Earticle

Japanese eel, Anguilla japonica is a commercially important species and catadromous fish that grows in fresh water, and moves to the sea to spawn. This study investigated the gametogenesis process based on artificially induced sexual maturity of A. japonica based on sexual maturity where it acclimated to the aquatic environment of the seawater. 10 female A. japonica (mean TL 70.1 ± 2.3 cm, mean BW 727 ± 74 g) were used for the inducement of sexual maturity. And specimens were treated with salmon pituitary extracts (SPE) once per week, and induced sexual maturity after 8-12 weeks, and then gametogenesis process was observed. Male A. japonica (mean TL 47.2 ± 2.5 cm, mean BW 322.8 ± 14 g) were treated with human chronic gonadotropin (HCG) every week, and allocation was induced after 6-8 weeks, and then spermatogenesis was observed.

This study investigated gametogenesis, gonadal development, reproductive cycle in cultured Takifugu rubripes. Fish at SAJO CS Co., Ltd. 1-3 year old were sampled from July 2003 to June 2004. The gonadosomatic index (GSI) of male and female reached maximum values of 11.91±3.01 and 3.23±2.61 in April, respectively. The hepatosomatic index (HSI) of male reached a maximum of 13.80±1.32 in May and that of female reached a maximum of 14.60±1.08 in June. The reproductive cycle could be divided into following successive stages in the ovary: growing stage (July to June), mature stage (November to April), and degenerative stage (April to July). Likewise, in the testis, the following stages were observed: growing stage (July to March), mature stage (November to June), spent stage (February to July), and degenerative and recovery stage (May to August).

We cloned and sequenced the FSHβ and LHβ subunits from the pituitary of the Chromis notata. The partial-length cDNAs of FSHβ and LHβ were 346 bp and 275 bp, encoding 114 amino acid (aa) and 91 aa, respectively. The deduced amino acid sequences of FSHβ and LHβ were highly homologous (75-93%) to those of other Perciformes; Channa maculata, European seabass, TOreochromis mossambicus and Dicentrarchus labrax. Phylogenetic analysis showed that the deduced FSHβ amino acid sequences is closely related to the rainbow trout and tilapia, and LHβ amino acid sequences were are closely related to the Mozambique tilapia and C. maculata. The FSHβ was present in brain, pituitary, liver, gonad but LHβ mRNA exhibited high abundance in the pituitary gland, as determined by RT-PCR.

Sex determination in some reptiles, amphibians, and fishes is known to be influenced greatly by environmental factors. Aromatase is the key enzyme in estrogen production and therefore is a reliable marker of female differentiation. Aromatase cytochrome P450 (P450arom) is the enzyme complex responsible for conversion of androgens to estrogens in vertebrates. Consequently, in some fishes its activity appears critical to ovarian differentiation. Olive flounder (Paralichthys olivaceus) is a commercially important flatfish in which females grow larger than males and sex determination is temperature sensitive. Through cloning of the P450arom gene in ovary and quantitative reverse transcription-polymerase chain reaction, we developed a biomarker for early female differentiation in olive flounder. The deduced amino acid sequence for olive flounder P450arom is similar to other teleosts. The part of a gonad was subjected to sex discrimination experiment using aromatase marker, and the rest part, by histological observation. The result of sex discrimination by using markers developed in this study was absolutely correspondent to the result acquired from histological observation, confirming its high accuracy as an useful marker. Gonadal histology confirmed predictions of sex based on P450arom expression in juvenile flounder, demonstrating that the patterns of P450arom expression observed relate to sex-specific differentiation. Also, in order to apply the method, developed in this study, juvenile (fry) flounder from fish farm were examined, and it revealed that sex discrimination of flounders under early sex differentiation is successful. This research represents a unique approach to assessing sex differentiation in a natural population, and a powerful technique for better understanding mechanisms of flounder sex determination and rapidly defining conditions for controlling sex for aquaculture assessing sex responses using the aromatase marker.

This experimental study was performed to investigate the mechanical characteristics of surface treated coarse aggregates and concrete using them, And, the applicability was confirmed and increasing effect in compressive strength was evaluated. Here, Surface treating is to remove the mortar paste bonded on the surface of recycled coarse aggregates and the grade of surface treatment which is the principal test variable is the number of drum rotation in Los-Angeles abrasion test. Test result showed the increase of about 30% in compressive strength was developed when recycled coarse aggregates treated with 300 rotations were used in the concrete. However, there was no increase in the concrete using recycled coarse aggregate treated with more than 300 rotations. Considering the limit of increase in compressive strength and the cost effectiveness in surface treating, the grade of surface treating with 300 rotations was the optimized one. The characteristics of recycled coarse aggregate, density, absorption, and unit weigh, was linearly improved with the increase of the grade of surface treatment. Loss in weigh in abrasion test showed high rate in increase in the range of 100 rotations and low rate in the range of more than 100 rotations. The slump in the concrete with recycled coarse aggregate linearly increase with the increase of the grade of surface treatment.

In order to clarify the characteristics of emulsified fuel which is blended diesel fuel and water, an experimental study was carried out using a real diesel engine. The experimental apparatus was composed of high speed diesel engine with 4 cylinder, dynamometer, main controller and smoke analyzer. As changing engine speeds, brake specific fuel consumption, engine torque, engine power, thermal efficiency and smoke emission were measured in detail. The results are as follows. 1) As engine speed was increased, engine torque for SPG emulsified fuel became higher, while that for diesel fuel became lower. 2) When engine speed was 2,200 rpm, brake horse power for SPG emulsified fuel was higher than that for diesel fuel, but the difference was very small. 3) When engine speeds were 1,500 rpm and 2,200 rpm, brake specific fuel consumption for SPG emulsified fuel increased to 17.3% and 5.7%, respectively compared with that for diesel fuel. 4) In case of 2,200 rpm, thermal efficiency for SPG emulsified fuel was 30.3%, and it was larger than that for diesel fuel. 5) Smoke concentration for SPG emulsified fuel was less than half of that for diesel fuel.