Showing papers by "National University of Cuyo published in 2008"

Guidelines for the use and interpretation of assays for monitoring autophagy in higher eukaryotes

Abstract: Research in autophagy continues to accelerate,(1) and as a result many new scientists are entering the field Accordingly, it is important to establish a standard set of criteria for monitoring macroautophagy in different organisms Recent reviews have described the range of assays that have been used for this purpose(2,3) There are many useful and convenient methods that can be used to monitor macroautophagy in yeast, but relatively few in other model systems, and there is much confusion regarding acceptable methods to measure macroautophagy in higher eukaryotes A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers of autophagosomes versus those that measure flux through the autophagy pathway; thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from fully functional autophagy that includes delivery to, and degradation within, lysosomes (in most higher eukaryotes) or the vacuole (in plants and fungi) Here, we present a set of guidelines for the selection and interpretation of the methods that can be used by investigators who are attempting to examine macroautophagy and related processes, as well as by reviewers who need to provide realistic and reasonable critiques of papers that investigate these processes This set of guidelines is not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to verify an autophagic response

Azospirillum brasilense Sp 245 produces ABA in chemically-defined culture medium and increases ABA content in arabidopsis plants

Abstract: Azospirillum sp. are plant growth promoting bacteria (PGPB) that increase grain yield in cereals and other species via growth promotion and/or stress alleviation. The PGPB beneficial effects have been partially attributed to bacterial production of plant hormones, especially growth promoters like auxins, gibberellins and cytokinins. This paper reports the characterization of the stress-like plant hormone abscisic acid (ABA) by GC-EIMS in cultures of A. brasilense Sp 245 after 120 h of incubation in chemically-defined media, and chemically-defined media with moderate stress (100 mM NaCl). Chemical characterization of ABA was done by gas chromatography-electron impact mass spectrometry (GC-EIMS) and quantification by selected ion monitoring (SIM) with a stable isotope of the hormone as internal standard in the media. A. brasilense cultures produced higher amounts of ABA per ml of culture when NaCl was incorporated in the culture medium. Inoculation of Arabidopsis thaliana with A. brasilense Sp 245 enhanced two-fold the plant’s ABA content. These results contribute to explain, at least to some extent, the beneficial effects of Azospirillum sp. previously found in inoculated plants placed under adverse environmental conditions.

Synergistic effect of methyljasmonate and cyclodextrin on stilbene biosynthesis pathway gene expression and resveratrol production in Monastrell grapevine cell cultures.

Abstract: Plant cell cultures have been shown as feasible systems for the production of secondary metabolites, being the elicitation with biotic or abiotic stimuli the most efficient strategy to increase the production of those metabolites. Vitaceae phytoalexins constitute a group of molecules belonging to the stilbene family which are derivatives of the trans-resveratrol structure and are produced by plants and cell cultures as a response to biotic and abiotic stresses. The potential benefits of resveratrol on human health have made it one of the most thoroughly studied phytochemical molecules. The aim of this study was to evaluate the elicitor effect of both cyclodextrin (CD) and methyljasmonate (MeJA) on grapevine cell cultures by carrying out a quantitative analysis of their role on resveratrol production and on the expression of stilbene biosynthetic genes in Vitis vinifera cv Monastrell albino cell suspension cultures. MeJA and CD significantly but transiently induced the expression of stilbene biosynthetic genes when independently used to treat grapevine cells. This expression correlated with resveratrol production in CD-treated cells but not in MeJA-treated cells, which growth was drastically affected. In the combined treatment of CD and MeJA cell growth was similarly affected, however resveratrol production was almost one order of magnitude higher, in correlation with maximum expression values for stilbene biosynthetic genes. The effect of MeJA on cell division combined with a true and strong elicitor like CD could be responsible for the observed synergistic effect of both compounds on resveratrol production and on the expression of genes in the stilbene pathway.

Beyond the Quantum Adiabatic Approximation: Adiabatic Perturbation Theory

Abstract: Aside from interpretation, Quantum Mechanics (QM) is undoubtedly one of the most successful and use- ful theories of modern Physics. Its practical impor- tance is evidenced at microscopic and nano scales where Schrodinger's Equation (SE) dictates the evolution of the system's state, i.e., its wave function, from which all the properties of the system can be calculated and confronted against experimental data. However, SE can only be ex- actly solved for a few problems. Indeed, there are many reasons that make the solution of such a differential equa- tion a difficult task, such as the large number of degrees of freedom associated with the system one wants to study. Another reason, the one we want to address in this pa- per, is related to an important property of the system's Hamiltonian: its time dependence. For time independent Hamiltonians the solution to SE can be cast as an eigenvalue/eigenvector problem. This allows us to solve SE in many cases exactly, in particular when we deal with systems described by finite dimen- sional Hilbert spaces. For time dependent Hamiltonians, on the other hand, things are more mathematically in- volved. Even for a two-level system (a qubit) we do not, in general, obtain a closed-form solution given an arbi- trary time dependent Hamiltonian, although a general statement can be made for slowly varying Hamiltonians. If a system's Hamiltonian H changes slowly during the course of time, say from t = 0 to t = T, and the system is prepared in an eigenstate of H at t = 0, it will re-

Phenolic Composition in Grape (Vitis vinifera L. cv. Malbec) Ripened with Different Solar UV-B Radiation Levels by Capillary Zone Electrophoresis

Abstract: The responses of Vitis vinifera L. cv. Malbec to different solar ultraviolet-B radiation (UV-B) levels were assessed in two contrasting situations, under sunlight with full UV-B (+UV-B) and filtered UV-B (-UV-B), in three different locations at 500, 1000, and 1500 m above sea level (asl). To evaluate the effects of radiation, a simple, accurate, and rapid method for the separation and simultaneous determination of representative phenolic compounds in grape berry skins by capillary zone electrophoresis was developed. Separation was carried out in less than 20 min with 20 mM sodium tetraborate buffer containing 30% methanol, pH 9.00. The procedure is fast and reliable, and extracted grape berry skins can be directly analyzed without prior sample cleanup procedure. Berry skins from the +UV-B treatment at 1500 m asl showed the highest levels of total polyphenols anthocyanins, and resveratrol, compared with the -UV-B treatment at this altitude.

P-Cadherin and β-catenin are useful prognostic markers in breast cancer patients; β-catenin interacts with heat shock protein Hsp27

Abstract: The cadherin–catenin proteins have in common with heat shock proteins (HSP) the capacity to bind/interact proteins of other classes. Moreover, there are common molecular pathways that connect the HSP response and the cadherin–catenin protein system. In the present study, we have explored whether in breast cancer the HSP might interact functionally with the cadherin–catenin cell adhesion system. β-Catenin was immunoprecipitated from breast cancer biopsy samples, and the protein complexes isolated in this way were probed with antibodies against HSP family members. We are thus the first to demonstrate a specific interaction between β-catenin and Hsp27. However, β-catenin did not bind Hsp60, Hsp70, Hsp90, gp96, or the endoplasmic reticulum stress response protein CHOP. To confirm the finding of Hsp27-β-catenin interaction, the 27-kDa immunoprecipitated band was excised from one-dimensional polyacrylamide gel electrophoresis gels and submitted to liquid chromatography–tandem mass spectrometry with electrospray ionization, confirming a role for Hsp27. In addition, β-catenin interacted with other proteins including heat shock transcription factor 1, P-cadherin, and caveolin-1. In human breast cancer biopsy samples, β-catenin was coexpressed in the same tumor areas and in the same tumor cells that expressed Hsp27. However, this coexpression was strong when β-catenin was present in the cytoplasm of the tumor cells and not when β-catenin was expressed at the cell surface only. Furthermore, murine breast cancer cells transfected with hsp25 showed a redistribution of β-catenin from the cell membrane to the cytoplasm. When the prognostic significance of cadherin–catenin expression was examined by immunohistochemistry in breast cancer patients (n = 215, follow-up = >10 years), we found that the disease-free survival and overall survival were significantly shorter for patients expressing P-cadherin and for patients showing expression of β-catenin in the cytoplasm only (not at the cell surface). The interactions of β-catenin with Hsp27 and with HSF1 may explain some of the molecular pathways that influence tumor cell survival and the clinical significance in the prognosis of the breast cancer patients.

Primary tumour expression of the cysteine cathepsin inhibitor Stefin A inhibits distant metastasis in breast cancer

Abstract: Using the clinically relevant 4T1-derived syngeneic murine model of spontaneous mammary metastasis to bone, we have identified the cysteine cathepsin inhibitor Stefin A as a gene differentially expressed in primary and metastatic mammary tumours. In primary tumours, Stefin A expression correlated inversely with metastatic potential in 4T1-derived lines and was not detected in tumour cells in culture, indicating induction only within the tumour microenvironment. Enforced expression of Stefin A in the highly metastatic 4T1.2 cell line significantly reduced spontaneous bone metastasis following orthotopic injection into the mammary gland. Consistent with the mouse data, Stefin A expression correlated with disease-free survival (absence of distant metastasis) in a cohort of 142 primary tumours from breast cancer patients. This was most significant for patients with invasive ductal carcinoma expressing Stefin A, who were less likely to develop distant metastases (log rank test, p = 0.0075). In a multivariate disease-free survival analysis (Cox proportional hazards model), Stefin A expression remained a significant independent prognostic factor in patients with invasive ductal carcinoma (p = 0.0014), along with grade and progesterone receptor (PR) status. In human lung and bone metastases, we detected irregular Stefin A staining patterns, with expression often localizing to micrometastases (<0.2 mm) in direct contact with the stroma. We propose that Stefin A, as a cysteine cathepsin inhibitor, may be a marker of increased cathepsin activity in metastases. Using immunohistology, the cathepsin inhibitor was detected co-expressed with cathepsin B in lung and bone metastases in both the murine model and human tissues. We conclude that Stefin A expression reduces distant metastasis in breast cancer and propose that this may be due to the inhibition of cysteine cathepsins, such as cathepsin B.

2D stream hydrodynamic, sediment transport and bed morphology model for engineering applications

Abstract: A 2D depth-averaged hydrodynamic, sediment transport and bed morphology model named STREMR HySeD is presented. The depth-averaged sediment transport equations are derived from the 3D dilute, multiphase, flow equations and are incorporated into the hydrodynamic model STREMR. The hydrodynamic model includes a two-equation turbulence model and a correction for the mean flow due to secondary flows. The suspended sediment load can be subdivided into different size classes using the continuum (two-fluid) approach; however, only one bed sediment size is used herein. The validation of the model is presented by comparing the suspended sediment transport module against experimental measurements and analytical solutions for the case of equilibrium sediment-laden in a transition from a rigid bed to a porous bed where re-suspension of sediment is prevented. On the other hand, the bed-load sediment transport and bed evolution numerical results are compared against bed equilibrium experimental results for the case of a meander bend. A sensitivity analysis based on the correction for secondary flow on the mean flow including the effect of secondary flow on bed shear stresses direction as well as the downward acceleration effect due to gravity on transverse bed slopes is performed and discussed. In general, acceptable agreement is found when comparing the numerical results obtained with STREMR HySeD against experimental measurements and analytical solutions.

Natural programmed cell death in T. cruzi epimastigotes maintained in axenic cultures

Abstract: Trypanosoma cruzi, a parasitic protozoan, is the agent of Chagas' disease or American trypanosomiasis, an endemic pathology in Latin America, affecting up to 18 million people, with high public health costs. Programmed cell death (PCD) has many functions in development and tissue remodeling in metazoans. In protozoa, it could represent concomitant or alternative mechanisms for clonal selection, immune response evasion, and population size regulation. In this work, we describe the natural occurrence of PCD in T. cruzi epimastigotes during the stationary phase of growth in axenic culture or under nutrient deprivation. Thus, we have observed phosphatidylserine externalization, cellular volume decrease, caspase-like protein activity, and DNA fragmentation. Additionally, serum deprivation also induces autophagic characteristics such as monodansylcadaverine-labeled vesicles accumulation and redistribution of proteins homologous to Atg8. In agreement with our results, apoptosis may play an important role in parasite survival. Then, identification and modulation of molecular targets inducing programmed cell death in T. cruzi may lead to new potential therapeutic approaches for Chagas' disease.

Selenium and mercury in native and introduced fish species of patagonian lakes, Argentina.

Abstract: A survey of mercury (Hg) and selenium (Se) contents was performed in fish collected from lakes located in two National Parks of the northern patagonian Andean range. Two native species, catfish (Diplomystes viedmensis) and creole perch (Percichthys trucha), and three introduced species, brown trout (Salmo trutta), rainbow trout (Oncorhynchus mykiss), and brook trout (Salvelinus fontinalis), were caught from lakes Nahuel Huapi, Moreno, Traful, Espejo Chico, and Guillelmo belonging to Nahuel Huapi National Park and from lakes Futalaufquen and Rivadavia, Los Alerces National Park. In lake Moreno, fish diet items were analyzed and rainbow trout grown in a farm. Hg and Se were measured in muscle and liver tissues by instrumental neutron activation analysis. The average concentrations in muscle of Hg for all species, ages, and lakes are between 0.4 to 1.0 μg g−1 dry weight (DW) with a few fish, mainly native, exceeding the United States Environmental Protection Agency health advisory for freshwater fish limited consumption, and from 0.8 to 1.5 μg g−1 DW for Se. Average concentrations in liver of Hg in all species range from 0.4 to 0.9 μg g−1 DW. Brown trout, the top predator in these lakes, showed the lowest average Hg burden in both tissues. Se concentrations in the liver of brown and rainbow trout, up to 279 μg g−1 DW, are higher than those expected for nearly pristine lakes, exceeding 20 μg g−1 DW, the threshold concentration associated with Se toxicity. These species show lower Hg contents in muscle, suggesting a possible detoxification of Hg by a Se-rich diet. Creole perch and velvet catfish livers have lower Se concentrations, with a narrower span of values (2.3 to 8.5 μg g−1 and 3.3 to 5.5 μg g−1 DW respectively).

Natural Sesquiterpene Lactones are Active Against Leishmania mexicana

Abstract: In this paper, the effects of 3 natural sesquiterpene lactones, i.e., helenalin (Hln), mexicanin (Mxc), and dehydroleucodine (DhL), were evaluated using cultured Leishmania mexicana promastigotes. It was observed that the compounds inhibited the in vitro growth of the parasites at relatively low concentrations. The effect was rapid and irreversible with an estimated IC50 of 2–4 μM, while all the lactones were more effective than ketoconazole. Moreover, these compounds exhibited low cytotoxicity for mammalian cells. Hln induced strong vacuolization of the parasite cytoplasm, although pericellular microtubules were preserved. The 3 lactones induced DNA fragmentation as judged by the high labeling with the fluorescent TUNEL method, which was confirmed by electrophoresis on agarose gels. The ability of the parasites to invade Vero cells was also decreased by exposure to low concentrations of the compounds. We conclude that these compounds can affect the parasite's life cycle, possibly through multiple mechani...

Autophagy: For Better or for Worse, in Good Times or in Bad Times …

Abstract: Autophagy is a bulk cytosolic degradative process which in the last few years has become a key pathway for the advancement of molecular medicine. Autophagy (cellular self-eating) has several implications in human disorders involving accumulation of cytosolic protein aggregates such as Alzheimer, Parkinson, Huntington diseases, as well as in myopathies caused by deficient lysosomal functions and in cancer. Moreover, autophagy affects intracellular microorganism lifespan, acting either as a cellular defense mechanism or, on the contrary, promoting pathogen replication. Furthermore, autophagy also participates in antigen presentation, as a part of the adaptive immune response. Therefore, autophagy association with cell survival or cell death would depend on cell nutrition conditions, presence of cell intruders, and alterations in oncogene or suppressor gene expression. In this review we will focus on the wide spectra of disease-related topics where autophagy is involved, particularly, in those processes concerning microorganism infections.

Simulating picosecond x-ray diffraction from shocked crystals using post-processing molecular dynamics calculations

Abstract: Calculations of the patterns of x-ray diffraction from shocked crystals derived from the results of non-equilibrium molecular dynamics (NEMD) simulations are presented. The atomic coordinates predicted from the NEMD simulations combined with atomic form factors are used to generate a discrete distribution of electron density. A fast Fourier transform (FFT) of this distribution provides an image of the crystal in reciprocal space, which can be further processed to produce quantitative simulated data for direct comparison with experiments that employ picosecond x-ray diffraction from laser-irradiated crystalline targets.

Cognición, metacognición y escritura

Abstract: Este articulo presenta una contribucion a la compleja problematica de la ensenanza de la escritura. Tiene como base tanto investigaciones teoricas como empiricas realizadas con alumnos de escolaridad comun de nivel basico y medio. En primer lugar, explicitamos el marco teorico. A continuacion, enfatizando especialmente los aspectos cognitivos y metacognitivos, desarrollamos un modelo didactico de fases interactivas para la ensenanza de la produccion escrita, el cual fue aplicado en cursos experimentales. Final-mente, exponemos las principales conclusiones.

Vertebrados cretácicos de la Formación Loncoche en Calmu-Co, Mendoza, Argentina

Abstract: Se dan a conocer nuevos vertebrados fosiles procedentes de la Formacion Loncoche aflorante en el area de Calmu-Co, provincia de Mendoza, Argentina. En esta localidad los niveles inferiores de la formacion corresponden a ambientes lacustres y fluviales meandriformes (asociaciones de facies A y B, respectivamente) mientras que los niveles suprayacentes se asignan a depositos marino-marginales (asociacion de facies C). Los vertebrados, procedentes de la asociacion de facies C, comprenden peces (por ej. Chondrichthyes, Teleostei, Lepisosteidae y Dipnoi) tortugas Chelidae (cf. Yaminuechelys, cf. Prochelidella), dinosaurios (Titanosauria) y plesiosaurios (Elasmosauridae). Provienen de facies clasticas y calcareas (mudstones y grainstones) asignadas a canales y planicie deltaica. El caracter fragmentario de estas concentraciones esqueletales constituidas por taxa de requerimientos ecologicos diversos (terrestres, dulceacuicolas y marinos), sugiere la mezcla de restos de ambientes litorales con los provenientes de sistemas fluviales. Estas evidencias indican que la ingresion marina procedente del Atlantico que cubrio el norte de Patagonia, se extendio hasta Calmu-Co, area occidental de la Cuenca Neuquina. Los vertebrados de Calmu-Co se asignan al Campaniano tardio-Maastrichtiano temprano en base a similitudes con asociaciones de vertebrados halladas en otros sitios de Mendoza (Ranquil-Co) y norte de Patagonia (provincias de Rio Negro y Chubut, formaciones Allen, La Colonia y Los Alamitos).

Hsp70/nitric oxide relationship in apoptotic modulation during obstructive nephropathy.

Abstract: The functional integrity of the kidney depends on normal development as well as on physiological cell turnover. Apoptosis induction is essential for these mechanisms. Multiple mechanisms are unleashed during obstructive nephropathy, one of the most complex being programmed cell death that leads to renal tubular atrophy and tubular loss. This review will focus on the interaction of nitric oxide and Hsp70 and on the regulation of renal antiapoptotic and protective oxidative stress responses.

‘The Economic’ According to Aristotle: Ethical, Political and Epistemological Implications

Abstract: A renewed concern with Aristotle’s thought about the economic aspects of human life and society can be observed. Aristotle dealt with the economic issues in his practical philosophy. He thus considered ‘the economic’ within an ethical and political frame. This vision is coherent with a specific ontology of ‘the economic’ according to Aristotle. In a recent paper, I analysed this ontology and left its consequences, especially for Ethics and Politics, for another paper. In this article, I firstly summarise the reasoning and conclusions of the aforementioned paper. Then, I extract the ethical and political “lessons” of the Aristotelian conception. I finally add a section with epistemological “lessons”, and consequences for the teaching of Economics.