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At least 19 recordsLinked to original sources
PubMed1992

Eel insulin: isolation, characterization and stimulatory actions on [35S]sulphate and [3H]thymidine uptake in the branchial cartilage of the eel in vitro.

Our previous studies have shown that mammalian and salmon insulins stimulate sulphate uptake by cultured eel cartilage, suggesting the possible involvement of insulin in the regulation of cartilage matrix synthesis. In the present study, homologous eel insulin was isolated and characterized, and its effects on cartilage matrix synthesis and DNA synthesis were examined in vitro. Insulin was extracted from eel pancreas with acid-ethanol, and subsequently purified by isoelectric precipitation at pH 5.3, gel filtration on Sephadex G-50, and reversed-phase high-performance liquid chromatography. The amino acid composition and complete sequence (50 residues) of eel insulin revealed high homology to teleostean and mammalian insulins. The isolated eel insulin produced a more pronounced and longer lasting hypoglycaemic effect than bovine insulin in the eel. Homologous eel insulin, like bovine insulin-like growth factor (IGF-I) and insulin, stimulated sulphate uptake by cultured eel cartilage in a dose-dependent manner (16-1000 ng/ml). Combination experiments using maximal concentrations of bovine IGF-I (250 ng/ml) and increasing amounts of eel insulin (10-250 ng/ml) showed no additive effects of insulin on sulphate uptake, suggesting that insulin and IGF-I may share a common mechanism(s) of action. Eel insulin and bovine IGF-I also enhanced thymidine incorporation by eel cartilage in a dose-dependent manner (4-1000 ng/ml); eel insulin was equipotent with bovine IGF-I. These results suggest that insulin, like IGF-I, may exert direct growth-promoting actions in branchial cartilage of the eel.

Amino Acid Sequence↗
PubMed1992

Effects of eel atrial natriuretic peptide on NaCl and water transport across the intestine of the seawater eel.

Eel atrial natriuretic peptide inhibited the serosa-negative transepithelial potential difference and short-circuit current, accompanied by a decrease in NaCl and water absorption across the seawater eel intestine. Similar effects were obtained after treatment with N-terminally truncated eel atrial natriuretic peptide (5-27), indicating that N-terminal amino acids are not essential for the action of eel atrial natriuretic peptide. Although mammalian atrial natriuretic peptides also inhibited the short-circuit current, a 100-fold higher concentration was required to obtain the same effect as with eel atrial natriuretic peptide, indicating that eel atrial natriuretic peptide is 100 times as potent in eel intestine as the mammalian atrial natriuretic peptides. Similarly, in mammalian atrial natriuretic peptide, the four N-terminal amino acids had no significant effects. However, when the C-terminal tyrosine was removed, the potency of rat atrial natriuretic peptide was lowered. Compared with the effects of acetylcholine, serotonin and histamine, eel atrial natriuretic peptide was the most potent inhibitor, with 100% inhibition at 10(-7) M; 50% inhibition was obtained at 10(-2) M in acetylcholine, and 30% inhibition in serotonin (10(-5) M) and histamine (10(-3) M). These inhibitory effects of eel atrial natriuretic peptide were not diminished even in the presence of tetrodotoxin, and were mimicked by 8-bromoguanosine 3',5'-cyclic monophosphate. Based on these results, structure-activity relationships of eel atrial natriuretic peptide and a possible mechanism of action of eel atrial natriuretic peptide are discussed.

Amino Acid Sequence↗
PubMed1994

Somatostatin-related peptides isolated from the eel gut: effects on ion and water absorption across the intestine of the seawater eel.

Four somatostatin-related peptides were isolated from eel guts. Two of them were the same as eel SS-25II (eSS-25II) and eel SS-25I (eSS-25I) isolated from European eel pancreas. The remaining two peptides were C-terminal tetradecapeptides (eSS-14II and eSS-14I) of eSS-25II and eSS-25I, respectively. These four peptides all enhanced the serosa-negative transepithelial potential difference and short-circuit current across the seawater eel intestine after pretreatment with isobutylmethylxanthine, serotonin (5-HT) and methacholine, an agonist of acetylcholine (ACh). Among these peptides, eSS-25II was the most potent enhancer, followed by eSS-25I and eSS-14II. Since the large peptide (eSS-25II) acts at a lower concentration than the small somatostatin (eSS-14II), the 11 N-terminal amino acid residues seem to potentiate somatostatin action in the eel intestine. In contrast, eSS-14II was more potent than mammalian SS-14, indicating that the three amino acid residues (Tyr18, Gly21, Pro22) in the C-terminal portion also contribute to the potency of somatostatin. Endogenous somatostatin (eSS-25II) activated net Na+, Cl- and water fluxes across the seawater eel intestine. This stimulatory action was not inhibited by tetrodotoxin or yohimbine, an adrenergic antagonist, indicating that eSS-25II does not act through neuronal firing or through catecholamine release. Thus, eel somatostatins may act directly on the enterocytes, but on a distinct receptor from that for adrenaline, to antagonize the inhibition of NaCl and water absorption by 5-HT and ACh in the seawater eel intestine.

1-Methyl-3-isobutylxanthine↗
PubMed1977

Stability of [Asu1,7]-eel calcitonin and eel calcitonin in vitro and in vivo.

Stability of [Asu1,7]-eel calcitonin was compared with that of eel calcitonin by the radioimmunoassay method. [Asu1,7]-Eel calcitonin cross-reacted with anti-eel calcitonin antisera. [Asu1,7]-Eel calcitonin was as stable as eel calcitonin in rabbit liver or rabbit kidney extracts when incubated at 37 degrees C. Disappearance curves from the plasma of [Asu1,7]-eel calcitonin and eel calcitonin following iv injection in rabbits were quite similar.

Animals↗
PubMed2005

European eels, Anguilla anguilla (L.), infected with Anguillicola crassus exhibit a more pronounced stress response to severe hypoxia than uninfected eels.

The parasite, Anguillicola crassus is a non-native species that infects naive European eels, Anguilla anguilla, and causes pathological damage to the swimbladder, potentially compromising their ability to cope with hypoxic conditions. This study aimed to elucidate whether anguillicolosis exacerbates the stress responses to exposure to hypoxic water, conditions that have been implicated in mass mortalities of wild infected European eels. Blood parameters in infected and uninfected eels were measured during exposure to severe hypoxia over an 8-h period. Infected fish showed significantly higher levels of plasma cortisol compared with uninfected eels after 4 h of hypoxia. Uninfected fish showed an almost twofold increase in plasma glucose after 8-h exposure to hypoxia but infected fish showed no significant change, so that the plasma glucose concentration was significantly higher in uninfected eels than in infected eels. Both groups showed similar elevations in blood haematocrit, suggesting a similar catecholamine response in infected and uninfected eels. The lack of a hyperglycaemic response in infected eels, despite indirect evidence of a catecholamine response to hypoxia, may reflect an increase in glucose turnover. The data suggest that anguillicolosis results in a significantly greater corticosteroid stress response to hypoxia accompanied by a higher metabolic cost.

Air Sacs↗
PubMed1988

Retinal fine structure in the European eel Anguilla anguilla. VI. Photoreceptors of the sexually immature silver eel stage.

This report deals with the fine structure of the photoreceptors of the sexually immature silver eel and compares these findings with previous observations on the glass and yellow eel stages of the life cycle of the European eel. The photoreceptors of the sexually immature glass eel are readily categorized as either rods or cones. No multiple cones are observed. The rod:cone ratio is about 100:1, which is greater than that of either the glass or yellow eel stages. Rods and perhaps cones also are capable of retinomotor responses. In the light-adapted condition, rod inner segments are the same width as the outer segments but narrow abruptly below the ellipsoid to form the myoid. Rod outer segments in the immature glass eel are longer but much the same diameter as that noted for the glass and yellow eel. Cone inner segments are much wider than the outer segments which taper distally. Both rods and cones display organelles in the inner segment region indicative of protein production. Most of the cones observed at this stage showed some degenerative signs mostly as empty vacuoles within their cytoplasm. Cone nuclei are large and vesicular and in the light-adapted state are invariably located sclerad to the external limiting membrane while rod nuclei are small and dense and located vitread to this membrane. Both rods and cones display both invaginated and superficial synaptic sites. The most obvious changes noted in the immature silver eel photoreceptor population are a marked rise in the rod:cone ratio and a lengthening of rod outer segments.

Anguilla↗
PubMed1991

Presence of prolactin receptors in eel liver and carp kidney and growth hormone receptor in eel liver.

1. 125I-labelled ovine prolactin and bovine growth hormone were used to test for the presence of prolactin and growth hormone receptors in membrane prepared from tissues of the white eel Anguilla japonica, the carp Ctenopharynogodon idellus and the ricefield eel Monopterus albus. 2. High levels of specific 125I-labelled ovine prolactin binding were found in white eel liver membranes and carp kidney membranes. 3. High levels of specific 125I-labelled bovine growth hormone binding were detected in white eel liver membranes. 4. Tissues of the ricefield eel did not bind 125I-labelled ovine prolactin or bovine growth hormone. 5. The results suggest the presence of prolactin receptors in white eel liver and carp kidney membranes and growth hormone receptors in white eel liver membranes.

Animals↗
PubMed1993

Comparative effects of eel calcitonin, salmon calcitonin and [Asu1,7]eel calcitonin on hypophyseal and osteoblastic function.

Three different calcitonins: salmon calcitonin, eel calcitonin and the semi-synthetic analog [Asu1,7]eel calcitonin have been evaluated for their ability to affect phosphoinositide hydrolysis in primary cultures of anterior pituitary cells and in the osteoblast-like UMR-106 cells. In both cellular systems a repeated treatment with any form of calcitonin induced an inhibition of inositol phospholipid turnover. Eel calcitonin and its analog were always more potent than salmon calcitonin, but the efficacy of the three polypeptides was comparable. In cultured anterior pituitary cells, the inhibitory effect on phosphoinositide hydrolysis observed after chronic treatment with calcitonin was accompanied by a reduction of prolactin release. In contrast, a single treatment of cultured anterior pituitary cells with eel calcitonin or its analog [Asu1,7]eel calcitonin induced an increase of inositol phosphate accumulation, while salmon calcitonin was inactive. Accordingly, eel and [Asu1,7]eel calcitonin, but not salmon calcitonin, induced a slight but significant stimulation of prolactin secretion. In UMR-106 cells, the three calcitonins exhibited similar potency and efficacy in reducing parathyroid hormone-stimulated 4 beta[3H]-phorbol-12,13-dibutyrate ([3H]PdBu) binding, an indirect index of protein kinase C activation. Taken together, these results suggest that, either at the pituitary or in osteoblast-like cells, some of the effects exerted by calcitonin may be ascribed to an interference with the intracellular events initiated by modulation of phosphoinositide turnover.

Analysis of Variance↗
PubMed1991

The primary structure of glucagon-like peptide but not insulin has been conserved between the American eel, Anguilla rostrata and the European eel, Anguilla anguilla.

Insulin was isolated from the pancreas of the American eel, Anguilla rostrata, and its primary structure was established as (Formula: see text). Eel insulin contains unusual substitutions at B-21, B-22, and B-26 in the putative receptor-binding region of the molecule compared with other mammalian and fish insulins. The A-chain of insulin from the European eel contains an asparagine rather than a serine residue at position A-12. Similarly, amino acid composition data indicate the B-chain of insulin from the European eel is appreciably different from that from the American eel. The primary structure of glucagon-like peptide (GLP) from the American eel is identical to that from the European eel, Anguilla anguilla. The primary structure of the peptide was established as (Formula: see text). Fast-atom bombardment mass spectrometry demonstrated that the COOH-terminal arginyl residue is alpha-amidated. The strong evolutionary pressure to conserve the structure of GLP provides further support for the assertion that the peptide plays an important regulatory role in teleost fish.

Amino Acid Sequence↗
PubMed2001

Antidipsogenic effects of eel bradykinins in the eel Anguilla japonica.

A peptide with bradykinin (BK)-like immunoreactivity was isolated from an incubate of heat-denatured eel plasma with porcine pancreatic kallikrein. The purified peptide had the following amino acid sequence: Arg-Arg-Pro-Pro-Gly-Ser-Trp-Pro-Leu-Arg. This decapeptide, named eel [Arg(0)]BK, was identical to two previously identified BK homologs from cod and trout. High conservation of the BK sequence among distant teleost species suggests an important function in this vertebrate group. Bolus intra-arterial injections of eel [Arg(0)]BK, BK, and [Arg(0)]-des-Arg(9)-BK (1-10 nmol/kg) caused significant (P < 0.05) inhibition of drinking in seawater-adapted eels. The potency of the inhibition was ranked in the following order: [Arg(0)]BK > [Arg(0)]-des-Arg(9)-BK = BK. The BK peptides also produced an immediate, transient increase followed by a sustained increase in arterial blood pressure and an initial decrease followed by an increase in heart rate. Strong tachyphylaxis occurred for the cardiovascular effect but not for the antidipsogenic effect. The order of the potency of the cardiovascular actions, [Arg(0)]BK > BK > [Arg(0)]-des-Arg(9)-BK, was different from that of the antidipsogenic action. Slow infusions of eel [Arg(0)]BK in the dose range 1-1,000 pmol x kg(-1) x min(-1) produced concentration-dependent inhibition of drinking without changes in arterial pressure, plasma osmolality, and hematocrit. At the infusion rate of >100 pmol x kg(-1) x min(-1), plasma concentrations of angiotensin II, a potent dipsogenic hormone in eels, increased, suggesting an interaction of the kallikrein-kinin and renin-angiotensin systems. In mammals, BK is dipsogenic and vasodepressor, so that our data demonstrate opposite effects on fluid and cardiovascular regulation of BK in the eel and suggest a new physiological role for the kallikrein-kinin system in teleost fish.

Angiotensin II↗
PubMed1988

Retinal fine structure in the European eel Anguilla anguilla. VIII. Photoreceptors of the sexually mature silver eel stage.

The morphology of the photoreceptors of the sexually mature silver eel has been investigated by electron microscopy and these findings compared with observations made on the photoreceptors of the glass, yellow and sexually immature silver eel stages of the lengthy life cycle of the European eel (Anguilla anguilla). As in previous stages the photoreceptors of the sexually mature silver eel are adequately described as either rods or single cones. The rod: cone ratio at this stage is about 200: 1 which is the highest ratio of any of the stages investigated. Rods and perhaps also cones are capable of photomechanical movements. In the light-adapted stage studied, rod inner segments are the same width in the ellipsoid region as the outer segments but the rod myoid region is much thinner. Rod outer segments in the mature silver eel are slightly longer than that observed in the immature silver eel but remain much the same diameter as in previous stages. Cone outer segments taper distally and are not as wide as the inner segments. Both rods and cones display organelles in the inner segment region indicative of active protein production as it is well established that the inner segment is the synthetic center of these cells. In most cones degenerative changes were noted in the mitochondria of the ellipsoid and in the presence empty vacuoles within their cytoplasm. Cone nuclei are large and vesicular and in the light-adapted state are always located sclerad to the external limiting membrane. Rod nuclei are smaller and more electron dense and located within the outer nuclear layer. Both rods and cones still show both invaginated (ribbon) and superficial synaptic sites. In the sexually mature silver eel, therefore, the rod: cone ratio becomes higher still; the rod outer segments become somewhat longer in length and cone cell degenerative changes are even more widespread.

Anguilla↗
PubMed2001

First report of the invasive eel pest Pseudodactylogyrus bini in North America and in wild American eels.

We detected 2 species of monogenean gill worms, Pseudodactylogyrus bini (Kikuchi, 1929) Gusev, 1965 and P. anguillae (Yin & Sproston, 1948) Gusev, 1965 (Monopisthocotylea: Pseudodactylogyridae), on American eel Anguilla rostrata in 2 rivers in South Carolina, USA. One of these, P. anguillae, was reported 5 yr ago from Nova Scotia; as well as in South Carolina, we also discovered it in 2 localities in Chesapeake Bay. Differences in the morphologies of specimens of either species of worm from North America and northeastern Asia were negligible. Similarly, the level of variation in sequences in the ITS2 (internal transcribed spacers) region of ribosomal RNA was minor, and not consistent with geographical origin. These data indicate that these monogeneans invaded North America only recently, possibly in parallel with the nematode Anguillicola crassus (which is known to have been introduced with commercial imports of foreign eels). We map the current global occurrence of these monogeneans, and conclude that their dispersal from northeastern Asia was largely as a result of the eel trade, and has probably been secondarily augmented by longshore migration of infected eels, and possibly also by transport in ballast waters. With present technology, all eel stocks must still be collected from the wild; unless shipments are disinfected at quarantine, these and other eel pathogens (such as A. crassus) are likely to continue to colonise other regions of the world.

Animals↗
PubMed1997

A telephone survey of eel fishermen regarding external lesions and mortalities of American eels (Anguilla rostrata) from Lake Ontario and the St. Lawrence River basin, Canada.

Signs of decreasing landings and recruitment have been observed during the last decade in American eels (Anguilla rostrata) from the St. Lawrence River basin, Canada. A study was undertaken to examine whether important manifestational diseases among commercial catches could be associated with these declines. During this survey, 56 fishermen from Lakes Ontario, Saint-François and Saint-Pierre, the Richelieu River, the Québec City area and the St. Lawrence Estuary were interviewed. Most fishermen from every area reported decreasing catches since the 1980s. Eel mortalities were reported from 1990 to 1992 in Lake Saint-François, Lake Saint-Pierre and the Québec City area, but in apparently lower magnitude than in the past decades. The lesions observed on dead eels in Lake Saint-François indicated that the cause of the mortalities might be associated with the upstream hydroelectric dam. Eels with 'scratches all over the body' were only observed in the St. Lawrence Estuary. Fishermen from almost every area reported that they had observed eels with 'crooked tail', 'humpback' and 'cut tail' in low frequency in 1992. The questionnaire data were validated by comparing some of the results of the questionnaire survey and a processing plant survey in 1992. The use of questionnaires for assessing fish diseases in commercial species is discussed. The results of this survey do not indicate that the health of the American eels from the St. Lawrence River basin is severely impaired. However, the magnitude of diseases and mortalities was probably underestimated.

Anguilla↗
PubMed2001

Persistence of herpesvirus of eel Herpesvirus anguillae in farmed European eel Anguilla anguilla.

Herpesvirus of eel Herpesvirus anguillae (HVA) was isolated repeatedly from farmed eel of an outwardly healthy stock, but virus isolation was much greater in an experimental group of fish that were injected with dexamethasone. The results suggest that HVA can establish a latent infection in eel. Previous exposure of these eels to HVA virus was shown by detection of HVA-specific antibodies. These eels did not show clinical signs after a secondary infection with HVA. Tracing of seropositive eel stocks, which had previous contact with HVA, and of HVA carrier fish can be useful to control disease outbreaks due to HVA infection.

Anguilla↗
PubMed1985

Retinal fine structure in the European eel Anguilla anguilla. IV. Photoreceptors of the yellow eel stage.

The complex life cycle of the European eel (Anguilla anguilla) involves a long catadromous migration during which the eye undergoes a number of morphological alterations. This report deals with the fine structure of the photoreceptors of the yellow eel stage and is part of a comparative study of the retina of the eel during the major stages of its life cycle. The photoreceptors of the yellow eel are easily divisible into rods and single cones and the rods at least appear to be capable of retinomotor responses. Rods are more elongated and more numerous than cones. In the light-adapted state the inner segment of rods is of the same diameter as the outer segment but narrows abruptly in the myoid region. Cone inner segments on the other hand are much wider than the outer segments which taper distally. Both rods and cones display organelles in the inner segment indicative of high metabolic activity. Cone nuclei are located scleral to the external limiting membrane while rod nuclei are vitreal to this boundary. Both rods and cones display both invaginated and superficial synaptic sites. Except for an apparent increase in number and outer segment width of the rods, the photoreceptors of the yellow eel have changed only slightly from that described for the glass eel stage.

Age Factors↗
PubMed1990

Effects of recombinant eel growth hormone on the uptake of [35S]sulfate by ceratobranchial cartilages of the Japanese eel, Anguilla japonica.

Effects of growth hormone (GH) on the synthesis of mucopolysaccharide by ceratobranchial cartilages of the Japanese eel, Anguilla japonica, were examined by monitoring the in vitro uptake of [35S]sulfate. The [35S]sulfate uptake decreased rapidly to one-third of the initial level during the first 3 days after hypophysectomy, and decreased gradually thereafter. When hypophysectomized eels were injected intramuscularly with recombinant eel GH (2 micrograms/g), the plasma GH concentrations increased maximally after 6 hr, and declined rapidly thereafter. On the other hand, the sulfate uptake increased significantly after 12 hr, and high levels were maintained until 48 hr. The stimulating effect of GH was dose dependent (0.02-2 micrograms/g). However, the addition of eel GH (0.05-5 micrograms/ml) to the culture medium did not affect the sulfate uptake by hypophysectomized eel cartilages, suggesting that the stimulative action of GH on the sulfate uptake by the cartilages is indirect.

Anguilla↗
PubMed2000

Eel WT1 sequence and expression in spontaneous nephroblastomas in Japanese eel.

Nephroblastomas spontaneously developing in Japanese eel reared at farms for 5 to 9months after collection from the wild [Masahito et al., Cancer Res., 52 (1992) 2575-2579] were investigated to cast light on the role of Wilms' tumor 1 gene (WT1) in eel kidney tumorigenesis. Cloning of the WT1 counterpart, EWT1, revealed that conservation of an alternative splice II site, located between the third and fourth zinc fingers, was conserved. The zinc finger domain was highly conserved. The transregulator region, sequences corresponding to exons 4 and 5 in WT1, were lacking in EWT1 cDNA. EWT1 was found to be expressed in kidney, testis and spleen and in situ hybridization revealed dark-stained immature cells in elver kidney to be positive. Although no EWT1 gene mutations were found in 38 eel nephroblastomas, 26 polymorphic nucleic acid changes were observed. Aberrant WT1 expression was noted in epithelial (12 out of 27; 44%) and nephroblastic cell histological types (three out of five; 60%) of eel nephroblastomas. On in situ hybridization the EWT1 expressive cells resembled human blastema cells, similar to those in human Wilms' tumor. These data demonstrated strong signals that the EWT1 protein may function in the development of eel kidney and play a role in genesis of nephroblastomas as in mammals.

Amino Acid Sequence↗