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Biomedical subjects

G V Mitchell

Publications and source records attributed to G V Mitchell.

At least 19 recordsLinked to original sources
PubMed2001

Supplementation of rats with a lutein mixture preserved with vitamin E reduces tissue phylloquinone and menaquinone-4.

The modulation of tissue concentrations of vitamin K by a lutein supplement preserved with natural vitamin E was studied in Fischer 344 rats. Vitamin K is necessary for blood coagulation and may be essential for tissue and bone health. Weanling male rats were fed the AIN-93G diet (control) or modified AIN-93G diets containing 0.3, 0.6, 1.2, 2.4 and 4.8 g supplement/100 g diet for 8 weeks. The supplement contained 5% lutein, 0.22% zeaxanthin and 2.2% natural vitamin E as a preservative. Concentrations of trans-phylloquinone in the plasma (nmol/mmol triglycerides) and heart were significantly reduced (P < or = 0.05) in rats fed the supplement. The reductions in trans-phylloquinone in the heart ranged from approximately 20 to 60% of the control. Concentrations of phylloquinone in the liver were significantly lower in the rats fed the supplement at levels > or = 1.2 g/100 g diet than in the control rats. Ratios of cis/trans phylloquinone in liver and heart increased and concentrations of menaquinone-4 in heart decreased as the dietary level of the lutein supplement increased. The results suggest that the lutein supplement affected the absorption, tissue uptake and/or turnover rate of vitamin K. The presence of other components in the supplement confounded the interpretation of the biological effects of lutein alone on vitamin K metabolism.

Animal Feed↗
PubMed2000

Nutritional and hematological impact of dietary flaxseed and defatted flaxseed meal in rats.

An 8-week study was conducted to determine the impact of dietary ground flaxseed (FS) or defatted flaxseed meal (FLM) on plasma lipids, minerals, hematological parameters and vitamin E status of weanling female Sprague-Dawley rats. These rats were fed isocaloric modified AIN-76 diets supplemented with 0.0, 5.0, 10.0% (w/w) FS or 6.2% (w/w) FLM for 56 days. Total and HDL cholesterol were not influenced by any of the dietary treatments. Plasma triglyceride was significantly increased by FLM, but not affected by FS. Total RBC counts and hematocrit were significantly higher in FS groups than in the control group; however, hemoglobin was not affected by FS. Dietary FLM had no effect on any of the above hematological parameters. Plasma alkaline phosphatase, an indicator of Zn status and a marker of bone formation, was significantly lower in the FS and FLM groups than in the control group. Plasma vitamin E content was not influenced by dietary treatment. Liver vitamin E was significantly higher in groups fed 10% FS and 6.2% FLM. In summary, moderate amounts of dietary FS may have the potential to increase liver vitamin E level and improve iron status. However, FS/FLM consumption may have a negative effect on zinc status, as indicated by decreased alkaline phosphatase levels.

Animals↗
PubMed2000

Natural tocopherols in a dietary supplement of lutein affect tissue distribution of tocopherols in young rats.

The effects of graded levels of Flora GLO (FG), a dietary supplement containing lutein derived from marigold flowers, on tissue concentrations of lutein and alpha- and gamma-tocopherol were determined. Six groups of male weanling Fischer 344 rats (15/group) were fed ad libitum modified AIN-93G diets containing 0%, 0.30%, 0.60%, 1.20%, 2.40%, or 4.80% FG for eight weeks. FG provided 0%, 0.015%, 0.030%, 0.060%, 0.120%, or 0.240% lutein; corresponding levels of tocopherols were approximately 0%, 0.006%, 0.012%, 0.023%, 0.046%, and 0.092%, respectively. Maximal uptakes of lutein in plasma, spleen, and liver were observed with 4.8% FG. Lutein was not detectable in brain, heart, lung, testes, and kidney. Concentrations of alpha-tocopherol in the plasma (microgram/mg triglycerides) were reduced in all rats fed FG (p < 0.05). alpha-Tocopherol increased nonlinearly in lung, heart, and spleen with increased FG level. alpha-Tocopherol in liver increased with increased dietary FG; alpha-tocopherol in kidney, testes, and brain did not increase. At each dietary level of FG, the spleen had a higher percentage of gamma-tocopherol, and testes and brain had a lower percentage of gamma-tocopherol than all other tissues. For all tissues, the concentrations of alpha-tocopherol were always higher than those of gamma-tocopherol. Tocopherols added to the dietary supplement for functional purposes appeared to have a significant effect on tissue levels of tocopherols. Therefore, changes in alpha- and gamma-tocopherol levels in tissues of rats fed FG cannot be attributed solely to effects of lutein.

Animals↗
PubMed1999

Dietary vitamin E and beta-carotene sources influence vitamin A and E storage in young rats fed marginal and adequate vitamin E.

The effects of two vitamin E levels (30 and 75 IU/kg diet) and the interrelation of two vitamin E sources [dl-alpha-tocopheryl acetate (dl-alpha-TA) and d-alpha-tocopheryl acid succinate (d-alpha-TAS)] and three vitamin A sources [retinyl palmitate (RP), all-trans synthetic beta-carotene (SBC), and natural beta-carotene (NBC)] were studied. Dietary vitamin A sources provided 4,000 IU/kg. Twelve groups of Fischer 344 rats (10/group) were fed designated diets for eight weeks. For RP, SBC, and NBC, the increase in each vitamin E source from a marginal to an adequate dietary level caused a significant increase in liver and heart alpha-tocopherol. Among rats fed diets with an adequate level of vitamin E, d-alpha-TAS was not as effective as dl-alpha-TA in increasing liver alpha-tocopherol levels. Plasma retinol was lower in rats fed d-alpha-TAS than in those fed dl-alpha-TA. Among rats fed diets with an adequate level of dl-alpha-TA, those fed SBC had significantly higher liver and heart alpha-tocopherol concentrations than did all other groups (p < 0.05). Liver retinol equivalents for rats fed NBC were approximately 66% lower than those in rats fed SBC or RP (p < 0.05). The roles of the two vitamin E sources in alpha-tocopherol metabolism are not equivalent. These data indicate that vitamin A source influences the magnitude of the tissue vitamin A and E changes in response to the two vitamin E sources.

Animals↗
PubMed1993

Dietary carotenoids influenced biochemical but not morphological changes in adult male rats fed a choline-deficient diet.

In a study of the effects of carotenoids, canthaxanthin (CA), beta-apo-8'-carotenal (BA), or beta-carotene in an extract of Spirulina-Dunaliella algae (AE) was fed at 0%, 0.1%, or 0.2% in a choline-deficient (CD) diet. In each of eight groups, 10 adult male Fischer 344 rats were fed diets with designated carotenoid sources and levels or a choline-sufficient diet for 12 weeks. Carotenoids altered some of the changes induced by the CD diet. Increases in enlargement of fatty livers and low plasma cholesterol levels occurred in rats fed 0.2% BA. Plasma retinol was further reduced 35% by BA or AE. BA and AE increased liver total vitamin A about 80% and 305%, respectively. Liver lipid peroxidation was enhanced and plasma alpha-tocopherol was reduced further by 1.0% AE. AE, BA, and CA (mg/g fat) depressed liver alpha-tocopherol about 49%, 67%, and 78%, respectively. The decreased liver alpha-tocopherol was concurrent with an increase in carotenoid stores of CA > BA > AE. Histopathological examination of sections of liver tissue by light microscopy showed fatty and cirrhotic changes in all rats fed CD diets. Histochemical evaluation based on a semiquantitative assay revealed a marked increase in peroxisome enzyme activity in the livers of all CD rats. None of the carotenoids appeared to have any effect on the development of morphological changes in the liver. Although carotenoids can function as antioxidants, they did not prevent changes observed in rats fed CD diets.

Alanine Transaminase↗
PubMed1991

Canthaxanthin and excess vitamin A alter alpha-tocopherol, carotenoid and iron status in adult rats.

beta-Carotene and excess vitamin A have been shown to reduce plasma alpha-tocopherol when fed to young rats. The present study assessed the effects of beta-carotene, excess vitamin A and canthaxanthin (4,4'-diketo-beta-carotene) on carotenoid, alpha-tocopherol and iron status in adult retired breeder rats. Male 8- to 10-mo-old rats (10/group) were fed varying levels of vitamin A as retinyl palmitate, beta-carotene and canthaxanthin ad libitum for 8 wk. The AIN-76A diet was modified to contain 16% (wt/wt) fat and 50% carbohydrate (control) plus beta-carotene or canthaxanthin at 0, 0.048 (BC1 or CX1) and 0.2% (BC2 or CX2) of the diet. These compounds were fed with and without excess retinyl palmitate (RP, 220 mg/kg). Higher relative liver weights were observed in CX- and RP-fed groups. Plasma retinyl esters were detected in all RP-fed groups. Plasma retinyl palmitate was 1.6- and 1.5-fold higher in RP-BC and RP-CX groups, respectively, than in the RP groups. Plasma and liver beta-carotene and canthaxanthin were 11-54% and 26-74% lower, respectively, with excess retinyl palmitate feeding. Feeding canthaxanthin and retinyl palmitate but not beta-carotene, resulted in lower levels of plasma alpha-tocopherol. Liver non-heme iron levels were also lower in CX-fed rats irrespective of retinyl palmitate feeding. These results extend to adult rats previous findings that excess retinyl palmitate alters vitamin E and carotenoid status prior to the manifestation of clinical signs of hypervitaminosis A. Additionally, canthaxanthin feeding lowers alpha-tocopherol and iron status in adult rats.

Administration, Oral↗
PubMed1990

Effects of graded dietary levels of Spirulina maxima on vitamins A and E in male rats.

The effects of ingesting the alga Spirulina maxima on the storage and utilization of vitamins A and E were investigated by feeding diets containing 0, 2.7, 10.7, 18.7 and 26.7% S. maxima to male rats for 6 wk. All diets contained 18% protein, which was contributed by S. maxima or by casein or by a mixture of them. Growth results indicated that rats did not utilize the diets containing S. maxima as well as the casein control diet (0% S. maxima) when levels were 10.7% or more of the diet. The ingestion of S. maxima caused a significant increase in dry matter and chloroform-extractable crude fat in the feces. A low level of 2.7% S. maxima caused a significant reduction in plasma, liver and heart alpha-tocopherol levels. The concentrations of alpha-tocopherol in these tissues showed a marked decline with 10.7% S. maxima in the diet, followed by a lesser decline at higher levels. Liver retinoid levels of rats increased when S. maxima was added to the diet, suggesting conversion of the naturally occurring carotenoids in S. maxima to vitamin A. However, the plasma levels of retinol decreased when S. maxima was fed at 10.7% or more. These data demonstrate that S. maxima can significantly alter the storage and utilization of vitamins A and E.

Administration, Oral↗
PubMed1989

Protein efficiency ratios and net protein ratios of selected protein foods.

As a part of a cooperative study initiated to assess both in vitro and in vivo protein quality methods, the protein efficiency ratio (PER) and net protein ratios (NPR) of 15 different protein sources were determined. Male weanling Sprague-Dawley rats were fed a 10% protein diet. Fourteen-day NPR and relative NPR (RNPR) values and 14- and 28-day PER and relative PER (RPER) values were calculated for each protein source. When protein quality values were expressed relative to ANRC casein, the 14- and 28-day PER data ranked the protein sources essentially in the same order. RPER values of nonfat dried skim milk (unheated) and tuna were more than 100% that of casein; nonfat dried skim milk (heated), chickpeas, and breakfast sausage were between 50 and 70% of that of casein; and pinto beans and rice-wheat gluten cereal did not support substantial growth of the rat. The NPR method did not always rank the protein sources in the same order as the PER method. For the poor quality proteins, RNPR values were much higher than the RPER values; however, the RNPR and RPER values agreed closely for high quality protein sources.

Animals↗
PubMed1989

Nutritional and pathological changes in male and female rats fed modifications of the AIN-76A diet.

Male and female weanling Sprague-Dawley rats were fed either an AIN-76A diet or a modification of the AIN-76A diet containing no added DL-methionine but with higher levels of vitamins, fluoride and magnesium than in the AIN-76A diet. Both diets were fed, to groups of ten rats of each sex, at 18% protein or a reduced protein level of 13% for 12 wk. Within each sex, all diets produced comparable weight gains in rats at the end of 12 wk, except that the reduced-protein modified AIN-76A diet was associated with a reduction in weight gain in male rats. Both diet and protein level had statistically significant effects on the relative weights of some organs, particularly the kidney. The AIN-76A and the reduced-protein AIN-76A diets significantly increased the relative kidney weights (% body weights) of female rats, when compared with the effects of both modified AIN-76A diets (18 and 13% protein). Male rats fed both of the diets containing 18% protein had higher relative kidney weights than did those consuming both 13% protein diets. Females fed the modified diet containing 13% protein had significantly lower liver weights than the other groups. In both sexes, the two diets containing 18% protein caused significantly higher plasma urea nitrogen concentrations than did the lower protein diets. Kidney calcium concentrations varied with the diet, with dietary protein level, and with the sex of the animal. All diets caused small mineral (calcific) concretions of minimal to mild severity in the lumina of scattered renal tubules in the cortex and/or medulla of male rats. All female rats fed the AIN-76A and the reduced-protein AIN-76A diet had large, moderate or severe mineral concretions in the tubules at the corticomedullary junction and this was associated with increased renal calcium levels. The higher concentration of renal calcium at the lower dietary protein level (13%) was associated with severe corticomedullary junction mineralization. The higher protein diets were associated with an increased incidence of hyaline droplets in the cytoplasm of kidney cortical tubules in male rats.

Animal Feed↗
PubMed1983

Effect of excess L-lysine on rat growth and on plasma and tissue concentrations of copper, iron and zinc.

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.

Animals↗
PubMed1975

Influence of excess vitamin E on vitamin A toxicity in rats.

Male Holtzman rats (78 g) were fed semipurified 16% protein diets for 8 weeks using a food grade soy protein concentrate as the protein source. The basal diet (A) contained added DL-methionine (0.26%) and adequate amounts of vitamins A (14,535 IU/kg as retinyl acetate) and E (60 IU/kg as DL-alpha-tocopheryl acetate) and all other required nutrients. Experimental diets included: (B) basal plus 600 IU of vitamin E/kg; (C) basal plus 6,000 IU of vitamin E/kg; (D) basal plus 2.9 X 10(6) IU of vitamin A/kg; (E) basal plus 2.9 X 10(6) IU of vitamin A plus 600 IU of vitamin E/kg; and (F) basal plus 2.9 X 10(6) IU of vitamin A plus 6,000 IU of vitamin E/kg. Both vitamin A and vitamin E had a significant (P less than 0.05) effect on growth. There was an increase in growth with vitamin E intake and a decrease in growth with vitamin A intake. The net result of these two effects was that the groups fed both vitamins tended to be quite close in mean values to the group fed only the basal diet. Vitamin A significantly (P less than 0.05) increased relative weights of spleen and testes; vitamin E reduced that effect. Vitamin E also significantly (P less than 0.05) reduced relative adrenal weight whereas vitamin A significantly increased it. The two effects tend to cancel each other in the sense that the group fed both vitamins had an average relative adrenal weight quite close to that of the group fed only the basal diet. However, vitamin A still had an effect even when 6,000 IU of vitamin E was fed. The interaction effect of the two vitamins was significant (P less than 0.05) for plasma total protein and liver vitamin A. There was an increase in liver vitamin A with increasing levels of vitamin E in the diet. Blood urea nitrogen and plasma cholesterol were unchanged. A significant interaction of vitamins A and E was found to effect plasma total protein, liver vitamin A, and relative weight of spleen and testes.

Animals↗