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Results for “Dehydroascorbic Acid”

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PubMedDate not supplied

[Status of the glucocorticoid function of the adrenal glands of the rat after pinealectomy].

The effect of epiphysis removal on the mass of the adrenals, the content of ascorbic acid in them and the level of II-OCS in the blood plasma were investigated in experiments on albino male rats. One and two mos. after pinealectomy signs of the activation of adrenal glucocorticoid function: an increase in the gland mass, a decrease in the content of ascorbic acid in the glands and an increase in II-OCS concentration in the blood plasma, were observed.

11-Hydroxycorticosteroids↗
PubMed1985

Monodehydroascorbate reductase from cucumber is a flavin adenine dinucleotide enzyme.

Monodehydroascorbate reductase (EC 1.6.5.4) was purified from cucumber fruit to a homogeneous state as judged by polyacrylamide gel electrophoresis. The cucumber monodehydroascorbate reductase was a monomer with a molecular weight of 47,000. It contained 1 mol of FAD/mol of enzyme which was reduced by NAD(P)H and reoxidized by monodehydroascorbate. The enzyme had an exposed thiol group whose blockage with thiol reagents inhibited the electron transfer from NAD(P)H to the enzyme FAD. Both NADH and NADPH served as electron donors with Km values of 4.6 and 23 microM, respectively, and Vmax of 200 mol of NADH and 150 mol of NADPH oxidized mol of enzyme-1 s-1. The Km for monodehydroascorbate was 1.4 microM. The amino acid composition of the enzyme is presented. In addition to monodehydroascorbate, the enzyme catalyzed the reduction of ferricyanide and 2,6-dichloroindophenol but showed little reactivity with calf liver cytochrome b5 and horse heart cytochrome c. The kinetic data suggested a ping-pong mechanism for the monodehydroascorbate reductase-catalyzed reaction. Cucumber monodehydroascorbate reductase occurs in soluble form and can be distinguished from NADPH dehydrogenase, NADH dehydrogenase, DT diaphorase, microsome-bound NADH-cytochrome b5 reductase, and NADPH-cytochrome c reductase by its molecular weight, amino acid composition, and specificity of electron acceptors and donors.

Amino Acids↗
PubMed1981

Adenylate cyclase and guanylate cyclase activity in normal and leukemic human lymphocytes.

Adenylate cyclase (AC) and guanylate cyclase (GC) activities were studied in normal B-enriched and T-enriched lymphocytes, in lymphocytes of children with acute lymphocytic leukemia (ALL), and in lymphocytes of adults with chronic lymphocytic leukemia (CLL). AC activity was greater in normal B than T lymphocytes (215 pmole/min/mg protein versus 80 pmole in the membrane-enriched fraction) and i both increased greatly after stimulation with isoproterenol and more so with prostaglandins E and F2 alpha. In leukemic lymphocytes, AC showed depressed activity (20 pmole in ALL cells and 55 pmole in CLL cells) and was less sensitive to hormonal stimulation: this loss of sensitivity occurred to a greater extent in ALL than in CLL lymphocytes. GC activity was greater in normal T than B cells (in membrane-enriched fraction: 10.2 pmole versus 5.3 pmole). It increased little with isoproterenol and prostaglandins stimulation, and much more with sodium azide and dehydroascorbic acid stimulation. GC activity was increased in both types of leukemic lymphocytes (23 pmole for ALL cells and 18 pmole for CLL cells) and was insensitive to stimulation. Possible derangement of cyclase and cyclic nucleotide regulation in leukemic cells is suggested.

Adenylyl Cyclases↗
PubMed1984

Chronic lymphocytic leukemia lymphocytes: membrane anomalies and H2O2 vulnerability.

This paper reviews selected biochemical and functional studies characterizing B lymphocytes from patients with chronic lymphocytic leukemia. When compared to B lymphocytes from the circulation of normal subjects, a number of differences are noted. Functionally, the CLL B lymphocyte is impaired in mitogen response, cap formation following attachment of multivalent ligands, and the density of surface immunoglobulins. It also differs from normal in the content of the ectoenzyme 5' nucleotidase, which is often decreased, and the concentration of ascorbic and dehydroascorbic acid, which are markedly elevated in these cells. The level of tocopherol is decreased. CLL and normal B lymphocytes are more vulnerable than T lymphocytes to the toxic effect of H2O2. This sensitivity is Ca2+ dependent and inhibited by nanomolar concentrations of nonsteroidal antiinflammatory agents. These studies identify the human B lymphocyte as a cell that should be a suitable target for selective killing by H2O2.

B-Lymphocytes↗
PubMedDate not supplied

[Nature of the vitamin composition of mare's milk and koumiss depending on the time of year].

It was shown that the content of vitamins E, C, thiamine, riboflavin and niacin in mare's milk and kumyss varies depending on the season. The highest level of vitamins E, C and niacin was noted in May-June. The technological processing of mare's milk leads to the decreased content of vitamin C and niacin. Mare's milk and kumyss were found to contain dehydroascorbic acid in a considerable amount, especially in summer.

Animals↗
PubMed1978

[Very low temperature (quick freezing) and pseudo-stabilization of the chemical composition of food of plant origin].

The consequences of freezing at -18, -30 degrees C are presented: slowing down or acceleration of enzymatic or non enzymatic reactions, concentration effect, consequences of the death of cells, (time--temperature relation). The most characteristic examples of nutritive value adulterations are presented: ascorbic and dehydroascorbic acids, other vitamins, derivatives of the insaturated fatty acids oxidation, changes in proteins. Other damages more related to sensorial quality are summarized: "chlorophyll, phenolic substances, aroma, pectins. These chemical changes occurring at low temperatures are generally less important than the losses in nutritional value of frozen plant products related to the necessary treatments preceding or following cold storage. Particularly, the losses during blanching and thawing (drip) are discussed. Finally, quick freezing as it is used now industrially does not exactly stabilize the nutritive quality of plant products but protects this quality satisfactorily. Progress is however possible, concerning the cold treatments (storage temperature lowering) and especially the losses before and after freezing and storage (blanching, transport, distribution, thawing).

Drug Stability↗
PubMed1980

[Influence of monodehydroascorbate on the acyl-CoA-desaturase system of rat liver microsomes (author's transl)].

The microsomal NADH- as well as the ascorbate-dependent fatty acid desaturation are diminished by monodehydroascorbate. This effect can be neutralized by borate. Borate forms an adduct with didehydroascorbate and thus prevents the formation of monodehydroascorbate. The ascorbate-dependent oleate formation is increased significantly by the same reaction (p less than 0.01). The NADH-dependent reaction is diminished by parallel reactions of the desaturase system and L-ascorbate: ferricytochrome b5 oxidoreductase at ferrocytochrome b5. In the case of the ascorbate-dependent reaction the diminished oleate formation is caused by the more positive oxidation state of cytochrome b5 in presence of monodehydroascorbate.

Animals↗
PubMedDate not supplied

[Effect of anabolic substances on the state of the individual components of the glutathione-ascorbic acid system].

Experiments on rats have shown the lowered content of ascorbic acid in blood and urine during administration of retabolil, nerobol or potassium orotate. Retabolil and potassium orotate increased the content of ascorbic acid in tissues and the content of reduced glutathion in blood. Nerobol produced a rise in vitamin C blood content in the test organs.

Anabolic Agents↗
PubMed1998

Thioltransferase from Schizosaccharomyces pombe: purification to homogeneity and some properties.

Two types of thioltransferase were identified in the cytosolic extract of Schizosaccharomyces pombe, a fission yeast. In the present study, the major one of them was purified to homogeneity using chromatography processes such as ion-exchange chromatography and gel filtration. Purification was monitored by the transhydrogenase activity of thioltransferase with 2-hydroxyethyl disulfide as a substrate. Its molecular weight was estimated to be about 14,000 on SDS-polyacrylamide gel electrophoresis. The purified enzyme catalyzes the reduction of various disulfide compounds such as S-sulfocysteine, L-cystine, and insulin. It was also found to contain the reducing activity on non-disulfide substrates such as dehydroascorbic acid and alloxan. Its activity was greatly activated by high concentrations of reduced glutathione. It was found to be very heat-stable as like other thioltransferases. It was characterized on other aspects such as kinetic parameters and optimal reaction conditions.

Antidotes↗