Spontaneous generation of reactive oxygen species and effect on motility and fertilizability of sea urchin spermatozoa.

We investigated the generation of reactive oxygen species (ROS) by spermatozoa in two species of sea urchin. ROS generation was accompanied by the initiation of motility and respiration and influenced the motility and fertilizability of spermatozoa. The sea urchin performs external fertilization in aerobic seawater. Sperm motility was initiated after spawning through Na+/H+ exchange. ROS generation was dependent on the respiration and sperm concentration and its generation was first observed at initiation of motility, via activation of respiration through ATP/ADP transport. The ROS generation rate increased at higher dilution ratios of spermatozoa, in a manner that was synchronous with the respiratory rate. This phenomenon resembled the previously defined 'sperm dilution effect' on respiration. The loss of motility and fertilizability was induced not only by treatment with hydrogen peroxide but also by sperm dilution. Storage of spermatozoa with a higher dilution ratio also accelerated the decrease in fertilizability. Thus, optimum sea urchin fertilizability is maintained by storage of undiluted spermatozoa on ice, in order to minimize oxidative stress and to maximize longevity.

An epidemiological study on Japanese autism concerning routine childhood immunization history.

To assess the causal association of autism with measles, mumps, and rubella (MMR) vaccine versus that with monovalent measles, mumps, and rubella immunization, a 1:2 sex-adjusted logistic regression analysis was conducted using data on subjects who were growing up in the Tokyo area between 1988 and 1992. When MMR immunization was used as a reference, monovalent measles immunization (odds ratio [OR] = 5.33, 99% confidence interval [CI]: 1.03-27.74), non-mumps immunization (OR = 8, 99%CI: 1.33-48.2), and non-rubella immunization (OR = 8.57, 99%CI: 1.30-56.4) with development of autistic spectrum disorders (ASD) were significantly increased. These results suggest a decreased risk of developing ASD with MMR compared to monovalent antigens. However, our findings may reflect potential selection bias due to requiring written consent, possible delayed vaccination in suspected autism cases, and small sample size (case = 21). For the case group and the control group, immunization completeness rate of each antigen, regardless of the timing of immunization, was 90.5% versus 100% in measles, 42.9% versus 78.6% in mumps (P < 0.01), 52.3% versus 83.3% in rubella (P < 0.01), 14.3% versus 45.2% in varicella (P < 0.01), 100% versus 90.5% in polio>2, 100% versus 97.6% in Diphtheria (D), pertussis, and tetanus (T)>3, 85.7% versus 66.7% in DT, 95.2% versus 92.9% in BCG, and 52.4% versus 81.0% in Japanese encephalitis>3 (P<0.01). Only two case subjects and four control subjects received their measles, mumps, and rubella immunizations separately, suggesting that few Japanese parents might have had concerns about the safety of MMR vaccine. A nation-wide study would be a practical measure to scientifically judge the safety of MMR and other routine childhood immunizations.