La Investigación como modus vivendi

Asociación Argentina para el Progreso de las Ciencias, merecida o no, me produce cierto halago y quiero agradecer a quienes me consideraron para hacerla. Sin embargo, para que la misma adquiera algún sentido, quisiera que esta pequeña crónica de mi camino en la investigación pueda significar algo menos mezquino que la satisfacción de mi ego y sirva para motivar y alentar a los jóvenes que se inician en este camino. Intentaré describir, lo más objetivamente posible el camino que inicié hace más de 50 años intentando develar los mecanismos básicos de la función cardíaca, camino que sigo transitando con entusiasmo. A los datos precisos he agregado algunas anécdotas contadas tal como han quedado en mi memoria después de tantos años.Fil: Mattiazzi, Ramona Alicia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani". Universidad Nacional de La Plata. Facultad de Ciencias Médicas. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; Argentin

The role of CaMKII regulation of phospholamban activity in heart disease

Phospholamban (PLN) is a phosphoprotein in cardiac sarcoplasmic reticulum (SR) that is a reversible regulator of the Ca(2)(+)-ATPase (SERCA2a) activity and cardiac contractility. Dephosphorylated PLN inhibits SERCA2a and PLN phosphorylation, at either Ser(16) by PKA or Thr(17) by Ca(2)(+)-calmodulin-dependent protein kinase (CaMKII), reverses this inhibition. Through this mechanism, PLN is a key modulator of SR Ca(2)(+) uptake, Ca(2)(+) load, contractility, and relaxation. PLN phosphorylation is also the main determinant of β1-adrenergic responses in the heart. Although phosphorylation of Thr(17) by CaMKII contributes to this effect, its role is subordinate to the PKA-dependent increase in cytosolic Ca(2)(+), necessary to activate CaMKII. Furthermore, the effects of PLN and its phosphorylation on cardiac function are subject to additional regulation by its interacting partners, the anti-apoptotic HAX-1 protein and Gm or the anchoring unit of protein phosphatase 1. Regulation of PLN activity by this multimeric complex becomes even more important in pathological conditions, characterized by aberrant Ca(2)(+)-cycling. In this scenario, CaMKII-dependent PLN phosphorylation has been associated with protective effects in both acidosis and ischemia/reperfusion. However, the beneficial effects of increasing SR Ca(2)(+) uptake through PLN phosphorylation may be lost or even become deleterious, when these occur in association with alterations in SR Ca(2)(+) leak. Moreover, a major characteristic in human and experimental heart failure (HF) is depressed SR Ca(2)(+) uptake, associated with decreased SERCA2a levels and dephosphorylation of PLN, leading to decreased SR Ca(2)(+) load and impaired contractility. Thus, the strategy of altering SERCA2a and/or PLN levels or activity to restore perturbed SR Ca(2)(+) uptake is a potential therapeutic tool for HF treatment. We will review here the role of CaMKII-dependent phosphorylation of PLN at Thr(17) on cardiac function under physiological and pathological conditions

SERCA is critical to control the Bowditch effect in the heart

The Bowditch effect or staircase phenomenon is the increment or reduction of contractile force when heart rate increases, defined as either a positive or negative staircase. The healthy and failing human heart both show positive or negative staircase, respectively, but the causes of these distinct cardiac responses are unclear. Different experimental approaches indicate that while the level of Ca2+ in the sarcoplasmic reticulum is critical, the molecular mechanisms are unclear. Here, we demonstrate that Drosophila melanogaster shows a negative staircase which is associated to a slight but significant frequency-dependent acceleration of relaxation (FDAR) at the highest stimulation frequencies tested. We further showed that the type of staircase is oppositely modified by two distinct SERCA mutations. The dominant conditional mutation SERCAA617T induced positive staircase and arrhythmia, while SERCAE442K accentuated the negative staircase of wild type. At the stimulation frequencies tested, no significant FDAR could be appreciated in mutant flies. The present results provide evidence that two individual mutations directly modify the type of staircase occurring within the heart and suggest an important role of SERCA in regulating the Bowditch effect.Fil: Balcazar, Dario Emmanuel. Universidad Nacional de La Plata; ArgentinaFil: Regge, María Victoria. Universidad Nacional de La Plata; ArgentinaFil: Santalla, Manuela. Universidad Nacional de La Plata; ArgentinaFil: Behrensmeyer, Anna Kay. Universität Osnabrück;Fil: Achimón, Fernanda. Universität Osnabrück;Fil: Mattiazzi, Ramona Alicia. Universidad Nacional de La Plata; ArgentinaFil: Ferrero, Paola Viviana. Universidad Nacional de La Plata; Argentin

Decomposition of Feynman Integrals on the Maximal Cut by Intersection Numbers

We elaborate on the recent idea of a direct decomposition of Feynman integrals onto a basis of master integrals on maximal cuts using intersection numbers. We begin by showing an application of the method to the derivation of contiguity relations for special functions, such as the Euler beta function, the Gauss ${}_2F_1$ hypergeometric function, and the Appell $F_1$ function. Then, we apply the new method to decompose Feynman integrals whose maximal cuts admit 1-form integral representations, including examples that have from two to an arbitrary number of loops, and/or from zero to an arbitrary number of legs. Direct constructions of differential equations and dimensional recurrence relations for Feynman integrals are also discussed. We present two novel approaches to decomposition-by-intersections in cases where the maximal cuts admit a 2-form integral representation, with a view towards the extension of the formalism to $n$-form representations. The decomposition formulae computed through the use of intersection numbers are directly verified to agree with the ones obtained using integration-by-parts identities.Comment: 115 pages, 29 figures; references added; additional examples added; matches published versio

Aging and CaMKII alter intracellular Ca2+ transients and heart rhythm in Drosophila Melanogaster

Aging is associated to disrupted contractility and rhythmicity, among other cardiovascular alterations. Drosophila melanogaster shows a pattern of aging similar to human beings and recapitulates the arrhythmogenic conditions found in the human heart. Moreover, the kinase CaMKII has been characterized as an important regulator of heart function and an arrhythmogenic molecule that participate in Ca2+ handling. Using a genetically engineered expressed Ca2+ indicator, we report changes in cardiac Ca2+ handling at two different ages. Aging prolonged relaxation, reduced spontaneous heart rate (HR) and increased the occurrence of arrhythmias, ectopic beats and asystoles. Alignment between Drosophila melanogaster and human CaMKII showed a high degree of conservation and indicates that relevant phosphorylation sites in humans are also present in the fruit fly. Inhibition of CaMKII by KN-93 (CaMKII-specific inhibitor), reduced HR without significant changes in other parameters. By contrast, overexpression of CaMKII increased HR and reduced arrhythmias. Moreover, it increased fluorescence amplitude, maximal rate of rise of fluorescence and reduced time to peak fluorescence. These results suggest that CaMKII in Drosophila melanogaster acts directly on heart function and that increasing CaMKII expression levels could be beneficial to improve contractility.Fil: Santalla, Manuela. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; Argentina. Universidad Nacional del Noroeste de la Provincia de Buenos Aires. Departamento de Ciencias Básicas y Experimentales; ArgentinaFil: Valverde, Carlos Alfredo. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Harnichar, Alejandro Ezequiel. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Lacunza, Ezequiel. Universidad Nacional de La Plata. Facultad de Ciencias Medicas. Centro de Investigaciones Inmunologicas Basicas y Aplicadas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Aguilar Fuentes, Javier. Universidad Autónoma de Chiapas; MéxicoFil: Mattiazzi, Ramona Alicia. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Ferrero, Paola Viviana. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; Argentina. Universidad Nacional del Noroeste de la Provincia de Buenos Aires. Departamento de Ciencias Básicas y Experimentales; Argentin

Measurement of cosmic-ray Helium flux in extended acceptance with the CALET experiment

State-of-the-art detectors operating in space have paved the way for high-precision direct measurements of galactic cosmic-ray (CR) spectra. Recent results for proton and helium nuclei have shown unexpected spectral features that deviate from the single power law predicted by the standard CR model. From a few hundred GeV to a few TeV, a hardening of the spectral index, i.e. an enhancement of the flux, has been measured by several experiments (e.g. AMS-02, PAMELA, DAMPE, and CALET) using different experimental techniques (magnetic spectrometers, calorimeters). At tens of TeV, both the DAMPE and CALET calorimeters have recently observed a flux softening. These results have pushed the boundaries of direct measurements of CR spectra, helping to shed light on the acceleration and propagation mechanisms of CRs in the Galaxy. Nevertheless, the high energy region of the spectra, from tens to hundreds of TeV, still suffers from significant uncertainties, mainly due to the very limited statistics. In this context, the main objective of this thesis is to improve the statistical precision of the CR helium flux measurement with CALET data, focusing on the high-energy region. This is achieved by extending the fiducial geometrical acceptance of the present analysis. The CALorimetric Electron Telescope (CALET) is a multi-purpose space-based experiment that has been acquiring data onboard the International Space Station (ISS) since mid-October 2015. The mission is sponsored by JAXA (Japan Aerospace Exploration Agency) with the collaboration of ASI (Italian Space Agency) and NASA (National Aeronautics and Space Administration). The CALET instrument consists of three sub-systems. The Total AbSorption Calorimeter (TASC), a deep homogeneous calorimeter with an equivalent thickness of 27 radiation lengths (X0 ), measures the particle energy. The IMaging Calorimeter (IMC) is a sampling calorimeter with an equivalent thickness of 3 X0 , primarily designed to visualize the particle trajectory and its early shower profile. The CHarge Detector (CHD) is a two-layer hodoscope for identification of nuclear species over a wide dynamic range, up to Z = 40. The first chapters of this thesis provide both an overview of the physics of cosmic-rays, focusing on the galactic component investigated by the CALET telescope, and a detailed description of the instrument. The event reconstruction procedure for in-flight and simulated data is described as well. The core chapters of the thesis are dedicated to the newly developed analysis strategy for helium flux measurements with higher statistical accuracy. The main novelty is the implementation of a multivariate analysis based on Boosted Decision Trees (BDT) to improve the analysis performance, while mitigating the issues arising from the extension of the geometric acceptance. The stability of the unfolding procedure for inferring the primary energy from the fraction of energy deposited in the calorimeter, is also validated using both simulated and in-flight data. Finally, the helium flux measurements in fiducial and enlarged acceptances are presented showing a statistical gain up to 60%, and the consistency with the previously published analysis

Increased Na+ /Ca2+ exchanger expression/activity constitutes a point of inflection in the progression to heart failure of hypertensive rats

Spontaneously hypertensive rat (SHR) constitutes a genetic model widely used to study the natural evolution of hypertensive heart disease. Ca2+ -handling alterations are known to occur in SHR. However, the putative modifications of Ca2+ -handling proteins during the progression to heart failure (HF) are not well established. Moreover, the role of apoptosis in SHR is controversial. We investigated intracellular Ca2+ , Ca2+ -handling proteins and apoptosis in SHR vs. control Wistar rats (W) from 3 to 15 months (mo). Changes associated with the transition to HF (i.e. lung edema and decrease in midwall fractional shortening), occurred at 15 mo in 38% of SHR (SHRF). In SHRF, twitch and caffeine-induced Ca2+ transients, significantly decreased relative to 6/9 mo and 15 mo without HF signs. This decrease occurred in association with a decrease in the time constant of caffeine-Ca2+ transient decay and an increase in Na+ /Ca2+ exchanger (NCX) abundance (p, 0.05) with no changes in SERCA2a expression/activity. An increased Ca2+ -calmodulin-kinase II activity, associated with an enhancement of apoptosis (TUNEL and Bax/Bcl2) was observed in SHR relative to W from 3 to 15 mo. Conclusions: 1. Apoptosis is an early and persistent event that may contribute to hypertrophic remodeling but would not participate in the contractile impairment of SHRF. 2. The increase in NCX expression/activity, associated with an increase in Ca2+ efflux from the cell, constitutes a primary alteration of Ca2+ -handling proteins in the evolution to HF. 3. No changes in SERCA2a expression/activity are observed when HF signs become evident.Fil: Rodriguez, Jesica S.. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Velez Rueda, Jorge Omar. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Salas, Margarita. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Becerra, Romina Valeria. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; ArgentinaFil: Di Carlo, Mariano Nahuel. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Said, Maria Matilde. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Vittone, Leticia Beatriz. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Rinaldi, Gustavo Juan. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Portiansky, Enrique Leo. Universidad Nacional de la Plata. Facultad de Ciencias Veterinarias; ArgentinaFil: Mundiña, Cecilia Beatriz. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Palomeque, Julieta. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Mattiazzi, Ramona Alicia. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; Argentin

Mitophagy and the therapeutic clearance of damaged mitochondria for neuroprotection

Mitochondria are the foremost producers of the cellular energy currency ATP. They are also a significant source of reactive oxygen species and an important buffer of intracellular calcium. Mitochondrial retrograde signals regulate energy homeostasis and pro-survival elements whereas anterograde stimuli can trigger programmed cell death. Maintenance of a healthy, functional mitochondria network is therefore essential, and several mechanisms of mitochondrial quality control have been described. Mitochondrial dysfunction is linked to several neurodegenerative conditions including Parkinson, and Huntingdon diseases as well as Amyotrophic lateral sclerosis. Understanding the mechanisms governing mitochondrial quality control may reveal novel strategies for pharmacological intervention and disease therapy

Ryanodine receptor phosphorylation by CaMKII promotes spontaneous Ca2+ release events in a rodent model of early stage diabetes: The arrhythmogenic substrate

Background: Heart failure and arrhythmias occur more frequently in patients with type 2 diabetes (T2DM) than in the general population. T2DM is preceded by a prediabetic condition marked by elevated reactive oxygen species (ROS) and subclinical cardiovascular defects. Although multifunctional Ca2+ calmodulin-dependent protein kinase II (CaMKII) is ROS-activated and CaMKII hyperactivity promotes cardiac diseases, a link between prediabetes and CaMKII in the heart is unprecedented. Objectives: To prove the hypothesis that increased ROS and CaMKII activity contribute to heart failure and arrhythmogenic mechanisms in early stage diabetes. Methods–Results: Echocardiography, electrocardiography, biochemical and intracellular Ca2+ (Ca2+i) determinations were performed in fructose-rich diet-induced impaired glucose tolerance, a prediabetes model, in rodents. Fructose-rich diet rats showed decreased contractility and hypertrophy associated with increased CaMKII activity, ROS production, oxidized CaMKII and enhanced CaMKII-dependent ryanodine receptor (RyR2) phosphorylation compared to rats fed with control diet. Isolated cardiomyocytes from fructose-rich diet showed increased spontaneous Ca2+i release events associated with spontaneous contractions, which were prevented by KN-93, a CaMKII inhibitor, or addition of Tempol, a ROS scavenger, to the diet. Moreover, fructose-rich diet myocytes showed increased diastolic Ca2+ during the burst of spontaneous Ca2+i release events. Mice treated with Tempol or with sarcoplasmic reticulum-targeted CaMKII-inhibition by transgenic expression of the CaMKII inhibitory peptide AIP, were protected from fructose-rich diet-induced spontaneous Ca2+i release events, spontaneous contractions and arrhythmogenesis in vivo, despite ROS increases. Conclusions: RyR2 phosphorylation by ROS-activated CaMKII, contributes to impaired glucose tolerance-induced arrhythmogenic mechanisms, suggesting that CaMKII inhibition could prevent prediabetic cardiovascular complications and/or evolution.Fil: Sommese, Leandro Matías. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Valverde, Carlos Alfredo. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Blanco, Paula Graciela. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias; ArgentinaFil: Castro, María Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Cientifico Tecnológico La Plata. Centro de Endocrinologia Experimental y Aplicada (i); Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Velez Rueda, Jorge Omar. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Kaetzel, Marcia. University Of Cincinnati; Estados UnidosFil: Dedman, John. University Of Cincinnati; Estados UnidosFil: Anderson, Mark E.. University of Iowa; Estados UnidosFil: Mattiazzi, Ramona Alicia. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; ArgentinaFil: Palomeque, Julieta. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico la Plata. Centro de Investigaciones Cardiovasculares "Dr. Horacio Eugenio Cingolani"; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Médicas; Argentin