The transcriptional landscape of polyploid wheat.

The coordinated expression of highly related homoeologous genes in polyploid species underlies the phenotypes of many of the world's major crops. Here we combine extensive gene expression datasets to produce a comprehensive, genome-wide analysis of homoeolog expression patterns in hexaploid bread wheat. Bias in homoeolog expression varies between tissues, with ~30% of wheat homoeologs showing nonbalanced expression. We found expression asymmetries along wheat chromosomes, with homoeologs showing the largest inter-tissue, inter-cultivar, and coding sequence variation, most often located in high-recombination distal ends of chromosomes. These transcriptionally dynamic genes potentially represent the first steps toward neo- or subfunctionalization of wheat homoeologs. Coexpression networks reveal extensive coordination of homoeologs throughout development and, alongside a detailed expression atlas, provide a framework to target candidate genes underpinning agronomic traits in wheat.

Extended endoscopic endonasal approach to the skull base.

OBJECTIVE: Different approaches to the skull base have been developed through the sphenoidal sinus. Traditional boundaries of the trans-sphenoidal approach can be extended in antero-posterior and lateral planes. We review our experience with the extended endoscopic endonasal approach in the first 12 cases. METHODS: We used the extended endoscopic endonasal approach in 12 patients with different lesions of the skull base. This study specifically focuses on the type of lesions, surgical approach, outcome and surgical complications. RESULTS: The extended endoscopic endonasal approach was used in 12 patients with the following lesions: 4 invasive adenomas to the cavernous sinus, 2 clival chordomas, 2 craniopharyngiomas, 1 hypothalamic astrocytoma and 3 pituitary adenomas extended upon the tuberculum. Gross total resection was achieved in 8 cases (66.7%) subtotal resection in 3 and just a biopsy could be accomplished in the case of astrocytoma. This last patient developed meningo-encephalitis and died two weeks later. CONCLUSIONS: The extended endoscopic endonasal approach is a promising minimally invasive alternative for selected cases with sellar, parasellar or clivus lesions. As techniques and technology advance, this approach may become the procedure of choice for most lesions and should be considered an option in the management of the patients with these complex pathologies by skull base surgeons.

Quorum sensing signal profile of Acinetobacter strains from nosocomial and environmental sources.

A set of 43 strains corresponding to 20 classified and unclassified genomic Acinetobacter species was analyzed for the production of typical N-acyl homoserine lactone quorum sensing molecules in culture broths. A large percentage of the strains (74%) displayed quorum sensing signals that could be separated into three statistically significantly different chromatographic groups (p < 0.001) based on their retention factor in TLC, i.e., Rf1 (0.22 +/- 0.02); Rf2 (0.40 +/- 0.02) and Rf3 (0.54 +/- 0.02). Noteworthy, 63% of the strains tested produced more than one quorum signal. The frequency of signal appearance was Rf3 > Rf2 > Rf1. None of the three signals could be specifically assigned to a particular species in the genus; furthermore, no distinction could be made between the quorum sensing signals secreted by typical opportunistic strains of the A. calcoaceticus-A. baumannii complex, isolated from patients, with respect to the other species of the genus, except for the Rf1 signal which was present in all the QS positive strains belonging to this complex and DNA group 13 TU. In conclusion, quorum sensors in Acinetobacter are not homogenously distributed among species and one of them is present in most of the A. calcoaceticus-baumannii complex.

Quorum sensing signal profile of Acinetobacter strains from nosocomial and environmental sources / Perfil de sensores de quórum en cepas nosocomiales y ambientales de Acinetobacter

A set of 43 strains corresponding to 20 classified and unclassified genomic Acinetobacter species was analyzed for the production of typical N-acyl homoserine lactone quorum sensing molecules in culture broths. A large percentage of the strains (74%) displayed quorum sensing signals that could be separated into three statistically significantly different chromatographic groups (p < 0.001) based on their retention factor in TLC, i.e. Rf1 (0.22 ± 0.02); Rf2 (0.40 ± 0.02) and Rf3 (0.54 ± 0.02). Noteworthy, 63% of the strains tested produced more than one quorum signal. The frequency of signal appearance was Rf3 > Rf2 > Rf1. None of the three signals could be specifically assigned to a particular species in the genus; furthermore, no distinction could be made between the quorum sensing signals secreted by typical opportunistic strains of the A. calcoaceticus-A. baumannii complex, isolated from patients, with respect to the other species of the genus, except for the Rf1 signal which was present in all the QS positive strains belonging to this complex and DNA group 13 TU. In conclusion, quorum sensors in Acinetobacter are not homogenously distributed among species and one of them is present in most of the A. calcoaceticus-baumannii complex.

Se analizó la producción de moléculas típicas de N-acil homoserina lactona con actividad de quorum sensing en cultivos líquidos de un grupo de 43 cepas correspondientes a 20 especies genómicas clasificadas y no clasificadas de Acinetobacter. Un porcentaje alto de las cepas (74%) mostraron señales de quorum sensing que pudieron ser separadas en tres grupos cromatográficos significativamente diferentes entre sí (p < 0,001) sobre la base de sus factores de retención en TLC, a saber: Rf1 (0.22 ± 0.02); Rf2 (0.40 ± 0.02) y Rf3 (0.54 ± 0.02). Es de notar que 63% de las cepas ensayadas produjeron más de una señal de quorum. La frecuencia de aparición de las señales fue Rf3 > Rf2 > Rf1. Ninguna de las tres señales pudo ser asignada a una especie en particular dentro del género; es más, no se encontró diferencia entre las señales producidas por las cepas típicamente oportunistas (complejo A. calcoaceticus-A. baumannii) aisladas de pacientes respecto de las producidas por otras cepas del mismo género, excepto para el caso de Rf1, que se encontró presente en todos los aislamientos quorum sensing positivos del mencionado complejo y en las cepas del grupo de DNA 13TU. En conclusión, los sensores de quórum en Acinetobacter no están homogéneamente distribuidos entre especies y uno de ellos (Rf1) está presente en la mayoría de los miembros del complejo calcoaceticus-baumannii.

Detection and characterization of quorum sensing signal molecules in Acinetobacter strains.

Quorum sensing is a widespread regulatory mechanism among Gram-negative bacteria. In this study, Acinetobacter strains were assayed for the presence of quorum sensing signal molecules capable of activating N-acylhomoserine lactone biosensors. By using an Agrobacterium tumefaciens reporter strain it was shown that all the cultures produced two to four detectable signal molecules with different chromatographic patterns. In A. calcoaceticus BD413 supernatants four compounds were detected in a time-dependent manner, and maximal activity was reached at stationary phase. The number of signal molecules was dependent on medium composition; typically, cultures in minimal medium displayed one or two more signals, as compared to complex medium. None of the Acinetobacter supematants showed autoinduction activity with an Chromobacterium violaceum reporter strain, neither in direct or competition assays.

Physiological factors affecting production of extracellular lipase (LipA) in Acinetobacter calcoaceticus BD413: fatty acid repression of lipA expression and degradation of LipA.

The extracellular lipase (LipA) produced by Acinetobacter calcoaceticus BD413 is required for growth of the organism on triolein, since mutant strains that lack an active lipase fail to grow with triolein as the sole carbon source. Surprisingly, extracellular lipase activity and expression of the structural lipase gene (lipA), the latter measured through lacZ as a transcriptional reporter, are extremely low in triolein cultures of LipA+ strains. The explanation for this interesting paradox lies in the effect of fatty acids on the expression of lipA. We found that long-chain fatty acids, especially, strongly repress the expression of lipA, thereby negatively influencing the production of lipase. We propose the involvement of a fatty acyl-responsive DNA-binding protein in regulation of expression of the A. calcoaceticus lipBA operon. The potential biological significance of the observed physiological competition between expression and repression of lipA in the triolein medium is discussed. Activity of the extracellular lipase is also negatively affected by proteolytic degradation, as shown in in vitro stability experiments and by Western blotting (immunoblotting) of concentrated supernatants of stationary-phase cultures. In fact, the relatively high levels of extracellular lipase produced in the early stationary phase in media which contain hexadecane are due only to enhanced stability of the extracellular enzyme under those conditions. The rapid extracellular degradation of LipA of A. calcoaceticus BD413 by an endogenous protease is remarkable and suggests that proteolytic degradation of the enzyme is another important factor in regulating the level of active extracellular lipase.

Resource concentration hypothesis: effect of host plant patch size on density of herbivorous insects.

The resource concentration hypothesis (Root 1973) predicts that specialist herbivorous insects should be more abundant in large patches of host plants, because the insects are more likely to find and stay longer in those patches. Between August 1989 and January 1990 we experimentally tested Root's hypothesis by analyzing the numerical response of four species of herbivorous insects associated with patches of 4, 16, 64 and 225 cabbage plants, Brassica oleracea var. capitata. In addition, we studied the colonization of patches by adults of Plutella xylostella (L.) (Lepidoptera: Plutellidae), and the migration of their larvae in patches of different sizes. No herbivorous insect densities differed significantly with patch size. Adults of P. xylostella colonized all kind of patches equally. Larvae did not migrate between patches, and their disappearance rate did not differ between patches. The resource concentration hypothesis is organism-dependent, being a function of the adult and juvenile herbivore dispersal behavior in relation to the spatial scale of patchiness.

Propuesta para la estandardización de la espirometría en la ciudad de Buenos Aires / A proposal for spirometry standardization in the city of Buenos Aires

Se trata de un estudio multicéntrico que abarcó 8 Hospitales de Buenos Aires, referido al Control de Calidad de 17 espirómetros (9 volumétricos, 5 neumotacómetros y 3 medidores de FEFmx) de uso corriente en ellos. Se realizó mediante un Simulador de Espirometría por Descompresión Explosiva. Este instrumento portátil proporciona un flujo aéreo similar a una espiración forzada, cuyos CVF, VEF1 y FEF25-75 se conocen con precisión. Aplicándolo a los espirómetros se pudo comprobar si la exactitud de sus mediciones se ajustaba, o no a las recondaciones de la American Thoracic Society. Sólo el 42// (6/14) de los aparatos logró medir corectamente los parámetros básicos (CVF y VEF1, observándose que los de registro volumétrico presentaban mejor rendimiento que los que miden primariamente el flujo. Si bien la magnitud de los errores (igual o menor del 11//) no parece excesiva, en realidad sí lo es, ya que representa la mitad del rango de variación de los valores teóricos. Se concluye que los Controles de Calidad mensuales recondados por el American College of Chest Physicians constituyen una sugerencia bien fundamentada

Propuesta para la estandardización de la espirometría en la ciudad de Buenos Aires / A proposal for spirometry standardization in the city of Buenos Aires

Se trata de un estudio multicéntrico que abarcó 8 Hospitales de Buenos Aires, referido al Control de Calidad de 17 espirómetros (9 volumétricos, 5 neumotacómetros y 3 medidores de FEFmx) de uso corriente en ellos. Se realizó mediante un Simulador de Espirometría por Descompresión Explosiva. Este instrumento portátil proporciona un flujo aéreo similar a una espiración forzada, cuyos CVF, VEF1 y FEF25-75 se conocen con precisión. Aplicándolo a los espirómetros se pudo comprobar si la exactitud de sus mediciones se ajustaba, o no a las recondaciones de la American Thoracic Society. Sólo el 42// (6/14) de los aparatos logró medir corectamente los parámetros básicos (CVF y VEF1, observándose que los de registro volumétrico presentaban mejor rendimiento que los que miden primariamente el flujo. Si bien la magnitud de los errores (igual o menor del 11//) no parece excesiva, en realidad sí lo es, ya que representa la mitad del rango de variación de los valores teóricos. Se concluye que los Controles de Calidad mensuales recondados por el American College of Chest Physicians constituyen una sugerencia bien fundamentada (AU)