Comparison of arterial wall integration of different flow diverters in rabbits: The CICAFLOW study

BACKGROUND AND PURPOSE

New coated flow diverters (FDs) claim antithrombotic properties and increased arterial wall integration. The aim of this study is to compare in vivo endothelial coverage of coated and uncoated FD in the context of different antiplatelet regimens.

METHODS

Different FDs (Silk Vista - SV, Pipeline with Shield technology - PED shield and Surpass Evolve - SE) were implanted in the aorta of rabbits, all 3 in each animal with 3 different antiplatelet regimens: no antiplatelet therapy, aspirin alone, or aspirin and ticagrelor. Four weeks after FD implantation, angiography, flat-panel CT, and optical coherence tomography (OCT) were performed before harvesting the aorta. Extensive histopathology analyses were performed including environmental scanning electron microscopy (ESEM), multiphoton microscopy (MPM) and histological staining with qualitative and/or quantitative assessment of device coverage.

RESULTS

All 23 FDs that were implanted remained patent without hyperplasia. Qualitative stent coverage assessment revealed that there were no statistically significant differences between the FD groups (p = 0.19, p = 0.45, p = 0.40, and p = 0.84 for OCT, ESEM, MPM and histology, respectively). Quantitative neointimal measurement of histological sections also showed similar results in all 3 FD groups (p = 0.70). However, there were significant differences between the 3 groups of antiplatelet regimens (p = 0.07) with a higher rate in the no antiplatelet group (p = 0.05 versus aspirin alone and p = 0.03 versus aspirin and ticagrelor).

CONCLUSION

Our study provides evidence that FD integration into the arterial wall is similar with coated (PED shield) and uncoated devices (SV, SE), regardless of the antiplatelet regimen. FD integration with specific surface coverage should be promoted.

TRIAL REGISTRATION

APAFIS #2022011215518538.

[Methodology of neuroepidemiological studies in tropical countries: a challenge?]

The purpose of this paper is to highlight the difficulties of applying neuroepidemiological methods in low income countries or developing countries, which are mostly tropical countries, taking advantage of the experience of the Institute of Neuroepidemiology and Tropical Neurology, which was created in Limoges in 1982. These difficulties could be related to several aspects: methodological, logistical, political or economical, linked to ethical issues, even difficulties to publish the studies. However, concept and neuroepidemiological methods should stay the same worldwide, even if their translation into practice could sometimes raise some problems in developing countries. Study protocol should be more detailed. Some specific epidemiological methods could be useful. Collection of data should be standardized. True cooperation at every level is needed for these researches to be valid.

[Epidemiology of epilepsy in sub-Saharan Africa: a review]

Epilepsy is, above all tropical, moreover, very african in its frequency and gravity. Data on the prevalence of epilepsy shows it to be two or three times more prevalent in tropical zones than in industrialized countries in non tropical areas, however it is rare to find data on the incidence and prognosis of epilepsy in sub-Saharan Africa. It is difficult to determine the relative contribution of each of the causes of epilepsy. Only a few case-control studies have been carried out in sub-Saharan Africa. Infectious diseases, in particular parasitic diseases such as neurocysticercosis or cerebral malaria, seem to be the cause of the majority of the cases of epilepsy. However it is necessary to do additional epidemiological studies to determine the etiologies of epilepsy more precisely in sub-Saharan Africa.

Epilepsy and traditional medicine in Bobo-Dioulasso (Burkina Faso)

OBJECTIVES

To contribute to a better knowledge of how epilepsy is perceived by traditional healers in Burkina Faso; what means they use to treat it, and how they think about modern treatment.

MATERIAL AND METHODS

Individual interviews with 65 traditional healers chosen at random from members of the Reelwende Association.

RESULTS

All traditional practitioners were of male gender. Most of them were above 50 years of age, and 75% had more than 10 years' experience. Epilepsy was considered to be contagious by 44% of the traditional practitioners, and hereditary according to 40% of them. Roughly, 15% of the healers think that the problem is localized in the head of a person and 7.8% think that they have worms in their head. Thirty-one per cent of them diagnose epilepsy if there is a combination of 'convulsions, sudden fall, dribbling and amnesia'. Another 15% require a combination of 'convulsions, amnesia and dribbling', the remaining 54% make the diagnosis based on one symptom or various combinations of two symptoms of 'grand mal' (generalized tonic clonic) seizures and most claim they have a treatment for it. For a quarter of them, therapeutic-means include concoctions of herbs or roots, baths and infusions. During the fit, 31% of the traditional practitioners think that nothing should be performed. According to 75% of them, traditional and modern treatments are complementary.

CONCLUSION

Notwithstanding important differences in culture and religions (Muslim, Christian and Original), there is great similarity between the knowledge and beliefs about epilepsy reported from other parts of Africa and those presented by our study-group, suggesting an ancient origin of the concepts. Further study is needed to find out how other facets of epilepsy (e.g. complex partial seizures, absences) are perceived and how these are being treated. Ways need to be found to raise awareness about epilepsy without interfering with religious and cultural beliefs.

[Cyclosporin A eyedrops: manufacturing, toxicity, pharmacokinetics and indications in 2000]

INTRODUCTION

Cyclosporin eye-drops allow local immunoregulation without systemic side effects and is an alternate to local steroids. In this article we review specific problems of product setup and clinical studies published over the past 20 years. PRODUCT SETUP: The main problems in eye-drop preparation are sterility, pH, particles, and its lipophilic properties. Numerous excipients have been tested including oil solvents, alphacyclodextrin, collagen shields, liposomes, polyester nanocapsules, but documentation on stability of the molecule is inadequate.

TOXICITY

Epithelial toxicity is well known and is probably mainly due to the excipient. No endothelial toxicity has been described in vivo. Repeated doses lead to uveal reactions in animals, which could limit the indications for intraocular diseases.

PHARMACOKINETICS

Bioavailability is mainly limited by the lipophilic properties. Oil excipients, the most widely used, lead to good corneal penetration but low intraocular concentrations. Cyclosporin bioavailability is improved when using hydrophilic excipients.

INDICATIONS

Every ocular surface disease that involves cytokines is a potential indication for cyclosporine eyedrops: keratoconjunctivitis sicca, vernal keratitis, adjuvant therapy of filtering surgery, stromal herpes keratitis, immunity limbal keratitis, and Thygeson's keratitis. There is biological evidence of efficacy, and encouraging results from many studies, yet few have tested a large number of patients. A large multicenter study on dry eye is currently in progress.

Rheological behavior of drug suspensions in Gelucire mixtures and proxyphylline release from matrix hard gelatin capsules

Mixtures of Gelucires 50/02 and 50/13 showing different hydrophilic-lipophilic balances (HLB) and of proxyphylline were used to prepare suspensions at a concentration of 25% and to manufacture extended release hard gelatin capsules by cooling. The rheological behaviors of Gelucire mixtures with and without drug were determined by adjustment of the rheograms to the Ostwald power-law and by statistical assessment of the flow index. Pure Gelucire mixtures were very slightly shear thickening whereas proxyphylline suspensions had a thixotropic shear thinning behavior. These rheological behaviors can be explained by the chemical composition and by the ratio of the two Gelucires used. Extended release of proxyphylline was obtained with all these mixtures. Drug release increased with Gelucire mixture HLB owing to higher erosion. A viscosity-release relationship was found and allowed, with these two Gelucires of extreme HLB and viscosities, to define the formulations which will give an optimal drug release, by the determination of their suspension viscosity. Modeling of dissolution kinetics has generally shown the predominance of surface erosion of the plugs relative to drug diffusion inside the matrix. This was confirmed by the better linearization of percentage released, according to Hixson-Crowell as compared with Higuchi.

Effect of formulation on the rheology of theophylline compound suspensions in Gelucires

The theophylline derivatives, etofylline, diprophylline and proxyphylline, which exhibit increasing aqueous solubility, were used to prepare suspensions in seven saturated polyglycolyzed glycerides (Gelucires) characterized by their rising hydrophilic-lipophilic balance (HLB). Drug concentration was set at 25% w/w and the production temperature was set at the Gelucire melting point plus 30 degrees C in order to obtain suitable suspensions. Various formulation factors were studied. Ostwald flow indices revealed that the suspensions had a thixotropic shear-thinning behaviour and a relative viscosity which increased as drug aqueous solubility rose and Gelucire HLB decreased. These rheological properties could be explained by the chemical composition of Gelucires and drugs used. A microstructure was proposed for the liquid suspension such that colloidal particles and aggregates formed in these suspensions directly influenced the observed rheological properties. Observation of solidified suspensions by scanning electron microscopy confirmed this hypothesis. Moreover, a correlation between the relative viscosity of drug suspensions on the one hand and drug concentration, drug solubility and Gelucire HLB on the other allowed for the calculation of the required concentration of each theophylline derivative in each Gelucire to obtain a given viscosity.

Rheological behaviour of saturated polyglycolysed glycerides

Seven saturated polyglycolysed glycerides (Gelucires) of melting points varying from 42 to 53 degrees C and hydrophilic-lipophilic balance values from 2 to 14 were selected. Their rheological behaviour was determined by adjustment of the flow curves to the Ostwald power-law and by statistical assessment of the flow index. The flow of Gelucires was slightly shear thickening. This shear thickening rose when the temperature and the lipophilic specificity of the Gelucire increased. This behaviour accounted for a reorganization of the particles under the shear which became easier when the temperature increased and when the degree of condensation of the polyethylene glycol chains decreased with lipophilicity of the Gelucires.