Larval Stages and Phylogeny as Exemplified by the Lung Fluke of Turtles

The effects of certain 19-norsteroids on reproductive processes in mammals are presented. 17alpha-ethinyl-19-nortestosterone 17alpha-ethinyl-5(10)estraeneolone 17alpha-ethyl-19-nortestosterone 17alpha-methyl-19-nortestosterone and progesterone were studied using the Clauberg assay in rabbits the Rubin assay in mice the deciduomagenic activity in rats the conception-inhibiting activity in rats and in the ability to induce and sustain implantation of fertilized ovum in female rabbits castrated 1 day after a fertile mating. These studies reveal a group of substances which by reason of certain similarities to progesterone may be classified as progestins. 17alpha-ethyl-19-nortestosterone appears to have typical progesteronelike activity in all of the tests but it is quantitatively more active than progesterone in the Clauberg assay and in deciduomagenic activity and less active in the others. Normal reproductive processes such as ovulation may be inhibited or stimulated such as endometrial proliferation with these compounds.