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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↗
PubMed1981

Methionine requirement of weanling Large White x Landrace pigs and determined by plasma urea concentration, nitrogen retention and some urinary nitrogenous components.

The methionine requirements of weanling Large White x Landrace pigs fed a 20% protein cassava flour-soybean meal diet were evaluated using nitrogen balance, plasma urea concentration, urinary nitrogenous end products and the index--(allantoin/urinary urea) x protein intake (A/U x Ip). Sensitivities of the response criteria to sex differences in methionine requirements were compared. Allantoin excretion consistently and significantly (P less than 0.05) increased with increasing methionine levels to a maximum of 0.55% total methionine. Maximum nitrogen retention was observed in diets containing 0.55, 0.47 and 0.55% total methionine for castrated males, females and the pooled data for both sexes, respectively. Minimum urea concentration in plasma was obtained with the diets containing 0.55% methionine. The index, + A/U x Ip, showed that the diet was better utilized when it contained 0.63, 0.55 and 0.63% total methionine in castrates, females and combination of the two sexes, respectively.

Allantoin↗
PubMed2004

Nitrogen mobilization, nitrogen uptake and growth of cuttings obtained from poplar stock plants grown in different N regimes and sprayed with urea in autumn.

Nitrogen mobilization, nitrogen uptake and growth of cuttings obtained from poplar stock plants fertigated with different nitrogen (N) treatments and sprayed with urea in autumn were studied. Stock plants propagated from poplar cuttings were trained to a single shoot and fertigated with 0, 5, 10, 15 or 20 mmol l(-1) N during the first growing season. In October, a subset of stock plants from each N fertigation treatment was sprayed twice with either 3% urea or water, and overwintered outside. In March, total tree biomass and total N concentration and content of stems were estimated for stock plants in each treatment, and cuttings were taken from the middle of each stock plant and stored in plastic bags at 2 degrees C. In mid-April, cuttings were planted in 7.5-l pots containing N-free medium and grown outdoors with a weekly fertigation with nutrient solution containing 0 or 10 mmol l(-1) 15NH4 15NO3. In mid-July, cuttings were harvested, and new shoot (new stems and leaves), shank (old cutting stem) and roots were analyzed for new biomass growth and total N and 15N content. Growth of stock plants was positively related to N supply in the previous growing season. Foliar urea application in autumn had no effect on subsequent stock plant growth even though urea sprays increased both N concentration and content in stem tissues. Biomass growth of cuttings obtained from stock plants was closely related to their N content when the cuttings were grown in an N-free medium regardless of previous treatments applied to the stock plants. When N was supplied in the growth medium, the strength of the relationship between regrowth and N content of cuttings was significantly reduced. Cuttings from stock plants treated with foliar urea and grown in a N-free medium remobilized between 75 and 82% of their total N for new growth, whereas cuttings from plants receiving no urea spray remobilized only between 60 and 69% of their total N for new growth. Current N fertilization of the cuttings reduced the percentage of N remobilized. We conclude that new growth of poplar cuttings in spring was more dependent on currently applied N than on reserve N, and urea N applied as a spray in autumn was more easily remobilized than N taken up by roots during the previous season.

Nitrogen↗
PubMed1998

Repression of nitrogen catabolic genes by ammonia and glutamine in nitrogen-limited continuous cultures of Saccharomyces cerevisiae.

Growth of Saccharomyces cerevisiae on ammonia and glutamine decreases the expression of many nitrogen catabolic genes to low levels. To discriminate between ammonia- and glutamine-driven repression of GAP1, PUT4, GDH1 and GLN1, a gln1-37 mutant was used. This mutant is not able to convert ammonia into glutamine. Glutamine-limited continuous cultures were used to completely derepress the expression of GAP1, PUT4, GDH1 and GLN1. Following an ammonia pulse, the expression of GAP1, PUT4 and GDH1 decreased while the intracellular glutamine concentration remained constant, both in the cytoplasm and in the vacuole. Therefore, it was concluded that ammonia causes gene repression independent of the intracellular glutamine concentration. The expression of GLN1 was not decreased by an ammonia pulse but solely by a glutamine pulse. Analysis of the mRNA levels of ILV5 and HIS4 showed that the response of the two biosynthetic genes, GDH1 and GLN1, to ammonia and glutamine in the wild-type and gln1-37 was not due to changes in general transcription of biosynthetic genes. Ure2p has been shown to be an essential element for nitrogen-regulated gene expression. Deletion of URE2 in the gln1-37 background prevented repression of gene expression by ammonia, showing that the ammonia-induced repression is not caused by a general stress response but represents a specific signal for nitrogen catabolite regulation.

Amino Acid Transport Systems↗
PubMed2001

Optimizing nitrogen management in food and energy production and environmental protection: summary statement from the Second International Nitrogen Conference.

Human efforts to produce food and energy are changing the nitrogen (N) cycle of the Earth. Many of these changes are highly beneficial for humans, while others are detrimental to people and the environment. These changes transcend scientific disciplines, geographical boundaries, and political structures. They challenge the creative minds of natural and social scientists, economists, engineers, business leaders, and decision makers. The Second International Nitrogen Conference was designed to facilitate communications among all stakeholders in the "nitrogen community" of the world. The Conference participants" goal in the years and decades ahead is to encourage every country to make optimal choices about N management in food production and consumption, energy production and use, and environmental protection. Scientific findings and recommendations for decision makers that emerged from the Conference are presented.

Agriculture↗
PubMed1992

Role of nitrogen regulator I (NtrC), the transcriptional activator of glnA in enteric bacteria, in reducing expression of glnA during nitrogen-limited growth.

During nitrogen-limited growth, transcription of glnA, which codes for glutamine synthetase, requires sigma 54-RNA polymerase and the phosphorylated from the nitrogen regulator I (NRI; also called NtrC). In cells in which the lac promoter controlled expression of the gene coding for NRI, increasing the intracellular concentration of NRI lowered the level of glutamine synthetase. The reduction in glutamine synthetase does not appear to result from the NRI-dependent sequestering of any protein that affects transcription of glnA. Our results also suggest that the negative effect of a high concentration of NRI on glnA expression is a major determinant of the level of glutamine synthetase activity in nitrogen-limited cells of a wild-type strain. We propose that the inhibition results from an impairment of the interaction between NRI-phosphate and RNA polymerase that stimulates glnA transcription. We discuss a model that can account for this reduction in glutamine synthetase.

Bacteriophage lambda↗
PubMed1984

[Nitrogen retention in germ-free and conventional mice reared on an antigen-free diet and the significance of the appearance of protein nitrogen in their feces].

The nutritional state of animals removed from as much antigenic stimuli as possible--germ-free mice on an antigen-free liquid diet--was compared with that of conventional mice through assessment of their protein metabolism. Both the germ-free and conventional mice reared on the antigen-free liquid diet for 7 weeks exhibited relatively stable body weight throughout the experimental period. Although the nitrogen retention rate was generally higher for the conventional mice, even in the germ-free mice with the exception of one observation in a male, positive nitrogen retention rates were observed, and this suggests nutritional adequacy of the diet. The amount of protein-nitrogen excreted in the feces due to the physiological processes, such as the digestive tract cell turnover, digestive juice secretions, etc, (4.2-5.3 mg/mouse/week), and the amount that was influenced by the presence of intestinal bacteria and due to bacterial protein per se (2.3-4. 4 mg /mouse/week) could be estimated through the comparison of the fecal protein values obtained from germ-free and conventional mice reared on the antigen-free liquid diet.

Animals↗
PubMedDate not supplied

Soil temperature, nitrogen concentration, and residence time affect nitrogen uptake efficiency in citrus.

We try to elucidate which environmental and soil factors control nitrogen uptake efficiency in citrus. Effects of residence time and nitrogen (N) concentration (three 500-mL applications of 7 mg N L(-1), representative of reclaimed water used for citrus irrigation in central Florida, or one 150-mL application of 70 mg N L(-1)) on nitrogen uptake efficiency (NUE) of young citrus seedlings were studied. Increasing residence times from 2 to 8 h increased NUE from 36 to 82% and from 17 to 34% for high and low application frequencies, respectively. We developed a model to predict N uptake based on root density, N concentration, and soil temperature (Ts). Assuming a base temperature (Tb) of 10 degrees C, N uptake temperature sum (UTS) = sigma(Ts - Tb)/24 (degrees CdN, degree day units of N uptake). To eliminate the risk of N leaching for young seedlings, minimum uptake periods of 5 and 16 degrees CdN were required at initial soil N concentrations of 0.9 and 2.5 mg N L(-1), respectively. After correcting for differences in root length, this information was then used to predict the effect of irrigation practices on N uptake from reclaimed water for mature trees. Applying 2500 mm yr(-1) vs. 400 mm yr(-1) reclaimed water reduced the NUE of N in this water from 100 to 63% during the summer and from 100 to 28% during the winter. Reductions in NUE at higher irrigation rates appeared to be related to N displacement below the root zone prior to complete N uptake.

Citrus↗
PubMedDate not supplied

Long-term effects of clipping and nitrogen management in turfgrass on soil organic carbon and nitrogen dynamics: the CENTURY model simulation.

Experiments to document the long-term effects of clipping management on N requirements, soil organic carbon (SOC), and soil organic nitrogen (SON) are difficult and costly and therefore few. The CENTURY ecosystem model offers an opportunity to study long-term effects of turfgrass clipping management on biomass production, N requirements, SOC and SON, and N leaching through computer simulation. In this study, the model was verified by comparing CENTURY-predicted Kentucky bluegrass (Poa pratensis L.) clipping yields with field-measured clipping yields. Long-term simulations were run for Kentucky bluegrass grown under home lawn conditions on a clay loam soil in Colorado. The model predicted that compared with clipping-removed management, returning clippings for 10 to 50 yr would increase soil C sequestration by 11 to 25% and nitrogen sequestration by 12 to 28% under a high (150 kg N ha(-1) yr(-1) nitrogen (N) fertilization regime, and increase soil carbon sequestration by 11 to 59% and N sequestration by 14 to 78% under a low (75 kg N ha(-1) yr(-1)) N fertilization regime. The CENTURY model was further used as a management supporting system to generate optimal N fertilization rates as a function of turfgrass age. Returning grass clippings to the turf-soil ecosystem can reduce N requirements by 25% from 1 to 10 yr after turf establishment, by 33% 11 to 25 yr after establishment, by 50% 25 to 50 yr after establishment, and by 60% thereafter. The CENTURY model shows potential for use as a decision-supporting tool for maintaining turf quality and minimizing negative environmental impacts.

Biodegradation, Environmental↗
PubMedDate not supplied

Influence of chemical oxygen demand/total Kjeldahl nitrogen ratio and sludge age on nitrification of nitrogenous wastewater.

Four laboratory-scale biological nitrification units (influent total Kjeldahl nitrogen [TKN] = 1002 to 1062 mg/L) were operated at chemical oxygen demand (COD)/TKN ratios of approximately 0.5, 1.0,15, and 2.0 and at three different sludge ages of 30, 20, and 10 days to study the influence of COD/TKN, sludge age, COD loading, and TKN loading on nitrification and nitrifiers. Percent nitrification was found to increase with decreases in COD/TKN and increases in sludge age. The average nitrifier concentration increased from 460 mg/L at a COD/TKN of 2.22 and a sludge age of 10 days to 706 mg/L at a COD/TKN of 0.676 and a sludge age of 30 days. The nitrifier fraction was found to be higher at a lower COD/TKN and lower at a higher COD/TKN. The nitrifier fraction increased with the decrease in sludge age and COD loadings and the increase in TKN loadings. The effect of sludge age on the nitrifier fraction was amplified at a COD/ TKN of approximately 0.5 rather than at approximately 2.0. The nitrification rate (kilograms TKN oxidized per kilograms nitrifiers per day) was shown to be dependent on COD/TKN and sludge age. The activity performed by Nitrobacter was affected at all COD/TKN ratios studied as well as at a sludge age of 10 days. This was manifested by the accumulation of high levels of nitrite-nitrogen in the nitrified effluent. The presence of heterotrophs did not affect nitrification rates and the growth of nitrifiers, which were found to be beneficial. High sludge age and COD loadings resulted in a higher sludge volume index of more than 200 mL/g mixed liquor suspended solids. Microscopic examination showed filamentous structure of sludge under these conditions. It is concluded from the investigations that a sludge age of 30 days and a COD/TKN of approximately 1.0 are optimal to yield maximum nitrification and nitrifier growth rates for treating high-strength nitrogenous wastewater.

Bioreactors↗
PubMed2000

Nitrogen metabolism and fertility in cattle: I. Adaptive changes in intake and metabolism to diets differing in their rate of energy and nitrogen release in the rumen.

The ruminal degradability, intake, and metabolism of diets differing in their relative rate of energy and nitrogen release in the rumen were characterized prior to their use in a study of the effects of high peripheral levels of ammonia on reproductive function in cattle. In a 2 x 2 factorial experiment, replicated four times, 16 heifers were offered isocaloric and isonitrogenous diets containing two sources of fermentable carbohydrate, fiber (slow energy release, SE) or starch (fast energy release, FE), and two rates of nitrogen release, which were either synchronous (S) or asynchronous (A) to that of energy release. Throughout the experiment, the amount of feed offered was held constant, at a level equivalent to 1.5 x maintenance. Four ruminally fistulated sheep were used to determine the in situ degradability of these diets. The 16 heifers were bled before feeding at 0800 and at 0900, 1000, 1100, 1200, 1400, and 1600 on d 0 (introduction to dietary treatments) and on d 4, 7, 11, 14, 21, and 28. Diet refusals were recorded at hourly intervals after feeding. The rapidly degradable nitrogen fraction of the SE:A and FE:A diets was greater than that of the SE:S and FE:S diets. Postprandial jugular plasma ammonia levels rose to a peak of around 300 micromol/L in heifers offered the SE:A and FE:A diets but did not rise in heifers offered the SE:S and FE:S diets. All feed offered was consumed within 1 h on diets SE:S and FE:S throughout the experiment. The proportion of feed consumed within 1 h of feeding declined from 100% on d 0 to around 70 and 56% by d 21 for heifers given the SE:A and FE:A diets, respectively. Peak postprandial plasma ammonia levels were accordingly lower, at around 160 micromol/L. Plasma urea levels averaged 7 mmol/L and were unaffected by dietary treatment. High plasma ammonia levels were associated with a suppression in the normal postprandial rise in insulin. There was no significant metabolic adaptation to high-ammonia-generating diets, and heifers given these diets modified their pattern of intake in an apparent attempt to avoid excessively high levels of plasma ammonia.

Adaptation, Physiological↗
PubMed1991

Cyclic variations in nitrogen uptake rate of soybean plants: effects of pH and mixed nitrogen sources.

To determine if the daily pattern of NO3- and NH4+ uptake is affected by acidity or NO3- : NH4+ ratio of the nutrient solution, non-nodulated soybean plants (Glycine max) were exposed for 21 days to replenished, complete nutrient solutions at pH 6.0, 5.5, 5.0, and 4.5 which contained either 1.0 mM NH4+, 1.0 mM NO3- [correction of NO3+], 0.67 mM NH4+ plus 0.33 mM NO3- (2:1 NH4+ : NO3-) [correction of (2:1 NH3+ : NO4-)], or 0.33 mM NH4+ plus 0.67 mM NO3- (1:2 NH4+ : NO3-). Net uptake rates of NH4+ and NO3- were measured daily by ion chromatography as depletion from the replenished solutions. When NH4+ and NO3- were supplied together, cumulative uptake of total nitrogen was not affected by pH or solution NH4+ : NO3- ratio. The cumulative proportion of nitrogen absorbed as NH4+ decreased with increasing acidity; however, the proportional uptake of NH4+ and NO3- was not constant, but varied day-to-day. This day-to-day variation in relative proportions of NH4+ and NO3- absorbed when NH4+ : NO3- ratio and pH of solution were constant indicates that the regulatory mechanism is not directly competitive. Regardless of the effect of pH on cumulative uptake of NH4+, the specific nitrogen uptake rates from mixed and from individual NH4+ and NO3- sources oscillated between maxima and minima at each pH with average periodicities similar to the expected interval of leaf emergence.

Biological Transport↗
PubMed1992

[The correlation between urine urea nitrogen and total urine nitrogen output in perioperative patients].

Daily urine urea nitrogen (UUN) and total urine nitrogen output (TUNO) concentrations were measured in 19 patients undergoing G-I surgery during the perioperative period of 114 days. The results showed that there was a strong correlation between UUN and TUNO in statistic regression analysis. A formula is worked out TUNO = UUN + 0.7 which is of great value in estimating the nitrogen balance of TPN patients.

Adult↗
PubMed2004

Nitrification-denitrification via nitrite for nitrogen removal from high nitrogen soybean wastewater with on-line fuzzy control.

This study is to demonstrate the performance of a new technology for complete nitrogen removal from soybean wastewater with high nitrogen concentrations. Nitrification-denitrification via nitrite was performed in three kinds of operating condition, i.e. nitrification-denitrification via nitrite under traditional SBR process, nitrification-denitrification via nitrite by alternating oxic/anoxic under fixed-time control and nitrification-denitrification via nitrite by alternating oxic/anoxic under on-line fuzzy control. The best one is nitrification-denitrification via nitrite by alternating oxic/anoxic under on-line fuzzy control. It not only improves both nitrification and denitrification rates and decreases total reaction time, but also saves the amount of added carbon source and alkalinity. In addition, reaction time can be shortened and operation cost can be saved by using real-time fuzzy control aeration and mixing time. So this method enhances the efficiency and the stability of nitrogen removal, and reduces operating costs and construction investment in the process of wastewater treatment.

Agriculture↗
PubMed1977

Studies on the purification of wastes from the nitrogen fertilizer industry by intensive algal cultures. IV. growth of Chlorella vulgaris in wastes with high nitrogen content in continuous and intermittent light.

The growth and utilization of nitrogen by intensive Chlorella vulgaris in wastes from production of urea, containing 1300 mg NH4+-N and 4000 mg urea-N/1, was investigated. In these conditions only Chlorella vulgaris AA strain, adapted to high concentrations of ammonia nitrogen, was able to grow. The elimination of nitrogen by continuous cultures was 750 mg urea-N/1 with 5-day flow rate. A considerable part of the urea was hydrolized by urease bacteria and removed in the form of NH3. The effect of intermittent light on the growth of algae was also studied. The better growth than in continuous light, was obtained with alternate one hour periods of light and darkness. Good results were also obtained with the use of 12 hour light and 12 hour darkness.

Ammonia↗
PubMed1979

Effect of high concentrations of nitrogen on mixed populations of nitrifying bacteria isolated from industrial nitrogenous wastewaters.

The effect of high concentrations of different forms of nitrogen (NH4+, NO2-, NO3- and urea N) on nitrification by mixed populations of nitrosobacters isolated from nitrogen fertilizer plant wastewaters and nitrobacters isolated from effluents from a biological bed treating these wastewaters was determined. The inhibitory activity (within the concentration values for industrial wastewaters) of only the reaction products was observed, i.e. nitrites for nitrification phase I and nitrates for nitrification phase II. A mixed population of phase II nitrifying bacteria is highly resistant to high concentrations of ammonia nitrogen (50% inhibition at 3,000 mg N/l).

Ammonia↗
PubMed1987

Analogues and derivatives of tenoxicam. 1. Synthesis and antiinflammatory activity of analogues with different residues on the ring nitrogen and the amide nitrogen.

The synthesis of tenoxicam, 4-hydroxy-2-methyl-N-2-pyridyl-2H-thieno[2,3-e]-1,2-thiazine-3-carboxami de 1,1-dioxide (1e), and of the analogues with various residues on the ring nitrogen and the amide nitrogen is described. This new class of "oxicams" has pronounced antiinflammatory and analgesic properties. The very specific structure-activity relationship of isomeric and isosteric groups at the amide nitrogen has been evaluated. The substituent in position 2 also has a great influence on the pharmacological properties. Tenoxicam is presently undergoing clinical trials.

Animals↗
PubMed1999

Influence of canopy light environment and nitrogen availability on leaf photosynthetic characteristics and photosynthetic nitrogen-use efficiency of field-grown nectarine trees.

Relationships between CO(2) assimilation at light saturation (A(max)), nitrogen (N) content and weight per unit area (W(A)) were studied in leaves grown with contrasting irradiances (outer canopy versus inner canopy) and N supply rates in field-grown nectarine trees Prunus persica L. Batsch. cv. Fantasia. Both A(max) and N content per unit leaf area (N(A)) were linearly correlated to W(A), but leaves in the high-N treatment had higher N(A) and A(max) for the same value of W(A) than leaves in the low-N treatment. The curvilinear relationship between photosynthesis and total leaf N was independent of treatments, both when expressed per unit leaf area A(maxA) and N(A)) and per unit leaf weight (A(maxW) and N(W)), but the relationship was stronger when data were expressed on a leaf area basis. Both A(maxA) and N(A) were higher for outer canopy leaves than for inner canopy leaves and A(maxW) and N(W) were higher for leaves in the high-N treatment than for leaves in the low-N treatment. The relationship between A(max) and N resulted in a similar photosynthetic nitrogen-use efficiency at light saturation (A(max)NUE) for both N and light treatments. Photosynthetic nitrogen-use efficiency was similar among treatments throughout the whole light response curve of photosynthesis. Leaves developed in shade conditions did not show higher N-use efficiency at low irradiance. At any intercellular CO(2) partial pressure (C(i)), photosynthetic CO(2) response curves were higher for outer canopy leaves and, within each light treatment, were higher for the high-N treatments than for the low-N treatments. Consequently, most of the differences among treatments disappeared when photosynthesis was expressed per unit N. However, slightly higher assimilation rates per unit N were found for outer canopy leaves compared with inner canopy leaves, in both N treatments. Because higher daily irradiance within the canopies of the low-N trees more than compensated for the lower photosynthetic performances of these leaves compared to the leaves of high-N trees, daily carbon gain (and N-use efficiency on a daily assimilation basis) per leaf was higher for the low-N treatment than for the high-N treatment in both outer and inner canopy leaves.

Journal Article↗