| Popis: |
Alterations in the expression of glycoconjugate structures during cartilage development in the chondrocranium, nasal skeleton, Meckel's cartilage, limb buds, vertebral bodies and ribs were investigated comparatively in 13 to 21-d-old rat embryos. The binding patterns of 24 biotinylated lectins were analysed in serial sections and compared with results obtained using histochemical methods. Proteoglycan distribution, assessed by conventional staining procedures, was not associated with lectin binding sites. During early fetal development, hyaluronate concentrations were enhanced in areas of prospective chondrogenesis. With few exceptions, the lectins showed a general increase in intensity of binding to mesenchymal structures. Con A (Canavalia ensiformis), DSL (Datura stramonium), and WGA (Triticum vulgare) displayed a ubiquitous distribution of binding sites. After incubation with LCA (Lens culinaris), PSA (Pisum sativum), STL (Solanum tuberosum), and VAA (Viscum album), characteristic differences in binding intensity between focal areas of developing mesenchyme were seen. DBA (Dolichus biflorus), ECL (Erythrina cristagalli), GSL I (Griffonia simplicifolia), LTA (Lotus tetragonobolus), SJA (Saphora japonica), UEA I (Ulex europaeus) and VVL (Vicia villosa) consistently failed to bind. During chondrogenesis a general reduction of lectin staining was detected. In early stages of development GSL II (Griffonia simplicifolia) was a specific marker of the prechondral blastema in the viscerocranium. PNA (Arachis hypogaea) selectively labelled the prevertebral blastema. In contrast, condensing mesenchyme of limb buds and viscerocranium was not stained. Using RCA (Ricinus communis), it was possible to distinguish chondroblasts from mature cells. All chondrocytes were stained by PSA, PHA-E, PHA-L (Phaseolus vulgaris E and L), and WGA, whereas Con A, LCA, and GSL II detected distinct differences between cartilage with different localisations. Cartilage matrix was constantly negative. Applying GSL II it was possible to distinguish specific segments of the perichondrium. From our results we conclude that especially high mannose oligosaccharides are amplified during development. Terminal sialic acid molecules, branched intralaminar glucose and/or mannose, respectively, internal galactose-(beta 1,4)-N-acetylglucosamine sequences as well as galactose-(beta 1,3)-N-acetylgalactosamine sequences in a preterminal position are diffusely distributed in mesenchymal tissue. In contrast, no evidence for the presence of terminal GlcNAc(beta 1,4)GlcNAc sequences and terminal alpha-fucosyl residues in (1,2) or (1,3)-linkage was obtained. Chondrogenesis appears to be correlated with a general reduction in the extent of expression of oligosaccharide structures. No proof of terminal N-acetylgalactosamine and alpha-galactose moieties was found, whereas our staining results document the expression of terminal beta-galactose structures in restricted areas of the developing mesenchyme.(ABSTRACT TRUNCATED AT 400 WORDS) |
