Streamflow variability in the Chilean Temperate-Mediterranean climate transition (35\ub0S\u201342\ub0S) during the last 400\ua0years inferred from tree-ring records

As rainfall in South-Central Chile has decreased in recent decades, local communities and industries have developed an understandable concern about their threatened water supply. Reconstructing streamflows from tree-ring data has been recognized as a useful paleoclimatic tool in providing long-term perspectives on the temporal characteristics of hydroclimate systems. Multi-century long streamflow reconstructions can be compared to relatively short instrumental observations in order to analyze the frequency of low and high water availability through time. In this work, we have developed a Biobío River streamflow reconstruction to explore the long-term hydroclimate variability at the confluence of the Mediterranean-subtropical and the Temperate-humid climate zones, two regions represented by previous reconstructions of the Maule and Puelo Rivers, respectively. In a suite of analyses, the Biobío River reconstruction proves to be more similar to the Puelo River than the Maule River, despite its closer geographic proximity to the latter. This finding corroborates other studies with instrumental data that identify 37.5°S as a latitudinal confluence of two climate zones. The analyzed rivers are affected by climate forcings on interannual and interdecadal time-scales, Tropical (El Niño Southern Oscillation) and Antarctic (Southern Annular Mode; SAM). Longer cycles found, around 80-years, are well correlated only with SAM variation, which explains most of the variance in the Biobío and Puelo rivers. This cycle also has been attributed to orbital forcing by other authors. All three rivers showed an increase in the frequency of extreme high and low flow events in the twentieth century. The most extreme dry and wet years in the instrumental record (1943–2000) were not the most extreme of the past 400-years reconstructed for the three rivers (1600–2000), yet both instrumental record years did rank in the five most extreme of the streamflow reconstructions as a whole. These findings suggest a high level of natural variability in the hydro-climatic conditions of the region, where extremes characterized the twentieth century. This information is particularly useful when evaluating and improving a wide variety of water management models that apply to water resources that are sensitive to agricultural and hydropower industries.Fil: Muñoz, Ariel A.. Pontificia Universidad Católica de Valparaíso; ChileFil: González Reyes, Alvaro. Universidad de Chile; ChileFil: Lara, Antonio. Universidad Austral de Chile; ChileFil: Sauchyn, David. University of Regina; CanadáFil: Christie, Duncan. Universidad Austral de Chile; ChileFil: Puchi, Paulina. Pontificia Universidad Católica de Valparaíso; ChileFil: Urrutia Jalabert, Rocío. Universidad Austral de Chile; ChileFil: Toledo Guerrero, Isadora. Pontificia Universidad Católica de Valparaíso; ChileFil: Aguilera Betti, Isabella. Pontificia Universidad Católica de Valparaíso; ChileFil: Mundo, Ignacio Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Sheppard, Paul R.. University of Arizona; Estados UnidosFil: Stahle, Daniel. University of Arkansas for Medical Sciences; Estados UnidosFil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Szejner, P.. University of Arizona; Estados UnidosFil: LeQuesne, Carlos. Universidad Austral de Chile; ChileFil: Vanstone, Jessica. University of Regina; Canad

DNA methylation of the glucagon-like peptide 1 receptor (GLP1R) in human pancreatic islets

Background: Insulin secretion is enhanced upon the binding of Glucagon-like peptide-1 (GLP-1) to its receptor (GLP1R) in pancreatic β cells. Although a reduced expression of GLP1R in pancreatic islets from type 2 diabetic patients and hyperglycaemic rats has been established, it is still unknown if this is caused by differential DNA methylation of GLP1R in pancreatic islets of type 2 diabetic patients.Methods: In this study, DNA methylation levels of 12 CpG sites close to the transcription start site of GLP1R were analysed in pancreatic islets from 55 non-diabetic and 10 type 2 diabetic human donors as well as in β and α cells isolated from human pancreatic islets. DNA methylation of GLP1R was related to GLP1R expression, HbA levels and BMI. Moreover, mRNA expression of MECP2, DNMT1, DNMT3A and DNMT3B was analysed in pancreatic islets of the non-diabetic and type 2 diabetic donors.Results: One CpG unit, at position +199 and +205 bp from the transcription start site, showed a small increase in DNA methylation in islets from donors with type 2 diabetes compared to non-diabetic donors (0.53%, p=0.02). Furthermore, DNA methylation levels of one CpG site located 376 bp upstream of the transcription start site of GLP1R correlated negatively with GLP1R expression (rho=-0.34, p=0.008) but positively with BMI and HbA (rho=0.30, p=0.02 and rho=0.30, p=0.03, respectively). This specific CpG site is located in an area with known SP1 and SP3 transcription factor binding sites. Moreover, when we compared the DNA methylation of the GLP1R promoter in isolated human β and α cells, we found that it was higher in α- compared with β-cells (p=0.009). Finally, there was a trend towards decreased DNMT3A expression (p=0.056) in type 2 diabetic compared with non-diabetic islets.Conclusions: Together, our study shows that while BMI and HbA are positively associated with DNA methylation levels of GLP1R, its expression is negatively associated with DNA methylation of GLP1R in human pancreatic islets

The domains of intellectual capital: an integrative discourse across perspectives

This chapter explores the domains of intellectual capital (IC) more commonly known as human, organisation and social capital. This theoretical analysis draws together these three disciplinary domains through an integrative discourse in terms of leveraging accumulative resources, connecting complementary themes and distinguishing between interdependent cognitions and behaviours. It seeks to answer scholarly concerns that the IC construct is vague and misleading, resulting in erroneous and generalised relationships. The chapter adopts a theoretical lens and explores complementary discourses of the relationships between human capital (HC), human capital resources (HCR), organisational capital and social capital (SC). For HC and HCR, the discussions build on the resource-based view and the micro-foundations approaches in the strategy literature, where recent research has explored linkages between HCR and competitive advantage. The SC literature is outlined and the discourse between internal SC and external SC is spelled out. The discourses between the domains suggest that through a process of emergence, firms can develop dynamic capabilities that enable them to achieve competitive advantage in factor markets. In light of this, the chapter builds on and complements other recent research that has extended scholarly concerns about the lack of an integrative framework by which the IC linkages and variables can be developed and tested