The effect of thyroxine on the development of fetal rabbit lungs was evaluated. In the first series of experiments involving 26 animals, thyroxine was given intramuscularly to pregnant does for two days prior to premature delivery of fetuses at 26 to 28 days gestation (full term: 30 days). There was no evidence of accelerated lung maturation in the fetuses treated with thyroxine. In a second series of experiments of 20 pregnant does, thyroxine was injected directly into the fetuses and amniotic sacs in one uterine horn at 24 to 25 day gestation: saline was given to the fetuses in the other horn which served as controls. When delivered two days later, thyroxine treated fetuses in comparison to the controls showed a significant increase in surface activity of the lung although there was no appreciable difference in body length and weight, and lung weight. Electronmicroscopy revealed accelerated maturation of the fetal lung evidenced by an increase in the number of inclusion bodies and early disappearance of glycogen in the Type II alveolar cells in the treated fetuses.

As an extension of our earlier work, procoagulant activity of erythrocyte [red blood cell (RBC)] membrane was examined using biochemical and rheological techniques. Western blot analysis of coagulation factors incubated with erythrocytes (RBCs) showed that only factor IX (FIX) was activated by RBC membranes in the presence of calcium ions. A fluorogenic assay suggested that activated FIX is capable of activating factor X. A preliminary crude extraction of the substance from RBC membranes suggested that a FIX-activating enzyme may be located on the RBC membrane. The initiation of FIX activation by RBCs was enhanced by an elevation in hematocrit. Moreover, the rate of FIX activation by RBCs from normal pregnant women and diabetic patients was much faster than that from normal subjects. In addition, glucose treatment of normal RBCs resulted in the increase in procoagulant activity. It is suggested that FIX activation by RBC membranes may serve as a triggering mechanism for blood coagulation, although further study will be required to clarify the putative FIX activating enzyme on the RBC membrane and to permit more extensive physiological experiments to be performed.