Hypertension in Prenatally Undernourished Young-Adult Rats Is Maintained by Tonic Reciprocal Paraventricular–Coerulear Excitatory Interactions

Prenatally malnourished rats develop hypertension in adulthood, in part through increased α₁-adrenoceptor-mediated outflow from the paraventricular nucleus (PVN) to the sympathetic system. We studied whether both α₁-adrenoceptor-mediated noradrenergic excitatory pathways from the locus coeruleus (LC) to the PVN and their reciprocal excitatory CRFergic connections contribute to prenatal undernutrition-induced hypertension. For that purpose, we microinjected either α₁-adrenoceptor or CRH receptor agonists and/or antagonists in the PVN or the LC, respectively. We also determined the α₁-adrenoceptor density in whole hypothalamus and the expression levels of α_1A-adrenoceptor mRNA in the PVN. The results showed that: (i) agonists microinjection increased systolic blood pressure and heart rate in normotensive eutrophic rats, but not in prenatally malnourished subjects; (ii) antagonists microinjection reduced hypertension and tachycardia in undernourished rats, but not in eutrophic controls; (iii) in undernourished animals, antagonist administration to one nuclei allowed the agonists recover full efficacy in the complementary nucleus, inducing hypertension and tachycardia; (iv) early undernutrition did not modify the number of α₁-adrenoceptor binding sites in hypothalamus, but reduced the number of cells expressing α_1A-adrenoceptor mRNA in the PVN. These results support the hypothesis that systolic pressure and heart rate are increased by tonic reciprocal paraventricular–coerulear excitatory interactions in prenatally undernourished young-adult rats.     

Cryopreservation of embryogenic cultures from mature Quercus suber trees using vitrification

Recent progress in somatic embryogenesis from selected mature trees of Quercus suber, has led to a demand for maintenance of a large number of selected embryogenic lines. To facilitate the management of this material a protocol for the long-term storage of this germplasm should be defined. This study reports on the use of a simple vitrification procedure for the successful cryopreservation of three cork oak embryogenic lines. High embryo recovery levels (88-93 percent) were obtained by first preculturing 2-4 mg clumps of two or three globular embryos on semisolid medium containing 0.3 M sucrose for three days, followed by incubation in PVS2 vitrification solution at 0 degree C for 60 min before direct immersion in liquid nitrogen. The mean number of embryos produced per explant was significantly greater for cryostored embryos than for untreated stock cultures, but the productivity of the latter was recovered in subsequent subcultures of the material produced by cryostored embryos. The germination and plant regeneration rates achieved by cultures derived from cryostored embryos, around 60 percent, were similar to those of non-cryopreserved stock cultures.     

Synthesis and characterization of hollow ��-Fe2O3 sub-micron spheres prepared by sol�Cgel

In this work we report the preparation of magnetic hematite hollow sub-micron spheres (??-Fe₂O₃) by colloidal suspensions of ferric nitrate nine-hydrate (Fe(NO₃)₃·9H₂O) particles in citric acid solution by following the sol?Cgel method. After the gel formation, the samples were annealed at different temperatures in an oxidizing atmosphere. Annealing at 180°C resulted in an amorphous phase, without iron oxide formation. Annealing at 250°C resulted in coexisting phases of hematite, maghemite and magnetite, whereas at 400°C, only hematite and maghemite were found. Pure hematite hollow sub-micron spheres with porous shells were formed after annealing at 600°C. The characterization was performed by X-ray diffraction (XRD), Mössbauer spectroscopy (MS) and scanning electron microscopy (SEM).     

Reorientation Response of Magnetic Microspheres Attached to Gold Electrodes Under an Applied Magnetic Field

In this work, we report the mechanical reorientation of thiolated ferromagnetic microspheres bridging a pair of gold electrodes under an external magnetic field. When an external magnetic field (7 kG) is applied during the measurement of the current–voltage characteristics of a carboxyl ferromagnetic microsphere (4 μm diameter) attached to two gold electrodes by self-assembled monolayers (SAMs) of octane dithiol (C₈H₁₈S₂), the current signal is distorted. Rather than due to magnetoresistance, this effect is caused by a mechanical reorientation of the ferromagnetic sphere, which alters the number of SAMs between the sphere and the electrodes and therefore affects conduction. To study the physical reorientation of the ferromagnetic particles, we measure their hysteresis loops while suspended in a liquid solution.     

Crystalline and amorphous nanostructures in porous silicon

We report ab initio molecular dynamic simulations of several supercells of crystalline porous silicon, that are first relaxed and then analyzed by their radial distribution functions (RDF). The porosities vary from 10% to 80% of the total volume of the supercell. The interatomic distance is determined by the position of the first peak of the RDF. We manipulated a maximum of 500 atoms of silicon and a minimum of 32. The interatomic distance of the model with a porosity of 10% was 2.35 Å, for those models with porosity from 11% to 50% was 2.45 Å and finally, 2.55 Å for those with a porosity greater than 50%. If the supercell backbone structure is small compared with the void of the supercell, then the interatomic distance between the silicon atoms run out of the crystalline value. Our results agree with experiment.     

Computational alternatives to generate amorphous nanoporous structures using ab initio molecular dynamics

We present two approaches to generate amorphous nanoporous structures based on the geometrical handling of crystalline supercells and ab initio molecular dynamics. The first approach has been partially reported previously and consists in expanding a crystalline supercell (the expanding lattice approach) by lengthening the edges (proportionally increasing the interatomic distance) to obtain the desired porosity (density). Then, molecular dynamics is applied at diverse constant temperatures to allow the atoms to rearrange and create the corresponding atomic topology. The other one, inspired by the experimental process called dealloying is similar to that process which is used to generate porous metals by etching away one or several of the elements of an alloy. Both processes are applied to semiconducting (carbon, silicon) and metallic (copper, silver) materials and the results compared. Pair distribution functions are obtained in order to show that although both techniques may be similar, the dealloying technique seems to be more adequate when dealing with alloy systems. An interesting byproduct is that pair distribution functions tend to values lower that 1 for intermediate-to-long range distances in a region commensurate with the pore size.