Publications
| Title | Abstract | Year Filter | PMID(sorted ascending) Filter |
|---|
| the haemocytology and histology of the haemopoietic organs of south african fresh water fish. i. the haemopoietic organs of clarias gariepinus and sarotherodon mossambicus. | the haemopoietic organs of the catfish, clarias gariepinus, and the mozambique bream, sarotherodon mossambicus, were studied. in both species the primary haemopoietic organs are the pronephros, the mesonephros and the spleen. the peritoneum and, particularly in catfish, the omentum are of secondary importance in haemopoiesis. | 1979 | 551371 |
| introducing foreign genes into fish eggs with electroporated sperm as a carrier. | a new method has been developed for introduction of foreign genes into fish eggs. the procedure is based on the incubation of fish sperm cells suspended in dilute citrate solution with plasmid dna, followed by application of high-field-strength electrical pulses (electroporation) to increase dna binding., uptake, or both. tissue homogenates and genomic dna extracts of free swimming fry developed from eggs fertilized with treated sperm was tested to evaluate the efficiency of gene transfer. dot b ... | 2012 | 1308817 |
| maturational gonadotropin from the african catfish, clarias gariepinus: purification, characterization, localization, and biological activity. | a gonadotropic hormone of the african catfish, clarias gariepinus, was was purified and chemically characterized. its biological activity was tested and its localization in the gonadotropic cells of the pituitary demonstrated. an ethanolic extract of 500 pituitaries of adult male and female african catfish was subjected to ion-exchange chromatography on de-52. the 31- to 38-kda fraction was further purified on sephadex g-75. on rphplc over an ods 120t column two major components appeared as sing ... | 1992 | 1426937 |
| two gonadotropin-releasing hormones from african catfish (clarias gariepinus). | two forms of gonadotropin-releasing hormone (gnrh) have been purified from brain extracts of the african catfish, clarias gariepinus, using reverse-phase high performance liquid chromatography (hplc) and radioimmunoassay (ria). the amino acid sequences of both forms of african catfish gnrh were determined using edman degradation after digestion with pyroglutamyl aminopeptidase. in addition, both gnrhs were studied by mass spectrometry. the primary structure of african catfish gnrh i is identical ... | 1992 | 1520292 |
| application of cryosubstitution in neurohormone- and neurotransmitter-immunocytochemistry. | pituitaries of the african catfish, clarias gariepinus, were prefixed in aldehyde fixatives, frozen in liquid propane and submitted to a cryosubstitution procedure. ultrathin sections of the lowicryl hm20-embedded tissue were treated with primary antisera raised in rabbits to gonadotropin releasing hormone (gnrh), vasopressin or gamma amino butyric acid (gaba) respectively. binding of the primary antisera was visualized with goat anti-rabbit (gar) labeled with gold. the general morphology of the ... | 1992 | 1559844 |
| the emergence of electroreceptor organs in regenerating fish skin and concurrent changes in their transduction properties. | the process of regeneration of skin patch denervated empullary electroreceptor organs of the african catfish clarias gariepinus has been investigated at an ambient temperature of 28 degrees c with both electrophysiological and histological methods. at day 1 after denervation none of the receptor organs on the skin patch showed afferent activity. at this stage none of the ampullary organs previously recorded showed a normal appearance. degenerative changes consisted of a decreased number of recep ... | 1991 | 1754064 |
| treatment of cyprinus carpio l. and clarias gariepinus (burchell) embryos with formalin and malachite green: effect of concentration and length of treatment on their survival. | malachite green and formalin were investigated as prophylactic dip treatments for developing embryos of cyprinus carpio and clarias gariepinus. based on the findings, recommendations are made on the respective concentrations to be used and exposure periods to be followed for both formalin and malachite green for both fish species. | 1991 | 1780123 |
| investigations into the effects of concentration and duration of exposure to formalin and malachite green on the survival of the larvae and juveniles of the common carp cyprinus carpio l. and the sharptooth catfish clarias gariepinus (burchell). | prophylactic dip treatments using formalin and malachite green were applied to 4-day old larvae and 12- and 20-day old juveniles of the european common carp, cyprinus carpio and the african sharptooth catfish, clarias gariepinus. treatments consisted of 100 mg/l malachite green for exposure periods of 10, 30 or 90 s and 200 mg/l formalin, administered for 30, 60 or 90 min. larvae and juveniles of c. gariepinus could be treated with 100 mg/l malachite green for 10 s, or with 200 mg/l formalin for ... | 1991 | 1780124 |
| steroid glucuronides as male pheromones in the reproduction of the african catfish clarias gariepinus--a brief review. | after ovulation, female african catfish are strongly attracted by the odor of male conspecifics. this attraction depends on the presence of the seminal vesicle, a part of the male reproductive organs. removal of the seminal vesicle illustrates this fact. a low dose of seminal vesicle fluid, added to the water, appears to be highly attractive for catfish which have ovulated. fractionation of the fluid and testing of the different fractions shows that steroid glucuronides could be responsible for ... | 1991 | 1958557 |
| distribution of serotonin- and dopamine-immunoreactivity in the brain of the teleost clarias gariepinus. | the distribution of serotonergic and dopaminergic cell bodies and varicose fibres in the brain of the teleost clarias gariepinus was studied immunohistochemically using antisera against formaldehyde-conjugated serotonin and dopamine. many serotonergic and dopaminergic fibres innervated the areas dorsalis telencephali pars medialis and pars lateralis dorsalis, as well as the area ventralis telencephali pars ventralis. in the diencephalon, a large number of serotonergic and some dopaminergic fibre ... | 2013 | 2059346 |
| stimulation of gonadal development by sexual interaction of pubertal african catfish, clarias gariepinus. | stimulation and inhibition of gonadal development by intersexual contact was studied in pubertal african catfish, clarias gariepinus. the effect of a possible interaction was studied by evaluation after a 98-day experimental period of gonadal development in combinations of intact and anosmic males and females. in addition, separate groups of males and females, respectively, were exposed to holding water from these combinations. a tentative model of stimulation of gonadal development by intersexu ... | 1991 | 2062890 |
| characterization of dopamine d2 receptors in the pituitary of the african catfish, clarias gariepinus. | dopamine receptors in the pituitary of the african catfish, clarias gariepinus, were characterized using [3h]spiperone as radioligand. specific binding of [3h]spiperone to pituitary membranes reached equilibrium within 60 min of incubation. the binding of the radioligand was tissue specific since the amount of binding was linear with pituitary membrane content in the incubations. in addition, pituitary membranes were observed to bind considerably more [3h]spiperone, compared to membrane preparat ... | 1990 | 2148730 |
| ultrastructural localization of calcium and ca(2+)-atpase activity in gonadotropes and stellate cells of the catfish pituitary. | in the pituitary of the african catfish, clarias gariepinus, calcium precipitates were ultrastructurally visualized with the oxalate-pyroantimonate procedure (opp). the presence of calcium in these precipitates was validated with several methods, including "electron energy loss spectrometry" (eels). in the opp-treated tissue calcium precipitates were seen in a) non-secretory stellate cells and b) gonadotropic (gth-) cells. in the latter the amount of precipitate is generally low, but stimulation ... | 1990 | 2149132 |
| conversion of 11-ketoandrostenedione to 11-ketotestosterone by blood cells of six fish species. | blood cells from baltic salmon, salmo salar, three-spined stickleback, gasterosteus aculeatus, eel pout, zoarces viviparus, crucian carp, carassius carassius, african catfish, clarias gariepinus, and reedfish, calamoichthys calabaricus, were incubated with tritiated 11 beta-hydroxyandrostenedione (oha) or 11-ketoandrostenedione (oa). in all fish there was conversion of oa to 11-ketotestosterone (ot), indicating that 17 beta-hydroxysteroid dehydrogenase activity was present in the blood cells. on ... | 1990 | 2295425 |
| role of calcium ions in action of gonadotropin-releasing hormone on gonadotropin secretion in the african catfish, clarias gariepinus. | the aim of the present study was to establish the role of calcium ions in the mechanism of action of gonadotropin-releasing hormone (gnrh) in stimulating gonadotropin (gth) release in the african catfish, clarias gariepinus. for that purpose, gth release from pituitary fragments was monitored in a perifusion system. gth release, induced by the gnrh analog buserelin, was strongly diminished in the absence of ca2+, as well as in the presence of the ca2+ channel antagonist nifedipine. in addition, ... | 1989 | 2513245 |
| a new member of the gonadotropin-releasing hormone family in teleosts: catfish gonadotropin-releasing hormone. | two forms of immunoreactive gonadotropin-releasing hormone (gnrh) were detected in extracts of brain-pituitary tissue from the african catfish, clarias gariepinus. catfish i gnrh eluted first from reverse-phase hplc and was present in larger amounts compared with catfish ii gnrh. chromatographic and immunological studies with four antisera provide evidence that catfish i gnrh is unique compared with identified gnrhs from mammal, chicken, salmon, and lamprey. catfish ii gnrh elutes in the same po ... | 1989 | 2676702 |
| comparative pharmacokinetics of oxytetracycline in rainbow trout (salmo gairdneri) and african catfish (clarias gariepinus). | a comparative pharmacokinetic study was conducted in rainbow trout (salmo gairdneri) and african catfish (clarias gariepinus) following intravenous (i.v.) and intramuscular (i.m.) administration of oxytetracycline (otc) at a dose rate of 60 mg/kg body weight. trout and catfish were kept in aerated tap water in tanks at constant temperatures of 12 degrees c and 25 degrees c, respectively. the two- and three-compartment open models adequately described plasma drug disposition in african catfish an ... | 1989 | 2746722 |
| resting discharge and sensitivity of ampullary electroreceptors in clarias gariepinus related to convergence ratio during ontogeny. | the ampullary electroreceptor organs of the teleost fish clarias gariepinus converge to single afferent neurons. during the first 4 months of ontogeny the convergence ratio (cr) increases from 1 to 3. extracellular single-unit recordings show that a 3-fold increase in cr results on average in a 3.6-fold increase in sensitivity measured at stimulus frequencies of 2, 8 and 20 hz, and in a small but significant 1.1-fold increase in resting discharge. adaptation of the primary afferents could accoun ... | 2007 | 2819409 |
| estrogen-2-hydroxylase in the brain of the male african catfish, clarias gariepinus. | estrogen-2-hydroxylase activity, involved in the biosynthesis of catecholestrogens, was localized in the brain of the male african catfish, clarias gariepinus, by means of a radiometric assay using [2-3h]estradiol as substrate. fore- and midbrain were divided in 18, 500-microns thick, transverse sections from which small defined areas were punched out and assayed. the estrogen-2-hydroxylase activity was calculated from the release of tritium during hydroxylation, and expressed in femtomole catec ... | 1988 | 2848743 |
| the dopaminergic regulation of gonadotropin-releasing hormone receptor binding in the pituitary of the african catfish, clarias gariepinus. | in several teleost species, including the african catfish, dopamine acts as an endogenous inhibitor of gonadotropin-releasing hormone (gnrh)-stimulated gonadotropin (gth) release. the present in vivo study was carried out to investigate whether this inhibitory action of dopamine can be explained by an effect on the pituitary gnrh receptors. to that end, sexually mature female catfish were treated with dopamine and the dopamine antagonist pimozide (pim), respectively. at different time intervals ... | 1988 | 2853682 |
| steroid metabolism in the seminal vesicles of the african catfish, clarias gariepinus (burchell), during the spawning season, under natural conditions, and kept in ponds. | steroid metabolism in the seminal vesicles of clarias gariepinus, collected in the hula nature reserve and in a fish pond in north israel during the spawning season, was studied in vitro by homogenate and tissue incubations with [3h]pregnenolone, [3h]dehydroepiandrosterone, or [3h]androstenedione as precursor. the seminal vesicles were able to synthesize androgens, 11-oxygenated androgens, and 5 beta-reduced c19- and c21-steroids; a pregnenolone ester was also formed. furthermore a potent synthe ... | 2010 | 2937683 |
| the skin of the male african catfish, clarias gariepinus: a source of steroid glucuronides. | steroid metabolism in the skin of mature male african catfish, clarias gariepinus, reared in the laboratory, was studied in vitro by tissue incubations with [3h]pregnenolone, [3h]dehydroepiandrosterone, [3h]17 alpha-hydroxyprogesterone, [3h]androstenedione, [14c]11 beta-hydroxyandrostenedione, and [3h]testosterone as precursors. while pregnenolone was not converted to any other steroid, dehydroepiandrosterone was transformed mainly to 5-androstene-3 beta, 17 beta-diol. the products of 17 alpha-h ... | 1987 | 2956154 |
| immunocytochemical evidence for peptidergic (gnrh) and dopaminergic innervation of the gonadotropic cells in the pituitary of the african catfish, clarias gariepinus. | the proximal pars distalis (ppd) of the pituitary of the african catfish, clarias gariepinus, was studied with immunocytochemical methods at the ultrastructural level. anti-serum raised against synthetic mammalian luteinizing hormone-releasing hormone (lhrh) was applied on lowicryl-embedded pituitaries and the antigenic sites were visualized with protein a-gold. in nerve fibers contacting the gonadotropic cells, granulated vesicles with a diameter of 90-120 nm were labeled after this procedure, ... | 1987 | 3311872 |
| 5 beta-pregnane-3 alpha,6 alpha,17 alpha,20 beta-tetrol and 5 beta-pregnane-3 alpha,6 alpha,17 alpha-triol-20-one: steroids of ovarian origin in the african catfish, clarias gariepinus, during oocyte maturation. | at the stage of oocyte maturation, three very polar steroids were demonstrated by in vitro incubations with tritiated pregnenolone in the ovaries of the african catfish, clarias gariepinus. two of these compounds could be identified by chromatography, derivatization, and oxidation as 5 beta-pregnane-3 alpha,6 alpha,17 alpha,20 beta-tetrol and 5 beta-pregnane-3 alpha,6 alpha,-17 alpha-triol-20-one. blood plasma analysis by means of gas chromatography followed by mass spectrometry confirmed the pr ... | 1988 | 3366354 |
| quantitative analysis of steroids and steroid glucuronides in the seminal vesicle fluid of feral spawning and feral and cultivated nonspawning african catfish, clarias gariepinus. | the seminal vesicles of african catfish, clarias gariepinus, can produce at least seven different steroid glucuronides, especially during the breeding season. in the present experiments quantification of the seven compounds and their free steroids was carried out by means of gas chromatography-mass spectrometry in particular by selected ion monitoring, using seminal vesicle fluid of african catfish collected in the hula nature reserve (israel) and from a nearby fish farm. some of the feral fish ... | 2012 | 3371653 |
| measurement of aromatase activity in the brain of the african catfish, clarias gariepinus--a comparison of two assay methods. | in the brain of the african catfish aromatase activity was demonstrated with two different methods using [7-3h]androstenedione and [19-3h]androstenedione as substrates. kinetic analysis of estrogen formation following incubations of a cell-free fraction of brain homogenates showed that the apparent km is the same for both substrates (0.03 micro m), but the vmax is smaller with [19-3h]androstenedione as substrate. this indicates a so-called isotope effect. a time course study showed that after an ... | 1987 | 3427894 |
| gas chromatographic-mass spectrometric analysis of steroids and steroid glucuronides in the seminal vesicle fluid of the african catfish, clarias gariepinus. | gas chromatographic-mass spectrometric analysis was carried out to identify steroids and steroid glucuronides in the seminal vesicle fluid of african catfish, clarias gariepinus, collected in the hula nature reserve (israel) during the breeding season. full mass spectra of 5 beta-pregnane-3 alpha, 17 alpha-diol-20-one and cholesterol were obtained. after treatment with beta-glucuronidase the following steroid glucuronides were determined by full mass spectra of the corresponding free steroids: e ... | 2012 | 3436514 |
| the seminal vesicle of the african catfish, clarias gariepinus. a histological, histochemical, enzyme-histochemical, ultrastructural and physiological study. | the seminal vesicle of the african catfish, clarias gariepinus, consists of 36-44 fingerlike lobes built up of tubules in which a fluid is secreted containing acid polysaccharides, acid-, neutral- and basic proteins, and phospholipids. in this fluid sperm cells are stored. the seminal vesicle fluid immobilizes the sperm cells. after ejaculation, it prolongs the period of sperm activity. the seminal vesicle fluid is secreted by the epithelium lining the tubules. the tubules in the proximal part o ... | 1987 | 3471349 |
| purification of gonadotropic hormone from the pituitary of the african catfish, clarias gariepinus (burchell), and the development of a homologous radioimmunoassay. | glycoprotein gonadotropic hormone (gth) was purified from 2000 pituitaries of male and female african catfish, clarias gariepinus. the first step was chromatography on concanavalin a-sepharose followed by filtration on ultrogel aca 54, chromatography on deae-cellulose, and filtration on ultrogel aca 54, respectively. finally, the purified fractions were analyzed by polyacrylamide gel electrophoresis. the gonadotropic activity in the different fractions was characterized using two tests: the radi ... | 1986 | 3536658 |
| the dopaminergic inhibition of the gonadotropin-releasing hormone-induced gonadotropin release: an in vitro study with fragments and cell suspensions from pituitaries of the african catfish, clarias gariepinus (burchell). | pituitary fragments and pituitary cell suspensions of the african catfish in a perifusion system released gonadotropic hormone (gth) spontaneously. after a few hours of perifusion a baseline of gth release was established. the dopamine (da) agonist apomorphine (apo) caused a decreased in the release from pituitary fragments but not from pituitary cell suspensions. apo abolished the luteinizing hormone-releasing hormone analog (lh-rha)-induced gth release from both pituitary fragments and cell su ... | 1986 | 3536659 |
| localization of aromatase in the brain of the male african catfish, clarias gariepinus (burchell), by microdissection and biochemical identification. | aromatase activity was determined in small discrete areas of the brain of the african catfish, clarias gariepinus, by a radiometric assay. the fore- and midbrain were divided into eighteen 500-microns transverse sections. from these sections several punches (0.3 mg of tissue) were taken and incubated with [19-3h]-androstenedione. the aromatase activity, calculated from the release of tritium label during aromatization, is expressed in pmol mg-1 tissue hour-1. the highest activity (3.7 pmol) was ... | 2013 | 3584544 |
| quantitative studies of steroid bioconversions in the seminal vesicles of spawning male african catfish, clarias gariepinus (burchell), under natural conditions, and of non-spawning catfish under natural and fish farm conditions. | 1. steroid bioconversions in the seminal vesicles of clarias gariepinus were studied quantitatively in vitro by tissue incubations with [3h]pregnenolone, [3h]androstenedione and [14c]11 beta-hydroxyandrostenedione, respectively. 2. spawning and non-spawning catfish, collected in the hula nature reserve in northern israel during the spawning period, and non-spawning animals, collected from a fish pond in the same region during the same period, were studied. 3.spawning animals showed a significant ... | 1987 | 3665422 |
| reproductive biology of clarias gariepinus (syn. lazera) burchel (claridae) in lake manzalah, egypt. i. structure of the ovaries. | 1986 | 3781403 | |
| reproductive biology of clarias gariepinus (syn. lazera) burchell (claridae) in lake manzalah, egypt. ii. structure of the testes. | 1986 | 3781404 | |
| a quantitative study of steroid bioconversions in the testis of the african catfish, clarias gariepinus (burchell), under natural spawning and natural and cultivated non-spawning conditions. | quantitative aspects of bioconversions in the testes of the african catfish (clarias gariepinus) were studied in vitro by incubation of tissue with [3h]pregnenolone or [3h]androstenedione. during the breeding period, spawning and non-spawning animals were collected from their natural habitat, the hula nature reserve, in northern israel. in the same period, non-spawning animals were collected from a fish pond in the same region. it was shown that spawning was accompanied by significant changes in ... | 1987 | 3819643 |
| gonadotropin-releasing hormone-immunoreactive neuronal structures in the brain and pituitary of the african catfish, clarias gariepinus (burchell). | the distribution of gonadotropin-releasing hormone (gnrh) immunoreactivity was studied in the african catfish, clarias gariepinus, by means of immunofluorescence and immunoperoxidase techniques. immunoreactive neurons were found throughout the preoptic nucleus (npo). however, only a portion of the secretory perikarya in the npo showed a positive reaction by use of an anti-lhrh serum. numerous immunoreactive fibres were found to enter the pituitary and to terminate in its proximal pars distalis, ... | 1985 | 3896512 |
| steroid metabolism in the testes of the african catfish, clarias gariepinus (burchell), during spawning season, under natural conditions and kept in ponds. | steroid metabolism in the testes of clarias gariepinus, collected in the hula nature reserve and a fish pond in north israel during the spawning season, was studied in vitro by homogenate and tissue incubations with [3h]pregnenolone or [3h]androstenedione as precursors. it could be demonstrated that [3h]pregnenolone was mainly converted via progesterone and 17 alpha-hydroxyprogesterone into androstenedione, 11 beta-hydroxyandrostenedione, and 11 beta-hydroxytestosterone. the final products from ... | 1986 | 3940929 |
| dynamics in immunocytochemical labelling of granules in the gonadotrops of the african catfish clarias gariepinus, as a function of induced release. | 1985 | 4028176 | |
| steroid aromatase, 2-hydroxylase and comt activity in gonadotropic cells of the african catfish, clarias gariepinus. | 2014 | 4028182 | |
| aromatase, estrogen 2-hydroxylase, and catechol-o-methyltransferase activity in isolated, cultured gonadotropic cells of mature african catfish, clarias gariepinus (burchell). | isolated gonadotropic cells were able to convert androstenedione into estrone. subsequently, estrone could be metabolized via catecholestrone into 2-methoxyestrone. from these results it can be concluded that the gonadotropes of mature catfish contain the enzymes aromatase, estrogen 2-hydroxylase, and catechol-o-methyltransferase. the possible function of these enzymes in the steroid negative feedback regulation of gonadotropic hormone release is discussed. | 1985 | 4065528 |
| parasites of south african freshwater fish. ii. redescription of the african species of the genus phyllodistomum braun, 1899 (trematoda: gorgoderinae) and the description of a new species. | during 1980 a survey of the parasites of freshwater fish was conducted in the sabie and crocodile rivers in the southern part of the kruger national park, transvaal. a new species of phyllodistomum, braun, 1899, for which the name phyllodistomum bavuri is proposed, was found in the urinary bladder of many of the catfish, clarias gariepinus (burchell, 1822), examined. the new species resembles phyllodistomum linguale odhner, 1902 and phyllodistomum vanderwaali prudhoe & hussey, 1977, but may be d ... | 1984 | 6493727 |
| parasites of south african freshwater fish. i. some nematodes of the catfish [clarias gariepinus (burchell, 1822)] from the hartbeespoort dam. | a seasonal study of the parasites of fish in the hartbeespoort dam was undertaken in 1979. this paper deals with 4 nematode species recovered from catfish, namely, paracamallanus cyathopharynx (baylis, 1923), procamallanus laeviconchus (wedl, 1862), contracaecum sp. and skrjabinocara sp. total numbers of parasites recovered are tabulated and their seasonal variation illustrated diagrammatically. paracamallanus cyathopharynx was recovered from 23 out of 43 catfish examined and procamallanus laevi ... | 1982 | 7122064 |
| the haematology and histology of the haemopoietic organs of south african freshwater fish. iii. the leucocytes, plasma cells and macrophages of clarias gariepinus and sarotherodon mossambicus. | the various leucocytes, plasma cells and macrophages are described and illustrated. eosinophils and basophils are lacking in clarias gariepinus but present in sarotherodon mossambicus. the leucocytes of c. gariepinus resemble those found in mammals, as do the plasma cells and macrophages of both species. a possible mechanism for their formation is postulated. | 1981 | 7345385 |
| the haemocytology and histology of the haemopoietic organs of south african freshwater fish. iv. ultrastructure of some cells of clarias gariepinus and sarotherodon mossambicus. | this paper describes the ultrastructure of several cells found in the blood and haemopoietic tissues of the catfish (clarias gariepinus) and the mozambique bream (sarotherodon mossambicus). the cells are haemocytoblasts, small lymphoid haemoblasts, thrombocytes, monocytes, lymphocytes, developing and mature neutrophilic granulocytes, plasma cells and macrophages. the various organelles normally found in mammalian haemocytes, plasma cells and macrophages were observed in those of fish. with the e ... | 1981 | 7345386 |
| the haemocytology and histology of the haemopoietic organs of south african freshwater fish. ii. erythrocytes ad thrombocytes of clarias gariepinus and sarotherodon mossambicus. | this paper describes the light-microscopic appearance of both the erythrocytes and the thrombocytes and their developmental stages of catfish (clarias gariepinus) and mozambique bream (sarotherodon mossambicus). apart from some minor differences in the shape and staining affinities of the polychromatophilic erythrocytes, the erythrocytic series is similar in catfish and bream. the thrombocytes and the reactive stages of thrombocytes of both species are similar to those of birds. a possible mecha ... | 1980 | 7426115 |
| micronucleated erythrocytes as an assay to assess actions by physical and chemical genotoxic agents in clarias gariepinus. | an in vivo study on the effects of both physical (gamma-radiation) and chemical (mitomycin c) genotoxic agents was carried out with the catfish species, clarias gariepinus. the fish were either exposed to gamma-radiation at doses of 0-9 gy or injected intraperitoneally with mitomycin c at concentrations of 0-2 mg/kg. micronucleated erythrocytes were sampled from 0 to 60 days post treatment. data obtained showed a time-dependent response of the induction of micronucleated erythrocytes with both g ... | 1994 | 7519306 |
| the effect of copper on the blood chemistry of clarias gariepinus (clariidae). | environmental stressors, both natural and humanly induced, could cause changes in cellular function which alter the physiology of organ systems in fish. the need to comprehend and predict the condition which stress metals will pose on fish, and extrapolate the effect of pollutants from laboratory to population levels, have forced scientists to search for physiological and biochemical indicators of health and sublethal toxicant effects. hematological evaluation of fish blood provides valuable fac ... | 1994 | 7533710 |
| gas chromatographic-mass spectrometric (gc-ms) analysis of gonadal steroids in plasma of the male african catfish, clarias gariepinus: effects of castration or treatment with gonadotropin releasing hormone analogue. | to identify testicular steroids that may be involved in the feedback mechanisms of the hypothalamus-pituitary-gonad axis in african catfish, clarias gariepinus, steroids, which are known to be produced by the testis in vitro, were identified and quantified in blood plasma before and after castration using gas chromatography followed by mass spectrometry. before castration 20 testicular steroids were detected. quantitatively dominant steroids were testosterone (16.9 +/- 4.3 ng/ml), androstenedion ... | 1994 | 7851729 |
| parasites of south african freshwater fish. vi. nematode parasites of some fish species in the kruger national park. | the nematode parasites of 30 spot-tailed robbers, brycinus imberi, five tiger-fish, hydrocynus vittatus, 77 large-scaled yellowfish. barbus marequensis, two mudsuckers, labeo molybdinus, 114 catfish, clarias gariepinus, 46 silver barbel, schilbe intermedius, 66 squeakers, synodontis zambezensis, three eels, anguilla spp., 83 mozambique bream, oreochromis mossambicus, 81 red-breasted bream, tilapia rendalli swierstrae and 32 large-mouthed bream, serranochromis meridianus, caught in the sabie, cro ... | 1994 | 7898896 |
| isolation, characterization and expression of cdnas encoding the catfish-type and chicken-ii-type gonadotropin-releasing-hormone precursors in the african catfish. | the cdnas encoding the catfish prepro-gonadotropin-releasing hormone and the chicken prepro-gonadotropin-releasing hormone ii of the african catfish (clarias gariepinus) have been isolated and sequenced. the catfish gonadotropin-releasing-hormone precursor and the chicken gonadotropin-releasing-hormone-ii precursor have the same overall architecture as other gonadotropin-releasing-hormone precursors identified so far; each is composed of a signal peptide, gonadotropin-releasing hormone and a gon ... | 1994 | 8020492 |
| replication, expression, and fate of foreign dna during embryonic and larval development of the african catfish (clarias gariepinus). | the transfer of exogenous dna in fish represents a powerful strategy to study the regulation of gene expression in vivo. the african catfish (clarias gariepinus) was chosen for this study because of its scientific and economic importance due to its easy husbandry, its short developmental period, and its value as a protein source in africa and asia. fertilized eggs (1- and 2-cell stage) were cytoplasmatically injected with either supercoiled or linearized plasmids harboring the fusion genes encod ... | 1994 | 8087184 |
| presence of gonadotropin-releasing hormone (gnrh) binding sites and compounds with gnrh-like activity in the ovary of african catfish, clarias gariepinus. | gnrh binding was characterized in the african catfish ovary by use of an analog of salmon gnrh (sgnrh- ; [d-arg6, trp7, leu8, pro9-net]-gnrh) as a labeled ligand. binding of sgnrh-a to catfish ovarian membrane preparation was found to be saturable, displaceable, reversible, and dependent on time, temperature, and tissue concentration. optimal binding was achieved after 70 min of incubation at room temperature (approximately 22 degrees c) at ph 7.6. addition of unlabeled sgnrh-a displaced the bou ... | 1994 | 8167236 |
| effects of gonadotrophin-releasing hormone during the pubertal development of the male african catfish (clarias gariepinus): gonadotrophin and androgen levels in plasma. | the sensitivity of the pituitary to gonadotrophin-releasing hormone (gnrh) and that of the testis to gonadotrophin (gth) was monitored in african catfish in vivo at different stages of pubertal development (20, 21, 24, 31, 39, 42 and 49 weeks of age). the fish were injected i.p. with chicken gnrh-ii (cgnrh-ii) or catfish gnrh (cfgnrh), their two endogenous gnrhs. blood samples were collected to quantify lh-like gth-ii and three androgens 11-ketotestosterone (11-kt), testosterone and 11 beta-hydr ... | 1994 | 8169559 |
| treatment of fish parasites. 11. morphogenesis of henneguya laterocapsulata landsberg, 1987 (myxosporea, myxozoa), and the effects of a new triazine derivative, hoe 092 v, on its developmental stages: a light and electron microscopy study. | the ultrastructure of sporogenesis was studied in henneguya laterocapsulata parasitizing the skin of hybrid catfish (clarias gariepinus x heterobranchus bidorsalis) in nigeria. sporogenesis started when a generative cell was surrounded by a second nondividing cell (i.e., envelope cell). by subsequent divisions of the generative cell, ten cells were produced, which finally became arranged into two spore-producing units. each unit consisted of a binucleate sporoplasm, two capsulogenic cells, and t ... | 1993 | 8295904 |
| parasites of south african freshwater fish. v. description of two new species of the genus spinitectus fourment, 1883 (nematoda: cystidicolidae). | spinitectus petterae n. sp. was recovered from catfish, clarias gariepinus (burchell, 1822) and spinitectus zambezensis n. sp. from squeakers, synodontis zambezensis peters, 1852 in the kruger national park. the nematodes are easily differentiated from each other in that spinitectus petterae has an additional pair of papillae on the pseudolabia, the males have considerably longer spicules and a different configuration of the tips of the left spicule, and the vulva of the females is considerably ... | 1993 | 8332324 |
| two gonadotropin-releasing hormones in the african catfish, clarias gariepinus: localization, pituitary receptor binding, and gonadotropin release activity. | two gnrh peptides have recently been identified in brain extracts of the african catfish, chicken-ii gnrh ([his5,trp7,tyr8]gnrh, cgnrh-ii) and catfish gnrh ([his5,asn8]gnrh, cfgnrh). using three experimental approaches, we investigated whether both peptides are involved in the regulation of pituitary gonadotropin secretion. first, the presence of cfgnrh and cgnrh-ii in the pituitary was studied by biochemical and immunocytochemical techniques, as gnrh reaches the pituitary via axonal transport i ... | 1993 | 8404596 |
| the effect of dietary l-carnitine on the growth performance in fingerlings of the african catfish (clarias gariepinus) in relation to dietary lipid. | the effect of dietary l-carnitine on the growth and growth efficiency of african catfish (clarias gariepinus, burchell 1822) fingerlings was investigated. six dietary levels of l-carnitine, varying from the control level (about 125 mg/kg) to 3920 mg/kg, were each tested at two dietary lipid levels (96 and 155 g/kg). the diets were isonitrogenous and were fed to thirty-six experimental groups of 100 fish weighing 5 g at a feeding level of 25.2 g/kg live weight (w)0.8 per d, during 18 d. the avera ... | 1993 | 8457535 |
| efficient transient expression system based on square pulse electroporation and in vivo luciferase assay of fertilized fish eggs. | electroporation mediated dna transfer into fish eggs has been improved by using a train of square pulses. fertilized eggs of african catfish (clarias gariepinus), zebrafish (brachydanio rerio) and rosy barb (barbus conchonius) were dechorionated enzymatically followed by application of pulses. efficiency of plasmid dna delivery was significantly increased by applying multiple pulses on dechorionated eggs. optimization of physical parameters such as field strength, pulse width and pulse numbers r ... | 1993 | 8504855 |
| pubertal development of male african catfish (clarias gariepinus). pituitary ultrastructure and responsiveness to gonadotropin-releasing hormone. | pubertal development was studied in male african catfish by immunocytochemical examination of pituitary gonadotrophs and by monitoring the responsiveness of gonadotropin (gth) secretion to salmon gnrh analogue (sgnrha) in vitro. experiments were carried out with fish from 9 to 28 wk of age. fish were assigned to four groups, according to the stage of spermatogenesis: i, spermatogonia alone; ii, spermatogonia and spermatocytes; iii, spermatogonia, spermatocytes, and spermatids; iv, all germ cell ... | 1995 | 8547491 |
| isolation and characterization of microsatellite markers in the african catfish clarias gariepinus (burchell, 1822). | 1996 | 8873472 | |
| one-step immunoaffinity purification and partial characterization of hypophyseal growth hormone from the african catfish, clarias gariepinus (burchell). | growth hormone (gh) was purified from african catfish (clarias gariepinus) pituitary extracts in a single step by use of immunoaffinity chromatography. a monoclonal antibody to chicken gh, which labels the catfish hypophyseal somatotropes in immunocytochemistry, was coupled to cnbr-activated sepharose, and crude alkaline pituitary extracts were run over the immunoadsorbent. reversed-phase high-performance liquid chromatography analysis of the eluted material suggested heterogeneity, whereas silv ... | 1996 | 8925443 |
| a radioimmunoassay for african catfish growth hormone: validation and effects of substances modulating the release of growth hormone. | a highly sensitive radioimmunoassay has been developed for measuring plasma growth hormone (gh) concentrations in the african catfish (clarias gariepinus). the lower detection limit of the assay was 0.1 ng/ml and the standard curve had an ed50 value of 0.5 ng/ml. the validity of the assay was established and the effects of several neurotransmitters on the release of gh were examined. in vitro experiments, using a static culture system for dispersed pituitary cells, demonstrated that the gh relea ... | 1996 | 8930605 |
| gonadotrophs but not somatotrophs carry gonadotrophin-releasing hormone receptors: receptor localisation, intracellular calcium, and gonadotrophin and gh release. | gonadotrophs are the primary target cells for gnrh in the pituitary. however, during a limited period of neonatal life in the rat, lactotrophs and somatotrophs respond to gnrh as well. also, in the adults of a number of teleost fishes (e.g. carp, goldfish, and tilapia but not trout), gnrh is a potent gh secretagogue. in studying hypophysiotrophic actions of the two forms of gnrh present in the african catfish (clarias gariepinus), chicken gnrh-ii ([his5,trp7,tyr8]gnrh; cgnrh-ii) and catfish gnrh ... | 1997 | 9071965 |
| control of microbiological quality and shelf-life of catfish (clarias gariepinus) by chemical preservatives and smoking. | fresh catfish (clarias gariepinus) were subjected to different concentrations of sodium benzoate or potasium sorbate and smoked traditionally before evaluation for microbiological, chemical and organoleptic characteristics during ambient tropical storage. unsmoked fish samples showed diverse microflora (enterobacter, escherichia, serratia, bacillus, staphylococcus, streptococcus, penicillium, aspergillus and achlya genera) while smoked samples were dominated by gram-positive bacterial flora (bac ... | 1996 | 9072517 |
| effect of route and frequency of administration of apomorphine on growth hormone release in african catfish (clarias gariepinus). | apomorphine is known to stimulate growth hormone release in african catfish following an intraperitoneal (ip) injection. in the present study the effect of apomorphine (5 or 20 mg/kg body weight) on plasma gh levels was evaluated after gastro-intestinal or parenteral delivery. apomorphine increased the plasma gh concentration regardless of the route of administration, indicating that apomorphine can be absorbed from the intestinal tract. the effect of repeated administration of apomorphine diffe ... | 1997 | 9150417 |
| production of fish chimeras from embryonic cells. | the efficiency of two cell-transplantation methods were compared for the production of embryonic cell derived fish chimeras. the classic microinjection technique (blastula stage donor cells are microinjected into blastula embryos) was compared to a novel aggregation method for fish developed by our group. this method utilises the ability of dechorionated fish embryos to aggregate. morula cells dissociated in ca2+, mg2+ free medium were aggregated to recipient embryos of different developmental s ... | 1997 | 9199704 |
| pituitary gonadotrophs are strongly activated at the beginning of spermatogenesis in african catfish, clarias gariepinus. | pituitary gonadotrophs were studied in male african catfish between 1 and 37 wk of age using antisera against the lh subunits for immunohistological and radioimmunological purposes, and crna probes for in situ hybridization. immunoreactive material was already detectable at the earliest age examined. in juveniles, the signal for the common glycoprotein alpha subunit (gp alpha) was stronger than that for the lh beta subunit. accordingly, an excess of radioimmunoassayable gp alpha 100 times that o ... | 1997 | 9209092 |
| the cranial lateral-line system in clarias gariepinus (burchell, 1822) (siluroidei:clariidae): morphology and development of canal related bones. | the cranial lateral-line system, as well as the canal bones are well developed in the african clariid catfish clarias gariepinus. a generalised cranial lateral-line pattern is present (supraorbital, infraorbital, preoperculo-mandibular, otic, postotic and temporal canals). the supratemporal commissure, however, is missing, although a supraorbital commissure is present (formed through the fusion of the epiphysial branches). in addition to canals, some pit-lines are present which cover both canal ... | 1997 | 9263757 |
| histopathological changes induced by environmental stress in common carp, japanese coloured carp, european eel, and african catfish. | histopathological changes caused by stress during catching and transport were examined in four fish species, the common carp (cyprinus carpio), the japanese coloured carp (koi, the coloured variant of the asian carp, cyprinus carpio haematopterus), the european eel (anguilla anguilla), and the african catfish (clarias gariepinus). in all species, the goblet cells of the gills and skin were decreased in number and slight detachment of the epithelium of the secondary gill lamellae was seen. loss o ... | 1997 | 9270124 |
| morphological abnormalities in african catfish (clarias gariepinus) larvae exposed to malathion. | newly hatched larvae of clarias gariepinus were exposed to malathion concentrations ranging from 0.3 mg/l to 5.0 mg/l. their development was observed through five days posthatch, i.e., the stage in which the vertebral elements are not yet present and the notochord is the only functional body axis. a significant higher proportion of c. gariepinus larvae with deformed notochord and pericardial edema was detected at 2.5 mg/l malathion and higher. the results suggested that (1) deformed notochord wa ... | 1997 | 9377105 |
| modulation of testicular androgen production in adolescent african catfish (clarias gariepinus). | at 6 months of age the first spermatozoa appear in the testes of the african catfish considered to be adolescent, since the development to adulthood (12 months of age) is accompanied by further morphological and functional differentiation of leydig cells. there are increasing plasma levels of 11-ketotestosterone (11-kt) and an increasing responsiveness to luteinizing hormone (lh) of testicular androgen secretion in vitro. whether treatment of adolescent males with key hormones of the brain-pitui ... | 1997 | 9378274 |
| characterization of mboi satellites in cirrhina mrigala and clarias batrachus (pisces). | we have cloned and characterized two highly reiterated, tandemly repeated, and a+t rich mboi dna fragments, one in cirrhina mrigala (cyprinidae), with a monomer size of 266 bp, and one in clarias batrachus (clariidae), with a monomer size of 227 bp. the mboi fragment in c. mrigala is species-specific and absent in other carps, such as catla catla and labeo rohita. the mboi fragment in c. batrachus was also present in two other catfishes tested, namely clarias gariepinus and heteropneustes fossil ... | 1998 | 9549057 |
| toxicity of ozone to fish larvae and daphnia magna. | ozone can be used as an alternative to chlorination to control biofouling in cooling water systems. the possible negative environmental impact of a discharge of ozone-containing cooling water was investigated. the acute toxicity of dissolved ozone was determined for fish larvae of three species [cyprinus carpio (at 27 degrees c), leuciscus idus (at 27 degrees c) and clarias gariepinus (at 32 degrees c)] and to daphnia magna (at 21 and 27 degrees c). the results indicate that ozone is very harmfu ... | 1998 | 9756705 |
| testosterone accelerates the development of the catfish gnrh system in the brain of immature african catfish (clarias gariepinus). | the effects of two endogenous steroids on the maturation of the catfish gnrh and the chicken gnrh-ii system in the african catfish were investigated. immature fish (2 weeks of age, which is before sexual differentiation; thus male and female genotypes present) were fed with food pellets containing either testosterone (t), 11beta-hydroxyandrostenedione (oha) or no steroid (control). after 2 and 4 weeks of treatment, the effects on the two gnrh systems were investigated immunocytochemically, using ... | 1998 | 9843644 |
| sex steroids and the initiation of puberty in male african catfish (clarias gariepinus). | the effects of sex steroids on spermatogenesis and testicular androgen secretion were studied in juvenile (spermatogonia present in testes) african catfish. fish were implanted with silastic pellets containing 11-ketotestosterone (kt), 11beta-hydroxyandrostenedione (oha), androstenetrione (oa), androstenedione (a), testosterone (t), 5alpha-dihydrotestosterone (dht), or estradiol-17beta (e2). control groups received steroid-free pellets. two weeks later, testis tissue fragments were incubated wit ... | 1998 | 9843868 |
| innervation and control of the adenohypophysis by hypothalamic peptidergic neurons in teleost fishes: em immunohistochemical evidence. | previous light microscopic studies have revealed neuropeptide-immunoreactive neurosecretory fibers in the teleostean neurohypophysis, and ultrastructural work has reported direct innervation of endocrine cells by the terminals of fibers penetrating the adenohypophysis. this paper reviews our recent data from ultrastructural, immunohistochemical, receptor localization, and superfusion studies, which suggest a role for neuropeptides in the control of teleost pituitary secretion. we have used a com ... | 1999 | 9915561 |
| effects of dieldrin on life stages of the african catfish, clarias gariepinus (burchell). | early life stages of clarias gariepinus were found to be less sensitive to acute dieldrin toxicity than were those of nile tilapia, oreochromis niloticus; 96-h lc50 values for 37-day-old fry were 11. 7 and 4.95 microg liter-1, respectively. the growth of c. gariepinus fry was unaffected by 30 days of exposure to 2.4 microg liter-1 dieldrin under static conditions with water renewal every 96 h, whereas growth of o. niloticus fry was significantly reduced. adult c. gariepinus exposed to dieldrin f ... | 1999 | 9931234 |
| susceptibility of embryonic and larval african catfish (clarias gariepinus) to toxicants. | 1999 | 9933322 | |
| the african monogenean gyrodactylid genus macrogyrodactylus malmberg, 1957, and the reporting of three species of the genus of clarias gariepinus in south africa. | three different species of the genus macrogyrodactylus malmberg, 1957, collected from the gills and skin of clarias gariepinus (burchell, 1822) from the middle letaba dam and mokgoma-matlala dam in south africa were examined and identified. this is the first record of a species of the genus in south africa. the three species are m. congolensis (prudhoe, 1957)--found on the skin, m. clarii gussev, 1961 and m. karibae douellou & chishawa, 1995--found on the gills. the last species is elevated to t ... | 1998 | 10192833 |
| androgen-induced changes in leydig cell ultrastructure and steroidogenesis in juvenile african catfish, clarias gariepinus. | the present report focuses on the mechanism(s) involved in the steroid-induced decrease of androgen production in immature african catfish testes that was observed in previous studies. juvenile animals were implanted with silastic pellets containing different 11-oxygenated androgens (11-ketotestosterone, kt; 11 beta-hydroxyandrostenedione, oha; 11-ketoandrostenedione, ka), testosterone (t) or estradiol-17 beta (e2). control groups received steroid-free pellets. two weeks later, testis tissue fra ... | 1999 | 10470499 |
| structure and vascularization of the ventricular myocardium of piaractus mesopotamicus and clarias gariepinus (teleostei). | the structural characteristics of the ventricular myocardium and the arterial distribution of the ventricular wall were studied in two freshwater teleost fish species (piaractus mesopotamicus and clarias gariepinus). the ventricular myocardium consists of two distinct layers, an external compact layer and an internal spongy layer. in piaractus mesopotamicus the compact layer contains fibres with an external longitudinal arrangement and an internal circular arrangement. the arterial vascularizati ... | 1999 | 10488629 |
| a comparative study of spermatozoal chromatin using acridine orange staining and flow cytometry. | spermatozoa obtained from fish (clarias gariepinus), human (homo sapiens), turkeys (meleagris gallapova), rats (rattus norvegicus), hamsters (mesocricetus auratus), and monkeys (macaca fascicularis) were stained with acridine orange before measuring fluorescence by flow cytometry. these mature sperm from various species produced different intensities of fluorescence while displaying similar ratios of red/green fluorescence. comparison of the green fluorescence values for the various species show ... | 1999 | 10629954 |
| inhibitory and stimulatory interactions between endogenous gonadotropin-releasing hormones in the african catfish (clarias gariepinus). | in the brain of all vertebrate classes, chicken (c) gnrh-ii ([his(5), trp(7),tyr(8)]gnrh, cgnrh-ii) is expressed in the mesencephalon. in addition, at least one other form of gnrh is expressed in the preoptical area/hypothalamus. in the human pituitary stalk and the mouse median eminence, cgnrh-ii is present together with mammalian gnrh. similarly, in the pituitary of several teleost fish (e.g., goldfish and eel, but not salmon or trout), a teleost gnrh is found together with cgnrh-ii. these gnr ... | 2000 | 10684817 |
| regulation of steady-state luteinizing hormone messenger ribonucleic acid levels, de novo synthesis, and release by sex steroids in primary pituitary cell cultures of male african catfish, clarias gariepinus. | primary pituitary cell cultures from sexually mature adult male african catfish, clarias gariepinus, were used to study the regulation of lh biosynthesis by sex steroids. the cell cultures were exposed to testosterone (t), estradiol (e(2)), or 5alpha-dihydrotestosterone (dht), a nonaromatizable analogue of t, and to the likewise nonaromatizable 11-ketotestosterone (kt) and 11beta-hydroxyandrostenedione (oha), physiologically relevant androgens in fish. both t and e(2) elevated glycoprotein alpha ... | 2000 | 10727254 |
| physical constraints on body size in teleost embryos. | all members of the subphylum "vertebrata" display the characteristics of the vertebrate body plan. these characteristics become apparent during the phylotypic period, in which all vertebrate embryos have a similar body shape and internal organization. phylogenetic constraints probably limit the morphological variation during the phylotypic period. physical laws, however, also limit growth and morphogenesis in embryos. we investigated to what extent oxygen availability-as a physical constraint-mi ... | 2000 | 10772852 |
| growth response of african catfish, clarias gariepinus (burchell) to varied protein and lipid levels. | to study the growth response of african catfish (clarias gariepinus) to the diets containing two protein (30 and 35%) and two lipid levels (12 and 18%) in a closed recirculatory system for 60 days, fish were fed to satiation twice daily. the experiment was carried out in triplicate groups. fortnightly sampling of fish and water samples was carried out. the best result in terms of growth was obtained with the diet containing 34.62% protein and 12.12% lipid. the protein to lipid ratio was 18.57 in ... | 1999 | 10783758 |
| mechanisms of gastrointestinal copper absorption in the african walking catfish: copper dose-effects and a novel anion-dependent pathway in the intestine. | in mammals, copper (cu) absorption occurs mostly in the small intestine, and some of the cu transporters involved in its uptake have been characterised. in fish, however, the regions of the gut involved in cu absorption and the membrane transport mechanisms responsible for gastrointestinal cu uptake are unknown. everted gut sacs and isolated perfused intestine of clarias gariepinus were used to explore cu absorption (at 22 degrees c). gut sacs exposed to 100 micromol l(-1) mucosal solution cu ([ ... | 2000 | 10887075 |
| gonadotropin-releasing hormone fibers innervate the pituitary of the male african catfish (clarias gariepinus) during puberty. | the development of the catfish gonadotropin-releasing hormone (cfgnrh) fiber network in the pituitary of male african catfish (clarias gariepinus) was investigated in relation to puberty. double immunolabeling studied by confocal laser scanning microscopy revealed a concomitant development of gonadotropes and of pituitary cfgnrh innervation during the first wave of spermatogenesis. catfish gnrh-immunoreactive fibers in the proximal pars distalis (ppd) of the pituitary were initially observed at ... | 2000 | 11070429 |
| sperm cryopreservation of african catfish, clarias gariepinus: cryoprotectants, freezing rates and sperm:egg dilution ratio. | methods for cryopreserving spermatozoa and optimizing sperm:egg dilution ratio in african catfish clarias gariepinus were developed. five percent to 25% dmso and methanol were tested as cryoprotectants, by diluting semen in ginzburg fish ringer and freezing in 1-milliliter cryovials in a programmable freezer. to avoid an excess of spermatozoa per egg, post-thaw semen was diluted 1:20, 1:200 or 1:2,000 before fertilization. highest hatching rates were obtained by spermatozoa frozen in 10% methano ... | 2000 | 11191864 |
| ontogenetic shift in mouth opening mechanisms in a catfish (clariidae, siluriformes): a response to increasing functional demands. | during ontogeny, larval fish have to deal with increasing nutritional and respiratory demands as they grow. as early ontogeny is characterized by an increasing complexity of moving structural elements composing a fish skull, some constraints will have to be met when developing mechanisms, which enable feeding and respiration, arise at a certain developmental stage. this article focuses on the presence/absence of a possible functional response in mouth opening during ontogeny in clarias gariepinu ... | 2001 | 11223928 |
| quality control of refrigerated and cryopreserved semen using computer-assisted sperm analysis (casa), viable staining and standardized fertilization in african catfish (clarias gariepinus). | a new integrated approach including computer-assisted sperm analysis (casa), viability staining and fertilization was used to study the quality of cryodiluents used in fish sperm cryopreservation. as an example the sperm quality of an african catfish, clarias gariepinus (burchell, 1822), was assessed by its fertilizing ability, motility and viability at day 0 (fresh), after 2 days' storage at 4 degreesc and after 2 days, 5 months and 10 months frozen at -196 degreesc using solutions containing d ... | 2001 | 11245263 |
| steroid hormones stimulate gonadotrophs in juvenile male african catfish (clarias gariepinus). | in juvenile african catfish (clarias gariepinus), the pituitary lh content strongly increased after the beginning of spermatogonial proliferation. we hypothesized that a signal of testicular origin is involved in stimulating the gonadotrophs. we investigated the effects of castration and sex steroid treatment on gonadotrophs in juvenile males by quantifying lh production and release and lh subunit transcript levels and by examining gonadotroph morphology and proliferation. castration reduced but ... | 2001 | 11319139 |
| trace metal accumulation in clarias gariepinus (teugels) exposed to sublethal levels of tannery effluent. | the concentration and distribution of cr, cu, pb and zn among the tissues of a freshwater fish, clarias gariepinus exposed to combined (composite) tannery effluent was investigated at two sublethal concentrations (2 and 6%) in static bioassay for 8 weeks. the distribution of the four metals in fish was of the order of pb > cr > cu > zn and the accumulation was found to be dose- and time-dependent. the metal levels in the liver were significantly higher (p > 0.05) than other tissues. this was fol ... | 2001 | 11346032 |
| discrepancy between molecular structure and ligand selectivity of a testicular follicle-stimulating hormone receptor of the african catfish (clarias gariepinus). | a putative fsh receptor (fsh-r) cdna was cloned from african catfish testis. alignment of the deduced amino acid sequence with other (putative) glycoprotein hormone receptors and analysis of the african catfish gene indicated that the cloned receptor belonged to the fsh receptor subfamily. catfish fsh-r (cffsh-r) mrna expression was observed in testis and ovary; abundant mrna expression was also detected in seminal vesicles. the isolated cdna encoded a functional receptor since its transient exp ... | 2001 | 11369589 |
| gonadal steroids and the maturation of the species-specific gonadotropin-releasing hormone system in brain and pituitary of the male african catfish (clarias gariepinus). | the effect of testosterone (t), 11-ketotestosterone (kt) and estradiol (e(2)) on the development of the catfish gonadotropin-releasing hormone system (cfgnrh) of male african catfish (clarias gariepinus), at the onset of puberty [between 10 and 12 weeks post hatching (ph)] was investigated. the cfgnrh neurons, located in the ventral forebrain, were visualized by immunofluorescence and their numbers were determined and the amounts of cfgnrh-associated peptide (cfgap) in the pituitary were measure ... | 2001 | 11399472 |
| pathways for urea production during early life of an air-breathing teleost, the african catfish clarias gariepinus burchell. | embryos and larvae of the african catfish clarias gariepinus excrete significant quantities of urea. the present study focused on the potential urea-generating pathways during early development of this teleost; uricolysis, argininolysis and the ornithine-urea cycle (ouc). uricase, allantoinase, allantoicase and ureidoglycollate lyase of the uricolytic pathway were expressed in all early life stages and in adult liver of c. gariepinus. uricase activity increased in starved larvae compared with yo ... | 2001 | 11441057 |
| development of three distinct gnrh neuron populations expressing two different gnrh forms in the brain of the african catfish (clarias gariepinus). | the early development of both the catfish gonadotropin-releasing hormone (cfgnrh)- and the chicken gnrh-ii (cgnrh-ii) system was investigated in african catfish by immunocytochemistry by using antibodies against the gnrh-associated peptide (gap) of the respective preprohormones. weakly cfgnrh-immunoreactive (ir) neurons and fibers were present at 2 weeks after hatching (ph) but only in the ventral telencephalon and pituitary. two weeks later, cfgnrh fibers and neurons were also observed in more ... | 2001 | 11494258 |
| the bathyclarias-clarias species flock. a new model to understand rapid speciation in african great lakes. | phylogenetic relationships between seven species of the catfish species flock from lake malawi (genus bathyclarias) and other clariid catfish have been investigated using cytochrome b partial sequences. here we demonstrate that this species flock originated from a widespread, generalist species, clarias gariepinus, still occurring in the lake. bathyclarias species and their ancestor c. gariepinus form a simple model that can be used to understand the mechanisms of adaptation and rapid speciation ... | 2001 | 11510413 |
| effects of 17alpha-methyltestosterone on seminal vesicle development and semen release response in the african catfish, clarias gariepinus. | the effects of 17alpha-methyltestosterone on seminal vesicle development in the african catfish, clarias gariepinus, were investigated in an attempt to improve semen collection from this species. treatment of larvae with dietary 17alpha-methyltestosterone at 50 mg kg(-1) for days 12-33 or days 12-40 after hatching, or at 20 mg kg(-1) for days 12-26, 12-33, 12-40 or 12-47 after hatching inhibited the development of the seminal vesicle finger-like extensions in male catfish, but did not affect the ... | 2001 | 11690543 |
| chaetotaxy of the monogeneans macrogyrodactylus clarii and m. congolensis from the gills and skin of the catfish clarias gariepinus in egypt, with a note on argentophilic elements in the nervous system. | a comparison has been made between the chaetotaxy of the gyrodactylid monogeneans macrogyrodactylus clarii gussev, 1961 and m. congolensis (prudhoe, 1957) yamaguti, 1963 from the gills and skin, respectively, of the catfish clarias gariepinus (burchell) from the river nile in egypt. bilaterally arranged argentophilic structures on the surface of these parasites are presumed to be sensilla and are more abundant in m. clarii than in m. congolensis especially on the ventral surface (124 vs. 66). in ... | 2001 | 11699655 |