Early free access to hypertonic NaCl solution induces a long-term effect on drinking, brain cell activity and gene expression of adult rat offspring.

Exposure to an altered osmotic environment during a pre/postnatal period can differentially program the fluid intake and excretion pattern profile in a way that persists until adulthood. However, knowledge about the programming effects on the underlying brain neurochemical circuits of thirst and hydroelectrolyte balance, and its relation with behavioral outputs, is limited. We evaluated whether early voluntary intake of hypertonic NaCl solution may program adult offspring fluid balance, plasma vasopressin, neural activity, and brain vasopressin and angiotensinergic receptor type 1a (AT1a)-receptor gene expression. The manipulation (M) period covered dams from 1 week before conception until offspring turned 1-month-old. The experimental groups were (i) Free access to hypertonic NaCl solution (0.45 M NaCl), food (0.18% NaCl) and water [M-Na]; and (ii) Free access to food and water only [M-Ctrol]. Male offspring (2-month-old) were subjected to iv infusion (0.15 ml/min) of hypertonic (1.5M NaCl), isotonic (0.15M NaCl) or sham infusion during 20 min. Cumulative water intake (140 min) and drinking latency to the first lick were recorded from the start of the infusion. Our results indicate that, after systemic sodium overload, the M-Na group had increased water intake, and diminished neuronal activity (Fos-immunoreactivity) in the subfornical organ (SFO) and nucleus of the solitary tract. They also showed reduced relative vasopressin (AVP)-mRNA and AT1a-mRNA expression at the supraoptic nucleus and SFO, respectively. The data indicate that the availability of a rich source of sodium during the pre/postnatal period induces a long-term effect on drinking, neural activity, and brain gene expression implicated in the control of hydroelectrolyte balance.

Effect of surface charge on colloidal charge reversal.

The objective of this research work is to understand the effect of the surface charge density on the charge reversal phenomenon. To this end, we use experimental results and computer simulations. In particular, we measure the electrophoretic mobility of latex particles (macroions) in the presence of a multivalent electrolyte. We have focused on the electrolyte concentration range at which a reversal in the electrophoretic mobility is expected to happen. In particular, the role of the surface charge on the charge reversal process is looked into from several latexes with the same functional group but different surface charge densities. Although the mechanism responsible for the colloidal charge reversal is still a controversial issue, it is proved that ionic correlations are behind the appearance of such phenomenon (especially near the macroion surface). This conclusion can be inferred from a great variety of theoretical models. According to them, one of the factors that determine the charge reversal is the surface charge density of the macroions. However, this feature has been rarely analyzed in experiments. Our results appear therefore as a demanded survey to test the validity of the theoretical predictions. Moreover, we have also performed Monte Carlo simulations that take the ion size into account. The correlation found between experiments and simulations is fairly good. The combination of these techniques provides new insight into the colloidal charge reversal phenomena showing the effect of surface charge.

Interaction between poly(ethylene glycol) and two surfactants investigated by diffusion coefficient measurements.

Dynamic light scattering (DLS) and fluorescence recovery after pattern photobleaching (FRAPP) were used to study the interaction of low molecular weight poly(ethylene glycol) (PEG) with micelles of two different surfactants: tetradecyldimethyl aminoxide (C(14)DMAO, zwitterionic) and pentaethylene glycol n-dodecyl monoether (C(12)E(5), non-ionic). By using an amphiphilic fluorescent probe or a fluorescent-labeled PEG molecule, FRAPP experiments allowed to follow the diffusion of the surfactant-polymer complex either by looking at the micelle diffusion or at the polymer diffusion. Experiments performed with both fluorescent probes gave the same diffusion coefficient showing that the micelles and the polymer form a complex in dilute solutions. Similar experiments showed that PEG interacts as well with pentaethylene glycol n-dodecyl monoether (C(12)E(5)).

Determinacion de triptofano en suero total y en una fraccion precipitada con sulfato de amonio. / Determination of tryptophan in total serum and in an ammonium sulfate precipitated fraction

En este articulo se describe un procedimiento alternativo para investigar los niveles de triptofano libre en suero sanguineo. Para esto, se determinaron mediante un metodo fluorometrico la concentracion de triptofano en suero total y en fracciones precipitadas con sulfato de amonio a 30, 35, 40, 45, 50 y 55 por ciento de saturacion. La concentracion de triptofano en suero total fue siempre mayor que la de las fracciones estudiadas. Se encontrarion pocas variaciones entre la concentracion de triptofano en las fracciones que se obtuvieron a 30, 35 y 40 por ciento de saturacion se observo un ligero incremento en el contenido de triptofano. Los datos obtenidos sugieren que, a partir de estas mediciones, se puede determinar con precision y relativa facilidad el contenido de triptofano libre en suero