Denis P.A.,University of Montevideo
Journal of Physical Chemistry C | Year: 2014
By means of first principle calculations, we have performed a theoretical characterization of the stability and electronic properties of sheets and nanoribbons that were recently synthesized employing octafunctionalized biphenylenes as building blocks. We found that the biphenylene sheet has a strong metallic character that is difficult to inhibit employing low levels of functionalization. Hydrogenation at full coverage induces a metal to insulator transition, but the band gap opened is very large, i.e., 6.6 eV. When other functional groups such as fluorine or chlorine are attached, the band gap can be regulated. The most effective chemical modification, in terms of gap opening, is the combination of hydrogen/chlorine or fluorine/chlorine. For the latter functional groups, band gaps similar to those of rutile were calculated at the HSEH1PBE/6-31G∗ level of theory. The biphenylene sheet functionalized on one side with fluorine and with chlorine on the other presented a CC bond length equal to 1.76 Å, one of the longest reported up to date. In contrast with recent claims, we found that, for armchair biphenylene nanoribbons, the twist induced by the functionalization of the edges does not increase the band gaps of the nanoribbons. Moreover, in some cases the gaps were reduced as we observed when the edges where saturated with hydrogen atoms. Finally, the high reactivity of the sheet indicated that it is may have promising applications in catalysis. © 2014 American Chemical Society.
Manzanares W.,University of Montevideo |
Hardy G.,Massey University
Current Opinion in Clinical Nutrition and Metabolic Care | Year: 2010
Purpose of review: To analyse the anti-inflammatory and antioxidant properties of vitamin B12 and evaluate current evidence on vitamin B12 status in the critically ill with systemic inflammation. Recent findings: Data on vitamin B12 status of intensive care unit patients are scarce. Cobalamins could potentially be useful agents for inhibiting nitric oxide synthase and nitric oxide production, controlling nuclear factor-kappa B activation, and restoring optimal bacteriostasis and phagocytosis in which transcobalamins play a proven role. The antioxidant properties of vitamin B12, with a glutathione-sparing effect, are secondary to stimulation of methionine synthase activity and reaction with free oxygen or nitrogen radicals. Large parenteral doses are routinely administered for cyanide poisoning, with only mild, reversible side-effects. Current evidence suggests that high-dose parenteral vitamin B12 may prove an innovative approach to treat critically ill systemic inflammatory response syndrome patients, especially those with severe sepsis/septic shock. In this setting, vitamin B12 and transcobalamins could modulate systemic inflammation contributing to the anti-inflammatory cascade and potentially improve outcome. Summary: Despite evidence from animal studies, so far there are no clinical intervention trials that have studied vitamin B12 as a pharmaconutrient strategy for critical care. Well designed animal and clinical studies are required to clarify several outstanding questions on the optimal posology, safety, and efficacy of high-dose vitamin B12 in the critically ill. © 2010 Wolters Kluwer Health. Lippincott Williams & Wilkins.
Lessa E.P.,University of Montevideo |
D'ElIa G.,University of Concepcion |
PardiNas U.F.J.,Centro Nacional Patagonico
Molecular Ecology | Year: 2010
Species are impacted by climate change at both ecological and evolutionary time scales. Studies in northern continents have provided abundant evidence of dramatic shifts in distributions of species subsequent to the last glacial maximum (LGM), particularly at high latitudes. However, little is known about the history of southern continents, especially at high latitudes. South America is the only continent, other than Antarctica, that extends beyond 40 °S. Genetic studies of a few Patagonian species have provided seemingly conflicting results, indicating either postglacial colonization from restricted glacial refugia or persistence through glacial cycles and in situ differentiation. Using mitochondrial DNA sequences of 14 species of sigmodontine rodents, a major faunal ensemble of Patagonia and Tierra del Fuego, we show that at least nine of these species bear genetic footprints of demographic expansion from single restricted sources. However, timing of demographic expansion precedes the LGM in most of these species. Four species are fragmented phylogeographically within the region. Our results indicate that (i) demographic instability in response to historical climate change has been widespread in the Patagonian-Fueguian region, and is generally more pronounced at high latitudes in both southern and northern continents; (ii) colonization from lower latitudes is an important component of current Patagonian-Fueguian diversity; but (iii) in situ differentiation has also contributed to species diversity. © 2010 Blackwell Publishing Ltd.
Manzanares W.,University of Montevideo |
Hardy G.,Massey University
Current Opinion in Clinical Nutrition and Metabolic Care | Year: 2011
Purpose of Review: To summarize the properties of thiamine and evaluate current evidence on thiamine status and supplementation, for different populations of critically ill patients. Recent Findings: Thiamine, in the form of thiamine pyrophosphate, is a critical co-factor in the glyocolysis and oxidative decarboxylation of carbohydrates for energy production. Different studies have shown that critical illness in adults and children is characterized by absolute or relative thiamine depletion, which is associated with an almost 50% increase in mortality. Thiamine deficiency should be suspected in different clinical scenarios such as severe sepsis, burns, unexplained heart failure or lactic acidosis, neurological disorder in patients with previous history of alcoholism, starvation, chronic malnutrition, long-term parenteral feeding, hyperemesis gravidarum, or bariatric surgery. Nonetheless, thiamine supplements are not routinely given to critically ill patients. Clinicians should be able to suspect and recognize risk factors for the occurrence of severe neurological disorders secondary to thiamine deficiency, as early treatment can prevent the appearance of permanent neurological damage. Summary: Symptoms and signs associated with thiamine deficiency lack sensitivity and specificity in critically ill patients. Consequently, depletion is frequently unrecognized and underdiagnosed by clinicians. Potentially deleterious consequences of thiamine depletion should be avoided by early and appropriate supplementation. © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins.
Salinas G.,University of Montevideo
Antioxidants and Redox Signaling | Year: 2013
Parasite redox biology is vital for understanding parasite-host interactions and adaptations. Studies in this area are leading to discoveries regarding drug targets and drug leads to treat infections caused by protozoan and worm parasites for which there are few effective drugs. Parasite unique and nonredundant core redox enzymes are choke points of metabolism and pharmacological targets. This Forum revises this concept and proposes new drug targets. It also highlights recent studies using genetically manipulated and natural strains that reveal emerging regulatory functions of antioxidant enzymes in parasite differentiation, apoptosis, virulence, acute infection, and disease progression and outcome. The challenge ahead is to understand the redox changes linked to differentiation and drastic transitions between environments that take place during parasitic complex life cycles. The combined use of new tools and techniques, such as genetically-manipulated parasites, live imaging, redox sensors, and proteomics, allow the challenge to be undertaken. Some of these methodologies, for example, transgenic parasites encoding redox biosensors, can also be applied to drug high throughput screening and to assess the effect of currently known drugs that affect redox homeostasis. Antioxid. Redox Signal. 19, 661-664. © Copyright 2013, Mary Ann Liebert, Inc. 2013.