Comportamento do maracujazeiro amarelo, variedade Afruvec, ante uma população de Fusarium solani, agente causal da podridão do colo / Behaviour of yellow passion fruit, Afruvec variety, in relation to a population of Fusarium solani, causal agent of collar rot

O objetivo do presente trabalho foi verificar o comportamento do maracujazeiro amarelo, variedade Afruvec, ante uma população de Fusarium solani, obtida desse mesmo hospedeiro. O delineamento adotado foi o de blocos ao acaso, contendo dez tratamentos (nove isolados e tratamento testemunha), com quatro repetições, sendo cada parcela representada por um vaso contendo uma planta. Um disco do meio de cultura, colonizado com cada isolado do fungo, foi inoculado no colo ferido das plantas da variedade Afruvec, dois meses após a semeadura. Avaliou-se a patogenicidade, a incidência (número de plantas mortas) e a severidade da doença (comprimento da lesão no colo), até os sessenta dias após a inoculação. A variedade Afruvec foi suscetível ao fungo e apresentou variabilidade quanto à incidência e severidade da doença diante dos diferentes isolados. A população do fungo apresentou variabilidade em relação à agressividade. Com a evidência de diversidade genética na população do fungo, recomenda-se, também, nos testes de seleção de materiais ao patógeno, a avaliação desses materiais em diferentes localidades com histórico da doença ou inoculação com uma mistura de isolados do fungo, a fim de se conhecer a resistência ampla do genótipo ao patógeno.

The objective of the present work was to verify the behavior of yellow passion fruit, Afruvec variety, in relation to a population of Fusarium solani, obtained from this crop. The experimental delineation was random blocks, containing 10 treatments [9 isolates and 1 control treatment], with 4 repetitions, each plot being represented by a vase containing a plant. A disk of culture medium colonized by each isolate of the fungus was inoculated in the wounded collar region of the plants of the Afruvec variety two months after sowing. The appraised parameters were: the pathogenicity, the incidence (number of dead plants) and the severity of the disease (length of the lesion in the collar region), until 60 days after inoculation. The Afruvec variety was susceptible to the fungus and also presented variability as to the severity of the disease and incidence in relation to the different isolates. The population of the fungus showed variability in regard to aggressiveness. In light of the evidence of genetic diversity in the F. solani population, it is also suggested, in the tests of selection of materials to the pathogen, that these materials should be evaluated in different places with a history of the disease or inoculation with a pool of isolates of the fungus, in order to know the wide resistance of the genotype to the pathogen.

Electrical parameters and water permeability properties of monolayers formed by T84 cells cultured on permeable supports

T84 is an established cell line expressing an enterocyte phenotype whose permeability properties have been widely explored. Osmotic permeability (P OSM), hydraulic permeability (P HYDR) and transport-associated net water fluxes (J W-transp), as well as short-circuit current (I SC), transepithelial resistance (R T), and potential difference (deltaV T) were measured in T84 monolayers with the following results: P OSM 1.3 ± 0.1 cm.s-1 x 10-3; P HYDR 0.27 ± 0.02 cm.s-1; R T 2426 ± 109 omega.cm², and deltaV T 1.31 ± 0.38 mV. The effect of 50 æM 5,6-dichloro-1-ethyl-1,3-dihydro-2H-benzimidazol-2-one (DCEBIO), a "net Cl- secretory agent", on T84 cells was also studied. We confirm the reported important increase in I SC induced by DCEBIO which was associated here with a modest secretory deltaJ W-transp. The present results were compared with those reported using the same experimental approach applied to established cell lines originating from intestinal and renal epithelial cells (Caco-2, LLC-PK1 and RCCD-1). No clear association between P HYDR and R T could be demonstrated and high P HYDR values were observed in an electrically tight epithelium, supporting the view that a "water leaky" barrier is not necessarily an "electrically leaky" one. Furthermore, the modest secretory deltaJ W-transp was not consistent with previous results obtained with RCCD-1 cells stimulated with vasopressin (absorptive fluxes) or with T84 cells secreting water under the action of Escherichia coli heat stable enterotoxin. We conclude that, while the presence of aquaporins is necessary to dissipate an external osmotic gradient, coupling between water and ion transport cannot be explained by a simple and common underlying mechanism.

Aquaporins and water transfer across epithelial barriers

The cloning and molecular characterization of water channels, generically called aquaporins have marked a pivotal point in our understanding of water movements across epithelial barriers. Nevertheless, the mechanisms underlying water transfer across these barriers at the molecular and cellular level are not yet clarified. We analyze here the role of the different driving forces moving water across epithelia and the biophysical properties of the water channels. We will also review the recently cloned epithelial members of the aquaporin family, including their expression and distribution in different tissues.

Water and ion coupling in the rat cecum during dietary potassium loading

Se midió a minuto el movimiento neto de agua transepitelial (Jw) en el ciego de ratas Wistar adaptadas a una dieta con alto potasio (HKD). También se midió la diferencia de potencial (PD), la corriente de cortocircuito (SCC) y los flujos unidireccionales de 22Na, 36Cl 89Rb. Cuando se utilizó un buffer bicarbonato, las permeabilidades hidrostática y osmótica no se modificaron con la adaptación al potasio. La adaptación al potasio implicó el desarrollo de un Jw secretorio asociado al transporte (Jw), relacionado con un incremento en la PD transepitelial, la SCC y el transporte neto de sodio. Contrariamente al caso de las ratas controles, no se observó ningún transporte neto de cloruro en las ratas HKD. En la presencia de sodio, cloruro y bicarbonato, el Jwt secretorio compensó un Jwt absortivo. La secreción de agua se acopló a una secreción neta de potasio. El reemplazo de iones cloruro por iones sulfato estuvo acompañado por el desarrollo de un Jw neto absortivo y por incrementos en la PD transepitelial y la permeabilidad hidrostática. El reemplazo del buffer bicarbonato por un buffer tris-hepes hizo decaer el Jw absortivo observado y la PD. Por último, se observó el cambio de una reabsorción de NaCI no electrogénica a una entrada electrogénica de Na+ sensible al amiloride

Acción del factor de crecimiento epidérmico sobre la secreción de tirotrofina en la rata / The effect of epidermal growth factor on thyrotropin secretion in rats

El factor de crescimiento epidérmico (EGF) es un polipéptido de potente acción mitogénica. La probable influencia de esto factor sobre la fisiología del eje hipofiso-tiroideo no ha sido establecida. En el presente trabajo se estudió la acción del EGF sobre la secreción de TSH por hipófisis de ratas Wistar macho in vitro. Cada adenohipófisis fue colocada en una cámara de purifusión conectada a una bomba peristáltica que impulsaba el fluído de perifusión (medio 199, pH 7,3) a un ritmo de 100 *l/min. Cada cámara, conteniendo una hipófisis y 600 *l de fluído de perifusión, fue mantenida en un baño a 37§C. Se obtuvieron muestras del effluente (1 ml cada 10 min.) durante 60 min. para medir TSH basal. Luego se agregó en cámaras individuales, TRH en concentración final de 10-8 M o EGF en concentraciones de 10-8 M a 10-11 M, luego de lo cual se continuócon la colección del efluente cada 10 min. por otros 60 minutos. En cada muestra se midió TSH (ng/ml) por RIA (NIADDK, rTSH-RP 2 standard). Resultados: en el estudio con TRH, la TSH basal promedió 32,1 ñ 6,5 ng/ml con un pico post-TRH de 105 ñ 13,8 ng/ml a los 10 min. (P<0,005), retornando al valor basal ...