Early Lipid Raft-Related Changes: Interplay between Unilateral Denervation and Hindlimb Suspension

Muscle disuse and denervation leads to muscle atrophy, but underlying mechanisms can be different. Previously, we have found ceramide (Cer) accumulation and lipid raft disruption after acute hindlimb suspension (HS), a model of muscle disuse. Herein, using biochemical and fluorescent approaches the influence of unilateral denervation itself and in combination with short-term HS on membrane-related parameters of rat soleus muscle was studied. Denervation increased immunoexpression of sphingomyelinase and Cer in plasmalemmal regions, but decreased Cer content in the raft fraction and enhanced lipid raft integrity. Preliminary denervation suppressed (1) HS-induced Cer accumulation in plasmalemmal regions, shown for both nonraft and raft-fractions; (2) HS-mediated decrease in lipid raft integrity. Similar to denervation, inhibition of the sciatic nerve afferents with capsaicin itself increased Cer plasmalemmal immunoexpression, but attenuated the membrane-related effects of HS. Finally, both denervation and capsaicin treatment increased immunoexpression of proapoptotic protein Bax and inhibited HS-driven increase in antiapoptotic protein Bcl-2. Thus, denervation can increase lipid raft formation and attenuate HS-induced alterations probably due to decrease of Cer levels in the raft fraction. The effects of denervation could be at least partially caused by the loss of afferentation. The study points to the importance of motor and afferent inputs in control of Cer distribution and thereby stability of lipid rafts in the junctional and extrajunctional membranes of the muscle.     

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.     

IR Spectroscopic Study of the Organic Component of Ultrafine Diamond Produced by Detonation Synthesis

IR spectra of ultrafine diamonds produced by different teams of researchers are studied. The effects of heating and radiation on the properties of ultrafine diamonds are studied. Quantitative assumptions on the kinetics of formation of ultrafine diamonds are made from analysis of IR spectra.     

Electrodeposition, composition and structure of Zn—Cr alloys

The effect of polyethylene glycol (PEG 1500) as additive and of deposition conditions on Zn—Cr alloy electrodeposition from an acidic sulfate electrolyte at room temperature, without agitation was investigated. PEG polarizes the overall cathodic reaction and inhibits Zn deposition. Cr codeposition with Zn starts at a cathodic potential of about –1,95 V vs Hg/Hg₂SO₄, which is reached at current density of about 20 A dm^–2 in galvanostatic conditions. Zn—Cr alloy coatings containing up to 28 at % Cr were obtained depending on the plating conditions. SEM observations showed an island-like structure, formed by the local growth of crystals, which covered the surface during further deposition. In the first stages of electrodeposition the powder diffraction spectra contain lines of b.c.c. -(Zn,Cr) phase (a 3.02 Å). After 30 s deposition time weak lines of Zn-based phase (a 2.67 Å, c 4.90 Å) appear, and become clearly visible in coatings deposited for 90 s. The average Cr content in the alloy coatings decreases with advancing deposition. The as-plated surface contains C in organic compounds and Zn(OH)₂. After 50 min sputtering, Zn and a mixture of Cr, Cr₂O₃ and Cr₇C₃ were found. The presence of organic C and O, probably from inclusions of PEG, were also detected.     

Silver–carbon electrocatalyst for air cathodes in alkaline fuel cells

A method for producing electrocatalysts containing silver supported on different carbons was developed. The catalysts were investigated in air (oxygen) diffusion electrodes in alkaline electrolyte (7 M KOH). Depending on the carbon support used, up to a threefold improvement in electrode performance was achieved compared with the activity of the uncatalysed carbon in this media. At ambient temperature and atmospheric pressure, a current density of 150 mA/cm^–2 was obtained at electrode potential 1.2 V vs zinc (0.75 vs HE). A correlation between electro catalytic activity and wetted surface area of the electrocatalysts was found.     

Polyamide‐6‐b‐polybutadiene block copolymers: Synthesis and properties

Polyamide‐6 (PA6)/polybutadiene (PB) block copolymers were synthesized with macroactivators (MAs) based on hydroxyl‐terminated polybutadiene functionalized with diisocyanates and having three N‐acyllactam chain‐growing centers per molecule. Two different diisocyanates, hexamethylene diisocyanate and isophorone diisocyanate, were applied as precursors for the MAs. The sodium salt of ε‐caprolactam was chosen as an initiator. The influence of the MA type and concentration on the anionic ring‐opening polymerization of ε‐caprolactam at 180°C was studied. A large percentage of the gel fraction in the copolymers was estimated, indicating crosslinked macromolecules. The structure and phase behavior of the copolymers were investigated with differential scanning calorimetry, wide‐angle X‐ray scattering, thermogravimetric analysis, and dynamic mechanical thermal analysis. In the copolymers, only the PA6 chains crystallized, and the crystallinity depended on the PB content. Different glass‐transition temperatures for the PB blocks and PA6 blocks were observed, indicating microphase separation in the copolymers. The mechanical properties of the copolymers were studied by notched impact testing and hardness measurements. The impact strength increased linearly with the soft component concentration up to 10 wt % and reached values six times higher than those of the PA6 homopolymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 711–717, 2003     

Strength properties of chamotte concretes based on phosphate binders

Conclusions The authors have investigated the strength properties of chamotte concretes based on phosphate binders over a wide range.They have shown the dependence of the compressive strength of the concretes on the type of phosphate binder used, the heat treatment temperature of the concrete, and its test temperature. Maximal compressive strength is exhibited by concretes roasted at 1450°C.They have established a relation between the physicochemical transitions taking place in a phosphate binder during heating and the strength characteristics of the concrete.Simultaneous introduction of phosphate binder and clay to the extent of 10–20% into chamotte concretes increases their strength at 20°C and during heating.Translated from Ogneupory, No. 6, pp. 32–36, June, 1979.