A key to the literature of total parenteral nutrition: update 1987

This comprehensive bibliography is intended to enhance the education of the practitioner, student, and academician in the area of parenteral nutrition. This bibliography is not all-inclusive but serves as an update from the original published in 1983. Of particular note in this work is the addition of topics that reflect a growing interest in medical specialties with regard to patient nutritional status and support.

Antioxidants in relation to lipid peroxidation

The role of antioxidants in lipid peroxidation is reviewed. Specifically, the rate and mechanism of inhibition of lipid peroxidation by water-soluble and lipid-soluble, chain-breaking antioxidants have been discussed.

Nutrients, brain biochemistry, and behavior: a possible role for the neuronal membrane

Nutrients can modify brain biochemistry and behavior. Many studies indicate that one possible mode of action of nutrients is to induce alterations in the bioavailability of neurotransmitter precursors within the brain. However, a series of studies has also indicated that: (a) learning induces a decrease in the level of cholesterol in specific brain regions; (b) an iron-deficient diet induces changes in dopaminergic D receptor activity and in dopamine-associated behaviors (thermoregulation and motor activity) as well as in learning and memory capacities; and (c) dietary manipulation of a specific type of fatty acid resulted in an improved learning capacity, modification of the pain threshold level, and in thermoregulatory response. The most parsimonious explanation for these results seems to be that the treatments (learning, iron-deficient and fatty acid diets) induced changes in the lipid composition of the neuronal membrane. Such changes, in turn, resulted in changes in the membrane functions. Supportive evidence for this hypothesis is presented in this review. The "neuronal membrane functional modification hypothesis" should not be considered as contradictory to the accepted "brain neurotransmitter precursors bioavailability rates model" of nutrient effects, but as a complementary hypothesis.

Metabolism of cis-12-octadecenoic acid and trans-9,trans-12-octadecadienoic acid and their influence on lipogenic enzyme activities in mouse liver

High carbohydrate (65% glucose) diets containing cis-12-octadecenoic acid (12c-18:1) or trans-9,trans-12-octadecadienoic acid (9t,12t-18:2) were fed to weanling mice to investigate the influence of fatty acid structure on six hepatic enzyme activities involved in lipid metabolism. Results with these diets were compared to those with diets containing no fatty acids, saturated fatty acids; cis-9-octadecenoic acid (9c-18:1) and cis-9,cis-12-octadecadienoic acid (9c,12c-18:2). These comparisons show saturated fatty acids, 9c-18:1, 12c-18:1, and 9t,12t-18:2, had little or no influence on the activity levels of fatty acid synthetase, malic enzyme (EC 1.1.1.40)citrate cleavage enzyme (EC 4.1.3.8), glucose-6-phosphate dehydrogenase (EC 1.1.1.49), 6-phosphogluconate dehydrogenase (EC 1.1.1.44) and acetyl-CoA carboxylase (EC 6.4.1.2). Neither 12c-18:1 nor 9t,12t-18:2 produced the dramatic enzyme-lowering effect exhibited by the diet containing 9c,12c-18:2 when compared to the diet devoid of fat. Thus, both the 9 and 12 bonds must be present in the same molecule. Also, at least one and probably both bonds must be in the cis configuration to depress liver enzyme activities. Capillary gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) were both used for analysis of the methyl esters derived from the hepatic lipids. The GC and GC-MS data provided (a) direct evidence for incorporation of both isomers into hepatic lipids and (b) indirect evidence that 9t,12t-18:2 lowered liver delta 9-desaturase activity. In addition, since these products were found in the complex liver lipids, there is no doubt that the various enzymes concerned with activation and acylation utilize both of these isomeric fatty acids as substrates.

Alcohol, calorie intake, and adiposity in overweight men

The relation of alcohol use to calorie intake and adiposity was studied in 155 non-smoking, overweight men. Alcohol use and calorie intake were assessed by 7-day dietary record, and body composition was determined by hydrostatic weighing. Increased intake of food calories (i.e., non-ethanol calories only) on alcohol-drinking days was compensated for by decreased food consumption on non-drinking days of the week. Added alcohol calories were not offset during the week and resulted in a surplus intake of over 4,000 kcal/wk for men in the highest drinking group. Although alcohol calories were "added" to food intake, alcohol use was unrelated to level of adiposity. This finding was not accounted for by concomitant differences in exercise status. Basal metabolic rate, however, was elevated in men imbibing one or more "drinks" per day (as compared to abstainers and light-drinkers). Increased basal energy expenditure may have partially offset the alcohol calories of men at lower levels of alcohol intake, but it did not substantially offset the large calorie surplus seen at higher levels of consumption. Our results support recent speculation that alcohol consumption may not be as "fattening" as traditionally believed.

Species differences in polysaccharide and sugar taste preferences

This study compared the polysaccharide and sugar taste preferences of humans and four rodent species (laboratory rats, Rattus norvegicus; Golden Syrian hamsters, Mesocricetus auratus; Mongolian gerbils, Meriones unguiculatus; Egyptian spiny mice, Acomys cahirinus). In Experiment 1 human subjects rated the pleasantness, sweetness, and flavor intensity of polysaccharide (Polycose), sucrose, and maltose solutions at concentrations of 0.0125 M to 0.4 M, and 1% to 32% concentrations. At the higher molar concentrations Polycose was rated as less sweet and less pleasant than the sucrose and maltose solutions; there were no differences in the flavor intensity ratings. With the percent concentrations Polycose was rated as less sweet and less flavorable as the sucrose and maltose solutions; there were no reliable differences in the pleasantness ratings. In Experiment 2, the Polycose, sucrose, and maltose preferences of rats, hamsters, gerbils, and spiny mice were compared using 24 hr two-bottle tests (saccharide vs. water) at concentrations of 0.001 M, 0.005 M, 0.01 M, and 0.1 M. In general, the rats displayed stronger preferences for Polycose and maltose than did the other three species. In addition, the gerbils showed a stronger Polycose preference at the 0.1 M concentration than did the hamsters and spiny mice, and the spiny mice display a weaker preference for sucrose than did the other three species. Within species comparisons revealed that all four species displayed preferences for Polycose that were as strong or stronger than their preferences for sucrose and maltose. With only a few exceptions, male and female rodents did not differ in their saccharide preferences. Thus, while rats show the most robust Polycose preference of the four rodent species, all four species were attracted to the taste of polysaccharides. Humans, on the other hand, reported that Polycose solutions were unpleasant. The results suggest that rodents have taste receptors for starch-derived polysaccharides that humans lack.

Amelioration of ethionine toxicity in the chick

Several chick bioassays were conducted to evaluate means of ameliorating ethionine toxicity. Supplementing a corn-soy diet marginally deficient in sulfur amino acids (methionine + cystine) with .075% D,L-ethionine reduced weight gain in 8-day-old chicks by 70% compared to gains of unsupplemented controls. Dietary addition of .50% DL-methionine prevented reduction in weight gain and feed intake resulting from ethionine supplementation whereas feeding supplemental L-cystine was without effect. Supplementation of the ethionine-containing diet with either choline or betaine ameliorated the growth depression, although neither compound was able to completely overcome the toxic effects of ethionine. Dietary ethionine did not affect plasma levels of free methionine or cystine but did increase plasma free glycine 6-fold. Dietary addition of .50% DL-methionine caused normalization of plasma glycine levels whereas it elevated plasma methionine concentration. Although results suggested the possibility of ethionine-induced serine or threonine deficiency, dietary additions of .75% L-serine or .75% L-threonine failed to improve chick weight gain. These studies suggest that ethionine, in addition to affecting transsulfuration and transmethylation activity may exert specific effects on certain amino acids in tissue pools.

Bradyrhizobium japonicum mutants defective in nitrogen fixation and molybdenum metabolism

Bradyrhizobium japonicum JH mutants deficient in molybdenum metabolism into the enzymes nitrogenase and nitrate reductase were isolated by using the vector pSUP1011, which carries transposon Tn5 (streptomycin and kanamycin resistance). Mutants in Mo metabolism were obtained at a frequency of 3.6 X 10(-3) (per Kan Strr colony). The mutants were detected by their poor ability to grow in nitrate-containing medium without added Mo. One of the mutant types required 10(5) times more molybdate than the wild type to obtain maximal nitrogen fixation activity. Double-reciprocal plots of Mo uptake versus concentration indicated that the wild-type strain had a high- and a lower-affinity component for Mo binding. Mutant strains JH-90 and JH-119 lacked the high-affinity Mo uptake component and were also clearly deficient in Mo accumulation into a nonexchangeable form. Nitrogenase activity as well as Mo uptake ability could be restored in strains JH-90 and JH-119 by the addition of the sterile supernatant fraction of the wild type. Therefore, mutant strains JH-90 and JH-119 appeared to be deficient in an extracellular Mo-binding factor produced by the wild type. Mutant strains JH-14 and JH-143 had Mo uptake kinetics like those of the wild type (both high- and low-affinity binding for Mo) and appeared to be deficient in intracellular Mo metabolism processes. The addition of the wild-type supernatant did not restore Mo uptake or nitrogenase activity in these strains.

Plasma and lipoprotein fatty acid composition in glycogen storage disease type I

Nocturnal intragastric feeding has been shown to be an effective means to improve clinical and biochemical features in glycogen storage disease type I (GSD-I). In this study, we investigated the fatty acid patterns in a whole plasma and in circulating lipoproteins in patients on this therapy. The results demonstrated massive concentration of total fatty acids coupled with higher levels of triglycerides, free cholesterol, cholesterol ester and phospholipids. This hyperlipidemia involved all fatty acids without distinction of carbon or bond numbers. However, the increase was more pronounced for saturated than polyunsaturated fatty acids, as was demonstrated by the ratios of both oleic acid to linoleic acid (1.91 +/- 0.40 vs 0.80 +/- 0.09 in controls) and of omega 3 + omega 6 to omega 9 fatty acid families (0.92 +/- 0.11 vs 1.66 +/- 0.08 in controls). The fatty acid patterns in very low (VLDL), low (LDL) and high (HDL) density lipoprotein showed substantial differences in composition, reflecting an association between an abnormal lipoprotein pattern and essential fatty acid deficiency. Furthermore, GSD-I patients exhibited a significant increase in VLDL (17 +/- 2 vs 47 +/- 7 mg/dl) and LDL cholesterol (124 +/- 7 vs 206 +/- 24 mg/dl), coupled with a decrease in HDL cholesterol (49 +/- 4 vs 28 +/- 3 mg/dl). These data documenting high LDL cholesterol and low HDL cholesterol associated with an increased concentration and proportion of saturated fatty acids suggest that GSD-I patients on nocturnal intragastric feeding are at high risk for atherosclerosis and its complications.

Branched-chain amino acid metabolism in rat muscle: abnormal regulation in acidosis

Branched-chain amino acid (BCAA) metabolism is frequently abnormal in pathological conditions accompanied by chronic metabolic acidosis. To study how metabolic acidosis affects BCAA metabolism in muscle, rats were gavage fed a 14% protein diet with or without 4 mmol NH4Cl X 100 g body wt-1 X day-1. Epitrochlearis muscles were incubated with L-[1-14C]-valine and L-[1-14C]leucine, and rates of decarboxylation, net transamination, and incorporation into muscle protein were measured. Plasma and muscle BCAA levels were lower (P less than 0.05) in acidotic rats. Rates of valine and leucine decarboxylation and net transamination were higher (P less than 0.05) in muscles from acidotic rats; these differences were associated with a 79% increase in the total activity of branched-chain alpha-keto acid dehydrogenase and a 146% increase in the activated form of the enzyme. We conclude that acidosis affects the regulation of BCAA metabolism by enhancing flux through the transaminase and by directly stimulating oxidative catabolism through activation of branched-chain alpha-keto acid dehydrogenase.

Operator sequences of the aerobactin operon of plasmid ColV-K30 binding the ferric uptake regulation (fur) repressor

The promoter region of the pColV-K30-encoded operon specifying biosynthesis and transport of the siderophore aerobactin was subjected to deletion analysis to determine the smallest DNA sequence affording iron regulation of a iucA'-'lacZ gene fusion. A 78-base-pair (bp) region containing the main (P1) promoter retained the character of inducibility under iron starvation. A 250-bp fragment carrying this sequence was examined for protection against DNase I by the Fur protein, the product of a gene (fur) required for negative control of several iron-regulated functions. The DNase I footprints, in the presence of various divalent heavy-metal ions added as corepressors, revealed two contiguous binding sites with different lengths and affinities for Fur. Increased concentrations of the protein appeared to elicit formation of repressor oligomers which bind to the upstream and downstream regions of the P1 promoter in a metal-dependent fashion, but with a presently undefined stoichiometry. The primary site for Fur binding spans 31 bp and contains two overlapping symmetry dyads which share the sequence 5'-TCATT-3'. It also contains extensive homology with a 19-bp consensus sequence for iron-regulated genes as deduced from comparison with the fhuA and fepA putative promoter sequences.

Nodular liver lesions associated with chronic home hyperalimentation after massive enterectomy for ileal carcinoma

A case of an ileal carcinoma involving the entire midgut treated with a massive enterectomy of the small bowel distal to the ligament of Treitz, the right colon, and part of the transverse colon is discussed. After 1 year on home hyperalimentation, hepatic nodules were seen on CT scans; metastases could not be proven. At 3 years a hepatic wedge resection was performed, multiple areas of necrosis and fibrosis were found, but no carcinoma. This case is presented as an example of an alternative in treatment for this type of carcinoma and to illustrate the problems of differential diagnosis of liver defects on the CT scan in patients on longterm hyperalimentation.

Metabolism of cysteine in rat hepatocytes. Evidence for cysteinesulphinate-independent pathways

The metabolism of cysteine and cysteinesulphinate was studied in freshly isolated rat hepatocytes. Over 80% of the 14CO2 formed from [1-14C]cysteinesulphinate could be accounted for by production of hypotaurine plus taurine in incubations of rat hepatocytes with either 1 mM- or 25 mM-cysteinesulphinate. In similar incubations with 1 mM- or 25 mM-cysteine, less than 10% of 14CO2 evolution from [1-14C]cysteine could be accounted for by production of hypotaurine plus taurine. In incubations with cysteine, but not with cysteinesulphinate, the production of urea and ammonia was substantially increased above that observed in incubations without substrate. Addition of unlabelled cysteinesulphinate did not affect 14CO2 production from [1-14C]cysteine. Addition of 2-oxoglutarate resulted in a marked increase in cysteinesulphinate catabolism via the transamination pathway, but addition of neither 2-oxoglutarate nor pyruvate to the incubation system had any effect on cysteine catabolism. Inhibition of cystathionase with propargylglycine decreased 14CO2 production from [1-14C]cysteine about 50% and markedly decreased production of ammonia plus urea N; cysteinesulphinate catabolism by cysteinesulphinate-independent pathways in the rat hepatocyte and, furthermore, that cleavage of cyst(e)ine by cystathionase may be an important physiological pathway for cysteine catabolism in rat liver.

Bioenergetic and metabolic response to continuous v intermittent nasoenteric feeding

Resting thermal energy losses and metabolic balances of N, K, P, Ca, Na, and Mg were compared during continuous and intermittent nasoenteric formula infusion in four healthy men. Each feeding protocol lasted 1 week in a 4-week double crossover experiment. The initial feeding schedule was established randomly. Continuous nasoenteric formula infusion produced no increase in thermal energy losses above the fasting level; energy expenditure fell with sleep to the same extent as with intermittent feeding. Thermal losses were similar during intermittent feeding with the exception of the thermic effect of food that produced an additional average energy loss of 115.7 kcal/d. The total resting and sleeping 24-hour energy expenditure was significantly lower (P less than .01) during continuous formula infusion (means +/- SD for n = 8 balance periods, 1344 +/- 119 kcal) compared to intermittent feeding (1457 +/- 179 kcal). No significant differences in nutrient absorption or balances of N, Na, Ca, and Mg were detected between the two feeding protocols. In contrast, continuous infusion of formula was accompanied by negative balances of K and the cytosolic portion of P; weight balance was slightly negative. Weight, K, and cytosolic P balances were all positive during intermittent feeding (P = NS, less than 0.01, and P less than .05 compared to respective continuous infusion periods). Hence, 1 week of continuous nasogastric formula infusion is associated with similar nutrient absorption, a significant reduction in thermal energy losses, and equivalent protein (N) balance relative to intermittent feeding. Differences in weight balance between the two feeding protocols can be ascribed largely to fluid and mineral shifts. These results suggest that energy requirements are lower during continuous formula infusion by about 100 kcal/d compared to regular meal ingestion.

Effect of E. coli endotoxin on temperature, oxygen consumption and brown adipose tissue thermogenesis in rats and mice

The effects of E. coli endotoxin 0127 B8 on oxygen consumption, temperature, and on the activity of the proton conductance pathway in brown adipose tissue (BAT) were investigated in rats and mice. In rats an increase was observed in rectal and skin temperature, whole body oxygen consumption and GDP binding in BAT. In mice only the rise in rectal and skin temperature were significantly changed by endotoxin administration. These findings suggest that in some species BAT is involved in the production of endotoxin induced fever and increased energy expenditure.

Sex differences in nitrogen balance following marrow grafting for leukemia

A sex difference in nitrogen balance was investigated in 40 adults, 21 men and 19 women, undergoing chemoradiotherapy and marrow transplantation for leukemia and receiving total parenteral nutrition. Twenty-four hour collections of urine and mixed urine-stool were analyzed for total nitrogen daily through day 14 posttransplant. Nitrogen balance, corrected for changes in blood urea nitrogen, decreased significantly over time (p less than 0.005) in both men and women, but men experienced a greater negative nitrogen balance during the time period (p less than 0.001). Mean daily nitrogen balance in men was -6.0 g for week 1 and -9.2 g for week 2, corresponding to -3.3 g and -5.6 g in women for week 1 (p less than 0.005) and 2 (p less than 0.01), respectively. The differences remained after controlling for stress level and adjusting for total calorie intakes. There were no differences in age, disease status, or nitrogen intakes per kg ideal body weight, and no effects on nitrogen balance by arm muscle area at admission, cyclosporine use, or the branched-chain amino acid content of the parenteral solution. The average rise in 3-methylhistidine excretion was 23% in men and 11% in women. These results suggest higher per kg nutrient needs in males during stress and may indicate differing metabolic responses to stress. The possibility of gender differences should be considered in research evaluating nitrogen metabolism during severe stress.

Production of abnormal prothrombin (des-gamma-carboxy prothrombin) by hepatocellular carcinoma. A clinical and experimental study

We measured plasma abnormal prothrombin (des-gamma-carboxy prothrombin; DCP) levels in normal subjects and in patients with hepatocellular carcinoma and other various diseases using the enzyme-linked immunosorbent assay developed by Motohara et al. (Pediatr Res 1985; 19: 354-357). Fifty-eight percent of 52 patients with hepatocellular carcinoma had elevated DCP levels; 24 of 28 patients with advanced or moderately advanced hepatocellular carcinoma were positive. By contrast, 50 normal controls, 13 pregnant women and 10 patients with acute hepatitis had normal levels. Three of 55 patients with chronic liver disease, and 6 of 32 patients with other malignancies, showed a slight increase. Thus, increased plasma DCP appears useful for the diagnosis of hepatocellular carcinoma. To elucidate the mechanism for the increase of DCP in hepatocellular carcinoma, we cultured a human hepatoma cell line, huH-2, and measured the levels of this abnormal prothrombin in the medium. The huH-2 cells produced large amounts of DCP in the medium without added vitamin K. It increased in a cell concentration- and time-dependent fashion. These cells produced no detectable amount of DCP in the medium with added vitamin K. Thus, human hepatoma cell line huH-2 produces DCP, and its production is dependent on the amount of vitamin K available in the medium. Des-gamma-carboxy prothrombin may be a useful tumor marker for the diagnosis of hepatocellular carcinoma.

Evidence for a warfarin-sensitive serum factor that participates in factor X activation by Lewis lung tumor cells

Mouse Lewis lung (LL) carcinoma cells possess a factor X activator (procoagulant) that is inhibited in vivo by warfarin treatment or diet-induced vitamin K deficiency. This inhibition suggests that vitamin-K-dependent proteins are involved in LL cell activation of factor X. A LL primary tumor clone (LL13) was isolated which contained a warfarin-sensitive vitamin-K cycle of metabolism and expressed factor X procoagulant activity. LL13 cells exposed to media containing warfarin or deficient in vitamin K grew as well as cells in normal media, and activated factor X to similar extents. In contrast, administration of warfarin to mice bearing LL13 cells inhibited factor X procoagulant activity as well as the vitamin K cycle of metabolism in the primary tumors. In relation to LL13 cells grown in media containing fetal bovine serum, those incubated for 20 hr in media containing mouse serum or the sera from LL13-bearing mice exhibited 9- to 10-times higher levels of factor X procoagulant activity. However, LL13 cells exposed to media containing the sera of warfarin-treated LL-13-bearing mice or to barium-sulfate-adsorbed normal mouse serum activated factor X much less efficiently. Collectively, these data suggest that inhibition of vitamin K function in LL cells does not affect the extent of factor X activation and thus the intrinsic factor X procoagulant is not a vitamin-K-dependent protein. They further suggest that both a warfarin-sensitive (vitamin-K-dependent) protein present in normal mouse serum and a LL13 cell component participate in factor X procoagulant activity.

Detection of oxygen activation and determination of the activity of antioxidants towards reactive oxygen species by use of the chemiluminigenic probes luminol and lucigenin

Reactive oxygen metabolites can transfer, via oxygenation, the chemiluminigenic probes luminol and lucigenin to an excited state and thus induce light emission from these probes. This technique has been applied to a study of the effect of common food antioxidants on the availability of reactive oxygen species in aqueous model systems and in microsomal preparations. In all systems tested, propyl gallate and its congener octyl gallate proved to be the most active scavengers of the oxygenating species involved in the chemiluminescence reaction. In aqueous model systems, butylated hydroxyanisole was 10 times less efficient than the gallic acid ester antioxidants. In biological material, the lower scavenger activity of butylated hydroxyanisole is further compromised by its ability to induce a marked increase in production of hydrogen peroxide in the endoplasmic reticulum. Butylated hydroxytoluene is only marginally active in aqueous media and in biological material. It is concluded that gallic acid ester antioxidants may possess a significant protective potential towards toxic and carcinogenic agents due to their ability to remove toxic oxygen metabolites.

Selection for Streptococcus mutans with an altered xylitol transport capacity in chronic xylitol consumers

The effect of long-term consumption of refined xylitol on the natural populations of S. mutans in the human oral cavity has been investigated. Fifty-four S. mutans strains were isolated from adults and children who had been consuming commercial food products containing xylitol for a period of from 1 1/2 to 10 years. Twenty isolates were also obtained from control subjects who had never consumed xylitol-containing commercial food products. The inhibitory effect of xylitol on the isolated strains was determined by monitoring growth on glucose in the presence or absence of xylitol. This was used to define the sensitivity of each isolate to xylitol. Phosphoenolpyruvate:sugar phosphotransferase (PEP-PTS) activities were measured by means of the soluble and membrane fractions prepared from strains from both study populations. It was found that 87% of the fresh isolates from xylitol consumers were xylitol-resistant (XR), compared with only 10% of the strains isolated from the control subjects. The XR strains had low constitutive fructose PTS activity and very low xylitol-phosphorylating capacity. The xylitol-sensitive (XS) strains, however, had much higher levels of constitutive fructose PTS activity and phosphorylated xylitol 16 times more rapidly than did the XR strains. Evidence for the phosphorylation of xylitol by a fructose PEP-PTS in the XS strains was obtained. The growth inhibition by the intracellular accumulation of non-metabolizable toxic xylitol phosphate and its prevention by the presence of fructose are discussed.

Induction of siderophore activity in Anabaena spp. and its moderation of copper toxicity

Growth of Anabaena sp. strain 7120 (in the absence of chelators or added iron) was inhibited by the addition of 2.1 to 6.5 microM copper and was abolished by copper concentration of 10 microM or higher. When the copper was chelated to schizokinen (the siderophore produced by this organism in response to iron starvation), the toxic effects were eliminated. Analysis of culture filtrates showed that the cupric schizokinen remains in the medium, thereby lowering the amount of copper taken up by the cells. Although this organism actively transports ferric schizokinen, it apparently does not recognize the cupric complex. Thus, Anabaena sp. is protected from copper toxicity under conditions in which siderophore is being produced. For cells grown in low iron, the accumulation of extracellular schizokinen was observed to parallel cell growth and continue well into stationary phase. The actual iron status of the organism was monitored by using iron uptake velocity as an assay. Cultures grown on 0.1 microM added iron were found to be severely iron limited upon reaching stationary phase, thus explaining the continued production of schizokinen. These data show that the siderophore system in Anabaena spp. has developed primarily as a response to iron starvation and that additional functions such as alleviation of copper toxicity or allelopathic inhibition of other algal species are merely secondary benefits.

The effects of fruit juices and fruits on the absorption of iron from a rice meal

The effects of the chemical composition of fruit juices and fruit on the absorption of iron from a rice (Oryza sativa) meal were measured in 234 parous Indian women, using the erythrocyte utilization of radioactive Fe method. The corrected geometric mean Fe absorptions with different juices varied between 0.040 and 0.129, with the variation correlating closely with the ascorbic acid contents of the juices (rs 0.838, P less than 0.01). Ascorbic acid was not the only organic acid responsible for the promoting effects of citrus fruit juices on Fe absorption. Fe absorption from laboratory 'orange juice' (100 ml water, 33 mg ascorbic acid and 750 mg citric acid) was significantly better than that from 100 ml water and 33 mg ascorbic acid alone (0.097 and 0.059 respectively), while Fe absorption from 100 ml orange juice (28 mg ascorbic acid) was better than that from 100 ml water containing the same amount of ascorbic acid (0.139 and 0.098 respectively). Finally, Fe absorption from laboratory 'lemon juice' (100 ml orange juice and 4 g citric acid) was significantly better than that from 100 ml orange juice (0.226 and 0.166 respectively). The corrected geometric mean Fe absorption from the rice meal was 0.025. Several fruits had little or no effect on Fe absorption from the meal (0.013-0.024). These included grape (Vitis vinifera), peach (Prunus persica), apple (Malus sylvestris) and avocado pear (Persea americana). Fruit with a mild to moderate enhancing effect on Fe absorption (0.031-0.088) included strawberry (Fragaria sp.) (uncorrected values), plum (Prunus domestica), rhubarb (Rheum rhaponticum), banana (Musa cavendishii), mango (Mangifera indica), pear (Pyrus communis), cantaloup (Cucumis melo) and pineapple (Ananas comosus) (uncorrected values). Guava (Psidium guajava) and pawpaw (Carica papaya) markedly increased Fe absorption (0.126-0.293). There was a close correlation between Fe absorption and the ascorbic acid content of the fruits tested (rs 0.738, P less than 0.0001). There was also a weaker but significant correlation with the citric acid content (rs 0.55, P less than 0.03). Although this may have reflected a direct effect of citric acid on Fe absorption, it should be noted that fruits containing citric acid also contained ascorbic acid (rs 0.70, P less than 0.002).(ABSTRACT TRUNCATED AT 400 WORDS)

The Fao cell. A tissue culture model for lipoprotein synthesis and secretion. I. Characterization of the system

In this study we found that a differentiated cultured rat hepatocyte cell line, Fao, synthesizes and secretes lipoproteins qualitatively similar to those synthesized by the rat hepatocyte in vivo, but quantitatively differing considerably in apoprotein composition and density distribution. Immunoprecipitation demonstrates that all the major apoproteins are synthesized, including both forms of apoB, apoE and apoA-I. Particles of all density classes are formed, apoB associating with the lighter particles and apoA-I with the heavier. ApoE is a major apoprotein in all but the lightest density classes. The general finding is that most particles formed have a density exceeding 1.10 g/ml, while very few of the lighter, apoB-containing particles form, probably because the normal growth medium of the cultured cells is lipid-poor as compared with rat serum. In ref. [20] we show that the composition of the lipoproteins synthesized can be effectively modulated by lipid depletion and lipid supplementation of the growth medium.

Detraining of exercise-trained rats: effects on energetic efficiency and brown adipose tissue thermogenesis

Complete energy balance measurements were made in exercise-trained (treadmill running) rats subjected to 27 d of exercise detraining. The 20% difference in body-weight that existed at the end of the training period between sedentary and trained rats was negated by detraining. Detrained rats had twice the body-weight gain of their untrained controls. An elevation (12%) in metabolizable energy (ME) intake (relative to body-weight) was observed in detrained rats while their gross energetic efficiency was augmented by 60%. Energy expenditure, excluding the estimated costs of fat and protein storage, was similar for detrained and untrained rats. Complementing the latter was the finding that thermogenesis in brown adipose tissue, a known energy buffering process, was also similar. Elevated ME intake (relative to body-weight) largely contributed to the increased energetic efficiency of detrained rats.

Activation mechanisms to chemical toxicity

The pathobiology of chemical toxicity may involve "acute lethal injury" (necrosis), "autoxidative injury" (oxygen toxicity), "immunological injury" (neoantigen formation), and malignancy. Toxic chemicals may be activated by reduction, conjugation, radical formation, or oxidation. Oxidative activation may be effected by cytochromes P-450/P-448, flavoprotein monooxygenases, or hydroxyl radicals. The alternative pathways of oxidative metabolism of toxic chemicals, namely, detoxication and activation, are catalysed by the phenobarbital-induced cytochromes P-450 and by the 3-methylcholanthrene-induced cytochromes P-448 respectively. Oxidative metabolism by cytochromes P-450 is followed by conjugation and detoxication, whereas oxidative metabolism by cytochromes P-448 yields reactive intermediates which are not readily conjugated, and thus react with vital intracellular macromolecules, resulting in necrosis, redox cycling and oxygen radical formation, neoantigen production, and mutations. The molecular dimensions of specific substrates, inhibitors and inducers of the PB-cytochromes P-450 indicate that they are globular and are different from those of the cytochromes P-448 which are planar, suggesting that the active sites of the two families of enzymes are different. Oxidative metabolism of planar substrates of cytochromes P-448 results in conformationally-hindered oxygenations, which inhibits subsequent conjugations. Cytochrome P-448 activity may be quantified by the oxidative deethylation of 7-ethoxyresorufin which, unlike benzo(a)pyrene hydroxylation (AHH) is a specific reaction for this family of enzymes. Oxidative metabolism of chemicals varies inversely with the body weight of the animal species, so that chemical toxicity involving oxidative activation, redox cycling, and reactive oxygen is greater the smaller the animal species.

Characterization of Pyoverdin pss , the Fluorescent Siderophore Produced by Pseudomonas syringae pv. syringae

Pseudomonas syringae pv. syringae B301D produces a yellow-green, fluorescent siderophore, pyoverdin pss , in large quantities under iron-limited growth conditions. Maximum yields of pyoverdin pss of approximately 50 μg/ml occurred after 24 h of incubation in a deferrated synthetic medium. Increasing increments of Fe(III) coordinately repressed siderophore production until repression was complete at concentrations of ≥ 10 μM. Pyoverdin pss was isolated, chemically characterized, and found to resemble previously characterized pyoverdins in spectral traits (absorbance maxima of 365 and 410 nm for pyoverdin pss and its ferric chelate, respectively), size (1,175 molecular weight), and amino acid composition. Nevertheless, pyoverdin pss was structurally unique since amino acid analysis of reductive hydrolysates yielded β-hydroxyaspartic acid, serine, threonine, and lysine in a 2:2:2:1 ratio. Pyoverdin pss exhibited a relatively high affinity constant for Fe(III), with values of 10 25 at pH 7.0 and 10 32 at pH 10.0. Iron uptake assays with [ 55 Fe]pyoverdin pss demonstrated rapid active uptake of 55 Fe(III) by P. syringae pv. syringae B301D, while no uptake was observed for a mutant strain unable to acquire Fe(III) from ferric pyoverdin pss . The chemical and biological properties of pyoverdin pss are discussed in relation to virulence and iron uptake during plant pathogenesis.

Trace element status of PKU children ingesting an elemental diet

We assessed the trace metal status of 10 children (3.5 to 13.3 yr) with phenylketonuria (PKU) who were successively treated for at least 6 months with a semi-synthetic formula restricted in phenylalanine, then for 6 months with a reformulated formula. The reformulated product contained higher concentrations of magnesium (Mg), potassium (K), phosphorus (P), selenium (Se), and zinc (Zn) and lower concentrations of calcium (Ca), sodium (Na), and unsaturated fats. Diet records, blood samples, and urine specimens were collected from each subject. Mean intakes of Mg, K, and Zn increased significantly when subjects were switched to the reformulated product. The subject's mean intakes of Se (for all age groups) and Zn (children 11 to 14 yr old) were below 67% of recommended intakes while they were ingesting the original formula. The mean trace metal concentrations of urine, blood, and serum did not differ significantly during the two periods. Mean serum Zn, Se, and Cu concentrations of the subjects were less than those reported for normal children. Significant negative correlations were obtained between serum Zn concentrations and the molar ratio of dietary (Ca + P):Zn, and the molar ratio of dietary Fe:Zn. No significant differences in mean urinary Cu and Zn excretion (mg/g creatinine) were observed in subjects after they were changed to the reformulated product. Individuals whose primary source of energy and protein is derived from semi-synthetic elemental diets are especially at risk for multiple trace element deficiencies.

Outer membrane protein mediating iron uptake via pyoverdinpss, the fluorescent siderophore produced by Pseudomonas syringae pv. syringae

In an iron-limited environment Pseudomonas syringae pv. syringae B301D produces a yellow-green fluorescent siderophore called pyoverdinpss which functions in high-affinity iron transport. Two-dimensional electrophoretic comparisons of the outer membrane proteins of strain B301D identified nine proteins which were expressed at low (50 nM) but not at high (10 microM) iron concentrations. Except for the minor protein 8e, the iron-regulated proteins exhibited high molecular weights ranging from approximately 74,000 to 80,000. A mutant of strain B301D incapable of iron uptake (Iu-) from ferric pyoverdinpss lacked the 74,000-molecular-weight protein 4a, which was the major iron-regulated outer membrane protein. In contrast, a nonfluorescent mutant (Flu-) unable to synthesize pyoverdinpss showed no quantitative or qualitative difference in its outer membrane profile from that of the wild-type strain. In plant pathogenicity tests the Iu- and Flu- strains caused typical brown necrotic and sunken lesions in immature sweet cherry fruit which were indistinguishable from those of the wild-type strain. Thus, excretion of pyoverdinpss and subsequent Fe(III) uptake do not have a determinative role in the pathogenicity or virulence of P. syringae pv. syringae.

Factors influencing the absorption of iron from soya-bean protein products

The absorption of iron from soya-bean (Glycine hispida)-based and milk-based infant formulas was assessed in 138 multiparous Indian women, using the erythrocyte utilization of radioactive Fe method. Fe absorption was significantly greater from the basal milk formula (1.5 g protein) than it was from the basal soya-bean formula (2.3 g protein), with geometric mean values of 0.083 and 0.044 respectively. Ascorbic acid markedly increased Fe absorption from the milk-based formula in a dose-dependent fashion. The increase was fivefold when the ascorbic acid:Fe ratio on a weight-for-weight basis was 6:1 and over tenfold when it was 20:1. In contrast, ascorbic acid had a less-marked effect on the absorption of Fe from the soya-bean-based formula, with only a two- to threefold increase at an ascorbic acid:Fe ratio of 20:1. The geometric mean Fe absorption from the soya-bean formula (1.27 mg Fe, 2.3 g isolated soya-bean protein (ISP] was somewhat less than that from the same amounts of ISP and ascorbic acid made up in milk (0.075 and 0.113 respectively). However, a direct comparison between the soya-bean formula in milk and in water showed no significant difference (0.043 and 0.060 respectively). Fe absorption from a drink containing 10 g ISP and 30 mg ascorbic acid was significantly better than that from a similar drink containing the soya-bean flour from which ISP is extracted (0.044 and 0.027 respectively). Heating ISP to 200 degrees for 2 h before its use had no effect on Fe availability.(ABSTRACT TRUNCATED AT 250 WORDS)

Resting energy expenditure in patients with end-stage liver disease and in normal population

Resting energy expenditure (REE) was measured in 10 patients with end-stage liver disease (ELD) and in 31 normal controls. Basal energy expenditure (BEE) was also predicted by the Harris-Benedict equation. In order to correlate REE to lean body mass, the 24-hr urinary creatinine was measured in patients with ELD and in normal controls and expressed as kcal/g urinary creatinine. Linear regression analysis showed a statistically significant (p less than 0.0001) correlation (r = 0.72) between the REE and the 24-hr urinary creatinine in normal controls, irrespective of age and sex. Mean BEE (1580 +/- 160 vs 1575 +/- 210) and REE (1755 +/- 215 vs 1800 +/- 330) were not significantly different between patients with ELD and controls. However, the mean REE was 1900 +/- 610 kcal/g creatinine in patients with ELD and 1180 +/- 260 (p less than 0.0001) in controls. When related to lean tissue, patients with ELD had increased energy expenditure, confirming the hypermetabolic state suggested on clinical grounds. The use of urine creatinine to estimate energy expenditure may be a simple clinical technique to predict dietary energy needs in malnourished, unstressed patients. When this estimated energy expenditure/g creatinine (EEE) is compared to measured energy expenditure/g creatinine in malnourished, stressed patients, the EEE provides an index of the extent of hypermetabolism.

Topical fluorides: a discussion of risks and benefits

Inadvertent ingestion of fluoride from topical procedures poses the risk of dental fluorosis in age-susceptible users. This risk can be minimized for mouthrinsing by restricting it to those above the age-susceptible limit. Operators administering topical fluoride treatments can take practical precautions that have been shown to reduce the amount of fluoride retained and, thus, reduce ingestion. Clinical and epidemiological studies have failed to establish that dentifrice ingestion by young children constitutes a serious fluorosis risk. Discussion of risk must consider the effect of perceived risks upon the public.

Modulation of rat skeletal muscle branched-chain alpha-keto acid dehydrogenase in vivo. Effects of dietary protein and meal consumption

The effects of dietary protein on the activity of skeletal muscle branched-chain alpha-keto acid dehydrogenase (BCKAD) were investigated. BCKAD is rate-limiting for branched-chain amino acid (BCAA) catabolism by muscle; its activity is modulated by phosphorylation-dephosphorylation. In rats fed an adequate protein (25% casein) diet, BCKAD was approximately 2% active postabsorptively and increased to 10% or 16% active after a 25% or 50% protein meal, respectively. Prolonged feeding of a 50% protein diet increased postabsorptive BCKAD activity to 7% with further increases to 40% active postprandially. On a low protein (9% casein) diet BCKAD remained approximately 2% active regardless of meal-feeding. Dose-dependent activation of BCKAD by intravenous leucine in postabsorptive rats was blunted by a low protein diet. We conclude that excesses of dietary protein enhance the capacity of skeletal muscle to oxidize BCAA, muscle conserves BCAA when protein intake is inadequate, and skeletal muscle may play an important role in whole-body BCAA homeostasis.

Regulation of hepatic very-low-density lipoprotein secretion in rats fed on a diet high in unsaturated fat

Rats were fed ad libitum on either a standard, high-carbohydrate, chow diet or a similar diet supplemented with 15% unsaturated fat (corn oil). Hepatocytes were prepared either during the dark phase (D6-hepatocytes) or during the light phase (L2-hepatocytes) of the diurnal cycle. In hepatocytes from rats fed on the unsaturated-fat-containing diet, secretion of very-low-density lipoprotein (VLDL) triacylglycerol was inhibited to a greater extent in the D6- than in the L2-hepatocytes. Plasma non-esterified fatty acid concentrations were elevated to the same extent at both D6 and L2 in the unsaturated-fat-fed animals. The secretion of VLDL esterified and non-esterified cholesterol was relatively insensitive to changes in the unsaturated-fat content of the diet. This resulted in proportionate increases in the content of these lipid constituents compared with that of triacylglycerol in the nascent VLDL. There was also an increase in the ratio of esterified to non-esterified cholesterol in the nascent VLDL produced by hepatocytes of the unsaturated-fat-fed animals. In the D6-hepatocytes from the unsaturated-fat-fed animals, the decrease in the secretion of VLDL triacylglycerol could not be reversed by addition of exogenous oleate (0.7 mM) to the incubation medium. In contrast, addition of a mixture of lactate (10 mM) and pyruvate (1 mM) stimulated both fatty acid synthesis de novo and the rate of VLDL triacylglycerol secretion. Secretion of esterified and non-esterified cholesterol also increased under these conditions. Insulin suppressed the secretion of VLDL triacylglycerol and cholesteryl ester under a wide range of conditions in all types of hepatocyte preparations. Non-esterified cholesterol secretion was unaffected. In hepatocytes prepared from the fat-fed animals, these effects of insulin were more pronounced at D6 than at L2. Glucagon also inhibited VLDL lipid secretion in all types of hepatocyte preparations. The decrease in cholesterol secretion was due equally to decreases in the rates of secretion of both esterified and non-esterified cholesterol.

Selenium and immune responses

Selenium (Se) affects all components of the immune system, i.e., the development and expression of nonspecific, humoral, and cell-mediated responses. In general, a deficiency in Se appears to result in immunosuppression, whereas supplementation with low doses of Se appears to result in augmentation and/or restoration of immunologic functions. A deficiency of Se has been shown to inhibit resistance to microbial and viral infections, neutrophil function, antibody production, proliferation of T and B lymphocytes in response to mitogens, and cytodestruction by T lymphocytes and NK cells. Supplementation with Se has been shown to stimulate the function of neutrophils, production of antibodies, proliferation of T and B lymphocytes in response to mitogens, production of lymphokines, NK cell-mediated cytodestruction, delayed-type hypersensitivity reactions and allograft rejection, and the ability of a host to reject transplanted malignant tumors. The mechanism(s) whereby Se affects the immune system is speculative. The effects of Se on the function of glutathione peroxidase and on the cellular levels of reduced glutathione and H2Se, as well as the ability of Se to interact with cell membranes, probably represent only a few of many regulatory mechanisms. The manipulation of cellular levels of Se may be significant for the maintenance of general health and for the control of immunodeficiency disorders and the chemoprevention of cancer.

Caffeine-resistant mutants of Caenorhabditis elegans

Wild-typeCaenorhabditis elegansfails to reach adulthood if L1 larvae are incubated in the presence of 30 mM or greater concentrations of caffeine. Eleven mutants have been isolated in which caffeine has a less pronounced effect on development. The mutations are recessive, define two genes, and have been mapped. The mechanism(s) of resistance is unknown.

In vivo regulation of human mononuclear leukocyte 3-hydroxy-3-methylglutaryl coenzyme A reductase. Studies in normal subjects

In vivo regulation of microsomal HMG CoA reductase activity was investigated in freshly isolated mononuclear leukocytes from 26 healthy adult males. Reductase activity exhibited a diurnal rhythm and decreased during fasting. Enzyme activity was also modulated in vivo by alterations in dietary and plasma cholesterol, suggesting the existence of an operative cholesterol feedback regulatory system. A single, high cholesterol meal decreased reductase activity within 2 h. In addition, rapid depletion of circulating cholesterol levels by plasmapheresis led to an approximately twofold elevation in enzyme activity within 90 min of treatment. Finally, reductase activity was inhibited by dichloroacetate, a compound known to lower plasma cholesterol in man and inhibit the human leukocyte enzyme in vitro. The regulatory mechanisms controlling HMG CoA reductase activity in the human mononuclear leukocyte in vivo thus are similar to those that modulate the mammalian liver enzyme in vivo. Assessment of mononuclear leukocyte reductase activity may provide insight into the in vivo regulation of human cholesterol metabolism.

Screening for late neonatal vitamin K deficiency by acarboxyprothrombin in dried blood spots

Acarboxyprothrombin (protein induced by vitamin K absence or antagonist-II (PIVKA-II] concentrations in dried blood spots were determined in 19,029 infants at about 1 month of age as an indicator of vitamin K deficiency. We observed 51 cases with raised blood concentrations of PIVKA-II (greater than 4 AU/ml), nine of whom showed very high concentrations (greater than 20 AU/ml). For infants who did not receive vitamin K prophylaxis at birth, the incidence of the PIVKA-II test yielding positive results was significantly higher in those solely breast fed (0.51%) compared with those fed formula milk (0.18%). Among solely breast fed infants, the incidence of a very high result of the PIVKA-II test was 0.14% in those who had not received vitamin K prophylaxis at birth, 0.04% in those who received 2 mg orally, and 0.03% in those who received 2 mg orally plus a further dose of 2-4 mg orally at 7 days. Thus vitamin K prophylaxis at birth did not completely prevent vitamin K deficiency at 1 month. We administered vitamin K therapeutically to all infants whose PIVKA-II test yielded a positive result at 1 month. Only one infant with a positive result developed late neonatal intracranial haemorrhage.

Biological efficacy of partial hepatectomy and hepatopoietin in long-term selenium-deficient mice

After partial hepatectomy the normal low proliferation rate of hepatocytes increases dramatically. This is based on a feed-back system whose central link is a liver cell proliferation hormone, the so-called hepatopoietin. This glycoprotein is organ-specific but not species-specific, i.e. an extract from rats is also active in mice. In order to examine the influence of selenium on liver cell proliferation, male albino NMRI mice were fed a selenium-deficient diet containing less than 10 ppb Se for at least 2 months (Se-). In the plasma protein profile and in the basic DNA synthesis rate of Se(-)-animals, no significant changes were observed compared to controls. However, liver cell proliferation induced by hepatopoietin or by partial hepatectomy was increased about 3-fold in Se-deficient mice. We assume a compensated metabolic Se-deficiency state in mice under these nutritional conditions, which leads to expression of enhanced metabolic capacity when induced by stress.

Purification and characterization of the major iron-regulated protein expressed by pathogenic Neisseriae

This report describes a method to purify the major iron-regulated protein (MIRP) expressed by N. gonorrhoeae and N. meningitidis. This purification procedure involves maximal expression of the MIRP by growing the organisms on iron-limited media; cellular disruption by sonication followed by centrifugal fractionation; selective solubilization of the MIRP with the cationic detergent hexadecyltrimethylammonium bromide; cation-exchange chromatography in the presence of this detergent; and gel filtration chromatography. The MIRP purified by this technique migrates as a single band when analyzed by SDS-PAGE. The purified MIRP displayed an unusually basic isoelectric point, this value being greater than 9.35. Further biochemical analysis revealed the highly conserved nature of this protein isolated from the two pathogenic species of the genus Neisseria. For example, the amino acid composition of the meningococcal and gonococcal MIRPs were nearly identical and amino terminal sequence analysis showed that both shared the identical primary sequence through residue 48. Surprisingly, the first five NH2-terminal residues of the MIRPs exhibited homology with the first five residues of the gonococcal porin, protein I. Purified preparations of the MIRP exhibited a characteristic pink color reminiscent of the basic iron-binding protein lactoferrin. This observation coupled with the property of iron-regulation prompted us to analyze purified MIRP for iron-content. Approximately 0.5 mol iron per 1 mol of MIRP was detected. This study is the first to show that iron is associated with the MIRP, a property that may implicate this protein as playing a direct role in neisserial iron assimilation. While the precise function of the MIRP is not known, the availability of this protein in pure and biologically relevant quantities will allow further studies to elucidate its pathobiologic function.