Abstract. We study the Drinfeld-Sokolov hierarchies of type A ð1Þ n associated with the regular conjugacy classes of W ðA n Þ. A class of fourth order Painlevé systems is derived from them by similarity reductions.

A new human extrahepatic bile duct carcinoma cell line (TFK-1) was established from a surgically resected tumor specimen, which was histologically diagnosed as partly papillary adenocarcinoma and partly differentiated tubular adenocarcinoma. The tumor cells cultured in RPMI-1640 medium supplemented with 10% FBS grew as monolayers showing epithelial-like morphology with a population doubling time of 37 hr during exponential growth at passage 40. Chromosome number was distributed in the range of 72 to 76, with a modal number of 73. Tumor markers (CEA, CA19-9, ST-439, DUPAN-2) were negative in culture supernatant and plasma of SCID mice grafted with TFK-1 cells. Though no point mutation at 12 colon of K-ras was detected, expression of c-erbB-2 product and MUC 1 antigen was positive. TFK-1 is the third cell line established from extrahepatic bile duct carcinomas in the world literature, and should provide useful information on various aspects of this type of neoplasm.extrahepatic bile duct carcinoma; cell line; TFK-1; c-erbB-2; MUC1In cases of bile duct carcinoma (BDC), massive infiltration of tumor cells along the bile duct tree and a multicentric origin of tumors are very frequently observed (Suzuki et al. 1989). Therefore curative resection of BDC is usually difficult, resulting in a poor prognosis of BDC patients. The limits of surgery for BDC indicate the need for adjuvant therapy to control residual BDC tissues. To develop an effective therapy for BDC, it is necessary to establish cell lines for

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Mechanisms generating diverse cell types from multipotent progenitors are crucial for normal development. Neural crest cells (NCCs) are multipotent stem cells that give rise to numerous cell-types, including pigment cells. Medaka has four types of NCC-derived pigment cells (xanthophores, leucophores, melanophores and iridophores), making medaka pigment cell development an excellent model for studying the mechanisms controlling specification of distinct cell types from a multipotent progenitor. Medaka many leucophores-3 (ml-3) mutant embryos exhibit a unique phenotype characterized by excessive formation of leucophores and absence of xanthophores. We show that ml-3 encodes sox5, which is expressed in premigratory NCCs and differentiating xanthophores. Cell transplantation studies reveal a cell-autonomous role of sox5 in the xanthophore lineage. pax7a is expressed in NCCs and required for both xanthophore and leucophore lineages; we demonstrate that Sox5 functions downstream of Pax7a. We propose a model in which multipotent NCCs first give rise to pax7a-positive partially fate-restricted intermediate progenitors for xanthophores and leucophores; some of these progenitors then express sox5, and as a result of Sox5 action develop into xanthophores. Our results provide the first demonstration that Sox5 can function as a molecular switch driving specification of a specific cell-fate (xanthophore) from a partially-restricted, but still multipotent, progenitor (the shared xanthophore-leucophore progenitor).

A higher order Painlevé system of type D (1) 2n+2 was introduced by Y. Sasano. It is an extension of the sixth Painlevé equation (P VI ) for the affine Weyl group symmetry. It is also expressed as a Hamiltonian system of order 2n with a coupled Hamiltonian of P VI . In this paper, we discuss a derivation of this system from a Drinfeld-Sokolov hierarchy.