We have studied, by a nonisotopic in situ end-laveling(ISEL) technique, frequency of apoptosis in the external granular layer(EGL) of the cerebellum of immature mice by Y-rays irradiation from 60Co or diagnostic ultrasound exposure. The total number of normal cells and cells showing morphological features of apoptosis were counted. The frequency of apoptotic cells was expressed as a percentage of the total number of cells in EGL. The extent of changes following 200 cGy(1090 cGy/min) was studied at 2, 4, 6, 8, 12, or 24 hours after exposure. The maximal frequency was found 6~8 hours after exposure. The immature mice that received 18, 36, 54, 108, 198, 396, cGY of y-rays or diagnostic ultrasound(7.5MHz, 4.2mW, Ispta=7.9mW/cm2, Ispta=114.3W/cm2) for 10 or 30 minutes were examined 6 hours after irradiation. Measurements performed after y-ray irradiation showed a dose-related increase in apoptotic cells in each of the mice studied. The dose-response curves were analyzed by a linear-quadratic model;frequency of apoptotic cell in the EGL was y=(0.1349+_0.01175)D+(-0.0001522+_0.0000334)D2+0.048(r2=0.981, D-dose in cGy). In the experiment of ultrasound exposure, the frequency of apoptotic cell was 0.106+_0.130(10 minutes exposure) and 0.167+_0.220(30 minutes exposure). We estimated the relative dose of the yield from the experiment with ultrasound by substituting the yield from ultrasound exposure into the curve from the y-irradiation. The relative dose of ultrasound exposure compared with y-irradiation were 0.432 cGY(10 minutes exposure) and 0.885 cGY(30 minutes exposure). We have found that there is no evidence to indicate that diagnostic ultrasound involves a significant risk.

Over periods of 22 and 14 months, IgG antibody concentrations in serum samples obtained monthly from 14 mares and 19 foals, respectively, were measured by use of ELISA against antigens of the following environmental microbes: Aspergillus umbrosus, Penicillium brevicompactum, Rhodotorula glutinis, Absidia corymbifera, Aspergillus fumigatus, Humicola grisea, Micropolyspora faeni, and Thermoactinomyces vulgaris. The mares and foals were on pasture from early June until early October, then were stabled during the winter season until the following June. In the mares, increased antibody concentrations against most microbes were observed typically in midwinter and late spring when the horses were stabled; antibody concentrations against R glutinis, however, peaked in August. Concentrations differed between the summer and winter seasons and, in most instances, between 2 consecutive years and correlated with amounts of rainfall during the previous harvest season. In the foals, circulating passively acquired antibodies disappeared within 3 to 4 months after birth. During the first year of life, substantially increased autogenous antibody concentrations were observed only against R glutinis. Antibody concentrations against the other microbes increased gradually toward the end of the indoor season. In a group of foals transferred indoors in autumn, 6 weeks later than the other foals, antibody concentrations were lower when measured in December. Results supported the view that, to minimize exposure to microbial spores during the winter season, horses should be kept outdoors as much as possible and attention should be focused on improving the ventilation in stables and the quality of feeds and beddings.