Effects of long-term administration of riboflavin, sodium butyrate or riboflavin 2', 3', 4', 5'-tetrabutyrate (RTB) on the activities of renal and hepatic enzymes that catalyze the β-oxidation of fatty acid were determined in the rat. Feeding of riboflavin or sodium butyrate for 5 weeks had no effect on all the enzymes examined. By contrast, feeding of RTB resulted in an increase in the hepatic activity of 3-ketoacyl-CoA thiolase [EC 188.8.131.52] by 50% of the control level, while the activities of renal 3-ketoacyl-CoA thiolase and of hepatic and renal acyl-CoA synthetase [EC 184.108.40.206] and acyl-CoA dehydrogenase [EC 220.127.116.11] remained unaffected. The increase in hepatic 3-ketoacyl-CoA thiolase activity suggests that prolonged RTB administration results in an increased β-oxidation of fatty acid in the liver, which may explain the reported reduction in the concentration of tryglyceride in plasma during RTB treatment.
The changes of bone γ-carboxyglutamic acid-containing protein (BGP) levels in bone and serum were studied in relation to those in calcium metabolism using chick embryos and chicks aged from 13 days' incubation to 8 weeks old. Chick BGP was determined by radioimmunoassay using antiserum to purified chick BGP. BGP levels in bone and serum increased significantly at hatching and then decreased until 3-5 days of age. Thereafter, BGP levels in bone and serum increased gradually until 8 weeks of age. These changes of BGP levels were well correlated with those of serum calcium and inorganic phosphorus concentrations, serum alkaline phosphatase activity and bone calcium content. The molecular size of increased serum BGP at hatching was not different from that of bone BGP. These results suggest that BGP plays a role in hatching and bone formation during chick development.
Zinc cation performed a role of activator as well as inhibitor for production of lactate from glucose 6-phosphate in the cytosol fraction of rat muscle. The pH optimum for glycolysis was 7.3 when Zn2+ acted as an activator. At concentrations lower than 0.46mM, Zn2+ was shown to be a more effective activator than Mg2+ with an apparent K1/2 of approximately 0.1mM. However, at concentrations higher than 0.5mM, Zn2+ inhibited lactate production. The activatory as well as inhibitory effect of Zn2+ on lactate production was investigated by the estimation of glycolytic intermediates. From the crossover plot, lactate production reflected phosphofructokinase activity, when Zn2+ was used as a catalytic cation for both reactions. Phosphofructokinase activity in purified muscle was activated by Zn2+ with an apparent Km of approximately 0.05mM, but at high Zn2+ concentrations, the enzyme activity was inhibited with an I50 of 0.23mM in the presence of ATP. From these findings, it appears that lactate production might also depend on phosphofructokinase activity when Zn2+ is used as an activating cation.
The effect of voluntary wheel-running to modulate sucroseinduced hypertriacylglycerolemia was investigated on both sedentary and exercised rats in relation to the timing of sucrose feeding. The exercised group was allowed voluntary wheel-running between 21.00-08.00. Rats of both groups were daily meal-fed a 35% sucrose diet at 20.00-21.00 and a basal diet at 08.00-09.00, or inversely meal fed the two diets at the reversed time for 7 weeks each. At the end of the feeding period, plasma or serum triacylglycerol (TG) levels of exercised rats, as compared to sedentary rats, showed smaller diurnal changes regardless of the timing of sucrose feeding. Hepatic-intestinal TG secretion rates measured during both resting and physically active periods were lower in the exercised rats than in the sedentary control rats, whereas the cardiac and adipose tissue lipoprotein lipase activity of the two groups was not significantly different. These results suggest that voluntary wheel-running exercise may modulate the hypertriacylglycerolemic effect of sucrose in rats regardless of the timing of sucrose feeding, with decreased TG secretion.
Lambda DNA-fragmenting actions of ascorbic acid (AsA) and triose reductone (TR) in the presence of Cu2+ were studied. The mixture of AsA or TR and Cu2+ caused a marked fragmentation ofλ, DNA (3.2×107 daltons) within the first 1 min of reaction. Further incubation resulted in accumulation of the most abundant species of fragmented λDNA having a molecular weight of 1.3×105 daltons. The mixture of AsA or TR and Cu2+ fragmented calf thymus DNA to produce the fragmented DNA of which 5'-OH terminal groups have a mixture of free OH groups and phosphodiester linkage. The mixture of AsA or TR and Cu2+ was also found to fragment, DNA to produce dCMP predominantly as 5'-OH terminal nucleotides.
The gelation of the complex between κ-casein and β-lactoglobulin was examined. The apparent viscosity of the mixture of κ-casein and β-lactoglobulin increased by heat treatment. The mixture formed a gel at the concentration of 8% (w/w). The gel formation was accelerated by the chymosin treatment. The mixture of κ-casein and β-lactoglobulin in each concentration of 1.5% gelled by the addition of chymosin after heat treatment. Forming the complex between κ-casein and β-lactoglobulin was necessary to the gel formation. Therefore, heat treatment of above 70°C was demanded. Turbidity increased and the relative content of soluble protein decreased accompanied with gel formation. The addition of calcium ion to the heated solution produced an increase in turbidity. The larger the protein concentration was, the larger the breaking stress of the formed gel was. The addition of calcium ion weakened the breaking stress of the gel.
When rats adapted to a stock diet were fed on various highcarbohydrate diets, the hepatic activities of glucose-6-phosphate dehydrogenase, malic enzyme and acetyl-CoA carboxylase were more greatly increased by fructose than by any other carbohydrate. Even in the diabetic state, the enzyme activities were somewhat increased by fructose feeding. After feeding on the diets for 9 days, the hepatic concentrations of intermediates of carbohydrate metabolism were generally lower in the diabetics than in the normals. Moreover, in both the normal and diabetic rats, the concentrations of fructose 1-phosphate, acetyl-CoA, citrate and malate were increased by fructose as were the enzyme activities. These results suggest that the metabolic pathway of fructose is predominant with respect to that of glucose and consequently lipogenesis may be able to be increased in the fructose-fed rats.
Typtophan (Trp) is usually catabolized to CO2, H2O and urea in mammals. Quantitatively, minor branches from this pathway lead to the production of picolinate (PA) and NAD+. Although niacin is a required nutrient when NAD+ synthesis from Trp is insufficient, it is not known if dietary PA is beneficial in such conditions. Two kinds of experiment were used to investigate the effects of dietary PA. First, mice were fed on a diet deficient in Trp for six weeks to diminish endogenous PA synthesis and stores. After this time the body mass of the mice was reduced by approximately 30%. Tryptophan-deficient mice subsequently fed a nutritionally complete diet gained weight more rapidly during the first but not subsequent week(s) of recovery when PA was added to their food. Second, mice were fed on a diet deficient in Trp, niacin and vitamin B-6 during the preimplantation period of pregnancy in an attempt to acutely lower PA synthesis and perhaps alter the embryos thus produced. The rate at which preimplantation blastocysts formed trophoblastic outgrowths when cultured in vitro was stimulated by dietary PA only if these blastocysts came from mice fed on a nutritionally deficient diet. The results suggest that PA serves as a beneficial nutrient under some conditions where its endogenous synthesis may be diminished.
A 28-day feeding study was conducted to test the effect of excess dietary lysine on rat growth and the concentration of copper, iron and zinc in plasma and liver. Young male Sprague-Dawley rats were fed a 10% protein casein diet with or without excess lysine. There were no significant differences in body weight gain, food intake or plasma proteins among the dietary treatment groups. Supplementation of the basal diet with 2.1% L-lysine caused a 53% reduction in hepatic copper and a significant reduction in hepatic iron. The addition of 0.7% or 2.1% lysine to the basal diet caused significant reductions in levels of plasma copper. The 2.1% level of lysine tended to lower the concentration of zinc in plasma. The data suggest that lysine may interfere with the availability of selected minerals by reducing tissue utilization or promoting excretion, or both.