RESUMEN
The mechanism leading to the termination of superoxide production of phagocytes is poorly understood. The aim of the present study was to investigate the involvement of the active (GTP-bound) form of the GTP-binding proteins in maintaining continuous electron transport through the reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex. Activation of the enzyme was carried out under in vitro conditions and a shift from the active to the inactive form of the GTP-binding protein was attained (i) by addition of an excess of GDP to the assembled enzyme complex or (ii) by variation of the Rac-GTPase activating (Rac-GAP) capacity of the constituents of the cell-free system. Significant inhibition of O2*- production was observed when guanine dinucleotides were added after the assembly of the active enzyme complex. The effect was specific for GDP and GDP,S whereas ADP, CDP and UDP were ineffective. GTP was significantly less efficient in inducing superoxide production in a cell-free system containing endogenous GAP activity than in a system devoid of GAP activity. It is suggested that the active, GTP-bound form of Rac is required for sustained catalytic function and Rac-GAP proteins are involved in the downregulation of the oxidase.
Asunto(s)
Neutrófilos/enzimología , Superóxidos/metabolismo , Proteínas de Unión al GTP rac/metabolismo , Animales , Grupo Citocromo c/metabolismo , Transporte de Electrón , Activación Enzimática , Escherichia coli/enzimología , Regulación Enzimológica de la Expresión Génica , Guanosina Difosfato/farmacología , Guanosina Trifosfato/análogos & derivados , Guanosina Trifosfato/farmacología , NADPH Oxidasas/metabolismo , Neutrófilos/metabolismo , Fluoruro de Sodio/farmacología , PorcinosRESUMEN
There is an international trend shortening postpartum hospital stay. While less than 2 days care initiated harsh response in the USA, questions and anxiety were provoked here by reducing puerperal hospital stay from 5-7 to 2 days. Thousand cases out of 7,277 deliveries were discharged early following appropriate education and normal pregnancy. Response from the affected patients and local doctors are discussed. Maternal and neonatal readmission rate call for careful decision making concerning early discharge. Social motivation has to enjoy priority over economic measures.
Asunto(s)
Maternidades , Tiempo de Internación , Periodo Posparto , Femenino , Humanos , Hungría , Masculino , EmbarazoRESUMEN
The possible mechanism of activation of the NADPH oxidase by fluoride was investigated in the cell-free system. It is shown that the stimulatory effect of fluoride is inhibited by guanosine 5'-O-(2-thiodiphosphate) (GDP[S]) and potentiated by GTP. The effect of fluoride is not additive with GTP[S]. Fluoride activation requires the presence of Mg2+ in millimolar concentration but is independent of Al3+. The activating effect of fluoride is preserved in solubilized membrane extract after removal of the majority of heterotrimeric GTP-binding proteins by immunoadsorption. Fluoride has no direct action either on the nucleotide exchange of GTP hydrolysis of the isolated Rac protein. In contrast, fluoride effectively inhibits Rac-GTPase activity enhanced by a membrane component. In this way, fluoride could prolong the prevalence of Rac in the GTP-bound state and, as a consequence, activate NADPH oxidase. The possibility of the involvement of a membrane-bound Rac GTPase-activating protein activity in the physiological regulation of the enzyme is raised.