Biomedical subjects

Jacques Didelon

Publications and source records attributed to Jacques Didelon.

4 recordsLinked to original sources

PubMed2007

Gap junctional intercellular communication capacity by gap-FRAP technique: a comparative study.

Gap junctions play an important role in vital functions, including the regulation of cell growth and cell differentiation. Connexins 43 (Cx43) are the most widely expressed gap junction proteins. Cellular localization of phosphorylated Cx43 has been implicated in the capacity of gap junctional intercellular communication (GJIC). To follow the functionality of GJIC of different cell types, in monolayer cultures, characterized by different patterns of phosphorylated Cx43, we used a fluorescence recovery after photobleaching (FRAP) technique, and compared two tracers, 5(6)-carboxyfluorescein diacetate (CFDA) and calcein acetoxymethylester (AM). The GJIC capacity was quantified by estimating fluorescence redistribution parameters. The functionality of GJIC was in relation with the staining localization of phosphorylated Cx43 to the cell-cell contact areas, corresponding to gap junctions between contacting cells. GJIC involvement in fluorescence restitution after photobleaching was checked by a gap junction channel inhibition assay. We demonstrated that the choice of the dye did not significantly influence the fluorescence recovery percentages despite a cell line-dependent CFDA release, whereas it had an important impact on fluorescence kinetic profiles. This study reinforces the interest of the gap-FRAP approach to quantify modifications in the functionality of gap junctions and, above all, argues about the limits of CFDA for 3-D future approaches.

Cell Communication↗

PubMed2005

The 2-aminoglucosamide motif improves cellular uptake and photodynamic activity of tetraphenylporphyrin.

Several strategies have been proposed to improve the efficiency of photosensitizers used in photodynamic therapy (PDT). In this context, the synthesis of mono- (1) and di-glucosylated (2) porphyrins, and mono-glucosylated chlorin (3) was performed. HT29 human adenocarcinoma cells were significantly more sensitive to asymmetric and less hydrophobic glucosylated photosensitizers-mediated PDT (1, 3), compared to tetraphenylporphyrin (TPP). The lowest photosensitivity observed for TPP was consistent with the lowest uptake. Moreover, the most pronounced photodynamic activity measured for 3 was in relation with the improvement of cellular uptake, the singlet oxygen quantum yield and the high extinction coefficient value at 650 nm compared to porphyrins. Cellular localization analysis showed that 1 and 3 accumulated mainly inside the endoplasmic reticulum.

Cell Proliferation↗

PubMed2005

Experimental comparison between autofluorescence spectra of constrained fresh and cryopreserved arteries.

The study of mechanical properties of the arterial wall is an important step in the comprehension of the vascular physiopathological functioning. However, cryopreserving biological tissues using very low temperatures can induce biological and structural modifications which may involve complications (dilatation, bursting, stenosis) after reimplantation. Many procedures of mechanical tests (traction, dilatation) developed in research allow us to comprehend and analyse rheological behaviour of the arterial wall. The study presented in this article offers a new perspective to detect changes of mechanical properties of cryopreserved arterial samples. In fact, the original idea is to couple a mechanical test bed (uniaxial traction of arterial rings) with spectroscopic measurements (autofluorescence) for the purpose of correlating mechanical modifications and spectral variations. Ultimately, this new approach could lead to develop a device allowing atraumatic and contactless optical examinations of arterial graft to determine its mechanical state before reimplantation.

Animals↗

PubMed2002

Biodistribution of hypericin in orthotopic transitional cell carcinoma bladder tumors: implication for whole bladder wall photodynamic therapy.

In a recent clinical study, we reported a selective uptake of hypericin in superficial bladder tumors. The results suggested that hypericin, a potent photosensitizer, could be used not only for diagnosis but also for photodynamic therapy (PDT) of superficial bladder tumors. In the present study, we investigated the biodistribution of hypericin in an orthotopic rat bladder tumor model by assessing the extent of hypericin penetration and the kinetics of accumulation into rat bladder tumors and normal bladder wall. Hypericin (8 or 30 microM) was instilled into the bladder via the catheter for 1, 2 or 4 hr. The fluorescence of hypericin in the bladder tumors and normal bladder was documented using fluorescence microscopy. In situ quantification of hypericin fluorescence in the tumor or normal bladder was performed using the laser-induced fluorescence technique. There was much more hypericin fluorescence in the tumor than in the normal bladder, with the tumor-to-normal-bladder ratio mounting to 12:1 after 4 hr of hypericin (30 microM) instillation. Moreover, hypericin was retained in the tumor for at least 1 hr before it was gradually lost from the tissue. Microscopically, the fluorescence of hypericin was restricted to the urothelial tumor and normal urothelium without fluorescence in the submucosa and the muscle layers. Subsequently no hypericin was detected in plasma, indicating that under these conditions systemic side effects should not be expected. Because the conditions used in this study were similar to those used in our previous clinical study, it is therefore likely that whole bladder wall PDT in the clinic under these conditions will produce selective urothelial tumor destruction without causing damage to the underlying muscle layers.

Animals↗