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At least 307 records · Page 17Linked to original sources
PubMed1983

Immunocytochemical identification of the prolactin-secreting cells in the teleost pituitary with an antiserum to chum salmon prolactin.

An antiserum raised to highly purified chum salmon (Oncorhynchus keta) prolactin (sPRL) was used to identify prolactin-producing cells in the adenohypophysis of 15 species of teleosts by the immunocytochemical peroxidase-antiperoxidase method. In the chum salmon, the only pituitary cells that reacted with sPRL antibody were the PRL cells organized as follicular structures in the rostral pars distalis. When the antiserum was absorbed with sPRL, on the other hand, no immunoreactive cell was observed in the pituitary, indicating the specificity of the antiserum. Furthermore, the antibody to sPRL reacted only with PRL cells in the pituitaries of three species of salmonids, a plecoglossid, eel, carp, goldfish, killifish, tilapia, and five species of marine fishes, thus showing no species specificity of the antibody among the teleosts tested. The PRL cells of the eel decreased in number and also in immunoreactivity after adaptation to seawater for 1 month. On the other hand, highly immunoreactive PRL cells were observed in the pituitaries of marine fishes, although the cells were much fewer in number than in eels and in other fishes in fresh water.

Animals↗
PubMed1985

Aromatase and 5 alpha-reductase in the teleost brain, spinal cord, and pituitary gland.

The distribution of aromatase and 5 alpha-reductase was investigated in the brain, spinal cord, and pituitary of adult goldfish (Carassius auratus) and toadfish (Opsanus tau) of both sexes. Tissue homogenates were incubated with [3H]androstenedione in the presence of an NADPH-generating system and, following validation of assay conditions, radiolabeled products (estradiol, estrone, 5 alpha-androstanedione), were measured as an index of enzyme activity. Neuroendocrine tissue of both species produced exceptionally large amounts of estrogen, thus confirming previously observed differences between teleosts and other vertebrates. By contrast, 5 alpha-reductase levels resembled the vertebrate norm. In general, aromatase was concentrated in the pituitary and various forebrain regions, especially the hypothalamus/preoptic area; however, estrogen yields from the medulla and anterior spinal cord of toadfish were high compared to adjacent midbrain, hindbrain, and cord regions. This same neural region in toadfish, but not in goldfish, is known to control a sex dimorphic behavior, the courtship boatwhistle. In contrast to aromatase, 5 alpha-reductase was more uniformly distributed throughout the brain, although somewhat higher activity was obtained in the pituitary. High levels of aromatase in the neuroendocrine tissues of teleosts recommend them as animal models for further studying the enzyme, its regulation, and its role in governing androgen-dependent responses in central targets.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1986

Diverse molecular forms of gonadotropin-releasing hormone in an elasmobranch and a teleost fish.

Immunoreactive and biologically active gonadotropin-releasing hormones (GnRHs) in dogfish (Poroderma africanum) and teleost (Coris julis) brain extracts were studied by high-performance liquid chromatography (HPLC), radioimmunoassay with region-specific antisera, and assessment of luteinizing hormone (LH)-releasing activity in a chicken dispersed pituitary cell bioassay. In dogfish brain extract, seven GnRH molecular forms with LH-releasing activity were demonstrated. Three of these forms coeluted with synthetic mammalian GnRH; His5,Trp7,Tyr8-GnRH; and Trp7,Leu8-GnRH on HPLC. The peaks coincident with His5,Trp7,Tyr8-GnRH and Trp7,Leu8-GnRH had immunological and biological properties identical to those of the synthetic peptides. However, the molecular form coeluting with mammalian GnRH had immunological and biological properties different from those of mammalian GnRH and is thus a novel molecular variant of GnRH. The four remaining forms are also novel GnRHs or structurally unrelated peptides with LH-releasing activity. Dogfish systemic blood contained immunoreactive GnRH. In teleost brain extract, three biologically active GnRH forms with LH-releasing activity were present. The major peak of GnRH immunoreactivity coeluted with Trp7,Leu8-GnRH, and a second immunoreactive form coeluted with His5,Trp7,Tyr8-GnRH. The third biologically active peak is a novel, early-eluting molecular variant of GnRH or a structurally unrelated peptide with LH-releasing activity.

Animals↗
PubMed1992

Tetrapod-like hypothalamo-hypophysial portal system in the teleost Megalops cyprinoides (Broussonet).

A tetrapod-like hypothalamo-hypophysial portal system and a persistent bucco-hypophysial canal are present in Megalops cyprinoides. The complicated loops of the primary capillary plexus are seen on the ventral side of the infundibular floor and contact the perikarya of the nucleus lateralis tuberis and the preoptico-hypothalamo-neurohypophysial-neurosecretory tract. Although the pars intermedia receives part of its vascular supply from the pars distalis, the caudal hypophysial artery directly vascularizes the neurointermedia interface and forms the plexus intermedialis. The bucco-hypophysial canal is short and narrow in the fry and fingerlings but becomes long and tortuous as the fish grows. Megapopidae seem to be closer to the polypteriformids than to the teleosts. The possession of the pituitary portal system in megalopids may be a connecting link between the polypteriformids and other advanced teleosts.

Animals↗
PubMed1989

Ammonia and urea dynamics in the Lake Magadi tilapia, a ureotelic teleost fish adapted to an extremely alkaline environment.

The tilapia Oreochromis alcalicus grahami, which thrives under harshly alkaline conditions in Lake Magadi, Kenya, was studied in its natural environment (pH = 10, total CO2 = 180 mmol/L, osmolality = 525 mOsm/kg, 30-36.5 degrees C). At rest, this species excretes all nitrogenous waste as urea. This is the first known instance of complete ureotelism in an entirely aquatic teleost fish. Very small 'apparent' ammonia excretion (less than 5% of overall N excretion) was attributable to faecal/bacterial production. Ammonia excretion could not be induced by feeding, reduced temperature, or exposure to pH 7. Exhaustive exercise induced only a small efflux of ammonia. Urea output was inhibited completely by pH 7 water and partly by exhaustive exercise, and greatly stimulated by exposure to 500 mumol/L NH3 (at pH 10). A related species, nominally Oreochromis nilotica, which lives in freshwater at circumneutral pH in the same geographic region, excretes 85% ammonia-N and 15% urea-N at pH 7 in the standard teleost fashion. Urea-N efflux increased to 33% upon transfer of O. nilotica to pH 10 in freshwater. Urea output in this species was only marginally stimulated by exposure to 500 mumol/L NH3 (at pH 7). Plasma and white muscle urea levels were 4- to 5-fold higher in O. a. grahami than in O. nilotica, and plasma levels increased between caudal and cardiac sampling sites, indicating hepatic ureagenesis. Blood pH and PNH3 levels, when corrected for sampling artifact, were unusually high in O. a. grahami. We hypothesize that complete ureotelism in O. a. grahami is an evolutionary response to the problems of excreting ammonia into highly buffered water at pH 10 and/or acid-base balance in this extreme environment.

Acid-Base Equilibrium↗
PubMed1992

Steroid metabolism in teleost gonads: purification and identification of metabolites by high-performance liquid chromatography.

A simple, efficient, and comprehensive technique for the purification, identification, and quantitation of the common steroid metabolites synthesized by the gonads of teleosts involving five systems of high-performance liquid chromatography (HPLC) was developed. Steroid standards were identified in HPLC by UV absorption at 254 nm or 280 nm, by differential refractive index, or by using radioactive standards. Metabolites that do not absorb UV light and are not resolved in the isocratic HPLC systems were identified in thin-layer chromatography following purification by HPLC. By using this technique, most of the steroid metabolites, including some polar metabolites, synthesized by the gonadal tissues of the teleosts can be purified within three steps of chromatography. The HPLC systems reported here are also useful in identifying the chromium trioxide oxidized products of metabolites, such as triols and tetrols, which considerably narrows down the number of probable metabolites.

Animals↗
PubMed1991

Light onset stimulates tyrosine hydroxylase activity in isolated teleost retinas.

The action of tyrosine hydroxylase is the rate-limiting step in the synthesis of dopamine, the most abundant catecholamine in vertebrate retinas. I have examined the activation and regulation of this enzyme in isolated retinas of green sunfish, Lepomis cyanellus. Exposing previously dark-adapted retinas to constant illumination for a period of 10 min increased enzymatic activity 2.2-fold over that present in retinas incubated in darkness. Thus, light onset activates tyrosine hydroxylase in teleost retinas. Stimulation of the activity of tyrosine hydroxylase under these conditions was associated with a decrease in the apparent Km of the enzyme for its pteridine cofactor without a change in the apparent Vmax of the reaction. This result suggests that short-term exposure to light increases dopamine synthesis by enhancing the affinity of the enzyme for its naturally occurring cofactor. These findings are consistent with the idea that light activates dopaminergic neurons in teleost retinas.

Animals↗
PubMed1995

Some functional properties of teleost antithrombin.

Antithrombin from bony fish (Teleostei), represented by an ancient salmonid, Atlantic salmon (Salmo salar L.), and a more evolved species from the same family, rainbow trout (Oncorhynchus mykiss Walbaum), functions in vitro as does its human counterpart: it inactivates thrombin almost instantaneously in the presence of heparin and only slowly when heparin is absent. The inhibitory activity of salmonid antithrombin towards the homologous thrombin did not differ noticeably from its inactivating capacity in heterologous (teleost) systems, and enzyme-inhibitor reactions between reagents from fish and man proceeded just as efficiently. In all enzyme-inhibitor reactions with salmonid thrombin the inactivation by salmonid antithrombin or diluted fish plasma was maximal at pH 7.8-8.4. The inactivation was clearly dependent on heparin in all systems and maximal at concentrations between 1.5 and 6 U/ml. What particularly distinguishes the salmonid thrombin-antithrombin interaction from the human one is that the former has to function over a wide range of temperatures. And the thrombin inactivating capacity of purified antithrombin and diluted plasma in the presence of heparin was indeed present at temperatures down to 3 degrees C, a capacity that human antithrombin also has retained. Even more interesting was that the teleost enzyme-inhibitor reaction was nearly independent of temperature under the conditions studied.

Animals↗
PubMed1992

DiI tracing in combination with immunocytochemistry for analysis of connectivities and chemoarchitectonics of specific neural systems in a teleost, the Atlantic salmon.

An important goal in neuroanatomical research is to identify the neurotransmitters in specific neural pathways. One step towards this goal is to combine experimental neuronal tracing with immunocytochemistry. Unfortunately, optimal procedures for nerve tracing and immunocytochemistry are not always compatible. Carbocyanine compounds have recently been shown to be efficient tracers both in vivo and in paraformaldehyde-prefixed neural tissue. The possibility to apply them to prefixed tissue make them suitable for tracing of neural pathways that are not easily accessible in vivo. We have optimized the procedures for neural tracing with one carbocyanine compound, DiI (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate), in the CNS of a teleost fish, and evaluated its compatibility with different immunocytochemical protocols. We have compared several immunocytochemical protocols, taking into account cryostat and vibratome sectioning, glutaraldehyde post-fixation to stabilize DiI, antibodies with different capacity for tissue penetration and the use of detergents, and antibodies with different sensitivity to prolonged paraformaldehyde fixation. We have also evaluated the choice of marker for immunoreactivity and compared indirect immunofluorescence techniques using different fluorophores, and the peroxidase-antiperoxidase (PAP) technique with or without nickel enhancement of the diaminobenzidine reaction product. It appears that DiI tracing of neural connections in the teleost CNS yields very consistent results and that the combination with immunocytochemistry is very reliable. We present four different basic protocols for combined DiI tracing and immunocytochemistry, with notes on their specific applicability. Owing to their reliability, the protocols may prove useful in comparative neuroanatomical studies of other vertebrates, particularly fish and amphibians, as well as in studies of developmental changes and neural plasticity in fish and amphibians.

Animals↗
PubMed1993

Regulation of cell division and rod differentiation in the teleost retina.

We tested the effects of several growth factors on the proliferation and differentiation of cells in the teleost retina which typically become rod photoreceptors to understand their regulation. Using organotypic slice cultures of differentiated teleost fish retinal tissue, we found that insulin and insulin-like growth factor I (IGF-I) stimulate proliferation of rod precursor cells whereas basic fibroblast growth factor (bFGF) does not. In the presence of bFGF, however, a greater proportion of the cells that had divided expressed a rod photoreceptor-specific phenotype than did control slices. This suggests insulin and the related IGF-I can influence the regulation of neuronal cell division whereas bFGF promotes the differentiation of neuronal stem cells into rod photoreceptors in retinal slice culture. These results support the idea that cell division and differentiation are differentially regulated and diffusible factors play a role in this process.

Animals↗
PubMed1987

The influence of mammalian and teleost somatostatins on the secretion of growth hormone from goldfish (Carassius auratus L.) pituitary fragments in vitro.

The effect of various vertebrate somatostatins (SRIF) on basal growth hormone (GH) secretion from goldfish pituitary fragments was studied using an in vitro perifusion system. SRIF-14 caused a rapid and dose-dependent decrease in the rate of GH release from goldfish pituitary fragments. The half-maximal effective dose (ED50) of SRIF-14 was calculated as 1.3 nM following exposure to two minute pulses of increasing concentrations of SRIF-14, whereas the ED50 of SRIF-14 calculated after continuous exposure to sequentially increasing doses of SRIF-14 was 65 nM. This difference suggests that the pituitary fragments were less responsive to SRIF-14 in the latter experiment, possibly as a result of previous exposure to SRIF-14. SRIF-28 was found to be equipotent with SRIF-14 in decreasing basal GH secretion from the goldfish pituitary. In contrast, catfish SRIF-22, a uniquely teleost SRIF isolated from catfish pancreatic islets, did not alter GH secretion. These results provide further support for the hypothesis that SRIF-14 or a very similar molecule functions as a GH release-inhibiting factor in teleosts, indicating that this action of SRIF-14 has been fully conserved throughout vertebrate evolution.

Animals↗
PubMedDate not supplied

Localization of CRF-like immunoreactivity in the brain and pituitary of teleost fish.

Immunocytochemical techniques were applied to brain and pituitary sections of eleven teleost species. A corticotropin-releasing factor (CRF)-antiserum allowed the identification of a CRF-like system in these species. Perikarya were labeled in the preoptic nucleus. Labeled fibers were traced laterally, then ventrally close to the optic chiasma, forming two symmetrical tracts running through the basal hypothalamus. These ended in the rostral neurohypophysis (NH) close to ACTH cells as shown by double immunostaining. Other fibers, often more variquous, ended in the caudal NH close to melanocorticotropic cells. In Salmo fario, small perikarya also stained in the nucleus lateralis tuberis. The CRF-like system appears distinct from that of somatostatin. In Anguilla, adjacent sections stained with CRF- and vasotocin (AVT)-antisera respectively showed that these two peptides coexist in some perikarya. As few fibers containing only AVT end in the rostral NH, they probably do not control ACTH cells directly. AVT fibers terminate mostly in the caudal NH close to melanocorticotropic cells. Some extra-hypothalamic fibers suggest that CRF may also act as a neurotransmitter. The plurality of hormones showing a CRF-like activity in teleosts is considered.

Anguilla↗
PubMed1990

Anatomical distribution of galanin-like immunoreactivity in the brain and pituitary of teleost fishes.

Immunohistochemical study of brains of five teleost fishes (molly, sea bass, killifish, flounder, tilapia) revealed similar extensive systems of galanin immunoreactive (GAL-ir) neurons. Cell bodies were located in the anterior preoptic recess (where coexistence with corticotrophin-releasing factor-like-ir was found), posterior tuberal hypothalamus and vagal lobe of the medulla oblongata. Fibres in the fingers of neurohypophysial tissue penetrating the pituitary pars distalis suggested an anatomical relationship between GAL-ir terminals and the hormone secreting cells. Electron microscopic studies on sea bass pituitary revealed contacts of GAL-ir fibres with growth hormone cells and gonadotrophs. Thus a GAL-like peptide may be released from nerve terminals in the teleost pituitary, where it may act locally to modulate the secretion of one or more pituitary hormones.

Animals↗
PubMed1984

Glucose dehydrogenase in teleosts: tissue distribution and proposed function.

Tissue extracts of skeletal muscle, heart, eye, brain, liver, kidney, gill and stomach were electrophoretically examined for glucose dehydrogenase (EC 1.1.1.47) activity in 21 species of marine teleost fishes. Glucose dehydrogenase expression was detected only in liver extracts. Considerable interordinal variation was found in levels of enzymatic activity. Available data support the hypothesis that glucose dehydrogenase provides NADPH for the mixed-function oxidase system in teleosts.

Animals↗
PubMed1986

The optic tectum of gymnotiform teleosts Eigenmannia virescens and Apteronotus leptorhynchus: a Golgi study.

Golgi, Nissl, Bielschowsky and cholinesterase techniques have been used to analyze the optic tectum of the weakly electric teleost fish Eigenmannia virescens and Apteronotus leptorhynchus. Six layers are readily distinguished: a fairly thick stratum marginale, a narrow stratum opticum and stratum fibrosum et griseum superficiale, a well-developed stratum griseum centrale, a stratum album centrale and a compact stratum periventriculare. Fifty-six neuronal types are present. In regard to comparative aspects of tectal organization, it became apparent that although most neuronal types are similar to those reported in other teleostean fish, there are certain obvious differences such as: pyramidal cell somata not confined to stratum fibrosum et griseum superficiale, but also clustered in the adjacent stratum opticum, presenting stratified or diffuse basilar dendritic arbors; and a change from vertical to oblique and almost horizontal neuronal orientation in the ventral and caudal tectum. The presence of pyramidal cells with aligned and misaligned apical and basal dendritic fields. A cell of stratum griseum centrale with an ascending axon to stratum opticum. A special projection type of fusiform cell of stratum griseum centrale, with an efferent axon of somatic origin. A cell rich stratum griseum centrale, with a wider variety of multipolar and bipolar cell population than reported in other teleosts. Fourteen types of pyriform cells are present, four of which are efferent. Our observations are suggestive of regional differences in regard to the caudalmost tectum in Apteronotus: presumably this is related to the extremely sparse retinal input to this part of the tectum. A close functional correlation has been found between some multipolar and pyriform cells identified in our material with similar cells reported by Rose and Heiligenberg as multisensory cells, following recordings and horseradish peroxidase fillings of these cells. Based on the observation of patchy torus semicircularis input to stratum fibrosum et griseum superficiale, disjunct from the retinal input to this layer, it is proposed that perhaps this arrangement is the result of competition for synaptic targets during development.

Animals↗
PubMed1983

Different distribution of serotonin in an elasmobranch (Scyliorhinus stellaris) and in a teleost (Conger conger) fish.

1. A comparative quantitative study on the occurrence of 5-HT in several tissues and organs of the elasmobranch Scyliorhinus stellaris and the teleost Conger conger has been carried out. 2. In Scyliorhinus, the richest source of the amine is the brain, in which 5-HT is twice as concentrated as in the teleost brain. Significant levels have been also detected in the intestine, followed by gills and heart. 5-HT is also concentrated in other epithelial organs, such as the rectal gland and the olfactory organ. 3. In Conger, the gills show the highest content of 5-HT, in which, like in the kidney, serotonin is 2-3 times more concentrated than in the corresponding organs of the elasmobranch. 4. These differences are discussed in relation to the distinct phylogenetic and ecophysiological features of the two animals. In addition, the possible functional significance of 5-HT in the fish heart is taken into consideration.

Animals↗
PubMed2003

Occurrence of two distinct types of tissue inhibitor of metalloproteinases-2 in teleost fish.

We have cloned for the first time two cDNAs encoding distinct types of tissue inhibitor of metalloproteinases-2 (TIMP-2) from teleost fish, Japanese flounder, and designated these types as jfTIMP-2a and jfTIMP-2b. The open reading frames of the jfTIMP-2a and jfTIMP-2b cDNAs are composed of 663 and 657 nucleotides and 221 and 219 amino acids, respectively. Both jfTIMP-2s contain 12 cysteine residues, which might form six disulfide bonds as in other animals' TIMP-2s. The predicted full-length amino acid sequence of jfTIMP-2a has lower identity to jfTIMP-2b (63%) than to those of human (74%) and chicken (73%) TIMP-2s, but higher than to those of other human TIMPs (TIMP-1: 39%, TIMP-3: 43%, TIMP-4: 45%), indicating that jfTIMP-2a is a common TIMP-2, while jfTIMP-2b is unique to Japanese flounder. However, the C-terminal region including the last three disulfide bonds of jfTIMP-2b has higher amino acid identity to those of other animal TIMP-2s than to that of jfTIMP-2a. Reverse-transcribed polymerase chain reaction (RT-PCR) analysis showed the mRNAs of jfTIMP-2a and jfTIMP-2b to be ubiquitously expressed in all tissues examined, but with different expression patterns. These findings suggest that the two distinct jfTIMP-2s might perform different functions in teleost tissues.

Amino Acid Sequence↗