Mécanismes fondamentaux et dynamique d'interdiffusion dans les boîtes quantiques auto-assemblées INAS/INP

Généralités sur les BQ InAs/InP -- Principes physiques et techniques d'interdiffusion -- État des structures après croissance et influence du recuit conventionnel -- Interdiffusion assistée par les défauts de croissance -- Interdiffusion assistée par implantation ionique

Laser-Based Single-Axon Transection for High-Content Axon Injury and Regeneration Studies

The investigation of the regenerative response of the neurons to axonal injury is essential to the development of new axoprotective therapies. Here we study the retinal neuronal RGC-5 cell line after laser transection, demonstrating that the ability of these cells to initiate a regenerative response correlates with axon length and cell motility after injury. We show that low energy picosecond laser pulses can achieve transection of unlabeled single axons in vitro and precisely induce damage with micron precision. We established the conditions to achieve axon transection, and characterized RGC-5 axon regeneration and cell body response using time-lapse microscopy. We developed an algorithm to analyze cell trajectories and established correlations between cell motility after injury, axon length, and the initiation of the regeneration response. The characterization of the motile response of axotomized RGC-5 cells showed that cells that were capable of repair or regrowth of damaged axons migrated more slowly than cells that could not. Moreover, we established that RGC-5 cells with long axons could not recover their injured axons, and such cells were much more motile. The platform we describe allows highly controlled axonal damage with subcellular resolution and the performance of high-content screening in cell cultures

Disclosure of HSV-2 serological test results in the context of an adolescent HIV prevention trial in Kenya

HSV-2 biomarkers are often used in adolescent sub-Saharan HIV prevention studies, but evaluations of test performance and disclosure outcomes are rare in the published literature. Therefore, we investigated the proportion of ELISA-positive and indeterminant samples confirmed by Western blot (WB); the psychosocial response to disclosure; and whether reports of sexual behavior and HSV-2 symptoms are consistent with WB confirmatory results among adolescent orphans in Kenya

Analysis of pulsatile retinal movements by spectral-domain low-coherence interferometry: influence of age and glaucoma on the pulse wave.

Recent studies have shown that ocular hemodynamics and eye tissue biomechanical properties play an important role in the pathophysiology of glaucoma. Nevertheless, better, non-invasive methods to assess these characteristics in vivo are essential for a thorough understanding of degenerative mechanisms. Here, we propose to measure ocular tissue movements induced by cardiac pulsations and study the ocular pulse waveform as an indicator of tissue compliance. Using a novel, low-cost and non-invasive device based on spectral-domain low coherence interferometry (SD-LCI), we demonstrate the potential of this technique to differentiate ocular hemodynamic and biomechanical properties. We measured the axial movement of the retina driven by the pulsatile ocular blood flow in 11 young healthy individuals, 12 older healthy individuals and 15 older treated glaucoma patients using our custom-made SD-OCT apparatus. The cardiac pulse was simultaneously measured through the use of an oximeter to allow comparison. Spectral components up to the second harmonic were obtained and analyzed. For the different cohorts, we computed a few parameters that characterize the three groups of individuals by analyzing the movement of the retinal tissue at two locations, using this simple, low-cost interferometric device. Our pilot study indicates that spectral analysis of the fundus pulsation has potential for the study of ocular biomechanical and vascular properties, as well as for the study of ocular disease

Schematic diagram of a FD-LCI system.

<p>Schematic diagram of a FD-LCI system.</p

Eye movement at the macula and optic disk region was investigated for the three subject groups.

<p>In (a) are compared the effective amplitude of the movement, in (b) the FFT integrated amplitude ratio between the movement fundamental frequency and the movement second harmonic, in (c) the phase shift between the movement fundamental frequency with respect to the oximeter signal fundamental frequency, and in (d) the phase shift between the movement second harmonic with respect to movement fundamental frequency.</p

Representative data and movement analysis.

<p>(a) Typical A-scan produced by the retina where the nerve fiber layer (NFL) and retinal pigment epithelium (RPE) are clearly observed. (b) Position of the retina in the macula region as a function of time along with oximeter signal, as recorded by the SD-LCI for a 30-years-old normal female subject. Movement and oximeter signal FFT analysis are shown in (c) and (d).</p

Disclosure of HSV-2 serological test results in the context of an adolescent HIV prevention trial in Kenya

OBJECTIVES: HSV-2 biomarkers are often used in adolescent sub-Saharan HIV prevention studies, but evaluations of test performance and disclosure outcomes are rare in the published literature. Therefore, we investigated the proportion of ELISA-positive and indeterminant samples confirmed by Western blot (WB); the psychosocial response to disclosure; and whether reports of sexual behavior and HSV-2 symptoms are consistent with WB confirmatory results among adolescent orphans in Kenya. METHODS: In 2011, 837 Kenyan orphan youth in grades 7 and 8 enrolled in an HIV prevention clinical trial with HSV-2 biomarker outcomes. We used a modified algorithm for the Kalon HSV-2 ELISA to improve specificity; positive and indeterminate results were WB-tested. We developed culturally sensitive protocols for disclosing positive results and documented psychosocial responses, reports of sexual contact, and HSV-2 symptoms. RESULTS: 28 adolescents (3.3%) were identified as HSV-2 seropositive; 6 as indeterminate. Of these, 22 positive and all indeterminants were WB-tested; 20 and 5, respectively, were confirmed positive. Most youth reported moderate brief stress after disclosure; 22% reported longer and more severe distress. Boys were more likely to be in the latter category. Self-reported virginity was highly inconsistent with WB confirmed positives. CONCLUSIONS: The higher than manufacturer cut-off for Kalon ELISA modestly reduced the rate of false positive test results but also increased false negatives. Investigators should consider the risk-benefit ratio in deciding whether or not to disclose HSV-2 results to adolescent participants under specific field conditions