Intercellular bridges and division patterns of rat spermatogonia
Tóm tắt
The pattern of intercellular cytoplasmic bridges between rat spermatogonia and between spermatocytes is illustrated from electron microscopy of serial sections. Clones, or syncytia, containing as many as 22 connected spermatogonia and as many as 74 connected spermatocytes were observed. The absence of closed rings of cells agrees with the observation that intercellular bridges are the result of incomplete cell division, rather than cell fusion. The bridges thus are a record of spermatogonial divisions within a clone. In early spermatogonial generations there is a predominantly linear arrangement. The groups of spermatocytes have more side branches. From the presence of synaptonemal complexes it is concluded that the connected spermatocytes of a given clone are in about the same developmental stage. The pattern of intercellular bridges indicates, however, that not all nuclei in a clone undergo mitosis in the same cycle. The connected cells of a clone are therefore not all of the same generation. From unconnected bridges it is assumed that new clones originate from single cells or groups of spermatogonia which separate from an existing clone.
Tài liệu tham khảo
Clermont, Y.: Quantitative analysis of spermatogenesis of the rat; a revised model for the renewal of spermatogonia. Amer. J. Anat. 111, 111–129 (1962).
Clermont, Y., Bustos-Obregon, E.: Re-examination of spermatogonial renewal in the rat by means of seminiferous tubules mounted “in toto”. Amer. J. Anat. 122, 237–248 (1968).
Dym, M., Clermont, Y.: Role of spermatogonia in the repair of the seminiferous epithelium following x-radiation of the rat testis. Amer. J. Anat. 128, 265–281 (1970).
Dym, M., Fawcett, D. W.: Further observations on the numbers of spermatogonia, spermatocytes, and spermatids connected by intercellular bridges in the mammalian testis. Biol. Reprod. 4, 195–215 (1971).
Fawcett, D. W.: Intercellular bridges. Exp. Cell. Res. Suppl. 8, 174–178 (1961).
Fawcett, D. W., Ito, S., Slautterback, D.: The occurrence of intercellular bridges in groups of cells exhibiting synchronous differentiation. J. biophys. biochem. Cytol. 5, 453–460 (1959).
Galey, F. R., Nilsson, C. E. G.: A new method for transferring sections from the liquid surface of the trough through staining solutions to the supporting film of a grid. J. Ultrastruct. Res. 14, 405–410 (1966).
King, C. R., Akai, H.: Spermatogenesis in Bombyx mori. I. The canal system joining sister spermatocytes. J. Morph. 134, 47–56 (1971).
Koch, E. A., King, R. C.: The origin and early differentiation of the egg chamber of Drosophila melanogaster. J. Morph. 119, 283–304 (1966).
Koch, E. A., Smith, P. A., King, R. C.: The division and differentiation of Drosophila cystocytes. J. Morph. 121, 55–70 (1967).
Mahowald, A. P.: The formation of ring canals by cell furrows in Drosophila. Z. Zellforsch. 118, 162–167 (1971).
Moens, P. B.: Serial sectioning in electron microscopy. Proc. Can. Fed. Biol. Sci. vol. 13, p. 160. London, Canada: Hunter Printing Ltd. (1970a).
Moens, P. B.: Premeiotic DNA synthesis and the time of chromosome pairing in Locusta migratoria. Proc. nat. Acad. Sci. (Wash.) 66, 94–98 (1970b).
Monesi, V.: Autoradiographic study of DNA synthesis and the cell cycle in spermatogonia and spermatocytes of mouse testis using tritiated thymidine. J. Cell Biol. 14, 1–18 (1962).
Moses, M. J.: Synaptinemal complex. Ann. Rev. Genet. 2, 363–412 (1968).
Oakberg, E. F.: A new concept of spermatogonial stem-cell renewal in the mouse and its relationship to genetic effects. Mutation Res. 11, 1–7 (1971).