A specific high-performance liquid chromatography assay for dehydroascorbic acid shows an increased content in CLL lymphocytes

A method for the assay of dehydroascorbic acid using high-performance liquid chromatography with uv detection is described. The dehydroascorbic acid is separated from ascorbic acid and reduced with dithiothreitol, and is then quantitated as ascorbic acid following rechromatography. Since as little as 22 pmol can be detected, sensitivity is at least 40-fold greater than that of other currently available procedures. This method was used to measure the level of dehydroascorbic acid in normal and chronic lymphocytic leukemia lymphocytes. A significantly higher concentration of dehydroascorbic acid was found in leukemic (21.80 +/- 3.55 nmol/10(8) cells, mean +/- SE) than in normal lymphocytes (9.32 +/- 1.15 nmol/10(8) cells) (P less than 0.03). Analysis of extracts from normal B cell lymphocytes revealed comparable dehydroascorbic acid levels to unfractionated lymphocytes, indicating that the elevated level in chronic lymphocytic leukemia was not simply a reflection of the increased percentage of B lymphocytes in this disorder. These studies illustrate that the technique can be used to measure the dehydroascorbic acid content from sources where only scanty material is available or low levels are found.     

Inhibitory effect of dihydroxyacetone onGluconobacter oxydans: Kinetic aspects and expression by mathematical equations

Summary Microbial conversion of glycerol into dihydroxyacetone (DHA) byGluconobacter oxydans was subjected to inhibition by excess substrate. Comparison of cultures containing increasing initial DHA contents (0 to 100 g l^–1) demonstrated that DHA also inhibited this fermentation process. The first effect was on bacterial growth (cellular development stopped when DHA concentration reached 67 gl^–1), and then on oxidation of glycerol (DHA synthesis only occurred when the DHA concentration in the culture medium was lower than 85 g l^–1). Productivity, specific rates and, to a lesser extent, conversion yields decreased as initial concentrations of DHA increased. The changes in the specific parameters according to increasing initial DHA contents were described by general equations. These formulae satisfactorily express the concave aspect of the curves and the reduction in biological activity when the cells were in contact with DHA concentrations of up to 96 g l^–1.Abbreviations X, S, P biomass, substrate, product concentrations - r _x,r _s,r _p rates of growth, consumption and production - ,q _s,q _p specific rates of growth, glycerol consumption and DHA production - Y _x/s, Y_p/s conversion yields of substrate into biomass and product - K _s constant of affinity of cells to the substrate - K _ip product inhibition constant - P _m threshold concentration of DHA in substrate     

Failure to detect delta 5-3 beta-hydroxysteroid oxidoreductase activity in the preimplantation rabbit embryo

Preimplantation rabbit embryos were incubated with pregnenolone and dehydroisoandrosterone under conditions which gave formazan precipitation by the histochemical technique. The metabolic fate of the labeled steroids was assessed simultaneously. There was no concomitant transformation of pregnenolone to progesterone and dehydroisoandrosterone was not transformed to androstenedione. It is concluded that the formazan precipitation is coupled with an "activity" other than delta 5-3 beta-hydroxysteroid oxidoreductase.     

Antioxidative responses in Vitis vinifera infected by grapevine fanleaf virus

The antioxidative response of grapevine leaves (Vitis vinifera cv. Trebbiano) affected by the presence of grapevine fanleaf virus was studied during the summer of 2010 at three different harvest times (July 1st and 26th, and August 30th). At the first and second harvest, infected leaves showed increases in the concentration of superoxide radical and hydrogen peroxide, the latter increasing for enhanced activity of superoxide dismutase. In contrast, at the last harvest time, increases in the ascorbate pool and ascorbate peroxidase activity maintained hydrogen peroxide to control levels. The glutathione pool was negatively affected as summer progressed, showing a decrease in its total and reduced form amounts. At the same time, increases in the ascorbate pool were observed, making antioxidant defenses of grapevine effective also at the last harvest time. Increases in phenolic acids, and in particular in p-hydroxybenzoic acid, at the first and second harvest might have enhanced the efficiency of the antioxidant system through an interrelation between a peroxidase/phenol/ascorbate system and the NADPH/glutathione/ascorbate cycle. The lack of increase in p-hydroxybenzoic acid at the third harvest could be due instead to the enhanced utilization of this acid for hydrogen peroxide detoxification. With time, grapevine plants lost their capacity to contrast the spread of grapevine fanleaf virus, but acquired a greater ability to counteract pathogen-induced oxidative stress, being endowed with more reduced antioxidant pools.     

Tiller number is altered in the ascorbic acid-deficient rice suppressed for l-galactono-1,4-lactone dehydrogenase

The tiller of rice (Oryza sativa L.), which determines the panicle number per plant, is an important agronomic trait for grain production. Ascorbic acid (Asc) is a major plant antioxidant that serves many functions in plants. l-Galactono-1,4-lactone dehydrogenase (GLDH, EC 1.3.2.3) is an enzyme that catalyzes the last step of Asc biosynthesis in plants. Here we show that the GLDH-suppressed transgenic rices, GI-1 and GI-2, which have constitutively low (between 30% and 50%) leaf Asc content compared with the wild-type plants, exhibit a significantly reduced tiller number. Moreover, lower growth rate and plant height were observed in the Asc-deficient plants relative to the trait values of the wild-type plants at different tillering stages. Further examination showed that the deficiency of Asc resulted in a higher lipid peroxidation, a loss of chlorophyll, a loss of carotenoids, and a lower rate of CO₂ assimilation. In addition, the level of abscisic acid was higher in GI-1 plants, while the level of jasmonic acid was higher in GI-1 and GI-2 plants at different tillering stages. The results we presented here indicated that Asc deficiency was likely responsible for the promotion of premature senescence, which was accompanied by a marked decrease in photosynthesis. These observations support the conclusion that the deficiency of Asc alters the tiller number in the GLDH-suppressed transgenics through promoting premature senescence and changing phytohormones related to senescence.     

Docosahexaenoic acid and tetracyclines as promising neuroprotective compounds with poly(ADP-ribose) polymerase inhibitory activities for oxidative/genotoxic stress treatment

The human genome is exposed to oxidative/genotoxic stress by several endogenous and exogenous compounds. These events evoke DNA damage and activate poly(ADP-ribose) polymerase-1 (PARP-1), the key enzyme involved in DNA repair. The massive stress and over-activation of this DNA-bound enzyme can be responsible for an energy crisis and neuronal death. The last data indicated that product of PARP-1, i.e. poly(ADP-ribose) (PAR), acts as a signalling molecule and plays a significant role in nucleus-mitochondria cross-talk. PAR translocated to the mitochondria can be involved in mitochondrial permeability, the release of an apoptosis-inducing factor (AIF). Its translocation into the nucleus leads to chromatin condensation, fragmentation and cell death. The exact mechanism of this novel death pathway has not yet fully been understood.     

Involvement of pigment epithelium-derived factor,docosahexaenoic acid and neuroprotectin D1 in corneal inflammation and nerve integrity after refractive surgery

Alterations in corneal innervations result in impaired corneal sensation, severe dry eye and damage to the epithelium that may in turn lead to corneal ulcers, melting and perforation. These alterations can occur after refractive surgery. We have discovered that pigment epithelium-derived factor (PEDF) plus docosahexaenoic acid (DHA or the docosanoid bioactive neuroprotectin D1 (NPD1)) induces nerve regeneration after corneal surgery that damages the stromal nerves. We found that PEDF is released from corneal epithelial cells after injury, and when DHA is provided to the cells it stimulates the biosynthesis of NPD1 by an autocrine mechanism. The combination of PEDF plus DHA also decreased the production of leukotriene B4 (LTB4), a neutrophil chemotactic factor, thereby decreasing the inflammation induced after corneal damage. These studies suggest that PEDF plus DHA and its derivative NPD1 hold promise as a future treatment to restore a healthy cornea after nerve damage.     

Influence of Age on the Fatty Acid Composition of Breast and Thigh Muscles of Male Turkeys

Large White male turkeys were sacrificed at 4-week intervals from 4 to 28 weeks of age to study the fatty acid distribution in lipid of breast and thigh muscles. A total of 70 turkeys were sampled for this experiment.

Fatty acid distribution varied with advancing maturity and between muscle types. The most abundant fatty acids in the tissues were those with carbon chain lengths of 15:0, 16:0, 18:0, 18:1, 18:2, 20:4 and 24:0. Thigh muscle contained significantly more linoleate (18:2) than did breast. Larger proportions of pentadecanoic (15:0), arachidonic (20:4) and lignoceric (24:0), however, appeared in breast. Indications of minor fatty acids appeared on the chromatograms, but their low concentrations made their estimation and identification difficult.