Samples of anatomically and functionally distinct regions of the skin of a variety of altricial and precocial animals were taken at various stages of development from birth to beyond maturity. The glycosaminoglycan (GAG) content and composition of the tissues were determined by chemical analysis and the collagen fibril diameters measured by transmission electron microscopy. The fibril diameters of the skins of two fish and a bird were also assessed for comparison. Analysis and comparison of the data collected show that there was a significant correlation between collagen fibril diameter distribution, GAG type and amount, and functional load-bearing of the various skins, and that the variations in the biochemical and physical composition of the tissues at different stages of development could be related to both their post-conceptual maturity and their prospective functional loading.
The glycosaminoglycan content and the axial periodicity of collagen was determined in various regions of the rabbit flexor digitorum profundus tendon. This tendon, which passes from the calf to the toes round the inner side of the ankle, contains a thickened sesamoid-like pad where it is subjected to friction and pressure. Other regions of the tendon are subject only to longitudinal tension. In tensional areas the axial periodicity of collagen was of the order of 62 nm and the tissue contained less than 0.2% proteoglycan on a dry weight basis. In the sesamoid-like region, however, the axial periodicity was a significant 13-15% less, and the proteoglycan constituted about 3.5% of the dry weight. Also, in the tensional areas the predominant glycosaminoglycan was dermatan sulphate, whereas in the sesamoid the predominant glycosaminoglycan was chondroitin sulphate. The possible interrelationships between collagen axial peroidicity and proteoglycan content in this tissue are discussed.
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