Chromatin-nuclear envelope complex from rat liver: isolation and purification

We describe a method for the isolation of a fraction of nuclear envelope (NE) from rat liver. The method includes mild treatment of pure nuclei with either endonuclease of DNase I under low ionic strength conditions in the presence of magnesium, which allows the nucleomeric organization of the chromatin (Ch) to be preserved. The NEs were purified by centrifugation in sucrose gradients followed by floatation in sucrose. No more than 3% of the Ch present in the purified Ch-NE complexes was due to the non specific adsorption of Ch to the NE. The main components of the complex (Ch and NE) retained their in situ ultrastructure. The complex consisted of 9--10% DNA, 3--4% RNA, about 63% protein and about 24% phospholipids.     

Physiological Mechanisms of the Effectiveness of Bilateral Stereotactic Cingulotomy against Strong Psychological Dependence in Drug Addicts

It is now generally believed that psychological dependence in drug addicts is determined not only socially, but also physiologically. At the Institute of the Human Brain (Russian Academy of Sciences), bilateral stereotactic cryocingulotomy has been used for treatment of drug addiction since 1998. To date, the surgery has been performed on 348 patients, which has made it possible to study long-term consequences of the surgery, perform the necessary psychological studies, and summarize the results. Interviewing of 187 patients with catamneses of more than two years has shown that 45% of them have entirely abstained from addictive drugs after the surgery and 17% have entirely abstained from drugs for more than two years after one or two instances of drug-taking within the first two months after the surgery; there are no data on 13% of the patients. The remaining patients exhibit either a partial improvement (they have found at least temporary work and have decreased the drug dosage and the frequency of intake) or show no change (13 and 12% of the cases, respectively). The results of catamnestic study have demonstrated that the surgery is effective against heroinism and rarely causes complications. Apparently, the physiological mechanism of the therapeutic effect is the suppression of the mechanism of error detection. The duration of the resultant destabilization may vary depending on the individual characteristics of the patient and environmental factors. Therefore, this period should be included in the duration of treatment and patients must follow the rehabilitation regimen.     

Role of DNA methylation and histone modifications in structural maintenance of heterochromatin domains (chromocenters)

Effects of DNA methylation inhibitor; 5-azacytidine (5-aza-C); and histone acetylation inhibitor, trichostatine A (TSA), on the structure of pericentric heterochromatin of L929 mouse cells have been studied. 5-aza-C treatment for 48 h resulted in the transformation of ovoid chromocenters into elongated structures in 85% of cells. Hypotonic treatment of these cells reveals tandemly arranged DAPI-positive globules that are well distinguishable by light microscopy. Similar globular units can be observed in hypotonic-treated control cells. TSA treatment for 48 h causes dramatic decrease in HP1α content in cells. In 25% of treated cells chromocenters became highly decondensed and can not be reliably detected by light and electron microscopy. 85% cells demonstrate globular chromocenters with low HP1α content. Hypotonic treatment induces transformation of compact chromocenters into ring-like structures that can be either single or clustered. Rings are formed by uniform fiber in which no globular subunits are detected. The data obtained are discussed concerning several mechanisms of heterochromatin structure maintenance and the role of epigenetic factors.     

Crystal structure of carboxypeptidase T from Thermoactinomyces vulgaris.

The crystal structure of carboxypeptidase T from Thermoactinomyces vulgaris has been determined at 0.235-nm resolution by X-ray diffraction. Carboxypeptidase T is a remote homologue of mammalian Zn-carboxypeptidases. In spite of the low degree of amino acid sequence identity, the three-dimensional structure of carboxypeptidase T is very similar to that of pancreatic carboxypeptidases A and B. The core of the protein molecule is formed by an eight-stranded mixed beta sheet. The active site is located at the C-edge of the central (parallel) part of the beta sheet. The structural organization of the active centre appears to be essentially the same in the three carboxypeptidases. Amino acid residues directly involved in catalysis and binding of the C-terminal carboxyl of a substrate are strictly conserved. This suggests that the catalytic mechanism proposed for the pancreatic enzymes is applicable to carboxypeptidase T and to the whole family of Zn-carboxypeptidases. Comparison of the amino acid replacements at the primary specificity pocket of carboxypeptidases A, B and T provides an explanation of the unusual 'A+B' type of specificity of carboxypeptidase T. Four calcium-binding sites localized in the crystal structure of carboxypeptidase T could account for the high thermostability of the protein.     

Mechanisms of the adaptation of the Kildin cod <Emphasis Type="Italic">Gadus morhua kildinensis</Emphasis> Derjugin, 1920 (Pisces: Gadidae) to the specific conditions of Lake Mogilnoye

The mechanisms of the adaptation of the Kildin cod to the conditions of a meromictic lake were analyzed based on the study of morphological, biological, and genetic characteristics. Significant differences between the Kildin cod and Atlantic cod have been found in their morphological and genetic characteristics. The results of an X-ray microanalysis of otoliths, which were conducted for the first time, confirm that the distribution range of the Kildin cod in Lake Mogilnoye also extends to brackish waters. It has been shown that the formation of the reproductively isolated lacustrine population of Kildin cod is accompanied by specialization in a number of characteristics (body color, feeding strategy, behavior, etc.) and by a decrease in genetic diversity.     

Desynchronization and synchronization of EEG related to stimuli triggering or forbidding sensory-motor reaction in adolescents: II. The peculiarities in case of the attention deficit and hyperactivity syndrome

Evoked desynchronization and synchronization of EEG in θ (4–7.5 Hz), α (7.5–14 Hz) and β (14–20 Hz) ranges were recorded by 19 electrodes in healthy volunteer adolescents and those with attention deficit hyperactivity syndrome in the modified GO/NO-GO test. Two stimuli (high and low tone) were presented in pairs with 1 s intervals inside the pair and 1.5 s intervals between the pairs. Test subjects had to push the button in response to presentation of a pair of high tones and to ignore other stimulus combinations. The components of evoked EEG synchronization in α-θ range that were revealed in the frontocentral and temporoparietal brain regions in connection with inhibition of action (inhibition of movements and making a decision to cancel sensory-motor task performance) were statistically significantly lower in subjects with attention deficit hyperactivity disorder compared with that in healthy subjects.     

Synergistic effects of mycelial fungus (Pleurotes ostreatus) extracts and some cytostatic drugs on proliferation and apoptosis in transformed human cells

Effects of mycelial fungus (Pleurotes ostreatus) extracts used separately and in combination with the cytostatic drugs doxorubicine and cyclophosphamide on cultured transformed human cells (HeLa and myeloid leukemic cells) were investigated. Cell viability was assessed by calculating mitotic and apoptotic indexes and other characteristics of dividing cells. The functional status of cell membranes was estimated by staining with Trypan blue. Individual application of mycelium extracts failed to induce apoptosis, but caused abnormal segregation of chromosomes in metaphase cells and formation of chromosome bridges in anaphase and telophase. Combined application of P. ostreatus extracts and cyclophosphamide produced pronounced synergistic effect, which depended on reagent concentration and treatment protocol and was manifested in partial suppression/enchancement of cell proliferation and in drastic increase of the apototic index. The data obtained are discussed within the framework of a hypothesis on intracellular targets for P. ostreatus extracts.