[Effects of thymus tissue transplantation on the survival of mice exposed to a lethal X-Ray dose.]

During the radiation exposure of the body, processes similar to those characteristic of the natural aging of mammals occur. This phenomenon is most often referred to as accelerated aging. By transplanting the thymus tissue, it is possible to achieve a normalization of food and water consumption, a stabilization of weight gain, and a significant increase in the life expectancy of experimental animals, even after their lethal irradiation.

Skin microcirculation reactivity to local thermal hyperaemia in patients with COVID-19 - A pilot observational study.

BACKGROUND: Endothelial dysfunction and microvascular disturbances are suggested to play a key role in higher morbidity and worse prognosis in patients with COVID-19 and cardiometabolic diseases. OBJECTIVE: Study was aimed to establish relationships between the skin microcirculation parameters and various clinical and laboratory indicators. METHODS: The study included 18 patients with moderate disease according to WHO criteria. Skin microcirculation measurements were performed by laser Doppler flowmetry using a heating test on the hairy skin of the right forearm. RESULTS: Baseline perfusion only correlated with C-reactive protein (Rs = 0.5, p = 0.034). Microcirculation indices characterising the development of hyperaemia during the first minute of heating (LTH1 and AUC60) showed significant correlations (Rs from 0.48 to 0.67, p < 0.05) with indices of general blood analysis and blood coagulation (fibrinogen, D-dimer, haemoglobin, erythrocyte count and haematocrit). Indexes characterising the dynamics of hyperaemia development over longer time intervals showed correlation with the glomerular filtration rate (Rs = 0.6, p = 0.009). CONCLUSION: Known COVID-19 risk factors (haemorheological parameters, age) are correlated with the microvascular reactivity to heating in patients with COVID 19. We suggest that, prospectively, the method of laser Doppler flowmetry could be used for non-invasive instrumental assessment of microcirculatory disorders in patients with COVID-19.

The Influence of Spatial Effects on the Dynamics of Solutions in Keynes' Mathematical Model of the Business Cycle.

We consider the special case of the mathematical model of Keynes' business cycle with the spatial interaction. In this model we assume that macroeconomic factors affect a certain geographical region and economic indicators. The dependence occurs on the spatial (geographical) coordinates in addition to the dependence on the temporal evolution, even if the economic subject is externally homogeneous in space. Spatial interaction led us to analyze a system of two differential equations of the 'reaction-diffusion' type, which replaces a system of two ordinary differential equations. This method is often used to analyze the dynamics of complex nonlinear systems and macroeconomic entities. An analysis of such a mathematical model is based on the use of modern methods of the theory of dynamical systems indicate the presence of new nonlinear effects in addition to those used in the traditional version of the Keynes model. We encountered the loss of stability of the homogeneous economic equilibrium state and the occurrence of economic cycles for some values of the parameters while investigating the characteristics of such a system. Meanwhile, another version of instability of a homogeneous economic equilibrium state with a different choice of parameters occurs, which in many cases leads to the appearance of a spatially non-homogeneous equilibrium state, which is characterized by the dependence of the corresponding economic indicators on the spatial (geographical) coordinates of the area in which the assigned macroeconomic entity is located.

Reactivity of skin microcirculation as a biomarker of cardiovascular events. Pilot study.

BACKGROUND: The role of microcirculatory disorders is progressively being accepted in the pathogenesis of cardiovascular diseases. OBJECTIVE: The purpose of current study is to assess whether we can consider skin microcirculation disorders as a biomarker of cardiovascular events. METHODS: Group 1 consisted of healthy volunteers (n = 31); group 2 (n = 42) consisted of patients with diseases that increase the risk of cardiovascular events; group 3 (n = 39) included patients with the history of cardiovascular events. Skin microcirculation measurement was performed using laser Doppler flowmetry during the heating test. RESULTS: LDF parameters reflecting the rapid response of microcirculation to heating ("Slope 120 s" and "Slope 180 s") significantly differed in three groups (p <  0.05). A decrease in the "Slope 180 s" parameter less than 0.5 PU/s is associated with cardiovascular events (sensitivity 69.2%, specificity 66.7%; the area under the ROC curve, 0.667; 95% confidence interval [CI], 0.545-0.788, p = 0.01). Multivariable logistic regression analysis revealed that "Slope 180 s≤0.5 PU/s" was significantly related to cardiovascular events (adjusted odds ratio = 3.9, p = 0.019, CI 95% 1.2-12). CONCLUSIONS: Reduced reactivity of the skin microcirculation may be useful as a biomarker of severe damage to the cardiovascular system and is promising as a risk factor for cardiovascular events.

[Correlation of cutaneous blood microcirculation parameters with biological age in diabetic patients.]

It has been established that the age together with the number of chronic diseases cause the decrease of the reactivity of the microcirculatory bed. This study aims to evaluate the relationship between cutaneous microcirculation parameters and biological and chronological age of patients with diabetes mellitus. 11 diabetic patients (median age 57 (51; 64) years) were examined in course of this study; biological age was figured by Aging.AI3.0 calculator. Cutaneous microcirculation parameters were measured by laser Doppler flowmetry with an occlusion-heating test. Spearman's rank correlation coefficients were calculated to analyze the relationships between quantitative parameters. Significant multiple negative correlations of biological age and microvascular reactivity indices on exposure to both heat and occlusion (correlation strength from -0,618, to -0,97, p<0,05) were found. Diabetic patients have decreased microvascular reactivity that is more associated with biological age than with chronological age.

Synchronization of Fluctuations in the Interaction of Economies within the Framework of the Keynes's Business Cycle Model.

In this paper, we will study two independent economies in a country (national, regional and urban), where the dynamics of fluctuations in each economy is described by Keynes's mathematical business cycle model. This is an interaction of two economies which include trade and competition. In the resulting system that consists of two independent economic entities, we show that fluctuations can emerge as two possible types of economic indicators (synchronous and antiphase) when the peaks and downturns of business activities in each of the economies are completely synchronized or on the contrary when the rise of one economy is accompanied by a recession (antiphase cycles). Our aim is to examine the stability question of solutions of the cognate mathematical model. Our analysis of the mathematical model will render methods of the theory of dynamical systems, such as the method of integral manifolds and the Poincare normal forms. This approach will provide a sufficient analysis of the dynamics of solutions of a system of differential equations, which is used as a mathematical model. Asymptotic formulas will be obtained for solutions that depict economic cycles.

Fibroin-Gelatin Composite Stimulates the Regeneration of a Splinted Full-Thickness Skin Wound in Mice.

The effects of composite fibroin-gelatin microparticles (100-250 µ) on the rate of wound healing and regeneration under conditions of contraction prevention were studied on the model of splinted full-thickness skin wound in a mouse. Subcutaneous injection of these particles into the defect area accelerated wound healing and promoted re-epithelialization and recovery of normal structure of the epidermis. In addition, the composite microparticles promoted the formation of connective tissue of characteristic structure, replacing the derma over the entire defect, and stimulated regeneration of subcutaneous muscle (panniculus carnosus) and skin appendages (sebaceous glands and hair follicles).

[Possible approaches to increase longevity of experimental animals.]

A statistically significant difference in the cumulative survival of Wistar rats born in different seasons has been shown: animals born in late November - early December had an average lifespan by 24,8% longer, a minimum lifespan by 14,3% longer, and a maximum lifespan by 20,7% longer in comparison with animals born in April. The geroprotective effect of the technique of thymus tissue transplantation into the immune privileged anterior chamber of the eye in animals born both in November and April has been shown.

Regeneration of jejunal wall defect using an implant based on silk fibroin fibers.

Regenerative properties of fibroin implant vitalized with allogeneic bone marrow cells were assessed. The study was performed using the experimental model of rat jejunum wall damage. Three weeks after surgery, we observed recovery of all layers of the jejunum wall at the site of injury and complete degradation of the implant material.

Osteogenic differentiation of mouse bone marrow stromal cells on fibroin microcarriers.

We investigated the proliferation and osteogenic differentiation of mesenchymal stem cells cultured on fibroin microcarriers. Effective cell proliferation on the surface of the microcarriers, determined by the large surface area, and the contribution of microcarrier mineralization to the stimulation of the osteogenic differentiation of mesenchymal stem cells was revealed.

New Silk Fibroin-Based Bioresorbable Microcarriers.

We fabricated bioresorbable microcarriers from water solution of Bombyx mori silk fi broin. The microcarriers are 3D structures with intricate surface and pores allowing penetration of culture medium, gas exchange, and cell adhesion. Fibroin molecules form hydrophobic structures and normally have a negative charge, which stimulates migration, but inhibits cell adhesion and makes it less effective. In order to improve adhesion efficiency and velocity, gelatin (hydrophilic biopolymer with integrin-recognizing RGD sequence) was added to the microcarrier composition. The resultant bioresorbable microcarriers support adhesion and proliferation of 3T3 murine fibroblasts.

Effects of allogenic fetal pancreatic tissue transplantation on regeneration of islet cells in recipient rats with alloxan-induced diabetes mellitus.

The linear parameters and number of Langerhans islets were evaluated in rats with alloxaninduced diabetes mellitus after transplantation of fetal pancreatic tissue to the anterior chamber of the eye. The islets significantly increased in size by week 3 after surgery and a trend to an increase in their number was observed.

[Fundamental bases for the use of silk fibroin-based bioresorbable microvehicles as an example of skin regeneration in therapeutic practice].

AIM: To assess whether silk fibroin-based microvehicles (MVs) may be used to grow fibroblasts (FBs) and keratinocytes (KCs), key cellular components in skin regeneration after injury. SUBJECTS AND METHODS: Cryogrinding was applied to derive MVs from fibroin-based and fibroin- and 30% gelatin-containing composite matrices. To examine the structure of the matrices and MVs, confocal microscopy was used to conjugate the polymer with the dye tetramethylrhodamine isothiocyanate. Microparticle size distribution was estimated by granulometric analysis. 3T3 mouse FBs and cultured primary mouse KCs expressing green fluorescent protein (GFP) were used to study whether fibroin-based MVs might be suitable for growing the cells involved in skin regeneration. KC growth was analyzed by confocal laser scanning microscopy from cellular GFP expression. The proliferation rate of FBs and KCs was estimated by a MTT assay. RESULTS: There were two derived MV types: fibroin-based and fibroin and 30% gelatin-containing composite ones. On day 1, 3T3 mouse FBs on the fibroin-based gelatin-free MVs actively proliferated and the presence of gelatin in MVs diminished the proliferation of these cells. Fibroin-based MVs were shown to be suitable for the effective in vitro growth of KCs expressing cytokeratins 5 and 14, the major markers of KCs in the basal layer. Gelatin did not give rise to accelerated KC growth. The investigation has demonstrated that is possible to regulate FB proliferation on MVs, which is of great importance in delivering the cells into the site of injury since intensive proliferation of FBs may lead to the development of fibrosis and the formation of scar tissue. Balanced FB growth is essential to the creation of optimal conditions for KC growth in composite tissue-engineering constructions. CONCLUSION: The use of fibroin-based MVs is promising for the design of novel therapeutic materials and injectable cell therapy for different diseases.

[Study of the accidental thymus involution during the formation of hierarchic communities by a novel physical method for recording the social stress].

A novel method for recording the aggressive behavior in newly formed hierarchic communities has been developed. A temporal and age-related dynamics of the accidental thymus involution in mammals has been studied.

[The increase of the average and maximum span of life by the allogenic thymic cells transplantation in the animals' anterior chamber of eye].

The effect of the allogenic thymic tissue transplantation in the immune-privileged anterior chamber of eye to the life expectancy of the recipient depending on its age was investigated. The thymic tissue transplantation from the young animals to the old ones leads to a significant increase in both the average and maximum life span of the recipient.

[Compensation of the rectum muscle dysfunction].

The possibility of compensating for the inborn pathology of the obturative apparatus of the rectum has been examined. An adequate experimental model of encopresis and a method of transplantological compensation of this pathological state have been developed.

[Atopically transplanted thymus tissues are capable of distantly changing the metabolic status of the body].

It has been found that the atopic transplantation of the thymus tissue from young animals in different variants is capable of significantly decreasing the rate of irreversible age-related atrophy of the thymus, which retards the age-dependent degradation of the T-cell unit of the immune system of the organism.