Purinergic signalling in the subretinal space: a role in the communication between the retina and the RPE

The retinal pigment epithelium (RPE) is separated from the photoreceptor outer segments by the subretinal space. While the actual volume of this space is minimal, the communication that occurs across this microenvironment is important to the visual process, and accumulating evidence suggests the purines ATP and adenosine contribute to this communication. P1 and P2 receptors are localized to membranes on both the photoreceptor outer segments and on the apical membrane of the RPE which border subretinal space. ATP is released across the apical membrane of the RPE into this space in response to various triggers including glutamate and chemical ischemia. This ATP is dephosphorylated into adenosine by a series of ectoenzymes on the RPE apical membrane. Regulation of release and ectoenzyme activity in response to light-sensitive signals can alter the balance of purines in subretinal space, and thus coordinate communication across subretinal space with the visual process

La sostenibilidad social de la agricultura intensiva almeriense: una mirada desde la organización social del trabajo

Este artículo tiene como principal objetivo explicar la organización social del trabajo en el modelo de producción hortofrutícola almeriense desde una perspectiva de sostenibilidad social. Para ello, parte de una noción compleja de trabajo que contempla sus dimensiones socioculturales, las relaciones sociales de clase, interétnicas y de sexo-género sobre las que se configura y el modo en que se halla arraigado en el conjunto de instituciones sociales. Como primera hipótesis se plantea que existe una contradicción entre el papel central que ocupa el trabajo de las mujeres y las personas inmigrantes para la continuidad del modelo, y la tendencia a minusvalorarlo. La segunda hipótesis mantiene que la organización del trabajo se estructura sobre un conjunto de insostenibilidades sociales que ponen en jaque las condiciones de trabajo y la vida de quienes lo realizan. El texto se basa en una metodología cualitativa apoyada en las técnicas de la entrevista y la observación participante.This article approaches the social organization of labour in Almería’s fruit and vegetable farming from the viewpoint of social sustainability. The article is grounded on a complex notion of labour, involving sociocultural dimensions as well as class, ethnic, and sex-gender social relationships, and taking into account the way in which labour is rooted into social institutions as a whole. Our first hypothesis suggests that a contradiction exists between the major role that labour plays in the continuity of farming among women and immigrants, on the one hand, and the tendency to undervalue these forms of work, on the other. Our second hypothesis is that labour organization is structured upon a set of socially unsustainable factors, which put workers’ labour and life conditions at stake. The text is based on a qualitative analysis, supported by interviewing and participant observation techniques

Alterations in Bacterial Metabolism Contribute to the Lifespan Extension Exerted by Guarana in Caenorhabditis elegans

Guarana (Paullinia cupana) is a widely consumed nutraceutical with various health benefits supported by scientific evidence. However, its indirect health impacts through the gut microbiota have not been studied. Caenorhabditis elegans is a useful model to study both the direct and indirect effects of nutraceuticals, as the intimate association of the worm with the metabolites produced by Escherichia coli is a prototypic simplified model of our gut microbiota. We prepared an ethanoic extract of guarana seeds and assessed its antioxidant capacity in vitro, with a 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, and in vivo, utilizing C. elegans. Additionally, we studied the impact of this extract on C. elegans lifespan, utilizing both viable and non-viable E. coli, and assessed the impact of guarana on E. coli folate production. The extract showed high antioxidant capacity, and it extended worm lifespan. However, the antioxidant and life-extending effects did not correlate in terms of the extract concentration. The extract-induced life extension was also less significant when utilizing dead E. coli, which may indicate that the effects of guarana on the worms work partly through modifications on E. coli metabolism. Following this observation, guarana was found to decrease E. coli folate production, revealing one possible route for its beneficial effects

Alterations in Bacterial Metabolism Contribute to the Lifespan Extension Exerted by Guarana in Caenorhabditis elegans

Guarana (Paullinia cupana) is a widely consumed nutraceutical with various health benefits supported by scientific evidence. However, its indirect health impacts through the gut microbiota have not been studied. Caenorhabditis elegans is a useful model to study both the direct and indirect effects of nutraceuticals, as the intimate association of the worm with the metabolites produced by Escherichia coli is a prototypic simplified model of our gut microbiota. We prepared an ethanoic extract of guarana seeds and assessed its antioxidant capacity in vitro, with a 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, and in vivo, utilizing C. elegans. Additionally, we studied the impact of this extract on C. elegans lifespan, utilizing both viable and non-viable E. coli, and assessed the impact of guarana on E. coli folate production. The extract showed high antioxidant capacity, and it extended worm lifespan. However, the antioxidant and life-extending effects did not correlate in terms of the extract concentration. The extract-induced life extension was also less significant when utilizing dead E. coli, which may indicate that the effects of guarana on the worms work partly through modifications on E. coli metabolism. Following this observation, guarana was found to decrease E. coli folate production, revealing one possible route for its beneficial effects

The social sustainability of intensive agriculture in Almería (Spain): a view from the social organization of labour

[ES] Este artículo tiene como principal objetivo explicar la organización social del trabajo en el modelo de producción hortofrutícola almeriense desde una perspectiva de sostenibilidad social. Para ello, parte de una noción compleja de trabajo que contempla sus dimensiones socioculturales, las relaciones sociales de clase, interétnicas y de sexo-género sobre las que se configura y el modo en que se halla arraigado en el conjunto de instituciones sociales. Como primera hipótesis se plantea que existe una contradicción entre el papel central que ocupa el trabajo de las mujeres y las personas inmigrantes para la continuidad del modelo, y la tendencia a minusvalorarlo. La segunda hipótesis mantiene que la organización del trabajo se estructura sobre un conjunto de insostenibilidades sociales que ponen en jaque las condiciones de trabajo y la vida de quienes lo realizan. El texto se basa en una metodología cualitativa apoyada en las técnicas de la entrevista y la observación participante.[EN] This article approaches the social organization of labour in Almería’s fruit and vegetable farming from the viewpoint of social sustainability. The article is grounded on a complex notion of labour, involving sociocultural dimensions as well as class, ethnic, and sex-gender social relationships, and taking into account the way in which labour is rooted into social institutions as a whole. Our first hypothesis suggests that a contradiction exists between the major role that labour plays in the continuity of farming among women and immigrants, on the one hand, and the tendency to undervalue these forms of work, on the other. Our second hypothesis is that labour organization is structured upon a set of socially unsustainable factors, which put workers’ labour and life conditions at stake. The text is based on a qualitative analysis, supported by interviewing and participant observation techniques.S

Stimulation of an α1-adrenergic receptor downregulates ecto-5′ nucleotidase activity on the apical membrane of RPE cells

The purines ATP and adenosine play an important role in the communication between the photoreceptors and the retinal pigment epithelium (RPE). While the RPE is known to release ATP into subretinal space, the source of extracellular adenosine is unclear. In other tissues, ecto-nucleotidases mediate the consecutive dephosphorylation of ATP to AMP, and AMP is converted to adenosine by ecto-5′ nucleotidase (CD73). This study identifies ecto-5′ nucleotidase on RPE cells and investigates modulation of enzyme activity. The RPE was the most active site of 5′AMP dephosphorylation in the posterior rat eye. The ecto-5′ nucleotidase inhibitor αβmADP prevented the production adenosine by the apical membrane of the bovine RPE. Cultured human ARPE-19 cells expressed mRNA and protein for ecto-5′ nucleotidase. The production of phosphate from 5′AMP by ARPE-19 cells was inhibited by αβmADP, but the ecto-alkaline phosphatase inhibitor levamisole had no effect. Degradation of 5′AMP was blocked by norepinephrine, epinephrine and phenylephrine, with inhibition by antagonists prazosin and corynanthine implicating the α1 adrenergic receptor. The block of enzyme activity by norepinephrine was rapid, occurring within 1 min, and was similar at both 4 and 37°C, consistent with cleavage of the enzyme from its GPI anchor. HPLC measurements indicated norepinephrine reduced levels of adenosine in the bath. In the apical face of the bovine-RPE eyecup, norepinephrine reduced the production of phosphate from 5′AMP, suggesting that both receptor and enzyme face sub-retinal space. In conclusion, RPE cells express ecto-5′ nucleotidase, with activity on the apical membrane, and stimulation of α-1 adrenergic receptors downregulates activity. As epinephrine is released at light onset, and adenosine can inhibit phagocytosis, the corresponding decrease in subretinal adenosine levels may contribute to the enhanced the phagocytosis of rod outer segments that occurs at this time