Effect of Composition and Freeze-Thaw on the Network Structure, Porosity and Mechanical Properties of Polyvinyl-Alcohol/Chitosan Hydrogels.

We report the synthesis and characterization of poly (vinyl alcohol) (PVA)/Chitosan (CT) cryogels for applications involving the uptake and entrapment of particulate and bacterial colonies. In particular, we systematically investigated the network and pore structures of the gels as a function of CT content and for different freeze-thaw times, combining Small Angle X-Ray Scattering (SAXS), Scanning Electron Microscopy (SEM), and confocal microscopy. The nanoscale analysis obtained from SAXS shows that while the characteristic correlation length of the network is poorly affected by composition and freeze-thaw time, the characteristic size of heterogeneities associated with PVA crystallites decreases with CT content. SEM investigation evidences a transition to a more homogeneous network structure induced by the incorporation of CT that progressively builds a secondary network around the one formed by PVA. A detailed analysis of confocal microscopy image stacks allows to characterize the 3D porosity of the samples, revealing a significantly asymmetric shape of the pores. While the average volume of single pores increases with increasing CT content, the overall porosity remains almost unchanged as a result of the suppression of smaller pores in the PVA network with the progressive incorporation of the more homogeneous CT network. Increasing the freezing time in the FT cycles also results in a decrease of porosity, which can be associated with a growth in the crosslinking of the network due to PVA crystallization. The linear viscoelastic moduli measured by oscillatory rheology show a qualitatively comparable frequency-dependent response in all cases, with a moderate reduction with increasing CT content. This is attributed to changes in the structure of the strands of the PVA network.

Beyond the standard model of solubilization: Non-ionic surfactants induce collapse of lipid vesicles into rippled bilamellar nanodiscs.

HYPOTHESIS: Although solubilization of lipid membranes has been studied extensively, questions remain regarding the structural pathways and metastable structures involved. This study investigated whether the non-ionic detergent Triton X-100 follows the classical solubilization pathway or if intermediate nanostructures are formed. EXPERIMENTS: Small angle X-ray and neutron scattering (SAXS/SANS) was used in combination with transmission electron cryo-microscopy and cryo-tomography to deduce the structure of mixtures of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) vesicles and Triton X-100. Time-resolved SAXS and dynamic light scattering were used to investigate the kinetics of the process. FINDINGS: Upon addition of moderate detergent amounts at low temperatures, the lipid vesicles implode into ordered rippled bilamellar disc structures. The bilayers arrange in a ripple phase to accommodate packing constraints caused by inserted TX-100 molecules. The collapse is suggested to occur through a combination of water structure destabilization by detergents flipping across the membrane and osmotic pressure causing interbilayer attraction internally. The subsequently induced ripples then stabilize the aggregates and prevent solubilization, supported by the observation that negatively charged vesicles undergo a different pathway upon TX-100 addition, forming large bicelles. The findings demonstrate the richness in assembly pathways of simple lipids and detergents and stimulate considerations for the use of certain detergents in membrane solubilization.

Clusters in colloidal dispersions with a short-range depletion attraction: Thermodynamic identification and morphology.

HYPOTHESIS: Particle aggregation is ubiquitous for many colloidal systems, and drives the phase separation or the formation of materials with a highly heterogeneous large-scale structure, such as gels, porous media and attractive glasses. While the macroscopic properties of such materials strongly depend on the shape and size of these particle aggregates, the morphology and underlining aggregation physical mechanisms are far from being fully understood. Recently, it has been proposed that for reversible colloidal aggregation, the cluster morphology in the case of colloids interacting with short-range attractive forces is determined by a single variable, namely, the reduced second virial coefficient, B2∗. EXPERIMENTS: We examined this proposal by performing confocal microscopy experiments and computer simulations on a large collection of short-ranged attractive colloidal systems with different values of the attraction strength and range. FINDINGS: We show that in all cases a connection between the colloidal cluster morphology and B2∗ can be established both in experiments and simulations. This physical scenario holds at all investigated thermodynamic conditions, namely, in the fluid state, in the metastable region and in non-equilibrium conditions. Our findings support the connection between reversible colloidal aggregation and the so-called extended law of corresponding states.

Potential-invariant network structures in Asakura-Oosawa mixtures with very short attraction range.

We systematically investigated the structure and aggregate morphology of gel networks formed by colloid-polymer mixtures with a moderate colloid volume fraction and different values of the polymer-colloid size ratio, always in the limit of short-range attraction. Using the coordinates obtained from confocal microscopy experiments, we determined the radial, angular, and nearest-neighbor distribution functions together with the cluster radius of gyration as a function of size ratio and polymer concentration. The analysis of the structural correlations reveals that the network structure becomes increasingly less sensitive to the potential strength with the decreasing polymer-colloid size ratio. For the larger size ratios, compact clusters are formed at the onset of network formation and become progressively more branched and elongated with increasing polymer concentration/attraction strength. For the smallest size ratios, we observe that the aggregate structures forming the gel network are characterized by similar morphological parameters for different values of the size ratio and the polymer concentration, indicating a limited evolution of the gel structure with variations of the parameters that determine the interaction potential between colloids.

Consenso chileno de técnicas de kinesiología respiratoria en pediatría / Chilean consensus about pediatric chest physioterapy

Chest physiotherapy is currently an outstanding therapeutic tool for the management of pediatric respiratory patients. Many and varied techniques, manual and assisted, have been developed, some requiring patient collaboration. The development of knowledge and the pathophysiological understanding of respiratory diseases in recent years has generated the need to agree on the terminology, the fundamentals and the application of each of the kinesthetic techniques of respiratory treatment in the pediatric field. The objective of this document was to compile the available literature related to the physiological mechanisms, indications, procedural aspects and most frequently used techniques in our country, with the purpose of being a guideline for the clinical practice of professionals and students. The following techniques were included: prolonged slow expiration, slow expiration with glottis opened, autogenic drainage, assisted autogenic drainage, active cycle, compression/decompression, airway clearance, forced expiration techniques, cough and respiratory exercises.

La kinesiología respiratoria es actualmente una herramienta terapéutica destacada para el manejo de los pacientes respiratorios pediátricos. Se han desarrollado muchas y variadas técnicas, manuales y asistidas, algunas requiriendo colaboración del paciente. El desarrollo del conocimiento y la comprensión fisiopatológica de las enfermedades respiratorias en los últimos años ha generado la necesidad de consensuar la terminología, los fundamentos y la aplicación de cada una de las técnicas kinésicas de tratamiento respiratorio en el ámbito pediátrico. El objetivo de este documento fue recopilar la literatura disponible relacionada con los mecanismos fisiológicos, indicaciones, aspectos procedimentales y técnicas más utilizadas en nuestro país, con el propósito de ser una directriz que oriente la práctica clínica de profesionales y estudiantes en formación. Se incluyeron así las siguientes técnicas: espiración lenta prolongada, espiración lenta con glotis abierta, drenaje autógeno, drenaje autógeno asistido, ciclo activo, presión/descompresión, bloqueos torácicos, técnicas de espiración forzada, tos y ejercicios respiratorios.

First Complete Genome Sequence of Piscine Orthoreovirus Variant 3 Infecting Coho Salmon (Oncorhynchus kisutch) Farmed in Southern Chile.

We report here the complete genome of an isolate of piscine orthoreovirus variant 3 sequenced from a moribund coho salmon with jaundice that was reared in a seawater farm in southern Chile. The genome consists of 23,627 bp, including 10 segments that range from 1,052 bp (segment S4) to 4,014 bp (segment L1).

The Genome Sequence of an Oxytetracycline-Resistant Isolate of the Fish Pathogen Piscirickettsia salmonis Harbors a Multidrug Resistance Plasmid.

The amount of antibiotics needed to counteract frequent piscirickettsiosis outbreaks is a major concern for the Chilean salmon industry. Resistance to antibiotics may contribute to this issue. To understand the genetics underlying Piscirickettsia salmonis-resistant phenotypes, the genome of AY3800B, an oxytetracycline-resistant isolate bearing a multidrug resistance plasmid, is presented here.

First Complete Genome Sequence of Tenacibaculum dicentrarchi, an Emerging Bacterial Pathogen of Salmonids.

Tenacibaculum-like bacilli have recently been isolated from diseased sea-reared Atlantic salmon in outbreaks that took place in the XI region (Región de Aysén) of Chile. Molecular typing identified the bacterium as Tenacibaculum dicentrarchi. Here, we report the complete genome sequence of the AY7486TD isolate recovered during those outbreaks.

Comparative Genome Analysis of Two Isolates of the Fish Pathogen Piscirickettsia salmonis from Different Hosts Reveals Major Differences in Virulence-Associated Secretion Systems.

Outbreaks caused by Piscirickettsia salmonis are one of the major threats to the sustainability of the Chilean salmon industry. We report here the annotated draft genomes of two P. salmonis isolates recovered from different salmonid species. A comparative analysis showed that the number of virulence-associated secretion systems constitutes a main genomic difference.

Draft Genome Sequence of the Fish Pathogen Yersinia ruckeri Strain 37551, Serotype O1b, Isolated from Diseased, Vaccinated Atlantic Salmon (Salmo salar) in Chile.

We sequenced the genome of a motile O1b Yersinia ruckeri field isolate from Chile, which is causing enteric redmouth disease (ERM) in vaccinated Atlantic salmon (Salmo salar). The draft genome has 3,775,486 bp, a G+C content of 47.1%, and is predicted to contain 3,406 coding sequences.

Nicotinamide is not a substrate of the facilitative hexose transporter GLUT1.

It has been proposed that GLUT1, a membrane protein that transports hexoses and the oxidized form of vitamin C, dehydroascorbic acid, is also a transporter of nicotinamide (Sofue, M., Yoshimura, Y., Nishida, M., and Kawada, J. (1992) Biochem. J. 288, 669-674). To ascertain this, we studied the transport of 2-deoxy-D-glucose, 3-O-methyl-D-glucose, and nicotinamide in human erythrocytes and right-side-out and inside-out erythrocyte membrane vesicles. The transport of nicotinamide was saturable, with a K(M) for influx and efflux of 6.1 and 6.2 mM, respectively. We found that transport of the hexoses was not competed by nicotinamide in both the erythrocytes and the erythrocyte vesicles. Likewise, the transport of nicotinamide was not affected by hexoses or by inhibitors of glucose transport such as cytochalasin B, genistein, and myricetin. On the other hand, nicotinamide blocked the binding of cytochalasin B to human erythrocyte membranes but did so in a noncompetitive manner. Using GLUT1-transfected CHO cells, we demonstrated that increased expression of GLUT1 was paralleled by a corresponding increase in hexose transport but that there were no changes in nicotinamide transport. Moreover, nicotinamide failed to affect the transport of hexoses in both control and GLUT1-transfected CHO cells. Therefore, our results indicates that GLUT1 does not transport nicotinamide, and we propose instead the existence of other systems for the translocation of nicotinamide across cell membranes.

Modulation of Immune Response of BALB/Mice Bearing Lymphoma L5178Y Treated with Bitter Yellow Juice of Aloe vera (L) in vivo.

Aloe vera (L), a plant of African origin, has been introduced in Mexico since XVIth century. It has been used in the treatment of many diseases of immune system. In the present study we investigated a specific and non-specific immune response of BALB/c mice, healthy and immunosuppressed with murine lymphoma L5178Y, treated with bitter yellow juice (extract) of Aloe vera (L). We observed that the immunosuppressed mice, treated with the whole extract of the bitter yellow juice achieved restoration of immunological parameters in cellular immune response and phagocytosis. On the other hand, the humoral immunity was not restored. Also, in the healthy rodents treated with the extract, it caused the stimulation of specific and non-specific responses, the results had significant differences with the obtained ones in untreated mice.

Effect of phorbol myristate acetate (PMA) and ionophore A23187 on interleukin-2 levels and proliferation of activated T lymphocytes from patients with lepromatous leprosy

The immunodeficiency present in patients with lepromatous leprosy is characterized by the limited proliferation of T lymphocytes, and is explained in part by the impaired synthesis of interleukin-2 (IL-2). Diacylglycerol (DAG) and calcium produce the activation of PKC, ERK and JNK kinases, implying a normal IL-2 response. Phorbol esters, such as PMA, can substitute for DAG and are mitogenic to human T and B cells activating several cytokine-encoding genes. Ionophore A23187 increases calcium permeability across the cellular membrane to the cytosol of lymphoid cells and is considered a co-mitogen of T lymphocytes. Here we report that: 1) PHA-activated T lymphocytes from LL patients can be separated in vitro into two groups: a) responders (R) with a stimulation index (SI) of > 10 and (b) nonresponders (NR) with a SI of < 10. 2) The proliferative responses of cells from LL(R), LL(NR) and normal subjects were measured after being stimulated with: I, PHA, PMA, PMA + I PHA + PMA and PHA + PMA + ionophore (PPI). The most important result occurs in LL(NR) patients whose cells did not respond to PHA stimulation but increased to normal levels of proliferation when they were stimulated with PMA. Furthermore, the three groups, (NR, R and normals) strongly increased their responses when they were incubated with PPi. 3) Finally, Il-2 concentrations in the supernatants of cultures of T lymphocytes from LL(NR), LL(R) and controls were relatively low when they were incubated with PHA or PMA, but the addition of ionophore to PMA and the combination of PHA + PMA strongly increased the production of IL-2 in all of them, reaching the optimum IL-2 concentration when PPI is used. It can be concluded that the use of PMA, analogous to DAG, and ionophore A23187 (calcium increaser) in cultures of mitogen-activated T lymphocytes from LL patients induced the expression of the IL-2 gene, thus correcting the inadequate proliferation of T cells from LL patients.

Quiste epidermoide de testículo: comunicación de 4 casos y revisión de la literatura / Testis epidermoid cyst: report of 4 cases and literature review

Los quistes epidermoides del testículo son raros, representando solo el 1 por ciento de todos los tumores de esta gónada. Los autores analizan 4 casos tratados, en ninguno de los cuales hubo sospecha clínica preoperatoria. Esto llevó a realizar cirugía radical en tres casos y parcial en un paciente. La naturaleza benigna de esta lesión podría permitir realizar cirugía conservadora en casos con sospecha preoperatoria, ecografía concordante y biopsia contemporánea confiable