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.

[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.

[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.

[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.

[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.

[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.

[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.

[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.

[Cytokinin inducing and antiviral activity of cycloferon on experimental herpetic infection]. / Tsitokinindutsiruiushchaia i protivovirusnaia aktivnost' tsikloferona pri éksperimenta'noi gerpeticheskoi infektsii.

Experimental data on the protective activity and the capacity for inducing the biosynthesis of some cytokins, the low molecular inductors of cycloferon, endogenic interferon of the acridanon group, in herpetic infection are presented. The herpes infection was modelled by intraperitoneal injection of herpes simplex virus, type 1 into BALB/c mice. In the animals with normal immune status cycloferon induced the formation of serum interferon (INF) in high titers (up to 1:20,000) with the peak achieved 4-8 hours after the injection of the preparation. In addition, cycloferon stimulated the synthesis of IL-2 and gamma INF, but decreased the concentration of IL-1b. Following immunosuppression caused by gamma-radiation or cyclophosphamide the titers of serum interferon decreased 4-8 times. In generalized herpes infection in non-inbred white mice with undamaged immune status cycloferon increased survival rate by 30-100% in comparison with the controls (untreated mice), while in case of immunosuppression the protective effect of this preparation was considerably lower. In infected mice the concentrations of gamma INF, IL-2, IL-1b were found to be elevated in comparison with their concentrations in healthy animals. In the course of the infectious process cycloferon suppressed the production of IL-2 and IL-1b, but did not influence the synthesis of gamma INF.