Sensitivity of Escherichia coli cell membranes to various classes of detergents

The mechanisms of interaction between non-ionic or cationic surfactants with Escherichia coli K-12 cell membranes were studied using an approach based on the registration of changes in the membrane permeability to ethidium bromide, a fluorescent dye for nucleic acids. Triton X-100, a non-ionic detergent, was shown to exert no effect on the permeability of intact cell membranes. Triton X-100 interacted with the bacteria only after treatment with EDTA, a complexing agent for bivalent cations. Cetyltrimethyl ammonium bromide increased the permeability to ethidium bromide and the action of this cationic detergent did not require the pretreatment with the complexing agent. SDS, an anionic detergent, damaged E. coli K-12 and this could be registered by the lowering of intensity of light scattering by the bacterial suspension. The surface charge of E. coli K-12 cells was shown to influence the interaction of ionic detergents with bacterial cell membranes. Its variation by changing the pH of the incubation medium did not make E. coli K-12 sensitive to Triton X-100.     

Alcohol-drug interaction in rat embryogenesis: the effect of separate and combined action of sodium salicylate and ethanol

A combined administration of sodium salicylate and ethanol to female rats in threshold embryotoxic doses on the 9th, 10th, 12th and 13th days of pregnancy results in a sharp increase of embryolethal and teratogenic effects. The embryotoxic effect of sodium salicylate and ethanol at their combined injection exceeds the summational embryotoxic effect at the separate action of the preparations. The spectrum of malformations after their combined effect does not differ from that induced with sodium salicylate.     

Permeability of the membrane of the Escherichia coli envelope for ethidium bromide

The interaction of ethidium bromide, a fluorescent dye, with Escherichia coli cells was studied. The envelope of intact cells was shown to be impermeable for ethidium bromide molecules. The dye penetrated however into E. coli spheroplasts. The barrier properties of the cell envelope against ethidium bromide were ruptured if the cells were treated with EDTA. The results suggest that the outer membrane serves as a principal barrier against penetration of ethidium bromide inside the cells while the cytoplasmic membrane of E. coli is permeable for the dye.     

Dating pregnancy times in rats and the effect of ovum supermaturation on the quantity of live embryos]

The fecundity of white rats was compared for the night and morning matings (late and early). The mating of animals at the stage of oestrus for 1.5 hrs early in the morning is the optimum one for obtaining females with the precisely dated time of pregnancy. The progeny of females fertilized after 10-11 hours in the morning, i. e. 9-11 hrs after the ovulation, decreases almost twice at the expense of embryonic mortality both prior and after the implantation due to the low viability of "overmatured" eggs.     

Influence of Random Inhomogeneities on Fluctuation Spectra in Nonequilibrium Plasma

Plasma Physics Reports - A method for calculating fluctuations in the nonequilibrium plasma-containing random inhomogeneities is developed. Using this method, the fluctuation spectrum in the region...     

Effect of epidermal chalones on the development and growth of cheek pouch tumors in the hamster

To the cheek pouch mucosa of 118 male Syrian golden hamsters 0.5% acetone solution of 7,12-dimethylbenz (a) anthracene was applied 3 times a week during 2 months. Two months after beginning of the experiments all the hamsters developed tumors. Since that time a mixture of epidermal G1 and G2 chalones was applied to the cheek pouch mucosa of the experimental animals 5 times a week. The control hamsters received saline alone. As compared to the control, the experimental hamsters demonstrated an increase in the life-span, tumor growth retardation and regression of part of the tumors. The data obtained attest to the anti-neoplastic action of chalones.     

Longitudinal fluctuations in a nonuniform collisional plasma with nonequilibrium particle distributions

The amplitudes of high-frequency longitudinal fluctuations excited by a nonequilibrium source in a nonuniform plasma are calculated. The results obtained are applicable to arbitrary nonequilibrium distributions of plasma particles in the absence of parametric instabilities. The spectra of probing waves scattered by fluctuations in a linear ionospheric plasma layer under conditions typical of experiments on incoherent radio wave scattering are found. The effects of electron-ion collisions and electron temperature anisotropy on the scattering intensity are demonstrated.     

Polycationic amphiphiles based on triethylenetetramine and their transfection efficacy

Novel polycationic amphiphiles derived from triethylenetetramine, a spermine analogue, containing cholesterol or dialkylglycerol residues as hydrophilic domains were synthesized. The amphiphiles and a helper lipid 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine) served for the preparation of cationic liposomes, physicochemical properties of which were evaluated. A comparative study of cytotoxicity and transfection efficiency demonstrated that the replacement of spermine by triethylenetetramine decreased transfection activity of cationic liposomes.