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Histamine H2 receptor activity (cAMP generation) has been characterized in U-937 cells before and after retinoic acid-induced differentiation into monocyte-/macrophage-like cells. The differentiation is associated with a decreased capacity of U-937 monocytes to generate cAMP under basal conditions or after cell surface receptor stimulation by histamine,(More)
Essentially pure phenylalanine hydroxylase from rat liver can be activated between 2.5- and 3.0-fold by treatment with Mg2+, ATP, protein kinase, and cyclic AMP. The activation is seen when the hydroxylase is assayed in the presence of tetrahydrobiopterin, but not in the presence of 2-amino-4-hydroxy-6,7-dimethyltetrahydropteridine. In the presence of(More)
Retinoic acid, which induces the differentiation of HL 60 cells to granulocytes, produces a cell alkalinization from pHi = 7.03 to pHi = 7.37. The half-maximum effect of retinoic acid is observed at 10 nM. The effect of retinoic acid on the pHi develops slowly, and it precedes the differentiation of the cells. A cell alkalinization is also observed after(More)
The differentiation-inducer activity of the aromatic retinoid etretin and of its ethyl ester etretinate (Tigazon) was tested on the human myelomonocytic leukemia cell lines HL-60 and U-937 and compared to that of retinoic acid. Whereas all-trans and 13-cis isomers of retinoic acid were equally potent in inducing the differentiation of about 80% of the cells(More)
The magnitude, the potency, the duration, and the specificity of histamine-induced cyclic AMP formation has been compared in human promyelocytic leukemic HL-60 cells and in human peripheral neutrophils. In HL-60 cells incubated at 37 degrees in the absence of phosphodiesterase inhibitor, histamine caused a 20-fold stimulation of basal cyclic AMP levels,(More)
The binding of 125I-Tyr4 bombesin was investigated on plasma membranes of 8 human breast cancer cell lines and 2 long-term cultures of normal human breast epithelial cells. Scatchard plots were compatible with high-affinity, single-site class of receptors in 3 cell lines (KD of 0.75 x 10(-9) and 10(-9) M, Bmax of 0.75 x 10(-13) and 9.7 x 10(-13) M/mg(More)
H466-B and T47-D breast carcinoma cell lines were treated with recombinant gamma interferon (r gamma IFN) to study major histocompatibility complex (MHC) class I and class II antigen responses. Untreated H466-B cells released B2 microglobulin (B2M) into the culture medium and expressed B2M and class I heavy chain on 100% of the cells. The expression of(More)
The effects of polypeptide neurotoxin from Anemonia sulcata on nerve conduction in crayfish giant axons and on frog myelinated fibers have been analyzed. The main features of toxin action are the following: (i) the toxin acts at very low doses and its action is apparently irreversible. (ii) The toxin selectively affects the closing (inactivation) of the Na+(More)