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PubMed2002

Dry deposition of reactive nitrogen to marine environments: recent advances and remaining uncertainties.

Many highly productive marine ecosystems exhibit nitrogen limitation or co-limitation. This article is a status review of research into the exchange of nitrogen between the atmosphere and these ecosystems with a particular focus on reactive nitrogen compounds. A summary of research conducted over the past ten years is presented and a perspective given as to remaining uncertainities and research needs. Looking toward development of coastal management modeling tools, we illustrate the processes that need to be resolved in order to accurately simulate the flux from the atmosphere and provide guidance on the required resolution of such models.

Air Pollutants↗

PubMed1998

Effects of nitrogenous components of urine on sperm motility: an in vitro study.

The effects of the major nitrogenous components of urine (ammonia, creatinine, urea and uric acid) on sperm motility were investigated. Semen samples were obtained by masturbation from a young volunteer with a normal spermiogram and fertility. Sperm motility was measured using a Sperm Quality Analyzer and Makler Chamber. When semen was mixed with a urine sample for which acidity and osmolality were adjusted to pH 7.5 and 340 mOsm/kg, the higher the concentration of the urine, the poorer the sperm motility. When solutions of various concentrations of the nitrogenous compounds which are excreted in urine were mixed with semen, sperm motility decreased in proportion to ammonia levels and was markedly decreased after 30 min. However, in the case of creatinine, urea and uric acid, good motility was maintained for 30 min regardless of their amounts. In conclusion, urine ammonia content is detrimental to sperm motility and may be an important factor in retrograde ejaculation.

Adult↗

PubMed1990

A convenient microtitre tray procedure for yeast identification.

Media for yeast identification tests were incorporated into the wells of a microtitre tray. The tests included fermentation and assimilation of carbohydrates, assimilation of nitrogen compounds, growth in vitamin-free medium, resistance to cycloheximide, and observations for cell morphology and sporulation. Results of tests conducted in the trays showed very good agreement with those obtained by conventional methods. Eighteen reference yeasts were correctly identified from tests conducted in the trays. The trays of media could be stored, and provided a convenient system for yeast identification.

Carbohydrate Metabolism↗

PubMed2004

A solid-state 14N magic-angle spinning NMR study of some amino acids.

Experimental strategies for the acquisition of high-quality 14N magic-angle spinning (MAS) NMR spectra of the simple amino acids, which exhibit 14N quadrupole coupling constants (C(Q)) on the order of 1.2 MHz, are devised. These are the first useful 14N MAS spectra reported for nitrogen compounds having a C(Q)(14N) value in excess of 1 MHz. The complete manifolds of spinning sidebands (ssbs), i.e., about 300 ssbs for a spinning frequency of 6.0 kHz, have been observed in the 14N MAS NMR spectra of a series of amino acids. In their crystal structure these amino acids all exhibit the zwitterionic form and thus the 14N MAS NMR spectra represent those of a rotating -NH(3)(+) group and not of an amino (-NH(2)) group. Computer simulations combined with fitting of simulated to the experimental ssb intensities result in the determination of precise values for the 14N quadrupole coupling (C(Q)) and its associated asymmetry parameter (eta(Q)) for the nitrogen sites in these molecules. For some of the amino acids the 14N MAS NMR spectra exhibit overlap between the manifolds of ssbs from two different nitrogen sites in accordance with their crystal structures. Computer analysis of these spectra results in two different sets of (C(Q), eta(Q)) values which mainly differ in the magnitudes for eta(Q).

Amino Acids↗

PubMed2006

Transpiration, and nitrogen uptake and flow in two maize (Zea mays L.) inbred lines as affected by nitrogen supply.

BACKGROUND AND AIMS: The influence of two nitrogen (N) levels on growth, water relations, and N uptake and flow was investigated in two different inbred lines of maize (N-efficient Zi330 and N-inefficient Chen94-11) to analyse the differences in N uptake and cycling within a plant. METHODS: Xylem sap from different leaves of the inbred lines cultured in quartz sand was collected by application of pressure to the root system. Plant transpiration was measured on a daily basis by weighing five pots of each of the treatments. KEY RESULTS: N-efficient Zi330 had a higher relative growth rate and water-use efficiency at both high (4 mm) and low (0.08 mm) N levels. At a high N level, the amount of N taken up was similar for the two inbred lines; the amount of N transported in the xylem and retranslocated in the phloem was slight greater in Chen94-11 than in Zi330. At a low N level, however, the total amount of N taken up, transported in the xylem and retranslocated in the phloem of Zi330 was 2.2, 2.7 and 2.7 times more, respectively, than that of Chen94-11. Independent of inbred line and N level, the amounts of N transported in the xylem and cycled in the phloem were far more than that taken up by roots at the same time. Low N supply shifted NO(3)(-1) reduction towards the roots. The major nitrogenous compound in the xylem sap was NO(3)(-1), when plants grew at the high N level, while amino acid-N was predominant when plants grew at the low N level. CONCLUSIONS: The N-efficient maize inbred line Zi330 had a higher ability to take up N and cycle N within the plant than N-inefficient Chen94-11 when grown under N-deficiency.

Nitrogen↗

PubMed1986

Clinical use of branched-chain amino acids in liver disease, sepsis, trauma, and burns.

The branched-chain amino acids (BCAAs)--leucine, isoleucine, and valine--share unique biochemical properties that may make them useful in altered physiologic states. They can be metabolized independently of liver function to provide energy, other amino acids, or small nitrogenous compounds. This unique ability makes the BCAAs a desirable supplement in liver disease with encephalopathy and, to a lesser extent, in sepsis with hepatic dysfunction. Furthermore, the BCAAs play a role in the regulation of protein synthesis, suggesting beneficial effects in catabolic states such as postoperative stress, trauma, renal failure, and burns. However, initial studies in these areas have presented equivocal results.

Amino Acids, Branched-Chain↗

PubMed1984

Nitrogen movement between host and tumor in mice inoculated with Ehrlich ascitic tumor cells.

Tumors function as a nitrogen trap, and they compete with the host for nitrogen compounds. In experiments with whole animals infected with Ehrlich ascitic tumor cells, the glutamine, glutamate, asparagine, and aspartate concentrations were determined for host plasma, ascitic liquid, and tumor cells, throughout the period of tumor growth. Concentration gradients of glutamine or asparagine were created from the host tissues towards the ascitic liquid. The countergradient step from ascitic liquid to tumor cells may be overcome by an active transport process with an apparent Km for glutamine of 3.1 X 10(-4) M. On the other hand, a reverse flux of glutamate and aspartate was seen to take place from cells to plasma. In vitro incubations of tumor cells with near physiological concentrations of glutamine, or asparagine plus glucose, confirmed the host-to-tumor nitrogen movement previously deduced from the relative amino acid concentrations in plasma, ascitic liquid, and tumor cells. The ammonemia detected in tumor-bearing mice at the terminal stage could result from the hydrolysis of glutamine, which was rapidly metabolized by the tumor cells.

Ammonia↗

PubMed2004

Submerged yeast fermentation of acid cheese whey for protein production and pollution potential reduction.

Bench-scale batch bioreactors were used to study the effectiveness of cheese whey fermentation for single-cell protein production using the yeast Kluyveromyces fragilis in reducing the pollution potential of whey as measured by solids, chemical oxygen demand (COD) and nitrogenous compounds concentrations. The four principal phases (lag, exponential, stationary and death) encountered in the history of a microbial culture grown under batch conditions were clearly recognized in the growth, temperature and dissolved oxygen curves. The lactose concentration and soluble COD displayed three distinct phases corresponding to the lag, exponential and stationary phases of the yeast growth. The minimum dissolved oxygen and maximum temperature observed in this study (at an air flow of 3 VVM, a mixing speed of 400 rpm and an ambient temperature) were 2.49 mg/L and 31.6 degrees C, respectively. About 99% of lactose (90.6% of soluble COD) was utilized after 28 h. The total COD continued to decline due to cell death resulting in a reduction of 42.98%. The total nitrogen concentration remained unchanged while the organic nitrogen increased during the exponential phase and then declined during the death phase. The ash content remained unchanged while a substantial reduction (56%) of the volatile solids was observed. These results indicated that sufficient oxygen for yeast growth was present in the medium and no cooling system was needed for this type of fermenter under similar experimental conditions. Recovering the yeast biomass with ultrafiltration reduced the total COD by 98% of its initial value in the raw whey.

Bioreactors↗

PubMed2000

Crude protein content and amino acid composition in Taiwanese human milk.

Breast milk provides the essential nutrients for infants in readily available form. The content of nitrogen in human milk is of great importance because it relates to the growth of infants in the early stage, and the composition of nitrogenated compounds varies according to the lactational stage. Three-hundred-and-three human milk specimens were obtained from 240 healthy mothers living in two different districts in Taiwan, and 264 specimens were used for the analysis. The crude protein content, total and free amino acid compositions as well as urea content were evaluated using pooled milk samples according to different lactational stages and geographical location. The crude protein content decreased sharply from colostrum (2.51 g/100 mL) to mature milk (1.25 g/100 mL). Total amino acids account for 80-85% of the crude protein throughout the whole lactation period. Crude protein also contained 30 to 35 mg/ 100 mL urea and 41 to 48 mg/ 100 mL free amino acids as non-protein nitrogen components. The ratio of essential to non-essential amino acids remained constant throughout the lactation period in spite of a decline in amino acid content. The amino acid composition per 1 g of nitrogen varied during the lactation period. The differences of these lactational changing patterns of individual amino acids were probably reflected by variation of the protein composition during lactation. The sum of free amino acid content ranged from 43 to 50 mg/100 mL in Taipei and 40 to 45 mg/100 ml, in Kaohsiung. Although the variations of free amino acids during the lactation period differed among amino acids, glutamic acid predominated in mature milk while phosphoethanolamine was predominant in colostrum.

Adult↗

PubMedDate not supplied

Posttreatment of a brewery wastewater using a sequencing batch reactor.

This study concerns the application of a sequencing batch reactor (SBR) for the posttreatment of an effluent rejected by an upflow anaerobic sludge blanket (UASB) reactor operating in a brewery. The goal was to achieve the required wastewater quality for discharge to surface water. The primary target was the removal of nitrogen compounds, but chemical oxygen demand and suspended solids were also concerns. Phosphorus concentration and protozoan population were also monitored during SBR operation. Two different strategies were tested: an operation based on an aerobic-anoxic sequence and another based on applying a predenitrification step, that is, an anoxic-aerobic-anoxic sequence. Ammonium (NH4-N) removal was achieved in all assays. Nitrification efficiency reached 97%, and the maximum observed rate was 0.175 kg NH4-N/kg volatile suspended solids.d. A denitrification process was detected during the aerated periods, despite a dissolved oxygen concentration in the bulk liquid of 2.8 to 3.7 mg O2/L. However, denitrification was suppressed when the bulk liquid oxygen concentration was increased to 7 mg O2/L. The carbon-to-nitrogen ratio of the UASB effluent was too low and hindered the postdenitrification phase. This fact was confirmed by complete nitrate removal when an acetate supplement was added. On the other hand, the insertion of a primary anoxic phase in the reaction cycle was the best treatment strategy, leading to nitrogen values within the legal framework. The protozoan population showed significant changes in response to the aerobic-anoxic conditions. However, periodic nonaerated conditions were not detrimental to aerobic protozoa, which recovered as soon as oxygen was again available.

Animals↗

PubMed1989

Protective effects of a specific platelet activating factor (PAF) antagonist, WEB 2086, in traumatic shock.

We have investigated the role of platelet activating factor (PAF) in the pathogenesis of a murine model of traumatic shock using WEB 2086, a specific antagonist of PAF. WEB 2086 (0.5 mg/kg) significantly reversed the decrease in mean arterial blood pressure (MABP) induced by PAF (0.3 micrograms/kg) in anesthetized rats. Anesthetized rats were subjected to Noble-Collip drum trauma. Traumatized rats treated with WEB 2086 (0.5 mg/kg bolus followed by infusion at 0.5 mg/kg/hr) maintained a higher MABP than those receiving only the vehicle (0.9% NaCl). Improvement in MABP paralleled a significant increase in overall survival time (p less than 0.01) in rats receiving WEB 2086 (0.5 mg/kg). WEB 2086 also significantly attenuated the plasma accumulation of the lysosomal hydrolase, cathepsin D and of free amino-nitrogen compounds, compared to shocked rats receiving only the vehicle. Furthermore, the production of the cardiotoxic peptide, myocardial depressant factor (MDF) was also blunted by WEB 2086. These results suggest that PAF may be an important mediator in the pathogenesis of traumatic shock in rats. Furthermore, PAF receptor antagonists may be useful as therapeutic agents when given early in the course of ischemic and shock states.

Animals↗

PubMed2003

Heterocyst development in Anabaena.

Many filamentous nitrogen-fixing cyanobacteria protect nitrogenase from oxygen in differentiated cells called heterocysts. Heterocyst development is controlled by the availability of nitrogen compounds in the environment and by intrinsic factors that regulate the frequency and pattern of heterocysts along vegetative cell filaments. Recent progress in understanding heterocyst development in these simple multicellular organisms includes demonstrating the role of 2-oxoglutarate in regulating the activity of the transcription factor NtcA, the identification of additional genes in the regulatory network, such as hetF, and the further characterization of previously identified genes and proteins, including DevR/HepK, hetR, hetN, patS and patB.

Anabaena↗

PubMed2005

Changes in the concentration of yeast-derived volatile compounds of red wine during malolactic fermentation with four commercial starter cultures of Oenococcus oeni.

The effects of malolactic fermentation (MLF) on the concentration of volatile compounds released by yeasts during the production of red wine were investigated by inoculation with four commercial starters of Oenococcus oeni. Volatile compounds in wine at the end of MLF were extracted, analyzed by GC-MS and GC, and compared with those extracted form a noninoculated reference sample. Several esters known to play a role in the aroma profile of red wine, such as C4-C8 ethyl fatty acid esters and 3-methylbutyl acetate, were found to increase with MLF, and their final concentration was dependent on the bacterial starter employed for the induction of MLF. The overall increase of ethyl fatty acid esters was generally larger than the one observed for acetate esters. Ethyl lactate, 3-hydroxybutanoate, 2-phenylethanol, methionol, and gamma-butyrolactone were also increased by bacterial metabolism. The impact of MLF on other volatiles or red wine, including several higher alcohols, fatty acids, and nitrogen compounds, was generally negligible.

Chromatography, Gas↗

PubMedDate not supplied

Nutritional status of men under hypokinesia.

Hypokinesia (diminished muscular activity) elicits substantial changes in energy and nutritional requirements in humans. The objective of this investigation was to determine the nutritional status of six physically healthy men aged 19 to 21 years under 95 days of hypokinesia without the use of any preventive measures. For the simulation of the hypokinetic effect the men were placed under 95 days of an ad libitum bed rest regimen. During the background period, that is, prior to exposure to hypokinesia, the caloric value of the diet was 3124 kcal per day; under hypokinesia, the caloric value was 2745 kcal per day. In calculating the nutritional requirements of men under hypokinesia, several biochemical parameters were measured. Effects of hypokinesia demonstrated included certain changes in the enzymatic activity of glands; increased excretion of nitrogenous compounds in the urine; increased blood cholesterol content; changes in the amount of blood sugar; changes in acid-base balance; increased elimination of fluid, calcium, and phosphorus; impaired supply of vitamins to the organism; and increased energy expenditure. It was concluded that the nutritional status of men underwent substantial changes under conditions of diminished muscular activity.

Acid-Base Equilibrium↗

PubMed1989

Features of myocardial metabolism of some amino acids and ammonia in patients with coronary artery disease.

Fractional myocardial extraction/release of glutamate, glutamine, alanine, ammonia, asparagine, glucose and lactate was studied in 12 subjects with normal coronary anatomy (controls) and 28 patients with coronary artery disease (CAD) during rest and atrial pacing. At rest patients with CAD showed an increased myocardial extraction of glutamate, glucose and lactate and an augmented glutamine and alanine release compared with controls. In all CAD patients myocardial ammonia and asparagine release was found at rest, while all controls showed myocardial extraction of these compounds. Myocardial glutamate extraction correlated positively with glucose and lactate extraction, glutamine and alanine release and inversely with ammonia release in CAD patients at rest. In patients with two- and three-vessel disease pacing-induced ischaemia resulted in a pronounced decrease in myocardial glutamate extraction and glutamine release, augmented myocardial production of ammonia and asparagine and a conversion of lactate extraction into lactate release. During pacing myocardial glutamate extraction was related to alanine and glutamine release and correlated inversely with ammonia and lactate release in these patients. The results indicate that glutamate extraction is closely connected with glucose and lactate extraction and ammonia binding via glutamine formation in the hearts of CAD patients and, thus, with the energy supply of ischaemic myocardium. An assessment of myocardial exchange of the nitrogenous compounds we have studied, complimentary to lactate, is a promising biochemical test for the identification of ischaemic heart disease in man.

Adult↗

PubMed1985

The effect of portocaval shunt on hepatic glycogen stores during fasting.

The effect of a prolonged fast was studied in surgically portocaval shunted (PCS) rats. This shunt excludes the liver from the direct effect of pancreatic and enteric hormones, thus facilitating the study of the biochemical and metabolic effects of these hormones. In portocaval shunted rats, liver glycogen was lower than that of control rats, and remained unaffected during fasting. No remarkable difference was observed in blood glucose, plasma and liver free fatty acids and blood ketone bodies. Among blood nitrogen compounds, total protein, alanine and urea did not show any significant variation, while, in PCS rats, the initial low levels of creatinine resulted in an increase after fast. Skeletal muscle protein decreased only slightly in control rats, while their loss was remarkable in PCS rats. The possibility of a differential activation of gluconeogenesis and glycogenolysis in control and PCS rats is discussed.

Animals↗

PubMed2006

A solid-phase microextraction chamber method for analysis of manure volatiles.

Odors from livestock operations are a complex mixture of volatile carbon, sulfur, and nitrogen compounds. Currently, detailed volatiles analysis is both time consuming and requires specialized equipment and methods. This work describes a new method that utilizes a dynamic flux chamber, solid-phase microextraction (SPME), and gas chromatography-mass spectroscopy (GC-MS) to describe and compare the odorous compounds emitted from cattle and swine feces. Evaluation of method parameters produced a protocol for comparing relative emissions based on fixed sample temperature (20 degrees C) and exposed surface area (approximately 523 cm(2)), air flow rates (1 L min(-1) or 16 cm s(-1)), SPME exposure time (5 min), and chamber cleaning procedures (70% ethanol rinse and drying for 30 min at 105 degrees C) to minimize cross-contamination between samples. A variety of volatile organic compounds (VOCs) including alcohols, volatile fatty acids, aromatic ring compounds, ketones, esters, and sulfides were routinely detected and the relative emissions from fresh and incubated (37 degrees C overnight) swine and cattle feces were compared as a measure of potential to produce odorants during manure storage. Differences in the types and relative quantities of volatiles emitted were detected when animal species (cattle or swine), diet, fecal incubation, or sample storage conditions (20, 4, or -20 degrees C) were varied.

Animals↗

PubMed1992

Effects of air filtration on spring wheat grown in open-top field chambers at a rural site. II. Effects on mineral partitioning, sulphur and nitrogen metabolism and on grain quality.

In 1988 the effect of ambient levels of air pollutants on the nutrients status and grain quality of spring wheat (Triticum aestivum cv. Pelican) was investigated by comparing plants grown in open-top chambers (OTC) ventilated with ambient air (NF treatments) and charcoal-filtered air (CF treatments) at a rural site (Tervuren, Belgium). Spring wheat cultivated in NF OTC showed only minor differences in the P, K, Ca, Mg, Mn and Na concentrations of the different plant parts at final harvest, as well as organic and inorganic S fractions, compared to those of the plants grown in CF air. The plants' total P content was reduced, as well as the P and K concentration of the flour. The total S concentration of the flour was increased by 4%. Effects on N concentrations and grain quality were much more pronounced. At final harvest the N concentrations of straw and flour of the NF air treated plants were much higher compared to CF air. However, the N content of the aerial biomass and the grain N yield were not significantly affected, implying a reduction of other structual compounds. Nitrogen harvest index (NHI) and the ratio of NHI over grain harvest index (GHI), indicated a significant reduction of N translocation from the above-ground biomass to the grain. Changes in the N status and partitioning of spring wheat had an effect on the baking quality of wheat flour. Several parameters that are commonly used as an indication of baking quality have been significantly increased in the NF treatment: total protein concentration, Zeleny value, dry and wet gluten concentration. A slightly increased Hagberg value indicated a reduced alpha-amylase activity. The possibility of foliar N uptake as an additional N source, especially after anthesis and implications of increased protein production instead of carbohydrate synthesis are discussed.

Journal Article↗