Paul D. Bruns

Clearance of inert molecules, Na, and Cl ions across the primate placenta☆

Abstract Transplacental clearances of antipyrine, tritiated water, urea, Na, and Cl ions were studied in the rhesus monkey. In order of decreasing placental permeability determined in vivo, these experiments showed the following order: tritiated water and antipyrine, urea, chloride, and sodium ions. Clearances of tritiated water and antipyrine were equal. The placental clearances of tritiated water and antipyrine were significantly different when determined across the chorion laeve in vitro. These observations suggest that the transplacental diffusion of these molecules is flow limited. The diffusion rates of urea, Na, and Cl ions were limited primarily by the permeability of the placental membrane. The placenta of the rhesus monkey is more permeable to Na and Cl ions than the sheep placenta. Permeability to urea per kilogram of fetal body weight is of the same order of magnitude in both species.

The placental transfer of water from fetus to mother following the intravenous infusion of hypertonic mannitol to the maternal rabbit.

Abstract 1. When pregnant rabbits near term were given an intravenous infusion of hypertonic mannitol solution, there was a 2 to 4 per cent loss in fetal body water concentration, indicating a movement of water from the fetus to the mother. 2. A prompt and significant increase in maternal total solute concentration occurred: this was followed by a similar but less marked rise in fetal total solute concentration. 3. Approximately 50 per cent of the increase in fetal total osmotic pressure is ascribed to the placental transfer of mannitol. 4. Under these circumstances, water is lost in equal proportions from both the intracellular and extracellular compartments of the fetus.

Effect of maternal exposure to high altitude upon fetal oxygenation

Abstract Acute exposure to high altitude of 6 pregnant ewes in the last third of pregnancy produced a significant decrease in oxygen content in the umbilical vein in the first 48 hours. With continued exposure to high altitude there was an increase in oxygen content in the umbilical vein toward normal values. Two of 6 animals attained normal values in about 2 weeks. This process of adaptation was detectable as early as the fourth day of exposure to low barometric pressure. The rise in oxygen content in the umbilical vein was due in part to an increased umbilical vein oxygen tension and in part to an increased oxygen capacity. The rise of oxygen tension in the umbilical vein was parallel to a rise of oxygen tension in the uterine vein.

Placental Transfer and Fetal Tissue Uptake of Mg28 in the Rabbit

Summary Mg28 was injected intravenously into 11 pregnant rabbits between 28 and 30 days of gestation. Fetuses and placentas were removed at intervals ranging from 7 minutes to 26 hours. Maternal tissue uptake of Mg28 resembled that previously found in nonpregnant young adult rabbits, except that uptake in bone and muscle was slower. Concentration of Mg28 in the placenta rapidly rose above the maternal plasma level. Specific activity of magnesium in all fetal tissues studied reached a fairly constant value by 26 hours. Magnesium turnover in tissues of the fetus in utero, especially in bone and muscle, is considerably more rapid than that in the respective tissues of the mother. Mg28 was supplied by Brookhaven Laboratory on allccation from U. S. Atomic Energy Comm.

Effect of respiratory acidosis on the rabbit fetus in utero

Abstract This report deals with acid-base relationships between maternal and fetal bloods. The new aspect is the presentation of nonsteady state measurements made simultaneously in both mother and fetus during the production of respiratory acidosis in the mother. Pure respiratory acidosis was induced in 12 pregnant rabbits near term by allowing them to breathe selected concentrations of carbon dioxide. The pH, Pco 2 , and standard HCO 3 − determinations were made on maternal arterial and fetal umbilical vein blood. In all instances, both the mother and the fetus showed a decrease in pH and an elevation of arterial Pco 2 without a change in standard HCO 3 − concentrations. Severe respiratory acidosis over a 90 minute period did not produce metabolic acidosis in the mother or the fetus. In the presence of pure respiratory acidosis in the pregnant rabbit, measurements of pH, Pco 2 , and standard HCO 3 − in the mothers blood provide reasonably accurate information of their concentrations in fetal blood. However, it cannot be concluded that other types of acid-base changes in the mother will be reflected by similar changes in the fetus.

Amniocentesis and intrauterine fetal transfusion in erythroblastosis.

Abstract Sixty-one Rh-sensitized pregnancies from whom a total of 95 samples of amniotic fluid were analyzed are presented. The 450 mμ peak of the absorption curve plotted on a logarithmic scale was found to be a useful adjunct in the management of Rh-sensitized mothers. The amniotic fluid absorption curve at 450 mμ has been more helpful when the values are very low (below 0.05 OD) and when they are very high (above 0.15 OD). The range between these values (0.05 to 0.15 OD) is a difficult area for making predictions of the extent of hemolysis or anemia by examination of amniotic fluid alone. This is especially true of single samples. Determinations of the 450 mμ peak repeated at intervals from 28 to 37 weeks gestation have proved more informative than single observations. Seven patients who were managed with a total of 12 intrauterine fetal transfusions are reported. Three infants survived, 2 infants died of erythroblastosis and 2 infants died as a result of the procedure. Intrauterine fetal transfusions should be regarded as being in an investigational stage and are not recommended as a routine.