but does not enhance the expression of noninducible genes. Likewise, a 2-deoxy-D-glucose, a nonmetabolized sugar, is also effective. When a deletion was introduced into the virA gene in the region encoding the periplasmic portion of the VirA protein, enhancement by glucose disappeared, but vir expression was induced by acetosyringone in this mutant. These results suggest that these sugars directly enhance a signaling process initiated by phenolic inducers that results in an-increase in expression of the vir genes.

A series of substituted oxindole derivatives was synthesized and evaluated for growth hormone (GH) releasing activity using cultured rat pituitary cells. (+)-6-Carbamoyl-3-(2-chlorophenyl)-(2-diethylaminoethyl)-4-trifluoromethyloxindole (SM-130686, 37S) was found to have potent activity (EC(50) = 3.0 nM), while the other enantiomer 37R had reduced activity. The absolute configuration of 37S was confirmed by X-ray crystallographic analysis. Compound 37S showed a good pharmacokinetic profile in rats with 28% oral bioavailability at 10 mg/kg and excellent in vivo activity as evidenced by a significant weight gain after 4 days of oral administration at 10 mg/kg twice a day. Compound 37S displaced the binding of (35)S-MK-677 to human GHS-R with an IC(50) value of 1.2 +/- 0.2 nM.

Only 10-15% of unseparated thymocytes adhered to culture plates precoated with fibronectin (FN), but 60-70% of the CD4-8-(double-negative) thymocyte population did. This population bound to FN but not to collagen, laminin, or vitronectin. Its binding to FN was inhibited by anti-FN antibody or a mixture of synthetic peptides corresponding to two different sites of EN, termed the V10 sequence and the RGDS (Arg-Gly-Asp-Ser) sequence, which interact, respectively, with the VLA-4 and VLA-5 FN receptors expressed on T-lineage cells. CD4-8-thymocytes also adhered to a monolayer of a thymic stromal cell clone, MRL104.8a, that induces growth-maintenance and differentiation of such thymocytes. . Most important, blocking the adhesion of CD4-8-thymocytes to the thymic stromal cell monolayer resulted in potent inhibition of the differentiation of these thymocytes, which was otherwise induced toward the expression of CD4 and/or CD8 molecules. These results indicate that immature CD4-8-thymocytes adhere to thymic stromal cells preferentially through FN-FN receptor interaction and that such adhesion has a critical role in inducing and/or supporting the differentiation of these thymocytes.Lymphocytes express a number of surface molecules that mediate the adhesion of cells to one another or to extracellular matrix (ECM) components (1-4). For example, cell-cell interaction molecules such as CD2 and LFA-3 are used to augment specific adhesion of T cells to antigen-presenting cells (5), and other cell-cell interaction molecules function as homing receptors (6, 7). Thus, these cell surface molecules have been recognized as regulating the migration of lymphocytes as well as the interactions of activated lymphocytes during immune responses.Another type of cell adhesion mechanism involves the interaction of cells with ECM (2, 4). While the importance of such cell-cell interactions in developmental biology has been documented (8-12), few studies have investigated the role of cell-ECM adhesion mechanisms in lymphocyte development in lymphopoietic microenvironments such as the bone marrow and thymus. This may be ascribed to the lack of in vitro systems for such analyses and to the complexity arising from the expression of various forms of ECM molecules regulated in a tissue-and cell-specific fashion, as exemplified by fibronectin (FN) molecules (13-15). In this context, several lines of marrow and thymic stromal cells have been isolated to provide tools for analyzing the interaction between developing lymphocytes and stromal cells (16). We have also established a thymic stromal cell clone that is capable of providing an in vitro model for intrathymic T-cell development (17-19).The present study investigates the role of FN molecules expressed on thymic stromal cells in thymocyte-stromal cell adhesion and thymocyte differentiation. The results demonstrate that CD4-8-("double-negative") thymocytes adhere to thymic stromal cells through FN molecules on the stromal cells. Molecular analyses revealed that two adhesion sites, the classic...

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