Plasticity of histamine H3 receptor expression and binding in the vestibular nuclei after labyrinthectomy in rat

Background: In rat, deafferentation of one labyrinth (unilateral labyrinthectomy) results in a characteristic syndrome of ocular and motor postural disorders (e.g., barrel rotation, circling behavior, and spontaneous nystagmus). Behavioral recovery (e.g., diminished symptoms), encompassing 1 week after unilateral labyrinthectomy, has been termed vestibular compensation. Evidence suggesting that the histamine H3 receptor plays a key role in vestibular compensation comes from studies indicating that betahistine, a histamine-like drug that acts as both a partial histamine H1 receptor agonist and an H3 receptor antagonist, can accelerate the process of vestibular compensation. Results: Expression levels for histamine H3 receptor (total) as well as three isoforms which display variable lengths of the third intracellular loop of the receptor were analyzed using in situ hybridization on brain sections containing the rat medial vestibular nucleus after unilateral labyrinthectomy. We compared these expression levels to H3 receptor binding densities. Total H3 receptor mRNA levels (detected by oligo probe H3X) as well as mRNA levels of the three receptor isoforms studied (detected by oligo probes H3A, H3B, and H3C) showed a pattern of increase, which was bilaterally significant at 24 h post-lesion for both H3X and H3C, followed by significant bilateral decreases in medial vestibular nuclei occurring 48 h (H3X and H3B) and 1 week post-lesion (H3A, H3B, and H3C). Expression levels of H3B was an exception to the forementioned pattern with significant decreases already detected at 24 h post-lesion. Coinciding with the decreasing trends in H3 receptor mRNA levels was an observed increase in H3 receptor binding densities occurring in the ipsilateral medial vestibular nuclei 48 h post-lesion. Conclusion: Progressive recovery of the resting discharge of the deafferentated medial vestibular nuclei neurons results in functional restoration of the static postural and occulomotor deficits, usually occurring within a time frame of 48 hours in rats. Our data suggests that the H3 receptor may be an essential part of pre-synaptic mechanisms required for reestablishing resting activities 48 h after unilateral labyrinthectomy

Entropy driven key-lock assembly

The effective interaction between a sphere with an open cavity (lock) and a spherical macroparticle (key), both immersed in a hard sphere fluid, is studied by means of Monte Carlo simulations. As a result, a 2d map of the key-lock effective interaction potential is constructed, which leads to the proposal of a self-assembling mechanism: there exists trajectories through which the key-lock pair could assemble avoiding trespassing potential barriers. Hence, solely the entropic contribution can induce their self-assembling even in the absence of attractive forces. This study points out the solvent contribution within the underlying mechanisms of substrate-protein assembly/disassembly processes, which are important steps of the enzyme catalysis and protein mediated transport

Overcharging: The Crucial Role of Excluded Volume

In this Letter we investigate the mechanism for overcharging of a single spherical colloid in the presence of aqueous salts within the framework of the primitive model by molecular dynamics (MD) simulations as well as integral-equation theory. We find that the occurrence and strength of overcharging strongly depends on the salt-ion size, and the available volume in the fluid. To understand the role of the excluded volume of the microions, we first consider an uncharged system. For a fixed bulk concentration we find that upon increasing the fluid particle size one strongly increases the local concentration nearby the colloidal surface and that the particles become laterally ordered. For a charged system the first surface layer is built up predominantly by strongly correlated counterions. We argue that this a key mechanism to produce overcharging with a low electrostatic coupling, and as a more practical consequence, to account for charge inversion with monovalent aqueous salt ions.Comment: 7 pages, 3 figs (4 EPS files). To appear in Europhysics Letter

The electrical double layer for a fully asymmetric electrolyte around a spherical colloid: an integral equation study

The hypernetted chain/mean spherical approximation (HNC/MSA) integral equation is obtained and solved numerically for a totally asymmetric primitive model electrolyte around a spherical macroparticle. The ensuing radial distribution functions show a very good agreement when compared to our Monte Carlo and molecular dynamics simulations for spherical geometry and with respect to previous anisotropic reference HNC calculations in the planar limit. We report an analysis of the potential vs charge relationship, radial distribution functions, mean electrostatic potential and cumulative reduced charge for representative cases of 1:1 and 2:2 salts with a size asymmetry ratio of 2. Our results are collated with those of the Modified Gouy-Chapman (MGC) and unequal radius Modified Gouy-Chapman (URMGC) theories and with those of HNC/MSA in the restricted primitive model (RPM) to assess the importance of size asymmetry effects. One of the most striking characteristics found is that,\textit{contrary to the general belief}, away from the point of zero charge the properties of an asymmetric electrical double layer (EDL) are not those corresponding to a symmetric electrolyte with the size and charge of the counterion, i.e. \textit{counterions do not always dominate}. This behavior suggests the existence of a new phenomenology in the EDL that genuinely belongs to a more realistic size-asymmetric model where steric correlations are taken into account consistently. Such novel features can not be described by traditional mean field theories like MGC, URMGC or even by enhanced formalisms, like HNC/MSA, if they are based on the RPM.Comment: 29 pages, 13 figure

Insulator phases of Bose-Fermi mixtures induced by next-neighbor interactions between fermions

We study a one-dimensional mixture of two-color fermions and scalar bosons at the hard-core limit, focusing on the effect that the next-neighbor interaction between fermions has on the zero-temperature ground state of the system for different fillings of each carrier. Exploring the parameters of the problem, we observed that the non-local interaction modifies the well-known mixed and spin-selective Mott insulators, and we also found the emergence of three unusual insulating states with peculiar charge density wave orderings, a fully out-of-phase density of carriers for bosonic half-filling, an insulator with the same bosonic and fermionic fillings, and a different spin-selective insulator where the bosonic filling matches the density of one kind of fermion. Modern cold-atom setups correspond to the ideal experimental setting where these incommensurable insulators can be observed.Comment: 11 pages, 9 figures. Comments are welcom

Drying Kinetics of Oca (Oxalis Tuberosa)

One of the most important steps for agro-industrial industrialization is examining the kinetic behavior of products, to determine the ideal parameters to maintain their characteristics throughout the production chain. This study experimentally determined the drying kinetics of oca, an indigenous product of the Andean region, because there is no established information on the drying techniques of this tuber. The Andean region is the cradle of a large number of food crops that were domesticated and exploited by indigenous people thousands of years ago, even long before the expansion of the Inca civilization. In Ecuador, oca is perhaps the most important element of the daily diet, and an acceptable level of purity and hygiene has been reached. Oca provides fiber, essential amino acids and a low level of fat. In this study, a temperature of 60ºC was set at the beginning of each experimental run. The weight of the oca slices was measured every 10 min. The experiments were carried out in triplicate. Data were analyzed using StatGraphics software. Two drying periods were observed: the initial period of constant drying speed, where the removal of moisture corresponded to moisture not linked to the oca, while in the second stage, the internal moisture of the tuber was removed. Keywords: kinetic, drying, goose. RESUMEN Uno de los pasos más importantes para la industrialización agroindustrial es el comportamiento cinético de productos, esto en especial para conocer cuáles son los parámetros ideales para mantener las características sensoriales durante toda la cadena de producción. El presente documento determina experimentalmente la cinética de secado para un producto autóctono de la Región Andina, como lo es la oca, puesto que no existe información sobre las técnicas de secado de este tubérculo. En el Ecuador se ha alcanzado un aceptable nivel de pureza e higiene, la Oca es quizás el elemento más importante de la dieta diaria. La región andina es cuna de un gran número de cultivos alimenticios que fueron domesticados y aprovechados por pueblos autóctonos hace miles de años, inclusive mucho antes de la expansión de la civilización Inca. Aporta fibra, aminoácidos esenciales y un nivel bajo en grasa. La experimentación para conocer las curvas que modelan el comportamiento cinético del secado, se llevó a cabo por triplicado; luego de realizar la recolección de datos, estos fueron analizados utilizando el software estadístico StatGraphics. donde se obtuvo el respectivo análisis de varianza y las curvas. En el estudio se configuró una temperatura de 60ºC al inicio de cada corrida experimental, Se midió el peso de las rodajas de Oca cada 10 min, los datos fueron registrados y se procesó las tablas resultantes. En el estudio se pudo observar dos periodos de secado: Periodo inicial de velocidad de secado constante, donde la eliminación de humedad corresponde a la humedad no ligada a la oca, mientras en la segunda etapa se eliminó la humedad interna del tubérculo. Palabras claves: cinética, secado, oca

Uric Acid and Chronic Kidney Disease: Still More to Do

Gout and hyperuricemia are present in 25% and 60% of patients with chronic kidney disease (CKD), respectively. Despite the common association, the role of uric acid in the progression of kidney disease and in metabolic complications remains contested. Some authorities argue that the treatment of asymptomatic hyperuricemia in CKD is not indicated, and some have even suggested hyperuricemia may be beneficial. Here, we review the various arguments both for and against treatment. The weight of the evidence suggests asymptomatic hyperuricemia is likely injurious, but it may primarily relate to subgroups, those who have systemic crystal deposits, those with frequent urinary crystalluria or kidney stones, and those with high intracellular uric acid levels. We recommend carefully designed clinical trials to test if lowering uric acid in hyperuricemic subjects with cardiometabolic complications is protective

Ion pairing in model electrolytes: A study via three particle correlation functions

A novel integral equations approach is applied for studying ion pairing in the restricted primitive model (RPM) electrolyte, i. e., the three point extension (TPE) to the Ornstein-Zernike integral equations. In the TPE approach, the three-particle correlation functions $g^{[3]}({\bf r}_{1},{\bf r}_{2},{\bf r}_{3})$ are obtained. The TPE results are compared to molecular dynamics (MD) simulations and other theories. Good agreement between TPE and MD is observed for a wide range of parameters, particularly where standard integral equations theories fail, i. e., low salt concentration and high ionic valence. Our results support the formation of ion pairs and aligned ion complexes.Comment: 43 pages (including 18 EPS figs) - RevTeX 4 - J. Chem. Phys. (in press

Vortices on demand in multicomponent Bose-Einstein condensates

We present a simple mechanism to produce vortices at any desired spatial locations in harmonically trapped Bose-Einstein condensates (BEC) with multicomponent spin states coupled to external transverse and axial magnetic fields. The vortices appear at the spatial points where the spin-transverse field interaction vanishes and, depending on the multipolar magnetic field order, the vortices can acquire different predictable topological charges. We explicitly demonstrate our findings, both numerically and analytically, by analyzing a 2D BEC via the Gross-Pitaevskii equation for atomic systems with either two or three internal states. We further show that, by an spontaneous symmetry breaking mechanism, vortices can appear in any spin component, unless symmetry is externally broken at the outset by an axial field. We suggest that this scenario may be tested using an ultracold gas of $^{87}$Rb occupying all three $F = 1$ states in an optical trap.Comment: 11 pages, 9 figures, (Accepted in PRA