Chromosome investigations of the Usubuchi sarcoma. I. Studies in seven transfers from the 1812th to 1895th generations.

Usubuchi sarcoma (US) is one of the methyicholanthrene-induced ascites tumors in the rat. It was established in 1953 by transforming a solid type tumor into the ascites type (Usubuchi et al. 1953). Since then, the US has been main tained over 1900 transfer generations in his laboratory by successive transfers. The chromosome investigations of the US have been made in some early stages before the 300th transfer generation (Makino et al. 1955, Koseki 1956, Makino 1957a, Taka hashi 1963). Viewed from current cytogenetic standpoint, the reinvestigation is needed on structural changes of the chromosomes in this tumor, because earlier studies were carried exclusively out by means of squash methods. Further, during the course of transfers, the cytogenetic profiles of tumors in general would undergo a considerable alteration particularly on the mode of the chromosome number, as well as on the chromosome constitution (Makino 1952, 1960, Makino and Sasaki 1958). Recently a remarkable development of the banding techniques has been achie ved, and it has made possible better analysis of the chromosome morphology as well as of the process of morphological alterations to a considerable extent. Then, evidence has been presented to show that the tumors undergone long-term serial transfers are generally characterized by the occurrence of many marker chromo somes, or otherwise by a relatively few normal complements, due largely to exten sive structural rearrangements with cell-to-cell karyotypic variation (Unakul and Hsu 1972, Sasaki et al. 1974, Mori and Sasaki 1974, Levan and Mitelman 1975, 1976). Under this situation, we have attempted a revised cytogenetic study of the US, use being made of current techniques. This paper is the first to deal with some accounts so far obtained, providing the detailed karyotype constitution of the US cells observed in seven transfers from the 1812th to 1895th generations, specially on their chromosome configurations of banding structures.