The use of chemical analyses of umbilical cord blood for the computation of instantaneous fetal growth

From the umbilical veno-arterial differences in the concentrations of carbohydrates, lipids and amino acids, and of oxygen, carbon dioxide and urea, one can calculate what fractions of the three fuels are burned and what fractions are deposited and constitute growth of the fetus. If umbilical blood flow is also measured, it is possible to calculate the instantaneous rate of fetal growth. Blood can be sampled from the umbilical artery and vein by means of indwelling catheters in unanesthetized sheep. Measurements of umbilical blood flow in unanesthetized sheep are available also. Application of the proposed analysis to published cord blood values for the fetal lamb lead to a predicted rate of growth that was in good agreement with the observed rate of growth. It also showed that a small uptake of a lipid like fuel is still being overlooked. It is concluded that analysis of a set of cord blood samples makes possible a calculation of the fraction of fuel uptake of the fetus that is being used for growth, at the time the samples were taken.     

Fetal nutrition: supply, combustion, interconversion, and deposition

The study of placental transport is confounded by species differences, gestational differences, and a permanent non-steady state. The histology of the interhemal membrane, the degree of steric hindrance to diffusional exchange, the discrimination of electric charge, the flow pattern, and the transfer of intact gamma globulins are all species specific. We suggest the creation of order based on the ultrastructure of the placental barrier. The gas diffusion capacity of the membrane changes during gestation. This change is initially due to an increase in placental mass, but the gas diffusion capacity continues to increase after placental growth has ceased, because of changes in surface area and thickness of the membrane. The non-steady state of fetal weight is accompanied by an uptake of nutrients far in excess of what is necessary to satisfy oxygen consumption. Measurements of venous and arterial cord blood chemistry are sufficient to distinguish the fraction of nutrient uptake that is dedicated to catabolism from the fraction that is dedicated to fetal growth.     

Cloning of Epstein-Barr virus (EBV) DNA fragments in pBR32 and Charon3A

Restriction fragments of Epstein-Barr virus (EBV; B95-8) DNA were cloned in the Tc gene of pBR322 (HindIII-F, -G, -I, -J, -K, -L, and -M) and in Charon3A (EcoRI-GI and -G2). Altogether these cloned fragments covered 39% of the entire viral genome. The cloned EcoRI-G2 fragment of EBV (B95-8) DNA was shown to contain, in addition to HindIII-J, two more HindIII-fragments : HindIII-M, which had not been located on the linkage map of the viral genome (Given and Kieff, 1978) and HindIII-N, which had been unrecognized up to now. The utility of this cloning method is discussed in regard to the detailed mapping of a viral genome and large-scale production of the viral DNA.