Competition experiments indicate that the cellular uptake of Ferumoxides involves scavenger receptor SR-A-mediated endocytosis. The comparison between Ferumoxides and Ferumoxtran-10 confirms that macrophage uptake of iron oxide nanoparticles depends mainly on the size of these contrast agents.

A new property of ursolic acid, lipoxygenasc and cyclooxygcnase inhibition, has been described in an acetonr-extract of heather flowers (Cufluna vulgnris) which could help explain Ihe an&inRammatory characteristics of this plani. In mouse periton& macrophagcs, human platelets and differentiated HL60 leukemic cells, ursolic acid, at I PM. blocks arachidonate metabolism.

No abstract

Abstract. C30H4803.C2H60 , M r = 502.78, orthorhombic, P2~2~2~, a=7.199 (1), b = 12.157 (2), c =

No abstract

Edited by Ulf-Ingo FlüggeKeywords: Bright Yellow-2 Clathrin Cryptogein Endocytosis Cell signaling a b s t r a c t Endocytosis has been recently implicated in the signaling network associated with the recognition of microbes by plants. In a previous study, we showed that the elicitor cryptogein was able to induce clathrin-mediated endocytosis (CME) in tobacco suspension cells. Herein, we investigate further the induced CME by means of a GFP-tagged clathrin light chain and a CME inhibitor, the hub domain of clathrin heavy chain. Hub constitutive expression does affect neither cell growth nor constitutive endocytosis but abolishes cryptogein-induced CME. Such an inhibition has no impact on early events in the cryptogein signaling pathway but reduces the expression of defense-associated genes.

The authors have previously isolated and purified ursolic acid from heather flowers (Calluna vulgarts). This terpene was found to inhibit HL-60 leukaemic cell proliferation and arachidonic acid oxidative metabolism in various cell species. The effects of ursolic acid and its analogues on soybean 15-lipoxygenase activity and on the proliferation of a human gastric tumour cell line (HGT), have been assessed. These triterpenes inhibited soybean 15-lipoxygenase at its optimal activity (pH 9). The proliferation ofHGT was decreased in a dose-dependent manner. At 20 μM the rank order is: ursolic acid > uvaol > oleanolic acid > methyl ursolate. The carboxylic group at the C28 position of ursolic acid appears to be implicated in the inhibition of both lipoxygenase activity and cell proliferation. Thus methylation of this group decreases these two inhibitory properties. Oleanolic acid, which differs by the position of one methyl group (C20 instead of C19) is less inhibitory than ursolic acid. The lipophilicity of the terpene is also implicated since uvaol appears to be more inhibitory than methyl ursolate.

The MCF-7 human breast cancer cell line responds to 5-androstene-3β,17β-diol, to dehydro-epiandrosterone and to its 3β-sulfate stimulation in vitro by increased proliferation. 5-Androstene-3β,17β-diol has the strongest mitogenic effect. Dehydroepiandrosterone has a more potent action on cell proliferation than its 3β-sulfate. These adrenal androgens do not stimulate proliferation of the estrogen receptors negative for the BT-20 cell line. In our conditions, we have failed to demonstrate MCF-7 estradiol formation when incubations were carried out in the presence of labeled adrenal androgens. These results suggest that adrenal androgens stimulate proliferation of MCF-7 cells directly by acting on estrogen receptors.