Radiation exposure of vascular surgery patients beyond endovascular procedures

BackgroundMedical imaging evaluations provide valuable information and are often imperative in the care of our patients. Radiation exposure in patients who undergo medical imaging procedures is not routinely monitored and the associated risks are often underestimated.MethodsRadiation exposure associated with computed tomography (CT) angiography and coronary intervention is reviewed.ResultsVascular surgeons are often involved in the decision-making process in roughly 30% of CT scans performed that are believed to be unnecessary. Society for Vascular Surgery (SVS) practice guidelines for patients with abdominal aortic aneurysms recommended eliminating a 6-month contrast surveillance CT if no endoleak was observed at 1 month after endovascular aneurysm repair (EVAR). Ultrasound and aortic duplex can help eliminate some of the CT scans.ConclusionVascular surgeons must remain vigilant in monitoring radiation exposure for their patients who have potential for coronary and vascular imaging with radiation. Judicious use of alternative imaging modalities when possible and maintaining the dose as low as reasonably achievable (ALARA) is the responsibility of vascular surgeons

Cytoskeletal Dynamics: A View from the Membrane

Many aspects of cytoskeletal assembly and dynamics can be recapitulated in vitro; yet, how the cytoskeleton integrates signals in vivo across cellular membranes is far less understood. Recent work has demonstrated that the membrane alone, or through membrane-associated proteins, can effect dynamic changes to the cytoskeleton, thereby impacting cell physiology. Having identified mechanistic links between membranes and the actin, microtubule, and septin cytoskeletons, these studies highlight the membrane’s central role in coordinating these cytoskeletal systems to carry out essential processes, such as endocytosis, spindle positioning, and cellular compartmentalization

Chiral Optical Stern-Gerlach Newtonian Experiment

We report on a chiral optical Stern-Gerlach experiment where chiral liquid crystal microspheres are selectively displaced by means of optical forces arising from optical helicity gradients. The present Newtonian experimental demonstration of an effect predicted at molecular scale [New J. Phys. 16, 013020 (2014)] is a first instrumental step in an area restricted so far to theoretical discussions. Extending the Stern-Gerlach experiment legacy to chiral light-matter interactions should foster further studies, for instance towards the elaboration of chirality-enabled quantum technologies or spin-based optoelectronics.Initiative d'excellence de l'Université de Bordeau

Chaotic rotations generated by light in nematic liquid crystals

Various nonlinear rotation regimes are observed in an optically excited nematic liquid crystal film under boundary conditions (for the light and the material) that are invariant by rotation. Th excitation light is circularly polarized, the intensity profile is circularly symmetric and the beam diameter at the sample location is a few times smaller than the cell thickness. A transition to chaos via quasiperiodicity is identified when the light intensity is taken as the control parameter. Transverse nonlocal effects are suggested to be the cause of the observed dynamics and a simple model consisting of a collection of coupled rotators is developed to provide a qualitative explanation

Mise en place de modèles cellulaires pour l'étude de l'absorption des médicaments

Le passage des barrières épithéliales constitue une étape limitante pour l absorption des médicaments. Dans le but de tester in vitro l efficacité de lipoaminoacides, promoteurs d absorption breveté par la société Physica Pharma, j ai mis en place au laboratoire deux modèles cellulaires de barrières épithéliales. Le premier modèle est un modèle de barrière épithéliale intestinale constitué par la lignée cellulaire humaine immortalisée, les cellules de colon Caco-2. Le deuxième modèle est un modèle de barrière épithéliale nasale constitué par des cultures primaires de cellules épithéliales nasales humaines issues d actes chirurgicaux. La perméabilité de quatre principes actifs a été étudiée sur ces modèles, en présence ou en absence de différents lipoaminoacides. Les études in vitro ont montré une augmentation de la perméabilité des molécules d intérêt, liée à l ouverture des jonctions intercellulaire, en présence des promoteurs d absorption. A l issu de ce travail, plusieurs formulations ont été sélectionnées pour des études précliniques sur l animal entier. Le modèle de barrière intestinale n a pas permis de prédire l absorption in vivo. En effet, les études de l administration par voie orale in vivo chez le chien n ont pas pu être corrélées avec les résultats in vitro. En revanche, ce travail de thèse a permis de valider un modèle de barrière épithéliale nasale pour l étude de la perméabilité de molécules à destinée nasale, qui a été validé par des études in vivo chez le mouton. Les cultures cellulaires mises en place ont donné un aspect qualitatif et non quantitatif des évènements complexes qui se produisent in vivo.The passage of the epithelial barriers constitutes a stage limiting for the absorption of drugs. With the aim of testing in vitro the effectiveness of lipoaminoacids, patented by the company Physica Pharma, as promoters of absorption, I set up at the laboratory two cellular models of epithelial barriers. The first model is a model of intestinal barrier constituted by immortalized human cells, the colon Caco-2 cell line. The second model is a model of nasal epithelial barrier consisting of primary cultures of human nasal epithelial cells available from surgical acts. The permeability of four active drugs was studied on these models. The in vitro studies showed an increase in the permeability of drugs, in the presence of different lipoaminoacids, owing to the opening of the intercellular junctions. From this work, several formulations were selected for preclinical studies on the whole animal. The intestinal model barrier didn t predict absorption in vivo. Indeed, the in vivo oral absorption studies carried out on the dog could not be correlated with the in vitro results. On the other hand, this work validates an epithelial nasal barrier model for permeability studies of molecules administered by nasal airway, which was validated by in vivo studies in the sheep. Cell cultures gave a qualitative but not a quantitative aspect of the complex events which occur in vivo.NICE-BU Sciences (060882101) / SudocSudocFranceF

Transverse nonlocal effects in optical reorientation of nematic liquid crystals

We reexamine the optical reorientation of a homeotropic nematic-liquid-crystal film under finite beam-size excitation and linear polarization. We study the case of normal and oblique incidence (extraordinary wave). Under the most basic assumptions (geometrical optics approximation, elastic isotropy) we systematically analyze the dependence of transverse nonlocal effects as a function of the angle of incidence, the beam size, and the intensity. Besides recovering some well-known results (Fréedericksz transition threshold and spatial extension of the molecular reorientation as a function of the beam size), we identify a series of nonmonotonous behaviors of the material response as well as shape variations of the reorientation profiles

Dynamics of light induced reorientation of nematic liquid crystals in spatially confined beams

Optically induced reorientation dynamics in a nematic liquid crystal is investigated for circularly polarized laser beams with spot sizes smaller than the sample thickness. Various dynamical regimes, such as periodic, quasi-periodic, intermittent, self-organized and possibly chaotic regimes are observed. The role finite beam size is identified and a qualitative interpretation based on the spatial walk-off of the ordinary and extraordinary beams arising from double refraction phenomenon is proposed