Electron microscopic and biochemical characterization of collagen in blattarian insects.

The occurrence of collagen in the cockroach Leucophaea maderae has been demonstrated by electron optical and biochemical techniques. Electron micrographs of tissues of this and a related species (Blaberus craniifer) are presented and they show that collagenous-type fibers occur in the stroma of nonneural as well as neural organs of these insects. Hydroxyproline and hydroxylysine, amino acids considered to be "markers" for collagen, have been shown to be present in proteins extracted from material rich in neuroglandular tissue (corpus cardiacum plus corpus allatum). Trimmed carcasses of Leucophaea maderae have been shown to contain a protein or proteins soluble in hot trichloroacetic acid, with compositional characteristics similar to those of collagens in general, including diagnostic proportions of glycine, proline, hydroxyproline, and hydroxylysine. This collagen is not soluble in dilute acetic acid or in concentrated solutions of guanidinium chloride. It is measurably digested by bacterial collagenase.