Competitive Tuning of Calmodulin Target Protein Activation Drives E-LTP Induction in CA1 Hippocampal Neurons

A number of neurological disorders are caused by disruptions in dynamic neuronal connections called synapses. Normally, electrical activity between neurons activates protein cascades that cause long-lasting, localized changes in the structure and molecular composition of synapses. These changes either increase or decrease the strength of synaptic connections, leading to long-term-potentiation (LTP) or long-term-depression (LTD), respectively. The protein cascades responsible for this synaptic plasticity are initiated in a stimulus-dependent manner by the Ca2+ sensor calmodulin (CaM). Ultimately, it is disruptions within these signaling pathways that cause disease. Traditionally, these protein networks are studied in the laboratory, but limitations in existing experimental technology have created demand for computational models capable of predicting molecular phenomena. These predictions can then guide focused experimental investigations. Although CaM binds and regulates over 100 different target proteins, the competitive dynamics of these proteins and their effect on LTP induction have not been investigated. Using a system of ordinary differential equations to model competition between four neuronal CaM target proteins, we found that the stimulus-dependence of target protein activation is tuned by competition and that this competitive tuning is unique to each protein. We therefore conclude that competition-free models fail to capture the true stimulus-dependence of Ca2+/calmodulin-dependent protein kinase II (CaMKII) and protein phosphatase 2B (PP2B/calcineurin/CaN) activation. Furthermore, these results suggest that competitive tuning drives early LTP (E-LTP) induction in CA1 hippocampal neurons and is an important dynamic process underlying learning and memory. Therapeutics that re-tune CaM-dependent proteins through competition may be useful in treating neurological disorders

The formation of the 8˚20’ N seamount chain, East Pacific rise

Near-axis seamounts provide a unique setting to investigate three-dimensional mantle processes associated with the formation of new oceanic crust and lithosphere. Here, we investigate the characteristics and evolution of the 8˚20’N Seamount Chain, a lineament of seamounts that extends ~ 175 km west of the East Pacific Rise (EPR) axis, just north of the fracture zone of the Siqueiros Transform Fault. Shipboard gravity, magnetic, and bathymetric data acquired in 2016 are utilized to constrain models of seamount emplacement and evolution. Geophysical observations indicate that these seamounts formed during four distinct episodes of volcanism coinciding with changes in regional plate motion that are also reflected in the development of intra-transform spreading centers (ITSCs) along the Siqueiros transform fault (Fornari et al. 1989; Pockalny et al. 1997). Although volcanism is divided into distinct segments, the magnetic data indicate continuous volcanic construction over long portions of the chain. Crustal thickness variations along the chain up to 0.75 km increase eastward, inferred from gravity measurements, suggest that plate reorganization has considerably impacted melt distribution in the area surrounding the Siqueiros-EPR ridge transform intersection. This appears to have resulted in increased volcanism and the formation of the 8˚20’N Seamounts. These findings indicate that melting processes in the mantle and subsequently the formation of new oceanic crust and lithosphere are highly sensitive to tectonic stress changes in the vicinity of fast spreading transform fault offsets

Constrained Cosmological Simulations of Dark Matter Halos

The formation and structure of dark matter (DM) halos is studied by means of constrained realizations of Gaussian fields using N-body simulations. A series of experiments of the formation of a 10^{12} Msun halo is designed to study the dependence of the density profile on its merging history. We confirm that the halo growth consists of violent and quiescent phases, with the density well approximated by the Navarro-Frenk-White (NFW) profile during the latter phases. We find that (1) the NFW scale radius R_s stays constant during the quiescent phase and grows abruptly during the violent one. In contrast, the virial radius grows linearly during the quiescent and abruptly during the violent phases. (2) The central density stays unchanged during the quiescent phase while dropping abruptly during the violent phase. (3) The value of \rs reflects the violent merging history of the halo, and depends on the number of violent events and their fractional magnitudes, independent of the time and order of these events. It does not reflect the formation time of the halo. (4) The fractional change in R_s is a nonlinear function of the fractional absorbed kinetic energy within R_s in a violent event.Comment: 5 pages, 2 postscript figures, ApJ emulator, submitted to ApJ Letter

Estudio de marcadores tumorales citológicos e histológicos relacionados con las alteraciones cromosómicas de tumores sólidos.

Si bien hay diferencias en cuanto a la incidencia y la tasa de morbilidad y mortalidad de cada una de las formas de cáncer en los diversos países, se calcula que aproximadamente una de cada cinco personas en el mundo mueren de cáncer. Aunque ha habido considerables avances en el tratamiento, incluyendo procedimientos de alta precisión en cirugía y protocolos detallados para radio y quimioterapia, los tumores malignos siguen siendo una de las causas de muerte más prominentes de la sociedad moderna. Las estrategias para el tratamiento dependen de un diagnóstico preciso y temprano. Algunos tumores presentan dificultades para clasificarlos, lo que lleva consigo una incertidumbre en el pronóstico y tratamiento. Los tumores sólidos tanto de órganos como de tejidos blandos y óseo, son un grupo de neoplasias muy diverso, que ocurren en todas las edades. El diagnóstico/ pronóstico puede ser complicado y el dilema del diagnóstico diferencial depende frecuentemente de los métodos histopatológicos y radiológicos. El presente proyecto intenta correlacionar los parámetros histopatológicos e inmunohistoquímicos con las aberraciones cromosómicas que ellos presentan a los efectos de contribuir en el diagnóstico y tratamiento más eficientes. La detección de alteraciones cromosómicas como anillos, cromosomas dicéntricos, deleciones, traslocaciones, etc., que están asociadas con tipos específicos de tumores sólidos relacionándolos con su morfología permitirá contribuir a un mejor diagnóstico y por ende tratamientos más precisos, ya que ciertos tumores, a pesar de morfología similar pueden tener comportamiento diferente

Isolation and characterization of an H9N2 influenza virus isolated in Argentina

As part of our ongoing efforts on animal influenza surveillance in Argentina, an H9N2 virus was isolated from a wild aquatic bird (Netta peposaca), A/rosy-billed pochard/Argentina/CIP051-559/2007 (H9N2) - herein referred to as 559/H9N2. Due to the important role that H9N2 viruses play in the ecology of influenza in nature, the 559/H9N2 isolate was characterized molecularly and biologically. Phylogenetic analysis of the HA gene revealed that the 559/H9N2 virus maintained an independent evolutionary pathway and shared a sister-group relationship with North American viruses, suggesting a common ancestor. The rest of the genome segments clustered with viruses from South America. Experimental inoculation of the 559/H9N2 in chickens and quail revealed efficient replication and transmission only in quail. Our results add to the notion of the unique evolutionary trend of avian influenza viruses in South America. Our study increases our understanding of H9N2 viruses in nature and emphasizes the importance of expanding animal influenza surveillance efforts to better define the ecology of influenza viruses at a global scale.Fil: Xu, Kemin. University of Maryland; Estados UnidosFil: Ferreri, Lucas. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Virología; ArgentinaFil: Rimondi, Agustina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Olivera, Valeria. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Virología; ArgentinaFil: Romano, Marcelo. Wildlife Conservation Society; ArgentinaFil: Ferreyra, Hebe. Wildlife Conservation Society; ArgentinaFil: Rago, María Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Uhart, Marcela María. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Chen, Hongjun. University of Maryland; Estados UnidosFil: Sutton, Troy. University of Maryland; Estados UnidosFil: Pereda, Ariel Julián. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Virología; ArgentinaFil: Perez, Daniel R.. University of Maryland; Estados Unido

Evolution of Characteristic Quantities for Dark Matter Halo Density Profiles

We investigate the effect of an assembly history on the evolution of dark matter (DM) halos of 10^{12} Msun/h using Constrained Realizations of random Gaussian fields. Five different realizations of a DM halo with distinct merging histories were constructed and evolved. Our main results are: A halo evolves via a sequence of quiescent phases of a slow mass accretion intermitted by violent episodes of major mergers. In the quiescent phases, the density is well fitted by an NFW profile, the inner scale radius Rs and the mass enclosed within it remain constant, and the virial radius (Rvir) grows linearly with the expansion parameter "a". Within each quiescent phase the concentration parameter ("c") scales as "a", and the mass accretion history (Mvir) is well described by the Tasitsiomi etal. fitting formula. In the violent phases the halos are not in a virial equilibrium and both Rs and Rvir grow discontinuously. The violent episodes drive the halos from one NFW dynamical equilibrium to another. The final structure of a halo, including "c", depends on the degree of violence of the major mergers and on their number. Next, we find a distinct difference between the behavior of various NFW parameters taken as averages over an ensemble of halos and those of individual halos. Moreover, the simple scaling relations c--Mvir do not apply to the entire evolution of individual halos, and so is the common notion that late forming halos are less concentrated than early forming ones. The entire evolution of the halo cannot be fitted by single analytical expressions.Comment: 17 pages, 16 postscript figures. Accepted for publication by the Astrophysical Journa

A Radial Velocity Survey of the Cygnus OB2 Association

We conducted a radial velocity survey of the Cygnus OB2 Association over a 6 year (1999 - 2005) time interval to search for massive close binaries. During this time we obtained 1139 spectra on 146 OB stars to measure mean systemic radial velocities and radial velocity variations. We spectroscopically identify 73 new OB stars for the first time, the majority of which are likely to be Association members. Spectroscopic evidence is also presented for a B3Iae classification and temperature class variation (B3 - B8) on the order of 1 year for Cygnus OB2 No. 12. Calculations of the intial mass function with the current spectroscopic sample yield Gamma = -2.2 +/- 0.1. Of the 120 stars with the most reliable data, 36 are probable and 9 are possible single-lined spectroscopic binaries. We also identify 3 new and 8 candidate double-lined spectroscopic binaries. These data imply a lower limit on the massive binary fraction of 30% - 42%. The calculated velocity dispersion for Cygnus OB2 is 2.44 +/- km/s, which is typical of open clusters. No runaway OB stars were found.Comment: 56 pages, 23 figures, 5 tables, accepted for publication in the Astrophysical Journa

Search for long-lived gravitational-wave transients coincident with long gamma-ray bursts

Long gamma-ray bursts (GRBs) have been linked to extreme core-collapse supernovae from massive stars. Gravitational waves (GW) offer a probe of the physics behind long GRBs. We investigate models of long-lived (~10–1000 s) GW emission associated with the accretion disk of a collapsed star or with its protoneutron star remnant. Using data from LIGO’s fifth science run, and GRB triggers from the Swift experiment, we perform a search for unmodeled long-lived GW transients. Finding no evidence of GW emission, we place 90% confidence-level upper limits on the GW fluence at Earth from long GRBs for three waveforms inspired by a model of GWs from accretion disk instabilities. These limits range from FtoFcm-2, depending on the GRB and on the model, allowing us to probe optimistic scenarios of GW production out to distances as far as = 33 Mpc. Advanced detectors are expected to achieve strain sensitivities 10x better than initial LIGO, potentially allowing us to probe the engines of the nearest long GRBs

Directed search for continuous gravitational waves from the Galactic center

We present the results of a directed search for continuous gravitational waves from unknown, isolated neutron stars in the Galactic center region, performed on two years of data from LIGO’s fifth science run from two LIGO detectors. The search uses a semicoherent approach, analyzing coherently 630 segments, each spanning 11.5 hours, and then incoherently combining the results of the single segments. It covers gravitational wave frequencies in a range from 78 to 496 Hz and a frequency-dependent range of first-order spindown values down to −7.86×10−8  Hz/s at the highest frequency. No gravitational waves were detected. The 90% confidence upper limits on the gravitational wave amplitude of sources at the Galactic center are ∼3.35×10−25 for frequencies near 150 Hz. These upper limits are the most constraining to date for a large-parameter-space search for continuous gravitational wave signals

Influence of ambient conditions on the evolution of wettability properties of an IR-, ns-laser textured aluminium alloy

Micro cell structures of different sizes were patterned using a nanosecond near-infrared laser source on Al2024 aluminium alloy plates with 2 mm thickness. The influence of laser parameters on the shape and size of the produced patterns were studied together with the evolution of wettability properties over time for different storage conditions. Samples were found to be superhydrophobic from a single step laser patterning, requiring no further treatment. Exposure to ambient air was shown to be a key factor in the property changes of the samples over time. The produced surface patterns with different laser parameter settings were correlated with the contact angle measurements, revealing a great influence of the amount of recast material on the hydrophobic properties. X-Ray photoelectron spectroscopy was used to study the impact of surface chemistry changes on hydrophobicity, analysis of elemental composition proved that chemisorbed organic molecules present in the ambient air were responsible for the hydrophilic to superhydrophobic transition