Calcitonin antibodies in experimental diabetes mellitus

Antibodies to calcitonin appear in blood of rats with experimental alloxan diabetes. This phenomenon is observed only under high blood sugar. At the stage of latent diabetes, i.e. during alloxan administration to the body and low blood sugar no antibodies to calcitonin are detected. It is possible that appearance of autoantibodies to calcitonin is one of pathogenetic factors of hyperglycemia development in rats with alloxan diabetes.     

Immune response to a synthetic polysaccharide and protein conjugate

Synthetic polysaccharide (S-PS) containing aglycone-spacer with a free amino group was really alpha 1,6-mannan with Cn approximately 10. S-PS was transformed into isothiocyanate derivative by treating it with thiophosgene and engaged into reaction with amino group of bovine serum albumin (BSA) lysine residues. Rabbits were immunized with S-PS-BSA conjugate and antibodies to S-PS titres were estimated by means of ELISA. S-PS-BSA conjugate was proved to provoke specific anti-polysaccharide antibodies formation in rabbits.     

PELDOR analysis of enzyme-induced structural changes in damaged DNA duplexes

PELDOR (pulsed electron-electron double resonance) spectroscopy was applied to determine spin-spin distances in spin-labeled DNA duplexes (13-mer and 17-mer) containing the damaged sites 8-oxoguanine or uncleavable abasic site analogue tetrahydrofuran. The lesions were located in one strand of the DNA, and two nitroxyl spin labels were attached at the 5'- and 3'-ends of the complementary strand. PELDOR data allow us to obtain distances between the two spin labels in DNAs, which turned out to be around 5 nm for the 13-mer DNA and around 6 nm for 17-mer DNA. Results of PELDOR measurements were supported by molecular dynamics calculations. Study of the interaction of DNA fragments with DNA repair enzyme 8-oxoguanine-DNA glycosylase from E. coli (Fpg protein) showed that this interaction leads to a noticeable decrease of the distance between spin labels, which indicates the enzyme-induced bending of the DNA duplex. This bending may be important for the mechanisms of recognition of damaged sites by DNA repair enzymes.     

Preferential DNA photocleavage potency of Zn(II) over Ni(II) derivatives of carboxymethyl tetracationic porphyrin: the role of the mode of binding to DNA

The porphyrin-based photosensitizers capable of binding to DNA are perspective drug candidates. Here we report the interactions with calf thymus DNA of 5,10,15,20-tetrakis(N-carboxymethyl-4-pyridinium)porphyrin (P1) and its derivatives containing Zn(II) or Ni(II) in the coordination sphere. These interactions were studied with absorption and circular dichroism spectroscopy. NiP1 and ZnP1 formed different types of complexes with DNA. NiP1 intercalated into the double helix, whereas ZnP1 bound the DNA groove. Compound P1 displayed both binding modes. The ZnP1-DNA binding constant was approximately three times smaller than the respective values for P1-DNA and NiP1-DNA complexes. Light induced degradation of the reactive oxygen species (ROS) trap 1,3-diphenylisobenzofuran in the presence of P1 and its metal derivatives revealed that NiP1 was a weaker photooxidative agent, whereas P1 and ZnP1 generated ROS to similar extents. Nevertheless, the DNA photodamaging effect of ZnP1 was the most pronounced. Illumination of the supercoiled plasmid caused single-strand DNA photocleavage in the presence of P1 and ZnP1; double strand breaks were detectable with micromolar concentrations of ZnP1. The concentration of ZnP1 required for plasmid photonicking was two times smaller than that of P1 and ~20 times lower than that for NiP1. Thus, the modes of P1, NiP1 and ZnP1 binding to DNA determine the differential photodamaging potency of these porphyrins. A greater accessibility to the solvent of the groove binder ZnP1, compared to the shielded intercalator NiP1 and the intercalated P1 molecules, allows for an efficient local generation of ROS followed by DNA photocleavage.     

Protection of HepG2 cells against acrolein toxicity by 2-cyano-3,12-dioxooleana-1,9-dien-28-imidazolide via glutathione-mediated mechanism

Acrolein is an environmental toxicant, mainly found in smoke released from incomplete combustion of organic matter. Several studies showed that exposure to acrolein can lead to liver damage. The mechanisms involved in acrolein-induced hepatocellular toxicity, however, are not completely understood. This study examined the cytotoxic mechanisms of acrolein on HepG2 cells. Acrolein at pathophysiological concentrations was shown to cause apoptotic cell death and an increase in levels of protein carbonyl and thiobarbituric acid reactive acid substances. Acrolein also rapidly depleted intracellular glutathione (GSH), GSH-linked glutathione-S-transferases, and aldose reductase, three critical cellular defenses that detoxify reactive aldehydes. Results further showed that depletion of cellular GSH by acrolein preceded the loss of cell viability. To further determine the role of cellular GSH in acrolein-mediated cytotoxicity, buthionine sulfoximine (BSO) was used to inhibit cellular GSH biosynthesis. It was observed that depletion of cellular GSH by BSO led to a marked potentiation of acrolein-mediated cytotoxicity in HepG2 cells. To further assess the contribution of these events to acrolein-induced cytotoxicity, triterpenoid compound 2-cyano-3,12-dioxooleana-1,9-dien-28-imidazolide (CDDO-Im) was used for induction of GSH. Induction of GSH by CDDO-Im afforded cytoprotection against acrolein toxicity in HepG2 cells. Furthermore, BSO significantly inhibited CDDO-Im-mediated induction in cellular GSH levels and also reversed cytoprotective effects of CDDO-Im in HepG2 cells. These results suggest that GSH is a predominant mechanism underlying acrolein-induced cytotoxicity as well as CDDO-Im-mediated cytoprotection. This study may provide understanding on the molecular action of acrolein which may be important to develop novel strategies for the prevention of acrolein-mediated toxicity.     

Effect of Bacillus Bacteria on Hydrogen Peroxide Content and Gene Expression of Hydrolase Inhibitors in Potato Plants Infected with Phytophthora infestans (Mont.) de Bary

Russian Journal of Plant Physiology - Late blight of potato (Solanum tuberosum L.) caused by the oomycete Phytophthora infestans (Mont.) de Bary was studied in respect to the disease resistance...     

Features of Structural Changes in the Plankton Community of an Alpine Lake with Increasing Fish Density in Summer and Autumn

Biology Bulletin - It is found that a large species of the order Cladocera, Daphnia (Ctenodaphnia) magna Straus, has disappeared from the zooplankton composition in the alpine Lake Sevan, Armenia,...