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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↗
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↗
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↗
PubMed1979

Minimum nitrogen requirement from glandless cottonseed protein for nitrogen balance in college women.

Seven women, 18 to 23 years of age, were fed cooked cottonseed products for 42 days in order to determine the minimum nitrogen requirements for glandless cottonseen flour after baking. The women consumed from 81 to 213 mg N/kg body weight from cottonseed protein. Nitrogen intake from each experimental period was calculated from the average nitrogen content of the cottonseed products consumed each day of the experiment period. Nitrogen excretion was determined from the measurement of nitrogen in a total collection of urine and feces for each experimental period plus an obligatory loss of 5 mg/kg body weight. Fasting blood samples were taken prior to the study and at the end of each 7-day experimental period thereafter. The minimum requirement for cottonseed protein to maintain a positive nitrogen balance was 106 mg N/kg body weight. For the "reference woman," weighing 58 kg, at least 6.1 g of cottonseed flour nitrogen would be required to maintain nitrogen equilibrium. Plasma amino acid values of threonine, proline, valine, isoleucine, leucine, tyrosine, and lysine decreased significantly from day 0 to day 7 of the study. There were no significant differences in these plasma amino acids thereafter. Cottonseed flour incorporated into baked products maintained nitrogen balance in college women with no change in their nutritional status.

Adolescent↗
PubMed1979

Effect of organic matter supplementation on nitrogen transformations in soils. II. Nitrogen balance and yield.

Under controlled laboratory conditions, the effect of the application of uncomposted plant materials (sawdust and maize stalks) or horns and hooves (narrow C/N ratio) on soil nitrogen and plant growth was investigated. From nitrogen balance calculations it was found that the addition of the wide C/N ratio materials alone either increased soil nitrogen through N2-fixation or lessened nitrogen loss through denitrification. Although such materials resulted in the immobilisation of mineral nitrogen, no nitrogen starvation symptoms were noted on the growing plants. Negative nitrogen balances were usually obtained when soils received mineral nitrogen fertilizers either alone or together with maize stalks or supplemented with the narrow C/N ratio organic material.

Fertilizers↗
PubMed1976

Parenteral nutrition in the septic patient: nitrogen balance, limiting plasma amino acids, and calorie to nitrogen ratios.

A series of eight septic patients was provided varying levels of beef fibrin protein hydrolysate by central vein in the presence of adequate calories for evaluation of nitrogen retention under septic conditions. The mean nitrogen intake to achieve nitrogen equilibrium was 240 mg/kg of body wt per day. This represents a 40% increase over that required to produce nitrogen equilibrium in normal adults. The mean caloric intake of these patients was 43.3 kcal/kg of body wt per day. The calorie to nitrogen ratio based on the above intake was calculated to be 180:1. In order to utilize effectively calorie to nitrogen ratios in the nutritional care of patients, it is suggested that ratios be standardized using daily total coloric expenditures. Correcting the mean measured resting calorie expenditures of these patients for minimal daily activity, a caloric to nitrogen ratio of 138:1 was obtained. The plasma amino acid ratios in these septic patients confirm the finding that valine and phenylalnine are limiting amino acids in a beef fibrin hydrolysate at infusion levels below 240 mg of N/kg of body wt per day. Analysis of the urinary excretion of total nitrogen, urea, and amino acids in two patients suggests that 30 to 50% of the infused peptides of a beef fibrin hydrolysate are lost in the urine in these septic patients.

Abscess↗
PubMedDate not supplied

Intensity of nitrogen fixation in yellow lupine in presence of different doses of mineral nitrogen.

The effect of different doses of mineral nitrogen on the nitrogen-fixing activity of lupine nodules during vegetation was studied. It was shown that 0.5 of the dose of mineral nitrogen had an inhibitory effect only in the initial period of development of the nodules, whereas full and double doses of mineral nitrogen inhibited nitrogen fixation throughout the period of vegetation. Supplements of mineral nitrogen switch the lupine nutrition from the symbiotic to the autotrophic type, which is accompanied by a decrease in the nitrogen-fixing activity in the nodules and by an increase in the nitrate-reducing capacity of the roots and leaves.

Fabaceae↗
PubMed1976

Pathway of nitrogen metabolism after fixation of 13N-labeled nitrogen gas by the cyanobacterium, Anabaena cylindrica.

Methods have been developed for identifying the pathway of assimilation of N2-derived nitrogen. The products of fixation of 13N-labeled nitrogen gas ([13N]N2), and the distribution of 13N within glutamine, were determined after short periods of labeling (approximately 1 to 120 s) and also in pulse-chase experiments. Ammonia, the amide nitrogen of glutamine, and the alpha-amino nitrogen of glutamate, in that order, were the first observed products of fixation of N2 by the cyanobacterium (blue-green alga), Anabaena cylindrica. This sequence of the formation of nitrogenous products was confirmed by the use of inhibitors. The presence of 1 mM methionine sulfoximine permitted continued formation of 13NH3, while virtually preventing 13N-labeling of amino acids. In the presence of 1 mM azaserine, glutamine was labeled, but not other amino acids. Our observations demonstrate unequivocally that N2-derived nitrogen fixed by this organism is metabolized initially by the glutamine synthetase/glutamate synthase pathway.

Cyanobacteria↗
PubMed1979

Effect of ruthenium on nitrogen fixation by some nitrogen fixers.

The effect of ruthenium chloride in the culture media on the nitrogen-fixing ability of the three nitrogen fixers (unidentified species of Azotobacter, designated here as D3, B3, and B), isolated from Allahabad soil, was studied. It was observed that the nitrogen-fixing ability of the organisms is much increased in presence of 25-75 micro M concentration of ruthenium chloride in the culture media, while sugar consumption remains more or less steady. Also, if mg nitrogen fixed/g carbon consumed in two culture media with successive increasing concentrations of ruthenium chloride is compared by calculating the difference in increase of the amount of nitrogen fixed and carbon consumed in these two culture media, it was observed that high amounts of nitrogen are fixed by B3 and B between 25-50 micro M, and between 50-75 micro M concentration of ruthenium chloride by D3.

Azotobacter↗
PubMed1976

Influence of sewage discharge on nitrogen fixation and nitrogen flux from coral reefs in Kaneohe Bay, Hawaii.

Nitrogen fixation was investigated in Kaneohe Bay, Oahu, Hawaii, a subtropical eutrophic estuary, by using the acetylene reduction technique on algal samples. No active, planktonic, N2-fixing blue-green algae or bacteria were observed. However, Calothrix and Nostoc capable of fixing N2 were cultured from navigational buoys and dead coral heads. Nitrogen fixation associated with these structures was greater in the middle sector than in the south and north sectors of the estuary. Experiments demonstrated that the fixation was photosynthetically dependent. Examination of the data showed that there was no significant correlation between rates of nitrogen fixation and concentration of combined nitrogen compounds in the Bay water. Fixation was significantly correlated to the inorganic N/P (atomic) ratio in the south and middle sectors but not in the north sector. The nutrient data indicate there was a flux of combined nitrogen, but not phosphate, from the reef flats.

Acetylene↗
PubMed1978

Nitrogen retention of young men who consumed selection patterns of essential amino acids at a constant nitrogen intake.

Six patterns of essential amino acids were devised to represent different sources or combinations of protein based on a daily intake of 6.0 g of nitrogen from these sources. In each diet, cereals furnished 70% and a specially designed amino acid mixture 30% of the total nitrogen. Nitrogen retention of young men who consumed amino acids equivalent to combinations of rice and soy or egg and potato did not differ from the pattern of egg, and these patterns were superior to a combination of rice and wheat; egg also was superior to corn plus beans and wheat plus milk. Relative amounts and proportions of essential amino acids could be modified without depressing nitrogen retention until one amino acid became limiting or the pattern became imbalanced. Therefore, more than one pattern of amino acids should be recognized as useful for adult human subjects; both minimal and total amounts of essential amino acids need to be considered.

Adult↗
PubMed1979

[Use of the combined Kjeldahl-wet digestion/Berthelot-reaction for determining nitrogen in biological materials. 2. Design and testing of a partially automated apparatus for routine determination of nitrogen].

The authors describe the design and the mode of operation of a partially automated analyzer system, based on the combination of the Kjeldahl wet digestion with the Berthelot reaction, for the determination of nitrogen in biological materials. The results from three years of operation are discussed from the view-points of variability of the materials to be tested, of accuracy and of precision. This analytical technique (with an accuracy of 98% and a precision of 4%) is suited for determining amino and amido nitrogen as well as non-aromatically bound ring nitrogen. The statistical evaluation of the analytical results revealed that the deviation of the measured values is mainly caused by the high-temperature digestion.

Amides↗
PubMed1977

[Studies on the determination of the part of bacterial nitrogen in relation to total nitrogen content in the duodenum of cows].

A method for estimation of content of bacterial nitrogen in duodenal intestine was described. The method of HUTTON et al. (1971) in modificated form for the own research was the best method. In two trials roughage (chopped dried forage) and ground corn were given to cows with duodenal bridge fistula in different order (90 min-intervall). Portion of bacterial nitrogen to total nitrogen was 72.5% (corn leads to roughage) and 64.7% (roughage leads to corn).

Animal Feed↗
PubMed1978

[Nitrogen and amino acid absorption in swine. 3. Endogenous secretion and absorption of nitrogen].

The endogenous nitrogen in the duodenum and the distal segment of the small intestine of 3 fistulated pigs fed a 15-N-labelled feed protein was determined using the isotope dilution technique. Over 24 hours, the endogenous N secretion was found at least 12.5 g at the end of the duodenum. For the upper segment of the small intestine, a statistically secured correlation between endogenous nitrogen and chyme amount was found to exist. It was possible to determine the true and apparent absorption of the nitrogen for both individual segments of and the whole digestive tract.

Amino Acids↗