Polyanionic Glycans of Cartilage, Bone, and Notochord

Abstract

There has been general agreement among biologists for a long time that bone is a uniquely vertebrate tissue. However, conflicting views have been held of the taxonomic distribution of cartilage. The earlier arguments in favor of the presence of “true” cartilage in invertebrates were summarized by NOWIKOFF (1912). Opinions, still widely prevalent, that cartilage is confined to vertebrates have been expressed by SCHAFFER (1930), LUBOSCH (1938), HYMAN (1940), ROMER (1942), and others. Recently, the entire question has been reopened and indisputably resolved in review articles by PERSON and PHILPOTT (1967, 1969a). To the older morphological and histological observations were added newer data including results from electronmicroscopic and chemical studies. Collagen as well as polyanionic glycans (discussed below) were clearly identified as essential components. PERSON and PHILPOTT (1969a, b) suggested that cartilage may have originated in invertebrates but recognized that this tissue type could also have evolved independently in both invertebrates and vertebrates in response to similar needs for structural support.

“Cartilage, like pornography, is usually not defined since it is easily recognized by experts.” ANON.