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Oxygen Delivery and Acute Hypoxia: Physiological and Clinical Considerations
Published in Anthony N. Nicholson, The Neurosciences and the Practice of Aviation Medicine, 2017
Common causes of metabolic acidosis include the excess production of lactic acid in heavy exercise or circulatory shock and ketoacids in starvation or uncontrolled diabetes. In renal failure, metabolic acidosis usually results from the failure to excrete the acid anions, such as sulphate and phosphate, produced by normal metabolic pathways. Patients with metabolic acidosis often show deep, gasping respiration at rest, the breathing described by Kussmaul (1822–1902). Lactic acidosis is the extra stimulus responsible for increased rate of rise of ventilation as exercise work rate rises above moderately severe. The work rate at which this happens is known as the anaerobic threshold (Wasserman et al., 1973).
Clinical Toxicology of Iron
Published in Debasis Bagchi, Manashi Bagchi, Metal Toxicology Handbook, 2020
Shilia Jacob Kurian, Sonal Sekhar Miraj, Ahmed Alshrief, Sreedharan Nair, Mahadev Rao
Fe toxicity has five clinical stages of manifestation (see Table 18.3). The first stage can be seen with doses as less as 10 mg/kg ingestion and is associated with damage to gastrointestinal (GI) mucosa. This phase exhibits vague GI symptoms such as diarrhea, vomiting, and GI blood loss. Additionally, early signs of shock and metabolic acidosis may also be seen. A lack of symptoms within 6 hours after ingestion predicts less chance to develop any further toxic sequelae. The second stage is referred to as the “latent phase” characterized by a marked improvement in GI symptoms. However, this phase has subtle evidence of cellular toxicity and metabolic acidosis. The latent phase usually occurs within 6–24 hours, although it may not be seen in all cases. The third stage occurs within 12–48 hours and accounts for most deaths associated with the toxicity. Apart from the oxidative phosphorylation pathway and generation of free radicals, this phase accounts for metabolic and cardiovascular symptoms. This has been associated with free Fe that inhibits thrombin and its related clotting pathway resulting in coagulopathy. In addition, metabolic acidosis develops due to the recurrence of vomiting and GI bleeding, which leads to hypovolemic shock. The fourth stage (although not always present) is characterized by hepatotoxicity and is seen within 48 hours. Hepatotoxicity is generally observed at serum Fe levels >1,000 mcg/dL and rarely at levels <700 mcg/dL. The fifth stage is usually observed in 3–6 weeks after the toxic ingestion, in which patients usually present with complaints of bowel obstruction due to stricture formations (Madiwale and Liebelt 2006; Chang and Rangan 2011).
Effective control of optical purity by chiral HPLC separation for ester-based liquid crystalline materials forming anticlinic smectic phases
Published in Liquid Crystals, 2021
Terézia Vojtylová-Jurkovičová, Petra Vaňkátová, Magdalena Urbańska, Věra Hamplová, David Sýkora, Alexej Bubnov
Direct enantioseparation employing chiral stationary phases has become the most often used approach for separating enantiomers. The CSP contains well-defined chiral centres, making them available for stereoselective interactions with enantiomers of analytes. This may result in different retention of the individual enantiomers on the column and, thus, their separation. Chiral sorbents based on derivatives of the polysaccharides amylose and cellulose are the most widespread and highly successfully utilised CSPs; they provide very broad applicability and excellent separation selectivity [8]. There are numerous situations where it is necessary to assess the enantiomeric excess of the target material with high precision and accuracy. A practical example of the successful utilisation of chiral HPLC includes the determination of the enantiomeric ratio of lactic acid for the diagnosis of metabolic acidosis for medical diagnostic purposes [9]. This technique is also widely used in the pharmacology and pharmaceutical industries [10–18], in agrochemistry to control chiral pesticides for agricultural needs [19,20] or in environmental studies to determine the occurrence and composition of pollutants or their residues in the environment [21–25].
Effects of three low-volume, high-intensity exercise conditions on affective valence
Published in Journal of Sports Sciences, 2020
Matthew Haines, David Broom, Warren Gillibrand, John Stephenson
Despite the time-efficiency of these exercise choices, the “peak-end rule” is a psychological heuristic that proposes that memory associated with pleasure or displeasure is influenced by the moment a peak response is experienced (Fredrickson, 2000). For REHIT and SCT the peak moment of displeasure is likely to be proximal to the high-intensity sprints and could influence retrospective evaluations of the activity, impacting motivational factors related to future adherence. Frequently, sprints result in considerable fatigue and feelings of nausea due to metabolic acidosis, particularly in inexperienced inactive individuals; thus, duration and recovery between sprints is an important consideration. Perception of exercise is related to muscle resistance to external force but becomes a function of duration when work is extended over time resulting from change in exercise capacity due to fatigue (Cafarelli, Cain, & Stevens, 1977). Currently, there is a paucity of methods for improving the affective experience of low-volume, high-intensity exercise (Zenko, Ekkekakis, & Ariely, 2016); thus, protocols with fewer or shorter sprints should be tested (Vollard & Metcalfe, 2017).
Acute effects of aerobic exercise performed with different volumes on strength performance and neuromuscular parameters
Published in European Journal of Sport Science, 2019
Natalia Ribeiro, Carlos Ugrinowitsch, Valéria Leme Gonçalves Panissa, Valmor Tricoli
Partially contradicting our hypothesis, central drive (i.e. VA and RMS reductions) declined similarly after all aerobic exercises and remained reduced after the strength tests. However, contractile properties (i.e. PT, TPT and RTD) impairments were greater after aerobic exercises followed by strength-endurance tests than followed by 1RM tests. Regarding the peripheral fatigue indices, PT reductions may indicate impairments in excitation–contraction coupling (Allen, Lamb, & Westerblad, 2008; Fitts, 1994; Place, Yamada, Bruton, & Westerblad, 2010), while TPT reductions possibly occurred in consequence of the lower PT values. Reductions observed on RTD may indicate impairments in cross-bridge force rate (Andersen & Aagaard, 2006; Metzger, Greaser, & Moss, 1989). These physiological events are important for muscle contraction process and may have occurred as a result of metabolic acidosis (e.g. pH reduction and/or Pi accumulation), impairments on the action potential propagation (e.g. K+ accumulation extracellular) and decreases in Ca2+ release or sensitivity, which is critical for the conversion of electrical stimuli to mechanical responses (Fitts, 2016; Place et al., 2010). Thus, we can conclude that strength was impaired by both central and peripheral fatigue, but strength-endurance test hampered the excitation-contraction coupling more than the maximum strength one.