistles contain a short-duration grunt embedded in the tonal portion of ...200212051450
metabolism of isolated fish gill cells: contribution of epithelial chloride cells.gill cell suspensions from freshwater (fw)- and seawater (sw)-adapted teleosts were obtained by density gradient centrifugation. the proportion of chloride cells (ccs) in the mixed cell suspensions was estimated using the fluorescent mitochondrial stain, daspmei, and ranged from less than 1% (fw-adapted tilapia) to approximately 13% (sw-adapted toadfish). the gill cells displayed relatively high viability based on trypan blue exclusion (greater than 75%), lactate dehydrogenase leakage (less than ...19892549165
early life-stage toxicity test methods for gulf toadfish (opsanus beta) and results using chlorpyrifos.gulf toadfish (opsanus beta) were continuously exposed as embryos, sac fry, and juveniles to technical chlorpyrifos in two 49-day early life-stage toxicity tests. survival was significantly (alpha = 0.05) reduced only in 150 micrograms/liter. however, toadfish exposed to chlorpyrifos concentrations from 3.7 to 150 micrograms/liter weighted significantly less than control fish: 9% lower in 3.7 micrograms/liter to 62% lower in 150 micrograms/liter. the 96-hr lc50 for juvenile fish was 520 microgra ...19862420554
immunohistochemical localisation of natriuretic peptides in the heart and brain of the gulf toadfish opsanus beta.the distribution of natriuretic peptide immunoreactivity was determined in the heart and brain of the gulf toadfish opsanus beta using the avidin-biotin peroxidase technique. four antisera were used: the first raised against porcine brain natriuretic peptide which cross-reacts with atrial natriuretic and c-type natriuretic peptides (termed natriuretic peptide-like immunoreactivity); the second raised against porcine brain natriuretic peptide which cross-reacts with c-type natriuretic peptide but ...19921423477
hco3-stimulated cl efflux in the gulf toadfish acclimated to sea water.unidirectional efflux of cl was examined in the gulf toadfish, opsanus beta, in artificial seawater solutions with modified concentrations of cl and hco3. removal of cl hco3 reduced cl efflux. addition of hco3 at typical seawater concentrations stimulated cl efflux, independent of changes in the transepithelial potential. this active, hco3-stimulated cl efflux is saturable, with a km of 2.4 mm, typical of the concentration of hco3 found in sea water, and independent of external ph. active extrus ...1979469477
differential branchial and renal handling of urea, acetamide and thiourea in the gulf toadfish opsanus beta: evidence for two transporters.the possible presence of a urea transporter in the kidney of the gulf toadfish (opsanus beta) and further characterization of the pulsatile facilitated transporter previously identified in its gills were investigated by comparing the extra-renal and renal handling of two urea analogues with the handling of urea. toadfish were fitted with caudal artery and indwelling urinary ureteral catheters and injected with an iso-osmotic dose of (14)c-labelled urea analogue (acetamide or thiourea) calculated ...200010683162
thynnascaris reliquens sp. n. and t. habena (linton, 1900) (nematoda: ascaridoidea) from fishes in the northern gulf of mexico and eastern u.s. seaboard.thynnascaris reliquens sp. n. is described from the type host, the sheepshead, archosargus probatocephalus (walbaum), and other fishes of the northern gulf of mexico and southern florida, including the gulf toadfish, opsanus beta (goode and bean); the spiny boxfish, chilomycterus schoepfi (walbaum); the slippery dick, halichoeres bivittatus (bloch); and the atlantic croaker, micropogon undulatus (linnaeus). its salient characters are: length up to approximately to 12.5 cm; lips broad, with pedun ...19751127562
metabolic actions of glucagon and dexamethasone in liver of the ureogenic teleost opsanus beta.injection with pharmacological doses of dexamethasone (5 mg/kg) and/or bovine glucagon (1 mg/kg) exerts pronounced effects on toadfish liver compared with vehicle-treated control fish. affected parameters include hepatic levels of glycogen and the activities of glutamate dehydrogenase, aspartate aminotransferase, malate dehydrogenase, and enzymes involved in nadph generation as well as the kinetics of pyruvate kinase. activities of tyrosine aminotransferase, however, a prime target for hormonal ...19921601263
pulsatile urea excretion in gulf toadfish (opsanus beta): evidence for activation of a specific facilitated diffusion transport system.when toadfish are made ureotelic by a crowding/confinement protocol, they excrete approximately 90 % of their urea nitrogen (urea-n) production in large, irregular pulses (1-2 pulses per day) from the gill region. we investigated three hypotheses as to the mechanism of pulsatile excretion: (i) the presence of an active reabsorptive 'back-transport' mechanism that is periodically inhibited to allow urea-n excretion to occur; (ii) the periodic occurrence of a generalized, non-specific increase in ...19989464961
n-acetyl-l-glutamate and the urea cycle in gulf toadfish (opsanus beta) and other fish.carbamoyl phosphate synthetase i (cpsase i) catalyzes the first reaction of the urea cycle in mammalian ureotelic species. the positive allosteric cofactor n-acetyl-l-glutamate (aga) is required for cpsase i activity and is important for regulation of the urea cycle. a similar enzyme, cpsase iii, catalyzes this reaction in fish; cpsase iii differs from cpsase i in that it utilizes glutamine as the nitrogen-donating substrate instead of ammonia. aga also stimulates the cpsase iii-catalyzed reacti ...19989466820
urea and water permeability in the ureotelic gulf toadfish (opsanus beta).the permeability of toadfish gills and skin to urea and water has been measured in order to investigate the mechanisms behind the pulsatile excretion of urea previously described in this species. a perfused gill preparation was used in the gill studies and isolated pieces of skin mounted in an ussing chamber in the skin studies. simultaneously, urea and water permeability was measured in vivo in free swimming fish. in vivo the nonpulsing urea permeability was exceptionally low compared to other ...19999990735
induction of carbamoyl phosphate synthetase iii and glutamine synthetase mrna during confinement stress in gulf toadfish (opsanus beta).gulf toadfish (opsanus &bgr;) rapidly switch to excretion of urea as their main nitrogenous waste product under several laboratory conditions, including confinement to small volumes of water. prior evidence suggested that the activities of two key enzymes of urea synthesis exhibited potentially different modes of upregulation during this switch, with carbamoyl phosphate synthethase iii (cpsase iii) activated allosterically by n-acetylglutamate, and glutamine synthetase (gsase) activated by incre ...200010607541
metabolic fate of exogenous 15nh4cl in the gulf toadfish (opsanus beta).this study was undertaken to determine whether gulf toadfish (opsanus beta) could metabolize ammonia from their environment into other, less toxic products. to this end, gulf toadfish were exposed to 3.8 mm 15nh(4)cl in seawater for 24 and 48 h. liver, kidney, gill, brain and muscle samples were analyzed for distribution of 15n within the tissue and among various nitrogen-containing metabolites (ammonia, amino-n, glutamine-n, urea and protein). the data reported here show that the toadfish can i ...200314559297
characterization and sequencing of glutamine synthetase cdna from liver of the ureotelic gulf toadfish (opsanus beta).the hepatic enzyme, glutamine synthetase (gsase) is a pivotal protein in the regulation of urea synthesis in fish. the sequence of the dna encoding for gsase from liver of the ureotelic gulf toadfish (opsanus beta) was analyzed through a suite of molecular techniques (including cdna cloning, race pcr, and genomic pcr). an open reading frame (orf) was identified in the cdna sequence which codes for a protein of 394 amino acids with high identity (86%) to dogfish shark gsase. in the course of gene ...199910631802
branchial and renal excretion of urea and urea analogues in the plainfin midshipman, porichthys notatus.this study investigated whether urea transport mechanisms were present in the gills of the ammoniotelic plainfin midshipman (porichthys notatus), similar to those recently documented in its ureotelic relative (family batrachoididae), the gulf toadfish (opsanus beta). midshipmen were fitted with internal urinary and caudal artery catheters for repetitive sampling of urine and blood in experiments and radiolabeled urea analogues ([(14)c]-thiourea and [(14)c]-acetamide) were used to evaluate the ha ...200212444469
the relation of na and cl extrusion in opsanus beta, the gulf toadfish, acclimated to seawater.a model has been proposed by silva et al. ('77) to describe the manner by which cl extrusion occurs across the gills of the eel and seawater fish in general. aspects of the model include (1) passive distribution of na across the gill surface, and (2) cl extrusion dependent on na-k-atpase and thus dependent on the transport of na. in order to test various aspects of this model, we examined, using the appropriate radiotracers, the relationship of na and cl efflux in the gulf toadfish, opsanus beta ...19827153723
cholinergic and adrenergic effects on diffusional water flux in the toadfish, opsanus beta.intraperitoneal injections of adrenaline resulted in increased tritiated water efflux rate in the toadfish, opsanus beta. adrenaline-stimulated water flux was inhibited by the beta-adrenergic blocker, propranolol, but not by the alpha-adrenergic blocker, phentolamine. propranolol on its own had no effect but phentolamine significantly stimulated water flux; this action was attributed to a beta-mimetic effect of the drug. the cholinergic neurotransmitter acetylcholine, had no effect while the par ...19836637525
a carrier enzyme basis for ammonium excretion in teleost gill. nh+4-stimulated na-dependent atpase activity in opsanus beta.1. branchial na+k+-atpase specific activity is some 20% greater in hyposaline adapted opsanus beta than in sw specimens. 2. ouabain insensitive atpase (mg2+-atpase) specific activities were similar, while whole body activity differences in low salinity and sw adapted fish could be accounted for by the 30% difference in extractable gill protein. 3. nh+4 ion was 15% more effective at dephosphorylation of the microsomal na-dependent phosphoenzyme than either rb+ or k+, and revealed a maximal atpase ...19836132737
structure and function of the axillary organ of the gulf toadfish, opsanus beta (goode and bean).the structure of the axillary organ of a batrachoidid species, the gulf toadfish (opsanus beta goode and bean 1879), has been examined and several simple experiments designed to elucidate its function performed. electron microscopy (em) studies revealed cells and structures suggesting secretory and iono regulatory roles (e.g., abundant intracytoplasmic secretory particles, rough endoplasmic reticulum, sparse golgi bodies, indented epithelial cells with microvilli, numerous endocytotic vesicles, ...199811253782
evolution of urea synthesis in vertebrates: the piscine connection.elasmobranch fishes, the coelacanth, estivating lungfish, amphibians, and mammals synthesize urea by the ornithine-urea cycle; by comparison, urea synthetic activity is generally insignificant in teleostean fishes. it is reported here that isolated liver cells of two teleost toadfishes, opsanus beta and opsansus tau, synthesize urea by the ornithine-urea cycle at substantial rates. because toadfish excrete ammonia, do not use urea as an osmolyte, and have substantial levels of urease in their di ...19892563172
vocal-acoustic circuitry and descending vocal pathways in teleost fish: convergence with terrestrial vertebrates reveals conserved traits.vocal behavior is multifaceted and requires that vocal-motor patterning be integrated at multiple brain levels with auditory, neuroendocrine, and other social behavior processes (e.g., courtship and aggression). we now provide anatomical evidence for an extensive vocal network in teleost fishes (batrachoididae: porichthys notatus; opsanus beta) that is strongly integrated with neuroendocrine and auditory pathways and that exhibits striking similarities to the vocal-acoustic circuitry known for m ...200212115710
glutamine synthetase expression in liver, muscle, stomach and intestine of bostrichthys sinensis in response to exposure to a high exogenous ammonia concentration.a previous study provided evidence that the adaptive strategy used by the teleost fish bostrichthys sinensis (sleeper) for detoxifying ammonia during extended periods of air exposure was to synthesize and store glutamine, primarily in the muscle, accompanied by an increase in glutamine synthetase (gsase) activity in liver. the aim of the present study was to assess the effect on gsase expression in various tissues of exposure of b. sinensis to exogenous ammonia. exogenous ammonia increases inter ...200212089209
relative sensitivity of six estuarine fishes to carbophenothion, chlorpyrifos, and fenvalerate.the acute toxicity (96-hr lc50) of carbophenothion, chlorpyrifos, and fenvalerate to six estuarine fishes was determined in flow-through laboratory tests. the atherinid fishes (menidia menidia, m. peninsulae, m. beryllina, and leuresthes tenuis) consistently were among the most sensitive species tested and were similar to each other in their sensitivity to pesticides. the sensitivity of sheepshead minnows (cyprinodon variegatus) to carbophenothion was the same as that of the atherinids. for fenv ...19852419075
metabolic and enzymatic heterogeneity in the liver of the ureogenic teleost opsanus beta.viable toadfish hepatocytes were separated into distinct subpopulations by gradient centrifugation. although 3-5 density subpopulations were obtained for each fish, only two metabolically and enzymatically different subpopulations could be discerned. in all cases, hepatocytes with the lowest density (less than 1.040 g ml-1) were more oxidative in scope, as judged by the activities of mitochondrial enzymes (citrate synthase, aspartate aminotransferase, glutamate dehydrogenase); activities of thes ...19912051131
nitrogen excretion and the cardiorespiratory physiology of the gulf toadfish, opsanus beta.gulf toadfish, opsanus beta, are facultatively ureotelic and can excrete the majority of their nitrogenous waste as urea. urea excretion occurs in "pulses." the hypothesis that pulsatile urea excretion reflects sudden, transient, generalized increases in the branchial conductance was investigated by the simultaneous monitoring of cardiorespiratory variables, oxygen uptake, and whole-body urea, ammonia, and/or 3h2o effluxes. the direct monitoring of both expired branchial water and water exiting ...19989754526
catalepsy in two common marine animals.two common marine animals of the south atlantic and gulf coasts, sicyonia brevirostris, a penaeid shrimp, and opsanus beta, a toadfish, may be induced to go into cataleptic states in the laboratory when they are threatened or molested. the behaviors of these two animals as they go into catalepsy are described. there is considerable paling in the fish but none in the shrimp.195913830307
high ammonia tolerance in fishes of the family batrachoididae (toadfish and midshipmen).three fish species of the family batrachoididae, the gulf toadfish (opsanus beta), the oyster toadfish (opsanus tau), and the plainfin midshipman (porichthys notatus) demonstrated exceptionally high tolerances to elevated water ammonia with 96-h lc50 values of 9.75, 19.72 and 6 mm total ammonia, respectively. using ph values we calculated the corresponding unionized ammonia (nh(3)) values to be 519, 691 and 101 µm, respectively. these values are well above typical values for most teleost fishes, ...200010958955
do circulating plasma avt and/or cortisol levels control pulsatile urea excretion in the gulf toadfish (opsanus beta)?previous work has shown that pulsatile urea excretion at the gills of the gulf toadfish is due to periodic activation of a facilitated diffusion transport system with molecular and pharmacological similarity to the ut-a transport system of the mammalian kidney. in mammals, avp and glucocorticoids are two important endocrine regulators of this system. the present study focused on the potential role of circulating avt (the teleost homologue of avp) and cortisol levels as possible triggers for urea ...200111440872
ammonia excretion and urea handling by fish gills: present understanding and future research challenges.in fresh water fishes, ammonia is excreted across the branchial epithelium via passive nh(3) diffusion. this nh(3) is subsequently trapped as nh(4)(+) in an acidic unstirred boundary layer lying next to the gill, which maintains the blood-to-gill water nh(3) partial pressure gradient. whole animal, in situ, ultrastructural and molecular approaches suggest that boundary layer acidification results from the hydration of co(2) in the expired gill water, and to a lesser extent h(+) excretion mediate ...200212115902
putative isotocin distributions in sonic fish: relation to vasotocin and vocal-acoustic circuitry.recent neurophysiological evidence in the plainfin midshipman fish (porichthys notatus) demonstrated that isotocin (it) and arginine vasotocin (avt) modulate fictive vocalizations divergently between three reproductive morphs. to provide an anatomical framework for the modulation of vocalization by it and to foster comparisons with the distributions of the it homologues mesotocin (mt) and oxytocin (ot) in other vertebrate groups, we describe putative it distributions in the midshipman and the cl ...200312761820
transport physiology of the urinary bladder in teleosts: a suitable model for renal urea handling?the transport physiology of the urinary bladder of both the freshwater rainbow trout (oncorhychus mykiss) and the marine gulf toadfish (opsanus beta) was characterized with respect to urea, and the suitability of the urinary bladder as a model for renal urea handling was investigated. through the use of the in vitro urinary bladder sac preparation urea handling was characterized under control conditions and in the presence of pharmacological agents traditionally used to characterize urea transpo ...200212115926
a second glutamine synthetase gene with expression in the gills of the gulf toadfish (opsanus beta).we characterized the expression of the nitrogen metabolism enzyme glutamine synthetase [gsase; l-glutamate: ammonia ligase (adp-forming), e.c. 6.3.1.2] in tissues of the gulf toadfish opsanus beta subjected to unconfined (ammonotelic) and confined (ureotelic) conditions. enzymological results demonstrate that mass-specific gsase activities rank in the order of brain > liver > stomach approximately kidney > intestine > gill > heart/spleen > muscle. when tissue mass is used to calculate a glutamin ...200312654891
branchial and renal handling of urea in the gulf toadfish, opsanus beta: the effect of exogenous urea loading.the objective of this study was to determine whether the pulsatile facilitated diffusion transport mechanism (tut) found in the gills of the gulf toadfish (opsanus beta) and the active secretion transporter thought to be present in its kidney could be saturated when faced with elevated plasma urea concentrations. toadfish were infused with four consecutive exogenous urea loads at a rate of 0, 150, 300 and 600 micromol kg(-1) h(-1). initial plasma and urine urea concentrations were 8.1+/-0.9 and ...200312814785
use of urea as a chemosensory cloaking molecule by a bony fish.because urea is bioenergetically expensive to synthesize, few aquatic teleostean (bony) fish make or excrete much urea beyond early development and excrete the majority of nitrogenous waste as the readily diffusible ammonia. the gulf toadfish is one of a few adult teleostean fish that excretes predominantly urea. most studies of chemosensing by fish predators have focused on amino acids as odorants, but we tested the chemo-attractiveness of both urea and ammonia. we report that characteristic "p ...200617050840
intestinal zinc uptake in two marine teleosts, squirrelfish (holocentrus adscensionis) and gulf toadfish (opsanus beta).zinc is a vital micronutrient, yet as an environmental toxicant it can be deleterious to aquatic organisms such as fish. consequently, the study of zinc uptake mechanisms is essential for understanding nutrition, toxicity, and metabolism of this metal. intestinal zinc uptake was studied in two marine teleosts, using both in vitro (in vitro perfusion and intestinal sacs) and in vivo techniques (in situ bolus). female squirrelfish (holocentrus adscensionis) exhibited significantly increased epithe ...200312905118
the effects of ph and the iron redox state on iron uptake in the intestine of a marine teleost fish, gulf toadfish (opsanus beta).in the marine teleost intestine the secretion of bicarbonate increases ph of the lumen (ph 8.4 -9.0) and importantly reduces ca2+ and mg2+ concentrations by the formation of insoluble divalent ion carbonates. the alkaline intestinal environment could potentially also cause essential metal carbonate formation reducing bioavailability. iron accumulation was assessed in the gulf toadfish (opsanus beta) gut by mounting intestine segments in modified ussing chambers fitted to a ph-stat titration syst ...200616431145
maintaining osmotic balance with an aglomerular kidney.the gulf toadfish, opsanus beta, is a marine teleost fish with an aglomerular kidney that is highly specialized to conserve water. despite this adaptation, toadfish have the ability to survive when in dilute hypoosmotic seawater environments. the objectives of this study were to determine the joint role of the kidney and intestine in maintaining osmotic and ionic balance and to investigate whether toadfish take advantage of their urea production ability and use urea as an osmolyte. toadfish were ...200616483812
differential handling of urea and its analogues suggests carrier-mediated urea excretion in freshwater rainbow trout.the possible presence of urea transport mechanisms in the gill and kidney of the freshwater rainbow trout (oncorhynchus mykiss) was investigated in vivo by comparing the branchial and renal handling of analogues acetamide and thiourea with the handling of urea. trout were fitted with indwelling dorsal aortic catheters and urinary catheters and injected with an isosmotic dose of [(14)c]-labeled urea analogue (acetamide or thiourea) calculated to bring plasma analogue concentrations close to plasm ...200314988794
effect of elevated ammonia on tissue nitrogen metabolites in the ureotelic gulf toadfish (opsanus beta) and the ammoniotelic midshipman (porichthys notatus).we investigated possible biochemical pathways explaining extreme ammonia tolerance by the gulf toadfish and specifically tested the prediction that the gulf toadfish opsanus beta is more tolerant than the plainfin midshipman porichthys notatus, two confamilial species, because it reverses brain glutamine accumulation during high ammonia exposure. this prediction stems from previous studies demonstrating that gulf toadfish produce urea from glutamine, a pathway not present in the ammoniotelic mid ...200919072135
dogmas and controversies in the handling of nitrogenous wastes: 5-ht2-like receptors are involved in triggering pulsatile urea excretion in the gulf toadfish, opsanus beta.when injected arterially, serotonin (5-hydroxytryptamine; 5-ht) has been shown to elicit naturally sized urea pulse events in the gulf toadfish, opsanus beta. the goal of the present study was to determine which 5-ht receptor(s) was involved in mediating this serotonergic stimulation of the pulsatile excretion mechanism. toadfish were surgically implanted with caudal arterial catheters and intraperitoneal catheters and injected with either 8-oh-dpat (1 micro mol kg(-1)), a selective 5-ht(1a) rec ...200415143134
molecular characterization of a urea transporter in the gill of the gulf toadfish (opsanus beta).urea excretion by the gulf toadfish (opsanus beta) has been shown in previous studies to be a highly pulsatile facilitated transport, with excretion probably occurring at the gill. the present study reports the isolation of an 1800 base pair (kb) cdna from toadfish gill with one open reading frame putatively encoding a 475-residue protein, the toadfish urea transporter (tut). tut, the first teleostean urea transporter cloned, has high homology with uts (facilitated urea transporters) cloned from ...200010887074
dogmas and controversies in the handling of nitrogenous wastes: ureotely and ammonia tolerance in early life stages of the gulf toadfish, opsanus beta.the marine gulf toadfish (opsanus beta) is an unusual teleost fish as it is able to switch between ammoniotelism and ureotelism in response to a variety of laboratory conditions. the present study integrates field work conducted in biscayne and florida bays, usa with laboratory studies to examine ureotelism during the early life history stages of o. beta. adult toadfish voluntarily nested in artificial shelters placed amongst seagrass beds and were found to be predominantly ureotelic under natur ...200415143135
effects of prolonged copper exposure in the marine gulf toadfish (opsanus beta). i. hydromineral balance and plasma nitrogenous waste products.acute (96 h) and prolonged (30 days) copper exposure induced osmoregulatory disturbance and impaired nitrogenous waste excretion in the marine teleost, the gulf toadfish (opsanus beta), which was found to be extremely tolerant to acute copper exposure with a 96 h lc50 exceeding 340 microm but exhibited disturbed mineral balance in response to both acute and prolonged exposure to approximately 12 microm copper. the main cause of copper toxicity was found to be na+ and cl- regulatory failure leadi ...200415159051
effects of prolonged copper exposure in the marine gulf toadfish (opsanus beta) ii: copper accumulation, drinking rate and na+/k+ -atpase activity in osmoregulatory tissues.gulf toadfish were exposed to sublethal levels of copper (12.8 or 55.2 microm) for 30 days. drinking in control fish averaged 1 ml kg(-1)h(-1) but exposure to 55.2 microm copper resulted in a complex biophasic pattern with initial (3 h and 1 day) inhibition of drinking rate, followed by an elevation of drinking rate from day 3 onwards. drinking led to copper accumulation in the intestinal fluids at levels three to five times higher than the ambient copper concentrations, which in turn resulted i ...200415159052
glucocorticoid receptors are involved in the regulation of pulsatile urea excretion in toadfish.the objectives of this study were to characterize the pattern of pulsatile urea excretion in the gulf toadfish in the wake of exogenous cortisol loading and to determine the receptors involved in the regulation of this mechanism. toadfish were fitted with indwelling arterial catheters and were infused with isosmotic nacl for 48 h after which fish were treated with cortisol alone, cortisol + peanut oil, cortisol + ru486 (a glucocorticoid receptor antagonist) or cortisol + spironolactone (a minera ...200415517282
influence of salinity and organic matter on silver accumulation in gulf toadfish (opsanus beta).to help extend the freshwater based biotic ligand model for silver (ag) into brackish and saltwater conditions, 50g gulf toadfish (opsanus beta) were acclimated to 2.5%, 5%, 10%, 20%, 40%, 80%, or 100% salt water and exposed for 6d to 1.0microm agno(3), with or without 10mg c/l organic matter. suwannee river natural organic matter collected by reverse osmosis was used. silver accumulation in toadfish gills and plasma decreased as salinity increased, indicating low bioavailability of agcl complex ...200616675040
bioavailability of silver and its relationship to ionoregulation and silver speciation across a range of salinities in the gulf toadfish (opsanus beta).silver is taken up as a na(+) analog (ag(+)) by freshwater organisms, but little is known about its bioavailability in relation to salinity. adult opsanus beta were acclimated to 2.5, 5, 10, 20, 40, 60, 80, and 100% seawater (cl(-)=545 mm) and exposed for 24 h to 2.18 microg l(-1) silver as (110m)ag-labelled agno(3), a concentration close to the u.s. epa marine criterion and less than 0.1% of the acute 96-h lc50 in seawater. plasma osmolality, na(+), and cl(-) remained approximately constant fro ...200415522431
rapid elevations in both steroid hormones and vocal signaling during playback challenge: a field experiment in gulf toadfish.it is well known that plasma androgens are rapidly released in response to aggressive or sexual stimuli in a broad array of vertebrates. however, experimental work on behavioral functions of rapid androgen elevation is rare. a combination of field-based behavioral experiments and lab-based neuroendocrinological approaches is beginning to show how steroid hormones rapidly regulate the expression of vocal communication signals in gulf toadfish (opsanus beta). male toadfish emit multiharmonic "boat ...200515708758
ammonia affects brain nitrogen metabolism but not hydration status in the gulf toadfish (opsanus beta).laboratory rodents made hyperammonemic by infusing ammonia into the blood show symptoms of brain cell swelling and increased intracranial pressure. these symptoms could be caused in part by an increase in brain glutamine formed when brain glutamine synthetase (gs) naturally detoxifies ammonia to glutamine. previous studies on the gulf toadfish (opsanus beta) demonstrated that it is resistant to high ammonia exposure (hae) (96 h lc(50)=10mm) despite an increase in brain glutamine. this study atte ...200515927282
feeding and osmoregulation: dual function of the marine teleost intestine.experiments on gulf toadfish opsanus beta demonstrate how feeding impacts osmoregulation in the marine teleost intestine. a high ca(2+) diet of pilchards sardina pilchardus ([ca(2+)]=404.2 mmol kg(-1)) was compared to a low ca(2+) diet of common squid loligo forbesi ([ca(2+)]=1.3 mmol kg(-1)), as high [ca(2+)] has been shown to stimulate intestinal anion exchange. gastrointestinal fluids and blood plasma were collected over a time course from pre-feeding to 216 h post feeding. following food int ...200616857878
from social behavior to neural circuitry: steroid hormones rapidly modulate advertisement calling via a vocal pattern generator.across vertebrates, androgens are rapidly elevated within minutes in response to aggressive or reproductive stimuli, yet it is unclear what the causal relationship is between fast androgen elevation and the ongoing (minute-by-minute) expression of behavior. this study tested the hypothesis that rapid increases in plasma steroid levels induce similarly rapid increases in both vocal behavior and the neurophysiological output of a central pattern generator that governs vocal behavior. in gulf toadf ...200616870192
hydromineral balance in the marine gulf toadfish (opsanus beta) exposed to waterborne or infused nickel.the effects of acute ni exposure on the marine gulf toadfish (opsanus beta) were investigated via separate exposures to waterborne nickel (ni) and arterially infused ni. of the plasma electrolytes measured after 72 h of waterborne exposure (215.3 and 606.1 microm ni in sw (salinity of 34)), only plasma [ca2+] was significantly impacted (approximately 55% decrease at both exposure concentrations). at both exposure concentrations, plasma [ni] was regulated for 24h, after which a linear accumulatio ...200616968655
pulsatile urea excretion in the gulf toadfish: mechanisms and controls.opsanus beta expresses a full complement of ornithine-urea cycle (ouc) enzymes and is facultatively ureotelic, reducing ammonia-n excretion and maintaining urea-n excretion under conditions of crowding/confinement. the switch to ureotelism is keyed by a modest rise in cortisol associated with a substantial increase in cytosolic glutamine synthetase for trapping of ammonia-n and an upregulation of the capacity of the mitochondrial ouc to use glutamine-n. the entire day's urea-n production is excr ...200314662293
does pulsatile urea excretion serve as a social signal in the gulf toadfish opsanus beta?this study evaluated the hypothesis that the pulsatile excretion of urea by toadfish could serve as a social signal. in the first experiment, physiological parameters were measured in pairs of dominant and subordinate toadfish. subordinate toadfish had elevated concentrations of circulating plasma cortisol, an effect maintained even after cannulation. in the second experiment, one fish of a pair was injected with 14c-urea, and the occurrence of urea pulses during social encounters was documented ...200516086266
the effects of acute and chronic ammonia exposure during early life stages of the gulf toadfish, opsanus beta.the gulf toadfish (opsanus beta) is unusual among teleosts in that it is facultatively ureotelic and adults and juveniles have a particularly high tolerance to environmental ammonia. male toadfish brood their offspring in confined nests. it has been hypothesized that the potential accumulation of ammonia in nests from the male and the offspring, coupled with suspected low ammonia tolerance in offspring would provide the selective pressure necessary for excretion of the less toxic urea by adult t ...200516171879
dolphin foraging sounds suppress calling and elevate stress hormone levels in a prey species, the gulf toadfish.the passive listening hypothesis proposes that dolphins and whales detect acoustic signals emitted by prey, including sound-producing (soniferous) fishes. previous work showed that bottlenose dolphins (tursiops truncatus) behaviorally orient toward the sounds of prey, including the advertisement calls of male gulf toadfish (opsanus beta). in addition, soniferous fishes constitute over 80% of tursiops diet, and toadfishes alone account for approximately 13% of the stomach contents of adult bottle ...200617079715
urea transporter and glutamine synthetase regulation and localization in gulf toadfish gill.the goal of the present study was to investigate the role of circulating cortisol and urea in the transcriptional regulation of branchial glutamine synthetase (gs), which incorporates nh(3) into glutamate to form glutamine, and the toadfish urea transporter, tut, which is involved in urea excretion across the gill of the gulf toadfish. gs (of which there are two isoforms, lgs and ggs) and tut mrna expression and activity were measured in toadfish exposed to treatments that would induce variable ...200919218522
fluoxetine treatment affects nitrogen waste excretion and osmoregulation in a marine teleost fish.measurable quantities of the selective serotonin reuptake inhibitor (ssri), fluoxetine, have been found in surface waters and more recently in the tissues of fish. this highly prescribed pharmaceutical inhibits the reuptake of the monoamine, serotonin (5-ht; 5-hydroxytryptamine), causing a local amplification of 5-ht concentrations. serotonin is involved in the regulation of many physiological processes in teleost fish including branchial nitrogen excretion and intestinal osmoregulation. since t ...200919443054
higher levels of aggression are observed in socially dominant toadfish treated with the selective serotonin reuptake inhibitor, fluoxetine.the following study set out to test the hypothesis that acute treatment with the selective serotonin reuptake inhibitor, fluoxetine, would result in a rise in circulating 5-ht levels and consequently a decrease in territorial aggression in the gulf toadfish, opsanus beta. size-matched pairs of toadfish were implanted intraperitoneally with the same dose of fluoxetine (0, 10 or 25 μg g⁻¹). after a social interaction between a pair of fish, circulating levels of serotonin (5-ht; 5-hydroxytryptamin ...201020883822
cardiovascular and respiratory reflexes of the gulf toadfish (opsanus beta) during acute hypoxia.the acute cardiovascular and respiratory responses of the gulf toadfish, opsanus beta, to acute hypoxia or exposure to the o(2) chemoreceptor stimulant, sodium cyanide (nacn) were characterized and the role of serotonin type 2 (5-ht(2)) receptors in mediating these responses was investigated. toadfish responded to hypoxia or nacn exposure with a decrease in heart rate (fh) and an increase in breathing amplitude (v(amp)) but no change in breathing frequency (fr). the bradycardia appeared to be me ...201020045083
identification of two glucocorticoid response elements in the promoter region of the ubiquitous isoform of glutamine synthetase in gulf toadfish, opsanus beta.unlike most teleosts, gulf toadfish have the capacity to switch from ammoniotely to ureotely as the predominate means of nitrogen excretion during periods of stress. the switch to ureotely is a result of increased glutamine synthetase (gs) mrna expression/enzyme activity in the liver and muscle, which is initiated by cortisol. cortisol typically affects gene expression through the action of cortisol-activated transcription factors, such as glucocorticoid receptors, which bind to glucocorticoid r ...200919657100
a comparative analysis of parvalbumin expression in pinfish (lagodon rhomboides) and toadfish (opsanus sp.).this study examines the role of a myoplasmic protein, parvalbumin, in enhancing muscle relaxation by fishes. parvalbumin is thought to bind free ca(2+) during muscle contraction, thereby reducing intracellular [ca(2+)] in muscle and speeding muscle relaxation by reducing ca(2+) availability to the troponin complex. we hypothesized that parvalbumin expression is ubiquitously expressed in fish muscle and that its expression levels and role in muscle relaxation would depend on the activity level an ...201019840861
the regulatory role of glucocorticoid and mineralocorticoid receptors in pulsatile urea excretion of the gulf toadfish, opsanus beta.gulf toadfish, opsanus beta, are one among a group of unusual teleosts that excrete urea as their predominant nitrogen end product in response to stressful conditions. under conditions of crowding or confinement, fasted toadfish excrete the majority of their nitrogen waste in large pulses of urea (>90% of total nitrogen) lasting up to 3 h. an earlier study demonstrated that cortisol has an inhibitory influence on urea pulse size. the present study tested the hypothesis that cortisol mediates cha ...200919483003
fluoxetine treatment affects nitrogen waste excretion and osmoregulation in a marine teleost fish.measurable quantities of the selective serotonin reuptake inhibitor (ssri), fluoxetine, have been found in surface waters and more recently in the tissues of fish. this highly prescribed pharmaceutical inhibits the reuptake of the monoamine, serotonin (5-ht; 5-hydroxytryptamine), causing a local amplification of 5-ht concentrations. serotonin is involved in the regulation of many physiological processes in teleost fish including branchial nitrogen excretion and intestinal osmoregulation. since t ...200920225343
cortisol-sensitive urea transport across the gill basolateral membrane of the gulf toadfish (opsanus beta).gulf toadfish (opsanus beta) use a unique pulsatile urea excretion mechanism that allows urea to be voided in large pulses via the periodic insertion or activation of a branchial urea transporter. the precise cellular and subcellular location of the facilitated diffusion mechanism(s) remains unclear. an in vitro basolateral membrane vesicle (blmv) preparation was used to test the hypothesis that urea movement across the gill basolateral membrane occurs through a cortisol-sensitive carrier-mediat ...200919458274
evidence for transcriptional regulation of the urea transporter in the gill of the gulf toadfish, opsanus beta.ureotelic gulf toadfish (opsanus beta) do not excrete urea continuously; instead, urea is accumulated internally until a branchial urea transport mechanism is activated to facilitate the excretion of urea in distinct pulses. this unusual pulsatile urea excretion pattern is regulated, in part, by permissive declines in circulating cortisol concentrations. the current study examined toadfish urea transporter (tut) and glucocorticoid receptor (gr) transcript levels in toadfish gill following chroni ...201121740977
a critical analysis of transepithelial potential in intact killifish (fundulus heteroclitus) subjected to acute and chronic changes in salinity.we investigated the in vivo salinity-dependent behavior of transepithelial potential (tep) in fundulus heteroclitus (3-9 g) using indwelling coelomic catheters, a technique which was validated against blood catheter measurements in a larger species (opsanus beta; 35-70 g). in seawater (sw)-acclimated killifish, tep was +23 mv (inside positive), but changed to -39 mv immediately after transfer to freshwater (fw). acute transfer to dilute salinities produced a tep profile, which rapidly attenuated ...200818379791
effects of salinity on intestinal bicarbonate secretion and compensatory regulation of acid-base balance in opsanus beta.marine teleosts have extracellular fluids less concentrated than their environment, resulting in continual water loss, which is compensated for by drinking, with intestinal water absorption driven by nacl uptake. absorption of cl(-) occurs in part by apical cl(-)/hco(3)(-) exchange, with hco(3)(-) provided by transepithelial transport and/or by carbonic anhydrase-mediated hydration of endogenous epithelial co(2). hydration of co(2) also liberates h(+), which is transported across the basolateral ...200818587127
Interactions between cortisol and Rhesus glycoprotein expression in ureogenic toadfish, Opsanus beta.In their native environment, gulf toadfish excrete equal quantities of ammonia and urea. However, upon exposure to stressful conditions in the laboratory (i.e. crowding, confinement or air exposure), toadfish decrease branchial ammonia excretion and become ureotelic. The objective of this study was to determine the influences of cortisol and ammonia on ammonia excretion relative to expression of Rhesus (Rh) glycoproteins and the ammonia-fixing enzyme, glutamine synthetase (GS). In vivo infusions ...201222189775
regulation of apical h⁺-atpase activity and intestinal hco₃⁻ secretion in marine fish osmoregulation.the absorption of cl(-) and water from ingested seawater in the marine fish intestine is accomplished partly through cl(-)/hco(3)(-) exchange. recently, a h(+) pump (vacuolar-type h(+)-atpase) was found to secrete acid into the intestinal lumen, and it may serve to titrate luminal hco(3)(-) and facilitate further cl(-)/hco(3)(-) exchange, especially in the posterior intestine, where adverse concentration gradients could limit cl(-)/hco(3)(-) exchange. the h(+) pump is expressed in all intestinal ...201121865541
Revisiting the effects of crowding and feeding in the gulf toadfish, Opsanus beta: the role of Rhesus glycoproteins in nitrogen metabolism and excretion.Models of branchial transport in teleosts have been reshaped by the recent discovery of Rhesus (Rh) glycoproteins, a family of proteins that facilitate the movement of NH(3) across cell membranes. This study examines the effects of crowding and feeding on ammonia excretion in gulf toadfish (Opsanus beta) within the context of Rh glycoproteins and the ammonia-fixing enzyme, glutamine synthetase (GS). Four Rh isoforms (Rhag, Rhbg, Rhcg1 and Rhcg2) were isolated from toadfish. Tissue distributions ...201222189774
effects of crowding on ornithine-urea cycle enzyme mrna expression and activity in gulf toadfish (opsanus beta).the gulf toadfish (opsanus beta) is a facultatively ureotelic fish that excretes primarily urea under conditions of crowding or confinement. to examine the relationship between ammonia production, urea production and the ornithine-urea cycle (o-uc) enzyme activity and mrna expression, we subjected toadfish to two-day and seven-day crowding regimes. plasma cortisol levels were measured and liver tissue was assayed for ammonia and urea concentrations. liver glutamine synthetase (gs), carbamoyl pho ...200919617432
basolateral nbce1 plays a rate-limiting role in transepithelial intestinal hco3- secretion, contributing to marine fish osmoregulation.although endogenous co2 hydration and serosal hco3- are both known to contribute to the high rates of intestinal hco3- secretion important to marine fish osmoregulation, the basolateral step by which transepithelial hco3- secretion is accomplished has received little attention. isolated intestine hco3- secretion rates, transepithelial potential (tep) and conductance were found to be dependent on serosal hco3- concentration and sensitive to serosal dids. elevated mucosal cl- concentration had the ...201020086131
ouabain-sensitive bicarbonate secretion and acid absorption by the marine teleost fish intestine play a role in osmoregulation.the gulf toadfish (opsanus beta) intestine secretes base mainly in the form of hco3- via apical anion exchange to serve cl- and water absorption for osmoregulatory purposes. luminal hco3- secretion rates measured by ph-stat techniques in ussing chambers rely on oxidative energy metabolism and are highly temperature sensitive. at 25 degrees c under in vivo-like conditions, secretion rates averaged 0.45 micromol x cm(-2) x h(-1), of which 0.25 micromol x cm(-2) x h(-1) can be accounted for by hydr ...200616709644
effects of waterborne silver in a marine teleost, the gulf toadfish (opsanus beta): effects of feeding and chronic exposure on bioaccumulation and physiological responses.marine teleosts drink seawater, and the digestive tract is a key organ of osmoregulation. the gastro-intestinal tract therefore offers a second site for the potential uptake and toxicity of waterborne metals, but how these processes might interact with the digestive functions of the tract has not been investigated previously. we therefore compared the responses of adult gulf toadfish (opsanus beta, collected from the wild) to a chronic 22d exposure to waterborne ag (nominally 200 microg l(-1)=1. ...201020472311
age and growth of the gulf toadfish opsanus beta based on otolith increment analysis.in the present study, sagittal otoliths of confirmed male and female specimens of the gulf toadfish opsanus beta that were collected monthly over the course of a year from biscayne bay, florida, u.s.a. were analysed. the timing and frequency of o. beta spawning seasons are reported by examination of the gonado-somatic index. the estimated ages of males and females ranged from <1 year to 6 and 5 years, respectively. strong sexual dimorphism in growth was apparent with von bertalanffy parameter es ...200920738646
comparison of the effects of ammonia on brain mitochondrial function in rats and gulf toadfish.we compared the effect of hyperammonemia on nadh levels in brain slices and on the rate of oxygen consumption from isolated nonsynaptic brain mitochondria in ammonia-sensitive wistar rats with that in ammonia-tolerant gulf toadfish (opsanus beta). the nadh content was significantly decreased (12% less than control after 45 min with 1 mm nh(4)cl) in rat brain slices, but it was not affected in brain slices from toadfish (with both 1 and 6 mm nh(4)cl). the rates of oxygen consumption of different ...200212184993
intracellular vesicular trafficking in the gill epithelium of urea-excreting fish.most teleost fish are ammoniotelic, and relatively few are ureotelic, in which the majority of nitrogenous waste is excreted as urea. this study aimed to determine whether the gill ultrastructure of ureotelic fish might have specific, unique characteristics compared with ammoniotelic fish. the gill morphology was studied in three closely related species of the family batrachoididae: opsanus beta, the gulf toadfish; opsanus tau, the oyster toadfish; and porichthys notatus, the plainfin midshipman ...200111291766
intestinal anion exchange in teleost water balance.simultaneous measurements of all major electrolytes including hco3(-) and h+ as well as water demonstrated that fluids absorbed by the anterior intestine of the marine gulf toadfish under in vivo-like conditions on an overall net basis are hypertonic at 380 mosm and acidic ([h+] = 27 mm). this unusual composition of fluids absorbed across the intestinal epithelium is due to the unusual intestinal fluid chemistry resulting from seawater ingestion and selective ion and water absorption along the g ...200717142078
diel patterns of nitrogen excretion, plasma constituents, and behavior in the gulf toadfish (opsanus beta) in laboratory versus outdoor mesocosm settings.nitrogen excretion by the gulf toadfish (opsanus beta) is of interest because of its high proportion of urea excretion compared with that of other teleosts. to better understand the factors influencing the timing of nitrogen excretion, the ratio of excreted urea∶ammonia, and the effector molecules regulating these processes, gulf toadfish were subjected to a series of experiments that moved them progressively from internal laboratory to outdoor mesocosm settings while assessing their behavior, n ...201020979496
evolutionary aspects of intestinal bicarbonate secretion in fish.experiments compared intestinal hco3- secretion in the intestine of marine teleost gulf toadfish, opsanus beta, to representatives of early chondrostean and chondrichthyan fishes, the siberian sturgeon, acipenser baerii, and white-spotted bamboo shark, chiloscyllium plagiosum, respectively. as seen in marine teleosts, luminal hco3- concentrations were 10-fold plasma levels in all species when exposed to hyperosmotic conditions. while intestinal water absorption left mg2+ and so4(2-) concentrated ...200616503178
the intestinal response to feeding in seawater gulf toadfish, opsanus beta, includes elevated base secretion and increased epithelial oxygen consumption.intestinal hco3- secretion is essential to marine teleost fish osmoregulation and comprises a considerable source of base efflux attributable to both serosal hco3- and endogenous co2 hydration. the role of intestinal hco3- secretion in dynamic acid-base balance regulation appears negligible in studies of unfed fish, but evidence of high intestinal fluid [hco3-] in fed marine teleosts led us to investigate the source of this hco3- and its potential role in offsetting the postprandial 'alkaline ti ...200919915130
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