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Normal fetal development is dependent on adequate placental blood perfusion. The functional role of the placenta takes place mainly in the capillary system; however, ultrasound imaging of fetal blood flow is commonly performed on the umbilical artery, or on its first branches over the chorionic plate. The objective of this study was to evaluate the structural organization of the feto-placental vasculature of the chorionic plate. Casting of the placental vasculature was performed on 15 full-term placentas using a dental polymer mixed with colored ink. Observations of the cast models revealed that the branching architecture of the chorionic vessel is a combination of dichotomous and monopodial patterns, where the first two to three generations are always of a dichotomous nature. Analysis of the daughter-to-mother diameter ratios in the chorionic vessels provided a maximum in the range of 0.6-0.8 for the dichotomous branches, whereas in monopodial branches it was in the range of 0.1-0.3. Similar to previous studies, this study reveals that the vasculature architecture is mostly monopodial for the marginal cord insertion and mostly dichotomous for the central insertion. The more marginal the umbilical cord insertion is on the chorionic plate, the more monopodial branching patterns are created to compensate the dichotomous pattern deficiency to perfuse peripheral placental territories.

The cellular branch of the immune defence in the newborn has been shown to differ from adults in a number of ways. This report presents new data on the functions of the histamine-secreting cells of the newborn. Mast cells of the newborn were obtained from the human umbilical cord by enzymatic dispersion. The granules of the mast cells of the umbilical cord were found to contain both chymase and tryptase by immunohistochemical staining, and the presence of cell-bound IgE on the mast cell surface was demonstrated by staining sections of umbilical cord with peroxidase-conjugated anti-IgE. The enzymatic dispersion yielded 12,660 mast cells per gram umbilical cord (median), range 2,500-60,300 (n = 48). The mast cells were found to constitute 3.1% of the total nucleated cells in the dispersate (median), range 1.5-3.8%. The histamine release from these cells was measured using a glass microfibre-based method. Both the umbilical cord mast cells and the cord blood basophils released histamine stimulated with anti-IgE, concanavalin A and the calcium ionophore A23187. In contrast to mast cells from adult tissue, the phorbol ester TPA was found to be an efficient secretagogue in both mast cells and basophils from the newborn. After maximal stimulation with anti-IgE and phorbol ester the quantity of histamine released per millilitre of blood was significantly higher in cord blood than in adult blood. The spontaneous histamine release from cord blood basophils was also significantly higher than from adult blood basophils. The mast cells found in the umbilical cord matrix and the cord blood basophils represent a readily available source of metabolically active histamine releasing cells for exploration of the role of histamine-secreting cells in newborn immune defence.