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PubMed1997

Decreased nitrogen rates and irrigation effect on celery yield and internal quality.

The effect of decreased nitrogen rates (90, 60 and 30 kg N/ha) with and without irrigation on celery yield quantity and internal quality were studied in field experiments in 1993 and 1994. The decreased nitrogen rates reduced yields in both years. In the dry and warm conditions of 1994 nitrogen x irrigation interaction was clearly observed; irrigation increased yield more at higher nitrogen rates than at lower nitrogen rates. In the rainy conditions of 1993 irrigation did not effect the yield level. On the other hand, in both years, decreased nitrogen rates increased dry matter, vitamin C and dietary fiber contents, and nitrogen had a minor effect on total sugar content. In 1994 alpha- and beta carotene and thiamin were also analyzed but nitrogen had no effect on them. Irrigation increased dry matter and total sugar contents at the two lowest nitrogen rates in 1994, but decreased vitamin C contents in both years. There was also slight evidence that irrigation might decrease alpha- and beta-carotene and thiamin contents.

Agriculture↗
PubMed2002

Nitrogen loss from unpolluted South American forests mainly via dissolved organic compounds.

Conceptual and numerical models of nitrogen cycling in temperate forests assume that nitrogen is lost from these ecosystems predominantly by way of inorganic forms, such as nitrate and ammonium ions. Of these, nitrate is thought to be particularly mobile, being responsible for nitrogen loss to deep soil and stream waters. But human activities-such as fossil fuel combustion, fertilizer production and land-use change-have substantially altered the nitrogen cycle over large regions, making it difficult to separate natural aspects of nitrogen cycling from those induced by human perturbations. Here we report stream chemistry data from 100 unpolluted primary forests in temperate South America. Although the sites exhibit a broad range of environmental factors that influence ecosystem nutrient cycles (such as climate, parent material, time of ecosystem development, topography and biotic diversity), we observed a remarkably consistent pattern of nitrogen loss across all forests. In contrast to findings from forests in polluted regions, streamwater nitrate concentrations are exceedingly low, such that nitrate to ammonium ratios were less than unity, and dissolved organic nitrogen is responsible for the majority of nitrogen losses from these forests. We therefore suggest that organic nitrogen losses should be considered in models of forest nutrient cycling, which could help to explain observations of nutrient limitation in temperate forest ecosystems.

Ecosystem↗
PubMed1978

Nitrogen balance during intermittent dialysis therapy of uremia.

Daily measurements of nitrogen balance were made at two levels of protein intake in five patients undergoing chronic intermittent dialysis therapy. During ingestion of high (1.4 g/kg of body wt) protein intake, nitrogen balance was positive on nondialysis days and negative on dialysis days, so that cumulative balance for the week of study was not different from zero. During ingestion of low (0.5 g/kg) protein intake, nitrogen balance was approximately zero on nondialysis days but was again negative on dialysis days, so that cumulative balance for this period was negative. The negative nitrogen balance observed on dialysis days was associated with a higher rate of urea nitrogen generation (Gu, g/24 hr, determined by a kinetic model of urea nitrogen in dialysis patients) that was most evident in the hours immediately following dialysis. Net protein catabolic rate (PCR, g/24 hr), derived from total nitrogen mass balance equations, correlated very closely with Gu:Gu = 0.154 PCR - 1.7, r = 0.96. This relationship agreed well with previous observations made in nondialyzed uremic patients under more steady-state conditions. These studies demonstrate that nitrogen balance is negative on dialysis days regardless of protein intake, and that Gu is higher on dialysis days. The negative nitrogen balance could result from amino acid loss in dialysate and from increased protein catabolism stimulated by loss of glucose into dialysate.

Adult↗
PubMed1981

Total body nitrogen and its relation to body potassium and fat-free mass in healthy subjects.

1. The amount of lean tissue in the body can be assessed by measuring total body nitrogen, total body potassium or fat-free mass. To compare these techniques we have measured total body nitrogen, total body potassium and fat-free mass in 91 healthy subjects (62 males, 29 females). 2. Total body nitrogen in the women and civilian men agreed closely with the few values reported previously and was closely related to total body potassium and fat-free mass. 3. The simplest estimate of total body nitrogen in a subject whose body content has not been measured is the mean value for healthy people of the same sex. The standard deviation of individual values about this mean is 253 g. The precision of the estimate can be improved considerably by predicting body nitrogen from fat-free mass (156 g) and somewhat more by predicting it from body potassium (115 g). The error of measuring total body nitrogen directly is approximately 76 g. 4. When an individual's total body potassium is measured in a search for potassium depletion, the observed value must be compared with the value expected if the subject were healthy. The standard deviation of the healthy values about the group means is 408 mmol. The precision of the estimate can be improved by predicting total body potassium from fat-free mass (SD 237 mmol), and rather more by predicting it from total body nitrogen (SD 186 mmol). If gross body composition is normal, measurement of total body nitrogen has little advantage over measurement of fat-free mass by the anthropometric technique. 5. These results suggest that the simpler measure of fat-free mass from body weight and skinfold thickness has a major role in the assessment of total body nitrogen, and thus lean body tissue, in the individual.

Adult↗
PubMed2004

Actin cytoskeleton is required for nuclear accumulation of Gln3 in response to nitrogen limitation but not rapamycin treatment in Saccharomyces cerevisiae.

Saccharomyces cerevisiae selectively utilizes good nitrogen sources in preference to poor ones by down-regulating transcription of genes encoding proteins that transport and degrade poor nitrogen sources when excess nitrogen is available. This regulation is designated nitrogen catabolite repression (NCR). When cells are transferred from a good to a poor nitrogen source (glutamine to proline) or treated with rapamycin, an inhibitor of the protein kinases Tor1/2, Gln3 (NCR-sensitive transcription activator) moves from the cytoplasm into the nucleus. Gln3 re-accumulates in the cytoplasm when cells are returned to a good nitrogen source. However, Gln3 is not uniformly distributed in the cytoplasm. Such non-uniform distribution could result from a variety of interactions including association with a cytoplasmic vesicular system or components of the cytoskeleton. We used latrunculin, a drug that disrupts the actin cytoskeleton by inhibiting actin polymerization, to determine whether the actin cytoskeleton participates in intracellular Gln3 movement. Latrunculin-treatment prevents nuclear accumulation of Gln3 and NCR-sensitive transcription in cells transferred from ammonia to proline medium but does not prevent its accumulation in the cytoplasm of cells transferred from proline to glutamine medium. In contrast, rapamycin-induced nuclear accumulation of Gln3 is not demonstrably affected by latrunculin treatment. These data indicate the actin cytoskeleton is required for nuclear localization of Gln3 in response to limiting nitrogen but not rapamycin-treatment. Therefore, the actin cytoskeleton either participates in the response of Gln3 intracellular localization to nitrogen limitation before Tor1/2, or Tor1/2 inhibition only mimics the outcome of nitrogen limitation rather than directly regulating it.

Actins↗
PubMedDate not supplied

Effects of nitrogen dioxide on elastin and collagen contents of lung.

Male Syrian hamsters were exposed to 30 +/- 5 ppm nitrogen dioxide for 22 hr daily for 3 wk. Nitrogen dioxide-exposed hamsters sacrificed at various times during the 3 wk exposure showed a general loss of body weight and an increased dry lung weight when compared with the controls, which were housed in a similar, but nitrogen dioxide-free environment. Analysis of total lung collagen and total lung elastin revealed a net decrease in the moieties within 4 and 10 days, respectively, following commencement of nitrogen dioxide exposure. Total lung collagen returned toward pre-exposure levels by the 14th day of nitrogen dioxide exposure. Total lung elastin did not return toward normal until termination of nitrogen dioxide exposure. Recovery in room air for 3 wk following 21 days of nitrogen dioxide exposure restored the total pulmonary collagen and elastin to valutin and collagen degradation and synthesis differ during and after nitrogen dioxide exposure. Lung collagen loss was observed earlier and was restored to normal values during the continuation of nitrogen dioxide exposure. Lung elastin loss occurred later and persisted during the entire period of exposure but returned to normal after exposure was terminated.

Animals↗
PubMed2000

Glutamine synthetase and protease enzyme activities and growth response of ruminal bacterium Prevotella ruminicola strain B(1)4 to nitrogen source and concentration.

The objective of this study was to determine the effects of varying nitrogen sources and concentrations upon glutamine synthetase and protease activities in Prevotella ruminicola strain B(1)4. Based on growth response it appears that ammonium chloride or pepticase limited P. ruminicola becomes nitrogen limited when nitrogen concentration is at 0.5 mM. However, when casein was provided as the sole source of nitrogen P. ruminicola becomes nitrogen limited at 2.5 mM. Glutamine synthetase activity was measured from mid-log phase cells grown in either nitrogen-limited or non-limited conditions. No activity was detectable in the non-limited treatments. However, in the N-limited treatments, pepticase had the highest activity (20.76 units), followed by ammonium chloride (18.72 units) and casein (14.42 units). Protease activity assays indicated that nitrogen-limited cultures had higher proteolytic activity than non-limited cultures. Moreover, these activities appeared to follow the same response pattern as the previously observed glutamine synthetase activities. The results of this study indicate that P. ruminicola strain B(1)4 protease activity may be influenced by nitrogen concentration such that activity increases when nitrogen availability decreases.

Animals↗
PubMed1987

Sex differences in nitrogen balance following marrow grafting for leukemia.

A sex difference in nitrogen balance was investigated in 40 adults, 21 men and 19 women, undergoing chemoradiotherapy and marrow transplantation for leukemia and receiving total parenteral nutrition. Twenty-four hour collections of urine and mixed urine-stool were analyzed for total nitrogen daily through day 14 posttransplant. Nitrogen balance, corrected for changes in blood urea nitrogen, decreased significantly over time (p less than 0.005) in both men and women, but men experienced a greater negative nitrogen balance during the time period (p less than 0.001). Mean daily nitrogen balance in men was -6.0 g for week 1 and -9.2 g for week 2, corresponding to -3.3 g and -5.6 g in women for week 1 (p less than 0.005) and 2 (p less than 0.01), respectively. The differences remained after controlling for stress level and adjusting for total calorie intakes. There were no differences in age, disease status, or nitrogen intakes per kg ideal body weight, and no effects on nitrogen balance by arm muscle area at admission, cyclosporine use, or the branched-chain amino acid content of the parenteral solution. The average rise in 3-methylhistidine excretion was 23% in men and 11% in women. These results suggest higher per kg nutrient needs in males during stress and may indicate differing metabolic responses to stress. The possibility of gender differences should be considered in research evaluating nitrogen metabolism during severe stress.

Adult↗
PubMed2005

Nitrogen removal from landfill leachate using single or combined processes.

The municipal solids waste (MSW) collected at Shanghai includes a high proportion of food waste, which is easily hydrolyzed to generate ammonia-nitrogen in leachate. This study investigated the efficiency of nitrogen removal from landfill leachate employing four different treatment processes. The simulated rainfall and direct leachate recycling produced strong leachate with high ammonia-nitrogen content, and resulted in the removal of only a small amount of nitrogen. Although pretreating the leachate using an aerobic reactor removed some nitrogen, most of which was transformed to biomass because of the high organic loading applied. Using the three-compartment system, which comprises a landfill column with fresh MSW, a column with well-decomposed refuse layer as the methane generator, and a nitrifier, the ammonia-nitrogen was converted into nitrogen gas and hence removed. Experimental results demonstrated the feasibility of adopting the three-compartment system for managing nitrogen in landfill leachate generated from high-nitrogen-content MSW.

Conservation of Natural Resources↗
PubMed1952

Changes in non-protein nitrogen metabolism during tobacco mosaic virus biosynthesis.

1. Discs cut from tobacco leaf tissue infected with tobacco mosaic virus and cultured in water contain less non-protein nitrogen than comparable uninfected discs during the time at which TMV is formed. This deficiency disappears when virus formation ceases. Discs cultured in nutrient solution form about twice as much TMV as discs cultured in water. The maximum non-protein nitrogen deficiency is comparable in magnitude to the amount of virus synthesized. 2. The largest difference between injected and uninfected tissue occurs in the ammonia content. Smaller, but significant differences in amide content are found. Infected discs cultured in water show no significant differences from control discs in free amino acid content; infected discs cultured in nutrient solution develop a small deficiency in amino acid nitrogen. 3. The general patterns of change in composition of the pool of soluble nitrogen are similar in both infected and uninfected discs. 4. The data indicate that the bulk of the nitrogen incorporated into virus protein is withdrawn from the leaf's pool of soluble nitrogen; virus is formed de novo from ammonia nitrogen and non-nitrogenous carbon sources. The effect of virus infection on host nitrogen metabolism appears to be due to the formation of virus rather than to its presence.

Carbon↗
PubMed1986

Expansion and photosynthetic rate of leaves of soybean plants during onset of and recovery from nitrogen stress.

This study reports on the effects of nitrogen stress and restoration of nitrogen availability after a period of stress on expansion and photosynthetic rate of soybean leaves of differing maturity. We hypothesized that nitrogen resupply would lead to additional accumulation of reduced nitrogen in the leaves and, ultimately, resumption of leaf initiation and expansion and photosynthetic activity. In continuously nitrogen-stressed plants, expansion of middle trifoliolates of main-stem trifoliates and leaf area at full expansion were severely restricted. Leaves showing the greatest effects were initiated after removal of nitrogen. When the reduced nitrogen concentration in mature leaves of continuously stressed plants fell below 9 mg dm-2, the photosynthetic rate per unit leaf decreased rapidly, reaching a minimum of ca. 6-8 mg dm-2 h-1. The older mature leaves tended to abscise at this point, while the youngest leaves remained on the plant and continued to photosynthesize slowly. When nitrogen was resupplied, leaf expansion and final leaf area increased. Leaf initiation was also stimulated as reduced nitrogen levels rose in the leaves. Photosynthetic rates of the oldest and youngest pair of mature leaves returned to values comparable to those of similar-aged leaves of nonstressed soybean plants.

Biomass↗
PubMedDate not supplied

Nitrogen requirement of the omnivorous greater bilby, Macrotis lagotis (Marsupialia: Peramelidae).

Mainly due to their utilisation of relatively low-fiber diets compared to herbivorous mammals, omnivores are expected to have correspondingly low maintenance nitrogen requirements (MNRs). The limited studies examining nitrogen requirements of omnivorous mammals to date have shown this to be the case. In this article, we determine the dietary MNR of greater bilbies (Macrotis lagotis), arid-zone omnivorous marsupials, by feeding them varying proportions of mixed seeds and dried currants (sun-dried grapes). We also examine the possibility that bilbies conserve nitrogen by recycling endogenous urea to their gastrointestinal tract. The dietary MNR of 127 mg N kg(-0.75) d(-1) calculated for the bilby falls within the range calculated for other marsupial omnivores and is lower than that of any of the herbivores. This low requirement for nitrogen was correlated with significant recycling of endogenous urea to the gut; bilbies recycled between 44% and 80% of urea synthesised in the liver, but the proportion recycled was independent of dietary nitrogen intake. The relatively low MNR of the bilby is consistent with its low rates of basal metabolism and the recycling of endogenous urea to the gut, both of which reduce urinary nitrogen losses, and a low-fiber diet that minimises metabolic fecal nitrogen loss. Because the bilby inhabits an environment where its food supply is unpredictable and of seasonally low nitrogen content, this species is likely to benefit from its low requirement for nitrogen.

Animal Nutritional Physiological Phenomena↗
PubMedDate not supplied

Nitrogen and energy requirements of the North American porcupine (Erethizon dorsatum).

We measured nitrogen and energy requirements in adult North American porcupines (Erethizon dorsatum) fed three experimental diets differing primarily in crude protein content. Porcupines ingested 497.3-865.4 kJ kg-0.75 d-1, and there was no significant loss of body mass on any dietary treatment. Individuals maintained nitrogen balance on a total nitrogen intake of 389.4 mg N kg-0.75 d-1. The true digestibility of nitrogen was high (88%) but within the range for eutherians. We found metabolic fecal nitrogen to be 0.92 mg N g-1 dry matter intake and endogenous urinary nitrogen to be 223 mg N kg-0.75 d-1. The low value of metabolic fecal nitrogen found for porcupines affects the dry matter intake required for nitrogen balance, and it may allow these animals to exploit nitrogen-poor diets.

Animals↗
PubMed2000

Postprandial modulation of dietary and whole-body nitrogen utilization by carbohydrates in humans.

BACKGROUND: Sucrose exerts a sparing effect on whole-body protein metabolism, mainly during the absorptive phase. OBJECTIVE: We aimed to characterize the acute postprandial effect of addition of sucrose on deamination of dietary and endogenous nitrogen, with particular consideration being given to the effects of bioavailability. DESIGN: Twenty-one subjects equipped with ileal tubes ingested (15)N-labeled soy protein combined with [(13)C]glycine, with (n = 10) or without (n = 11) sucrose. Dietary and endogenous ileal flow of nitrogen were determined from the ileal effluents. The kinetics of dietary amino acid transfer to the blood were characterized by (13)CO(2) enrichment in breath and (15)N enrichment in plasma amino acids. Deamination of dietary and endogenous amino acid was determined from body urea, urinary nitrogen, and (15)N enrichment. RESULTS: (13)CO(2) recovery in breath and (15)N plasma amino acid enrichments were highly correlated (R:(2) >/= 0.95, P: < 0.001, for both meals) and markedly delayed by sucrose (half-(13)CO(2) recovery: 274 min compared with 167 min), whereas exogenous and endogenous ileal nitrogen kinetics and balances remained unchanged. Addition of sucrose halved the early (0-2 h) deamination peak of dietary nitrogen and reduced endogenous nitrogen oxidation over the first 4 h. Both were reduced by 18-24% over the 8-h period after the meal. CONCLUSIONS: Without changing the nitrogen absorptive balance, sucrose markedly affected the bioavailability profile, which is governed by gastric emptying. Endogenous and dietary nitrogen were not spared in the same way and over the same periods, showing that the metabolism of endogenous and dietary nitrogen may be affected differently by nutritional modulation, even if the effects are of a similar magnitude over the entire postprandial period.

Adult↗
PubMed2003

Some quantitative relationships between leaf area index and canopy nitrogen content and distribution.

In a previous study (Yin et al. 2000. Annals of Botany 85: 579-585), a generic logarithmic equation for leaf area index (L) in relation to canopy nitrogen content (N) was developed: L=(1/ktn)1n(1+ktnN/nb). The equation has two parameters: the minimum leaf nitrogen required to support photosynthesis (nb), and the leaf nitrogen extinction coefficient (ktn). Relative to nb, there is less information in the literature regarding the variation of ktn. We therefore derived an equation to theoretically estimate the value of ktn. The predicted profile of leaf nitrogen in a canopy using this theoretically estimated value of ktn is slightly more uniform than the profile predicted by the optimum nitrogen distribution that maximizes canopy photosynthesis. Relative to the optimum profile, the predicted profile is somewhat closer to the observed one. Based on the L-N logarithmic equation and the theoretical ktn value, we further quantified early leaf area development of a canopy in relation to nitrogen using simulation analysis. In general, there are two types of relations between L and N, which hold for canopies at different developmental phases. For a fully developed canopy where the lowest leaves are senescing due to nitrogen shortage, the relationship between L and N is described well by the logarithmic model above. For a young, unclosed canopy (i.e. L < 1.0), the relation between L and N is nearly linear. This linearity is virtually the special case of the logarithmic model when applied to a young canopy where its total nitrogen content approaches zero and the amount of nitrogen in its lowest leaves is well above nb. The expected patterns of the L-N relationship are discussed for the phase of transition from young to fully developed canopies.

Algorithms↗
PubMed1977

Effects of dietary histidine and arginine on nitrogen retention of men.

Effects of dietary histidine and arginine on nitrogen retention were compared in six young men consuming for 1 week, each of six semipurified diets containing eight indispensable amino acids proportioned as in casein and 6.3 g nitrogen daily. Nonspecific nitrogen was either A) a mixture of six dispensable amino acids and arginine (diet 1) or arginine and histidine (diet 2) in casein proportions, or B) an isonitrogenous mixture of glycine and diammonium citrate alone (diet 3), with histidine (diet 4), arginine (diet 5), or histidine and arginine (diet 6). Nitrogen retention was significantly greater when the nonspecific nitrogen source was dispensable amino acids, arginine and histidine (diet 2) than when it was glycine and diammonium citrate (diet 3). mean balances were positive only when diets contained histidine (diets 2, 4, and 6). Histidine with arginine (diets 2 and 6) significantly improved nitrogen retention compared to arginine alone, but the balance, although positive, was not significantly improved when histidine was fed without arginine (diet 4). Urinary urea nitrogen confirmed these data. Indicators of erythrocyte status, plasma enzyme activities and proteins, and creatinine clearance were unaffected by diet. In summary, histidine supplementation of the low nitrogen diet improved total nitrogen utilization when arginine was present in the diet.

Adult↗
PubMed1982

The effect of burn wound size on ureagenesis and nitrogen balance.

Hypermetabolic burn patients are frequently in negative nitrogen balance despite provision of estimated caloric needs. We studied 18 thermally injured adult patients in order to evaluate the relationship of burn wound size to urea production and nitrogen balance. We selected data from 147 patient-days when the patients received 100 +/- 25% of their estimated caloric needs. Three significantly different burn size groups (by body surface area [BSA]) were identified by calculation of the catabolic index (CI): group 1, 0-10% BSA (CI = -0.1); group 2, 11-30% BSA (CI = 6.4); and group 3,31-60% BSA (CI = 10.5). The urine urea nitrogen (UUN) for groups 1,2, and 3 was 11.1, 18.9, and 25.3 gm/day, and nitrogen balance was 1.0, -3.9, and -5.8 gm/day, respectively. When nitrogen was given in a calorie:nitrogen ratio of 150:1, only those patients in group I were able to achieve positive balance. We conclude that large burn wounds are associated with increased ureagenesis and impaired nitrogen retention. The protein intake, at the customary calorie:nitrogen ratio of 150:1, may not provide adequate nitrogen to achieve equilibrium, even when energy demands have been met, in patients with burn wounds greater than 10% BSA.

Adult↗
PubMedDate not supplied

Caloric and nitrogen balances as predictors of nutritional outcome in patients with burns.

Measurement of energy expenditure with indirect calorimetry allows determination of caloric balance. The present study was done to determine the predictive value of caloric and nitrogen balances for nutritional outcome. Energy expenditure was obtained weekly and interpolated between measurements for daily caloric balance. Nitrogen balance was obtained weekly. Because nitrogen output fluctuated, interpolation of daily values was not possible. Nutritional outcome was defined by whether body weight was lost or maintained and by levels of visceral proteins (albumin, prealbumin, and transferrin). The study group included 12 patients with 7% to 82.5% total body surface area burns. Eleven patients survived their burn injuries, and one died of congestive heart failure at 38 days, after her burn wounds had healed. Nine patients had good nutritional outcomes (group 1) and three had poor nutritional outcomes (group 2) (including the one who died). Nitrogen balance was 1.3 +/- 1.0 gm/day in group 1 and 4.5 +/- 1.7 gm/day in group 2 (mean +/- SEM; p > 0.10). Caloric balance was 515 +/- 130 kcal/day in group 1 and -667 +/- 140 in group 2 (p < 0.001). Caloric balance was significantly different between the two groups, whereas nitrogen balance was not. Caloric intake correlated positively with nitrogen intake (r = 0.92). Nitrogen intake was 16% of total caloric intake. Nitrogen intake from blood products was appreciable and averaged 15% of total nitrogen intake (range, 0% to 47%); 11.3 +/- 1.6 gm/day in group 1 and 14.8 +/- 3 gm/day in group 2 (p > 0.10).(ABSTRACT TRUNCATED AT 250 WORDS)

Burns↗