Oxidative Stress Induced by Cadmium in the C6 Cell Line: Role of Copper and Zinc

In this report, we have investigated the role of copper (Cu) and zinc (Zn) in oxidative stress induced by cadmium (Cd) in C6 cells. Cells were exposed to 20 μM Cd, 500 μM Cu, and 450 μM Zn for 24 h. Then, toxic effects, cellular metals levels, oxidative stress parameters, cell death, as well as DNA damage were evaluated. Cd induced an increase in cellular Cd, Cu, and Zn levels. This results not only in the inhibition of GSH-Px, GRase, CAT, and SOD activities but also in ROS overproduction, oxidative damage, and apoptotic cell death not related to Cu and Zn mechanisms. The thiol groups and GSH levels decreased, whereas the lipid peroxidation and DNA damage increased. The toxicity of Zn results from the imbalance between the inhibition of antioxidant activities and the induction of MT synthesis. The increase in Cu and Zn levels could be explained by the disruption of specific transporter activities, Cd interference with signaling pathways, and metal displacement. Our results suggest that the alteration of Cu and Zn homeostasis is involved in the oxidative stress induced by Cd.     

Role of alpha-tocopherol in cadmium-induced oxidative stress in Wistar rat's blood, liver and brain

Cadmium (Cd) a highly toxic metal is considered to be a multitarget toxicant, and it accumulates principally in the liver and kidney after absorption. In vivo studies of mouse and rat liver have shown that apoptosis plays a primary role in Cd-induced hepatotoxicity. However, the detailed mechanisms by which toxic metals such as Cd produce their effects are still largely unknown. The present study aimed at investigating the consequences of exposure to Cd, alpha-tocopherol and their combination on stress biochemical parameters (lipoperoxidation and protein carbonyls levels). Male albino Wistar rats (1 month old) were treated intravenously with cadmium (2 mg CdCl(2)/kg body weight/day), and alpha-tocopherol (100 mg/kg body weight/day), or with alpha-tocopherol+Cd (100 mg Vit E/kg body weight, 2 mg CdCl(2)/kg). The lipoperoxidation was measured by the thiobarbituric acid reactive substances (TBARS) method and oxidatively generated damage to proteins by determining carbonyl (DNPH) levels. Among the hematological parameters measured the haematocrit value and haemoglobin concentration were significantly decreased in the blood of Cd-treated rats. A significant increase was observed in the level of malondialdehyde (MDA) and protein carbonyls in the cadmium exposed group compared to control group (p<0.001), and these values were decreased after administration of alpha-tocopherol (group 4). The activity of lactate dehydrogenase in rat liver and brain showed a significant increase as compared to that found in the control group and significant decrease of catalase and superoxide dismutase activities. In the liver of the Cd-treated group the contents of reduced glutathione were decreased. Our results suggest that cadmium induces an oxidation of cellular lipids and proteins and that administration of alpha-tocopherol can reduce Cd-induced oxidative stress and improve the glutathione level together with other biochemical parameters.     

A study of the polygalacturonase activity of several yeast strains isolated from cocoa

Summary During the traditional fermentation of cocoa, yeasts with pectinolytic activity are involved in the degradation of the pulp. Saccharomyces chevalieri, Torulopsis candila, and Candida norvegensis, as well as Kluyveromyces fragilis included in this study as a control strain all have a pectinolytic activity (endopolygalacturonase E.C. 3.2.1.15). The enzymes studied have the same optimal pH of activity [5] but are different from each other in their optimal temperature and their thermal stability. The enzymes of Torulopsis candida and Kluyveromyces fragilis have the highest optimal temperature (60° C). Among the strains studied, Candida norvegensis produced the greatest amount of exocellular enzyme.     

Inulin hydrolysis by an immobilized yeast-cell reactor

Whole cells of Pichia polymorpha have been shown to possess inulinase (2, 1-β-d-fructan fructanohydrolase, EC 3.2.1.7) activity. This activity was slightly different from that of the purified enzyme: optimum pH was modified, optimum temperature was higher and thermal stability was improved. Whole cell immobilization by adsorption on beech wood-shavings was straightforward. A reactor of this type permits the bioconversion of inulin into d-fructose (and d-glucose) with sufficient cell growth to ensure the stability of the system. A chicory extract was hydrolysed completely to a high fructose syrup during an experiment lasting 75 days.     

Inulinase ofDebaryomyces cantarellii

Debaryomyces cantarellii excretes into a buffered medium an inulinase of β-fructofuranosidase type, its synthesis being induced by inulin. The enzyme has a pH optimum at 4 and its optimum temperature is 50°C. ItsK _m for inulin is 15mm.     

Studies on the 5α-androstane-3β, 17β-diol-6α-hydroxylase and on the 5α-androstane-3β, 17β-diol-7α-hydroxylase in anterior hypophysis of male rats.

In anterior pituitaries from male rats, it appeared that 5α-androstane-3β, 17β-diol was quickly metabolized into 5α-androstane-3β,6α-17β-triol and 5α-androstane-3β,7α, 17β-triol by action of 6α- and 7α-hydroxylases. Hydroxysteroid hydroxylases were located in endoplasmic reticulum and were dependent on NADPH⁺. Their optimum pH was 8.0, optima temperature, 37°C, and their apparent Km was 2.7 μM. Hydroxylative reactions were not reversible and not modified by gonadectomy. Hydroxylation seemed an efficient control of the pituitary level of 5α-andros-tane-3β, 17β-diol.     

Vitamin B 12 formation by a gram-variable methanol-utilizing bacterium

Summary A methanol-utilizing bacterium isolated from soil was studied for ability to produce vitamin B 12. The isolated strain XF is gram-variable, pink-pigmented and rod-shaped. Effects of growth conditions on vitamin B 12 productivity were examined. The maximal yield of vitamin B 12 was 280 g/l in shaked flasks and 236 g/l in fermentation jars.     

Inulinase activity ofDebaromyces cantarellii

Debaromyces cantarellii Capriotti contains an inulinase activity which is inducible by growth on inulin but not on other β-fructosides. The induction is inhibited by glucose and fructose. The system is situated in the cell wall and can be best extracted with a 20 mm phosphate buffer at pH 8.5. The inulinase activity shows pH optima at 4 and 6, suggesting the presence of two enzymes, the latter being more tightly bound to the cell wall. Both enzymes degrade inulin from the nonreducin end. The cells also contain a constitutive β-fructofuranosidase with a specificity partly overlapping with that of the inulinase(s).