Miyoko Kubo-Irie

THE EFFECTS OF NANOPARTICLES ON MOUSE TESTIS LEYDIG CELLS IN VITRO

We have indicated the possibility that nanoparticles such as diesel exhaust particles (DEP) and titanium dioxide (TiO(2)) may impair the male mouse reproductive system. In this study, to evaluate the direct effect of nanoparticles on testis-constituent cells, we examined the effect of DEP, TiO(2) and carbon black (CB) on mouse Leydig TM3 cells, the testosterone-producing cells of the testis. The uptake of three nanoparticles into Leydig cells was detected using transmission electron microscopy (TEM) or field emission type scanning electron microscopy/energy-dispersive X-ray spectroscopy (FE-SEM/EDS). We examined the cytotoxicity and the effect on gene expression by treatment with nanoparticles. TiO(2) was more cytotoxic to Leydig cells than other nanoparticles. The proliferation of Leydig cells was suppressed transiently by treatment with TiO(2) or DEP. The expression of heme oxygenase-1 (HO-1), a sensitive marker for oxidative stress, was induced remarkably by treatment with DEP. Furthermore, CB and DEP slightly increased the gene expression of the steroidogenic acute regulatory (StAR) protein, the factor that controls mitochondrial cholesterol transfer. In this study, we found that DEPs, TiO(2) and CB nanoparticles were taken up by Leydig cells, and affected the viability, proliferation and gene expression. The patterns were unique for each nanoparticle.

Characterization of outer arm dynein in sea anemone, Anthopleura midori

Outer arm dynein was purified from sperm flagella of a sea anemone, Anthopleura midori, and its biochemical and biophysical properties were characterized. The dynein, obtained at a 20S ATPase peak by sucrose density gradient centrifugation, consisted of two heavy chains, three intermediate chains, and seven light chains. The specific ATPase activity of dynein was 1.3 micromol Pi/mg/min. Four polypeptides (296, 296, 225, and 206 kDa) were formed by UV cleavage at 365 nm of dynein in the presence of vanadate and ATP. In addition, negatively stained images of dynein molecules and the hook-shaped image of the outer arm of the flagella indicated that sea anemone outer arm dynein is two-headed. In contrast to protist dyneins, which are three-headed, outer arm dyneins of flagella and cilia in multicellular animals are two-headed molecules corresponding to the two heavy chains. Phylogenetic considerations were made concerning the diversity of outer arm dyneins.

Pre- and postnatal exposure to low-dose diesel exhaust impairs murine spermatogenesis

We investigated whether pre- and postnatal low-dose exposure to diesel exhaust (DE) affects male reproductive function in mice. The DE concentration is less than that indicated as the environmental quality standard for suspended particulate matter (SPM) in Japan. ICR mice were exposed prenatally to low-dose diesel exhaust (0.17 mg of DE particles/m3) through the airway for 8 h/day in an exposure chamber from gestational day 2 until the examination. In the DE-exposed groups, normal sperm morphology in the epididymis was reduced (p < 0.01), and seminiferous tubules showed degenerative changes in which the number of Sertoli cells was decreased (p < 0.01). Those changes were observed at 6 and 12 weeks of age. Furthermore, ultrastructural studies revealed an increase in damaged mitochondria in Sertoli cells (p < 0.001) and variform spermatozoa. These results indicate that pre- and postnatal exposure of low-dose DE is detrimental to Sertoli cell function and may cause abnormal spermatozoa.