For the comparison of surface fine structures in the proliferative forms of two major protozoan parasites, Toxoplasma gondii and Sarcocystis species in mammalian hosts, isolated from the artificially infected mice and from the naturally infected cattle, respectively, an SEM(Hitachi S-570) was applied to the fixed, dried and coated with gold ion on the microslide glasses. The tachyzoites of T. gondii from the peritoneal cavity of the mouse showed the crescent-like feature and measured as 5.57 micro m in length and 2.33 micro m in width, while the bradyzoites of Sarcocystis species from the heart muscle of slaughtered cattle was banana-shaped and measured 14.18 micro m in length and 2.85 micro m in width. On the surface of Sarcocystis species bradyzoite, a distinct elliptical micropore was identified in the high magnification observation of 60,000X, and it measured as 0.35 micro m in length and 0.18 micro m in width.

Effect of raising types and environmental conditions on the infection of Toxoplasma in the swine, the cat and the man were studied in Cheju Island from Sept. 1987 to Aug. 1988. Blood samples were taken from 214 conventionally raised swine in 6 villages and 506 swine raised in swine specialized farms, 122 cats raised under free moving or restrained conditions in 8 locations, 113 butchers, and 210 villagers. Toxoplasma antibody values of the blood sera were determined using the enzymelinked immunosorbent assay (ELISA). The eating type of viscera was also investigated by using questionnaires. When ELISA method was used, the percentage of Toxoplasma infect swine among the conventionally raised and of those raised in swine specialized farms were 60.7 % and 21.3 %, respectively. The respective antibody values (+- SD) were 0.589 (+- 0.310) and 0.385 (+- 0.237) and differed very significantly (p<0.01). A significant difference was also found in antibody values among 6 villages (p<0.05). The mean infection percentage of Toxoplasma in the cat was 38.2 %, the infection percentage for cats raised under free-moving and restrained condition were 37.0 % and 38.2 % respectively. The respective antibody values (+- SD) for Toxoplasma were 0.600 (+- 0.614) and 0.637 (0.645), and did not differ significantly. The infection percentage of Toxoplasma in villagers and butchers were 26.2 and 38.3 % respectively. The respective antibody values (SD) for toxoplasma were 0.429 (+- 0.195) and 0.341 (+- 0.236), and differed very significantly (p<0.01). There were also highly significant differences Pyo-sun and other village (p<0.01). Analysis of the questionnaires showed that 26.0 % of 392 villages ate liver and some villagers ate other viscera.

Demi-embryos were successfully produced by bisection of ICR mouse embryos at preimplantation stages. They were microsurgically bisected using a microsurgical blade attached to a micromanipulator after pretreatment with 0.5 % pronase in PBS for two minutes or not. Embryos with softened zona pellucida were more easily bisected and less damaged than intact embryos. The highest success rate in bisection has been achieved by selecting blastocysts (94.1 % in success rate with intact blastocysts and 100 % in success rate with zona softened blastocysts). Demi-embryos without zona pellucida were cultured in D-PBS or M-16 medium at 37deg C, 5 % CO2 in air for 72 hours for 2-cell stage embryos, 48 hours for 4-to 8-cell stage embryos, 24 hours for morula stage embryos and 6-12 hours for blastocyst stage embryos. For the in vitro culture of 2-cell stage embryos, 100 micro M 2Na-EDTA was added to the media. M-16 medium was better for the in vitro development of mouse embryos than PBS, and PBS is not considered to be suitable for long-term culture of embryos, especially at early stage of cleavage. In M-16 medium, developing rate of demi-embryos of which pair underwent development to form eublastocysts was 15.8 % at 2-cell stage, 16.8 % at 4-cell stage, 38 % at 8-cell stage, 89.6 % at morula stage and 94.4 % at blastocyst stage, respectively. The more rapid and efficient production of demi-embryos and higher viability after bisection can be expected by softening zona pellucida with pronase and by selecting morulae or blastocysts rather than embryos at early stage of cleavage.