On the origin of eukaryotic cells and their endomembranes.

A novel hypothesis for the origin of eukaryotic cells is presented. It is assumed that the universal ancestor was bounded by two membranes of heterochiral lipid composition. We propose that the prokaryotic cells (the hypothetical host entity for alpha proteic-bacteria), though sharing a common ancestor with Archaea, was bounded by two membranes. The hypothesis suggests that an alpha proteic-bacterial symbiont was enclosed in the prokaryotic cells intermembrane space. In this view, the eukaryotic nuclear membrane and endomembrane system arose from the prokaryotic cells inner membrane while the eukaryotic plasma membrane arose from the prokaryotic cells outer membrane. The outlined scenario agrees with the view that engulfment of an alpha-proteic-bacterial cell by a host entity and its transformation to a mitochondrion was the driving force leading to the appearance of the first eukaryotic cell. The hypothesis seems to be consistent with the pre-cell theory, theory of membrane heredity, and the phagocytosis-late scenario.     

Hereditary bleaching ofEuglena gracilis affected by 3-(5-nitro-2-furyl)acrylic acid

Light and elevated incubation temperature were found to be involved in the ability of four nitrofurans to cause the hereditary bleaching effect inEuglena gracilis. The enzyme activation by S9 mix also played a significant role in the case of 3-(5-nitro-2-furyl)acrylic acid. When using the combination of the above factors the most pronounced hereditary bleaching was reached.     

Quantitative relationships between lipophilicity and mutagenic effects of N-substituted amides of 3-(5-nitro-2-furyl)-acrylic acid on Salmonella typhimurium

Mutagenic effects of 10 N-alkylamides of 3-(5-nitro-2-furyl)-acrylic acid were assessed in two strains of Salmonella typhimurium TA100 (rfa+ and rfa-). Experimental data were confronted with physiologically based compartment model comprising passive membrane transport, metabolical inactivation in cytoplasm and formation of a reactive intermediate which is responsible for receptor modification. The quantitative dependences observed between mutagenicity and lipophilicity indicate that, in both cases, the drug-receptor interaction takes place in a hydrophobic compartment localized in the cytoplasm. The mutagenic potency of some derivatives was influenced also by stericity.     

Effect of elevated temperature on genotoxicity of chemotherapeuticals towardEuglena gracilis

A collection of 20 compounds was tested for their ability to induce a permanent loss of chloroplasts from Euglena gracilis cells under conditions increasing the sensitivity of the flagellate to genotoxic compounds, viz. in the resting medium and at an elevated temperature. Streptomycin, dihydrostreptomycin, gentamicin, kanamycin and partially chloramphenicol exhibited mutagenic effects. Eight antibiotics eliminated chloroplasts only from growing cultures and seven antibiotics did not induce the mutation at all.