High Levels Of Dietary Vitamin Research Articles

Effect of dietary vitamin C on the inflammatory response of mrigal, Cirrhinus mrigala (Hamilton), to Freund's complete adjuvant

Vitamin C de®ciency or excess can modulate the immune response and alter the disease susceptibility pattern in ®sh (Blazer 1992). The bene®cial effects of high dietary levels of vitamin C on different immune parameters (both speci®c and non-speci®c) and resistance to infection have been reported by a number of authors (Durve & Lovell 1982; Li & Lovell 1985; Wahli, Meier & P®ster 1986; Liu, Plumb, Guerin & Lovell 1989; Navarre & Halver 1989; Hardie, Fletcher & Secombes 1991; Meier, Schmitt & Wahli 1991; Verlhac & Gabaudan 1994; Ortuno, Esteban & Megeguer 1999). There has been very little research on this topic in Indian major carps. However, Agrawal & Mahajan (1980) have reported de®ciency syndromes of vitamin C in mrigal, Cirrhinus mrigala (Hamilton).

Immunomodulation by dietary vitamin C in healthy and aflatoxin B 1-induced immunocompromised rohu ( Labeo rohita)

The aim of this study was to examine the immunomodulatory effect of high levels of dietary vitamin C in healthy and immunocompromised rohu ( Labeo rohita) treated with aflatoxin B 1 (AFB 1). Four groups of rohu were fed experimental diets containing either no vitamin C or supplemented with vitamin C at 500 ppm for 60 days. On the first day of feeding, one group fed the high vitamin C diet and one fed the vitamin C deficient diet, were injected intraperitoneally with a single doses of AFB 1 at 1.25 mg kg −1 body weight. The effect of AFB 1 and high dietary vitamin C on specific and non-specific immunity, and disease resistance against Aeromonas hydrophila were examined in the rohu. The ability of vitamin C to counteract immunosuppression induced by AFB 1 was also examined. Specific immunity indicated by haemagglutination and haemolysin titres against sheep red blood cells (SRBC), and bacterial agglutination appeared to be unaffected by either the AFB 1 treatment or the vitamin C enriched diet. A significant reduction was observed in the non-specific immunity of AFB 1-treated fish, however, indicated by lowered bactericidal and lysozyme activities. High dietary vitamin C, on the other hand, enhanced the non-specific immunity of fish, including an enhanced phagocytic ratio and increased serum lysozyme activity. Feeding a high level of dietary vitamin C to AFB 1-treated fish increased these parameters to levels similar to those found in control fish. High dietary vitamin C significantly ( p<0.05) enhanced protection against Aeromonas hydrophila infection in both healthy and immunocompromised fish. Results from this study help to establish the beneficial effect of dietary vitamin C on AFB 1-induced immunosuppression, as well as confirming the immunostimulatory effect of vitamin C in rohu.

Vitamin E increases natural cytotoxic activity in seabream (Sparus aurata L.)

The natural cytotoxic activity of head-kidney leucocytes from gilthead seabream (Sparus aurata L.), after in vitro and in vivo vitamin E treatment, against tumor cells was studied by flow cytometry. Leucocytes were incubated in culture medium with different vitamin E supplementations (0·01–10μg ml−1) for 6, 24 or 48h and the results demonstrate that all the assayed vitamin E supplementations significantly enhanced the natural cytotoxic activity of leucocytes. To determine the effect of a high dietary level of vitamin E on this activity, fish were fed with 0 (control), 600, 1200 or 1800mg of vitamin E supplementation kg−1diet for 2, 4 or 6 weeks. After 2 and 4 weeks of treatment, the natural cytotoxic activity was significantly enhanced at the highest (1·8g kg−1diet) and lowest (600mg kg−1diet) vitamin E supplement dosage, respectively. No effect of the vitamin E supplemented diet on seabream leucocyte natural cytotoxic cell activity was observed after 6 weeks of treatment.

Implications of changing the housing conditions of pigs prior to slaughter for the eating quality of bacon

Commercial housing conditions are known to have an effect on the eating quality of bacon. Significant differences have been shown between pigs reared on solid concrete floors or straw-bedded accommodation (Maw et al. In press). Also high levels of dietary Vitamin E have been shown to improve pigmeat quality (Buckley et al., 1995). This experiment was carried out to examine whether the effects of housing could be eliminated or reversed by altering housing conditions or reduced by dietary supplementation with Vitamin E.

Glutathione peroxidase-1 gene knockout on body antioxidant defense in mice.

To determine the in vivo role of cellular glutathione peroxidase (E.C.1.11.1.9, GPX1), we challenged the GPX1 knockout [GPX1(-/-)], the GPX1 overexpressing [GPX1(+)], and their respective wild-type (WT) mice of different Se and vitamin E status with acute oxidative stress. After these mice were injected with pro-oxidants paraquat or diquat at 12 to 125 mg/kg of body weight, their survival rate and time were a function of their GPX1 activity levels. The GPX1 protection was associated with attenuation of NADPH and NADH oxidation, protein carbonyl and F(2)-isoprostanes formation, and alanine transaminase release in various tissues, and was irreplaceable by high levels of dietary vitamin E or other selenoproteins. The GPX1 expression was also protective against moderate oxidative stress induced by low levels of paraquat or diquat, particularly in the Se-deficient mice. Alteration of GPX1 expression showed no impact on the expression of other selenoproteins and antioxidant enzymes in unstressed mice. Total Se content in liver of the Se-adequate GPX1(-/-) mice was reduced by 60% the WT controls. In conclusion, normal expression of GPX1 is essential and overexpression of GPX1 is beneficial to protect mice against acute oxidative stress.

Effect of induced hyperoxia on the antioxidant status of Atlantic salmon Salmo salar L. fed three different levels of dietary vitamin E

Atlantic salmon smolt (64 g) were fed 40, 300 or 1100 mg kg−1 all-rac-α-tocopheryl acetate feed under normoxic and moderate hyperoxic conditions for 12 weeks. After 7 weeks, however, the hyperoxic fish were subjected to a temporary severe supersaturation of dissolved oxygen with development of gas bubble disease and substantial mortality as a result. Liver α-tocopherol (α-TOH) levels reflected the dietary input after 6 and 12 weeks of feeding. Increased levels of thiobarbituric-reactive substances (TBARS) in the liver of hyperoxygenated fish after 6 weeks indicate that moderate hyperoxic conditions may represent an oxidative challenge to the fish. After 12 weeks, liver ascorbic acid (AA) content was reduced in hyperoxygenated fish, and a decreasing tendency was also found in the liver content of α-TOH. Effects of oxygen supersaturation were also observed on liver antioxidant enzyme activities, content of glutathione and total mercapthans in liver, phagocytic chemiluminescent response and total plasma protein level, indicating a disturbed redox balance. No effects of dietary vitamin E were observed on any of the measured parameters, indicating that high levels of dietary vitamin E under these circumstances did not protect the fish against oxidative stress.

High Levels of Dietary Vitamin E Do Not Replace Cellular Glutathione Peroxidase in Protecting Mice from Acute Oxidative Stress

Our objective was to determine whether high levels of dietary vitamin E replaced the protection of the Se-dependent cellular glutathione peroxidase (GPX1) against paraquat- or diquat-induced acute oxidative stress in mice. Two experiments were conducted using GPX1 knockout [GPX1(−/−)] mice and wild-type (WT) mice (n = 78/group). In Experiment 1, mice were fed torula yeast–based, Se-adequate (0.4 mg/kg as sodium selenite) diets + 0, 75, 750 or 7500 mg all-rac-α-tocopheryl acetate for 5 wk before an intraperitoneal injection of 50 mg paraquat/kg body weight. In Experiment 2, mice were fed the diet + 0 or 750 mg all-rac-α-tocopheryl acetate for 5 wk and were killed 1 or 3 h after an injection of diquat at 12, 24 or 48 mg/kg. In Experiment 1, all mice died of the injection and there were 8- to 15-fold differences (P < 0.001) in survival times between the GPX1(−/−) and the WT mice. Although increasing tocopheryl acetate from 0 to 750 mg/kg extended the survival time of the GPX1(−/−) mice for 2 h (P = 0.06), the highest tocopheryl acetate level resulted in a decrease (P < 0.05) in survival time in the WT mice. The vitamin E–deficient GPX1(−/−) mice had the highest concentration of hepatic thiobarbituric acid reacting substances. In Experiment 2, the diquat-induced formation of hepatic F2-isoprostanes was accelerated (P < 0.05) by vitamin E deficiency and was also affected by the GPX1 knockout. Diquat produced much greater (P < 0.01) dose-dependent increases in plasma alanine transaminase (ALT) activities in the GPX1(−/−) than in the WT mice. Hepatic phospholipid hydroperoxide GPX activities were decreased (P < 0.05) by the diquat injection only in the vitamin E–deficient GPX1(−/−) mice. Despite a potent inhibition of hepatic lipid peroxidation, high levels of dietary vitamin E do not replace the protection of GPX1 against the paraquat-induced lethality or the diquat-induced plasma ALT activity increase in mice.

Influence of dietary vitamins A and E on serum α- and γ-tocopherols, retinol, retinyl palmitate and carotenoid concentrations in Humboldt penguins ( Spheniscus humboldti)

Serum retinol, retinyl palmitate, β-carotene, cryptoxanthin, lutein, α-tocopherol and γ-tocopherol were measured in 18 captive Humboldt penguins ( Spheniscus humboldti) prior to and following the removal of Columbia River (CR) smelt ( Thaleichthys pacificus) from the diet. Dietary vitamin A was reduced from 59.8 to 13.5 IU g −1 (dry matter basis) when CR smelt was removed from the diet. Minimal changes were noted in dietary vitamin E. Serum samples Without-CR smelt had significantly lower circulating retinol (1.19±0.09 vs. 1.94±0.08 μg ml −1) and retinyl palmitate (0.033±0.012 vs. 0.105±0.004 μg ml −1) compared to samples With-CR. The Without-CR smelt diet resulted in increased serum α-tocopherol from 26.4±0.94 to 39.1±3.72 μg ml −1. More serum samples taken Without-CR smelt had detectable levels of γ-tocopherol than those With-CR smelt. Serum lutein was higher for the samples taken Without versus With-CR smelt. Serum cryptoxanthin did not differ. β-Carotene was not detected. Data indicate that high levels of dietary vitamin A can affect circulating levels of retinol, retinyl palmitate and vitamin E. Thus, dietary vitamin A and the interrelationship between vitamins A and E should be considered when assessing captive penguins.

Effect of dietary dl-alpha-tocopherol on tissue alpha- and gamma-tocopherol and pulmonary hypertension syndrome (ascites) in broilers

The objectives of this experiment were to determine the effects of high dietary levels of vitamin E on growth performance and pulmonary hypertension syndrome (PHS) mortality. Male broiler chicks (Cobb 500) were randomly assigned to one of four dietary treatments consisting of standard starter and grower diets supplemented with 0, 17, 46, and 87 mg dl-alpha-tocopherol acetate/kg. To encourage the development of PHS, air temperature in the house was 32 and 28 C for Weeks 1 and 2, dropped to 18 C during Week 3, and kept between 10 and 15 C during Weeks 4 through 7. Also, chicks were placed in floor pens on litter used for five previous flocks and ventilation reduced to increase dust and ammonia in the house. Ammonia levels increased from an initial 18 to 36 ppm on Day 42 with the increase in ammonia corresponding to an obvious increase in dust in the air. Lung and liver tissue obtained at 2, 5, and 7 wk of age were analyzed for tissue alpha- and gamma-tocopherol by liquid chromatography. Dietary vitamin E had no effect on body weight, feed intake, or feed efficiency. Cumulative PHS mortality through 7 wk of age was 21% and was also unaffected by dietary treatment. Liver and lung alpha-tocopherol concentrations exhibited a dose-response increase to dietary tocopherol and there was a high correlation between lung and liver tissue alpha-tocopherol (r = 0.72, P < 0.05). Whereas gamma-tocopherol concentrations in lung and liver were unaffected by dietary treatment, liver and lung exhibited age-dependent increases in both alpha- and gamma-tocopherol. Despite dose-dependent increases in tissue alpha-tocopherol, supplementation of diets with up to 87 mg dl-alpha-tocopherol acetate had no effect on growth performance or PHS mortality in broilers under the conditions used in this study.

Effect of dietary vitamin A on forestomach tumorigenesis during the total and postinitiation stages in mice treated with high- or low-dose benzo(a)pyrene.

The effects of dietary vitamin A on forestomach tumorigenesis during the total stage of the initiation and postinitiation periods and during the postinitiation stage were evaluated in ICR/Jcl mice treated with either high or low doses of benzo(a)pyrene (B(a)P). In experiment 1, the animals were initiated with a high carcinogenic dose of B(a)P to a total of 20 mg, while in experiment 2 the animals were treated with a low dose of B(a)P to a total of 2 mg. A control group of animals received no carcinogens. Five different dietary levels of vitamin A supplements were used in each experiment and in the control study. In experiment 1, a high incidence of tumorigenesis was observed in every group, with 74% to 96% developing papilloma and 19% to 46% developing carcinoma. In experiment 2, the incidence of tumorigenesis in the high-dose vitamin A groups, including those given during the total and postinitiation stages, was found to be significantly reduced at 7.4%, compared with that in the low-dose vitamin A group of 57.7% (P < 0.05). These results suggest that a high dietary level of vitamin A can reduce the incidence of tumorigenesis when low carcinogenic dose levels of B(a)P are given in both the total and postinitiation stages.

Characteristics of nonsmoking women in NHANES I and NHANES I epidemiologic follow-up study with exposure to spouses who smoke.

Few studies have examined the relation between passive smoking and dietary intake in a large population. This report examines the nutrition and behavioral characteristics of 3,896 nonsmoking women from the first National Health and Nutrition Examination Survey (NHANES I) population in relation to exposure to environmental tobacco smoke. The data indicate that nonsmoking women who were exposed to husbands who smoked were more likely to be older, have lower education, live in the city, and have other health behaviors that could increase their risk of lung cancer compared with nonsmoking women with husbands who did not smoke. The nonexposed women were more likely to take vitamin supplements, to not drink alcohol, and to consume higher levels of dietary vitamin A, vitamin C, and calcium. The exposed and nonexposed women showed no difference in the levels of fatty acid intake nor in the levels of several other foods from the food frequency list after correction for age. Many of the differences that the authors observed between the women who were exposed and nonexposed to passive smoking could affect the risk of cancer. Therefore, they recommend that future studies of nonsmokers examine the influence of both passive smoking and diet on the risk of disease rather than examine the influence of a single factor.

Bioavailability and interaction of vitamin A and vitamin E in ruminants.

Recent interest in antioxidant vitamins and animal nutrition has resulted in the investigation of feeding levels of vitamin E which are considerably higher than NRC requirements. Relatively high levels of vitamin E are required to improve animal product quality such as extending beef color stability and minimizing off-flavors in milk due to lipid oxidation. Concerns regarding a negative effect of vitamin A on vitamin E utilization and the suitability of currently used standard activity values for vitamin E supplements for ruminants have been raised. High dietary levels of vitamin A have depressed vitamin E utilization in most animals studied. In the dairy cow, 675,000 IU of vitamin A acetate per head per day is required to significantly depress vitamin E utilization. This is approximately 10-fold greater than the highest levels currently fed to dairy or beef cattle and therefore should not cause a practical problem. Synthetic and naturally derived alpha-tocopherol, and their ester forms, are commonly used as vitamin E supplements. These various forms give rise to isomer differences, ester differences and formulation differences that can affect their absorption and subsequent utilization. The current research indicates that the commonly used standard activity values based on a value of 1.00 IU per mg of all-rac-alpha-tocopheryl acetate are probably too low for the ruminant. The roles of isomeric forms and gastrointestinal tract absorption have not been completely resolved regarding their effects on the bioavailability of vitamin E supplements.

The effect of excessive dietary vitamin A on performance and vitamin E status in swine fed diets varying in dietary vitamin E

A study was conducted to evaluate the effects of high dietary vitamin A on vitamin E status and performance of growing-finishing pigs fed diets supplemented with varying levels of vitamin E. Treatments consisted of corn-soybean meal-based diets supplemented with retinyl acetate to provide 2,000 or 20,000 IU of vitamin A/kg of diet and with DL-alpha-tocopheryl acetate to provide 0, 15, or 150 IU of added vitamin E/kg in a 2 x 3 factorial arrangement. The trial involved 84 crossbred pigs (26 kg initial BW) allotted to pens of two pigs each (one gilt, one barrow). Serum was obtained from all pigs on d 0, 3, 7, 21, 35, 63, and 77 of the 83- or 90-d feeding period. Tissue samples (liver, leg, and neck muscle, backfat, and leaf fat) were collected from one pig (barrow) in each pen at the end of the feeding period. Average daily gain and gain:feed were .93 kg and .30, respectively, without treatment differences (P > .10). Serum alpha-tocopherol increased linearly (P < .01) by d 3 with increasing level of dietary vitamin E supplementation. High dietary vitamin A resulted in a small decrease (P < .01) in serum alpha-tocopherol on d 3, but serum alpha-tocopherol concentration was not affected (P > .10) on other days. Tissue alpha-tocopherol increased linearly (P < .001) as dietary vitamin E increased in all tissues examined. No consistent evidence was found to indicate that a high level of dietary vitamin A interfered with performance or with blood serum or tissue alpha-tocopherol concentrations in growing-finishing swine.

Effects of high levels of vitamin e supplementation in heat stressed laying hens

It was investigated in a small-scale study using a climate-controlled room at IAPGR, Roslin, that the effects of feeding a high level of supplemental vitamin E (500 mg/kg) on egg production and plasma concentrations of egg-associated metabolites in laying hens subjected to a short exposure (7 days) to a moderate heat stress (temperature of 32°C). The study showed, on small group sizes (12 birds / group), that in control birds (fed 30 mg supplemental vitamin E/kg), this degree of heat stress depressed egg production by about 30%. In the birds receiving the high level of vitamin E, egg production was maintained at levels very close to those prior to the heat stress. The objective of this experiment was to confirm in a larger scale the effects of high levels of dietary vitamin E on egg production of hens exposed to a chronic heat stress and during a period of recovery at thermoneutral temperatures.

Effects of high levels of vitamin e supplementation in heat stressed laying hens

It was investigated in a small-scale study using a climate-controlled room at IAPGR, Roslin, that the effects of feeding a high level of supplemental vitamin E (500 mg/kg) on egg production and plasma concentrations of egg-associated metabolites in laying hens subjected to a short exposure (7 days) to a moderate heat stress (temperature of 32°C). The study showed, on small group sizes (12 birds / group), that in control birds (fed 30 mg supplemental vitamin E/kg), this degree of heat stress depressed egg production by about 30%. In the birds receiving the high level of vitamin E, egg production was maintained at levels very close to those prior to the heat stress. The objective of this experiment was to confirm in a larger scale the effects of high levels of dietary vitamin E on egg production of hens exposed to a chronic heat stress and during a period of recovery at thermoneutral temperatures.

Influence of dietary fat source on oxidative stability and fatty acid composition of milk from cows receiving a low or high level of dietary vitamin E

Fifteen primiparous Holsteins were used in a latin square design with three periods and three treatments to assess the effect of fat source on milk flavour, yield and composition, and composition of milk fat. A basal diet was supplemented with one of three concentrates offered twice daily: soybean meal (no supplemental fat); cracked, micronized soybeans (containing 20 g kg−1 oil); and soybean meal plus CSFA which supplies an amount of fat similar to that of the soybeans. Periods lasted 6 wk, and each cow received 6000 IU dL α-tocopheryl acetate d−1 for the last 2 wk of each period. Measurements of milk yield, composition and flavour were made at the end of weeks 4 and 6 of each period. Feeding CSFA reduced DM intake (P = 0.064), but fat supplemented diets tended to supply more NE1 than the unsupplemented diet (P = 0.085). Yields of milk (P &lt; 0.001), fat (P &lt; 0.001) and energy (P = 0.003) were increased by fat supplementation. Protein yield was reduced (P = 0.003) when CSFA were fed. Soybeans reduced fat concentration in milk, but only before supplemental vitamin E was given. Soybeans increased α-tocopherol output in milk (P &lt; 0.05). Milk from cows fed soybeans was most susceptible to oxidation (P &lt; 0.01). Intensity of oxidized flavour was similar before and during vitamin E supplementation. Fat supplementation reduced the proportion of short- and medium-chain fatty acids (P &lt; 0.001) and increased the proportion of C18 fatty acids in milk (P &lt; 0.001). Soybeans increased the proportion of polyunsaturated fatty acids in milk but CSFA did not. Soybeans can escape biohydrogenation in the rumen and render milk susceptible to oxidation by increasing the proportion of polyunsaturated fatty acids. At the levels fed, vitamin E did not prevent oxidation due to its low transfer to milk. Key words: Oxidized milk, fatty acids, soybeans, tocopherol, dairy cow

Influence of vitamin C on the immune system of salmonids

Abstract. Trials were run to determine the immunomodulatory effect of dietary vitamin C in rainbow trout. Oncorhynchus mykiss (Walbaum), and Atlanticsalmon, Salmo Salar L. We first investigated whether depletion of ascorbic acid (AA) could depress the immune system. Subsequently, we focused our studies on the stimulatory effect of a high dietary dose of stable vitamin C derivatives (1000mg AA-equivalent per kg of feed) in order to determine their prophylactic role. Three trials were run with rainbow trout fed, for periods of time varying from 2 to 6 months, a high dietary dose of ascorbate-2-polyphosphate (AAPP) or L-ascorbate-2-monophosphate calcium salt (AAMP) equivalent to 1000mg AA per kg of feed. The high dietary level of vitamin C was compared to 60mg AA-equivalent per kg of feed. Another experiment was conducted with Atlantic salmon pre-fed AAPP at 60mg/kg for 6 months followed by AAPP at 1000mg/kg for 2 months. Various immune parameters were tested such as mitogen-induced proliferation, serum complement level, phagocytosis and natural cytotoxicity. Leucocyte and plasma AA contents were also determined. The immune response in vitamin-C deficient trout was not strongly different from that in trout fed the minimal growth requirement level. Serum complement level was not affected by vitamin C. A high dietary dose of vitamin C was found to increase trout and salmon leucocyte AA content, mitogen-induced proliferation of lymphocytes, and chemiluminescence response of leucocytes with a higher constancy, when the cells were stimulated with opsonized zymosan and with luminol as a substrate. Natural cytotoxicity was enhanced in trout fed a high dietary dose of vitamin C. The results of these immunity studies support supplementation levels of vitamin C which are much higher than the minimal requirement known to prevent deficiency symptoms and promote normal growth. Further investigations on the time-dose response are needed to define quantitatively the high dietary dose of vitamin C.

Effect of dietary vitamin E on L-[3H]glutamate binding in rabbit cerebellum.

To demonstrate the role of vitamin E on cerebellar function, studies on rabbits fed low and high levels of dietary vitamin E were performed. The L-[3H]glutamate binding to cerebellar membranes of rabbits fed normal, high and low vitamin E diet showed receptor density (Bmax) values (mean +/- SEM) of 274 +/- 13, 637 +/- 37, and 265 +/- 60 pmol/mg protein, respectively, and dissociation equilibrium constant (KD) values of 257 +/- 99, 233 +/- 77, and 120 +/- 15 nM, respectively. Significant difference of Bmax from control was observed in the high dietary vitamin E group and of KD from control for the low dietary vitamin E group. These results indicate that dietary vitamin E levels have demonstrable effects on the central nervous system, especially the glutamate neurotransmitter system in rabbit cerebellum.

Enhancement of immune status by high levels of dietary vitamin B‐6 without growth inhibition of human malignant melanoma in athymic nude mice

The effects of dietary vitamin B-6 supplementation on the development of human malignant melanoma (M21-HPB) xenografts and on in vitro responses of leukocytes were examined. Male athymic nude mice, five weeks old, were divided into two groups of 48 each and fed 20% casein diets containing pyridoxine (PN) at 4.1 (control diet) and 61.6 mg/kg diet for 10 weeks. After four weeks of dietary treatment, 20 animals from each dietary group were injected subcutaneously with 3 x 10(7) melanoma cells. After 4, 8, and 10 weeks of dietary regimen, animals from each group were killed and blood, liver, and spleen samples were obtained. Food consumption and mouse body weights were similar between groups, and no difference was noted in tumor incidence or volume. Noninjected and tumor-bearing mice given the PN 61.6 diet generally exhibited greater oxygen radical production by phagocytic cells from blood and spleen than did animals fed the PN 4.1 diet. Spleen and blood B lymphocyte proliferation in response to lipopolysaccharide (LPS) was enhanced (10 and 30%) in the noninjected animals given the PN 61.6 diet. In addition, tumor-bearing mice fed the PN 61.6 diet had significantly greater LPS-induced spleen cell proliferation at eight weeks when compared with mice consuming the PN 4.1 diet. Despite immune enhancement, tumor incidence and progression was not modified by a high level of dietary vitamin B-6. Therefore, it is tempting to speculate that tumor inhibition by high dietary vitamin B-6 may be mediated by T lymphocyte-dependent mechanisms that are lacking in these genetically immuno-deficient mice.

Potentiation of atherosclerotic lesions in rabbits by a high dietary level of vitamin E.

1. Two experiments were conducted to determine whether or not high dietary levels of vitamin E affect the development of atherosclerotic lesions in aortas of cholesterol-fed (5 g/kg diet) rabbits that were mechanically deendothelialized by balloon catheterization. 2. In the first experiment, the aortas of rabbits fed 2000 mg vitamin E/kg diet (i.e. 50-fold their nutritional requirement) for 8 weeks showed no gross morphological differences, either within or outside experimentally damaged areas, from those of rabbits fed the nutritionally adequate control level (40 mg/kg) of the vitamin. 3. In the second experiment, rabbits fed 10,000 mg vitamin E/kg diet (i.e. 250-fold requirement) for 14-15 weeks showed significantly greater endothelial loss and plaque formation at aortic sites outside of the mechanically damaged area than did controls. Plasma cholesterol levels were very high (9000-14,000 mg/l) and were not affected by dietary vitamin E level until 10-12 weeks when they were reduced moderately (18%). 4. It is concluded that very high levels of vitamin E can potentiate spontaneous atherosclerotic lesions, and it is suggested that this effect may depend on high cholesterol status.