Semiparametric partial linear modeling of risk factors for ear infections: the Early Childhood Longitudinal Study.

The Early Childhood Longitudinal Study-Kindergarten Class of 2010-2011 (ECLS-K:2011) ascertained timing of ear infections within age specified intervals and parent's/caregiver's report of medically diagnosed hearing loss. In this nationally representative, school-based sample of children followed from kindergarten entry through fifth grade, academic performance in reading, mathematics, and science was assessed longitudinally. Prior investigations of this ECLS-K:2011 cohort showed that age has a non-linear, monotonically increasing functional relationship with academic performance. Because of this knowledge, a semiparametric partial linear model is proposed, in which the effect of age is modeled by an unknown monotonically increasing function along with other regression parameters. The parameters are estimated by a semiparametric maximum likelihood estimator. A test of a constant effect of age is also proposed. Simulation studies are conducted to evaluate the performance of the proposed method, as compared with the commonly used linear model; the former outperforms the latter based on several criteria. We then analyzed ECLS-K:2011 data to compare results of the partial linear parametric model estimation with that of classical linear regression models.

Access to fruit and vegetable markets and childhood obesity: A systematic review.

The lack of access to fruit/vegetable markets (FVMs) is thought to be a risk factor for childhood obesity by discouraging healthy dietary behaviours while encouraging access to venues that offer more unhealthy food (and thus the compensatory intake of those options). However, findings remain mixed, and there has not been a review of the association between FVM access and childhood obesity. A comprehensive and systematic understanding of this epidemiologic relationship is important to the design and implementation of relevant public health policies. In this study, a literature search was conducted in the Cochrane Library, PubMed, and Web of Science for articles published before 1 January 2019 that focused on the association between neighbourhood FVM access and weight-related behaviours and outcomes among children and adolescents. Eight cross-sectional studies, two longitudinal studies, and one ecological study conducted in five countries were identified. The median sample size was 2142 ± 1371. Weight-related behaviours and outcomes were used as the outcome variable in two and eight studies, respectively, with one study using both weight-related behaviours and outcomes as outcome variables. We still found a negative association between access to FVMs in children's residential and school neighbourhoods and weight-related behaviours and an inconclusive association between FVM access and overweight or obesity. This conclusion should be regarded as provisional because of a limited amount of relevant evidence and may not be a strong guide for policymaking. Nonetheless, it points to an important research gap that needs to be filled if successful public health interventions are to be undertaken.

Analysis of endogenous epinephrine and norepinephrine enantiomers in rat plasma and application to a stereoselective pharmacokinetics.

Epinephrine and norepinephrine are a class of chiral endogenous catecholamines, which are known as major neurotransmitters. This work described a new LC-MS/MS method coupled with pre-column derivatization, enabling the simultaneous enantiomeric separation of epinephrine and norepinephrine in rat plasma. After protein precipitation procedure, the samples were derivatized with (S)-N-(4-nitrophenoxycarbonyl) phenylalanine methoxyethyl ester, [(S)-NIFE]. The derivatives resolved with good baseline separation on an ACQUITY UPLC BEH C18 column (100 mm × 2.1 mm, 1.7 µm) with mobile phase composed of methanol with 0.2% formic acid in water at a flow rate of 0.2 mL/min. Analysis was performed by multiple reaction monitoring in positive ionization mode. The linear ranges were 1.0-500 ng/mL for epinephrine enantiomers and 1.5-750 ng/mL for norepinephrine enantiomers. The lower limits of quantification for epinephrine and norepinephrine enantiomers were 1.0 and 1.5 ng/mL, respectively. The intra-day and inter-day precision were all less than 10.7% and accuracy ranged from 96.0 to 101.5%. Recoveries for all the analytes were more than 80.3%. The proposed method was successfully applied to simultaneously determine endogenous epinephrine and norepinephrine enantiomers in rat plasma. l-epinephrine and l-norepinephrine were sensitively and accurately quantified while both the d-enantiomers were not detected. Additionally, epinephrine enantiomers were analyzed for stereoselective pharmacokinetics in rats after intravenous administration of racemic epinephrine for the first time. The pharmacokinetic results indicated that the disposition of epinephrine enantiomers was stereoselective and chiral inversion did not occur in rats.

Compositional characterization study on high -molecular -mass polymeric polyphenols in red wines by chemical degradation.

High-molecular-mass polymeric polyphenols (HPPCs) is the major group of polyphenols in red wine. However, owing to the diversity and structural complexity, its compositional characterization remains a difficulty. In this study, purified high-molecular-mass polymeric polyphenols (PHPPCs) was isolated by solid phase extraction combined with semi-preparative HPLC from red wine. Different chemical degradation methods (NaOH, HCl and benzyl mercaptan degradation) were used to decompose the PHPPCs into low molecular weight fragments. The chemical structures of the degradation fragments were verified by HPLC/UPLC-DAD and HPLC-FT-ICR-MS. The results showed that three proanthocyanidins, five proanthocyanidins benzylthioether, quercetin and fifteen anthocyanins were detected by degradation in the presence of benzyl mercaptan. Nine bound phenolic acids were found by NaOH degradation and twelve bound amino acids were proved by HCl. Among these different fragments detected,delphinidin-3-O-glucoside pyruvic adduct, four acylated anthocyanins, four hydroxyphenyl pyranoanthocyanins, quercetin, protocatechuic acid, vanillic acid, and cinnamic acid were first found in the PHPPCs. For the first time amino acids as constitutive units of polymeric polyphenols in red wines were verified. Based on the degradation fragments, the possible compositional characterization of HPPCs in red wine was postulated.

Novel Catechin-Tiopronin Conjugates Derived from Grape Seed Proanthocyanidin Degradation: Process Optimization, High-Speed Counter-Current Chromatography Preparation, as Well as Antibacterial Activity.

Tiopronin, as a novel thiol-containing nucleophile, was introduced for depolymerizing polymeric proanthocyanidins from grape seed into catechins and three new proanthocyanidin-tiopronin degradation products: (+)-catechin-4ß-S-tiopronin methyl ester (CT), (-)-epicatechin-4ß-S-tiopronin methyl ester (ECT), and (-)-epicatechin gallate-4ß-S-tiopronin methyl ester (ECGT). A Box-Behnken design was employed to optimize degradation conditions based on single-factor experiments to obtain target products. Each of the new degradation compounds was isolated by the high-speed counter-current chromatography combined with semipreparative high performance liquid chromatography in large amounts, and then, their structures were identified by 1H NMR, 13C NMR, 2D-NMR, as well as mass spectrometry analysis. The absolute configurations were further confirmed by comparison between the calculated electronic circular dichroism and experimental spectra. Further evaluation of antibacterial activities of these compounds showed that CT and ECT possessed more inhibiting capacity against Staphylococcus aureus and Escherichia coli than parent compound catechin and epicatechin. However, ECGT has no bacteriostatic capacity against these two bacteria.