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PubMedDate not supplied

Xylitol normalizes the accelerated hepatic capacity for conversion of amino nitrogen to urea nitrogen in diabetic rats.

In diabetes, the capacity of urea nitrogen synthesis, ie, a substrate-independent measure of the hepatic conversion of amino nitrogen to urea nitrogen, is increased. Xylitol decreases urea synthesis in normal rats. Capacity of urea nitrogen synthesis and nitrogen balance were measured during intravenous alanine loading in control rats, rats with experimental diabetes (streptozocin 75 mg/kg), and rats with experimental diabetes infused with xylitol to 1 mmol/L. In control rats, capacity of urea nitrogen synthesis was 9.4 +/- 1.1 mumol/min per 100 g of body weight, and nitrogen balance -2.7 +/- 1.2 mumol/min per 100 g of body weight. In the diabetics, these values were markedly increased to 26.6 +/- 1.9 and -16.3 +/- 2.1 mumol/min per 100 g of body weight, respectively (p < 0.01). The infusion of xylitol normalized these values to 11.2 +/- 1.0 and -3.6 +/- 2.1 mumol/min per 100 g of body weight for capacity of urea nitrogen synthesis and nitrogen balance, respectively. Xylitol did not change glucagon or insulin. Xylitol improved the nitrogen economy of uncontrolled diabetic rats by decreasing urea synthesis. The mechanism is not settled, but it does not involve insulin or glucagon.

Amino Acids↗
PubMed1992

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

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

Adrenalectomy↗
PubMed1984

Comparative genotoxicity of nitrogen mustard and nor-nitrogen mustard.

Nitrogen mustard and nor-nitrogen mustard were investigated in Salmonella typhimurium and human lymphocytes for genotoxicity. Point mutations were assessed using the plate test, the conventional spot test and a method in which the substances were not in direct contact with the microorganisms. Both compounds were active, but nor-nitrogen mustard was far more potent than nitrogen mustard in all bacterial systems. Cytogenetic experiments with human lymphocytes revealed that both compounds induced a dose dependent increase in chromosomal aberrations and sister chromatid exchanges, but that nitrogen mustard was 10 times more potent than nor-nitrogen mustard. Thus, the spectrum of activity for nor-nitrogen mustard and nitrogen mustard differ. Nor-nitrogen mustard was more effective in inducing point mutation damage than nitrogen mustard and a reversal of potency was found for cytogenetic damage. These results indicate that although these two substances induce the same type of DNA lesions the amounts of the different DNA adducts vary.

Chromosome Aberrations↗
PubMed2004

Genome-wide patterns of carbon and nitrogen regulation of gene expression validate the combined carbon and nitrogen (CN)-signaling hypothesis in plants.

BACKGROUND: Carbon and nitrogen are two signals that influence plant growth and development. It is known that carbon- and nitrogen-signaling pathways influence one another to affect gene expression, but little is known about which genes are regulated by interactions between carbon and nitrogen signaling or the mechanisms by which the different pathways interact. RESULTS: Microarray analysis was used to study global changes in mRNA levels due to carbon and nitrogen in Arabidopsis thaliana. An informatic analysis using InterAct Class enabled us to classify genes on the basis of their responses to carbon or nitrogen treatments. This analysis provides in vivo evidence supporting the hypothesis that plants have a carbon/nitrogen (CN)-sensing/regulatory mechanism, as we have identified over 300 genes whose response to combined CN treatment is different from that expected from expression values due to carbon and nitrogen treatments separately. Metabolism, energy and protein synthesis were found to be significantly affected by interactions between carbon and nitrogen signaling. Identified putative cis-acting regulatory elements involved in mediating CN-responsive gene expression suggest multiple mechanisms for CN responsiveness. One mechanism invokes the existence of a single CN-responsive cis element, while another invokes the existence of cis elements that promote nitrogen-responsive gene expression only when present in combination with a carbon-responsive cis element. CONCLUSION: This study has allowed us to identify genes and processes regulated by interactions between carbon and nitrogen signaling and take a first step in uncovering how carbon- and nitrogen-signaling pathways interact to regulate transcription.

Arabidopsis↗
PubMed1986

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

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

Animal Feed↗
PubMed1985

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

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

Adult↗
PubMed2005

Symbiosome-like intracellular colonization of cereals and other crop plants by nitrogen-fixing bacteria for reduced inputs of synthetic nitrogen fertilizers.

It has been forecast that the challenge of meeting increased food demand and protecting environmental quality will be won or lost in maize, rice and wheat cropping systems, and that the problem of environmental nitrogen enrichment is most likely to be solved by substituting synthetic nitrogen fertilizers by the creation of cereal crops that are able to fix nitrogen symbiotically as legumes do. In legumes, rhizobia present intracellularly in membrane-bound vesicular compartments in the cytoplasm of nodule cells fix nitrogen endosymbiotically. Within these symbiosomes, membrane-bound vesicular compartments, rhizobia are supplied with energy derived from plant photosynthates and in return supply the plant with biologically fixed nitrogen, usually as ammonia. This minimizes or eliminates the need for inputs of synthetic nitrogen fertilizers. Recently we have demonstrated, using novel inoculation conditions with very low numbers of bacteria, that cells of root meristems of maize, rice, wheat and other major non-legume crops, such as oilseed rape and tomato, can be intracellularly colonized by the non-rhizobial, non-nodulating, nitrogen fixing bacterium, Gluconacetobacter diazotrophicus that naturally occurs in sugarcane. G. diazotrophicus expressing nitrogen fixing (nifH) genes is present in symbiosome-like compartments in the cytoplasm of cells of the root meristems of the target cereals and non-legume crop species, somewhat similar to the intracellular symbiosome colonization of legume nodule cells by rhizobia. To obtain an indication of the likelihood of adequate growth and yield, of maize for example, with reduced inputs of synthetic nitrogen fertilizers, we are currently determining the extent to which nitrogen fixation, as assessed using various methods, is correlated with the extent of systemic intracellular colonization by G. diazotrophicus, with minimal or zero inputs.

Crops, Agricultural↗
PubMed1985

Prediction of total urinary nitrogen from urea nitrogen for burned patients.

Although many of the current nutrition assessment techniques are inappropriate for burned patients, we have found nitrogen balance to be a helpful measure of the effectiveness of nutrition therapy if it is used in conjunction with other measures of nutritional status. Many clinicians suggest that a 24-hour urinary urea nitrogen (UUN) measurement, in addition to a correction term of 2 to 4 gm nitrogen, will accurately represent all nitrogen losses (urinary non-urea nitrogen, fecal, integumental). However, since no burned patients were used in the development of that method, its use may not be appropriate for burned patients. As an alternative to total urinary nitrogen (TUN), which is costly and time consuming, we have developed a simple way to predict TUN from UUN, percent initial total body surface area burn, and age for pediatric and adult burned patients. We propose that nitrogen balance may then be determined from the predicted TUN by an equation showing that nitrogen balance equals daily nitrogen intake minus predicted TUN plus fecal and normal nitrogen loss.

Adolescent↗
PubMed1998

A study of solvent polarity and hydrogen bonding effects on the nitrogen NMR shielding of isomeric tetrazoles and ab initio calculation of the nitrogen shielding of azole systems

High-precision nitrogen NMR shieldings, bulk susceptibility corrected, are reported for the N-methyl derivatives of the two existing isomeric tetrazoles (I, II) in a variety of solvents which represent a wide range of solvent properties from the point of view of polarity as well as hydrogen bond donor and acceptor strength. The observed range of solvent-induced nitrogen shielding variations of I and II is significant for the pyrrole-type nitrogens (N-Me), up to 9 ppm, and even more so for pyridine-type nitrogen atoms, where it can attain a value of 20 ppm. There is a clear distinction between the two types of nitrogen atoms in that the former exhibit a deshielding effect with increasing polarity of the medium while the latter experience an increase in the magnetic shielding of their nuclei. The latter effect is significantly augmented by solvent-to-solute hydrogen-bond formation where the pyridine-type nitrogens are involved directly. It is also quite diversified throughout the pyridine-type nitrogen atoms and seems to constitute a measure of relative basicity with respect to hydrogen-bond formation of the nitrogens concerned. This basicity seems to parallel that with respect to a full transfer of a proton, as can be reckoned from ab initio calculations of the relevant protonation energies reported in the present study. The experimental data for the tetrazoles in cyclohexane solutions are combined with those obtained in our earlier extensive studies on azole, diazole, and triazole ring systems, for a comparison with ab initio calculations of the nitrogen shieldings concerned. The latter were carried out using the coupled Hartree-Fock/GIAO/6-31++G** approach and geometry optimizations employing the same basis set; they show a good linear correlation with the experimental data and reproduce not only major changes but also most of the subtle variations in the experimental nitrogen shieldings of the azole systems as a whole. Copyright 1998 Academic Press.

Journal Article↗
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↗
PubMed1993

Effect of water and nitrogen additions on free-living nitrogen fixer populations in desert grass root zones.

In this study we measured changes in population levels of free-living N2-fixing bacteria in the root zones of potted Bouteloua eriopoda and Sporobolus flexuosus plants as well as the photosynthetic indices of the plants in response to added nitrogen, added water, and added water plus nitrogen treatments. In addition, N2 fixer population changes in response to added carbon source and nitrogen were measured in plant-free soil columns. There were significant increases in the numbers of N2 fixers associated with both plant species in the water and the water plus nitrogen treatments. Both treatments increased the photosynthetic index, suggesting that plant exudates were driving N2 fixer population changes. Population increases were greatest in the water plus nitrogen treatments, indicating that added nitrogen was synergistic with added water and suggesting that nitrogen addition spared bacteria the metabolic cost of N2 fixation, allowing greater reproduction. Plant-free column studies demonstrated a synergistic carbon-nitrogen effect when carbon levels were limiting (low malate addition) but not when carbon was abundant (high malate), further supporting this hypothesis. The results of this study indicate the presence of N2 fixer populations which interact with plants and which may play a role in the nitrogen balance of desert grasslands.

Acetylene↗
PubMed2002

Intestinal urea metabolism: could the bacteria involved in nitrogen cycle lead to reutilization of intestinal urea nitrogen in uremic rabbits?

We aimed to evaluate the effect of bacteria involved in the nitrogen cycle on the reutilization of intestinal urea nitrogen in uremic rabbits. New Zealand white rabbits were made uremic via bilateral nephrectomy. Study and control rabbits were given live and heat-inactivated bacteria through their jejunostomies. After they were injected with 99mTc biurea intravenously, serial serum and stool levels of labeled nitrogen were assessed by instant thin-layer chromatography, and the change in the labeled-nitrogen level was determined. The serum labeled-nitrogen level increased significantly in the study group (r=0.990); however, this level decreased in the control group (r=0.662). Furthermore, the labeled-nitrogen level in the stool samples increased throughout the study in the control rabbits, but it decreased after the 6th hour in the study group. In conclusion, the results of this study suggest that when the bacterial flora of the intestinal system is changed to include bacteria involved in the nitrogen cycle in uremic rabbits, the intraintestinal and systemic nitrogen metabolisms could both be altered in favor of positive nitrogen balance.

Animals↗
PubMed2007

Structure-dependent response of a chemiluminescence nitrogen detector for organic compounds with adjacent nitrogen atoms connected by a single bond.

High-throughput screening (HTS) of chemical libraries is indispensable for drug discovery research. However, the HTS data quality for lead discovery, lead optimization, and quantitative structure activity relationship studies has been severely compromised due to the uncertain compound concentrations in screening plates. In order to address this issue, we compared various high-throughput technologies for quantification of compounds in microtiter plate format without the need for authentic compounds as standards and identified the chemiluminescence nitrogen detector (CLND) as the method of choice at the present time. However, the structure dependence of this detector has not been well studied. A proposed rule suggested that the only exception to equimolar response is for compounds that contain adjacent nitrogen atoms. The response should be zero when the adjacent nitrogen atoms are connected by a double bond and 0.5 when they are connected by a single bond. In this investigation, we studied a broad range of compounds with isolated and adjacent nitrogen atoms. We confirmed that compounds with isolated nitrogen atoms produce an equimolar response with a 15-20% variation depending on structures and compounds with adjacent nitrogen atoms connected by a double bond giving nearly zero response. We discovered that the CLND response for compounds containing adjacent nitrogen atoms that are connected with a single bond is highly structure dependent. Substitutions on the nitrogen atoms or nearby in the molecule can increase the CLND response to approach a value higher than the predicted value 0.5 (maximal value 0.82/nitrogen atom). Without substitution, much lower values than predicted (minimal value 0.0-0.08/nitrogen atom) are obtained. Therefore, the prediction of response of 0.5/nitrogen atom for compounds with adjacent nitrogen atoms connected by a single bond should be abandoned. Compounds with similar structures should be used to generate calibration curves for quantification of this class of compounds.

Luminescence↗
PubMed1980

The effect of an energy-restricted diet on the protein metabolism of obese adolescents: nitrogen-balance and whole-body nitrogen turnover.

1. The effect of an energy-restricted (46 kJ day-1 kg-1), adequate protein diet (1.47 g day-1 kg-1) on the nitrogen metabolism of five obese rapidly growing adolescents (two males and three females) was assessed by means of nitrogen-balance measurements and determination of whole-body nitrogen turnover. 2. The energy-restricted diet had no significant effect on nitrogen balance (P more than 0.1) for the entire group when compared with the control dietary intake; however, significant (P less than 0.01) differences in nitrogen balance were noted among individuals at each dietary interval. 3. Mean values for whole-body nitrogen turnover, protein synthesis and breakdown for the control period were: 45.5 +/- 13.2 mg of nitrogen day-1 kg-1, and 5.72 +/- 1.96 and 5.74 +/- 1.92 g of protein day-1 kg-1 respectively. These values are 82% of those measured in infants. 4. Reducing the mean non-protein energy intake to 20 kJ day-1 kg-1 had no significant effect on whole-body nitrogen turnover, protein syn;thesis or protein breakdown. 5. The results are discussed in relation to the regulation of whole-body nitrogen metabolism, by dietary protein and energy intakes.

Adolescent↗
PubMed1985

Interval nitrogen excretion and maintenance nitrogen requirements for parenteral nutrition in primates.

This paper discusses a regression technique for determining maintenance nitrogen requirements in well-nourished primates (M fascicularis) on total parenteral nutrition. Animals were administered a continuous glucose infusion, and parenteral nitrogen intake was varied at constant time intervals in a random order (from 0 to 1 g nitrogen/kg/day). Interval nitrogen balance (intake minus urinary nitrogen output) was plotted against interval nitrogen intake. The x-intercept was defined as the maintenance nitrogen requirement. First, 24-h intervals were used at a nonprotein caloric intake of 85 kcal/kg/day (approximately 175% of primate resting energy expenditure) and the nutritional adequacy of the estimated requirement evaluated prospectively. Next, 8-h balance intervals were used and the maintenance nitrogen requirements predicted by this abbreviated technique were compared to those obtained using the longer method. Finally, the short-interval technique was repeated at two other levels of continuous glucose infusion (60 kcal/kg/day and 8 kcal/kg/day) and the effect on predicted nitrogen requirement examined. Maintenance parenteral nitrogen requirements for primates may be determined in 48 h using the abbreviated techniques.

Animals↗
PubMed1991

Hepatic amino-nitrogen clearance to urea-nitrogen in control subjects and in patients with cirrhosis: a simplified method.

The functional hepatic nitrogen clearance during amino acid infusion is a measure of liver cell mass. The clinical feasibility of the test has so far been limited by methodological problems. A simplified procedure was used to measure the urea-nitrogen synthesis rate and functional hepatic nitrogen clearance in nine subjects with normal liver function and in nine patients with cirrhosis. The method was based on only four consecutive 2-hr urine collections and five blood samples. Total body water was calculated from a nomogram based on age and anthropometric data, whereas the gut urea hydrolysis was assigned one fixed fraction of synthesis (0.17 in control subjects and 0.26 in patients with cirrhosis). Finally, a solution of a single amino acid, alanine, was infused as substrate for urea synthesis. Urea-nitrogen synthesis rate increased linearly with increasing alpha-amino-nitrogen concentration, and the slope of the regression (functional hepatic nitrogen clearance) was reduced in cirrhosis from 37.5 +/- 7.0 L/hr to 18.4 +/- 6.7 L/hr; p less than 0.005. The hepatic nitrogen clearance was linearly related to the clinical status (Child-Pugh score), to routine liver function tests and to galactose elimination capacity (r = 0.869), a well-established, quantitative, liver function measure. The simplified method makes the measurement of hepatic nitrogen clearance suitable for routine clinical use. The test might prove useful to study the alterations of nitrogen metabolism in cirrhosis, with special reference to hepatic encephalopathy.

Adult↗
PubMed1990

Chemiluminescent measurement of total urinary nitrogen for accurate calculation of nitrogen balance.

This instrumental method for total urinary nitrogen (TUN) is based on the principle of gas-phase chemiluminescence. Results correlate well with measurements of TUN by the Kjeldahl method, which has long provided the means to calculate nitrogen balances for nutritional management. In recent years, because of speed and convenience of measurement, determination of urinary urea nitrogen (UUN) has been substituted for Kjeldahl TUN. However, in patients requiring aggressive nutritional support, the UUN may not be a valid indicator of total nitrogen excretion. We compared nitrogen balances calculated for patients, using both UUN and chemiluminescence TUN data. For both normal and hospitalized populations, nitrogen balance calculated from UUN data exceeded that calculated from TUN data. We show that use of UUN data in calculating nitrogen balance may result in an incorrect assessment of many patients as being in positive nitrogen balance. TUN determined by chemiluminescence evidently provides a simple means of calculating nitrogen balance more nearly accurately.

False Positive Reactions↗