Induction of mast cell proliferation, maturation, and heparin synthesis by the rat c-kit ligand, stem cell factor (developmental ABSTRACTWe investigated the effects of a newly recognized multifunctional growth factor, the c-kit ligand stem cell factor (SCF), on mouse mast cell proliferation and phenotype.Recombinant rat SCF'64 (rrSCF"64) induced the development of large numbers of dermal mast cells in normal mice in vivo.Many of these mast cells had features of "connective tissue-type mast cells" (CTMC), in that they were reactive both with the heparin-binding fluorescent dye berberine sulfate and with safranin. In vitro, rrSCFI64 induced the proliferation of cloned interleukin 3 (IL-3)-dependent mouse mast cells and primary populations of IL-3-dependent, bone marrow-derived cultured mast cells (BMCMC), which represent immature mast cells, and purified peritoneal mast cells, which represent a type of mature CTMC. BMCMC maintained in rrSCF164 not only proliferated but also matured. Prior to exposure to rrSCF'"4,

A physical map of Arabidopsis thaliana chromosome 4 was constructed in yeast artificial chromosome clones and used to analyze the organization of the chromosome. Mapping of the nucleolar organizing region and the centromere integrated the physical and cytogenetic maps. Detailed comparison of physical with genetic distances showed that the frequency of recombination varied substantially, with relative hot and cold spots occurring along the whole chromosome. Eight repeated DNA sequence families were found in a complex arrangement across the centromeric region and nowhere else on the chromosome.

We recently succeeded in purifying a monocyte chemotactic factor (MCF) from the conditioned media of a myelomonocytic cell line (THP-1) (1). We have molecularly cloned the cDNA of MCF (2), and shown that MCF, in addition to its monocyte chemotactic activity, also activates monocytes to be more cytostatic against several types ofhuman tumor cells in vitro (1) . Therefore, we termed this molecule monocyte chemotactic and activating factor (MCAF). Subsequently, MCAF has been shown to be produced by several additional cell types, namely fibroblasts and endothelial cells (3) . We describe here that MCAF, which was purified from human fibrosarcoma cell line-conditioned media, also induces superoxide anion and lysosomal enzyme release from human monocytes and has potent in vivo monocyte recruitment activity. Materials and MethodsPurification of MCAF. Confluent fibrosarcoma cells, 8387 (4), were stimulated with 100 ng/ml rTNF-a in serum-free media overnight. The culture supernatants were centrifuged, concentrated, and dialyzed against 0.05 M Tris-HCI, pH 7.5, before being applied to a 50-ml heparin Sepharose column . MCAF was eluted with 0.05 M Tris-HCI, pH 7.5, containing 0.5 M NaCl. The eluate was further concentrated and loaded on to a gel filtration column of Sephacryl S-200 (Pharmacia Fine Chemicals, Uppsala, Sweden), which was equilibrated with D-PBS. The fractions containing monocyte chemotaxis activity in the molecular mass range of 10-20 kD were pooled and then applied to a carboxymethyl-silica gel column (7.5 x 150-mm CM-3SW) (Toyo Soda, Tokyo, Japan) connected to an HPLC system (2150 ; LKB Instruments, Inc., Uppsala, Sweden) . The starting buffer was 0.02 M 3-[N-morpholino] propanesulfonic acid (MOPS), pH 6.5, and MCAF was eluted with a linear increase of salt concentration up to 0.5 M NaCl. Finally, samples were applied to a reverse phase chromatography column (4.6 x 750-mm TMS-250 Ultropac column, 10,m; Toyo Soda) with the starting

No abstract