Nuclear and cytoplasmic annulate lamellae in trophoblast giant cells of rat placenta

AbstractSingle stranded profiles of nuclear annulate lamellae were identified in giant cells of rat trophoblast from the day when the chorioallantoic placenta first becomes vascularized, viz., day 12 post coitum, until the day before term, viz., day 22. Cytoplasmic annulate lamellae were observed only in giant cells from placentas at day 12. Occasionally cytoplasmic annulate lamellae were found in parallel array. Often the lamellar membranes were continuous with both granular and agranular membranes of endoplasmic reticulum; they closely resembled doubled outer nuclear membrane. Nuclear annulate lamellae resembled doubled inner nuclear membrane; and often the two were found in continuity. In addition, at later gestational ages (17 and 22 days), nuclear lamellae often were related anatomically to the variety of nuclear inclusions which characterize giant trophoblast cells during late pregnancy. A possible relationship of annulate lamellae to the synthesis of DNA, RNA and protein is considered.