THE DYNAMICS OF RETICULOENDOTHELIAL BLOCKADE

The dynamics of "reticuloendothelial blockade" were studied in living rabbits and isolated, perfused rabbit livers utilizing gelatin as a blockading agent and Au(198) stabilized in gelatin as a tracer. Employing the above experimental model, the following observations were made. (a) RES blockade was specific and dependent on the surface properties of the particle under study. (b) RES blockade was not caused by saturation of hepatic removal mechanisms. (c) RES blockade was not caused by depletion of demonstrable serum opsonins. (d) RES blockade appeared to correlate with high circulating levels of the blockading agent, per se. Thus, under the conditions employed, the term "reticuloendothelial blockade" was a misnomer. Although specificity of liver macrophage-particle interaction was evident and deserves further study, the data suggest that blockade as usually studied is a laboratory phenomenon induced by the continuing circulation of the blockading agent.

THE EFFECTS OF DECREASING DOSES OF OESTROGEN AND INCREASING DOSES OF PROGESTERONE ON THE TRANSPORT OF ARTIFICIAL EGGS THROUGH THE REPRODUCTIVE TRACT OF OVARIECTOMIZED RABBITS

By means of the technique of tracing the movement of 'artificial eggs' (radioactive spheres) by autoradiography (Harper, Bennett, Boursnell & Rowson, 1960) a study has been made of the effects of a decreasing oestrogen and various increasing progesterone doses on egg movement through the reproductive tract of ovariectomized rabbits. Five or more animals were autopsied at 8, 24, 48 and 56 hr. after insertion of the spheres into the ampulla of the Fallopian tube.

It was hoped that such treatments would produce hormonal conditions similar to those in intact rabbits after ovulation, and that therefore normal tubal transport would occur. The treatments used produced normal movement of the spheres through the ampulla and the isthmus, and most of them were retained in the Fallopian tube up to 48 hr. after insertion. However, by 48 hr. one or more spheres were observed to have entered the vagina in all treatment groups. None of the treatments caused most of the spheres to enter the uterus between 48 and 56 hr. after insertion, as would be the case in intact animals at a similar time after ovulation. It was concluded, however, that such treatments could produce tubal transport normal up to 48 hr. in ovariectomized rabbits, and that the presence of oestrogen appeared to be the controlling factor.