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On Being Human – Frailties, Vulnerabilities and Their Effect on Performance
Published in Norman MacLeod, Crew Resource Management Training, 2021
The sleep process is dynamic, and the brain will move through the various stages over cycles lasting approximately 90 minutes. The stages may vary in duration. For example, the first REM episode may last just 10 minutes while the final episode may last an hour. For most people, between 6 and 9 hours of sleep per night is normal although 8 hours of sleep is considered necessary to be fully restorative. It seems that no single ‘sleep centre’ exists in the brain. Instead, a series of sleep circuits take inputs from the brainstem and the hypothalamus. The sleep cycle does appear to be synchronised with the body’s circadian rhythm with periods of wakefulness associated with a rise in the body core temperature while sleepiness coincides with a fall in core temperature. Two physiological processes regulate the need for sleep. First, during the hours of wakefulness, adenosine, a by-product of energy consumption, builds up in the body, and this increase triggers the need for sleep so that energy reserves can be replenished. Second, exposure to light produces melatonin. During the hours of darkness, melatonin production is inhibited and that synchronises the sleep cycle with the period of darkness. Humans are diurnal animals, after all.
Neuroscience of Sleep and Circadian Rhythms
Published in Gerald Matthews, Paula A. Desmond, Catherine Neubauer, P.A. Hancock, The Handbook of Operator Fatigue, 2017
Siobhan Banks, Melinda L. Jackson, Hans P.A. Van Dongen
The neurobiological nature of the sleep homeostatic process is largely unknown. However, it appears to be reflected in increased adenosine production in the extracellular space in the basal forebrain and areas of the cortex (Porkka-Heiskanen et al., 1997). Adenosine is a metabolic by-product of the brain’s use of adenosine triphosphate (ATP), the primary source of cellular energy. Adenosine serves as a neuromodulator, signalling sleepiness through binding to the adenosine receptor (for review, see Basheer et al., 2004). Caffeine binds to this receptor and thereby blocks adenosine signaling, which is how caffeine promotes alertness (Nehlig, Daval & Debry, 1992). It is not clear, however, what processes go on during sleep, in relation to adenosine, that reduce the homeostatic propensity for sleep (Benington & Heller, 1995). Most likely, a large number of additional sleep regulatory substances are involved (Krueger, Obál & Fang, 1999), with adenosine being a part of a complicated cascade of compounds and interactions (Van Dongen, Belenky & Krueger, in press).
Nanobiosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
For what purposes is adenosine sensing necessary? Adenosine is an endogenous (growing or developing from within, e.g., endogenous cholesterol is cholesterol that is made inside the body and is not obtained in the diet) nucleoside (a structural subunit of nucleic acids: any of various compounds consisting of a sugar, usually ribose or deoxyribose, and a nitrogen base) interacting in various physiological processes which are also regulated by hormones and neurotransmitters (chemicals located and released in the brain to allow an impulse from one nerve cell to pass to another nerve cell). Adenosine modulates blood flow and neurotransmission and may be protective during pathological (concerned with disease) conditions such as ischemia (restricted blood flow within tissues) and stroke. Adenosine triphosphate (ATP), having the empirical formula C10H16N5O13P3 and chemical formula C10H8N4O2NH2(OH)2(PO3H)3H, has important responsibilities in regulating cellular metabolism and biochemical pathways. ATP is a molecule found in any biological system, where it works as an energy carrier. Detecting ATP within cells can help observe energetic physiological processes, e.g., signal cascades, transport processes, etc. A signal cascade amplifies the initial signal caused by binding of the ligand to a receptor. ATP depletion is related to certain diseases, such as Parkinson’s disease and ischemia (a restriction in blood supply). An adenosine sensor is needed for improved understanding of its physiological actions and the extent of receptor activation.
On inlet pressure boundary conditions for CT-based computation of fractional flow reserve: clinical measurement of aortic pressure
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
Jincheng Liu, Suqin Huang, Xue Wang, Bao Li, Junling Ma, Yutong Sun, Jian Liu, Youjun Liu
Simulating the maximum hyperemic state of blood vessels and the influence of adenosine on lowering the peripheral resistance of coronary microcirculation is a specific problem in the non-invasive numerical calculation of FFR (Sdringola et al. 2011). Studies have shown that the total coronary artery resistance drops to 0.24 in the resting state of venous blood when the blood vessels are in the maximum hyperemic state. At this time, 140 mg/kg/min of vascular adenosine is clinically administered. In coronary microvascular ischemia, the vasodilation response is reduced, and in certain extreme cases, adenosine does not cause changes in resting blood vessels (Wilson et al. 1990). In the FFR model, it is assumed that the maximum congestion state is simulated based on CT calculation, and the microcirculation resistance was changed to the original 0.24 (Taylor et al. 2013). However, because the diastolic ability of micro-vessels varies based on individuals and regions, the resistance of microcirculation also exhibit a certain influence on the flow of coronary arteries.
Photocatalytic, antioxidant and antibacterial potential of bio-synthesized ZnO nanoparticles derived from espresso spent coffee grounds: optimization by central composite design
Published in Inorganic and Nano-Metal Chemistry, 2023
Nikoo Ostovar, Nima Mohammadi, Farnaz Khodadadeh
The major sections of the phenolic compounds are caffeic acids and chlorogenic which can use as natural antioxidants in cosmetic, pharmaceutical, feed-stock, and food industries. One of the fascinating properties of methylxanthines is the stimulation of the central nervous system. Their significance in cancer diseases has been related to the antagonism of adenosine receptors. Caffeine is the main methylxanthine retrieved from SCG which can be used in the production of energy drinks or dermatological preparation for cellulite, and chewing gum,[22] whereas theobromine and theophylline can be applied by the pharmaceutical industry.[23] SCG comprises great amounts of valuable organic materials such as cellulose, lignin, hemicellulose, fatty acids, proteins, and antioxidants that can be used as a basis for value-added products.[24] Hence, the existence of polyphenols in SCG provides appropriate reduction properties for it, which makes it a tremendous reducing agent for the green method for synthesizing NPs. Moreover, SCG polyphenols are regarded as being nontoxic that are safe for the environment.[25]
Review on the current treatment status of vein of Galen malformations and future directions in research and treatment
Published in Expert Review of Medical Devices, 2021
Panagiotis Primikiris, Georgios Hadjigeorgiou, Maria Tsamopoulou, Alessandra Biondi, Christina Iosif
Adenosine is a purine nucleotide used as first-line treatment for supraventricular tachycardias causing hemodynamic instability [90,91]. Given as bolus dose, adenosine inhibits adenyl cyclase, causing hyperpolarization of the sinus and atrioventricular nodes leading to cardiac standstill, which allows the atrioventricular node to reset [88,91]. Several boluses of adenosine were administered in progressively larger doses to assess sensitivity and tolerability until a bolus dose which induced a few seconds of cardiac standstill [88]. The objective of this treatment strategy is to temporarily reduce the high-flow in the fistulous target so as to improve the delivery and stability of detachable coils and liquid embolic materials, without propagation to unwanting downstream locations [88].