Limb outgrowth is arguably the most fundamental aspect of limb development. The development of the limb skeleton is characterized simply by pre-condensation of the mesenchyme, such condensations represent the primordial of several future elements. The undifferentiated limb bud mesenchyme consists of at least two separate progenitor cells, one that gives rise exclusively to skeletal muscle and the other gives rise to the cartilage and connective tissue of the limb. Carbohydrate Histochemistry and the biochemical analysis was done in this study to identify the factors controlling the mesenchymal morphogenesis of the limb buds.
Fertilized chick eggs were incubated for 3 to 7days, the embryo were blocked in paraffin, serial sagittal sections of 8um thickness were cut using the electrical microtome. The histochemical stains, the cationic dye Alcian blue and specialized periodic acid Schiff (PAS) stain were used. The biochemical assay of the homogenized limb bud tissues copper, zinc, and magnesium was evaluated, also the tissue content of the enzyme superoxide dismutase was determined. The earlier stages of the limb bud showed high Cu/Zn ratio indicating growth of undifferentiated mesenchyme. Magnesium has the same feature and function as zinc. Also these early stages showed low superoxide dismutase (SOD). Sulfated and carboxylated are the contents of the mesenchyme near the apical ectoderm. More developed limb bud tissues containing condensed mesenchymal regions with low Cu/Zn ratio that may indicate growth of differentiated mesenchyme. Also these stages showed high superoxide dismutase (SOD) content. The sulfated and carboxylated were found in the condensed mesenchyme. Sulfated was found in the loose mesenchyme.
Later stages showed the precartilagenous and premyogenic premordia with the lower concentration of tissue copper, zinc and magnesium, and higher superoxide dismutase (SOD). Sulfated and carboxylated were found in the precartilagenous and premyogenic primordia.