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A battery of seven different horseradish peroxidase-labelled lectins (PNA, ConA, DBA, SBA, LTA, WGA and UEA I) was used to study the distribution and changes of carbohydrate moieties of glycoconjugates in the caecal epithelium (proximal and distal tracts) of the chick embryo and of the 3 days old chicken. The chief results showed that: 1. The appearance of some sugar residues was earlier observed at the epithelium of the distal tract than the proximal one (Tab. 2). 2. The presence of sialic acid was detected only after hatching (Fig. 4, Tab. 2). 3. During the embryonic caecal development enterocytes and goblet cells were characterized by the presence of the same sugar residues (Tab. 2). 4. By a quantitative point of view, differences in sugar residues content between the epithelium of the proximal and distal tract were observed. The epithelial cells of the distal tract were generally characterized by an higher content of saccharide moieties (Tab. 2). 5. At the end of the incubation period and after hatching enterocytes and goblet cells showed differences in content of some sugar residues (Fig. 1-3, Fig. 5-8, Tab. 2).

The glycosaminoglycans of the human bone are Chondroitin-4 sulfate, Chondroitin-6 sulfate and Keratosulfate. Their quantity presents variations with ageing. The Keratosulfate shows a prevalent localisation in the bone matrix just around the osteocytes.

A battery of seven different horseradish-peroxidase labelled lectins (DBA, PNA, SBA, UEA I, WGA, ConA, LTA) was used to study the distribution of sugar residues in the glycoconjugates along the nephron and the collecting duct of the kidney of Gallus domesticus. As far as the glomerular components are concerned, we have demonstrated that the podocytes and, with a lesser extent, the mesangial cells are characterised by the presence of D-mannose, D-galactose-(beta 1- greater than 3)-N-acetyl-D-galactosamine and sialic acid. The glomerular capillary wall shows the presence of the disaccharide D-galactose-(beta 1- greater than 3)-N-acetyl-D-galactosamine and sialic acid. With regards to the tubules, the proximal tubule, the descending limb of the loop of Henle, the connecting tubule and the collecting one, are characterised by N-acetyl-D-galactosamine, (1- greater than 6)-alpha-L-fucose, D-mannose, N-acetyl-D-galactosamine and D-galactose-(beta 1- greater than 3)-N-acetyl-D-glucosamine. The cells of the connecting and collecting ducts show the presence of intracellular sialic acid, found also as component of the mucous secretion. The ascending limb of the loop of Henle and the distal tubule contain only three saccharidic residues, i.e. (1- greater than 6)-alpha-L-fucose, D-mannose and N-acetyl-D-glucosamine. Lectin histochemistry was also useful to define the saccharidic components of the mucus, which is normally present within the connecting and collecting ducts of the kidney of the birds. The cellular variability of the connecting and the collecting ducts is similar to that found in the kidney of some mammals. Such a variability seems to suggest a possible cell specialization along a single kidney tubule.

The histochemical characteristics of colonic epithelial mucins were investigated in the chick embryo. At the 14th day of incubation it was possible to demonstrate the presence of glycogen. At the 15th day a few epithelial cells showed the presence of neutral and sialylated mucins. On the 16th day, also sulfated secretory material was detectable together with neutral and sialylated mucins in cells with the typical shape of goblet cells. From the 17th day to the 20th day of incubation the two types of acid mucins appeared in some cells to be placed in distinct zones of the supranuclear cytoplasm. At the 21st day, neutral, sialylated and sulfated mucins were all present in the majority of goblet cells, which were found mainly in the epithelium lining the crypts.

The authors have investigated the morphological aspects of the wall components of the developing colon in the chick embryo (Gallus domesticus) from the 7th to th 15th day of incubation. Particular attention has been given to the lumen recanalization, phenomenon which occurs also in other animal species. The most significant results can be summarized as follows: 1) the lumen is recanalized at the 7th day only at the proximal part of the colon (Fig. 1, Tav. 1), while at the distal tract it is still completely filled by an epithelial plug (Fig. 2, Tav. 1). Therefore the recanalization of the lumen takes place cranio-caudad. 2) At the 8th day the process of recanalization of the lumen shows, in the distal part of the colon, well defined modalities. Radially oriented intraepithelial spaces within the epithelium filling the lumen join other semilunar intercellular spaces, which are placed near the central part of the occluded lumen (Fig. 3). By the junction of a couple of radially oriented spaces with one semilunar space, an U-shaped intercellular space derives, which delimits an incoming epithelial fold (Tav. 3). Such a phenomenon is continued also during the 9th and 10th day of incubation (Fig. 6, Tav. 2). 3) At the 11th day the colonic lumen is completely open and, in its distal part, the appearance of the primordial previllous ridges can be observed (Fig. 7). In the proximal tract the previllous ridges develop one day later (Fig. 8). 4) At the 13th day, in the distal part of the colon, the first appearance of crypts occurs (Fig. 10). So, while the process of recanalization of the lumen is cranio-caudad, the formation of previllous ridges and crypts proceeds caudo-cranially. 5) From the 11th day onwards the lamina propria is actively involved in the process of formation of the previllous ridges. Only at the 14th day, in the distal part of the colon anlage, the appearance of the muscularis mucosae is observed (Fig. 11). 6) The muscle layer and the subserous stratum do not show appreciable morphological changes in the course the considered period of incubation.