Respiratory, ventilatory, and cardiovascular responses to experimental anaemia in the starry flounder, Platichthys stellatus.
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Unrestrained, quiescent starry flounder maintained approximately normal levels of O2 uptake in the face of severe experimental anaemia. At haematocrits above about 5%, the only major compensation was a reduction in venous O2 tension which lowered venous saturation and thereby kept a constant difference between arterial and venous O2 contents. Below a haematocrit of about 5%, this difference decreased, and many additional compensations were invoked, including increases in ventilation, expired O2 tension, arterial O2 tension, and cardiac output, and decreases in systemic vascular resistance and blood pH. All changes could be reversed by restoration of haematocrit. Exercise performance and post-exercise changes in blood pH and lactate differed only slightly between anaemic and normal flounder. In wild flounder, anaemia commonly occurs and apparently only causes death at the haematocrit value (about 5%) below which most major compensations are implemented. The respiratory strategy of the flounder during anaemia is compared with that of the rainbow trout. (+info)
Disposition of 14C-flumequine in eel Anguilla anguilla, turbot Scophthalmus maximus and halibut Hippoglossus hippoglossus after oral and intravenous administration.
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The absorption, distribution and elimination of 14C-labelled flumequine were studied using whole body autoradiography and liquid scintillation counting. Flumequine was administered to eel Anguilla anguilla, turbot Scophthalmus maximus and halibut Hippoglossus hippoglossus intravenously and orally as a single dose of 5 mg kg(-1), corresponding to 0.1 mCi kg(-1). The turbot and halibut studies were performed in salt water (salinity of 32%) at temperatures of 16 +/- 1 degrees C (turbot) and 9.5 +/- 0.5 degrees C (halibut). The eel study was conducted in fresh water at 23 +/- 1 degrees C. In the intravenously administered groups flumequine was rapidly distributed to all major tissues and organs. After oral administration flumequine also appeared to have rapid and extensive absorption and distribution in all 3 species. After the distribution phase, the level of flumequine was higher in most organs and tissues than in the blood, except in muscle and brain. The most noticeable difference between the species was the slow elimination of flumequine from eel compared to turbot and halibut. In orally administered eels, substantial amounts of flumequine remained in all major organs/tissues for 7 d. At 28 d significant levels of flumequine were present in liver, kidney and skin (with traces in muscle), and at the last sampling point (56 d) in eye, bone, bile and posterior intestine. In orally administered turbot significant levels of flumequine were observed over 96 h in bile, urine, bone, skin, intestine and eye, and traces were detected over 28 d in bone and eye in addition to a significant level in bile. In orally administered halibut, significant levels of flumequine were observed in bile, skin, intestine and eye over 96 h. Traces were present in skin and eye over 7 d. The maximal flumequine concentrations in blood were calculated to be 2.5 mg equivalents l(-1) (eel at 12 h), 0.8 mg l(-1) (turbot at 6 h) and 0.6 mg l(-1) (halibut at 6 h) after oral administration. (+info)
Isolation and characterization of a Japanese flounder clonal line, reversed, which exhibits reversal of metamorphic left-right asymmetry.
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We have isolated a clonal line reversed (rev) of homozygous Japanese flounder through gynogenesis. The homozygous offspring gynogenetically produced from rev exhibited reversal of organization of the metamorphic L/R asymmetry such as the direction of eye-migration at a high frequency (20-30%). The molecular analysis using a left-specific marker pitx2 revealed that the embryonic L/R axis was ambiguously established: in more than half of rev embryos, pitx2 was expressed bilaterally in the lateral plate mesoderm (LPM). Previous studies in other animals demonstrated that ectopic pitx2 expression in the LPM could cause laterality defects of the visceral organs. Likewise, our results using rev imply that bilateral pitx2 expression could lead to randomization of the visceral organs. Coincidence of ectopic pitx2 expression and reversal of the direction of eye-migration in the population of rev offspring suggests that the rev locus is critical in specification of both the metamorphic and the visceral L/R asymmetries. However, reversal of the sidedness of the orientation of the visceral organs was not always accompanied by reversal of the direction of metamorphic eye-migration, suggesting that different mechanisms should be involved downstream of the rev locus in directing these two phases of asymmetric morphogenesis in the Japanese flounder. (+info)
In vivo oocyte hydration in Atlantic halibut (Hippoglossus hippoglossus); proteolytic liberation of free amino acids, and ion transport, are driving forces for osmotic water influx.
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The in vivo swelling and hydration of maturing oocytes of Atlantic halibut Hippoglossus hippoglossus were studied in order to characterise the osmotic mechanism underlying oocyte hydration in oviparous marine teleosts that spawn pelagic eggs. Sequential biopsies from two females, spanning four hydration cycles, were examined by osmometry, solute analysis and electrophoresis of dissected hydrating oocytes and ovulated eggs. The hydration cycle of the biopsied halibuts lasted 33-54 h. The majority of ovarian oocytes existed in a pre-hydrated condition (individual wet mass approx. 3.7 mg, diameter approx. 1.87 mm, 63 % H(2)O) with easily visible, non-coalesced, yolk platelets. Group-synchronous batches of the pre-hydrated oocytes increased in individual wet mass, diameter and water content to reach the ovulated egg stage of approximately 15 mg, 3.0 mm and 90 % H(2)O, respectively. The yolk osmolality of the hydrating oocytes was transiently hyperosmotic to the ovarian fluid (range 305-350 mOsmol l(-1)) with a peak osmolality of about 450 mOsmol l(-1) in oocytes of 6-8 mg individual wet mass. The transient hyperosmolality was well accounted for by the increase in oocyte content of free amino acids (FAAs; approx. 2300 nmol oocyte(-1)), K(+) (approx. 750 nmol oocyte(-1)), Cl(-) (approx. 900 nmol oocyte(-1)), total ammonium (approx. 300 nmol oocyte(-1)) and inorganic phosphate (P(i); approx. 200 nmol oocyte(-1)) when relating to the increase in cellular water. The oocyte content of Na(+) did not increase during the hydration phase. Extensive proteolysis of yolk proteins, in particular a 110 kDa protein, correlated with the increase in the FAA pool, although the latter increased by approx. 20 % more than could be accounted for by the decrease in the oocyte protein content. Both indispensable and dispensable amino acids increased in the FAA pool, and particularly serine, alanine, leucine, lysine, glutamine and glutamate. Taurine content remained stable at approx. 70 nmol oocyte(-1) during oocyte hydration. The results show that final hydration of Atlantic halibut oocytes is caused by an osmotic water uptake in which FAAs, derived mainly from the hydrolysis of a 110 kDa yolk protein, contribute approximately 50 % of the yolk osmolality and ions (Cl(-), K(+), P(i), NH(4)(+)) make up the balance. (+info)
Diseases, prophylaxis and treatment of the Atlantic halibut Hippoglossus hippoglossus: a review.
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After substantial investments in research, the Atlantic halibut Hippoglossus hippoglossus is now being cultivated commercially in Norway, Iceland, Scotland and Canada. As with other domesticated species, disease problems have been experienced. This review summarizes the current state of knowledge of diseases of the Atlantic halibut, and their diagnosis, prophylaxis and treatment. In economic terms, the most important losses have been suffered at the larval and juvenile stages. The most important infections are caused by nodaviruses, causative agents of Viral Encephalopathy and Retinopathy (VER), which are the major reason why Norway's production of halibut fry has been level since 1995. An aquatic birnavirus, Infectious Pancreatic Necrosis Virus, is also an important agent of mortality. Vibrio anguillarum, Flexibacter ovolyticus and atypical Aeromonas salmonicida are the major bacterial pathogens. The protozoan parasites recorded include Ichthyobodo sp., the microsporidium Enterocytozoon sp., Trichodina hippoglossi, and the metazoan pathogens include myxozoans, helminths, Entobdella hippoglossi, Lepeophtheirus hippoglossi and other parasitic copepods. Experimental vaccines have been tested against V anguillarum and atypical A. salmonicida, with good results. A recombinant vaccine against nodaviruses is under development. A few trials have been carried out on non-specific immunostimulants, but no such treatment is currently available. A number of efficacy and pharmacokinetic trials with various antibacterial agents have also been published. (+info)
Solution structure of a hydrophobic analogue of the winter flounder antifreeze protein.
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The solution structure of a synthetic mutant type I antifreeze protein (AFP I) was determined in aqueous solution at pH 7.0 using nuclear magnetic resonance (NMR) spectroscopy. The mutations comprised the replacement of the four Thr residues by Val and the introduction of two additional Lys-Glu salt bridges. The antifreeze activity of this mutant peptide, VVVV2KE, has been previously shown to be similar to that of the wild type protein, HPLC6 (defined here as TTTT). The solution structure reveals an alphahelix bent in the same direction as the more bent conformer of the published crystal structure of TTTT, while the side chain chi1 rotamers of VVVV2KE are similar to those of the straighter conformer in the crystal of TTTT. The Val side chains of VVVV2KE assume the same orientations as the Thr side chains of TTTT, confirming the conservative nature of this mutation. The combined data suggest that AFP I undergoes an equilibrium between straight and bent helices in solution, combined with independent equilibria between different side chain rotamers for some of the amino acid residues. The present study presents the first complete sequence-specific resonance assignments and the first complete solution structure determination by NMR of any AFP I protein. (+info)
Functional differences between flounder and rat thiazide-sensitive Na-Cl cotransporter.
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The purpose of the present study was to determine the major functional, pharmacological, and regulatory properties of the flounder thiazide-sensitive Na-Cl cotransporter (flTSC) to make a direct comparison with our recent characterization of the rat TSC (rTSC; Monroy A, Plata C, Hebert SC, and Gamba G. Am J Physiol Renal Physiol 279: F161-F169, 2000). When expressed in Xenopus laevis oocytes, flTSC exhibits lower affinity for Na(+) than for Cl(-), with apparent Michaelis-Menten constant (K(m)) values of 58.2 +/- 7.1 and 22.1 +/- 4.2 mM, respectively. These K(m) values are significantly higher than those observed in rTSC. The Na(+) and Cl(-) affinities decreased when the concentration of the counterion was lowered, suggesting that the binding of one ion increases the affinity of the transporter for the other. The effect of several thiazides on flTSC function was biphasic. Low concentrations of thiazides (10(-9) to 10(-7) M) resulted in activation of the cotransporter, whereas higher concentrations (10(-6) to 10(-4) M) were inhibitory. In rTSC, this biphasic effect was observed only with chlorthalidone. The affinity for thiazides in flTSC was lower than in rTSC, but the affinity in flTSC was not affected by the Na(+) or the Cl(-) concentration in the uptake medium. In addition to thiazides, flTSC and rTSC were inhibited by Hg(2+), with an apparent higher affinity for rTSC. Finally, flTSC function was decreased by activation of protein kinase C with phorbol esters and by hypertonicity. In summary, we have found significant regulatory, kinetic, and pharmacological differences between flTSC and rTSC orthologues. (+info)
Mitochondrial ATP-sensitive K+ channels influence force development and anoxic contractility in a flatfish, yellowtail flounder Limanda ferruginea, but not Atlantic cod Gadus morhua heart.
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The influence of ATP-sensitive K+ channels (K(ATP) channels) on cardiac performance during anoxia and reoxygenation was investigated in two species of fish showing different cardiac responses to anoxia. Force production in isometrically contracting ventricular muscle preparations from yellowtail flounder is potentiated at the onset of anoxia, while force immediately declines in Atlantic cod preparations. Glibenclamide, a general K(ATP) blocker, impaired oxygenated force development in yellowtail flounder heart but was without effect on cod preparations. The mitochondrial K(ATP) (mK(ATP))-specific blocker 5-hydroxydecanoic acid (5HD) improved oxygenated force production in yellowtail flounder heart without influencing contractility during anoxia or reoxygenation. The specific mK(ATP) agonist diazoxide preserved resting tension and eliminated anoxic force potentiation in yellowtail flounder heart preparations. Neither 5HD nor diazoxide affected contractility in cod ventricle preparations. Results indicate that K(ATP) channels can modulate contractility in yellowtail flounder heart and are potentially important in cardiac hypoxia survival in this species. (+info)