Constance S. Tsao

Effect of exogenous ascorbic acid intake on biosynthesis of ascorbic acid in mice

The effect of exogenous ascorbic acid intake on biosynthesis of ascorbic acid in mice has been studied. After the mice were on diets containing added ascorbic acid for two months, the activities of ascorbic acid synthesizing enzymes in the mouse liver homogenates were measured using L-gulono-gamma-lactone as a substrate. Exogenous ascorbic acid intake (0.5, 1 or 5% in the diet) was able to increase the concentration of ascorbic acid in the blood and to decrease the activities of ascorbic acid synthesizing enzymes in mouse liver. The results suggest that ascorbic acid synthesis was controlled by local regulatory mechanism or by the concentration of ascorbic acid in the hepatic portal blood. Ingestion of dietary erythorbic acid, a stereoisomer of ascorbic acid, had no effect on the activities of ascorbic acid synthesizing enzymes.

Preparation of an optimum mobile phase for the simultaneous determination of neurochemicals in mouse brain tissues by high-performance liquid chromatography with electrochemical detection

A systematic method is described for the optimization of a mobile phase for the simultaneous determination of 24 neurochemicals consisting of catecholamine, serotonin, their precursors and metabolites and related materials. This mobile phase contained sodium acetate (0.04 M), citric acid (0.01 M), sodium chloride (0.0126 M), sodium octyl sulfate (91 mg/l), tetrasodium EDTA (50 mg/l) and 10% (v/v) methanol. When this optimum mobile phase was applied to the analysis of brain tissues of the Swiss male mouse, twelve neurochemicals were quantified in the free state: tyrosine, L-beta-3,4-dihydroxyphenylanine, dopamine, 3,4-dihydroxyphenylacetic acid, 4-hydroxy-3-methoxyphenylacetic acid, norepinephrine, 3-methoxy-4-hydroxyphenylglycol, DL-3,4-dihydroxymandelic acid, DL-4-hydroxy-3-methoxymandelic acid, serotonin, L-tryptophan, 5-hydroxyindole-3-acetic acid and DL-synephrine and normetanephrine, appearing as a fused peak. This fused peak was present on the chromatogram tracings of all the mouse brain tissues. The separable neurochemicals not found by this procedure in the Swiss male mouse tissues were DL-3,4-dihydroxyphenylglycol,5-hydroxytryptophan, epinephrine, DL-octopamine, metanephrine, deoxyepinephrine, homovanillyl alcohol, N-acetylserotonin, tyramine and 3-methyltyramine.

SiC in Diamond and Kimberlites: Implications for Nucleation and Growth of Diamond

Dusty inclusions in diamonds from Fuxian, China contain an assemblage of moissanite (α-SiC) + β-SiC + quartz. Diamondiferous kimberlite from Kimberley, South Africa contains SiC microcrysts with rutile-bearing melt-inclusion tubes and deformation lamellae. They are blue or turquoise-green α-SiC (hexagonal) and the major difference between them is their Al content: 0.2 wt% in the blue and 100 ppm in the green variety. These findings suggest a possible genetic link between SiC and diamond. We propose a mechanism for heteroepitaxial nucleation and growth of diamond on cubic β-SiC substrates, mimicking interpenetrant twinning on {112}, which might provide a smooth, orderly transition from substrate to overgrowth. This growth mechanism may be effective in nature and should be of interest to material scientists who synthesize diamond thin films for industrial purposes.

Effect of Dietary Ascorbic Acid on Heat-Induced Eye Lens Protein Damage in Guinea Pigs

The effect of large intake of dietary ascorbic acid on heat-induced eye lens protein damage has been studied. Male guinea pigs of the Hartley strain were used. Ascorbic acid was administered to the experimental animals in the drinking water. The mean daily ascorbic acid intakes for the control and experimental animals were 10 and 366 mg/kg body weight, respectively. The ascorbic acid level in the lens of the experimental animals was significantly higher than in the controls, but no differences in the content of water-soluble lens proteins were observed. When a solution of water-soluble protein was incubated at 60 degrees C, insoluble aggregates were formed. The loss of water-soluble proteins from the lens of the experimental animals was significantly less than that of the controls. The results indicated that large quantities of dietary ascorbic acid were able to protect lens constituents against heat-induced damage.

Protection by dietary ascorbate of guinea pigs from neurolathyrism

The protection afforded by dietary vitamin C from the toxic effects of intraperitoneal injection of an aqueous solution of an air-dried ethanol extract of Lathyrus sativus peas is demonstrated in guinea pigs fed an ascorbate-fortified diet in contrast to those fed a diet devoid of vitamin C. Weakness and flaccid paraparesis occurred in most of the ascorbate-depleted animals, whereas all guinea pigs on the ascorbate-supplemented diet remained active and appeared well following injection of the extract. These results extend previous work on the role of dietary ascorbate in the protection of guinea pigs from neurolathyrism. In particular, spastic paralysis in some ascorbate-depleted guinea pigs is reported for the first time. Since guinea pigs, like all primates, including humans, do not synthesize vitamin C, their use as experimental models can partially simulate human neurolathyrism.

Effect of ascorbic acid intake on tissue dehydroascorbic acid in mice

Abstract The effect of ascorbic acid intake on tissue levels of ascorbic acid, dehydroascorbic acid and the ratio of dehydroascorbic acid to ascorbic acid in mice was studied. In general, the trend of changes in tissue concentrations was: ascorbic acid > dehydroascorbic acid ≫ ratio of dehydroascorbic acid to ascorbic acid. Mice fed a diet with 1% ascorbic acid had significantly higher concentration of dehydroascorbic acid in the kidney, lung and spleen than did control mice fed an ascorbic acid-free diet. Mice fed a diet with 5% ascorbic acid had elevated levels of dehydroascorbic acid in the brain, kidney, liver, lung and spleen. The kidney and lung had the greatest increase in dehydroascorbic acid concentration, suggesting that these two organs may be important sites for catabolism and elimination of ascorbic acid. In comparison with the corresponding control values, the ratio of dehydroascorbic acid to ascorbic acid was higher in the lung, not different in the liver and spleen, and lower in the kidney of mice fed a diet with 1 or 5% added ascorbic acid. These ratios were higher in the brain of mice fed a diet with 5% added ascorbic acid than in mice fed the ascorbic-acid-free diet. No apparent physiological abnormality in these animals was observed. These effects were stereospecific. Exogenous erythorbic acid, D-isoascorbic acid, a stereoisomer of ascorbic acid, increased dehydroascorbic acid equivalents (the sum of dehydroascorbic and dehydroerythorbic acid) in the kidney, lung, and spleen but the ratios of dehydroascorbic acid plus dehydroerythorbic acid to ascorbic acid plus erythorbic acid were essentially unaffected. A large glucose intake (1 or 5% in the diet) did not have an effect on levels of tissue ascorbic acid or dehydroascorbic acid.

Urinary excretion of calcium, dopamine, norepinephrine, and epinephrine in young women following ascorbic acid ingestion

Abstract The influence of a 1.75 g dose of ascorbic acid on subsequent 4-h urinary excretion of calcium and free dopamine, norepinephrine, and epinephrine was investigated in 38 young women. Small increases, relative to control values from the same subjects, were observed for both urinary calcium (p 2 ) of the variance in mg calcium (p

A Model of Early Cancer: The Effect of Ascorbate and Its Oxidation or Degeneration Products on Tumor Incidence and Growth in Syngeneic Guinea Pigs Given Minimal Numbers of Tumor Cells

In a series of experiments, minimal numbers of tumor cells were injected into guinea pigs, and the effect of administering vitamin C in their drinking water on tumor onset and tumor growth rate was investigated. In some of the work, air was bubbled through the water to ascertain if ascorbate or its oxidation products had any different effect on the onset times and growth rates. In all experiments, it was found that adding vitamin C to the drinking water significantly increases the tumor onset time but has no discernible effect on the tumor growth rate once the tumor is palpable. No significant change in the tumor-free survival times or the tumor growth rates results from bubbling air through the ascorbate-supplemented drinking water.