SPECIFICS OF GAS BUBBLE FORMATION AND GROWTH IN TISSUES DURING DECOMPRESSION AFTER SATURATION DIVES.

It is shown that the decompression schedule after saturation dives to a depth of 30 m designed to hold the nitrogen supersaturation for the most <> tissues at the acceptable levels is significantly shorter than the decompression schedules with zero supersaturation. of these tissues with nitrogen and all dissolved gases. Equality of the risk of decompression sickness (DCS) onset under this decompression schedule to the risk of DCS onset under the rapid ascent to the surface after saturation dives to a depth of 6.1 m indicates that the effect of the high ambient pressure decreases the concentration of seeds of gas bubbles in tissues and their subsequent growth rate. The DCS symptoms in experienced divers under dangerous decompression profiles not appear due to the lower concentration of gas bubble seeds in their tissues relatively to the average level inherent to the many of humans.

[Analysis of evolution of the size of decompression gas bubbles in diver tissues during schedules of medical recompression].

The mathematical model of gas bubble dynamics in body tissues was used for the analysis of evolution of their size during the treatment of decompression sickness in divers by means of recompression in accordance with RN table 72 and USN table 6A. It was shown that the duration of the process of bubble dissolution depends on the compression - decompression profile, as well on the initial size of a bubble, the oxygen content in the breathing mixture and the rate of nitrogen diffusion between a bubble and the surrounding tissue. The results of this study give the grounds to assume that the effect of recompression regimes used in the UK, USA and Russia promotes the treatment of DCS as a result of complete dissolution or significant reduction in the bubble sizes as well as due to therapeutic action of moderately hyperoxic breathing mixture on the tissues affected by bubbles.

[Simulation of tissue nitrogen supersaturation and the risk of tissue lesion by gas bubbles at non-stop dives].

The given study shows that a relationship between the coefficients of critical nitrogen supersaturation of theoretical tissues and the values of their nitrogen wash in and washout half-times can be mapped into a curve that goes around the family of curves that define the degree of tissue nitrogen supersaturation after extremely safe non-stop dives from the surface with air as breathing mixture. Our calculations of the growth dynamics of gas bubbles formed in theoretical tissues after these dives indicate that the sizes of tissue bubbles are not in themselves a measure of the risk of developing decompression sickness (DCS). At the same time, the original probabilistic model of the DCS proposed by us previously shows that the risk of lesion of any real tissue by bubbles and appearance of the appropriate DCS symptoms depends on the size of gas bubbles as well on their density and tissue volumes. The theoretical analysis of specific character for the risk of lesion of various body tissues by gas bubbles at equiprobable safe non-stop dives was carried out in the context of this model.

[Some problems of pathogenesis and clinical symptoms of atherosclerosis (coronary heart disease, hypertension) in the Far North].

Cardiovascular diseases now have a trend to greater prevalence in the direction from the South to the North. This trend is more pronounced in the North of Russia including Far East Federal Region. It is suggested that such trend is caused by different eating behavior responsible for increasing blood pressure in population from colder region, low temperature of the environment, chronic stress in conditions of the North. These risk factors aggravate standard risk factors which operate independently of the geographic region of living. Intensive industrial development of the North Far East regions of Russia demands introduction of effective measures of cardiovascular disease prophylaxis.

[Theoretical analysis of causes for prolonged delay of decompression sickness onset in divers].

The analysis of probable causes for anomalously prolonged latent time of developing decompression sickness in divers after completion of air dives was carried out in the content of the theory of formation and subsequent evolution of gas bubbles in body tissues. This phenomenon gives grounds to consider that certain of the decompression bubbles have a prolonged lifetime and gradually increase their affect on adjacent tissues. The main causes of increasing the lifetime of these bubbles are the increase of their sires due to the reduction of tissue perfusion during decompression and the coalescence them to one another, as well the encrustation of bubbles by a layer of intercellular fluid elements that reduces the rate of nitrogen diffusion from bubbles to tissues and retards their dissolution. The bubble layer decreases also the gas pressure inside bubbles due to reduction of the surface tension action of intercellular fluid that results in additional reduction of the diffusion flow of nitrogen from bubbles and the rate of their dissolution. Moreover, taken alone, the process of bubble layer formation seems as one of the main mechanisms of tissue lesions by gas bubbles.

[Theoretical analysis of recompression-based therapies of decompression illness].

Theoretical analysis is concerned with the benefits of oxygen, air and nitrogen-helium-oxygen recompression schedules used to treat decompression illness in divers. Mathematical modeling of tissue bubbles dynamics during diving shows that one-hour oxygen recompression to 200 kPa does not diminish essentially the size of bubble enclosed in a layer that reduces tenfold the intensity of gas diffusion from bubbles. However, these bubbles dissolve fully in all the body tissues equally after 2-hr. air compression to 800 kPa and ensuing 2-d decompression by the Russian navy tables, and 1.5-hr. N-He-O2 compression to this pressure followed by 5-day decompression. The overriding advantage of the gas mixture recompression is that it obviates the narcotic action of nitrogen at the peak of chamber pressure and does not create dangerous tissue supersaturation and conditions for emergence of large bubbles at the end of decompression.

[A theoretical estimation of the safety of dives culminating in an uninterrupted lifting].

It has been shown using the previously developed model of decompression sickness, which determines the cumulative probability of the development of the symptoms of this illness by the exponential equation whose index is the integral function of cumulative risk of damage to all body tissues by bubbles, Fcum(t) = SigmaFn(t), that underwater dives are practically safe if the function Fcum(t) during its growth will not exceed some small value Fcum-max = SigmaFn-max. Using the hypothetical values of parameters of tissues and functions Fn(t), the curves depth-duration for practically safe non-stop dives on respiration with air and with mixtures of oxygen with helium, neon, and argon have been calculated. The distributions of Fn-max values relative to the half-times of washout of the inert gas from tissues have been obtained, which show that the tissues that experience the largest risks of bubble lesions are different for dives of different duration. A comparison of the curves shows that the short-term dives with air are less dangerous and the long-term dives are more dangerous than the dives with helium-oxygen mixture. It has been shown that the least risk of bubble lesions of tissues arises on dives with neon-oxygen mixture and the greatest risk, on dives with argon-oxygen mixture.

[Thermodynamic forecasting of reagents composition for soils decontamination].

Based on thermodynamic studies, the authors conducted laboratory experiments on searching optimal composition of leaching reagents solution for soils decontamination, when contaminated with Cs-137, of activity coefficient for caesium sulfate microquantities in macrocomponents solutions. The method could be used for modelling the radionuclides phase equillibrium and relocations in soils.

[Modeling dynamics of decompression disease risk under high-altitude decompression].

The probabilistic model of the development of decompression disease was modified by introducing the corrections into its equation that refine the dependence of the risk of the injury of tissues by gas bubbles on their blood supply and the intensity of nucleation processes. The parameters of the "worst" virtual tissues and theoretical curves were determined that correspond to the empirical data on the cumulative probability of the development of decompression disease symptoms during some procedures of high-altitude decompression. It was shown that the parameters of these hypothetical tissues depend on the final pressure, the physical load, and the duration ofpreoxygenation. The ways of constructing a working hypothesis about the gradation of real body tissues with respect to the parameters determining the risk of their injury by bubbles and developing the method for the theoretical prognosis of the probability of development of decompression disease during any decompression procedure are discussed.

[Theoretical evaluation of the risk of decompression illness during simulated extravehicular activity].

Theoretical analysis of the risk of decompression illness (DI) during extravehicular activity following the Russian and NASA decompression protocols (D-R and D-US, respectively) was performed. In contrast to the tradition approach to decompression stress evaluation by the factor of tissue supersaturation with nitrogen, our probabilistic theory of decompression safety provides a completely reasoned evaluation and comparison of the levels of hazard of these decompression protocols. According to this theory, the function of cumulative DI risk is equal to the sum of functions of cumulative risk of lesion of all body tissues by gas bubbles and their supersaturation by solute gases. Based on modeling of dynamics of these functions, growth of the DI cumulative risk in the course of D-R and D-US follows essentially similar trajectories within the time-frame of up to 330 minutes. However, further extension of D-US but not D-R raises the risk of DI drastically.

[Growth dynamics and the largest size of gas bubbles emerging in body tissues due to decompression].

Symptoms of decompression sickness (DCS) develop when the total volume of gas bubbles due to decompression reaches the magnitude critical for a body tissue. Number of the bubbles is a function of random nucleation intensity before, during or after decompression and tissue superaeration dynamics, whereas their size is unambiguously dependent on a tissue, decompression phase and bubbling time. A mathematical model of bubble tissue dynamics has been proposed for calculating the dynamics of mathematical expectation of the total gas in tissues and mounting a method for comparative analysis of the maximal DCS probability as a result of implementation of different decompression tables. Unequal intensity of nucleation during spaceflight EVA and its ground simulation w/o spacesuit is the course of inequality of decompression safety of these operations.

Effects of heterogeneous structure and diffusion permeability of body tissues on decompression gas bubble dynamics.

To gain insight into the special nature of gas bubbles that may form in astronauts, aviators and divers, we developed a mathematical model which describes the following: 1) the dynamics of extravascular bubbles formed in intercellular cavities of a hypothetical tissue undergoing decompression; and 2) the dynamics of nitrogen tension in a thin layer of intercellular fluid and in a thick layer of cells surrounding the bubbles. This model is based on the assumption that, due to limited cellular membrane permeability for gas, a value of effective nitrogen diffusivity in the massive layer of cells in the radial direction is essentially lower compared to conventionally accepted values of nitrogen diffusivity in water and body tissues. Due to rather high nitrogen diffusivity in intercellular fluid, a bubble formed just at completion of fast one-stage reduction of ambient pressure almost instantly grows to the size determined by the initial volume of the intercellular cavity, surface tension of the fluid, the initial nitrogen tension in the tissue, and the level of final pressure. The rate of further bubble growth and maximum bubble size depend on comparatively low effective nitrogen diffusivity in the cell layer, the tissue perfusion rate, the initial nitrogen tension in the tissue, and the final ambient pressure. The tissue deformation pressure performs its conservative action on bubble dynamics only in a limited volume of tissue (at a high density of formed bubbles). Our model is completely consistent with the available data concerning the random latency times to the onset of decompression sickness (DCS) symptoms associated with hypobaric decompressions simulating extravehicular activity. We believe that this model could be used as a theoretical basis for development of more adequate methods for the DCS risk prediction.

Evaluation of safety of hypobaric decompressions and EVA from positions of probabilistic theory.

Formation and subsequent evolution of gas bubbles in blood and tissues of subjects exposed to decompression are casual processes in their nature. Such character of bubbling processes in a body predetermines probabilistic character of decompression sickness (DCS) incidence in divers, aviators and astronauts. Our original probabilistic theory of decompression safety is based on stochastic models of these processes and on the concept of critical volume of a free gas phase in body tissues. From positions of this theory, the probability of DCS incidence during single-stage decompressions and during hypobaric decompressions under EVA in particular, is defined by the distribution of possible values of nucleation efficiency in "pain" tissues and by its critical significance depended on the parameters of a concrete decompression. In the present study the following is shown: 1) the dimensionless index of critical nucleation efficiency for "pain" body tissues is a more adequate index of decompression stress in comparison with Tissue Ratio, TR; 2) a priory the decompression under EVA performed according to the Russian protocol is more safe than decompression under EVA performed in accordance with the U.S. protocol; 3) the Russian space suit operated at a higher pressure and having a higher "rigidity" induces a stronger inhibition of mechanisms of cavitation and gas bubbles formation in tissues of a subject located in it, and by that provides a more considerable reduction of the DCS risk during real EVA performance.

[Modification of the indirect hemagglutination test for rapid detection and identification of arbovirus antigens in brain suspensions from infected suckling mice]. / Modifikatsiia reaktsii nepriamoi gemaggliutinatsii dlia bystrogo vyiavleniia i identifikatsii arbovirusnykh antigenov v suspensiiakh mozga infitsirovannykh myshei-sosunkov

It has been found possible to use erythrocytes sensitized by antibody from immune ascitic fluids of white mice for detection and identification of arbovirus antigens in suspensions of brains from infected suckling mice. Nonspecific agglutination of sensitized erythrocytes by animal brain suspensions could be eliminated considerably by increasing NaCl concentration in the reaction ingredient mixture pu to 1.3 M. Specific hemagglutination by the virus antigens present in the brain suspensions was retained. The diagnostic titer of the test was 1:8. Preliminary addition of homologous immune globulin to the antigenic material specifically inhibited agglutination of sensitized erythrocytes.

[Experience with using the indirect hemagglutination reaction in studying natural foci of tick-borne encephalitis]. / Opyt primeneniia reaktsii nepriamoi gemaggliutinatsii pri izuchenii prirodnykh ochagov kleshchevogo éntsefalita.

Using the indirect hemagglutination test, tick-borne encephalitis (TBE) virus could be detected in the nutrient medium of the infected cell cultures, in brain suspensions of the infected suckling mice and in most specimens of suspensions of Ixodid ticks containing active virus. Positive results were obtained only with erythrocyte immunoglobulin diagnostic preparation to TBE virus but not with the diagnostic preparation for Omsk hemorrhagic fever. In the indirect hemagglutination inhibition test sera from human patients similarly inhibited antigens of tick-borne encephalitis and Omsk hemorrhagic fever.

[Detection of the antigens of the virus of Congo-Crimean hemorrhagic fever by solid-phase immunoenzyme analysis and by the indirect hemagglutination reaction]. / Vyiavlenie antigenov virusa Kongo-Krymskoi gemorragicheskoi likhoradki s pomoshch'iu tverdofaznogo immunofermentnogo analiza i reaktsii nepriamoi gemaggluitinatsii.

From a batch of immunoglobulin to Crimean-Congo hemorrhagic fever virus, an immunosorbent and a conjugate with peroxidase (RZ-2.7) for solid-phase enzyme immunoassay (EIA) as well as erythrocyte diagnostic preparation for indirect hemagglutination test (IHA) were obtained. Direct EIA and IHA were used to study the time course of accumulation of virus antigen in brain tissue of newborn white mice. Antigen titres by EIA were 4-8 times as low as by IHA. No functional relationship was found between antibody titres and those of infectious virus.

[Rapid solid-phase immunoenzyme analysis for detecting viral antigens]. / Tverdofaznyi immunofermentnyi ékspress-analiz dlia obnaruzheniia virusnykh antigenov.

A method of rapid direct solid-phase enzyme immunoassay cutting the time of the test down to 50 min has been developed using immunoglobulin from mouse immune ascitic fluid to Crimean-Congo hemorrhagic fever virus.

[Determination of arbovirus group affiliation in the indirect hemagglutination reaction]. / Opredelenie gruppovoi prinadlezhnosti arbovirusov v reaktsii nepriamoi gemaggliutinatsii

A dry polyvalent erythrocyte immunoglobulin diagnostic preparation for arboviruses of Group B may be prepared to be used in the indirect hemagglutination test. The preparation detects antigens of arboviruses of this group in the tissue culture fluid and in suckling mouse brain tissue treated with sucrose-acetone. The test with Group B arbovirus antigens is inhibited specifically by the homologous polyvalent immune gamma globulin. Inhibition of hemagglutination by species-specific immune globulins to individual members of Group B arboviruses permits typing of tick-borne encephalitis birus only. In making the erythrocyte diagnostic preparation, the optimal concentration of the sensitizing immune gamma globulin should be determined experimentally.

[A natural focus of sandfly fever in the Republic of Afghanistan]. / O prirodnom ochage moskitnykh likhoradok v Respublike Afganistan.

The serological study of persons contacting dengue-like fever in 1987 in Afghanistan (in Rukha, Parwan Province) revealed that in 74% of cases an increase in the titers of antibodies to Sicilian and Neapolitan sandfly [correction of mosquito-borne] fever viruses was registered. Considering that such diseases appeared here for a number of years and were linked in time with the activity of sandflies [correction of mosquitoes] of the species Phlebotomus papatasii, the suggestion was made on the existence of a stable natural focus of sandfly [correction of mosquito-borne] fevers in the region of Rukha.