Minipuberty in Male Full-term Neonates Appropriate and Small for Gestational Age and in Preterm Babies: Data from a Single Centre

Objective

The postnatal activation of the hypothalamic-pituitary-gonadal (HPG) axis is usually known as “minipuberty”. There are still open questions about its biological function and significance depending on sex, gestational age (GA) and birth weight (BW) with few available longitudinal data.

Methods

A single-centre, longitudinal study to quantify urinary follicle stimulating hormone (uFSH), luteinizing hormone (uLH) and testosterone (uTs) in male neonates. Neonates were enrolled and stratified into three subgroups: full-term boys appropriate for GA (FT AGA); FT boys with BW ≤3rd centile [FT small for gestational age (SGA)]; and preterm (PT) boys ≤33 weeks of GA. Urinary hormones were correlated to simultaneous auxological parameters, linear growth and external genitalia at scheduled time-points.

Results

Forty-six boys were recruited, with subgroup sizes FT AGA n=23, FT SGA n=11 and PT n=12. PT boys display a pulsatile pattern of urinary gonadotropins (uGns) with higher levels of uLH and a gradual increase of uTs. Testicular descent started from 29-32 weeks with the peak of uTs. During the first 12-months post-term age (PTA), FT AGA boys displayed a better linear growth (p<0.05). PT showed higher uGns levels until 3-months PTA. PT babies had higher uLH levels than FT AGA, with a peak at 7 and 30 days, during the first 90 days of life (p<0.001) and higher uTs levels. Correlation analysis between penile growth of all neonates and uTs was significant (p=0.04) but not within subgroups.

Conclusion

This study investigated postnatal HPG axis activation in term and PT infants. Minipuberty may involve an early window of opportunity to evaluate the functionality of the HPG axis. Further studies with a long-term follow-up are needed with a special focus on possible consequences of GA and BW.

Electrostatically Driven Protein Adsorption: Charge Patches versus Charge Regulation

The mechanisms of electrostatically driven adsorption of proteins on charged surfaces are studied with a new theoretical framework. The acid-base behavior, charge distribution, and electrostatic contributions to the thermodynamic properties of the proteins are modeled in the presence of a charged surface. The method is validated against experimental titration curves and apparent p K_as. The theory predicts that electrostatic interactions favor the adsorption of proteins at their isoelectric points on charged surfaces despite the fact that the protein has no net charge in solution. Two known mechanisms explain adsorption under these conditions: (i) charge regulation (the charge of the protein changes due to the presence of the surface) and (ii) charge patches (the protein orients to place charged amino acids near opposite surface charges). This work shows that both mechanisms contribute to adsorption at low ionic strengths, whereas only the charge-patch mechanism operates at high ionic strength. Interestingly, the contribution of charge regulation is insensitive to protein orientation under all conditions, which validates the use of constant-charge simulations to determine the most stable orientation of adsorbed proteins. The present study also shows that the charged surface can induce large shifts in the apparent p K_as of individual amino acids in adsorbed proteins. Our conclusions are valid for all proteins studied in this work (lysozyme, α-amylase, ribonuclease A, and β-lactoglobulin), as well as for proteins that are not isoelectric but have instead a net charge in solution of the same sign as the surface charge, i.e. the problem of protein adsorption on the "wrong side" of the isoelectric point.

Self-assembly of model short triblock amphiphiles in dilute solution

In this work, a molecular theory is used to study the self-assembly of short diblock and triblock amphiphiles, with head-tail and head-linker-tail structures, respectively. The theory was used to systematically explore the effects of the molecular architecture and the affinity of the solvent for the linker and tail blocks on the relative stability of the different nanostructures formed by the amphiphiles in dilute solution, which include spherical micelles, cylindrical fibers and planar lamellas. Moreover, the theory predicts that each of these nanostructures can adopt two different types of internal organization: (i) normal nanostructures with a core composed of tail segments and a corona composed of head segments, and (ii) nanostructures with a core formed by linker segments and a corona formed by tail and head segments. The theory predicts the occurrence of a transition from micelle to fiber to lamella when increasing the length of the tail or the linker blocks, which is in qualitative agreement with the geometric packing theory and with experiments in the literature. The theory also predicts a transition from micelle to fiber to lamella as the affinity of the solvent for the tail or linker block is decreased. This result is also in qualitative agreement with experiments in the literature but cannot be explained in terms of the geometric packing theory. The molecular theory provides an explanation for this result in terms of the competition between solvophobic attractions among segments in the core and steric repulsions between segments in the corona for the different types of self-assembled nanostructures.

Dynamics of dissipative self-assembly of particles interacting through oscillatory forces

Dissipative self-assembly is the formation of ordered structures far from equilibrium, which continuously uptake energy and dissipate it into the environment. Due to its dynamical nature, dissipative self-assembly can lead to new phenomena and possibilities of self-organization that are unavailable to equilibrium systems. Understanding the dynamics of dissipative self-assembly is required in order to direct the assembly to structures of interest. In the present work, Brownian dynamics simulations and analytical theory were used to study the dynamics of self-assembly of a mixture of particles coated with weak acids and bases under continuous oscillations of the pH. The pH of the system modulates the charge of the particles and, therefore, the interparticle forces oscillate in time. This system produces a variety of self-assembled structures, including colloidal molecules, fibers and different types of crystalline lattices. The most important conclusions of our study are: (i) in the limit of fast oscillations, the whole dynamics (and not only those at the non-equilibrium steady state) of a system of particles interacting through time-oscillating interparticle forces can be described by an effective potential that is the time average of the time-dependent potential over one oscillation period; (ii) the oscillation period is critical to determine the order of the system. In some cases the order is favored by very fast oscillations while in others small oscillation frequencies increase the order. In the latter case, it is shown that slow oscillations remove kinetic traps and, thus, allow the system to evolve towards the most stable non-equilibrium steady state.

Serum ferritin as a predictor of treatment outcome in patients with chronic hepatitis C

OBJECTIVES

Antiviral treatment in chronic hepatitis C (CHC) involves ribavirin, a hemolytic agent. We planned a prospective study to evaluate whether drug-induced iron perturbation is clinically relevant as it relates to therapeutic outcome.

METHODS

Iron variables were sequentially assessed in 206 CHC patients undergoing antiviral therapy and were correlated with pretreatment iron status and histology, hemolysis, and therapeutic outcome.

RESULTS

At week 1 of therapy, serum iron (SI), transferrin saturation (TS), and serum ferritin (SF) increased markedly in all patients. All iron parameters correlated with hemolysis up to week 4; this correlation was lost for SF at later time points. SF rise during treatment was inversely related to baseline SF and iron deposits in hepatic mesenchymal/Kupffer cells. Both baseline SF and mesenchymal iron significantly correlated with fibrosis at multivariate analysis (P=0.015 and 0.008, respectively). Interestingly, baseline SF, despite good specificity (89%), had low sensitivity in predicting siderosis (25%). During therapy, SI, TS, and hemolysis parameters did not correlate with sustained virological response (SVR), whereas SF rise became an independent predictor of therapeutic response: a 2.5-fold increase of SF at week 12 associated with higher likelihood of SVR (odds ratio 1.91, P=0.032). Accordingly, lack of mesenchymal iron deposits at the baseline biopsy correlated with SVR (odds ratio 3.02, P=0.043).

CONCLUSIONS

In CHC, SF is a useful marker for assessing disease duration and progression before starting treatment and for predicting therapeutic response while on therapy. SF rise during antiviral therapy is largely independent of hemolysis and likely indicates activation of macrophages in response to antivirals.

Oxidation-reduction dynamics in layer-by-layer self-assembled redox polyelectrolyte multilayer modified electrodes

The oxidation-reduction dynamics of layer-by-layer (LbL) self-assembled redox polyelectrolyte multilayer films on electrodes has been studied by cyclic voltammetry, chrono-amperometry, electrochemical quartz crystal microbalance (EQCM), ellipsometry, and Fourier transform reflection-absorption infrared spectroscopy (FT-IRRAS). Thin layer electrochemistry with fast electron transfer at the underlying metal-film interface and charge propagation by electron hopping between adjacent redox sites in the finite thin film has been observed. An almost ideal cyclic voltammetry for a fixed number of redox sites in the thin surface film suggests that the multilayer can be fully oxidized and reduced in the time scale of the experiment (RT/vF > or = 0.05 sec). The electron hopping diffusion coefficient 3 x 10(-10) cm2 s(-1) was obtained from the chronoamperometric current transient and the ellipsometric thickness. Both cyclic voltammetry and potential step yield a surface osmium bipyridyl redox concentration of gamma Os = 4 x 10(-10) mol x cm(-2) for (PAH-Os)5(PVS)4 film. Exchange of ions and solvent occur simultaneously to the charge injection as revealed by the EQCM mass change and the ellipsometric thickness change. From the end-to-end mass-to-charge linear relationship, the molar mass of the ionic and neutral species exchanged largely exceeds the molar mass of any ions or solvent which suggests an important flux of solvent during redox switching. An initial "break in" effect is observed for the first oxidation-reduction cycles when a newly self-assembled film equilibrates with the electrolyte as charge is injected during the electrochemical perturbation.

Dielectric Properties of Binary Mixtures of 1,2-Dichloroethane+Ethane-1,2-diol and 1,2-Dichloroethane+2-Methoxyethanol

The dielectric behaviour of binary mixtures of 1,2-dichloroethane (DCE)/ethane-1,2-diol (ED) and DCE/2-methoxyethanol (ME) has been studied at 19 temperatures in the range from -10 to +80°C. The DCE/ED system is immiscible, except in a narrow range near the ED-rich region. The DCE/ME system, which is completely miscible, has been investigated over the whole composition range. Fitting procedures have been applied in order to check the suitability of empirical or semiempirical functions of the type є(T), є(XI) and є(T,XI). Furthermore, the excess static dielectric constant, єE, has been evaluated in order to investigate the possibility of the existence of complex entities. A DCE.2ME species appears to be the only stable adduct.

Associating Behavior of Mixed Liquids: Dielectric Properties of the Ethane-1,2-Diol+1,4-Dioxan Solvent System From -10 to +80°C

The associating behaviour of ethane-1,2-diol (component 1)+1,4-dioxan (component 2) in their binary mixtures has been investigated through their dielectric properties. The experimental measurements of the relative permittivity (є) in the temperature range -10 ≤ X1 ≤ 80 for nine binary mixtures covering the whole miscibility field 0 ≤ X1 ≤ 1 have been utilized to test empirical equations representing the functions є = є(T), є = є (X1) and є = є(T,X1). Furthermore, the excess mixing function, єE, has been evaluated to obtain qualitative and quantitative information about the possibility of 'solvent- cosolvent ' complex formation.

Thermodynamics of Viscous Flow in Ethane-1,2-diol+Water Binary Mixtures

Kinematic viscosities (v) of pure ethane-1,2-diol (component 1) and of nine mixtures with water (component 2) were measured at 19 temperatures ranging from -10 to +80°C, and for binary compositions covering the whole miscibility field expressed by the relation 0 ≤ X1 ≤ 1. The property fitted some empirical equations in terms of the dependences v = v(T) and v(X1), where T is the thermodynamic temperature and X1 is the mole fraction of ethane-1,2-diol. Furthermore, the excess function (vE) and the excess Gibbs energy of activation of viscous flow (∆G*E) have been investigated. The trend of vE against binary composition of the mixtures shows negative deviations from ideal behaviour, while the contrary is true for ∆G*E The results indicate specific molecular interactions between the components, and an overview is given on the basis of the molecular dynamics of the pure species.

Electrolytic dissociation of sodium tetraphenylborate in 2-methoxyethanol/water binary solvent mixtures

Thermodynamic properties from conductance data are reported for the NaBPh4 electrolytic solutions in 2-methoxyethanol (component 1)/water (component 2) binary solvent mixtures, working at 19 temperatures ranging from −10 to +80 °C and for 6 mixtures covering the 0.1865 ≤ x1 ≤ 1 composition range. Experimental conductivity data were analysed using the Fuoss–Hsia equation, and the chosen salt was found to associate to a certain extent in these solvent mixtures. The resulting dissociation constants (K) of the ion-pair have been used to test some empirical equations K = K(T), K = K(x1), and K = K(T, x1). Furthermore, the present findings have been compared with our previously reported results from working with picric acid in the same mixtures and experimental conditions.

Thermodynamic Analysis of Viscosity Data of Ethane-1,2-diol+1,4-Dioxan Binary Mixtures

Kinematic viscosities (v) have been measured for pure ethane-1,2-diol, 1,4-dioxan and for nine of their mixtures covering the entire composition range and, where possible, at 19 temperatures from -10 to +80°C. The experimental values were converted into dynamic viscosities (η) and were correlated with temperature and binary composition by some empirical equations. Furthermore, the excess function ηE and the excess Gibbs energy of activation of viscous flow ΔG*E have been evaluated. Negative deviations from ideality are always observed for this binary system, this fact indicating strong specific interactions between unlike entities in solution to form stable solvent- cosolvent adducts. Activation enthalpies and entropies for viscous flow have been derived, and their dependence on binary composition is also discussed.

Volumetric Behavior of 2-Methoxyethanol+1,2-Dimethoxyethane Binary Mixtures

Thermodynamic interactions in 2-methoxyethanol (component 1)+1,2-dimethoxyethane (component 2) binary mixtures have been studied in terms of the excess molar volume from the densities, measured at 19 temperatures between -10 and 80°C, for nine binary mixtures covering the whole miscibility field expressed by the mole fraction 0 ≤ X1 ≤ 1. Excess molar volumes are discussed in terms of induced conformational changes in each component in the presence of the other. The present findings support a hypothesis about the formation of a solvent-cosolvent complex species which has a well defined 1:1 stoichiometric composition and is thermostable under the experimental conditions.

A Non-Linear Correlation Model for the Relative Permittivity of Ternary Amphiprotic (Solvent) Mixtures

Relative permittivities (є) were determined for ternary ethane-1,2-diol (component 1)/2- methoxyethanol (component 2)/water (component 3) mixtures at five temperatures ranging from 5 to 25°C and over the mole fraction composition range 0 ≤ Xi ≤ 1. The data have been fitted to a model equation that could be useful for predictive є calculations. From the measured є values, the excess relative permittivity єE has been evaluated in order to test for three-component adducts. The values of єE have been found to be negative for all the ternary mixtures under all the experimental conditions, which suggests a strong interaction network through hydrogen bonding, although evidence for a discrete three-component adduct was not forthcoming.

Viscosity Data and Viscous Flow Thermodynamics of 2-Methoxyethanol+ Water Binary Mixtures

Kinematic viscosities (v) have been measured for pure 2-methoxyethanol, pure water, and nine of their mixtures over the entire composition range and, where possible, at 19 temperatures ranging from -10 to +80°C. The above property was fitted by empirical equations stating its dependence on temperature (T) and mole fraction (X1) of the mixtures. The experimental data for the binary mixtures were used to test the validity of mixing rules at different temperatures.

The Relative Permittivity of 1,2-Dimethoxyethane/Water Solvent Mixtures From -10 to 80°C

Relative permittivities (є) and the excess property (єE) for the binary mixtures formed by 1,2-dimethoxyethane with water have been measured at various temperatures in the range from -10 to +80°C. These mixtures have interesting properties for electroanalytical applications. Their study should help in understanding the phenomenology of cosolvency towards ionizable and inert solutes. The results of the єE analysis are discussed in terms of the influence of interactions between the components, order and degree of packing in the mixtures, and any other structural effect which occurs in solution.

Dissociation equilibria of picric acid in the binary N, N-dimethylformamide/2-methoxyethanol solvent system

Three empirical equations are proposed to fit the experimental values of the dissociation constant for picric acid, chosen as guide-solute working in the N, N-dimethylformamide/2-methoxyethanol solvent system. The work was performed operating at 19 temperatures ranging from − 10 to + 80 °C in the pure solvents and in their nine mixtures, identified by the mole fraction (X) of one component. This empirical treatment, which describes the dependence of the dissociation constant on temperature and composition of the solvent mixture, is represented by functions of the type K = K(T), K = K(X), and K = K(T, X). The K = K(T, X) equation in its complete form is composed of 20 terms, some of which can be eliminated because of small statistical weight; the number and type of these terms vary on passing from one solvent system to another and the best-fitting form is suggested. A comparison among various K = K(T, X) equations proposed in the present and in previous works has been made. Key words: dissociation equilibria, binary nonaqueous solvent mixtures, picric acid, N,N-dimethylformamide, 2-methoxyethanol.

Crystal Structure of N,N'-Diphenyl-guanidinium m-Chlorobenzeneseleninate

The synthesis, and crystal and molecular structure of N,N′- diphenylguanidinium m- chlorobenzeneseleninate (C19H18CIN3O2Se), Mr 434.78, are reported. The crystal lattice of the compound belongs to the monoclinic space group P21/c with a 7.277(1), b 12.793(2), c 20.013(4) Ǻ, β 94.733(12)°, V 1859.8 Ǻ3, Z 4, Dobs 1.53 (by flotation), Dcalc 1.555 g cm-3, λ(Mo Kα ) 0.71069 Ǻ, μ 21.0 cm-1, F(000) 880, T 293 K, R 0.057 and Rw 0.059 for 1745 unique observed reflections with I>2.0σ(I). The crystal packing consists of parallel layers of anions intercalated with cations interacting through electrostatic contacts. Vibrational spectra have been also recorded, and are discussed.