Enhancement by streptozotocin of O−2 radical generation by the xanthine oxidase system of pancreatic β-cells

AbstractSpin-trapping techniques and electron spin resonance (ESR) spectroscopy were used to study the relationship between the effect of streptozotocin (STZ) on pancreatic β-cells and free radical formation by these cells. Results showed that STZ enhanced generation of the DMPO-OH radical adduct, which is a degradation product of the superoxide anion (O−2) in the presence of cellular components, in a hypoxanthine-xanthine oxidase (XOD) system with a homogenate of β-cells. This enhancing effect was also observed in a system without cellular components; STZ increased the signal height due to the O−2 radical in a concentration-dependent manner and caused a maximum of 150% enhancement at a concentration of 1.5 mM. Thus, STZ seemed to enhance the generation of the O−2 radical in the XOD system, probably by some mechanism of its interaction with XOD. Pancreatic β-cells exhibited a high XOD activity and a very low superoxide dismutase activity. Therefore, the present result supports the possibility that the cytotoxic effect of STZ is closely related to free radical generation in pancreatic β-cells

IGF-1 Induction by Acylated Steryl β-Glucosides Found in a Pre-Germinated Brown Rice Diet Reduces Oxidative Stress in Streptozotocin-Induced Diabetes

BACKGROUND: The pathology of diabetic neuropathy involves oxidative stress on pancreatic β-cells, and is related to decreased levels of Insulin-like growth factor 1 (IGF-1). Acylated steryl β-glucoside (PR-ASG) found in pre-germiated brown rice is a bioactive substance exhibiting properties that enhance activity of homocysteine-thiolactonase (HTase), reducing oxidative stress in diabetic neuropathy. The biological importance of PR-ASG in pancreatic β-cells remains unknown. Here we examined the effects of PR-ASG on IGF-1 and glucose metabolism in β-cells exposed to oxidative stress. METHODOLOGY/PRINCIPAL FINDINGS: In the present study, a pre-germinated brown rice (PR)-diet was tested in streptozotocin (STZ)-induced diabetic rats. Compared with diabetic rats fed control diets, the PR-diet fed rats showed an improvement of serum metabolic and neurophysiological parameters. In addition, IGF-1 levels were found to be increased in the serum, liver, and pancreas of diabetic rats fed the PR-diet. The increased IGF-1 level in the pancreas led us to hypothesize that PR-ASG is protective for islet β-cells against the extensive injury of advanced or severe diabetes. Thus we examined PR-ASG to determine whether it showed anti-apoptotic, pro-proliferative effects on the insulin-secreting β-cells line, INS-1; and additionally, whether PR-ASG stimulated IGF-1 autocrine secretion/IGF-1-dependent glucose metabolism. We have demonstrated for the first time that PR-ASG increases IGF-1 production and secretion from pancreatic β-cells. CONCLUSION/SIGNIFICANCE: These findings suggest that PR-ASG may affect pancreatic β-cells through the activation of an IGF-1-dependent mechanism in the diabetic condition. Thus, intake of pre-germinated brown rice may have a beneficial effect in the treatment of diabetes, in particular diabetic neuropathy

Japon

Sato Shuichiro, Nukatsuka Yasue. Japon. In: Annuaire international de justice constitutionnelle, 12-1996, 1997. L'école, la religion et la Constitution - Constitution et élections. pp. 781-796

Adsorption of Chondroitin Sulphate a onto Zirconia Nanoparticles

The adsorption equilibria between chondroitin sulphate A (CSA), a polyanionic biopolymer, and zirconium(IV) dioxide (zirconia) nanoparticles were investigated to characterize the extraction of CSA using the metal oxide. Adsorption isotherms were prepared using sample solutions adjusted to pH values in the range 1.5–7.8, employing various buffer systems, NaCl concentrations and temperatures. The maximum amounts of CSA adsorbed, n a m , and the adsorption constants, K L , were calculated from non-linear curve fits to the Langmuir adsorption model. The buffer components suppressed CSA adsorption to varying degrees; however, the reversibility of the adsorption equilibria improved in the presence of the buffers, as indicated by the large values of K L and the small standard deviations. The temperature-dependent adsorption properties showed that a large n a m value was obtained at 318 K. The extraction of glycosaminoglycans with zirconia was optimal in the presence of acetate ions and at high temperatures, and subsequent desorption was achieved using a NaH 2 PO 4 eluent solution

Integration of Solid-phase Extraction with Electrothermal Atomic Absorption Spectrometry for Determination of Trace Elements

An enrichment step in a sample treatment is essential for trace analysis to improve the sensitivity and to eliminate the matrix of the sample. Solid-phase extraction (SPE) is one of the widely used enrichment technique. Electrothermal atomic absorption spectrometry (ETAAS) is a well-established determination technique for trace elements. The integration of SPE with ETAAS leads to further improvement of sensitivity, an automation of the measurement and the economy in the sample size, amounts of the reagents and time for the sample pretreatment. The integration is achieved by introducing the solid phase used for the enrichment directly into ETAAS for a batch method, or on-line coupling of a SPE column with ETAAS. Fine particles of various materials, including an activated carbon, an ion-exchange resin, a cellulose nitrate resin and biomass materials were used as adsorbents for batch method. A membrane filterwas also used. A simultaneous multi-elements extraction and a speciation analysis were accomplished. A microcolumn packed with resin beads or an open tubular column such as a PTFE tube or a silica capillary tube having the chemically modified inner wall were used for the on-line coupling