Imaging lipid bodies in cells and tissues using third-harmonic generation microscopy.

International audienceLipid bodies have an important role in energy storage and lipid regulation. Here we show that lipid bodies are a major source of contrast in third-harmonic generation (THG) microscopy of cells and tissues. In hepatocytes, micrometer-sized lipid bodies produce a THG signal 1-2 orders of magnitude larger than other structures, which allows one to image them with high specificity. THG microscopy with approximately 1,200 nm excitation can be used to follow the distribution of lipid bodies in a variety of unstained samples including insect embryos, plant seeds and intact mammalian tissue (liver, lung). We found that epi-THG imaging is possible in weakly absorbing tissues because bulk scattering redirects a substantial fraction of the forward-generated harmonic light toward the objective. Finally, we show that the combination of THG microscopy with two-photon and second-harmonic imaging provides a new tool for exploring the interactions between lipid bodies, extracellular matrix and fluorescent compounds (vitamin A, NADH and others) in tissues

Comparing pharmacologic measures of tenofovir exposure in a U.S. pre-exposure prophylaxis randomized trial

<div><p>It is critical to assess adherence to pre-exposure prophylaxis (PrEP) in clinical trials. The relationship between pharmacokinetic measures of PrEP adherence and other adherence measures used in PrEP trials requires further characterization. Plasma, peripheral blood mononuclear cells (PBMCs), and hair samples were collected from 88 HIV-uninfected men who have sex with men in a placebo-controlled randomized PrEP trial; announced pill counts, medication electronic monitoring (MEMS), and self-report using visual analog scale (VAS) were also collected. Tenofovir (TFV or TFV-DP) in plasma, hair, and PBMCs were quantified. Proportions with drug detection, Spearman correlation coefficients, and univariate and multivariable regression models were used. Drug detection in plasma, PBMC, and hair samples was highly concordant with treatment arm assignment. TFV or TFV-DP levels were detected in most active-arm participants: 44/47 (94%) in plasma, 46/47 (98%) in hair, and 44/47 (94%) in PBMCs and in only 1/41 placebo arm participant. Correlation coefficients were r = 0.59 for plasma and PBMC, r = 0.34 for PBMC and hair and r = 0.36 for plasma and hair. MEMS and announced pill-counts were moderately correlated (r = 0.52) but less so with pharmacologic measures (range of r = 0.12 to 0.38). Self-reported adherence by visual analog scale demonstrated essentially no correlation with drug levels (r = 0.06 for hair, PBMC or plasma) and was a poor indicator of exposure to study product. Indices of drug exposure are important indicators in assessing adherence to PrEP; accounting for variability between measures may improve interpretation and use of adherence measures in future PrEP studies.</p><p>Clinical trial registration</p><p>Clinical Trials.gov <a href="https://clinicaltrials.gov/ct2/show/NCT00131677" target="_blank">NCT00131677</a></p></div