Summary
Ultrastructural studies were undertaken to investigate the temporal relationship between loss of the zona pellucida around the blastocyst and the appearance of decidual changes in the endometrial stroma during normal implantation in rats. Blastocyst-free and blastocyst-containing sites of pregnant uterine horns were studied and compared with control sites from contralateral salpingectomized horns and horns of pseudopregnant animals from 24.00 h on Day 4 and onwards. There were no membrane contacts between the blastocyst and the uterine epithelium at 10.00 h on Day 5 and earlier because of an intervening zona pellucida. From 14.00 h onwards, however, such contacts were present and at 18.00 h, the zona pellucida had disappeared and the blastocyst had attached onto the uterine epithelium.
The stromal cells of pregnant and control horns were indistinguishable from each other at 24.00 h on Day 4, but from 06.00 h on Day 5 onwards specific changes were noted in the stromal cell nucleoli of the pregnant horns. The results therefore suggest that the first morphological sign of decidualization occurs about 12 h before the Pontamine Blue reaction and is initiated by the blastocyst early on Day 5 while it is still encased by the zona pellucida.
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References
Enders AC, Schlafke S (1967) A morphological analysis of the early implantation stages in the rat. Am J Anat 120:185–226
Finn CA (1971) Biology of the decidual cells. In: Bishop MWH (ed) Advances in reproductive physiology. Logas Press Limited, London, pp 1–26
Finn CA, McLaren A (1967) A study of the early stages of implantation in mice. J Reprod Fert 13:259–267
Finn CA, Porter DG (1975) The decidual cell reaction. In: Finn CA (ed) The uterus. Elek Science, London, pp 74–85
Heald PJ, O'Grady JE, O'Hare A, Vass M (1975) Nucleic acid metabolism of cells of the luminal epithelium and stroma of the rat uterus during early pregnancy. J Repord Fert 45:129–138
Ljungkvist I, Nilsson O (1974) Blastocyst-endometrial contact and pontamine blue reaction during normal implantation in the rat. J Endocrinol 60:149–154
Lundkvist Ö (1978a) Ultrastructural studies of the endometrial stromal cells in rats during estradiol-induced implantation after an experimental delay. Biol Reprod 18:306–316
Lundkvist Ö (1978b) Morphological studies of the stromal changes after artificial induction of the decidual reaction in rats. Cell Tissue Res 194:287–296
Lundkvist Ö, Ljungkvist I (1977) Morphology of the rat endometrial stroma at the appearance of the Pontamine Blue Reaction during implantation after an experimental delay. Cell Tissue Res 184:453–466
Lundkvist Ö, Nilsson O, Bergström S (1979) Studies on the trophoblast-epithelial complex during decidual induction in rats. Am J Anat 154:211–230
Psychoyos A (1971) Methods for studying changes in capillary permeability of the rat endometrium. In: Daniel JC (ed) Methods in mammalian embryology. WH Freeman and Company, San Francisco, pp 334–338
Recher L, Sykes JA, Chan H (1976) Further studies on the mammalian cell nucleolus. J Ultrastruct Res 56:152–163
Recher L, Whitescarves J, Briggs L (1969) The fine structure of a nucleolar constituent. J Ultrastruct Res 29:1–14
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Supported by grants from the Swedish Medical Research Council, Project No 12X-70 to Prof. O. Nilsson
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Lundkvist, Ö., Nilsson, B.O. Ultrastructural studies of the temporal relationship between loss of zona pellucida and appearance of blastocyst-induced stromal changes during normal pregnancy in rats. Anat Embryol 170, 45–49 (1984). https://doi.org/10.1007/BF00319456
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DOI: https://doi.org/10.1007/BF00319456