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1.
Eur J Clin Nutr ; 51(2): 107-15, Feb. 1997.
Artigo em Inglês | MedCarib | ID: med-2031

RESUMO

OBJECTIVE: We have measured urea kinetics in normal adult men and women of different body composition to determine whether adiposity is associated with differences in the rate of urea production or endogenous urea hydrolysis. DESIGN: Urea kinetics were determined from the excretion of [15N15N] urea in urine over a period of 48 h following a single oral dose of [15N15N] urea, in nine lean and nine obese women and in seven light and seven heavy males while they were consuming their habitual diets. Urinary 5-L-oxoproline was measured as an index of glycine metabolic status. SETTING: The studies were carried out in the research ward of the Tropical Metabolism Research Unit, University of the West Indies. RESULTS: Successful studies were completed in eight obese and five lean women and in six heavy and five light men. When compared with lean women, in obese women the rate of urea production and hydrolysis was significantly greater and this difference could not be accounted for by the greater fat-free mass alone, and was in part associated directly with the increase in fat mass. The rate of urea production and hydrolysis was greater in heavy men than in light men, a difference which was attributed to an increase in dietary protein. In obese women and heavy men there was a significantly higher rate of excretion of 5-Loxoproline in urine when compared with lean women and lean men respectively. CONCLUSION: This paper highlights the difficulty in identifying an appropriate reference with which to express results in people of different body composition. In obese women urea production and the hydrolysis of urea are increased, in part related to the increase fat-free mass, but also related to the increased fat mass itself. In obese women and men on high protein diets the greater rate of hydrolysis urea may be a reflection of an increased demand for the sythesis of non-essential amino acids, especially glycine.(AU)


Assuntos
Adulto , Feminino , Humanos , Masculino , Composição Corporal , Proteínas na Dieta/administração & dosagem , Obesidade/metabolismo , Índice de Massa Corporal , Hidrólise , Jamaica , Cinética , Nitrogênio/urina , Isótopos de Nitrogênio , Ácido Pirrolidonocarboxílico/urina
2.
Am J Clin Nutr ; 60(3): 341-6, Sept. 1994.
Artigo | MedCarib | ID: med-10776

RESUMO

The pattern of aggregated nitrogen demand during pregnancy and the fetal and maternal components are unclear. Excess demand enhances efficiency of nitrogen utilization. Urea salvage contributes to enhanced efficiency. Dietary protein intake, urea production, and salvage of urea nitrogen were measured in eight nonpregnant control subjects, and trimesterly in nine pregnant women. Production was measured after prime-intermittent intravenous doses of [15N15N]-urea by dilution of label in urinary urea. Dietary protein intake was greater in trimester 1 than in nonpregnant women (167 ñ 36 vs 224 ñ 60 mg N.kg-1.d-1), and increased further in trimester 2 (266 ñ 59 mg N.kg-1.d-1). Urea production was not higher during pregnancy. Despite higher protein intake urea salvage was higer in pregnancy (40 ñ 24 nonpregnant vs 77 ñ 23, 61 ñ 31, and 51 ñ 12 mg N.kg-1.d-1). Therefore, the demand-supply gap for nitrogen was greatest early in pregnancy when fetoplacental growth is slowest, and implies heightened maternal demand (AU)


Assuntos
Humanos , Feminino , Adulto , Proteínas na Dieta/metabolismo , Nitrogênio/metabolismo , Gravidez/metabolismo , Ureia/metabolismo , Proteínas na Dieta/administração & dosagem , Jamaica , Cinética , Estudos Longitudinais , Necessidades Nutricionais , Estudo Comparativo
3.
West Indian med. j ; 42(Suppl. 1): 30-1, Apr. 1993.
Artigo em Inglês | MedCarib | ID: med-5144

RESUMO

There is need for an increase in protein deposition during pregnancy. However, the requirement for dietary protein and also the pattern of the increased needs throughout gestation remains unclear. Based on nitrogen balance studies, a single value for the daily allowance throughout pregnancy has been proposed by various expert committees with recognition of the inherent limitations of this recommendation. Urea kinetics which represent a sensitive marker for the adequacy of dietary protein was measured in trimesters 1, 2, and 3 in 13 healthy pregnant women and in 8 healthy non-pregnant women (controls) using the prime/intermittent intravenous presentation of 15N 15N urea. The results are given in a Table. P/I indicates that although more protein was consumed in pregnancy compared to the controls, less was oxidised. Also E/I was significantly less at all stages of pregnancy. T, that portion of P that was salvaged and not excreted, was highest in the 1st trimester. It contributes to the nitrogen available for metabolism and is 20 - 30 per cent of P when protein intake is adequate. T+I, the total nitrogen available for metabolism was highest in the 2nd trimester. The results suggest that the demand for nitrogen is not constant throughout pregnancy and that there is an increased demand in early pregnancy. In particular, this increase was not met by the quantity and/or quality of the deitary intake in the first trimester. These changes in nitrogen metabolism have important implications for making recommendations for dietary protein intake during pregnancy (AU)


Assuntos
Humanos , Feminino , Gravidez , Ureia/metabolismo , Nitrogênio/metabolismo , Gravidez/metabolismo
4.
Plant Foods Hum Nutr ; 43(2): 105-14, Mar. 1993.
Artigo em Inglês | MedCarib | ID: med-8490

RESUMO

Protein quality of sorghum grains having 25, 50 and 75 percent infestation caused by mixed population of Trogoderma granarium Everts and Rhizopertha dominica Fabricius was biologically evaluated by rat growth and nitrogen balance studies. Feeding of diet containing insect infested sorghum grains (50 and 75 percent) resulted in marked decrease in food intake, protein intake, gain in body weight, food efficiency ratio, protein efficiency ratio, nitrogen consumption, nitrogen absorption, biological value, net protein utilization, dry matter digestibility, net protein retention and protein retention efficiency. These parameters showed negative association with insect infestation levels. However, 25 percent level of grain infestation did not affect these parameters significantly (AU)


Assuntos
Camundongos , Ratos , 21003 , Masculino , Besouros , Grão Comestível/análise , Contaminação de Alimentos , Proteínas de Plantas , Análise de Variância , Ingestão de Alimentos , Nitrogênio/urina , Valor Nutritivo , Proteínas de Plantas/metabolismo , Ratos Endogâmicos/crescimento & desenvolvimento , Aumento de Peso
5.
Eur J Clin Nutr ; 46(10): 697-706, Oct. 1992.
Artigo em Inglês | MedCarib | ID: med-8185

RESUMO

During recovery from severe wasting, malnourished children gain weight at greatly accelerated rates. To determine if additional zinc added to their basal therapeutic diets increased the retention of lean tissue and stimulated protein metabolism, we studied three groups of children taking either the basal diet alone or the basal diet supplemented with either 76 mumol (5 mg) or 153 mumol (10 mg) Zn/kg diet. The zinc-supplemented children gained similar weight and consumed the same amount of diet as the unsupplemented children. Zinc supplementation resulted in a greater net absorption of nitrogen and a higher rate of protein turnover, as estimated from urinary ammonia 15N enrichment after oral [15N] glycine. We conclude that additional zinc affected the composition of newly synthesized tissue and intermediary nitrogen metabolism (AU)


Assuntos
Humanos , Lactente , Pré-Escolar , Masculino , Alimentos Fortificados , Desnutrição Proteico-Calórica/dietoterapia , Zinco/administração & dosagem , Nitrogênio , Desnutrição Proteico-Calórica , Aumento de Peso , Estudo Comparativo
6.
Br J Nutr ; 63(2): 145-54, Mar. 1990.
Artigo em Inglês | MedCarib | ID: med-15857

RESUMO

Six male children, aged 8-28 months, were studied for three consecutive periods of 1 week each. They were given diets that provided 1.7g protein/kg per d and supplements of minerals and vitamins, with a metabolizable energy intake during the 1st, 2nd and 3rd week of 419, 293 and 335 kJ (100, 70 and 80 kcal)/kg per d, diets 1, 2 and 3 respectively. All the food offered was consumed. Each child was weighed at the same time each day on an electronic balance. On the 6th and 7th day of each study period urine and stool were collected for 24h to assess nitrogen balance. Using linear regression analysis it was shown that all children gained weight on diet 1, 2.3(SD 1.3)g/kg per d, and five of six children gained weight on diet 3, the mean for the whole group being 2.7(SD 2.3)g/kg per d, not significantly different. On diet 2 all children lost weight, -5.4(SD 1.3)g/kg per d, highly significantly different from each of the other dietary periods. Using asymptotic regression analysis it could be shown that the rate of weight loss during the first part of the week on diet 2, -11g/kg per d, was greater than at the end of the week, -2g/kg per d, with a tendency towards a steady weight by day 7. Apparent N retention (mg/kg per d) was positive at the end of each of the three dietary periods: diet 1, 112(SD 25); diet 2, 54(SD 34); diet 3, 82(SD20). In five of the six children there was a marked reduction in stool frequency on diet 2 compared with diet 1, that was maintained to the period on diet 3. The findings suggest that during the period on diet 2 there was a saving of energy of the order of 105 kJ(25 kcal)/kg per d, which lasted through into the period on diet 3


Assuntos
Humanos , Lactente , Pré-Escolar , Masculino , Adaptação Fisiológica/fisiologia , Metabolismo Energético , Ciências da Nutrição , Estatura , Peso Corporal , Ingestão de Energia/fisiologia , Nutrição da Criança , Dieta , Nutrição do Lactente , Nitrogênio/metabolismo , Deficiência de Proteína/metabolismo
7.
Clin Sci ; 77(1): 93-7, Jan. 1989.
Artigo em Inglês | MedCarib | ID: med-13070

RESUMO

Whole body protein turnover and resting metabolic rate were measured in six adults with homozyguous sickle cell disease (genotype HbSS) and in six normal adults (genotype HbAA) of similar age. Turnover was measured with prime/intermittent oral doses of [15N]glycine over 18 h and resting energy expenditure was measured by indirect calorimetry. In HbSS, nitrogen flux (0.9 ñ 0.08 g day-1 kg-1), protein synthesis (6.0 ñ 0.5 g day-1 kg-1) and protein degradation (5.6 ñ 0.5 g day-1 kg-1) were significantly increased compared with HbAA nitrogen (flux 0.5 ñ 0.02g day-1 kg-1, protein synthesis 3.2 ñ 0.2 g day-1 kg-1 and protein degradation 2.8 ñ 0.2 g day-1 kg-1). Resting energy expenditure was significantly higher in HbSS compared with HbAA when expressed per unit of body weight (115 ñ 3 and 94 ñ 4 kj day-1 kg-1 respectively) or weight 0.75(317 ñ 6 and 269 ñ 8 kj day-1kg-0.75, respectively). The increase in protein turnover and energy expenditure suggest that patients with HbSS exist in a hypermetabolic state that requires greater dietary energy compared with HbAA. (AU)


Assuntos
Humanos , Adulto , Masculino , Anemia Falciforme/metabolismo , Doença da Hemoglobina SC/metabolismo , Proteínas/metabolismo , Amônia/urina , Metabolismo Energético , Doença da Hemoglobina SC/urina , Hemoglobinas/biossíntese , Nitrogênio/metabolismo , Ureia/urina
8.
Kingston; s.n; 1989. xv,172 p. tab, ills.
Tese em Inglês | MedCarib | ID: med-13695

RESUMO

When dietary nitrogen intake is adequate to satisfy the body's metabolic demand for nitrogen, adaptive mechanisms are involved whereby nitrogen losses are minimised. The most significant reduction in nitrogen loss is effected by reduced urea production and excretion and there is a concomitant increase in the proportion of urea hydrolysed and recycled in the body. This work was designed to explore the mechanisms by which nitrogen equilibrium is maintained in the whole body when the metabolic demands for nitrogen exceed the supply. Urea kinetics was measured in normal healthy controls (HbAA) and patients with homozygous sickle cell disease (HbSS). HbSS is characterised by an increased metabolic demand for nitrogen for erythropoesis, which is significantly higher than normal. Urea production (P), excretion (Eu), hydrolysis (T) and recycling (Pr) of hydrolysed urea to urea synthesis, were determined using isotopic urea(urea-30) orally or intravenously, and the two methods compared. The reliability of the methods was examined and demonstrated to be satisfactory. All aspects of urea metabolism were increased in HbSS compared with HbAA, except Eu which tended to be lower in HbSS. The proportion of urea hydrolysed in the colon was raised in HbSS, regardless of the route by which the isotope was given and the kinetics was measured. Individuals with sickle cell trait (HbAS), were also studied and exhibited rates of urea hydrolysis that were either similar to the HbAA values or raised to values corresponding to the HbSS. Urea nitrogen incorporated into haemoglobin in both the HbAA and HbSs. This finding confirmed the utilisation of endogenous urea nitrogen for protein synthesis in the body. The proportion of hydrolysed urea nitrogen is small (10 percent) compared to a larger pool of enteric nitrogen to which it contributes, suggesting that there may be a more significant contribution of enteric nitrogen metabolism to the nitrogen economy, than of hydrolysed urea alone. The possibility that glycine may be limited in HbSS has been indicated and warrants more detailed investigation. The metabolism of urea has been shown to be affected by depleting the body glycine pool and alternatively by glycine supplements. Results from this work support the idea that urea kinetics is modulated by dietary nitrogen intake (AU)


Assuntos
Humanos , Adulto , Masculino , Feminino , Doença da Hemoglobina SC/metabolismo , Urea Nitrica , Cinética , Nitrogênio/metabolismo , Glicina/deficiência , Jamaica , Nitrogênio da Ureia Sanguínea
9.
Eur J Clin Nutr ; 42(6): 491-6, June 1988.
Artigo em Inglês | MedCarib | ID: med-12711

RESUMO

The kinetics of urea metabolism were measured in four adults with homozyguous sickle cell disease (HbSS). On a dietary intake of 1.2 to 2.7g protein /kg/d. A relatively small proportion of the urea was excreted in the urine (40 per cent), with a high fixed rate of hydrolysis in the bowel, 145 mg nitrogen /kg/d. Although 50 per cent of the nitrogen from hydrolysed urea was resynthesized to urea, and a further 10 per cent may have been lost in the stool, it is estimated that 58 mg nitrogen /kg/d was available for synthetic metabolic activity. Urea kinetics in sickle cell disease subjects are markedly different from normals, and this may be a reflection of the metabolic demands for increased red cell synthesis. (AU)


Assuntos
Humanos , Adulto , Anemia Falciforme/metabolismo , Traço Falciforme/metabolismo , Ureia/metabolismo , Dieta , Homozigoto , Hidrólise , Traço Falciforme/urina , Nitrogênio/urina , Ureia/urina
10.
Hum Nutr Clin Nutr ; 41(4): 263-76, July 1987.
Artigo em Inglês | MedCarib | ID: med-11757

RESUMO

Studies were carried out in eight normal adults to simplify the continuous infusion-end product method for measuring whole-body protein turnover using 15 N-glycine. When a priming dose of label suitable for the urea pool was followed by intermittent oral doses of label, plateau enrichment was maintained in urinary urea and ammonia from 9 to 18 h, giving values for nitrogen flux. (18h) of 0.69ñ0.05 g N/kg/d with urea and 0.46ñ0.01 g N/kg/d with ammonia. With a priming dose appropriate for the ammonia pool, plateau was reached in urinary ammonia in less than 120 min an maintained for up to 6h. Nitrogen flux (3h) with oral 15N-glycine was 0.96ñ0.12 g N/kg/d, and with intravenous label was 0.61ñ0.13 g N/kg/d. There was a significant linear relationship between flux measured with oral and intravenous isotope. It is suggested that different components of protein turnover are measured with the different approaches, and that the short method in particular measures rapidly turning over proteins associated with the gastrointestinal tract.(AU)


Assuntos
Humanos , Adulto , Masculino , Glicina/diagnóstico , Proteínas/metabolismo , Amônia/urina , Proteínas na Dieta/administração & dosagem , Glicina/metabolismo , Cinética , Nitrogênio/metabolismo , Isótopos de Nitrogênio , Ureia/urina
11.
Hum Nutr Clin Nutr ; 39(3): 167-79, May 1985.
Artigo em Inglês | MedCarib | ID: med-8755

RESUMO

A cross-sectional study was carried out among 18 Jamaican pregnant women divided in three groups of 6 subjects according to the stage of pregnancy: group B, 12 weeks, group C, 24 weeks and group D, 33 weeks. A group (group A) of 6 non-pregnant women was selected as control. The rate of whole-body protein turnover was measured by continuous oral administration of 15N-glycine and the resting metabolic rate by the open circuit method. All subjects had a normal pregnancy outcome. The composition of the diet on the day of the study was comparable between the four groups (approximately 80 g protein and 9.45 MJ energy) and not significantly different from the composition of the diet during the 2 d prior to the experiment. The rates of protein synthesis and breakdown were higher in groups Band C compared to group A and lower in group D where they reached values slightly higher than in group A. Estimated from urea enrichment, these rates did not vary significantly among the groups, while estimated from ammonia enrichment the difference was significant (P less than 0.05) and there was a negative correlation between the gestational age and the rate of snythesis (r= -0.63) and breakdown (r= -0.69). Nitrogen retention was comparable between the three groups of pregnant women and significantly higher than in the group A. The resting metabolic rate was similar between the groups of pregnant women. These results suggest that the rates of protein turnover observed during gestation reflect more the changes that occur in maternal than those in fetal tissues. The values for protein synthesis and nitrogen retention indicate that the amount of protein deposited during pregnancy is greater than that expected on the basis of body composition analysis. It is also suggested that as pregnancy proceeds whole-body protein turnover represents a smaller part of the resting metabolic rate. (AU)


Assuntos
Humanos , Recém-Nascido , Adulto , Feminino , Gravidez , Proteínas/metabolismo , Metabolismo Basal , Estatura , Peso Corporal , Ingestão de Energia , Estudos Transversais , Idade Gestacional , Jamaica , Nitrogênio/metabolismo , Nitrogênio/urina
12.
Kingston; 1985. x,80 p. tab.
Tese em Inglês | MedCarib | ID: med-13791

RESUMO

Whole body protein turnover and basal metabolic rate were measured in 6 patients with homozygous sickle cell disease, HbSS, and 6 normal controls. A technique using oral prime/intermittent infusion of 15N glycine as tracer, and enrichment in urinary urea and ammonia was used to measure protein turnover. The subjects received a priming dose containing 90æg15Nkg-1 followed, six hours later, by a continuous infusion at the rate of 5æg15Nkg-1 hr-1. Feeds were given intermittently along with the tracer. Plateau enrichments were mostly achieved by 9-12 hours in both ammonia and urea. Protein turnover in the sickle cell patients was 66-81 percent more than in the normals and represented an increase in synthesis and breakdown. A theoretical increase in haemoglobin turnover accounted for 20-26 percent of the increase in turnover. The average basal metabolic rate, as measured by oxygen consumption, was also significantly higher in sickle cell patients, despite subnormal nutritional status in 5 of the 6 patients. It was 7 percent (P<.05) more than in the normals and the difference was even greater when expressed in terms of body weight and muscle mass, being 22 percent, P<0.005 and 20 percent (P<.005) respectively. Protein turnover is an energy demanding process and with no other obvious cause, it seems that the process of protein turnover contributed to most of the increase in energy expenditure. With this assumption, protein turnover accounted for 40-44 percent of the energy expended in the sickle cell subjects compared to 27-32 percent in the normals. If the cost of protein turnover in normals is as much as 27-34 percent, this is further evidence that previous estimates based on the energy required for protein synthesis is significantly underestimated. The significant increase in protein turnover and energy expenditure indicates that there is a higher requirement for energy in HbSS compared to normal that could be relevant to the generalised poor growth, high susceptibility to infection, poor wound healing and the general ill health observed in the patients (AU)


Assuntos
Humanos , Adulto , Masculino , Anemia Falciforme/metabolismo , Hemoglobinopatias/metabolismo , Metabolismo Basal , Nitrogênio/metabolismo , Creatinina/urina , Hemoglobinas/metabolismo , Metabolismo Energético , Jamaica
13.
Hum Nutr Clin Nutr ; 38(5): 339-54, Sept., 1984.
Artigo em Inglês | MedCarib | ID: med-9919

RESUMO

A two-pool model is described for the non-invasive measurement of urea kinetics in man. The isotope, 15N-urea, was given until an isotopic steady state was reached in urine and the time taken achieve this is defined. During an isotopic steady state, a comparison was made of the effect of giving the isotope orally, intravenously and intragastrically; no differences were found between the different routes. Measurements of enrichment were made on excretion products in urine. In six normal adults with a protein intake of 200 mg N/kg/d, the urea production rate was 139 ñ 15 mg N/kg/d, 70 percent of which was excreted in urine. Of the 34 mg N/kg/d produced by hydrolysis of urea in the gastrointestinal tract, 41 percent was resynthesized to urea, and about 48 percent was available for other synthetic processes.(AU)


Assuntos
Humanos , Adulto , Masculino , Feminino , Nitrogênio/metabolismo , Ureia/metabolismo , /metabolismo , Intubação Gastrointestinal , Cinética , Modelos Biológicos , Isótopos de Nitrogênio , Espectrometria de Massas , Ureia/administração & dosagem , Ureia/urina
14.
In. Velazques, Antonio; Bourges, Hector. Genetic factors in nutrition. New York, Academic Press, 1984. p.297-313.
Monografia em Inglês | MedCarib | ID: med-12104
15.
Hum Nutr Clin Nutr ; 37(6): 433-46, Dec. 1983.
Artigo em Inglês | MedCarib | ID: med-9326

RESUMO

Nitrogen balance and whole-body protein turnover were measured in children aged about one year taking diets which provided 1.7 or 0.7 g milk protein/kg/d at three levels of metabolizable energy, 80, 90 and 100 kcal/kg/d. All the children were in positive nitrogen balance at all levels of energy intake on 1.7 g protein/ kg/d. Nitrogen equilibrium was maintained on 0.7 g protein/kg/d when the energy intake exceeded 90 kcal/kg/d, but on 80 kcal/kg/d nitrogen balance was negative. Whole-body protein turnover was measured from the enrichment in urinary ammonia following a continuous infusion of15N-glycine. The variation between individuals on the same diet was significantly greater than the variation within individuals at different levels of energy intake. For the group as a whole protein synthesis on 1.7 g protein/kg/d was 0.74, 0.75 and 0.87 g N/kg/d on 100, 90 and 80 kcal/kg/d respectively;whereas on 0.7 g protein/kg/d it was 0.37, 0.38 and 0.40 g N/kg/d. These results show that over this range of intakes protein synthesis decreased as dietary protein fell, but tended to increase as energy intake fell. (AU)


Assuntos
Humanos , Lactente , Masculino , Ingestão de Energia , Proteínas na Dieta/administração & dosagem , Alimentos Infantis , Nitrogênio/metabolismo , Proteínas/metabolismo , Amônia/urina , Estatura , Peso Corporal , Creatinina/urina , Alimentos Infantis/análise , Metilistidinas/urina , Ureia/urina
16.
Anal Biochem ; 121(2): 349-55, Apr. 1982.
Artigo em Inglês | MedCarib | ID: med-13013

RESUMO

The amide nitrogen from L-glutamine has been isolated from an artificial plasma, in a form suitable for mass spectrometry, by a macromodification of the glutaminase reaction. The prior removal of free ammonia was carried out by alkaline aeration. When this was performed at 0§C for 3 h, spontaneous hydrolysis of glutamine was 1.4 percent. Cross-contamination with nitrogen liberated from the amide group of asparagine can be avoided by preincubation with asparaginase for 2h and removal of the freed ammonia prior to reacting with glutaminase. Hydrolysis of glutamine during this step is 12 percent. Measurements of enrichment can be made on samples yielding more than 1 æmol of glutamine amide-derived ammonia.(AU)


Assuntos
Ratos , 21003 , Amidas/isolamento & purificação , Glutamina , Nitrogênio/isolamento & purificação , Química Encefálica , Glutamina/sangue , Rim/análise , Intestinos/análise , Fígado/análise , Músculos/análise , Espectrometria de Massas
17.
Clin Sci ; 62(3): 299-305, Mar. 1982.
Artigo em Inglês | MedCarib | ID: med-12607

RESUMO

Glutamine [15N]amide was infused at a steady rate of 33.34 micromoles/h into seven male adult volunteers who were in the fed state and normal acid-base status. Plasma glutamine amide N enrichment and urinary ammonia N enrichment rose to a constant value within 3h. The glutamine production rate was 51.8 ñ 7.9 millimoles/h. The total ammonia execretion rate was 0.87 millimoles/h. Of this excreted ammonia 62.6 ñ 9 percent was derived from the amide N atom of glutamine. The excreted glutamine amide N (0.53 millimoles/h) was only 1 percent of the glutamine production. If half the ammonia formed by the kidney is excreted in urine and half liberated into the renal vein in subjects with normal acid-base status [E. E. Owen & R. R. Robinson (1963) Journal of Clinical Investigation, 42, 263-276], then the kidney accounts for only 2 percent of glutamine disposal. Whole body protein turnover, measured from the urinary [15N]ammonia enrichment, was 30.3 ñ 7.7 g of N/day (2.8 g of protein/day/kg). (AU)


Assuntos
Humanos , Adulto , Masculino , Amônia/urina , Glutamina/metabolismo , Glutamina/farmacologia , Intestinos/metabolismo , Rim/metabolismo , Nitrogênio/metabolismo , Proteínas/metabolismo
18.
Kingston; s.n.; 1982. 347 p. tabs.
Tese em Inglês | MedCarib | ID: med-8698

RESUMO

The intermediary metabolism of 6 isotopic amino acids, 15N-aspartic acid, 15N-glutamic acid, 15N-alanine, 15N-glutamine (amide-15N), 15N-glycine and 15N-lysine (O-15N), and 15N-ammonium chloride were investigated. The aim of this study was to establish the precursor-product relationships existing between these amino acids, ammonia and urea in the amino-N pools of the major organs and tissue beds of the normal postprandial rat with the specific objective of following the movement of nitrogen to urea synthesis. It was hoped to ascertain whether glutamic acid played a central role in providing nitrogen for urea synthesis and whether there existed any relationship between 15N distribution patterns of the different isotopes and WBTP rates calculated from hepatic and renal urea-N enrichments. The method employed involved the administration of tracer quantities of the isotopes by the constant infusion technique and measuring the 15N excess of ammonia-N, glutamine amide-N, alanine-N, glutamate-N, aspartate-N and urea-N. It was found that nitrogen from 15N-alanine, 15N-aspartic acid and 15N-glutamic acid was distributed evenly in most of the amino-N pools studied. Nitrogen from the other four isotopes was distributed unevenly, preferentially to ammonia, glutamine amide and urea. 15N-glycine and 15N-lysine were only sparingly metabolised. WBPT rates obtained from urea-N enrichments were not affected by the nitrogen distribution patterns of the isotopes but by the extent to which they metabolised. WBPT rates calculated from ammonia-N enrichments were unduly affected by the extent to which each isotope contributed nitrogen to ammoniagenesis. Glutamic acid does not seem to be the precursor of both nitrogens used for urea synthesis. It supplies only one nitrogen. It is possible that urea is synthesised from an amino-N received via the glutamate to aspartate pathway and an amide-N received via the glutamine to ammonia to carbamyl phosphate pathway. Free ammonia entering the liver is first fixed as glutamine amide before being used for urea synthesis. (AU)


Assuntos
Ratos , 21003 , Nitrogênio/metabolismo , Aminoácidos/metabolismo , Ratos/metabolismo , Radioisótopos de Nitrogênio/diagnóstico , Fígado/metabolismo , Rim/metabolismo , Proteínas Musculares/metabolismo , Sistema Digestório/metabolismo , Nitrogênio da Ureia Sanguínea , Amônia/metabolismo , Ureia/metabolismo
19.
Pediatr Res ; 15(11): 1454-61, Nov. 1981.Aug. 1985.
Artigo em Inglês | MedCarib | ID: med-12382

RESUMO

Nitrogen metabolism was studied in three preterm infants (mean gestation 32 wk) by the method of consecutive metabolic balance. The absorption and retention of nitrogen from breast milk was measured, and protein turnover, synthesis, and breakdown were calculated from isotopic plateau of urinary urea and ammonia using an intermittent oral administration of 15N-glycine. Weight gain and nitrogen retention were compared with the weight gain and nitrogen accumulated for a foetus of equivalent gestational age in utero (AU)


Assuntos
Humanos , Recém-Nascido , Glicina/metabolismo , Recém-Nascido Prematuro , Leite Humano , Nitrogênio/metabolismo , Proteínas/metabolismo , Peso Corporal
20.
Clin Sci;58(6): 517-22, June 1980.
| MedCarib | ID: med-10569

RESUMO

[15N]Glycine was infused into fed, fasted or acidotic humans. In all metabolic states there was considerable transfer of labelled nitrogen to urea and amonia, but alanine and glutamate did not become enriched. The findings show that free exchange of nitrogen between all amino acids does not take place. Glycine, serine, threonine, lysine and histidine cannot be considered part of the a-amino-nitrogen pool as classically conceived, although they form up to one-half of that pool. (AU)


Assuntos
Humanos , Adulto , Masculino , Glicina/metabolismo , Nitrogênio/metabolismo , Acidose/mortalidade , Alanina/metabolismo , Amônia/metabolismo , Desaminação , Jejum , Glutamatos/metabolismo , Ureia/metabolismo
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