Utilizing Fluorescence Microscopy to Characterize the Subcellular Distribution of the Novel Protein Acheron

All cells carry the genetic machinery required to commit cell suicide; a process known as programmed cell death (PCD). While the ability to initiate PCD serves a number of useful purposes during development and homeostasis, misregulation of PCD is the underlying basis of most human diseases, including cancer, autoimmunity disorders and neurodegeneration. Using the tobacco hawkmoth Manduca sexta as a model organism, the Schwartz lab at UMass has demonstrated that PCD requires de novo gene expression and has cloned many death-associated genes. One of these genes encodes a novel protein that was named Acheron after one of the rivers of the Underworld in Greek mythology. Acheron (also known as Lupus Antigen Related Protein 6; Larp6) is an RNA binding protein that mediates a number of cellular processes, including cell survival, angiogenesis, migration, and differentiation. The molecular mechanisms that mediate Acheron’s diverse roles are poorly understood, but several lines of evidence suggest that it is mediated in part by protein protein interactions and motifs that target it to different cellular compartments. In this thesis, I employed immunofluorescence and confocal microscopy to conduct two studies employing mammalian cells. The first study was to determine the subcellular localization for Acheron in normal cells and cells treated with growth factors. I found that Acheron predominantly coincides with the microtubule cytoskeleton. In our second study, I tested the hypothesis that Acheron’s binding partners BAD, Human Homolog of Ariadne-1 (HHARI) and Calcium/Calmodulin-dependent Serine Protein Kinase (CASK) colocalize with Acheron. As part of this analysis, I sought to determine if Acheron could facilitate the translocation of CASK to the nucleus. I found that Acheron localizes predominantly to microtubules, with some expression in the cytoplasm and nucleus. When Acheron and its partners are co-labeled in cycling mouse C2C12 myoblasts or human U2-OS osteosarcoma cells, Acheron did not colocalize with BAD, HHARI or CASK on microtubules. However, I found that when Acheron is driven into the nucleus with high levels of growth factors, CASK also appeared to translocate to both the nucleus and to microtubules, where it colocalized with Acheron. The data acquired through these studies should provide not only insights into the subcellular distribution of Acheron and its potential binding partners but may also help elucidate its roles in programmed cell death, differentiation, and pathogenesis in mammalian models

Quark Propagator and Meson Correlators in the QCD Vacuum

Equal time, point to point correlation functions for spatially separated meson currents are calculated with respect to a variational construct for the ground state of QCD. Given such an ansatz we make no further approximations in the evaluation of the correlators. Our calculations for the vector, axial vector and scalar channels show qualitative agreement with the phenomenological predictions, whereas the pseudoscalar channel does not. However, the pseudoscalar correlator, when approximated by saturating with intermediate one pion states agrees with results obtained from spectral density functions parameterised by pion decay constant and $$ value obtained from chiral perturbation theory. We discuss this departure in the pseudoscalar channel, in context of the quark propagation in the vacuum.Comment: 13 pages (including 3 figures), Latex, uses epsf style option and ijmpe1.sty file, submission in the form of uufile containing paper,3 figure ps files and ijmpe1.st

Hadronic Correlators and Condensate Fluctuations in QCD Vacuum

Phenomenological results of equal time, point to point spatial correlation functions of hadronic currents are used to deduce the structure of the QCD vacuum. It is found that a model with only quark condensate is not adequate to explain the observations. Inclusion of condensate fluctuations (explicit four point structure in the vacuum) leads to excellent overall agreement with the phenomenological curves and parameters in various channels.Comment: 11 pages (inluding 1 Figure and 2 Tables); Revtex file with EPSF styl

Temporal variations in CO2 and CO at Ahmedabad in western India

About 70% of the anthropogenic CO2 is emitted from the megacities and urban areas of the world. In-situ simultaneous measurements of carbon dioxide (CO2) and carbon monoxide (CO) have been made using a state-of-the-art laser based cavity ring down spectroscopy technique at Ahmedabad, an urban site in western India, from November 2013 to May 2015 with a break during March to June 2014. Annual average concentrations of CO2 and CO have been found to be 413.0+/-13.7 ppm and 0.50+/-0.37 ppm respectively. Both the species show strong seasonality, with lower concentrations of 400.3+/-6.8 ppm and 0.19+/-0.13 ppm, respectively during the south-west monsoon, and higher values of 419.6+/-22.8 ppm and 0.72+/-0.68 ppm, respectively in autumn (SON). Strong diurnal variations are also observed for both the species. The common factors for diurnal cycles of CO2 and CO are the vertical mixing and rush hour traffic, while the influence of biospheric fluxes is also seen in CO2 diurnal cycle. Using CO and CO2 covariation, we differentiate the anthropogenic and biospheric components of CO2 and found that significant contributions of biospheric respiration and anthropogenic emission in the late night (00:00-05:00 IST) and evening rush hours (18:00-22:00 IST) respectively. We compute total yearly emission of CO to be 69.2+/-0.07 Gg for the study region using the observed CO:CO2 correlation slope and bottom-up CO2 emission inventory. This calculated emission of CO is 52% larger than the estimated emission of CO by the EDGAR inventory. The observations of CO2 have been compared with an atmospheric chemistry transport model (i.e., ACTM), which incorporates various components of CO2 fluxes. ACTM is able to capture the basic variabilities, but both diurnal and seasonal amplitudes are largely underestimated compared to the observations. We attribute this underestimation by model to uncertainties in terrestrial biosphere fluxes and coarse model resolution. The fossil fuel signal from the model shows fairly good correlation with observed CO2 variations, which supports the overall dominance of fossil fuel emissions over the biospheric fluxes in this urban region.Discussion Pape

A study of the atmospheric photochemical loss of N<SUB>2</SUB>O based on trace gas measurements

Nitrous oxide (N2O) plays an important role in ozone chemistry as well as in greenhouse warming. It is the source of NOx radicals in the stratosphere which are the dominant catalysts for ozone depletion. Recently, doubts have been raised on the global N2O budget. One approach to solve this problem has been the consideration of new mechanisms for atmospheric production and destruction of N2O. In parallel, N2O sinks have been constrained from observed tracer correlations in the lower stratosphere based on aircraft measurements, which are limited up to an altitude of only 20 km. We use vertical distributions of N2O and other trace gases measured simultaneously from Hyderabad, India (17.5&#176;N, 78.6&#176;E) in 1987, 1990, 1994 and 1998 using balloon-borne cryogenic air samplers covering the altitude range of about 8-37 km to study these issues together with 2-D model simulations. The slopes of N2O correlations with CH4, CFC-12 and CFC-11 compare well with the model derived slopes, with exceptions in cases where dynamical perturbations are strong. Average N2O lifetimes of 85&#177;43 and 111&#177;38 years have been estimated using the observed slopes and two sets of reference lifetimes for the correlated tracers. This average lifetime compares well within the spread, with the lifetime estimated from the sink of N2O in the model, suggesting that the present estimate of the N2O photochemical sink incorporated in the model is adequate

Long-term variability of dust optical depths on Mars during MY24-MY32 and their impact on subtropical lower ionosphere: climatology, modeling, and observations

Dust optical depths (τ) for nine Martian years (MY24–MY32) in the subtropical region (25–35°S) have been used to classify distinct dust scenarios. These data are based on observations at 9.3 µm from the Mars Global Surveyor and Mars Odyssey missions and encompass the regional dust storms which occur every year around solar longitude (Ls) ~ 220° and the two major dust storms of MY25 and MY28. Constrained by these observations and the Mars Climate Sounder observations of detached dust layers, we estimate altitude profiles of dust concentrations. We discuss the characteristics of dust aerosol particles of different size between 0.2 and 3.0 µm by assuming a modified gamma distribution. We then use a comprehensive ion-dust model to calculate ion densities and conductivities in the lower ionosphere of Mars in the absence of dust storm at τ = 0.1 and Ls = 150° and for three dust storm periods viz., (1) major dust storm at τ = 1.7 and Ls = 210°, (2) major dust storm at τ = 1.2 and Ls = 280°, and (3) regional dust storm at τ = 0.5 and Ls = 220°. The model with 12 neutral species considers galactic cosmic rays as a source of ionization. Results show that the density of the dominant hydrated cluster ions and the electrical conductivity are reduced by an order of magnitude near the surface for a few months until the dust storm settles down to its normal condition

Calculated production and loss rates of ions due to impact of galactic cosmic rays in the lower atmosphere of Mars

Our understanding of the daytime lower ionosphere of Mars is limited due to lack of observations in this region. We have calculated the production rates, the loss rates and the densities of electrons and 35 ions, in the daytime lower atmosphere of Mars using the energy loss method and the continuity equation controlled by the steady state chemical equilibrium condition. The primary ionization source in the model is taken as galactic cosmic rays. The chemical model couples ion–neutral, electron–neutral, photodissociation of positive and negative ions, electron photo-detachment, ion–ion and ion–electron recombination processes through 101 chemical reactions. The electron density is calculated using charge neutrality condition. Of the 35 ions considered in the model, we discuss in detail the source and sink processes of 20 ions that are most dominant. These are the positive ions H3O+(H2O)2, H3O+(H2O)3, H3O+(H2O)4, H3O+H2O, H3O+, CO2+CO2, O2+(CO2)2, O2+CO2, O2+, CO2+ and negative ions CO3−(H2O)2, NO2−H2O, CO3−H2O, NO2−(H2O)2, CO3−, CO4−, NO3−(H2O)2, NO2−, NO3−H2O, O2−. The model calculation suggests that maximum electron density of 0.5×102 cm−3 occurs at about 35 km due to high efficiency of electron attachment to Ox molecules, which entails that concentrations of negative ions is higher than that of electron below 35 km. Impact of galactic cosmic rays initially produces CO2+ and O2+ ions, but the ion chemistry eventually leads to the dominance of hydrated positive and negative ions with maximum densities of ∼103 cm−3. It is found that out of all the processes included in the model, the most important process is the ion–neutral collisions wherein the reaction of H3O+(H2O)2,3 with water and air molecules having the highest rates of ∼105 cm−3 s−1takes place

Odd oxygen photochemistry of Martian atmosphere and the role of dust

International audienceThough the photochemistry of Mars is comparatively simple, the orbital properties of Mars and its exposure to solar influx lead to pronounced seasonal and latitudinal variations of short lived species (trace gases). In a recent analysis of SPICAM observations in the UV, we have studied spatio-temporal variability of ozone. We further use the photochemistry coupled LMD GCM to study in detail the important source and sink processes of odd oxygen Ox (ozone and oxygen atoms) and their contribution in different locations and seasons. Ox is in photochemical equilibrium up to about 30 km in the aphelion season and up to 45 km in the perihelion season. In the photochemical equilibrium domain, HO$_{2}$+O is the dominant loss process of Ox, while above this domain, the HO$_{x}$+O, H+O$_{3}$ and O+O reactions have comparable contributions to the Ox loss. From SPICAM observations, we have found a correlation of ozone with dust. In southern tropical latitudes, the columnar ozone is seen to increase during a global dust storm year (MY 28) compared to the ozone column values during a year without global dust storm (MY 27). This indicates towards the radiative impact of dust on ozone. We have also studied the role of heterogeneous chemistry on dust in determining production of ozone and related tracers, by a 1D photochemical model developed at PRL and the LMD GCM. The sensitivity of input parameters taken by us in the study of heterogenous chemistry such as sticking coefficients, was also analysed