1D-confinement of polyiodides inside single-wall carbon nanotubes

International audience1D-confinement of polyiodides inside single-wall carbon nanotubes (SWCNT) is investigated. Structural arrangement of iodine species as a function of the SWCNT diameters is studied. Evidence for long range one dimensional ordering of the iodine species is shown by X-ray and electron diffraction experiments independently of the tube diameter. The structure of the confined polyiodides is investigated by X-ray absorption spectroscopy. The confinement influences the local arrangement of the chains. Below a critical diameter Fc of 1 nm, long linear polyiodides are evidenced leading to a weaker charge transfer than for nanotube diameter above Fc. A shortening of the polyiodides is exhibited with the increase of the nanotube diameter leading to a more efficient charge transfer. This point reflects the 1D-confinement of the polyiodides inside the nanotubes

Langerhans cell (LC) proliferation mediates neonatal development, homeostasis, and inflammation-associated expansion of the epidermal LC network

Most tissues develop from stem cells and precursors that undergo differentiation as their proliferative potential decreases. Mature differentiated cells rarely proliferate and are replaced at the end of their life by new cells derived from precursors. Langerhans cells (LCs) of the epidermis, although of myeloid origin, were shown to renew in tissues independently from the bone marrow, suggesting the existence of a dermal or epidermal progenitor. We investigated the mechanisms involved in LC development and homeostasis. We observed that a single wave of LC precursors was recruited in the epidermis of mice around embryonic day 18 and acquired a dendritic morphology, major histocompatibility complex II, CD11c, and langerin expression immediately after birth. Langerin+ cells then undergo a massive burst of proliferation between postnatal day 2 (P2) and P7, expanding their numbers by 10–20-fold. After the first week of life, we observed low-level proliferation of langerin+ cells within the epidermis. However, in a mouse model of atopic dermatitis (AD), a keratinocyte signal triggered increased epidermal LC proliferation. Similar findings were observed in epidermis from human patients with AD. Therefore, proliferation of differentiated resident cells represents an alternative pathway for development in the newborn, homeostasis, and expansion in adults of selected myeloid cell populations such as LCs. This mechanism may be relevant in locations where leukocyte trafficking is limited

Spatiotemporally Controlled Cardiac Conduction Block Using High-Frequency Electrical Stimulation

Background: Methods for the electrical inhibition of cardiac excitation have long been sought to control excitability and conduction, but to date remain largely impractical. High-amplitude alternating current (AC) stimulation has been known to extend cardiac action potentials (APs), and has been recently exploited to terminate reentrant arrhythmias by producing reversible conduction blocks. Yet, low-amplitude currents at similar frequencies have been shown to entrain cardiac tissues by generation of repetitive APs, leading in some cases to ventricular fibrillation and hemodynamic collapse in vivo. Therefore, an inhibition method that does not lead to entrainment – irrespective of the stimulation amplitude (bound to fluctuate in an in vivo setting) – is highly desirable. Methodology/Principal Findings: We investigated the effects of broader amplitude and frequency ranges on the inhibitory effects of extracellular AC stimulation on HL-1 cardiomyocytes cultured on microelectrode arrays, using both sinusoidal and square waveforms. Our results indicate that, at sufficiently high frequencies, cardiac tissue exhibits a binary response to stimulus amplitude with either prolonged APs or no effect, thereby effectively avoiding the risks of entrainment by repetitive firing observed at lower frequencies. We further demonstrate the ability to precisely define reversible local conduction blocks in beating cultures without influencing the propagation activity in non-blocked areas. The conduction blocks were spatiotemporally controlled by electrode geometry and stimuli duration, respectively, and sustainable for long durations (300 s). Conclusion/Significance: Inhibition of cardiac excitation induced by high-frequency AC stimulation exhibits a binary response to amplitude above a threshold frequency, enabling the generation of reversible conduction blocks without the risks of entrainment. This inhibition method could yield novel approaches for arrhythmia modeling in vitro, as well as safer and more efficacious tools for in vivo cardiac mapping and radio-frequency ablation guidance applications

Etude de la biologie des cellules de Langerhans

PARIS5-BU Méd.Cochin (751142101) / SudocSudocFranceF

Development of a Reference Model for Keratoconus Progression Prediction Based on Characterization of the Course of Nonsurgically Treated Cases

Purpose: To evaluate and characterize long-term clinical changes in keratoconus cases not requiring surgical treatment because of the absence of clinically significant visual degradation and to design a predictive model for the progression rate. Methods: This retrospective longitudinal study enrolled 68 nonsurgically treated keratoconic eyes of 46 patients (age range, 18–66 years), with a follow-up period of 6 years ± 12 months. Visual, refractive, topographic, and aberrometric changes were evaluated, detecting the abnormal levels of longitudinal changes in each clinical variable analyzed (percentiles 10% or 90%). Subsequently, the eyes were stratified into progression and no-progression groups based on the different variables evaluated, analyzing baseline differences between them. A progression index (PI%) was defined, and its relationship with baseline data was modeled using multiple linear regression analysis. Results: Significant differences were detected in more quantity of baseline parameters between progression and no-progression groups for changes in sphere, spherical-like and coma-like root mean square, central mean keratometry (KM3mm), corneal asphericity (Q80mm), and central astigmatism (Ast3mm). The progression index (PI%) was defined using these variables, obtaining a mean value of 24.39 ± 51.09% and a median of 1.85%. This parameter was significantly related to the baseline sphere, K23 mm (steepest central keratometry), and Q80 mm (P < 0.001, R2 = 0.429). Conclusions: More pronounced progression seems to be present in myopic eyes with central localized steepening but normal mid-periphery flattening. A new index has been defined to characterize and predict the level of progression in nonsurgically treated keratoconus in a medium–long term.D. P. Piñero has been supported by the Ministry of Economy, Industry and Competitiveness of Spain, within the program Ramón y Cajal, RYC-2016-20471