Chronic malnutrition: protein metabolism.
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Amino Acids, Essential↗
Biomedical subjects
A A Jackson
Publications and source records attributed to A A Jackson.
Variability of fecal energy content measured in healthy women.
The variability of daily stool energy losses was examined in six healthy adult women over a complete menstrual cycle. On average, stool energy was 0.74 +/- 0.15 kJ/d (mean +/- SD) for the group. For a given individual, daily stool energy varied up to twofold. The variability for rolling averages of daily fecal energy losses over 3-, 5-, and 7-d periods showed no significant differences between collection periods of 3 and 5 d and 5 and 7 d. There was a close linear relationship between the energy content of the stool and either the wet or dry weight of stool (range 17-460 g wet wt). In metabolic studies of healthy women representative values for daily losses of energy in stool can be obtained from a 3-d collection. The energy content of wet stool was approximately 7 kJ/g. Under field conditions, weighing the stool provides a simple, useful method of assessing fecal energy losses.
Adult↗
Interactions between growth and nutrient status in school-age children of urban Bangladesh.
The relationship between biochemical, anthropometric, and sociodemographic indexes was investigated in 242 children aged 5-12 y from five schools in Dhaka City, Bangladesh. As height-for-age increased so too did the mean serum concentrations of hemoglobin, protein, vitamin A, and zinc; serum copper concentrations were highest in the shortest group. Serum copper concentrations were highest in those with the lowest serum vitamin A concentrations. By multiple regression analysis, family income, age, weight-for-age, hemoglobin, and serum copper were strongly related to serum vitamin A. For every unit change in serum vitamin A there was a 4.92 unit change in hemoglobin, when all the other factors were taken into account. This study shows that there is a complex interaction between concentrations of biochemical indexes of nutritional status and other anthropometric, biochemical, and sociodemographic variables.
Aging↗
A noninvasive method for measuring urea kinetics with a single dose of [15N15N]urea in free-living humans.
A noninvasive method is described in which the endogenous rate of urea production can be determined in normal, free-living adults. A single dose of [15N15N]urea was given orally, and the amount of label excreted as [15N15N]urea and [15N14N]urea in urine over the subsequent 48 h was measured. From the rates of excretion of labeled and unlabeled urea the rate of urea production was derived. Using this single-dose protocol the rate of urea production was 207 +/- 56 (mean +/- SD) mg N/(kg.d) in six normal adult men consuming 74 g protein/d. These results were not different when compared with rates of urea production obtained with a prime/intermittent protocol in an earlier study in the same individuals [199 +/- 20 mg N/(kg.d)]. We conclude that urea kinetics can be measured noninvasively with a single dose of [15N15N]urea and that this method may be suitable for use in free-living individuals to determine urea production rates for habitual dietary intakes.
Administration, Oral↗
Vegetarians and longevity.
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Diet, Vegetarian↗
Urea kinetics in neonates receiving total parenteral nutrition.
Urea kinetics were measured on 10 occasions in eight neonates who had not received an oral intake from birth and were maintained on total parenteral nutrition. After a prime/intermittent oral dose of 15N15N-urea over 14 hours urine was collected every three to four hours, urea isolated, and kinetics determined from the plateau level of enrichment in urea, measured by isotope ratio mass spectrometry. The total parenteral nutrition provided 393 kJ (94 kcal)/kg/day and 360 mg nitrogen/kg/day. Urea production was mean (SD) 84 (44) mg nitrogen/kg/day, or 50% of intake. Urinary excretion of urea, 39 (16) mg nitrogen/kg/day, was 40% of production. Therefore 54% of urea production was salvaged through the lower bowel, 45 (35) mg nitrogen/kg/day. It is concluded that even in infants who have never had a regular dietary intake the microflora of the lower bowel is sufficiently developed to salvage urea nitrogen for further metabolic interaction, however it is not clear whether the rate of salvage is adequate to satisfy the metabolic demand.
Ammonia↗
Urea salvage in a neonate with cloacal exstrophy.
Urea kinetics were measured in a child with congenital absence of the colon on days 15, 19, and 23 of age. Urea salvage was 5% of urea production in the first study, increasing to 79% by the third. This provides evidence that the colonic microflora play a more active part in urea salvage than the mucosa and that the establishment of an active lower ileal microflora takes over some of the metabolic functions of the intact colon.
Cloaca↗
Modest restriction of dietary protein during pregnancy in the rat: fetal and placental growth.
Pregnant rats were fed to appetite on diets containing 6, 9, 12 or 18% protein and the fetuses were delivered at 20 days. Compared with the 18% protein diet (7.4 MJ), there was a significant increase in food and energy intake in the rats on the 9% (8.7 MJ) and 12% (8.4 MJ) diets, but not on the 6% (7.4 MJ) diet. The efficiency with which the dietary energy was used for weight gain was reduced on the 6, 9 and 12% diets compared with the 18% diet. The trend towards a decrease in the number of viable fetuses and an increase in the number of resorptions on the 9% and 6% diets did not reach statistical significance. The placental weight was not different to the 18% group (520 mg) on the 12% diet (540 mg), but was significantly increased on the 9% diet (590 mg) and significantly decreased on the 6% diet (510 mg). Fetal weight was greatest on the 12% diet (1.81 g) and significantly decreased on the 9% diet (1.71 g). The fetal:placental ratio, around 3.3 for the 18 and 6% diets, was significantly increased on the 12% diet (3.7) and significantly decreased to 2.9 on the 9% diet. After adjusting for the effect of the fetal position in the uterine horn, the number of pups per litter and an estimate of the number of failed implantations the effect of diet on placental weight was no longer statistically significant, but the effect of dietary protein on fetal weight was more significant statistically, with little change overall on the fetal:placental ratio.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Rapid determination by centrifugal ultrafiltration of inter-mixed micellar/vesicular (non-lecithin-associated) bile salt concentrations in model bile: influence of Donnan equilibrium effects.
We have developed the technique of rapid (< 2 h) centrifugal ultrafiltration to measure the inter-mixed micellar/vesicular (non-lecithin-associated) bile salt (BS) concentrations (IMC) of individual BS in model biles. This methodology uses a centrifugal concentrator with a reinforced membrane, through which a small fraction (< 15% total volume) of model biles was ultrafiltered by low centrifugal forces (1500 g 5-60 min). Total and individual BS concentrations in the filtrate were measured by high performance liquid chromatography. However, non-filterable anions, in this case BS/lecithin/cholesterol mixed micelles and unilamellar vesicles, induce an asymmetric distribution of ions across the membrane. Therefore, BS concentrations in the filtrate exceeded the true IMC, which was estimated taking into account Donnan equilibrium effects. To confirm the hypothesis that a correction for Donnan forces was necessary, distributions of BS and another filterable anion, chloride, were measured in systems containing the non-filterable polyanion dextran sulfate as an analogue for non-filterable polyanionic mixed micelles and vesicles. An asymmetric distribution of the monovalent anions chloride and BS monomers as well as polyvalent simple BS micelles was indeed present during centrifugal ultrafiltration. This new methodology was validated by comparing IMC values with those obtained by modified equilibrium dialysis also corrected for Donnan equilibrium effects (Donovan, J.M., et al. 1991. J. Lipid Res. 32: 1501-1512). Centrifugal ultrafiltration, which utilizes < 1 ml of bile, determines the composition in the IMC necessary to separate micelles and vesicles of native biles by techniques that involve dilution of bile such as gel filtration chromatography.
Bile↗
Molecular species composition of inter-mixed micellar/vesicular bile salt concentrations in model bile: dependence upon hydrophilic-hydrophobic balance.
We systematically studied the bile salt (BS) species composition of the intermixed micellar/vesicular (non-lecithin-associated) BS concentrations (IMC) of model biles using physiological biliary compositions prepared with mixtures of 12 common BS of humans. BS distributions in the IMC, which was composed of monomers plus simple micelles, were determined by rapid centrifugal ultrafiltration and/or modified equilibrium dialysis as functions of total lipid concentration, BS/lecithin ratio, cholesterol content, pH, and the weighted hydrophobic index of BS species. IMC values increased from 3 to 9.5 mM with increases in total lipid concentration and BS/lecithin ratio, but decreased appreciably as the overall BS composition of physiological BS mixtures became more hydrophobic. However, IMC values were not altered by increases in cholesterol content (0-10%) that induced a phase transition from a one-phase micellar system to a two-phase system of micelles and vesicles. As pH values were decreased (8 to 5), with partial protonation but not precipitation of glycine-conjugated BS (pK'a approximately 4.3 by titration), IMC values decreased slightly. For all model biles studied, IMC values of BS mixtures were markedly smaller than those previously found for model biles composed with taurocholate (Donovan, J. M. et al. 1991. J. Lipid Res. 32: 1501-1512). Hydrophilic BS were preferentially distributed in the IMC, whereas hydrophobic BS were preferentially associated with lecithin in mixed micelles and vesicles. Hence, BS composition, in addition to total lipid composition and BS/lecithin ratio, is a critical determinant of the relative and absolute concentrations of the BS species in the inter-mixed micellar/vesicular bile salt concentration.
Bile↗
Function of the human colon.
Despite the volume of research on human colonic dysfunction, little is known about colonic function in health. This has stemmed partly from the difficulty in obtaining access to the organ. Two approaches have been used: studies on patients with stomas, and intestinal intubation techniques. The colonoscope has also recently been used to gain access. All these methods have limitations and results must be interpreted with caution. The accepted roles of the colon include the conservation of water and electrolytes and the controlled evacuation of faeces. Recent research has demonstrated its importance as a metabolic organ with an influence on overall metabolism, an effect that may in large part be attributed to the activity of colonic microflora. Evidence demonstrating that the defunctioned colon behaves differently from the functioning colon in the same individual has implications for a proper understanding of the organ, as practically all previous in vivo studies have been conducted in cleansed or defunctioned human colon.
Colon↗
Adaptation to a diet low in protein: effect of complex carbohydrate upon urea kinetics in normal man.
1. Urea kinetics were measured by using prime/intermittent oral doses of [15N15N]urea in five healthy men taking formula diets adequate in energy and containing either 70 or 35 g of protein/day. In some studies the low-protein diet was supplemented with non-starch polysaccharides in the form of ispaghula husk or ripe bananas. 2. On the 70 g of protein/day diet urea production was 132% of intake. Only 54% of the urea produced was excreted in the urine with 46% being salvaged in the colon; 90% of the salvaged nitrogen was retained in the metabolic nitrogen pool. 3. On the 35 g of protein/day diet the small decrease in urea production rate compared with that on the 70 g of protein/day diet was not significant, but only 36% of the urea produced was excreted in urine, with the majority, 64%, being salvaged. 4. The extent of urea-nitrogen salvaging on the 35 g of protein/day diet was similar in magnitude to the decrease in nitrogen intake, with the effect that the sum of intake and salvaged nitrogen did not differ between the 35 and the 70 g of protein/day diets. This implies that quantitative control is exerted over the rate at which urea nitrogen is salvaged. 5. The addition of non-starch polysaccharides to the 35 g of protein/day diet had a demonstrable effect upon faecal weight and composition, but did not exert any significant influence upon urea kinetics.(ABSTRACT TRUNCATED AT 250 WORDS)
Adaptation, Physiological↗
Limits of adaptation to a diet low in protein in normal man: urea kinetics.
1. Urea kinetics were measured using prime/intermittent oral doses of [15N15N]urea in six healthy men taking diets adequate in energy and containing either 74 or 30 g of protein/day. 2. On 74 g of protein/day, urea production (199 mg of N day-1 kg-1) was 121% of intake, with 60% of the urea produced being excreted in the urine and 40% being salvaged in the colon; 69% of the salvaged nitrogen was retained in the metabolic nitrogen pool. 3. Nitrogen balance was not maintained on 30 g of protein/day. There was a significant decrease in the urea production rate (123 mg of N day-1 kg-1) and 54% of production was excreted in urine, with 46% being salvaged. 4. The pattern of urea production and salvaging on 30 g of protein/day was different to that seen in an earlier study on 35 g of protein/day, with a significant decrease in both production (71%) and salvaging (50%). 5. These data reinforce the conclusions drawn from an earlier study, that the salvaging of urea nitrogen by the colon is an integral part of the process of adaptation to low protein diets. The salvage system appears to fail on an intake of 30 g of protein/day and nitrogen is no longer conserved in sufficient amounts for balance to be maintained. 6. The changes seen in urea kinetics reinforce the conclusion based upon nitrogen balance that the minimum physiological requirement for protein in normal adult man lies between 30 and 35 g of protein/day.
Adaptation, Physiological↗
Urea kinetics and total parenteral nutrition.
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Humans↗
Cysteine and glycine supplementation modulate the metabolic response to tumor necrosis factor alpha in rats fed a low protein diet.
Responses to cytokines entail synthesis of substances rich in cysteine and glycine, such as glutathione (GSH), metallothionein and some plasma proteins. To examine the importance of an adequate supply of cysteine and glycine, we fed rats a low protein diet supplemented with L-cysteine and glycine, separately or in combination, or L-alanine, or a high protein diet for 1 wk before injection with tumor necrosis factor alpha (TNF) or saline. The high protein diet-fed group had greater liver weight and zinc and GSH concentrations after TNF than the group fed the low protein diet supplemented with alanine. Glycine and cysteine supplementation resulted in greater liver weight after TNF treatment than did alanine supplementation. Cysteine supplementation had a similar influence on GSH concentration. Ceruloplasmin, alpha-2-macroglobulin and alpha-1-acid glycoprotein were higher in TNF-treated rats than in saline controls in each dietary group. However, feeding supplementary glycine and cysteine and the high protein diet often resulted in different values than seen in animals fed the low protein diet supplemented with alanine. Paradoxically, lower ceruloplasmin concentrations were observed in animals fed the former diets than in those fed the latter. alpha-2-Macroglobulin concentration was lower in all animals fed low protein diets than in those fed the high protein diet. alpha-1-Acid glycoprotein was lowest in groups fed cysteine-supplemented diets and highest in the glycine-supplemented group.(ABSTRACT TRUNCATED AT 250 WORDS)
Alanine↗
Effect of family size and income on the biochemical indices of urban school children of Bangladesh.
The relationship between family size and income and the biochemical indices of 242 children (aged from 5 to 12 years) from five schools in Dhaka City, Bangladesh, was investigated. Socio-economic data were collected by questionnaire and blood samples were drawn by visiting each school on a prefixed date. Mean levels of all measures, except for serum zinc, fell within the normal range. Older boys, but not girls (10-12 years of age) had statistically significantly higher haemoglobin, serum protein and serum vitamin A levels compared with those of the younger boys (5-9 years of age). The children were divided into three family size groups (small, up to 4 members; medium, 5-7 members; and large, 8 or more) to investigate the effect of family size on the biochemical data. The children from smaller families showed significantly higher levels of haemoglobin and serum vitamin A compared with the children from large families. For serum protein, copper and zinc, there was no statistically significant difference between the children of different family size groups. To analyse the effect of family income, children were divided into three income groups (low, up to taka 2000; medium, taka 2001-4500; and high, 4501 or more). The children from the low family income group had significantly lower serum protein (7.5 g/100 ml) and haemoglobin (13.4 g/100 ml) levels compared with those of the children from the high family income group (for protein, 7.7 g/100 ml and haemoglobin, 14.1 g/100 ml).(ABSTRACT TRUNCATED AT 250 WORDS)
Analysis of Variance↗
Urea kinetics: comparison of oral and intravenous dose regimens.
Urea kinetics were measured on two separate occasions in five adults with normal haemoglobin genotype (HbAA) and in four who were homozygous for sickle cell disease (HbSS). Prime/intermittent doses of [15N15N]urea were given orally on one occasion and intravenously on the other. In three of the nine individuals there appeared to be significant hydrolysis of the oral dose of urea before absorption, leading to spurious results for the urea kinetics. When only the studies in which isotope was given intravenously were considered, there was a difference in the rate at which urea-N was salvaged, with more urea-N being salvaged by HbSS subjects than HbAA. It is concluded that the oral presentation of isotope can be used to measure urea kinetics provided care is taken to exclude those subjects who are likely to display upper intestinal hydrolysis, and that there are differences in aspects of urea kinetics between HbAA and HbSS which may be of metabolic importance.
Absorption↗
A model for the measurement of whole-body protein turnover incorporating a protein pool with lifetime kinetics.
The hypothesis is proposed that the body contains a pool of protein turning over by lifetime rather than traditional first-order kinetics. The basis of the hypothesis is the observation of a step in the labelling curve or urinary ammonia during constant infusion of [15N]glycine. A four pool model has been constructed with different values for the rate of uptake of tracer into the lifetime pool; the calculated curves of tracer concentration show a step quite similar to that observed experimentally. It is concluded that it is possible, from an experimental curve, to derive an approximate estimate of the relative flux to the lifetime protein pool. Some suggestions are proposed for the physiological nature of this pool.
Adult↗