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At least 37 records · Page 2Linked to original sources
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↗
PubMed1996

Whole body autoradiography and microautoradiography in eels after intra-arterial administration of 125I-labeled eel ANP.

125I-labeled eel atrial natriuretic peptide (ANP) was administered into the ventral or dorsal aorta of freshwater (FW) and seawater (SW) eels, Anguilla japonica, and the major target organs were explored by whole body autoradiography. Localization of the ANP binding in the target organs was also examined at tissue and cell levels by microautoradiography using tissue sections. Whole body autoradiography revealed that the specific label was accumulated predominantly in the gill, with lesser amounts in the atrium, kidney, liver, and urinary bladder. Autoradiographic grains were most dense in the secondary lamellae of the gill, particularly on the side of the efferent filamental artery. Other binding sites in target tissues were the glomerulus of the kidney, epicardium and endocardium of the atrium, bile duct/blood vessels of the liver, and interrenal cells of the head kidney. There was no difference in the distribution and density of grains between injections into the ventral aorta and dorsal aorta, although, in the former, injected 125I-labeled eel ANP passes through the gill before reaching peripheral target tissues. There was a tendency for downregulation of ANP binding sites in SW eels, especially in the gill. These results show that specific ANP binding sites are present in organs that are implicated in osmoregulation and cardiovascular regulation in eels and further suggest that the number of ANP binding sites varies according to changes in the environmental salinity.

Anguilla↗
PubMed1985

Detection of endocrine cells by immunofluorescence method in the gastroenteropancreatic system of the adult eel, glass-eel, and leptocephalic larva (Anguilla anguilla L.).

Five antisera against insulin (Ins), glucagon (Glu), somatostatin (SRIF), met-enkephalin (met-enk), and serotonin (5-HT) were used for immunofluorescence detection of endocrine cells in pancreas and gastrointestinal tract (GIT) of the European eel (Anguilla anguilla L.) at three stages of development (leptocephalic larva, glass-eel, and adult eel). Comparable distribution of endocrine cells was observed for adults and glass-eels. In their pancreatic islets, positive immunoreactions were obtained only for Ins, SRIF, and Glu; this later was also present in the pancreatic ducts. 5-HT cells were present throughout the GIT. SRIF cells were situated mostly in the stomach and less in the intestine. Met-enk cells were abundant in the pyloric cecum, but less frequent in the intestinal mucosa. Glu cells were present only in the intestine. No insulin-immunoreactive cells could be detected in the GIT. The pancreatic islets of leptocephalic larvae exhibited a strong reaction for SRIF, a weak reaction for Glu, and none at all for Ins, met-Enk, or 5-HT. The GIT of these larvae contained numerous met-enk cells, mainly in the foregut. In the fore- and midgut, cells exhibited a weak fluorescence after treatment with Glu antiserum. No positive immunoreactive cells were observed with 5-HT, SRIF, or Ins antisera.

Anguilla↗
PubMed2004

Differences in susceptibility of the European eel (Anguilla anguilla) and the Japanese eel (Anguilla japonica) to the swim-bladder nematode Anguillicola crassus.

The swim-bladder nematode Anguillicola crassus originates from the Far East where it is a parasite of the Japanese eel (Anguilla japonica). After A. crassus was introduced to Europe, it became a predominant parasite of the European eel (Anguilla anguilla). A study performed with experimentally infected eels (98 days, 23 degrees C) revealed significant differences in the susceptibility of the two eel species to this parasite. The recovery rate of 30 administered infective A. crassus larvae (L3) from A. japonica was less than half of that from A. anguilla (33.2% and 13.8%, respectively). Almost 60% of the worms recovered from A. japonica were found as dead, encapsulated and necrotic larvae in the swimbladder wall. In contrast, no dead larvae were found in A. anguilla. Additionally, the development of the worms was shown to be significantly slower in A. japonica compared with A. anguilla. The lower survival rate of the worms, together with their slower development, resulted in a significantly lower adult worm burden (11 and 428 mg wet weight, respectively) and in a decreased reproductive success in A. japonica compared with A. anguilla. These results demonstrate that the original host, A. japonica, possesses more effective defence mechanisms against A. crassus than does the non-adapted host, A. anguilla.

Air Sacs↗
PubMed1988

Retinal fine structure in the European eel Anguilla anguilla. V. Pigment epithelium of the sexually immature silver eel stage.

The fine structure of the retinal pigment epithelium (RPE), Bruch's membrane and choriocapillaris has been investigated in the sexually immature silver eel and compared with previous observations made at the glass and yellow eel stages of the lengthy life cycle of the European eel. As in the previous stages the retinal pigment epithelium of the sexually immature silver eel consists of a single layer of cuboidal to squamous cells joined laterally by apically located cell junctions. The basal (scleral) and lateral borders of these cells are relatively smooth while apical (vitreal) processes enclosing photoreceptor outer segments are plentiful. Internally the epithelial cells display a vesicular pleomorphic nucleus, abundant mitochondria and melanosomes as well as myeloid bodies, phagosomes and polysomes. Smooth endoplasmic reticulum (SER) is abundant while rough endoplasmic reticulum (RER) is uncommon. Lipid droplets are also scarce. Wandering phagocytes are a regular feature amongst the retinal epithelial cells. Bruch's membrane is trilaminate and remains thin as in the previous stages investigated. The choriocapillaris is a single discontinuous layer of capillaries showing fenestrations on the side facing Bruch's membrane. A stratum argenteum remains in the choroid but separated from the retinal epithelium by pigment cells of the choroid.

Anguilla↗
PubMed1988

Retinal fine structure in the European eel Anguilla anguilla. VII. Pigment epithelium of the sexually mature silver eel stage.

This report describes the morphology of the retinal pigment epithelium (RPE), Bruch's membrane and choriocapillaris in the sexually mature silver eel and compares these observations with previous descriptions of this region in the glass, yellow and sexually immature silver eel stages of the lengthy life cycle of the European eel. The retinal epithelium in the sexually mature silver eel is a single layer of cuboidal to squamous cells joined laterally by apically located cell junctions. Both the basal (scleral) and lateral borders of the epithelial cells are relatively smooth while apically (vitreally) numerous processes enclose a photoreceptor inner and outer segments. The epithelial cells contain abundant profiles of smooth endoplasmic reticulum (SER), numerous small mitochondria and melanosomes and a single pleomorphic, vesicular nucleus. Lipid droplets are large and abundant at this stage. Myeloid bodies, phagosomes and lysosomes are also present. Rough endoplasmic reticulum (RER) is not plentiful. Wandering phagocytes are a constant feature of this region. Bruch's membrane is still trilaminate but is now much thicker than at any previous stage. The choriocapillaris remains as a single layer of fenestrated capillaries adjacent to Bruch's membrane. The stratum argenteum is still present in the choroid and separated from the RPE by pigmented cells. Single cells presumed to be from the stratum argenteum are, however, often located close to Bruch's membrane.

Anguilla↗
PubMed1984

Retinal fine structure in the european eel Anguilla anguilla. II. Photoreceptors of the glass eel stage.

The eye of the European eel (Anguilla anguilla) undergoes marked morphological changes during its long and complex life cycle. This report describes the fine structure of the photoreceptors of the glass eel stage and forms part of a comparative study of the retina of the eel during the major stages of its life cycle. The photoreceptors of the glass eels are readily divisible into rods and cones based on morphological criteria. Rods are more numerous and much longer than cone cells, reaching to the pigment epithelial layer. In rods the inner and outer segments are of the same diameter whereas in cones, inner segments are much wider than the outer segments which taper distally. While the nuclei of rods are located at all levels within the outer nuclear layer, in the light-adapted condition at least, cone nuclei are predominantly located scleral to the external limiting membrane. The synaptic terminal of rods displays 2-3 invaginated (ribbon) synaptic sites while cones have 8-10 such sites. Both rods and cones also possess superficial synaptic sites. Apparent cellular degeneration is quite widespread amongst rods and is also occasionally noted for cone photoreceptors.

Anguilla↗
PubMed1984

Retinal fine structure in the European eel Anguilla anguilla. III. Pigment epithelium of the yellow eel stage.

The catadromous migrations of the European eel (Anguilla anguilla) are accompanied by a number of morphological and biochemical alterations within the visual system. This report describes the morphology of the retinal pigment epithelium, choriocapillaris and Bruch's membrane of the yellow eel and forms the third in a series describing the morphological changes in the retina of the eel during its life cycle. The retinal epithelium of the yellow eel stage consists of a single layer of cuboidal cells joined laterally by tight junctions. Apically, numerous processes enclose photoreceptor cells while basally and laterally the cell borders are relatively smooth. Internally the epithelial cells display abundant smooth endoplasmic reticulum, mitochondria, melanosomes, phagosomes and myeloid bodies. Rough endoplasmic reticulum, polysomes and Golgi zones are present but not plentiful. The nucleus is pleiomorphic and basally located. Bruch's membrane (complexus basalis) is trilaminate. The choriocapillaris is typically fenestrated facing the retina. A stratum argenteum is present in the outer choroid and wandering phagocytes are noted at the retinal epithelium-photoreceptor interface.

Anguilla↗
PubMed2003

Evolution of the deep-sea gulper eel mitochondrial genomes: large-scale gene rearrangements originated within the eels.

Recent studies have demonstrated that deviations from the typical vertebrate mitochondrial gene order are more frequent than initially thought. Such deviations, however, are minor, with inversions and/or translocations of a few genes being involved and tandem duplication of the gene regions followed by deletions of genes having been invoked as mechanisms originating in such novel gene order. During the course of molecular phylogenetic studies on the Elopomorpha (eels and their allies), we found that mitochondrial genomes (mitogenomes) from the two deep-sea gulper eels, Eurypharynx pelecanoides (Eurypharyngidae) and Saccopharynx lavenbergi (Saccopharyngidae), exhibit an identical gene order which greatly differs from that of any other vertebrates. Phylogenetic analysis using the mitogenomic data from 59 species of fish not only confirmed a single origin of such a gene order with confidence but also indicated that it had been derived from the typical vertebrate gene order. Detailed comparisons of the gulper eel gene order with that of typical vertebrates suggested that occurrence of a single step, large-scale duplication of gene region extending >12 kb, followed by deletions of genes in a common ancestor of the two species, most parsimoniously accounts for this unusual gene arrangement.

Animals↗
PubMed1990

Glucose transport in fish erythrocytes: variable cytochalasin-B-sensitive hexose transport activity in the common eel (Anguilla japonica) and transport deficiency in the paddyfield eel (Monopterus albus) and rainbow trout (Salmo gairdneri).

Erythrocytes from individual common eels (Anguilla japonica Temminck and Schlegel) exhibited widely variable initial rates of cytochalasin-B-sensitive 3-O-methyl-D-glucose (3-OMG) zero-trans influx, in the range of 0-19.5 mmol l-cells-1 h-1 (5 mmol l-1 extracellular concentration at 20 degrees C, 50 animals tested). Storage of cells at 4 degrees C in a glucose-containing medium for up to 72 h had no effect on 3-OMG uptake, and there was no correlation between the sugar permeabilities of erythrocytes from different fish and intracellular ATP levels. Adrenaline and noradrenaline increased cytochalasin-B-sensitive 3-OMG transport activity; half-maximal stimulation occurred at catecholamine concentrations in the region of 1 mumol l-1. This catecholamine-induced stimulation of sugar transport appeared to be independent of the basal cytochalasin-B-sensitive 3-OMG permeability of the cells. Kinetically, catecholamines increased the Vm of transport without changing the apparent Km (approx. 1.4 mmol l-1). Saturable 3-OMG influx was inhibited by phloretin, D-glucose, D-deoxyglucose and D-galactose, but not by D-fructose and L-glucose. Transporter stereoselectivity was confirmed by direct measurements of D- and L-glucose uptake. Erythrocytes from two other fish species, Monopterus albus Richardson (paddyfield eel) and Salmo gairdneri Richardson (rainbow trout), unlike those from the common eel, were uniformly deficient with respect to cytochalasin-B-sensitive 3-OMG and D-glucose transport activity. Catecholamines had no effect on sugar uptake in these species.

3-O-Methylglucose↗
PubMed1999

An enhanced humoral immune response against the swimbladder nematode, Anguillicola crassus, in the Japanese eel, Anguilla japonica, compared with the European eel, A. anguilla.

The humoral immune response in the two eel species, Anguilla japonica and Anguilla anguilla against two fractions of antigens in Anguillicola crassus were studied. Within species, both eel species showed significantly elevated titres compared with controls when immunized with antigens from Anguillicola crassus. In interspecific comparison, Anguilla japonica showed significantly elevated titres in comparison with Anguilla anguilla. Immunization of Anguilla anguilla caused a significantly decrease in the plasma levels of protein in comparison with control fish and all groups of Anguilla japonica. In contrast, Anguilla japonica showed significantly lower plasma levels of Ig in all groups compared with Anguilla anguilla. The different susceptibilities to Anguillicola crassus between the natural host, Anguilla japonica, and the naive, Anguilla anguilla, is partly due to differences in the ability of the two eel species to mount a humoral immune response.

Anguilla↗
PubMed1982

Retinal fine structure in the European eel Anguilla anguilla. I. Pigment epithelium of the glass eel stage.

The European eel (Anguilla anguilla) has a complex life cycle during which it changes habitat and to some extent morphology. During this time the eye undergoes modifications in both size and photopigments. This report forms the first of a comparative morphological study of the retina of the eel during the major stages of its life cycle. The retinal pigment epithelium of the glass eel stage consists of a single layer of cuboidal cells joined laterally by cell junctions. Both the basal (scleral) and lateral borders of these cells are relatively smooth while apically (vitreally) numerous processes enclose photoreceptor outer segments. Within the epithelial cells are abundant mitochondria, melanin granules, lipid droplets, myeloid bodies and a peculiar "multitubular body". Phagosomes are present but not numerous. Bruch's membrane is relatively thin and homogeneous. The choriocapillaris although present is not widespread and displays typically fenestrated endothelium.

Anguilla↗
PubMed1984

Ca2+-dependent phosphatase and Ca2+-dependent ATPase activities in plasma membranes of eel gill epithelium--III. Stimulation of branchial high-affinity Ca2+-ATPase activity during prolactin-induced hypercalcemia in American eels.

Infusions of ovine prolactin for 10 days induced hypercalcemia in unfed American eels, Anguilla rostrata LeSueur, that tentatively was related to stimulation of branchial Ca2+-uptake mechanisms. Analysis of ATPase activities in the plasma membranes of the branchial epithelium in prolactin treated eels showed a specific stimulation of high-affinity Ca2+-ATPase. The results of this study form further evidence that the high-affinity Ca2+-ATPase activity represents the Ca2+-pump of the branchial epithelium.

Animals↗
PubMed1996

Effects of eel neuropeptide Y on ion transport across the seawater eel intestine.

A neuropeptide Y (eNPY) was isolated from the intestinal extract of eels. This peptide enhanced significantly the serosa-negative transepithelial potential difference (PD) and short-circuit current (Isc) across the intestine of the seawater eel after pretreatment with isobutylmethylxanthine, serotonin and methacholine. The effects of eNPY on the Isc were concentration-dependent with a threshold concentration of 3 x 10(-9) M and a maximal effect at 3 x 10(-7) M. Similar concentration-response curve was obtained by porcine peptide YY (pPYY). Since 9 amino acid residues are replaced in the pPYY, this result indicates that these substitutions do not change the potency and the efficacy. These stimulatory actions of eNPY were not blocked by tetrodotoxin, an inhibitor of neural firing, or yohimbine, an alpha 2-adrenoceptor antagonist, indicating that eNPY acts without enteric neural firing or catecholamine release. When eNPY and adrenaline (AD) were applied simultaneously, the effects were additive only at lower dosage (3 x 10(-8) M for eNPY, 3 x 10(-8) M for AD), but not at high dosage (10(-6) M eNPY, 10(-7) M AD). The ceiling effect at high dosage suggests that these two regulators act through common signal transduction systems and affect the Na(+)-K(+)-Cl- cotransport system, since both effects were completely blocked by bumetanide, a specific inhibitor of Na(+)-K(+)-Cl- cotransporter.

Amino Acid Sequence↗
PubMed1983

Sex determination in the European eel (Anguilla anguilla, L.). A hypothesis based on cytogenetic results, correlated with the findings of skewed sex ratios in eel culture ponds.

Metaphase chromosomes from cultured blood cells of female, male, and hermaphroditic European eels were analyzed. In addition, both gonads from each of the specimens were examined microscopically to ensure correct sexing. The karyological investigation revealed that in some of the specimens a heteromorphic chromosome pair was present. This heteromorphism appeared in both sexes and in the hermaphrodite. C-banding and silver nitrate staining demonstrated that the heteromorphism was due to quantitative differences in constitutive heterochromatin and nucleolar organizing regions in the short arm of chromosome 8. In G-banded preparations it was demonstrated that, except for the heteromorphism mentioned, the karyotypes from both sexes and the hermaphrodite were identical. With the G-band technique it was also easily demonstrated that both the largest metacentric (No. 1) and the smallest metacentric (No. 11) had homologs. Therefore, in contrast to some earlier reports which claimed that these two chromosomes were a heteromorphic pair of sex chromosomes, it is concluded that Anguilla anguilla has no heteromorphic sex chromosomes. The implication of these findings are discussed in relation to the many reports of strongly skewed sex ratios found in commercial eel farms. It is tentatively hypothesized that sex determination in A. anguilla may be metagamic and that sex inversion may occur in this species.

Anguilla↗
PubMed1990

International Standards for salmon calcitonin, eel calcitonin, and the Asu1-7 analogue of eel calcitonin: calibration by international collaborative study.

Regulatory specifications in most countries require that the potency of salmon calcitonin (sCT) clinical products be expressed in International Units (IU) defined by the World Health Organization (WHO) International Standard. The first ampouled standard was prepared in 1972 and has been distributed world-wide since then. A batch of ampoules to serve as the replacement standard is now required. Other piscine calcitonins, eel calcitonin (eCT) and an amino-suberic acid analogue of eCT (Asu1-7 eCT) are now clinical products in some countries and international standards are required for these peptides which are similar to, but not identical with, sCT. This paper describes the preparation of three new ampouled standards and their biological calibration by international collaborative study comprising 17 participants from 10 countries. Following the recommendations in the final report of the collaborative study, the 2nd International Standard (IS) for sCT, the 1st IS for eCT and the 1st IS for Asu1-7 eCT were recently established by WHO, each with an assigned potency in IU, and are now available for issue.

Animals↗
PubMed1969

The rate of the root shift in eel red cells and eel haemoglobin solutions.

1. We have measured the rate of the exchange of O(2) between eel red blood cells and their suspending fluid in a modified Hartridge-Roughton continuous-flow rapid-reaction velocity apparatus using an oxygen electrode to follow the progress of the reaction.2. The half-times for the uncomplicated oxygenation and deoxygenation reactions in red cells at 24 degrees C were approximately 0.025-0.08 sec.3. The rate of the Root shift in cell suspensions varied widely, depending on the initial condition of the CO(2)-bicarbonate buffer system in the suspending fluid, with the rate of oxygenation or deoxygenation of the intracellular haemoglobin as an upper limit.(a) The most rapid Root shift was produced by a change in extracellular P(CO2) with minimal contributions from CO(2) hydration-dehydration reactions in the suspending fluid or from ion exchanges across the membrane, and had a half-time as short as 0.040 sec.(b) The slowest Root shift was produced by an increase in the extracellular lactic acid concentration in the absence of any form of CO(2) or in the presence of acetazolamide. This process is presumed limited by the rate of H(+) or OH(-) transfer across the membrane and had a half-time in excess of 10 sec.(c) The Root off-shift produced by an increase in P(CO2) plus a decrease in extracellular pH showed no significant trend as temperature was lowered from 30 degrees to 11 degrees C.(d) The Root on-shift produced by a decrease in P(CO2) and increase in extracellular pH had a half-time of 3 sec at 30 degrees C, 9 sec at 24 degrees C and 20 sec at 11 degrees C. These changes appeared limited by the uncatalysed rate of extracellular CO(2) hydration.4. Root off- and on-shifts in cell haemolysates at 24 degrees C, produced predominantly by changing pH but with unavoidable subsequent readjustments of the CO(2)-bicarbonate buffer systems, had an initial rapid phase with half-times as low as 0.01 sec. However, the curves were not monotonic, although they became so in the presence of carbonic anhydrase, indicating partial rate limitation by CO(2) reactions.

Acetazolamide↗