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At least 793 records · Page 44Linked to original sources
PubMed1990

Effects of vitamin D3, 25(OH) vitamin D3, 24,25(OH)2 vitamin D3, and 1,25(OH)2 vitamin D3 on the in vitro intestinal calcium absorption in the marine teleost, Atlantic cod (Gadus morhua).

The role of vitamin D3, 25(OH) vitamin D3, 24,25(OH)2 vitamin D3, and 1,25(OH)2 vitamin D3, in the regulation of calcium absorption across the intestine in the marine teleost, Gadus morhua, was investigated. The intestine was perfused, in vitro, both vascularly and through the intestinal lumen, and the calcium influx was measured using 45Ca. Vitamin D3 and its metabolites were tested in perfusate concentrations of 10 ng.ml-1.25(OH)D3 increased the intestinal calcium uptake by 65%, while 24,25(OH)2D3 decreased it by 36%. Vitamin D3 and 1,25(OH)2D3, on the other hand, did not affect the calcium influx across the intestinal mucosa. This indicates that 25(OH)D3 and 24,25(OH)2D3 may be active regulators of calcium transport across the intestine of Atlantic cod.

24,25-Dihydroxyvitamin D 3↗
PubMed1990

Regulation of the testicular activity in the marine teleost fish, Gobius paganellus.

Seasonal variations of intratesticular steroid hormones (androgens and estradiol-17 beta) and spermatogenic activity have been studied in the marine teleost fish, Gobius paganellus. In addition, in vivo and in vitro experiments have been carried out in order to investigate the control of androgen production by the testis. While estradiol was never detected, androgens were at low values in autumn and reached maximal levels in spring concomitantly with the highest testis weight and the highest efficiency of the spermatogenic wave. In vitro incubations were carried out using ovine luteinizing hormone (oLH) (400, 4000, and 40,000 micrograms/liter; 20 degrees for 6 and 24 hr). The effective dose 40,000 micrograms/liter was used to induce androgen stimulation in both autumn and spring testes. The responsiveness to oLH was enhanced in spring testis. Estradiol and a gonadotropin-releasing hormone analog GnRHA (HOE766) were ineffective in modulating androgen production either alone (1-1000 nmol/liter) or in concert with oLH during short-term incubations. In intact animals, GnRHA elicited, 3 hr after the injection (10 micrograms), a three-fold increase of intratesticular androgen content. In conclusion, we show that the annual androgen profile in G. paganellus parallels the spermatogenic activity and that the androgen production is not affected in these experimental conditions by putative intratesticular factors (e.g., estradiol-17 beta and GnRH-like substances) which, conversely, are effective in inducing androgen changes in several vertebrate species.

Androgens↗
PubMed1991

Effects of osmotic pressure and somatostatin on the cAMP messenger system of the osmosensitive prolactin cell of a teleost fish, the tilapia (Oreochromis mossambicus).

Altered osmotic pressure and somatostatin (SRIF) rapidly alter prolactin (PRL) release from the pituitary gland of the euryhaline teleost, the tilapia. The present studies were undertaken to determine whether altered osmotic pressure and SRIF influence cAMP metabolism in a manner that is correlated with the pattern of PRL release observed previously. Although PRL release is stimulated within 10-20 min when medium osmotic pressure is reduced, cAMP metabolism was not altered. However, following 1 hr of incubation in the presence of IBMX, cAMP accumulation was higher in PRL tissue exposed to medium of reduced osmotic pressure. This suggests that cAMP does not initiate an increase in PRL release in response to reduced osmotic pressure. By contrast, SRIF reduced the forskolin-stimulated increase in cAMP levels in a manner consistent with its rapid effects on PRL release. Moreover, the ability of SRIF to suppress the forskolin-stimulated increase in cAMP levels suggests that SRIF may act to render adenylate cyclase less responsive to direct stimulation by forskolin.

1-Methyl-3-isobutylxanthine↗
PubMed1991

Estradiol-induced vitellogenin gene expression in a teleost fish, Oreochromis aureus.

Vitellogenesis presents a versatile model for the study of hormone-induced gene expression. We report here the effects of estradiol-17 beta-propionate on vitellogenin gene expression in male Oreochromis aureus, a teleost fish. Vitellogenin mRNA of 6500 nucleotides has been elucidated from the livers of female and estradiol-treated male O. aureus. By hybridization with a specific O. aureus cDNA probe, the vitellogenin mRNA transcript was detected as early as 1 hr following primary and secondary estradiol-stimulations, although for the latter, the rate of accumulation of vitellogenin-specific mRNA was 20-fold higher. The vitellogenin mRNA peaked at 72 and 48 hr, respectively, for primary and secondary stimulations. At the translational level, the increase in plasma vitellogenin was further enhanced during the secondary stimulation. There was a distinct shift in the peak of plasma vitellogenin from Day 14 in the primary induction to Day 3 in the secondary stimulation. The plasma vitellogenin presented in two forms, 300 and 500 kDa, both of which were immunologically confirmed by Western blot analysis to be vitellogenin proteins.

Animals↗
PubMed1992

Somatostatin 14- and somatostatin 25-like peptides in pancreatic endocrine cells of Sparus aurata (teleost): a light and electron microscopic immunocytochemical study.

An immunocytochemical investigation demonstrates the presence of somatostatin (SST) 14- and salmon somatostatin (sSST) 25-like peptides in two populations of somatostatin (D) cells in the islets of gilthead sea bream (Sparus aurata). Both cell types were identified by their differing immunoreactivities to the somatostatin antisera used. D1 cells in the islet periphery between glucagon cells showed sSST 25-like immunoreactivity and contained large moderate to low electron-dense granules. D2 cells, present only in the central region of the islets between insulin cells, were immunoreactive to the SST 14 antisera and had smaller electron-dense granules. In S. aurata, as in other teleosts, preprosomatostatin I and II are probably synthesized and processed to SST 14- and sSST 25-like peptides, respectively, in different D cell types.

Animals↗
PubMed1992

17 alpha,20 beta-dihydroxy-4-pregnen-3-one 20-sulphate: a major new metabolite of the teleost oocyte maturation-inducing steroid.

This paper describes the discovery of 17 alpha,20 beta-dihydroxy-4-pregnen-3-one 20-sulphate (17,20 beta-P-sulphate) in urine of male and female plaice Pleuronectes platessa, in female Atlantic salmon Salmo salar and in female Dover sole Solea solea. 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) induces oocyte final maturation in teleosts and, whereas levels of the free steroid in maturing/ovulating female plaice are generally less than 1 ng ml-1 and poorly associated with the stage of maturation, the levels of 17,20 beta-P-sulphate are around 1500 ng ml-1 urine, 11 ng ml-1 blood plasma and six-fold higher in maturing than in nonmaturing fish. There are also high levels in spermiating male plaice (ca. 2300 ng ml-1 urine and 20 ng ml-1 blood plasma). 17,20 beta-P-sulphate cannot be hydrolysed by snail (Helix pomatia) sulphatase, but can be completely solvolysed by treatment with trifluoroacetic acid (TFA)/ethyl acetate (1/100, v/v) at 45 degrees for 18 hr. A number of other sulphated steroids have been identified in plaice urine: cortisol, 11-deoxycortisol and 3 alpha,17 alpha,21-trihydroxy-5 beta-pregnan-20-one (which can all be hydrolysed by snail juice); 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one and 17 alpha,20 beta,21-trihydroxy-4-pregnen-3-one (which can both be solvolysed by TFA/ethyl acetate).

Analysis of Variance↗
PubMed1992

A response to light in an adult encotyllabine (capsalid) monogenean from the pharyngeal tooth pads of some marine teleost fishes.

A response to light in an adult monogenean is reported for the first time. Living encotyllabine (capsalid) monogeneans, identified tentatively as Encotyllable caballeroi Velasquez, 1977, attached to pharyngeal tooth pads excised from two species of teleost fish, contracted rapidly when the intensity of the incident illumination was suddenly increased. Contracted individuals were immobile and largely concealed in crevices in the tooth pads. Parasites habituated to the higher light intensity after 60-100 s and re-extended their bodies and resumed activity. Contracted, immobile individuals re-extended prematurely if the light intensity was reduced during the habituation period. Detached parasites responded in the same way to abrupt changes in the illumination intensity. The possible significance of this response in relation to the biology of the hosts is briefly discussed.

Animals↗
PubMed1983

Effects of fenthion on the blood and tissue chemistry of a teleost fish (Heteropneustes fossilis).

Exposure of a freshwater teleost, Heteropneustes fossilis, to a concentration of 14 . 625 mg per 1 (0.9 of 96 h LC50) fenthion induced muscle and hepatic glycogenolysis with concomitant hyperglycaemia at 2, 6, 12 and 48 h after treatment. The pesticide evoked an initial fall (at 2 and 6 h) and later a rise (at 48 and 96 h) in blood chloride concentration. The treatment also caused anaemia with simultaneous increase in ESR and hypo-coagulability of whole-blood. The results are compared with organophosphate poisoning in this and in other fish species.

Animals↗
PubMed1987

Evidence for the direct intervention of angiotensin II in the release of cortisol in teleost fishes.

The steroidogenic response to angiotensin II (AII) has been studied in freshwater trout, using a perifusion technique applied to the "head kidneys". AII used alone had no effect on cortisol release. When associated with forskolin or ACTH, it enhanced the stimulation response to these agents. This potentiation was not related (at least directly) to extracellular and intracellular calcium while arachidonate metabolism remained a probable intermediate in the expression of AII action. Experiments using quinacrine and indomethacin suggested that prostaglandin synthesis is involved to mediate AII effect at a step subsequent to cyclic AMP production. These data provide direct evidence that the major components regulating corticosteroid production in teleost fishes are ACTH and AII and that they operate synergistically.

Adrenocorticotropic Hormone↗
PubMed1977

Cutaneous respiration in three freshwater teleosts.

Cutaneous oxygen consumption and oxygen uptake from the external medium were investigated in three species of freshwater teleosts:eel(Anguilla anguilla L.)(silvered stage), trout (Salmo gairdnerii R.) and tench (Tinca tinca L.). The oxygen consumption of the skin is the same in the three species: 4.5 nmol-cm-2-min-1. It accounts for 35% of total Mo2 in the eel; 23% in the tench, which lives in poorly oxygenated water; and 13% in the trout living in highly oxygenated water. Cutaneous oxygen consumption is equal to (Salmo and Tinca) or greater than (Anguilla) cutaneous oxygen uptake from the external medium. Consequently, the skin in these three species is not an oxygen exchange for the benefit of other organs.

Animals↗
PubMed1978

Cutaneous respiration in seven sea-water teleosts.

The oxygen consumption of excised skin (MO2 is.cut.) and the normal cutaneous oxygen uptake by the skin in situ from the external medium (MO2 ext.cut.) were investigated in seven species of teleosts in normoxic sea water: butterfish (Pholis gunnellus L.), cod (Gadus morhua L.), five-bearded rockling (Ciliata mustela L), shanny (Blennius pholis L.), flounder (Platichthys flesus L.), sole (Solea solea L.) and eel (Anguilla anguilla L.). In the butterfish, cod and rockling, all the oxygen absorbed by the skin is consumed by the skin tissue itself, whereas in the other species there is a net inward transcutaneous oxygen flux. The gain of oxygen through the skin is obtained either by a low MO2is.cut. (shanny, flounder) and/or by high MO2ext.cut. (sole and eel). The blind side of the sole is particularly efficient in oxygen uptake. The results are discussed in relation to the biota of the different species.

Animals↗
PubMedDate not supplied

Identification of 17 alpha,20 beta,21-trihydroxy-4-pregnen-3-one as the major ovarian steroid produced by the teleost Micropogonias undulatus during final oocyte maturation.

This study describes the identification of 17 alpha,20 beta, 21-trihydroxy-4-pregnen-3-one (20 beta-dihydro-11-deoxycortisol, 20 beta-S) as a major steroid product of the ovary of Atlantic croaker (Micropogonias undulatus) incubated in vitro. This is the first report which describes 17 alpha,20 beta,21-trihydroxy-4-pregnen-3-one as a major product of teleost steroidogenic tissue. The steroid was identified by a variety of methods, including HPLC, TLC, GC-MS, UV absorbance, and reactions with specific enzymes. Full grown oocytes, prior to final oocyte maturation (FOM), accumulated only small amounts of 20 beta-S. However, a substantial increase in 20 beta-S production occurred at the time of FOM. These results suggest that 20 beta-S is a maturational steroid in this species.

17-Hydroxycorticosteroids↗
PubMed1980

Elastoidin actinotrichia in Coelacanth fins: a comparison with teleosts.

In this work, we present the first ultrastructural evidences of actinotrichia in the Coelacanth Latimeria. We describe its actinotrichia with the electron microscope (SEM and TEM) and compare their structure to Teleost actinotrichia. Both elements present similar fine structure, i.e. a periodic cross-striation of 60-65 nm; the plesiomorphic character of actinotrichia is discussed in Osteichthyes.

Animals↗
PubMed1981

The fine structure of calcified Mandl's corpuscles in teleost fish scales.

Calcified Mandl's corpuscles present in the internal layer (or fibrillary plate) of the teleost fish scale were studied by transmission and scanning electron microscopy for a better understanding of this special type of mineralization process. The corpuscles show a great variability in their structure, form and surface features depending on the arrangement of the collagen fibrils in the internal layer of the different fish species studied, on the localization of the corpuscles in the scale and on the technical treatment to which the scale is subjected.

Animals↗
PubMed1989

The penetration of exogenous tracers through the enameloid organ of developing teleost fish teeth.

In order to determine whether exogenous materials permeate to the forming tooth enameloid matrix, teleost species were injected intramuscularly with horseradish peroxidase (HRP) or myoglobin, or; intracardially with lanthanum nitrate or HRP, then killed a predetermined intervals post-injection. Tooth bearing bones were processed for transmission electron microscopy. At the enameloid matrix formation stage, capillaries associated with the enameloid organ were few in number and rarely fenestrated. Both organic tracers reached the matrix at cervical but not coronal, regions of the teeth in all species examined. Lanthanum was rarely observed extravascularly and never extended to the enameloid matrix at the secretion stage. At the enameloid mineralization stage, fenestrated capillaries were closely associated with the outer dental epithelial cells (ODE). All tracers were observed in the plasma membrane invaginations of the ODE. Only intracardially injected HRP compromised the apical intercellular junctions of the inner dental epithelial cells (IDE) to reach the mineralizing enameloid Lanthanum did not extend past the ODE-IDE cell junctions. It is concluded that the close association of mineralization stage fenestrated capillaries with the highly invaginated ODE cells result in increased tracer penetration compared to the secretory stage. The deeper penetration of the organic tracers, compared with lanthanum, between mineralization stage IDE cells may be due to longer in vivo circulation of the former material. The apical junctions of mineralization stage IDE cells, however, remained impermeable to the organic tracers. The absence of mineral in secretory stage enameloid mineral could not be due to specialized cell junctions preventing access of molecules to the matrix. It is suggested that controlling factors other than cellular permeability initiate enameloid mineralization.

Animals↗
PubMed1987

Species characteristics of the hepatic xenobiotic and steroid biotransformation systems of two teleost fish, Atlantic cod (Gadus morhua) and rainbow trout (Salmo gairdneri).

Groups of Atlantic cod and rainbow trout were treated (ip) with beta-naphthoflavone (BNF), phenobarbital, or peanut oil (controls), and properties of the hepatic xenobiotic and steroid metabolizing enzyme systems were evaluated. In both species, BNF treatment resulted in significant induction of microsomal 7-ethoxycoumarin O-deethylase, 7-ethoxyresorufin O-deethylase, biphenyl 4-hydroxylase, and phenanthrene oxidation, especially at the 1,2-position. Immunochemical studies with rabbit IgG prepared against the major BNF-inducible cytochrome P-450 in cod, P-450c, revealed increased amounts of immunoreactive protein in liver slices from both species after BNF treatment. The molecular weight of the induced protein was approximately 58,000 Da, as shown by Western blotting. When titrating biphenyl 4-hydroxylation, however, the antibodies distinguished between the two species, inhibiting the activity of BNF-induced cod 90% and that of rainbow trout 40% at 10 mg IgG/nmol P-450. Furthermore, cytochrome b5 content and UDP-glucuronyltransferase activity were significantly induced only in rainbow trout, whereas the specific content of cytochrome P-450 was significantly increased only in cod. Differences between the two species were observed in the levels of constitutive activities, the amount of induction, and in the regioselectivity of phenanthrene oxidation and androstenedione metabolism. Treatment with phenobarbital showed no effect on any of the parameters investigated in either species. The results show that although there are many common features of the hepatic xenobiotic and steroid biotransformation systems of the two teleosts, certain species characteristics exist in constitutive properties and induction responses.

7-Alkoxycoumarin O-Dealkylase↗
PubMed1983

Biochemical and biophysical studies of isolated horizontal cells from the teleost retina.

Neurons in the vertebrate retina are interconnected by a complex network of chemical and electrical synapses which make it difficult to study the intrinsic biochemical and biophysical properties of individual cells. During the past decade, enzymatic methods have been developed for dissociating adult retinas into viable and readily identifiable single cells. Using this preparation, we and other investigators have studied the physiological and biochemical properties of several classes of isolated retinal cells. In particular, we have shown that a type of retinal interneuron, the GABA-ergic horizontal cell of teleost retinas, may be an excellent model system for examining the intrinsic membrane properties as well as the cellular mechanisms regulating GABA uptake, synthesis and release from an identified CNS neuron.

Animals↗
PubMed1987

Serotonin containing neurons in the retina of the teleost Eugerres plumieri.

The concentration and localization of serotonin was determined in the retina of the teleost Eugerres plumieri by using high performance liquid chromatography (HPLC) and immunohistochemical techniques. Serotonin and dopamine were measured simultaneously, their concentrations in the retina being 77 +/- 8 and 516 +/- 23 ng/mg tissue respectively. Treatment of the animals with pargyline significantly increased the levels of dopamine and serotonin. When retinas were treated with the neurotoxin 5,6-dihydroxytryptamine, the level of serotonin was reduced by more than 90% while the dopamine content only diminished by 20% when compared to controls. By using immunohistochemistry with a monoclonal anti-serotonin antibody it was possible to localize this amine in cell bodies of a population of amacrine cells with processes extending mainly into a thin layer of the most external lamina of the inner plexiform layer. Very few ramifications were seen projecting to the internal lamina of this layer. When visualized in flat mount preparations, dense arborization of fluorescent processes was observed. This is the first direct evidence that serotonin is apparently present in amacrine cells of the retina of E. plumieri with a distribution of the serotonergic terminals similar to goldfish but somewhat different when compared to other species.

5,6-Dihydroxytryptamine↗