Segmental order and dynamics of polymer chains confined in block copolymer lamellar mesophases: NMR and dielectric relaxation studies.

The PDMS lamellar sublayers of a poly(styrene)-poly(dimethylsiloxane) diblock (PS-PDMS) and PS-PDMS-PS triblocks are investigated by NMR and dielectric spectroscopy. Some segments of the confined PDMS chains display anisotropic orientational fluctuations along the interfaces with the PS glassy blocks, whereas the others display fluctuations rather parallel to the lamellae normal. This coexistence results from a competitive ordering effect induced by the glassy interfaces and the chain-end anchoring junctions.

Methyl group dynamics in a confined glass.

We present a neutron scattering investigation on methyl group dynamics in glassy toluene confined in mesoporous silicates of different pore sizes. The experimental results have been analysed in terms of a barrier distribution model, such a distribution following from the structural disorder in the glassy state. Confinement results in a strong decreasing of the average rotational barrier in comparison to the bulk state.

Determinants of insulin sensitivity and secretion in very-low-birth-weight children.

In prepubertal children, low birth weight is related to reduced insulin sensitivity, particularly if a history of rapid postnatal weight gain is present. We sought to determine whether these associations were also evident in premature, very-low-birth-weight (VLBW) children. We studied 60 VLBW prepubertal children aged 5-7 yr (mean age 5.

Fluorometric determination of chemically available lysine: adaptation, validation and application to different milk products.

A spectrophotometric method based on the reaction between available lysine and ortho-phthaldialdehyde (OPA) was adapted and validated for fluorometric determination of the chemically available lysine contents in milk matrices (UHT and conventional in-bottle sterilized cow milk, milk-based infant formulas and infant formula ingredients). The values of the analytical parameters show its usefulness as a routine method (linearity, r = 0.9992; detection limit, 0.

Out of equilibrium dynamics of poly(vinyl methyl ether) segments in miscible poly(styrene)-poly(vinyl methyl ether) blends.

The local dynamics of the low-T(g) component in a polymer blend, dynamically asymmetric poly(styrene)-poly(vinyl methyl ether) (PS-PVME), is studied below the glass transition, via dielectric relaxation spectroscopy. A particular attention has been paid to blends with a high PS content (PS weight fraction higher than 50%). A relaxation process, slower than the localized motions inducing the PVME secondary relaxations, is detected.

[Prophylaxis of RhD isoimmunization: a proposal of management].

Isoimmunisation RhD has an important perinatal morbidity and mortality. Since prophylaxis was introduced in the sixties, the incidence of haemolytic disease of the newborn has decreased. When administred in due time and in the right dosage anti-D immunoglobulin can prevent sensibilization.

Glucose and lipid metabolism in small for gestational age infants at 48 hours of age.

Objective: To study the consequences of low birth weight on glucose and lipid metabolism 48 hours after delivery.

Methods: We studied 136 small for gestational age (SGA) and 34 appropriate for gestational age (AGA) term neonates who were born in Santiago, Chile. Prefeeding venous blood was obtained 48 hours after birth for determination of glucose, free fatty acids, beta-hydroxy butyrate, insulin, C-peptide, leptin, sex hormone-binding globulin, insulin-like growth factor-binding protein-1 (IGFBP-1), and cortisol.

Effect of traditional, microwave and industrial cooking on inositol phosphate content in beans, chickpeas and lentils.

An high-performance liquid chromatography method for determining inositol phosphate fractions was adapted to legumes. The validity of the method was assessed by estimating the following analytical parameters: linearity (linear response between 125 and 5000 microg inositol hexaphosphate (IP(6))/ml); instrumental precision and method precision (relative standard deviation, %) were 1.9% (IP(6)) for instrumental, and 2.

Reductive activation of terpenylnaphthoquinones.

Four terpenylnaphthoquinones were found to enhance the rate of superoxide production in the presence of ascorbate as detected from the superoxide dismutase (SOD)-inhibitable initial oxygen consumption rates. Initial rates of oxygen consumption in the presence of ascorbate plus quinone increase with an increase in the half-wave reduction potentials of the quinones. These quinones also enhance the rate of Cyt(III)c reduction by xanthine/xanthine oxidase (X/XO) in both air- and nitrogen-saturated aqueous solutions at pH 7.

Dielectric investigation of the temperature dependence of the nonexponentiality of the dynamics of polymer melts.

Using broad band dielectric spectroscopy (10(-5)-10(9) Hz), combining time domain and frequency domain techniques, we study the temperature dependence of the non-Debye character of the alpha relaxation of polymer melts in the glass transition temperature T(g) range. The alpha relaxation process is described in terms of the Kohlrausch-Williams-Watts relaxation function which has a single parameter beta to characterize the nonexponentiality of the relaxation. At high temperatures, beta remains nearly insensitive to temperature changes, whereas in the vicinity of T(g) a nearly linear increasing of beta with temperature is found.

High-performance liquid chromatographic determination of tocopherols in infant formulas.

A method for the simultaneous determination of alpha-tocopherol acetate and alpha-, delta-, and gamma-tocopherols by normal-phase high-performance liquid chromatography (HPLC) with a fluorescent detector in infant formula is proposed. The values obtained in the determination of the analytical parameters: linearity, precision, limit of detection and accuracy (analysis of a standard reference material, SRM 1846), confirm the quality of the method. The proposed method is useful for the determination of alpha-, delta-, and gamma-tocopherols and alpha-tocopherol acetate in infant formulas at a low cost and in a total time of 2 h.

High-performance liquid chromatographic determination of furfural compounds in infant formulas. Changes during heat treatment and storage.

Furfural contents in adapted and follow-up infant formulas were measured by RP-HPLC. The evolution of furfural compound contents during storage (a year at 20 and 37 degrees C) was studied. 2-Furylmethylketone and 5-methyl-2-furaldehyde were not detectable in analysed samples.

[Other indications for surfactant].

Objective: The introduction of surfactant replacement therapy in the management of respiratory distress syndrome in the premature infant was a remarkable advance in neonatal intensive care. In the last few years, recognition of the role played by surfactant inactivation in the pathogenesis of other respiratory diseases of the newborn has justified new therapeutic applications. The aim of this study was to evaluate the efficacy of treatment with natural exogenous surfactant in situations with secondary surfactant deficiency.

Role of membrane charge and semiquinone structure on naphthosemiquinone derivatives and 1,4-benzosemiquinone disproportionation and membrane-buffer distribution coefficients.

Semiquinone membrane/buffer partition coefficients have been determined for 1,2-naphthosemiquinone (ONQ.-), 1,4-naphthosemiquinone (NQ.-) and two of its hydroxylated derivatives, 5,8-dihydroxy-1,4-naphthosemiquinone (NZQ.

Amino acid profile of milk-based infant formulas.

The protein content and amino acid profile of three milk-based infant formulas, two of which were powdered (adapted and follow-on) and the third liquid, were determined to check their compliance with the EU directive and to evaluate whether or not they fulfil an infant's nutritional needs. To obtain the amino acid profile proteins were subjected to acid hydrolysis, prior to which the sulfur-containing amino acids were oxidized with performic acid. The amino acids were derivatized with phenylisothiocyanate (PITC) and then determined by ion-pair reverse phase high performance liquid chromatography (HPLC) In the case of tryptophan a basic hydrolysis was applied and there was no need of derivatization.

In vitro dialyzability of zinc from different salts used in the supplementation of infant formulas.

Seven zinc salts--acetate, chloride, lactate, sulfate, citrate, gluconate, and oxide--were added to milk--and soy-based infant formulas to estimate possible differences in zinc availability depending on the type of salt used. For this purpose, an in vitro method that estimates the dialyzability of the element (i.e.

Selenium, copper, and zinc indices of nutritional status: influence of sex and season on reference values.

The objective was to estimate the possible influence of season or season and sex on the selenium, glutathione peroxidase (GSH-Px), copper, zinc, and superoxide dismutase (SOD) values in plasma with a view to establishing reference values. For this purpose, 55 healthy volunteers (36 women and 19 men) were selected and their whole-blood samples were collected four times a year at the beginning of each season. In the population as a whole, no statistically significant seasonal differences were detected in copper, selenium, and GSH-Px values in plasma, whereas zinc and SOD values in plasma depended on the season.

High-performance liquid chromatographic determination of Maillard compounds in store-brand and name-brand ultra-high-temperature-treated cows' milk.

Furosine and furfural products of the Maillard reaction are used as specific indicators of the effect of heating treatments on milk quality. Their contents were measured in representative samples of store- and name-brand ultra-high-temperature-treated milks using RP-HPLC with UV detection. Furosine contents ranged from 40.

Effects of thermal processing and storage on available lysine and furfural compounds contents of infant formulas.

The Maillard reaction-related effects that thermal treatments during the manufacturing process and storage (at 20 and 37 degrees C) have on powdered adapted and follow-up milk-based infant formulas were estimated by measuring the available lysine and furfural compounds contents of raw cow milk used in manufacturing, intermediate products and formulas. A fluorimetric method was used to measure the available lysine contents, and free and total furfural compounds were determined by HPLC. Statistically significant losses in available lysine (about 20%) in the infant formulas with respect to raw milk were found.

Effect of proteins, phytates, ascorbic acid and citric acid on dialysability of calcium, iron, zinc and copper in soy-based infant formulas.

The possible effect of ascorbic acid, citric acid, proteins and phytate on dialysability of Ca, Fe, Zn and Cu in soy-based infant formulas is studied, taking dialysability as a measure of the amount of element available for absorption. Different dialysis percentages for similar element contents in different formulas are found. A regression analysis was applied between Ca, Zn, Cu and Fe dialysis percentages and soy-based formula components to estimate the possible influence of the latter on the dialysability of the elements.

Sonochemistry of quinones in argon-saturated aqueous solutions: enhanced cytochrome c reduction.

Sonolysis of argon-saturated aqueous quinone solutions resulted in an enhancement in ferricytochrome c (Cyt c) reduction. Upon addition of superoxide dismutase, Cyt c reduction was partially inhibited, thus implying a role of superoxide ion in this reduction process. Neither quinone hydrophobicity nor reduction potential exclusively controls the Cyt c reduction enhancement, although a preference for hydrophobicity versus reduction potential is noted.

Selenium contents of human milk and infant formulas in Spain.

The selenium content of Spanish human milk samples and different milk-based and soy-based infant formulas has been estimated by using a flow injection hydride atomic absorption spectrometric method after microwave digestion of the organic matter. Mean values of 11.4 +/- 3.

Lipid peroxidation and antioxidant enzyme activities in patients with type 1 diabetes mellitus.

To evaluate oxidative stress in type I diabetes mellitus, two antioxidant enzymes in erythrocytes, copper-zinc superoxide dismutase (SOD EC 1.15.1.