On the basis of previous results on IFN gene expression in the trophectoderm, we assumed that in pregnant uteri the relative proportion of each IFN species was unchanged from Day 11 to Day 14. A unique mixture was then prepared corresponding to the day of the highest injected dose (Day 14 postestrus). The amount of IFN-7 and IFN-8 in this mixture was established as twice the mean dose detected for each IFN in a uterine flushing of a Day 14 pregnant Meishan gilt. Other mixtures (Day 11 to Day 13) were obtained by 1:10, 1:5, and 1:2 dilutions of this Day 14 mixture, respectively (Table 1). Total international units per milliliter in the mixture are given as intervals corresponding to the estimated precision of the antiviral test. Each IFN mixture was prepared in PBS (pH 7.4) containing 0.1% BSA and divided into 2.5-ml aliquots in di-methyl-chlorosilan-treated vials, which were frozen at — 80°C before use. Re-assay of antiviral activity of the same aliquot fractions after completion of the experiment showed a complete stability of the biological activity. ventolin inhaler
The gilts were randomly allocated to one of two experimental groups. In treated gilts, the IFN was injected into the two uterine horns on Days 11-14 of the estrous cycle. The injections (1 ml) were done slowly twice daily (0930 and 1730 h), with increasing doses of IFNs each day (Table 1). After injection, each catheter was filled (1 ml) with the same solution without IFN. In the control group, gilts were mock-treated with PBS containing BSA according to the same protocol.