Long monolithic silica-C18 capillary columns of 100 microm i.d. were prepared, and the efficiency was examined using reversed-phase HPLC under a pressure of up to 47 MPa. At linear velocities of 1-2 mm/s, 100,000-500,000 theoretical plates could be generated with a single column (90-440 cm in length) using an acetonitrile-water (80/20) mobile phase with a column dead time (t0) of 5-40 min. It was possible to prepare columns with a minimum plate height of 8.5 +/- 0.5 microm and permeability of (1.45 +/- 0.09) x 10(-13) m(2). The chromatographic performance of a long octadecylsilylated monolithic silica capillary column was demonstrated by the high-efficiency separations of aromatic hydrocarbons, benzene derivatives, and a protein digest. The efficiency for a peptide was maintained for an injection of up to 0.5-2 ng. When three 100 microm i.d. columns were connected to form a 1130-1240 cm column system, 1,000,000 theoretical plates were generated for aromatic hydrocarbons with retention factors of up to 2.4 with a t0 of 150 min. The fact that very high efficiencies were obtained for the retained solutes suggests the practical utility of these long monolithic silica capillary columns.

We examined the effect of nitric oxide (NO) on cytokine production in T helper (Th) cell subsets, using murine splenic CD4+ T cells and two types of Th clones. Interferon-gamma-treated murine peritoneal exudate cells (IFN-PEC) suppressed DNA synthesis to 60% of the control level in CD4+ T cells stimulated with the anti-CD3 monoclonal antibody. The production of IL-2 and IL-4 in the CD4+ T cells decreased to 63.2 % and 9.2%, respectively, of the control value by co-culture with IFN-PEC. The addition of NGmonomethyl-L-arginine (L-NMMA) partially recovered the suppression of DNA synthesis. In the presence of indomethacin, the suppression of DNA synthesis was partially inhibited and the reduction in the cytokine production caused by IFN-PEC was partially recovered.The simultaneous addition of NGmonomethyl-L-arginine (L-NMMA) and indomethacin completely inhibited not only the suppression of DNA synthesis but also the reduction in the cytokine production caused by IFN-PEC. Moreover, DNA synthesis in the Th2 clone was suppressed to a greater extent than that in the Thl clone by co-culture with IFN-PEC. This suppression in the Thl clone was inhibited by the addition of L-NMMA, whereas the DNA synthesis in the Th2 clone was not recovered by L-NMMA. In addition, sodium nitroprusside (SNP) suppressed IL-4 production in the Th2 clone but had no effect on IL-2 production in the Thl clone. In the experiment of the co-culture with IFN-PEC, the inhibitory-effect of NO on T cell activation was not clarified by the influence of prostaglandins.However, in conclusion, cytokine production in Th2 cells may be more susceptible to NO than that in Thl cells.

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