Electron Microscopical Study of the Morphogenesis of Collagen Fibers

Abstract

The writer used as materials dermal rudiments, film samples or mashed ones of dermis of a Rana japonica, from its germ in early tail-bud stage through the metamorphostic stage to the adult frog, and investigated the genesis and morphogenesis of collagen fibers electron microscopically.
1. Even in germs in early tail-bud stage, very thin, transparent filmy stroma is perceived between epidermal layer and mesodermal one. This thin layer develops into the dermis.
2. In this thin membrane comes out many a minute granule with a diameter of 70-100Å without immediate morphological regard to cells, and after a while the formation of procollagen fibers begins with taking lattice like arrangement in double files at 210Å intervals in a certain direction.
3. The fibrils in which granules are arranged in double files in latticework join together and polymerize with a contiguous fibril, and the same process is repeated again and again. Besides this, the size of granules itself increases, and the fiber grows thicker, but the interval of the lattice is still 210Å in this stage.
4. This lattice-work is perceived as striations at 210Å intervals in comparatively low magnification.
5. The fibrous formation shows characteristic change from the late outergills stage to the early innergills stage. The genesis of thick striations at 530-640Å intervals is perceived in some part of fibers which have increased their thickness by polymerization. These thick striations seem to appear because protein molecules have become particularly concentrated owing to the increase of the granules constituting the fibers and the genesis of the comparatively small ones connecting them.
6. The problem what the substance which polymerizes and binds the granules is still a matter of guess work now, but glycoprotein, tyrosine hyaluronic acid etc. are supposable. Perhaps electric charge of molecules has some connection with the problem.
7. In the fiber of an adult frog are perceived striation at 640Å intervals which show characteristics of collagen completely and, besides, some five thin striations between each two of them. Moreover lattice-work is observed in some part of the fiber. This view is consistent from the genesis of the fiber in the earliest stage to the last, therefore it can be justly said that it shows quality of protein molecules of the fiber and the process of their polymerization and development electron microscopically.