The effect of dietary protein levels on mineral toxicity in chicks.

Studies have been conducted to determine the influence of dietary protein levels of 10, 20, and 30% fed as soybean meal on the toxicity of selenium, cadmium, vanadium, cobalt, and nickel to chicks. The toxicity was evaluated in terms of growth retardation and a decrease in resistance to S. gallinarum infection as measured by mortality. The toxicity of selenium or cadmium was unaffected by the protein level of the diet while the toxicity of vanadium, cobalt and nickel was decreased by increased dietary protein as measured by the interactions on growth. The interactions apparent on growth were not as apparent on resistance to infection indicating that the latter parameter is much less sensitive to these dietary manipulations than is growth.     

Effect of dietary vitamin C on ascites in broiler chicks

A total of 480 day-old broiler chicks were divided randomly into 4 equal groups, each of 4 replicates, and reared for two weeks. To their rations, which contained sodium chloride at 2.5% ascorbic acid was added at the rate of 0, 150, 300 and 450 mg/kg for groups 1, 2, 3 and 4 respectively. Incidences of ascites cases were 20.8, 10.8, 7.5 and 7.5% for the groups 1, 2, 3 and 4 respectively. When vitamin C was added to their rations body weights were increased significantly, but feed consumption remained unchanged. There were no significant differences in water consumption or body moisture. The total serum protein was significantly increased. The packed cell volume was only increased in the chicks that had received 450 mg vitamin C/kg of feed and there were no significant differences in the ascorbic acid content of the plasma. It was concluded that the addition of vitamin C to the chicks' rations reduces the incidence of ascites caused by toxic dietary levels of sodium chloride.     

25-Hydroxyvitamin D 1 alpha- and 24-hydroxylase activities in pig kidney homogenates: effect of vitamin D deficiency

A method was developed for simultaneous assay of 25-hydroxyvitamin D 1 alpha- and 24-hydroxylase in pig kidney homogenates. The products of these enzymes, 1,25-dihydroxycholecalciferol and 24,25-dihydroxycholecalciferol, were extracted from the in vitro incubation mixtures, isolated and purified by gel filtration and high-performance liquid chromatography, identified by ultraviolet absorption spectrometry, and high performance liquid chromatography with a second solvent system and quantified relative to authentic standards with a 254-nm detector system. Assay conditions included 12.5 microM substrate (25-hydroxycholecalciferol) concentration and an incubation time of 15 minutes at 37 degrees C, which was on the linear portion of time curves for both enzymes. Maximum enzyme velocity was 1548 pmol/minute per gram kidney tissue for 1 alpha-hydroxylase and 286 pmol/minute per gram kidney tissue for 24-hydroxylase. The apparent Km for pig kidney 25-hydroxyvitamin D 1 alpha-hydroxylase (1 alpha-hydroxylase) was 445 nM and for 25-hydroxyvitamin D 24-hydroxylase (24-hydroxylase) was 833 nM. We also demonstrated the use of this assay in pigs fed a semisynthetic diet with or without vitamin D. Pigs fed vitamin D-deficient diet had a 5- to 10-fold increase in 1 alpha-hydroxylase activity, severe hypocalcemia, low plasma, 1,25-dihydroxycholecalciferol, very low plasma (undetectable) 24,25-dihydroxycholecalciferol concentration, and no detectable 24-hydroxylase activity compared to those fed the vitamin D-replete diet.     

The influence of dietary vitamin E and calcium status on intestinal tumors in rats.

Male Sprague-Dawley rats were fed from weaning low (1-5 ppm) and normal (26-50 ppm) vitamin E diets for 30-34 weeks. Dietary fat was also varied from 5% (Experiment 1) to 20% (Experiments 2 and 3). Intestinal tumors were induced by 1,2-dimethylhydrazine given subcutaneously as 10 weekly doses at 20 mg/kg body wt. Tumor incidence was lower by 30% and burden was 25%-50% lower for low vitamin E rats than for vitamin E-replete rats. This result was independent of the fat content of the diet. In Experiment 3, vitamin E and calcium were assessed for their influence on intestinal tumors at two levels, with dietary vitamin E at 5 and 50 ppm and calcium at 0.2% and 1.0% in a 2 x 2 factorial experiment. The high calcium-low vitamin E diet produced the greatest fall in tumor incidence and burden relative to the other treatments. In this experiment, vitamin E deficiency reduced tumor incidence and calcium supplementation reduced tumor burden, with a significant interaction of the two. However, this group also showed evidence of reduced food intake and kidney change (calcification), which may have confounded the result. This points to a risk associated with this combination of nutrients at these levels in long-term experiments.     

The effect of vitamin D3 and dietary calcium level on the cadmium-induced morphological and biochemical changes in rat intestinal mucosa.

The effect of vitamin D3 and dietary calcium level on the cadmium-induced changes was observed in the duodena of rats raised on various diets differing in vitamin D and calcium levels. Observation with scanning electron microscopy revealed that vitamin D and dietary calcium were required for normal intestinal villi and microvilli formation. The damaged cells were observed in the intestinal villi of cadmium-exposed rats. Furthermore, dietary cadmium reduced the enzyme activities in microvilli. Especially, alkaline phosphatase activity was reduced in the cadmium-exposed groups, even though it was still responsive to vitamin D3. These effects with cadmium were modulated by vitamin D3 and dietary calcium level. That is, in the presence of vitamin D3 and calcium, the effect of cadmium on intestinal villi and microvilli was reduced.     

Influence of dietary vitamin E on nutritional pancreatic atrophy in selenium-deficient chicks

Studies were conducted to determine the relationship between dietary vitamin E (VE) and the development of nutritional pancreatic atrophy (NPA) in selenium (Se)-deficient chicks. Selenium- and VE-depleted chicks reared on a low Se, amino acid-based diet containing 100 IU VE (as all-rac-alpha-tocopheryl acetate) per kilogram were found to have exceedingly low pancreatic activities of Se-dependent glutathione peroxidase (SeGSHpx) at 8 d of age. Supplementation of the purified diet with 500 or 1,000 IU VE/kg prevented both NPA and the associated growth depression. Use of graded dietary VE levels showed that addition of at least 300 IU/kg was required to overcome the growth depression associated with severe Se deficiency. Although tissue alpha-tocopherol concentrations increased linearly with increasing dietary levels of VE, the response in pancreas was less than (about one-half of) those in liver and heart and, unlike the response in heart, was not affected by dietary Se level. That protection against NPA involved the antioxidant action of VE was suggested by results showing that NPA is promoted by high dietary levels of linoleic acid, that high VE levels correct membrane unsaturated fatty acid losses due to Se deficiency and that NPA is prevented by high levels of other antioxidants. It is suggested that the normally low activities of SeGSHpx and concentrations of alpha-tocopherol in the pancreas may predispose that organ to lesions due to oxidative stress under conditions of severe nutritional Se deficiency that results in further depletion of SeGSHpx. This situation may be overcome by feeding VE at 15-20-fold excesses over the levels normally regarded as nutritionally required.     

Effect of dietary calcium and lead status on intestinal calcium absorption

Dietary lead intake was demonstrated to result in two very different effects on intestinal calcium absorption and associated parameters, depending on dietary calcium status. Normal growing 14-day-old chicks were fed diets either low (0.05%) or adequate (1.2%) in calcium and containing varying levels of lead (0%-0.8%) for an additional 10 days. In chicks fed the low calcium diet, ingested lead inhibited intestinal 47Ca absorption, and intestinal calbindin D and alkaline phosphatase synthesis in a dose-dependent fashion. Even at the highest levels of lead, however, this inhibition was limited to the stimulation of these parameters by low dietary calcium. In chicks fed the normal calcium diet, lead exposure did not diminish intestinal 47Ca absorption, or calbindin D or alkaline phosphatase synthesis, but actually elevated the values of these parameters at the higher lead exposure levels. The results indicate that the primary effect of lead, in both cases, occurs at or prior to intestinal protein synthesis and most likely involves the cholecalciferol endocrine system rather than any direct interactions between lead and calcium at the intestinal level.     

Biological activity of 1 alpha,25-dihydroxyergocalciferol in rachitic chicks and in rats

The bioactivity of chemically synthesized 1 alpha,25-dihydroxyergocalciferol (1,25(OH)2D2) was investigated in rachitic chicks and in vitamin D-deficient rats. In prophylactic and in curative chick assays 1,25(OH)2D2 is about 10 times less active than 1 alpha,25-dihydroxycholecalciferol (1,25(OH)2D3). Since in the same bioassay vitamin D2 is more than 80 times less active than vitamin D3, discrimination against vitamin D2 in chickens must occur at two points, before and after the formation of 1,25(OH)2D2. Receptor binding studies revealed that the chick duodenal receptor binds 1,25(OH)2D2 with the same capacity as 1,25(OH)2D3. In rats 1,25(OH)2D2 proved to have the same antirachitic activity as 1,25(OH)2D3 and might become of therapeutic interest for application in man and domestic animals if the expectations of lower toxicity are confirmed.     

Stimulatory effect of inulin on intestinal absorption of calcium and magnesium in rats is modulated by dietary calcium intakes

Summary Previous studies have shown that short–term intake of fermentable oligosaccharides (OS), including inulin, can increase mineral intestinal absorption in humans and animals. While the stimulatory effect of these substances on intestinal magnesium (Mg) absorption is generally high and consistent, their effect on calcium (Ca) seems to depend on experimental conditions, particularly the duration of fermentable OS intake. The aim of this study was to determine how the short– and long–term dietary Ca intake may modulate the effect of inulin on Ca absorption. Sixty male Wistar rats, weighing 275 g, were randomized into two groups to receive or not 10% of inulin in their diet. Each group was divided into three sub–groups to receive one of the following dietary Ca levels 0.25%, 0.50% and 0.75% in their food. The animals were fed fresh food and water ad libitum for 40 days. Apparent intestinal absorptions of Ca and Mg were determined at D13 and D36 of the experiment. As expected, inulin feeding increased Ca and Mg absorption in both periods at all dietary Ca levels. However, the effect of inulin on intestinal Ca absorption was dependent on dietary Ca levels and on experiment duration. In the short–term period, the inulin effect was prominent in the groups receiving high or low Ca levels, but in long–term period inulin improved intestinal Ca absorption much more in the group receiving the low Ca level. In addition, efficiency of intestinal absorption of Ca and Mg (%) was negatively affected by Ca intake levels. These results show that the beneficial effect of inulin on intestinal Ca absorption may be more marked in cases where the Ca intake is low or where the organism’s Ca requirement is high. Further studies are required to confirm these results in humans.     

The effect of dietary fiber on the postprandial serum vitamin A concentration in man.

In 11 normal female subjects, ages 19 to 22 years, the postprandial serum vitamin A concentration was measured 3, 5, 7, and 9 hr after oral administration 300,000 IU vitamin A-palmitate given with a formula diet to which was added 40 g wheat bran, 40 g microcrystalline cellulose, 15 g apple pectin, 15 g guar flour, 15 g carob bean flour, or 20 g carrageenan. When vitamin A was given together with guar flour and apple pectin 3 hr after starting the experiment, the mean serum vitamin A concentration was significantly higher than in controls. Areas under serum vitamin A concentration curves, taken as a measure of the amount of vitamin A absorbed, were significantly higher when the vitamin was administered together with the investigated dietary fiber substances.     

The effect of dietary vitamin A on NO2 exposure on the hamster lung.

The effect of dietary vitamin A and NO2 exposure on the hamster lung was evaluated by histopathology, electron microscopy, and thymidine uptake studies. Hamsters were maintained on deficient (0 micrograms), adequate (100 micrograms), and high (200 micrograms) dose levels of vitamin A while being exposed repeatedly to 10 ppm of NO2 for 5 hours once a week over an 8-week period. Hamsters of the deficient group exhibited clinical and morphologic changes characteristic of vitamin A deficiency. Animals maintained on adequate and high dose levels of vitamin A were not affected by vitamin A deficiency. Hypertrophy and hyperplasia of the epithelial cells of the terminal bronchiolar alveolar region of lungs of adequately and highly dosed animals were greater than those observed in the deficient animals, when NO2 exposure was given. However, the extent of the lesions observed in all three groups was less than that seen in normal hamsters given a single, 5-hour NO2 exposure. Ultrastructural changes observed in vitamin A-deficient hamsters exposed to NO2 were hypertrophy and hyperplasia of bronchiolar epithelial cells, diffuse loss of cilia, membrane damage, and mitochondrial damage manifested by calcium deposition. Tritiated thymidine uptake studies of lungs of animals exposed repeatedly revealed a rather erratic cell renewal pattern following NO2 exposure in comparison to the group of animals exposed singly.     

Effects of dietary aluminum on chicks Gallus gallus domesticus with different dietary intake of calcium and phosphorus

Birds that feed in acidified areas may be exposed to an increased intake of aluminum, while their intake of calcium and phosphorus may simultaneously be low. In particular, juvenile birds foraging in acidified areas may suffer from increased effects of aluminum due to high demands of calcium. Day old chicks were fed six different diets where aluminum was combined with normal and low concentrations of dietary calcium and phosphorus for 14 days. The normal calcium-available phosphorus (Ca-P) level was 1.05%–0.45%, and the low dietary Ca-P level was 0.49%–0.21%. Aluminum was given in dietary levels of 0%, 0.13%, and 0.31%. Aluminum had no effects on growth, mortality, or hematocrit, but induced hypocalcemia.Bones accumulated more aluminum than kidneys. A high dietary concentration of aluminum (0.31%) increased the accumulation of aluminum twofold in bones and threefold in kidneys when the dietary concentration of calcium and phosphorus was halved. Opposed to the predictions, bone mineralisation was stimulated by an intermediate increase in dietary aluminum (0.13%) at both levels of dietary calcium and phosphorus. Bone stiffness was also stimulated at this dietary aluminum concentration, but only at the diet low in calcium and phosphorus. A high dietary aluminum concentration did not have any effect on bone stiffness or calcium concentration. Bone stiffness correlated positively with the calcium concentration in bone, and negatively with the aluminum concentration in bone. The effect of dietary aluminum on bone stiffness is probably caused by an alteration in bone mineralization, rather than by the presence of aluminum in bones.     

维生素K和钙对去卵巢大鼠骨质疏松的影响

切除雌鼠双侧卵巢以造成骨快速丢失作为模拟女性绝经后骨质疏松症的动物模型,从骨计量学、骨生物力学等方面综合观察单纯补充维生素Ｋ（９０ｍ ｇ／ｋｇ）、钙（５ｇ／ｋｇ）及两者联合作用６个月对骨丢失的影响。结果发现：与正常对照组（Ａ）大鼠相比,模型对照组（Ｂ）大鼠骨量显著减少,骨脆性增加。与模型对照组相比,单纯补充维生素Ｋ组（Ｄ） 股骨中点骨密度值显著提高,股骨干骺端及腰椎骨密度、股骨近侧端矿物质含量都有增高趋势,表明补充维生素Ｋ 可在一定程度上减少骨丢失;同时补充维生素Ｋ及钙组（Ｅ）股骨的最大挠度与最大应变值,与模型对照组相比也有增高趋势,表明补充维生素Ｋ可提高骨的柔韧性,改善股骨的力学性能。综合骨计量学与骨力学观察结果,发现各种实验措施对密质骨的效果皆优于松质骨,并且维生素Ｋ与钙的联合作用效果优于单纯补充维生素Ｋ 或钙。本实验结果提示：绝经后妇女,作为骨质疏松危险人群,增加膳食维生素Ｋ 与钙的摄入是有帮助的     

The effect of carbohydrates in milk on the absorption of calcium by postmenopausal women.

The purpose of this investigation was to determine if the presence of carbohydrate in milk, either lactose or its hydrolysis products, enhance the bioavailability of calcium (Ca) in milk. Two studies were performed. In study A, fractional Ca absorption was measured in 11 lactose-tolerant postmenopausal women after an oral dose of 47Ca-equilibrated milk formula containing no carbohydrate (NOCHO), lactose (LACTOSE), or an equivalent amount of glucose plus galactose (SUGAR); all participated in three absorption studies in random order. The NOCHO formula contained 10.0 g protein and 217 mg Ca from a combination of milk mineral and protein isolates; the LACTOSE and SUGAR formulae contained in addition 12 g lactose or 6 g glucose plus 6 g galactose, respectively. In study B, fractional Ca absorption was measured in five postmenopausal women after an oral dose of 47Ca-equilibrated skim milk (217 mg Ca) and lactase-treated milk, each with sufficient carbohydrate added to equal 12 g. For both studies, the increase in forearm radioactivity 4 and 8 hours after oral 47Ca administration relative to the increase observed after IV administration was used to estimate fractional Ca absorption. The addition of lactose but not glucose plus galactose to the NOCHO formula enhanced Ca absorption (p less than 0.05). Fractional absorption at 4 hours was 0.386 from the LACTOSE formula compared with 0.310 for both the NOCHO and SUGAR formulae. Those individuals with the lowest absorption in the absence of carbohydrate had the greatest increase with lactose. In contrast, Ca absorption was the same from skim milk as from lactase-treated skim milk (study B).(ABSTRACT TRUNCATED AT 250 WORDS)