Oliviero Fagioli

Lectin histochemical detection of sulfoglycans in the zona pellucida of mammalian antral oocytes.

Sulphated esters are important to increase effectiveness of specific biological activities of carbohydrates. Biochemical studies revealed the presence of distinct sulphated glycoproteins in mammal zona pellucida (ZP) that bind proacrosin and thus participate in the sperm-egg fusion processes. In the present study, 6 lectin-horseradish peroxidase conjugates (SBA, PNA, RCA-I, GSA-IB4, GSA-II and DBA) were used in combination with desulphation and sialidase digestion to identify sulphocarbohydrates in the terminal and/or subterminal position of oligosaccharide side chains of glycoproteins in the ZP of bovine, ovine, caprine and porcine antral oocytes. In particular, we identified the following terminal sulphoglycans located in the outer layer of the ZP only: SO4-GalNAc in bovine ZP; SO4-Galbeta1,3GalNAc in bovine and ovine ZP; SO4-Galbeta1,4GlcNAc in bovine, ovine and caprine ZP; SO4-alpha-Gal in bovine, caprine and porcine ZP. Subterminal sulphoglycans linked to sialic acid residues were evenly distributed throughout the entire thickness of the ZP: Neu5Ac-SO4-Galbeta1,3GalNAc in bovine and porcine ZP; Neu5Ac-SO4-Galbeta1,4GlcNAc in caprine ZP; Neu5Ac-SO4-alpha-Gal in porcine ZP; Neu5AcSO4-GlcNAc in bovine ZP. The results demonstrate that the chemical composition of the ZP differs among species determining the species-specificity of gamete interactions.

Topographical localisation of glucidic residues and their variations in the canine zona pellucida during folliculogenesis

SummaryIn the present ultrastructural study, horseradish peroxidase-labelled lectins, in conjunction with antiperoxidase antibody and protein A-gold, were used to characterise and localise the oligosaccharide sequences of zona pellucida glycoproteins at different stages of follicular development in the canine ovary. Deacetylation and sialidase digestion were also performed before lectin cytochemistry. The zona pellucida of oocytes present in unilaminar primary follicles reacts with WGA- and RCA-I-lectins. The zona pellucida of oocytes present in bilaminar and trilaminar secondary follicles displays positivity to WGA, RCA-I, Con-A, UEA-I, and sialidase/SBA. This labelling pattern persists in the zona pellucida of oocytes present in antral tertiary follicles with the exception of WGA and RCA-I reactive sites which are differently distributed throughout the zona pellucida. The topographical distribution of these carbohydrates is not uniform throughout the zona pellucida, indicating the regionalization of oligosaccharide chains within three concentric bands of the zona matrix: an inner surface close to the oocyte plasmamembrane, an intermediate portion and an outer layer in contact with the follicular cells. Our results demonstrated variations in the presence and distribution of the carbohydrate residues in the canine zona pellucida during different stages of follicular growth. We also observed the presence of vesicles in both the ooplasm and granulosa cells, showing a similar lectin binding pattern to that of the zona pellucida.

Glucidic determinants expressed by the digestive apparatus of Umbrina cirrosa (L.) fries as revealed by lectin histochemistry.

Glycoconjugates present in the various parts of the digestive apparatus (oesophagus, stomach, intestine) of 27, 34 and 44 days-old Umbrina cirrosa (L.) fries were characterised by means of lectin histochemistry in conjunction with sialidase digestion and KOH treatment. High amounts of carbohydrates were detected especially in goblet cells of the oesophagus. Positivity obtained with the various lectins in oesophagus, stomach and intestine did not change during the development of the fries examined. D-Gal and D-GalNAc appeared to occupy a terminal position in oligosaccharidic chains whereas they are linked to sialic acid residues in adult subjects, which suggests an incomplete chemical structure of the glycoconjugates secreted by the digestive apparatus of fries.