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A comparison among rat sperm motility test methods including percent of motile sperm (% Motile), scoring method (Scoring), Ishii's method, Progressive Motility Test (PMT) and Sperm Quality Analyzer (SQA), was conducted using data gathered from eleven laboratories. As a unified study design, mature male rats were orally treated daily for approximately 1 week with alpha-chlorohydrin (ACH), which is known to affect the sperm motility at the epididymis, at dose levels of 2.5, 5 and 10 mg/kg, and then subjected to more than two test methods for sperm motility in each laboratory. Scoring (4 or 5 grades), Ishii's method, PMT and SQA showed high sensitivity for the detection of the effects of ACH, which were not considered to be inferior to a computer-assisted sperm analyzer (CASA). Longer incubation time before testing was considered to contribute to detecting the effects of ACH. In particular, we realized that Scoring was a favorable method even if the demerit of poor objectivity was allowed for. Percent Motile showed lower sensitivity than other test methods. The differences in sensitivity between % Motile and other methods were considered to be based on whether the defects of progressive motion could be detected. Although % Motile cannot clearly judge whether immotile sperm are dead or alive, the value is a great help for the interpretation of the result from other methods. Based on the characters for detectability, objectivity and efficiency, the most suitable method of sperm motility should be selected according to the purpose of the toxicity study.

Di-n-butylin dichloride (DBTCl), which is commonly used as heat and light stabilizer for polyvinyl chloride (PVC) plastics, is a teratogen in vivo. In the present study, the toxic effects were investigated of DBTCl on cultured rat embryos during three different stages of organogenesis. Rat embryos explanted on gestational day (GD) 8.5, GD 9.5, and GD 11.5 were cultured for 68, 46, and 48 h and were exposed to a range of DBTCl concentrations for the first 24, 46, and the last 46 h of culture, respectively. Significant decreases in the placental diameter at > or = 10 ng/ml and in the number of somite pairs and the morphological score at 30 ng/ml were noted in embryos cultured from GD 8.5. Significant decreases in the yolk sac diameter and the crown-rump length at 100 ng/ml, in the number of somite pairs at > or = 50 ng/ml, and in the morphological score at > or = 30 ng/ml were found in embryos cultured from GD 9.5. No adverse effects on these parameters were detected in embryos cultured from GD 11.5 even at 300 ng/ml. Dysmorphogenesis in embryos cultured from GD 8.5, GD 9.5, and GD 11.5 was observed at > or = 10, > or = 50, and 300 ng/ml, respectively. Incomplete turning and craniofacial defects in embryos cultured from GD 8.5 and GD 9.5 and defects of the forelimb buds and tail in embryos cultured from GD 11.5 were frequently observed. These results show that in vitro exposure to DBTCl interferes with normal development of embryos during three different stages of organogenesis and that susceptibility to the embryotoxicity, including the dysmorphogenic potential of DBTCl, varies with developmental stage.

Ion implantation of nitrogen (N) into 6H-SiC{0001} epilayers was systematically investigated. The N profiles simulated with a TRIM (transport of ions in matter) program showed good agreement with experimental results when the tilt angle was set larger than 5°. The sheet resistance of implanted layers decreased with increasing annealing temperature, and a low sheet resistance of 820 Ω/\Box was obtained by annealing at 1600° C. The implanted p-n junction diodes showed a small reverse leakage current of 2.9×10-9 A/cm2 at a bias voltage of -10 V, and a high breakdown voltage of 446 V at room temperature. The diodes operated with good rectification at a high temperature of 350° C. The characteristics of the diodes showed very little change after gamma-ray irradiation with total doses up to 10 Mrad.