Endogenous Activation and Neurophysiological Functions of Acid-Sensing Ion Channels
Tian-Le Xu, Long-Jun Wu in Nonclassical Ion Channels in the Nervous System, 2021
Carbon dioxide (CO2) is an important environmental cue associated with many biological activities such as respiration, photosynthesis, and decomposition of organic matter. CO2 may act as a signaling molecule by itself or it can change pH homeostasis by generating metabolites, such as carbonic acid and bicarbonate ions, when dissolved in aqueous fluid. The CO2 signal is critical in many invertebrates as it regulates insect innate behaviors, such as seeking food and hosts (19,20). However, with the exception of studies on the sensory system (21,22), the role of the CO2 signal in mammalian nervous systems remains poorly understood. It is important to determine the sensor(s) and the downstream signaling pathway(s) of CO2 in mammalian brain. Inhalation of CO2 can reduce brain pH by 0.1–0.2 unit due to the catalytic function of carbonic anhydrase that converts CO2 and water to carbonic acid, which subsequently produces bicarbonates, carbonates, and protons. With the ability to sense the physiological pH reduction and the wide expression in nervous systems, ASICs are well suited to be the sensors and downstream targets of the CO2 signal.
Euthanasia and Necropsy
Yuehuei H. An, Richard J. Friedman in Animal Models in Orthopaedic Research, 2020
Butler et al.14 have shown that carbon dioxide alters arachidonic acid metabolism and smooth muscle responses to acetlycholine. Carbon dioxide had also been documented to alter lymphoproliferation and cell mediated lympholysis.15 This has always been considered a painless agent. However, a recent study using human subjects has shown that high concentrations of carbon dioxide, 80-100%, can be noxious and painful to the nose and throat.16 This is believed to be due to the formation of carbonic acid on mucous membranes. The authors concluded that rats exposed to the same concentrations may also experience pain and discomfort. They further suggested that carbon dioxide could still be considered a humane agent if the animals were not exposed to concentration greater than 70% until after they had become unconscious. Carbon dioxide does not alter the histologic integrity of most tissues including the brain but it may cause vascular congestion, pulmonary edema or microhemorrhages in the lungs of rodents.13
Gastrointestinal tract and salivary glands
A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha in Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020
The patient must stop taking a number of drugs (e.g. antibiotics and antacids) and is required to fast for 6 hours. The patient ingests carbon-13- or carbon-14-labeled urea either via capsule or a flavoured liquid. The labelled urea then diffuses through the mucosal gel layer of the gastric epithelia in which the bacteria reside. H. pylori splits the ingested urea into ammonia and labelled carbon dioxide via urease activity. The patient breaths out and the carbon dioxide is collected. The sample is then measured in a scintillation counter or infrared spectrophotometer in order to measure the amount of labelled carbon dioxide. This is an indirect measure of urease activity and subsequent presence of H. pylori. Figure 5.34a presents the process by which the results are collected for the breath test.
Human in vitro blood barrier models: architectures and applications
Published in Tissue Barriers, 2023
Brittany E. Watson, Julia A. Miles, Melissa A. Moss
Transport of molecules into and out of the blood is critical for physiological function yet requires highly evolved barriers for protection from outside toxins.1 Oxygen and nutrients surpass these barriers for transport from the lungs and digestive system via blood to organs throughout the body.1 Carbon dioxide and other waste products are transported to the lungs, kidneys, and digestive system for removal from the body. Simultaneously, blood barriers protect from external agents inhaled or digested and are especially important in the brain to protect the central nervous system.2 Such controlled transport is achieved via the formation of a polarized cellular monolayer within which adjacent cells are coupled by tight junctions, complexes formed from cell surface proteins including myelin and lymphocyte (MAL) and related proteins for vesicle trafficking and membrane link (MARVEL) domain proteins, claudin family proteins, occuldins, and junctional adhesion molecules (JAMs).3–5 Disruption of blood barriers is a commonality in many diseases, rendering the study of barrier function necessary to fully understand disease states.6,7 Therefore, accurate modeling of these systems in vitro is crucial to elucidate disease mechanisms and develop therapeutic interventions.
Effect of altered human exposome on the skin and mucosal epithelial barrier integrity
Published in Tissue Barriers, 2022
Yagiz Pat, Ismail Ogulur, Duygu Yazici, Yasutaka Mitamura, Lacin Cevhertas, Ozan C. Küçükkase, Sanne S. Mesisser, Mübeccel Akdis, Kari Nadeau, Cezmi A. Akdis
Anthropogenic activities are responsible for global warming,47–49 with a mean temperature increase of 0.2°C per decade.18 A recent study predicts global warming of 2.6°C (1.9°C to 3.7°C) by 2100, taking into account only the current energy policies and measures being developed by the countries participating in the Paris agreement. Nonetheless, the authors noted that warming can be limited to 1.9–2.0°C if all the conditional and unconditional pledges of the Paris agreement are met in full and on time.50 The generation of large quantities of greenhouse gases has been a key driver of climate change, in particular carbon dioxide emissions. Moreover, deforestation cripples the Earth’s natural ability to remove atmospheric CO2, further aggravating global warming and causing extreme weather events.26,51 In the future, increases in morbidity and mortality are estimated due to climate change-related adverse effects such as heat-related illnesses, poor air quality, and undernutrition due to reduced food quality and security.18 It should be noted that the global risks from toxic pollution and climate change are highly correlated, with low- and middle-income countries being the most affected by both.17
An overview on cyanobacterial blooms and toxins production: their occurrence and influencing factors
Published in Toxin Reviews, 2022
Isaac Yaw Massey, Muwaffak Al osman, Fei Yang
Carbon dioxide is a prerequisite for toxic cyanoblooms in terms of photosynthesis and growth. In the process of blooms generation, the concentration of dissolved CO2 in water can be depleted to create a concentration gradient across the air to water interface (Verspagen et al.2014). Low-Décarie et al. (2011) reported that at low dissolved CO2 concentration, cyanobacteria became predominant competitors compared to eukaryotic phytoplankton (green algae) that benefited from high dissolved CO2 concentration. On the contrary Ji et al. (2017) found that green algae can be strong competitors under CO2 depleted conditions, and bloom-forming cyanobacteria having high-flux bicarbonate uptake systems may gain from increased CO2 concentrations. In a recent publication regarding laboratory and field studies, Sandrini et al. (2016) investigated the ability of Microcystis sp. to generate toxic cyanoblooms and both laboratory and field evidence showed that the increasing carbon concentrations caused rapid adaptive alterations in the genotype composition of cyanoblooms. Also Verspagen et al. (2014) through laboratory experiments and mathematical models speculated that cyanoblooms will intensify when CO2 level increases. These findings signify that rising CO2 concentrations are capable to facilitate the intensification of bloom-forming cyanobacteria in eutrophic and hypertrophic waters.
Related Knowledge Centers
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- Chemical Compound
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- Carbohydrate
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- Carbon
- Parts-Per Notation
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