Biomedical subjects

Tsuneo Honjo

Publications and source records attributed to Tsuneo Honjo.

At least 19 recordsLinked to original sources

PubMed2006

Effects of tributyltin on the energy metabolism of pen shell (Atrina pectinata japonica).

We examined the effects of tributyltin (TBT) on aerobic and anaerobic energy metabolism of pen shell (Atrina pectinata japonica). We exposed pen shells to TBT at nominal concentrations of 0 (control) and 1.0microg/l for 72h under aerobic condition. At the end of the exposure, half of the pen shells in each treatment were wrapped in plastic wrap to simulate exposure to hypoxia and held at 25 degrees C for another 12h. The concentrations of the products of energy metabolism, namely lactate, pyruvate, fumarate and succinate, in adductor muscle were measured. The exposure to TBT under aerobic condition significantly elevated lactate, pyruvate and fumarate concentrations (p<0.001). After subsequent exposure to anaerobic condition, the mean concentration of succinate in the TBT treatment group was 64% of that in the control group, but there were no significant differences. Our results suggest that the energy metabolism of pen shell is disrupted by exposure to TBT.

Aerobiosis↗

PubMed2006

Effect of tributyltin on veliger larvae of the Manila clam, Ruditapes philippinarum.

We investigated the effects of waterborne and maternal exposure to tributyltin (TBT) on veliger larvae of the Manila clam, Ruditapes philippinarum. In a waterborne exposure test, veliger larvae (D-larvae stage: 24h after fertilization) were exposed to TBT at measured concentrations of <0.01 (control), 0.055, 0.130, 0.340, and 0.600microg/l for 13d. The percentage of normal veliger larvae (the ratio of normal veliger larvae to all larvae) decreased significantly in all TBT treatment groups compared with that in the control group. In a maternal exposure test, 100 clams were exposed to TBT at measured concentrations of <0.01 (control), 0.061, and 0.310microg/l at 20-22 degrees C for 3 weeks, and the percentage of normal veliger larvae assessed for 13d. No maternal effects on veliger larvae from TBT were observed in TBT treatment groups as compared with the control group. These results demonstrate that waterborne TBT affects Manila clam veliger larvae, and indicates that TBT may have reduced Manila clam populations by preventing the development and survival of veliger larvae.

Animals↗

PubMed2006

Anti-androgen flutamide affects gonadal development and reproduction in medaka (Oryzias latipes).

The effects of an anti-androgenic chemical on the reproduction of medaka (Oryzias latipes) were examined. Six mating pairs of medaka were exposed to flutamide (FLU) at measured concentrations of 0.101, 0.202, 0.397, 0.787, or 1.56 mg/L for 3 weeks. During the exposure period, one female died in the 1.56-mg/L treatment group, but no lesions or pathological abnormalities were observed. The fecundity and fertility of paired medaka were significantly decreased at 1.56 mg/L compared with those of the controls. Histological examination showed intersex gonads (testis-ova) in males exposed to FLU at 0.202, 0.397, and 0.787 mg/L. However, concentrations of hepatic vitellogenin (Vtg) in both sexes were not statistically different from those in the controls. These results demonstrate that FLU affected gonadal development in male medaka and reproductive capacity in paired medaka. This is the first report of testis-ova in male medaka exposed to FLU.

Androgen Antagonists↗

PubMed2006

Effect of tributyltin on reproduction in Japanese whiting, Sillago japonica.

We examined the effect of tributyltin (TBT) on reproduction in the Japanese whiting, Sillago japonica. Mature fish were placed in indoor 500-L polyethylene tanks (five males and three females per tank) with a flow-through system and received dietary exposure to tributyltin oxide at concentrations of 2, 20, or 200 microg/g for 30 days during the active spawning period. Eggs spawned from the fish were collected daily, and the floating egg rate, larval deformity, hatchability, and viable hatch were monitored. TBT concentration in eggs of 200-microg/g group ranged from 85.0 to 159.6 ng/g in the evaluation period (days 5-30). In this period, the floating egg rate (83.2%), viable hatchability (82.2%), and total number of viable larvae (422,000 larvae per 100 g of female) were all significantly decreased in the 200-microg/g group compared with the control group (93.0%, 91.9%, and 709,000 larvae, respectively). The rate of deformity (2.6%) in the 200-microg/g group was about three times that in the control group (0.8%), although this difference was not significant. From these results, the lowest observed effect concentration of TBT in eggs on reproduction in Japanese whiting was estimated to be less than 159.6 ng/g-eggs.

Animals↗

PubMed2006

Tributyltin contamination of bivalves in coastal areas around northern Kyushu, Japan.

We determined tributyltin (TBT) concentrations in bivalve samples of blue mussel (Myitlus edulis), Manila clam (Ruditapes philippinarum) and pen shell (Atrina pectinata) collected from coastal areas around northern Kyushu in 1998 and 2001. TBT was detected in all bivalve samples collected, ranging in concentration from 0.008 to 0.135 microg/g wet wt. In Hakata Port, which is an industrial area, high TBT concentrations were detected in bivalves (blue mussel, maximum concentration of 0.135 microg/g wet wt). In the Ariake Sea, which is an important bivalve habitat, TBT concentrations in Manila clams ranged from 0.062 to 0.125 microg/g wet wt in 1998 and from 0.008 to 0.033 microg/g wet wt in 2001. In addition, concentrations of TBT in pen shells collected from the Ariake Sea in 2001 ranged from 0.009 to 0.095 microg/g wet wt. These results clearly demonstrate that, despite the regulation of TBT usage since 1990 in Japan, contamination of bivalves by TBT has persisted in coastal areas around northern Kyushu.

Animals↗

PubMed2005

Effects of tributyltin maternal and/or waterborne exposure on the embryonic development of the Manila clam, Ruditapes philippinarum.

We examined the effect of tributyltin (TBT) on embryonic development of the Manila clam, Ruditapes philippinarum. In a maternal exposure test, 100 clams were exposed to TBT at measured concentrations of <0.01 (control), 0.061, 0.310, or 0.350 microg/l at 20-22 degrees C for 3 weeks, and the embryo developmental success (the ratio of normal D-larvae to all larvae) was measured. There was a significant negative correlation between embryo developmental success and TBT concentration in the female Manila clams (p < 0.001). These results indicated that TBT accumulated in the female clam decreased embryo developmental success. In a waterborne exposure test, fertilized eggs (4 h after fertilization) were exposed to TBT at measured concentrations of <0.01 (control), 0.062, 0.140, 0.320, or 0.640 microg/l for 23 h. Embryo developmental success was also significantly decreased in all TBT treatment groups compared with that in the control group. TBT accumulated in female adults and waterborne TBT clearly inhibit reproductive success of the clam.

Animals↗

PubMed2005

Quantitative bio-imaging analysis for evaluation of sexual differentiation in germ cells of olvas-GFP/ST-II YI medaka (Oryzias latipes) nanoinjected in ovo with ethinylestradiol.

We examined the effects on sexual differentiation of nanoinjecting ethinylestradiol (EE2) into embryos of olvas-GFP/ST-II YI medaka (Oryzias latipes). This strain contains the green fluorescent protein (GFP) gene fused to the regulatory region of the medaka vasa gene, and germ-cell-specific expression of GFP can be visualized in living (transparent) individuals. The number of germ cells in untreated genotypic females (XX) was approximately 10-fold that in untreated genotypic males (XY) at 10 d posthatch (dph). Germ cell proliferation was prevented in XX females that developed from embryos nanoinjected with 0.5, 2.5, or 5.0 ng of EE2. Some 10-dph XY males from embryos injected with 0.5 ng or more of EE2 showed a larger fluorescent area and more germ cells than those of pooled control groups. Males and females from embryos injected with 5.0 ng of EE2 had no significant difference in germ cell number or fluorescent area. Thus, EE2 injection into embryos caused abnormal gonadal development in both sexes. Observations of external secondary sex characteristics and histological examination of adult gonads showed complete sex reversal in some males after 0.5-, 2.5-, and 5.0-ng treatments but no changes in XX females after any treatment. Thus, quantitative bio-imaging can aid in evaluating the effects of endocrine-disrupting chemicals on fish within 10 dph.

Animals↗

PubMed2005

Early-life-stage toxicity in offspring from exposed parent medaka, Oryzias latipes, to mixtures of tributyltin and polychlorinated biphenyls.

The present study examined the effects of tributyltin (TBT), polychlorinated biphenyls (PCBs), and mixtures of both chemicals on reproduction in Japanese medaka, Oryzias latipes. For 21 d we gave groups of medaka freeze-dried brine shrimp flakes contaminated with a mixture of either 0, 1, 5, or 25 microg TBT g(-1) plus 0 or 25 .micro PCBs g(-1). We measured the fecundity and fertility of the parent fish and assessed the deformity, hatchability, time-to-hatching, and swim-up failure rate of the next generation. Fertilization success in the third week of the administration period was significantly decreased by administration of 25 microg TBT g(-1) (77%) compared with the control group (87%). Both TBT and PCBs were transferred maternally into the eggs of the next generation, causing early life-stage toxicity. Administration of 1 microg TBT g (-1) was not toxic to embryological development, but abnormal eye development (i.e., small eyes or no eyes) occurred when TBT at the same concentration was mixed with PCBs (6.4%). Administration of TBT alone significantly decreased hatchability and increased swim-up failure, and administration of PCBs alone significantly increased time-to-hatching. Statistical analysis by two-way analysis of variance detected an interaction between TBT and PCBs in these three parameters. TBT induces abnormal development of the eyes, reduced hatchability, and increased swim-up failure, whereas PCBs delay time-to-hatching. Administration of mixtures of TBT and PCBs has more adverse effects on the developmental stage of medaka than does that of each chemical alone.

Animals↗

PubMed2005

Effects of polychlorinated biphenyls on the schooling behavior of Japanese medaka (Oryzias latipes).

The effects of polychlorinated biphenyls (PCBs; Kanechlor 400) on the schooling behavior of Japanese medaka (Oryzias latipes) were tested after feeding with various concentrations of PCBs (0, 1, 5, 25, and 125 microg/g). To test schooling, three PCB-exposed medaka and three untreated fish were placed in one chamber, and their swimming trajectories were recorded. Swimming velocity, turning angle, and nearest-neighbor distance (NND) were analyzed individually, and the polarization and expanse of each schooling group were analyzed. Fractal dimension analysis was performed for trajectory, swimming velocity, and turning angle. Six behaviors (school formed by six swimming medaka, school formed by six stationary medaka, school formed by three to five swimming medaka, school formed by three to five stationary medaka, swimming without schooling, and stationary without schooling) were quantified with time. Behavioral parameters were the same for PCB-exposed and unexposed medaka in the same schooling group. Swimming velocity decreased in a dose-dependent manner, and NND in the group exposed to 25 microg/g of PCBs was significantly longer (126%) than that in the controls. The fractal dimensions of trajectory and turning angle increased significantly in the highest PCB-exposure group, indicating that schools containing PCB-exposed individuals frequently changed direction. The PCBs shortened the time of school formed by six swimming fish, which was 23.7% of the control value in the group exposed to 25 microg/g of PCBs. The frequency of collisions between individuals was significantly greater in the highest-exposure group (31.3) than in the controls (13.3). Thus, PCB exposure influences the behavior of unexposed fish in the same school, consequently affecting schooling behavior.

Animals↗

PubMed2004

Fertilization success and sexual behavior in male medaka, Oryzias latipes, exposed to tributyltin.

We evaluated the effects of tributyltin (TBT), polychlorinated biphenyls (PCBs), and a mixture of TBT and PCBs on reproduction, gonadal histology, and sexual behavior in Japanese medaka (Oryzias latipes). We administered TBT (1 microg g(-1) body weight [b.w.] daily), PCBs (1 microg g(-1) b.w. daily), or both to medaka for 3 weeks. We assessed reproductive success during week 3 and the sexual behavior of male medaka after the exposure period. Fertilization success was significantly decreased in groups that received TBT. The profiles of fertility developed a bimodal distribution in the TBT and TBT+PCBs groups, and the numbers of males that performed "following" and "dancing" were significantly decreased in the TBT+PCBs group. The frequency of "dancing" also decreased after treatment with TBT, whereas fish that received PCBs only showed no difference in sexual behavior. Testes that had oocytes showed normal spermatogenesis, even though two of the five males treated with TBT+PCBs had some indication of testis-ova, which did not occur in any other group. Our results indicate that TBT, but not PCBs, affects sexual behavior and reproduction in medaka.

Animals↗

PubMed2004

Production of superoxide anion and hydrogen peroxide by the red tide dinoflagellate Karenia mikimotoi.

We found that the red tide dinoflagellate Karenia mikimotoi (Gymnodinium mikimotoi) generates reactive oxygen species (ROS). In chemiluminescence analysis using an O2- specific probe, a slightly lower but significant level of O2- was detected in a K. mikimotoi cell suspension as compared to one containing Chattonella marina, a well-known ROS-producing red tide phytoplankton. Interestingly, the chemiluminescence response pattern caused by K. mikimotoi was different from that of C. marina, although both responses were almost completely abolished in the presence of superoxide dismutase (SOD). By fluorescence spectrophotometric analysis, H2O2 was also detected in the K. mikimotoi cell suspension, but the level of H2O2 was approximately 10% of that in the C. marina suspension based on the cell number. No significant increase in O2- generation by K. mikimotoi was observed in the presence of lectins such as concanavalin A (Con A) and wheat germ agglutinin (WGA) or fish mucus substances prepared from the skin and gills of yellowtail, whereas C. marina generated an increased level of O2- in response to these stimuli. Furthermore, O2- production in C. marina, but not in K. mikimotoi, was inhibited by treatment with proteinase K.

Journal Article↗

PubMed2004

Effect of maternal exposure to tributyltin on reproduction of the pearl oyster (Pinctada fucata martensii).

We examined the effect of tributyltin (TBT) on reproduction of the pearl oyster (Pinctada fucata martensii). In a maternal exposure test, five female pearl oysters were exposed to TBT at measured concentrations of 0 (control), 0.092, or 0.191 microg/L at 25 degreesC for one week, and the embryo developmental success (the ratio of normal D-larvae to all larvae) was measured. The embryo developmental success was significantly decreased in the 0.191-microg/L treatment group (65.5%) compared to that in the control group (82.5%; p = 0.031). Concentrations of TBT in the ovary reached 0.088 microg/g in the 0.191-microg/L treatment group. In a waterborne exposure test, inseminated eggs were exposed to TBT at measured concentrations of 0 (control), 0.020, 0.045, 0.091, 0.192, or 0.374 microg/L for 24 h. The embryo developmental success also was significantly decreased in the 0.192-microg/L treatment group (78.3%; p = 0.020) and no development at all was observed in the 0.374-microg/L treatment group compared with that in the control group (95.4%). These results clearly demonstrate that TBT accumulating in the bodies of bivalves has the potential to inhibit reproduction.

Animals↗

PubMed2003

Suppression of sexual behavior in male Japanese medaka (Oryzias latipes) exposed to 17beta-estradiol.

Mating pairs of Japanese medaka (Oryzias latipes) received 17beta-estradiol (E2; dose, 3 and 30 microg/g body weight daily) in their diet and E2-free diet (control) for two weeks. The effect on reproductive success was assessed in the mating pairs, and sexual and nonsexual behaviors in the male were quantified. The fecundities of the E2-treated groups were reduced significantly (p < 0.05) compared with those of control, and the sexual behaviors (following, dancing, floating, and crossing) of male fish in response to prostaglandin F2alpha (PG)-injected E2-unexposed females were suppressed dramatically. While the fertility of spawned eggs and the frequencies of the nonsexual behaviors of resting and swimming in a straight line performed by male were unchanged in E2-exposed groups. Therefore, sexual behavior in male may be linked with reproductive success in mating pair of madaka exposed to E2. This assay for sexual behavior using PG may provide a useful tool for assessing the effect of endocrine-disrupting chemicals.

Animals↗

PubMed2003

Effects of 4-nonylphenol on reproduction of Japanese medaka, Oryzias latipes.

We exposed mature Japanese medaka (Oryzias latipes) to 4-nonylphenol (4-NP) to elucidate its reproductive effects and estrogenic responses. For each treatment, eight breeding pairs were exposed for 3 weeks at measured 4-NP concentrations of 24.8, 50.9, 101, and 184 micrograms/L. Egg production of the pairs during the third week of exposure (15-21 d) was significantly decreased in the > or = 101-microgram/L treatment group, and fertility was significantly decreased in the 184-microgram/L group. Induction of testis-ova was observed in male fish at all 4-NP concentrations, whereas abnormality of spermatogenesis was found only in those receiving the 184-microgram/L treatment. The gonadosomatic index of the males in the 184-microgram/L group was also remarkably reduced. Hepatic vitellogenin (VTG) levels were significantly increased in both sexes receiving 4-NP treatments of > or = 50.9 micrograms/L. Overall, the lowest-observed effective concentrations (LOECs) of 4-NP for decreasing reproductive capacity (fecundity and fertility) and eliciting estrogenic responses (induction of testis-ova and VTG) were 101 and < or = 24.8 micrograms/L, respectively. The LOEC for reduced reproduction in medaka was at least four-fold greater than that required to elicit estogenic responses in male fish. Thus, we suggest that the estrogenic responses expressed in male fish are not responsible for the reduction in reproductive capacity.

Animals↗

PubMed2003

Tributyltin causes masculinization in fish.

We examined the effect of tributyltin (TBT) on the sex differentiation process in genetically female Japanese flounder (Paralichthys olivaceus). The fish were fed an artificial diet containing tributyltin oxide (TBTO) at concentrations of 0.1 and 1.0 microg/g diet from 35 to 100 d after hatching, which includes the sex differentiation period. The ratio of sex-reversed males significantly increased to 25.7% of the flounder fed the 0.1 microg/g diet and to 31.1% of those fed the 1.0 microg/g diet compared with the control (2.2%). From morphological and histological examination of the fish in the TBT-treated groups, normal females had typical ovaries and sex-reversed males had typical testes. These results clearly demonstrated the masculinization of flounder exposed to TBTO. This is the first report of TBT inducing sex reversal in vertebrates.

Animals↗

PubMed2002

Effect of 17beta-estradiol on the reproduction of Japanese medaka (Oryzias latipes).

Estrogenic compounds such as 17beta-estradiol (E2) and its analogs are present in the aquatic environment and can adversely affect the reproductive systems of aquatic organisms. Although E2 has been detected at a maximum concentration of 64 ng/l in effluents of sewage treatment works (STWs), few reports address the associated effects on reproduction in fish. Therefore, we exposed adult medaka (Oryzias latipes) to mean measured E2 concentrations of 29.3, 55.7, 116, 227, and 463 ng/l for 21 d and assessed the effects on the egg number and fertility of paired medaka during the exposure period. In addition, we determined the hepatic vitellogenin (Vtg) concentration and histologically assessed the gonads of these fish. The number of egg produced and fertility of the paired medaka exposed to 463 ng/l E2 were significantly less compared with those of the control fish. Males in all treatment groups had developed testis-ova. Males treated with E2 concentrations = 55.7 ng/l contained relating great concentrations of hepatic Vtg. Therefore, although only the greatest E2 concentration tested in our study affected fecundity and fertility, effects of E2 were observed on induction of Vtg and testis-ova in male medaka exposed to environmentally relevant concentrations of E2.

Animals↗

PubMed2002

Photosensitizing hemolytic toxin in Heterocapsa circularisquama, a newly identified harmful red tide dinoflagellate.

Red tides of Heterocapsa circularisquama (H. circularisquama), recently identified as a novel species of dinoflagellate, have frequently caused mass mortality of several species of bivalves in Japan, while no harmful effects of this flagellate on fish have been reported so far. We found that the cell-free ethanol extract prepared from H. circularisquama caused hemolysis of rabbit erythrocytes and demonstrated cytotoxic effects in HeLa cells and on the microzooplankton rotifer (B. plicatilis) in a dose- and time-dependent manner. Interestingly, the hemolytic activity and cytotoxic effects of the extract were completely dependent on the presence of light. When the experiments were conducted in the dark, no hemolysis was observed even at very high concentration of the extract. These results suggest that H. circularisquama has photosensitizing hemolytic toxin which can be easily extracted into ethanol. This may be the first report documenting the occurrence of photosensitizing hemolytic toxin in marine phytoplankton species.

Animals↗

PubMed2002

Possible factors responsible for the toxicity of Cochlodinium polykrikoides, a red tide phytoplankton.

Cochlodinium polykrikoides, a harmful red tide dinoflagellate, is highly toxic to fish, but the toxic mechanism is still unknown. Recent study has suggested that C. polykrikoides generates reactive oxygen species (ROS) such as superoxide anion (O(2)(-)) and hydrogen peroxide (H(2)O(2)), and the ROS-mediated ichthyotoxicity has been proposed. In this study, we found that the levels of O(2)(-) and H(2)O(2) detected in C. polykrikoides were trace levels as compared with those of Chattonella marina which is well-known to produce ROS. Furthermore, no significant increase in O(2)(-) generation by C. polykrikoides was observed in the presence of lectins such as concanavalin A (Con A) and wheat germ agglutinin (WGA) or fish mucus prepared from skin and gill of yellowtail, whereas C. marina generated increased level of O(2)(-) responding to these stimuli. Interestingly, the cell-free aqueous extract prepared from C. polykrikoides showed toxic effect on the HeLa cells, but the extract of C. marina had no significant effect. Furthermore, gradual accumulation of polysaccharides in the medium was observed during the growth of C. polykrikoides, and the medium gradually became viscous, but no such changes were observed in the medium of C. marina. These results suggest that multiple factors may be responsible for the toxic mechanism of C. polykrikoides.

Animals↗