The Protective Effect of Kefir and Vitamin C on Azoxymethane Induced Toxicity and Induction of Metallothionein in Mice

The present study was conducted to investigate whether vitamin C or kefir (a milk-based fermentation  product) protected Swiss albino mice from azoxymethane (AOM) toxicity. We also investigated the effect  of AOM administration on the induction of metallothionein (MT) expression in mice tissues. 40 12-weekold  male/female (20:20) Swiss albino mice with a mean weight of 31.4 g were allocated into four groups.  Animals in the first group were the control group. Animals in the other three groups were treated with  AOM (5mg/kg body weight) subcutaneously twice weekly for a total of 7 weeks. Animals in the second  group were treated only with AOM. Those in the third group were allowed access to kefir (50% wt/vol) ad  libitum. Those in the fourth group received vitamin C subcutaneously (500 mg/kg) per day for 7 weeks. Six  weeks after the final AOM treatment, all animals were sacrificed and necropsied. AOM administration  caused severe liver lesions including enlarged hepatocytes (megalocytes) and many contained enlarged  nuclei. Vitamin C and kefir administration clearly reduced the severity of AOM induced liver lesions.  Induction of MT expression was observed in the liver and kidneys, particularly in the centrilobular zones  and renal cortex, mainly in the distal renal tubules, collecting tubules, Henle's loop, and medulla, respectively.  In conclusion, vitamin C and kefir supplementation were found to be able to reduce the severity of  hepatotoxic lesions.,

Optically induced density depletion of the two-dimensional electron system in GaAs/AlxGa1-xAs heterojunctions

We report measurements of optically induced density depletion of the two-dimensional electron system formed at the interface of a GaAs/AlxGa1-xAs heterojunction with a δ-doped layer of Be acceptors in the GaAs 250 Å from the interface. Our measurements show that at low laser power the depletion effect is controlled by the recombination of two-dimensional electrons with photoexcited holes that have become bound to the Be acceptors. The point at which all the Be acceptors in the sample have been neutralized by photoexcited holes is indicated by the sudden appearance of free holes in the GaAs, which then control the density depletion in the high-power regime. We present a comprehensive dynamic model of the depletion effect that includes both regimes, and calculate the densities and mobilities of the carriers involved in the process