Biosynthesis and characterization of polyhydroxyalkanoates produced by an extreme halophilic bacterium, Halomonas nitroreducens, isolated from hypersaline ponds.

AIMS: Morphological, biochemical and genotypic characterization of a halophilic bacterium isolated from hypersaline ponds located at Las Coloradas (Río Lagartos, Yucatán, Mexico). Characterization of polymer produced by this strain was also performed. METHODS AND RESULTS: Twenty strains were isolated from water samples of salt ponds and selected based on both morphological features and their PHA storage capacity, which were determined by SEM and staining methods with Nile red and Nile blue, respectively; strains were also analysed by the fluorescence imaging technique. Among them, JCCOL25.8 strain showed the highest production of PHA's reason why phenotypic and genotypic characterization was performed; this strain was identified as Halomonas nitroreducens. Polymer produced by this strain was characterized by FTIR, DSC, GPC and EDX spectroscopy. Results indicated that the biosynthesized polymer was polyhydroxybutyrate (PHB) which had a melting peak at 170°C and a crystallinity percentage of about 36%. CONCLUSIONS: Based on phenotypic and genotypic aspects, JCCOL25.8 strain was identified as H. nitroreducens and it was capable to accumulate PHB. SIGNIFICANCE AND IMPACT OF THE STUDY: To our knowledge, there is only one study published on the biosynthesis of PHA's by H. nitroreducens strains, although the characterization of the obtained polymer was not reported.

Distinct mechanisms of antibody-mediated enzymatic reactivation in beta-galactosidase molecular sensors.

The antibody-mediated reactivation of engineered Escherichia coli beta-galactosidases [Benito et al. (1996) J. Biol. Chem. 271, 21251-21256] has been thoughtfully investigated in three recombinant molecular sensors. Proteins M278VP1, JX772A and JX795A display the highly antigenic G-H loop peptide segment of foot-and-mouth disease virus VP1 protein, accommodated in different solvent-exposed loops of the assembled tetramer. These chimaeric enzymes exhibit a significant increase in enzymatic activity upon binding of either monoclonal antibodies or sera directed against the inserted viral peptide. In JX772A but not in M278VP1, the Fab 3E5 antibody fragment promotes reactivation to the same extent as the complete antibody. On the other hand, M278VP1 Km is reduced by more than 50% in the presence of activating serum, this parameter remains invariable in JX772A and it is only slightly modified in JX795A. In these last two proteins, significant k(cat) variations can account for the increased enzymatic activity. Alternative reactivation mechanisms in the different beta-galactosidase probes are discussed in the context of the bacterial enzyme structure and its tolerance to antibody-induced conformational modifications.

Electrochemical impedance spectroscopy of preoxidized MA 956 superalloy during in vitro experiments.

Preoxidation treatment of MA 956 superalloy at 1100 degrees C produces a fine and tightly adherent alpha-alumina layer at the surface, which provides the alloy with an excellent barrier against a great variety of aggressive environments. In this work the protective capacity of the alumina/alloy system is evaluated in a physiological medium by means of electrochemical impedance spectroscopy. The electrochemical response of the material is modelled by equivalent circuits which provide the most relevant corrosion and protection parameters applicable to MA 956 in both preoxidized and as-received conditions (passivated state). The high protective capacity of preoxidized MA 956 superalloy holds for long-term tests, which indicates that the corrosion phenomena, if any, would be characterized by very slow kinetics. The corrosion resistance of the preoxidized material is at least two orders of magnitude higher than that of the non-treated alloy.

Influence of the acid type in the production of chitosan films reinforced with bacterial nanocellulose.

Chitosan films reinforced with bacterial cellulose (BC) nanoribbons were studied to understand the influence of acid (acetic and lactic acids) on the reinforcing effect. For both acids, the maximum concentration of the reinforcing constituent was 5wt% with respect to the dry weight of chitosan. The infrared spectra, mechanical properties, morphology and antimicrobial activity of the films were analyzed. The results showed a difference between the acids in their behavior and effect on the reinforcement, with a tensile strength of 12.3MPa for the acetic acid films and 3.3MPa for the lactic acid films. Additionally, the bacterial inhibition tests were shown to be positive for the lactic acid films and negative for the acetic acid films. Therefore, exchanging the acid used in these films may be desirable for certain applications.

Evaluation of the pathogenicity and transmissibility of a chilean isolate of porcine reproductive and respiratory syndrome virus.

The objective of this study was to determine clinical features, shedding and transmission of a Chilean Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) strain upon experimental inoculation of 4-week-old pigs. Six groups of five animals each were used. The G1 (donor) group was inoculated with PRRSV, maintained in an isolation unit for 35 days, and sampled daily to determine shedding in mucosal secretions and faeces, viraemia and seroconversion. An uninfected control group (G6) was equally maintained and sampled under strict isolation. Four other groups (G2 to G5) were exposed to PRRSV via direct contact with G1 for 5-day periods in a staggered manner, throughout the 35-day period, and were later placed in an independent isolation unit to monitor infection status for 7 days. All the animals in G1 and G6 were killed at 35 days post-inoculation (dpi) and the contact groups at 12 days post-contact (dpc). Samples were obtained from diverse organs for histopathological, immunohistochemical (IHC) and virological analysis. No clinical symptoms were evident in any group, except for a transient fever observed in G1. Histopathologically, all the animals of G1 had interstitial pneumonia, although scarce PRRSV-positive cells were detected in the lung using IHC. PRRSV-positive cells (IHC) were detected in the lymphoid tissue of all animals in infected groups, but especially in G3 and G4. Viraemia was detected in G1 (3-35 dpi) and in the all contact groups (5-12 dpc). Likewise, ranging from 3 to 19 dpi, PRRSV was detected in at least one animal from the tonsils and lungs in all infected groups, in nasal and ocular secretions, saliva or faeces. These results indicate that the donor group excreted infectious PRRSV and was able to transmit the infection to susceptible pigs. The critical shedding period was 7-19 dpi, during which, most likely, transmission took place.

Phase equilibria in model surfactants forming Langmuir monolayers.

The study of Langmuir monolayers has generated the attention of researchers because of their unique properties and their not well understood phase equilibrium. These monolayers exhibit interesting phase diagrams where the unusual liquid-liquid equilibrium can be observed for a single component monolayer. Monte Carlo computer simulations in the virtual Gibbs ensemble were used to obtain the phase diagram of Langmuir monolayers. The liquid-vapor and liquid-liquid phase equilibria were considered by constructing the Cailletet-Mathias phase diagrams. By using the Ising model and the rectilinear approximations the identification of the critical properties for both equilibria was determined. These critical parameters were calculated as a function of the strength of the interaction between the surfactant molecules and the aqueous subphase. As a result, we have identified the coexistence between a liquid expanded state (LES)-vapor and the liquid condensed state-LES, in agreement with experimental and theoretical evidence in the literature. We obtained a clear separation of phases and a strong dependence on the strength of the solvent used. Namely, as the interaction between the solvent and the head of the surfactant increases, the critical properties also increase. Equilibrium states were characterized by computing thermodynamic quantities as a function of temperature and solvent strength.

Effect of added Pharmatose DCL11 on the sustained-release of metronidazole from Methocel K4M and Carbopol 971P NF floating matrices.

In vitro dissolution of metronidazole from sustained release floating tablets was studied with varied proportions of sodium bicarbonate (SB) and Pharmatose DCL 11. Two polymers with different hydration characteristics, Methocel K4M and Carbopol 971P NF, were used to formulate the matrices. The variables studied include the matrices' release profile, hydration volume, and floating behavior. All Methocel matrices floated more than 8 h with SB proportions up to 24%, while Carbopol matrices floated more than 8 h with SB proportions only up to 12%. Matrices' hydration increased with time until reaching a peak and declining thereafter. Methocel matrices showed greater hydration volumes and greater drug dissolution compared to Carbopol matrices. After adding increasing quantities of Pharmatose to matrices containing 12% SB, hydration volume decreased while dissolution increased. These results were attributed to water-filled pores that formed following the Pharmatose dissolution and to reduced polymer proportions. Carbopol matrices showed greater susceptibility to the added Pharmatose, becoming more erodible and releasing higher quantities of metronidazole. The greater Carbopol susceptibility to added Pharmatose was attributed to its faster hydration. Methocel matrices hydrate rapidly only at the surface, delaying hydration and Pharmatose dissolution.

Estudio histológico del tracto digestivo del neón cardenal paracheirodon axelrodi (Characidae) / Histological study of digestive tract of the neón cardenal paracheirodon axelrodi (Characidae)

Paracheirodon axelrodi es el pez ornamental que más se exporta en Colombia. Sin embargo, se desconocen varios aspectos de su biología básica. Se estudió la histología del tracto digestivo. Se sacrificaron 15 ejemplares (MS 222, 0,5 g/L), fijados en formaldehído al 4 por ciento y decalcificados con ácido nítrico 7 por ciento. Se siguió el procedimiento para H&E. El tracto digestivo de P. axelrodi presentó cuatro capas constitutivas: mucosa, submucosa, muscular y serosa. La mucosa de la boca presentó un epitelio escamoso estratificado no queratinizado con células caliciformes y sin botones gustativos, una submucosa de tejido conectivo laxo y una capa de músculo estriado esquelético. Los dientes son cónicos y abundantes. La capa serosa a lo largo del tracto digestivo es delgada compuesta de tejido conectivo laxo. La capa mucosa, submucosa y muscular del esófago posee la misma conformación tisular de la boca, sin embargo, la capa muscular presenta dos orientaciones. La mucosa del estómago está compuesta por epitelio cilíndrico simple con glándulas gástricas, submucosa de tejido conectivo laxo y una capa de músculo liso en dos orientaciones. Las capas del intestino exhi-bieron una composición tisular similar a la del estómago, sin glándulas gástricas. La mucosa presentó células caliciformes especialmente hacia la región posterior y un aumento en la longitud de los pliegues intestinales. La conformación tisular y morfológica del tracto digestivo de P. axelrodi lo ubica como un pez de hábitos alimenticios carnívoros pero de pequeñas presas.

Cardinal neon, Paracheirodon axelrodi is the most exported ornamental fish in Colombia. However, many aspects of its biology are unknown. A histological study of the digestive tract was carried out and 15 specimens were sacrificed with MS 222, 0.5 g/L, fixed in 4 percent formaldehyde and decalcified with 7 percent nitric acid. H&E technique was followed. P. axelrodi digestive tract showed four constitutive layers: mucosae, submucosae, muscular, and serosa. Mouth mucosae presents a stratified nonkeratinized squamous epithelium with many goblet cells, and no taste buds, submucosae with areolar connective tissue, and skeletal muscular layer. Teeth were conical and abundant. Along the whole intestinal tract the serous was a very thin connective tissue layer. Esophagus mucosae, submucosae, and muscular layer were similar to those of the mouth. However, muscular layer presented two layers in different orientations. Stomach mucosae were made of simple cylindrical epithelium with gastric glands. Submucosa did present areolar connective tissue, and muscular layer exhibited smooth muscle in two different orientations. The intestinal layers were similar to those of the stomach, but without gastric glands. Mucosae presented goblet cells especially at the posterior region. Intestinal folds were also observed. Tisular and morphological structure of P. axelrodi digestive tract suggests a small prey carnivorous fish.

On carbide dissolution in an as-cast ASTM F-75 alloy.

The solution treatment of an as-cast ASTM F-75 alloy was investigated. Microstructural evolution was followed during thermal processing, in particular with regard to the content and type of carbides formed. To evidence any probable carbide transformations occurring during the heating stage, as well as to clarify their effect on the carbide dissolution kinetics, three heating rates were studied. Image analysis and scanning electron microscopy techniques were used for microstructural characterization. For the identification of precipitates, these were electrolytically extracted from the matrix and then analyzed by X-ray diffraction. It was found that the precipitates in the as-cast alloy were constituted by both a M(23)C(6) carbide and a sigma intermetallic phase. The M(23)C(6) carbide was the only phase identified in solution-treated specimens, regardless of the heating rate employed, which indicated that this carbide dissolved directly into the matrix without being transformed first into an M(6)C carbide, as reported in the literature. It was found that the kinetics of dissolution for the M(23)C(6) carbide decreased progressively during the solution treatment, and that it was sensitive to the heating rate, decreasing whenever the latter was decreased. Because the M(23)C(6) carbide was not observed to suffer a phase transformation prior to its dissolution into the matrix, the effect of the heating rate was associated to the morphological change occurred as the specimens were heated. The occurrence of the observed phases was analyzed with the aid of phase diagrams computed for the system Co-Cr-Mo-C.

Rheological behavior of Phanerochaete chrysosporium broth during lignin degradation.

Rheological behavior of a lignin-degrading culture of Phanerochaete chrysosporium CDBB-H-298 was determined. Rheological characteristics revealed a Newtonian behavior in the culture medium without fungi, and a non-Newtonian dilatant behavior with fungi. In addition, the rheological behavior of the lignin-containing culture medium was complex, and changed from dilatant to pseudoplastic. During fungal growth without lignin in Kirk media rheological behavior exhibited a parabolic profile, and thixotropy showed a tendency to increase. Results indicated a small increase in the apparent viscosity in the presence of lignin; however, this may not affect the oxygen and mass transfer coefficients. The present findings can be applied to bioreactor desing for waste water treatment.

Ulceras venosas tratadas con apósitos de hidrogel de polimanosa, estudio comparativo con grupo control / Venous ulcers treated with polymanose hydrogel dressing, a comparative study with a control group

Objetivo: Comunicar la experiencia obtenida al tratar úlceras venosas con apósitos de hidrogel de polimanosa comparándola con un grupo control. Antecedentes: La frecuencia de presentación de úlceras venosas es muy alta y requieren tratamiento local efectivo para lograr su cicatrización. Un producto natural derivado del ALOE-VERA cuyo principio activo es la polimanosa, parece que favorece y acelera la cicatrización. Material y métodos: Se estudiaron 40 pacientes divididos en 2 grupos, 20 tratados con apósitos de hidrogel de polimanosa y 20 tratados sólo con solución físiológica y jabón a los cuales se les hizo seguimiento por 16 semanas y se valoró la velocidad de cicatrización. Resultados: El grupo tratado con polimanosa cicatrizó en un 50 por ciento más rápido que el tratado con agua y jabón. Conclusión: El hidrogel de polimanosa aumenta el doble la velocidad de cicatrización de las úlceras venosas comparado con la curación con solución fisiológica y jabón.

Frecuencia de pérdida de primeros molares permanentes en niños que acudieron al servicio de cirugía de la Facultad de Odontología de la Universidad Nacional de Asunción en el año 2010 / Ferceuncia loss of first permanent molars in children we hire the surgery department of the Faculty of Dentistry, National University of Asuncion in 2010

El primer molar permanente es una pieza fundamental en la cavidad bucal, realiza el levante de mordida en la dentición permanente, estabiliza la oclusión y favorece la masticación. Es una pieza clave para la armonía oclusal y por desconocimiento de los padres suele ser una de las primeras piezas permanentes en perderse. Se realizó un estudio observacional descriptivo de corte transversal con componente analítico temporalmente restrospectivo, en la cátedra de Odontopediatría e Higiene de la Facultad de Odontología, de la Universidad Nacional de Asunción, con el objetivo de determinar la frecuencia de pérdida de primeros molares permanentes. La muestra estuvo constituída por 100 niños que acudieron al servicio de cirugía en el año 2010. La frecuencia de exodoncia fue 75%, el 65% de la muestra correspondió al sexo femenino y 35% a niños con dentición permanente. Mayor cantidad de molares fueron extraídos en la arcada inferior, siendo mayor el número en el lado izquierdo. Considerando la alta frecuencia, se realizaron charlas educativas destinadas a los padres que acompañaron a sus hijos a la institución, para concienciar a los mismos sobre la importancia de la higiene bucal para la preservación de los dientes, dando especial énfasis al primer molar permanente explicando la importancia de su mantenimiento en boca y su etapa de erupción, considerando que por lo general se lo confunde con un diente de leche