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At least 19 recordsLinked to original sources
PubMed1977

Protein metabolism in human neonates: nitrogen-balance studies, estimated obligatory losses of nitrogen and whole-body turnover of nitrogen.

1. Aspects of nitrogen metabolism in the human neonate were assessed in one full-term infant and six premature infants by means of nitrogen-balance measurements, estimates of obligatory nitrogen losses and determinations of whole-body nitrogen turnover. 2. Our data indicate that the mean protein requirement for maintenance is 1-1 g of protein day-1 kg-1 and that 3-8 g of protein day-1 kg-1 should be sufficient for adequate growth in healthy premature babies. 3. The mean obligatory urinary, faecal and total nitrogen losses were estimated to be 24, 106, 145 mg day-1 kg-1 respectively. These figures are compared with published values for older infants, and the possible metabolic basis for changes in nitrogen losses during growth and development is discussed. 4. Mean values for whole-body protein synthesis and breakdown were 26-3 +/- 7-0 and 23-8 +/- 7-4 g of protein day-1 kg-1 respectively. Dietary nitrogen intake accounted for 6--18% of the nitrogen flux through the metabolic pool; urea excretion accounted for 2% of the nitrogen flux. 5. The net protein gain, estimated from nitrogen-balanced data, accounted for 9-6% of total daily protein synthesis. 6. These results are discussed in relation to published estimates of whole-body protein synthesis and breakdown at various ages. Their possible significance in the assessment of a "maintenance" requirement for protein and amino acids during the period of rapid growth and development is also considered.

Body Weight↗
PubMed1991

Importance of glucagon for nitrogen loss in diabetes--via an accelerated hepatic conversion of amino nitrogen to urea nitrogen.

In diabetes mellitus amino nitrogen is lost from organs and excreted as urea. Traditionally it has been assumed that the only explanation of this phenomenon was lack of insulin. The blood amino acid concentration in diabetic patients is, however, reduced, which suggests that the hepatic uptake of amino acids is accelerated. Glucagon accelerates the hepatic uptake and conversion of amino nitrogen into urea nitrogen, and hyperglucagonaemia is present in diabetes. This survey describes the significance of hyperglucagonaemia in the abnormal diabetic nitrogen metabolism. Rats with experimental diabetes and hyperglucagonaemia, given the same amount of food as controls, double the urinary excretion of urea-N within 4 days. This increase can be completely normalized by an intensive insulin treatment regimen, which normalises the hyperglucagonaemia as well. Selective hyperglucagonaemia in otherwise optimally insulin treated diabetic rats raises the urinary urea-N excretion by one third, also within 4 days. The kinetics of urea synthesis in experimental diabetes is changed towards an increased maximum rate, but only after 14 days, so this alone cannot explain the increased urea excretion. Constant hyperglucagonaemia increases the spontaneous rate of urea synthesis within 2 days. In uncontrolled diabetes nitrogen is lost from most organs, and most is lost from muscles. Selective hyperglucagonaemia in insulin treated diabetic rats leads to a loss of muscle nitrogen of about one third of that seen in uncontrolled diabetes. It is suggested that he glucagon induced loss of muscle nitrogen is due to an increased flux of amino nitrogen from muscle to liver.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

Nitrogen balance studies in humans: long-term effect of high nitrogen intake on nitrogen accretion.

Six healthy young adult male participants were confined to a metabolic ward for 105 days. Two nutritionally adequate purified diets providing 12 and 36 g of nitrogen per day were randomized in two metabolic periods of approximately 50 days each. The objective of this study was to verify whether or not positive nitrogen balance is a concomitant of increased nitrogen intake under the most rigorously controlled conditions, and if so, whether adaptation could occur if the experiment was conducted for sufficiently long periods of time. The mean nitrogen balance was slightly negative for most participants when fed the 12 g N diet. However, individual variability was so large that statistically all the participants can be considered in balance. In view of this, we agree with other investigators who have suggested that balance should be considered as an area which takes into account variabilities such as intake, output and biological factors. On the 36 g N diet, all the participants exhibited strong positive balances, about 1.6 g/day, which were not as high as reported by other investigators but which persisted for as long as they were fed this diet. This positive balance could not seem to be explained on the basis of methodological errors or to any unmeasured nitrogen losses. There was no significant trend towards adaptation as claimed.

Adaptation, Physiological↗
PubMed1988

[Differences in nitrogen and RNA contents between free bacteria and bacteria fixed to food particles in the rumen contents, in the case of different diets; consequences for estimating the ratio of bacterial nitrogen in duodenal nitrogen].

Differences in nitrogen and RNA contents were found between liquid-associated and solid-adherent bacteria isolated from the reticulo-rumen of ruminants offered various diets. Consequences on the estimation of the bacterial nitrogen flow to the duodenum are discussed.

Animal Feed↗
PubMedDate not supplied

Inaccuracy of nitrogen balance determinations in thermal injury with calculated total urinary nitrogen.

Many burn centers use nitrogen balance studies to estimate the adequacy of nutritional support. Nitrogen loss includes the sum of urinary urea nitrogen, nonurea urinary nitrogen, and losses from skin, wound, and stool. Urinary urea nitrogen is often used to calculate total urinary nitrogen by multiplying the urinary urea nitrogen by a factor of 1.25 to account for nonurea urinary nitrogen. This formula is appropriate when applied to a nonstressed individual who has fasted overnight but is not appropriate for patients who have undergone surgery or experienced trauma. We have undertaken this study to assess the predictability of this formula in patients with thermal injuries. Twenty-seven patients with major thermal injuries had random 24-hour urine collections, which were analyzed for both urinary urea nitrogen and total urinary nitrogen. In these patients with burns we found that urinary urea nitrogen represented approximately 65% of the directly measured total urinary nitrogen rather than 80% as assumed by the formula. This increase in the nonurea nitrogen loss is greater than that found after surgery or trauma. Individual measurements may underestimate losses by 20% to 60%. Directly measured total urinary nitrogen should replace calculated total urinary nitrogen as the index of urine nitrogen losses for nitrogen balance studies in patients with burns.

Burns↗
PubMed1987

The effect of stress level, amino acid formula, and nitrogen dose on nitrogen retention in traumatic and septic stress.

Eighty-seven patients were entered into a randomized, prospective, double-blind, six-center study to evaluate the effect of amino acid loading and a formula that was branched chain enriched (50%) on nitrogen retention in metabolic stress. The patients had varying levels of metabolic stress (0-3) after major surgery, polytrauma, or surgical sepsis. The study was isocaloric and isonitrogenous and lasted for 7 days. The patients received either a standard amino acid formula (SAA) (Travasol) or a 50% branched chain enriched formula that was equimolar, leucine, isoleucine, and valine (MAA) (Travasol + Branchamin concentrate) at a dose of 1.0-2.0 g/kg/day in a fixed ratio with 114 glucose calories per gram of nitrogen administered. The nitrogen retention was proportionate to the nitrogen (and, therefore, caloric) load in both groups. The MAA group, however, had better nitrogen retention, reached nitrogen equilibrium at a lower dose of amino acids, and had less urinary nitrogen excretion per gram of nitrogen administered. Since the groups were isonitrogenous and the calorie to nitrogen ratios were fixed, it appears that nitrogen equilibrium in surgical stress is proportionate to the amino acid load over a range of 0.05-0.4 g/kg/day of nitrogen; and that MAA are more efficient at inducing nitrogen retention and a reduction in urea excretion. These effects on nitrogen retention were more significant at level 2 stress or greater. At these higher stress levels, a dose of 2 +/- 0.2 g/kg/day of MAA seemed most efficient in promoting nitrogen retention.

Adult↗
PubMed1975

Influence of dry matter and nitrogen intakes on fecal nitrogen losses in cattle.

Dietary factors influencing loss of fecal nitrogen in Holstein steers have been examined in data on metabolism from forage diets. Two factors- total nitrogen and dry matter intake, accounted for a large part of the variation in fecal nitrogen. Nitrogen intak expressed as grams per kilogram dry matter intake more accurately accounted for variability in total fecal nitrogen than did nitrogen intake expressed as grams per animal per day. Data were from trials on 68 forages covering a range of nitrogen intakes and of nitrogen concentration in dry matter of forage. Correlations were .93 between total fecal nitrogen and dry matter intake, .90 between total fecal nitrogen and total nitrogen intake, and .95 between total fecal nitrogen and total fecal dry matter. However, at high and low nitrogen intake there was evidence of departure from a linear relationship. The relative usefulness of three regression analyses to estimate metabolic fecal nitrogen is discussed.

Animal Feed↗
PubMed1975

[Effect of the ruminal amino nitrogen level on the nitrogen passage into the isolated rumen of sheep].

Eight trials were performed with two sheep to study the passage of ammonia nitrogen, urea nitrogen, and amino nitrogen into an isolated rumen at different amino nitrogen levels in rumen after a single intraruminal application of enzymatic casein hydrolyzate. After casein hydrolyzate application the level of amino nitrogen in rumen increased; consequently, the passage of ammonia to the isolated rumen rapidly decreased. The passage of nitrogen as urea and amino nitrogen to the isolated rumen is the same, both at a higher and a lower level of amino nitrogen in the rumen. The total quantity of urea and ammonia nitrogen (N-NH3 + N-urea) and amino nitrogen (N-NH3 + N-urea + amino-N) present in the isolated rumen shows a highly significant correlation with ammonia passage. This quantity reaches its maximum before the application of casein hydrolyzate to the rumen. An intensive drop occurs within one and two hours after application. The results of our study testify to the fact that the chemical composition of rumen content plays an important role in the ruminohepatic circulation of nitrogen, particularly when endogenic nitrogen passes into the rumen through rumen wall, and that the passage of nitrogen compounds from blood to the rumen is influenced not only by the concentration ratio between blood and rumen content but also by neurohumoral effects.

Amino Acids↗
PubMed2025

Effects of nitrogen allocation and photosynthetic proteins response in peanut leaves on photosynthesis under conditions of water scarcity and nitrogen deficiency.

Leaf nitrogen allocation and photosynthetic proteins response can affect net photosynthetic rate (Pn), ultimately influencing crop yield under diverse environmental stresses. However, the internal relationship between Pn with leaf nitrogen allocation and photosynthetic proteins response under nitrogen or water scarcity in peanut (Arachis hypogaea L.) remains elusive. Here, comprehensive physiological property and proteomic analyses of peanut were conducted, revealing that both nitrogen and water scarcity remarkably impeded leaf growth and reduced Pn. Nitrogen deficiency significantly reduced the total nitrogen content per unit leaf area (Narea), chlorophyll content, and Pn, whereas drought stress caused a greater decline in photosynthetic nitrogen use efficiency (PNUE). The allocation of leaf nitrogen to photosynthetic components, including the carboxylation system and electron transport system in leaves, was significantly reduced when subjected to individual or combined deficiency. Proteomic analyses exhibited that several key photosynthetic proteins underwent a decrease under both single and combined water and nitrogen deficiency conditions. Thereby, Pn may decline due to the disruption of nitrogen allocation and down-regulated expression of photosynthetic proteins under these stress conditions. Our findings establish a benchmark for future research exploring the roles of leaf nitrogen allocation and photosynthetic proteins in the plant's response to nitrogen or water deficiency.

Nitrogen↗
PubMed1991

Use of nitrogen-15 determinations of purine nitrogen fraction of digesta to define nitrogen metabolism traits in the rumen.

A method for direct purine N isolation and determination was modified from the method of Zinn and Owens for rapid determination of purines. By this method, N derived from purines in digesta was measured and collected for 15N determinations. Measurements of purine N in 33 samples of ruminal contents and duodenal digesta of sheep and goats were compared with purine determinations in the same samples. The results showed that essentially all the N in the purines that could be isolated by the Zinn and Owens procedure also could be detected by N isolation and determination. Determinations of 15N in the NH3 N, NAN, and purine N fractions in a continuous culture in vitro showed significant differences in the 15N enrichment curves between diets based on either roasted or raw soybean meal.

Animals↗
PubMed1990

Effects of glucose on nitrogen balance during high nitrogen intake in malnourished patients.

1. The effects of increasing glucose intake on nitrogen balance, energy expenditure and fuel utilization were measured in 12 malnourished adult patients receiving parenteral nutrition with constant, very high nitrogen intake (500 mg of N/kg), high (105 kJ/kg) or low (30 kJ/kg) glucose intake and constant fat intake (7 kJ/kg). Each patient received each diet for 8-day periods in random order. 2. Energy balance and nitrogen balance were determined daily. Blood samples, taken at admission, during 5% (w/v) dextrose (D-glucose) infusion and at the end of days 7 and 8 of each diet, were analysed for urea, glucose, lactate, triacylglycerols, fatty acids, glycerol, 3-hydroxybutyrate, insulin and glucagon. 3. The effect of increasing glucose intake was to increase nitrogen balance by 0.60 +/- 0.25 (SEM) mg/kJ. At zero energy balance, nitrogen balance was 48 mg day-1 kg-1. This confirms findings of previous studies: that the effects of glucose on nitrogen balance are greater at high than at low nitrogen intakes, and that, in malnourished patients, unlike in normal adults, markedly positive nitrogen balance can be achieved at zero or negative energy balances. 4. Changes in nitrogen balance were due almost entirely to changes in urea excretion. 5. The high nitrogen intake markedly increased plasma insulin and glucagon concentrations and reduced glycerol, fatty acid and 3-hydroxybutyrate concentrations, independent of any glucose effect. Glucagon concentrations were significantly decreased by added glucose intake, an effect not previously seen at low nitrogen intakes. At this high nitrogen intake, the effects of added glucose appear to be mediated by both insulin and glucagon.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxybutyric Acid↗
PubMed1975

Sweat nitrogen losses by and nitrogen balance of preadolescent girls consuming three levels of dietary protein.

A nitrogen balance study was undertaken to determine the effects of three levels of nitrogen intake on the loss of nitrogen through sweat and to assess the impact of sweat nitrogen on the protein needs of preadolescent girls. Values were determined through the collection of 24-hour, total body sweat samples from 15 healthy girls with a mean age of 8 years, 7 months. Mean height and weight of the subjects were 132 cm and 28.9 kg, respectively. Mean sweat nitrogen losses, collected under uncontrolled environmental conditions, were 201 mg, 263 mg and 319 mg/day on 34 g, 57 g and 88 g of protein intake. The environmental conditions throughout the study remained fairly constant. Mean nitrogen balances per day were 0.04 g, 0.55 g and 1.42 g on the respective levels of nitrogen intake, with the inclusion of sweat nitrogen loss, however, a negative nitrogen balance per day was found in 8 and 2 subjects on 34 g and 57 g protein intake. After considering nitrogen retention of 0.3 g which has been recommended by NRC for the minimum nitrogen allowance for growth of preadolescent children, protein intakes higher than that recommended by the NRC-RDA for preadolescent girls may be required for support of normal growth.

Body Surface Area↗
PubMed1992

Effects of corticosterone administration on nitrogen excretion and nitrogen balance in adrenalectomized rats.

Adrenalectomized rats were implanted with pellets containing corticosterone in proportions varying from 0% to 100%, plus cholesterol. Stable concentrations of plasma corticosterone resulted, varying from subnormal (A) to physiologic (B) to supraphysiologic (C). When food was ingested ad libitum, weight gain was maximal in B at plasma corticosterone concentrations of 0.14-0.20 mumol/L; weight loss occurred in C, despite higher food intake. Even when rats had constant limited food intake, weight gain and positive nitrogen balance were significantly reduced in A compared with B because fecal nitrogen rose significantly and the retention of absorbed nitrogen for growth decreased. In C, weight decreased despite constant intake, and nitrogen balance became negative because urinary nitrogen increased markedly. We conclude that glucocorticoid insufficiency reduces nitrogen balance by impairing intestinal absorption of dietary protein and the utilization of absorbed nitrogen, whereas glucocorticoid excess reduces nitrogen balance by augmenting urinary nitrogen despite constant nitrogen intake.

Adrenalectomy↗
PubMed1986

Effects of diet nitrogen and forage nitrogen insolubility on performance of cows in early lactation.

Thirty-six Holsteins were allotted at parturition to six treatments to measure effects of diet nitrogen and increased insolubility of silage nitrogen on performance and ruminal, plasma, and milk constituents during the first 100 d of lactation. Diets contained 40% concentrate and 60% silage in dry matter. The six silage treatments were untreated corn silage (low nitrogen); untreated corn silage and untreated alfalfa silage (1:1); untreated corn silage and formaldehyde and formic acid-treated alfalfa silage (1:1); ammonia-treated corn silage (low nitrogen); treated corn silage and untreated alfalfa silage (1:1); or treated corn silage and treated alfalfa silage (1:1). Diets containing ammonia-treated corn silage had higher hot water-insoluble nitrogen and diets containing formaldehyde and formic acid-treated alfalfa had higher autoclaved rumen fluid-insoluble and hot water-insoluble nitrogen that their respective untreated silage diets. Dry matter intake, daily yields of milk and its constituents, ruminal NH3 nitrogen, and plasma urea nitrogen were lower for cows consuming low nitrogen diets containing only corn silage compared with cows consuming high nitrogen diets containing alfalfa. Dry matter intake and milk protein yields were greater for cows consuming treated alfalfa compared with untreated alfalfa in the diet. Daily 4% fat-corrected milk yields tended to be higher for diets containing treated alfalfa than untreated alfalfa. Cows fed diets containing NH3-treated corn silage had similar milk, fat, and protein yields compared with diets containing untreated corn silage and urea in the concentrate.

Animal Feed↗
PubMed1985

Effect of season and exercise on dermal nitrogen losses and their relation to urinary nitrogen excretion.

The present study was designed to estimate dermal nitrogen losses in summer and winter under the conditions of minimal daily activities, on a diet of standard Japanese protein intake level and to determine whether the increased dermal nitrogen losses induced by hot climate or exercise were compensated for by the decrease in urinary nitrogen excretion. Six healthy male university students served as the subjects. The daily dermal nitrogen losses (mean +/- SD) were 0.22 +/- 0.07 g or 3.10 +/- 0.58 mg/kg in winter and 0.44 +/- 0.19 g or 6.35 +/- 2.46 mg/kg in summer, showing significantly higher dermal nitrogen losses in summer than in winter. On the contrary, urinary nitrogen excretion tended to be larger in winter than in summer. Thus, renal compensation seemed to exist for the seasonal changes in dermal nitrogen losses. In the summer experiment, the subjects took light exercise besides the minimal daily activities for a 2-day exercise period. The pooled mean of daily dermal nitrogen losses during the exercise period was significantly larger than that during the sedentary period, while the urinary nitrogen excretion was almost the same in the two periods. No compensatory reduction in the urinary nitrogen excretion during the exercise period was observed under the conditions of the present study.

Adult↗