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Bioenergetics
Published in Michael H. Stone, Timothy J. Suchomel, W. Guy Hornsby, John P. Wagle, Aaron J. Cunanan, Strength and Conditioning in Sports, 2023
Michael H. Stone, Timothy J. Suchomel, W. Guy Hornsby, John P. Wagle, Aaron J. Cunanan
The relative contributions of anaerobic and aerobic mechanisms to maximal sustained efforts can be examined using a cycle ergometer (modified Wingate test); values are shown in Figure 2.10 (255, 287, 301). During maximum sustained efforts on a cycle ergometer, contributions from anaerobic mechanisms are the primary energy-supplying systems for about 0 to approximately 60 s; thereafter, aerobic metabolism becomes the primary. Thus, maximal sustained efforts to complete exhaustion may depend greatly on aerobic metabolism. The total contribution of anaerobic metabolism to this type of exercise represents the anaerobic capacity (190, 287).
Biochemical and Metabolic Limitations to Athletic Performance
Published in Peter M. Tiidus, Rebecca E. K. MacPherson, Paul J. LeBlanc, Andrea R. Josse, The Routledge Handbook on Biochemistry of Exercise, 2020
Another important by-product of ATP generation during intense bouts of contracting muscle is the formation of reactive oxygen species (ROS). Multiple systems within muscle generate ROS during exercise. The most established is aerobic metabolism via the mitochondrial electron transport chain. Superoxide anions are generated as a result of incomplete reduction of oxygen at complex I and III (45). Another well-defined source of superoxide is the NADPH oxidase, which has isoforms constitutively expressed in skeletal muscle. As with most metabolites or by-products generated by metabolism of skeletal muscle during exercise, it is not entirely clear if ROS directly contributes to fatigue in a physiological setting. However, similarly to other by-products mentioned here, a series of mechanistic investigations provide evidence supporting this assertion. For example, direct exposure of intact contracting mouse muscle fibres to hydrogen peroxide reduces force during submaximal tetani (45). One mechanism by which ROS may interfere with force during skeletal muscle contraction is by promoting Ca2+ release from the sarcoplasmic reticulum and slowing Ca2+ reuptake. Endurance athletes thus have improved defences against ROS build-up during exercise in the form of scavenger molecules and enzymes which “safely” metabolize ROS.
The immune and lymphatic systems, infection and sepsis
Published in Peate Ian, Dutton Helen, Acute Nursing Care, 2020
Michelle Treacy, Caroline Smales, Helen Dutton
Lactate is a normal product of anaerobic metabolism that is released into the bloodstream and metabolised by the liver. Aerobic metabolism produces energy from glucose in the form of adenosine triphosphate (ATP) in the presence of oxygen. Pyruvate (which is the end product of glycolysis), formed as part of this process, can also be metabolised without oxygen if it is not available in sufficient quantities. The end-product of anaerobic pyruvate metabolism is lactate, and this pathway is helpful in health, in terms of meeting a short-term oxygen deficit. Serum lactate, though, may be raised in a number of clinical circumstances, such as in hyperthermia, seizures, liver problems and cardiac arrest. A normal serum lactate level is less than 1mmol/L in both arterial and venous blood.
Mitochondrial biogenesis alteration in arsenic-induced carcinogenesis and its therapeutic interventions
Published in Toxin Reviews, 2023
Kshirod Bihari Sathua, Rakesh Kumar Singh
Mitochondria is the main energy production machinery inside the cells through cellular metabolism and production of ATP. On the contrary, the electron carriers of the respiratory chain of mitochondria are the main site and source of reactive oxygen species (ROS) production during its aerobic metabolism. The extent of cellular ROS regulates mitochondrial redox status and determines the mitochondrial homeostasis and biogenesis (Sabharwal and Schumacker 2014, Ippolito et al. 2020, Popov 2020). Literature reports have depicted the enhancement of mitochondrial biogenesis during tumorigenesis (Porporato et al.2018). A high dose of arsenic exposure causes induction of apoptosis by cytochrome c cascades, whereas low-dose exposure to arsenic can check the apoptotic pathway and eventually leading to carcinogenesis (Yousefsani et al.2018). Such paradoxical effects have demonstrated that mitochondria might play a judgemental role through which the arsenic exposure may either lead to carcinogenesis or anticancer effects in a ROS-dependent manner. Hence, cellular mitochondria biogenesisis an emerging topic of discussion for understanding the underlying mechanism pertaining to arsenic-induced carcinogenesis. Thus, in this review, we have made efforts to evaluate the role of mitochondrial biogenesis in the development of arsenic-induced carcinogenesis in addition to the possible therapeutic option for modulation of such signaling mechanisms.
Effects of aerobic exercise on waist circumference, VO2 max, blood glucose, insulin, and lipid index in middle-aged women: A meta-analysis of randomized controlled trials
Published in Health Care for Women International, 2022
Aerobic exercise increases fat breakdown through oxidation of fat during exercise through aerobic metabolism (Horowitz and Klein, 2000), so it lowers triglycerides and low-density lipoproteins and increases high-density lipoproteins (Kraus, et al., 2002; Galvao et al., 2011). As a result, it helps to reduce abdominal fat and improve cardiopulmonary function (Takeshima et al., 2004; Tang et al., 2013). In addition, aerobic exercise improves insulin resistance (Williams & Franklin, 2007). The reason is that insulin resistance is lowered and insulin sensitivity is increased by increasing the absorption of blood glucose into the muscle by increasing affinity with the insulin receptor substrate through regular and continuous muscle contraction (Dohm, 2002). As the amount of glycogen in the muscle increases to 50–65% of the maximum oxygen consumption, and at 85%, the amount of glycogen in the muscle doubles (Romijn, et al., 1993), it helps to improve insulin resistance (O'Donovan et al., 2005).
Uncontrolled Oxygen Levels in Cultures of Retinal Pigment Epithelium: Have We Missed the Obvious?
Published in Current Eye Research, 2022
O2 is required for the synthesis of ATP, the energy currency of the cell, in the mitochondria of mammals during aerobic metabolism.74 In static culture system, O2 molecules must be moved from the gas phase (atmosphere) to the liquid phase (medium) before being available to the cells. The rate and extent of achieved O2 equilibrium in the medium depends on the cell density, O2 consumption rates, oxygenation method, culture temperature, and the characteristics of the medium itself, including ionic strength and volume.92 However, until date, there has been very little discussion about the effects of these factors in the cultures of RPE. For example, the volume of medium has not been clearly stated in the main body of published RPE culture methods.