5,711 research outputs found
Overexpression of lpxT Gene in Escherichia coli Inhibits Cell Division and Causes Envelope Defects without Changing the Overall Phosphorylation Level of Lipid A
LpxT is an inner membrane protein that transfers a phosphate group from the essential lipid undecaprenyl pyrophosphate (C-55PP) to the lipid A moiety of lipopolysaccharide, generating a lipid A tris-phosphorylated species. The protein is encoded by the non-essential lpxT gene, which is conserved in distantly related Gram-negative bacteria. In this work, we investigated the phenotypic effect of lpxT ectopic expression from a plasmid in Escherichia coli. We found that lpxT induction inhibited cell division and led to the formation of elongated cells, mostly with absent or altered septa. Moreover, the cells became sensitive to detergents and to hypo-osmotic shock, indicating that they had cell envelope defects. These effects were not due to lipid A hyperphosphorylation or C-55PP sequestering, but most likely to defective lipopolysaccharide transport. Indeed, lpxT overexpression in mutants lacking the L,D-transpeptidase LdtD and LdtE, which protect cells with outer membrane defects from osmotic lysis, caused cell envelope defects. Moreover, we found that pyrophosphorylated lipid A was also produced in a lpxT deletion mutant, indicating that LpxT is not the only protein able to perform such lipid A modification in E. coli
VTMR, a new speech audiometry test with verbal tasks and motor responses
Objectives: The aim of this study was to design a complementary speech audiometry test using verbal tasks and motor responses (VTMR) to assess the ability of a subject to understand and perform simple motor tasks with 3-dimensional objects, to describe its construction, and to show the preliminary results of a pilot study on the Italian version of the test.
Methods: The items used in the test setting included 1 base, 1 hammer, 1 wooden structure with 4 sticks, and 5 rings of different colors and 20 lists with 5 verbal tasks per list. The VTMR test and bisyllabic speech audiometry were evaluated in normal-hearing subjects with and without cognitive impairment and in subjects with sensorineural hearing loss.
Results: All normal-hearing subjects without cognitive impairment performed the VTMR tasks (100%) correctly at 35 dB sound pressure level. In subjects with sensorineural hearing loss, the percentage of correct answers was significantly higher for the VTMR test than for bisyllabic speech audiometry above 50 dB sound pressure level. This percentage was higher for the VTMR also in normal-hearing subjects with poor cognitive skills.
Conclusions: The VTMR might make it easier to check patients\u2019 ability to understand verbal commands than does traditional speech audiometry, in particular in those patients with poor test-taking skills
Polymerizable deep eutectic solvents: Convenient reactive dispersion media for the preparation of novel multi-walled carbon nanotubes-based functional materials
A new straightforward and green approach for the covalent functionalization of multi-walled carbon nanotubes (MWCNTs) was developed. This carbon nanostructure was efficiently derivatized by polymerizing proper deep eutectic monomers (DEM), a subclass of deep eutectic solvents (DES), based on a series of mono- and bis-vinyl imidazolium salts endowed with different functional groups (–OH, –NH2, –NH3+Br–) in the side chain or in the spacer. Herein, DEM systems played a triple role as convenient dispersion media for MWCNTs, efficient reactive systems, and also as structure-directing agents for the radical-initiated polymerization process onto the surface of MWCNTs. In addition, the new methodology allowed obtaining highly functionalized hybrid materials, as shown by thermogravimetric analyses, in short reaction times (<1h). Transmission electron microscopy (TEM) revealed that the polymeric network orderly develops along the surface of the nanotubes, which act as templating agent for both mono- and bis-vinyl imidazolium salts, despite the random nature of the polymerization process for the latter species. This new functionalization strategy of MWCNTs stands out for its environmentally friendly and time-saving nature leading to the formation of materials with significant potential for applications in a plethora of research fields. As a proof of their possible application, we tested these new hybrid materials as recoverable and recyclable catalysts for the conversion of CO2 into cyclic carbonates under solvent-free conditions, showing good catalytic performances, even in the absence of additional co-catalysts
Effect of eye lateralization on contralateral suppression of transient evoked otoacoustic emissions
Several studies have previously demonstrated that postural changes modify evoked otoacoustic emission. In order to evaluate a possible interaction between eye muscles and ciliated cells in the inner ear, we studied the effects of eye lateralization on the contralateral suppression of transient evoked otoacoustic emissions (TEOAEs). Thirty-eight normal hearing subjects with TEOAEs were recruited. Their TEAOEs at threshold level were recorded with contralateral suppression (white noise) via straight ahead fixation and right or left lateral fixation. Eye lateralization in the same direction of the white noise significantly decreased the suppression at 4 kHz (p = 0.003). The signal-to-noise ratio in the suppression condition with straight ahead was 1.54 (± 4.610) dB, while the ratio was 3.48 (± 4.631) dB in the suppression condition with gaze toward the white noise. Eye lateralization seems to reduce the contralateral suppression effect of TEOAEs at 4 kHz. However, further studies are necessary to investigate the possible mechanisms of this phenomenon
Cannabis consumption and the risk of psychosis
Summary
Objectives: Cannabis is the most widely used illicit drug globally and its use
has been linked to an increased risk for psychotic disorders. An association
between cannabis consumption and psychotic symptoms was consistently reported
by several studies. This case-control study aimed to widen the current
findings about the impact of cannabis exposure on the risk of psychosis, by
investigating the pattern of cannabis consumption in a sample of first-episode
of psychosis (FEP) patients compared to healthy controls.
Material and methods: 68 individuals who presented for the first time to mental
health services of Palermo (Italy) with an ICD-10 diagnosis of psychotic disorders
and 74 healthy were enrolled as part of the Sicilian Genetics and Psychosis
study. Psychopathological assessment and diagnosis were carried out by
the Schedule for Clinical Assessment in Neuropsychiatry (SCAN). Socio-demographic
data were collected by the modified version of the Medical Research
Council (MRC) socio-demographic scale. All participants were interviewed using
the Cannabis Experience Questionnaire \u2013 Modified Version to obtain a detailed
assessment of lifetime patterns of cannabis and other illicit drug consumption.
Logistic regression was applied to investigate the relationships between various
aspects of cannabis use (lifetime use, age at first use, duration, and frequency of
use) and case-control status while controlling for potential confounders.
Results: Patients started cannabis consumption about 3 years earlier than
the control group (t = 3.1, p = 0.002) and were 8 times more likely to having
started using cannabis before 15 years (adjusted OR = 8.0, 95% CI 2.4-27)
than controls. Furthermore cases were more likely to smoke more frequently
than controls (adjusted OR = 4.4, 95% CI 1.08-18). We did not find a difference
in duration of cannabis use between cases and controls.
Conclusions: The findings suggest that cannabis exposure, and especially
daily cannabis consumption, is associated with the risk for psychosis; however,
the retrospective study design does not allow drawing firm conclusions about
causality
Study of the a_0(980) meson via the radiative decay phi->eta pi^0 gamma with the KLOE detector
We have studied the phi->a_0(980) gamma process with the KLOE detector at the
Frascati phi-factory DAPhNE by detecting the phi->eta pi^0 gamma decays in the
final states with eta->gamma gamma and eta->pi^+ pi^- pi^0. We have measured
the branching ratios for both final states: Br(phi->eta pi^0 gamma)=(7.01 +/-
0.10 +/- 0.20)x10^-5 and (7.12 +/- 0.13 +/- 0.22)x10^-5 respectively. We have
also extracted the a_0(980) mass and its couplings to eta pi^0, K^+ K^-, and to
the phi meson from the fit of the eta pi^0 invariant mass distributions using
different phenomenological models.Comment: 17 pages, 6 figures, submitted to Physics Letters B. Corrected typos
in eq.
Charged kaon lifetime at KLOE
Preliminary result on the charged kaon lifetime, obtained by the KLOE
experiment operating at DANE, the Frascati -factory, is presentedComment: 3 pages, 3 figures, to appear in the proceedings of 42nd Rencontres
de Moriond on Electroweak Interactions and Unified Theories, La Thuile, Aosta
Valley, Italy, 10-17 Mar 200
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