The pig blastocyst: Its ultrastructure and the uptake of protein macromolecules
- 50 Downloads
Between days 8 and 11 of pregnancy spherical blastocysts from 0.3 to 10 mm in diameter were flushed from the uterine horns of Dutch Landrace pigs. A description of their ultrastructure is given, and the uptake of horseradish peroxidase and ferritin is demonstrated.
The ultrastructure of the trophoblast was similar at all ages studied. The trophoblast which has many apical microvilli is able to take up and digest the macromolecules which were offered in the in vitro incubation medium.
The hypoblast consists of flattened cells. In blastocysts 2 mm and larger, compact cells bearing microvilli are found below the embryoblast. Cell organelles indicating protein synthesis are found within hypoblast cells of such blastocysts.
In the embryoblast, local concentrations of cell organelles are visible, indicating that differentiation has started. After the disappearance of Rauber's layer, which takes place when the blastocyst reaches a diameter of about 2 mm, superficial embryoblast cells develop short microvilli. The cells do not absorb ferritin or peroxidase but are dependent on the trophoblast for their food requirements.
All cell layers in the blastocyst contain mitochondria that have characteristics of those found in steroidproducing cells.
The significance of the uptake and digestion of macromolecules by trophoblast cells, the synthesis of protein by hypoblast cells and the possible synthesis of steroids is discussed with respect to the relationship between the cell layers of the blastocyst and in the context of conceptomaternal relationships.
Key wordsBlastocyst Ultrastructure Pig
Unable to display preview. Download preview PDF.
- Aitken RJ, Burton J, Hawkins J, Kerr-Wilson R, Short RV, Steven DH (1973) Histological and ultrastructural changes in the blastocysts and reproductive tract of roe deer (Capreolus capreolus). J Reprod Fertil 34:481–493Google Scholar
- Anderson LL (1974) Early embryonic development in the pig. J Anim Sci 39:986 (abstr)Google Scholar
- Anderson LL (1978) Growth, protein content and distribution of early pig embryos. Anat Rec 190:143–154Google Scholar
- Bazer FW, Thatcher WW (1977) Theory of maternal recognition of pregnancy in swine based on estrogen controlled endocrine versus exocrine secretion of prostaglandin F2α by the uterine endometrium. Prostaglandins 14:397–400Google Scholar
- Belt WD, Pease DC (1956) Mitochondrial structure in sites of steroid secretion. J Biophys Biochem Cytol suppl 2:369–374Google Scholar
- Belt WD, Cavazos LF, Anderson LL, Kraeling RR (1970) Fine structure and progesterone levels in the corpus luteum of the pig during pregnancy and after hysterectomy. Biol Reprod 2:98–113Google Scholar
- Brackett BG, Oh YK, Evans JF, Donawick WJ (1980) Fertilization and early development of cow ova. Biol Reprod 23:189–205Google Scholar
- Calarco PG, McLaren A (1976) Ultrastructural observations of preimplantation stages of the sheep. J Embryol Exp Morphol 36:609–622Google Scholar
- Davies J, Hesseldahl H (1971) Comparative embryology of mammalian blastocysts. In: Blandau RJ (ed) The biology of the blastocyst. Univ of Chicago Press, pp: 27–48Google Scholar
- Dongen JM van (1976) Ultrastructural development and cellular kinetics in intestinal epithelium. Rotterdam: ThesisGoogle Scholar
- Enders AC (1971) The fine structure of the blastocyst. In: Blandau RJ (ed) The biology of the blastocyst. Univ of Chicago Press, pp:71–94Google Scholar
- Enders AG (1973) Cytology of the corpus luteum. Biol Reprod 8:158–182Google Scholar
- Enders AC, Schlafke S (1965) The fine structure of the blastocyst: Some comparative studies. In: Wolstenholme GE, O'Connor M (eds) Preimplantation stages of pregnancy. Ciba Foundation Symposium, Churchill, London, pp: 29–59Google Scholar
- Findlay JK, Maule Walker FM, Heap RB (1980) The sheep as a model to study embryomaternal relationships in the preimplantation period. In: Serio M, Martini L (eds) Animal models in human reproduction. Raven press, New York, pp: 283–297Google Scholar
- Flint APF (1981) A unifying hypothesis for the control of blastocyst growth based on observations of the pig. J Reprod Fertil. Suppl 29:215–227Google Scholar
- Geisert RD, Renegar RH, Thatcher WW, Rober RM, Bazer FW (1982a) Establishment of pregnancy in the pig: I Interrelationships between preimplantation development of the pig blastocyst and uterine endometrial secretions. Biol Reprod 27:925–939Google Scholar
- Geisert RD, Brookbank JW, Roberts RM, Bazer FW (1982b) Establishment of pregnancy in the pig: II Cellular remodelling of the porcine blastocyst during elongation on day 12 of pregnancy. Biol Reprod 27:941–955Google Scholar
- Gemmell RT, Stacy BD, Thorbarn GD (1974) Ultrastructural study of secretory granules in the corpus luteum of the sheep during the estrous cycle. Biol Reprod 11:447–462Google Scholar
- Graham RC, Karnovsky MJ (1966) The early stages of absorption of injected horseradish peroxidase in the proximal tubules of mouse kidney: ultrastructural cytochemistry by a new technique. J Histochem Cytochem 14:291–302Google Scholar
- Hafez ESE (1971) Some maternal factors affecting physicochemical properties of blastocysts. In: Blandau RJ (ed) The biology of the blastocyst. Univ of Chicago press, pp: 139–192Google Scholar
- Hanly S (1961) Prenatal mortality in farm animals. J Reprod Fertil 2:182–194Google Scholar
- Heap RB, Flint APF, Gadsby JE, Rice C (1979) Hormones, the early embryo and the uterine environment. J Reprod Fertil 55:267–275Google Scholar
- Hunter RHF (1977) Physiological factors influencing ovulation, fertilization, early embryonic development and establishment of pregnancy in pigs. Br Vet J 133:461–470Google Scholar
- Karnovsky MJ (1965) A formaldehydeglutaraldehyde fixative of high osmolality for use in electronmicroscopy. J Cell Biol 27:137a-138aGoogle Scholar
- Linares T, Ploen L (1981) On the ultrastructure of seven day old normal (blastocysts) and abnormal bovine embryos. Anat Histol Embryol 10:212–226Google Scholar
- Lutwak-Mann C (1971) The rabbit blastocyst and its environment: Physiological and biochemical aspects. In: Blandau RJ (ed) The biology of the blastocyst. Univ of Chicago press, pp: 243– 260Google Scholar
- Massip A, Mulnard J, Huygens R, Hanzen C, van der Zwalmen P, Ectors F (1981) Ultrastructure of the cow blastocyst. J Submicr Cytol 13:31–40Google Scholar
- Mohr LR, Trounson AO (1981) Structural changes associated with freezing of bovine embryos. Biol Reprod 25:1009–1025Google Scholar
- Mohr LR, Trounson AO (1982) Comparative ultrastructure of hatched human, mouse and bovine blastocysts. J Reprod Fertil 66:499–504Google Scholar
- Norberg HS (1973) Ultrastructural aspects of the preattached pig embryo. Cleavage and early blastocyst stage. Z Anat Entwicklungsgeschichte 143:95–114Google Scholar
- Owers NO (1971) Ingestive properties of guinea pig trophoblast grown in tissue culture: a possible lysosomal mechanism. In: Blandau RJ (ed) The biology of the blastocyst. Univ of Chicago Press, pp:225–242Google Scholar
- Perry JS, Rowlands IW (1962) Early pregnancy in the pig. J Reprod Fertil 4:175–188Google Scholar
- Perry JS, Heap RB, Amoroso ED (1973) Steroid hormone production by pig blastocysts. Nature (London) 245:45–47Google Scholar
- Sasaki H, Niimura S, Ishida K (1979) Ultrastructure of blastocysts on day 13 of gestation in the pig. Jpn J Zootech Sci 50:721–726Google Scholar
- Schlafke S, Enders AC (1975) Cellular basis of interaction between trophoblast and uterus at implantation. Biol Reprod 12:41–65Google Scholar
- Willingham MC, Rutherford AV, Gallo MG, Wehland J, Dickson RB, Schlegel R, Pastan IH (1981) Receptor mediated endocytosis in cultured fibroblasts: cryptic coated pits and formation of receptosomes. J Histochem Cytochem 29:1003–1012Google Scholar
- Winterberger-Torrès S, Fléchon JE (1974) Ultrastructural evolution of the trophoblast cells of the preimplantation sheep blastocysts from day 8 to day 18. J Anat 188:143–153Google Scholar