The sorption of homologous monodisperse alcohol ethoxylates in cuticles isolated from the leaves of bitter orange (Citrus aurantium L.) and thoroughly extracted with chloroform (yielding polymer matrix membranes, MX) has been investigated. Sorption isotherms exhibited a linear phase at low aqueous concentrations of surfactant, while above the critical micelle concentrations (cmc) the concentration sorbed in the MX was independent of external concentration. MX/water partition coefficients (25-148 000, depending on the homologue), maximum concentrations in the MX (91-318 mmol/kg), and cmc were derived from the isotherms. Quantitative structure-property relationships were established for estimating the MX/water partition coefficients, cmc, and maximum cuticular concentrations of alcohol ethoxylates from the number of carbon atoms and oxyethylene groups of their alcohol and poly(oxyethylene) moieties, respectively. These relationships were used for analyzing the effects of monodisperse alcohol ethoxylates and primary alcohols on the mobility of (2,4-dichlorophenoxy)acetic acid in isolated cuticular membranes from bitter orange leaves.

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The effect of retinoic acid (RA), 1,25-dihydroxyvitamin D3 (1,25-D3) or human recombinant interferon-gamma (IFN-gamma) on the induction of NADPH oxidase was studied in premonocytic U937 cells. Differentiation with the combination of either RA (1 microM) or 1,25-D3 (10 nM) with IFN-gamma (100 IU/ml) induced NADPH oxidase activity as demonstrated by increased superoxide anion (O2-) generation in response to stimulation with phorbol myristate acetate (PMA, 100 nM). Induction of NADPH oxidase activity was preceded by increases in mRNA levels of p47-phox, p67-phox and gp91-phox, which encode three subunits of the enzyme, and immunoblot analysis of the p47-phox and p67-phox proteins revealed that the increases in mRNA levels were equally reflected by increases in protein levels. In contrast, RA, 1,25-D3 or IFN-gamma alone did not induce NADPH oxidase activity which correlated with their failure to increase p67-phox and gp91-phox mRNA levels. The mRNA of p21 rac1, a GTP-binding protein that regulates NADPH oxidase activity in macrophages, was constitutively expressed in undifferentiated cells and was not affected by differentiation. These data indicate that induction of a functional NADPH oxidase in premonocytic U937 cells requires the cooperative actions of IFN-gamma plus RA or 1,25-D3 and is reflected in the increased expression of p67-phox and gp91-phox.

The effect of long chain polyunsaturated fatty acids (PUFA) on cell growth and differentiation was assessed in human premonocytic U937 cells. Addition of either 10 microM arachidonic acid (AA, 20:4n-6), eicosapentaenoic acid (EPA, 20:5n-3) or docosahexaenoic acid (DHA, 22:6n-3) resulted in the rapid incorporation of these fatty acids into cellular phospholipids. Their uptake was greatest in the first 2 h. AA and EPA reached steady-state levels after 8 h, while levels of DHA increased steadily over 72 h. In parallel, fatty acid metabolites derived from AA and EPA, 22:4n-6, 22:5n-6 and 22:5n-3, 22:6n-3, respectively, increased continuously indicating an active fatty acid elongation and desaturation. The effects of PUFA on monocytic differentiation were examined in cells which had been enriched with AA, EPA or DHA for 8 h and subsequently treated with retinoic acid (RA), 1,25-(OH)2-vitamin D3 (1,25-D3), interferon-gamma (IFN-gamma) or their combinations for 72 h. Growth of differentiating or non-differentiating U937 cells was not affected by enrichment with PUFA. However, in cells differentiated with 1,25-D3 plus IFN-gamma, prior enrichment with all three PUFA slightly but significantly (P < 0.05) increased the expression of the monocytic surface antigens CD11b and CD14 and generation of superoxide anion. The data indicate that although n-6 and n-3 PUFA are rapidly incorporated into phospholipids, they do not affect cell growth. However, enrichment with PUFA increases monocytic differentiation of U937 cells when induced most effectively with 1,25-D3 plus IFN-gamma.