Dynamic instability of microtubules: effect of catastrophe-suppressing drugs

Microtubules are stiff filamentary proteins that constitute an important component of the cytoskeleton of cells. These are known to exhibit a dynamic instability. A steadily growing microtubule can suddenly start depolymerizing very rapidly; this phenomenon is known as ``catastrophe''. However, often a shrinking microtubule is ``rescued'' and starts polymerizing again. Here we develope a model for the polymerization-depolymerization dynamics of microtubules in the presence of {\it catastrophe-suppressing drugs}. Solving the dynamical equations in the steady-state, we derive exact analytical expressions for the length distributions of the microtubules tipped with drug-bound tubulin subunits as well as those of the microtubules, in the growing and shrinking phases, tipped with drug-free pure tubulin subunits. We also examine the stability of the steady-state solutions.Comment: Minor corrections; final published versio

Assessment of Microbial Diversity in Biofilms Recovered from Endotracheal Tubes Using Culture Dependent and Independent Approaches

Ventilator-associated pneumonia (VAP) is a common nosocomial infection in mechanically ventilated patients. Biofilm formation is one of the mechanisms through which the endotracheal tube (ET) facilitates bacterial contamination of the lower airways. In the present study, we analyzed the composition of the ET biofilm flora by means of culture dependent and culture independent (16 S rRNA gene clone libraries and pyrosequencing) approaches. Overall, the microbial diversity was high and members of different phylogenetic lineages were detected (Actinobacteria, beta-Proteobacteria, Candida spp., Clostridia, epsilon-Proteobacteria, Firmicutes, Fusobacteria and gamma-Proteobacteria). Culture dependent analysis, based on the use of selective growth media and conventional microbiological tests, resulted in the identification of typical aerobic nosocomial pathogens which are known to play a role in the development of VAP, e.g. Staphylococcus aureus and Pseudomonas aeruginosa. Other opportunistic pathogens were also identified, including Staphylococcus epidermidis and Kocuria varians. In general, there was little correlation between the results obtained by sequencing 16 S rRNA gene clone libraries and by cultivation. Pyrosequencing of PCR amplified 16 S rRNA genes of four selected samples resulted in the identification of a much wider variety of bacteria. The results from the pyrosequencing analysis suggest that these four samples were dominated by members of the normal oral flora such as Prevotella spp., Peptostreptococcus spp. and lactic acid bacteria. A combination of methods is recommended to obtain a complete picture of the microbial diversity of the ET biofilm

A Polarised Population of Dynamic Microtubules Mediates Homeostatic Length Control in Animal Cells

An analysis of cells grown on micro-patterned lines, and of cells during zebrafish development, identifies a population of microtubules that align along the long axis of cells to mediate homeostatic length control

From Delta to Omicron SARS-CoV-2 variant : switch to saliva sampling for higher detection rate

Background: Real-time polymerase chain reaction (RT-PCR) testing on a nasopharyngeal swab is the current standard for SARS-CoV-2 virus detection. Since collection of this sample type is experienced uncomfortable by patients, saliva- and oropharyngeal swab collections should be considered as alternative specimens. Objectives: Evaluation of the relative performance of oropharyngeal swab, nasopharyngeal swab and saliva for the RT-PCR based SARS-CoV-2 Delta (B.1.617.2) and Omicron (B.1.1.529) variant detection. Study design: Nasopharyngeal swab, oropharyngeal swab and saliva were collected from 246 adult patients who presented for SARS-CoV-2 testing at the screening centre in Ypres (Belgium). RT-PCR SARS-CoV-2 detection was performed on all three sample types separately. Variant type was determined for each positive patient using whole genome sequencing or Allplex SARS-CoV-2 variants I and II Assay. Results and conclusions: Saliva is superior compared to nasopharyngeal swab for the detection of the Omicron variant. For the detection of the Delta variant, nasopharyngeal swab and saliva can be considered equivalent specimens. Oropharyngeal swab is the least sensitive sample type and shows little added value when collected in addition to a single nasopharyngeal swab

Symptomatic hypoglycemia in a patient with chronic hemodialysis

We describe the case of a 71-years-old man in chronic hospital hemodialysis who was admitted to the hospital because of symptomatic hypoglycemia. We discovered that this was due to a documented intoxication with cibenzoline, an antiarrhythmic drug, used to treat (supra-)ventricular tachyarrhythmia. In addition we made a short review of the literature concerning cibenzoline intoxication.status: publishe

L'évaluation des politiques paysagères : entre dimension cognitive et normative

National audienceL'évaluation des politiques paysagères pose deux types de problèmes, liés respectivement à la définition de leur objet, le paysage, et à la nature des dispositifs mis en place. La pluralité des définitions du paysage induit une diversité de questionnements évaluatifs possibles, opposant des approches constructivistes, analysant les représentations du paysage, et des conceptions centrées sur ses composantes physiques. Par ailleurs, les politiques paysagères se présentent comme des objets complexes, articulant des dispositifs sectoriels aux finalités diverses, et relevant d'une logique d'offre d'intervention plus que d'une réponse à une demande préalablement constituée. Des méthodes d'évaluation du paysage ont été élaborées, principalement dans deux axes de recherche : l'analyse des structures matérielles du paysage, et l'évaluation économique du paysage. Ces méthodes peuvent être mobilisées pour l'évaluation des politiques paysagères, mais n'en constituent qu'une facette. En s'inspirant des principes d'évaluation de politiques territoriales, les auteurs proposent une démarche pluridisciplinaire d'évaluation de politiques paysagères intercommunales, qui fonde leurs travaux actuels sur des territoires auvergnats et limousins. Après avoir analysé les caractéristiques des programmes d'intervention paysagère (conditions d'élaboration, théorie d'action, objectifs), ils cherchent à mesurer les effets du programme tant en termes de réalisation de services environnementaux que d'effets sur les éléments matériels du paysage et les pratiques ou représentations des acteurs