Enhancement of the human plasma lipid transfer protein reaction by apolipoproteins

Transfer of cholesteryl ester between triacylglycerol/phospholipid microemulsions catalyzed by human plasma lipid transfer protein was investigated with a pyrene-containing analogue of which fluorescent properties depend on its concentration in the core of the microemulsions. The transfer of pyrene-cholesteryl ester between the emulsions was increased by the transfer protein linearly with its concentration, but maximally only to the extent of twice as much as spontaneous transfer in the given experimental conditions. When human apolipoproteins A-I or A-II are present in the reaction mixture enough to saturate the surface of the emulsion, the enhancement of the pyrene-cholesteryl ester transfer reaction by the transfer protein was 7.5-times more than in the absence of the apolipoproteins while the rate of spontaneous transfer was not affected significantly by the apolipoproteins. Bovine serum albumin did not have such an effect. Furthermore, the enhancement of the lipid transfer protein reaction by apolipoprotein A-I was linearly proportional to the percent saturation of the surface of the microemulsion with the apolipoprotein.     

Effect of some quaternary benzylammonium salts on physiology of yeast

In order to determine the biological activity of eight compounds belonging to a group of quaternary ammonium salts, their influence on the active methionine transport, the integrity of cell membranes, respiration, and viability of Saccharomyces cerevisiae and some other yeast species has been investigated. The earliest effect observed during ammonium salts action on yeast cells is an immediate methionine transport abolishment followed by its fast leakage, which indicates increasing cell membrane degradation. Gradual decline of other biological functions such as respiration and viability is thus a result of disintegration and lack of tightness of the cell membranes. The studied compounds are characterized by a rather unspecific spectrum of action on yeast resulting in irreversible damage of cell walls and cell membranes, which in consequence leads to cell death.     

Effects of cyclosporin A on contractile activity and cytoskeleton in chick embryo cardiomyocytes.

The effects of cyclosporin A (CsA), a clinically used immunosupressive drug, on contractile activity of chick cardiomyocytes grown as small aggregates or explants suspended on a network of elastic glass fibres or cultured in a monolayer were analysed in vitro with computer-aided image cytometry methods. At therapeutic concentrations (200-1500 ng/mL), CsA induced changes in the frequency and amplitude of the beating activity of cardiomyocytes 15 min after application. Longer treatment of cardiomyocytes, for 20-24 h, additionally induced changes in their shape and cytoskeleton organization (F-actin and alpha-actinin distribution). These results indicate that CsA is able to affect directly the contractile activity, morphology, and cytoskeleton architecture of heart cells.     

Isolation and sequence of a tomato cDNA clone encoding subunit II of the photosystem I reaction center

We report here the isolation and nucleotide sequence of a cDNA clone encoding a phtosystem I polypeptide that is recognized by a polyclonal antibody prepared against subunit II of the photosystem I reaction center. The transit peptide processing site was determined to occur after Met₅₀ by N terminal sequencing. The decuced sequence of this protein predicts that the polypeptide has a net positive charge (pI=9.6) and no membrane spanning regions are evident from the hydropathy plot. Based on these considerations and the fact that subunit II is solubilized by alkali treatment of thylakoids, we concluded that subunit II is an extrinsic membrane protein. The absence of hydrophobic regions characteristic of thylakoid transfer domains furthermore implies that subunit II is localized on the stromal side of the membrane.     

Actinobacillus actinomycetem-comitans: Fermentative Capabilities of 140 Strains

Fermentative capabilities of 140 strains of Actinobacillus actinomycetem-comitans were studied. Findings correspond closely with those reported previously by Heinrich and Pulverer (12 strains), and by King and Tatum (33 strains). All strains ferment glucose, levulose, and maltose and reduce nitrate to nitrite. Reactions with glycogen and starch are exceedingly diverse. Eight different biotypes have been identified on the basis of their reactions with galactose, mannitol, and xylose.     

Growth temperature affects O2 consumption rates and plasticity of respiratory flux to support shoot growth at various growth temperatures

The temperature dependence of respiration rates and their acclimation to growth temperature vary among species/ecotypes, but the details remain unclear. Here, we compared the temperature dependence of shoot O₂ consumption rates among Arabidopsis thaliana ecotypes to clarify how the temperature dependence and their acclimation to temperature differ among ecotypes, and how these differences relate to shoot growth. We examined growth analysis, temperature dependence of O₂ consumption rates, and protein amounts of the respiratory chain components in shoots of twelve ecotypes of A. thaliana grown at three different temperatures. The temperature dependence of the O₂ consumption rates were fitted to the modified Arrhenius model. The dynamic response of activation energy to measurement temperature was different among growth temperatures, suggesting that the plasticity of respiratory flux to temperatures differs among growth temperatures. The similar values of activation energy at growth temperature among ecotypes suggest that a similar process may determine the O₂ consumption rates at the growth temperature in any ecotype. These results suggest that the growth temperature affects not only the absolute rate of O₂ consumption but also the plasticity of respiratory flux in response to temperature, supporting the acclimation of shoot growth to various temperatures.