Stimulation of human platelets with concanavalin A involves phospholipase C activation.

In response to concanavalin A, cytoplasmic calcium movement was observed in human platelets, both in the presence of 1 mM Ca2+ or 1 mM EGTA in the medium. Concanavalin A also caused the activation of inositide turnover and the production of inositol phosphates, suggesting that activation of phospholipase C occurs. The mechanism by which concanavalin A stimulates phospholipase C does not depend on GTP-binding transducers, because it was not inhibited by GDP beta S, while experiments performed in the presence of cytochalasin B suggested a role for membrane glycoprotein IIb-IIIa-cytoskeleton interaction in this process. Ca(2+)-proteases and Na+/H+ antiport also seemed to be related to concanavalin A-induced phospholipase C activation, as suggested by experiments performed in the presence of leupeptin and amiloride.     

DNA methylation of embryogenic carrot cell cultures and its variations as caused by mutation,differentiation, hormones and hypomethylating drugs

Summary The level of auxin - both natural and synthetic — in the medium has a strong effect on the level of 5-methyl-cytosine in the DNA of carrot cells in culture. This level may vary from approximately 15% to 70% of total cytosine without apparent effects on growth rate and cell morphology. No effect was seen with cytokinin. During somatic embryogenesis, in the absence of hormones, variations were seen in the level of methylation according to a characteristic pattern. If hypomethylation is induced with drugs such as azacytidine, ethionine or ethoxy-carbonyl-pyrimidine, embryogenesis is immediately blocked. A mutant was isolated which is resistant to the action of hypomethylating drugs. It shows variations in the methylation pattern and variations in indole-acetic acid metabolism. In addition its regeneration is often associated with the production of tumors.Deceased     

Effect of GPIIb-IIIa complex ligands on calcium ion movement and cytoskeleton organization in activated platelets

We studied the influence of the occupancy of the fibrinogen receptor (GP IIb-IIIa complex) on two early aspects of agonist induced platelet activation: the increase of the intracellular Ca2+ concentration and the cytoskeleton reorganization. A monoclonal antibody, a peptide containing the RGD sequence and fibrinogen purified from human plasma were used as GP IIb-IIIa ligands. The obtained results demonstrated that fibrinogen receptor occupancy inhibits Ca2+ movement and cytoskeleton reorganization caused by low thrombin concentration and ADP.     

A New Basal Subfamily of mariner Elements in Ceratitis rosa and Other Tephritid Flies

Several copies of highly related transposable elements, Crmar2, Almar1, and Asmar1, are described from the genomes of Ceratitis rosa, Anastrepha ludens, and A. suspensa, respectively. One copy from C. rosa, Crmar2.5, contains a full-length, uninterrupted ORF. All the other copies, from the three species contain a long deletion within the putative ORF. The consensus Crmar2 element has features typical of the mariner/Tc1 superfamily of transposable elements. In particular, the Crmar2 consensus encodes a D,D41D motif, a variant of the D,D34D catalytic domain of mariner elements. Phylogenetic analysis of the relationships of these three elements and other members of the mariner/Tc1 superfamily, based on their encoded amino acid sequences, suggests that they form a new basal subfamily of mariner elements, the rosa subfamily. BLAST analyses identified sequences from other diptera, including Drosophila melanogaster, which appear to be members of the rosa subfamily of mariner elements. Analyses of their molecular evolution suggests that Crmar2 entered the genome of C. rosa in the recent past, a consequence of horizontal transfer.