21 research outputs found
Antioxidant status and hypoxia severity in various compensatory-adaptive reaction types among young men with mitral valve prolapse
No full textAim. To assess antioxidant system (AOS) enzyme activity and red blood cell hypoxia severity, according to compensatory-adaptive reaction type in young men with mitral valve prolapse (MVP). Material and methods. In 137 young men with MVP, red blood cell activity of catalase (C), glutathione reductase (GR), superoxide dismutase (SOD), lactate, pyruvate concentration, lactate/pyruvate (L/P) coefficient were measured by standard methods, together with cardiohemodynamic parameters. Results. In Group I (high compensatory-adaptive potential), L/P was 2,2 times higher than in controls. In Group II (decreased compensatory-adaptive potential), this parameter was higher than in controls by 14,6% (p<0,05). In Group I, L/P was higher than in Group II by 93,8% (р<0,05). Comparing to control group, in Group I, C activity was 3,26 times lower, and SOD and GR activity was 3,99 and 2,03 times higher (p<0,05). C activity was 4,59 times lower, and SOD and GR activity was 6,23 and 1,85 times higher than in controls (p<0,05). In Group I, comparing to Group II, C and SOD activity was higher by 40,6% and 58,5%, respectively (p<0,05). Conclusion. In MVP patients, first-line AOS dysbalance and glutathionedependent mechanism strain were more manifested in Group II. Red blood cell aerobic metabolism predominance was of adaptive nature in Group I, being a factor of cell and tissue damage in Group II
Clinical and Diagnostic Significance of Measurement of Blood Activity of Endopeptidases and Their Inhibitors in Youths with Mitral Valve Prolapse
No full textCombination of magnesium and pyridoxine: effects on hemostasis in young men with primary mitral valve prolapse
No full textAim. To study the prevalence and severity of hemostasis disturbances in young men with mitral valve prolapse (MVP) and reduced compensatory and adaptive organism potential; to assess corrective therapy variants.Material and methods. In 500 young men with MVP, 16 hemostasis parameters were studied by standard methods. Among patients with reduced compensatory and adaptive potential (n=73), the combination of magnesium and pyridoxine (2 tablets 3 times per day for one month) was administered to correct functional and metabolic disturbances.Results. At baseline, platelet (PL) functional activity was 16,9 % higher than in control group. The number of spontaneous PL aggregates was 5,8 times higher, disaggregation — 47,6 % lower, and levels of paracoagulation products (fibrinogen B, fibrin-monomer complexes, soluble fibrin) — by 6,7, 4,28 and 5,3 times higher, respectively, than in controls. Reduced concentration of endogenous heparin (-94,5 %; p<0,001) and decreased antithrombin III production (-14,3 %) pointed to suppression of endogenous anticoagulant protection system. Concentrations of fibrinogen-heparin and fibrin degradation products were higher than normal levels by 2,58 and 3,38 times, respectivel. Hematocrit was 15,8 % higher, free red blood cell sedimentation — 16,4 % lower, and red blood cell aggregation — 18,64 times higher than in the control group. Therapy reduced blood coagulation potential and increased endogenous heparin activity, with parallel activation of enzyme fibrinolysis.Conclusion. Magnesium and pyridoxine therapy improved hemostasis parameters investigated. The absence of clear effect on blood rheology warrants additional administration of agents actively improving microcirculation in young men with MVP
Buckling of Rectangular Plates under Nonlinear Creep
No full textIntroduction. The task of analyzing the stability of plates and shells under creep conditions is critical for structural elements made of materials with the property of aging, which are under the action of long-term loads, since the loss of stability can occur abruptly and long before the exhaustion of the strength resource of the material. Currently, the issues of joint consideration of geometric nonlinearity and creep in the problems of buckling plates remain poorly studied, existing software systems do not provide such calculations. The objective of this work is to develop an algorithm for calculating the stability of rectangular plates with initial deflection, which are subjected to loads in the middle plane, taking into account geometric nonlinearity and creep.Materials and Methods. When obtaining the resolving equations, the geometric and static equations of the theory of flexible elastic plates were taken as the basis. Physical equations were derived from the assumption that total strains were equal to the sum of elastic strains and creep deformations. Finally, the problem was reduced to a system of two differential equations, in which the desired functions were the stress and deflection functions. The resulting system of equations was solved numerically using the finite-difference method in combination with the method of successive approximations and the Euler method. As the boundary conditions for the stress function, the frame analogy was used, as in the case of a plane problem of elasticity theory.Results. The solution to the problem for a plate compressed in one direction by a uniformly distributed load has been presented. The nature of the growth of displacements at different load rates and initial deflection was studied. It has been established that when the vertical displacements reach values comparable to the thickness of the plate, their growth rate begins to decay even at a load greater than the long-term critical one.Discussion and Conclusion. The results of stability analysis using the developed algorithm show that the growth of plate deflection under the considered boundary conditions is limited, stability loss is not observed at any load values not exceeding the instantaneous critical one. This indicates the possibility of long-term safe operation of such structures with a load less than instant critical one
Prediction of Rheological Parameters of Polymers by Machine Learning Methods
No full textIntroduction. All polymer materials and composites based on them are characterized by pronounced rheological properties, the prediction of which is one of the most critical tasks of polymer mechanics. Machine learning methods open up great opportunities in predicting the rheological parameters of polymers. Previously, studies were conducted on the construction of predictive models using artificial neural networks and the CatBoost algorithm. Along with these methods, due to the capability to process data with highly nonlinear dependences between features, machine learning methods such as the k-nearest neighbor method, and the support vector machine (SVM) method, are widely used in related areas. However, these methods have not been applied to the problem discussed in this article before. The objective of the research was to develop a predictive model for evaluating the rheological parameters of polymers using artificial intelligence methods by the example of polyvinyl chloride.Materials and Methods. This paper used k-nearest neighbor method and the support vector machine to determine the rheological parameters of polymers based on stress relaxation curves. The models were trained on synthetic data generated from theoretical relaxation curves constructed using the nonlinear Maxwell-Gurevich equation. The input parameters of the models were the amount of deformation at which the experiment was performed, the initial stress, the stress at the end of the relaxation process, the relaxation time, and the conditional end time of the process. The output parameters included velocity modulus and initial relaxation viscosity coefficient. The models were developed in the Jupyter Notebook environment in Python.Results. New predictive models were built to determine the rheological parameters of polymers based on artificial intelligence methods. The proposed models provided high quality prediction. The model quality metrics in the SVR algorithm were: MAE – 1.67 and 0.72; MSE – 5.75 and 1.21; RMSE – 1.67 and 1.1; MAPE – 8.92 and 7.3 for the parameters of the initial relaxation viscosity and velocity modulus, respectively, with the coefficient of determination R2 – 0.98. The developed models showed an average absolute percentage error in the range of 5.9 – 8.9%. In addition to synthetic data, the developed models were also tested on real experimental data for polyvinyl chloride in the temperature range from 20° to 60°C.Discussion and Conclusion. The approbation of the developed models on real experimental curves showed a high quality of their approximation, comparable to other methods. Thus, the k-nearest neighbor algorithm and SVM can be used to predict the rheological parameters of polymers as an alternative to artificial neural networks and the CatBoost algorithm, requiring less effort to preset adjustment. At the same time, in this research, the SVM method turned out to be the most preferred method of machine learning, since it is more effective in processing a large number of feature
Scrotal variceal bleeding during rivaroxaban therapy as alarming sign in senescent patients: A clinical case
No full textBackground. The past decade has witnessed the advent of direct oral anticoagulants (DOACs) into clinical practice for the prevention and treatment of venous thromboembolism, as well as stroke prevention in atrial fibrillation (AF) patients. A serious complication of anticoagulant treatment is bleeding. Randomised controlled trials have shown that the risk of already developed bleeding does not reduce upon a DOAC replacement. In such cases, the bleeding cause diagnosis and elimination are recommended instead of a anticoagulant replacement. An anticoagulant treatment can only be resumed once the elimination is completed.Clinical Case Description. Patient K., 81 yo, was emergently admitted to a cardiology ward of the Rostov Regional Clinical Hospital with a clinical picture of bilateral pulmonary embolism of small arterial branches confirmed in multislice computed angiopulmonography. Apart from venous embolism, persistent atrial fibrillation was detected as an additional indication for DOAC treatment. A CHA2DS2-VASc risk of thrombosis was 6, HAS-BLED risk of bleeding — 2. Glomerular filtration rate at bleeding was 90 mL/min/1.73 m2. The patient was prescribed rivaroxaban at 20 mg daily. Past 2 years and 3 months, rivaroxaban has been withdrawn due to bleeding developing from scrotal veins. An urologist examination revealed a bilateral spermatic cord veins dilation. A Valsalva test revealed persistent retrograde veinous blood flow. Varicocele detected on both sides.The patient underwent venous occlusion of left internal spermatic vein following an Ivanissevich procedure. The cause of bleeding was eliminated. The patient resumed rivaroxaban 1 week since the operation.Conclusion. The case describes a rare cause of bleeding that has been established at a continued new DOAC therapy
Mitral valve prolapse as cause of terminal ventricular complex ischaemia: a clinical case
No full textBackground. Mitral valve prolapse has common prevalence of 1% in population. Patients with mitral valve prolapse (MVP) continue to pose a major challenge in practical cardiology for its nonspecific manifestations, usually, palpitations and atypical chest pain. Several studies have demonstrated a high incidence of ventricular arrhythmias in individuals with MVP. MVP was observed in 2.3% of patients with sudden cardiac death. Comparing to the common population with sudden cardiac death, MVP patients belonged to a younger age group and less frequently had concomitant cardiovascular pathology.Clinical Case Description. Patient T. referred with complaints of transient constricting chest pain at rest and exercise, dyspnoea at exercise. A total duration of ST-T segment displacement episodes was 168 min, with painless episodes prevailing. Spiral computed angiography did not reveal calcinosis, soft coronary atherosclerotic plaques or abnormal arterial origins. Severe ventricular repolarisation abnormalities with sinusoidal T-U waves morphology in MVP are harbingers of sudden cardiac death, despite a normal QT interval duration. The T wave inversion in the lower lead and ventricular extrasystole also comprise the risk factors for sudden cardiac death in patients with MVP.Conclusion. Mitral valve prolapse caused an ischaemic ST-T segment depression in a young woman indicating a high risk of sudden cardiac death and need for immediate drug therapy. The Russian recommendations on treatment of connective tissue dysplasia and known literature suggest magnesium preparations as a preferred medication. Beta-blockers are effective in increased sympathetic nervous system reactivity or tone. Collagen synthesis stimulators, vitamins C, D, P, group B, preparations of magnesium, calcium, manganese, copper and antihypoxants are also recommended. Treatment with bisoprolol and magnesium orotate eliminated ischaemia and ventricular extrasystoles and improved the patient’s condition
Myocardial bridging: non-invasive diagnostics and management
No full textThe article discusses a case of episodes of asymptomatic ST-T depression during exercise in a 37-year-old patient with complaints of irregular heartbeat, tachycardia up to 100 bpm, not related to exercise. According to contrast-enhanced multislice computed tomography, in the middle third, a muscle bridge with stenosis of up to 30% was found. The diagnosis was made: Congenital coronary artery anomaly: transmyocardial muscular bridge of the middle third of left anterior descending artery with stenosis up to 30%. Class 1 silent myocardial ischemia. Stage 0, class 0 chronic heart failure. Using non-invasive coronary imaging, it was possible to identify the cause of transient ST-T depression and to choose the appropriate therapy
THE MECHANISMS OF ATROPHIC COLPITIS FORMATION IN WOMEN IN POST-REPRODUCTIVE PERIOD
No full textPurpose: too analyse a set of parameters of fatty acid composition of vaginal tissue as well as vitamin D, calcium and phosphorus content in blood of women with atrophic colpitis in the post-reproductive period.Materials and methods: we have examined vaginal tissue and blood of 35 women (age 51 ± 2.8 years), having objective signs of moderate atrophy. Control group included 35 women (age 48 ± 3.6 years) lacking any pathological urogenital symptomatics. The fatty acid composition of vaginal tissue, and also the levels of vitamin D, calcium and phosphorus in blood have been analysed.Results: in atrophic colpitis the content of higher unsaturated fatty acids increases in vaginal tissue. At the same time the stable level of phosphorus and calcium metabolism is maintained in the blood.Summary: in atrophic colpitis a pathogenic chain forms associated with the changes in direction of different metabolic pathways, the disruption of cell transport systems functioning. This leads to different systemic alterations on the cellular level, which can be related not only to steroidogenesis decrease, but also to the disruption of hormone-receptor transmission in differential signaling systems
