Browsing by Subject "Magnesium"

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    Guideline for the management of acute asthma in adults: 2013 update
    (2013) Lalloo, U G; Ainslie, G M; Abdool-Gaffar, M S; Awotedu, A A; Feldman, C; Greenblatt, M; IRUSEN, E M; Mash, R; Naidoo, S S; O\'Brien, J; Otto, W; Richards, G A; Wong,, M L
    Acute asthma attacks (asthma exacerbations) are increasing episodes of shortness of breath, cough, wheezing or chest tightness associated with a decrease in airflow that can be quantified and monitored by measurement of lung function (peak expiratory flow (PEF) or forced expiratory volume in the 1st second) and requiring emergency room treatment or admission to hospital for acute asthma and/or systemic glucocorticosteroids for management. The goals of treatment are to relieve hypoxaemia and airflow obstruction as quickly as possible, restore lung function, and provide a suitable plan to avoid relapse. Severe exacerbations are potentially life-threatening and their treatment requires baseline assessment of severity, close monitoring, and frequent reassessment using objective measures of lung function (PEF) and oxygen saturation. Patients at high risk of asthma-related death require particular attention. First-line therapy consists of oxygen supplementation, repeated administration of inhaled short-acting bronchodilators (beta-2-agonists and ipratropium bromide), and early systemic glucocorticosteroids. Intravenous magnesium sulphate and aminophylline are second- and third-line treatment strategies, respectively, for poorly responding patients. Intensive care is indicated for severe asthma that is not responsive to first-line treatment. Antibiotics are only indicated when there are definite features of bacterial infection. Factors that precipitated the acute asthma episode should be identified and preventive measures implemented. Acute asthma is preventable with optimal control of chronic asthma.
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    Roles of Conserved P Domain Residues and Mg 2+ in ATP Binding in the Ground and Ca 2+-activated States of Sarcoplasmic Reticulum Ca 2+-ATPase
    (2004) McIntosh, David B; Clausen, Johannes D; Woolley, David G; MacLennan, David H; Vilsen, Bente; Andersen, Jens Peter
    Residues in conserved motifs (625)TGD, (676)FARXXPXXK, and (701)TGDGVND in domain P of sarcoplasmic reticulum Ca(2+)-ATPase, as well as in motifs (601)DPPR and (359)NQR(/K)MSV in the hinge segments connecting domains N and P, were examined by mutagenesis to assess their roles in nucleotide and Mg(2+) binding and stabilization of the Ca(2+)-activated transition state for phosphoryl transfer. In the absence of Mg(2+), mutations removing the charges of domain P residues Asp(627), Lys(684), Asp(703), and Asp(707) increased the affinity for ATP and 2',3'-O-(2,4,6-trinitrophenyl)-8-azidoadenosine 5'-triphosphate. These mutations, as well as Gly(626)--> Ala, were inhibitory for ATP binding in the presence of Mg(2+) and for tight binding of the beta,gamma-bidentate chromium(III) complex of ATP. The hinge mutations had pronounced, but variable, effects on ATP binding only in the presence of Mg(2+). The data demonstrate an unfavorable electrostatic environment for binding of negatively charged nucleotide in domain P and show that Mg(2+) is required to anchor the phosphoryl group of ATP at the phosphorylation site. Mutants Gly(626) --> Ala, Lys(684) --> Met, Asp(703) --> Ala/Ser/Cys, and mutants with alteration to Asp(707) exhibited very slow or negligible phosphorylation, making it possible to measure ATP binding in the pseudo-transition state attained in the presence of both Mg(2+) and Ca(2+). Under these conditions, ATP binding was almost completely blocked in Gly(626) --> Ala and occurred with 12- and 7-fold reduced affinities in Asp(703) --> Ala and Asp(707) --> Cys, respectively, relative to the situation in the presence of Mg(2+) without Ca(2+), whereas in Lys(684) --> Met and Asp(707) --> Ser/Asn the affinity was enhanced 14- and 3-5-fold, respectively. Hence, Gly(626) and Asp(703) seem particularly critical for mediating entry into the transition state for phosphoryl transfer upon Ca(2+) binding at the transport sites.