Blockers of Ca2+ channels in the plasmalemma of perfused Characeae cells.

Ionic currents in the plasmalemma of perfused Nitella syncarpa cells identified as currents through Ca2+ channels were registered for the first time. The effect of 1,4-dihydropyridine derivatives (nifedipine, nitrendipine, riodipine) and phenylalkylamines (verapamil, D600) as well as the agonist CGP-28392 on the Ca2+ channels in the plasmalemma of perfused cells of Nitellopsis obtusa and Nitella syncarpa have been studied. A blocking effect of 1,4-dihydropyridine derivatives and phenylalkylamines on the plasmalemma Ca2+ channels has been detected. Phenylalkylamines have been found to block both inward and outward Ca2+ currents. The activating effect of the agonist CGP-28392 on the Ca2+ channels of plasmalemma has been shown.

Organization of the surface and adhesive properties of cleavage furrows in loach (Misgurnus fossilis) eggs.

The experiments with chimerous embryos of teleost loach (Misgurnus fossilis) have shown that before furrows of the 1st cleavage appeared, the eggs were completely nonadhesive. At the stages of cleavages II-IV whole eggs were able to adhere and then make extended junctions in the blastodisc region. Adhesive domains of blastomeres were discovered by using carmine dye particles which attached primarily in the region of blastomere cleavage furrows. Scanning electron microscopy (SEM) showed that the cells in the depth of the cleavage furrows have domains with a smoother relief than their outer surface with numerous folds. Moreover, most adhesive flat lamellar formations (ruffles) with microvilli at their ends were discovered in the furrow region, particularly in its apical part (in the sites of intercellular contact formation and carmine absorption). Colchicine (5 X 10(-4) M) treatment affects the reorganization of the cleavage furrow surface, and the eggs, one by one, lose their ability to adhere, and then to attach dye particles. Mechanisms of formation of an adhesive contact between divided cells are discussed.