Midge-stabilized sediment drives the composition of benthic cladoceran communities in Lake Mývatn, Iceland

The importance of environmental disturbances as drivers of ecological communities depends not only on the magnitude of the disturbance, but also on the disturbance-specific sensitivity of the community. Organisms that alter the physical structure of their surroundings can affect the sensitivity of their habitat to environmental disturbance, and may alter the potential for disturbance to shape ecological communities. Such organisms therefore act as ecosystem engineers by indirectly modifying the resources available to other species. The benthos of shallow, eutrophic Lake Mývatn, Iceland, is frequently disturbed by wind events that lead to sediment resuspension. The impact of wind, however, depends on the abundance of midges (Chironomidae) whose larval tubes bind sediment and reduce wind-driven resuspension. Here, we investigate the long-term effect of fluctuations in midge abundance on the benthic cladoceran community using two lake sediment cores representing 30 and 140 years of deposition. In both cores, midge remains show a significant positive correlation with abundance of a large benthic surface-dwelling cladoceran, Eurycercus lamellatus, relative to the abundance of a small within-sediment-dwelling cladoceran, Alona rectangula. To experimentally investigate whether this shift could have been caused by midges acting as ecosystem engineers, we subjected cladoceran communities to sediment resuspension events within mesocosms. We found a significant decrease in abundance of the large epibenthic E. lamellatus relative to the abundance of small infaunal Alona spp. when subjected to disturbance. These findings show that physical alteration of benthic sediment and hence the sensitivity of the sediment to disturbance may explain the community shift in cladocerans observed with fluctuating midge abundance in Lake Mývatn.National Science Foundation Graduate Research Fellowship. Grant Number: DGE-1256259 LTREB. Grant Number: DEB-1052160Peer Reviewe

TP53-inducible Glycolysis and Apoptosis Regulator (TIGAR) Metabolically Reprograms Carcinoma and Stromal Cells in Breast Cancer.

A subgroup of breast cancers has several metabolic compartments. The mechanisms by which metabolic compartmentalization develop in tumors are poorly characterized. TP53 inducible glycolysis and apoptosis regulator (TIGAR) is a bisphosphatase that reduces glycolysis and is highly expressed in carcinoma cells in the majority of human breast cancers. Hence we set out to determine the effects of TIGAR expression on breast carcinoma and fibroblast glycolytic phenotype and tumor growth. The overexpression of this bisphosphatase in carcinoma cells induces expression of enzymes and transporters involved in the catabolism of lactate and glutamine. Carcinoma cells overexpressing TIGAR have higher oxygen consumption rates and ATP levels when exposed to glutamine, lactate, or the combination of glutamine and lactate. Coculture of TIGAR overexpressing carcinoma cells and fibroblasts compared with control cocultures induce more pronounced glycolytic differences between carcinoma and fibroblast cells. Carcinoma cells overexpressing TIGAR have reduced glucose uptake and lactate production. Conversely, fibroblasts in coculture with TIGAR overexpressing carcinoma cells induce HIF (hypoxia-inducible factor) activation with increased glucose uptake, increased 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3 (PFKFB3), and lactate dehydrogenase-A expression. We also studied the effect of this enzyme on tumor growth. TIGAR overexpression in carcinoma cells increases tumor growth in vivo with increased proliferation rates. However, a catalytically inactive variant of TIGAR did not induce tumor growth. Therefore, TIGAR expression in breast carcinoma cells promotes metabolic compartmentalization and tumor growth with a mitochondrial metabolic phenotype with lactate and glutamine catabolism. Targeting TIGAR warrants consideration as a potential therapy for breast cancer

Taking the trophic bypass: aquatic-terrestrial linkage reduces methylmercury in a terrestrial food web

Abstract. Ecosystems can be linked by the movement of matter and nutrients across habitat boundaries via aquatic insect emergence. Aquatic organisms tend to have higher concentrations of certain toxic contaminants such as methylmercury (MeHg) compared to their terrestrial counterparts. If aquatic organisms come to land, terrestrial organisms that consume them are expected to have elevated MeHg concentrations. But emergent aquatic insects could have other impacts as well, such as altering consumer trophic position or increasing ecosystem productivity as a result of nutrient inputs from insect carcasses. We measure MeHg in terrestrial arthropods at two lakes in northeastern Iceland and use carbon and nitrogen stable isotopes to quantify aquatic reliance and trophic position. Across all terrestrial focal arthropod taxa (Lycosidae, Linyphiidae, Acari, Opiliones), aquatic reliance had significant direct and indirect (via changes in trophic position) effects on terrestrial consumer MeHg. However, contrary to our expectations, terrestrial consumers that consumed aquatic prey had lower MeHg concentrations than consumers that ate mostly terrestrial prey. We hypothesize that this is due to the lower trophic position of consumers feeding directly on midges relative to those that fed mostly on terrestrial prey and that had, on average, higher trophic positions. Thus, direct consumption of aquatic inputs results in a trophic bypass that creates a shorter terrestrial food web and reduced biomagnification of MeHg across the food web. Our finding that MeHg was lower at terrestrial sites with aquatic inputs runs counter to the conventional wisdom that aquatic systems are a source of MeHg contamination to surrounding terrestrial ecosystems

Taking the trophic bypass : aquatic-terrestrial linkage reduces methylmercury in a terrestrial food web

Ecosystems can be linked by the movement of matter and nutrients across habitat boundaries via aquatic insect emergence. Aquatic organisms tend to have higher concentrations of certain toxic contaminants such as methylmercury (MeHg) compared to their terrestrial counterparts. If aquatic organisms come to land, terrestrial organisms that consume them are expected to have elevated MeHg concentrations. But emergent aquatic insects could have other impacts as well, such as altering consumer trophic position or increasing ecosystem productivity as a result of nutrient inputs from insect carcasses. We measure MeHg in terrestrial arthropods at two lakes in northeastern Iceland and use carbon and nitrogen stable isotopes to quantify aquatic reliance and trophic position. Across all terrestrial focal arthropod taxa (Lycosidae, Linyphiidae, Acari, Opiliones), aquatic reliance had significant direct and indirect (via changes in trophic position) effects on terrestrial consumer MeHg. However, contrary to our expectations, terrestrial consumers that consumed aquatic prey had lower MeHg concentrations than consumers that ate mostly terrestrial prey. We hypothesize that this is due to the lower trophic position of consumers feeding directly on midges relative to those that fed mostly on terrestrial prey and that had, on average, higher trophic positions. Thus, direct consumption of aquatic inputs results in a trophic bypass that creates a shorter terrestrial food web and reduced biomagnification of MeHg across the food web. Our finding that MeHg was lower at terrestrial sites with aquatic inputs runs counter to the conventional wisdom that aquatic systems are a source of MeHg contamination to surrounding terrestrial ecosystems

Efectivitat de l'aprenentatge basat en problemes (ABP) en l'assignatura de Teràpia Gènica i Molecular d'Odontologia

Podeu consultar la Vuitena trobada de professorat de Ciències de la Salut completa a: http://hdl.handle.net/2445/66524L’aprenentatge basat en problemes (ABP) és una estratègia didàctica innovadora centrada en l’estudiant, que facilita l’adquisició d’unes habilitats i competències indispensables en l’entorn professional i que proporciona el context adequat per afavorir el treball en grup i l’aprenentatge significatiu. L’experiència que aquí descrivim neix de la necessitat de motivar i implicar els estudiants d’Odontologia (2n-4t curs) en l’aprenentatge i assoliment de les competències transversals i les específiques definides en el pla docent de l’assignatura optativa de 3 ECTS Teràpia gènica i molecular durant el curs 2013-2014. Han participat un total de 32 estudiants distribuïts en 4 grups La dinàmica de l’ABP consisteix en la resolució d’un cas entre 6 dissenyats prèviament per l'equip de profesors, que cada grup d'estudiants ha de solucionar aplicant conceptes de Teràpia Gènica per a dissenyar una estratègia terapèutica innovadora aplicada a un desordre de la salut. En aquesta comunicació es descriu l’experiència realitzada, tenint en compte aspectes metodològics, descripció de les dinàmiques de grup, avaluació de l’experiència per part dels estudiants i dels tutors, així com la seva incidència en els resultats globals de l’assignatura. Tambè se ha fet una anàlisi comparativa dels resultats d'aquest curs amb els dels cursos previs. Aquest projecte ha constituït la primera experiència amb l

High mountain lakes: extreme habitats and witnesses of environmental changes.

33 páginas, 14 figuras, 3 tablas.[EN]High mountain lakes offer research opportunities beyond what could be expected from their quantitative relevance in the Earth system. In this article we present a brief summary of the research carried out in the lakes of the Pyrenees in the last twenty years by the group of limnology of the Centre for High Mountain Research (CRAM) of the University of Barcelona. The studies can be included in three main topics: life in extreme conditions, catchment-lake relationships and environmental changes.[ES]Los lagos de montaña ofrecen oportunidades de estudio que van mucho más allá de lo que su disposición en el territorio y abundancia pudieran sugerir. En este artículo presentamos un breve resumen de los temas que hemos abordado a lo largo de poco más de veinte años de investigación en los lagos de los Pirineos por parte del grupo de limnología del Centro de Investigaciones de Alta Montaña (CRAM) de la Universidad de Barcelona. Los estudios se enmarcan fundamentalmente en tres líneas generales: la vida en condiciones extremas, las relaciones cuenca-lago y los cambios ambientales.Peer reviewe

TP53-inducible Glycolysis and Apoptosis Regulator (TIGAR) Metabolically Reprograms Carcinoma and Stromal Cells in Breast Cancer

A subgroup of breast cancers has several metabolic compartments. The mechanisms by which metabolic compartmentalization develop in tumors are poorly characterized. TP53 inducible glycolysis and apoptosis regulator (TIGAR) is a bisphosphatase that reduces glycolysis and is highly expressed in carcinoma cells in the majority of human breast cancers. Hence we set out to determine the effects of TIGAR expression on breast carcinoma and fibroblast glycolytic phenotype and tumor growth. The overexpression of this bisphosphatase in carcinoma cells induces expression of enzymes and transporters involved in the catabolism of lactate and glutamine. Carcinoma cells overexpressing TIGAR have higher oxygen consumption rates and ATP levels when exposed to glutamine, lactate, or the combination of glutamine and lactate. Coculture of TIGAR overexpressing carcinoma cells and fibroblasts compared with control cocultures induce more pronounced glycolytic differences between carcinoma and fibroblast cells. Carcinoma cells overexpressing TIGAR have reduced glucose uptake and lactate production. Conversely, fibroblasts in coculture with TIGAR overexpressing carcinoma cells induce HIF (hypoxia-inducible factor) activation with increased glucose uptake, increased 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3 (PFKFB3), and lactate dehydrogenase-A expression. We also studied the effect of this enzyme on tumor growth. TIGAR overexpression in carcinoma cells increases tumor growth in vivo with increased proliferation rates. However, a catalytically inactive variant of TIGAR did not induce tumor growth. Therefore, TIGAR expression in breast carcinoma cells promotes metabolic compartmentalization and tumor growth with a mitochondrial metabolic phenotype with lactate and glutamine catabolism. Targeting TIGAR warrants consideration as a potential therapy for breast cancer