RESUMEN
FFQ are one of the most widely used tools of research into nutritional epidemiology, and many studies have been conducted in several countries using this dietary assessment method. The present study aimed to evaluate the relative validity of FFQ, in comparison with other methods, in assessing dietary intake of children and adolescents, through a systematic review. Four electronic databases (Embase, PubMed, Scopus and Web of Science) found sixty-seven articles, which met the inclusion criteria (healthy children and adolescents from 3 to 18 years of age; journal articles written in English, Spanish and Portuguese between 1988 and March 2019; results showing the comparison between the FFQ with other methods of assessment of dietary intake). The articles were analysed by two independent reviewers. A meta-analysis was conducted using correlation coefficients as estimate effects between the FFQ and the reference standard method. Subgroup analysis and meta-regression were performed to identify the probable source of heterogeneity. In fifty-five of the sixty-seven studies, a single dietary assessment method was used to evaluate the FFQ; nine combined the two methods and three used three reference methods. The most widely used reference method was the 24-h recall, followed by the food record. The overall relative validity of the FFQ to estimate energy, macronutrient, certain micronutrient and certain food item intakes in children and adolescents may be considered weak. The study protocol was registered in PROSPERO under number CRD42016038706.
RESUMEN
Sustained oscillations in the membrane potential have been observed in a variety of cellular and subcellular systems, including several types of non-excitable cells and mitochondria. For the plasma membrane, these electrical oscillations have frequently been related to oscillations in intracellular calcium. For the inner mitochondrial membrane, in several cases the electrical oscillations have been attributed to modifications in calcium dynamics. As an alternative, some authors have suggested that the sustained oscillations in the mitochondrial membrane potential induced by some metabolic intermediates depends on the direct effect of internal protons on proton conductance. Most theoretical models developed to interpret oscillations in the membrane potential integrate several transport and biochemical processes. Here we evaluate whether three simple dynamic models may constitute plausible representations of electric oscillations in non-excitable membranes. The basic mechanism considered in the derivation of the models is based upon evidence obtained by Hattori et al. for mitochondria and assumes that an ionic species (i.e., the proton) is transported via passive and active transport systems between an external and an internal compartment and that the ion affects the kinetic properties of transport by feedback regulation. The membrane potential is incorporated via its effects on kinetic properties. The dynamic properties of two of the models enable us to conclude that they may represent alternatives enabling description of the generation of electrical oscillations in membranes that depend on the transport of a single ionic species.
