Summary
The differentiation of chorionic layers II and III and alterations of intercellular junctions within the developing placental labyrinth were investigated in rats.
Between the 14th and 16th day of gestation, the trabecular structures of the labyrinth alter and increasing numbers of primary, secondary, and tertiary lamellae develop. Trophoblastic layer I remains multicellular. Layer III rearranges and cytoplasmic fusions result in a continuous cytoplasmic barrier intervening between the already syncytial trophoblastic layer II and fetal capillaries. Simultaneously, most of the “undifferentiated” cells within the labyrinth disappear.
Thin sectioning anf freeze-fracturing reveal multiple images of intercellular junctions, particularly gap and tight junctions in the cellular and syncytial parts of layers II and III. Continuous and regularly arranged tight junctions occur as well as fragmented structures which are spaced irregularly. Gap junctions are occasionally found between the juxtasinusoidal regions of layers II and III on the 14th day. More often they occur within restricted areas near the center of the trabeculae, integrated within extensive tight junctional strands. Gap junctions increase in later stages of pregnancy and eventually become distributed between the interfaces of layers II and III in the primary lamellae.
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Aoki A, Metz J, Forssmann WG (1978) Studies on the ultrastructure and permeability of the hemotrichorial placenta: II. Fetal capillaries and tracer administration into the fetal compartment. Cell Tissue Res 192:409–422
Bridgman J (1948a) A morphological study of the development of the placenta of the rat. I. An outline of the development of the placenta of the white rat. J Morphol 86:61–86
Bridgman J (1948b) A morphological study of the development of the placenta of the rat. II. A histological and cytological study of the development of the chorioallantoic placenta of the white rat. J Morphol 83:195–223
Carter JE (1964) Morphologic evidence of syncytial formation from the cytotrophoblastic cells. Obstet and Gynec 23:647–656
Davies J, Glasser SR (1968) Histological and fine structural observations of the placenta of the rat. Acta Anat 69:542–608
Duval M (1891) Le placenta des rongeurs: Le placenta de la souris et du rat. J Anat Physiol 27:344–395; 514–612
Enders AC (1965) A comparative study of the fine structure of the trophoblast in several hemochorial placentas. Am J Anat 116:29–68
Forssmann WG, Metz J, Heinrich D (1975) Gap junctions in the hemotrichorial placenta of the rat. Ultrastr Res 53:374–381
Franke H (1969) Feinstruktur der Placenta. Elektronenmikroskopische Untersuchungen über die reifende und reife Placenta der Ratte. Jena: VEB G Fischer
Jollie WP (1964) Fine structural changes in placental labyrinth of the rat with increasing gestational age. J Ultrastruct Res 10, 27–47
Karnovsky MJ Use of ferrocyanide-reduced osmium tetroxide in electron microscopy. J Cell Biol 50:ASCB abstracts, 146
Luft JH (1961) Improvements in epoxy-resin embedding methods. J Biophys Biochem Cytol 9:409–414
Marquard E, Merlo M, Heinrich D, Metz J (1979) Über die Ultrastruktur der wachsenden Rattenplacenta. Verh Anat Ges 73:445–451
Metz J, Heinrich D, Forssmann WG (1976) Ultrastructure of the labyrinth in the rat full term placenta. Anat Embryol 149:123–148
Metz J, Aoki A, Forssmann WG (1978) Studies on the ultrastructure and permeability of the hemotrichorial placenta: I. Intercellular junctions of layer I and tracer administration into the maternal compartment. Cell Tissue Res 192:391–407
Metz J, Weihe E, Heinrich D (1979) Intercellular junctions in the full term human placenta: I. Syncytiotrophoblastic layer. Anat Embryol 158:41–50
Midgley HR, Pierce GB, Denean GA, Gosling JRG (1963) Morphogenesis of syncytiotrophoblast in vivo: an autoradiographic demonstration. Science 141:349–350
Peel S, Bullmer D (1977) Proliferation and differentiation of trophoblast in the establishment of the rat chorio-allantoic placenta. J Anat 124:675–687
Pierce GB, Midgley AR, Beals TF (1964) An ultrastructural study of differentiation and maturation of trophoblast of the monkey. Lab Invest 13:451
Reynolds ES (1963) The use of lead citrate at high pH as an electron opaque stain in electron microscopy. J Cell Biol 17:208–212
Schiebler TH, Knoop A (1959) Histochemische und elektronenmikroskopische Untersuchungen an der Rattenplacenta. Z Zellforsch 50:494–552
Wislocki GB, Dempsey EW (1955) Electron microscopy of the placenta of the rat. Anat Rec 123:33–63
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Metz, J. On the developing rat placenta. Anat. Embryol. 159, 289–305 (1980). https://doi.org/10.1007/BF00317652
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DOI: https://doi.org/10.1007/BF00317652