Glycine Cytoprotection and Inhibition of Nonlysosomal Calcium-Dependent Proteolysis During Anoxic Injury of Rat Hepatocytes
John J. Lemasters, Constance Oliver in Cell Biology of Trauma, 2020
In summary, our results demonstrate that during anoxia: (a) glycine delays the onset of lethal hepatocellular injury in a concentration-dependent and structurally specific manner; (b) nonlysosomal proteolysis is stimulated during anoxia and is predominantly Ca2+-dependent; (c) glycine inhibits total cellular proteolysis, specifically Ca2+-dependent nonlysosomal proteolysis including calpain proteolysis; and (d) glycine cytoprotection during oxidative stress is also associated with inhibition of Ca2+-dependent proteolysis. The results suggest that glycine cytoprotection against anoxic hepatocellular injury may, in part, be due to a direct inhibition of Ca2+-dependent nonlysosomal proteases including calpains. These findings suggest that Ca2+-dependent nonlysosomal proteolysis and, specifically, calpain proteolysis, may be a critical intermediary event in many forms of hepatocellular injury.
The pressure cabin and oxygen systems
Nicholas Green, Steven Gaydos, Hutchison Ewan, Edward Nicol in Handbook of Aviation and Space Medicine, 2019
Functions of an aircraft oxygen systemPrevention of hypoxia. Civilian aircraft oxygen requirements specified as tracheal inspired PO2 (PiO2; easier to test); military requirement is alveolar PO2 (PAO2; harder to measure but more accurate). PAO2 should be maintained between 60–103 mmHg; lower levels of PAO2 (but not below 30 mmHg) may be tolerated for short-term emergency use.Removal of expirate. Prevents build-up of CO2 (potential physiological effects) and H2O vapour (potential misting of visors, freezing of valves).Protection against smoke and fumes. Prevents inhalation of toxins in aircraft fire, may also provide eye protection.Protection against decompression sickness. Reduces risk through denitrogenation including preoxygenation.Protection during escape. Supplies adequate oxygen to prevent loss of consciousness during high-altitude escape. Some military naval aircraft also provide protection during underwater escape.
Therapeutic Medicinal Mushroom (Ganoderma Lucidum): A Review of Bioactive Compounds and their Applications
Megh R. Goyal, Durgesh Nandini Chauhan in Plant- and Marine-Based Phytochemicals for Human Health, 2018
Stress is a state of threatened homeostasis that produces a different physiological as well as pathological changes depending on severity, type, and duration of stress.56 Hypoxia, whereas, is defined as an oxygen deprivation at the tissue level. As reported in the literature, exposure to extreme physiological stress induces various deleterious effects at cellular level. Recent findings suggest that there is an increased cellular oxidative stress with a consequent imbalance between excess ROS generated and antioxidant defense mechanism due to enhanced metabolic rate. These harmful ROS cause oxidative damage to various biomolecules and often leads to mitochondrial and muscular structure damage. Thereby, compromising cell integrity and reducing capacity to maintain cellular energy levels. These results in muscular atrophy and muscle fatigue leading to stress-induced decreased performance of an individual.42
Do we have scientific evidence about the effect of hypoxaemia on cognitive outcome in adult patients with severe acute respiratory failure?
Published in Upsala Journal of Medical Sciences, 2018
Bernhard Holzgraefe, Anders Larsson, Laura Von Kobyletzki
The occurrence of hypoxaemia is a common feature in severe ARF and other conditions with severely impaired pulmonary gas exchange. Hypoxaemia is defined as haemoglobin oxygen saturation below the normal value. The term ‘normoxaemia’ is defined as a PaO2 of 10.7–13.3 kPa (80–100 mmHg) or a SaO2 of >94% at sea level (6). On the other hand, the term hypoxia describes a lack of oxygen at the cellular level. The terms hypoxaemia and hypoxia are often mixed up, but it is important to keep in mind that they describe two different situations. Hypoxaemia may not lead to cellular hypoxia per se because the physiological compensation of reductions in oxygen saturation might maintain capillary oxygen content at an adequate level (7), which seems to be the most important factor for sufficient cerebral oxygenation (8). Tissue hypoxia is usually caused by an ischemic event, i.e. cerebral infarction. Therefore, in our view, it is unlikely that hypoxaemia per se will lead to tissue hypoxia as long as organ perfusion is preserved. Attempts to maintain normoxaemia during treatment with mechanical ventilation with or without ECMO in patients with hypoxaemic respiratory failure are associated with a risk of serious complications, e.g. ventilator-induced lung injury (9) and cerebral haemorrhage (10). This risk could even out the potential benefit of increasing blood oxygen saturation. Thus, it is important to clarify whether hypoxaemia is associated with decreased cognitive function.
5-Hydroxymethylfurfural (HMF) formation, occurrence and potential health concerns: recent developments
Published in Toxin Reviews, 2021
Ankit Choudhary, Vikas Kumar, Satish Kumar, Ishrat Majid, Poonam Aggarwal, Sheenam Suri
Oxygen is necessary for cell survival. Hypoxic condition (deficiency of oxygen) has various harmful and life-changing effects on human health. Hypoxia may be induced by many factors, including altitude and self-related conditions i.e. degenerative diseases (atherosclerosis, cancer and ischemia) (Pattinson et al.2005, Shapla et al.2018). Several cellular mechanisms are studied and that can alter hypoxic conditions, among which extracellular signal-regulated kinase (ERK) -mediated transactivation of the transcription factor and hypoxia-inducible factors (HIF) are believed to play a major role (Sung et al.2013). The mitochondrial membrane potential is also decreased and affects hypoxic cells in a negative way (Iijima et al.2018). In vitro study of the cell line ECV304 (human umbilical cord vein endothelial cell), Wilhelm et al. (2011) showed that cells pretreated with HMF (200 μg/ml for 1 h) before being exposed to hypoxic conditions (0.3% oxygen for 24 h) exhibited increased activity of mitochondrial membrane potential and reduced the levels of ERK levels. In their further study with a Kunming mice model, the authors showed that pre-exposure to HMF (100 μg/ml, 1 h) significantly decrease the extent of hypoxia-induced permeability of the blood-brain barrier (BBB). Therefore, HMF increases the survival rate under hypobaric hypoxic conditions. Also, it can be a therapeutic agent against high-altitude cerebral edema (HACE), high-altitude pulmonary edema (HAPE) and acute mountain sickness (AMS) (Wilhelm et al.2011, Shapla et al.2018).
Exercise and anemia in cancer patients: could it make the difference?
Published in Expert Review of Hematology, 2021
Alice Avancini, Lorenzo Belluomini, Daniela Tregnago, Ilaria Trestini, Michele Milella, Massimo Lanza, Sara Pilotto
However, the human body usually reacts to anemia triggering a series of compensatory mechanisms, finalized to introduce and deliver an increased oxygen level. The reduced tissue oxygenation and the low Hb levels induce the cardiovascular system to shift blood from nonvital organs to those organs that are oxygen-sensitive, such as the central nervous system, heart, kidneys, and skeletal muscles, to augment the peripheral vasodilatation and to increase the stroke volume and, therefore, the cardiac output [19]. Moreover, to supply the lack of oxygen, the respiratory system increases the respiratory rate to introduce more oxygen from the environment, while the kidney responds to hypoxia by enhancing EPO production [19]. Such mechanisms lead to anemia symptoms, such as palpitations, tachycardia, dyspnea, pallor, and cold skin. On the other hand, other symptoms may be the direct result of anemia-related hypoxia, such as fatigue, dizziness, vertigo, depressed mood, and impaired cognitive function [20,21]. Anemia also impacts other organs (e.g. genital tract and immune and gastrointestinal systems) and profoundly impairs the subject’s exercise tolerance and capacity [20,22]. However, the severity of the symptoms is influenced by various factors: the degree of anemia, comorbidities, doses, and exposure of anticancer treatments, which may also compromise patients’ quality of life [22].