The “Angiogenic Switch” and Functional Resources in Cyclic Sports Athletes

Regular physical activity in cyclic sports can influence the so-called “angiogenic switch”, which is considered as an imbalance between proangiogenic and anti-angiogenic molecules. Disruption of the synthesis of angiogenic molecules can be caused by local changes in tissues under the influence of excessive physical exertion and its consequences, such as chronic oxidative stress and associated hypoxia, metabolic acidosis, sports injuries, etc. A review of publications on signaling pathways that activate and inhibit angiogenesis in skeletal muscles, myocardium, lung, and nervous tissue under the influence of intense physical activity in cyclic sports. Materials: We searched PubMed, SCOPUS, Web of Science, Google Scholar, Clinical keys, and e-LIBRARY databases for full-text articles published from 2000 to 2020, using keywords and their combinations. Results: An important aspect of adaptation to training loads in cyclic sports is an increase in the number of capillaries in muscle fibers, which improves the metabolism of skeletal muscles and myocardium, as well as nervous and lung tissue. Recent studies have shown that myocardial endothelial cells not only respond to hemodynamic forces and paracrine signals from neighboring cells, but also take an active part in heart remodeling processes, stimulating the growth and contractility of cardiomyocytes or the production of extracellular matrix proteins in myofibroblasts. As myocardial vascularization plays a central role in the transition from adaptive heart hypertrophy to heart failure, further study of the signaling mechanisms involved in the regulation of angiogenesis in the myocardium is important in sports practice. The study of the “angiogenic switch” problem in the cerebrovascular and cardiovascular systems allows us to claim that the formation of new vessels is mediated by a complex interaction of all growth factors. Although the lungs are one of the limiting systems of the body in cyclic sports, their response to high-intensity loads and other environmental stresses is often overlooked. Airway epithelial cells are the predominant source of several growth factors throughout lung organogenesis and appear to be critical for normal alveolarization, rapid alveolar proliferation, and normal vascular development. There are many controversial questions about the role of growth factors in the physiology and pathology of the lungs. The presented review has demonstrated that when doing sports, it is necessary to give a careful consideration to the possible positive and negative effects of growth factors on muscles, myocardium, lung tissue, and brain. Primarily, the “angiogenic switch” is important in aerobic sports (long distance running). Conclusions: Angiogenesis is a physiological process of the formation of new blood capillaries, which play an important role in the functioning of skeletal muscles, myocardium, lung, and nervous tissue in athletes. Violation of the “angiogenic switch” as a balance between proangiogenic and anti-angiogenic molecules can lead to a decrease in the functional resources of the nervous, musculoskeletal, cardiovascular, and respiratory systems in athletes and, as a consequence, to a decrease in sports performance.     

Stable flow regions for highly concentrated solutions of polyacrylonitrile in dimethyl sulfoxide

Conclusions Conclusions about the decrease in critical values of shear stress and shear rate with increase in the ratio of capillary length to capillary diameter at constant flow rates, and about the increase in critical values of shear stress and shear rate on the use of spinnerets with a conical inlet have been confirmed on polyacrylonitrile solutions having a high concentration.A second region of stable flow of polyacrylonitrile solutions having concentrations of 17.7% by wt. has been found in short capillaries (with a length of 3 or 10 mm).Translated from Khimicheskie Volokna, No. 2, pp. 23–24, March–April, 1990.     

The Macroporosity of Polyacrylonitrile Fibre

The closed porosity of polyacrylonitrile fibres wet-spun from dimethyl acetamide solutions was investigated in raising the spinning bath temperature from 2 to 20°C. The dependence of the porosity of the fibre on the conditions of plasticization treatment is established. The fibre treated in saturated vapor medium has higher porosity values (narrow transmission factors in chlorobenzene) than the fibre treated with a hot aqueous solution of dimethyl acetamide. The dependence of the fibre porosity on the drying and repeated washing and subsequent drying temperatures is demonstrated. The mobility of the structural elements increases and the porosity of the fibre decreases with an increase in the drying temperature.     

The renal factor in the post-traumatic "fluid overload" syndrome

Hypervolemia with hypertension often occurs 36-72 hours following massive blood and fluid replacement for hypovolemic shock. This syndrome of "fluid overload" has been attributed to the rapid intravascular flux of previously sequestered fluid in patients with impaired diuresis. This hypothesis was tested in 35 injured patients who received a mean of 9.3 L of blood and 17.4 L of salt during resucitation. The renal parameters measured soon after resuscitation included: 1) renal clearance of inulin (GFR), para-amino hippurate (ERPF), milliosmoles, sodium, and free water; 2) inulin space, renal vascular resistance (RVR), O2 consumption, renin, renal blood flow (RBF), and response to furosemide. Eighteen patients developed hypertension, hypervolemia, and respiratory insufficiency. When compared to the 17 normovolemic, non-hypertensive patients, the 18 hypervolemic patients had significantly increased RVR, with a significant decrease in RBF despite an increase in plasma volume and cardiac output. Furosemide produced less diuresis and natriuresis in the hypertensive patients. The balance between hypovolemia and "fluid overload" seemed percarious in the hypertensive patients. Peripheral renin and catecholamine levels were normal in both groups. Patients with post-traumatic "fluid overload" appear to have a combination of hypervolemia, respiratory insufficiency, hypertension, increased cardiac output, decreased extracellular fluid space, and decreased renal perfusion. These findings suggest that decreased interstitial fluid space compliance rather than "fluid overload" is the underlying factor leading to respiratory insufficiency. The therapeutic aspects of these findings are discussed.     

Determination of thermophysical characteristics of high heat-conductance materials on thin samples

A method is proposed that makes it possible to eliminate the contact thermal resistances in the determination of the thermophysical characteristics of high heat conductance materials on samples with thickness h5 · 10^–3 m.Translated from Inzhenerno-Fizicheskii Zhurnal Vol. 29, No. 6, pp. 1049–1056, December, 1975.     

137Cs vertical migration and contamination density in the soil of southern transbaikal

The mechanism of vertical migration of radionuclides along the soil profile is studied. For large averaging, the process can be described by the sum of the rates of effective diffusion and vertical advection of a radionuclide. The results of theoretical calculations of the¹³⁷Cs concentration profiles in light and heavy soils for actually observed atmospheric fallout in 1954–1999 are compared with the experimental profiles in mountain frozen-taiga and mountain frozen-forest tundra soils of southern Transbaikal. The rate of vertical migration is estimated and the reasons for the high¹³⁷Cs contamination density of soil in this region are discussed. 4 figures, 27 references. Scientific and Industrial Association “Taifun.” GP “Sosnovgeolservis.” Translated from Atomnaya énergiya, Vol. 88, No. 3, pp. 207–213, March, 2000.     

Dependence of the signal of a multimode fiber-optic interferometer on the mode power distribution

Multimode fiber-optic interferometer (MFI) signals formed under conditions of external actions and a change in the optical power distribution between modes along the fiber have been studied. It is experimentally established that parameters of the MFI signal significantly depend on the number of propagating modes in the region of external action upon the fiber.     

System for measuring the static and dynamic characteristics of choke-controlled executive mechanisms

Systems are described for measuring the static and dynamic characteristics of components in electrohydraulic steering mechanisms with a hydraulic power source of constant productivity.