Showing papers in "Journal of Nutrition in 1985"

Influence of Dietary Calcium, Phosphorus, Zinc and Sodium Phytate Level on Cataract Incidence, Growth and Histopathology in Juvenile Chinook Salmon (Oncorhynchus tshawytscha)

Abstract: To determine the influence of wide variations in dietary levels of calcium, zinc and phytic acid (as sodium phytate) on growth and cataract incidence, juvenile chinook salmon held at 10-11 degrees C were fed daily to satiation for 105 d one of nine purified diets containing one of three levels (grams/kilogram) of calcium (averaged 48, 177, 502), zinc (averaged 005, 015, 039) and phytic acid (162, 646, 258) Diets were formulated to have a calcium-phosphorus ratio of close to unity when considering phosphorus sources other than sodium phytate High dietary phytic acid concentration (258 g/kg) depressed chinook salmon growth, food and protein conversion [protein efficiency ratio (PER)] and thyroid function, increased mortality, promoted cataract formation (zinc at 005 g/kg) and induced anomalies in pyloric cecal structure Calcium at 51 g/kg (or phosphorus) exacerbated the effects of high dietary phytate and low dietary zinc on cataract incidence Moreover, high dietary levels of calcium (48-51 g/kg) coupled with phosphorus significantly impaired the growth and appetite of low phytic acid (162 g/kg) groups and led to nephrocalcinosis in low and high phytic acid groups Plasma zinc levels were directly related to dietary zinc concentration and inversely related to dietary phytic acid level Calcium (51 g/kg) and/or phosphorus reduced zinc bioavailability when the diet concurrently contained 005 g zinc and 258 g of phytic acid per kilogram It is concluded that zinc is essential for normal eye development in juvenile chinook salmon Further, zinc deficiency could not be induced in chinook salmon fed diets with high ratios of calcium (or phosphorus) to zinc alone This required the simultaneous presence of a strong mineral (zinc)-binding agent

Elevated Levels of Dietary Ascorbic Acid Increase Immune Responses in Channel Catfish

Abstract: Channel catfish fingerlings were fed purified diets containing 0 to 3000 mg/kg of ascorbic acid until external signs of scurvy were seen in the fish fed the ascorbic acid-deficient diet. At this time, resistance to bacterial infection, antibody production, complement activity and phagocytic activity were assessed for fish from the various dietary treatments. Mortality rates of fish experimentally infected with Edwardsiella ictaluri, the bacterium causing enteric septicemia in channel catfish, decreased with increases in dietary ascorbic acid doses, ranging from 100% for fish fed the ascorbic acid-deficient diet to 15% for fish fed 300 mg ascorbic acid per kilo gram diet and 0 for fish fed 3000 mg ascorbic acid per kilogram diet. Antibody response to E. ictaluri antigen, hemolysis of sensitized sheep erythrocytes by comple ment activity and phagocytic engulfment of E. ictaluri by peripheral phagocytes were each impaired in fish fed the diet without supplemental ascorbic acid; intracellular bactericidal activity of the phagocytes was not affected by ascorbic acid deficiency. There were no differences in antibody production, complement activity, or phago cytic activities among fish fed diets containing 30-300 mg ascorbic acid/kg of diet. However, the dose level of 3000 mg ascorbic acid/kg significantly enhanced antibody production and complement activity. J. Nutr. 115: 123-131, 1985.

Digestion and absorption of lipids in poultry

Abstract: Ingested lipids undergo intestinal emulsification, digestion, micellar solubilization, cell membrane permeation, intracellular esterification and incorporation into lipoproteins before release to the interstitial fluid. Bile salts secretion, essential to both emulsification and micelle formation in the intestine, has been found to be influenced by quantity and quality of dietary lipids and by other emulsifiers. Modifications of dietary lipid contents cause changes in pancreatic lipase content and secretion. Colipase secretion by the pancreas seems dependent on both lipid and protein intakes. Intracellular processes essential for lipid absorption increases in rate as lipid intake increases. Bile salts seem to play important roles as moderators of these processes. The ability to digest lipids is not fully developed in the newly hatched poultry. Addition of bile salts, lipase or phospholipids to chick diets improves the digestibility of animal fats, demonstrating that lipid digestive processes are not fully functional in the very young. Physiological studies support these indications. Lipase concentration in pancreatic tissue and intestinal contents of poultry increases several-fold during the first few weeks after hatch. Similar changes with age have been observed in bile salt secretion. The development in enterocytes of fatty acid-binding protein activity seems to parallel the development in lipase activity and bile salt secretion in poultry.

Oral α-Tocopherol Supplements Decrease Plasma γ-Tocopherol Levels in Humans

Abstract: In a cross-sectional survey of 86 elderly persons, it was observed that subjects with elevated plasma alpha-tocopherol levels had depressed plasma gamma-tocopherol. Tocopherols were measured by both reverse-phase and normal-phase high performance liquid chromatography (HPLC). When eight human volunteers (age range 30-60) were given 1200 IU of all-rac-alpha-tocopherol daily for 8 wk, plasma gamma-tocopherol and beta-tocopherol decreased in all subjects. After supplementation, gamma-tocopherol values were typically 30-50% of initial values, and alpha-tocopherol values were typically 200-400% of initial values. These results suggest that intestinal uptake and/or plasma transport make more efficient use of alpha-tocopherol than of gamma- or beta-tocopherol. Moreover, the results indicate that the ratio of gamma- to alpha-tocopherol in plasma would be a more satisfactory index to measure compliance in trials involving supplementation with alpha-tocopherol.

Oral Iron, Dietary Ligands and Zinc Absorption

Abstract: The effect of iron on zinc absorption in humans was investigated by using 65Zn and whole-body counting after 2 wk. Increasing the molar ratio of ferrous iron (with ascorbic acid) to zinc from 1:1 to 2.5:1 did not affect absorption of zinc from water when given in a fasting state; 59 and 58% was absorbed, respectively. However, at an Fe:Zn ratio of 25:1, zinc absorption from water decreased significantly to 34%. When oral iron in the same ratio to zinc was given with a meal, no inhibitory effect was observed (25, 23 and 22%, respectively). Addition of the zinc ligand, histidine, to the water solution decreased the inhibitory effect of the higher dose of iron, resulting in a zinc absorption of 47%. Two weeks of iron preloading did not affect zinc absorption from water. The results demonstrate that when a multimineral supplement is taken on an empty stomach, excessive iron levels can negatively affect zinc absorption. Intake of the supplement with a meal or with a zinc ligand (such as histidine) may overcome this inhibitory effect.

Assessment of interrelationships among levels of intake and production, organ size and fasting heat production in growing animals.

Abstract: Although the concept of metabolic body size (kg075) has gained widespread use in the field of energy metabolism, its application to the growing animal has been questioned Fasting heat production, or maintenance, rather than being a constant function of body size, has been shown to vary because of breed, sex, condition, physiological state, production level, nutrition level and environmental conditions Data are presented to show that fasting heat production and maintenance vary with nutritional level or rate of growth in animals postweaning Variation in these energy expenditures are related to variation in weight of metabolically active internal organs Weights of liver and gut and fasting heat production are shown to be functions of body size and level of production More information is needed to ascertain the primary components of energy expenditures in animals and to quantitatively relate these components to animal energy metabolism

Digestion and absorption of carbohydrates in fowl and events through perinatal development.

Abstract: Starch is the main carbohydrate in the food of poultry. Starch granules are digested by pancreatic alpha-amylase in the small intestine. Intestinal villi have enterocytes that project microvilli with a fibrous glycocalyx from the surface. These fine structures are envisaged to entrap water that is mixed with mucin from nearby goblet cells to form the "unstirred water layer." Maltose, maltotriose and alpha-limit dextrins must diffuse across this first barrier to absorption to be hydrolyzed by maltase and sucrase-isomaltase immobilized at the membrane; however, the resultant glucose, once formed, accrues at the surface to provide a concentration advantage. Fowl adjust to changes in dietary starch by altering the amount of amylase released, intestinal surface area and enterocyte carbohydrase concentration. Enterocytes arising during embryonic development have no carbohydrases and are not involved with glucose absorption, but they appear to be specialized for maternal immunoglobin transfer in ovo. Embryonic villi are stimulated by transfer activity, and their growth depends on enterocytes arising from the crypt. Mature crypt cells are capable of digestion-absorptive activities and dominate the villus shortly after the chick hatches when yolk sac reserves are depleted.

Reduced and compensatory growth: endocrine and metabolic changes during food restriction and refeeding in steers.

Abstract: Effects of food restriction, followed by refeeding, on energy and nitrogen metabolism, growth rates and blood levels of hormones and metabolites were studied in steers. During the restriction period, which lasted for almost 5 mo, allowance for energy and nitrogen were close to maintenance requirements. Heat production and growth rates were markedly lowered. In response to reduced food intake concentrations of thyroxine (T4), 3,5,3'-triiodothyronine (T3), insulin (IRI), glucose and alpha-amino-acid nitrogen (AAN) were reduced, those of growth hormone (GH) and nonesterified fatty acids (NEFA) were elevated, whereas 3,3',5'-triiodothyronine (rT3) and albumin were not different from levels measured in nonrestricted animals. During refeeding heat production and energy balances increased, nitrogen balances were transiently elevated and the animals exhibited compensatory growth. In response to refeeding, concentrations of T4, T3 and IRI increased within days. In contrast, GH decreased whereas rT3 did not change. Within 2 d of refeeding there was a rapid fall of NEFA, and an increase of glucose, and beta-hydroxybutyrate within 2 and 12 d, respectively. The data demonstrate the ability of growing ruminants to adapt rapidly to variations in food intake by closely linked metabolic and endocrine changes, which are associated with shifts in energy and nitrogen metabolism and, finally, by reduced or compensatory growth.

Adaptation of rats to diets containing different levels of protein: effects on food intake, plasma and brain amino acid concentrations and brain neurotransmitter metabolism.

Abstract: Food intake, plasma and brain amino acid concentrations, liver amino acid catabolic enzyme activities, and whole-brain neurotransmitter and metabolite concentrations were measured in young rats adapted for 11 d to diets containing from 5 to 75% (in increments of 5%) casein. Food intake was depressed initially in rats fed diets containing 5, 10% or greater than 35% casein. For the duration of the experiment, food intakes of the groups fed the higher protein diets improved on successive days; the length and severity of the depression were proportional to the protein content of the diet fed. Rats fed low levels of protein grew poorly, and their food intake remained depressed. The gradual improvement in growth and food intake of rats fed diets containing more than 35% casein was accompanied by dramatic increases in the activities of serine-threonine dehydratase (SDH, EC 4.2.1.16) and glutamate-pyruvate aminotransferase (GPT, EC 2.6.1.1) in liver. The increase in amino acid catabolic activity was accompanied by decreases in the concentrations of most amino acids in plasma and brain. However, concentrations of branched-chain amino acids, in both plasma and brain, increased in direct proportion to the protein concentration of the diet fed. As a result of these reciprocal responses, the total concentration of indispensable amino acids in brain (IAA) was maintained within a narrow range of values, despite a sixfold range of protein intakes. Whole-brain concentrations of norepinephrine, dopamine and serotonin were not correlated with dietary protein concentration, total food intake or protein intake. Brain concentrations of homovanillic acid and 5-hydroxyindoleacetic acid were correlated inversely with protein intake and that of 3,4-dihydroxyphenylacetic acid was correlated directly with food intake. Protein intake appeared to be related to the animal's ability to maintain brain total IAA content between some upper and lower limits. Our results indicate that this was accomplished initially through downward adjustment of protein intake and subsequently through an increase in catabolic capacity for the amino acids.

Copper and zinc absorption in the rat: mechanism of mutual antagonism.

Abstract: The influence that copper and zinc exert on each other's absorption was studied by using the isolated, vascularly perfused rat-intestine system. In the first series of experiments, rats were fed for 1 wk one of nine diets, with different copper and zinc concentrations representing low, adequate and high dietary metal intakes. Copper concentrations were 1, 6 and 36 mg/kg diet and zinc concentrations were 5, 30 and 180 mg/kg. The small intestine was perfused with M199tissue culture medium containing 6 mg/L copper and 30 mg/L zinc. Neither metal was found to significantly alter the other's absorption. High dietary zinc increased metallothionein-bound copper but did not change the intracellular copper concentration. In the second series of experiments, the dietary copper and zinc concentrations were held at 6 mg/kg and 30 mg/kg, respectively, while the metal concentrations in the luminal perfusate were changed (from 1 to 36 mg/L and from 5 to 180 mg/L for copper and zinc, respective ly). The higher copper concentrations in the perfusate increased zinc accumulation in mucosal cells and decreased the zinc transferred to the portal perfusate at the highest luminal zinc concentration. These data indicate that a competition and/or inhibition of a pathway for zinc out of the mucosal cell occurs at high luminal copper con centrations. High luminal zinc concentrations in the perfusate decreased the copper concentration in the mucosal cell cytosol and the amount transferred to the portal effluent. These results taken together indicate that a competition and/or inhibition of copper or zinc uptake into intestinal cells occurs when the luminal concentration of the respective congener is very high. J. Nutr. 115: 159-166, 1985.

Stimulation of Absorption of Volatile Fatty Acids and Minerals in the Cecum of Rats Adapted to a Very High Fiber Diet

Abstract: The effects of a high fiber diet containing about 50% pectin, gum, crude potato starch and the fiber components of wheat bran and soya seed cake on the cecal absorption of substrates were studied by parallel measurements of cecal arteriovenous differences and blood flows. Rats fed the high fiber diet had heavier cecae and higher cecal wall weight and blood flow than rats fed a fiber-free diet. Very high arteriovenous differences in volatile fatty acids (VFA) were observed and VFA absorption in cecal vein reached 17.5 mumol/min in the high fiber diet group. This process was concomitant to a moderate absorption of Na+ and partly offset by a secretion of Cl-. In contrast, K+, Mg2+ and Ca2+ were absorbed in large amounts along a favorable concentration gradient. About 10% of arterial urea was removed, and there was a substantial reabsorption of ammonia, despite the lower cecal ammonia and the acidic pH in the cecum when the high fiber diet was fed. The present study suggests that rats may tolerate large amounts of diversified fibers or related compounds in the diet. Such a model could contribute to the assessment of the role of VFA in the effect of fiber.

Nutrition and aging: a current assessment

Abstract: A literature review summarizes and discusses recent findings on the associations between nutritional status and aging. Specific attention is focused on 2 aspects: (1) aging retardation via food intake restriction (considering experimental rodent studies on the effects of food restriction on survival in aging and on the possible mechanisms of action associated with increased longivity in food restriction); and (2) the purported influence of specific nutrients (protein, fat, carbohydrate) on aging. The relevance of the findings of experimental animal studies to the human situation also is discussed.(wz)

Zinc utilization in young men fed adequate and low zinc intakes.

Abstract: Zinc absorption and balances were measured in six young men who were confined while participating in a 75-d metabolic study. A diet of conventional food providing either 16.5 or 5.5 mg Zn/d was fed. Apparent absorption of zinc was calculated from the zinc balance data and from the absorption of a zinc stable isotope added to the diet. The apparent zinc absorption calculated from the isotope data was about 25% when 16.5 mg zinc was fed; it increased to about 53 and 49% after 13 and 42 d, respectively, when 5.5 mg zinc was fed. Total zinc absorption fell from 4.1 mg/d to 2.7-2.9 mg/d during the low zinc period, however. This zinc absorption was sufficient to maintain crude zinc balances in five of the six subjects. Neither serum nor urinary zinc levels changed significantly during the period of feeding low levels of zinc. It appears that zinc absorption readily responds to changes in dietary zinc and that an intake of 5.5 mg Zn/d for about 8 wk does not cause serum or urinary zinc level to fall.

Energy costs of ion pumping by animal tissues.

Abstract: Results from recent in vitro studies indicate that in excess of 20% of the energy expenditure of skeletal muscle, duodenal epithelium and liver of domestic ruminants is to achieve Na+ and K+ transport across the plasma membrane. The energy cost of active Ca2+ transport is less clear but is likely less than 10% of the total expenditure of skeletal muscle at rest. Energy expenditure on Na+ and K+ transport was quite sensitive to the physiological state of the animal. During lactation, Na+ and K+ transport accounted for nearly half of the in vitro O2 uptake of skeletal muscle, duodenal epithelium and liver. The energetic cost of supporting Na+ and K+ transport was also elevated in young, as compared with older animals, by feed intake and by exposure to cold. Na+ and K+ transport appears to be a substantial component of the maintenance energy expenditure of ruminant tissues. Its variation, therefore, implies that change of maintenance energy expenditures with physiological state of the animal warrants serious attention.

Energy intake, weight gain and fat deposition in rats fed flavored, nutritionally controlled diets in a multichoice ("cafeteria") design.

Abstract: The effect of flavor variety on diet selection, energy intake, weight gain and fat deposition was studied in male rats fed flavored, nutritionally controlled, purified diets in a multichoice "cafeteria" (CAF) arrangement. Serum insulin, L-3,3',5-triiodothyronine (T3) and thyroxine (T4) levels were also determined. Rats fed nutritionally balanced diets containing a variety of preferred flavors and textural forms ad libitum in a CAF design did not consume more energy nor did they gain more weight than rats fed a single choice of nutritionally balanced diet with no modifications in flavor or texture. Feeding high fat, high sucrose diets containing a variety of flavors in a CAF arrangement resulted in higher energy intake, body weight gain, lipid content in fat pads and serum T3 levels than did feeding the nutritionally balanced diet. However, the high fat diet with no added flavors also resulted in an energy intake, body weight gain and lipid content of fat pads at a level equal or close to that produced by the CAF feeding of the flavored, high fat, high sucrose diet. It is therefore concluded that the effect of a variety of food flavors on hyperphagia and fat deposition is of minor importance in purified diets compared to the stimulating effect of the fat in the diet.

Feeding time differentially affects fattening and growth of channel catfish.

Abstract: Channel catfish (Ictalurus punctatus) were held on a 12-h light, 12-h dark photoperiod (light onset 0600 h) and fed a nonpurified diet daily at either 0730 or 1600 h or a half ration at both of these times of day. The feeding time conducive to total growth (0730 h) differed from that conducive to fattening (1600 h). Fish fed a half ration at both times of day had body weights similar to those fed a single early meal but also had high abdominal fat weights similar to those fed a single late meal. Feeding schedule appears to be an important factor in determining the metabolic fate of nutrients.

The effects of dietary minerals and electrolytes on the growth and physiology of the young chick.

Abstract: The effects of the mineral elements, calcium and available phosphorus (aP), and the electrolytes, sodium, potassium and chloride in the diet on the growth and physiology of male broiler-type chickens were investigated. The concepts of total dietary cation-anion and electrolyte (Na + K - Cl, meq/kg) balance were compared for their ability to describe observed growth and various parameters to 42 d of age. There were 12 dietary treatments; each was given to four replicates of 32 birds housed in a deep-litter, environmentally controlled shed. Diets were nutritionally adequate and were based on practical ingredients. Total cation-anion balance was varied from 327 to 700 meq/kg and electrolyte balance, from -29 to 553 meq/kg. Results showed that total dietary cation-anion balance did not describe the growth of chickens as well as electrolyte balance. Low (less than 180 meq/kg) or high (greater than 300 meq/kg) electrolyte balance in a diet led to depressed liveweight at 42 d of age. There was an optimum electrolyte balance from 250 to 300 meq/kg. The extent of liveweight depression from feeding diets with an electrolyte balance greater than 300 meq/kg depended on the type of cation added to the diet (Na or K): the range of the Na:K ratio for optimum growth was 0.5-1.8. Acid-base balance was influenced mainly by a diet with a low electrolyte balance (-29 meq/kg). Plasma ion levels (Ca, inorganic P, Mg, Na, K, Cl) were unaffected by dietary treatment, except that high dietary calcium reduced plasma inorganic P levels. Increasing calcium from 1.30 to 1.74% reduced liveweight at 42 d of age by 5%, but subsequent increases up to 2.30% Ca had relatively minor effects. Liveweight tended to be lower for birds fed a diet containing 1.30% Ca and 0.81% aP compared to 0.45% aP with 1.30% Ca. Total cation-anion balance cannot be used in preference to dietary electrolyte balance to describe growth of broiler chickens. However, even though there was a good relationship between growth and dietary electrolyte balance, there were specific cation effects (Na and K) independent of electrolyte balance.

Effect of zinc deficiency on methionine metabolism, methylation reactions and protein synthesis in isolated perfused rat liver.

Abstract: A perfusion technique was utilized to assess the rate of absorption and metabolism of L-methionine by livers isolated from rats fed a diet deficient in zinc. The endogenous concentration of S-adenosyl-L-methionine in the livers from the zinc-deficient rats was near normal, while the concentration in pair-fed controls was approximately 50% of that found in normal livers (ad libitum fed). The rate of uptake of methionine by the livers isolated from zinc-deficient rats was significantly less than in the pair-fed or ad libitum-fed controls. The synthesis of L-methionine, S-adenosyl-L-homocysteine and S-adenosylmethionine was not impaired in the livers from the zinc-deficient rats. However, the methyl group of the S-adenosylmethionine turned over much more slowly in the livers from zinc-deficient rats than in either control group. This was reflected in the depressed rates of methylation of various macromolecules, particularly DNA and histones. The synthesis of nuclear proteins (histones and nonhistone chromosomal proteins) was depressed in the livers from zinc-deficient rats. The reduced synthesis of chromosomal proteins and marked reduction in DNA methylation would be consistent with the finding that DNA biosynthesis and cellular proliferation are markedly depressed in zinc-deficient animals.

Conversion of Glutamate to Ornithine and Proline: Pyrroline-5-Carboxylate, a Possible Modulator of Arginine Requirements

Abstract: The many enzyme reactions involved in the interconversion of glutamate, ornithine, proline and arginine are interrelated to one another by the metabolite pyrroline-5-carboxylate. This chemical is synthesized de novo from glutamate by the intestinal mucosa and to a lesser degree by the thymus. Pyrroline-5-carboxylate can be metabolized to ornithine (and arginine), proline and glutamate. Several futile cycles could exist because of the common utilization of pyrroline-5-carboxylate for these pathways. This does not appear to occur because of the tissue distribution of these enzymes, the various isozymes of the enzymes that may have different regulatory or kinetic properties and amino acid transport systems that differ from tissue to tissue.

Requirement for ascorbic acid in a rat mutant unable to synthesize ascorbic acid.

Abstract: The activities of several enzymes involved in hepatic ascorbic acid synthesis and the requirement of dietary ascorbic acid were investigated in the OD (osteogenic disorder) rat, which has a hereditary defect in ascorbic acid-synthesizing ability. No activity of hepatic L-gulonolactone oxidase was detected in OD rats. However, OD rats maintained the normal activities of hepatic UDPglucose dehydrogenase, UDPglucuronyl transferase and beta-glucuronidase. Hemorrhage in muscle and leg joints, lower hepatic content of cytochrome P-450 and lower activities of hepatic drug-metabolizing enzymes, higher serum and adrenal levels of corticosterone and lower urinary excretion of hydroxyproline were observed in ascorbic acid-deficient OD rats than in OD rats fed 300 mg ascorbic acid/kilogram diet. Consequently, we conclude that OD rats cannot synthesize ascorbic acid because of the lack of activity of hepatic L-gulonolactone oxidase and that the dietary addition of about 300 mg ascorbic acid (per kilogram diet) is enough to prevent signs of vitamin C deficiency and to achieve maximum growth, and that more than 300 mg ascorbic acid per kilogram diet may be required for the maximum activity of hepatic drug-metabolizing enzymes.

Effect of selenium deficiency on hydroperoxide-induced glutathione release from the isolated perfused rat heart.

Abstract: Selenium deficiency has been implicated as a cause of the cardiomyopathy known as Keshan disease in China. Selenium is an essential constituent of glutathione peroxidase, an enzyme that destroys hydroperoxides by using the reducing equivalents of reduced glutathione (GSH). We studied glutathione-dependent hydroperoxide metabolism in isolated perfused rat hearts. Hearts from selenium-deficient rats contained 5% of the glutathione peroxidase activity found in control hearts. Glutathione reductase activity and glutathione content were not affected by selenium deficiency. Infusion of t-butylhydroperoxide into control hearts caused an increase in heart glutathione disulfide (GSSG) concentration proportional to the rate of hydroperoxide infusion up to 200 nmol/(g heart X min). GSSG was released into the perfusate in proportion to the hydroperoxide infusion rate up to 150 nmol/(g heart X min), but GSSG release did not increase further with higher infusion rates. Thus, GSSG release by the heart is saturable. It had a maximum rate of about 14 nmol GSH equivalents/(g heart X min) when stimulated by t-butylhydroperoxide infusion. This indicates that GSSG release by the heart is carrier-mediated and is not due to passive diffusion. Infusion of hydroperoxide into selenium-deficient hearts failed to cause increases in heart GSSG concentration and in GSSG release. This indicates that selenium-deficient heart cannot metabolize hydroperoxides through glutathione-dependent pathways. We suggest that selenium deficiency might predispose the heart to injury from oxidant stress.

Red cell superoxide dismutase activity as an index of human copper nutrition.

Abstract: Red cell superoxide dismutase (SOD) activity was evaluated as a biochemical index of copper nutrition in a double-blind study of 17 infants recovering from malnutrition and receiving marginal copper intakes. Children were paired on admission by sex, birth weight, nutritional status and antecedents of diarrhea and breast feeding. Nine served as controls receiving a copper sulfate supplement (80 micrograms/kg daily for 120 d; eight received a placebo and were supplemented only if plasma copper levels dropped below 90 micrograms/dl or on d 90 for at least 30 d. After copper supplementation there was a significant rise (paired t-test; P less than 0.05) in plasma copper (96 vs. 165 micrograms/dl); ceruloplasmin (33 vs. 50 mg/dl) and SOD (1073 vs. 1371 U/g Hb). After supplementation these values were similar to those of the controls. SOD was correlated with plasma copper (r = 0.78; P less than 0.001) and not with weight-for-age or weight-for-length. Addition of copper in vitro did not modify the SOD activity. Red cell SOD is a good marker of copper nutrition in humans and correlates well with plasma copper.

The Effect of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) on the Uptake, Distribution and Excretion of a Single Oral Dose of [11,12-3H]Retinyl Acetate and on the Vitamin A Status in the Rat

Abstract: TCDD (2,3,7,8-Tetrachlorodibenzo-p-dioxin, 10 /ig/kg body weight, p.o.) was given to male Sprague-Dawley rats 4 d before the oral administration of a physiological dose of (ll,12-3H)retinyl acetate (RA). The rats were kept in metabolic cages for up to 192 h after RA administration. Radioactivity and/or vitamin A were determined in tissues and excreta. TCDD-pretreated and control rats excreted 41 and 23%, respectively, of the radioactivity of RA during the 192 h after administration. In control animals, 30 % of the radioactivity of RA entered the liver within 6 h, the stores reaching 42% after 192 h. Maximum storage in TCDD-treated rats was 13% and after 192 h only 9 % of the dose remained. A lag period of 12-24 h preceded the TCDD-induced increase in renal (175-671%) and serum (85-145%) radioactivity. In TCDD-treated rats less radioactivity was found in the intestine (45-79% decrease) and adrenals (14-73% decrease). Relative to the total body content, significantly more radioactivity was found in the kidney, serum, testes and epididymis of TCDD-treated rats. The decrease in vitamin A content after TCDD-treatment was 39-53 % in the liver, 19-67% in the intestine and 18-44% in the epididymis. The kidneys of TCDD- treated rats contained more vitamin A (3-30 times more). TCDD treatment initially increased (42 %) and later decreased (40 %) the vitamin A content in the thymus as compared to controls. Pretreatment with a single low dose of TCDD thus affects both storage and excretion of radioactivity from newly administered RA as well as the vitamin A content in several tissues. J. Nutr. 115: 759-771, 1985.

Vitamin a during Lactation: Relationship of Maternal Diet to Milk Vitamin a Content and to the Vitamin a Status of Lactating Rats and their Pups

Abstract: We have investigated the effects of maternal vitamin A intake during pregnancy and lactation or during lactation alone on the concentration of vitamin A in rat's milk and on vitamin A levels in plasma and liver of dams and their pups. Groups of Sprague-Dawley rats were fed diets having either a high vitamin A content [15 retinol equivalents (R.E.)/g diet] or a low vitamin A content (0.6 R.E./g) for 42 d, including 7-8 d prior to pregnancy, pregnancy, and for 14 d of lactation. The concentration of vitamin A in milk on d 14 of lactation was significantly greater on the high vitamin A diets [114 +/- 16 micrograms/dl (mean +/- SEM; n = 8) versus 52 +/- 7.3 micrograms/dl (n = 11), P less than 0.005]. However, milk vitamin A concentration on d 1 of lactation did not vary with maternal vitamin A intake during pregnancy. In a second study in which supplementation with vitamin A (30 R.E./g diet) was begun on d 1 postpartum, the milk vitamin A content increased progressively with duration of lactation. Maternal plasma vitamin A concentrations did not differ between rats fed the higher or lower vitamin A diets. However, liver vitamin A concentrations both of dams and of their 14-d-old pups were significantly higher when dams were fed the higher vitamin A diets during pregnancy and/or lactation. The results of these studies indicate that the transfer of vitamin A from mother to offspring by milk and the vitamin A status of dams and their suckling neonates is influenced by maternal vitamin A intake during lactation.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of Dietary Polyunsaturated/Saturated Fatty Acid Ratio and Dietary Vitamin E on Lipid Peroxidation in the Rat

Abstract: The effects of the dietary ratio of polyunsaturated/saturated fatty acids (P/S) and dietary vitamin E on lipid peroxidation (LP) were examined to determine whether the vitamin E requirement is elevated by increased P/S in ratios comparable to those found in human diets. Twelve groups of male weanling rats (six/group) were fed purified diets containing 20% fat with P/S ratios of 0.38, 0.82 or 2.30. At each P/S level, groups of rats received either 0, 10, 40 or 100 IU vitamin E/kg diet supplied as all-rac-alpha-tocopherol. After the diets were fed for 16 wk, in vivo LP was assessed by measuring pentane in expired breath. Pentane levels were significantly elevated in rats fed 0 IU vitamin E at all P/S levels. Both 40 and 100 IU vitamin E decreased pentane production to minimal levels for all P/S groups. Liver malondialdehyde levels and in vitro spontaneous red blood cell hemolysis results also indicated a significant effect of vitamin E in reducing in vitro LP, but no overall effect of P/S. Testicular and epididymal histology showed no effect of dietary P/S on the vitamin E requirement. These data demonstrated 40 IU vitamin E to be adequate for maximal inhibition of LP at the P/S levels tested and indicated that these levels of dietary P/S had no significant impact on the vitamin E requirement for the growing rat.

Nutritional and metabolic responses to arginine deficiency in carnivores.

Abstract: The metabolic basis for the high dietary arginine requirement of the cat appears to be primarily the low activity of the enzyme pyrroline-5-carboxylate synthase (P5C synthase) in the intestinal mucosa. P5C synthase is required for de novo production of glutamyl-gamma-semialdehyde, the immediate precursor for the synthesis of ornithine from glutamate. The next enzyme in ornithine synthesis, ornithine amino-transferase, in the cat intestinal mucosa shows low activity, which provides an additional barrier to ornithine and citrulline formation. It is suggested that the low activities of these enzymes corroborate other evidence that indicates that the cat evolved as a strict carnivore. The dog has a requirement for arginine intermediate between the cat and the rat, which is consistent with the dog having an omnivorous diet during its evolution. It is suggested that during periods of fasting, depletion of urea cycle intermediates in the cat results in some conservation of nitrogen while maintaining urea cycle enzymes at a relatively high level. However, after ingestion of animal protein (and arginine) the urea cycle of cats is capable of rapidly responding to the ammonia load, which rises from the deamination of amino acids. By this method of regulation the cat can respond rapidly to short-term fluctuations in protein intake.

The influence of dietary essential fatty acids on rat immunocompetent cell prostaglandin synthesis and mitogen-induced blastogenesis.

Abstract: Sprague-Dawley rats were fed diets including 10% corn oil (CO), 10% hydrogenated coconut oil (HCO) or 10% linseed oil (LO), and immune cell populations isolated from peripheral blood and spleen were examined for alterations in prostaglandin E (PGE) synthesizing capacity and mitogen-induced blastogenesis. Culture conditions were optimized by incubating the cells in serum obtained from animals fed the same diet. The fatty acid profiles of these sera reflected the composition of the dietary fat ingested. Both the LO and HCO diet treatments resulted in significantly lower PG-synthesizing capacity by both unstimulated and phytohemagglutinin (PHA)-stimulated peripheral blood mononuclear cells or splenocytes when compared to the CO group. Mitogen-induced [3H]thymidine uptake by splenocytes from rats fed the HCO diet was twofold higher than responses observed in cells from animals fed the LO or CO diets. The results suggest that mitogenesis is not influenced by the diet-induced change in immune cell PGE2 synthesizing capacity. Enhanced [3H]thymidine incorporation was associated with a greater degree of saturation of dietary fat.

Deficiency of pyrroline-5-carboxylate synthase in the intestinal mucosa of the cat.

Abstract: Pyrroline-5-carboxylate synthase activity of the intestinal mucosa of cats was compared to that of rats and found to be only 18% as high per gram of mucosa and only 5% as high per kilogram body weight This severe limitation in the first step in the de novo synthesis of ornithine may be the metabolic basis for the severe hyperammonemia found in cats fed an arginine-deficient diet This lack of ornithine synthesis makes the cat completely dependent on dietary arginine for the ornithine required for the removal of ammonia via urea synthesis in the liver

In Vivo Intestinal Absorption of Selenate and Selenite by Rats

Abstract: Intestinal absorption of selenate and selenite was investigated in rats by using an in vivo perfusion technique. Different segments of the intestine were perfused with an isotonic solution containing different concentrations of SeO42- or SeO32-. The site of greatest SeO42- absorption was found to be the ileum followed in descending order by the proximal jejunum and large intestine (cecum and colon). Furthermore, SeO42- was absorbed significantly faster from the ileum than SeO32-. The concentration dependence of SeO42- absorption indicates that SeO42- is absorbed by a saturable transport mechanism of the ileal mucosa. Absorption of SeO42- at a concentration of 0.01 mM was not affected by the presence of 1 mM SeO42- in the perfusate. When the SeO42- concentration of the perfusate was increased to 1 mM, the absorptive functions of the ileal epithelium appeared to be generally impaired. It is concluded that selenate is absorbed from the ileum by a carrier-mediated mechanism.