The possible role of factor C in common scab disease development.

The Gram-positive soil-borne streptomycetes exhibit a complex life cycle that is controlled by extracellular regulatory molecules. One interesting autoregulator is the protein factor C, originally isolated from the culture fluid of S. albidoflavus 45H. Southern hybridizations and database searches revealed that although homologues of factor C are not present in most Streptomyces strains, an exception is the plant pathogenic S. scabies , which causes common scab disease on potato. In S. scabies and related strains pathogenicity involves a large pathogenicity island that carries thaxtomin biosynthetic genes, the nec1 necrogenic factor and other putative virulence genes. Extracellular enzymes, including extracellular esterases, that attack the surface of the tubers and disintegrate the external protective layer are also known to be involved in pathogenicity. In S. albidoflavus 45H, factor C coordinates the expression of many secreted hydrolases. To find out whether esterase is also regulated by factor C, we made a factor C null mutant of strain 45H. The mutant showed a bald phenotype and was impaired in pathogenicity and esterase activity. This is a first indication that extracellular regulatory factors may play a role in the development of potato scab.

Toxicity of botanical insecticides on golden apple snail (Pomacea canaliculata).

The molluscicidal activity of crude extracts from five highly potential plants, Annona squamosa seed, Nerium indicum Leaves, Stemona tuberose root, Cyperus rotundus corm and Derris elliptica root was assessed to Pomacea canaliculata. D. elliptica root and C. rotundus corm extracts showed the highest toxicity against 3-month old snails which have LC50 as 23.68 +/- 2.96 mg/l and 133.20 +/- 7.94 mg/l, respectively. The C. rotundus corm extracts were chosen for detoxification enzyme in vivo assay which shows esterase and glutathione S-transferase activity in stomach, intestinal tracts and digestive glands of survival treated P. canaliculata were inhibited.

Extraction systems for isolating esterases having interfacial adsorption / Sistemas de extracción para el aislamiento de esterasas con adsorción interfacial

En el presente trabajo se optimizaron las condiciones de extracción de esterasas con actividad en interfaces, a partir de la anémona marina Stichodactyla helianthus y del camarón peneido Litopenaeus vannamei Las esterasas interfaciales, cuya presencia en estas especies había sido informada previamente, presentan características funcionales que las hacen muy atractivas para su empleo industrial. Los homogenados de los animales se trataron con los detergentes Tritón X-100, Tween 20 y Tween 80 en dos concentraciones cada uno: la Concentración Micelar Crítica (CMC) y la mitad de ésta. Además se empleó NaCl 0,5 mol/L y n-butanol a las proporciones 5, 10 y 20%. Cada variante fue comparada con el método tradicional de extracción con agua destilada, que fue tomado como control. Los mejores resultados se obtuvieron empleando n-butanol al 20%, para recuperar las actividades esterasa y fosfolipasa, y al 10%, en el aislamiento de la actividad lipasa. La efectividad de este solvente en el aislamiento de estas enzimas con afinidad por las interfaces lípido/agua, pudiera estar dada por su capacidad para romper los agregados entre estas moléculas y causar la desorción de las mismas a los restos de membrana y tejidos presentes en la preparación.

Interfacial esterases present great functional versatility, making them very attractive molecules for industrial applications. The conditions for extracting interfacial esterases previously detected in the sea anemone Stichodactyla helianthus and the shrimp Litopenaeus vannamei were optimised in this work. Animal homogenates were treated with Triton X-100, Tween 20 and Tween 80 detergents at two different concentrations: critical micellar concentration (CMC) and half of that concentration; 0.5 mol/L NaCl and n-butanol at 5%, 10% and 20% v/v ratios were also tested. Each procedure was compared to the control extraction method using distilled water. The best results were obtained with 20% n-butanol for recovering esterase and phospholipase activity whilst 10% n-butanol extraction was the most effective for lipase activity isolation. This solvent’s suitability for isolating interface-activated enzymes could be explained by its ability to dissociate biomolecule aggregates and cause enzyme desorption from the membranes and tissues remaining in the preparation.

Importancia de la hidrólisis estereoespecífica en la evaluación de riesgos tóxicos de insecticidas fosforamidatos / The importance of stereospecific hydrolysis in the risk assessment of phosphoramidate insecticides

Los principales efectos tóxicos de los insecticidas organofosforados derivan de la inhibición y envejecimiento de la acetilcolinesterasa y la esterasa diana de la neuropatía. Las fosfotriesterasas son esterasas capaces de hidrolizar insecticidas organofosforados. En este trabajo se estudia en varios tejidos de conejo, rata y gallina la estereoespecificidad de las fosfotriesterasas implicadas en la hidrólisis del insecticida O-hexil O-2,5-diclorofenil fosforamidato. También se ha caracterizado la capacidad de los isómeros R y S de dicho fosforamidato para inhibir y envejecer la esterasa diana de neuropatía. Entre todas las especies estudiadas los tejidos de conejo mostraron los mayores niveles de actividades hidrolizantes de insecticida, siendo la gallina la especie con menores niveles de esta actividad. En conejo y rata la mayoría de las fosfotriesterasas de los tejidos estudiados mostraron preferencia por la hidrólisis del isómero S del compuesto. Sin embargo, no se pudieron extraer conclusiones claras respecto a la estereoespecificidad de la hidrólisis en gallina. El isómero S del O-hexil O-2,5-diclorofenil fosforamidato inhibió la esterasa diana de la neuropatía de cerebro de gallina con I50 de 7.6 nM, siendo 190 nM el valor para la inhibición por el correspondiente isómero R. La citada esterasa inhibida por el compuesto de configuración S pudo ser reactivada por KF transcurridas 22 horas de la inhibición, reactivación que no ocurrió cuando el inhibidor fue el compuesto de configuración R. Así pues, los niveles de fosfotriesterasas y su estereoespecificidad van a determinar qué isómero alcanza las dianas tóxicas y en qué concentración y por tanto cuáles serán los efectos tóxicos que se manifiestan. Se concluye que se deben considerar los niveles de fosfotriesterasas y su estereoespecificidad en la evaluación de riesgos tóxicos de insecticidas fosforamidatos (AU)

Age-related sensitivity of the nervous system to neurotoxic insults.

Complex genomic activity and environmental factors regulate neuronal plasticity, which operates during pre- and postnatal development, can be reactivated after injury, and is impaired during aging. In these contexts, the effects of chemicals are often unpredictable because the developing and aging nervous system may or may not be equally susceptible as that of the adult. Thus, the developing central nervous system may be more susceptible to the acute toxicity of certain organophosphorus esters, whereas the developing peripheral nervous system is resistant to organophosphate-induced delayed polyneuropathy. Reasons for age-related susceptibility are manifold, including both differences in toxicokinetics and toxicodynamics and in intrinsic susceptibility of the nervous system, which is related to given physiological conditions. Therefore, the identification of genetic and environmental factors regulating neuronal plasticity becomes critical to the understanding of age-related sensitivity to chemicals. The example of age-related sensitivity to organophosphate-induced delayed polyneuropathy is illustrated together with that of the promotion of axonopathies by certain esterase inhibitors, which also seem modulated according to age. The identification of the molecular targets of both organophosphate neuropathy and promotion of neuropathy might allow the understanding of processes involved in the expression of peripheral neurotoxicities according to age.