Abstract:In a comparative study on erythrocytes (RBCs) drawn from mountaineers before and after a high-altitude stay, we observed that upon returning to sea level, their RBCs displayed a senescent-like phenotype as indicated by their density and the partial loss of membrane proteins which are shed by ageing RBCs. The aim of this study was to investigate possible changes in the membrane skeleton of these RBCs and to compare them with pathological RBCs. We analysed the proteins of RBC ghosts obtained from our subjects be… Show more
“…The ATP content of RBCs isolated during the deacclimatization from hypoxia was significantly higher than that of the control populations. Furthermore, alteration in the membrane-skeleton was found by a proteomic analysis, i.e., fragmentation of spectrin and actin (Risso et al, 2010). Finally in an investigation on blood samples drawn from mountain climbers, over and immediately after a 17 days' time spent at 3100–5600 m a.s.l., we observed that high altitude induced the expression of foetal haemoglobin.…”
Neocytolysis is the hypothesis formulated to explain experimental evidence of selective lysis of young red blood cells (RBCs) (neocytes) associated with decreased plasma levels of erythropoietin (EPO). In humans, it appears to take place whenever a fast RBC mass reduction is required, i.e., in astronauts during the first days of spaceflight under weightlessness, where a fast reduction in plasma volume and increase in haematocrit occur. EPO plasma levels then decline and a decrease in RBC mass takes place, apparently because of the selective lysis of the youngest, recently generated RBCs (neocytes). The same process seems to occur in people descending to sea level after acclimatization at high altitude. After descent, the polycythaemia developed at high altitude must be abrogated, and a rapid reduction in the number of circulating RBCs is obtained by a decrease in EPO synthesis and the lysis of what seem to be young RBCs. In vivo, neocytolysis seems to be abolished by EPO administration. More recent research has ascribed to neocytolysis the RBC destruction that occurs under such disparate pathophysiologic conditions as nephropathy, severe obstructive pulmonary disease, blood doping, and even malaria anaemia. According to the theory, EPO's central role would be not only to stimulate the production of new RBCs in conditions of anaemia, as maintained by the orthodox view, but also that of a cytoprotective factor for circulating young RBCs. Why neocytes are specifically destroyed and how is this related to decreased EPO levels has not yet been elucidated. Changes in membrane molecules of young RBCs isolated from astronauts or mountain climbers upon return to normal conditions seem to indicate a higher susceptibility of neocytes to ingestion by macrophages. By limiting the context to space missions and high altitude expeditions, this review will address unresolved and critical issues that in our opinion have not been sufficiently highlighted in previous works.
“…The ATP content of RBCs isolated during the deacclimatization from hypoxia was significantly higher than that of the control populations. Furthermore, alteration in the membrane-skeleton was found by a proteomic analysis, i.e., fragmentation of spectrin and actin (Risso et al, 2010). Finally in an investigation on blood samples drawn from mountain climbers, over and immediately after a 17 days' time spent at 3100–5600 m a.s.l., we observed that high altitude induced the expression of foetal haemoglobin.…”
Neocytolysis is the hypothesis formulated to explain experimental evidence of selective lysis of young red blood cells (RBCs) (neocytes) associated with decreased plasma levels of erythropoietin (EPO). In humans, it appears to take place whenever a fast RBC mass reduction is required, i.e., in astronauts during the first days of spaceflight under weightlessness, where a fast reduction in plasma volume and increase in haematocrit occur. EPO plasma levels then decline and a decrease in RBC mass takes place, apparently because of the selective lysis of the youngest, recently generated RBCs (neocytes). The same process seems to occur in people descending to sea level after acclimatization at high altitude. After descent, the polycythaemia developed at high altitude must be abrogated, and a rapid reduction in the number of circulating RBCs is obtained by a decrease in EPO synthesis and the lysis of what seem to be young RBCs. In vivo, neocytolysis seems to be abolished by EPO administration. More recent research has ascribed to neocytolysis the RBC destruction that occurs under such disparate pathophysiologic conditions as nephropathy, severe obstructive pulmonary disease, blood doping, and even malaria anaemia. According to the theory, EPO's central role would be not only to stimulate the production of new RBCs in conditions of anaemia, as maintained by the orthodox view, but also that of a cytoprotective factor for circulating young RBCs. Why neocytes are specifically destroyed and how is this related to decreased EPO levels has not yet been elucidated. Changes in membrane molecules of young RBCs isolated from astronauts or mountain climbers upon return to normal conditions seem to indicate a higher susceptibility of neocytes to ingestion by macrophages. By limiting the context to space missions and high altitude expeditions, this review will address unresolved and critical issues that in our opinion have not been sufficiently highlighted in previous works.
“…Hypoxia-reoxygenation diminishes band 3 protein functions in human erythrocytes, leading to actin rupture and cytoskeletal destabilization in vivo. 38 Figure 2 Hypoxia affects the deformability of erythrocyte membrane (A) Competition of deoxyHb with ankyrin for band 3 reduces erythrocyte membrane deformability by separating the cytoskeleton from the membrane. (B) The way of NO production under different hypoxia levels and its multiple effects on erythrocyte membrane deformability.…”
“…The transition from discoid to spherocytes vividly depends on intracellular calcium increase. It also correlates with microvesicle decrease in extracellular liquid and varying sensitivity to hydrolytic phospholipase A 2 [50,51]. Phosphatidylcholine content change (a key component of the RBC membrane bilipid layer) affects the discoid-to-echinocyte and discoid-tostomatocyte transitions significantly.…”
Blood oxygen transport regulation by physical activity increase within training dynamics is provided with different mechanisms: from the quantitative and qualitative erythron restructure (including endogenous erythropoietin rise and main erythrocyte index shifts) to change in haemoglobin affinity to oxygen, its heterogeneous structure and blood flow growth as a result of endothelium hyperpolarisation. However, the erythrocyte itself remains a key performer in blood velocity control, due to its structure and functions. This review summarizes the data of modern scientific literature on the characteristics of erythrocytes, which make these cells one of the key links in the oxygen transport system of the blood. The focus on this property of erythrocytes during physical activity is based on the fact that the athlete’s muscles must be supplied with enough oxygen to ensure high performance. Specific training and extra-training factors affecting the content of erythrocytes have been determined. The membrane structure is treated as a significant erythrocyte part in determining its deformation and microvascular blood transport. Enzymes associated with the erythrocyte membrane and affecting cell viability and performance are described. Besides, it is stressed on monitoring erythrocyte indices via modern equipment and assessing lipid peroxidation, which leads to disorders in erythrocyte membrane structure and functions.
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