Interaction between particles with inhomogeneous surface charge distributions: Revisiting the Coulomb fission of dication molecular clusters.

An analytical solution describing the electrostatic interaction between particles with inhomogeneous surface charge distributions has been developed. For particles, each carrying a single charge, the solution equates to the presence of a point charge residing on the surface, which makes it particularly suitable for investigating the Coulomb fission of doubly charged clusters close to the Rayleigh instability limit. For a series of six separate molecular dication clusters, center-of-mass kinetic energy releases have been extracted from experimental measurements of their kinetic energy spectra following Coulomb fission. These data have been compared with Coulomb energy barriers calculated from the electrostatic interaction energies given by this new solution. For systems with high dielectric permittivity, results from the point charge model provide a viable alternative to kinetic energy releases calculated on the assumption of a uniform distribution of surface charge. The equivalent physical picture for the clusters would be that of a trapped proton. For interacting particles with low dielectric permittivity, a uniform distribution of charge provides better agreement with the experimental results.

High-resolution NMR structure of the antimicrobial peptide protegrin-2 in the presence of DPC micelles.

PG-1 adopts a dimeric structure in dodecylphosphocholine (DPC) micelles, and a channel is formed by the association of several dimers but the molecular mechanisms of the membrane damage by non-α-helical peptides are still unknown. The formation of the PG-1 dimer is important for pore formation in the lipid bilayer, since the dimer can be regarded as the primary unit for assembly into the ordered aggregates. It was supposed that only 12 residues (RGGRL-CYCRR-RFCVC-V) are needed to endow protegrin molecules with strong antibacterial activity and that at least four additional residues are needed to add potent antifungal properties. Thus, the 16-residue protegrin (PG-2) represents the minimal structure needed for broad-spectrum antimicrobial activity encompassing bacteria and fungi. As the peptide conformation and peptide-to-membrane binding properties are very sensitive to single amino acid substitutions, the solution structure of PG-2 in solution and in a membrane mimicking environment are crucial. In order to find evidence if the oligomerization state of PG-1 in a lipid environment will be the same or not for another protegrins, we investigate in the present work the PG-2 NMR solution structure in the presence of perdeuterated DPC micelles. The NMR study reported in the present work indicates that PG-2 form a well-defined structure (PDB: 2MUH) composed of a two-stranded antiparallel ß-sheet when it binds to DPC micelles.

[Structure of amyloid-beta peptides in a complex with model membranes].

Structures of amyloid-beta peptides Aß1-40, Aß10-35, Aß13-23 and Aß16-22 in a complex with model membranes in solution were obtained on the analysis of NMR experimental data. It has been established that the process of peptide-micelle complex formation occurs through the amino acid residues L17, F19, F20 and G29-M35.

[Objectivization of the choice of the amputation level in patients with lower limb critical ischaemia].

The authors compared the informative value of the intraoperative criteria for assessing viability of muscles in high amputations of limbs for chronic critical ischaemia. It was revealed that such signs as subjectively evaluated bleeding, contractility and oedema of muscles possess low specificity in relation to the development of early postoperative complications. Intraoperative macroscopic histochemical study (IHCS) of the activity of muscular tissue lactate dehydrogenase at the level of amputation showed sensitivity of 96,3% and specificity of 92,9 %. Taking into consideration the results of IHCS for objectivization of the choice of the level of amputation made it possible to save the knee joint in 8,9 % of patients with gangrene on the background of high occlusion of lower limb arteries and to decrease the frequency of postoperative necrosis of muscle of the stump from 15,0% to 3,5%.

[Intra-operative histochemical detection of vitalized muscular tissue during lower limb amputation for chronic critical ischemia].

Direct results of 747 lower limb amputations for chronic critical lower limb ischemia were analyzed. Early postoperative complications were observed in 45,1% of cases. Among them 45,4% were caused by tissue ischemia. Basing on detection of lactate dehydrogenase activity in muscular tissue method of intra-operative evaluation of tissue ischemia at the level of amputation is proposed. Relationship between this index and frequency of early postoperative complications is proved.

Lateral diffusion in sphingomyelin bilayers.

Sphingomyelin (SM) is an important lipid of eukaryotic cellular membranes and neuronal tissues. We studied lateral diffusion in macroscopically oriented bilayers of synthetic palmitoylsphingomyelin (PSM) and natural sphingomyelins of egg yolk (eSM), bovine brain (bSM) and bovine milk (mSM) by pulsed field gradient NMR (PFG NMR) in the temperature range 45-60 °C. We found that the mean values of lateral diffusion coefficients (LDCs) of SMs are 1.9-fold lower compared with those of dipalmitoylphosphatidylcholine (DPPC), which is similar in molecular structure. This discrepancy could be explained by the characteristics of intermolecular SM interactions. The LDCs of different SMs differ: egg SM is most similar to PSM; both of them have a 10% higher LDC value compared with the other two natural SMs. Besides, all natural SMs show a complicated form of the spin-echo diffusion decay (DD), which is an indicator of a distribution of LDC values in bilayers. This peculiarity is explained by the broad distributions of hydrocarbon chain lengths of the natural SMs studied here, especially mSM and bSM. We confirmed the relationship between chain length and LDC in the bilayers by computer analysis of a set of (1)H NMR spectra obtained by scanning the value of the pulsed field gradient. There is a correlation between lower LDC values and SM molecules with longer acyl chains. The most probable mechanisms by which long-chain SM molecules decrease their lateral diffusion relative to the average value are protrusion into the other side of the bilayer or lateral separation into areas that diverge with their LDCs.

[Effectiveness of new diagnostic drug Diaskintest in children for tuberculosis diagnostic].

DST was ascertained to have a high sensitivity in virtually all patients with tuberculosis and a positive reaction was first noted in the infected. With stabilization and regression, the response to DST was much less pronounced than that in clinical and primary infection (that to the Mantoux test being more evident). DST showed its use as a marker of active tuberculosis not only in its local forms, but also in latent tuberculous infection. This makes it possible to apply DST when preventive treatment is performed. The agent may be used to monitor the progress of treatment. DST has a high specificity--healthy individuals had a negative response to DST while the Mantoux test was positive in many cases. The high specificity of DST was suggested by the fact that the persons vaccinated with (this caused BCG ostitis) had a negative reaction to DST while the Mantoux test was positive in all cases BCG-vaccinated BCG. The findings warrant the use of DST for the differential diagnosis of tuberculosis and BCG-associated complications and the possibility of differentiating postvaccinal and infection allergy in children and adolescents.

[An NMR study of the temperature dependence of the coefficient of water self-diffusion through lipid bilayer membranes].

The temperature dependence of the coefficient of water self-diffusion through plane-parallel lipid multilayers of the phospholipid dioleoylphosphatidylcholine oriented on a glass support has been studied in the temperature range of 20-60 degrees C by the method of NMR with magnetic field pulse gradient. The values of the coefficients of transbilayer water diffusion are by four orders of magnitude less than for bulky water and ten times less than the coefficients of lateral diffusion of the lipid under the same conditions. The temperature dependence of the coefficient of water diffusion is described by the Arrhenius law with an apparent activation energy of about 41 kJ/mol, which far exceeds the activation energy for the diffusion of bulky water (18 kJ/mol). The experimental data were analyzed using a "dissolving-diffusion" model, by simulating the passage of water through membrane channels, and by analyzing the exchange of water molecules in states with different modes of translation mobility, including pore channels and bilayer "defects". Each of the approaches used made it possible to take the significance of bilayer permeability for the apparent energy of activation of water diffusion into account and estimate the energies of activation of water diffusion in the hydrophobic moiety of the bilayer, which were found to be close to the values for bulky water. The coefficients of water diffusion in the system under examination and the coefficients of permeation of water through the bilayer were estimated, and the effect of bilayer "defects" on the coefficients of water diffusion along and across bilayers was studied.

[Comparative analysis of tuberculosis morbidity in children and adolescents from Moscow and the Penza Region].

Tuberculosis morbidity was comparatively analyzed in the children and adolescents of Moscow and the Penza Region. The epidemiology of tuberculosis in the children and adolescents was established to be universal in the compared regions in the study period. This manifested itself as a stable tendency for higher morbidity rates (MR), increased incidence of destructive tuberculosis, inadequate use of the existing methods for active detection of tuberculosis in these age groups, and, among those who had fallen ill with this disease, an increase in the number of persons from the foci of tuberculous infection and persons with established contact with patients with tuberculosis. Along with a steady MR growth for tuberculosis among the children and adolescents, there has been a quantitative modification to the proportion of all epidemiologically hazardous forms of tuberculosis, such as the bacillary and destructive forms of pulmonary tuberculosis complicated by extrapulmonary tuberculosis. Hypodiagnosis of tuberculous pleurisy and extrapulmonary tuberculosis has been recently noted in the general health care network. The analysis also leads to the conclusion that the quality of mass tuberculin diagnosis remains poor. In both regions, general pediatricians are not adequately alert to tuberculosis, extrapulmonary tuberculosis in particular. With a rise in tuberculosis endemic, the incidence of tuberculosis in 18-21-year-old persons is 2-3 times greater than that in adolescents, which is associated with the greater activity of this population group and with the underdetection of the asymptomatic forms of tuberculosis in adolescents.

[State of water and its diffusion across lipid bilayers: effect of hydration degree].

The state of adsorbed water (estimated from the dependence of the shape of the 1H NMR spectrum on the angle between the normal to the bilayers and the direction of the magnetic field) and the diffusion of water molecules in the direction of the normal to the bilayers (estimated by 1H NMR spectroscopy with the impulse gradient of magnetic field) in microscopically oriented dioleoylphosphatidylcholine bilayers have been studied depending on hydration. The dependences of the shape of the NMR spectrum on angle differ qualitatively only at concentrations of water greater and less than the concentration that is achieved upon hydration from saturated vapors chi(eq) (about 23 weight %). At concentrations below chi(eq), all water present in samples enters the hydrate shells of polar "heads" of lipids or is in the state of "rapid exchange" with the water of hydrate shells, with the result that the signal of spin echo for water is observed only in a narrow range of angles close to the "magic angle", 54 degrees C. At concentrations above xhi(eq), the signal of spin echo for water is retained at all orientations, indicating probably that part of water between the bilayers ("quasi-free water") is in the state of a "slow exchange" with water "bound" to polar "heads". It was found that the coefficient of self-diffusion of water across the system of bilayers inversely depends on the degree of hydration, which is described in the Tanner model with consideration of the self-diffusion of water molecules in the hydrophobic moiety of the bilayer. The permeability of the bilayer, the coefficient of distribution of molecules between the water and lipid phases, and the coefficient of self-diffusion of water in the hydrophobic moiety of the bilayer were estimated.

[Lateral diffusion of saturated phosphatidylcholines in cholesterol-containing bilayers].

Lateral diffusion in oriented bilayers of saturated cholesterol-containing phosphatidylcholines, dipalmitoylphosphatidylcholine and dimyrilstoylphosphatidylcholine upon their limiting hydration has been studied by NMR with impulse gradient of magnetic field. For both systems, similar dependences of the coefficient of lateral diffusion on temperature and cholesterol concentration were observed, which agree with the phase diagram showing the presence of regions of ordered and unordered liquid-crystalline phases and a two-phase region. Under similar conditions, the coefficient of lateral diffusion for dipalmytoylphosphatidylcholine has lower values, which is in qualitative agreement with its greater molecular mass. A comparison of data for dipalmytoylphosphatidylcholine with the results obtained earlier for dipalmytoylsphyngomyelin/cholesterol under the same conditions shows, despite a similarity in phase diagrams, greater (two- to threefold) differences in the values of the coefficient of lateral diffusion and a different mode of dependence of the coefficient on cholesterol concentration. A comparison of data for dimyrilstoylphosphatidylcholine with the results obtained previously shows that the values of the coefficient of lateral diffusion and the mode of its dependence on cholesterol concentration coincide in the region of higher concentrations (more than 15 mole %) and differ in the region of lower concentrations (below 15 mole %). The discrepancies may be explained by different contents of water in the systems during the measurements. At a limiting hydration (more than 35%) of water, the coefficient of lateral diffusion decreases with increasing cholesterol concentration. If the content of water is about 25% (as a result of equilibrium hydration from vapors), the coefficient of lateral diffusion of phosphatidylcholine is probably independent of cholesterol concentration. This results from a denser packing of molecules in the bilayer at a lower water concentration, an effect that competes with the ordering effect of cholesterol.

[Preoperative diagnosis of metastatic involvement of perirectal lymph nodes]. / Preoperatsionnaia diagnostika metataticheskogo porazheniia perirektal'nykh limfaticheskikh uzlov.

Condition of perirectal lymph nodes was examined by endorectal sonography in 93 patients with rectal cancer prior to surgery. Precision of diagnosis of involvement by endorectal sonography was 62.5% and depended on the size of lymph node. There was a sizable correlation between the sensitivity of the procedure and the number of involved lymph nodes: it reached 80% when 3 or more nodes were involved. Preoperative assessment of the perirectal lymph nodes helped correct the extent and procedure of operation.

Crystallisation of crystallizable and amorphous polymer mixtures and peculiarities of their structure: an NMR study.

After isothermal crystallization of the crystallizable poly(ethylene oxide)/amorphous poly(propylene oxide) mixture, partially crystalline structures were formed. They present a specific heterogeneous medium with a hard frame composed of the crystal phase. The isothermal crystallization of the mixture and molecular self-diffusion processes in the amorphous phase of the crystallized mixture was studied by nuclear magnetic resonance relaxation and nuclear magnetic resonance (NMR) with pulsed field gradient. The temporal dependencies of the apparent self-diffusion coefficient were analyzed and the heterogeneity sizes were estimated. The dependence of the heterogeneity size on the crystallization temperature can be qualitatively described by parameter delta, which includes the linear growth rate of the crystal and diffusion coefficient of the amorphous (more mobile) component.

Crystallization of poly(ethylene oxide) confined in pores of active carbon.

The kinetics of isothermal crystallization of poly(ethylene oxide) confined in pores of active carbon was studied by nuclear magnetic resonance relaxation. At equal temperatures the induction period of crystallization in pores differs from that in the bulk polymer. A model was developed that allows estimation of the effect of porous media on the statistical sum of the macromolecule considering the change of the polymer chain conformation in the melt. This model describes the following observed effects: invariability of the induction period temperature dependence in pores, the weak temperature dependence of the ratio of induction period for e bulk, and pore material. The change in the induction period in cylindrical pores was predicted with satisfactory precision.

[The functional results of abdomino-anal resection of the rectum with the formation of a reservoir from the large intestine]. / Funktsional'nye rezul'taty briushno-anal'noi rezektsii priamoi kishki s formirovaniem tolstokishechnogo rezervuara.

Under study were clinical and functional results of 27 patients aged 36 to 68 years with adenocarcinoma (pT2-T3) of the ampullar part of the rectum who were submitted to abdomino-anal resection with the formation of J-shaped colonic reservoir. In the nearest postoperative period partial incompetence of the coloanal anastomosis, necrosis of the reservoir wall and its inflammation appeared in 4 patients. In 6 months after closure of the protective transversostomy full continence was noted in 24 patients. In 3 patients only there was a periodic incontinence of liquid stools and flatus. The formation of J-shaped colonic reservoir in patients requiring the formation of low colorectal or coloanal anastomoses gives considerably better functional results of total resection of the rectum.

[The diagnosis and treatment of Dieulafoy's syndrome]. / Diagnostika i lechenie sindroma D'elafua.

Dieulafoy's lesion is one of numerous causes of acute gastrointestinal bleedings. A prospective study of the Dieulafoy lesion were carried out from 1989 till 1995. Under study there were 8 patients. Acute Dieulafoy ulcers are most often localize in the upper third of the stomach and cause massive bleedings. The authors consider urgent laparotomy with gastrotomy, dissection of the ulcer and suturing the vessel to be the operation of choice.

[Tuberculin-BCG therapy in combined treatment of patients with pulmonary tuberculosis]. / Tuberkulin-BTsZh-terapiia v kompleksnom lechenii bol'nykh tuberkulezom legkikh.

The efficacy of combined use of tuberculin and BCG vaccine (tuberculin-BCG-therapy) given to 70 patients with new-onset and recurrent pulmonary tuberculosis was compared to that of BCG treatment only received by 24 patients. Bacterial discharge and caverns were registered in 80 and 78 patients, respectively. 25 patients underwent stimulating, 37, 8 paradoxical tuberculin-BCG-therapy. BCG vaccine (1-4 injections) was given 2 weeks after the course of individual tuberculin therapy with the low efficacy of the latter. Tuberculin-BCG-therapy produced marked response in 52 patients against 11 responses on BCG only, increased the number of T-lymphocytes and T-helpers. It is concluded that the above combination improves regulation of an immune response by cellular mechanisms.

[The hemostatic effect of vagotomy in acute gastroduodenal ulcers complicated by massive hemorrhage]. / Gemostaticheskii éffekt vagotomii pri ostrykh gastroduodenal'nykh iazvakh, oslozhnennykh massivnym krovotecheniem.

The clinico-experimental investigation has shown high efficiency of the bilateral subdiaphragmatic truncal vagotomy in treatment of patients with acute gastroduodenal ulcers complicated by massive hemorrhage. The haemostatic effect of the operation is related to the inhibited acid gastric secretion, proteolytic activity of the intragastric content as well as to the activation of serotonin-containing cells and increased tonus of the sympathetic nervous system, which is responsible for gastric vessel spasm, shortens time of bleeding, increases the amount of thrombocytes and their aggregation. When vagotomy with interventions draining the stomach is not possible, suturing (dissection) of bleeding acute ulcers is recommended in combination with prolonged novocain blockade of vagus nerves.