Toshitaka Ikeuchi

Bioactive jatrophane diterpenes from Euphorbia guyoniana

Chromatographic investigation of the methylenechloride/methanol extract of the aerial parts of Euphorbia guyoniana afforded two jatrophane diterpenes, designated guyonianins E and F, in addition to a known jatrophane diterpene. The structures of the compounds were determined by comprehensive NMR analyses, including DEPT, COSY, HMQC, HMBC, NOESY and HRMS. These compounds exhibited cytotoxicity against human embryonic kidney 293 (HEK293) cells with IC(50) values of 35-100 microM.

Natural-photosynthesis-inspired photovoltaic cells using carotenoid aggregates as electron donors and chlorophyll derivatives as electron acceptors

Carotenoids (Cars) and chlorophylls (Chls) are major pigments playing key roles in light-harvesting and energy transfer processes in natural photosynthetic apparatus. We demonstrated, in this study, photovoltaic cells with entire active layers consisting of a linear Car, lycopene, as the electron donor and Chl derivatives, either methyl 32,32-dicyano-pyropheophorbide-a (Chl-1) or methyl 131-deoxo-131-(dicyanomethylene)pyropheophorbide-a (Chl-2), as the electron acceptor.

Growth, energetics and the cortisol-hepatic glucocorticoid receptor axis of medaka (Oryzias latipes) in various salinities.

We examined growth of euryhaline Japanese medaka (Oryzias latipes) after transfer to freshwater or seawater from isotonic saline. Growth was unaffected by the different salinities for 1 week, but the body weight increase and BMI of fish kept in freshwater for 2-3 weeks were significantly higher than those in the isotonic controls. These results may reflect the usual habitat of this species. To assess the basis for the difference in growth, energetics and the hepatic stress axis were evaluated 1 week after the transfer. Unexpectedly, despite the higher growth rate, the rate of routine oxygen consumption was significantly higher in freshwater. Plasma cortisol levels in freshwater were significantly higher than those in seawater, and the mRNA levels of the glucocorticoid receptor (GR1) in the liver were significantly lower in freshwater and seawater, compared to that in isotonic saline. Branchial Na(+)/K(+)-ATPase activities were also reduced significantly in freshwater and seawater, compared to that in isotonic saline. The higher levels of hepatic GR1 expression and branchial Na(+)/K(+)-ATPase activity in isotonic salinity than those in freshwater and seawater for 1 week may account for the lower growth rate under the isotonic condition. After 3 weeks, however, the Na(+)/K(+)-ATPase activity in seawater was significantly higher than that in freshwater. No significant difference in growth rate between freshwater and seawater groups indicates that medaka is a good model for studies of hypo- and hyperosmotic adaptations, since osmoregulation is not strongly associated with size and growth.

Synthesis of carboxylated chlorophylls and their application as functional materials

A series of chlorophyll derivatives possessing a carboxy group were synthesized aiming at their application as sensing materials and to dye-sensitized solar cells (DSSCs). Their absorption and fluorescence responses to amine concentrations in THF and photovoltaic performance of DSSCs on TiO2 films were investigated.

Principal function of mineralocorticoid signaling suggested by constitutive knockout of the mineralocorticoid receptor in medaka fish

As in osmoregulation, mineralocorticoid signaling is implicated in the control of brain-behavior actions. Nevertheless, the understanding of this role is limited, partly due to the mortality of mineralocorticoid receptor (MR)-knockout (KO) mice due to impaired Na+ reabsorption. In teleost fish, a distinct mineralocorticoid system has only been identified recently. Here, we generated a constitutive MR-KO medaka as the first adult-viable MR-KO animal, since MR expression is modest in osmoregulatory organs but high in the brain of adult medaka as for most teleosts. Hyper- and hypo-osmoregulation were normal in MR-KO medaka. When we studied the behavioral phenotypes based on the central MR localization, however, MR-KO medaka failed to track moving dots despite having an increase in acceleration of swimming. These findings reinforce previous results showing a minor role for mineralocorticoid signaling in fish osmoregulation, and provide the first convincing evidence that MR is required for normal locomotor activity in response to visual motion stimuli, but not for the recognition of these stimuli per se. We suggest that MR potentially integrates brain-behavioral and visual responses, which might be a conserved function of mineralocorticoid signaling through vertebrates. Importantly, this fish model allows for the possible identification of novel aspects of mineralocorticoid signaling.

Bromotheoynic acid, a brominated acetylenic acid from the marine sponge Theonella swinhoei

A new brominated C17 acetylenic acid (1) designated as bromotheoynic acid has been isolated from the marine sponge Theonella swinhoei, collected off the coast of Tanegashima, Kagoshima Prefecture, Japan. The structure was determined on the basis of the analysis of its extensive 2D NMR spectroscopic data as well as HRMS. Bromotheoynic acid (1) inhibited maturation of starfish oocytes and cell division of fertilised starfish eggs. Bromotheoynic acid (1) also inhibited proliferation of human leukaemia U937 and HL60 cells, human lung cancer A549 and H1299 cells, and human embryonic kidney 293 (HEK293) cells.

Petroacetylene, a new polyacetylene from the marine sponge Petrosiasolida that inhibits blastulation of starfish embryos.

A new C30 linear polyacetylene compound designated petroacetylene (1) has been isolated from the marine sponge Petrosia solida Hoshino 1981, collected off the coast of Amami-Oshima, Kagoshima Prefecture, Japan. The structure was elucidated on the basis of spectroscopic data and chemical means. Petroacetylene (1) inhibited blastulation of starfish embryos at a concentration of 3.1 μg mL− 1 or greater.

Response to fish specific reproductive hormones and endocrine disrupting chemicals of a Sertoli cell line expressing endogenous receptors from an endemic cyprinid Gnathopogon caerulescens.

Fish Sertoli cells play a critical role in spermatogenesis by mediating androgen and progestogen signaling. Their hormonal response, however, considerably differ among species. Therefore it would be ideal to use Sertoli cells originated from the fish of interest to investigate the effects of hormones as well as endocrine disrupting chemicals (EDCs). The aim of this study was to investigate the responses to reproductive hormones and EDCs of a Sertoli cell line that we established from an endemic cyprinid Gnathopogon caerulescens. As the Sertoli cell line expressed endogenous androgen and progestogen receptors, we were able to detect hormone responses by transfecting only a reporter vector (pGL4.36) expressing luciferase under the control of the mouse mammary tumor virus-long terminal repeat (MMTV-LTR) promoter into the cell line. Unlike previous reporter gene assays using fish steroid hormone receptors expressed in mammalian cell lines, luciferase activities were induced by the fish specific androgen (11-ketotestosterone) and progestogen (17α,20β-dihydroxy-4-pregnen-3-one), but not by testosterone and progesterone, at physiologically relevant concentrations. Furthermore, we found 4-nonylphenol (NP) but not bisphenol A showed strong anti-androgenic effects, implying that NP may have direct anti-androgenic effects on fish Sertoli cells in vivo. This is the first evidence, to the best of our knowledge, of anti-androgenic effects of NP in a fish Sertoli cell line. In addition, neither NP nor BPA showed anti-progestogenic effects. These results suggest that the Sertoli cell line established from the fish of interest can be a useful in vitro tool for investigating the mechanisms of reproductive hormones and EDCs in the specific fish.