Akihiro Takemura

Learn More
This study examined the importance of mycosporine-glycine (Myc-Gly) as a functional antioxidant in the thermal-stress susceptibility of two scleractinian corals, Platygyra ryukyuensis and Stylophora pistillata. Photochemical efficiency of PSII (F(v)/F(m)), activity of antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT), and composition and(More)
As the first step in understanding the molecular oscillation of the circa rhythms in the golden rabbitfish Siganus guttatus—a reef fish with a definite lunar-related rhythmicity—we cloned and sequenced a Period gene (rfPer). The rfPer gene contained an open reading frame that encodes a protein consisting of 1,452 amino acids; this protein is highly(More)
Two distinct vitellogenins (VTG) were purified from the blood of estradiol-17beta (E(2))-injected tilapia, Oreochromis mossambicus. Enzyme-linked immunosorbent assays (ELISA) of each VTG were developed to examine effects of E(2) treatment on induction of VTG synthesis in the primarily cultured tilapia hepatocytes. Two VTG molecules (VTG210 and VTG140) had(More)
The Mozambique tilapia (Oreochromis mossambicus) is a euryhaline species that does not survive direct seawater exposure. Cortisol is involved in re-establishing electrolyte homeostasis in seawater and is thought to play a role in allowing tilapia to cope with abrupt seawater exposure, but the mechanism(s) are far from clear. Recently, osmotic stress(More)
Cortisol is one of the central hormones in osmoregulation in fish, especially in seawater adaptation. A cDNA of 453 bp was cloned from liver mRNA of freshwater-reared tilapia (Oreochromis mossambicus), by reverse transcription polymerase chain reaction (RT-PCR) with primers designed for the hormone-binding domain of glucocorticoid receptors (GRs) in mammals(More)
The golden rabbitfish Siganus guttatus is a reef fish with a restricted lunar-synchronized spawning cycle. It is not known how the fish recognizes cues from the moon and exerts moon-related activities. In order to evaluate the perception and utilization of moonlight by the fish, the present study aimed to clone and characterize Period2 (Per2), a(More)
Feeding time is a major synchronizer of many physiological rhythms in many organisms. Alteration in the nutritional status, specifically fasting, also affects the secretion rhythms of growth hormone (GH) and insulin-like growth factor-I (IGF-I). In this study, we investigated whether the expression patterns for the mRNAs of GH, prolactin (PRL) and(More)
Mature spermatozoa of two perciform teleost fishes, Paraupeneus spilurus (Mullidae) and Siganus fuscescens (Siganidae) from Taiwan were examined using transmission and scanning electron microscopy. Despite the fact that spermatozoa of both species are of the primitive type, the results of the present study highlight the potential application of spermatozoal(More)
The purpose of the present investigation was to determine at what stages of embryonic development the sodium pump (Na+,K+-activated ATP phosphohydrolase, EC appears and whether the ontogeny of the sodium pump plays a role in the matrotrophic viviparity ofSebastes. Early larval stages (stages 1–14) had embryonic tissues nearly devoid of Na, K-ATPase(More)
Euryhaline tilapia Oreochromis mossambicus acclimates to the external spawning environment by modulating its mechanism for regulating sperm motility. Adaptation of sperm was performed by acclimating fish in various environments. In this paper, regulatory mechanisms of freshwater-acclimated tilapia were studied in detail. Tilapia sperm motility was vigorous(More)