The sand rat, Psammomys obesus, develops type 2 diabetic retinopathy similar to humans.

PURPOSE: Diabetic retinopathy (DR) is a leading cause of blindness, yet pertinent animal models are uncommon. The sand rat (Psammomys obesus), exhibiting diet-induced metabolic syndrome, might constitute a relevant model. METHODS: Adult P. obesus (n = 39) were maintained in captivity for 4 to 7 months and fed either vegetation-based diets (n = 13) or standard rat chow (n = 26). Although plant-fed animals exhibited uniform body weight and blood glucose levels over time, nearly 60% of rat chow-raised animals developed diabetes-like symptoms (test group). Animals were killed, and their eyes and vitreous were processed for immunochemistry. RESULTS: Compared with plant-fed animals, diabetic animals showed many abnormal vascular features, including vasodilation, tortuosity, and pericyte loss within the blood vessels, hyperproteinemia and elevated ratios of proangiogenic and antiangiogenic growth factors in the vitreous, and blood-retinal barrier breakdown. Furthermore, there were statistically significant decreases in retinal cell layer thicknesses and densities, accompanied by profound alterations in glia (downregulation of glutamine synthetase, glutamate-aspartate transporter, upregulation of glial fibrillar acidic protein) and many neurons (reduced expression of protein kinase Cα and Cξ in bipolar cells, axonal degeneration in ganglion cells). Cone photoreceptors were particularly affected, with reduced expression of short- and mid-/long-wavelength opsins. Hypercaloric diet nondiabetic animals showed intermediate values. CONCLUSIONS: Simple dietary modulation of P. obesus induces a rapid and severe phenotype closely resembling human type 2 DR. This species presents a valuable novel experimental model for probing the neural (especially cone photoreceptor) pathogenic modifications that are difficult to study in humans and for screening therapeutic strategies.journal articleresearch support, non-u.s. gov't2011 Nov 212011 11 21importe

Corrélations entre méthode de préparation, hauteur de barrière et états d'interface dans les contacts métal-GaAs

Interface states distribution in metal-semiconductor contacts can be determined by studying variations of Schottky diode capacitance as a function of frequency, temperature and forward bias. This method, called Schottky Capacitance Spectroscopy is applied to contacts between Ag, Au, Al and diversely prepared surfaces : cleavage under ultra-high vacuum or controlled gazeous atmosphere, cleavage followed by ion-bombardment, chemical etch, molecular beam epitaxy. So, the rôle played by a great number of physical parameters on interface states distribution and barrier height can be determined. It is established that only the creation of a severely perturbed interfacial zone of a few angströms width can significantly modify the properties of the barrier.La distribution des états d'interface dans un contact métal-semiconducteur peut être déterminée à partir de l'étude du comportement de la capacité dynamique d'une diode Schottky sous polarisation directe en fonction de la fréquence, la température et la tension appliquée. Cette méthode, appelée Spectroscopie de Capacité Schottky est appliquée à des dépôts d'Ag, Au et Al sur des surfaces de GaAs préparées de manières très diverses : clivage sous ultravide ou sous gaz, clivage suivi de bombardement ionique, nettoyage chimique, épitaxie par jets moléculaires. Ceci permet de tester le rôle joué par un grand nombre de paramètres sur la distribution des états d'interface et la hauteur de barrière. On constate que ces propriétés ne sont affectées de manière importante que par la création d'une zone interfaciale fortement perturbée, s'étendant sur plusieurs couches atomiques

Chloroform leaf extract of Daphne gnidium inhibits growth of melanoma cells and enhances melanogenesis of B16-F0 melanoma

AbstractThe antiproliferative potential of chloroform, methanol and butanol extracts from Daphne gnidium leaves on B16-F0 and B16F-10 melanoma cells was assessed. Cell viability was determined using the MTT assay, and flow cytometry was used to analyse effects of extract on progression through the cell cycle and apoptosis. In addition, amounts of melanin and tyrosinase activity were measured spectrophotometrically at 475nm. Chloroform extract exhibited significant anti-proliferative activity after incubation with the two types of tumour skin cells. Increase of tyrosinase activity, and of melanin synthesis which are markers of differentiation of malignant melanoma cells, were observed with the chloroform extract. Furthermore, cell cycle analysis revealed that B16-F0 and B16-F10 cells treated with chloroform extract were arrested predominantly in S phase