41 research outputs found
Morphological and Bactericidal Effects of Different Antibiotics on Helicobacter pylori
Background: Helicobacter pylori (H. pylori) is a spiral Gram negative bacteria that can transform to the coccoid form in adverse conditions.
Objectives: The aim of this study was to determine the in vitro morphological and bactericidal effects of metronidazole, amoxicillin and
clarithromycin on H. pylori.
Materials and Methods: The standard strain 26695 of H. pylori was cultured on Brucella agar (BA) and the minimum inhibitory
concentrations (MICs) of three antibiotics were determined by E-test method. The bacteria were exposed to antibiotics at 1/2 MIC, MIC and
2X MIC concentrations in Brucella broth (BB). Induced coccoid forms were confirmed by Gram staining and light microscopy. The viability
of cells as well as the susceptibility of viable coccoids to antibiotics were examined using the flow cytometry method.
Results: All of the three antibiotics at sub-MIC induced coccoid forms. The highest rates of coccoids (> 90%) were induced at 0.008 μg/
mL concentration (1/2 MIC) of amoxicillin, 72 hours postexposure. Metronidazole and clarithromycin with 1/2 MIC (0.5 and 0.125 µg/mL
respectively) induced lower rates of coccoid forms (60% and 40% respectively). Potent bactericidal effects on coccoids were observed with
Metronidazole at 2X MIC and clarithromycin at MIC (0.25 µg/mL) (80 - 90%). Amoxicillin with MIC and 2X MIC had no bactericidal effect on
coccoid forms.
Conclusions: Despite the good in vitro bactericidal effect of amoxicillin on spiral forms of H. pylori, this antibiotic has little effect on
induced coccoids that may develop after the inappropriate in vivo antibacterial treatment. Hence, for successful therapy, it is essential not
only to eradicate the spiral forms, but to eliminate the viable coccoids
Water-induced modulation of Helicobacter pylori virulence properties
While the influence of water in Helicobacter pylori culturability and membrane integrity has been extensively studied, there are little data concerning the effect of this environment on virulence properties. Therefore, we studied the culturability of water-exposed H. pylori and determined whether there was any relation with the bacterium’s ability to adhere, produce functional components of pathogenicity and induce inflammation and alterations in apoptosis in an experimental model of human gastric epithelial cells. H. pylori partially retained the ability to adhere to epithelial cells even after complete loss of culturability. However, the microorganism is no longer effective in eliciting in vitro host cell inflammation and apoptosis, possibly due to the non-functionality of the cag type IV secretion system. These H. pylori-induced host cell responses, which are lost along with culturability, are known to increase epithelial cell turnover and, consequently, could have a deleterious effect on the initial H. pylori colonisation process. The fact that adhesion is maintained by H. pylori to the detriment of other factors involved in later infection stages appears to point to a modulation of the physiology of the pathogen after water exposure and might provide the microorganism with the necessary means to, at least transiently, colonise the human stomach.FCT (SFRH/BD/24579/2005) (to NMG
Molecular Trajectories Leading to the Alternative Fates of Duplicate Genes
Gene duplication generates extra gene copies in which mutations can accumulate without risking the function of pre-existing genes. Such mutations modify duplicates and contribute to evolutionary novelties. However, the vast majority of duplicates appear to be short-lived and experience duplicate silencing within a few million years. Little is known about the molecular mechanisms leading to these alternative fates. Here we delineate differing molecular trajectories of a relatively recent duplication event between humans and chimpanzees by investigating molecular properties of a single duplicate: DNA sequences, gene expression and promoter activities. The inverted duplication of the Glutathione S-transferase Theta 2 (GSTT2) gene had occurred at least 7 million years ago in the common ancestor of African great apes and is preserved in chimpanzees (Pan troglodytes), whereas a deletion polymorphism is prevalent in humans. The alternative fates are associated with expression divergence between these species, and reduced expression in humans is regulated by silencing mutations that have been propagated between duplicates by gene conversion. In contrast, selective constraint preserved duplicate divergence in chimpanzees. The difference in evolutionary processes left a unique DNA footprint in which dying duplicates are significantly more similar to each other (99.4%) than preserved ones. Such molecular trajectories could provide insights for the mechanisms underlying duplicate life and death in extant genomes
MicroRNA Genes Derived from Repetitive Elements and Expanded by Segmental Duplication Events in Mammalian Genomes
MicroRNAs (miRNAs) are a class of small noncoding RNAs that regulate gene
expression by targeting mRNAs for translation repression or mRNA degradation.
Many miRNAs are being discovered and studied, but in most cases their origin,
evolution and function remain unclear. Here, we characterized miRNAs derived
from repetitive elements and miRNA families expanded by segmental duplication
events in the human, rhesus and mouse genomes. We applied a comparative genomics
approach combined with identifying miRNA paralogs in segmental duplication pair
data in a genome-wide study to identify new homologs of human miRNAs in the
rhesus and mouse genomes. Interestingly, using segmental duplication pair data,
we provided credible computational evidence that two miRNA genes are located in
the pseudoautosomal region of the human Y chromosome. We characterized all the
miRNAs whether they were derived from repetitive elements or not and identified
significant differences between the repeat-related miRNAs (RrmiRs) and
non-repeat-derived miRNAs in (1) their location in protein-coding and intergenic
regions in genomes, (2) the minimum free energy of their hairpin structures, and
(3) their conservation in vertebrate genomes. We found some lineage-specific
RrmiR families and three lineage-specific expansion families, and provided
evidence indicating that some RrmiR families formed and expanded during
evolutionary segmental duplication events. We also provided computational and
experimental evidence for the functions of the conservative RrmiR families in
the three species. Together, our results indicate that repetitive elements
contribute to the origin of miRNAs, and large segmental duplication events could
prompt the expansion of some miRNA families, including RrmiR families. Our study
is a valuable contribution to the knowledge of evolution and function of
non-coding region in genome
Search for natural and split supersymmetry in proton-proton collisions at root s=13 TeV in final states with jets and missing transverse momentum
A search for supersymmetry (SUSY) is performed in final states comprising one or more jets and missing transverse momentum using data from proton-proton collisions at a centre-of-mass energy of 13 TeV. The data were recorded with the CMS detector at the CERN LHC in 2016 and correspond to an integrated luminosity of 35.9 fb(-1). The number of signal events is found to agree with the expected background yields from standard model processes. The results are interpreted in the context of simplified models of SUSY that assume the production of gluino or squark pairs and their prompt decay to quarks and the lightest neutralino. The masses of bottom, top, and mass-degenerate light-flavour squarks are probed up to 1050, 1000, and 1325 GeV, respectively. The gluino mass is probed up to 1900, 1650, and 1650 GeV when the gluino decays via virtual states of the aforementioned squarks. The strongest mass bounds on the neutralinos from gluino and squark decays are 1150 and 575 GeV, respectively. The search also provides sensitivity to simplified models inspired by split SUSY that involve the production and decay of long-lived gluinos. Values of the proper decay length CT0 from 10(-3) to 10(5) mm are considered, as well as a metastable gluino scenario. Gluino masses up to 1750 and 900 GeV are probed for CT0 = 1mm and for the metastable state, respectively. The sensitivity is moderately dependent on model assumptions for CT0 greater than or similar to 1 m. The search provides coverage of the CT0 parameter space for models involving long-lived gluinos that is complementary to existing techniques at the LHC.Peer reviewe
Search for new phenomena in final states with two opposite-charge, same-flavor leptons, jets, and missing transverse momentum in pp collisions at root s=13TeV
Search results are presented for physics beyond the standard model in final states with two opposite-charge, same-flavor leptons, jets, and missing transverse momentum. The data sample corresponds to an integrated luminosity of 35.9 fb−1 of proton-proton collisions at s√=13 TeV collected with the CMS detector at the LHC in 2016. The analysis uses the invariant mass of the lepton pair, searching for a kinematic edge or a resonant-like excess compatible with the Z boson mass. The search for a kinematic edge targets production of particles sensitive to the strong force, while the resonance search targets both strongly and electroweakly produced new physics. The observed yields are consistent with the expectations from the standard model, and the results are interpreted in the context of simplified models of supersymmetry. In a gauge mediated supersymmetry breaking (GMSB) model of gluino pair production with decay chains including Z bosons, gluino masses up to 1500–1770 GeV are excluded at the 95% confidence level depending on the lightest neutralino mass. In a model of electroweak chargino-neutralino production, chargino masses as high as 610 GeV are excluded when the lightest neutralino is massless. In GMSB models of electroweak neutralino-neutralino production, neutralino masses up to 500-650 GeV are excluded depending on the decay mode assumed. Finally, in a model with bottom squark pair production and decay chains resulting in a kinematic edge in the dilepton invariant mass distribution, bottom squark masses up to 980–1200 GeV are excluded depending on the mass of the next-to-lightest neutralino
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Search for new phenomena in final states with two opposite-charge, same-flavor leptons, jets, and missing transverse momentum in pp collisions at root s=13TeV
Search results are presented for physics beyond the standard model in final states with two opposite-charge, same-flavor leptons, jets, and missing transverse momentum. The data sample corresponds to an integrated luminosity of 35.9 fb−1 of proton-proton collisions at s√=13 TeV collected with the CMS detector at the LHC in 2016. The analysis uses the invariant mass of the lepton pair, searching for a kinematic edge or a resonant-like excess compatible with the Z boson mass. The search for a kinematic edge targets production of particles sensitive to the strong force, while the resonance search targets both strongly and electroweakly produced new physics. The observed yields are consistent with the expectations from the standard model, and the results are interpreted in the context of simplified models of supersymmetry. In a gauge mediated supersymmetry breaking (GMSB) model of gluino pair production with decay chains including Z bosons, gluino masses up to 1500–1770 GeV are excluded at the 95% confidence level depending on the lightest neutralino mass. In a model of electroweak chargino-neutralino production, chargino masses as high as 610 GeV are excluded when the lightest neutralino is massless. In GMSB models of electroweak neutralino-neutralino production, neutralino masses up to 500-650 GeV are excluded depending on the decay mode assumed. Finally, in a model with bottom squark pair production and decay chains resulting in a kinematic edge in the dilepton invariant mass distribution, bottom squark masses up to 980–1200 GeV are excluded depending on the mass of the next-to-lightest neutralino
Search for new phenomena in final states with two opposite-charge, same-flavor leptons, jets, and missing transverse momentum in pp collisions at root s=13TeV
Search results are presented for physics beyond the standard model in final
states with two opposite-charge, same-flavor leptons, jets, and missing
transverse momentum. The data sample corresponds to an integrated luminosity of
35.9 fb of proton-proton collisions at 13 TeV collected
with the CMS detector at the LHC in 2016. The analysis uses the invariant mass
of the lepton pair, searching for a kinematic edge or a resonant-like excess
compatible with the Z boson mass. The search for a kinematic edge targets
production of particles sensitive to the strong force, while the resonance
search targets both strongly and electroweakly produced new physics. The
observed yields are consistent with the expectations from the standard model,
and the results are interpreted in the context of simplified models of
supersymmetry. In a gauge mediated supersymmetry breaking (GMSB) model of
gluino pair production with decay chains including Z bosons, gluino masses up
to 1500-1770 GeV are excluded at the 95% confidence level depending on the
lightest neutralino mass. In a model of electroweak chargino-neutralino
production, chargino masses as high as 610 GeV are excluded when the lightest
neutralino is massless. In GMSB models of electroweak neutralino-neutralino
production, neutralino masses up to 500-650 GeV are excluded depending on the
decay mode assumed. Finally, in a model with bottom squark pair production and
decay chains resulting in a kinematic edge in the dilepton invariant mass
distribution, bottom squark masses up to 980-1200 GeV are excluded depending on
the mass of the next-to-lightest neutralino.Comment: Replaced with the published version. Added the journal reference and
the DOI. All the figures and tables, including additional supplementary
figures and tables, can be found at
http://cms-results.web.cern.ch/cms-results/public-results/publications/SUS-16-034/
(CMS Public Pages