Background: Acylcarnitines are biomarkers of fatty acid metabolism, and examining their patterns in preterm newborn may reveal metabolic changes associated with particular conditions related to prematurity. Isomeric acylcarnitines in dried blood spots (DBS) and plasma have never been assessed in preterm infants. Methods: We studied 157 newborn divided into four groups by weeks of gestational age (GA), as follows: 22-27 wk in group 1; 28-31 wk in group 2; 32-36 wk in group 3; and 37-42 wk in group 4. Samples were collected on the third day of life. Acylcarnitines were separated and quantified using ultra-performance liquid chromatography tandem mass spectrometry. results: Acylcarnitine concentrations correlated significantly with GA and birth weight in both DBS and plasma samples. Concentrations were lower in preterm newborn, except for acylcarnitines derived from branched-chain amino acids, which were higher and correlated with enteral feeding. On day 3 of life, no correlations emerged with gender, respiratory distress syndrome, bronchopulmonary dysplasia, surfactant administration, or mechanical ventilation. conclusion: We established GA-based reference ranges for isomeric acylcarnitine concentrations in preterm newborn, which could be used to assess nutritional status and the putative neuroprotective role of acylcarnitines.F atty acid metabolism takes place in the mitochondria, and β-oxidation is the main process by which fatty acids are oxidized by means of a sequential removal of two-carbon units from the acyl chain. Fatty acids are activated primarily in the cytosol by fatty acyl-CoA synthase to carnitine derivatives, then they are carried by specific acylcarnitine (AC) transferases and translocases into the mitochondrial matrix where β-oxidation can begin. In successive cycles of reactions, this process generates a series of ACs that are one two-carbon unit shorter and it continues until only two or three carbons are left (forming acetyl-CoA or propionyl-CoA, respectively). AC detection is of great interest for the purpose of assessing the carnitine pool, which is essential to the diagnosis of several metabolic disorders. AC profiling is a powerful tool for the neonatal screening and diagnosis of fatty acid oxidation and organic acid disorders (1). Alongside the importance of AC in tissues such as heart and muscle, recent data indicate an involvement of these compounds in neurological protection and disorders. ACs are believed to have both energy-providing and neuroprotective roles in the brain (2,3), based on the assumption that the fatty acid oxidation pathway is active in neurons, given the localization of carnitine palmitoyltransferase enzyme 1 (CPT1) (2,4). Investigating AC profiles in preterm infants may therefore reveal metabolic changes associated with perinatal brain injury.Mass spectrometry (MS) is commonly used to quantify ACs. Millington and co-workers pioneered tandem mass spectrometry (MS/MS) methods for assaying carnitine and ACs in urine and plasma samples (5), and in dried blood spots (DBS...

Este estudio se propone estimar econométricamente el impacto de los componentes sistémicos de ciertos agregados macroeconómicos sobre el grado de morosidad de la cartera de crédito del sistema bancario en Venezuela. Con sustentación en la teoría, las estimaciones usan series trimestrales que van desde el cuarto trimestre de 1992 hasta el cuarto trimestrede 2004, y el modelo estimado ulteriormente se usa para predecir la evolución de corto plazo de calidad de la cartera. Dos versiones dinámicas usando un modelo ADL muestran buenos resultados en términos de los errores de proyección de la variable ajustada dentro de la muestra (insample), de los errores que derivan de una proyección ex-post y de la proyección condicionada para los cuatro trimestres de 2005.