Study of the action of phytohemagglutinin on continuous human cells]

A study was made of the agglutinating and growth-stimulating properties of phitohemaagglutinin (PHA) preparations in experiments on continuous human cells (clone line HeLa k-41 and CaVe). PHA and PHA gamma-globulin fraction possessed poor hemagglutination properties against human erythrocytes of A, B and O groups, but expressed marked cytoagglutination properties against HeLa k-41 and CaVe cells. With high PHA doses (100 and 500 microng/ml) proliferation and mitotic indx of the culture cells was lower and the percentage of dead cells and the agglutinin titre in the preparations was greater (1 : 256). With lower PHA doses (5 and 25 microng/ml) the growth was much stronger and the percentage of dead cells lower. The agglutinin titre in the preparations decreased to 1 : 16-1 : 32. PHA gamma-globulin fraction produced the strongest growth-stimulating action with the least amount of dead cells. However, the agglutinin titre in the preparations remained high (1 : 128). A conclusion was drawn that the action of PHA preparations stimulating and inhibiting the growth of continuous human cells proved to be directly connected with the agglutinin content in the preparations, since gamma-globulin PHA fraction expressed the greatest cytoagglutinating and growth-stimulating action.     

Red blood cell dielectrophoresis in axisymmetric fields

Dielectrophoretic velocities of human red blood cells in an axisymmetric field were measured as a function of the applied voltage and the distance from the axis of symmetry. The voltage of the alternating electric field (frequency 2 MHz), applied between two concentric cylindrical metal electrodes (outer and inner radii 0.24 and 1 mm, respectively), was varied up to 19 V. Two kinds of mediums were used: (a) 90% of 2.1% glycine solution and 10% of 5.5% glucose solution and (b) 5.4% sorbitol solution. The results have shown that in both mediums the cell velocities are proportional to the square of the applied voltage and inversely proportional to the cube of the distance from the axis of symmetry, as predicted by the theory. The coefficient of proportionality (dielectrophoretic coefficient) is on the order of 10(-25) A2S4kg-1. It depends on the donor of red blood cells and might be used for diagnostic purposes. These results will be used in future investigations of membrane adhesion, stability and fusion.     

Electrofusion of fragile mutants of Saccharomyces cerevisiae

This communication presents experimental evidence that intact fragile (osmotic sensitive) yeasts can be electrofused and give viable hybrids. The yield increases with one order of magnitude for electrofusion of intact fragile yeasts with protoplasts of non-fragile ones. The yield of viable hybrids, obtained by electrofusion of protoplasts of fragile and non-fragile yeasts, is one order of magnitude higher than the yield from protoplasts of non-fragile yeasts. The destabilized cell wall and plasma membrane of the mutant yeasts could be a possible explanation for this phenomenon.     

Type III CRISPR-Cas Systems: Deciphering the Most Complex Prokaryotic Immune System

Biochemistry (Moscow) - The emergence and persistence of selfish genetic elements is an intrinsic feature of all living systems. Cellular organisms have evolved a plethora of elaborate defense...     

Effect of Cytokinins on Photosynthetic Pigments and Chlorophyllase Activity in in Vitro Cultures of Axillary Buds of Dianthus caryophyllus L.

The effect of benzyladenine (BA) and two phenylurea cytokinins, N-phenyl-N′-(2-chloro-4-pyridyl)urea (4-PU-30) and thidiazuron (TDZ), on the growth, photosynthetic pigment content, and activity of chlorophyllase (chlorophyll-chlorophylliodhydrolase, EC 3.1.1.14) of in vitro cultures of carnations was studied. All cytokinins caused a rise in the fresh weigth and a drop in the dry weight of leaf mass produced by the explanted buds. Both 4-PU-30 and TDZ increased the chlorophyll content and this correlated with changes in chlorophyllase activity. The effect of 4-PU-30 and TDZ was similar to that caused by BA but at 10-fold or 100-fold lower concentrations. The application of higher concentrations of the phenylurea cytokinins caused an increase in the chlorophyll a/chlorophyll b ratio. However, at equimolar concentrations, the purine and both phenylurea cytokinins had opposite effects, probably indirect and related to some malformations caused by phenylureas. 4-PU-30 increased, but TDZ decreased, photosynthetic membrane stability, which argues for a different molecular organization of the chloroplast membranes. Received February 26, 1996; accepted May 30, 1997