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PubMedDate not supplied

Estimation of nitrogen excretion based on abbreviated urinary collections in patients on continuous parenteral nutrition.

The physiologic response to stress can create a net loss of nitrogen, which is indicative of a catabolic state. Nitrogen balance has been demonstrated to be a useful clinical indicator of a patient's catabolic state and the effectiveness of parenteral nutrition, but requires an estimate of total urinary nitrogen excretion. The standard method for determining total urinary nitrogen excretion is 24-hour urinary urea nitrogen excretion. Unfortunately, the 24-hour urine collection is inconvenient, cumbersome, sometimes inaccurate, and induces a lag in response time to changes in therapy. Although shorter collection times have been proposed, the validity of shorter-timed determinations remains open to question. To evaluate the estimation of 24-hour urine urea excretion from shorter-timed determinations, the urinary urea nitrogen excretion of 4-, 8-, and 12-hour durations was regressed against the 24-hour collection in 56 critically ill adult patients. The 12-hour determination provided satisfactory estimates of the 24-hour nitrogen excretion, but the 4-hour and 8-hour determinations did not. Thus, two times the 12-hour urine urea nitrogen determination can be substituted for the 24-hour determination in calculating nitrogen balance. A 12-hour determination can provide a more rapid turnaround of biochemical analysis, allow more timely nutritional intervention, decrease nursing time, and reduce the frequency of inaccurate or lost specimens.

Humans↗
PubMedDate not supplied

Evaluation of serum visceral protein levels as indicators of nitrogen balance in thermally injured patients.

The use of serum visceral protein concentrations as predictors of nitrogen balance was assessed during the first 4 weeks following thermal injury. The correlation between nitrogen balance and serum albumin was not significant. Statistically significant correlations were found between nitrogen balance and serum prealbumin, retinol-binding protein, and transferrin. However, even the best correlation (retinol-binding protein, r = 0.388) was too weak to permit prediction of nitrogen balance on the basis of the visceral protein concentration. The correlation between change in direction of nitrogen balance and change in direction of protein concentration over time showed all four visceral proteins to be poor predictors of change in nitrogen balance. The efficiency was less than 50% for each visceral protein. Stepwise multiple regression analysis performed to determine which indices were most closely correlated with nitrogen balance showed that a calculation using readily available information (nitrogen intake, postburn day, percent total body surface burned, and age) provided better prediction of nitrogen balance (r = 0.765) than any of the visceral protein concentrations. In view of these findings, measurement of serum visceral protein concentrations to monitor adequacy of nutritional support seems an unwarranted expense in patients with thermal injury.

Blood Proteins↗
PubMedDate not supplied

Anabolic effects of insulin and amino acids in promoting nitrogen accretion in postoperative patients.

The present study evaluates the effect of insulin and amino acids on nitrogen balance in the immediate postoperative period in moderately stressed patients who have undergone major abdominal surgical operations. Patients were randomly assigned into two large groups (n = 16 each) and four subgroups (n = 8 each). Groups ICON and IINS received an infusion of total parenteral nutrition solution containing 0.25 g of nitrogen per kilogram per day with a calorie:nitrogen (C:N) ratio of 150:1. Groups IICON and IIINS received twice the load of nitrogen with a C:N ratio of 75:1. Groups IINS AND IIINS received an additional continuous infusion of insulin at a rate of 1.0 mU/kg per minute for 7 days. During the total parenteral nutrition period, the patients were kept NPO, and 24-hour urine output was collected for estimation of total nitrogen excretion and nitrogen balance. Net nitrogen excretion (grams per kilogram per day) averaged 0.143 +/- 0.06 in IINS and 0.23 +/- 0.08 in ICON (p < .05) and 0.178 +/- 0.6 in IIINS and 0.25 +/- 0.10 in IICON (p < .05). Nitrogen balance (grams per day) was positive in the four groups: +0.65 +/- 3.8 in IINS and +6.74 +/- 2.94 in ICON (p < .05), and +14.4 +/- 2.61 in IIINS and +11.63 +/- 6.44 in IICON (p = not significant). The average nitrogen incorporation (percent per day) was: 41.3 +/- 6.2 in IINS and 14.6 +/- 20.1 in ICON (p < .05), and 58.3 +/- 4.5 in IIINS and 38.7 +/- 26.2 in IICON (p = not significant).(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗
PubMed1981

Nitrogen metabolism in preterm infants fed human donor breast milk: the possible essentiality of glycine.

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. The average composition of the milk was 289 +/- 19 KJ dl-1 and 1.44 +/- 24 g protein dl-1. The intake of energy was 572 +/- 61 KJ kg-1 day -1 and of nitrogen 447 +/- 99 mg kg-1 day-1. Stool output of nitrogen was 100 +/- 32 mg kg-1 day-1 giving an absorption of 348 +/- 78 mg kg-1 day-1, as urinary excretion was 91 +/- 17 mg kg-1 day-1 retained nitrogen was 256 +/- 71 mg kg-1 day-1, or 56% of intake. The specific weight gain was 15.6 +/- 2.6 g kg-1 day-1 and 53% of this comprised lean tissue (range 34 to 89%). In all but one study the postnatal retention of nitrogen fell far short of calculated in utero accumulation. The results of protein turnover were surprising. In six of the eight studies urinary urea failed to become enriched at all. Protein turnover calculated from the ammonia plateau was 1.94 +/- 0.54 g nitrogen kg-1 day-1, synthesis 10.9 +/- 3.4 g protein kg-1 day-1 and breakdown 9.3 +/- 3.4 g protein kg-1 day-1. It is concluded that the amino acid composition of breast milk may be inappropriate for supporting rates of lean tissue deposition equivalent to in utero accumulation.

Body Weight↗
PubMed1984

Calculation of lung volume in newborn infants by means of a computer-assisted nitrogen washout method.

A clinically adapted method for the calculation of the functional residual capacity in newborn infants has been developed. The method is based on a multiple breath nitrogen washout test, during which the ventilatory air flow and the nitrogen concentration signals are sampled by a minicomputer, which also performs the calculations. The ventilatory air flow is measured by a pneumotachometer connected to a face-out volume displacement body plethysmograph, and the nitrogen concentration by a nitrogen analyzer. The functional residual capacity volume is calculated from the sampled signals by adding the expired nitrogen volumes during each expiration, and finally dividing this sum by the initial alveolar nitrogen concentration. Before the calculations, the sampled signals are adjusted regarding nitrogen analyzer delay and plethysmograph characteristics. The method presented is designed to minimize the test equipment influence on the baby's respiration and also to inhibit the necessity of pneumotachometer compensations normally connected with washout methods. Furthermore, the calculated breath-by-breath values of end-expiratory nitrogen concentration, nitrogen volume, inspired and expired tidal volume, are stored on disk for further analysis and resimulation of the test. The method has been tested on a mechanical lung model and on washouts from healthy newborn infants. The model tests indicate that the accuracy and the reproducibility of the method are good, and the results from the infants are in good agreement with previously obtained results.

Computers↗
PubMed2006

15N in symbiotic fungi and plants estimates nitrogen and carbon flux rates in Arctic tundra.

When soil nitrogen is in short supply, most terrestrial plants form symbioses with fungi (mycorrhizae): hyphae take up soil nitrogen, transport it into plant roots, and receive plant sugars in return. In ecosystems, the transfers within the pathway fractionate nitrogen isotopes so that the natural abundance of 15N in fungi differs from that in their host plants by as much as 12% per hundred. Here we present a new method to quantify carbon and nitrogen fluxes in the symbiosis based on the fractionation against 15N during transfer of nitrogen from fungi to plant roots. We tested this method, which is based on the mass balance of 15N, with data from arctic Alaska where the nitrogen cycle is well studied. Mycorrhizal fungi provided 61-86% of the nitrogen in plants; plants provided 8-17% of their photosynthetic carbon to the fungi for growth and respiration. This method of analysis avoids the disturbance of the soil-microbe-root relationship caused by collecting samples, mixing the soil, or changing substrate concentrations. This analytical technique also can be applied to other nitrogen-limited ecosystems, such as many temperate and boreal forests, to quantify the importance for terrestrial carbon and nitrogen cycling of nutrient transfers mediated by mycorrhizae at the plant-soil interface.

Arctic Regions↗
PubMedDate not supplied

Nitrogen contamination in the Yellow River basin of China.

Nitrogen contamination is one of the most serious problems in the Yellow River of China. This study was conducted to analyze monitoring data on nitrogen contamination for the Yellow River basin in the years 1980, 1990, 1997, and 1999. Several significant results have arisen from the study. First, in conjunction with an increase in economic indexes from the Yellow River's upper basin to its lower basin, the nitrogen concentration in the tributaries also showed an increasing trend from the upper to the lower basin, which, in turn, led to an increase in the nitrogen concentration of the mainstream from the upper to the lower reaches. Second, nitrogen in the river water in the mainstream and the tributaries of the Yellow River was attributed mainly to point sources. In spite of the fact that the ratio of point to nonpoint sources decreased from 2.7 in 1990 to 1.8 in 1997 for total inorganic nitrogen in river water at the Tongguan Station in the lower basin, point sources increased more than nonpoint sources. Third, the ammonium nitrogen and total inorganic nitrogen content of the river water increased significantly in the mainstream and the tributaries during the 1980-1999 period, a change caused by an increase in wastewater discharge and nitrogenous fertilizer application in the Yellow River catchment.

Ammonia↗
PubMed1980

Nitrogen absorption following small-intestinal resection.

A nitrogen balance study was performed in 40 patients with various small-bowel resections. Twenty-two patients had part of or the whole colon in function; 18 had an ileostomy. The patients had body weights that were about 95% of their ideal body weight (range, 133% to 71%). Net nitrogen absorption was significantly lower in patients with extensive small-bowel resection (greater than or equal to 150 cm) (median, 8.0 g/day approximately 64% of the dietary nitrogen intake) compared with patients with small-bowel resection less than 150 cm (median, 9.6/day approximately 82% of the dietary nitrogen intake). No difference in nitrogen balance was observed between the two groups. The median nitrogen balance was not significantly different from zero. No difference in nitrogen absorption, nitrogen balance, or body weight could be demonstrated between patients with part of or the whole colon in function and patients with an ileostomy. We conclude that patients with extensive small-bowel resection may have a significant nitrogen absorption, even in the presence of an ileostomy.

Adolescent↗
PubMed2001

Nitrogen metabolism and bone metabolism markers in healthy adults during 16 weeks of bed rest.

BACKGROUND: The associations between nitrogen metabolism and bone turnover during bed rest are still not completely understood. METHODS: We measured nitrogen balance (nitrogen intake minus urinary nitrogen excretion) and biochemical metabolic markers of calcium and bone turnover in six males before head-down tilt bed rest (baseline), during 2, 10, and 14 weeks of immobilization, and after reambulation. RESULTS: The changes in nitrogen balance were highest between baseline and week 2 (net change, -5.05 +/- 1.30 g/day; 3.6 +/- 0.6 g/day at baseline vs -1.45 +/- 1.3 g/day at week 2; P<0.05). In parallel, serum intact osteocalcin (a marker of bone formation) was already reduced and renal calcium and phosphorus excretions were increased at week 2 (P <0.05). Fasting serum calcium and phosphorus values and renal excretion of N-telopeptide (a bone resorption marker) were enhanced at weeks 10 and 14 (P <0.05-0.001), whereas serum concentrations of parathyroid hormone, calcitriol, and type I collagen propeptide (a marker of bone collagen formation) were decreased at week 14 (P <0.05-0.01). Significant associations were present between changes of serum intact osteocalcin and 24-h calcium excretion (P <0.001), nitrogen balance and 24-h phosphorus excretion (P <0.001), nitrogen balance and renal N-telopeptide excretion (P <0.05), and between serum osteocalcin and nitrogen balance (P <0.025). CONCLUSIONS: Bone formation decreases rapidly during immobilization in parallel with a higher renal excretion of intestinally absorbed calcium. These changes appear in association with the onset of a negative nitrogen balance, but decreased bone collagen synthesis and enhanced collagen breakdown occur after a time lag of several weeks.

Adult↗
PubMed2003

Comparison of cryopreserved sperm in vaporous and liquid nitrogen.

OBJECTIVE: To evaluate the feasibility of using the vaporous phase of liquid nitrogen as a storage medium for human semen samples. STUDY DESIGN: Human semen samples were used in a 2-armed study. In the first arm, semen samples were rapidly frozen and randomly assigned to storage in either liquid nitrogen (-196 degrees C) or vapor-phase nitrogen (-189 degrees C). In the second arm, sperm specimens were frozen in a controlled, stepwise process and randomly assigned to storage in either the vaporous or liquid phase of liquid nitrogen. The samples were subsequently thawed and analyzed for sperm viability. RESULTS: The rapid freezing technique demonstrated no differences in the examined viability parameters between semen specimens stored in either liquid or vaporous nitrogen. Similarly, semen samples prepared by the slower, controlled freezing process also showed no differences in viability parameters after storage in either the liquid or vaporous phase of liquid nitrogen. The rapid freezing technique was equal to the slow, controlled freezing method in terms of preserving the integrity of the sperm when the specimens were subsequently stored in either liquid or vaporous nitrogen. CONCLUSION: Cryopreservation of human semen in the vapor phase of nitrogen is a viable alternative to storage in liquid-phase nitrogen.

Cryopreservation↗
PubMed2004

Human acceleration of the nitrogen cycle: drivers, consequences, and steps toward solutions.

Human activity has greatly altered the nitrogen cycle on Earth over the past few decades, with major effects on both human health and the ecological functioning of natural ecosystems, particularly coastal marine systems where nitrogen is now the largest pollution problem. Agriculture is the largest driver of this change, with pollution from fossil-fuel combustion being a smaller but still significant driver globally. Much of the nitrogen pollution from agriculture derives from animal-production systems, both as a direct result of nitrogen leakage to the atmosphere and waters from these systems, and from the demand for increased crop production that these animal-production systems demand. Wastewater from urban centers is also a significant component of the nitrogen problem, contributing 12% of the nitrogen pollution in rivers in the US, 25% in Europe, and 33% in China. Wastewater sources dominate the inputs of nitrogen to some coastal ecosystems, but globally and in most regions the non-point sources are larger. Many technical solutions to reducing nitrogen pollution exist, so to some extent the current problem reflects policy and political failures. Nonetheless, further technical solutions can and should be developed. These should recognize the significantly greater mobility of nitrogen than phosphorus in the environment.

Agriculture↗
PubMed2004

Nitrogen removal characteristics analyzed with gas and microbial community in thermophilic aerobic digestion for piggery waste treatment.

In order to characterize the nitrogen conversion characteristics in a thermophilic aerobic digestion (TAD) system, a laboratory study has been conducted with the analysis of effluent gas and microbial community in the sludge samples. The lab TAD system was operated with HRT of 3 days and 60 degrees C. Based on the nitrogen mass balance, it has been found that about 2/3 of the daily load of nitrogen was converted to the gaseous form of nitrogen whereas cellular transformation and unmetabolized nitrogen accounted for about 1/3. Among the gaseous nitrogen transformation, significant amount of influent nitrogen had been converted to N2 gas (29% of influent N) and N2O (9% of influent N). Ammonia conversion was only 28% of influent N. The detection of N2O gas is a clear indication of the biological nitrogen reduction process in the thermophilic aerobic digester. No conclusive evidence for the existence of aerobic deammonification has been found. The microbial community analysis showed that thermophilic bacteria such as Bacillus thermocloacae, Bacillus sp. and Clostridial groups dominated in this TAD reactor. The diverse microbial community in TAD sludge may play an important role in removing both strong organics and nitrogen from piggery waste.

Agriculture↗
PubMed2004

[Accumulation pattern of dry matter, nitrogen, phosphorus, potassium and silicon in rice genotypes and their relationships].

The accumulation of dry matter, nitrogen, phosphorus, potassium and silicon in 30 rice genotypes and their relationships under field condition were studied. The results showed that dry matter accumulated at ripening stage linearly increased with increase of nitrogen, phosphorus, potassium and silicon accumulation with highly significant correlation coefficients at both early and late season. At the same time balance of nitrogen, phosphorus, potassium and silicon accumulation was beneficial for dry matter accumulation, which linearly increased with increase of nutrient balance index and decreased with increase of nutrient deviation index. The nitrogen, phosphorus, potassium and silicon were accumulated at the rate of 3.76:1:4.55:7.10 at early season and 2.88:1:4.54:8.09 at late season. During growth period, dry matter accumulation was the highest at middle stage, then late stage and early stage. But nitrogen accumulation was the highest at early stage, then middle stage and late stage. The dry matter accumulated before heading was mainly distributed in stem and leaf sheath, with the highest ratio of stem and leaf sheath to total dry matter at heading stage. In contrast, nitrogen accumulated before heading was mainly distributed in leaf blade, and the ratio of nitrogen in leaf blade to total nitrogen was higher than that of dry matter at either growth stages. Dry matter, nitrogen, phosphorus accumulated at ripening stage were mainly distributed in panicle with rates of 58.01%, 66.42% and 70.06%, respectively. But potassium accumulated at ripening stage was mainly distributed in stem and leaf sheath with the rate of 62.08%. Silicon was largely distributed in stem and leaf sheath at early season with the rate of 43.11%, but distributed largely in panicle at late season with the rate of 46.99%.

Genotype↗
PubMed2004

The performance of a nitrogen-fixing SBR.

A laboratory study has successfully demonstrated that a nitrogen deficient thermomechanical pulping wastewater can be effectively treated in a sequencing batch reactor (SBR) operated under conditions of biological nitrogen fixation (the N-ViroTech process). In comparison to continuous stirred tank reactor activated sludge (CSTR-AS) configurations operated under either nitrogen fixing or nitrogen supplemented conditions, slightly lower removals of dissolved organic material were observed in the SBR. However, this was largely offset by significantly better suspended solids removal in the SBR, which contributes to the overall COD discharge. The settleability and dewaterability of sludge produced by the SBR was significantly better than that obtained from the nitrogen fixing CSTR-AS reactors, and comparable to that of a nitrogen supplemented system. Consistently low total and dissolved nitrogen discharges from the N-ViroTech systems demonstrated the advantage of this system over ones requiring nitrogen supplementation. The feast-famine regime of an SBR-type configuration has significant potential for the application of this technology in the treatment of nitrogen deficient waste streams, particularly those in which conventional single-stage systems may be susceptible to sludge bulking problems.

Bioreactors↗
PubMed2005

[Relationships between net primary production and nitrogen cycling in Chinese forest ecosystems].

In order to better understand the relationships between net primary production (NPP) of forest ecosystem and nitrogen cycling, we studied and analyzed the relationships between NPP, litter nitrogen, plant nitrogen retention, and soil net nitrogen mineralization rate in Chinese forest ecosystems. The results indicated that NPP was linearly and positively related to litter nitrogen, plant nitrogen retention and soil net nitrogen mineralization rate, with the most correlation with soil net nitrogen mineralization rate (R2 = 0.74, n = 37), and the next with plant nitrogen retention (R2 = 0.60, n = 37).

Biomass↗
PubMed2005

[Distribution characteristics of nitrogen and its source in core sediments from Pearl River Estuary].

Based on the measurement of the concentration of nitrogen in four core sediments from Pear River Estuary, the forms and the depth-dependent changes characteristics of nitrogen were studied, and the possible sources of nitrogen in the sediments were discussed. The results indicate that the content of total nitrogen ranged from 850.62mg/kg to 2 340.85mg/kg, with mean content of 1 502.73mg/kg. There is a general tendency for an upward increase in core sediments, which is more evident in the middle than in two ends. Organic nitrogen had a range of content from 655.42mg/kg to 2 029.86mg/kg, with mean content of 1 187.86mg/kg. And the content of organic nitrogen decreases gradually with the increase of depth or lower in the middle than in two ends. The content of NH4-N was relatively high, ranging from 47.59mg/kg to 739.61mg/kg, with mean content of 271.69mg/kg, and increases obviously with the increase of depth. The TOC/TN ratios were most between 5 and 17, which show organic matter is the mixture of aquatic and terrestrial sources. The total nitrogen has distinct synchronization phenomenon with the organic nitrogen in sedimentation course,but has little relativity with the NH4-N. There is large difference of synchronization phenomenon between total nitrogen and NH4-N at different sites.

China↗
PubMed2005

[Effects of different nitrogenous compounds on growth and nodulation of Abrus cantoniensis].

OBJECTIVE: The research aimed at the effects of different nitrogenous compounds on growth and nodulation of Abrus cantoniensis. METHOD: After the seedlings of the herb were inoculated with rhizobia in potted culture, they were supplied with nutrition solutions which contained the three nitrogenous compounds, KNO3, NH4NO3, (NH4)2SO4 of different nitrogen concentration. The growth and nodulation of seedlings was determined after 70 days. RESULT: Different nitrogenous compounds were able to enhance the vegetable growth of seedlings variously. The effect of (NH4)2SO4 and NH4NO3 on growth was better than that of KNO3. Seedlings nodulation was obviously inhibited by these nitrogenous compounds. Their inhibitory effects ranked NH4NO3 > (NH4)2SO4 > KNO3. The treatments of KNO3 and the lower concentration treatments of NH4NO3 and (NH4)2 SO4 didn't inhibit the nodulation of seedlings, but the higher concentration treatment of NH4NO3 and (NH4)2SO4 severely inhibited nodulation or even made a no formation of nodule. CONCLUSION: The results showed that ammonium nitrogen the higher inhibitory ability to the nodulation of seedlings of A. cantoniensis than nitrate nitrogen. Therefore, the application of ammonium nitrogen fertilizer should be controlled in culture of the herb, which is in favor of increasing the function of biological nitrogen fixation and the quality of the medicinal materials of A. cantoniensis.

Abrus↗
PubMedDate not supplied

The effect of endurance training on the rate of nitrogen elimination in women.

INTRODUCTION: The rate of nitrogen elimination may be an important factor in evaluating the risk of DCS following dives. The present study determined the reproducibility of a method for evaluating nitrogen elimination (series I), and the effect of chronic training on the nitrogen elimination in healthy young women (series II). METHODS: Nitrogen elimination was determined with subjects wearing an AGA full-face mask breathing pure oxygen. To evaluate the reproducibility of the method for nitrogen elimination, three tests were performed in six subjects in series I. Nitrogen elimination in series II was measured before and after the training period. The training protocol (series II) consisted of interval training, three times per week for eight weeks. Four repeated intervals alternated between four minutes at 90-95% of maximum heart rate and three minutes at 50-60%. RESULTS: There was no significant difference between the three repeated tests. Interval training for eight weeks increased maximum oxygen uptake by 22.1%. Endurance training did not influence the total nitrogen elimination at rest. CONCLUSION: The method for evaluating nitrogen elimination at rest was found to be reproducible. Improved aerobic capacity does not increase the rate of nitrogen elimination at rest.

Adult↗