ß-Cell Insulin Resistance Plays a Causal Role in Fat-Induced ß-Cell Dysfunction In Vitro and In Vivo.

In the classical insulin target tissues of liver, muscle, and adipose tissue, chronically elevated levels of free fatty acids (FFA) impair insulin signaling. Insulin signaling molecules are also present in ß-cells where they play a role in ß-cell function. Therefore, inhibition of the insulin/insulin-like growth factor 1 pathway may be involved in fat-induced ß-cell dysfunction. To address the role of ß-cell insulin resistance in FFA-induced ß-cell dysfunction we co-infused bisperoxovanadate (BPV) with oleate or olive oil for 48 hours in rats. BPV, a tyrosine phosphatase inhibitor, acts as an insulin mimetic and is devoid of any antioxidant effect that could prevent ß-cell dysfunction, unlike most insulin sensitizers. Following fat infusion, rats either underwent hyperglycemic clamps for assessment of ß-cell function in vivo or islets were isolated for ex vivo assessment of glucose-stimulated insulin secretion (GSIS). We also incubated islets with oleate or palmitate and BPV for in vitro assessment of GSIS and Akt (protein kinase B) phosphorylation. Next, mice with ß-cell specific deletion of PTEN (phosphatase and tensin homolog; negative regulator of insulin signaling) and littermate controls were infused with oleate for 48 hours, followed by hyperglycemic clamps or ex vivo evaluation of GSIS. In rat experiments, BPV protected against fat-induced impairment of ß-cell function in vivo, ex vivo, and in vitro. In mice, ß-cell specific deletion of PTEN protected against oleate-induced ß-cell dysfunction in vivo and ex vivo. These data support the hypothesis that ß-cell insulin resistance plays a causal role in FFA-induced ß-cell dysfunction.

Preservation of histology by phenol-based fixative: mini review of recent findings / Preservación de la histología mediante un fijador basado en fenol: una mini revisión de los hallazgos recientes

SUMMARY: In surgical and anatomical training, use of cadaver remains the most ideal technique. Standard formaldehyde solution preserves cadaveric tissues for an extended period comparing to the unfixed tissues. However, it fails to retain the natural texture, color, and biomechanical features. Phenol based soft embalming methods were developed to maintain these properties, while simultaneously decreasing the biohazard risk. Soft embalming techniques have made the bodies more 'lifelike' and wellfitted for training. Though phenol fixation displays rewarding morphological maintenance, we have scanty evidences on the histological preservation. This mini review primarily discussed the latest reports regarding the effect of phenol-based fixation on the tissue histology. Published literatures revealed phenol-based fixation displayed comparable histological preservation to that ofgold standard paraformaldehyde-based solution. It was concluded that phenol-based solution is an excellent fixative used to preserve tissues for microscopic analysis.

RESUMEN: En el entrenamiento quirúrgico y anatómico, el uso de cadáveres sigue siendo la técnica más ideal. La solución estándar de formaldehído conserva los tejidos cadavéricos durante un período prolongado en comparación con los tejidos no fijados. Sin embargo, no conserva la textura, el color y las características biomecánicas naturales. Se desarrollaron métodos de embalsamamiento blando a base de fenol para mantener estas propiedades y, al mismo tiempo, disminuir el riesgo biológico. Las técnicas de embalsamamiento suaves han hecho que los cuerpos sean más "realistas" y estén mejor preparados para la enseñanza. A pesar que la fijación de fenol muestra un buen mantenimiento morfológico, existe evidencia escasa sobre la preservación histológica. Esta mini revisión se refirió principalmente a los últimos informes sobre el efecto de la fijación en base de fenol en la histología del tejido. La literatura publicada reveló que la fijación a base de fenol mostró una preservación histológica comparable a la de la solución a base de paraformaldehído. Se concluyó que la solución a base de fenol es un excelente fijador utilizado para preservar tejidos para análisis microscópico.