P. Depaz et al., ULTRASTRUCTURAL-LOCALIZATION OF LECTIN RECEPTORS IN THE PREIMPLANTATION OVINE EMBRYO, The Anatomical record, 240(4), 1994, pp. 537-544
Background: Preimplantation development of mammalia is characterized b
y cell surface changes functioning in intercellular communication and
adhesion. The glycoconjugate role in cellular interactions has been an
alysed for several groups but not in sheep embryos. The binding patter
ns of eleven lectins during sheep preimplantation development were inv
estigated and the role of glycoconjugates in early development was dis
cussed. Methods: Ultrathin sections from preimplantation ovine embryos
(3-7 days) were incubated with different colloidal gold conjugated le
ctins and the frequency of gold particles on the cell membrane, some o
rganelles, and the zona pellucida was evaluated. Results and Conclusio
ns: We observed a higher staining of WGA, DBA, and SBA lectins in the
intercellular contact zone with respect to the free cell surface of bl
astomeres during cleavage. This indicates that the N-acetyl galactosam
ine and N-acetyl glucosamine residues may be involved in sheep morula
compaction. In contrast, the trophoblast cell displays an increase of
staining of some lectins previously identified during cleavage (LcH, W
GA, SBA, MPA, and PNA) on the free membrane, and a lack of sugar resid
ues in the intercellular surface. This polarization of the trophoblast
cell surface is not observed in the inner cell mass and could provide
a mechanism for differentiation within the blastocyst. Intracytoplasm
ic vesicles show a cytochemical identity with lysosomes in the blastoc
yst (abundant GlcNAc and Man/Glc residues) that may reflect a function
al relationship between both organelles in an intracellular cycle. The
zona pellucida presents abundant GlaNAc, GlcNAc, and Gal residues dur
ing preimplantation ovine development. (C) 1994 Wiley-Liss, Inc.