The effect of D-isoascorbic acid, an epimer of L-ascorbic acid, on viruses was investigated using a wide variety of bacterial viruses (phages) as model systems. D-Isoascorbic acid exerted an inactivating effect on all phages examined. The reaction mechanism of virus inactiva-tion by D-isoascorbic acid was investigated using phage J 1 as a model system. Bubbling oxygen through the reaction mixture and the addition of H2O2 or transition metal ions into the reaction mixture enhanced the phage inactivation by D-isoascorbic acid. In contrast, nitrogen bubbling and the addition of reducing agents, chelating agents or radical scavengers prevented phage inactivation. Experiments using specific radical scaven-gers, superoxide dismutase or catalase showed that OH⋅ could be mainly responsible for phage inactivation by D-isoascorbic acid. These findings are similar to those obtained with L-ascorbic acid, and indicate that phage-inactivating activity is independent of the stereoisomerism with inversion of the hydroxyl group at carbon 5 of ascorbic acids.
To study the relationship between age-related stimulation of sympathetic nervous activity and vitamin E, excretion of urinary catecholamine and the contents of organ catecholamine were measured in rats receiving a vitamin E-deficient or control diet for 95 weeks. Rats exhibited about 95% hemolysis after 4 weeks on the vitamin E-deficient diet and this value remained the same for 95 weeks. a-Tocopherol in plasma was not detectable in the deficient diet-fed rats, and lipid peroxide concentrations in the plasma, liver and adrenal glands of rats receiving the vitamin E-deficient diet for 95 weeks were 3- to 30-fold higher than those of control rats. Urinary excretion of catecholamine (norepinephrine (NE), epinephrine (E) and dopamine (DA)) increased with age. Excretion of NE in 24-h urine of rats receiving the vitamin E-deficient diet for 50 and 95 weeks was 2- to 3-fold higher than that of control rats, although no significant difference was observed at week 12. Contents of NE and E in the adrenal glands and of NE in the heart from the deficient rats were significantly lower than those of control rats at week 95. These results suggest that sympathetic nervous activity is enhanced in aged rats and that the sympathetic nervous activity in vitamin E-deficient rats is greater than in control rats.
The effects of rice fiber on fecal weight, transit time, frequency of defecations, digestibility of nutrients and blood status were investigated in S healthy young men. Each of them consumed a brown rice diet and then a polished rice diet for 2 weeks respectively. Both diets contained 1.2g protein per kg body weight. The brown rice diet contained 2 times as much dietary fiber as the polished rice diet. When they consumed the brown rice diet, it showed an increase of fecal weight and decrease of digestibility of energy, nitrogen and fat. Nitrogen balance was not significantly different and kept zero balance on both diets. Concen-tration of plasma cholesterol was not significantly different. The results suggest that rice fiber produced an increase in fecal weight, which is assumed to be effective in preventing colonic disease in advanced countries and does not affect plasma lipid level.
The stability and inhibitory specificity of rice bran trypsin inhibitor (RBTI) was investigated in an attempt to understand its nutritional significance. RBTI retained about 100% of its original activity over a pH range from 4 to 10 during 24-h incubation at 37°C. In heat treatment, RBTI at acidic and neutral pH values still possessed about 50 of its initial activity after 30-min incubation at 100°C, although it was completely inactivated during 15-min incubation at pH 10 and 100°C. The effects of metal ions and some reagents on RBTI were examined and it was found that Hg ion reduced RBTI's inhibitory activity: The inhibitor lost 30-100% of its original activity upon incubation with a reducing, an oxidizing or a thiol reagent. Digestion tests on RBTI indicated that α-chymotrypsin did not affect the inhibitory activity and pepsin caused only a 30% loss of the initial inhibitory activity after 24-h digestion. To determine inhibitory specificity, bovine, hog, rat, and human trypsins were used as target enzymes bound to an immobilized RBTI column. Titrations of the purified enzymes with RBTI showed that bovine, hog, and rat trypsins were powerfully inhibited by the inhibitor, while human trypsin was only weakly inhibited.
Rats were nourished by intravenous infusion of four dif-ferent experimental solutions: total parenteral nutrition (TPN) solution (group I); glucose-depleted TPN solution (group II); amino acid-depleted TPN solution (group III); and glucose- and amino acid-depleted TPN solution (group IV). All except group I animals lost body weight and showed negative nitrogen balance during a 7-day experimental period; glucose-depleted groups II and IV generally suffered more severely than amino acid-depleted group III. However, the concentration of plasma albumin in group III was significantly lower than that in the other groups. The weights of liver and gastrocnemius muscles after 7 days of infusion with different nutrient compositions were fairly well correlated with the RNA/DNA ratios in these tissues. Infusion of nutritionally deficient solutions caused progressive disaggregation of polysomes in both liver and gastrocnemius muscles, indicating variable degrees of impairment of protein synthesis in these tissues. The changes in polysomal profiles were rapid and sensitive; the polysomal disaggregation was evident within one day of infusion with deficient solutions. The determination of polysomal profiles in various tissues may be useful in optimizing the composition of TPN solutions.
Effects of tea catechins (tannins) on lipid metabolism were studied in male weanling rats fed a 25% casein diet containing 15% lard and 1% cholesterol for 28 days. Crude tea catechins prepared from green tea powder were supplemented at a 1% and 200 of the lard-cholesterol diet. The addition of 2% tea catechins slightly depressed growth but at the 1 level was without effect. Tea catechins decreased plasma total cholesterol, cholesterol ester, total cholesterol - HDL-cholesterol (VIDL-+ LDL-cholesterol) and atherogenic index (VLDL-+ LDL-cholesterol/HDL-cholesterol). Hematocrit and plasma glucose were not altered by the addition of tea catechins. The liver weight, liver total lipids and cholesterol concentrations in rats fed the lard-cholesterol diet increased more than in the control rats, but the addition of tea catechins to the lard-cholesterol diet decreased those parameters. Tea catechin supplementation increased fecal excretion of total lipids and cholesterol. The results demonstrate that tea catechins exert a hypocholesterolemic effect in cholesterol-fed rats.
The effect of individual amino acids added to a cholesterol containing casein diet on the plasma cholesterol level of rats was systematically investigated with objective of confirming the possibility that specific amino acids are responsible for the regulation of plasma cholesterol level by dietary proteins. Half the amino acids tested were effective to some degree in influencing the plasma cholesterol level when amino acids were added singly to the diet at a 5% level. However, only sulfur containing amino acids had significant effects when added to the diet at a 1% level; Met enhanced and Cys reduced the plasma cholesterol level. In addition, the results of an experiment with amino acid mixture diets with different Met, Cys, and/or Gly contents indicated the importance of sulfur amino acids and also of Gly in plasma cholesterol regulation. The results obtained here support the notion that the plasma cholesterol level of rats can be influenced by specific amino acids or amino acid compositions of dietary proteins, at least under the experimental conditions used.
That flavonoids inhibit xanthine oxidase from cow milk was confirmed by measuring oxygen consumption with an oxygen electrode. In contrast, flavonoids did not inhibit glucose oxidase, another oxygen consuming enzyme. Among the flavonoids tested, quercetin, kaempferol, myrlcetln, chrysin, quercitrin, and morin were potent inhibitors of xanthine oxidase; their inhibition rates (%) were 80, 70, 69, 62, 59, and 51 at 100μM (except chrysin at 50μM), respectively. The xanthine oxidase-inhibiting activities of the flavonoids were not always well correlated with the suppressive activities of the flavonoids on cytochrome c reduction by a xanthine-xanthine oxidase system. The inhibition of xanthine oxidase by quercetin was not affected by cupric ion. The partition rates of the flavonoids between n-butanol and a buffer solution seemed to account for some of the inhibition.
The effects on hypercholesterolemia of dietary additions of cystine (Cys), methionine (Met), glycine (Gly), and a combination of Met and Gly to a 20% casein diet were studied in male Donryu rats subcutaneously implanted with an ascites hepatoma line of AH109A cells. The hepatoma-bearing rats fed the 20% casein diet lapsed into both endogenous hypertriglyceridemia and hypercholesterolemia when compared to hepatoma-free (normal) rats fed the same diet. The hypercholesterolemia was due to an elevation (3.2 fold) in the very low-density lipoprotein plus low-density lipoprotein (VLDL+LDL)-cholesterol (Ch) level. The high-density lipoprotein (HDL)-Ch level was slightly but significantly decreased. These lipoprotein changes in hepatoma-bearing rats resulted in a marked (4.5 fold) increase in the atherogenic index (AI, (VLDL+LDL)-Ch/HDL-Ch) in comparison with that of tumor-free rats. The dietary additions of l.2% Met, l.2% Cys, and a combination of 1.2% Met and 2.5% Gly significantly suppressed the hepatoma-induced increase in (VLDL+LDL)-Ch with no influence on the hepatoma-induced decrease in HDL-Ch, leading to a noticeable fall in AT. These results indicate that hepatoma-bearing rats are useful as an endogenously hyperlipidemic model and that some dietary amino acids are capable of improving hepatoma-induced hypercholesterolemia and abnormal serum lipoprotein profiles.