Tetsuya Adachi

Effect of UV screens and preservatives on vitellogenin and choriogenin production in male medaka (Oryzias latipes).

Ultra violet (UV) screens and preservatives are widely and increasingly used in cosmetics and pharmaceuticals. In the present study, we examined the estrogenicity of 4-methyl-benzylidene camphor (4-MBC), octyl-methoxycinnamate (OMC), and propyl paraben (n-propyl-p-hydroxy-benzoate; PP), among UV screens and preservatives, using male medaka (Oryzias latipes), in regard to production of vitellogenin (VTG) and choriogenin (CHG) which are known to be estrogen-responsive gene products. First, using a VTG enzyme-linked immunosorbent assay (ELISA) system, we determined the increase in VTG plasma concentration in medaka due to exposure to 4-MBC, OMC, and PP, and compared this concentration to the non-treated control. Next, we found increases in mRNA expression levels of VTG subtypes VTG-1 and VTG-2, and CHG subtypes CHG-L and CHG-H, in liver due to exposure to 4-MBC, OMC, and PP compared to the non-treated control. In addition, we also found increased mRNA expression levels of estrogen receptor (ER) alpha, among sex hormone receptors in the liver, due to exposure to 4-MBC, OMC, and PP compared to the non-treated control. In this study, we showed that 4-MBC, OMC, and PP have estrogenic activity in fish.

Bisphenol A affects glucose transport in mouse 3T3‐F442A adipocytes

Recently, environmental chemicals have appeared in daily human life, and these chemicals have been incidentally taken in by humans. The serum concentrations of some of these chemicals have been found to be associated with the onset and incidence rate of diabetes mellitus. It has been suggested that one of the environmental chemicals, bisphenol A (BPA), has hormone‐like activity. It has also been demonstrated that some hormones affect insulin resistance and fat distribution in the body. To study the effects of these environmental chemicals on glucose metabolism, the effect of BPA on glucose transport in mouse 3T3‐F442A adipocytes was investigated. The 3T3‐F442A adipocytes were incubated with various concentrations of BPA in a medium. Deoxyglucose uptake assay was performed with and without insulin. Immunoblot analysis was performed with a glucose transporter (GLUT) 4‐specific antibody and antiphosphotyrosine antibody. The BPA treatment enhanced basal and insulin‐stimulated glucose uptake, and caused an increased amount of GLUT4 protein. Thus, the enhanced glucose uptake resulting from the BPA treatment was at least partially due to the increased amount of GLUT4. Tyrosine phosphorylation of insulin receptor substrate‐1 with insulin stimulation was not significantly affected. In conclusion, it was demonstrated that BPA, one of the chemicals that we intake incidentally, affects the glucose transport in adipocytes, and also that the environmental chemicals may be identified as one of the environmental factors that affect diabetes and obesity.

Analysis of toxicogenomic response to endocrine disruptors in the mouse testis

In order to evaluate the feasibility of cDNA microarrays for the risk assessment of endocrine disruptors (EDs), alteration of gene expression profiles was analyzed in adult mouse testes after neonatal exposure to diethylstilbestrol (DES), bisphenol A (BPA) or genistein (Gen), using cDNA microarrays. Analysis with Mouse GEM I revealed that the expression levels of 34, 38 and 12 genes were changed in testes of DES-, Gen- and BPA-treated 12-week old mice, respectively. Gene expression profiles were very similar between DES- and Gen-treated mice, but that of the BPA-treated mice was quite different. These results suggest that gene expression profiles might be feasible for the grouping of EDs in terms of their effects. Further, it is suggested that mechanisms of BPA action may be different from those of DES and Gen, although they are all estrogen-like compounds. Next, we investigated the transition of the expression profiles in testes of DES-treated mice using in-house cDNA microarrays. Many of the genes affected by DES were up- or down-regulated at restricted periods, but some genes were continuously up-regulated or shifted from the down-regulated state to the up-regulated state. These results suggest that the transition patterns may represent the gene expression cascades that were affected by EDs. We propose that the cDNA microarray is a useful tool, which provides us a bird’s eye view of the global effects of EDs on gene expression.

Association of testicular undescent induced by prenatal flutamide treatment with thickening of the cremaster muscle in rats

Background and AimsPreviously, in cryptorchid rats, which were induced by prenatal exposure to flutamide, we found a thickening of the cremaster muscle. This study was undertaken to quantify the increase of the cremaster muscle thickness in the cryptorchid rats, and to examine its possible relationship with the proliferation of muscle cells.MethodsTo obtain cryptorchid rats, pregnant Wistar rats were subcutaneously injected with flutamide (100 mg/kg per day) during gestational days 16–17. Serial sections of the scrotum, containing the testis and cremaster muscle, were prepared from the control and cryptorchid rats that were 2–6 weeks of age, and stained with hematoxylin-eosin for morphometry, or stained with antibody against the proliferating cell nuclear antigen (PCNA) to analyze the cell proliferation ability.ResultsThe thickened cremaster muscle was always associated with cryptorchid testis and, in the case of unilateral cryptorchidism, the cremaster muscle of the contralateral (descended testis) side exhibited normal thickness. The average thickness of the affected cremaster muscle was 0.80 and 1.89 mm at 4 and 6 weeks of age, respectively, although that of the normal muscle was 0.28 and 0.33 mm at the same time period, respectively.ConclusionOur results showed that the cremaster muscle of the cryptorchid rats was significantly thicker than that of the control rats. The immunohistochemical analysis revealed that a thickened cremaster muscle contained many PCNA-positive nuclei even at 4 weeks of age, in contrast to the control, which had only a few positive nuclei. Our present study indicates that continuous proliferation of the muscle cells associated with cryptorchid testis increases the thickness of cremaster cells in rats exposed to flutamide prenatally.