Interactions between the cyclin-dependent kinase inhibitor (CDKI) flavopiridol (FP) and phorbol 12-myristate 13-acetate (PMA) were examined in U937 human leukemia cells in relation to differentiation and apoptosis. Simultaneous, but not sequential, exposure of U937 cells to 100 nM FP and 10 nM PMA significantly increased apoptosis manifested by characteristic morphological features, mitochondri...

We have recently demonstrated that bufalin is a new potent inducer of the differentiation of human myeloid leukemia cells. The present work was carried out to examine further the effect of bufalin on the growth and characteristics of human leukemia-derived cell lines U937, ML1, and HL60. At concentrations of 5-10 nM, bufalin decreased the growth of ML1 cells preferentially at the G2 phase and U...

BACKGROUND Regarding the strong differentiation and anti-leukemic activity of Dendrostellera lessertii extract, an active agent with similar capabilities was isolated from the crude extract of the plant leaves. The aim of this study was to determine whether the anti-proliferative effect observed for this compound, is differentiation-dependent among the drug-treated cells, using U937 cells. ME...

The 70% methanol soluble fraction from a licorice acetone extract was found to inhibit cell proliferation in human monoblastic leukemia U937 cells by inducing apoptosis. Separation by the methods including preparative HPLC provided us with an active compound, which was identified as licocoumarone. Several lines of evidence indicated that licocoumarone induced apoptosis in U937 cells. Thus, lico...

We examined the role of the flagella of Legionella pneumophila in the infection of amoebae and human monocyte-like cells. Insertional mutants were constructed with mini-Tn10. Ten mutants (F-) which did not react with polyclonal L. pneumophila antiflagellar antisera were identified. Ten randomly selected mutants (F+) that did react with the polyclonal antiflagellar antiserum were also identified...

Three aspects of the involvement of tumor necrosis factor in human immunodeficiency virus (HIV) pathogenesis were examined. Tumor necrosis factor alpha (TNF-alpha) mRNA production was analyzed by polymerase chain reaction amplification in monocytic U937 cells and in a chronically HIV infected U937 cell line (U9-IIIB). TNF-alpha RNA was undetectable in U937 cells, whereas a low constitutive leve...

Tumor necrosis factor alpha (TNF alpha) mediates proliferation, functional activation, and apoptotic cell death depending on the target cell type. Although sphingomyelin (SPM) hydrolysis and ceramide generation may function as an important mediator in TNF alpha signaling, the molecular mechanisms of the signaling pathway(s) are still not well understood. The aim of the present study is to compa...

NF-IL6 is an important transcriptional regulator of genes induced in activated monocytes/macrophages, and NF-IL6 is the only CCAAT/enhancer-binding protein (C/EBP) family member whose steady-state mRNA levels increase upon activation of monocytes (1). We show that increased transcription of the NF-IL6 gene is responsible, at least in part, for induction of NF-IL6 mRNA following activation of U9...

We report that Xenopus laevis oocytes can efficiently translate and insert heterologous membrane receptors into the oocyte plasma membrane, where they can be detected by the binding of either monoclonal antibodies or ligands. Thus, oocytes injected with mRNA from the mouse J774 macrophage-like cell line, the rat RBL-1 basophilic leukemia, and the U937 promonocyte cell line, bound 2.4G2 Fab, rat...