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Urinary free and total carnitine excretions were measured in 41 normal adults and seven surgical patients on fat-free total parenteral nutrition for 8 to 45 days. The means (+/-SEM) of urinary free and total carnitine excretion in normal adults were 162 +/- 19 and 328 +/- 28 micrometers/days, respectively. All of the patients exhibited protein-calorie malnutrition with a mean carnitine intake of 11.6 +/- 1.5 micrometers/day. Under this stringent carnitine economy with the adequate supply of lysine and methionine, urinary total carnitine excretion significantly reduced to 127 to 162 micrometers/day. This probably reflects the carnitine biosynthetic rate. However, during the periods of operation and/or infection, urinary total carnitine excretion significantly increased 2- to 7-fold that of normal levels. Significant positive correlation was found between the two forms of urinary carnitine and total nitrogen excretions. Serum free and total carnitine levels in patients were significantly higher than normal adults. Such findings can be explained by the endocrine responses to the stress phenomenon and indicate a catabolic response of skeletal muscle in which most of the body carnitine resides. This can impair their carnitine status.
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PMID:Urinary carnitine excretion in surgical patients on total parenteral nutrition. 680 Dec 84

Total cobalamin and methylcobalamin levels were determined in tissues of male F344 rats fed a complete, amino acid-defined diet or a diet deficient in methionine, choline and/or cyanocobalamin. Total cobalamin levels in rats fed the complete diet were (picograms/milligram tissue +/- SEM): liver, 67 +/- 13; kidneys, 738 +/- 133; spleen, 23 +/- 2; and adrenals, 268 +/- 36. Corresponding methylcobalamin levels were: liver, 1.6 +/- 0.5; kidneys, 107.6 +/- 22.2; spleen, 0.3 +/- 0.1; and adrenals, 26.9 +/- 5.3; these values represent 2.4, 14.5, 1.4 and 9.7%, respectively, of the total cobalamin levels. Total cobalamin levels of all tissues studied were altered by cobalamin deprivation alone or in conjunction with methionine and/or choline deprivation. Methylcobalamin levels were more resistant to dietary alteration. Regardless of the presence or absence of methionine and cobalamin in the diet, choline deprivation always decreased the proportion of methylcobalamin in the liver. Kidney levels of methylcobalamin, like those of total cobalamin, were decreased by removal of cobalamin from the complete or the methyl-deficient diets. The results demonstrate that cobalamin, methionine and choline exert quite different effects on tissue levels of the cobalamins in rats.
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PMID:Tissue distribution of methylcobalamin in rats fed amino acid-defined, methyl-deficient diets. 682 83

Six purified amino acid diets containing 6.0 g cystine/kg and the following levels of L-methionine (g/kg diet): 2.1, 2.7, 3.3, 3.9, 4.5, 9.0 were presented to twelve weanling kittens (six male and six female) for six periods of 10 d each. Kittens were assigned to the diets in accordance with a 6 x 6 balanced Latin-square design. Body-weight gains of males and females attained apparent plateaux at 3.3 g methionine/kg diet and were respectively (mean +/- SEM) 22 +/- 4 and 18 +/- 2 g/d. Daily food intakes attained apparent plateaux at 2.7 g methionine/kg diet for male and female kittens and were 63 +/- 10 and 49 +/- 4 g/d respectively. Nitrogen retentions (calculated as dietary-N intake minus faecal- and urinary-N excretion) attained apparent plateaux at 3.9 g methionine/kg diet for both male and female kittens and were 0.85 +/- 0.15 and 0.65 +/- 0.05 g/d respectively. Previous work has shown that the kitten's L-methionine requirement, in a diet lacking cystine, is 7.5 g/kg diet. Our results indicate that the kitten's L-methionine requirement is 3.9 g/kg diet when 6.0 g cystine/kg is provided, thus approximately 50% of the animal's sulphur amino acid requirement can be met by cystine.
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PMID:Methionine requirement of kittens given amino acid diets containing adequate cystine. 686 Jun 23

The single isotopic-enzymatic assay of histamine was modified to increase its sensitivity and to facilitate measurement of plasma histamine levels. The modification involved extracting 3H-1-methylhistamine (generated by the enzyme N-methyltransferase acting on histamine in the presence of S-[methyl-3H]-adenosyl-L-methionine) into chloroform and isolating the 3H-1-methylhistamine by thin-layer chromatography (TLC). The TLC was developed in acetone:ammonium hydroxide (95:10), and the methylhistamine spot (Rf = 0.50) was identified with an o-phthalaldehyde spray, scraped from the plate, and assayed in a scintillation counter. The assay in plasma demonstrated a linear relationship from 200 to 5000 pg histamine/ml. Plasma always had higher readings than buffer, and dialysis of plasma returned these values to the same level as buffer, suggesting that the baseline elevations might be attributable to histamine. However, all histamine standard curves were run in dialyzed plasma to negate any additional influences plasma might exert on the assay. The arithmetic mean (+/- SEM) in normal plasma histamine was 318.4 +/- 25 pg/ml (n = 51), and the geometric mean was 280 +/- 35 pg/ml. Plasma histamine was significantly elevated by infusion of histamine at 0.05 to 1.0 micrograms/kg/min or by cold immersion of the hand of a cold-urticaria patient. Therefore this modified isotopic-enzymatic assay of histamine is extremely sensitive, capable of measuring fluctuations in plasma histamine levels within the normal range, and potentially useful in analysis of the role histamine plays in human physiology.
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PMID:Measurement of plasma histamine: description of an improved method and normal values. 709 24

Human erythrocyte (RBC) catechol-O-methyltransferase (COMT) is under genetic control. Experiments were performed to determine whether COMT in the human lymphocyte is regulated in parallel with RBC COMT. Supernatants of lymphocyte homogenates contained COMT activity. However, they also contained a potent COMT inhibitor, the effect of which could be negated by dilution. Lymphocyte COMT activity was maximal at a reaction pH of 7.7 an at a MgCl2 concentration of 0.67 mM. The apparent Km value for 3,4-dihydroxybenzoic acid, the catechol substrate for the reaction, was 1.2 x 10(-5) M and that for S-adenosyl-L-methionine, the methyl donor, was 2.3 x 10(-6) M. An average of 48.3 /+- 3.3% (mean /+- SEM) of the enzyme activity in crude lymphocyte homogenates from 3 subjects was removed by centrifugation at 100,000 g for 1 hr and was presumed to be membrane associated. The average COMT activity in lymphocytes isolated from blood of 23 randomly selected adult subjects was 14.0 /+- 1.2 units/10(6) cells (mean /+- SEM) or 913 /+- 69 units/mg protein. There was a significant correlation of relative RBC with relative lymphocyte COMT activity in these 23 subjects. The correlation coefficient was 0.733 (P less than 0.001) when lymphocyte enzyme activity was expressed per milligram of protein and 0.649 (P less than 0.001) when lymphocyte activity was expressed per 10(6) cells. These results are compatible with the conclusion that the genetic polymorphism which regulates RBC COMT activity may also regulate the level of human lymphocyte COMT activity.
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PMID:Catechol-o-methyltransferase biochemical genetics: human lymphocyte enzyme. 733 86

Urinary and proximal tubular iron are increased after subtotal nephrectomy, and iron depletion has been shown to be beneficial in proteinuric models of chronic renal disease in rats. In this study, iron depletion by low iron pair-fed diet and periodic phlebotomy was induced for 6 months in rats with partial (5/6) nephrectomy, resulting in a reduction in hematocrit and serum iron in all iron-deficiency subgroups. Tubular iron, assessed by energy dispersive analysis and electron microscopy, was reduced in quantity but not number of iron-containing lysosomes only within 1 subgroup of severe iron deficiency (p < 0.05). There was no improvement in serial isotopic glomerular filtration rate measurements, urinary protein and transferrin excretion, tubular damage scores, serum creatinine, or measures of reactive oxygen species (ROS) generation. In a subgroup of rats with no supplementation of sulfhydryl amino acids (cysteine and methionine) which can act as ROS scavengers, iron deficiency increased urinary protein excretion (213.3 +/- 23.0 mg/24 h, mean +/- SEM, vs. 87.4 +/- 16.1, p < 0.001), urinary transferrin excretion (p < 0.05), kidney weight (p < 0.05) and tissue malondialdehyde, a lipid peroxidation product (0.78 +/- 0.16 nmol/mg protein vs. 0.57 +/- 0.19, p < 0.05), consistent with increased ROS generation. Hence, no beneficial effect of iron-deficiency was demonstrated by any measure of structure of function in the remnant kidney, and it may enhance damage if sulfhydryl repletion is not provided.
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PMID:Iron depletion in the remnant kidney. 747 24

The role of ATP-sensitive potassium channels (KATP) in the mechanism of ischemic preconditioning (PC) is controversial, partly because descriptions of inhibition of PC by KATP blockers in the literature are inconsistent. We sought a reason for the discrepant findings regarding the effects of glibenclamide (Glib), a specific blocker of KATP, in preventing the reduction of infarct size (IS) induced by PC. The effect of Glib pretreatment (0.3 mg/kg i.v.) on PC was examined in three conditions: (a) when PC was performed with 3- and 5-min ischemia (i.e., potency of PC differs), (b) when rabbits were pretreated with prazosin and metoprolol (0.15 mg/kg i.v. each) to reduce myocardial O2 consumption, and (c) when xylazine was added to pentobarbital anesthesia. In rabbits under pentobarbital anesthesia, the left coronary artery was occluded for 30 min and then reperfused. The area at risk (AAR) and IS were determined 72 h after reperfusion in the first series of experiments and 3 h after reperfusion in the second and third series. IS as a percentage of AAR (%IS/AR) were 31.7 +/- 2.8 and 19.6 +/- 2.5% (SEM) after PC with 3- and 5-min ischemia, respectively, values significantly smaller than %IS/AR in the untreated control group (49.2 +/- 3.3%). The limitation of IS observed with 3- or 5-min PC was not prevented by Glib. Glib also failed to block %IS/AR reduction by PC, even when rate-pressure product (RPP) was reduced to approximately 65% by prazosin/metoprolol (Praz/Met) pretreatment.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Glibenclamide, a blocker of ATP-sensitive potassium channels, abolishes infarct size limitation by preconditioning in rabbits anesthetized with xylazine/pentobarbital but not with pentobarbital alone. 759 19

Ninety-five female pigs from 20 to 45 kg body weight were used to elucidate the effects of energy and protein intake on the amino acid composition of the protein in the carcass, organs and empty body of growing pigs. In a 2 x 15 factorial arrangement, protein intake ranged from 127 to 350 g/d in 15 graduated steps; and the digestible energy allowances were 15.8 and 18.8 MJ/d. Whole-body amino acid contents (g/16 g nitrogen) were (means +/- SEM) lysine 6.64 +/- 0.028, methionine 2.11 +/- 0.012; threonine 3.62 +/- 0.016 and total essential amino acids 42.8 +/- 0.16. The organ fraction contained 14.8 and 15.8% (SEM 0.13) of whole-body protein at the low and high energy levels, respectively. The concentrations of essential amino acids were 41.8 +/- 0.19 and 48.4 +/- 0.13 g/16 g nitrogen in the carcass and organs, respectively. Concentrations of a number of amino acids (in carcass, organ and whole-body protein and in protein deposited between 20 and 45 kg, were affected by protein and/or energy intake. The amino acid pattern of the newly deposited protein was slightly different from that of the empty body protein. The changes in amino acid contents were presumably the result of effects of protein and energy intake on the proportions of muscle and non-muscle carcass tissues and on relative weights of blood and viscera. Consequences of these changes for the amino acid requirements are discussed.
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PMID:Amino acid composition of growing pigs is affected by protein and energy intake. 793 5

Vasoactive intestinal polypeptide (VIP) and peptide histidine methionine (PHM) originate from the same precursor molecule, prepro VIP. In the present study we examined the concentrations of VIP and PHM in human follicular fluid and their effects on cultured human granulosa/lutein cells. Follicular fluid and cells were obtained from patients undergoing in-vitro fertilization for tubal infertility. The concentrations of VIP and PHM in pre-ovulatory human follicular fluid were measured radioimmunochemically. Granulosa/lutein cells isolated from follicular fluid were cultured under serum-free conditions with VIP and PHM in varying concentrations (0.1, 10, 1000 nmol/l). [3H]Thymidine incorporation in the cells and oestradiol as well as progesterone concentrations in the culture medium were measured. The mean (+/- SEM) concentrations of VIP and PHM were 6.8 +/- 0.1 and 7.7 +/- 0.8 pmol/l, respectively. VIP at a concentration of 10 nmol/l caused a significant increase in [3H]thymidine incorporation, and at 1000 nmol/l a significant increase in oestradiol secretion was observed. VIP had no effect on progesterone secretion. PHM at the concentrations tested did not influence any of the activities. We conclude that VIP and PHM are present in human preovulatory follicular fluid and that VIP stimulates DNA synthesis and oestradiol secretion in cultured human granulosa/lutein cells. This indicates that VIP and perhaps PHM participate in the local nervous regulation of human ovarian function.
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PMID:Vasoactive intestinal polypeptide and peptide histidine methionine. Presence in human follicular fluid and effects on DNA synthesis and steroid secretion in cultured human granulosa/lutein cells. 796 75

Two experiments were conducted to determine the utilization of ileal digestible isoleucine by growing pigs. In the first, the apparent ileal digestibility of amino acids in cottonseed meal, lupin-seed meal and soya-bean meal was determined in pigs fitted with 'T'-shaped cannulas. In the second, three isoleucine-deficient diets were formulated to 0.23 g ileal digestible isoleucine/MJ digestible energy (DE) with the three protein concentrates contributing the only source of isoleucine in sucrose-based diets. An additional three diets were formulated with supplements of isoleucine to confirm that isoleucine was limiting in the first three diets. The growth performance and retention of isoleucine by pigs given the six diets over the 20-45 kg growth phase were then determined. The apparent ileal digestibility of isoleucine in the three protein concentrates (proportion of total) was: cottonseed meal 0.68, lupin-seed meal 0.86, soya-bean meal 0.86. There were no significant differences (P > 0.05) in growth rates (g/d) and crude protein deposition rates (g/d) of the pigs given the three diets formulated to 0.23 g ileal digestible isoleucine/MJ DE: cottonseed meal 590, 84; lupin-seed meal 613, 87; soya-bean meal 594, 91 (SEM 13.0, 2.9) respectively. The response of pigs to the addition of isoleucine confirmed that isoleucine was limiting in these diets. The proportion of ileal digestible isoleucine retained by pigs given the cottonseed meal (0.65) was slightly lower than that retained by pigs given soya-bean meal (0.73; P < 0.05). These results indicate that values for the ileal digestibility of isoleucine in protein concentrates more closely reflect the proportion of isoleucine that can be utilized by the pig than occurs for other amino acids such as lysine, threonine and methionine.
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PMID:Utilization of ileal digestible amino acids by growing pigs: isoleucine. 801 6


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