Thermodynamic and kinetic study of thermal denaturation of Kunitz soybean trypsin inhibitor by differential scanning microcalorimetry

The thermal denaturation of soybean trypsin inhibitor (Kunitz inhibitor) has been studied in pH-region from 2.0 to 11.0 by differential scanning microcalorimetry. The thermodynamic characteristics have been determined. It has been established that the denaturation transition of protein may be described by a two-state model. It has been shown, that two side hydrogen bonds between carboxylate-ion and tyrosyl and carboxylate-ion and lysyl take part in the stabilization of the inhibitor's native structure. The activation of denaturation is accompanied by cleavage of one side hydrogen bond.     

Electron microscopic research on the mitochondria-rich bladder cells of the frog

The ultrastructural peculiarities of mitochondria-rich cells of the frog urinary bladder are analysed using three electron microscopic methods: ultrathin sections, scanning electron microscopy, freeze fracture. The mitochondria and tubular and vesicular structures are most abundant in the apical region of cytoplasm. The P-face (PF) of the apical plasma membrane is characterized by the presence of rod-shaped intramembrane particles (IMP), whereas the E-face (EF) possesses complementary pits. Depending on the distribution density of the rod-shaped IMP, three types of cells are described. The apical plasma membrane has an invert distribution of the globular IMP: a great quantity of IMP on the EF and a few particles on the PF. This structure of the apical plasma membrane is supposed to correlate with its very low water permeability. Using filipin as a marker of cholesterol localization, it has been shown that the mitochondria-rich cell apical membrane contains more cholesterol than that of the granular cells. The nature of the rod-shaped IMP and their role in the transmembrane ion transport have been discussed.     

Effect of mitogenic stimulation and heat shock on protein syntheses in human T cells

Effects of moderate (42 degrees C, 1 hour) and strong (44 degrees C, 1 hour) heat shocks on resting (TR) and phytohemagglutinin stimulated human T-cells (TP) were studied. Both treatments were shown to cause in the latter considerable fall of the level of protein synthesis, as compared to resting cells. Mitogen-stimulated cells stopped their proliferation irreversibly and part of them (approx: 40%) died after even mild shock (at 42 degrees C). Following heat treatment in both the cell types the synthesis of heat shock 70 and 90 kDa proteins was induced which was much more pronounced in TR. These and earlier results of the authors allow a conclusion that involvement of cells in active proliferation may decrease their resistance to stress, and that this phenomenon coincides with the diminishing in synthesis and accumulation of stress proteins.     

The x-ray picture of pulmonary circulation in the course of acute myocardial infarct

A study was made of the time course of lesser circulation (LC) in 80 patients with acute transmural myocardial infarction and in 20 patients with chronic coronary heart disease with the help of chest x-ray. A possibility of preclinical detection of left ventricular insufficiency was confirmed. The capacity of roentgenography to reflect objectively the time course of LC disorder and its correlation with primary determination of a degree of changes, age, cardiac sizes, the expression of aortic atherosclerosis, pleurocardiac reactions and site of myocardial infarction were defined.     

Spectral features of amines of 2-phenylbenzazoles upon interaction with DNA

Absorption and fluorescent spectra of various synthetic aminophenyl derivatives of benzoxazole, benzothiazole and benzimidazole have been studied to estimate the efficiency of their binding with DNA. The significance of different functional groups of the fluorochromes for their interaction with DNA was determined, and main demands are formulated to the compounds to be used as potential fluorescent probes for DNA studies.     

Status of the electrolyte balance of the gastric juice during stimulation of secretion by histamine

The content of electrolytes (Na+, K+, Ca2+) in human basal secrete has been determined before and after injection of histamine in gastric juice and insoluble mucus in healthy people. Electrolytes in the mucous membrane of the stomach, gastric juice and insoluble mucus have been determined in dogs with stomach fistula after Basow. Species peculiarities have been marked in electrolyte content change during gastric secretion.     

Immunostimulating properties of synthetic derivatives of muramyl dipeptide and glucosaminyl muramyl dipeptide in vitro

Production of tumor necrosis factor (TNF) and interleukin-1 (IL-1) by macrophages of the spleen and peritoneal exudate of mice as well as cytotoxic factors (CFs) by murine splenocytes after in vitro activation was estimated. All the derivatives of muramyldipeptide (MDP) and glucosaminylmuramyldipeptide (GMDP) were able to induce production of TNF and CFs. In the presence of lipopolysaccharide (LPS), the effect was always higher. The response of the spleen macrophages to the effect of the preparations was higher than that of the peritoneal ones and ++non-fractionated splenocytes. GMDP and GMDP4 especially in the presence of LPS had the highest effect on induction of IL-1 by the murine peritoneal macrophages. On the contrary, MDP induced higher IL-1 synthesis by the spleen macrophages. The most active substances with respect to production of TNF, CFs and IL-1, i.e. MDP3 and GMDP4, might be recommended for immunotherapy of syngeneic tumors in animals.     

Effect of beta-lactam antibiotics on lipid bilayer membranes. I. Penicillin antibiotics

Interaction between penicillins and model membrane systems, flat black bilayer lipid membranes (BLM) composed of vegetable or bacterial phospholipids was studied with an account of the complicated structure of bacterial cell membranes and possible presence in them of "pure" bilayer lipid areas. By their effect on electroconductivity of the BLM the antibiotics could be divided into three groups: those having no effect on the BLM electroconductivity at the maximum concentrations i.e. benzylpenicillin, carbenicillin, piperacillin (at pH 6.0 and 7.0) and ampicillin (at pH 6.0), those insignificantly changing electroconductivity of the BLM i.e. carfecillin and azlocillin and those having a significant effect on the BLM electroconductivity i.e. ampicillin N-acyl derivatives and 6-APA. The effect of ampicillin on the BLM conductivity markedly depended on the electrolite pH. The penicillins bound to the bilayer and induced changes in the transmembrane potential (evident from the changes in the second harmonic of the capacitive current) and the BLM elasticity-capacitance parameters (evident from the changes in the ratio of the amplitudes of the first and third harmonics). It was shown that all the penicillins penetrated through the BLM composed of either vegetable or bacterial phospholipids. The capacity for the transmembrane transfer without changing of the bilayer conductivity must be connected with the fact that the penetrating antibiotics did not induce any changes in the BLM structure. The effect on the conductivity probably depended in its turn on the form of the molecule and the ratio of the hydrophilic and hydrophobic parts in it.     

Effector modeling of the action of GABA-receptor complex ligands. Functional interactions of subunits of the complex

The distribution of the minimum effective doses of bicuculline, corasole and picrotoxin was studied in intact mice and in mice administered different doses of 1.4-benzodiazepines (phenazepam and its 1,2,4,5-tetrahydroxy derivatives) and sodium barbital. The changes in the "dose-response" relationship for thiosemicarbazide have been observed with the administration of the increasing doses of phenazepam and sodium barbital. The effects registered correspond to the modifications of the GABA-receptor complex by exogenous ligands. The forms of the "dose-response" relationship observed, the types of the antagonism between pharmacological agents and the cooperation of their interaction correspond to the indices obtained from the "quartet" model of the receptor-channel complex.     

Antigenic polysaccharides of bacteria. 35. Establishment of the structure of polysaccharide chains of lipopolysaccharides of Pseudomonas cepacia IMV 4176 and IMV 4202 (Serotype 3)

On mild acid degradation of the Pseudomonas cepacia strain IMV 4176 lipopolysaccharide, two polysaccharides were obtained, one of which is a homopolymer of N-acetyl-D-galactosamine and the other is composed of equal amounts of N-acetyl-D-galactosamine and D-ribose. Partial hydrolysis with aqueous oxalic acid caused depolymerization of the heteropolysaccharide, and the homopolysaccharide was isolated in the individual state. On the basis of methylation and 13C NMR analysis, it was concluded that both polysaccharides are built up of disaccharide repeating units having the following structures: ----4)-alpha-D-GalpNAc-(1----4)-beta-D-GalpNAc-(1---- and ----4)-alpha-D-GalpNAc-(1----2)-beta-D-Ribf-(1----. The heteropolysaccharide from P. cepacia strain 4176 is identical by the structure of the repeating unit to the O-specific polysaccharide of P. cepacia strain IMV 4202 (serotype 3), Pseudomonas aeruginosa O12 and Serratia marcescens O14.