5,328 research outputs found
Preparation of Dipteran Larvae for Scanning Electron Microscopy with Special Reference to Myiasigen Dipteran Species
Although controversy exists concerning the role of chemical fixatives in scanning electron microscopy (SEM) studies of Dipteran larvae, we have observed that filtered 10% formaldehyde solution gives excellent results as a preservative. After immersing in vivo in formaldehyde, the larvae material is preserved for prolonged periods (up to 8 months), before examination with SEM. As a fixative, formaldehyde preserves the structure of the larval cuticle and produces no visible artifacts. Moreover, postfixation is not necessary.
Due to pecularities of the way of life of Wohlfahrtia magnifica (principally the accumulations of necrotic tissue, purulent particles, and other types of substances that often adhere to the numerous spines of larvae), this species must be cleaned before examination by SEM. Manual cleaning with alternating bidistilled water and 0.9% saline solution proved to be a rapid, easy and inexpensive method that gave good results.
Both lyophilization drying and critical point drying were used before sputtering the material. While lyophilization drying proved to be the most effective method for instars II and III, critical point drying was the best technique for study of specimens belonging to instar I. The optimum time for drying and conditions for lyophilization and sputter-coating with gold were determined experimentally. Samples were mounted on SEM stubs with double-sided adhesive and silver conductive paint.
The method proposed is easy and effective for the SEM study of larvae myiasis-producing diptera
V-shaped pyranylidene/triphenylamine-based chromophores with enhanced photophysical, electrochemical and nonlinear optical properties
We report the synthesis and comprehensive study of two chromophores based on 4H-pyranylidene moiety as a part of the p-conjugated spacer. Triphenylamine (TPA) acts as donor and tricarbonitrile-based electron-accepting groups complete these V-shaped D-A-D architectures (A, acceptor; D, donor). Their electrochemical, photophysical and nonlinear optical properties are analyzed in detail by using a joint experimental and theoretical approach. The two chromophores exhibit near-infrared fluorescence, large Stokes shift, enhanced emission in tetrahydrofuran/water mixtures and good photostability. Additionally, the dimerization of triphenylamine groups to tetraphenylbenzidine (TPB) takes place upon electrochemical and chemical oxidation showing their peculiar electrochemical behavior and film formation capabilities. Interestingly, high molecular first hyperpolarizabilities and two-photon absorption cross-sections were found, highlighting their potential applications in electro-optical devices. Overall, our work demonstrates that these near-infrared (NIR) fluorescent chromophores are versatile materials with a myriad of applications ranging from optoelectronics to biological applications. Š 2021 The Royal Society of Chemistry
RNase H2, mutated in Aicardi-Goutières syndrome, promotes LINE-1 retrotransposition
Long INterspersed Element class 1 (LINE-1) elements are a type of
abundant retrotransposons active in mammalian genomes. An
average human genome contains ~100 retrotransposition-competent
LINE-1s, whose activity is influenced by the combined action
of cellular repressors and activators. TREX1, SAMHD1 and ADAR1
are known LINE-1 repressors and when mutated cause the autoinflammatory
disorder Aicardi-Goutières syndrome (AGS). Mutations
in RNase H2 are the most common cause of AGS, and its activity
was proposed to similarly control LINE-1 retrotransposition. It has
therefore been suggested that increased LINE-1 activity may be
the cause of aberrant innate immune activation in AGS. Here, we
establish that, contrary to expectations, RNase H2 is required for
efficient LINE-1 retrotransposition. As RNase H1 overexpression
partially rescues the defect in RNase H2 null cells, we propose a
model in which RNase H2 degrades the LINE-1 RNA after reverse
transcription, allowing retrotransposition to be completed. This
also explains how LINE-1 elements can retrotranspose efficiently
without their own RNase H activity. Our findings appear to be at
odds with LINE-1-derived nucleic acids driving autoinflammation
in AGS.M.B.-G. is funded by a âFormacion Profesorado
Universitarioâ (FPU) PhD fellowship from the Government of Spain (MINECO,
Ref FPU15/03294), and this paper is part of her thesis project (âEpigenetic
control of the mobility of a human retrotransposonâ). R.V.-A. is funded by a
PFIS Fellowship from the Government of Spain (ISCiii, FI16/00413). O.M. is
funded by an EMBO Long-Term Fellowship (ALTF 7-2015), the European
Commission FP7 (Marie Curie Actions, LTFCOFUND2013, GA-2013-609409) and
the Swiss National Science Foundation (P2ZHP3_158709). S.R.H. is funded by
the Government of Spain (MINECO, RYC-2016-21395 and SAF2015-71589-P).
A.P.Jâs laboratory is supported by the UK Medical Research Council (MRC University Unit grant U127527202). J.L.G.Pâs laboratory is supported by CICEFEDER-
P12-CTS-2256, Plan Nacional de I+D+I 2008-2011 and 2013-2016 (FISFEDER-
PI14/02152), PCIN-2014-115-ERA-NET NEURON II, the European
Research Council (ERC-Consolidator ERC-STG-2012-233764), by an International
Early Career Scientist grant from the Howard Hughes Medical Institute
(IECS-55007420), by The Wellcome Trust-University of Edinburgh Institutional
Strategic Support Fund (ISFF2) and by a private donation from Ms Francisca
Serrano (Trading y Bolsa para Torpes, Granada, Spain)
Distinct mechanisms of loss of IFN-gamma mediated HLA class I inducibility in two melanoma cell lines
BACKGROUND: The inability of cancer cells to present antigen on the cell surface via MHC class I molecules is one of the mechanisms by which tumor cells evade anti-tumor immunity. Alterations of Jak-STAT components of interferon (IFN)-mediated signaling can contribute to the mechanism of cell resistance to IFN, leading to lack of MHC class I inducibility. Hence, the identification of IFN-Îł-resistant tumors may have prognostic and/or therapeutic relevance. In the present study, we investigated a mechanism of MHC class I inducibility in response to IFN-Îł treatment in human melanoma cell lines. METHODS: Basal and IFN-induced expression of HLA class I antigens was analyzed by means of indirect immunofluorescence flow cytometry, Western Blot, RT-PCR, and quantitative real-time RT-PCR (TaqMan(ÂŽ )Gene Expression Assays). In demethylation studies cells were cultured with 5-aza-2'-deoxycytidine. Electrophoretic Mobility Shift Assay (EMSA) was used to assay whether IRF-1 promoter binding activity is induced in IFN-Îł-treated cells. RESULTS: Altered IFN-Îł mediated HLA-class I induction was observed in two melanoma cells lines (ESTDAB-004 and ESTDAB-159) out of 57 studied, while treatment of these two cell lines with IFN-Îą led to normal induction of HLA class I antigen expression. Examination of STAT-1 in ESTDAB-004 after IFN-Îł treatment demonstrated that the STAT-1 protein was expressed but not phosphorylated. Interestingly, IFN-Îą treatment induced normal STAT-1 phosphorylation and HLA class I expression. In contrast, the absence of response to IFN-Îł in ESTDAB-159 was found to be associated with alterations in downstream components of the IFN-Îł signaling pathway. CONCLUSION: We observed two distinct mechanisms of loss of IFN-Îł inducibility of HLA class I antigens in two melanoma cell lines. Our findings suggest that loss of HLA class I induction in ESTDAB-004 cells results from a defect in the earliest steps of the IFN-Îł signaling pathway due to absence of STAT-1 tyrosine-phosphorylation, while absence of IFN-Îł-mediated HLA class I expression in ESTDAB-159 cells is due to epigenetic blocking of IFN-regulatory factor 1 (IRF-1) transactivation
Search for the standard model Higgs boson decaying to a pair in events with no charged leptons and large missing transverse energy using the full CDF data set
We report on a search for the standard model Higgs boson produced in
association with a vector boson in the full data set of proton-antiproton
collisions at TeV recorded by the CDF II detector at the
Tevatron, corresponding to an integrated luminosity of 9.45 fb. We
consider events having no identified charged lepton, a transverse energy
imbalance, and two or three jets, of which at least one is consistent with
originating from the decay of a quark. We place 95% credibility level upper
limits on the production cross section times standard model branching fraction
for several mass hypotheses between 90 and . For a Higgs
boson mass of , the observed (expected) limit is 6.7
(3.6) times the standard model prediction.Comment: Accepted by Phys. Rev. Let
Search for the standard model Higgs boson decaying to a bb pair in events with one charged lepton and large missing transverse energy using the full CDF data set
We present a search for the standard model Higgs boson produced in
association with a W boson in sqrt(s) = 1.96 TeV p-pbar collision data
collected with the CDF II detector at the Tevatron corresponding to an
integrated luminosity of 9.45 fb-1. In events consistent with the decay of the
Higgs boson to a bottom-quark pair and the W boson to an electron or muon and a
neutrino, we set 95% credibility level upper limits on the WH production cross
section times the H->bb branching ratio as a function of Higgs boson mass. At a
Higgs boson mass of 125 GeV/c2 we observe (expect) a limit of 4.9 (2.8) times
the standard model value.Comment: Submitted to Phys. Rev. Lett (v2 contains clarifications suggested by
PRL
Measurement of the t t-bar production cross section in the dilepton channel in pp collisions at sqrt(s) = 7 TeV
The t t-bar production cross section (sigma[t t-bar]) is measured in
proton-proton collisions at sqrt(s) = 7 TeV in data collected by the CMS
experiment, corresponding to an integrated luminosity of 2.3 inverse
femtobarns. The measurement is performed in events with two leptons (electrons
or muons) in the final state, at least two jets identified as jets originating
from b quarks, and the presence of an imbalance in transverse momentum. The
measured value of sigma[t t-bar] for a top-quark mass of 172.5 GeV is 161.9 +/-
2.5 (stat.) +5.1/-5.0 (syst.) +/- 3.6(lumi.) pb, consistent with the prediction
of the standard model.Comment: Replaced with published version. Included journal reference and DO
Combined search for the quarks of a sequential fourth generation
Results are presented from a search for a fourth generation of quarks
produced singly or in pairs in a data set corresponding to an integrated
luminosity of 5 inverse femtobarns recorded by the CMS experiment at the LHC in
2011. A novel strategy has been developed for a combined search for quarks of
the up and down type in decay channels with at least one isolated muon or
electron. Limits on the mass of the fourth-generation quarks and the relevant
Cabibbo-Kobayashi-Maskawa matrix elements are derived in the context of a
simple extension of the standard model with a sequential fourth generation of
fermions. The existence of mass-degenerate fourth-generation quarks with masses
below 685 GeV is excluded at 95% confidence level for minimal off-diagonal
mixing between the third- and the fourth-generation quarks. With a mass
difference of 25 GeV between the quark masses, the obtained limit on the masses
of the fourth-generation quarks shifts by about +/- 20 GeV. These results
significantly reduce the allowed parameter space for a fourth generation of
fermions.Comment: Replaced with published version. Added journal reference and DO
Search for the standard model Higgs boson decaying to a bb pair in events with two oppositely-charged leptons using the full CDF data set
We present a search for the standard model Higgs boson produced in
association with a Z boson in data collected with the CDF II detector at the
Tevatron, corresponding to an integrated luminosity of 9.45/fb. In events
consistent with the decay of the Higgs boson to a bottom-quark pair and the Z
boson to electron or muon pairs, we set 95% credibility level upper limits on
the ZH production cross section times the H -> bb branching ratio as a function
of Higgs boson mass. At a Higgs boson mass of 125 GeV/c^2 we observe (expect) a
limit of 7.1 (3.9) times the standard model value.Comment: To be submitted to Phys. Rev. Let
Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV
A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay
channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7
TeV is presented. The data were collected at the LHC, with the CMS detector,
and correspond to an integrated luminosity of 4.6 inverse femtobarns. No
significant excess is observed above the background expectation, and upper
limits are set on the Higgs boson production cross section. The presence of the
standard model Higgs boson with a mass in the 270-440 GeV range is excluded at
95% confidence level.Comment: Submitted to JHE
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