América Latina en las cadenas globales de valor

Este informe analiza la inserción de América Latina en las cadenas globales de valor (CGV) y su impacto sobre el comercio, la inversión y el desarrollo económico de los países de la región. Se estudia el sector textil, la industria automovilística y la electrónica en América Central, y los sectores de alimentos, textil y de calzados en América del Sur. Se concluye que en muchos casos los países de la región crecieron y se integraron a las cadenas de valor a impulsos de la inversión extranjera directa, generando una dependencia excesiva de algunos mercados y de ciertos productos, fundamentalmente commodities. Frente a la fuerte competencia de los países asiáticos, el crecimiento de la región depende sobre todo de diseñar estrategias nacionales para incorporar cada vez más valor a los procesos productivos, incrementar las competencias tecnológicas, y diversificar mercados y productos

Impactos de la crisis internacional en América Latina y las alternativas de políticas

El comercio internacional fue uno de los principales canales mediante el cual la crisis internacional —que comenzó en Estados Unidos en 2008 como una crisis financiera—, se transmitió hacia los mercados de América Latina. En 2009 el comercio mundial se redujo y cayó la demanda de productos de países latinoamericanos, los cuales reaccionaron adoptando diversas medidas de política comercial para enfrentar los efectos adversos de la crisis. De las investigaciones desarrolladas por la Red Mercosur surge que en la región hay posibilidades reales de aplicar políticas para mitigar los impactos causados por turbulencias internacionales, y potenciar el comercio intrarregional, así como oportunidades para una mayor coordinación de modo que las medidas aplicadas individualmente por cada país no afecten negativamente a sus vecinos o socios comerciales regionales

Presentación

Presentation of the special issue coordinated by Carmen Alemany Bay and Cecilia Eudave. New perspectives on the fantastic: Hispanic-American and Spanish female authors (21st century)Presentación del monográfico coordinado por Carmen Alemany Bay y Cecilia Eudave. Lo fantástico y sus nuevas perspectivas: narradoras hispanoamericanas y españolas (s. XXI

Glycerol is synthesized and secreted by adipocytes to dispose of excess glucose, via glycerogenesis and increased acyl-glycerol turnover

White adipose tissue (WAT) produces large amounts of lactate and glycerol from glucose. We used mature epididymal adipocytes to analyse the relative importance of glycolytic versus lipogenic glycerol in adipocytes devoid of external stimuli. Cells were incubated (24/48 h) with 7/14 mM glucose; half of the wells contained 14C-glucose. We analysed glucose label fate, medium metabolites, and the expression of key genes coding for proteins controlling glycerol metabolism. The effects of initial glucose levels were small, but time of incubation increased cell activity and modified its metabolic focus. The massive efflux of lactate was uniform with time and unrelated to glucose concentration; however, glycerol-3P synthesis was higher in the second day of incubation, being largely incorporated into the glyceridesglycerol fraction. Glycerophosphatase expression was not affected by incubation. The stimulation of glycerogenic enzymes' expression was mirrored in lipases. The result was a shift from medium glycolytic to lipolytic glycerol released as a consequence of increased triacylglycerol turnover, in which most fatty acids were recycled. Production of glycerol seems to be an important primary function of adipocytes, maintained both by glycerogenesis and acyl-glycerol turnover. Production of 3C fragments may also contribute to convert excess glucose into smaller, more readily usable, 3C metabolites

Higher lactate production from glucose in cultured adipose nucleated stromal cells than for rat adipocytes

White adipose tissue (WAT) nucleated stromal cells (NSC) play important roles in regulation, defense, regeneration and metabolic control. In WAT sites, the proportions and functions of NSC change under diverse physiological or pathologic conditions. We had previously observed the massive anaerobic wasting of glucose to lactate and glycerol in rat epididymal adipocytes. To test site variability, and whether the adipocyte extensive anaerobic metabolism of glucose was found in NSC, we analyzed, in parallel, subcutaneous, mesenteric and epididymal WAT of male adult Wistar rats. Adipocytes and NSC fractions, were isolated, counted and incubated (as well as red blood cells: RBC) with glucose, and their ability to use glucose and produce lactate, glycerol, and free fatty acids was measured. Results were computed taking into account the cells present in WAT samples. Cell numbers were found in proportions close to 1:13:100 (respectively, for adipocytes, NSC and RBC) but their volumes followed a reversed pattern: 7,500:10:1. When counting only non-fat cell volumes, the ratios changed dramatically to 100:10:1. RBC contribution to lactate production was practically insignificant. In most samples, NSC produced more lactate than adipocytes did, but only adipocytes secreted glycerol (and fatty acids in smaller amounts). Glucose consumption was also highest in NSC, especially in mesenteric WAT. The heterogeneous NSC showed a practically anaerobic metabolism (like that already observed in adipocytes). Thus, NSC quantitative production of lactate markedly contributed (i.e. more than adipocytes) to WAT global use (wasting) of glucose. We also confirmed that glucose-derived glycerol is exclusively produced by adipocyte

Use of 14C-glucose by primary cultures of mature rat epididymal adipocytes. Marked release of lactate and glycerol, but limited lipogenesis in the absence of external stimuli

White adipose tissue can metabolize large amounts of glucose to glycerol and lactate. We quantitatively traced glucose label to lactate, glycerol and fats in primary cultures of mature rat epididymal adipocytes. Cells were incubated with 7/14 mM 14C-glucose for 24/48 h. Medium metabolites and the label in them and in cells' components were measured. Gene expression analysis was done using parallel incubations. Glucose concentration did not affect lactate efflux and most parameters. Glycerol efflux increased after 24h, coinciding with arrested lipogenesis. Steady production of lactate was maintained in parallel to glycerogenesis. Changes in adipocyte metabolism were paralleled by gene expression. Glucose use for lipogenesis was minimal, and stopped (24h-onwards) when glycerol efflux increased because of triacylglycerol turnover. Lactate steady efflux showed that anaerobic glycolysis was the main adipocyte source of energy. We can assume that adipose tissue may play a quantitatively significant effect on glycaemia, returning 3C fragments thus minimizing lipogenesis

Quantitative analysis of rat adipose tissue cell recovery, and non-fat cell volume, in primary cell cultures (Raw data)

Dades primàries associades a un article publicat a la revista PeerJ disponible a l'adreça http://dx.doi.org/10.7717/peerj.2725Podeu consultar l'article a: http://hdl.handle.net/2445/104686Background. White adipose tissue (WAT) is a complex, diffuse, multifunctional organ which contains adipocytes, and a large proportion of fat, but also other cell types, active in defence, regeneration and signalling functions. Studies with adipocytes often require their isolation from WAT by breaking up the matrix of collagen fibres, however, it is unclear to what extent adipocyte number in primary cultures correlates with their number in intact WAT, since recovery and viability are often unknown. Experimental design. Epididymal WAT of 4-6 young adult rats was used to isolate adipocytes with collagenase. Careful recording of lipid content of tissue, and all fraction volumes and weights, allowed us to trace the amount of initial WAT fat remaining in the cell preparation. Functionality was estimated by incubation with glucose and measurement of lactate, glycerol and NEFA production. Non-adipocyte cells were also recovered and their sizes (and those of adipocytes) were also measured. The presence of non-nucleated cells (erythrocytes) was also estimated. Results. Cell numbers and sizes were correlated from all fractions to intact WAT. Tracing the lipid content, the recovery of adipocytes in the final, metabolically active, preparation was in the range of 70-75%. Adipocytes were 7%, erythrocytes 68% and other stromal (nucleated cells) 24% of total WAT cells. However, their overall volumes were, 91%, 0.05%, and 0.2% of WAT. Non-fat volume of adipocytes was 2.5% of WAT. Conclusions. The methodology presented here allows for a direct quantitative reference to the original tissue of studies using isolated cells. We have found, also, that the "live cell mass" of adipose tissue is very small (about 25 µL/g for adipocytes and 2 µL/g stromal, plus about 1 µL/g blood). This fact, translates (with respect to the actual "live cytoplasm" size) into an extremely high metabolic activity, which make WAT an even more significant agent in the control of energy metabolism

A method for the measurement of lactate, glycerol and fatty acid production from 14C-glucose in primary cultures of rat epididymal adipocytes.

We have developed a method for the analysis of the main metabolic products of utilization of glucose by isolated adipocytes. They were incubated for 24 h with 14C-glucose. The final label distribution and cold levels of medium glucose, lactate and glycerol were estimated. Medium lactate was extracted using ion-exchange resin minicolumns prepared with centrifugation-filtering tubes in which the filter was substituted by the resin. This allowed complete washing using only 0.2 mL. Repeated washings allowed for complete recovery of fractions with low volumes passing through or retained (and eluted), which permitted precise counting and a sufficient amount of sample for further analyses. Lactate was separated from glucose and glycerol; glucose was then separated by oxidizing it to gluconate with glucose oxidase, and glycerol was separated in parallel by phosphorylation with ATP and glycerol kinase. Cells' lipid was extracted with ether and saponified. Glycerides-glycerol and fatty acids (from the soaps) were counted separately. The complete analysis of cells incubated with labelled glucose resulted in about half of the glucose metabolized in 24 h, 2/3rds of the incorporated glucose label was found as lactate, and 14% as free glycerol. Their specific activities per carbon were the same as that of glucose. Production of fatty acids took about 5% of the label incorporated, an amount similar to that of glycerides-glycerol and estimated carbon dioxide. The procedure described is versatile enough to be used under experimental conditions, with a high degree or repeatability and with only about 3% of the label not accounted for