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1.
The presumptive Na+/H+ exchange sites of trout and eel erythrocytes were quantified using amiloride-displaceable 5-(N-methyl-N-[3H]isobutyl)-amiloride (3H-MIA) equilibrium binding to further evaluate the mechanisms of i) hypoxia-mediated modifications in the trout erythrocyte -adrenergic signal transduction system and ii) the marked differences in the catecholamine responsiveness of this system between the trout and eel. MIA was a more potent inhibitor of both trout apparent erythrocyte proton extrusion (IC50 = 20.1 ± 1.1 mol l–1, N = 6) activity (as evaluated by measuring plasma pH changes after addition of catecholamine in vitro) and specific 3H-MIA binding (IC50 = 257 ± 8.2 nmol l–1, N = 3) than amiloride, which possessed a proton extrusion IC50 of 26.1 ± 1.6 mol l–1 (N = 6) and a binding IC50 of 891 ± 113 nmol l–1 (N = 3). The specific Na+ channel blocker phenamil was without effect on adrenergic proton extrusion activity or specific 3H-MIA binding. Trout erythrocytes suspended in Na+-free saline and maintained under normoxic conditions possessed 37,675 ± 6,678 (N = 6) amiloride-displaceable 3H-MIA binding sites per cell (Bmax, presumptive Na+/H+ antiporters) with an apparent dissociation constant (KD) of 244 ± 29 nmol l–1 (N = 6). Acute hypoxia (PO2 = 1.2 kPa; 30 min) did not affect the KD, yet resulted in a 65% increase in the number of presumptive Na+/H+ antiporters. Normoxic eel erythrocytes, similarly suspended in Na+-free saline, possessed only 17,133 ± 3,716 presumptive Na+/H+ antiporters (N = 6), 45% of that of trout erythrocytes, with a similar KD (246 ± 41 nmol l–1, N = 6). These findings suggest that inter- and intra-specific differences in the responsiveness of the teleost erythrocyte -adrenergic signal transduction system can be explained, in part, by differences in the numbers of Na+/H+ exchange sites. 相似文献
2.
The involvement of the freshwater fish gill chloride cells (CCs) in trans-branchial calcium uptake (JinCa2+) was investigated. This was accomplished by assessing the interspecific relationships between the apical surface area of CCs exposed to the external environment and JinCa2+. Three species of freshwater teleosts, the rainbow trout (Oncorhynchus mykiss), the American eel (Anguilla rostrata) and the brown bullhead catfish (Ictalurus nebulosus), were used. Chronic (ten-day) treatment with cortisol in each species was used as a tool to evoke variations in both JinCa2+ and gill CC morphology in order to assess intraspecific relationships between CC surface area and JinCa2+. The results of quantitative morphometry, based on analysis of scanning electron micrographs, demonstrated that catfish possessed the lowest fractional area of exposed CC (CCFA) on the gill filament epithelium (12,744 ± 2248 m2/mm2) and was followed, in increasing order, by American eel (21,355 ± 981 m2/mm2) and rainbow trout (149,928 ± 26,545 m2/mm2). With the exception of catfish, chronic treatment with cortisol caused significant increases in CCFA owing to proliferation of CCs and/or enlargement of individual CCs (eel only). The rates of JinCa2+ closely reflected the CC fractional area in each species. The results of correlation analysis revealed significant correlations between CC fractional area and JinCa2+ in trout and eel. Owing to the absence of an effect of cortisol treatment, there was no significant correlation in catfish because of insufficient variation in CC fractional area in this species. CC fractional area was significantly correlated with JinCa2+ among the three species examined. These results suggest that CC is involved in calcium uptake in freshwater teleosts and that both intra- and interspecific differences in the rates of calcium uptake can be accounted for by variability in the surface area of exposed CCs on the gill epithelia. 相似文献
3.
Knut O. Strætkvern Arnt J. Raae Bernt T. Walther 《Fish physiology and biochemistry》1992,9(5-6):439-452
An alkaline deoxyribonuclease (DNase) from cod pancreatic tissue has been characterized. The enzyme is a DNase I type endonuclease and hydrolyzes effectively both native and denatured DNA. Monomeric actin inhibits the enzyme reaction. The enzyme obeys Michaelis-Menten kinetics and the apparent Km value for native linear duplex DNA is 33 µg/ml. The cod DNase opens supercoiled plasmid DNA, by introducing adjacent nicks in both strands, possibly separated by 5–10 nucleotides. DNA hydrolyzed by cod DNase functions as substrates both for DNA polymerase and ligase, and the nicks therefore contain 5-phosphoryl and 3-hydroxyl groups. Optimum concentrations of divalent cations are 5 mM Mg2+, 0.63 mM Mn2+ and 0.075 mM Ca2+. However, Ca2+ is apparently not essential for the enzymatic functions. The enzyme has a narrow temperature optimum at 42°C and is thermolabile above 50°C; however, Mn2+ shifts the optimum slightly to 45°C by causing increased temperature stability. The cod DNase reaction is inhibited by the DNA intercalating compounds actinomycin D and ethidium bromide. Histidine-modifying reagents such as tosyl phenylalanyl chloromethylketone and diethyl pyrocarbonate inhibit the enzyme activity, but the cod DNase is insensitive to disulfide-reducing agents. 相似文献
4.
The effects of severe experimental anaemia on red blood cell HCO3
– dehydrationin vitro were examined in rainbow trout,Oncorhynchus mykiss. After 5 days of anaemia (haematocrit=4.9±1.1%) induced by intraperitoneal injection of phenylhydrazine hydrochloride, fish displayed elevated arterial CO2 tensions (anaemic PaCO2=3.19±0.42 torrvs. control PaCO2=1.35±0.17 torr) and a significant acidosis (anaemic pHa=7.73±0.04vs. control pHa=7.99±0.04). However, after 15–20 days of anaemia (hct=6.6±0.8%) induced by blood withdrawal, the arterial CO2 tension was significantly lower than the control value, suggesting that physiological adjustments occurred within this time period to compensate for the lowered haematocrit. Compensation probably did not involve alterations in ventilation, which was unaffected by 5 days of anaemia (anaemic
;w=786±187 ml min–1 kg–1
vs. control
;w=945±175 min–1 kg–1), based on indirect Fick principle measurements.Potential adaptations to longer term anaemia at the level of the red blood cells were investigated using a radioisotopic HCO3
– dehydration assay. Owing to the difference in haematocrits, the HCO3
– dehydration rate for blood from anaemic fish was significantly lower than that for control fish following equilibration at the same CO2 tension. This difference was eliminated when HCO3
– dehydration rates were measured on blood samples adjusted to the same haematocrit, a result which implies that the intrinsic rate of CO2 excretion at the level of the red blood cell was not up-regulated during anaemia. The difference was also eliminated by equilibrating the blood samples with CO2 tensions appropriate for the group from which the sample was obtained,i.e., PCO2=1.4 torr for control samples and PCO2=3.2 torr for anaemic samples; each at the appropriate haematocrit. It is concluded that the elevated PaCO2 helps to reset CO2 excretion to the control level, but that some additional physiological adjustment occurs to lower the PaCO2 after 15–20 days of anaemia. 相似文献
5.
L.J.S. Brokken P.M. Verbost W. Atsma S.E. Wendelaar Bonga 《Fish physiology and biochemistry》1998,18(4):331-342
Biochemical and immunological characteristics of peroxidase activity of the skin epithelium of common carp (Cyprinus carpio) were investigated and compared with peroxidase activity of blood cells. Skin as well as blood-borne peroxidases eluted from the Superdex column as a 135 kDa protein and both probably are tetrameric molecules. Skin peroxidase activity was characterized by a Vmax of 51.5 ± 1.3 U mg-1 min-1 and a KM of 1.64 ± 0.18 mM ortho-phenylenediamine (OPD), whereas blood-borne peroxidase was characterized by a 1,000 fold higher specific activity (Vmax = 30.5 103 ± 2.5 103 U mg-1 min-1) and a higher affinity (KM = 0.875 ± 0.003 mM OPD). Polyclonal antibodies were raised against concanavalin-A purified skin peroxidase as well as blood-borne peroxidase. Immunocytochemical labelling showed that peroxidase is present in mucous cells and in mucus covering the skin and gill epithelia, as well as in erythrocytes and leucocytes. We conclude that the mucous cells of the skin produce a biochemically distinct peroxidase that is released in the mucus and may contribute to the antimicrobial properties of the mucous layer covering the skin. After exposure of the fish to cadmium the kinetic characteristics of the enzyme activity, as determined in skin homogenates, changed considerably. The Vmax increased significantly to 61.9 ± 1.1 U mg-1 min-1, and the affinity for OPD increased to the value demonstrated for blood-borne peroxidase (KM = 0.888 ± 0.045 mM OPD). Increased peroxidase levels after cadmium exposure were also demonstrated immunochemically in a dotblot assay. However, no significant changes were observed when the circulatory system of the fish was perfused prior to sampling, indicating that erythrocytes are a major contributor to the increased peroxidase activity in carp skin during cadmium exposure. This likely reflects the increased vascularization of the connective tissue layer underlying the skin epithelium, which takes place when the fish are exposed to chronic stressors including cadmium. In the cadmium-exposed fish this effect prevented the biochemical detection of stressor-related changes in epithelial peroxidase reported earlier with cytochemical methods. 相似文献
6.
Soft water acclimated (Ca2+ 0.02 mM; Na+ 0.03 mM; K+ 0.01 mM; pH 7.0), cannulated brown trout (Salmo trutta) were exposed to various pH and aluminium (Al) regimes (pH 7.0, pH 5.0, pH 5.0 plus Al: 50, 25, and 12.5 g l–1) for up to 5 days in order to determine (i) the sublethal concentration of Al at pH 5.0 for this species (ii) their ionoregulatory and respiratory status. No mortality or physiological disturbances were evident at pH 7.0 or pH 5.0. All trout died within 48 h at pH 5.0 in the presence of Al at 50 g l–1 and 67% died over the 5 day period at pH 5.0 in the presence of Al at 25 g l–1. Fish at these lethal Al concentrations showed significant decreases in arterial blood oxygen content (CaO2) but no changes in plasma osmolarity or the concentrations of plasma Na+, K+ and Cl–. Physiological disturbance was more marked at the 50 g l–1 Al concentration. The surviving fish at 25 g l–1 showed few signs of physiological recovery while continually exposed to this regime. No fish died during the exposure to water of pH 5.0 containing 12.5 g l–1 Al, but physiological disturbance was still apparent. These sublethally-stressed trout showed a transient decline in the plasma concentrations of Na+ and Cl–1. Although CaO2 decreased, recovery was evident. The data suggest that in the brown trout, environmental Al concentration is as important as pH and calcium concentration in determining the physiological status of the fish. 相似文献
7.
Liver is the main catabolic tissue for low density lipoprotein in rainbow trout (Gjøen and Berg 1992). We have investigated the interaction of LDL with isolated trout liver cells and liver membranes. 125I-TC labelled trout LDL bound to isolated trout liver cells in a time dependent and saturable manner with an apparant Kd of 20.1 g/ml, suggesting the existence of a specific binding site on the surface of these cells. The binding was Ca2+ dependent assessed by the 50% reduction obtained by 5 mM EDTA. Saturable binding to isolated trout liver membranes could also be demonstrated, but with lower affinity as compared to intact cells. Degradation of 125I-TC-LDL in hepatocytes was also saturable as degradation could be inhibited about 60% by a 100 fold surplus of unlabelled LDL. The rate of degradation increased with temperature up to 20°C. Both cell association (binding + uptake) and degradation were reduced down to 20% of control in the presence of microtubular and lysosomal inhibitors. Hepatic catabolism of trout LDL therefore seems to depend on receptormediated endocytosis, followed by lysosomal degradation.Abbreviations TC
tyramine cellobiose
- LDL
low density lipoproteins
- MeLDL
methylated low density lipoproteins
- VLDL
very low density lipoproteins
- HDL
high density lipoproteins
- VTG
vitellogenin
- EDTA
ethylenediamine tetraacetic acid
- PBS
phospate buffered saline
- SDS-PAGE
sodium dodecyl sulphatepolyacrylamide gel electrophoresis
- DMPC
L--phosphatidylcholine-dimyristoyl 相似文献
8.
Studies of the enzyme fructose-1,6-bisphosphatase (FBPase) of rainbow trout (Oncorhynchus mykiss) have been undertaken in order to illuminate aspects of skeletal muscle gluconeogenesis in these animals. Maximal activities in crude homogenates of several organs suggest that the liver possesses the greatest FBPase activity on a unit g–1 tissue basis but that the white muscle, owing to its bulk, contributes substantially to whole body FBPase activity. Studies of fructose-6-phosphate-1-kinase (PFK) and FBPase in crude homogenates of several organs suggests an important role for intracellular pH in regulating the relative carbon flux through the FBPase/PFK locus in vivo. Furthermore, a three-step purification scheme is described for trout white muscle FBPase by which a stable and homogeneous (by SDS PAGE) enzyme preparation (isoelectric point = 7.2; molecular weight = 37.6 kd) was obtained. Kinetic studies of the purified enzyme were undertaken at 20°C under conditions reflective of "rest" and "exercise/recovery" intramuscular pH in vivo. Affinity for substrate (F-1,6-P2) was increased (Km = 6.88 versus 2.44 mol 1-–1 as was enzyme activity when pH was lowered from 7.0 to 6.5. Various inhibitor metabolites are identified including F-2,6-P2 (mixed-type inhibitor, Ki = 0.201 mol 1–1, pH 7.0) and AMP (non-competitive inhibitor, Ki = 0.438 mol 1–1, pH 7.0). Inhibition by F-2,6-P2 was strongly alleviated by a reduction in pH from 7.0 to 6.5 (I50 increased from 0.14 to 0.32 mol 1–1). AMP on the other hand was a more potent inhibitor at pH 6.5 but this inhibition was totally reversed under conditions of citrate, NH4
+ and AMP typical of muscle during recovery from exercise in vivo. In purified white muscle enzyme preparations, FBPase demonstrated maximal activity at pH 6.5 whereas the optimal pH of PFK was 7.0 or greater. Indeed, it appears from these in vitro data that regulation by metabolite levels as well as pH are required for net FBPase flux in vivo. It is concluded, therefore that trout white muscle FBPase demonstrates the potential to play an important enzymatic role in the control of intramuscular gluconeogenesis in these animals. The results are discussed in relation to present knowledge regarding the metabolic responses of trout white muscle to, and its subsequent recovery from, exhaustive exercise. 相似文献
9.
Fabiana Trombetti Vittoria Ventrella Alessandra Pagliarani Rodolfo Ballestrazzi Marco Galeotti Gianni Trigari Maurizio Pirini Anna Rosa Borgatti 《Fish physiology and biochemistry》1996,15(3):265-274
With the aim of comparing the effects of oral T3 and NaCl administration on trout hypoosmoregulatory mechanisms, three groups of rainbow trout (Oncorhynchus mykiss Walbaum) held in freshwater (FW) were fed a basal diet (C), the same diet containing 8.83 ppm of 3,5,3-triiodo-L-thyronine (T3) (T) or 10% (w/w) NaCl (N) respectively for 30 d. They were then transferred to brackish water (BW) for 22 d and fed on diet C. Gill (Na++K+)-ATPase activity and its dependence on ATP, Na+ and pH, number of gill chloride cells (CC), serum T3 level as well as fish growth, condition factor (K) and mortality were evaluated. During the FW phase, as compared to C trout, T trout showed a two fold higher serum T3 level, had unchanged gill (Na++K+)-ATPase activity and increased CC number, whereas N trout showed higher gill (Na++K+)-ATPase activity and CC number. At the end of the experiment the enzyme activity was in the order T>N>C groups and all groups showed similar CC number. Both treatments changed the enzyme activation kinetics by ATP and Na+. A transient increase in K value occurred in N group during the period of salt administration. In BW, T and N groups had higher and lower survival than C group respectively. Other parameters were unaffected by the treatments. This trial suggests that T3 administration promotes the development of hypoosmoregulatory mechanisms of trout but it leaves the (Na++K+)-ATPase activity unaltered till the transfer to a hyperosmotic environment. 相似文献
10.
P. M. Verbost M. A. Salah El-Deen P. Pelt M. M. J. C. Bijvelds S. E. Wendelaar Bonga 《Fish physiology and biochemistry》1996,15(4):299-305
An intracellular ATP-dependent Ca2+ pumping mechanism, distinct from mitochondrial Ca2+ accumulation, was identified within tilapia gill cells. Cell suspensions treated with 0.003% saponin, which selectively permeabilizes the plasma membrane, were used to characterize the Ca2+ sequentering mechanisms as endoplasmic reticulum and mitochondria and to determine the effect of Zn2+ on their Ca2+ storing activity. Of the Ca2+ taken up by the endoplasmic reticulum, 80% was released by IP3 (10 mol l–1). The Ca2+ pump of the endoplasmic reticulum was 2.5 times less sensitive to Zn2+ (IC50=0.05 nmol l–1) than was the mitochondrial uptake mechanism (IC50=0.20 nmol l–1). The results indicate that Ca2+ is stored predominantly within the endoplasmic reticulum at 0.1 mol l–1 and that this storing capacity is seriously attenuated by namomolar concentrations Zn2+. 相似文献
11.
Annika Salama 《Fish physiology and biochemistry》1993,10(6):485-490
The -adrenergic response of teleost red blood cells (RBCs) enables the fish to maintain or even enhance the oxygen affinity of haemoglobin during various stress situations. The role of CAMP in the pronounced -adrenergic response of hypoxic rainbow trout RBCs was studied. Rainbow trout RBCs were incubated with three different -agonists (noradrenaline, adrenaline and isoproterenol, 10–9 - 10–4 M) at two oxygen tensions (PO
2, 155 and 8 mmHg), and thereafter cAMP accumulation and cellular water content were measured.The cAMP concentration of non-stimulated trout RBCs was ca. 1200 nmol/kg dw. Of the three -agonists used, isoproterenol was the most effective in formation of cAMP, followed by noradrenaline and adrenaline. Oxygen tension affected the accumulation of cAMP in two ways. At physiological catecholamine levels (1–100 nM) there was either no difference between normoxic and hypoxic cells or a slight increase in the normoxic ones. At high catecholamine concentrations the accumulation of cAMP was greater in the hypoxic than in the normoxic cells. Oxygen tension also affected the magnitude of cell swelling but had no effect on the catecholamine concentrations causing half-maximal swelling (EC50-values). The results indicate that, at physiological catecholamine levels, the -adrenergic response of rainbow trout RBCs is mainly regulated on the level of the Na+/H+ exchange. 相似文献
12.
Wild striped bass,Morone saxatilis, were collected from coastal waters and spawning areas to describe the endocrine correlates of oocyte development in non-captive, migratory fish. The fish were classified according to their most advanced oocytes. Serum levels of estradiol (E2), testosterone (T) and 17-20-dihydroxyprogesterone (DHP) were measured by radioimmunoassay (RIA). Females in the primary growth phase and early secondary growth phase (pre-vitellogenic) had low levels of plasma steroids, ovarian lipid content and gonadosomatic indices (GSIs). Significant increases in E2, T, ovarian lipid content and GSIs occurred during the vitellogenic phase. Maximum levels of all reproductive parameters were found in prespawning fish sampled in the Hudson River. Mean levels of E2, T, ovarian lipids and GSIs for these fish were 2.0±0.5 ng/ml, 3.0±0.3 ng/ml, 24±1 mg/g, and 5.6±0.3% (mean±SEM), respectively. In fish induced to spawn with human chorionic gonadotropin (HCG), DHP levels (1.9±0.4 ng/ml) were significantly elevated. Similar levels were found in two fish captured during the spawning season, suggesting that DHP may serve as the maturation-inducing steroid in this species. 相似文献
13.
Cytosol from brook trout ovarian follicles (stages 1–3) was photoaffinity (PA) labelled using synthetic progestin 17,21-dimethyl-19-nor-pregn-4,9-diene-3,20-dione ([3H]R5020). The covalently bound cytosol protein had a relative mass of 501,000 Mr following Sephacryl S-300 column chromatography. The zona radiata membrane fraction from brook trout oocytes which had gone through the first phase of meiotic maturation (stages 6–7) was isolated by ultracentrifugation of the whole oocytes. The zona radiata solubilized protein presumably from the oocyte membrane was also PA labelled and found to give a peak at 355,000 Mr. The SDS PAGE of the cytosol and zona radiata PA labelled protein gave very similar subunits indicating that the membrane protein and the cytosol protein, both of which bind the maturation inducing steroid (MIS) 17,20-dihydroxy-4-pregnen-3-one (17,20-DHP), have similar subunit structures. The isolated zona radiata protein showed cooperativity of binding to [3H]17,20-DHP and PA labelling to [3H]R5020. The association constant (Ka) was 2.0×107M–1 and maximum binding capacity (Nmax) 427 fmoles/mg protein with MIS [3H]17,20-DHP.No evidence for nuclear binding of MIS [3H]17,20-DHP or PA labelling of [3H]R5020 to nuclei was observed. The nuclei were isolated from stages 1 and 3 fresh ovarian follicles of brook trout. The experimental evidence presented demonstrates the presence of MIS 17,20-DHP receptor-like protein from the zona radiata membranes by PA labelling in brook trout oocytes during final stages of maturation. 相似文献
14.
Distribution and function of hepatic - and -adrenoceptors were examined in rainbow trout (Oncorhynchus mykiss) injected with slow release hydrogenated coconut oil implants alone (sham) or containing cortisol. - and -Adrenoceptors were assayed on purified hepatic membranes 10–14 days post-implantation using 3H-prazosin () and 3H-CGP (). At 10–14 days, plasma cortisol values were significantly elevated to approximately 220 compared with 35.0 ng ml-1 in cortisol implanted vs. sham trout. No significant differences were found between any of the experimental groups for either the affinity (Kd) or maximal number of binding sites (Bmax) for either receptor type. Epinephrine significantly stimulated glucose release from hepatocytes isolated from sham injected trout, but not from cortisol-treated fish. Epinephrine-induced glucose release was blocked by both - and -antagonists. These studies do not support the hypothesis that rainbow trout exposed to chronic cortisol alter properties of hepatic adrenoceptors. 相似文献
15.
The absorptions of 3,5,3-triiodo-L-thyronine (T3) and L-thyroxine (T4) from the intestinal lumen of the rainbow trout were compared in vivo. Tracer doses of [125I]T4 (+T4) or [125I]T3 (*T3) were injected through an anal cannula into the duodenum of trout fasted for 3 days at 12°C, and radioactivity was measured in blood and tissues at 4–48 h. *T3 was removed more extensively than *T4 from the intestinal lumen and more radioactivity was absorbed into the blood and tissues of u+T3-injected trout than *T4-injected trout. HPLC analysis showed that a high proportion of the radioactivity in the plasma, liver, kidney and intestinal lumen of *T3-injected trout remained as the parent *T3. However, in *T4-injected trout most plasma radioactivity was in the form of 125I–, and by 24 h a high proportion of luminal radioactivity was 125I–. By 48 h, over 4% of the injected *T3 and 1% of the injected *T4 dose resided in the gall bladder, primarily as derivatives of *T3 or *T4. We conclude that T3 is absorbed more effectively than T4 from the intestinal lumen of fasted trout, indicating the potential for an enterohepatic T3 cycle. 相似文献
16.
The role of Ca2+ and Na+ membrane transport in brook trout (Salvelinus fontinalis) spermatozoa motility 总被引:1,自引:0,他引:1
Olga Bondarenko Borys Dzyuba Jacky Cosson Marek Rodina Otomar Linhart 《Fish physiology and biochemistry》2014,40(5):1417-1421
The role of environmental ion composition and osmolality in Ca2+ signaled activation was assessed in spermatozoa of brook trout Salvelinus fontinalis. Milt from ten mature males was obtained by abdominal massage. Spermatozoa motility was evaluated in 0, 100, and 300 mOsm/kg NaCl or sucrose solutions, buffered by 10 mM Tris–HCl pH 8.5. For investigation of spermatozoa reaction to external Ca2+ concentration, 2 mM ethylene glycol tetraacetic acid (EGTA) was added to the activation media as a calcium ions chelator. For investigation of the effect of external Na+ concentration in conditions of low external Ca2+, 100 µM amiloride was added to the EGTA-containing solutions as a Na+ transport blocker. Low motility was observed in sucrose (Na+ free) solutions containing 2 mM EGTA but not in Na+ solutions containing 2 mM EGTA. Addition of amiloride led to significantly increased motility (P < 0.05) compared with sucrose (Na+ free) solutions containing 2 mM EGTA. We conclude that Na+ transport in Ca2+-free solutions plays a regulatory role in brook trout spermatozoa activation. The influence of competitive Na+ and Ca2+ transport on the control of spermatozoa activation requires further study with respect to its application for improvement of artificial activation and storage media. 相似文献
17.
The pattern of changes of activity of the urea cycle enzymes and the rate of urea-N excretion were studied in the perfused liver of an Indian air-breathing ureogenic walking catfish, Clarias batrachus. The liver was perfused with different concentrations of NH4Cl for a period of 60 min to determine the role of ammonia for stimulation of hepatic ureogenesis and the threshold level of ammonia loading needed to cause such stimulation. Both the urea-N excretion and the ammonia uptake by the perfused liver were found to be a saturable process. Ammonia accumulated significantly in the liver infused with 1.25 moles g liver –1 min–1 of NH4Cl, followed by a maximum accumulation of about 28.5 moles g wet wt–1 with the infusion of 5.08 moles g liver–1 min–1. The Vmax of the urea-N excretion (0.47 mol g liver–1 min–1) was obtained with the addition of 5.08 moles g liver–1 min–1 of NH4Cl. Both the tissue and the specific activity of the urea cycle enzymes, except ornithine transcarbamylase and arginase, were stimulated significantly with the infusion of either 1.25 or 5.08 moles g liver–1 min–1 of NH4Cl. Maximum stimulation of tissue activity of carbamoyl phosphate synthetase (about 120%) was seen with the infusion of 5.08 mol g liver–1 min–1, and for argininosuccinate synthetase (about 135%), and argininosuccinate lyase (about 50%) with the infusion of 10.81 mol g liver–1 min–1 of NH4Cl. Higher accumulation of ammonia of about 10–15 mol g wet wt–1 from the physiological level in the perfused liver while infusing with NH4Cl was suggested to be one of the major causes of stimulation of ureogenesis. The presence of such physiological adaptive strategy is probably necessary in this unique group of air-breathing walking catfish to survive under hyper-ammonia stress in their normal habitat or while living outside water or while burrowing inside mud. 相似文献
18.
Experimental evaluation of rainbow trout Oncorhynchus mykiss predation on longnose dace Rhinichthys cataractae
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Laboratory and in‐stream enclosure experiments were used to determine whether rainbow trout Oncorhynchus mykiss influence survival of longnose dace Rhinichthys cataractae. In the laboratory, adult rainbow trout preyed on longnose dace in 42% of trials and juvenile rainbow trout did not prey on longnose dace during the first 6 h after rainbow trout introduction. Survival of longnose dace did not differ in the presence of adult rainbow trout previously exposed to active prey and those not previously exposed to active prey ( = 0.28, P = 0.60). In field enclosures, the number of longnose dace decreased at a faster rate in the presence of rainbow trout relative to controls within the first 72 h, but did not differ between moderate and high densities of rainbow trout (F2,258.9 = 3.73, P = 0.03). Additionally, longnose dace were found in 7% of rainbow trout stomachs after 72 h in enclosures. Rainbow trout acclimated to the stream for longer periods had a greater initial influence on the number of longnose dace remaining in enclosures relative to those acclimated for shorter periods regardless of rainbow trout density treatment (F4,148.5 = 2.50, P = 0.04). More research is needed to determine how predation rates will change in natural environments, under differing amounts of habitat and food resources and in the context of whole assemblages. However, if rainbow trout are introduced into the habitat of longnose dace, some predation on longnose dace is expected, even when rainbow trout have no previous experience with active prey. 相似文献
19.
Jacques Rinchard Godfrey Mbahinzireki Konrad Dabrowski Kyeong-Jun Lee Mary-Ann Garcia-Abiado Joseph Ottobre 《Aquaculture International》2002,10(1):11-28
Five experimental diets containing increasing proportions of cottonseedmeal (CSM) protein (0, 25, 50, 75 and 100%; diets 1 to 5, respectively) toreplace fish meal (FM) protein were formulated for intensive culture of tilapiaOreochromis sp. Each diet was fed to three replicategroupsof fish (mean weight ± SE = 11.3 ± 3.9 g) in30L aquaria connected as a closed recirculating-water system andmaintained at 27 ± 1 °C. Fish were fed three times adayby hand at a rate of 3% of body weight during four weeks, after which thefeeding rate was gradually decreased to reach 1.5% at 16 weeks. Thesubstitutionof 75 and 100% of FM proteins by CSM proteins resulted in significantly lowerbody weights in both sexes. In both sexes, gonadosomatic indexes and plasmaconcentrations of sex steroids (testosterone, 11-ketotestoterone,estradiol-17 and 17,20-dihydroxy-4-pregnen-3-one) were notsignificantly different among dietary treatments. The concentration ofgossypol,an antifertility agent contained in CSM, was measured in reproductive tissues.The total gossypol concentration in the testis was consistently lower than thatmeasured in the ovaries of the same group. Moreover, in both sexes, theconcentration of the (+)isomer of gossypol was always higher than that of(–)isomer. The total gossypol concentrations in testes increasedsignificantly with the increase of CSM in the diet. The highest levels of the(+)isomer (7.64 ± 0.62 g g–1)were found in the testes of fish fed diet 4, whereas the (–)isomerreached its highest values in the testes of fish fed diet 5. The highest levelsof both enantiomers of gossypol were found in the ovaries of fish fed diet 4(14.2 ± 2.7 and 5.6 ± 1.5 g g–1for (+) and (–)isomers, respectively). In both sexes, thehistological analysis of the gonads did not reveal differences among the fishfed different levels of CSM. Although CSM at any levels did not affect thereproductive parameters examined in this study, it cannot be used to substitutemore than 50% of FM since at higher levels growth of tilapia was compromised. 相似文献
20.
Rasanthi M. Gunasekera Sena S. De Silva Brett A. Ingram 《Fish physiology and biochemistry》2001,25(4):255-268
The changes in proximate composition, amino acid (total and free) and fatty acid content of artificially propagated trout cod, Maccullochella macquariensis larvae from five mothers hatched, weaned and reared separately, each in two groups, one fed with Artemia naupli and the other starved, for 15 days (after yolk resorption), are presented. There was no significant change in the proximate composition of fed larvae with devlopment, but in starved larvae the protein (linearly) and lipid (curvi-linearly) content decreased significantly as starvation progressed. The essential amino acids (EAA) and non- essential amino acids (NEAA) found in highest amounts in trout cod larvae were lysine, leucine, threonine and arginine, and alanine, serine and glutamic acid, respectively. In fed larvae the total amino acid (TAA), TEAA and TNEAA content did not vary significantly as development progressed. In starved larvae the TAA, EAA and NEAA content, as well as all the individual amino acids decreased significantly (P<0.05) from the levels in day of hatch and/or yolk-sac resorbed larvae. The greatest decrease occurred in the TEAA content (7.38±0.76 at day of hatch to 1.96±0.09 15 day starved in moles larva–1; approximately a 74% decrease), whereas the decrease in TNEAA was about 38%. Unlike in the case of TAA distinct changes in the free amino acid (FAA) pool were discernible, from day of hatch and onwards, in both fed and starved trout cod larvae. In both groups of larvae the most noticeable being the decrease of % FEAA in TFAA, but not the % FAA in TAA. Four fatty acids together, accounted for more than 50% of the total in each of the major fatty acid categories in all larvae sampled; 16: 0, 18:1n-9, 22: 6n-3 and 20: 4n-6, amongst saturates, monoenes, n-3 PUFA and n-6 PUFA, respectively. Twelve fatty acids either decreased (14: 0, 16: 1n-7, 20: 1n-9, 20: 4n-6, 20: 5n-3, 22: 5n-3 and 22: 6n-3) or increased (18: 2n-6, 18: 3n-3, 18: 3n-6, 18: 4n-3 and 20: 3n-3) in quantity, after 15 days of feeding, from the base level in day of hatch and/ or yolk- sac resorbed larvae. The greatest increase occurred in 18: 3n-3 from 6.4±0.1 to 106.2±13.1 g mg lipid–1 larva–1, and the greatest decrease occurred in 22: 6n-3 (181.2±12.4 to 81.4±6.2 g mg lipid–1 larva–1). In starved larvae, at the end of 15 days, all the fatty acids, except 18: 0, 20: 3n-3 and 20: 4n-6, decreased significantly (P<0.05) from the levels in day of hatch and/or yolk- sac resorbed larvae. 相似文献