Abstract
The negative surface charges on the immature, mature and neuraminidase from Vibrio cholerae (VCN)-treated mature placental villi were investigated by electron microscopy using cationized ferritin as an ultrastructural marker. The degree and distribution of negative charge was also studied in comparison with surface ultrastructure and surface glycoprotein identified by ruthenium red staining. The negative charge on the cell surface was distributed in two different configurations: a strongly negative part and a weakly negative one, which corresponded to the distribution of surface glycoprotein as revealed by ruthenium red staining. The number of ferritin particles per 1 micron long basal line was 8, 412±2, 211 in the immature placenta, 1, 318±610 in a mature one and 375±173 in a VCN-treated mature one. The total surface length per 1 micron long basal line was 21.5±4.5 micron in immature villi and 6.3±1.8 micron in mature ones. From these findings it is simply calculated that an immature placenta in contrast to the mature one bears about twice as strong a negative charge per unit length of surface, about 6 to 7 times as strong a negative charge per unit length of basal line and about 36 to 50 times as strong a negative charge per unit, thus suggesting a possible role of the strong electrochemical repulsion in the immature placenta leading to its escaping attacks from maternal lymphocyte.
