The present work evaluates the effect of vacuum treatment on smoke penetration into boiled skipjack loins for the production of smoke-dried skipjack. Using a vacuum freeze-dryer, the boiled skipjack loins were vacuumed immediately after being boiled at a pressure of 400 Pa for 30 min in order to reduce the lipid and water contents. The vacuumed boiled meats were then smoked and dried at 90±10°C for 3 h a day for 6 days in a metal kiln (internal diameter 24 cm×24 cm×70 cm height), using an electric heater (1.2 kW) to heat and generate smoke from cherry tree wood chips. Also, non-vacuumed boiled meats were smoked in the same manner as a control. The vacuum treatment reduced the lipid and water contents by as much as 0.6% and 2.7% on the wet weight basis, respectively. Histological observations showed many clearances among the muscle fibers of the vacuumed boiled meats. The content of phenols that had penetrated the vacuumed boiled meats during the smoke drying procedure was significantly larger (P < 0.05) than that of the non-vacuumed boiled meats. Accordingly, the vacuum treatment accelerated the penetration of phenols into the boiled meats and enhanced the function of antioxidant substances, which improved the quality of the smoke-dried skipjack.

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The influence of different photoperiod cycles (3L:3D, 6L:6D, 12L:12D, and 24L:24D) on the metabolic rate and energy loss of either fed or unfed young tilapia Oreochromis niloticus (bodyweight 8.6-9.5 g) was investigated at 28°C. A computer-operated respirometer with a closed tank was used to prevent water from evaporating into the air or condensing from the air. The photoperiods acted as strong Zeitgeber (i.e., cue or synchronizer) during the experiments with either fed or unfed fish. A photoperiod-mediated metabolic cycle was demonstrated in fed and unfed fish in which oxygen consumption was higher during the light phase compared with during the dark phase for all photoperiods. Mean oxygen consumption during the 3L:3D, 6L:6D, 12L:12D, and 24L:24D periods for fed and unfed fish were 685.06 mg/kg per h and 299.33 mg/kg per h; 658.52 mg/kg per h and 284.80 mg/kg per h; 591.09 mg/kg per h and 249.62 mg/kg per h; and 500.64 mg/kg per h and 239.14 mg/kg per h, respectively. The highest post-prandial increase in energy loss was recorded during the 3L:3D period (145.88 kJ/kg per day), followed by 141.19 kJ/kg per day during the 6L:6D, 128.70 kJ/kg per day during the 12L:12D, and 99.92 kJ/kg per day during the 24L:24D periods. The results suggest that higher energy conservation would be achieved if fish are exposed to longer rather than shorter photoperiod cycles.

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A series of experiments were conducted to examine the effects of salinity, aeration and light intensity on oil globule absorption, feeding incidence, and growth and survival of early-stage Epinephelus coioides larvae. Newly hatched larvae were transferred to 40-L aquaria at a density of 1500 individuals/aquarium. Larvae were exposed to different levels of aeration (0 mL/min per L, 0.62 mL/min per L, 1.25 mL/min per L, 2.50 mL/min per L, or 3.75 mL/min per L); salinity (8 ppt, 16 ppt, 24 ppt, 32 ppt, or 40 ppt); and light intensity (0 lx, 120 lx, 230 lx, 500 lx, or 700 lx) for 4-6 days. Twenty larvae were sampled daily at 11:00 hours to measure for total length (TL), oil globule volume, and feeding incidence. Survival rates were determined by counting the total number of larvae remaining in each aquarium at the end of the experiment. Significantly higher survival rates (P<0.05) were observed at aeration levels of 0.62 mL/min per L and 1.25 mL/min per L, at salinity levels of 16 ppt and 24 ppt, and at light intensities of 500 lx and 700 lx. The influence of aeration level, salinity and light intensity on oil globule absorption, feeding incidence, and growth and survival of early-stage grouper larvae are discussed.

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The concentrations of Zn and sulfhydryl (SH) groups in the digestive tract tissue of common carp and some aquatic animals were studied. It was found that Zn and bound SH groups could be used as indicators for detecting the Zn-binding protein in the digestive tract tissue of common carp. The digestive tract tissue of the fish underwent subcellular fractionation, and it was found that the nuclei/cell debris fraction contained most of the DNA (85%), Na⁺/K⁺-ATPase (82%), organic phosphate (90%) and the Zn-binding protein (79%), but only part of the 5'-nucletidase and alkaline phosphatase (<23%). The nuclei/cell debris fraction of the digestive tract tissue of common carp was treated with either collagenase type I or type IV, and subfractionated by sucrose density centrifugation. It was found that treatment with collagenase type IV could release more than 50% of the Zn-binding protein, Na⁺/K⁺-ATPase and organic phosphate from collagen. Sections of digestive tract tissue of common carp were stained for Zn. It was observed that Zn can be found mainly on the edge of the epithelial layer, and everywhere in the ‘membrane-like’ portion of the submucosal and muscular layers. It is proposed that most of the Zn-binding protein in the digestive tract tissue of common carp is located on the basolateral plasma membranes of the epithelial cells and on the surrounding muscle cells that are attached to the collagen type IV of basal laminae.

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Variation within the growth hormone gene and its association with growth trait in the olive flounder (Paralichthys olivaceus) was investigated. Based on Southern blot analysis and using various kinds of restriction endonucleases, it was demonstrated that the growth hormone gene exists as a single copy gene in the olive flounder. Polymorphisms of various lengths were also detected by Southern blot analysis, and by the subsequent digestion of the polymerase chain reaction (PCR) -amplified growth hormone gene fragment with Sau3AI restriction enzyme. To study the possible association between variation in the growth hormone and weight, 60 progenies of the hatchery strain of three various sizes (large, medium and small weight) were selected and the entire genetic structure of the growth hormone gene was analysed. A total of 15 different genotypes was observed from the random association of six haplotypes. Significant heterogeneity of the growth hormone gene with haplotype and genotype frequencies was detected among the different-sized groups.

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Changes in tissue structures, rheological properties, and water content of abalone meat were studied in relation to boiling and steaming time. The adductor muscle of abalone Haliotis discus, which was removed directly from the shell, was boiled or steamed for 1 h, 2 h, and 3 h. When observed under a light microscope and by scanning electron microscopy, structural changes in the myofibrils were greatest in the boiled abalone meat compared with the steamed meat. When heating time was increased from 1 h to 3 h, the instantaneous modulus E₀ of boiled abalone meat decreased gradually with increased heating time, whereas the E₀ of steamed abalone meat was reduced when heated for 2h. When heated for 1 h, the relaxation time of steamed abalone meat was much longer than that of boiled meat. There were no significant changes in the relaxation time of abalone meat among the different boiling times, but the relaxation time of steamed abalone meat was reduced gradually with increasing heating times. The study's results confirmed that the difference in rheological properties between the boiled and steamed meats was due mainly to the denaturation level of myofibrils when heated for 1 h, as well as due to the changes in water and solid content and the manner in which the inner water was exchanged after heating time was increased from 1 h to 3 h.

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To investigate the effects of disproportionate levels of dietary arginine and lysine on juvenile Japanese flounder Paralichthys olivaceus, growth performance and biochemical parameters were evaluated by feeding five test diets, comprising different levels of arginine and lysine, to triplicate groups of juveniles (initial bodyweight 1.85g) for 40 days. Crystalline amino acids were supplemented to test diets to correspond to the amino acid pattern found in the whole body protein of the Japanese flounder, except for arginine and lysine. After the feeding trials, plasma arginine, lysine and urea levels, excreted ammonia-N, and liver arginase activity were analysed. Survival, specific growth rate, feed conversion efficiency, and apparent protein retention were adversely affected (P<0.05) by the deficiency in dietary arginine or lysine concentrations. An excess of either lysine or arginine in the diet did not depress growth when the diets contained adequate levels of either arginine or lysine, proving that there is no evidence for an arginine-lysine antagonism. Results for plasma arginine, lysine and urea levels, excreted ammonia, and liver arginase activity also demonstrated that Japanese flounder juveniles are not sensitive to excess dietary levels of lysine and arginine.

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The lipid profile was studied along the branch length, from the top, middle to base portion, of coral Montipora digitata to gain more insight into the physiological significance of lipids in the coral energy budget. The lipids of M. digitata consisted of seven major lipid classes: polar lipid, sterol, free fatty acid, unknown lipids 1 and 2, triacylglycerol (TG), and wax ester. The concentration of storage lipids, TG, and wax ester showed a top-base gradient along the length, whereas the levels of free fatty acid and unknown lipids showed a base-top gradient. The proportions of polar lipid and sterol in the top portion of the branch were slightly higher than those in the base portion. This observation appeared to be compatible with the view that the increased energy expenditure for proliferation enhanced the mobilization of the storage fuel lipids of wax ester and TG rather than the structure lipids of polar lipids and sterols at the top portion of the branch. Compositions of fatty acid also showed a length-wise diversity. The top portion had a lower proportion of palmitic acid (16:0) in all lipid classes of fatty acid ester, suggesting that this fatty acid was preferentially mobilized at the top portion, probably for the growth of coral cells.

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The reproductive value and population status of the big eye in the north-eastern Taiwan waters was estimated by demographic analysis using available life-history parameters. Life-history tables were constructed using estimates of natural mortality (M) of 10.4920/year for age 0 and 0.3256/year for ages 1-9, with a maximum age of 9. Age-specific batch fecundity (F_e) was from F_e=1391.34e^0.1782FL. The age-specific proportion of maturity was estimated from the relationship between the proportion of female maturity (Pr) and fork length (FL): Pr=1/(1+e^{15.081-0.796FL}). Females mature at age 3 and mature females reproduce every year. The population increase rate (λ) was estimated to be 20.5% per year and the generation time (G) was 6.25 years without exploitation. The net reproductive value (R₀), generation time and intrinsic rate of natural increase (r) decreased with increased fishing mortality. For fixed fishing mortality, when F=1.2/year and fishing started at age 3, R₀ was estimated to be 1.0 and the population was considered to be in equilibrium. For age-specific fishing mortality, when fishing started at age 3, R₀ was estimated to be 0.96/year, G being 6.18 years, and the population decreased 0.7% per year. The big eye population had a strong resilience as long as F<=1.3/year started at an age that was older than the age at maturity (i.e. 3 years old) but would decline when intensive fishing (F>=1.2/year) started at age 2 or younger. Sensitivity analysis indicated that the mortality of age 0 is the most sensitive parameter in demographic analysis.

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The entry and escape behavior of prawn Macrobrachium nipponense in relation to the pot may be controlled both by its design and population process in the pot's given interior space. To obtain the basic data on how the population process affects the number of individuals in the pot without bait, a comparative study of the experimental results obtained in the actual fishing ground and calculated values was conducted. The variation pattern in the number of individuals in a pot was consistent with that of the calculated value. The model equation proposed in this study might be effective for evaluating the daily variations in the number of individuals in a pot. The results suggest that both the population process and the pot's design control the entry and escape behavior of the prawn.

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Stocks of walleye pollock Theragra chalcogramma collected from: (i) the Sea of Japan (off Rebun Island and Kumaishi); (ii) the Pacific coast (off Shikabe and eastern Hokkaido); and (iii) Nemuro Strait off Hokkaido, northern Japan, were examined for anisakid nematodes during December 1999 to February 2000, and the prevalence and abundance of Anisakis simplex and Contracaecum osculatum larvae were compared among the various sampling sites for fish of the same size and age. Anisakis simplex was generally more abundant than C. osculatum. Infection by A. simplex varied between the aforementioned stocks of walleye pollock as well as within stocks, whereby fish from off Rebun Island and Nemuro Strait were infected the most, followed by those from off the Pacific coast and Kumaishi. Infection by C. osculatum differed between the host stocks, and C. osculatum was the most abundant among the fish from Nemuro Strait. The infection variations seemed to be due to differences in host growth rate, host feeding habit, and the distribution of marine mammal final hosts. The results indicate that these two larval nematodes are useful biological indicators for the population study of walleye pollock in Japanese waters.

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To study the influence of different photoperiod cycles on the metabolic rate and energy loss of fed and unfed adult tilapia Oreochromis niloticus (bodyweight 102-107 g) at 28°C, four photoperiod cycles (i.e. 3L:3D, 6L:6D, 12L:12D, and 24L:24D) were applied. A computer-operated respirometer with a closed tank was used so as to prevent water from condensing from the air or evaporating into the air. A photoperiod-mediated metabolic cycle was demonstrated during the routine state in which the metabolic rate was higher during the light phase compared with during the dark phase for all photoperiods. The combined effects of photoperiod and feeding episodes acted as a strong Zeitgeber (cue or synchronizer) for synchronizing the daily rhythm in fed fish. Fish exposed to short photoperiod cycles showed a higher metabolic rate and energy loss compared with those exposed to longer photoperiod cycles. Mean oxygen consumption in the fed and unfed fish were 295.7mg/kg per h and 149.8mg/kg per h, respectively, during the 3L:3D period; 286.5mg/kg per h and 143.3mg/kg per h during the 6L:6D period; 262.2mg/kg per h and 130.3 mg/kg per h during the 12L:12D period; and 238.3mg/kg per h and 120.4mg/kg per h during the 24L:24D period. The highest post-prandial increase in energy loss was recorded during the 3L:3D period (56.2kJ/kg per day), followed by 55.1 kJ/kg per day during the 6L:6D period, 50.7kJ/kg per day during the 12L:12D period, and 45.4kJ/kg per day during the 24L:24D period. The study's results demonstrated that the fish conserve energy when raised under longer photoperiod cycles.

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To clarify the habitats of the ayu in the early stages of development in the Shimanto Estuary, the size and hatching date of the larval and juvenile ayu were examined. Sizes of larvae and juveniles were larger in the center of the flow area than in the waters adjacent to the estuary's banks, which suggests that larvae shift habitat to the center of flow from the waters along the estuary's banks. This shift began at approximately 20 mm body length. However, the resident term in the waters adjacent to the estuary's banks changed with the hatching dates; that is, the early and late-hatched larvae became short and long-term residents, respectively. A similar phenomenon was found also in the juveniles collected in the freshwater section that were migrating upstream. The growth rates of larval ayu in the waters adjacent to the banks tended to decrease with hatching dates. The fluctuations in growth rate with hatching date appear to be a factor leading to the variation of resident term.

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The effect of all-trans retinoic acid (atRA) on pigmentation and skeletal formation of Japanese flounder Paralichthys olivaceus was investigated. Five groups of flounder larvae were fed live food enriched with 0.5 mL docosahexaenoic acid (DHA) 38G oil containing 100 mg of atRA/10 L of culture medium during different developmental stages; that is, A-B, C-D, E-F, G-H, and I. The control group was fed live food enriched with only DHA 38G oil. Flounder that were fed live food enriched with atRA during the A-B stages showed albinism, and mandible and severe caudal defects (albinism 75.7%, lower jaw defects 75%, caudal defects 100%). Occurrence of these abnormalities in other groups was 0%, 1-4%, and 4.5-10.7%, respectively. Administration of atRA during the A-B stages also caused a high number of vertebrae mainly in the caudal area. Moreover, additional abdominal vertebrae had formed in 25% of fish that were fed live food enriched with atRA in the A-B stages. These results indicate that the effect of atRA is dependent on the developmental stage of flounder larvae and they also suggest that morphological and color abnormalities in flounder were induced by atRA accumulated in live food (rotifers 13 mg/g; Artemia 1.6 mg/g), especially during the A-B stages.

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A thermotolerant, fermentative yeast strain named RND13 from a hot spring drainage was evaluated for its ethanol-producing ability at elevated temperatures at a high substrate concentration [15% (w/v) glucose] close to the level reflecting industrial practice. The RND13 was capable of utilizing glucose almost completely at 40°C with increasing inoculum size, producing ethanol up to 6.6% (w/v), which is comparable to levels (7.0-7.2%) at 30°C. The maximum rate of ethanol production by the RND13 was found to be 9.0 g/L per h at 40°C in an inoculum sized 5% (w/v). At 43°C, however, the RND13 could not utilize glucose to completion and showed a slight drop in the extent of produced ethanol [6.0% (w/v)]. Thus, the culture at 40°C with a 5% cell inoculum was considered to be the optimal condition for ethanol production at higher temperatures in terms of batch fermentation. In the phylogenetic analysis based on the small-subunit rDNA sequence, the strain was grouped together with both Candida glabrata and Kluyveromyces delphensis, which are relatively close to Saccharomyces cerevisiae.

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To clarify the total phosphorus (P) and nitrogen (N) loading from carp culture, five commercial diets were selected from a major location in Japan, Lake Kasumigaura, for a 12-week feeding trial. These diets were prepared as per the ‘Kasumigaura Feed Standard’ (crude protein <35% and digestible energy >3.5kcal/g), and total P ranged from 1.4% to 2.0%. However, for most of the diets the P available was lower than the requirement level. A control diet was formulated with 25% fishmeal to comply with that standard and contain adequate available P. Duplicate groups of juvenile carp were fed the aforementioned diets to satiation, three times a day, six days a week throughout the trial. Growth performance was significantly higher for the control group and values of P absorption (20.4-47.0%) and retention (14.0-36.3%) varied widely among the groups. Consequently, the total P loading (kg/t production) values based on retention fluctuated from 14.8 to 26.4 among the commercial diet groups compared with the low level of 8.5 for the control group. Similarly, the total N loading (kg/t production) values varied from 30.9 to 86.0 and was lowest for the control group. A higher whole body lipid and lower bone P and Ca confirmed the deficiency of the dietary available P in commercial diets. Better growth and comparatively less P and N loading rates were observed in the diet that had sufficient available P, not to mention that the control diet ranked best. It was concluded that an inadequacy of available P among the commercial diets affects the growth of carp and produces high P and N loading into the water. Therefore, if the commercial diets do not supply adequate levels of available P to carp, growth is negatively affected and may result in greater waste loading.

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The chemical components and body color of horse mackerel caught between July 1997 and May 2000 were studied. The fish were caught with small- to medium-sized purse seine offshore from Nagasaki and from Tsushima, and with bull trawl seine and medium- to large-sized purse seine in the East China Sea. The crude lipid content of the fish caught offshore from Tsushima was higher than that of the others, and there were no significant differences among the other catches. The extractive nitrogen content of the fish caught with bull trawl seine was somewhat lower than that of the others. The body colors of the fish differed from those suggested by their common names: Kuroaji (black), Kiaji (yellow), and Shiroaji (white). The crude lipid content and body color indicated that there was no difference in quality among the catches, with the exception of the crude lipid content of the Tsushima catch.

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This study was conducted to gather data on the reduction of environmental phosphorus (P) loading through the formulation of carp diets with different combinations of protein ingredients. Five experimental diets were formulated by substituting fishmeal (FM; 10-20%) with alternative protein sources such as meat meal (MM; 5-15%), blood meal (BM; 5-7%), and defatted soybean meal (dSBM; 6-10%). The control diet used was a commercial carp diet selected based on earlier experiments. Each diet was fed to duplicate groups of juvenile carp three times a day, until satiation for 12 weeks. Feed performance was proportional to the increase in dietary FM levels. Phosphorus absorption ranged between 41.6% and 52.0% among the experimental groups and was 42.6% for the control group, but there were no marked differences in nitrogen (N) absorption rates. Phosphorus retention ranged from 31.4% to 35.7% for the test diets, whereas N retention increased proportionally with dietary FM levels and ranged from 34.7% to 41.7%. The P and N retention values of the control diet were 27.6% and 41.2%, respectively. The total P loading (T-P) increased at the higher FM levels (9.1-10.7 kg/t production), whereas lower FM levels produced higher total N loading (T-N, 34.6-43.1 kg/t production), the figures for the control being 13.9 T-P kg/t production and 35.6 T-N kg/t production. These results indicate that the reduction of FM levels to 10-20% by replacing it with MM, BM, and dSBM in carp diets was effective in reducing the loading of P and N.

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Characterization was investigated on the 38 kDa and 42 kDa chitinase (EC3.2.1.14) isozymes from the liver of Japanese common squid Todarodes pacificus. Optimum pH toward colloidal chitin was observed at pH 3.0 for the 38 kDa chitinase, and pH 3.0 and 9.0 for the 42 kDa chitinase. K_m and k_cat of the 38 kDa and 42 kDa chitinases toward a longer substrate, glycol chitin, were 0.071 mg/mL and 1.22/s, and 0.074 mg/mL and 0.196/s, respectively. Alternatively, strong substrate inhibition of both chitinases were observed toward a short substrate, N-acetylchitopentaose (GlcNAc₅). Both chitinases decomposed not only chitin but also chitosan (D. A. 95%). The cleavage pattern and reaction rate were investigated using N-acetylchitooligosaccharides (GlcNAc_n, n=2-6). Both chitinases hydrolyzed GlcNAc_n (n=4, 5, and 6). The release of GlcNAc was not observed. The speed of the reaction was observed to be in the following order: GlcNAc₄>GlcNAc₅>GlcNAc₆ for the 38 kDa chitinase, and GlcNAc₆>GlcNAc₅>GlcNAc₄ for the 42 kDa chitinase. Both the chitinases released p-nitrophenol from p-nitrophenyl GlcNAc_n (n2, 3, and 4). N-terminal amino acid sequences of the 38 kDa and 42 kDa chitinases were YLLSXYFTNWSQYRPGAGKYFPQNI and EYRKVXYYTNWSQYREVPAKFFPEN, respectively.

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We have cloned a cDNA encoding the MMP-9 from a carp epidermal cell (EPC) cDNA library. The clone contains a 2025-base pair (bp) open reading frame encoding a protein of 674 amino acids. The deduced amino acid sequence shares 68% and 69% identity with medaka and Japanese flounder MMP-9. The hinge domain of the carp MMP-9, like those of the other non-mammalian species, lacks a type V collagen-like region that is typical of mammalian MMP-9. Gelatin zymography and immunoblot analysis of conditioned media of EPC cells and cDNA-transfected COS-7 cells detected a 76-kDa gelatinase. The apparent molecular mass of the carp zymogen is much smaller than those of its mammalian counterparts while almost identical with that of chicken 75-kDa gelatinase B-like enzyme. Although hypo-osmotic stress induced the elevation of MMP-9 mRNA level in EPC cells, no significant change in the protein in conditioned medium was detected during hypo-osmotic stress. Northern blot analysis detected a large amount of MMP-9 mRNA in carp kidney and spleen, suggesting the high expression of MMP-9 in blood cells, neutrophils, and macrophages. The smaller amount of MMP-9 mRNA was detected in gill, heart, fin, and eye, whereas none of the mRNA was detected in the hepatopancreas, intestine, brain, muscle, and skin.

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Toughness is one of the most important elements that define the commercial value of the raw meat of fish. Degradation of the extracellular matrix is thought to be a cause of postmortem tenderization of fish meat. A previous study has suggested that this tenderization is caused mainly by metalloproteinases. The present study seeks to identify the proteinase (s) involved in tenderization; hence, cloned cDNA of two gelatinases from Japanese flounder, which showed high homology with mammalian matrix metalloproteinase (MMP)-2 and MMP-9, were designated as jfMMP-2 and jfMMP-9, respectively. Northern blot analysis revealed that jfMMP-2 mRNA was expressed almost ubiquitously in adult tissues including the brain, muscle, gill, heart, gut, kidney, spleen, testis, and ovary. In contrast, the expression of jfMMP-9 mRNA was observed in those tissues which were abundant in blood cells, such as kidney, spleen, heart, and gill. Both recombinant proteins (jfMMP-2 and jfMMP-9) produced with the COS-7 cell system exhibited gelatin-degrading activity that was sensitive to 1, 10-phenanthroline, a typical metalloproteinase inhibitor.

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Heating temperatures of 30-40°C and KCl concentrations of 0.1-0.5 M altered the denaturation mode of carp myofibrils. In 0.1 M KCl medium, heating temperature affected the denaturation of rod more significantly than of subfragment-1 (S-1), and a slow decrease in solubility at 30°C was accompanied by a slow denaturation of rod. KCl concentration at heating altered the denaturation mode differently at 30°C and 40°C. Increased KCl concentrations for heating reduced the rod denaturation rate at 40°C, but it was increased at 30°C. At concentrations above 0.3 M KCl, the denaturation rate for rod became identical to that for S-1 at both temperatures. Upon heating of chymotryptic digest of myofibrils, S-1 denaturation was similarly detected as in intact myofibrils, whereas practically no rod denaturation was detected. Thus, it was concluded that myosin structure connecting S-1 and rod has an important role in the denaturation process.

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A novel sulfotransferase (O-ST), which transferred the sulfate group of 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to O-22 of 11-α, β-hydroxy saxitoxin (STX) and produced GTX2+3, was purified to homogeneity from the cytosolic fraction of clonal-axenic vegetative cells of the toxic dinoflagellate Gymnodinium catenatum GC21V. After four purification steps, including affinity chromatography and anion exchange chromatography, the enzyme was purified 500-fold and the yield was 4%. On affinity chromatography with a PAP-agarose column, O-ST was observed in the bound fraction, and N-ST specific to N-21 of STX and GTX2+3 was found in the unbound fraction. The molecular mass of the purified enzyme was determined by sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) to be 65 kDa. Gel filtration chromatography showed a native molecular mass of 67 kDa, indicating that O-ST is a monomeric enzyme. The enzyme was optimally active at pH 6.0 and 35°C. O-ST did not require metal cations for its activity. O-ST required PAPS as the sole source of sulfate. O-ST transferred a sulfate group from PAPS to only O-22 of 11-α, β-hydroxy STX and not to N-21 of these toxins. These observations suggested that two ST, N-ST and O-ST, participate in the sulfation of PSP toxins.

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Sequence variability of the control region of mitochondrial DNA in five Sebastes species (S. thompsoni, S. joyneri, S. inermis, S. schlegeli and S. owstoni) was investigated. Of 324 nucleotide sites in the control region of S. thompsoni, 56 sites (17.3%) varied, and all 20 individuals had different haplotypes. The other four species had between five and 17 sites (1.5-5.9%), which was fewer than that observed in S. thompsoni. The nucleotide diversity of S. thompsoni was highest (3.45%) among the five species, and that of S. schlegeli was the lowest (0.19%). The results demonstrated that sequence variability exists in the control region of the five Sebastes fishes investigated, and that sequence data in the control region may be suitable for stock structure analysis. Also, the extent of genetic variablitiy in the control region differed among these species. In particular, the mitochondrial DNA control region in S. thompsoni was characterized by high sequence variability, which may indicate a large effective population size.

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A total of 347 cDNA were isolated from the mantle of the oyster Crassostrea gigas by the suppression subtractive hybridization method. By northern blot analysis, we found the mRNA sequences of the several cDNA were highly expressed in the mantle. A total of 61 sequences showed close similarities to known sequences, and they were classified into seven groups: (i) protein synthesis; (ii) cytoskeleton; (iii) signal transduction; (iv) extracellular matrix; (v) metabolism; (vi) transcription factors; and (vii) others. Number 64 cDNA was more similar to the actin of Placopecten magellanicus than C. gigas, indicating that C. gigas has two isotypes of actin genes. This work is the first step to clarify functional activities of the mantle at the molecular level.

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Paralytic toxicity was detected by tetrodotoxin (TTX) bioassay in four and five specimens of new toxic xanthid crab Xanthia lividus collected from Lanyu, south-east Taiwan in April 1999 and Hsiaoliuchiu south-west Taiwan in November 1999, respectively. The average toxicity of crab specimens collected from Lanyu and Hsiaoliuchiu was 230±94 (mean±SD) mouse units (MU) and 241±114 MU, respectively. The toxin was partially purified by YM-1 membrane ultrafiltration and Bio-Gel P-2 column chromatography. Electrophoresis, high-performance liquid chromatography and gas chromatography-mass spectroscopy analyses showed that the crab toxin was composed mainly of tetrodotoxin (83%), as well as a small amount of gonyautoxin 1-4 (17%).

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In order to examine the effect of meat oxidation on the gel forming ability before grinding the meat with salt, fish meat was washed with CuCl₂ solution, and the gel strength as well as total sulfhydryl (SH) groups and sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) patterns were analysed. Washing with CuCl₂ solution resulted in a decrease in the total SH content of fish meat and the formation of myosin heavy chain (MHC) dimer through disulfide bonding. The plot of logarithmic gel strength versus protein concentration after heating the washed meat at 80°C in the presence of 3% NaCl to form a gel illustrated that the gel forming ability of meats washed with CuCl₂ solution was weaker than the control meat. The gel of meat washed with CuCl₂ showed the polymerization of MHC and MHC dimers through disulfide bonding much more than the control meat gel, although a small decrease in the SH group content after heating. Further washing with ethylene diamine tetra-acetic acid (EDTA) solution to remove CuCl₂ from the CuCl₂-washed meat also resulted in similar behavior for MHC polymerization and SH content as the CuCl₂-washed meat, and the gel was still weaker than the control gel. It was found that the oxidation of SH groups during washing with CuCl₂ solution accompanied by MHC dimer formation in the meat results in the weakening of its gel forming ability.

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To utilize Antarctic krill as functional food, protein hydrolysates were prepared by enzymatic hydrolysis. Their effects on the state of water in myofibrils of lizard fish and dehydration-induced denaturation were compared with those from two species of shrimp, glucose, and sodium glutamate. Peptides are major components in hydrolysates, occupying approximately 85-93% of the total materials. The Antarctic krill protein hydrolysates stabilized the bonding of water molecules, leading to suppressed denaturation of myofibrils during the dehydration process. Similar effects were observed for shrimp protein hydrolysates. The effect of the hydrolysate was less than that by glucose and sodium glutamate.

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The red seabream Pagrus major is a useful experimental fish for studying the endocrine control of oogenesis in teleosts. This study investigated the steroidogenic pathway for estradiol-17β (E2) biosynthesis in the ovarian follicles of red seabream. Intact follicles were isolated during vitellogenesis and incubated in vitro with different radiolabeled steroid precursors. When 17-hydroxyprogesterone (17-P), dehydroepiandrosterone (DHEA), or androstenedione (AD) were used as precursors, both testosterone (T) and estrone (E1) were synthesized by follicles, leading to estradiol-17β (E2) production. Serum steroid levels measured by enzyme-linked immunosorbent assay showed that T, E1, and E2 were present in the circulation at levels ranging from 1 ng/mL to 2 ng/mL throughout the day during the spawning season. In vitro conversion of E1 into E2, however, was 15.8-fold greater than T conversion into E2, suggesting that E2 is synthesized mainly via E1 rather than T. The results showed that E2 was synthesized from pregnenolone via 17-hydroxypregnenolone, DHEA, AD, and E1. Thus, the study demonstrated the complete steroidogenic E2 synthesis pathway in the ovarian follicles of red seabream, and revealed that E1 is the major precursor of E2.

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The low salt extract from scallop striated adductor muscle contained extra proteins in addition to sarcoplasmic proteins and was turned into a gel upon standing or immediately by the addition of Ca²⁺. The amount of extra protein, which was composed of a large amount of actin and a small amount of myosin, decreased with a decrease in adenosine triphosphate (ATP) content in the muscle during storage at 5°C. Actin was easily extracted from scallop myofibrils in low salt solution with ATP at 1 mM or above. Furthermore, ATP was required to induce the gelation of the low salt extract. A visual observation of the gelation of low salt extract is therefore a simple and easy method to inspect prerigor state of scallop adductor muscle.

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