The presence of water-soluble vitamin D and 25-OH-D sulfates in human breast and cow's milk was studied. We first confirmed that synthetic vitamin D2 and D3 sulfates could not be hydrolyzed by alkali but by acid. Breast or cow's milk was separated into milk whey containing water-soluble components and milk curd containing crude proteins and lipophilic components. The separated milk whey and curd were hydrolyzed by acid or alkali and each lipid extract was subjected to HPLC analysis. Neither peak due to vitamin D and 25-OH-D was observed in the chromatograms of acid- and alkali-hydrolyzed milk whey, whereas the peaks due to vitamin D3 and 25-OH-D3 were found in the chromatograms of both acid- and alkali-hydrolyzed milk curd and there was no significant difference between the respective peak heights. The eluates corresponding to the respective peaks observed on the latter's chromatograms were collected and subjected to UV, HPLC, GC-MS and GLC to identify the existence of vitamin D3 and 25-OH-D3, respectively. We concluded from these results that neither breast nor cow's milk contained water-soluble vitamin D and 25-OH-D sulfates, whereas they contained fat-soluble vitamin D3 and 25-OH-D3. The concentrations of vitamin D3 and 25-OH-D3 in breast milk were about 125 and 350ng/liter, while those in cow's milk were about 420 and 270ng/liter, respectively. The experiments on the transfer of 3H-D3 and 3H-25-OH-D3 perorally dosed to lactating rats into suckling pups through their milk also supported the above conclusion.
The direct cell-to-cell transfer of tocopherol between red blood cells (RBCs) was examined. Two kinds of RBCs were provided; 1) Tocopherol-deficient ones showing complete dialuric acid-hemolysis and 2) tocopherol-supplemented ones showing no dialuric acid-hemolysis. The two kinds of RBCs were mixed and incubated with gentle swirling in a buffer solution. If no tocopherol transfer occurred between the two kinds of RBCs in the cell suspensions, hemolysis should not change during incubation because hemolysis is limited only in the -deficient cells in the suspensions. However, it was actually observed that when RBCs with adequate amounts of tocopherol were incubated with tocopherol-deficient RBCs, dialuric acid-induced hemolysis decreased during a 3-h incubation period. Contrarily, when an inadequate amount of tocopherol constitut-ing a limiting level for inhibition of hemolysis, exsisted in RBCs which were mixed with -deficient ones, hemolysis increased after incubation. This indicates that tocopherol is transferred from the tocopherol-rich RBCs to the -deficient RBCs. The transfer was greater as the hematocrit of cell suspensions increased. Gum arabic contained in the suspensions inhibited the transfer, while bromelain (a protease which lowers the electric charge on the cell surface) increased it. These findings indicate that the transfer of tocopherol is related to the frequency of collision between cells.
Erythrocytes of vitamin E-deficient rats and normal rats were oxidized at 37°C by molecular oxygen using a free radical initiator. The erythrocytes were oxidized by a free radical chain mechanism with kinetic chain length considerably larger than 1 and resulted in hemolysis. Vitamin E suppressed both oxidation and hemolysis, but the extent of hemolysis was determined primarily by the extent of oxidation indepen-dent of the presence or absence of vitamin E.
Since it has been demonstrated that a high level of fat is a dietary factor in the etiology of colon cancer, the effect of carrageenan, a polysaccharide extracted from the red seaweeds, on 1, 2-dimethylhydra-zine-induced colonic tumors in rats fed a semipurified control diet containing an ordinary level of fat was studied. Nevertheless, the enhancing effect of carrageenan on colonic tumors was observed. The rats fed a carrageenan diet had approximately twice the fecal weight compared to the rats fed a control diet. While no significant differences were found in β-glucuronidase activities in colonic mucosa, liver or plasma in the car-rageenan-fed rats and controls, the activity in feces was significantly lower in the carrageenan-fed rats. At least, no β-glucuronidase activity seemed to be related to the tumor-enhancing effect of carrageenan.
Various meals being currently consumed by urban Japanese were determined for iodine, The meal samples were collected in 1982 and 1984. The habitual daily home meals of 4 middle-aged Japanese living in urban areas contained 45-1, 921μg (mean; 362, 361, 429 and 1, 023μg, respectively) of iodine per day. The regular meals served in two university hospitals contained 95-287μg (mean; 195μg) and 89-4, 746μg (mean; 1, 290μg) of iodine per day, respectively, and the diets for diabetes mellitus contained 59-144μg (mean; 96μg) of iodine per day. In the daily meals containing iodine exceeding ca. 300μg, some kinds of seaweeds and, in some cases, several foods containing a red food color with low iodine bioavailability, erythrosine, provided a large portion of iodine. The iodine contents of refectory meals in a university were 47-203μg (mean; 113μg) per meal and those of lunches in two elementary schools were 25-31μg (mean; 27μg) and 18-43μg (mean; 36μg) per lunch, respectively. These results suggest that the current daily iodine intake of urban Japanese is not great and that erythrosine elevates the iodine content of meals.
The effects of dietary manipulations on the fate of trans-octadecenoates deposited in the tissues of rats were examined. Male rats were fed on a 15% fat diet containing trans-octadecenoic acids (46.6% of total fatty acids) for 35 days followed by various diets free of traps-fatty acids. After removal of trans-fatty acids from the diet, there were phased disappearances of traps-octadecenoates from the circulation; a rapid and broad reduction in one day and a slow and gradual reduction thereafter. The rate of the initial reduction in serum trans-octadecenoates was highest on a high fat (20%) diet in relation to low fat (1 or 5%) diets. However, the disappearance rate at the later stage was apparently the same among the various groups and trans-fatty acid contents in the serum declined to about 10% of the initial value in 2 weeks and thereafter. After 35 days, the concentration of traps-octadecenoates remaining in the adipose tissue was markedly lower in rats fed on a high protein (40%) diet. The effects of dietary fat type and cholesterol on the fate of serum trans-octadecenoates were virtually the same, but livers from rats fed on the cholesterol-free safflower oil diet contained more trans-fatty acids than those from rats fed on the corresponding olive oil diet. Thus, the amounts of traps-fatty acids stored in the tissues cannot be merely predicted from serum levels. It seems that both dietary fat and protein affect the metabolic rate of trans-octadecenoates in rats.
The heat-labilities of liver glucose-6-phosphate dehydro-genase and malic enzyme of 1- and 12-month-old rats were observed by incubation of the crude enzymes at 52 and 55°C, respectively. The biphasic heat-inactivation curves were obtained for those enzymes of the 12-month-olds, whereas no biphasic curves were obtained for the enzymes of the 1-month-olds. The age-dependent rapid inactivations of glucose-6-phosphate dehydrogenase and malic enzyme were not relieved by addition of their substrates in the incubation media. However, the rapid age-dependent inactivations of these enzymes disappeared by addition of NADP. It is suggested that the age-dependent heat-inactivation of these enzymes is ascribed to the conformational modification of the proteins.
The effects of dietary protein on the maintenance energy requirement (MEm) and net utilization efficiency of metabolizable energy for growth (MEg) were investigated by regression analysis of energy balance with various energy intakes. Weanling rats of the Wistar strain, weighing about 85g, were given a diet containing 0 to 70% casein freely or in restricted amounts (equivalent to two-thirds or one-third of the intake of the ad libitum group) for 5 days. The MEm was fairly constant in rats given 10 to 50% casein diets, being about 29 kcal/ 100 g BW/day, but increased at higher or lower dietary protein levels, indicating inefficient energy utilization in protein-malnourished animals. From the slope of the regression line between energy balance and metabolizable energy intake, the net energetic efficiencies for growth were estimated as 68, 71, 74, 77, 82, 83, 80, 78, 77 and 74% with 0, 3, 6, 10, 20, 30, 40, 50, 60 and 70% casein diets, respectively. Weanling rats fed 20 to 30% casein diets utilized the dietary energy for growth most efficiently. At protein levels higher or lower than 20 to 30%, the efficiency was less, showing that MEg utilization depended on dietary protein. The energy necessary for 1g body weight gain was 2.6 kcal in rats receiving 30% casein diet, but increased with an increase or decrease in the protein level. These data on the food efficiency, MEm, the net efficiency of MEg and the energy necessary for 1g weight gain show that dietary protein affects energy utilization and that protein-malnourished animals use energy inefficiently.
The maintenance energy requirement (MEm) of pregnant rats and net energetic efficiency for fetal growth during late pregnancy were examined by regression analysis. Pregnant rats, weighing about 180g, were fed on 20% casein diet during early-mid pregnancy and then divided into three groups-ad libitum-fed, 50% food restricted, or starved. A linear relation between the energy balance (Y, kcal/100g BW/day) and the metabolizable energy intake (X, kcal/100g BW/day) was obtained as Y=0.81X-14.8 3 (n: 17, r=+0.99, p<0.001). The X-intercept, MEm, was calculated to be 18.31 kcal/100g BW/day. Pregnant animals fed ad libitum retained 6.1 and 1.1 kcal of energy daily in their conceptuses and their own body, respectively, during late pregnancy. Assuming that the net efficiency of maternal energy deposition is equal to that for size-and age-matched nonpregnant rats, the net energetic efficiency for fetal growth was calculated to be 82%. This value was very close to the net efficiency for weanling rats reported previously, suggesting that the net energetic efficiency for maximum growth in well-nourished rats is about 82%.
The comparative effects of methionine and its structurally and metabolically related compounds on plasma cholesterol level were investigated with rats fed a high cholesterol diet. The plasma cholesterol level was significantly enhanced by the dietary addition of methyl compounds such as L-methionine, D-methionine, choline and betaine. On the other hand, the intermediary metabolites of methionine such as homocystine, cysteine and 3-methylthiopropionate reduced plasma cho-lesterol. S-Methyl-L-cysteine and dimethylglycine had no significant effect. The plasma cholesterol-elevating effects of methionine, betaine and histi-dine were all prevented, more or less, by the concurrent addition of glycine to the diet, suggesting the existence of a common mechanism for their effects. The results support a possibility that the plasma cholesterol-elevating efficacy of methionine is attributable to its methyl group.
The effect of vitamin E on the thermal behavior of two saturated phosphatidylcholines was investigated by differential scanning calorimetry. For dimyristoyl and dipalmitoyl phosphatidylcholines, the addition of vitamin E at concentrations of 1, 5 and 10 mol% vitamin E, resulted in a lowering of the phase transition temperature and a broaden-ing of the temperature range of the phase transition indicating an increase in the fluidity of the phospholipids. Taken together with other physical studies on the effect of vitamin E on (unsaturated) phospholipids, these results indicate that vitamin E could influence the physical properties of membrane phospholipids in addition to its known antioxidant role. The likelihood of this interaction would be enhanced if vitamin E was not randomly distributed in biological membranes but rather was located in domains where its local concentration, relative to phospholipids, was elevated.