Mice lacking the gene encoding the receptor for prostaglandin F2alpha (FP) developed normally but were unable to deliver normal fetuses at term. Although these FP-deficient mice showed no abnormality in the estrous cycle, ovulation, fertilization, or implantation, they did not respond to exogenous oxytocin because of the lack of induction of oxytocin receptor (a proposed triggering event in parturition), and they did not show the normal decline of serum progesterone concentrations that precedes parturition. Ovariectomy at day 19 of pregnancy restored induction of the oxytocin receptor and permitted successful delivery in the FP-deficient mice. These results indicate that parturition is initiated when prostaglandin F2alpha interacts with FP in ovarian luteal cells of the pregnant mice to induce luteolysis.

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A comprehensive interpretation of the microstructure and mechanism of the formation of a versatile solid acid catalyst, Cs 2.5 H 0.5 PW 12 O 40 , has been attempted by combining the new results obtained with solid-state NMR, XRD, SEM, and N 2 porosimetry with the data reported previously. The precipitates of Cs 2.5 H 0.5 PW 12 O 40 just formed from aqueous solutions of H 3 -PW 12 O 40 and Cs 2 CO 3 consist of ultrafine crystallites in which the acid form, H 3 PW 12 O 40 , is epitaxially deposited on the surface of Cs 3 PW 12 O 40 crystallites. Calcination of the precipitates brings about the migration of H + and Cs + in the solid to form a nearly uniform solid solution in which protons distribute randomly through the entire bulk, as revealed by XRD and 31 P solid-state NMR. Impregnation of Cs 3 PW 12 O 40 with the aqueous solution of H 3 PW 12 O 40 also gives the uniform salt after calcination. Pore-size distribution evaluated by the analysis of N 2 desorption isotherm showed that Cs 2.5 H 0.5 PW 12 O 40 has mesopores as well as micropores that are interparticle voids of the crystallites. The initial heat of NH 3 sorption indicated the presence of very strong acid sites on Cs 2.5 H 0.5 PW 12 O 40 . High catalytic activity of Cs 2.5 H 0.5 -PW 12 O 40 reported for solid-liquid reaction systems is thus principally attributed to the strength and number of acid sites and the mesoporous structure appropriate for the rapid diffusion of molecules.

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