Effects of thyroxine and dexamethasone on kinetic characteristics of the small intestine enzymes in rat pups following a low-protein diet in female rats during lactation

It is shown, that the value of Km for maltase, alkaline phosphatase, aminopeptidase M and glycyl-L-leucinedipeptidase, prepared from the jejunum and ileum of 10-day rat litter in membrane and soluble forms in most cases differed but a little in control animals and the rat litter whose mothers in the period of lactation had a diet with 2.5-fold reduced content of protein, and did not change under action of injected thyroxin and dexamethasone. It may be assumed that in the given experimental conditions each of the investigated digestive hydrolases in membrane and soluble forms represents the same enzyme. In conditions of the protein insufficiency in lactating females diet and under action of exogene hormones, apparently, no significant changes occur in structure of synthesised enzymes.     

Epitope of the catalytic subunit of viscumin, exposed on its interaction with a lipid bilayer

It was previously shown that the catalytic subunit of the plant toxin viscumin induces aggregation of small unilamellar liposomes and this process is inhibited by the mab_TA7 monoclonal antibody produced to the denatured catalytic subunit of viscumin (Agapov, I.I. et al., FEBS Lett., 1999, vol. 464, pp. 63-66). The interaction of the synthetic F101-T105 and A96-T105 fragments of the viscumin catalytic subunit with the mab_TA7 monoclonal antibody was studied by 1H NMR spectroscopy. The results of this study demonstrated that only the A96-T105 fragment is capable of binding to mab_TA7. A nuclear Overhauser effect observed in the antigen-antibody complex and registered on the resonances of the free peptide and exchanging between the free state and the antibody-bound state was analyzed; the mab_TA7 antigen determinant (H99-T105) was identified; and its conformation and orientation within the complex with the antibody were determined. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2003, vol. 29, no. 6; see also http://www.maik.ru.     

Role of bacterial toxins in pathogenesis of hemolytic-uremic syndrome, caused by enterohemorrhagic Escherichia

The pathogenesis of the hemolytico-uremic syndrome (HUS) caused by enterohemorrhagic E. coli (EHEC) has been studied previously rather completely. HUS is characterized by the signs of microangiopathic hemolytic anemia, thrombocytopenia with renal lesions and manifestations of transient disturbances in the functions of the central nervous system. The adherence of EHEC to enterocytes was found to occur in the terminal section of the ileum and the large intestine. This process is realized with involvement intimin, EHEC outer membrane protein. Shiga-like toxins (SLT) produced by EHEC are the leading factor of their pathogenicity. The mechanism of the toxin translocation through enterocytes is not yet clear, still there is no doubt that SLT penetrates into the systemic blood stream. This is indicated by the results of histopathological studies it possible to find the toxin traces on the membranes of endothelial cells of blood vessels. The study reveals that the cells of the vascular epithelium are highly sensitive to SLT. These cells carry receptors Gb3, also known as CD77, on their membranes. Enterohemolysin, serine protease, causing disturbances in the barrier function of the intestine, can be regarded in the pathogenesis of hemorrhagic colitis which develops as the result of the damaging action of EHEC and the above-mentioned toxins. This leads to the increased level of blood systemic bacterial lipopolysaccharides, which may play, in combination with the action of SLT, an important role in the development of multi-organ pathology in HUS patients.     

Properties and clinical application of quasi-liquid form of lysozyme

The course of transendoscopic quasi-liquid form of lysozyme treatment of the relapse of peptic ulcer was microbiologically and clinically substantiated. A high antimicrobial and sorption activity of the quasi-liquid form of lysozyme with respect to the microflora isolated from the mucous membrane of the stomach and the duodenum was shown. The transendoscopic introduction of this form of lysozyme significantly reduces the time of the cicatrization of ulcers and the stay of patients in the hospital.     

Analysis of Linkage Between Biochemical and Morphological Markers of Rye Chromosomes 1R, 2R,and 5R and Mutations of Self-Fertility at the Main Incompatibility Loci

In F₂ hybrids between self-sterile plants of the Volkhova cultivar and self-fertile lines with established self-fertility mutations (sf mutations) at the major incompatibility loci S (1R), Z (2R), and T (5R), the effect of sf mutations on the inheritance of secalin-encoding, isozyme, and morphological markers located on the same chromosomes was investigated. Linkage between loci Prx7 and Sand locus Sec3 coding for high-molecular-weight secalins on chromosome 1R was shown for the first time. The frequency of recombination between Prx7andSec3and between S and Sec3was 29.1 ± 4.8% and 30.9 ± 7.0%, respectively. Independent inheritance of locus Z and isozyme markers of chromosome 2R, Est3/5 and -Glu, from locus Sec2 encoding 75-kDa -secalins was shown; in hybrids, the recombination frequency between Est3/5 and locus Z varied from 19.2 ± 8.1 to 50%. Independent inheritance of morphological (Ddw and Hs) and isozyme markers (Est4, Est6/9,and Aco2) of chromosome 5R from locus Tlocated on the same chromosome was demonstrated.     

Hydrolases in the large intestine in rats with various experimental pathologies

In the colon mucous membrane, activity of a wide range of membrane and mainly intracellular enzymes was studied in the organism at different conditions. The data obtained suggest participation of digestive hydrolases in the colon not only on postdigestive processes but, in certain states of the organism, in digestive processes too.     

Crystal structure and molecular modeling study of N-carbamoylsarcosine amidase Ta0454 from Thermoplasma acidophilum

A crystal structure of the putative N-carbamoylsarcosine amidase (CSHase) Ta0454 from Thermoplasma acidophilum was solved by single-wavelength anomalous diffraction and refined at a resolution of 2.35 Å. CSHases are involved in the degradation of creatinine. Ta0454 shares a similar fold and a highly conserved C-D-K catalytic triad (Cys123, Asp9, and Lys90) with the structures of three cysteine hydrolases (PDB codes 1NBA, 1IM5, and 2H0R). Molecular dynamics (MD) simulations of Ta0454/N-carbamoylsarcosine and Ta0454/pyrazinamide complexes were performed to determine the structural basis of the substrate binding pattern for each ligand. Based on the MD-simulated trajectories, the MM/PBSA method predicts binding free energies of ?24.5 and ?17.1 kcal/mol for the two systems, respectively. The predicted binding free energies suggest that Ta0454 is selective for N-carbamoylsarcosine over pyrazinamide, and zinc ions play an important role in the favorable substrate bound states.     

Elevated Temperatures Inhibit Ferredoxin-Dependent Cyclic Electron Flow around Photosystem I

In experiments with barley (Hordeum vulgare L.) leaves, absorbance changes at 830 nm induced by far-red light were measured as indicator of redox conversions of primary electron donor (P700) of photosystem I (PSI). Using this method, the action of elevated temperature (45°C, 5 min) on PSI-driven electron transport through alternative pathways was examined. Thermally induced inactivation was found to transform nonmonotonic photooxidation of P700, induced by far-red light in untreated leaves, into a fast and monotonic process completed within 1-s illumination. The short-term heating of leaves fully eliminated the fast component in the kinetics of P700⁺ dark reduction, related to operation of ferredoxin-dependent cyclic electron transport around PSI. At the same time, thermoinactivation substantially accelerated the slow and middle components of dark P700⁺ reduction, i.e., the components determined by arrival of electrons to PSI from reductants located in the chloroplast stroma. The latter effect was also observed after heating of leaves pretreated with antimycin A or methyl viologen; both agents are known to inhibit the ferredoxin-dependent electron transport. It is concluded that the heat treatment of leaves inhibits the ferredoxin-dependent pathway of electron transport around PSI and activates electron transport through alternative routes providing reducing equivalents to PSI from stromal reductants.