129 research outputs found
Search for a Technicolor omega_T Particle in Events with a Photon and a b-quark Jet at CDF
If the Technicolor omega_T particle exists, a likely decay mode is omega_T ->
gamma pi_T, followed by pi_T -> bb-bar, yielding the signature gamma bb-bar. We
have searched 85 pb^-1 of data collected by the CDF experiment at the Fermilab
Tevatron for events with a photon and two jets, where one of the jets must
contain a secondary vertex implying the presence of a b quark. We find no
excess of events above standard model expectations. We express the result of an
exclusion region in the M_omega_T - M_pi_T mass plane.Comment: 14 pages, 2 figures. Available from the CDF server (PS with figs):
http://www-cdf.fnal.gov/physics/pub98/cdf4674_omega_t_prl_4.ps
FERMILAB-PUB-98/321-
Photosynthesis-dependent H₂O₂ transfer from chloroplasts to nuclei provides a high-light signalling mechanism
Chloroplasts communicate information by signalling to nuclei during acclimation to fluctuating light. Several potential operating signals originating from chloroplasts have been proposed, but none have been shown to move to nuclei to modulate gene expression. One proposed signal is hydrogen peroxide (H2O2) produced by chloroplasts in a light-dependent manner. Using HyPer2, a genetically encoded fluorescent H2O2 sensor, we show that in photosynthetic Nicotiana benthamiana epidermal cells, exposure to high light increases H2O2 production in chloroplast stroma, cytosol and nuclei. Critically, over-expression of stromal ascorbate peroxidase (H2O2 scavenger) or treatment with DCMU (photosynthesis inhibitor) attenuates nuclear H2O2 accumulation and high light-responsive gene expression. Cytosolic ascorbate peroxidase over-expression has little effect on nuclear H2O2 accumulation and high light-responsive gene expression. This is because the H2O2 derives from a sub-population of chloroplasts closely associated with nuclei. Therefore, direct H2O2 transfer from chloroplasts to nuclei, avoiding the cytosol, enables photosynthetic control over gene expression
Presence of intestinal Mycobacterium avium subspecies paratuberculosis (MAP) DNA is not associated with altered MMP expression in ulcerative colitis
<p>Abstract</p> <p>Background</p> <p><it>Mycobacterium avium </it>subspecies <it>paratuberculosis </it>(MAP) is suspected to be a causative agent in human Crohn's disease (CD). Recent evidence suggests that pathogenic mycobacteria and MAP can induce the expression of Matrix Metalloproteinases (MMP), which are the main proteases in the pathogenesis of mucosal ulcerations in inflammatory bowel disease (IBD). Within this study we assessed the prevalence of intestinal MAP specific DNA in patients with Crohn's disease, ulcerative colitis (UC), and healthy controls. We further analysed regulation patterns of MMPs in mucosal tissues of UC patients with and without intestinal MAP DNA detection.</p> <p>Methods</p> <p>Colonic biopsy samples were obtained from 63 Norwegian and German IBD patients and 21 healthy controls. RNA was quantified by quantitative real-time polymerase chain reaction (PCR) to study MMP gene expression in both pathological and healthy mucosal specimens. The presence of MAP DNA in colonic mucosa was examined using MAP specific PCR.</p> <p>Results</p> <p>MAP DNA was detected in 20% of UC patients and 33% of healthy controls but only in 7% of patients with CD. UC patients treated with corticosteroids exhibited a significantly increased frequency of intestinal MAP DNA compared to those not receiving corticosteroids. Expression of MMP-1, -2, -7, -9, -13, -19, -28 and TNF-α did not differ between UC patients with presence of intestinal MAP DNA compared to those without. MMP-2, MMP-9 and MMP-13 were significantly decreased in UC patients receiving corticosteroids.</p> <p>Conclusions</p> <p>The presence of intestinal MAP specific DNA is not associated with altered MMP expression in UC <it>in vivo</it>. Corticosteroids are associated with increased detection of intestinal MAP DNA and decreased expression of certain MMPs. Frequent detection of MAP DNA in healthy controls might be attributable to the wide environmental distribution of MAP and its presence in the food-chain.</p
Integrated high-content quantification of intracellular ROS levels and mitochondrial morphofunction
Oxidative stress arises from an imbalance between the production of reactive oxygen species (ROS) and their removal by cellular antioxidant systems. Especially under pathological conditions, mitochondria constitute a relevant source of cellular ROS. These organelles harbor the electron transport chain, bringing electrons in close vicinity to molecular oxygen. Although a full understanding is still lacking, intracellular ROS generation and mitochondrial function are also linked to changes in mitochondrial morphology. To study the intricate relationships between the different factors that govern cellular redox balance in living cells, we have developed a high-contentmicroscopy-based strategy for simultaneous quantification of intracellular ROS levels and mitochondrial morphofunction. Here, we summarize the principles of intracellular ROS generation and removal, and we explain the major considerations for performing quantitative microscopy analyses of ROS and mitochondrial morphofunction in living cells. Next, we describe our workflow, and finally, we illustrate that a multiparametric readout enables the unambiguous classification of chemically perturbed cells as well as laminopathy patient cells
Search for second generation leptoquarks in the dimuon plus dijet channel of p-pbar collisions at sqrt{s}=1.8 TeV
We report on a search for second generation leptoquarks (Phi_2) using a data
sample corresponding to an integrated luminosity of 110 pb^{-1} collected at
the Collider Detector at Fermilab. We present upper limits on the production
cross section as a function of Phi_2 mass, assuming that the leptoquarks are
produced in pairs and decay into a muon and a quark with branching ratio beta.
Using a Next-to-Leading order QCD calculation, we extract a lower mass limit of
M_{\Phi_2} > 202 (160) GeV$/c^{2} at 95% confidence level for scalar
leptoquarks with beta=1(0.5).Comment: 11 pages, 2 figure
Search for New Particles Decaying to b bbar in p pbar Collisions at sqrt{s}=1.8 TeV
We have used 87 pb^-1 of data collected with the Collider Detector at
Fermilab to search for new particles decaying to b bbar. We present
model-independent upper limits on the cross section for narrow resonances which
excludes the color-octet technirho in the mass interval 350 < M < 440 GeV/c^2.
In addition, we exclude topgluons, predicted in models of topcolor-assisted
technicolor, of width Gamma = 0.3 M in the mass range 280 < M < 670 GeV/c^2, of
width Gamma = 0.5 M in the mass range 340 < M < 640 GeV/c^2, and of width Gamma
= 0.7 M in the mass range 375 < M < 560 GeV/c^2.Comment: 17 pages in a LaTex generated postscript file, with one table and
four figures. Resubmitted to Physical Review Letters. Minor clarifications
were added to the text. The displayed normalization of the resonance models
in Figure 2 was modified to correspond to our 95% CL upper limit on the cross
section (instead of arbitrary normalization which was used previously). All
results are identical to those in the previous submissio
Search for a W' Boson via the Decay Mode W' -> mu nu in 1.8 TeV p-pbar Collisions
We report the results of a search for a W' boson produced in p-pbar
collisions at a center-of-mass energy of 1.8 TeV using a 107 pb-1 data sample
recorded by the Collider Detector at Fermilab. We consider the decay channel W'
-> mu nu and search for anomalous production of high transverse mass mu-nu
lepton pairs. We observe no excess of events above background and set limits on
the rate of W' boson production and decay relative to Standard Model W boson
production and decay using a fit of the transverse mass distribution observed.
If we assume Standard Model strength couplings of the W' boson to quark and
lepton pairs, we exclude a W' boson with invariant mass less than 660 GeV/c**2
at 95% confidence level.Comment: 19 pages, 2 figure
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