Antimicrobial activity of per acetic acid for trans-operative disinfection of endodontic files

Reducing the accumulation of microorganisms on an endodontic file during endodontic treatment is important to limit recontamination of the root canal and increase likelihood of successful treatment outcome. Objective: To compare the antimicrobial activity of peracetic acid (PA), isopropyl alcohol and acetone against a range of bacteria and also for disinfection of contaminated endodontic K-files. Material and Methods: Antimicrobial activities of PA, isopropyl alcohol and acetone were compared against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, vancomycin resistant E. faecalis (VRE) and meticillin resistant S. aureus (MRSA), using minimum bactericidal concentration (MBC) and time-kill assays. Test solutions at different exposure times (15 s and 30 s) were assessed for treatment of endodontic files acting as carriers of E. faecalis-contaminated dental debris. Results: All bacteria were susceptible to PA (MBC range 0.25-1%), acetone (MBC range 50-60%) and isopropyl alcohol (30-40%). Using a time-kill assay of the antimicrobials at the determined MBC, all test microorganisms, with the exception of E. faecalis (VRE) 7766 were killed after 15 s exposure. In the case of E. faecalis 7766, viable cells remained detectable after 120 s exposure to acetone. Testing disinfection of endodontic K-files, previously coated with dental debris containing E. faecalis, it was found that PA (2%) completely killed E. faecalis after 15 s exposure. However, even after 30 s exposure, isopropyl alcohol (80%) and acetone (80%) had limited disinfecting activity. Conclusion: Extrapolation of these results to clinical practice would suggest that PA would be the most effective agent for trans-operative disinfection of endodontic K-files during treatment of a single patient

Comparative Transcriptional and Genomic Analysis of Plasmodium falciparum Field Isolates

Mechanisms for differential regulation of gene expression may underlie much of the phenotypic variation and adaptability of malaria parasites. Here we describe transcriptional variation among culture-adapted field isolates of Plasmodium falciparum, the species responsible for most malarial disease. It was found that genes coding for parasite protein export into the red cell cytosol and onto its surface, and genes coding for sexual stage proteins involved in parasite transmission are up-regulated in field isolates compared with long-term laboratory isolates. Much of this variability was associated with the loss of small or large chromosomal segments, or other forms of gene copy number variation that are prevalent in the P. falciparum genome (copy number variants, CNVs). Expression levels of genes inside these segments were correlated to that of genes outside and adjacent to the segment boundaries, and this association declined with distance from the CNV boundary. This observation could not be explained by copy number variation in these adjacent genes. This suggests a local-acting regulatory role for CNVs in transcription of neighboring genes and helps explain the chromosomal clustering that we observed here. Transcriptional co-regulation of physical clusters of adaptive genes may provide a way for the parasite to readily adapt to its highly heterogeneous and strongly selective environment

Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality

Asteroseismology of a star cooled by neutrino emission : the pulsating pre-white dwarf PG 0122+200

Observation of g-mode pulsations in the variable pre-white dwarf (GW Virginis) stars provides a unique means to probe their interiors and to study the late stages of stellar evolution. Multisite campaigns have in several cases proved highly successful in decoding preÈwhite dwarf light curves. Three previous attempts to untangle the pulsation spectrum of the coolest GW Virginis star, PG 0122+200, confirmed the existence of multiple g-modes but left the fundamental period spacing and therefore the star's mass and luminosity in doubt. We present an analysis based on new observations of PG 0122+200 obtained during a Whole Earth Telescope (WET) campaign conducted in the fall of 1996. Although our coverage was, because of bad weather, far poorer than in previous WET campaigns, we confirm the previous result that PG 0122+200 rotates once in 1.6±0.1 days. The most likely period spacing supported by the data implies a mass of 0.69±0.03 Mʘ. Based on the best seismology we can currently do, the cooling of PG 0122+200 is dominated by neutrino losses. This is not true for all pre-white dwarf stars and makes PG 0122+200 the prime candidate for learning useful physics. Constraints placed on the cooling rate of PG 0122+200 by future measurement of dII/dt could provide a unique test of the standard theory of lepton interactions in the (experimentally unexplored) region of phase-space appropriate to pre-white dwarf interiors