Scatter-spawning of the catfish,Silurus asotus

Reproductive behaviour of the catfish,Silurus asotus was studied in temporary waters around paddy fields. Spawning occurred nocturnally during the first week from the initiation of irrigation. In reproductive activities, a male first energetically pursued a female with its head near to the female’s belly (chasing) and then began to cling to the female’s body from the side, bending its tail or head (clinging). Finally the male enfolded the female’s body, with its anus near to the female’s (enfolding). In some cases, 2–4 males pursued a single female and two males enfolded a female at the same time. Although no aggressive behaviour was evident between males, it was always the largest male that could most frequently approach and enfold the female. The mating pair moved a long distance in a ditch, paddy field and/or creek, performing reproductive activities. It is thought that the spawning site and period of spawning of the fish enable the larvae to avoid the danger of predation and to efficiently feed, firstly on plankton and later on larvae of other fishes which become abundant during the irrigation period. Although some eggs and larvae may die due to the drying out or high water temperatures of such unstable temporary waters, scattering eggs may reduce the incidence of the annihilation of the young.     

Tandem repeat structure of rhamnose-binding lectin from catfish (Silurus asotus) eggs

The primary structure of catfish (Silurus asotus) egg lectin (SAL) was determined. SAL cDNA contained 1448-bp nucleotides and 308 amino acid residues, deduced from open reading frame. The SAL mature protein composed of 285-amino acid residues was followed by a predicted signal sequence having 23 residues. The mRNA of SAL was found to be expressed in eggs, but not in liver. SAL is composed of three tandem repeat domain structures divided into exactly 95 amino acid residues each, and all cysteine positions of each domain were completely conserved. Sequence homologies between the three domains, termed D1 (1-95), D2 (96-190) and D3 (191-285), were as follows; D1-D2, 28%; D2-D3, 33%; D1-D3, 43%. Two conserved peptide motifs, -(AN)YGR(TD)S(T)XCS(TGR)P- and -DPCX(G)T(Y)KY(L)-, appear to exist at the N- and C-terminal regions of each domain, respectively. The kinetic parameters of SAL obtained by measuring surface plasmon resonance were as follows: K(a) (M(-1)) for neohesperidosyl-BSA, 7. 1 x 10(6); for melibiosyl-BSA, 4.9 x 10(6); and for lactosyl-BSA, 5. 2 x 10(5). These results show that RBLs including SAL comprise a family of alpha-galactosyl binding lectins having characteristic tandem repeat domain structures.     

Difference in response by two cyprinid species to predatory threat from the nocturnal catfish Silurus asotus

Response to predators may not be identical between different prey species with different life histories and body sizes, particularly when the threat of predation is not great. To clarify this hypothesis, we introduced two prey species (10 Japanese dace, Tribolodon hakonensis, and 10 pale chub, Zacco platypus) into each experimental pond (in total, 8 ponds×4 trials) in which benthic algae had been allowed to grow. The presence or absence of Far Eastern catfish, Silurus asotus, and a refuge for prey fish was used to produce four treatments. The presence of catfish and/or a refuge did not affect either the feeding behavior or growth rate of Japanese dace. In contrast, when catfish were present and no refuge was available, the incidence of bottom feeding for pale chub greatly decreased. Pale chub growth rate was low when catfish were present and a refuge was available, indicating that pale chub spent more of their time in the refuge and lost opportunities of acquiring food. Japanese dace can reach a threshold size at which the prey are safe from predation, but pale chub cannot, and this may explain the differences in response to predators of the two species.     

Stereotyped sequence of mating behavior in the Far Eastern catfish, Silurus asotus, from Lake Biwa

 Mating behavior of the Far Eastern catfish, Silurus asotus (Siluriformes: Siluridae), was observed in a ricefield system facing the shore of Lake Biwa in mid-May to early June in 1990–1997. A set behavioral sequence similar to those of two other silurid fishes, S. biwaensis and S. lithophilus, both endemic to the Lake Biwa system, was observed: “chasing,”“clinging,”“enfolding” while “squeezing” by the male, and “circling” by the spawning pair. This form of mating behavior is quite different from that of S. asotus reported from the Ooi River system in Kyoto Prefecture, which mainly spawns in running water in ditches. Received: April 10, 2001 / Revised: November 5, 2001 / Accetped: November 20, 2001     

Spawning and season affect lipid content and fatty acid composition of ovary and liver in Japanese catfish (Silurus asotus)

The influences of spawning and season on lipid content, lipid classes, and fatty acid composition were assessed in ovary and liver of wild and cultured Japanese catfish (Silurus asotus). The lipid content (7.3+/-1.6 g/100 g wet wt.) of ovary from wild catfish at spawning was higher than that at post-spawn. However, no influence of spawning on the lipid content of liver was observed. Docosahexaenoic acid [DHA, C22:6(n-3)] in ovary lipids was 12.3+/-0.5% of total fatty acids. The percentage of n-7 monounsaturated fatty acids in triacylglycerol from the ovary and liver in the spawning season was high. Percentages of C22:6(n-3) in phosphatidylcholine and phosphatidylethanolamine from ovary were higher during spawning than after spawning. No significant differences were observed in the lipid content of ovary and liver from cultured catfish between seasons (summer vs. winter). Content of arachidonic acid (C20:4n-6) in ovary and liver from cultured catfish was higher in summer than in winter. There were differences in lipid classes of ovary and liver by spawning and season. These results suggest that the lipid metabolism in Japanese catfish is greatly influenced by spawning and season.     

Thresholds of retinal and extraretinal photoreceptors measured by photobehavioral response in catfish,Silurus asotus

Summary Light thresholds of retinal and extraretinal photoreceptors in catfish were examined by the photobehavioral response using a method in which reflex body movements are recorded. Thresholds were determined in six groups, (A) intact, (B) ophthalmectomized, (C) pinealectomized, (D) ophthalmectomized + pinealectomized, (E) ophthalmectomized, pinealectomized and skinless over the brain (skinless fish) and (F) ophthalmectomized, pinealectomized and dorsally covered with aluminum foil over the brain (covered fish). All these fishes displayed short term activity to white light stimulation after being dark adapted for more than 5 h. The lowest threshold was obtained in the intact group (2.0×10^–4 W/cm²). The thresholds of lateral eyes and the pineal organ were 3.4×10^–3 and 1.5×10^–2 W/cm², respectively. Without lateral eyes and pineal organ, catfish still responded to light, indicating the possible existence of extraretinal nonpineal photoreceptors (ENPs). The threshold of ENPs was 3.3 W/cm². The localization of ENPs was assumed to be in the brain from the experiment with the combination of skinless and covered fish.Abbreviation ENP extraretinal nonpineal photoreceptor     

Effect of meal size on postprandial metabolic response in Chinese catfish (Silurus asotus Linnaeus)

The effect of relative meal size (0.5–24% body mass) on specific dynamic action (SDA) was assessed in Chinese catfish (Silurus asotus Linnaeus) (30.90±1.30 g) at 25.0°C; the cutlets of freshly killed loach without viscera, head and tail were used as a test meal. There was no significant difference in either SDA duration or peak oxygen consumption (VO₂) among low meal size ranges. But both increased linearly as meal size increased from 2 to 24% without reaching a plateau. Factorial metabolic scope was 5.92 in fish fed with 24% body mass, the highest documented feeding metabolic scope value in fish till now. The Peak VO₂ of satiated meal size groups (175.85±10.55 mg O₂ h⁻¹) was above 80% of maximum metabolic rate during locomotion recovery process (215.48±7.07 mg O₂ h⁻¹). The relationship between energy expended on SDA (E) and energy ingested (I) was described as: E=0.0000432I ²+0.140I+2.12. The lowest value of SDA coefficient appeared at 2% body mass group.     

鲇的消化能力与营养价值分析

采用常规方法测定了鲇(Silurusasotus)的消化道指数,其比肠长、比胃重、比肠重、比肝胰脏重和比内脏重分别为0726±0087、0027±0015、0013±0008、0022±0004和0081±0041。体重与体长的回归方程Y=00124X2.8451(r=09940,P<001);鲇的胃、前肠、中肠和后肠中消化液的pH值分别为48～62、66～70、69～75、72～77,且消化道各部分具有较高的蛋白酶和淀粉酶活性,蛋白酶的活性为前肠>胰脏>胃>中肠>后肠;而淀粉酶的活性则为胰脏>胃>前肠>中肠>后肠;肌肉中粗蛋白的含量1881%,粗脂肪含量152%;必需氨基酸含量占氨基酸总量的4451%,鲜味氨基酸含量占氨基酸总量的4598%,综合肌肉的常规营养成分和氨基酸分析的结果,鲇是一种营养价值较高的优质鱼类。     

A unique epidermal mucus lectin identified from catfish (Silurus asotus): first evidence of intelectin in fish skin slime

The present study reports a new type of skin mucus lectin found in catfish Silurus asotus. The lectin exhibited calcium-dependent mannose-binding activity. When mannose eluate from chromatography with mannose-conjugated agarose was analysed by SDS-PAGE, the lectin appeared as a single 35-kDa band. Gel filtration showed that the lectin forms monomers and dimers. A 1216-bp cDNA sequence obtained by RACE-PCR from the skin encoded a 308 amino acid secretory protein with homology to mammalian and fish intelectins. RT-PCR demonstrated that the lectin gene was expressed in the gill, kidney and skin. Subsequent sequencing revealed the presence of an isoform in the gills. Antiserum detected the intelectin protein in club cells in the skin and gill, renal tubules and blood plasma. Although intelectin gene expression was not induced by in vivo bacterial stimulation, the intelectin showed agglutination activity against the pathogenic bacterium Aeromonas salmonicida, suggesting that the lectin plays an important role in self-defence against bacteria in the skin surface of the catfish. These findings represent one of the few examples of characterization and functional analysis of a fish intelectin protein.     

大口鲇和鲇鱼血清蛋白质及同工酶的比较研究

采用聚丙烯酰胺梯度凝胶垂直板电泳,分析了大口鲇和鲇鱼的血清蛋白质以及心脏、肝脏、眼和肌肉4种组织的EST及MDH同工酶。结果表明,大口鲇和鲇鱼的血清蛋白质均能分离出20条左右的谱带,两者既表现出相同的谱带,又表现出迁移率和含量都不同的带型。两者的EST和MDH同工酶在4种组织及血清中均能特异性地表达,存在明显的组织和物种特异性。本文认为肝脏是研究大口鲇和鲇鱼种群生化遗传结构与变异的理想材料,同时还探讨了两种鲇鱼的M DH同工酶位点。 Abstract:The serum proteins and isozymes in four tissues (heart,liver,eye and musele)of Smeridionalis Chen and S.asotus Linnaeus were analyzed by polyacrylamide gradient gel vertical electrophoresis.The isozymes are esterase(EST)and malate dehytrogenase(MDH).The results showed that electrophoretograme of serum proteins were about 20 protein pattens in two species catfish,they were either the same protein pattens or the different pattens.Electrophoretogram of isozymes(EST,MDH)in two species catfish indicated tissues and species specificity.Experiment considered that the liver was a good material studied biochemical genetic constitution and variation in species group of S.meridionalis Chen and S.asotus Linnaeus.     

Dietary and seasonal effects on the dorsal meat lipid composition of Japanese (Silurus asotus) and Thai catfish (Clarias macrocephalus and hybrid Clarias macrocephalus and Clarias galipinus)

The effects of dietary lipids and seasonal variation on the lipids of wild and cultured catfish (Japanese catfish, Silurus asotus; Thai catfish, Clarias macrocephalus and hybrid Clarias macrocephalus x Clarias galipinus) were determined by analysis of the lipid content and fatty acid composition of their dorsal meat. The predominant fatty acids of dorsal meat were 16:0, 18:1n-9, 18:2n-6, 20:4n-6 (arachidonic acid, AA), and 22:6n-3 (docosahexaenoic acid, DHA). The DHA content in the diet of Japanese catfish was higher than that in the diet of Thai catfish, and this was reflected in the dorsal meat of the Japanese catfish, which had a remarkably high percentage of DHA compared with the meat of the Thai catfish. Cultured Japanese catfish had a higher percentage of 18:2n-6 than Thai fish and a lower percentage of AA in winter than in summer season. There were also seasonal variations in the percentage of n-6 fatty acids in Japanese catfish. In summer, the fatty acid composition of the cultured Japanese catfish was similar to that of the wild catfish. These fatty acid changes in the lipid classes, triacylglycerol, phosphatidylcholine and phosphatidylethanolamine were similar to those observed for total lipids. These results indicate that the percentage of DHA in the dorsal meat of catfish is influenced by dietary fatty acid, and it may be that it can be increased in cultivated fish by administering a diet containing a large amount of DHA.     

Separation and analysis of the major forms of plasma fibronectin

Human plasma fibronectin exists in circulation in multiple molecular forms that are distinguishable by SDS-polyacrylamide gel electrophoresis (zone I, approx. 450 kDa dimers; zone II, 190-235 kDa; Zone III, 146-175 kDa). (Chen, A.B., Amrani, D.L. and Mosesson, M.W. (1977) Biochim. Biophys. Acta 493, 310-322). We report here on investigations of plasma fibronectin that had been purified from the 'heparin-precipitable fraction' of plasma by DEAE-cellulose chromatography using buffers containing a chaotropic salt (KSCN). Zone I fibronectin and zone II fibronectin were subsequently separated by Sepharose CL-6B chromatography in the presence of 0.3 M KSCN. Electrophoresis of reduced zone I fibronectin dimers showed the presence of three types of subunits (i.e., 220 kDa, 215 kDa, 207 kDa), evidently all having the same NH2-terminal sequence. Subunits of this size were also found in reduced zone II fibronectin, as well as another polypeptide of 190 kDa, the latter amounting to under 5% of the total. Unreduced zone I fibronectin was resolved by gel electrophoresis into a doublet. The upper component amounted to approx. 90% of the total and was comprised of 220 kDa and/or 215 kDa subunits; the lower component contained 207 kDa plus a 220 kDa or 215 kDa subunit. Scanning transmission electron microscopy indicated that under physiologic conditions zone II fibronectin molecules, like those in zone I, exist as pleiomorphic, loosely folded structures (approx. 16 X 8-12 nm) that are somewhat smaller than dimeric zone I molecules (approx. 24 X 16 nm). Circular dichroic spectral analyses suggests that both types have similarly folded local domains. Affinity chromatography experiments revealed a relative decrease in the binding of zone II fibronectin to gelatin but no difference from zone I fibronectin with respect to heparin or fibrin binding.     

Isolation and characterization of rat plasma fibronectin.

Rat plasma fibronectin has been isolated and characterized and monospecific antibodies were prepared to it. Two components of fresh rat plasma (in the presence of proteinase inhibitors) bound to a gelatin-Sepharose affinity column. One protein was eluted with 4.0 M-urea and was identified as fibronectin. Another protein was eluted from the gelatin-Sepharose column with 8.0 M-urea and was identified as a 70 000-Mr collagen-binding molecule. This 70 000-Mr fragment was found to be a normal constituent of blood plasma, and its presence did not represent a proteolytic degradation product formed during isolation. The antibodies prepared against rat fibronectin only weakly cross-reacted with plasma fibronectins of chicken, horse and human. These studies shed light on the metabolic interrelationships between fibronectin and other collagen-binding molecules.     

Isolation and identification of partial cDNA clones for endoplasmin, the major glycoprotein of mammalian endoplasmic reticulum

The amino acid sequences of peptides isolated from murine endoplasmin showed significant homology (approximately 50%) with sequences in the heat-shock proteins 90 and 83 of yeast and Drosophila, respectively, indicating that they are related proteins. Mixed oligonucleotide probes, deduced from the peptide sequences, were used to isolate cDNAs from a murine liver cDNA library. DNA sequencing confirmed the presence of a coding sequence for one of the endoplasmin peptides, formally establishing the authenticity of the cDNA. The identity of the murine and hamster endoplasmin sequences suggests a level of sequence conservation associated with proteins that perform a structural role in cells.     

Isolation and identification of androstanediol glucuronide from human plasma

[3H]Dihydrotestosterone (50 microCi) was infused into normal men and women for 8 h. It was previously shown that this was sufficient time for this material to reach a steady state. Venous plasma was obtained at 6 and 8 h, pooled, and the unconjugated steroids removed by ether extraction. The remaining plasma was adjusted to pH 4.9 and the steroid conjugate was extracted first with ethyl acetate and then with an ether-ethanol mixture. The extracts were combined and taken to dryness. Steroid sulfates were solvolyzed using dioxane, and the mixture partitioned between ether and 1% NaOH. The aqueous phase was acidified and added to an XAD-2 column, washed with water, and the glucuronide fraction eluted with methanol. The solvent was concentrated and the methanol extract was passed through a C18 Sep-Pak, filtered through an Acrodisc CR and then subjected to gradient high performance liquid chromatography [HPLC] (Nova-Pak C18, KH2PO4, pH 3, and methanol). The fractions containing steroid glucuronides were collected and esterified with diazomethane and then acetylated with acetic anhydride in pyridine. The glucuronide triacetyl methyl ester (GAME) derivatives were then run in a second HPLC system (3 Lichrosorb 5 mu columns, 4 mm x 25 cm) using a gradient of ethanol-heptane and heptane. We clearly established that this system separates 3 alpha-diol GAME conjugated at the 17 and 3 positions (44 vs 50 min) with authentic samples previously synthesized in our laboratory. We concluded that the pooled plasma contained only the 17-GAME conjugate. No significant activity of the 3-glucuronide was detected. The natural compound in circulation, therefore, is 5 alpha-androstane-3 alpha, 17 beta-diol 17-glucuronide.     

Isolation of the major glycoprotein from fat cell plasma membranes

The major glycoprotein of rabbit fat cell plasma membranes has been solubilized by Brij 99 extraction and purified to homogeneity by preparative polyacrylamide gel electrophoresis and concanavalin A-Sepharose affinity chromatography. The isolation procedure yielded a glycoprotein with an apparent molecular weight of 79,000 which appeared as a single component by Coomassie blue and periodic acid-Schiff staining as well as by distribution of radioactivity after ¹²⁵I labeling. The lectin chromatography was effective in removing polypeptides and Schiff-nonreactive glycoproteins which migrated in close proximity to the major glycoprotein during electrophoresis but were not retained on the concanavalin A column. Determination of the amino acid and sugar composition of the purified glycoprotein indicated that it contained 18% carbohydrate by weight which occurred in the form of 30 mannose, 14 galactose, 23 glucosamine, 3 galactosamine, 6 N-acetylneuraminic acid, and 1 fucose residues per molecule. Approximately one-fifth of the total protein-bound saccharide of the adipocyte plasma membrane was accounted for by this glycoprotein and its composition suggested that it was the source of some of the previously identified (Y. Kawai, and R. G. Spiro, 1977, J. Biol. Chem.252, 6236–6244) asparagine- and serine (threonine)-linked carbohydrate units of the fat cell surface.