Ewaryst Mendyk

Synergistic action of Galleria mellonella apolipophorin III and lysozyme against Gram-negative bacteria.

Insect immune response relies on the humoral and cellular mechanisms of innate immunity. The key factors are the antimicrobial polypeptides that act in concert against invading pathogens. Several such components, e.g. apolipophorin III (apoLp-III), lysozyme, and anionic peptide 2, are present constitutively in the hemolymph of non-challenged Galleria mellonella larvae. In the present study, we demonstrate an evidence for a synergistic action of G. mellonella lysozyme and apoLp-III against Gram-negative bacteria, providing novel insights into the mode of action of these proteins in insect antimicrobial defense. It was found that the muramidase activity of G. mellonella lysozyme considerably increased in the presence of apoLp-III. Moreover, apoLp-III enhanced the permeabilizing activity of lysozyme toward Escherichia coli cells. As shown using non-denaturing PAGE, the proteins did not form intermolecular complexes in vivo and in vitro, indicating that the effect observed was not connected with the intermolecular interactions between the proteins. Analysis of AFM images of E. coli cells exposed to G. mellonella lysozyme and/or apoLp-III revealed evident alterations in the bacterial surface structure accompanied by the changes in their biophysical properties. The bacterial cells demonstrated significant differences in elasticity, reflected by Youngs modulus, as well as in adhesive forces and roughness values in comparison to the control ones. The constitutive presence of these two defense molecules in G. mellonella hemolymph and the fact that apoLp-III enhances lysozyme muramidase and perforating activities indicate that they can be regarded as important antibacterial factors acting at the early stage of infection against Gram-negative as well as Gram-positive bacteria.

Hydrothermal modification of silica gels (xerogels) 1. Effect of treatment temperature on their porous structure

Abstract The effect of hydrothermal treatment temperature (in the range 150–300°C) on the structural parameters of silica gels was investigated. Silica gels with different starting porous structures were used for modification. The specific surface areas of the modified sorbents varied from 830 to 12 m2 g−1. Simple mathematical equations describing the changes in specific surface area and pore diameter with treatment temperature are proposed. From the mathematical and/or graphical dependences it is possible to program the hydrothermal treatment process to obtain silica gels with desired porous structures.

Synergistic action of Galleria mellonella anionic peptide 2 and lysozyme against Gram-negative bacteria.

Lysozyme and antimicrobial peptides are key factors of the humoral immune response in insects. In the present work lysozyme and anionic defense peptide (GMAP2) were isolated from the hemolymph of the greater wax moth Galleria mellonella and their antibacterial activity was investigated. Adsorption of G. mellonella lysozyme on the cell surface of Gram-positive and Gram-negative bacteria was demonstrated using immunoblotting with anti-G. mellonella lysozyme antibodies. Lysozyme effectively inhibited the growth of selected Gram-positive bacteria, which was accompanied by serious alterations of the cell surface, as revealed by atomic force microscopy (AFM) imaging. G. mellonella lysozyme used in concentrations found in the hemolymph of naive and immunized larvae, perforated also the Escherichia coli cell membrane and the level of such perforation was considerably increased by GMAP2. GMAP2 used alone did not perforate E. coli cells nor influence lysozyme muramidase activity. However, the peptide induced a decrease in the turgor pressure of the bacterial cell. Moreover, in the samples of bacteria treated with a mixture of lysozyme and GMAP2 the sodium chloride crystals were found, suggesting disturbance of ion transport across the membrane leading to cell disruption. These results clearly indicated the synergistic action of G. mellonella lysozyme and anionic peptide 2 against Gram-negative bacteria. The reported results suggested that, thanks to immune factors constitutively present in hemolymph, G. mellonella larvae are to some extent protected against infection caused by Gram-negative bacteria.

Effect of medium pH on hydrothermal treatment of silica gels (xerogels) in an autoclave

Abstract The effect of medium pH on the porous structure of hydrothermally modified silica gels at high pressures has been investigated. It has been stated that the alkaline medium accelerates and the acidic medium inhibits the process of hydrothermal treatment of silica gels. The effect of medium pH decreases with the increase of temperature of hydrothermal modification. The increase of modifier pH (above 8) permits the temperature of hydrothermal treatment to be reduced in comparison to modification processes performed in neutral media. The mechanism of chemical processes occurring during the chemical modification performed at different pH is discussed. The increased rate of hydrothermal treatment observed in basic alkaline media is connected with the catalytic action of OH− in the processes of depolymerization and condensation of silica.

Hydrothermal modification of silica gels (xerogels) 2. Effect of the duration of treatment on their porous structure

Abstract The effect of the duration of hydrothermal treatment (in the range 1–20 h) on the parameters of the pore structure of silica xerogels was investigated. Silica gels with different initial porous structure parameters were used. The specific surface area (S) of the adsorbents changed from 830 to 38 m2 g−1. A simple mathematical equation describing the dependence of the specific surface area S on the autoclaving treatment time is proposed. The main changes in the geometrical structure of silica gel occur during the first 6 h of treatment. A long-term (over 6 h) hydrothermal treatment can be recommended to improve the homogeneity of the pore structure of silica gels.

Effect of silica gel quantity on the course of hydrothermal treatment in an autoclave

Abstract An incompetently performed process of hydrothermal treatment may be a source of heterogeneous adsorbents. Silica gel samples modified hydrothermally in the temperature range of 150–250 °C were investigated. An effect of mass sorbent on the course of hydrothermal treatment as well as on the homogeneity of obtained materials was verified. The height of the material layer and, to a smaller degree, the ratio of SiO2 to H2O mass were the main parameters. Experiments have shown that a complete capillary condensation of water vapour in the adsorbent pores did not take place. Under such conditions the rate of the process of hydrothermal treatment is determined mainly by the thickness of the water film formed by the water molecules adsorbed on the silica surface.

Synthesis, structure elucidation and antitumour activity of N-substituted amides of 3-(3-ethylthio-1,2,4-triazol-5-yl)propenoic acid.

New N-substituted amides of 3-(3-ethylthio-1,2,4-triazol-5-yl)propenoic acid (2-12) were designed and prepared by the condensation reaction of exo-S-ethyl-7-oxabicyclo-[2.2.1]-hept-5-ene-2,3-dicarbonyl isothiosemicarbazide (1) with primary amines. The chemical structure of all compounds was confirmed by IR, (1)H NMR, (13)C NMR spectra, the X-ray crystallography (for compounds 8, 11, 12) and elemental analysis. Moreover, compounds 9-11 were screened for their anticancer activity. Compounds 9 (in concentrations of 0.32 mM and 0.16 mM), 10 (in concentrations of 0.28 mM and 0.14 mM), and 11 (in concentrations of 0.35 mM and 0.17 mM) were found to be evidently effective in vitro against lung cell line (IC50). The distinctly marked antiproliferative effect of compounds 9 and 10 in breast carcinoma cells in vitro was ascertained. Moreover, the lowest cytotoxicity of compound 9 in concentrations of 0.16 mM and 0.03 mM against the normal skin fibroblast cell line and breast carcinoma cell in vitro after 24- and 48-h periods of incubation was noticed in this study.

Effect of the hydrothermal treatment method in an autoclave on the silica gel porous structure

Two methods of hydrothermal treatment of silica gels (xerogels) in the gaseous and the liquid (under a water layer) phase - have been compared. The effect of these methods on the porous structure of xerogels was studied. It was found that the rate of hydrothermal treatment does not differ significantly in the gaseous and liquid phases, and it is most likely to be more chemical processes that occur during hydrothermal treatment in gaseous and liquid phases.

Properties of hydrothermally modified silica gels — Effect of the parameters of porous structure on the course of the modification process

Abstract The effect of the parameters of globular structure (diameter of globules and number of their contact points) on the course of a texture modification process has been examined. Modification of silica gels was carried out in an autoclave at elevated pressure in the temperature range 110–300°C and in a water vapour atmosphere. Silica gels having specific surface area of 64–830 m2/g and predominant pore radii of 40–1000 A were modified. The mechanism of hydrothermal treatment is relatively complex. It depends, among other things on different parameters of globular texture, the temperature of a process and on the presence of different admixtures in the adsorbent being modified. Above 200°C the course of hydrothermal modification depends only slightly on the nature of the silica gel (narrow or wide porous).

Anti-Candida albicans action of the glyco-protein complex purified from metabolites of gut bacterium Raoultella ornithinolytica isolated from earthworms Dendrobaena veneta

The aim of our research was to isolate the compounds from the metabolites of Raoultella ornithinolytica with the activity against Candida albicans and to analyse the action of the compounds on the metabolic activity and morphology of the fungus cells.