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Clinical Journal of the American... Oct 2016Hyperammonemia is an important cause of cerebral edema in both adults with liver failure and children with inborn errors of metabolism. There are few studies that have... (Review)
Review
Hyperammonemia is an important cause of cerebral edema in both adults with liver failure and children with inborn errors of metabolism. There are few studies that have analyzed the role of extracorporeal dialysis in reducing blood ammonia levels in the adult population. Furthermore, there are no firm guidelines about when to implement RRT, because many of the conditions that are characterized by hyperammonemia are extremely rare. In this review of existing literature on RRT, we present the body's own mechanisms for clearing ammonia as well as the dialytic properties of ammonia. We review the available literature on the use of continuous venovenous hemofiltration, peritoneal dialysis, and hemodialysis in neonates and adults with conditions characterized by hyperammonemia and discuss some of the controversies that exist over selecting one modality over another.
Topics: Adult; Ammonia; Brain Diseases; Humans; Hyperammonemia; Infant, Newborn; Renal Replacement Therapy
PubMed: 27197910
DOI: 10.2215/CJN.01320216 -
Biomolecules Feb 2023Hepatic encephalopathy (HE) is a neuropsychiatric syndrome derived from metabolic disorders due to various liver failures. Clinically, HE is characterized by... (Review)
Review
Hepatic encephalopathy (HE) is a neuropsychiatric syndrome derived from metabolic disorders due to various liver failures. Clinically, HE is characterized by hyperammonemia, EEG abnormalities, and different degrees of disturbance in sensory, motor, and cognitive functions. The molecular mechanism of HE has not been fully elucidated, although it is generally accepted that HE occurs under the influence of miscellaneous factors, especially the synergistic effect of toxin accumulation and severe metabolism disturbance. This review summarizes the recently discovered cellular mechanisms involved in the pathogenesis of HE. Among the existing hypotheses, ammonia poisoning and the subsequent oxidative/nitrosative stress remain the mainstream theories, and reducing blood ammonia is thus the main strategy for the treatment of HE. Other pathological mechanisms mainly include manganese toxicity, autophagy inhibition, mitochondrial damage, inflammation, and senescence, proposing new avenues for future therapeutic interventions.
Topics: Humans; Hepatic Encephalopathy; Ammonia; Liver Failure; Autophagy; Hyperammonemia
PubMed: 36830765
DOI: 10.3390/biom13020396 -
Journal of Enzyme Inhibition and... Dec 2023Urease is a kind of nickel-dependent metalloenzyme, which exists in the biological world widely, and can catalyse the hydrolysis of urea into ammonia and carbon dioxide... (Review)
Review
Urease is a kind of nickel-dependent metalloenzyme, which exists in the biological world widely, and can catalyse the hydrolysis of urea into ammonia and carbon dioxide to provide a nitrogen source for organisms. Urease has important uses in agriculture and medicine because it can catalyse the production of ammonia. Therefore, in this review, metal-based inhibitors of urease will be summarised according to different transition metal ions. Including the urease inhibition, structure-activity relationship, and molecular docking. Importantly, among these reviewed effective urease inhibitors, most of copper metal complexes exhibited stronger urease inhibition with IC values ranging from 0.46 μM to 41.1 μM. Significantly, the collected comprehensive information looks forward to providing rational guidance and effective strategies for the development of novel, potent, and safe metal-based urease inhibitors, which are better for practical applications in the future.
Topics: Urease; Ammonia; Molecular Docking Simulation; Metals; Metalloproteins
PubMed: 36446640
DOI: 10.1080/14756366.2022.2150182 -
Essays in Biochemistry Aug 2023Aerobic nitrification is a key process in the global nitrogen cycle mediated by microorganisms. While nitrification has primarily been studied in near-neutral... (Review)
Review
Aerobic nitrification is a key process in the global nitrogen cycle mediated by microorganisms. While nitrification has primarily been studied in near-neutral environments, this process occurs at a wide range of pH values, spanning ecosystems from acidic soils to soda lakes. Aerobic nitrification primarily occurs through the activities of ammonia-oxidising bacteria and archaea, nitrite-oxidising bacteria, and complete ammonia-oxidising (comammox) bacteria adapted to these environments. Here, we review the literature and identify knowledge gaps on the metabolic diversity, ecological distribution, and physiological adaptations of nitrifying microorganisms in acidic and alkaline environments. We emphasise that nitrifying microorganisms depend on a suite of physiological adaptations to maintain pH homeostasis, acquire energy and carbon sources, detoxify reactive nitrogen species, and generate a membrane potential at pH extremes. We also recognize the broader implications of their activities primarily in acidic environments, with a focus on agricultural productivity and nitrous oxide emissions, as well as promising applications in treating municipal wastewater.
Topics: Nitrification; Ammonia; Ecosystem; Oxidation-Reduction; Bacteria
PubMed: 37449414
DOI: 10.1042/EBC20220194 -
Microbiology (Reading, England) Jul 2022is a marine ammonia-oxidizing archaeon with a high affinity for ammonia. It fixes carbon via a modified hydroxypropionate/hydroxybutyrate cycle and shows weak...
is a marine ammonia-oxidizing archaeon with a high affinity for ammonia. It fixes carbon via a modified hydroxypropionate/hydroxybutyrate cycle and shows weak utilization of cyanate as a supplementary energy and nitrogen source. When oxygen is depleted, produces its own oxygen, which may explain its regular occurrence in anoxic waters. Several enzymes of the ammonia oxidation and oxygen production pathways remain to be identified.
Topics: Ammonia; Archaea; Carbon Cycle; Oxidation-Reduction; Oxygen
PubMed: 35852832
DOI: 10.1099/mic.0.001207 -
Metabolic Brain Disease Apr 2017Ammonia is diffused and transported across all plasma membranes. This entails that hyperammonemia leads to an increase in ammonia in all organs and tissues. It is known... (Review)
Review
Ammonia is diffused and transported across all plasma membranes. This entails that hyperammonemia leads to an increase in ammonia in all organs and tissues. It is known that the toxic ramifications of ammonia primarily touch the brain and cause neurological impairment. However, the deleterious effects of ammonia are not specific to the brain, as the direct effect of increased ammonia (change in pH, membrane potential, metabolism) can occur in any type of cell. Therefore, in the setting of chronic liver disease where multi-organ dysfunction is common, the role of ammonia, only as neurotoxin, is challenged. This review provides insights and evidence that increased ammonia can disturb many organ and cell types and hence lead to dysfunction.
Topics: Ammonia; Animals; Brain; Brain Chemistry; Hepatic Encephalopathy; Humans; Hyperammonemia; Muscle, Skeletal
PubMed: 28012068
DOI: 10.1007/s11011-016-9938-3 -
Journal of the American Association For... Mar 2019In this review, we describe the methods and technology used to measure intracage ammonia levels; the data were derived from 38 articles published since 1970. Ammonia... (Review)
Review
In this review, we describe the methods and technology used to measure intracage ammonia levels; the data were derived from 38 articles published since 1970. Ammonia concentration is commonly used as a surrogate for assessing environmental quality inside rodent cages. Data generated from this group of publications have been used to support new husbandry practices, determine the effect of ammonia on health, and establish the effectiveness of caging systems. Consequently, the data generated from these studies have a direct effect on animal welfare and therefore should demonstrate a high level of reproducibility. Obtaining reproducible results requires a critical understanding of the methodology and the technology used to collect ammonia concentration data. This review highlights the need for consistent methodology for measuring ammonia that considers the technology used to capture the data as well as the environmental parameters that affect ammonia concentrations, to facilitate the design of future studies.
Topics: Ammonia; Animal Husbandry; Animal Welfare; Animals; Housing, Animal; Laboratory Animal Science; Ventilation
PubMed: 30704550
DOI: 10.30802/AALAS-JAALAS-18-000006 -
Chemical Reviews Jun 2020The reduction of dinitrogen to ammonia by nitrogenase reflects a complex choreography involving two component proteins, MgATP and reductant. At center stage of this... (Review)
Review
The reduction of dinitrogen to ammonia by nitrogenase reflects a complex choreography involving two component proteins, MgATP and reductant. At center stage of this process resides the active site cofactor, a complex metallocluster organized around a trigonal prismatic arrangement of iron sites surrounding an interstitial carbon. As a consequence of the choreography, electrons and protons are delivered to the active site for transfer to the bound N. While the detailed mechanism for the substrate reduction remains enigmatic, recent developments highlight the role of hydrides and the privileged role for two irons of the trigonal prism in the binding of exogenous ligands. Outstanding questions concern the precise nature of the intermediates between N and NH, and whether the cofactor undergoes significant rearrangement during turnover; resolution of these issues will require the convergence of biochemistry, structure, spectroscopy, computation, and model chemistry.
Topics: Ammonia; Crystallization; Metals, Heavy; Models, Molecular; Nitrogen; Nitrogenase; Protein Conformation
PubMed: 32538623
DOI: 10.1021/acs.chemrev.0c00067 -
The Journal of Physical Chemistry... Oct 2022Here we prove that, in addition to temperature and pressure, another important thermodynamic variable permits the exploration of the phase diagram of ammonia: the...
Here we prove that, in addition to temperature and pressure, another important thermodynamic variable permits the exploration of the phase diagram of ammonia: the electric field. By means of (path integral) molecular dynamics simulations, we predict that, upon applying intense electric fields on ammonia, the electrofreezing phenomenon occurs, leading the liquid toward a novel ferroelectric solid phase. This study proves that electric fields can generally be exploited as the access key to otherwise-unreachable regions in phase diagrams, unveiling the existence of new condensed-phase structures. Furthermore, the reported findings have manifold practical implications, from the safe storage and transportation of ammonia to the understanding of the solid structures this compound forms in planetary contexts.
Topics: Ammonia; Thermodynamics; Molecular Dynamics Simulation; Temperature; Electricity
PubMed: 36255376
DOI: 10.1021/acs.jpclett.2c02576 -
Journal of the American Society of... May 2021Two papers, one in 1986 and another one in 1988, reported a strong inverse correlation between urinary anion gap (UAG) and urine ammonia excretion (UNH) in patients with... (Review)
Review
Two papers, one in 1986 and another one in 1988, reported a strong inverse correlation between urinary anion gap (UAG) and urine ammonia excretion (UNH) in patients with metabolic acidosis and postulated that UAG could be used as an indirect measure of UNH This postulation has persisted until now and is widely accepted. In this review, we discuss factors regulating UAG and examine published evidence to uncover errors in the postulate and the design of the original studies. The essential fact is that, in the steady state, UAG reflects intake of Na, K, and Cl. Discrepancy between intake and urinary output of these electrolytes (, UAG) indicates selective extrarenal loss of these electrolytes or nonsteady state. UNH excretion, which depends, in the absence of renal dysfunction, mainly on the daily acid load, has no consistent relationship to UAG either theoretically or in reality. Any correlation between UAG and UNH, when observed, was a fortuitous correlation and cannot be extrapolated to other situations. Furthermore, the normal value of UAG has greatly increased over the past few decades, mainly due to increases in dietary intake of potassium and widespread use of sodium salts with anions other than chloride as food additives. The higher normal values of UAG must be taken into consideration in interpreting UAG.
Topics: Acid-Base Equilibrium; Acidosis; Ammonia; Humans
PubMed: 33769949
DOI: 10.1681/ASN.2020101509